TECHNICAL HIGHLIGHTS

OFTHE -f'

NATIONAL BUREAU OF STANDARDS

Annual Report for: INSTITUTE FOR BASIC STANDARDS

INSTITUTE FOR MATERIALS RESEARCH

INSTITUTE FOR APPLIED TECHNOLOGY

CENTRAL RADIO PROPAGATION LABORATORY

UNITED STATES DEPARTMENT OF COMMERCE

Luther H. Hodges, Secretary

J. Herbert Hollomon, Assistant Secretary for Science and Technology

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director

1964

Technical Highlights

of the

National Bureau of Standards

Annual Report, Fiscal Year 1964

December 1964

Miscellaneous Publication 264

For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C., 20402 - Price $1.00
Library of Congress Catalog Card Number: 6-23979
Contents

Page

1. General review 1 Basic measurements and standards 2 Standard reference data 9

Engineering measurements and standards 11 Standard reference materials 13 Radio propagation 16 Data-processing systems 17 Clearinghouse for Federal scientific and technical information 18 Advisory services 18 General research 20

Internal technical services 23

International activities 23 Administrative activities 25 Technical information 27

2. Highlights of the technical program 30

2.1. Institute for Basic Standards 31

2.1.1. The National Standard Reference Data System 34

Status of technical area programs 35

Relationships with other government agencies 37

2.1.2. Applied mathematics 37 Numerical analyses 38 Asymptotic expansions and analysis 38 Eigenvalue determination 38 Quadrature and interpolation 38

Linear algebra, matrix theory, group theory, and number

theory 38 Machine translation 38

Pictorial data processing and artificial intelligence 38 Mathematical tables 39

Digital computation 39

Statistical engineering 40 Research and development 40

Cooperative activities 41

Operations research 41 Mathematical physics 42 Theory of satellite orbits 42 Research in plasma physics 43 Whisker growth 43 Mathematics group at the Boulder Laboratories 43

Statistical studies at the Boulder Laboratories 44

2.1.3. Electricity 44

Electrical units 44

Current 44

Capacitance 45 Standards 45

Stable capacitance standards 45

Voltage dependence of air capacitors 46

Galvanic cell with thallous sulfate 46 A-C voltage 46 High-accuracy current transformers 47 Measurement methods '. 47

Properties of matter 49 Gold anodes in electrolysis 49

Structure of garnets 50 Ferromagnetic alloys 50 Magnetic susceptibilities 50

Dielectrics 50 Advisory activity 51

Calibration service 51

iii
2 Highlights of the technical program—Continued

2.1. Institute for Basic Standards—Continued Page

2.1.4. Metrology 51 Load cell comparison devised for weight calibrations 51 Color-matching functions evaluated 53 Density measurements devised for small objects 53 Aging blemishes studied on microfilm 53 Microdensitometer calibration 55 Photographic knife edge devised 55

Chlorophyll measured in tree leaves 55

Infrared hazemeter developed 55

Spectral distribution of typical daylight 55

Fluorescent lamp color standards recalibrated 56 Check made of color-temperature scale 57 Standard published for the colors of signal lights 57 Wavelength standards for spectrophotometers 57 Master balls rapidly calibrated by interferometry 58 Tooth index positions measured on large gears 58 Roughness simulator constructed 58 Spectrometer designed for laser analysis 58

Special optical calibrations carried out 59

Refractometric research 59 Ophthalmic lenses 60

Line standard interferometer 60 Thermal expansion calibrations expanded 60

Superprecision gaging 60 Mossbauer radiation 60

2.1.5. Mechanics 61

Calibration of microphones 61 Measurement of earthquake motions by an acoustical tech- nique 62 Sound insulation in buildings 62 Audiometry 63

Single -crystal ice—elastic constants 64

Nonlinear distortion in hearing aids 64

Electromechanical coupling factor of condenser microphones . . 65

Pressure measurements 65 Damping of surface waves caused by turbulence 66 Highway culverts 66 New proving ring calibration report 67 Displacement measuring devices evaluated at elevated temperatures 67

Fatigue strength of aircraft structures 67

Test methods developed for aeronautical fasteners 67

Vibration standard modified with air bearings 68

Rheological constitutive equations 68

Failure of aircraft fuel hoses 69 Flow field of a flame 69 Thermocouple reference tables compiled 69

2.1.6. Heat 70 Paramagnetic resonance in gases 70 Molecular energy levels of small molecules 71 Plasma transport processes 71 Microsecond thermodynamics 72 New spectroradiometer 72

Precision manometer 73

Pressure transducer for gas-phase PVT measurements 74 Developments in the automation of calorimetry 74 Low-temperature scale improved by correlation with NBS

data 75 New low -temperature calibrations 76 Thermal conductivity at low temperatures 76 Superconducting semiconductors 76 Magnetic susceptibilities of rare-earth trichlorides 76 Neutron scattering from oriented 165 Ho nuclei 77

Statistical mechanical calculations of properties of many-body

systems 77

iv
2. Highlights of the technical program—Continued

2.1. Institute for Basic Standards—Continued Page

2.1.7. Atomic physics 78 Intermediate energy atomic physics 78 Atomic energy levels 80 Wavelength standards 80

Atomic transition probabilities 81 Infrared spectroscopy 81 Microwave spectroscopy 81 Experimental atomic collisions 82

Electron scattering in solids and liquids 82

Field-ion microscopy 83

Solid-state physics 83

2.1.8. Physical chemistry 84 Thermochemistry 85

Surface chemistry 86

Isotope effects 86

Stereochemistry and structure 87

Air pollution 87

Molecular spectroscopy 87 Shock-wave studies of unimolecular reactions 87

Diffusion coefficients determined 88 Mass spectrometry 89 Mass spectrometric reaction kinetics 89

Vacuum ultraviolet photochemistry 89

Radiation chemistry 89

2.1.9. Laboratory astrophysics 90

Astrophysics 90

Spectroscopic diagnostics 90

Solar studies 91

Stellar atmosphere studies 92

Physics of atomic collisions 92 Plasma transport properties 94 Resonance physics 94

Physical constants 94 Data center on atomic collision cross sections 95

2.1.10. Radiation physics 95 Dosimetry 96

Cavity chambers 96

Photographic dosimetry 96

Solid-state dosimetry 97 Response of Hurst neutron dosimeter

.

97 X- and gamma-ray standards 97

Radioactive sources 98 Standards of radioactivity 98

Spectrometer for neutron source studies 99

Radiation interactions with nuclei 99

Fast time-of-flight measurements of neutron cross sections 99 Nuclear size determinations from coherent neutral meson

photoproduction 99 Nuclear theory 99 Elementary particle theory 101 Photonuclear cross sections ]01 Detector for photonuclear reactions 101 Nuclear spectroscopy 101 New linear accelerator 101 Magnet testing program 102 Target chamber design 102 Data -handling system 103 Monitoring high -intensity electron beams 103

Electron scattering program 103 Theory of electron scattering 103

Accelerator shielding handbook 103 Compilation and evaluation of data 104

Photonuclear interactions 104

Electromagnetic interactions 104

Electromagnetic cross-section theory 104

V
2. Highlights of the technical program—Continued

2.1. Institute for Basic Standards—Continued

2.1.10. Radiation physics—Continued Page Radiation transport theory 105 Charged particles 105 Gamma rays 105 Neutrons 106

2.1.11. Radio standards laboratory 107

Theoretical physics 108

2.1.12. Radio standards physics 108 Frequency and time dissemination 108 Atomic frequency standard research ] 09

International comparison of atomic frequency standards 109 Quantum electronics 110 Radio and microwave materials Ill Magnetics Ill

Materials synthesis 112

Dielectrics 112 Microwave physics 112 Radiometry 113 Microwave-stimulated transitions 113

Interferometric measurements 113 Brush-cathode plasma 113 Plasma measurements. 114 Bounded plasmas 115

2.1.13. Radio standards engineering 115 Low-frequency calibration ]15

High-frequency standards 117 Electromagnetic measurements 117 High-frequency calibration 119 Microwave standards 120 Microwave calibration 122

2.2. Institute for Materials Research . 123

Preparation of research materials . 123 Standard reference materials . 124 Measurement of bulk properties of materials . 124

Acquisition of critical data on fundamental physical and

chemical properties of matter . 125

2.2.1. Analytical chemistry 125

Activation analysis improved 126 Improved Mossbauer spectrometer 126

Radioisotopic tracers used for analysis ]26 Clean room constructed 126 Spark source mass spectrograph acquired 126

Single reproducible pulse obtained with laser microprobe .... 127 X-ray spectrograph^ analysis of solutions ]27

Electron probe microanalyzer extends capabilities 127

Spectra excited in controlled atmospheres 128

Special cast iron standards prepared for the Malleable Research Foundation 129

Errors in the microscopical measurement of spheres studied .... 129 Thermodynamics of solutions in heavy water 129 />H standards in partially aqueous media investigated 130

Preconcentration polarography 130 Magnetic densimeter constructed 130 Copper-base and white iron standards issued 130 New uranium and plutonium isotopic standards issued 130 High-precision coulometry 131 Analysis and purification services provided 131

2.2.2. Polymers 131 Cooperative intramolecular transition found in a synthetic

polypeptide 132

Stress found proportional to double refraction in amorphous

polymers 132 Polypropylene crystals studied 134

Crystalline polymers 134 Thickening of chain-folded crystals 134

Lattice parameters of a copolymer 134 Mechanism of polymer adsorption investigated 135

vi
2. Highlights of the technical program—Continued

2. .2 Institute for Materials Research—Conlinued

2.2.2. Polymers—Continued Pa£e Polymer properties statistically calculated 135

Compressibility of natural rubber 135

Ultracentrifuge used to study polymer sedimentation 135 Heat of the vulcanization reaction 136

Fluorine chemistry „ . . 137 Polymer stability to radiation 137 Techniques devised to study polymer oxidation 137 Polymer degradation 137

Properties of coordination polymers 138 Microradiography of roofing materials 138

Centrifugal method for measuring tensile strength of dental amalgam 138

Properties of tooth structure 138

Rheological behavior of dental amalgam 139 Reinforcement of dental polymers 140

2.2.3. Metallurgy 140

Effects of notch geometry investigated at high temperature. . 140

Precision gage block materials 141 Deformation of metals studied 141

Slack-quenching effects studied , 141 Metal fatigue 141 Nuclear magnetic resonance 141 Highly pure metals and alloys prepared 142

Dislocations in metals 143 Stacking fault theory being developed 143

Electron probe modified 143 X-ray diffraction studies 143 Micrograpbic analysis performed by computer 143

Polarization technique for measuring corrosion rates applied

to iron-nickel alloys 144

Surface studies in corrosion 144

Steel pilings examined 144

Stress corrosion cracking 144

Corrosion failure of electroplated coatings 144

Properties of electrodeposited copper 145 Chemical deposition of tungsten from the vapor phase 146 Galvanostalametry 146

Kinetic equations for diffusion in a driving force 146

Stacking faults in high-temperature creep 147

Kinetics of whisker growth and evaporation 147

Nucleation studied by electron field emission 147 Metal single crystals 148

2.2.4. Inorganic materials 148 Growth of inorganic compounds investigated 148

Dislocations in nonmetallic crystals studied 149

Crystals of high perfection 149 Point defects studied using internal friction and dielectric loss . 150

Crystal structure determined by x-ray diffraction 151 Rate of vaporization of high-temperature materials investi- gated 151 High-temperature mass spectrometry 151

Liquid-liquid phase separation in inorganic oxides studied. . . 152 Boron compounds studied by nuclear resonance 152

Viscosity of glasses measured 152 Mechanical properties of glass studied at elevated temperatures 153

Configurational entropy is a criterion for glass transformation. . 154 Methane crystals formed ]54

Metal oxide melting point standards redetermined 154 Standard x-ray powder diffraction patterns 155 Inorganic materials studied by infrared spectroscopy 156

2.2.5. Reactor radiations 156 Flux standardization 157 Molecular motion 157

Lattice vibrations 157 Neutron moderation study 157

vii
2. Highlights of the technical program—Continued

2.2. Institute for Materials Research—Continued

2.2.5. Reactor radiations—Continued pase Neutron optics 157

Establishing vacua 158

2.2.6. Cryogenics 158

Viscosity of parahydrogen determined ] 58

Solid-vapor equilibrium in the hydrogen-methane system. . . . 159 Mixtures of solid and liquid hydrogen 159

Superconductivity 160 Metallurgy 160

Electronic properties of copper investigated 160 Aluminum cryogenic magnet tested 160 Thermophysical properties of cryogenic materials 160 Cryogenic literature service 161 Measurement methodology 162

Fluid flow and heat transfer 162

2.3. Institute for Applied Technology 165 The dissemination of technical information 165 The development of performance criteria 166 The development of tools for analysis of large-scale problems 166 The analysis of problems associated with introduction of new

technology 167

2.3.1. Clearinghouse for federal scientific and technical information. . . 167 Document input processing 169 Document and information request processing 169

2.3.2. Weights and measures 170 Technical services 171 Standards 172 Technical training 172 Technical information 172 National conference 172

Federal-state technical services 172

2.3.3. Engineering standards 173 Commodity standards 173 Technical standards coordination 174 Standards for developing countries 175

2.3.4. Building research 175 Strength of prestressed concrete beams investigated 176 Masonry racking test simplified 177 Models used in fire research 177

Fire performance of partially dried plasters 177 Water valves for refrigerating systems studied 178 Thermal properties of the earth 178

Air mixing techniques investigated 178 Asphalt hardening with reactive oxidants 179

Building codes and safety standards 179 Measuring thermal conductivity of materials 180 Moisture condensation in the insulation of refrigerated

facilities 180 Long-time cement test program 181 Thermal emittance of cavities : . . . 181

Porcelain enamel institute research associateship expanded. . 181 Cement-to-aggregate bond tested 181 Granular content of sulfur mortars determined 182

2.3.5. Information technology 183 Research information center and advisory service on information processing (RICASIP) 183

Standardization activities 184

Processor programming research 184

Studies of components and materials 184 Computer input-output devices 184

Technical assistance for NBS data processing 185 Automatic indexing by SADSACT 185 Automation of chemical search operations 186 Automatic character recognition 187

Simulation of a communications system 187

Detection of nuclear events 187 ACCESS 188

viii
2. Highlights of the technical program—Continued

2.3. Institute for Applied Technology—Continued

2.3.5. Information technology—Continued Page Global space information 188 Naval procurement procedures 189 Remote inquiry stations 189 The Vigilometer 189

Processing and storing microfilm 190

Three-dimensional information from photographs 190 Management data processing 190 Computers in management of recreational facilities 190 Automatic data processing for Public Housing Administration 191 Survey of federal information-storage systems 191 Data-handling systems for the Office of Technical Services. . 191 Automatic mail-sorting developments 19]

2.3.6. Instrumentation 192

Project FIST 192

Precise electrical characterization of semiconductors 193 Second breakdown , 194 Peak-reading ac-dc comparators as laboratory standards. . . . 194 VHF spectrum analyzer 195 FOSDIC applications 195 Vacuum physics 196

2.4. Central Radio Propagation Laboratory 197

Project HANDS, high -altitude nuclear detection studies 197 IQSY—the international years of the quiet sun 198 IGY—the international geophysical year 199

2.4.1. Ionosphere research and propagation 199

Vertical soundings research 199 Plasma resonances in the ionosphere 200

Persistence of solar flare activity at fixed longitudes 200

Active dark solar filaments 200

Noise storms in the solar atmosphere 200 VLF observations of solar flare ionization in the D region . . . 201

Effects of a solar eclipse on the D region 202

Effects of a solar eclipse in the F region 201 Geomagnetic pulsations in the 30 to 0.003 Hz range 202 Earth conductivity measurements 202 Magnetic dip coordinates 204

2.4.2. Troposphere and space telecommunications 204

Transmission loss prediction 204

Studies of antenna response 205

Diffraction at convex surfaces 205 Radio meteorology 205

Knife-edge diffraction studies 206

Propagation over long paths at SHF 206

Surface-satellite communication interference 207

Over-water transmission loss measurements 207 Bandwidth of the tropospberic propagation medium 207 Radio noise predictions 208 Manmade radio noise and transmission loss measurements. . . 208

Infrared properties of the atmosphere 209 Spectrum analyzer 210 Tracking accuracy research 210

2.4.3. Radio systems 210

Radio-frequency propagation determination and prediction

system 210

High-frequency ionospheric radar 211 Modulation research 212 HF channel characterization 213 Multipath microwave transmission 213 Antenna measurements and research 214 Antenna aperture synthesis 214 Frequency utilization 214

Radiodetermination 215 Applied electromagnetic theory 215

Laser atmospheric transmission studies 216

Infrasonics research 216

Solar proton event detection 217

ix
2. Highlights of the technical program—Continued

2.4. Central Radio Propagation Laboartory—Continued Page

2.4.4. Upper atmosphere and space physics 217

Theoretical and analytical atmospheric studies 217 Atmospheric collision processes 218 Gas discharge afterglow 219

Infrared absorption by charge transfer 219

Jicamarca radar observatory 219

Electron density and ionospheric constituents 219 Synchrotron radio noise measurements at Jicamarca 220 Plasma instability research at Jicamarca 220

Ionospheric absorption at conjugate points 220

Airglow arcs in the tropics 221 Model of natural sodium abundance 222

Ionospheric studies by reception of satellite signal 222

2.4.5. Electromagnetic research 223 Mode theory of the propagation of VLF radio waves 223

Influence of the lower ionosphere on propagation of VLF

waves 224

Effect of ionospheric perturbations at VLF 224

Reflection coefficients for a lossy magneto plasma 224

Diffraction effects at VLF for a localized ionospheric depression 224

D-layer characteristics studied by VLF propagation 225 Microwave models for VLF propagation 225 Impedance of a monopole antenna with a radial -wire ground

system 225 The electromagnetic field near a wedge apex 225

Oblique propagation of groundwaves across a coastline 226 Waves in cold plasma 226

Sources in plasma 226

3. Appendixes 227

3.1. Organization 227

3.2. Summary of NBS staff 236

3.3. Financial data on NBS program 236

3.4. Advisory committees 237

3.5. Awards and honors 242

3.6. Education, training, and University Liason 243

3.7. List of publications and patents 246

x
1. GENERAL REVIEW

To an increasing extent, the nature of the world in which we live is being

determined by the effects of new discoveries and advances in science and

technology. Industrial productivity increases and living standards rise as

the technologist finds ways to apply the achievements of science in the devel- opment of new products, processes, and resources. Recognizing the importance of scientific research to the Nation's economic

stability and growth, the Secretary of Commerce in January 1964 designated

the National Bureau of Standards to serve as a principal focal point within

the Federal Government for the application of the physical and engineering

sciences to the advancement of technology. At that time steps were also taken

to make the Bureau a more effective instrument for performing this function. Two other Department of Commerce activities, the Office of Technical Services

(OTS) and a textile technology program in the Office of the Secretary, were

transferred to the Bureau, and the resulting overall program, under the general

administration of NBS, was grouped into four institutes: Institute for Basic

Standards, Institute for Materials Research, Institute for Applied Technology,

and Central Radio Propagation Laboratory. These changes were designed

not only to provide more effective management but also to permit closer identification of NBS programs with the specific needs of American science,

industry, and commerce. The Institute for Basic Standards (IBS) provides the basis within the United States for a complete and consistent system of physical measurement.

It coordinates that system with the measurement systems of other nations, and

furnishes essential services leading to accurate and uniform physical meas- urements throughout the Nation. This measurement system is the foundation

of our mass production industry. It is the language by which scientists communicate with each other and by which scientific advances are transferred to the production line, and it provides a basis for the exchange of goods and

services in commerce. Principal activities of this Institute include the de- velopment and maintenance of the national standards for physical measure- ment; determination of fundamental physical constants; acquisition of ref- erence data on the properties of matter and administration of a National

Standard Reference Data System; research and development on measurement

techniques and instrumentation; and the calibration of master standards in terms of the national standards. The Institute for Materials Research (IMR) conducts a broad range of programs on the properties of matter and materials. Here the objective is to make possible a better understanding of the basic properties and behavior of

1
materials and to make available reliable quantitative data on their performance. From such knowledge come new scientific developments, new production processes, new or improved products, and whole new industries. This

Institute devises techniques for preparing experimental materials and for measuring their properties, develops criteria for evaluating materials per- formance, and develops and distributes standard reference materials. The mission of the Institute for Applied Technology (IAT) is to foster and stimulate the application of technology to national needs, both in govern- ment and in industry. This Institute's responsibilities include the development of criteria for evaluating technological products and services, the provision of specialized information services to meet the neeeds of our industrial technology, and studies on the nature of technological change. The Institute seeks to make new technology more readily available to American industry

by studying the technical-economic problems involved in technological in- novation and by encouraging the developmment of performance standards

that provide a sound basis for the acceptance of new technology.

The Central Radio Propagation Laboratory (CRPL) , which already existed as a separate unit within the Bureau, has for many years been the central agency of the Federal Government for the collection, analysis, and dissemination of information on the propagation of radio waves at all frequencies

along the surface of the earth, in the atmosphere, and in outer space. The

Laboratory conducts basic research on the nature of radio waves and the media through which they are transmitted, studies radio propagation mechanisms, provides advisory services on radio-frequency utilization and radio

systems; and issues predictions of radio propagation conditions. Because

of the tremendous extent of the communications industry and the increasing

importance of radio systems in national defense and space exploration, the work of CRPL has come to have far-reaching effects on the Nation's tech- nology.

This report attempts to present the highlights of the programs of the four

institutes for the fiscal year 1964. In Section 2, the body of the report, the work of each institute is considered separately, and in each case studies and

achievements from the various fields in which the institute is active have been

selected for brief presentation. As an introduction to the main body of the report the remainder of Section 1 is devoted to a brief summary of the more

important accomplishments and activities of the year at the National Bureau

of Standards.

BASIC MEASUREMENTS AND STANDARDS

To insure accurate, uniform measurements throughout the Nation, the Bureau must make its standards available to science and industry through

calibration services. As a foundation for this service the Bureau conducts

a variety of research programs on the frontiers of measurement science. As

science and technology continue their rapid advance, new fields are contin- ually opening up with new measurement requirements; at the same time

measurements in the older fields must be made with increasingly greater ac2
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105 The Bureau continued to develop State of the Art graphs in various fields of measurement. Among these were graphs depicting measurement capabilities

in the area of humidity, top, and d-c voltage, bottom. (See page 9) curacy and over broader ranges of values. Thus, both in its research and

in its measurement services programs, the Bureau tries to anticipate the measurement problems of tomorrow to make sure that measurement "gaps"

do not hold back the progress of science and technology.

During the last year, the Bureau's Advisory Committee on Calibration

and Measurement Services (Appendix, p. 242), whose members are chosen

for their broad knowledge of industrial measurement problems, continued

to be of great value in pointing out measurement needs. Particularly press- ing was the need for extension of the range of calibration services in the

3
high-frequency and microwave regions. Although initiation of new meas- urement research projects was curtailed in 1964 because of budgetary

limitations, work begun in previous years resulted in the offering of a number of new services. These included: extension of power calibration in WR62 waveguides (12.4 to 18 GHz) to include determination of the cali- bration factor of bolometer units and of bolometer-coupler units; measure- ment of the magnitude (range: 0.025 to 1.0) of the reflection coefficient of waveguide reflectors (mismatches) in WR62 waveguides; calibration of three-terminal capacitors at 110 kHz and 1 MHz; determination of fre- quency stability of signal sources in the range from 0 to 500 MHz; and ex- tension of field-strength calibration services for horizontally polarized dipole antennas from 300 to 1000 MHz.

A significant advance in low-temperature measurement was the establish- ment of a facility for the calibration of germanium resistance thermometers

over the range 2 to 5 °K. This new service should be of considerable

value to industry, as germanium resistance thermometry is widely used in low-temperature studies of fuels for rockets and missiles, solid-state devices

for space-borne computers, and the phenomenon of superconductivity. As

the result of experiments completed during the year, it is expected that a

calibration service in the range from 2 to 20 °K will be established in the coming year. On September 13, 1963, new facilities, providing greatly increased power

and range, were dedicated for NBS standard broadcast stations WWVB

(60 kHz) and WWVL (20 kHz). These low-frequency stations now pro- vide the most accurate and stable frequency transmissions in the world,

enabling scientific laboratories to calibrate their precision frequency sources

to an accuracy of better than 1 part in 1011 (one thousandth of a second in 3 years) . Such accuracy is required in many satellite and missile programs

and for basic research on atmospheric and ionispheric phenomena. Previ- ously the two stations had been used only for experimental low-frequency

transmissions—WWVB broadcasting from Boulder, Colo., and WWVL from

Sunset, Colo. The success of the experimental broadcasts provided tech- nical justification for the construction of new facilities at Ft. Collins and

establishment of the stations on a permanent basis. The new stations complement but do not replace the Bureau's higher frequency stations WWV

and WWVH, which are sufficiently accurate for many important applications.

The NBS atomic time scales (NBS-A which continuously maintains atomic

time and NBS-UA which continuously maintains an atomic approximation

to Universal time) were improved during the year by adding two additional

clocks to the three-clock system that was previously used for interpolating on these scales between calibrations with the U.S. Frequency Standard.

Through addition of the new clocks, the daily precision with which the scales measure time was improved from ±1X10-11 to =t3Xl0~12

, and thus the accuracy of either scale after several days becomes limited only bv the accuracy of the U.S. Frequency Standard. Since January 1964, the NBSUA time scale has directly controlled the low-frequency broadcasts of WWVB

4
and WWVL, and indirectly controlled the high-frequency broadcasts of WWV. This has improved the daily stability of these frequency trans- missions by almost an order of magnitude. As a result, clocks which are phase locked to the low-frequency broadcasts can maintain time sychronization with NBS-UA to within 10 microseconds.

The Bureau continued to restrict its calibration work, whenever possible, to master standards and high-precision instruments, leaving the cali- bration of lower-echelon standards to the standards laboratories of industry

and the military services. Requests for calibration of lower-echelon stand- ards declined during the year, with an attendant drop in the total volume

of calibrations from 75,361 items in fiscal 1963 to 65,353 items in fiscal 1964 (table 1) . With this reduction in the calibration load, the Bureau was

able to devote a somewhat greater proportion of its resources to the development of new and improved standards and measurement methods.

Efforts to accelerate calibration procedures through use of automation

continued. The calibration times for both gage blocks and surveying tapes were substantially reduced by the use of new equipment and electronic data

processing. Improved techniques were also developed for the handling and

presentation of data and results in the calibration of proving rings, elastic devices used as standards of force. A digital computer now performs the

tasks of accurately fitting the data to an equation, statistically analyzing

the fit, and printing out tables of load versus ring deflection. The automation of precise heat measurements was advanced by the completion of an automatic resistance bridge. For automatic determinations of temperature with a platinum resistance thermometer, the bridge has an

equivalent temperature precision within 0.0001 °C. Not only does the bridge release a scientist from routine measurements, but its operation is usually more accurate and faster than conventional manual operation, making

possible experiments that otherwise would be too difficult to perform.

An important advance in length measurement was the development of a

line standard interferometer which uses automatic fringe-counting tech- niques. This instrument was devised for calibrating graduated length scales such as are used on many types of precision machinery. For such measurements, it makes possible a precision within a millionth of an inch, performing in 15 minutes a calibration procedure that previously would have re- quired as long as 15 hours. Other research in length measurement was directed toward the development of more accurate methods of measuring long distances, as in the cal- ibration of tapes for surveying missile-tracking sites. In this project the Bureau has been investigating the use of a helium-neon laser as a light source

for interferometric measurements of length. In the course of the work, a

versatile, convenient-to-use spectrometer was constructed to study laser fre- quencies. The instrument automatically varies the separation between two

interferometer mirrors to scan the spectrum of a light source. The Bureau continued its program of research to develop procedures for

calibrating master gage blocks on a regular basis to 1 part in 10 million.

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This work was begun several years ago at the request of machine tool manufacturers, in order to meet the increasingly severe calibration requirements

of industry, particularly in the aerospace field. Both highly stable gage

blocks and ultraprecise measuring techniques are required. In 1964 the program included ( 1 ) a study of the use of polarized light to determine contact error in end standard gaging, and (2) the monitoring of stability

samples of steel to determine length changes with aging. Several combinations of materials and treatments have now yielded a dimensional stability better than 0.2 X 10~6 in. per in. over a period of a year, and a few samples

have had a stability better than 0.1 X 10~6 in. per in. per year. Large weights find wide application in the calibration of devices used to measure the thrust of missile and rocket engines. Periodically the weights

must be calibrated, so that the equipment is out of service while the weights

are shipped to NBS and back. During the year, the Bureau developed a comparative measuring technique which should permit any laboratory to use

readily available equipment in the calibration of its own large weights. With

a load cell used as a comparator in a double-substitution weighing scheme,

precisions of 5 parts per million have been achieved at 10,000 pounds. Over

the next few years this technique should save millions of dollars for Government and industry.

A program extending over many years culminated in the development of a

precision mercury manometer of extremely high accuracy for measuring

pressure in connection with the thermometery standards program. At a pressure of one atmosphere, the manometer provides a precision within 1 part per million and an accuracy within 3 parts per million. For a number of years the Bureau has performed spectral radiance calibra- tions in the wavelength region from 250 to 2,600 nanometers (nm) (2,500 to 26,000 A) with estimated uncertainties of about 8 percent at the shorter wavelengths and 3 percent at the longer wavelengths. Lack of calibrations having smaller uncertainties and extending below 250 nm has been a major

limitation to experimental work in plasma and space physics. During 1964

a concentrated effort to improve measurement capability in this area resulted

in the development of a spectroradiometer which reduces uncertainties of spectral radiance calibrations by a factor of 5 and extends the range of wavelengths covered down to 200 nm.

Advances in the precise measurement of x-ray wavelengths and the lattice parameters of crystals were made possible by the production of highly perfect crystals of ammonium dihydrogen phosphate in the laboratory. Be- cause of the extremely regular arrangement of their atoms, these crystals,

when used as diffraction gratings, have extended the high resolution of meas- urements in the ordinary x-ray range up to wavelengths of 1 nanometer. At the usual x-ray wavelengths the crystals offer what appears to be the highest resolving power yet reported for any crystals. This improved re- solving power will be of great utility as work is pressed toward gamma-ray

energies.

756-224 0—65 2 7
Many of the properties of polymeric systems depend on the distribution of molecular weights of macromolecules in the system, particularly on the extremely low and extremely high parts of the molecular weight distribution. The ultracentrifuge has been a valuable means for determining these molecular weights and their distributions. In 1964 an improved optical sys- tem was developed which increased the optical resolution of the ultracentri- fuge by a factor of 5 over that of present-day commercial equipment. Also,

the accuracy of molecular weight determinations by absorption measurements

in the ultracentrifuge was increased by a comprehensive study of the dependence of specific polymeric absorption on concentration.

One of the prime causes of deterioration of polymeric materials is at- mospheric oxidation. In a study of oxidation processes, several new tech- niques, involving gas chromatography and polarography, were developed

for measurement of the oxygen consumption of polymers as a function of temperature.

As part of the measurement program, a number of advances were made

in methods of precision chemical analysis. For example, the Bureau de- veloped an analytical method, called double radioisotopic dilution, which uses radioisotopic tracers for the analysis of small quantities of the elements.

Suitable for use in any standard industrial laboratory, the technique gives

sensitivities in the range of 0.1 microgram per gram of sample for the analysis

of such elements as silver, cobalt, and iron. Also, through use of coincidence

counting techniques, the sensitivity of the analytical method known as activ- ation analysis was increased by a factor of 1,000 for as many as 20 elements. An accurate coulometric method was developed for the determination of potassium dichromate, an important chemical oxidizing agent. By this pro- cedure, one-half-gram samples may be analyzed with a precision of a few

thousandths of a percent. A new method of low-level radioisotope dilution analysis was developed and applied to cerium 144. Other methods of analysis completed during the year included a new procedure for the determination of rhodium in uranium alloys, and a method for the analysis of zir- conia-yttria refractory materials. The Bureau continued to cooperate closely with the National Conference of Standards Laboratories, for which it serves as a sponsor. This Conference

and its continuing committees bring together representatives from military,

industrial, and university standards laboratories, to promote cooperative ac- tion on common problems of the management and operation of measurement

standards and calibration laboratories. During 1964 the Bureau played an

active part in a series of interlaboratory round-robin tests which NCSL

has initiated to encourage the development of methods for maintaining a high standard of quality in the services of its member laboratories. Plans were made for a 1964 Standards Laboratory Conference to be held in New

York City in October 1964 under the joint auspices of the NCSL, the Instru- ment Society of America, and the Precision Measurements Association.

To assist supervisors of standards laboratories and others concerned with

meaurements at radio frequencies, an intensive, three-week graduate-level 8
course in electromagnetic measurements and standards was offered in the sum- mer of 1963 by the NBS Graduate School in association with the University

of Colorado.

An important medium for the exchange of information on electronic measurements was the Conference on Precision Electromagnetic Measurements, held in June 1964 at the NBS Boulder Laboratories. The Conference was sponsored by the Institute of Electrical and Electronics Engineers, the International Scientific Radio Union, and the NBS Institute for Basic Standards; it was also supported in part by the National Science Foundation.

Forty-seven papers were presented during the four-day meeting, which was at- tended by more than 600 scientists and engineers from industry, universities,

and government.

In conformance with a policy adopted in fiscal 1963, all results of NBS

calibrations and tests were issued in report form, supplemented by a letter of formal certification when required by law or special conditions. The new

reporting policy was well received, and it is believed that it has been helpful

to industry in clarifying the respective responsibilities of manufacturer and

user in maintaining instrument accuracy as based on NBS calibration of a master standard. The preparation of charts showing NBS measurement capabilities for vari- ous physical quantities was continued as an aid to the planning of NBS

measurement services. Several of these charts are reproduced on page 3. STANDARD REFERENCE DATA

"Standard reference data" is defined as critically evaluated data on the physical and chemical properties of materials, authoritatively documented as

to reliability, accuracy, and source. The evaluating process includes the

definition of "best" values for selected properties and establishment of confidence limits for these values. At the close of fiscal 1963, NBS was given responsibility for administering

and coordinating the National Standard Reference Data System (NSRDS),

established at that time by the Office of Science and Technology. The aim of

the System is to develop a storehouse of standard reference data to assist in the advancement of science, technology, and the economy. It will provide

critically evaluated data in the physical sciences on a national basis. According to present plans, the data input to the NSRDS will come from

scientists in many different locations who will comprehensively review the

literature in their fields of specialization and critically evaluate the data it contains. Evaluated data, classified and stored at NBS, will be disseminated

through a series of services tailored to user needs in science and industry.

The first year of the NSRDS was mainly devoted to planning the data- compilation program. The field of physical science was tentatively divided

into a number of categories, each covering an area broad enough to include

a large number of standard reference data-compilation activities. Programs

were initiated in the following seven of these technical categories: Nuclear

9
data, atomic and molecular data, solid state data, thermodynamic and trans- port data, chemical kinetics, colloid and surface properties, and mechanical

properties of materials. Other programs are to be added as available re- sources permit. In each of the seven areas a survey of existing data-compilation activities has been made and is being followed by a detailed appraisal of needs and priorities for new or expanded programs. Competent groups are being sought to undertake the high-priority activities. In some cases these groups are within NBS ; in other cases they are in industrial, university, or

other Government laboratories. The Bureau continued to be active in research to develop standard reference

data, a field in which it has made numerous contributions over the years. In

the course of this work, two new research techniques were devised that pro- vide a powerful double-edged tool for exploring atomic structure. Through

application of these techniques, physicists were for the first time able to study

effectively the excitation of atoms and molecules in the intermediate energy range—from energies of about 10 to 1,000 electron volts. This type of ex- citation is normal in the high-temperature plasmas that occur in thermonuclear devices and stellar atmospheres.

The two new techniques utilize previously unavailable sources of photons

and electrons in the intermediate energy range. In the first case, the Bureau's

180-million electron-volt synchrotron has been modified to make it possible

to extract the very-short-wavelength ultraviolet light generated by the machine, with photons in the intermediate range, and to study the absorption of

The NBS high resolution electron spectrometer was displayed at the Annual

Meeting of the National Academy of Sciences. This new analytical tool has provided a breakthrough in detecting and measuring atomic properties.

(See page 10)

10
this light by various materials. The second technique uses a new ultra-highresolution electron spectrometer as a means of accelerating and controlling

electrons so that they travel at nearly identical speeds. With these techniques

Bureau scientists have observed hundreds of new atomic energy levels which

exhibit properties that are absent or not relevant in other energy ranges. Many of these levels belong to previously unknown negative ions. Other

atomic data can now be obtained which are of great importance to space and

chemistry research, thermonuclear control, and studies of the earth's upper

atmosphere.

A technique was also developed for accurately measuring binary gaseous

diffusion coefficients over a wide temperature range. With this technique it is possible to make measurements to a precision of 0.5 percent over a temperature range of 77 to 373 °K. To date, measurements have been completed on oxygen, nitrogen, argon, neon, and krypton diffusing in helium.

An ellipsometric technique was used to determine the optical constants

of iron single-crystal surfaces in ultra-high vacuum as a function of wavelength in the region of 360 to 700 namometers. Because of the extremely

clean crystals used, these data are thought to be the best optical-constant values ever obtained for iron in this spectral range. The new data will be

of definite value to theorists who are seeking additional knowledge about

transitions between energy levels in metals. As in previous years, the Bureau conducted a number of data centers for compilation and storage of critically evaluated data in such areas as chemical

thermodynamics, atomic transition probabilities, atomic cross sections, and

cryogenics.

The Cryogenic Data Center distributed an estimated 18,000 items of NBS

literature in response to some 1,900 requests, and over 6,000 new references were coded and entered into the Center's storage and retrieval system. Data

from the scientific literature on the thermophysical properties of materials were critically evaluated and compiled at the Center with support from the National Aeronautics and Space Administration and the NSRDS. Also completed during the year were extensive tables of thermodynamic data for car- bon monoxide, a bibliography on the thermophysical properties of argon, and a compilation of the dielectric constants of cryogenic fluids. ENGINEERING MEASUREMENTS AND STANDARDS

As part of its increased emphasis on engineering standards the Bureau is seeking to extend its cooperation with recognized standardizing bodies in the development of codes, specifications, standards of practice, and methods

of test for technological devices, products, and services. The Bureau is in a position to make significant contributions to such engineering standards

because of the active participation of its staff members in the work of numerous technical societies and standardization groups such as the American Standards Association, the American Society for Testing and Materials, the Optical Society of America, the Society of the Plastics Industry, and the

11
Electrochemical Society. In this cooperative activity, the Bureau assists by

conducting research to provide test methods, data on materials, and measure- ment standards; the sponsoring organization supplies other technical data and promulgates the finished documents in the form of codes, specifications, or engineering standards. Only a few standards of this kind, mostly con- cerned with safety and assigned by law to the Department of Commerce, are

set or promulgated by the Bureau. An example is the recent assignment to NBS of the responsibility for developing specifications for Seat Belts for Use

in Motor Vehicles. These specifications are to be promulgated by the Secre- tary of Commerce in accordance with the requirement of Public Law 88-201.

In a somewhat different category are the Commodity Standards which

are published by the Bureau. These are voluntary trade standards that define quality levels for products and aid in holding variety to a minimum.

When an industry group decides to initiate a Commodity Standard, it sub- mits a tentative draft to NBS and requests assistance in its development and

issuance. The Bureau acts as a secretariat in the further development of the standard, determining its feasibility and securing general acceptance of

its provisions by the industry. The standard is then published by NBS

either as a Commercial Standard (a quality-level standard) or as a Simplified

Practice Recommendation. During fiscal 1964. nine Commercial Standards

and five Simplified Practice Recommendations were issued. The Bureau also plays an active role in the development of Government

purchase specifications. During fiscal 1964, at the request of the General

Services Administration, the Bureau accepted responsibility for preparing

and maintaining one additional Federal Specification, making a total of 153

for which it now has this responsibility. The Bureau also reviewed approximately 550 proposed specifications both for GSA and for other agencies to determine their suitability for use by the Federal Government.

In the last year, the Bureau conducted a number of studies to develop per- formance criteria. For example, a method for measuring the tensile strength

of dental amalgam was developed in which specimens are stressed by high

rotational speeds. The method is especially well suited for observing the strength of small specimens of the material during hardening or setting.

Studies of rental car and truck odometer accuracy continued. In cooperation with representatives of the automotive industry, detailed test procedures were developed for vehicle odometers. These procedures have now been in- corporated in State weights and measures requirements for rental cars. As

a result, odometers on all cars furnished to rental fleets will comply with

tolerances by the end of 1964, and eventually all automobiles manufactured

in the Lnited States will more accurately register distance traveled. Accumulations of ice or moisture within the walls of refrigerated struc- tures seriously reduce the insulating value of the walls and often lead to physical injury to the structure. During the year the Bureau developed

criteria which establish minimum properties of the vapor barrier, the insulation, and the interior finish required to avoid moisture condensation. With

12
these criteria as a guide, designers of cold-storage facilities can avoid con- densation difficulties in the future. Asphaltic roofing materials are usually so opaque that it is difficult to evaluate them by conventional optical methods. However, when x rays were

used to produce images of the microstructure of asphalt-containing speci- mens, Bureau scientists were able to determine the distribution of reinforcing

materials in asphalt films and mats, as well as the origin and development of

failures in shingles and other structures. This technique not only reveals many details of the mechanism of deterioration, but is often able to demonstrate intrinsic weaknesses in design or formulation before they become ap- parent by other methods of analysis.

The U.S. Standard for the Colors of Signal Lights was published in 1964

as an NBS Handbook. This recommended standard was prepared to help

bring specifications used in this country for signal light colors into agree- ment with international usage as embodied in the recommendations of the International Commission on Illumination (CIE). With the growth of in- ternational travel, the signal lights of each country are coming to be used more and more by the citizens of other countries, and a need for international

standardization has become apparent. The standard was developed by the U.S. National Committee on the Colors of Signal Lights under the sponsorship of the U.S. National Committee of the CIE. NBS cooperated in this effort by providing the technical data upon which the Standard is based. During fiscal year 1964, the Bureau tested 51,784 items ranging from light

bulbs to concreting materials (table 2) . Most of the tests were on items pur- chased by other Federal agencies that lacked the facilities to make the tests themselves. STANDARD REFERENCE MATERIALS

During fiscal year 1964 the Bureau distributed to other laboratories 78,479

samples of standard reference materials having a value of $573,608 (table 3 ) . These standard materials are certified either for chemical composition

or for a particular physical or chemical property, such as radioactivity,

viscosity, or melting point. They thus provide a basis for making uniform

measurements of heat and temperature, for calibrating instruments that control the composition of metals used in rockets and jet engines, for calibrating

radioactive nuclides, and for controlling the composition of motor fuels. More than 600 different standard materials currently are available

principally chemicals, ceramics, metals, and radioactive nuclides. New

standard materials added during the year included a highly purified uranium

oxide, a variety of copper-base and steel standards for spectrochemical

analysis, a cesium-barium 137 point source, and a titanium-base alloy.

During the last year, the Bureau's standard reference materials program

was critically evaluated to assure that the program will provide maximum

assistance to the Nation's advancing science and technology. A result of this survey was the establishment of an Office of Standard Reference Materials

within the Institute for Materials Research. This new Office will provide a13
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15
national focal point for a wide spectrum of reference materials activities. Present-day measurement systems, which often are more sophisticated than

those of a decade ago, require increasingly more complex and more highly

characterized materials for their calibrations. The Office of Standard Refer- ence Materials will serve as a clearinghouse for such requirements throughout

the country and, particularly in the field of materials science, will provide

leadership to make measurements meaningful. To closely link the standard

reference materials program with research efforts in other laboratories, NBS

Miscellaneous Publication 260 (published in successive sections) was initiated as a medium for broad and rapid dissemination of the results of standard

materials investigations at the Bureau. Development of new and improved analytical techniques is an important

part of the standard materials program. During the year, an x-ray fluores- cence spectrographic method of analysis, giving highly accurate results, was

developed and applied to the analysis of brass standard reference materials in solution form. The data obtained by this method compare well with the

results of chemical analysis of the same samples, although the x-ray method

is considerably faster. Another advance in spectrographic analysis was the development of a device

for the spark excitation of atomic emission spectra in atmospheres other than

air. With this device, analyses can be performed in a controlled argon at- mosphere as rapidly as in air. The result is to reduce the number of standard

materials required to calibrate analytical equipment inasmuch as a single set of calibration curves obtained by spark excitation in argon can be applied to the analysis of several related alloys.

RADIO PROPAGATION

The Central Radio Propagation Laboratory continued to conduct a broad

range of studies directed toward the efficient use and conservation of the radio spectrum. One of the main areas of CRPL research concerned the ionosphere, the ionized region of the upper atmosphere covering the height range from roughly 50 to 1000 kilometers above the earth's surface. The

constant changes that occur in the heights of these layers have important

effects on radio wave propagation.

The total eclipse of the sun on July 20, 1963, which was visible over much

of northern North America, provided an excellent opportunity for observation of the effects of the eclipse on the ionosphere. Vertical soundings of the ionosphere were made by several laboratories, from a total of 22 loca- tions across the continent, providing the most extensive set of ionospheric

observations ever made for a solar eclipse. CRPL's analysis of the data

showed a well-marked geographical pattern of variation in the F region of the ionosphere with eclipse time, and maps of this variation are being pre- pared for use in testing theories of the physica lprocesses of the ionosphere.

CRPL played an important part in the planning, coordination, and execution of programs for the International Years of the Quiet Sun (IQSY) . This

16
international scientific effort will continue through 1964 and 1965, a period

chosen because it is at the minimum of the sunspot cycle, when solar dis- turbances are likely to have the least effect on the ionosphere and thus to cause the least interference to radio propagation. The IQSY program is co- ordinated domestically by the National Academy of Sciences and internationally by committees of the International Council of Scientific Unions. Current CRPL contributions include coordination and direction of ionosphere and

airglow projects, operation of the World Warning Agency which makes final selection of worldwide geophysical alerts, operation of the Western Hemisphere Radio Warning Service, and operation of the World Data Center-A

for Airglow and Ionosphere.

In October 1963 a program of high-altitude nuclear detection studies was

begun at CRPL under the sponsorship of the Advanced Research Projects

Agency. This program will be concerned with the development and evaluation of ground-based detection techniques for the planning of systems for use in connection with the Limited Test Ban Treaty.

DATA-PROCESSING SYSTEMS

Automatic systems for the processing and storage of information are playing an increasingly important role both in industry and in the operations of the Federal Government. In this rapidly advancing field, the information

technology laboratory of the Institute for Applied Technology serves as a

center within the Government for research, development, and provision of

technical services. It conducts investigations leading to the development of new and better tools for information processing, and it assists other agencies

in devising information-processing systems that will more effectively meet

their needs. It also operates a Research Information Center and Advisory

Service on Information Processing under the joint sponsorship of NBS and

the National Science Foundation, providing information on current research

and development in the field of Government and industry. In 1964, assistance to other Government agencies in problems of information processing covered a wide range of activities. Representative projects

included assistance to the Defense Communication Agency in devis- ing and using a computer program to simulate the Defense Communication

System; development of a data-processing system for use by CRPL on the Advanced Research Projects Agency project on the detection of nuclear

events in space; development of a high-capacity multipurpose data conversion

and editing system for the Office of Emergency Planning; development of plans for a global range information processing and control system in support

of future orbital and space programs of the Air Force; continued assistance

to the Navy Bureau of Supplies and Accounts on problems of procurement;

technical assistance to the Weather Bureau on the processing of data from

the NIMBUS satellite series; research for the Naval Training Device Center on techniques for automatically producing three-dimensional terrain information from stereophotographic information; advisory service to the Internal 17
Revenue Service in a study of the efficiency of methods of processing tax return information; a study conducted for the Department of the Interior on

the feasibility of applying automatic data-processing techniques to the devel- opment and management of a nationwide plan for outdoor recreation facili- ties; and technical assistance to the Public Housing Administration in the processing of reports relating to low-rent housing applications.

Work sponsored by the U.S. Army Personnel Office resulted in the devel- opment of the Vigilometer, a computer-type research apparatus for testing

and recording the alertness of human subjects. The machine was designed

to determine how the instrument-monitoring performance of Army personnel is affected by such factors as time on duty, distractions, and characteristics of displays to be monitored. The Vigilometer should also be useful to industry in developing information on optimum work methods and conditions. CLEARINGHOUSE FOR FEDERAL SCIENTIFIC AND

TECHNICAL INFORMATION

As the result of action by the Federal Council for Science and Technology,

a Clearinghouse for Federal Scientific and Technical Information was estab- lished within the Institute for Applied Technology in February 1964. The

Clearinghouse provides a central point of contact from which industry and

the technical community may obtain information on Government activities in the physical and engineering sciences. Such a facility should be of major

importance in assisting American industry to benefit from defense and space

research. In effect, the new activity is an extension of the information dissemination

program of the Institute's Office of Technical Services, which now operates

the Clearinghouse. Specific functions of the Clearinghouse are as follows:

(1) To make available all unclassified and unlimited Government technical reports to industry and the technical community; (2) to develop a unified Government-wide index to unclassified scientific and technical literature and

to provide prompt reference service; (3) to provide referral service to sources

of technical expertise in the Government technical community; and (4) to provide information concerning Government-sponsored research and development currently under way.

ADVISORY SERVICES

The advisory services performed by the Bureau are a natural result of the broad scope of its program and the special competence of many of its staff in the physical and engineering sciences. Numerous and diverse services of this kind are rendered to other Federal agencies, to State and municipal

governments, and to various industrial organizations. For example, during

the last year, a survey of the lightning protection problems associated with

the new Rayburn House Office Building was made for the Architect of the

Capitol, and technical assistance was given the Army in the selection of material for the Saturn rocket installation at Cape Kennedy, Fla. 18
A forward step in intra-Government cooperation was the establishment

of a Computer Sharing Exchange and a Computer Service Center at the Bureau on an experimental basis. The new facilities were created at the request of the Bureau of the Budget, which has found that great savings

in both time and money can be realized through computer sharing. The

Sharing Exchange will coordinate requests of Federal Government agencies

in the Washington, D.C., metropolitan area for help in locating appropriate

computer time and services for their essential work. The Center will provide electronic equipment and personal services at cost to participating

agencies.

Weights and measures continued to be an important area of assistance

to State and municipal governments. Although the Bureau does not have

regulatory powers, it offers technical advice and consultation to local regulatory bodies, and its calibrates and adjusts State standards of weights

and measures. A major medium of cooperation is the National Conference on Weights and Measures. Over 600 delegates from 41 States, Puerto Rico,

Canada, and the United Kingdom attended the 49th annual meeting of this Conference, held in Washington, D.C., in June 1964, under NBS sponsorship.

At the request of the legislature of Mississippi, the only State that still had no comprehensive weights and measures law, the Bureau conducted an intensive survey of weights and measures conditions in that State. The

conditions revealed by the survey led directly to the enactment, by Mississippi

in March 1964, of the National Conference on Weights and Measures Model

State Weights and Measures Law.

Within the Institute for Applied Technology, two important avenues of Bureau-industry cooperation were the Textile and Apparel Technology

Center and the Office of Invention and Innovation. The Center's program

is an attempt to catalyze and expand the textile and apparel industry's own

efforts to create and develop the technical institutions it needs for economic

development. The Center cooperates with trade associations, universities,

and other organizations to identify obstacles to technical innovation in the

textile industry and to formulate programs to overcome these. It also

collects and disseminates technical information of importance to the industry, and it supports studies of the relationship of technology to the economics

of the textile and apparel industry.

The Office of Invention and Innovation encourages inventors' programs

as a means of stimulating regional industrial activity based on new tech- nology. Pilot programs are now under way in Arkansas, Illinois, Missouri,

and Nebraska, with others scheduled for the midwestern area. Other valuable means of Bureau-industry cooperation were the Research

Associate Plan and the donor program. Under the Research Associate

Plan, technical, industrial, and commercial organizations can support work

at the Bureau that is of special interest to them, yet of sufficient general

interest to justify use of Government facilities. The work is done by re- 19
search associates who are paid by the sponsor but otherwise function as members of the Bureau staff. At the present time the following groups are supporting research associates at the Bureau

Sponsor

American Dental Association American Electroplaters' Society

American Society for Testing and

Materials American Standards Association Asphalt Roofing Industry Bureau Bone Char Research Project, Inc. Calcium Chloride Institute NBS—Joint Committee on Chemical Analysis by Powder Diffraction Methods:

Field of Activity Dental research Galvanic effects associated with coating

failure Properties of electrodeposited copper Cement and concrete reference laboratory

Codes, specifications, and standards Asphalt roofing research

Studies of adsorption and adsorbents Hydration of portland cement

Standard x-ray diffraction powder patterns

ASTM, American Crystallographic

Assoc., Institute of Physics (British), National Assoc. of Corrosion Engineers

National Academy of Sciences-National Research Council

Porcelain Enamel Institute

Atomic physics

Porcelain enameled metals The donor program was authorized in 1950 by Public Law 619 under

which the Bureau may accept funds for the purpose of furthering its work.

This arrangement permits individuals as well as technical, industrial, and

commercial organizations to support work at the Bureau when the results are expected to be of value to the general public. During the past year, the following projects were supported by gifts

Donor

American Iron and Steel Institute International Astronomical Union

International Commission on Radiological Units

National Association of Home Builders The Expanded Shale, Clay, and Slate

Institute

Field of Activity

Durability of steel pilings Publication costs of "The Solar Spectrum"

Support of ICRU Secretariat

Building materials research Creep and shrinkage of concrete contain- ing expanded shale aggregate GENERAL RESEARCH

In addition to those research activities that are directly related to the missions of the four institutes, the Bureau conducts a broad program of ex- ploratory or background research in the physical sciences. The primary

purpose of this work is to maintain and strengthen the general scientific competence of the staff so that the Bureau can keep abreast of new developments

in many fields, select the most effective techniques for solving problems, and

utilize quickly the results of scientific work elsewhere. The following para- graphs illustrate the diversity of the background research program during

the year. 20
In work sponsored by the Advanced Research Projects Agency, NBS scientists found that at very low temperatures the semiconductor strontium titanate becomes superconducting—that is, it completely loses its electrical resistance. Although superconductivity has been observed in at least one other semiconductor (germanium telluride), it is believed that this was the first observation

of superconductivity in an oxide-type semiconductor. Because the supercon- ducting properties of the material can be varied with treatment, further study

of this and related materials should lead to a more complete understanding of the nature of superconductivity. Such knowledge could be of immediate value

in the development of extremely high-field industrial magnets, highly compact

superspeed computers, and possibly other applications.

Until recently metals and alloys were the only substances known to be

superconducting. Unfortunately these materials have a complex structure

that is not completely understood by theorists. Semiconductors, on the other hand, are relatively simple materials which can be more easily treated

theoretically. Moreover, the composition of semiconductors can be precisely

controlled. Thus, using semiconducting materials, scientists can now study

the effect of both composition and treatment on superconductivity, and they can begin to predict what semiconducting materials will be superconductive.

Studies of this kind should round out present knowledge of superconductivity

and eventually lead to the development of more useful superconducting materials with controlled properties. Because of the enormous complexity of most plasmas, there has been a lack of accurate, convenient diagnostic techniques that might provide a better understanding of plasma characteristics. Recently the Bureau developed a new form of plasma—the brush-cathode plasma—which is both stable and

uniform and which thus lends itself to precision measurement of its characteristics. Extensive studies of this plasma were under way.

Research in culvert hydraulics, sponsored by the Bureau of Public Roads,

produced designs for culvert inlets which substantially improve the water- carrying capacity of highway culverts. Inlet designs developed in the study

will enable engineers to use culverts of smaller size and cost for any desired

capacity. As Federal and State costs for construction of culverts and similar drainage structures for highways are approximately $400,000,000 a year, this work promises to yield important savings.

For a number of years the Bureau has been conducting an extensive pro- gram of experimental and theoretical studies in polymer crystal physics.

The overall objective of this work is to gain an understanding, in terms of physical concepts, of the behavior and performance characteristics of semicrystalline polymers in bulk. Many polymers crystallize in the form of lamellar crystals many microns

in length and width, but only 10 to 30 nanometers thick. As the axes of the polymer molecules are largely perpendicular to the large flat faces of the

crystal, it appears that the polymer chains must be folded to form the crystal.

During 1964 two significant advances were made in the theory of these chain21
folded polymer crystals. First, a theory of the rate of thickening of chain- folded lamellae on isothermal storage was refined and tested experimentally

in low-angle x-ray diffraction measurements on polyethylene at the crystal- lization temperature. Secondly, the theory of the rate of formation of chain- folded lamellae was refined to include estimates of surface roughness.

Polymer adsorption is an important factor in the fabrication of numerous

composites such as glass fiber-reinforced plastics, tires, most adhesive joints,

and many protective coatings. Only a few segments of the polymer molecule

may actually be adsorbed on a surface; these segments then act as anchors

for the rest of the molecule, which takes the form of loops dangling in the

solution. Recent NBS work has shed new light on the mechanism of this adsorption process. Measurements were made of the extension of a polymer

molecule away from the adsorbing surface, and a new theory was worked

out for low-surface-coverage adsorption. The resulting information should

be useful in the development of improved composites using plastic materials. With the partial support of the Advanced Research Projects Agency, the

Institute for Materials Research has been conducting an accelerated program

of research on crystal growth and characterization. This program is de- signed to provide basic information on the nature of matter as well as in- formation of more immediate utility in military and space applications.

During the year, significant advances were made in the growth of pure

crystals from solution. Ammonium dihydrogen phosphate crystals of ex- tremely high physical perfection were grown and the perfection of their structure demonstrated by x-ray diffraction and etch-pit techniques. The

growth of these crystals was observed visually and found to involve the move- ment of spiral steps, elliptical in shape and emanating from screw disloca- tion centers on the prism faces; on the pyramid faces of the crystal no dis- location centers were observed and growth proceeded by the movement of

essentially straight steps from the edges of the face toward the center. This

program also resulted in the production of sizable single crystals of sparingly

soluble salts by interdiffusion of the component ions or oxidation-reduction

reactants in silica gel media.

Interest in the chemistry of boron hydrides has been widespread in recent years because of their value as reducing agents in chemistry and their potential utility as chemical fuels and fuel additives. In 1964 difluoroborane

(HBF2 ), the first example of a partially fluorinated boron hydride, was

synthesized at NBS. Although a few boron hydrides are known in which

one or more hydrogen atoms have been replaced by halogens, no fluorine derivatives of this type had been prepared before. Difluoroborane and com- pounds related to it are now being investigated intensively from a number

of points of view, including those of descriptive chemistry and reaction

mechanisms. This group of compounds provides a model system useful in studying the effect of substitution on the structure and reactivity of boron

hydrides. Moreover, availability of boron hydride in quantity will permit

detailed investigations of complex reactions believed to involve fluorinated hydrides as short-lived intermediates.

22
Today most of the buildings in the United States use asphalt roofing. For

this purpose, asphalts are hardened by blowing with air at high temperatures

(300 °C) and at high flow rates. Research showed that by replacing air with more reactive oxidants such as oxygen and nitrogen dioxide, asphalts can be hardened at a much faster rate using temperatures 150 °C below those employed commercially, reduced gas flow rates, and simple experimental

apparatus. The roofing-grade asphalts produced with these oxidants were more stable to photochemical oxidation than were commercial asphalts

from the same asphalt flux. The best least-squares method for estimating the slope of a straight line through the origin is well known and is readily applied when the correct weights of the plotted data are known. In practice, however, the weights

are usually known only approximately. The Bureau has recently completed

a study of the relative advantages and disadvantages of the most important

weighted estimates of straight-line slope when they are used without the correct weights being known. The results of this study will guide data analysts

in choosing the best method of estimating the slope in a particular situation. INTERNAL TECHNICAL SERVICES

Construction of a high-flux reactor facility and associated laboratories was

begun at the Bureau's new site at Gaithersburg, Md. The new research

reactor, to be known as the NBSR, will be used to advance the measurement, analysis, and understanding of radiation effects on substances of all kinds. It will be operated by the Institute for Materials Research and will be shared with other Government agencies in the Washington area having

the same general requirements as the Bureau.

Installation of the NBS linear accelerator, Linac, began at Gaithersburg

in the spring of 1964. This accelerator will produce one of the world's most

intense electron beams with energies up to 100 million electron volts, making it possible for the Institute for Basic Standards to enter new areas

of nuclear and atomic physics. At the close of the fiscal year almost all major components of the accelerator were in place, and various subsystems were being installed. Among these was a data-handling system that pro- vides concurrent on-line processing of data from several independent ex- periments. This versatile system will eliminate the need for costly specialpurpose analyzers which are subject to rapid obsolescence. INTERNATIONAL ACTIVITIES

On an international basis, the Bureau represents the interests of the Government and American science in matters dealing with the establishment

and maintenance of standards and the establishment of values for scientific constants. Most of this work is done through participation in a large number of international groups such as the General Conference on Weights and

Measures, International Union of Pure and Applied Physics, International

756-224 O—65 3 23
Union of Pure and Applied Chemistry, International Scientific Radio Union,

International Commission on Illumination, and International Organization

for Standardization.

The Bureau has been actively participating, through the American

Standards Association, in the development of pan-American standards for various commodities such as textiles; iron and steel; cement and concrete;

hides, leather, and tanning materials; and electrical equipment. This

program is basic to the economic development of the Latin American countries and to the expansion of trade among these countries and between them

and the United States. Several of the Latin American countries have re- quested and received assistance in the field of weights and measures. During 1964 translations of NBS weights and measures publications into Spanish and Portuguese were completed. New metric prototype standards, suit- able for use as the national standards of developing countries, were pro- cured for demonstration and training purposes. Another form of international cooperation is the reception of foreign

scientists as guest workers or visitors, and the training of foreign specialists

in the Bureau's laboratories. During the last year, 464 scientists from 54

countries came to the Bureau as visitors. In addition, 36 trainees and 30

guest workers were received from abroad.

The Bureau was host to a team of five Soviet metrologists during their month-long (January 8-February 2, 1964) visit to this country. The Soviet

visit was in exchange for the visit of a U.S. metrology delegation, composed

largely of NBS scientists, in June 1963. These visits were conducted under

the terms of a United States-U.S.S.R. agreement for the interchange of in- formation and exchange of visits by teams in 13 fields of technology. The

U.S. State Department, under whose general control the exchange program

is conducted in this country, requested that the Bureau arrange for the exchange of persons from the area of high-precision measurement standards. Before leaving this country, the Soviet delegation agreed in principle with

NBS on the desirability of cooperation in (1) exchange of data on observations of standard time and frequency signals from various radio stations,

(2) exchange of calibration information to compare various electrical and

electronic quantities, and (3) exchange of NBS publications with those of the U.S.S.R. Committee on Standards, Measures, and Measuring Instru- ments. It was recommended that the measurement exchanges be coordi- nated through the International Bureau of Weights and Measures.

In 1964 a total of $728,000 was granted to scientific laboratories in India,

Israel, and Pakistan for the support of work directly related to the Bureau's

mission. These grants are financed from excess balances of local-currency

funds accruing to the United States from the sale of surplus farm products

in past years; thus they create no drain on the cash budget of the United

States. In addition to the scientific findings that have resulted from the

grants, the program has been of notable value in stimulating communication between American scientists and those of the countries involved. 24
ADMINISTRATIVE ACTIVITIES

As previously indicated, a major reorganization of the scientific activities of the Department of Commerce occurred in January 1964 involving NBS,

the Office of Technical Services, and the textile technology program associated

with the Office of the Assistant Secretary for Science and Technology. All of these activities were combined at that time in a substantially reorganized

National Bureau of Standards with broadened responsibilities for assuring

maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. To facilitate coordination and management of the enlarged NBS program,

the four institutes were established, each having its own Institute Director.

The first two institutes—Institute for Basic Standards and Institute for Materials Research—were formed by regrouping existing NBS divisions which have programs involving similar technical objectives, staff, and facilities. The third institute, Institute for Applied Technology, brought together

previously scattered activities related to stimulation of technological progress

in industry. These included the extensive technical information services of the Office of Technical Services and the textile technology program, as well as

certain industry-oriented NBS programs. The Central Radio Propagation

Laboratory, the fourth institute, represented a continuation of a separate

program that had been under way for many years. The functions and activities of the four institutes are discussed on pages

31, 123, 165, and 197. The new organizational alinement (see p. 26) will enable the Bureau to meet both new and longstanding responsibilities with

improved focus on the special needs of science and industry for NBS services. For a more complete organizational listing see appendix 1. Construction of Phase I of the Bureau's new laboratories near Gaithersburg, Md., was completed during the year. The two buildings involved, the Engineering Mechanics Laboratory Building and the Boiler Plant, were

occupied and placed in operation. However, much work remained to be done

to complete and calibrate the large force-measuring machines that were

being erected in the new mechanics laboratory, and the 12-million-pound

testing machine for use in this building had not yet been delivered. Phase II of the Gaithersburg construction includes four buildings to house the administrative and service activities of the Bureau and the radiation

physics laboratory. These buildings were originally scheduled for occupancy

in the fall of 1964, but it now appears that occupancy will begin in January

1965 and will be completed by April 1965. Construction of a Nuclear Reactor Building should also be completed by June 1965.

On August 21, 1963, a contract was awarded, with a contemplated completion date in November 1965, for the Phase III superstructures for the seven general-purpose laboratory buildings. Work progressed well on these

buildings, and it is expected that they will be under roof and enclosed before

December 1964.

25
NATIONAL BUREAU OF STANDARDS

July I, 1964

DIRECTOR

A. V. As tin DEPUTY DIRECTOR

I. C. Schoonover

ASSOCIATE DIRECTOR FOR RESOURCES PLANNING

S. Si Iverman

« MANAGER

BOULDER LABORATORIES

R. B. Scott

ASSOCIATE DIRECTOR FOR TECHNICAL SUPPORT

L. S. Taylor

ASSOCIATE DIRECTOR FOR ADMINISTRATION

R. S. Wallelgh

INSTITUTE FOR BASIC

STANDARDS

R. D. Huntoon

INSTITUTE FOR

MATERIALS RESEARCH

I. C. Schoonover

(Acting)

•CENTRAL RADIO

PROPAGATION LABORATORY C.Gordon Little

INSTITUTE FOR APPLIED TECHNOLOGY

D. A. Schon

J.P. Eberhard, Deputy

OFFICE OF STANDARD

REFERENCE DATA

E. L. Brady

OFFICE OF STANDARD REFERENCE MATERIALS

W. W. Meinke

OFFICE OF TECHNICAL

SERVICES

D. A. Schon

(Acting)

TECHNICAL DOCUMENTA- TION CENTER B.M.Fry

OFFICE OF INDUSTRIAL

SERVICES

R.L. Stern

OFFICE OF WEIGHTS &

MEASURES

M.W. Jensen

OFFICE OF ENGINEERING

STANDARDS

DIVISIONS:

Elec trlcity—C.H.Page Metrology—A. G.McNlsh

Heat —R. P.Hudaon Radiation Physics —

H.W.Koch Mechanics—B.L. Wilson

Applied Mathematics —

E.W.Cannon

Atomic Physics —K.G. Kessler

Physical Chemistry

M.B.Wallensteln

Laboratory Astrophysics —L. M. Branacomb

Radio Standards Labora- tory—J.M.Richardson

Radio Standards Physics—Y. Beers Radio Standards En- gineering—G. E. Schafer

DIVISIONS: Analytical Chemis- try—W.W.Meinke Polymers—J.D.Hoff- man Metallurgy—L. M. Kushner

Inorganic Materials

H.C.Allen, Jr. Reactor Radiatlons- C.O.Muehlhause

'Cryogenics —B. W. Birmingham

(DIVISIONS: Ionosphere Research

and Propagation

R. W. Knecht Troposphere and Space Telecommunica

tlons —K.A.Norton Radio Systems

R. C. Kirby Upper Atmosphere & Space Physics

E.ICSmlth, Jr.

TEXTILES & APPAREL TECHNOLOGY CENTER

DIVISIONS: Building Research

A.A.Bates

Industrial Equipment TechnologyInformation Technol- ogy—S.N.Alexander

Performance Test De- velopment

Instrumentation—G.F. Montgomery

Transport Systems

S.M. Breunlng

« Located at Boulder, Colorado Planning of Phase IV, the special-purpose laboratory buildings, was well under way and bids were expected to be obtained and a contract placed

for these buildings in the late spring of 1965. Also in the planning stage was a major building to house the expanding

activities of the Radio Standards Laboratory at Boulder, Colo. At the end of the year, the full-time permanent staff of the Bureau totalled 3,905 persons. Of this number 2,675 were employed in the Washington

laboratories, and most of the remainder were attached to the Bureau's laboratories in Boulder, Colo. Additional information concerning the staff can be

found in appendix 3.2 (p. 236)

.

26
Funds obligated by NBS during fiscal year 1964 totalled $99,315,000

which included $43,272,000 for facilities. The total available for operation

of the Bureau's technical programs amounted to $47,893,000, of which

$30,009,000 came from direct appropriations to the Bureau and $17,884,000

from other Government agencies and private sources. In addition, calibrations, testing, information services, and other reimbursable technical services amounted to. $7,341,000. A more complete presentation of financial data can be found in appendix 3.3 (p. 236)

TECHNICAL INFORMATION

To be fully useful to the Nation, the large volume of scientific and

technical information that is continually being developed at NBS must

flow as rapidly as possible into science, industry, and commerce. Several channels were utilized to maintain this flow; they included seven series of nonperiodical publications, papers by NBS scientists in the Bureau's

periodicals as well as in professional journals, participation in exhibits,

and the production and dissemination of motion pictures.

During the year NBS publications totalled 1,112 formally published papers and documents. In addition, some 445 classified and unclassified reports were issued to other Government agencies. A list of publications

for the fiscal year is given in appendix 3.7 (p. 246)

Of the formal publications, 217 appeared in the Journal of Research,

and 685 in the journals of professional and scientific societies. Also, 121

summary articles were presented in the Bureau's monthly Technical News

Bulletin. A third periodical, the monthly Central Radio Propagation Laboratory Ionospheric Predictions, presented radio propagation data needed for determining the best radio frequencies for use in long-range radio communications. In the nonperiodical series, 89 documents were published : 9 in the Monograph series, 9 in the Handbook series, 1 in the Applied Mathematics

series, 10 in the Miscellaneous Publication series, 46 in the Technical Note

series, 9 Commercial Standards, and 5 Simplified Practice Recommendations. The Clearinghouse for Federal Scientific and Technical Information

(p. 167) processed 30,000 titles into its collection of reports, bibliographic

information, and translations. These were made available to the public

and announced in U.S. Government Research Reports and Technical Translations, both published semimonthly.

An outstanding publication of the year was the Handbook of Mathematical Functions—With Formulas, Graphs, and Tables (NBS Applied

Mathematics Series 55). This comprehensive reference work, the product

of seven years' effort, brings together, under one cover for the first time,

text, tables, graphs, and even bihliographies of the more important mathematical functions. It includes all functions normally needed by teachers,

students, mathematicians, engineers, physicists, chemists, biologists, bio- 27
28
chemists, and medical researchers. The Handbook was compiled with fi- nancial support from the National Science Foundation and technical advice

from a committee of the Mathematics Division of the National Research

Council. It has already gone into its second printing, and portions of the book are now being reprinted by private publishers.

Another major publication was Methods for the Dynamic Calibration of Pressure Transducers (NBS Mono. 67). The practicing engineer, faced

with the problem of making dynamic measurements and calculations of

the rapidly changing pressures in missiles and space vehicles, should have

at hand and be familiar with a large quantity of very precise information.

Monograph 67 provides this information, for the first time in a single reference source. Experimental Statistics (NBS Handbook 91), also issued this past year,

is a one-volume collection of statistical procedures useful in the design, de- velopment, and testing of materials; the evaluation of equipment performance; and the conduct and interpretation of scientific experiments. This

Handbook is for the user with an engineering background who occasionally

needs to use statistical techniques, but who does not have the time or inclina- tion to become an expert on statistical theory or methodology. Originally

developed for the Army and issued by that service in a series of pamphlets,

Experimental Statistics has now been made available to other groups con- cerned with research and development.

Among other nonperiodical publications of the year were Compilation of

the Melting Points of the Metal Oxides (NBS Mono. 68) , The NBS Standard

Hygrometer (NBS Mono. 73) , Tabulation of Data on Receiving Tubes (NBS

Handb. 83 )

, Tensile Impact Properties of Selected Materials from 20 to 300

°K. (NBS Mono. 63), Inspection of Processed Photographic Record Films

for Aging Blemishes (NBS Handb. 96) , and Creep and Drying Shrinkage of Lightweight and Normal Weight Concretes (NBS Mono. 74).

During the year, the Bureau participated in 13 exhibits, including those

of the National Academy of Sciences; Standards Engineers Society; Color

Marketing Group; Instrument Society of America; and Howard University

Engineers Day. An interest-arousing new exhibit was an audience-participation model of FIST (/^ault /solation by Semi-Automatic Techniques) (see

p. 192).

NBS films continued to convey Bureau information to an impressive number of people. Prints were loaned for 4,559 showings last year to an esti- mated total of nearly one-half million persons. This figure includes formal

screenings of the films on educational television, but does not include other

uses of the films on television channels. Released during the year was The

Calibration of the Platinum Resistance Thermometer, a film directed primarily toward standards and calibration laboratory supervisors and their staffs.

It is also of interest to other industrial and science groups concerned with

precision measurement. The NBS film, Scatter Radar: Space Research from

29
the Ground, produced in 1963, this year won third prize in the popular science category at the Festival of Technical-Scientific Films in Budapest, Hungary,

and was selected for entry in the Second International Congress of Scientific and Medical Films, held in Bologna, Italy.

2. HIGHLIGHTS OF THE

TECHNICAL PROGRAM

The Bureau's technical program is carried out through organizational

units within the four Institutes. These are shown in appendix 3.1 in numerical order within each Institute. A review of selected research and development programs is presented in this section under headings corresponding

generally to these organizational units.

30
2.1. INSTITUTE FOR BASIC

STANDARDS

The Institute for Basic Standards has primary responsibility for those

central national service provided by NBS which are related to standards for physical measurement and to critically evaluated standard reference data on the properties of matter and materials. It shares joint responsibility

with the other Institutes for those central national services of NBS which

are related to standard reference materials technological information, ac- quisition of reference data on properties of matter and materials, and consulting and advisory services. These responsibilities are met by means of a scientific and technical pro- gram which has essentially three missions: (a) the Standards Mission,

(b) the Reference Information Mission, and (c) the Consultative and

Advisory Services Mission, supported by a fourth, (d) Internal Support

Mission.

The Standards Mission is To provide the central basis within the United

States for a complete, consistent, stable system of physical measurement

properly coordinated with the systems of other nations. The measurement system refers to the group of physical quantities, basic

and derived, whose units of measure are usually defined on the basis of international agreement and to the relationships among them which must

be consistent with the system of physical equations used in their definition. These physical quantities of measurement are considered distinct from properties of matter and material which are essentially relationships between

physical quantities characterized by a particular kind and state of matter. Measurements in terms of these quantities provide the basis for scientific communication and for the technological operation of our mass production

industry. In fulfilling its measurement responsibility, the Institute for Basic Standards develops and maintains the national standards and coordinates them

with other nations. To disseminate the measurement system it calibrates the master standards for other standards laboratories and measurement

centers, circulates transfer standards, provides standard reference materials

to permit self-calibration, broadcasts standard frequencies, and provides

other essential services leading to accurate and uniform physical measure- ment throughout the nation. To keep pace with the most advanced requirements of science and tech- nology, it carries out research and development on improved standards,

measurement techniques, and instrumentation.

31
Strongly supplementing these activities are the Institute's projects relat- ing to the fundamental physical constants. These constants are, in effect, a set of universally accessible standards. For example, one can in principle

calibrate a thermometer with the aid of the Boltzman constant; an ammeter

with the aid of the Faraday constant; or a magnetometer against the known

value of the gyromagnetic ratio of the proton. Equally important, an

analysis of the values obtained for the same constant by different methods,

and of the relations between different constants, affords a sensitive check on the consistency and stability of the measurement system itself. Therefore the IBS keeps abreast of the measurements of fundamental constants made by other laboratories; and it makes determinations of them itself, especially when advances in technique, promising improved precision, have

made a redetermination valuable. Proper dissemination of the measurement system also involves the dissemi- nation of certain technological information related to techniques for measure- ment of physical quantities in typical engineering or production process measurements. IBS work in this area is closely coordinated with the work of the Institute of Applied Technology.

The Reference Information Mission is To provide the central basis for a

national system of critically evaluated standard reference data covering the properties of electromagnetic radiation, subatomic particles, nuclides, atoms,

molecules, bulk matter, and highly characterized materials, including the im- portant parameters characterizing their mutual interactions. In this mission is included the administration of the National Standard

Reference Data System (NSRDS), a responsibility assigned to the National

Bureau of Standards during the past year by the Federal Council for Science

and Technology. The NSRDS is the first organization to plan and coordinate

standard reference data on a continuing and national basis. Its scope is expected to embrace the following program areas; nuclear physics, atomic

and molecular physics, solid-state physics, thermodynamics and transport

properties, chemical kinetics, colloid and surface properties, and mechanical

properties, with others to be added as the need arises. In establishing and maintaining the NSRDS, the Institute for Basic Standards undertakes the following specific responsibilities:

(a) To develop a central system for the organization of the body of stand- ard reference data into a meaningful and useful pattern.

(b) To coordinate existing groups or regional centers and to establish new groups or centers, both in and out of NBS, for the collection, analysis,

and critical evaluation of existing data.

(c) To establish a system of national committees relative to selected subject-matter areas for expert advice and consultation on needs for data, priorities for acquisition, location of proper talent or facilities for data acquisition or analysis, and general guidance for the national system.

(d) To establish and operate a central coordinating office for activities relating to the NSRDS.

(e) To establish and operate a National Reference Data Center for collec- 32
tion and dissemination of evaluated data, including research on data-processing problems and procedures unique to the System.

An important aspect of the accomplishment of the Reference Information

Mission is the activities concerned with the development and dissemination of theory and measurement techniques which lead to the general improvement

nationally in the ability to determine properties of matter. It is the broad

base of technical and scientific competence in the determination of physical

and chemical properties and in the analysis and interpretation of measure- ments involved in these determinations which makes the National Bureau

of Standards a laboratory that can accept the responsibility for development

oftheNSRDS.

The program of acquisition and dissemination of reference information

and data is separated into two major areas. The first of these, the determination of the microscopic properties of matter, which includes measurement of parameters that characterize the interaction of elementary units of matter with electromagnetic radiation and with each other, is a primary responsibility

of IBS with selected activities in this area performed by other Institutes by

agreement. In the other area, i.e., of macroscopic properties of matter, IMR

has the primary responsibility. Because of the close interaction with statis- tical concepts and with the thermodynamic foundation of the temperature

scale, IBS assumes responsibility for those macroscopic properties in the general area of thermodynamics and transport phenomena. Electromagnetic

and optical properties of certain materials, the measurements of which are most appropriately conducted by elements of the IBS organization which are

closely tied to the standards mission, are undertaken by agreement with IMR.

In the area of consulting research and advisory services the staff of NBS

and, within its field of competence, that of IBS makes its principal direct contact with the scientific public. The activities involved here are almost entirely confined to the individual interactions between NBS staff members

and individuals or small groups in outside organizations.

A major implied responsibility resulting from this mission is that IBS

and the other Institutes incorporate in their program a continuous study and

evaluation of new scientific and technological discoveries to provide part of the basis for modifications of Institute programs, so that they can meet the impact of assimilation of these discoveries into current scientific and industrial practice.

Also ranged under this mission are extensive projects relating to the preparation of mathematical tables. Activities under the internal support mission are grouped under four

headings

(a) General research. Experimental or theoretical research on broader

physical problems whose results are needed as a basis for work elsewhere in the Bureau.

(b) Computing center. Operation of a center for research and service whose aim is to promote effective utilization of data processing facilities within the Federal Government.

33
(c) Technical services. Principally, consultation and collaboration on problems requiring statistical analysis and other techniques of applied

mathematics.

(d) Radiation sources. Design, construction, operation, and use-planning of the NBS linear accelerator ("Linac") and auxiliary equipment, Synchrotron, and Van de Graaf generators. In subject areas where the missions of more than one Institute are involved, the Institute for Basic Standards participates in inter-institute collaborative programs. Certain properties of bulk matter, for example, are of interest to both IBS and the Institute for Materials Research, and research programs

on these properties are being carried out under a joint arrangement of the two Institutes. 2.1.1. THE NATIONAL STANDARD

REFERENCE DATA SYSTEM

Last year the President's Office of Science and Technology established the National Standard Reference Data System (NSRDS) with the general objective of providing critically evaluated quantitative data in the physical sci- ences to the technical community of the United States. The Bureau was as- signed the administration of the system, which will coordinate and integrate

a large part of the present data compilation and evaluation activities of a number of Government agencies. To direct the program, an Office of Standard Reference Data (OSRD) was established within the Bureau's Institute for Basic Standards.

The specific responsibilities assigned by the President's Office are (1)

promotion of the general objective; (2) coordination of standard reference data activities of NBS and other Government agencies; (3) operation of a National Standard Reference Data Center at NBS; and (4) establishment of standards of quality and methodology.

The administrative plan for the NSRDS calls for decentralized data gathering and evaluating by many individual scientists and technical groups. Their

advice and active assistance will be utilized in implementing the program,

which is expected to have an ever-changing emphasis as the requirements

change over the years. The NSRDS is concerned with the production of compilations of critically

evaluated data and the dissemination of these data. The program includes

the collection and evaluation of data from the literature; the preparation of

critical reviews of the state of quantitative knowledge in a particular tech- nical field; and the computation of useful functions that are derived from

standard reference data or that are used in the interpretation of quantitative

experiments. These products may appear in a variety of forms, such as monographs, decks of data-processing cards, loose-leaf sheets, computer pro- grams, or computer tapes. For the initial phase of the program, the following technical areas have

been selected: (1) nuclear data; (2) atomic and molecular data; (3) solid- 34
state data; (4) thermodynamic and transport data; (5) chemical kinetics; (6) colloid and surface properties; and (7) mechanical properties of materials. In each of these areas a survey of existing activities was made.

Competent technical groups will undertake the high priority activities. In some cases these groups are within NBS; in others, they are in academic,

industrial, or Government laboratories. To make NSRDS products conveniently accessible, a variety of information services will be offered. The National Standard Reference Data Center

will ultimately house a complete collection of all compilations of critically

evaluated data produced throughout the world, adequately indexed and

stored for rapid retrieval. The Center will provide a centralized source for the output of all groups

designated as components of the NSRDS; however, localized distribution may be accomplished through existing mechanisms. A periodical publication

is being planned to describe the contents of the data file, current projects

underway, and other relevant information. A library of computer tapes will be maintained and printouts of stored or computed data will be prepared on

request. Replies to inquiries will provide either the best available data or a

referral to the best available source of data. Special problems connected with the collection and evaluation of quantitative data are being encountered. Attention is being given to the formulation

of these problems, so that they may be solved by means of new data-processing

techniques now available within the Bureau and from outside organizations.

Status of Technical Area Programs

(1) Nuclear Data. Consultations with nuclear physicists and compilers

of nuclear data indicate that compilation and evaluation activities covering

various types of nuclear data are perhaps more extensive than in any other

field. At present, the major requirements in this area are being adequately

met. However, new techniques are rapidly increasing the rate of data production. Improved efficiency and dissemination of data can probably be

achieved by sharing literature-scanning and indexing tasks among compilers

or by persuading authors to perform part of the job; by reaching agreement on a common format and on methods of presentation among the various

groups compiling and using neutron cross-section data; and by providing a mechanism for publication and distribution of a number of existing specialpurpose compilations which have not yet been published in the open

literature. (2) Atomic and Molecular Data. Some well-established activities in the field of atomic and molecular data have demonstrated their worth to the

technical community. NBS work in this field includes data compilations on

atomic energy levels, atomic transition probabilities, the interaction of elec- tromagnetic radiation with matter, and microwave spectra, and a literature survey of existing data on mass spectroscopy.

A contract was negotiated with the American Society for Testing and Materials for a joint program on the collection and evaluation of the infrared

35
spectra collections of various Government laboratories. Discussions were

held with users and producers of infrared spectral data in the Food and Drug

Administration, National Institutes of Health, Bureau of Customs, and the Army Chemical Corps. As a result, over 700 spectra of pure pharmaceutical

compounds are being readied for microfilming and evaluation.

(3) Solid-State Data. The dynamic growth of solid-state physics dur- ing the past 15 years has been surveyed and evaluated in a compilation entitled "Solid-State Physics,. Advances in Research and Applications," but a corresponding effort has not been made to evaluate and compile the available

quantitative data. A survey of needs and priorities by a panel of specialists

is planned prior to establishing a data compilation program. A cooperative

relationship was established with the Johns Hopkins University group, pro- ducing the compilation "Crystal Data," and other cooperative programs are being explored.

(4) Thermodynamic and Transport Properties. A survey of existing

programs indicates a need for expansion to provide the required coverage. Progress to date includes staffing of existing compilation centers, identifica- tion of the gaps in technical coverage, and establishment of a priority list of needed activities. In addition, cooperative programs were established with the Manufacturing Chemists Association and the American Institute of Chemical Engineers, and discussions regarding a joint project were held with representatives of the American Petroleum Institute. (5) Chemical Kinetics. From a survey of this field, it was concluded

that critical reviews of a number of special areas are needed. This conclusion was confirmed by an NAS-NRC panel whose members indicated

that they would either prepare critical reviews themselves or would arrange

for appropriate specialists to do so. Consequently, a series of monographs

is now planned. Thus far, specific proposals have been received for four

titles in the series from scientists who wish to take part in the program.

As an aid in the preparation of the reviews, a literature center was estab- lished at NBS to minimize the need for repetitive searching of the literature

to locate relevant material. (6) Colloid and Surface Properties. Shortly before the establishment

of the NSRDS, a subcommittee of the NAS-NRC Committee on Colloid and

Surface Chemistry, under the chairmanship of Dr. H. van Olphen of the

Shell Development Company in Houston, Tex., began to plan an extensive

program for data evaluation and compilation. The Office of Standard Refer- ence Data entered into a cooperative endeavor with the subcommittee to complete the plans and to make arrangements for the preparation of appropriate tables and reviews. Several proposals were received for support

of specific projects within the program.

(7) Mechanical Properties of Materials. A survey of this field identified areas in which compilations and reviews would be valuable. The

tentative program outline will be discussed with a group of specialists to develop final plans.

36
Relationships With Other Government Agencies, Discussions were

held with representatives of the Department of Defense (DOD), the Atomic

Energy Commission, National Aeronautics and Space Administration, National Science Foundation, and other agencies. These discussions explored

plans and existing programs, possible joint projects, and relationships be- tween the NBS program and existing data-compilation projects. Criteria

for designation of data centers as components of the NSRDS were developed

and agreement was reached with the DOD Director of Technical Information on the selection of several DOD data centers. During the year, two program reviews were presented to the Committee

on Scientific and Technical Information of the Federal Council for Science

and Technology (FCST). The formal action to establish the NSRDS originated with a recommendation of this committee, and the action taken by

the FCST directs NBS to report periodically on the plans and progress of

the program.

2.1.2. APPLIED MATHEMATICS

The Bureau's applied mathematics facility performs research and provides

assistance in the application of mathematical and statistical techniques. Its services are available to other Government agencies as well as to the Bureau's

staff. The facility uses modern computing equipment in support of the program.

During the past year the Bureau continued research in statistical and

numerical analysis, mathematical physics, and operations research—all of which are fundamental to its mission. Extensive assistance was rendered

in these areas and in digital computation. In the latter field, emphasis was

placed on problem formulation and analysis in order to select and develop

appropriate numerical methods. Automatic high-speed computing machines

were utilized when appropriate. The mathematical program was devoted

both to problems in engineering and the physical sciences and to government

problems of business management and operation, sometimes called data- processing problems. Progress continued in exploring the use of modern

digital computers in the mechanical translation of scientific publications.

A rapid translation method is urgently needed.

The Bureau's program in applied mathematics was strengthened by the

active interest and support of other Government agencies. The U.S. Army

Research Office, the National Aeronautics and Space Administration, and

the Office of Naval Research supported basic and applied research in numerical analysis and mathematical physics. The National Institutes of Health

and the National Science Foundation supported research in pictorial data

processing and artificial intelligence. The study of mechanical translation of scientific publications was jointly supported by the U.S. Army Signal Corps

and the U.S. Army Research Office. The Bureau's applied mathematics program is conducted at both the Washington and Boulder facilities. The following activities were carried out

in the Washington facilities, except for the last two items, as noted. 37
Numerical Analysis. Research in numerical analysis is of vital importance in contributing to the effective use of electronic digital computing

equipment, both in applying such equipment to scientific and engineering

problems and in utilizing it as an aid to decision-making by management.

To be effective, research in this area must be based on comprehensive knowledge of many underlying mathematical subjects. The numerical analysis

program is thus carried out by mathematicians who are experts in many

fields of mathematical analysis.

Asymptotic Expansions and Analysis. Error bounds for asymptotic

expansions of the solutions of ordinary differential equations were determined

and the results applied to the special functions of mathematical physics. The

entire solutions of functional equations were studied. Eigenvalue Determination. Eigenvalues were obtained for the Shrodinger equation with a Heitler-London potential. The computations were

carried out on the Bureau's electronic computer to check the accuracy of the second-order-WKB approximations to this operator. This work was done

in cooperation with and on the suggestion of the Physics Department of Georgetown University.

Similar work done in the theory of relaxation of a Lorentz gas led to a

typical but unsolved eigenvalue problem.

Systematic determinations of eigenvalues of different operators were car- ried out by lower-bound techniques combined with Rayleigh-Ritz upper

bounds. These techniques are of fairly recent origin and prove to be by far the most promising means of finding eigenvalues of ordinary and partial

differential operators when other methods fail. Quadrature and Interpolation. Methods for the evaluation of multiple

integrals by a modified Monte Carlo procedure and by number-theoretical

procedures were investigated, and theoretical error bounds were established and then verified by computational experiments.

Linear Algebra, Matrix Theory, Group Theory, and Number Theory.

Iterative sequences of vectors converging to the dominant eigenvalue of a

positive matrix were studied. The structure of various discrete matrix

groups of importance in the theory of automorphic functions was determined.

Multipliers of difference sets were investigated and new classes of multipliers were found. New classes of Hadamard matrices were constructed. A proof was given of the fundamental theorem that a bounded automorphic

form of dimension zero on a function group is constant. The tabulation

of basic number theoretic tables continued.

Machine Translation. The soundness of the "predictive analysis"

scheme initiated at the Bureau was demonstrated through on open test of

the method on Russian sentences composed of words formed from the limited number of stems presently stored in the computer's glossary.

Pictorial Data Processing and Artificial Intelligence. The National

Science Foundation sponsored an investigation of the techniques of syntax

direction for interpreting syntactically described information sources. The

38
technique developed for natural language sources was extended to include

schematic pictures. A computer algorithm capable of generating and

analyzing a large body of English sentences which describe pictorial images was developed.

The National Institutes of Health sponsored research on computer tech- niques for processing biological patterns. Photomicrographs of brain tissue are to be automatically processed in order to study, by simulation, the

specific future machines for implementing such processing.

Mathematical Tables. The Handbook of Mathematical Functions was

issued as Applied Mathematics Series 55. This volume extends the work

of past authors by increasing the number of functions covered, by presenting more extensive numerical tables, and by giving a larger collection of mathematical properties of the tabulated functions. Preparations are under

way for publication of Tables of Power Points of Analysis of Variance Tests and Tables of the Sievert Integral.

Digital Computation. The Bureau's computation facilities were improved by replacing the IBM 7090 computer with an IBM 7094 computer.

The arrangements with the Harry Diamond Laboratories, U.S. Army, for

the operation of an 1MB 1410 were continued. Both scientific and data

processing problems continue to require the extensive use of these facilities. The service role of the Bureau's Computation Laboratory to other Gov- ernment agencies was recognized and formalized, on an experimental basis,

by a Bureau of the Budget Bulletin designating the Computation Laboratory

as a Federal Service Center for the Washington, D.C., area. In addition, a Sharing Exchange was established to provide information on the avail- ability of computing facilities within Government to interested agencies.

Approximately one-third of the computing services performed during the year were on problems originating within the Bureau. On a continuing

basis, important computations were performed on problems in the thermal

dissociation of molecules, diffusion and reactions in gases, polymers, multi- layer adsorption studies, neutron cross sections, equation of state, and inter- action radiation. While new tasks were continually originating within the

technical areas of the Bureau, they were generally included as part of the continuing work. However, closer ties to the civilian economy and engineering needs were reflected in computations for a standards study of the lumber industry.

The remaining two-thirds of the computing services performed were for 31 other departments, agencies, and offices of the Government. In addition

to agencies regularly using these facilities, computations were performed for various segments of the Department of Health, Education, and Welfare, the

Office of Business Economics, the Bureau of International Commerce, the

Institute of Defense Analysis, the Defense Supply Agency, the Armed Forces

Institute of Pathology, and the Geological Survey. In addition to the computational services for these agencies, theoretical analysis on systems of

integro-differential equations and interplanetary and orbital calculations

756-224 0—65 4 39
were performed. Discussions on systems of differential equations describing

the flow of an electrical impulse in a neuron were also initiated. Among the many problems studied in the area of data processing are preparation of

tables relating to the status and career orientations of college faculties,

analysis of health examination data, and study of the requirements and

feasibility of supersonic transports. In cooperation with the National Institutes of Health, an evaluation was made of the organization of their computational facilities and their relation

to the scienific and administrative needs of the different Institutes. Research continues in the field of automatic programming and artificial programmer-oriented computer languages. Test problems were constructed which are used to measure and compare the efficiency of machines, pro- gramming languages, and compilers. One such problem, the calculation of eigenvectors and eigenvalues, was run under a variety of conditions which

included different machines, FAP coding. FORTRAN coding, and single and

double precision.

Statistical Engineering. The principal function of the Bureau's statis- tical engineering program is to advise the Bureau's scientific and technical personnel on the application of modern probability and statistical methods

in physical science and engineering experimentation. The aim is to help

the Bureau's scientists and technicians conduct their research, development,

and testing programs so as to reach conclusions of desired scope and reliability at the lowest possible cost. Effective use must be made of modern probability and statistical methods in an attempt to offset limitations of funds,

equipment, materials, and personnel. Extensive services were rendered rang- ing from short informal conferences to active collaboration with project leaders for periods of several months.

Research and Development. The Bureau conducts a continuing pro- gram of research in mathematical statistics and probability, to maintain and

increase the effectiveness of statistical services. Continued investigation of Youden's rank sum test for outliers led to the development of generalized

applications for the test. Tables of one-sided percentage points for the

test were prepared and published, so that both two-sided and one-sided

tables are now available. The best least-squares method for estimating the slope of a straight line through the origin is well known, and is readily applied when the correct weights are known. In practice, however, the correct weights are usually

known only approximately. The Bureau has recently completed a study

of the relative advantages and disadvantages of the most important weighted

estimates if they are used when the correct weights are not known. The

results of this study will guide data analysts in choosing the best estimator

in a particular situation. The Bureau conducted a numerical investigation of the properties of a

statistical estimation procedure in which measurements are taken until two

identical readings have been obtained. This procedure for making determina40
tions based on duplication of readings occurred as part of a tentative calibra- tion method published by the American Society for Testing Materials. Cooperative Activities. The major cooperative activities in statistical engineering were related to the Bureau's calibration programs. Methods for representing the precision and accuracy of measurement processes and

statistical designs for eliminating the effect of environmental factors are the subject of most of this work.

A good example of this collaborative activity has been with the engineering

mechanics laboratories (p. 61). As a result of this collaboration, a new

form of report of calibration has been adopted for the calibration of proving

rings. The new report, which replaces the type in use since 1948, includes a table of load values and detailed information on precision and accuracy

of the calibration. Another example is collaboration with the Bureau's radioactivity laboratory on studies of the calibration of radiation standards. These studies included,

in addition to the problems of design for the multiple comparisons among

the standards and the unknowns, the concomitant investigation of the effect of experimental factors, such as position and time trend, on the precision

and accuracy of the results. The Bureau has been active for a number of years in the statistical aspects of measurement and reporting of the precision and accuracy of measurement

processes. In addition to performing work directly for other NBS laboratories, the Statistical Engineering Section has cooperated with technical and

standardization associations and with other persons active in the field of precision measurement. An opportunity for more extensive personal as- sociation with personnel from measurement laboratories interested in the area of precision and accuracy in measurement and calibration was provided

by a week-long seminar conducted by members of the section and attended

by 14 meteorologists from industrial and governmental laboratories. Members of the section are active on committees of a number of professional and technical societies including committees of the American

Society for Testing Materials, the American Standards Association, and

the American Society of Tool and Manufacturing Engineers. An important

example of this work was assistance to the International Atomic Energy

Agency in the planning of interlaboratory tests for establishment of standard

samples for uranium and for trace elements associated with uranium.

Operations Research. General areas of investigation during the past year included linear programming and its extensions, graph theory, game

theory, stochastic processes, and mathematical models of distribution net- works.

Significant progress in graph theory and related optimization problems

continued, under the sponsorship of the Army Research Office. Past work on

finding maximum sets of isolated edges in linear graphs was both implemented computationally and extended theoretically to the problem of finding

maximum-weight sets of (weighted) edges with a quota on the number of 41
chosen edges allowed at each node. An efficient method was developed

for encoding graphs without circuits, a topic arising in connection with

storage and retrieval of chemical structure information. The convex hull of the incidence vectors describing the spanning trees of a graph was deter- mined, as were several related convex hulls. A characterization was found

for the possible node-degrees of a graph all of whose cut-sets of edges contain at least a prescribed number of edges.

A variety of investigations pertinent to postal mechanization were carried out for the Post Office Department. Some involved cost-benefit analysis of proposed mail-sorting subsystems and of alternative approaches to the en- coding of addresses for subsequent machine use. Others dealt with stochastic processes in certain mail-handling operations. Work was completed on a major exploration of mathematical methods and concepts relevant to the "warehouse" problem of locating a single processing facility (here, a large

mechanized sorting installation) so as to minimize the total cost of trans- portation between it and its customers. Results included analytical solution of idealized representative cases, development and testing (on Chicago data)

of a computer code for more realistic cases, and a clarification of several mathematical problems arising out of the asymmetry of travel costs between

a pair of points.

Demand for consulting and advisory services in operations research con- tinued to increase. There was particular emphasis on such areas as industrial modeling and economic analyses, with work in these respective areas being

performed for and with the program in textile technology and the Commerce

Department's supersonic transport project. A promising start was made on

developing (for the Veterans Administration) computer procedures for

facilitating hospital floor layout, with emphasis on translating into specific

algorithms the architect's assessment of the relative importance of proximity

for different types of functional units. Mathematical Physics. The function of the program in mathematical

physics is to aid and advice the Bureau's professional staff on the applica- tion of mathematical techniques to the solution of problems in engineering

and the physical sciences, and to conduct research in areas pertinent to this function. Studies were conducted on the formulation of realistic constitutive equations for nonlinear viscoelastic materials and fluids, the determination of bounds on the solutions of problems in elastic materials, partial

differential operators of hyperbolic type which satisfy Huygens' principle, the behavior of solutions of nonlinear differential equations occurring in oscillation problems, and the bending of elastic plates under point supports.

Theory of Satellite Orbits. Research in this area of great importance

to the National space program has been sponsored for several years by the National Aeronautics and Space Administration. The principal problem is how best to account for deviation of the earth's shape from that of a sphere.

A promising method based on spheroidal coordinates has been developed. Current efforts are concerned with corrections for the finer details of the 42
earth's shape, such as equatorial asymmetry. Work in progress on the effects of a constant force on such an orbit should have application to the problem

of radiation pressure. A preliminary study has been made of the feasibility of measuring or compensating the drag on a manned satellite. Information obtained in this manner would be helpful in determining atmospheric densities and the figure of the earth, and would eventually be useful in providing experience in the design and operation of a zero-G laboratory.

Research in Plasma Physics. Studies in the dynamics of plasms were

conducted essentially in two areas during the last year: interaction of plasmas

with a magnetic field, and statistical dynamics of plasmas with application to propulsion. The first research program was part of a Bureau-wide effort in this field, and was concerned with the transport properties of a plasma

interacting with a magnetic field. As part of this project, a seminar was con- ducted on the theory of plasma dynamics. The second research program was

started two years ago at the request of the National Aeronautics and Space

Administration, and centers about the kinetic equations of plasma theory,

plasma oscillations, and the bearing of these on the application of plasmas

for space propulsion. Numerical solution of some of the simpler nonlinear

problems is under way.

Whisker Growth. A theoretical study was started on the growth of mercury or potassium whiskers in vapor atmospheres (see p. 147). The

problem is nonlinear and requires an electronic computer for its solution. The mathematical formulation in terms of two simultaneous integral equations turned out to be most amenable to numerical computation. This study

is expected to give information on the validity of the screw-dislocation theory.

Mathematics Group at the Boulder Laboratories.* The workload of the Boulder, Colo., computation facility increased with greater utilization by

the Bureau of Reclamation, the U.S. Air Defense Command, the Geological

Survey, industrial laboratories, universities, and the National Center for Atmospheric Research. Effectiveness of the computer system is broadened

through the possibility of using a powerful new executive program and

through the increased availability of double-precision computer programs.

The computer has been programmed to write a magnetic tape suitable for input to a new high-speed plotting machine which prepares point or symbol

plots and contour line drawings.

Other technical computer programs were written to compute the error function of a complex variable, Airy functions of a complex argument, the near-zone electromagnetic field of a quarter-wavelength dipole antenna, the capacitance of a pair of hemispheres, the solution of a system of three simul- taneous first-order nonlinear differential equations for electromagnetic phase

corrections, and the values of certain integrals and derivatives connected with

the absorption of electron energy in the atmosphere.

Studies of two-phase fluid flow continued with the numerical calculation of

*This activity is a part of the Manager's Office, Boulder Laboratories. 43
neutral stability curves in a vertical pipe and the preliminary analysis of annular flow in a horizontal pipe. Numerical tests were made on a model for transient two-phase flow in a pipe with heat exchange.

A method for the computation of the error function of a complex variable was derived and published. This method was applied to the computation of the response to a swept frequency input of the general electrical circuit con- taining resistance, inductance, and capacitance.

A method and programs were prepared for the application of a large computer to billing procedures in the Boulder printshop and drafting rooms.

Statistical Studies at the Boulder Laboratories,* Four projects in or

related to mathematical statistics were completed, and several others con- tinued or initiated. These programs are directed primarily towards the planning or data analysis of investigations in radio propagation and radio

standards, but usually have more general applicability. Completed were

papers demonstrating the insensitivity (within limits) of the cost of heir- archies of calibration systems to accuracy ratios between echelons, papers on detailed comparison of several methods of estimating parameters of a generalization of the Poisson distribution, on approximating distributions of quadratic forms in normal random variables, and on statistical inference for Rayleigh distributions. Studies continued on precision of estimation of variance components from

time series, especially for atomic frequency standards; robust estimation of medians of symmetrical distributions, with applications to standards; and

tabulation of the distribution functions of the complete range of stable dis- tributions. A study of the robust estimation of percentiles from small samples was initiated as the result of interest by radio propagation scientists. 2.1.3. ELECTRICITY

The Bureau's work in electricity is primarily the development, improvement, and dissemination of the standards of measurement for electrical quantities; and procedures and techniques for very accurate electrical measurements, such as are needed in studying dielectric and magnetic properties of matter. Electrical standards must be established that are constant over long periods of time, uniform throughout the nation, and compatible

with other standards used throughout the world. Measurements of electrical quantities directly in terms of length, mass, and time ("absolute measure- ments") are extremely difficult and are made only in the realization and

confirmation of electrical standards of resistance, capacitance, inductance,

and voltage; calibration work is done by comparison with these electrical standards. Electrical Units,

Current. Repeated determinations of proton-precession frequency and

of rubidium Zeeman-transition frequency are necessary to the Bureau's con- tinuing surveillance of the constancy of the legal volt and ohm. The deter- *Tbis activity is a part of the Manager's Office, Boulder Laboratories. 44
minations are made in a 0.0012-tesla field stated in terms of the NBS

ampere, which is defined as the ratio of the NBS volt to the NBS ohm.

Analysis of such measurements over a four-year period indicated that the NBS ampere has remained constant to about one part in a million. This

uncertainty (1 ppm) results essentially from limitations in measuring the dimensions of the solenoid in which the precession-frequency measure- ments are made.

The possibility of monitoring and correcting variations in the earth's

field at the solenoid was investigated using a self-oscillating rubidium

magnetometer in a secondary Helmholtz-coil system, phase-locked to a standard frequency and supplying a correction signal to the principal Helmholtz-coil system surrounding the solenoid. This "dynamic shielding"

system was successfully operated, but cannot be used in the Bureau's present

location because of the differences in field conditions at the sensing element

and at the solenoid.

Capacitance. A new determination of the unit of capacitance in terms

of a gage-bar assembly checked within 1.5 ppm of the unit maintained in terms of a group of standards. Dr. Helmut Hoyer of Physikalisch-Technische Bundesanstalt in Braunschweig, Germany, who expects to build

a computable cross-capacitor in his laboratory, assisted in this year's

determination.

Parts for an improved calculable capacitor were constructed in the NBS

instrument shop and assembly was begun. A capacitance-probe gaging

technique was developed that permitted the individual electrodes to be

lapped within a 10-microinch tolerance. It is hoped that uncertainties in the determination of the unit can be reduced to a few parts in 108—

exclusive of the speed-of-light uncertainty.

Standards,

Stable Capacitance Standards. A group of 10-picofarad (pf) capaci- tance standards with fused-silica dielectric was built. The design and mounting used were those of a previous standard modified in an attempt to eliminate

sensitivity to voltage and shock. Measurements on the new standards

indicated that changes with voltage are less than 1 X 10~8 for applied voltages

up to 200 volts (V), and shock sensitivity is low. No change was detectable following an axial or radial drop of 15 cm to a hard wood surface. Ex- amination of stability with time and under more severe shock conditions

(i.e., shipment by parcel post) will show whether standards of this type can be used in international comparisons of the unit capacitance.

A new three-terminal capacitor was designed that has a direct capacitance

independent of the temperature of two electrodes and thus dependent only on the temperature of the third, which can be made of fused silica to give an overall temperature coefficient of capacitance of 0.6X10~6 /°C. The

value may be adjusted by simple machining operations on the other elec- trodes, which may be of any stable metal. The design is useful in the range below 10 pf, and a 5-pf capacitor has been built. 45
Voltage Dependence of Air Capacitors. The Bureau's 1-pf computable

capacitor serves as the starting point for assigning values stepwise to other

reference standard capacitors. This step-up process requires that the new

capacitors be subjected to alternately high and low voltages when bridge

measurements are made; thus voltage dependence must be minimum. A

Stable Capacitance Standards, A group of 10-picofarad (pf) capacitors of identical design having a coaxial-cylinder geometry that minimizes

changes due to electrostatic forces. A method was developed at NBS for measuring the "absolute" variation of capitance with voltage. With this method, changes amounting to less than 1 X 10~9 can be resolved. Observed changes amounted to no more than 3 X 10~9 between 10 and 200

V. Two effects were present in the general case—electrode distortion under

electrostatic forces, and migration of electrode surface films. Film effects usually amount to 1 part in 107 or less; electrode distortion may be neglible or range to several parts in 106

, depending on geometry and structure. Galvanic Cell with Thallous Sulfate. The Bureau maintains the unit

of electromotive force (emf ) for the United States with a group of cadmium

sulfate cells. The emf's of these cells are derived from the basic mechanical

units of length, mass, and time. During intervals between "absolute"

measurements, the emf's of the cadmium sulfate cells are assumed to be in- variant with time. However, it is obvious that all of a group of "identical"

cells may increase or decrease in emf with time without evident departures

from an assigned mean. Another type of standard cell of composition dif- ferent from the cadmium sulfate cell would therefore be of great value for changes in emf with time in two different systems would not be likely to fol- low the same pattern. In an attempt to develop a new type of standard cell, a group of thallous

sulfate cells was made with a thallium-amalgam anode and a mercury-mercurous sulfate cathode in a saturated solution of thallous sulfate. At 25 °C

this cell has an emf of 1.057511 V and an emf-temperature coefficient of 32 X 10~5 V per degree Celsius. This cell has an emf of approximately 0.04 V

higher than that of cadmium sulfate cells and an emf-temperature coefficient nearly seven times that of cadmium sulfate cells; however, it has shown

evidence of being sufficiently stable that studies of the ratio of the emf's

of thallium sulfate and cadmium sulfate cells may prove valuable in maintaining the national unit of emf. The changes in free energy, heat content, and entropy for the cell reaction were found to be —204,075 joules per mole

( J/mol) , 185,661 J/mol, and 61.76 J/°K mol, respectively.

A-C Voltage. A set of twelve thermal voltage converters was designed,

constructed, and evaluated. These converters are used in making highly ac- curate a-c voltage measurements from 1 to 1,000 V by comparison with d-c

standards. The frequency responses of these converters were identical within 5 ppm from 20 Hz to 20 kHz, with no evidence of systematic error in the step-up intercomparison process by which the response of each is known in terms of any other one. The a-c-d-c difference of the 1-V converter agreed

with that of the basic NBS set of converters to better than 5 ppm. Thus rms

46
Set of newly designed thermal voltage converters covering the 1 to 1000 volt range. These converters will increase appreciably the accuracy of a-c voltage measurements at audio freqviencies. (See page 46)

a-c voltage measurements at audio frequencies can be made with a new

order of accuracy. High-Accuracy Current Transformers. Two nearly identical multi- range current transformers for establishing ratios of alternating currents from 0.1 to 50 amperes at audio frequencies were designed and constructed. Their accuracy was determined to a few ppm up to 10 kHz with a 1:1 comparator and a unique intercomparison circuit for stepping up to ratios of

6:1.Measurement Methods, A passive direct-reading ratio set was built to compare audio frequency admittances. It has a difference range of ±500

ppm, and a least count of 1 part in 109

. The new device was built to supplement and perhaps replace an earlier active ratio set that was sensitive to har- monics in the power amplifier and bridge transformers because of nonlinearity in its operational amplifiers. The passive device uses compensated trans- former elements rather than operational amplifiers.

A 10:1, three-winding transformer was constructed with a voltage ratio

(at 10 kHz) between the secondaries equal, to a high order of accuracy, to the turns ratio. Its residual errors have been determined to better than a part in a million, and it has been used with capacitance ratio techniques to extend the upper frequency limit for the calibration of high precision inductive dividers from 1 to 10 kHz.

A high-voltage pulse generator was built. It consists of a group of pulseforming networks arranged in a Marx circuit and provides a rectangular

output pulse about 12 microseconds in length with an amplitude up to 125 kV.

Techniques have been developed for comparing the pulse performance of commercially available voltage dividers with specially constructed reference

dividers to an accuracy of the order of 1 percent.

At the request of the Bureau of Naval Weapons, Department of the Navy,

the Bureau developed a "Helicopter Battery Service Simulator" for testing

helicopter batteries of the silver-zinc and silver-cadmium types under simulated service conditions. The "Simulator" can simultaneously test three

batteries by automatically discharging them, first at 300 amperes for 1 second

and immediately thereafter at 100 amperes for 9 seconds. Three such

47
sequences are applied within 1 minute. The battery is then charged for 30

minutes at a constant potential. Helicopter batteries are subjected to 20

such discharge-charge cycles per day, five successive days per week. The

"Simulator" also provides a continuous record of the battery temperature,

charging current, and discharge voltage. A novel voltmeter having a scale of 27 to 28 V was designed and incorporated into the "Simulator" to monitor

the voltage during the charging of a battery with an accuracy of 0.1 percent.

A zener diode was used for the reference voltage in the voltmeter. A three-terminal cell, or holder, which permits more accurate dielectric measurements on solid specimens than any previous cell was designed and

built. It can be used in liquids with the two-fluid technique which, in con- junction with a bridge of improved sensitivity, permits measurement of the

dielectric constant of a disk specimen with an accuracy of 2 or 3 parts in 100,000 at 1,000 Hz without applying contact electrodes to the specimen or knowing the thickness of the specimen or the area of measurement. By

measuring a suitable specimen and then measuring this same specimen in other cells, it is possible to determine the effective measuring area of such

cells, thus improving the accuracy of the measurements made with them.

The new cell is made in two parts. The spacing between these parts is determined by three gage blocks placed near the edge of the assembly. The

cell is so precisely constructed that it can be disassembled and reassembled

with a change in capacitance of less than 2 parts in 100,000. Turning the cell upside down does not change the capacitance by as much as 2 parts in 100,000.

Five sections have been constructed so that by combining sections, three

different effective areas of measurement can be obtained.

The use of the new two-fluid cell and transformer bridge improved the precision of dielectric constant measurements on fused silica and teflon disks by a factor of up to 100 times under restricted conditions of very carefully controlled humidity, temperature, specimen preparation, and positioning of the specimen in the holder. In ideal cases the precision of measurement of e' now is of the order of 50 ppm.

A very simple two-terminal cell was developed for room temperature

measurements of a single 1- to 2-gram disk-shaped specimen without contact

electrodes over an unusually large range of frequencies—from 10" 2 to 6 X 108 Hz. Accuracies of better than ±1 percent for e and zh5 percent for e" are obtained over the entire frequency range. Calculations have been de- veloped to take into account the air gap, fringing fields, and residual circuit parameters. Several bridges and resonant circuits are used with the cell to cover the frequency range. A detailed theoretical analysis was completed of the effect on the effective area of a guard ring cell of the guard-gap width, electrode thickness, and

dielectric constant of the material in and around the guard gap. The results of the work permit assessment of experimental errors due to the guard gap

in precision measurement cells and allow measurements under conditions

where these errors are well below the desired 0.1 percent precision limits. 48
During the work, errors in existing guard-gap theory and application were

pointed out and corrected. Properties of Matter.

Gold Anodes in Electrolysis. As part of a broad investigation of electrolytic processes, gold anodes were studied in aqueous solutions of sulfuric acid free of or containing sodium oxalate. Depending on the magnitude of the electrical potential of the gold, oxygen gas may be evolved at the gold, or a "three-dimensional" oxide film or a "two-dimensional" chemisorbed

oxygen film may be produced on the gold. An elipsometer was used to ascertain changes in the surface of the gold; the potential of the gold was

controlled with potentiostat. It was observed that an oxide of gold and

not chemisorbed oxygen begins to form on gold anodes at a potential of

1.1 V and continues to form at all potentials above 1.1 V until 2 V is reached,

at which point oxygen is evolved. When the potential is decreased, complete and rapid removal of the oxide film occurs below 1.1 V. When oxalate ions are present in high concentrations, no oxide film forms on the gold at any potential ; or, if it does, it is removed as rapidly as it forms as ellipsometer measurements show no phase change on the surface of the gold.

With this equipment, the performance of three helicopter batteries of silver-zinc and silver-cadmium types can be tested simultaneously under simulated service conditions. (See page 47)

49
Structure of Garnets. Nuclear magnetic resonance techniques were

used to study the magnetic characterization of mixed crystals of yttrium-irongallium garnets as the ferromagnetic iron atoms are replaced by the "non- magnetic" gallium atoms. The primary objective of the work, which was

sponsored in part by the Advanced Research Projects Agency, was to measure the magnetic fields at the nucleus of the 57 Fe in these matrials. The nuclear magnetic resonances of ^Ga and 71 Ga were observed in these same samples. These latter results are particularly interesting because gallium is a diamagnetic atom and the hyperfine field at the gallium site arises through a transfer of the spin density from the neighboring oxygen atoms,

which are in turn polarized by their neighboring iron atoms. Thus, the hyperfine interactions at the gallium are associated with the superexchange

interactions between the gallium and the iron. Ferromagnetic Alloys. The nuclear relaxation times for 1 percent 61 Ni

in 99 percent iron, 1 percent 61 Ni in 99 percent cobalt, and 0.5 percent

59Co in 99.5 percent nickel were measured at several temperatures using the pulsed free precession method. Such measurements give information con- cerning the motion of domain walls around the impurity atoms. Relaxation

time studies on nuclei in the domains relate to the strength of the coupling

between the impurity atom spin and the conduction electrons. These results indicate that the strength of the conduction electron relexation mechanism

for the impurity nuclei is smaller than for the nuclei of the solvent atoms

in the pure solvent metals. Magnetic Susceptibilities. The electron resonance, optical spectra, and

magnetic susceptibilities of pure VC14 and of VC14 in TiCl4 were interpreted

by considering a distortion of the regular tetrahedral crystal field. A small

Jahn-Teller tetragonal distortion would fit these measurements, but a packing-type trigonal distortion is also under consideration. Calculations indi- cate that the resonance, optical spectra, and susceptibilities can be interpreted

by invoking a small tetragonal crystal field distortion. Spin-lattice relaxation

measurements made on single crystals of Mohr's salt show there are defi- nitely two relaxation times, and for certain crystal orientations a maser

effect appears to be present.

A calculation of the complex dielectric susceptibility of ionic crystals was completed. Higher-order effects due to distortion of the electronic clouds around the nuclei were taken into account.

Dielectrics. Techniques were developed to measure viscous liquids in- side a polystyrene cup. With this arrangement, the wide frequency capability

for measuring solid dielectrics was used to study viscous polyvinyl esters. Measurements from 101 to 109 Hz verified the validity of the frequencytemperature superposition principle for dielectric relaxation processes above

the glass transition temperature. This verification can be expected to lead

to a more satisfactory understanding of glass temperature relaxation

phenomena.

An extensive experimental study was made of the dielectric relaxation

fnonresonant absorption) of several symmetric-top gases (CH3 C1, CHF3 , 50
and S02 F2 ) and their mixtures with various foreign gases (He, Ar, H2 D2 , C02 , N2 , CH4 , and C3 F8 ) . Measurements over an extended temperature range

(—20 to 150 °C) determined the variation of the relaxation time and effec- tive collision cross section for molecular reorientation with temperature

and their dependence on the nature of the intermolecular forces. Measure- ments at room temperature were extended to a number of other symmetrictop gases and about 15 other foreign gases. Despite the lack of previous

theory, some progress is being made in the theoretical interpretation of the

results and in correlating the dielectric behavior with other dynamic properties, such as viscosity.

Advisory Activity, An extensive study of the lightning protection problems associated with steel-framed monumental buildings was completed

with the support of the Architect of the Capitol. Several changes were recommended for the Rayburn House Office Building lightning protection.

The Magnetic Measurements Section served as referee on the sale of a large order of silicon steel for use in the electrical industry. When the supplier and the purchaser were unable to agree on the value of core loss for the material, samples of it were submitted to the Bureau for a referee

test. After determining the core loss, the Bureau assisted the purchaser in locating the error in his determination.

Calibration Service. The large-volume calibration items were 1,576

resistors, 873 standard cells, 580 capacitors, and 332 inductors. The various

other items, such as potentiometers, current transformers, volt-boxes, etc., run

a few dozen each. In addition, 1,412 dry-cell batteries were tested for the General Services Administration and the Veterans Administration.

2.1.4. METROLOGY

The metrology laboratories of the Bureau maintain, develop, and dissemi- nate standards for commonly used physical quantities such as length, mass, volume, density, and angle, as well as for light, color, electromagnetic

radiation, and other optical and photographic quantities.

During the past year advances led to improved measurement capabilities.

The development of a load-cell technique for comparing large weights enables

other laboratories to calibrate their own weights, thus reducing "down time."

A gaseous laser operating in the visible region of the spectrum was built and

will be used in the interferometric determination of length. A line standard

interferometer, utilizing automatic fringe-counting techniques, was placed

in operation; thus both more accurate and more rapid calibrations of line standards are now possible. The use of new equipment and electronic data processing resulted in a reduction in the calibration time for both gage blocks

and base-line tapes. Load Cell Comparison Devised for Weight Calibrations. By means

of comparative rather than direct-reading techniques, precisions of 5 parts per million were achieved in the calibration of 10,000-lb weights. This

accomplishment, obtained with a load cell, demonstrates that other labora-51
Technique developed for load cell comparison of large weights should save millions of dollars by permitting any laboratory to calibrate its own weights.

Equipment consists of an hydraulic lift, a flexure (a), a load cell (b), another

flexure (c), and a means of hooking on to the weights. (See page 51)

tories can use readily available equipment in the calibration of their own

weights, and thus eliminate the need for NBS calibrations and the ensuing

down time. The essence of the development is not the assembly of any particular

set of equipment but rather the use of established comparative techniques

and careful statistical evaluation of the resulting data. The load cell, one

of several equally promising elastic devices, was investigated and proved

satisfactory. It offers the advantages of precision equal to the best of platform scales, portability, rapidity of weighing, and availability of equip- ment. The equipment for the weighings consists of a hydraulic lift, two flexures, a load cell, and a means of attaching the weights, all suspended from an over- head crane. The hydraulic lift is used to raise and lower the weights and

thus avoid sudden stress on the cell, and the flexures keep the stress in axial alinement with the cell. A variety of electronic assemblies may be used to determine the output of the strain-gage bridge in the load cell, as long as the

entire system is sufficiently sensitive and successive measurements of the same

quantity agree or follow a regular trend. Intercomparisons of three 10,000-lb

52
weights made with this equipment gave a standard deviation of 0.04 to 0.06

lb. These results are comparable to those obtained with the best of multiple

lever scales. Color-Matching Functions Evaluated, Industrial inspection of manufactured goods (textiles, paints, plastics, ceramics, papers) for conformity

to a color standard is usually carried out at close range so that the parafoveal

as well as foveal regions of the inspector's eyes are used. In this way he can

detect smaller color differences. Accordingly, in 1964 the International

Commission on Illumination recommended color-matching functions intended

to conform to observing fields subtending 10 degrees at the eye of the

inspector.

The Bureau carried out tests of these functions for moderately bright

fields. These tests indicate that the functions sometimes fail to predict the

color matches of actual observers with normal color vision, and suggest that

the failures are due to a disturbance of the match from responses of the

twilight vision part of the eye which, in the parafoveal region, is intermingled

with the color-perceiving part of the eye. To eliminate such disturbances, more light than is generally used for color measurements is required.

Density Measurements Devised for Small Objects. A Cartesian

diver system is being developed for weighing objects too small for reliable observation on ordinary hydrostatic balances. Such balances have uncertainties of 20 micrograms or more; hence, their percentage precision for very small objects is limited. Unfortunately, objects of greatest interest in hydrostatic weighing, for instance, highly purified substances, single

crystals, and sensitivity weights, are not readily available in large sizes. In

the new technique, density determinations are made by attachment of an

object to the outside of the diver and measurement of the pressure in the water that will result in zero vertical movement of the diver. At present, these hydrostatic weighings can be made reproducibly to a standard deviation of one or two micrograms. Experiments are being con- ducted on 1-gram objects occupying a volume of about 1/20 cm3

. Efforts are being devoted to obtaining volumetrically stable objects which can be used

as comparison standards in the weighings. Experiments are now being con- ducted on nichrome, gold, platinum, fused quartz, and silicon. As soon as

stable standards are developed and calibrated against mercury, they will be

compared hydrostatically with various single crystals, probably beginning

with rutile. Aging Blemishes Studied on Microfilm. Inspections of microfilms

of Government records revealed blemishes which apparently developed long

after the films were processed and placed in storage. Most of the blemishes

are small spots, usually reddish or yellowish in color, ranging from about

15 to 150 microns in diameter. These blemishes were classified on the

basis of size, shape, color, and character. Descriptions and colored photomicrographs of the various types and recommended inspection, sampling,

and reporting procedures were published in NBS Handbook 96, Inspection of Processed Photographic Record Films for Aging Blemishes. In cooperation

53
with the National Archives, NBS trained 100 microfilm inspectors. These

inspectors subsequently made detailed reports on 4,300 rolls of microfilm, a

statistical sampling of over 100 million feet of film. The mechanism of blemish formation and generally accepted preventive measures are not as yet known. The processing and storage conditions in various places are therefore being correlated with the incidence and severity

jf blemishes ; the chemical and physical structure of the blemishes are being

studied; and biological and chemical mechanisms of blemish initiation are being investigated.

A protective treatment developed by a microfilm manufacturer shows

promise of inhibiting blemish development. Enough empirical evidence was gathered to begin a revision of recommended practices for the preservation of microfilm records. Plans were laid for a joint industry and Govern- ment research effort on an expanded scale.

Cartesian Diver System being developed for water-weighing of objects too small

for reliable observation with ordinary hydrostatic balances. Reduction of uncertainties from 20 to one or two micrograms has already been achieved. (See page 53)

54
Microdensitometer Calibration. In the past, the density scales of microdensitometers have been calibrated by means of photographic step

tablets of known densities as denned in the American Standard for Diffuse

Transmission Density. This kind of density, however, is inappropriate for

the calibration of microdensitometers because the geometry of such instru- ments differs from the geometrical conditions specified in the American

Standard. Hence, a new kind of density was defined, having geometrical

conditions of illumination and sensing identical to those employed in microdensitometry. A "standard microdensitometer" was constructed to calibrate photographic step tablets for use in the calibration of microdensitometers.

Photographic Knife Edge Devised, In measurements of the capability of photographic film to produce sharp images, the films are exposed to

light while partly covered with a straight knife edge. Since actual metallic knife edges are unsatisfactory for such measurements, a straight-edge x-ray image of a thin tantalum foil was made on a high-resolution photographic

film for use as a "knife edge." This photographic "knife edge" is convenient

for measuring film characteristics and also for evaluating the spatial response

of microdensitometers.

Chlorophyll Measured in Tree Leaves. In 1952-53 the Bureau

studied the dying of a mature leaf of a white oak tree, wet and dry, by

measuring its spectral reflectance 25 times throughout the year. The regular

increase of reflectance obtained in the 680 nanometer region of the absorption

band of chlorophyll indicated the gradual disappearance of that plant pigment from the leaf. In the spring of 1964, a similar spectrophotometric

study was made of leaves picked from the same branch of a white oak tree at

five stages of development starting with a very young leaf and ending with a mature leaf. It was found that the chlorophyll absorption increased with the age of the leaf to maturity, following a pattern that was just the reverse of the pattern obtained in the earlier work. These studies were sponsored by

various agencies of the Department of Defense. Infrared Hazemeter Developed. In cooperation with the Advanced

Research Projects Agency, an infrared hazemeter was constructed to measure

the forward-scattered flux of infrared transmitting optical materials. The

instrument is similar in principle to the visible hazemeter used in ASTM

(American Society for Testing and Materials) Method D 1003. Radiant

flux scattered by a specimen is collected for measurement in an integrating

sphere. The wavelength range of the present instrument extends from the

visible region to about 4 microns in the infrared region. Preliminary meas- urements of several materials indicate that the haze depends on the type of specimen, the thickness, and the batch of material from which the specimens

are made. Data of this type will help optical designers select the most suit- able material for a particular wavelength region.

Spectral Distribution of Typical Daylight. Determinations of how

the energy of daylight is distributed in the ultraviolet and visible portions of

the spectrum were carried out in collaboration with the National Research

Council of Canada, the Eastman Kodak Company of Rochester, and Thorn

756-224 O—65 5 55
Aging blemishes on the leader of a 16 mm microfilm. The causes for the appearance of these spots on microfilm records, and possible corrective measures, are currently the subject of an intensive investigation. (See page 53)

Electrical Industries, Limited, of Enfield, England. Typical distributions were found ranging from the blue light of the clear sky, through light from

the gray overcast sky, to the yellowish combined light from the sun and partly

cloudy sky. This information will be useful in establishing standards of

artificial daylight for the color appraisal of industrial materials and manufactured goods of all kinds (textiles, paints, plastics, papers, ceramics) ; but

it is particularly useful for the appraisal of optical bleaches that make textiles whiter by transforming some of the incident ultraviolet energy into blue light. Artificial daylight currently available for this appraisal has insufficient ultraviolet content. Fluorescent Lamp Color Standards Recalibrated. The fluorescent- lamp industry has been maintaining the colors of its warm white, white, cool

white, and daylight lamps by using laboratory color standards. The calibrations of these standards are based on standards of the same colors calibrated

at NBS eight years ago by a visual match with incandescent lamp-and-filter

combinations of known chromaticity. Spectroradiometry, the fundamental

method by which fluorescent-lamp standards should be calibrated, previously gave systematic differences that were larger than the tolerable uncertainty.

As a result of recent progress in cooperation with the laboratories of the lamp manufacturers, NBS has now recalibrated spectroradiometrically the four groups of laboratory color standards that were furnished originally.

This recalibration of the same lamps provides the industry with data on the magnitudes of the color differences ascribable to the change in calibration method. The spectroradiometric method also provides data that permit

calculation of the color rendition of objects illuminated by the lamps. In- 56
formation on the color-rendition characteristic of a light source is apt to be of more interest to the ultimate user than the chromaticity of the lamp itself. Check Made of Color-Temperature Scale, Light sources for the

color appraisal of industrial materials and manufactured goods, and for appraisal of the performance of photographic materials and photocells, are

all defined by reference to gas-filled incandescent lamps of known color temperature. The present NBS color temperature scale is based on three

fixed points established in 1934 for the kinds of light coming from a cavity

whose walls are maintained at one of three known high temperatures, namely,

the freezing points of platinum (2,042 °K), of rhodium (2,233 °K), and of iridium (2,716 °K). Laboratory reference standards for color temperatures

up to 3,200 °K have been calibrated three times since 1934 by means of blue

filter standards. Comparisons in 1960-62 with similar standards calibrated at the National

Physical Laboratory in Great Britain indicated a discrepancy greater than the uncertainty estimated for the calibration by about a factor of three. The

NBS color-temperature scale above 2,716 °K was recalibrated this year by

the use of more filters and more cross-checks than were previously used. The

resulting adjustment in the color-temperature scale is such that at 2,854 °K,

for example, the voltage at which an incandescent lamp must be operated has

been increased by about 0.8 percent. This adjustment corresponds to about

9 °K and is only slightly larger than the NBS estimate (7 °K) of the uncertainty. The adjustment also reduces the difference between the American

and British scales. Standard Published for the Colors of Signal Lights. Traffic of all kinds (highway, railway, marine, and aviation) is controlled by colored

lights, and 15 different colors (three varieties of red, yellow, green, blue, and

white) denote the various required meanings involved in long- and short- range signaling. The Bureau, through the U.S. National Committee on the Colors of Signal Lights, led the way toward a coordination of these various

colors. This coordination involved a unified method of defining the colors, a standard method for testing signaling devices for conformity to the color requirements, and a selection of the glass standards of color to be used in the standard method. The agreement achieved by eight agencies of the Federal

Government, five national associations, and four manufacturers of components for signaling equipment is given in a new publication, NBS Handbook 95, U.S. Standard for the Colors of Signal Lights.

Wavelength Standards for Spectrophotometers. For over 20 years

the Bureau has issued commercial "didymium" glasses, together with a report

of the wavelengths of the sharpest of the absorption and transmission bands,

to users of spectrophotometers for checking the wavelength scale in the visible and near-infrared regions. With the advent of photoelectric recording

spectrophotometers for the ultraviolet, a commercial glass containing the oxide of the rare-earth element, holmium, similarly calibrated was made

available. The search continued, however, for glasses exhibiting more and

sharper lines over a broader wavelength range. 57
Recently, measurements were made of phosphate-base glasses (fabricated

in the M35 glass laboratory I containing the oxides of one. two. three, or four

of the rare-earth elements, to determine which combination of oxides would

result in the most useful standard. This study indicates a combination of two glasses, one containing the oxides of neodymium and samarium, the other

those of holmium and ytterbium, to be the most useful. This study was

financed in part by the Advanced Research Projects Agency of the Department of Defense. Master Balls Rapidly Calibrated by Interferometry. Requests from

spacecraft industries for calibrated master balls increased greatly over

the past two years. An instrument was therefore designed and built to measure rapidly and in a horizontal plane all sizes of balls up to one inch

in diameter. A complete set is stored on two turret tables and is fed by

remote control to an exact position between two interference plates. Posi- tioning of these plates is accomplished by an electric motor, but the orienta- tion of the interference fringes for exact fringe fraction readout is controlled by a micropositioning system employing air pistons and flexure levers. Measurements are made on a ball on six or more randomly selected horizontal diameters with a known applied force repeatable to less than 1 gram. The man hours for diameter calibration are reduced by a factor of 7 with

the new instrument.

Tooth Index Positions Measured on Large Gears. By means of an

improvised assemblage of available components, deviations from correct angular positions of gear teeth of a 20-in. pitch diameter gear were determined

to a precision of 2 arc-seconds and an accuracy of 5 arc-seconds. On the

basis of these results it appears that a tooth-index measuring machine having

a capacity of approximately 100-in. diameter could be designed and built. Such a machine would be a valuable tool in improving the reliability and

noise reduction of large gears. Roughness Simulator Constructed. In a recently constructed roughness simulator, a piezoelectric crystal driven by a generator provides a series of periodic waveforms that are imposed upon an analyzer's transducer. The equivalent roughness height of each wave can be determined by inter- ferometric measurements and compared to the indicated value of the

analyzer. The simulator offers a significant improvement over existing

techniques because of its capability for varying the waveforms' parameters.

It is being used for measurements of the finer finishes that cannot be measured

by the mechanical standards presently in use. Spectrometer Designed for Laser Analysis. A spectrometer was de- signed to study the spectral output of lasers and other light sources. Essentially, the instrument is a Fabry-Perot interferometer of variable plate separation, with a photomultiplier tube viewing the center of the interference ring pattern through a small circular diaphragm. A piezoelectric ceramic

tube, whose length is varied by applied voltages, is used as a spacer be- tween the two interferometer plates. As linear changes of the interferometer

58
plate separation are produced in this manner, the photomultiplier tube scans through the interference pattern.

With a steadily varying d-c voltage applied to the piezoelectric tube, a graph of the spectral intensity distribution is obtained with a chart recorder. High-frequency noise is easily suppressed by limiting the frequency re- sponse of the recorder and recording at low speeds ; this method is therefore

particularly suitable for the analysis of the fine and hyperfine structures of weak spectrum lines. An a-c voltage at the tube and display of the phototube output on an

oscilloscope screen provide the time-resolving spectrum of the light source. This method lends itself to the detection of instabilities of the frequency

output of lasers, for which it is presently used. Special Optical Calibrations Carried Out, Two calibrations per- formed during the past year were unusual in both the nature of the measure- ments and the high accuracy required. The first of these was the calibra- tion of a multiple-camera device which is used in three-dimensional photography of nuclear reactions that take place in a hydrogen bubble chamber.

The calibration involved the location of the principal point of autocollimation

for a target at a finite distance (213 cm in front of the lens) for each of four miniature precision-type photogrammetric cameras. In addition, the principal point had to be located with respect to a coordinate system de- termined by three, instead of the customary four, fiducial markers. The

four cameras are located in a large metal plate about a central opening,

and the lens of each camera is not centered with respect to the picture area. The deviation from parallelism of each of the four image planes was de- termined with respect to a common plane perpendicular to the axis of the system. Also determined were linear relationships to the nearest hundredth

of a millimeter and angular relationships to the nearest second existing be- tween the principal points of autocollimation of the four cameras. The second calibration, performed for the U.S. Army Engineers, involved

the measurement of distortions existing in the image plane at a 5 to 1 en- largement of six ultrawide angle projection lenses. This task was unique

in that the total angular field was 120 degrees instead of the usual 45 degrees. In addition, very tight tolerances required that all values of distortion re- ferred to the short conjugate distance be correct to within ±2 microns. In the course of this work, several new analytic methods were developed for checking the results of measurement. As a byproduct of the research, it was

found that the optimum magnification ratio resulting in minimum overall distortion could be predicted.

Refractometric Research, To demonstrate superachromatism without

interference from monochromatic aberrations, a five-element prism was de- signed and constructed. According to computations, this prism will deviate

a beam of light 27.5 degrees with no aberration greater than ±4 seconds

over a spectral range all the way from 4,047 Angstrom to 1.014 micron.

59
The aberrations of an ordinary achromatic prism producing the same devi- ation would be in excess of ±50 seconds over a more restricted spectral range. Ophthalmic Lenses. A newly published American Standard, "American Standard Prescription Requirements for First Quality Glass Ophthalmic

Lenses," incorporates the recommendations and suggested tolerances for re- fractive power contained in an NBS study of spectacle lens performance

made for the Veterans Administration.

Line Standard Interferometer, An interferometer designed to cali- brate length scales in terms of the international standard of length—the wavelength of light—was subjected to initial trial tests. The results were ex- tremely promising, indicating the instrument is precise to within 2.5 X 10"5 mm and has an accuracy that will advance the state of the art of line stand- ard measurement. Simple straightforward calibrations by the line standard

interferometer agreed with results obtained by long painstaking calibrations performed by older conventional methods.

Thermal Expansion Calibrations Expanded. Two instruments de- signed to increase the temperature range of thermal expansion measure- ments were constructed. The high-temperature instrument (up to 1,600 °C)

to be used for calibration of standard samples for high-temperature dila- tometers and for the investigation of the expansion of materials at extreme

temperatures, is undergoing final tests. One of the first assignments of the low-temperature instrument (down to —250 °C) will be the determination of the thermal expansion of vitreous silica. Such information is applicable to sonic interferometer determinations of a low-temperature scale. Superprecision Gaging. The monitoring of stability samples of steel and determinations of length changes with aging of numerous steel alloys

continued, in studies carried out in cooperation with the Bureau's metallurgy

laboratories (see p. 141). Work also progressed on the use of polarized

light to determine contact error in end standard gaging. The results thus far obtained, combined with an analysis of the propagation of errors involved,

indicate a present day experimental limitation to an accuracy of approximately 0.5 X 10~6 mm. This accuracy is sufficient; however, effort is being

directed toward making it more easily achievable.

Mossbauer Radiation. The metrology applications of the Mossbauer

effect were further investigated, and a high-precision Mossbauer spectrometer was developed. This spectrometer, using a fringe-counting technique, can measure velocity in the range of 0 to 5 cm/sec with a precision of 1 part in 104

. The instrument will be used to calibrate Mossbauer absorbers and for evaluating Mossbauer sources. Such information is required for the de- velopment of a Mossbauer geodimeter, for which a feasibility study was

made. The study showed that an accuracy of a part in a million could be

obtained in a geodimeter having a 50-meter range, even without controlled ambient conditions.

60
2.1.5. MECHANICS

The Bureau's work in mechanics is primarily in the development and

improvement of methods of measurement of mechanical phenomena in solids,

liquids, and gases; the establishment of required standards in mechanics

and the relation of such standards to the prototype standards; the sup- port of these activities by theoretical and experimental researches into mechanical phenomena; the determination of physical constants of particular

importance in mechanics; and provision of assistance to other laboratories

in relating their measurements to a common basis (or to established stand- ards) by transfer standards, calibration services, and other means. Measure- ment areas include sound pressure and intensity, shock, vibration, force,

strain, pressure, vacuum, viscosity, and rate of gas and liquid flow. These measurements areas are of great importance in science and engineering, including the missile and space programs, which require great

accuracies over widely extended ranges under extreme temperature environ- ments. Special emphasis is therefore given to research directed toward

meeting these needs. Most of the equipment used by the staff of the Engineering Mechanics

Section was moved to the new special-purpose Engineering Mechanics

Laboratory at Gaithersburg, Md. The employees engaged in the calibra* tion of force-measuring standards will continue to provide calibration services in this area with the equipment located in Washington until the new

equipment being installed at Gaithersburg is ready for use. All of the weights for the new 112,000-lb and 300,000-lb capacity deadweight machines have been received and work on the adjustment of these weights is nearing completion. Several of the 50,000-lb weights for the 1,000,000-lb

capacity deadweight machine have been delivered. Construction of the 12,000,000-lb capacity testing machine due for completion late in 1965 was

started. Design work progressed on the Sound and Fluid Mechanics

Laboratories.

Calibration of Microphones, Microphones are calibrated in two differ- ent ways. In one way, a known sound pressure is applied to the diaphragm

at various frequencies, yielding a "pressure sensitivity." In the other way,

the microphone is placed in a plane wave having a known sound pressure;

then the sound pressure at the diaphragm is different because of diffraction by the microphone. The latter way yields a "free-field sensitivity."

The ratio of the free-field sensitivity to the pressure sensitivity (known

as the free-field correction) of a group of laboratory condenser microphones was measured by performing separate absolute calibrations to obtain the two types of sensitivities. The free-field correction is of importance

because the free-field sensitivity is often determined by measuring the pres- sure sensitivity and multiplying it by the free-field correction, which is assumed to be the same for all microphones having the same external di- mensions. The Bureau's measurements uncovered differences in the freefield corrections between microphones of as much as 9 percent, indicating

61
that the use of a "standard" free-field correction can result in errors. The

only method presently known of avoiding such a systematic error is to perform microphone free-field calibrations in an anechoic chamber, either by reciprocity or by comparison with a microphone calibrated by reciprocity.

Measurement of Earthquake Motions by an Acoustical Technique.

The great Alaskan earthquake on Good Friday in 1964 produced unusually

large motions of the earth's surface in the Washington, D.C., area. The un- expected motions were so great as to make accurate measurements by conventional seismometers impossible. But the strong motions of the Rayleigh waves from the earthquake produced, as they passed through the Washington area, sound waves in the atmosphere. Although these occurred at a frequency far too low to be heard, they were nevertheless measured by the

infrasonic microphones of our Washington station. The sound pressures were in fact about 40 dynes/cm2

, at a period of oscillation of about 25 seconds. From this it was deduced that the earth motion in the Washington area was

almost 2 inches from trough to crest. The microphones with which the pressure measurements were made are located at various sites in Montgomery

County, as well as at the Bureau's site in Washington. An interesting feat- ure of the measurements is that the sound pressure represents motion of the

earth's surface averaged over a very considerable area, of the order of sev- eral hundred square miles. This is to be contrasted with measurements

by a conventional seismometer, which gives the actual motion of the earth

at the particular point where the seismometer is located. The entire sequence of acoustical phenomena caused by the passage of the earthquake waves through the Washington area occupied a period of sev- eral hours. Particularly puzzling are some waves which seem to have been

scattered by the Gulf of Mexico, with some of the scattered waves reaching

Washington. The geophysical causes of the scattering are still being in- vestigated.

Sound Insulation in Buildings. In recognition of the serious problem

of privacy-invading noise in multifamily dwellings, projects on sound in- sulation have been undertaken, leading eventually to residential noise control. FHA's activity in this field led to that agency's recent publication, "Guide

to Impact Noise Control in Multifamily Dwellings." The Bureau is curSAMPLERS S3

Superimposed recordings from four spaced infrasonic microphones show atmospheric sound waves caused by Rayleigh waves from the great Alaskan earthquake

passing through the Washington, D.C., area. These recordings indicate a total earth motion of almost 2 inches, too large a movement to be measured accurately by conventional seismometers. (See page 62)

62
rently engaged in a second study under FHA sponsorship dealing with the

technical control of both airborne and structure-borne noise in multifamily

dwellings. Airborne noise emanates from sources which radiate directly into the air, such as loudspeakers, musical instruments, the human voice,

barking dogs, etc. Structure-borne noise by contrast is produced when

wall, floor or other building structures are set into vibratory motion by direct mechanical contact with such noise sources as air-conditioning equipment,

dishwasher and disposal units, etc. The vibration is transmitted in various

ways throughout the building structure and is re-radiated as noise in other

areas. A summary publication, NBS Monograph 77, Sound Insulation of Wall,

Floor and Door Constructions, currently in press will contribute to the FHA

study. This publication contains acoustical test data and constructional

details of a wide variety of building assemblies useful in the control of both

airborne and impact or structure-borne noise. A roundrobin interlaboratory study of the impact sound transmission

through concrete floor structures and a companion field study on nominally

identical floor structures in existing buildings were completed, and the first draft of a "Tentative Recommended Practice for Laboratory and Field Measurement of Impact Sound Transmission" was written. This work, which

has been supported in part by the Army, Navy, and Air Force, will continue

until a standard method of test is adopted. The importance of this activity

is reflected in the fact that the eventual formulation and enforcement of noise

control criteria in building codes will hinge primarily on the development

of a reliable field test capable of checking building conformance with acoustical requirements.

The combined efforts of the FHA and the Sound Section of NBS in the

field of residential noise control are providing much-needed guidance to

architects, builders, building code authorities, and others involved in the design and construction of multifamily housing projects.

Audiometry. People usually hear by sound waves which travel down

the ear canal to the ear drum (air conduction). But sounds can also be

heard when a vibrator is applied to the bones of the head (bone conduction)

The relative sound levels of hearing by air conduction and bone conduction

are important in the medical diagnosis of impaired hearing.

One can make a quantitative measurement of this relationship by simultaneously impressing an audible pure tone signal through earphones on the two ears of a subject, and through a bone vibrator applied to the forehead. Each signal contributes to the displacement of the basilar membrane in the inner ear. By an adjustment of the magnitude and phase of the signals on

the earphones, the air-conduction signal can just cancel the bone-conduction

signal and the subject will hear nothing.

Apparatus, which included the design of a precision phase shifter continuously adjustable over 360°, and constant in output amplitude to within

I dB over the audio-frequency range, was constructed to measure the "boneair null." Preliminary results were obtained.

63
There is at present no standard method for calibrating the bone vibrators

used in the measurement of hearing. For a proper calibration, the vibrator

should be loaded with a mechanical impedance equal to that presented to the vibrator when applied to the bones of the head. That is, an artificial headbone is required. With the help of the Bureau's digital computer, results of measurements of the mechanical impedance of the forehead and mastoid

made here and at the National Physical Laboratories in England were combined for a vibrator designed to meet the requirements of the International

Organization for Standardization. The combined impedance values expressed

in terms of an equivalent four-parameter mechanical network, valid from 250

to 6,000 Hz, were presented to ISO to form the basis for the design of a standard artificial head-bone.

The present proposed ISO standard for threshold of hearing by air con- duction is in terms of five earphone-coupler combinations, described in the national standards of five countries. In order to facilitate calibration of audiometers, we have prepared a tabulation of the sound pressures corre- sponding to threshold produced by the five national standard earphones and

by six other commercially available earphones in one coupler, the Bureau's 9A Coupler, now in the process of being reported by the International Elec- trochemical Commission as an interim reference standard coupler.

Single-Crystal Ice—Elastic Constants. It has been known since 1959

that the thermal properties of regular ice as deduced from the elastic constants measured just below the ordinary freezing point, are at variance with

those measured directly at very low (i.e., liquid helium) temperatures. The

Bureau is engaged in a search for a low-temperature vibrational mode of the

ice lattice which might resolve the discrepancy.

The elastic constants are calculated from fairly high-precision measure- ments of the speed of longitudinal and transverse sound waves in singlecrystal specimens. A pulse-coincidence technique has been developed for

this purpose. Some difficult problems, which it is hoped will be solved soon, stem from

the instability of ice in the ordinary environment. The dimension and orien- tation of the crystals must be measured, and the machining of specimens done,

in a cold ( — 40 °C) , very dry atmosphere.

Nonlinear Distortion in Hearing Aids. A hearing aid, like other nonlinear electronic amplifying devices, produces frequencies in its acoustical output which can be audible, and which are not present in the input sound

signal. This nonlinear distortion has been evaluated in the past by introducing one frequency, or sometimes two frequencies, into the input signal to the hearing aid and measuring the frequency and amplitude of any spurious components in the output. However, it is not convenient and sometimes not

possible to determine by this method the distortion which will be produced

when the input sound is a complex signal having many frequencies such as speech. In work sponsored by the Veterans Administration, a method has been

64
developed in which the input signal has a distribution of energy (at fre- quencies and amplitudes) which is similar to that of a speech signal, except

that a large attenuation is introduced at a number of frequencies in the spec- trum. The acoustical output of a hearing aid, both at frequencies at which

the acoustical input signal is attenuated and at other frequencies as well, is measured. From such measurements is obtained an evaluation of the nonlinear distortion produced by the hearing aid when it is amplifying a speechlike signal.

Electromechanical Coupling Factor of Condenser Microphones,

A new and very direct method was developed for obtaining the electro- mechanical coupling factor of condenser microphones by means of static pres- sure measurements with a low-pressure manometer, and d-c voltage measurements. The procedure consists of applying a static pressure to the diaphragm

of the microphone and adjusting the polarizing voltage to keep the diaphragm

in its equilibrium position, which is observed by means of a carrier-frequency

circuit. Measurements were made over a range of static pressures up to 360 newtons/meter2 and up to changes in d-c voltage of about 200 volts. Over these ranges, the measured coupling factor was constant within approximately ±0.3 percent. Values of the coupling factor were compared with

determinations made at audio frequencies and found to agree within 1 percent.

The significance of this agreement is twofold. First, it indicates that the coupling factor can be used as a microphone sensitivity measure for sound

pressures in the infrasonic frequency range, since the factor appears to re- main constant as the frequency approaches zero. Second, since two inde- pendent methods for determining the coupling factor yield the same result, the assumptions and measurement techniques leading to its determination seem to be reliable. These techniques include the reciprocity method for

calibrating microphones which the Bureau uses to determine the absolute

sensitivity of reference standard microphones.

Pressure Measurements. The wide and still-expanding range of pres- sures used today in industry and science calls for continuous improvement

of existing methods of pressure measurement and calibration as well as for

the development of new techniques. A program has been initiated for the measurement, with improved accuracy, of the transition pressures for changes

in the crystalline form of bismuth (the so-called Bi i-ii and Bi il-m transitions near 400,000 psi), in order to meet the demand for improved fixed points on a high-pressure scale. The state of the art in the 100-kilobar

range (1,500,000 psi) was improved by a study of the behavior of silver chloride as a pressure-transmitting medium ir pyrophyllite and reconstituted mica gaskets.

For a greater accuracy in the measurement of low pressures, an improved

point-gage-type mercury manometer, developed at the Bureau, has been

adopted by a number of Bureau laboratories, and may prove to be the standard of choice for the calibration of anemometers used in manned air- craft flying in the 50,000- to 100,000-ft range. 65
Damping of Surface Waves Caused by Turbulence, A laboratory

investigation was conducted under the sponsorship of the Office of Naval

Research to determine whether turbulence in water has a damping action

(expressible in term of an eddy viscosity) on surface waves. The experi- ments were conducted in a wave tank. Although laboratory conditions

could not be expected to simulate any specific phenomenon, an attempt was made to create "turbulence" in the tank by upward directed water jets from

orifices uniformly distributed over the tank bottom, with a duplicate set of intake orifices interspersed to maintain constant water level. The wave

amplitude attenuation along the length of the tank was observed with and

without operation of the jets. The increase in damping with jet operation was small and difficult to isolate from other effects. Owing to the other effects, damping due to jet- induced turbulence was more easily measured with deep-water waves than

with shallow-water waves. This damping could be ascribed to an eddy

viscosity which for deep-water waves was approximately 15 times the viscosity of water, for the conditions investigated.

Highway Culverts, Research in culvert hydraulics conducted at NBS

under the sponsorship of the Bureau of Public Roads established that the water-carrying capacity of highway culverts can be substantially increased. A culvert (the pipe or duct under the road) does not generally flow full even though the entrance may be fully submerged; the principal factor influencing this condition is the shape of the entrance.

Increased calibration accuracy and stability has been obtained in electrodynamic

vibrators by using air bearings. Here, a velocity pickup is mounted on the moving element for calibration. Tube in foreground supplies air to the bearing.

(See page 66)

66
In the NBS study of culvert hydraulics, emphasis was placed on the design of entrance shapes to promote greater capacity. By the use of tapered inlets, the flow capacity of culverts can be increased from 50 to 75 percent above that obtained with commonly used entrance designs. This

work was done in the laboratory with model sizes ranging from 6 to 30

inches in diameter. Investigations over this range of sizes showed that the performance of a full-sized culvert could be adequately predicted over

a useful range of operating conditions from the small-scale model studies. In the field, culverts may be as large as 10 to 15 feet in diameter and may on

occasions exceed this size. Since Federal and State costs for the construction

of culverts and similar drainage structures for highways approximate

$400,000,000 per year, the research work on culvert hydraulics promises to yield significant savings.

New Proving Ring Calibration Report. A new and more convenient proving ring calibration report was issued by the Bureau to replace the calibration graph which required interpolation and tabulation by the user. The new report contains a load versus deflection table and statistical information of the standard deviation of a deflection reading and the standard error

for a tabled load value. The validity of the statistical information and the load versus deflection table values given in the report were both verified experimentally.

Displacement Measuring Devices Evaluated at Elevated Temperatures. To evaluate displacement measuring devices under adverse temperature conditions, apparatus was developed to produce displacements known

to within 25 microns at temperatures as high as 260 °C. Equipment for measuring the electrical characteristics of differential transformer type trans- ducers was also developed. Using these systems, evaluation tests were con- ducted on differential transformers over the temperature range of 25 to 260 °C to determine their calibration factor, linear range, zero shift with

temperature, and zero shift with time. Fatigue Strength of Aircraft Structures. Fatigue tests were carried out on a series of 2024—T3 aluminum-alloy riveted joints at room temperature

and at elevated temperatures to provide information pertinent to the development of supersonic aircraft. As a basis of comparison, fatigue tests were also performed on smooth sheet specimens. Results suggest that the temperature

effect on fatigue of riveted joints is considerably less serious than it is for smooth sheet specimens, particularly in the high-cycle, safe-life regime.

Furthermore, it was found that no significant creep took place beyond the first cycle or two, despite the fact that tests were conducted with positive mean

loads. This is expected to simplify design procedures in which a synergistic interaction between creep and fatigue in structural components is anticipated.

Although the results are not yet fully evaluated, it appears unlikely that dependable fatigue correlations between joint and sheet behavior will be

found.

Test Methods Developed for Aeronautical Fasteners. Standardized

test methods for determining the mechanical properties of aeronautical
Research on culvert hydraulics promises significant savings in highway construction costs. Here, a tapered inlet increases culvert flow capacity by 50—75 per- cent over commonly used entrance designs. (See page 68)

fasteners are necessary for comparisons between types and materials. Under

sponsorship of the Bureau of Naval Weapons, examinations were made of the factors influencing the values of single shear strength for high-strength aero- nautical fasteners. Experimental studies were made of these factors as applied to high-strength blind fasteners in aluminum alloy sheet and plate.

Vibration Standard Modified with Air Bearings. By substituting

two external-pressure, hydrostatic-type air bearings in a commercial electro- dynamic vibration exciter for the mechanical supports of the moving element

(armature), the amplitudes of transverse motions were reduced substantially.

An ideal exciter used for calibration of vibration pickups should produce

axial displacements without transverse motions of the moving element over

its full frequency range. The modified exciter, used as a vibration standard

from 10 to 2,000 Hz, made it possible to study the performance of pickups

sensitive to transverse motion.

Rheological Constitutive Equations, A number of materials, such as rubbers and plastics, flow like liquids under sustained forces, yet recover more or less like elastic solids when the forces are removed. To describe

the mechanical behavior of such materials in isothermal situations, a constitutive equation has been developed based on the concept that the elasticity of the material arises from energy related to both the present configuration

of the material and configurations in the past but with the influence of past

configurations diminishing as we go to the more distant past. This theory predicts that three material functions (of time) are adequate

for isothermal simple extension. These functions were calculated from

68
measurements made in stress relaxation, and then used to calculate successfully the results of measurements involving multiple step stress relaxation, creep and recovery, and constant rate of deformation, all for a particular

sample of polyisobutylene.

To extend this description of material properties to include nonisothermal

phenomena, it is necessary to create a thermodynamic theory valid for situa- tions far from equilibrium. A non-equilibrium thermodynamics has been

found which seems to have the correct qualitative behavior. This theory

includes a principle of time-temperature superposition, is consistent with the second law of thermodynamics, and predicts that the temperature increases

when work is done adiabatically on a material held at constant volume and

decreases when the material does work. The theory also agrees with measure- ments of apparent viscosity as a function of temperature and rate of shear. Failure of Aircraft Fuel Hoses, An investigation sponsored by the Bureau of Naval Weapons of the failure of thermoplastic fluorocarbon fuel hoses resulting from the generation and discharge of static electricity pro- duced by flowing fuel was completed. These hoses are used extensively to interconnect the various fuel handling components of aircraft and other in- ternal combustion engines. It is essential that their performance be both safe and reliable. The investigation established that conventional thermoplastic fluorocarbon

hose would fail as a result of static electricity under normal operating conditions. Extensive tests were undertaken to determine the effect of fuel flow

rate, fuel contamination, water, hose material, and fuel filter element material on this phenomenon. From these tests, the maximum anticipated electric currents under service conditions can now be accurately predicted.

Assistance was given to the Bureau of Naval Weapons in devising measure- ment techniques and determining certain properties of fuel hoses to be used

in purchase specifications. The Air Force and several major aircraft engine

manufacturers expressed the intention of using the revised specifications for future purchases of thermoplastic fluorocarbon fuel hose. Flow Field of a Flame, Flame speed measurement and design of combustion systems may be improved through a better understanding of a flame's flow field. A study of the field was carried out by the use of a flame front simulated by an assembly of fluid sources and sinks in a general stream. The direction and speed of the flow on both sides of the flame were ob- tained by computer techniques from an equation based on the source and

sink arrangement. The boundary shapes necessary to experimentally repro- duce the flame front were also derived in the computation.

Thermocouple Reference Tables Compiled, Several new noble

metal thermocouples were developed for accurate measurement of temperatures of oxidizing gases. Reference tables of temperature versus thermal emf

were compiled for the Platinel II thermocouple and several other thermocouples having varying percentage compositions of iridium-rhodium alloys versus iridium.
Reference tables for the Platinel II thermocouple are based on the cali- brations of 27 thermocouples. The tables cover the temperature range from — 100 to +1370 °C. Reference tables for 60 percent iridium — 40 percent

rhodium alloy versus iridium and for 50 percent iridium-50 percent rho- dium alloy versus iridium thermocouples, published in the past year, extend

from 0 to 2150 °C. 2.1.6. HEAT

Heat measurements, standards, and related research play a most important role in modern science and technology. The Bureau discharges important responsibilities in these areas through the maintenance of the National

standards for such heat measurements as enthalpy, heat capacity, and heat of combustion. Internationally agreed upon temperature standards are maintained to assure a common scale upon which all temperature measurements

are based. A strong research program aims to keep these standards adequate

for the expanding scientific needs. In addition, supporting research on the physical properties of solids and gases at both low and high temperatures

includes studies in low-temperature physics, statistical thermodynamics, hightemperature processes, high-pressure thermodynamics, and various aspects of plasma physics.

A program extending over many years culminated in the development of

a precision mercury manometer having the highest accuracy ever attained. A new spectroradiometer reduces uncertainties of spectral radiance calibrations by a factor of 5 and extends the range of wavelengths covered to 2,000 A. A facility for calibrating germanium resistance thermometers over the region 2 to 5 °K was established. A rugged and highly reproducible null- type transducer for high-pressure measurements was developed. The auto- mation of precise heat measurements was furthered by completion of an

automatic resistance bridge with an equivalent temperature precision of 0.0001 °C. Research items of major interest include the discovery of superconductivity in oxide semiconductors at very low temperatures; a theoretical treat- ment of quantum effects in the thermodynamic and transport properties of

the light gases; concordant measurements of the electron density in a magnetically confined arc plasma by a variety of methods, and derivation of a dispersion relation for the standing hydromagnetic wave and of a relation between the density correlation function and the diffusion coefficient; meas- urement of lifetime and spectra of short-lived simple molecules by pulsespectroscopy and by study of the afterglow from high-frequency electric discharges in flowing gases; development of greatly improved methods for producing gaseous free radicals within microwave cavities and thus for obtaining very accurate data on line frequencies for simple free radicals of astrophysical interest. Paramagnetic Resonance in Gases. A technique was found by which

dense vapors of the hydride radicals of sulfur, selenium, and tellurium are 70
produced. This technique, which involves reactions of atoms at solid surfaces, was used to measure and interpret the electron paramagnetic resonance (EPR) of these elements, and is being investigated further as a means of producing the astrophysically important radicals SiH and CH.

The chemical reaction between atomic hydrogen and N02 was found to pro- duce large quantities of OH radicals at total pressures as low as 1 micron of mercury. Eliminating pressure broadening at such low pressures made

possible measurement of the 18-cm absorption spectrum of OH to an accur- acy of one part per million in the line frequencies. These frequencies will be useful for determining Doppler shifts in the recently observed interstellar absorption spectrum of OH.

The EPR spectra of several rotational levels of 14N0 and 15 N0 were measured and interpreted to determine magnetic moments, hyperfine structure, and A-type doubling in these two molecules. This work is supported

in part by the Office of Naval Research.

Molecular Energy Levels of Small Molecules, Transient species were studied within a short time after their formation by two methods. The

first involves study of the afterglows from high-frequency electric discharges

in flowing gases with time resolution as short as about 100 microseconds

(fisec. ) . The admixture of gases downstream from the discharge was used

to study the results of collisional processes between the metastable helium and

the added species. Of particular interest, in this regard, has been the strong

preferential excitation of the ionic spectra of the added molecules. The technique of kinetic spectroscopy is the second approach used to study transient species. A high-intensity pulse of light causes a gaseous or

solid sample to decompose, and the absorption spectrum of the species thus formed is recorded by using as a continuum the radiation from a second

high-intensity flash. The second flash follows the decomposition flash at a

preselected time interval (which may be as short as 10 /xsec). The time

history, from 10 to 1,000 yusec, of the vibrational energy of oxygen molecules

formed in the photolysis of nitrogen dioxide was studied with this method.

In another experiment, the formation of iron oxide was observed following

the flash vaporization of iron wire in oxygen. Plasma Transport Processes. The microwave reflection technique de- veloped by S. Takeda and T. Tsukishima from the University of Nagoya,

Japan, was, with their collaboration, successfully applied to determine spatially resolved electron densities in the magnetically confined arc plasma. The

results are in good agreement (±20 percent) with densities determined from

the width of Stark-broadened Balmer series lines of hydrogen and from the ion saturation current to a Langmuir probe.

The standing hydromagnetic wave which appears on the plasma column

of this arc appears to obey a theoretically derived dispersion relation. This wave is of interest because its phase velocity is dependent on the mass density

of the plasma for sufficiently small wavelengths, and it may contribute to cross-field plasma transport.

756-224 0—65 6 71
The relation between the density correlation function and the diffusion

coefficient was extended to the plasma in a magnetic field. This extension

may provide a novel and useful experimental technique for the determination

of plasma diffusion coefficients. Microsecond Thermodynamics, A program was undertaken to de- velop new techniques for the measurement of thermodynamic and other

properties of dense substances (in solid, liquid, and dense gaseous phases)

at high temperatures (above 2000 °K) in experiments of short duration

(millisecond to microsecond) . The initial phase of the study was limited to millisecond measurement of specific heat and heat of fusion of a group of metallic elements at temperatures above 2000 °K.

An apparatus and related electrical and electronic circuitry were designed

and constructed for this determination. Preliminary experiments were con- ducted to understand some of the high-voltage, fast-transient characteristics of the electrical equipment. Exploratory results of the research on photoelectric and photographic techniques for the measurement of temperature

in the range 2000 to 4000 °K with time resolution of less than one milli- second were obtained. Investigations are under way to extend this to the microsecond time domain.

New Spectroradiometer, A spectroradiometer for spectral radiance

calibrations was developed with the joint support of the National Aeronautics and Space Administration. This new instrument extends the range

of wavelengths covered (2500 to 25000 angstroms (A)) down to 2000 A,

and reduces the uncertainties of previous calibrations (about 8 percent at shorter wavelengths and 3 percent at longer wavelengths) by about one-fifth. The spectroradiometer contains a grating-prism double monochromator,

a quartz-window multi-alkali halide cathode photomultiplier tube, a stable high-temperature blackbody, a specially selected vacuum tungsten strip lamp,

associated electrical equipment, and means to orient precisely and aline optically the radiation sources and to depolarize the instrument. The spec- troradiometer is also an accurate photoelectric pyrometer and is calibrated

at about 6500 A in terms of the International Practical Temperature Scale by using a gold point blackbody and a recently developed multiple beam

splitter.

The high-temperature blackbody is a graphite tube heated electrically in an argon atmosphere, operating routinely at temperatures up to 2600 °C

and for short periods at temperatures as high as 3000 °C. The temperature of the blackbody can be controlled so that variations in the blackbody

radiation are less than 0.2 percent. The blackbody's quality and uniformity

of temperature were determined with special techniques.

At a specified wavelength, the spectral radiance of a test source operating

at a given condition is obtained by adjusting the blackbody's temperature

so that its spectral radiance is equal, as indicated by the spectroradiometer,

to that of the test source. The blackbody temperature is measured by the spectroradiometer. and the spectral radiance of the blackbody at the given

72
wavelength is determined from Planck's radiation law as equal to the

spectral radiance of the test source. Current estimates are that spectral radi- ance can be determined with an accuracy ranging from about 0.3 percent at 8000 A to about 1.5 percent at 2100 A.

Precision Manometer, The advancing designs and techniques employed in revisions of the Bureau's precision mercury manometer have made

it an outstandingly accurate instrument during most of its 35-year existence. With a new mercury-level detection system, pressure is measured with the highest accuracy so far attained. The location of each meniscus with respect

to the lip of the cup is accurately determined by the capacitance between the

NBS precision mercury manometer, whose accuracy has been increased to within

a few parts per million, is used to establish the standard atmosphere required

for resistance thermometer calibrations and for constant volume gas thermometer determination of the Kelvin Scale. (See page 73)

73
crown of the meniscus and a plate and guard above it. The three-lead capacitance bridge was designed to be used with the mercury at ground

potential.

The height of the mercury column is established by gage blocks on which

the upper cell rests. All surfaces above the base which establish the vertical position of the mercury menisci and capacitance plates are optically

flat to obtain the height of the mercury column with high precision and

accuracy. The manometer has served for many years as a standard of one atmos- phere pressure for the fixed boiling points of the International Practical Temperature Scale. It has lately been improved and made more versatile for use in a gas thermometry program intended to determine the corres- ponding values of temperature on the International Practical Temperature

Scale and the Kelvin thermodynamic scale in the range of 0.01 to 1063 °C

(Int. 1948).

Pressure Transducer for Gas-Phase PVT Measurements, A rugged

and highly reproducible null-type transducer was developed for accurately

determining the equilibrium pressure between a Burnett PVT apparatus for gases and a counter-balancing pressure system. The transducer, closely

coupled to the PVT sample volume, is used at temperatures from 0 to 200

°C over the pressure range 4 to 240 atm. The transducer consists basically of a metallic diaphragm as the pressure responsive element and a stable capacitance sensor for detecting minute deflections of the diaphragm.

For pressure imbalances less than 1 atm and transducer pressures of 1 atm or less, the reproducibility is within 9X10-3 mm Hg, which is the equivalent resolution of the capacitance circuitry. The maximum uncertainty in the null for transducer pressures varying from 4 to 240 atm is, re- spectively, 0.003 percent to 0.00004 percent. The maximum uncertainty

in the constancy of the transducer volume is 7 X 10~5 cm3 and contributes a maximum error of 0.0003 percent in the constancy of the sample PVT

volume.

Developments in the Automation of Calorimetry. As a part of the Bureau's program to automate precise heat measurements, an automatic

bridge developed according to National Bureau of Standards specifications was completed and installed. This instrument is used in accurate deter- minations of temperature with a platinum resistance thermometer, which

is an accepted international standard for thermometry.

Not only does the automatic bridge release a scientist from routine measurements, but its operation is usually more accurate and faster than con- ventional manual operation, making possible experiments that otherwise

would be too difficult. Measurements can be made with a precision of 0.00001 ohm (usually equivalent to 0.0001 °C) on a resistance as large as 500 ohms. The time required for the bridge to make a measurement decision

varies from 0.2 to 3 seconds, depending on the precision required. The

bridge is used to measure a varying resistance, a situation that occurs fre- quently in heat measurements where temperature is changing. According

74
Automatic bridge for temperature measurements using platinum resistance ther- mometers. The bridge continuously and automatically displays the readings,

and transfers selected readings to a buffer storage for recording on punched

cards or tapes. (Developed and built by Leeds & Northrop to NBS specifications.) (See page 74)

to a preset program, the measured resistance values are displayed visually

in ohms and may be recorded on punched cards or tape for use with a computer, avoiding human errors in recording. The time of the measurement as determined by a standard clock is recorded also. The automatic bridge has been designed with considerable flexibility in the logic of operation so that it can be applied to many other problems in- volving precise resistance measurements. Low-Temperature Scale Improved by Correlation with NBS Data,

The Thermodynamic Temperature Scale is the accepted "ideal" scale describ- ing the behavior and properties of matter. The accepted practical scale is the International Practical Temperature Scale (IPTS), which is based on

a number of fixed temperatures together with specific formulas for inter- polating among these fixed temperatures. The interpolation formulas and

the values of the fixed temperatures are so chosen that the IPTS will be as nearly as possible like the ideal Thermodynamic Scale. In temperature

ranges where materials do not undergo transitions, the property of heat75
capacity is considered a "smooth" function of the Thermodynamic Scale. It

is possible, therefore, to use precise heat-capacity data to check the inter- polation formulas used in the temperature scales. Precise NBS heat capacity data in the range 10 to 300 °K were cor- related with the IPTS above 90 °K and with the NBS Provisional Temperature Scale below 90 °K, where there is no international scale. Both scales departed significantly from the Thermodynamic Scale, especially near 90 °K.

NBS heat-capacity data as a function of the resistance of a platinum resistance thermometer were used to derive interpolating functions for temperature

scales which are believed to give better agreement with the Thermodynamic

Scale. New Low-Temperature Calibrations. A facility providing calibrations from 2 to 5 °K was opened. The calibrations can be made every 0.100 °K

against a group of germanium resistance thermometers that have been cali- brated by reference to the T58 1958 helium-4 vapor pressure scale of temperature. Years of experience have shown that germanium resistors are

especially suitable for thermometry in this temperature region.

No facility has existed for the temperature range between 5 and 10 P K. When some time ago the Bureau undertook the development of a new method

of obtaining absolute temperature in this low range, the most promising

instrument was an acoustical thermometer. Absolute temperature would

be determined from a measurement with this instrument of the speed of sound in helium gas. Expectations for the acoustical thermometer have

been realized, and establishment of a calibration facility from 4 to 20 °K

is planned for late 1964.

Thermal Conductivity at Low Temperatures. The thermal conductivity of neodymium ethylsulfate was measured in the temperature range 0.02

to 0.05 °K using paramagnetic susceptibility and gama-ray anisotropy as thermometric parameters. This work may aid in developing useful methods

of temperature measurement below 0.3 °K. The thermal conductivity of paramagnetic single crystal materials at temperatures characteristic of transitions to the cooperative state is of theoretical interest. Superconducting Semiconductors. Studies of superconductive transi- tions occurring at temperatures below 1 °K in certain ordinarily semiconducting materials were undertaken in cooperation with the Solid-State Physics Section (page 83) . These transitions were predicted on the basis of the Bardeen-Cooper-Schrieffer (BCS) theory of superconductivity, and dur- ing the course of the NBS work were found in a number of materials. In

particular, various specimens of strontium tritanate (SrTi03 ) underwent such

transitions at temperatures ranging from 0.03 to 0.3 °K. A critical examination of the BCS theory of superconductivity is made possible by detailed knowledge of the energy-band structure of semiconductor materials. The

work was supported in part by the Advanced Research Projects Agency.

Magnetic Susceptibilities of Rare-Earth Trichlorides. Magnetic

susceptibility measurements on a number of rare-earth trichlorides at liquidhelium temperature and below gave results substantially different from the 76
known behavior of gadolinium chloride, which exhibits a ferromagnetic

transition at 2.2 °K. Other compounds studied were cerium chloride,

praseodymium chloride, neodymium chloride, and samarium chloride, all of which appear to become antiferromagnetic ; except for neodymium chloride, however, the evidence was suggestive rather than definitive. The

susceptibility of this chloride between 0.1 and 0.9 °K increased with in- creasing temperature; above 1.8 °K the reverse occurred. Two anomalous,

extremely narrow spikes exist between these regions—one at 1.03 °K and

the other at 1.75 °K. These spikes are extremely sensitive to an externally

applied d-c field—a field of 50 oersteds almost completely eliminates them.

Single crystals of samarium chloride could not be grown. However,

because the values are almost isotropic a polycrystalline sample was se- lected for study. Preliminary data obeyed the Curie law down to 1.7 °K

and showed an "antiferromagnetic" departure below this point.

Neutron Scattering From Oriented 165Ho Nuclei. The Bureau's

3 He cryostat was transported to the Oak Ridge National Laboratory for a

joint experiment by NBS and the ORNL Van de Graaff group. The ex- periment was designed to detect a possible spin-spin interaction between

a target of 165 Ho nuclei, polarized by low temperatures and a magnetic field from a superconducting solenoid, and incident polarized neutrons of 350

keV energy produced at the Van de Graaff generator by the 7 Li (p,n) reaction. A very small interaction was detected. Statistical Mechanical Calculations of Properties of Many-Body

Systems. Calculations relevant to the thermodynamic and transport properties of light gases, for which quantum effects are important, were made

using high-speed computers. Partly in collaboration with Los Alamos

Scientific Laboratory and Rice University, the quantum-mechanical second

and third virial coefficients for helium were computed. An important byproduct is increased insight into the relation of various approximation

methods. As part of a continuing program using the best available theory

to compute the thermodynamic properties of real gases, particularly at higher

temperatures, several computer programs were developed. Some, the de- velopment of which was partially supported by the Arnold Engineering

Development Center, analyze and correlate available PVT data for hydrogen

and deuterium and then compute the corresponding thermodynamic properties; another, developed with the support of the Air Force Special Weapons

Center, is relevant to the computation of the properties of a chemically

reacting gas. In a continuing program of basis research on the nonequilibrium behavior

of microscopic systems, partially supported by the Atomic Energy Commission, new general techniques for the calculation of transport coefficients of simple fluids were developed. On this basis, the first-order correction

in density to the transport coefficients (e.g., viscosity, thermal conductivity,

diffusion constant) of a hard-sphere gas is being computed. In connection

with this program, a review of the experimental data on transport coefficients, with particular emphasis on the critical region, was completed.

77
A new expression for the radial distribution function in terms of the probability density of the potential at two different points and a corresponding expression for the free energy were discovered. They were used to calculate the free energy and radial distribution function of a fully ionized

plasma according to a continuum approximation. This calculation and

corrections to it yielded new physical insights into previous work.

2.1.7. ATOMIC PHYSICS

The Bureau's atomic physics program is directed toward achieving a better understanding of the properties of atoms and molecules and of their inter- actions with electromagnetic radiation and with other particles. Spectroscopy

is a major tool in much of this work. The spectral range now available for these studies extends from the extreme ultraviolet wavelengths (100 A) into the microwave region (1 cm). Various problems in atomic and molecular

spectroscopy are under investigation, with emphasis on achieving the highest possible accuracy of measurement in order to permit the analysis of the

finest spectral details. The applications of an extremely high-resolution

electron scattering apparatus and of a far ultraviolet spectrometer employing

synchrotron light as a source yielded important new information on highly

excited states of atoms. Further insight into electronic levels in the crystal- line state was provided by the program in solid-state physics.

Intermediate Energy Atomic Physics, Atoms with excitation energies

from, roughly, 10 to 1,000 eV (intermediate energy) have been studied in the past only in a most fragmentary manner because of technical difficulties and lack of adequate tools of analysis. This type of excitation is normal in the high-temperature plasmas that exist in thermonuclear devices, in the up- per atmosphere, and in space. Two key analytical tools—namely, a far ultraviolet spectrometer utilizing

synchrotron light as a source for the study of absorption of 20 to 200 eV

photons and an ultra-high-resolution electron spectrometer for the study of 10 to 100 eV electron-atom collisions—were developed at NBS. Each of these

tools provided an independent opportunity to detect, measure, and analyze

atomic properties beyond the range of facilities available elsewhere. A coordinated effort among two groups utilizing these new tools and a

theoretical group has already led to observations of hundreds of new atomic

levels which exhibit properties that are absent or not relevant in other energy

ranges. Theory has been able to show how to identify these properties and

how to relate them to quantities of more general theoretical significance

(dipole and energy matrix elements)

.

The shape of the most prominent resonance in helium due to the twoelectron excitation of the 2s2p 1 P° state near 200 A was studied in detail with the synchrotron light spectrometer, and was found to be in good agree- ment with the theoretically predicted shape. In addition to the prominent

series of resonances found earlier in helium, several weaker series were

observed. In the continuum absorption of the heavier rare gases (krypton

78
Two key analytical tools, a far-ultra violet spectrometer using synchrotron light as a source and a high resolution electron spectrometer have provided a break- through in detecting and measuring atomic properties.

(Above) Scientists are adjusting the 180 Mev synchrotron used as a photon

source for the far ultraviolet spectrometer. The electron spectrometer (below)

provides a source of monochromatic electrons in the energy range from 1 to 100 eV. These tools detect, measure, and analyze atomic properties beyond

the range of facilities available elsewhere. (See page 78)
and xenon I . states representing the excitation of innersub-shell and innershell electrons were identified as were those due to the simultaneous excita- tion of two electrons. The synchrotron continuum was used successfully to observe high-lying

molecular electronic states in both neutral oxygen and nitrogen molecules. The vibrational structures of these new states were also observed. New complex negative ion states were discovered with the high-resolution

electron spectrometer in all the rare gases, in mercury, and in molecular

hvdrogen. hydrogen deuteride, and deuterium, demonstrating that such states are indeed a general property of atoms and molecules. These negative ion

states have an important effect on electron scattering from the parent atom

or molecule, and should lead to a more fundamental understanding of low- energy elastic and inelastic collisions. Some doubly excited states to which

optical transitions from the ground state are forbidden were measured by the electron scattering method.

The first excited negative ion state of helium produces a marked trans- parency for 19.3 eV electrons. This so-called helium window was successfully utilized both as an electron monochromator and as an electron energy

analyzer.

A second generation ultra-high-resolution electron spectrometer was constructed. It incorporates angular scanning of the scattered electrons, which

will permit even more detailed analysis of the mechanisms of electron scatter- ing and aid in the fitting of the new atomic states into a consistent framework

of contemporary theory.

Atomic Energy Levels. The observation and analysis of selected atomic

spectra continued, with emphasis on the lanthanide group of elements. In cerium ill. there are 2100 observed lines of which 75 percent were classified

in a new analysis. The first regularities in praseodymium (Pr ) I were found

from absorption data and Zeeman patterns. The line list for Pr I is essentially complete from 2,000 to 9,000 A. The hyperfine structure of Pr III was studied in detail, and a new value for the magnetic moment for Pr141 was obtained. Work is also in progress on cerium I and II. erbium I and II. and thulium I and n. A list of absolute gf values for 2000 lines of the astrophysically important

iron I spectrum was prepared by reducing a compendium of relative gf values

to the absolute scale of the NBS tables of transition probabilities.

The current revision of the 1928 edition of the solar table is nearing completion. Galley proof has been completed to 5,770 A, and press copy to 6.700 A. This work is being carried on in collaboration with M. Minnarert

and J. Houtgast at the Utrecht Observatory (The Netherlands).

Wavelength Standards. Work to obtain high-accuracy wavelength

standards in the vacuum ultraviolet region with the 35-ft vacuum spectrograph was begun. The first measurements of some neon and argon lines in the region 600 to 1.000 A are limited in accuracy only by the errors in the

best previously published wavelengths in this region. New wavelengths of neon I accurate to 0.0005 A were obtained. 80
The number of interferometric thorium wavelengths was increased from

200 to 430 in the region 3,300 to 6,900 A. Atomic Transition Probabilities, The determinations of atomic transition probabilities for the elements of interest in plasma and astrophysics are continuing with joint support of the Advanced Research Projects Agency

and the Bureau. The transition probabilities of the most important oxygen

lines in the visible and near infrared were precisely measured by the wall- stabilized arc method. Because of major technical difficulties, precision

determinations with this technique have been limited in the past to the

lighter elements. This year the technique was extended to the study of nickel by introducing nickel carbonyl gas into the arc chamber. Even though

nickel carbonyl is highly unstable and toxic, it was possible to operate the arc in a stable and reproducible condition for extended periods of time. The temperature at the arc axis was determined to be about 9000 °K, and

the transition probabilities of a large number of neutral and ionized nickel

lines are currently being measured. A similar experiment is under way for

sulfur, where the chemically aggressive sulfur dioxide gas is employed.

The measurement of the lifetimes of several atomic states in neon using a coincidence technique produced some very accurate transition probabilities of lines of the important 3s-3p array. These transition probabilities were

urgently needed for the data compilation of the first ten elements, which is in progress in the Data Center on Atomic Transition Probabilities. Theoretical studies resulted in the extension of modified Hartree-Fock

calculations to the determination of a large number of transitions in two-,

three-, and four-electron atoms and ions and selected carbon and neon ions. The transition probabilities for the first ionized spectrum of nickel were cal- culated and preliminary comparison with experimental determinations are very satisfactory.

Infrared Spectroscopy. High-resolution studies of the infrared

spectra of a number of molecules were carried out. These included various

isotopic species of acetylene, allene, methane, diborane, chlorocyanogen, and

others. The object of these measurements is to obtain accurate interatomic

distances and angles, as well as the constants which describe the nature of the molecular vibrations. In the course of this work, a number of higherorder effects were found which influence the vibration-rotation spectrum.

Such effects are of considerable importance in the theory of molecular vibrations. A scanning interferometer was placed in operation which permits spectra to be recorded at wavelengths as great as 500 microns. This instrument has

already been used to study the far infrared absorption spectra of several

liquids.

Microwave Spectroscopy. Encouraging progress was made in the very

difficult task of observing microwave spectra of highly reactive or short- lived molecular species. Microwave studies were made on several hightemperature systems, and detailed information concerning interatomic dis- stances, electric dipole moments, and quadrupole coupling constants was ob-81
tained on molecules such as the aluminum monohalides. Apparatus was

constructed which permits the measurement of microwave spectra of free radi- cals and other transient species produced in chemical reactions. The spec- trum of the SO radical was detected in the reaction of oxygen atoms with

various sulfur-containing compounds. This spectrum was analyzed to give accurate molecular contants for SO.

Experimental Atomic Collisions, A new instrument for the study oi the photodetachment of negative ions was completed. A photon beam inter- cepts a negative ion beam and the rate of removal of electrons from the negative ions is determined as a function of incident photon energy. The ions can be selected with 10 times greater resolution than previously available

in such experiments, allowing the study of more complex negative ions.

Initial priority will be given to negative ions of importance in the upper

atmosphere.

Electron Scattering in Solids and Liquids. A refined technique of Kikuchi-line diffraction with 80-keV electrons was evolved. The technique

gives direct measurements of elastic scattering amplitudes for carbon and

silicon atoms, in the small-scattering-angle region beween 10~2 and 10-1 radian. The method utilizes a conventional electron microscope with a tiny

High-resolution infrared spectrometer used to obtain accurate interatomic dis- tances and bonding angles, as well as the physical constants which describe the nature of molecular vibrations. (See page 81)

82
perfect single crystal of diamond or silicon as the optical resolving element

for an electron beam some 20 microns in diameter. Electron lenses magnify

the Kikuchi diffraction pattern, giving detailed high angular resolution of the lines from Bragg reflections. The widths of these lines, in turn, show

systematic agreement with the scattering amplitudes of these light elements

as calculated from the Born scattering approximation.

The quantities thus measured are of basic interest in the theory of electron

scattering, as well as being useful parameters for electron microscopy. The

technique shows promise for extension to higher energies (1 to 1.5 MeV)

on currently active high-voltage microscopes.

Measurements were begun of the energy losses of 10 keV electrons in liquid metals, complementing past NBS investigations of electron energy

losses in solids and more recently of energy losses in gases. The characteristic loss spectrum of liquid aluminum was found to be very similar to that of solid aluminum, as frozen from the liquid, with differences attributable

to density changes.

A liquid metal specimen drop was used in obtaining an atomically smooth

surface and then in retaining it on solidification. Large differences were found between the scattering characteristics of smooth solid aluminum sur- faces and the comparatively rough surfaces formed generally by evaporation of aluminum. For various electron scatering angles, and hence average

depths of penetration, it was possible to deduce the distribution of electron paths in the sample.

The determination of the complex dielectric constant of materials in the far

ultraviolet region (10 to 25 eV photon energy) from electron scattering data was carried out for aluminum and polystyrene. This method extends the

spectral range for which the dielectric constant can now be determined. Sums

of optical oscillator strengths were calculated for these materials. Field-Ion Microscopy. The field-ion microscope is capable of resolving

individual atoms both singly and when arranged in crystallographic planes.

This instrument was recently employed to study the mechanism of the con- densation of thermal tungsten atoms on a low-temperature tungsten surface. An atomically perfect tungsten surface was prepared and then tungsten atoms were evaporated onto the surface to a depth of about a monolayer. By

increasing the field at the tungsten surface it was possible to tear off the con- densed atoms a few at a time until the surface was again clean. A comparison

of successive photographs of the surface during the stepwise desorption of

the condensed atoms showed that the atoms were deposited in small piles. It was tentatively concluded that the tungsten atoms stick at the first site they encounter on the surface. Monte Carlo and statisical calculations based on

an idealized model verified this conclusion.

Solid-State Physics. In collaboration with the Cryogenic Physics Section (see p. 76) experiments were performed which established the occurrence

of superconductivity in strontium titanate. This phenomenon was predicted

from theoretical and experimental work of the Solid-State Physics Section, the Cryogenic Physics Section, and workers at the Bell Telephone Lab83
oratories, Murray Hill, N. J. The effect was measured both electrically

(resistance) and magnetically (susceptibility) at temperatures reached by

adiabatic demagnetization. Considerable effort was directed toward a study

of this effect and its dependence on conduction, electron concentration, stress, and crystal treatment. Other semiconducting materials are also being ex- amined for superconductivity.

A theoretical investigation of the electronic energy bands of strontium

titanate was completed. The detailed picture of the energy bands obtained

is in substantial agreement with the results of transport measurements, e.g., conductivity, Hall, and Seeback effects of doped and reduced strontium

titanate made over the range of 4.2 to 300 °K. The results are significant for the theory of superconductivity in this semiconductor, as well as for an understanding of the semiconducting properties. Analysis on transport

properties of rutile, particularly the Hall coefficient anisotropy, support the hypothesis of multiple conduction bands. This explanation is consistent with theoretical band structure calculations. A nuclear magnetic resonance study of potassium azide (KN3 ) was completed and the quadrupole coupling tensors for all of the nitrogen sites in the crystal were determined. Frequency shifts of the fluorine and rubidium

nuclei in the antiferromagnetic compound RbMnF3 were observed and re- lated to the covalent bonding of the crystal.

The study of impurities in rutile by paramagnetic resonance was con- tinued and led to the observation that tungsten can be substituted for tita- nium. Hyperfine and superhyperfine structure lines were identified. The

experiments utilized the high permittivity rutile sample as its own micro- wave cavity.

Photoconductive studies on cadmium sulfide (CdS) at wavelengths near

the absorption edge resulted in observation of quenching and enhancement

peaks which are identified with exciton and interband transitions. A precise

measurement of the temperature dependence of the bandgap was obtained

through this technique.

Optical absorption studies were performed on doubly ionized cobalt (Co2+

) ions in manganese fluoride. The spectrum was interpreted in terms of energy levels of the cobalt ion as modified by the local anisotropic crystal

fields. Color centers in magnesium fluoride were produced by exposure to x rays and electron bombardment. Optical bleaching and polarization studies are

in progress.2.1.8. PHYSICAL CHEMISTRY

The Bureau conducts an extensive program of experimental and theoretical research in physical chemistry. Integrated with this program are activities directed toward the development of new instrumental techniques and the compilation of critically evaluated fundamental data. The primary research objective is a better understanding of the detailed molecular basis of macroscopic chemical properties and processes. Atten- 84
New platinum-lined adiabatic solution calorimeter makes possible the measure- ment of the heat of solution of refractory materials by corrosive solvents. The

elaborate automatic control system for the adiabatic shield permits the calorimeter to operate with high precision at temperatures up to 100 °C. (See page 85)

tion is focused on two fields: (1) molecular structure, including structure of

short-lived reactive species; and (2) the kinetics of elementary reactions,

including reactions of neutral and ionic species, and interactions of gases with well-characterized surfaces. Supporting theoretical work is carried out on the calculation of molecular structure and energy levels, on energy

transfer in molecular collisions, and on transport phenomena.

Thermochemistry. Construction and preliminary testing of a new

platinum-lined adiabatic solution calorimeter was completed. This instru- ment, together with its energy- and temperature-measurement system, was

designed to measure the heat of solution of refractory materials by corrosive solvents such as aqueous hydrofluoric acid. An automatic control sys- tem for the adiabatic shield permits operation of the calorimeter with high

precision at temperatures up to 100° C, thus enabling measurements of many

reactions that are too slow for calorimetry at room temperature.

85
A publication summarizing the available thermochemical data on aqueous

univalent electrolytic solutions was prepared. It contains an analysis of

all the available data on the heat capacities and heats of dilution and solu- tion of a number of acids, bases, and salts. It also presents, in tabular form,

values of the heats of solution at 25° C and the apparent heat capacities and

apparent relative heat contents (as functions of concentration) of more than

60 different substances. Surface Chemistry, Carbon monoxide on niobium was studied with a

field emission microscope operated at liquid helium temperature. The

absence of surface migration from the chemisorbed layer was ascribed to the

existence of both a weak and a strong binding state. The weak state desorbs

before migration, and the strongly bound state desorbs at higher temperatures. Molecular clustering, which mottled the field emission pattern by

local field enhancement, appears to be related to surface defects of the niobium

emitter. Field emitters with a prescribed orientation were fabricated from single

crystals of tungsten by means of a spark erosion technique. Adsorption

studies on these emitters aid in evaluating the averaging process effect on work function determinations.

Flash desorption of carbon monoxide from single crystal ribbons of tungsten showed that the low energy state of chemisorbed carbon monoxide

has a higher population density than the higher energy state on the more

closely packed tungsten planes.

Infrared spectroscopy was used to investigate the matrix isolation of

free radical species. The infrared spectra of matrix isolated HO_>, CF2 , and

other species were obtained for the first time. The assignment of fundamental

vibration frequencies led, in some cases, to an evaluation of the configuration of free radical species.

Chemical reactions in the 77 to 90 °K range between atomic hydrogen

and condensed olefins were observed. After establishing the mechanism of the process, the investigators found that the disproportionation-combination

reactions of hydrogen with s-butyl radicals could be followed in great detail. Bond strengths in various hydrocarbon free radicals were evaluated by

observation of the rate of atomic hydrogen addition to each end of the

olefin double bond. An apparatus was devised for measuring the rate constant of atomic hydrogen addition to a condensed olefin. Isotope Effects. Isotope effects (differences in the behavior of isotopically labeled and nonlabeled molecules) are being used to test and extend

current theories of reaction mechanisms. Study of these effects in the oxidations of normal and tritium-labeled aldoses led to a clarification of the reactions of aldoses with bromine and with chlorites. Solvent isotope effects for D-glucose and D-fructose in water and deuterium oxide showed conclusively that the so-called alpha-beta pyranose interconversions and the pyra- nose-furanose interconversions take place by similar acid- and base-catalyzed

mechanisms.

86
Stereochemistry and Structure. A new sugar, 7-acetamido-7-deoxyL-galacto-heptopyranose, was synthesized and its structure established. The

sugar exhibits mutarotation and shows marked similarity to the structurally related sugars, D-fructose and perseulose.

It was found that the bis (phenylhydrazino) derivatives of triones exist in two modifications, one yellow, one red. Ultraviolet, infrared, and nuclear

magnetic resonance studies showed that the yellow form had the conventional

phenylhydrazone structure, and the red form, an unusual hybrid hydrazoneazo structure in which the imino hydrogen is united in a pseudo-aromatic ring.

Air Pollution. Under the sponsorship of the U.S. Public Health Service, a critical review was prepared on the oxidation of hydrocarbons that are commonly discharged into the atmosphere. Methods were devised to study

the interaction of the hydrocarbons with oxygen, nitrogen oxides, and

other atmospheric constituents. It was observed that photochemical oxidation

of certain polycyclic aromatic hydrocarbons takes place during thin-layer

chromatography. This observation led to the study of the oxidation of the hydrocarbons adsorbed on particulate matter. At least 10 products were

obtained by photochemical oxidation of pyrene adsorbed on silica gel and

on alumina.

Aldehydes and ketones are regarded as important air pollutants; hence,

their photochemical behavior in the presence of oxygen is also being studied. The interplay of the effects of energy transfer, phosphorescence, fluorescence,

and decomposition was investigated for systems which involve n-butyraldehyde, acetone, biacetyl and other carbonyl compounds.

Molecular Spectroscopy. As part of a broad effort to investigate the physical and chemical behavior of molecules in crystalline environments

at low temperatures, studies of photodecompositions, molecular motions,

and fluorine reactions are underway. The flash photolysis of molecules

trapped in solid argon near 4 °K was successfully carried out in research

supported by the Atomic Energy Commission. A new type of end-on flash tube was developed that is capable of emitting 1019 photons over a broad

spectral range in a single 30-microsecond pulse.

Experiments on molecular motions and interactions at low temperatures

showed that carbon monoxide molecules isolated in solid argon are capable

of rotational motion even at 4 °K. In a parallel study the effects of molecular

perturbations in quenching the rotation of hydrogen chloride molecules were demonstrated.

In research supported by the Advanced Research Projects Agency

(ARPA), the spectra and reactions of nitrogen-fluorine compounds were

studied at low temperatures in noble-gas matrices. In related high-temperature studies, the electronic absorption spectrum of yttrium monofluoride was

obtained and its vibrational and rotational constants were established. In

other ARPA-supported work, the bent configuration of the high-temperature

species ALO was deduced from an analysis of its infrared matrix spectrum.

Shock-Wave Studies of Unimolecular Reactions. Continuing in- vestigation of a single-pulse shock-wave heating technique for the study

756-224 0—65 7 87
of fast chemical reactions resulted in a new method for measuring the

relative rates of two reactions. In this method, two compounds are de- composed in the same reflected shock, and the relative decomposition rates are determined from the relative extent of unimolecular decomposition.

In these studies, the decomposition of isopropyl bromide to hydrogen

bromide and propylene was used as a "standard" reaction, because its rate

is considered well established, and the rates of other unimolecular reactions were referred to this standard rate. The relative decomposition rates of a variety of alkyl halides thus obtained showed that the technique affords a significant increase in the precision of shock tube kinetic studies. For

example, relative activation energies could be obtained to about 200

cal/mole.

Diffusion Coefficients Determined. As part of a fundamental investi- gation of the important processes occurring in gas chromatography, an

accurate technique was devised for determining binary gaseous diffusion

coefficients to a precision of 0.5 percent over a temperature range of from

77 to 373 °K. In this technique, the spread of a Gaussian concentration peak

of one component in a carrier gas (the second component) is measured

as the carrier gas flows through a long tube. Detectors stationed along the

As part of the U.S. Public Health Service program, NBS is developing methods to measure accurately and determine the interactions of the constituents of polluted

air. The chromatogram shows the separation of products from photochemical

oxidation of pyrene, one of the important pollutants. (See page 87)

88
tube record the change in peak shape as a function of time and distance. Measurements thus far made on oxygen, nitrogen, argon, neon, and krypton

diffusing in helium show good agreement with published data obtained

by other methods.

Mass Spectrometry. A mass spectrometer was built to study atomic

and molecular photoionization processes out to an energy of 20 eV. In

investigations of rare gases, and hydrogen, acetylene, and benzene, and their deuterated analogs with this device, precise information was obtained on

ionization potentials, isotopic effects on molecular ionization potentials,

and on the location and importance of autoionizing levels in atomic and

molecular systems.

An instrument that permits direct observation of individual molecular

ionization events produced by medium energy (1 keV) electrons was also constructed. The device was used to determine the relative amount of vari- ous charged species produced by electron impact, and to study the fragmentation of multiple charged molecular species. In studies carried out on

carbon dioxide, methane, carbon tetrafluoride, and propylene, a number

of distinct processes were found to occur. These processes involve the in- stantaneous decomposition of an ionized molecule into two charged frag- ments traveling with several electron volts of kinetic energy. Mass Spectrometric Reaction Kinetics, A mass spectrometric

method, developed to investigate the rates of very fast atomic reactions, was

used to study the reactions of nitrogen oxides with atomic oxygen. With

the use of oxygen 18 isotopes, it was found possible for the first time to de- termine the rates of a number of oxygen atom isotope exchange reactions

with molecular oxygen, nitric oxide, and nitrogen dioxide.

Vacuum Ultraviolet Photochemistry. The fragmentation mechanism

of a simple molecule upon absorption of a large quantum of energy just below

the ionization potential is being studied by vacuum ultraviolet photochemistry. For the first time, successful experiments were conducted in hightemperature (up to 400 °C) vacuum ultraviolet photolysis of ethane in the 1,200-A wavelength region. The photolysis of ethane in solution in liquid

nitrogen was also accomplished at 1,470 A and 1,236 A. During the year, and argon resonance lamp of high chromatic purity (1,048 A and 1,067 A)

and of moderately high intensity (>1014 quanta/sec) was developed for use

in these experiments.

Radiation Chemistry. The fragmentation mechanism of a molecule re- ceiving energy in excess of its ionization potential and the resulting frag- ments are studied by radiation chemistry. The technique was used to measure the cross sections or rate constants of hydride transfer, charge transfer,

and proton transfer reactions. The effect of an applied field upon gas- phase radiolysis was also studied. This technique provides an independent measure of the relative contributions of neutral excited species and ionic

species to the total chemistry.

89
2.1.9. LABORATORY ASTROPHYSICS

The Joint Institute for Laboratory Astrophysics (JILA) at Boulder, Colo.,

is a collaborative effort of the National Bureau of Standards and the University of Colorado. The purpose of the Institute is to provide a center for ad- vanced research and training in physics related to measurements of the properties of very hot gases. The participants, in addition to graduate stu- dents, are members of the NBS Laboratory Astrophysics Division, members

of the science and engineering faculties of the University, and eminent scientists participating on one-year appointments under the NBS-sponsored Visit- ing Scientist Program. Research areas include astrophysics, atomic physics,

aerodynamics, and statistical mechanics. During the past year very sig- nificant collaborative scientific efforts were developed among members of all of the groups participating in JILA. The activities of the NBS Laboratory Astrophysics Division have been

concentrated in the study of the physics of stellar atmospheres, the study of the physics of atomic collisions, and the study of atomic structure and inter- actions by special optical techniques, such as those using lasers. Participating in the support of the research of the NBS Group in JILA

are the Atomic Energy Commission, the Office of Naval Research, the Army

Research Office (Durham), Sacramento Peak Observatory of the Air Force Cambridge Research Laboratories, and the National Aeronautics and Space

Administration. Virtually all of the work reported here is in collaboration

with students and staff of the University of Colorado. In addition there are

joint research programs with the Sacramento Peak Observatory, the Nice

Observatory, the University of Hawaii Geophysical Institute, and the High

Altitude Observatory.

Astrophysics. During the past year, the astrophysics program within

JILA continued to emphasize the development of the analytical methodology

for quantitative spectroscopic measurements in hot gases. Programs in solar astrophysics were aimed at testing these diagnostic techniques in astronomical

observations—for astronomy offers the most extensive laboratory available. The primary effort is attempting by this means to understand solar features more satisfactorily. The program of collaborative investigation of aerodynamical phenomena in the solar atmosphere by aerodynamicists and astro- physicists continued, and the same kind of systematic investigations into stel- lar atmospheres began.

Spectroscopic Diagnostics. Work on spectroscopic diagnostics pro- gressed in two main directions: the development of broader and more precise

methods for solving the radiative transfer equation over the entire line profile

to give a more complete picture of the extent of non-LTE (local thermodynamic equilibrium) effects both within the gaseous ensemble and across the

spectral line; and the study of the problem of local and nonlocal effects on

the state of a gaseous ensemble, particularly as it affects the diagnostic

problem. In the first direction, parallel progress was made by Visiting

Fellows of JILA in collaboration with the Harvard-Smithsonian group and

90
Graduate student studies cross sections for proton excitation of gases important

in the theory of the aurora. This work is part of the JILA program sponsored

jointly by NBS and the University of Colorado. (See page 92)

by members of the Paris Observatory group with whom JILA is closely associated. Solar Studies. In collaboration with the Sacramento Peak (Sunspot, N. Mex.) and High Altitude (Boulder, Colo.) Observatories, work continued on the compilation of data taken during the 1962 eclipse. A prototype

photoelectric observation of the continuum on either side of the Balmer

limit was earried out during the 1963 eclipse in preparation for more extensive observation of the 1965 eclipse. In collaboration with the Sacramento

Peak Observatory, investigation continued of the mass and energy require- ments to maintain the coronal loop prominence system. A program of non- LTE abundance investigations was started in collaboration with the Paris

Observatory group. Detailed studies of individual lines in the solar spec- trum continue.

JILA is engaged in plans for two scientific -expeditions to the May 1965

total eclipse of the sun in the South Pacific. The project is supported in part by the Sacramento Peak Observatory and by NASA. One of the ex- peditions is in collaboration with St. Johns Observatory, New Zealand, and

the University of Pennsylvania Department of Astronomy. Two similar photoelectric spectrographic instruments to be used during the eclipse are being constructed. The scientific objectives are based on the very precise

height resolution obtainable at an eclipse and* to a lesser (but real) extent, on the low background sky emission. The spectral regions to be covered

91
involve continuum measurements to the red and blue of the Balmer and

Paschen discontinuities, i.e., the helium lines at wavelengths 5,876, 6,678, and

4,686 A, the coronal red and green lines, and continuum measurements at 1.6 and 2.25 /x. The chosen spectral regions span a range of excitation in the chromosphere in order to permit analysis using data which will give most

sensitive indications of temperature changes. In addition, this type of ex- periment will also yield (slitless) spectral data at the extreme edge of the sun on a number of wavelength regions.

Stellar Atmosphere Studies. The investigation of sources of stellar in- stabilities leading to aerodynamic motions continues, mainly through collab- oration with the University of Colorado Departments of Physics and Astro- physics and Aerospace Engineering Sciences. Efforts are presently concentrated on the study of variable stars generally and the Cepheids particularly; the latter project, in collaboration with the staff at Los Alamos, is aimed

at mapping the region of pulsational instability. Preparations were started for a 1965 symposium on this subject, with the secretariat at JILA. # The

symposium will be sponsored by the International Astronomical Union and

the International Union of Theoretical and Applied Mechanics, and will be

held in France at the Nice Observatory. Work also began on a more careful inclusion in astrophysical theory of the radiative loss from aerodynamical

energy dissipation in an effort better to understand the effects on atmospheric

structure. The non-LTE radiative transfer investigations mentioned in the

section on Solar Studies are used. The program of investigating the calcium n H and K lines in stars of a range of spectral types continued in collaboration with the Kitt Peak Observatory—University of Arizona group. Some investigations of novae and emission lines in stellar spectra were initiated in collaboration with the Paris Observatory group. The latter efforts are initially aimed at separating

non-LTE and aerodynamic heating from geometrical sources for emission

lines. Under way is an investigation seeking to explain the anomalous behavior

of certain rare-earth lines in the solar spectrum. These lines, which are observed in the wings of calcium H and K lines near but inside the solar limb, appear in emission relative to the local background. This study has

a bearing on the question of departures from local thermodynamic equilibrium in the solar photosphere and if successful would lead to revised values of some rare-earth abundances.

Physics of Atomic Collisions. A detailed calculation was made for photodissociation of positive ions of molecular hydrogen and deuterium.

Measurements of this cross section are in substantial disagreement with

the calculation. An explanation of the discrepancy may lie in possible

anomalous populations of the vibrational levels of the ions due to autoionization. Such effects have been indicated by work on photoionization molecular hydrogen at the NBS Washington Laboratories. This possibility is being explored and the experiment is being improved to give better accuracy

for comparison. This work is supported by the Atomic Energy Commission.

92
Experimental studies of the stripping by hydrogen gas of two electrons from the negative ions of hydrogen and deuterium were carried out. These

relative measurements as a function of energy join smoothly to Russian

work at higher energies. A surprising result, however, is that the deuterium

ion cross sections are larger than the hydrogen ion cross sections when the ion velocities are the same. Other ion-molecule collisions are being investi- gated to see if a similar isotope effect exists. A calculation of the free-free absorption coefficient of H— was completed

using 10-parameter e-H elastic scattering wave functions. The results are more accurate than the previous values, which have been widely used by

astrophysicists.

The compound (or autoionization) state energies for H- and He were

evaluated by a variational method. Excellent agreement was obtained with

the experimental results from NBS Washington, and new level positions were

evaluated. The mechanism of gas breakdown by means of intense laser beams is under investigation. Both classical and quantum treatments of the absorption of radiation by free electrons are being applied.

The theory of the rotational excitation of diatomic molecules by slow

electron impact is being improved by an application of the method of dis- torted waves. The discovery of large maxima in the rotational cross sections should allow a more reliable interpretation of experiments involving swarms

of electrons in diatomic gases.

This newly constructed crossed beam apparatus permits the study of the inter- actions of particles with those that are inherently unstable in nature. For

example, it will be used to study electron and photon interactions with ions and metastable atoms. (See page 92)

93
An experimental study of the excitation of radiation from hydrogen atoms by electron impact showed that the cross section for excitation of the lowest

optically allowed hydrogen transition has an anomalous behavior for the lowest electron energy capable of exciting it. Apparently the cross section

rises discontinuously, or nearly so, to a finite value at the threshold energy. This behavior has not been observed previously and will play a significant

role in understanding the production of radiation in the solar atmosphere

and in hot gases in general. The anomaly is presumably related to the permanent dipole moment of the hydrogen atom which results from the near- degeneracy of the two lowest excited states of hydrogen.

Plasma Transport Properties. A notable advance in high-precision

measurement if ion mobilities in gases was substantiated with the completion

of a detailed study of helium ion mobility in helium gas. The results led to a new method of measurement of ion-molecule reaction rates, and

the rate of the three-body reaction of atomic helium ions to form ions of the diatomic molecule was determined to an accuracy of a few percent, which

is rarely achieved in conventional chemical kinetics. The technique is now

being applied to the study of ion-molecule reactions involving negative ions, in view of the importance of these reactions in ionospheric physics.

Resonance Physics, Reliable measurements of absolute oscillator strengths for resonance lines of ions are difficult to obtain by conventional

techniques because of self-absorption of the resonance radiation and uncertain values of the ion density of the emitting plasma. An experimental pro- gram was initiated to measure lifetimes of ions of astrophysical interest by a technique which eliminates these difficulties; the technique involves a study

of the angular distribution of resonance fluorescence as a function of applied

magnetic field (Hanle effect)

.

Some attention was given to the factors that enhance spectral brightness

of ruby ^-switch lasers with the aim of obtaining as near "single-mode"

operation as feasible. This property is a necessary prerequisite for meaningful study of nonlinear optical behavior, such as stimulated Raman scat- tering, multiphoton absorption, and optical harmonic generation. The

Stokes Raman-shifted laser output from various liquids was used to study

the wavelength dependence of two-photon absorption and related nonlinear

processes in anthracene crystals. In addition, some effort was invested in high-stability gas laser sources for long path interferometry and measure- ment of millimeter wave difference frequencies between two gas laser spectral

lines. Physical Constants. A 30-meter vacuum Fabry-Perot interferometer is being set up in an unused gold mine near Boulder, Colo. Path stability

checks and a high-precision measurement of the path lengths are planned.

This instrument may be used in a laser velocity-of-light measurement if it appears that the long path will lead to susbtantially higher accuracy than can be achieved in a shorter path device. Work on a possible xenon laser wavelength standard for use with the long interferometer was started, and

the Lamb dip in one of the possible lines was observed. 94
Crossed beam apparatus for the study of interactions of light beams with ions. Current work includes photodissociation, and proton impact excitation studies. (See page 92)

A falling interferometer to measure the acceleration of gravity was de- signed. The question of a suitable release mechanism was solved and construction started. Data Center on Atomic Collision Cross Sections. The Data Center has issued a bibliography of data on low-energy (<10 keV) electron colli- sion cross sections. About 600 copies were distributed to research workers

in the areas of atomic and plasma physics and astrophysics. At the present

time, a critical review of data on electron impact ionization cross sections for atoms and diatomic molecules is being prepared.

2.1.10. RADIATION PHYSICS

The radiation physics research program of the Bureau is directed toward

obtaining basic experimental and theoretical data in the areas of radiation

interactions with nuclei, atoms, molecules, and bulk matter ; the development

of improved techniques and instruments for the detection and measurement

of radiation; and the investigation, development, and improvement of radiation sources and standards. Expanding applications of radiation in industrial processing have created a need for improved standards and dosimetry at high dose levels and at high

energies. Persons conducting research on the nature of the interactions be- tween radiation and materials are requesting more accurate cross sections. Improved accuracy in the determination of source output and absorbed dose

is required by medical radiologists.

95
Considerable effort was devoted to preparation for the implementation of an enhanced research program that will be made possible by a new lab- oratory building now nearing completion. New high-intensity sources, such

as the 1.5- and 4-MeV direct accelerators and the 100-MeV linear accelerator,

will enable the Bureau to satisfy many of the increased requirements. The

compilation and evaluation of critical data began in the areas of electro- magnetic and photonuclear interactions. Programs were initiated on the

investigation of low-level radioactive contamination in materials and on the

calculation of energy dissipation by fast electrons and associated gamma

radiation for given source and medium configurations.

Dosimetry

Cavity Chambers. Instruments used as laboratory standards for x- and

gamma-ray measurements by medical institutions, research laboratories,

manufacturers, atomic energy installations, the Military, and Civil Defense

are calibrated using the Bureau's x-ray and gamma-ray standards. The

accuracy of the measurement of the beams used in these calibrations is pres- ently better than 2 percent. During the past year, a toal of 102 calibrations was performed.

Effects of cavity-chamber geometry on the measurements of gamma-ray

beams used to calibrate secondary standard exposure meters were studied to find the corrections required for conversion of cavity-chamber measurement

data to exposure units. A collimating system for the high-exposure-rate cobalt 60 source was

constructed, and the rectangular beam obtained was calibrated. The system

permits calibration of instruments of ranges higher than 25 roentgens, under

controlled irradiation conditions. Leakage and stem effects in condenser R-meter chambers used as secondary standards were studied to develop

calibration procedures. Further study is needed to reconcile the measured

stem effects with the differences observed between calibrations for different irradiation conditions.

Photographic Dosimetry. Studies on enhancing x- and gamma-ray

responses in several photographic dosimetry emulsions included hypersensitization with certain salt baths, latensification by means of chemical treat- ments or post-exposures to selected narrow bands of light, special development procedures, and combinations of these. The study of special development procedures for reducing the energy dependence of dosimeter-film response to x and gamma radiation in the range from 0.025 to 1.25 MeV

continued. A reduction in energy dependence by over a factor of 2 was

achieved at the expense of some loss in sensitivity.

Characteristics of commercial x-ray dosimetry films exposed to photons of widely different energies were compared for processing in phenidone-thiosulfate monobaths and in x-ray and phenidone developers. For routine

dosimetry applications, monobath processing has the advantages of little dependence of response on processing time and temperature and, because of lower contrast, extended useful exposure range. Difficulties due to rate 96
dependence are more likely to occur, however, and film sensitivity is reduced.

Processes leading to solarization and other rate-dependent photographic

effects were investigated. The study of the total silver content of developed

photographic emulsions, concentration of silver grains, and grain structure was completed.

Solid-State Dosimetry. Comparative measurements were made to deter- mine the sensitivity, energy dependence, and voltage dependence of the response to x rays of diffused p-n junction, p-i-n junction, and surface-barrier- type silicon radiation detector cells. Measurements were limited to energies

of less than 250 keV to avoid radiation damage possibly produced in silicon by radiations of higher photon energy. Photocurrents observed in p-i-n junction cells were larger and showed a

smaller increase with increasing bias voltage than photocurrents measured in p-n junction and surface-barrier cells at the same exposure rate and with the same irradiated cell surface area. However, because of their smaller zero- voltage resistance, p-i-n junction cells have larger dark currents and may

show a smaller photovoltaic sensitivity than cells of other types when operated

with higher load resistances or under open-circuit conditions. When either a forward or reverse voltage was applied to the commercialtype surface-barrier cells, most of them showed similar, nearly symmetrical

current-voltage characteristics. This similarity apparently was due to the

existence in such cells of two opposing voltage barriers which are alternately

reduced or increased when a bias voltage is applied in these two different directions. Consequently, the photocurrent showed a reversal with reversing

bias voltage and the photovoltaic sensitivity was negligibly small. Surfacebarrier cells showing such performance characteristics can be used only as photodiodes.

The dependence of the photocurrent on the quality of the x rays (energy

dependence) was found to be similar for the three cell types investigated,

and changed only slightly when moderate bias voltages were applied.

Response of Hurst Neutron Dosimeter. Recently, the fast neutron dose

distribution in water from a D

3 He source was measured. The energy

response of the Hurst proportional counter dosimeter used in the measure- ments did not follow the predictions of the original paper describing the instrument. An investigation showed that an incorrect spectrum had been

assumed for the recoil particles incident on the cavity. A simple corrected

calculation led to much better agreement with the experimental measurements, and a more sophisticated calculation for the response of spherical and

cylindical counters of this type in an isotropic field was completed.

X- and Gamma-Ray Standards. Several years ago the National

Bureau of Standards designed, constructed, and calibrated some ionization

chamber transfer instruments for the Bureau International des Poids et Mesures (BIPM). Since that time, a number of large laboratories and

clinics have expressed an interest in such instruments, and the BIPM has

recommended that each national laboratory obtain its own transfer instru- 97
ment so that all could be intercompared at BIPM. On the basis of this broader need, one instrument was redesigned in a cooperative program ar- ranged with F. R. Shonka of St. Procopius College, Lisle, 111., who contributed knowledge of conducting plastics and molding techniques.

One model of the new version, with an outer wall thickness of 2.5 mm,

can be used to measure 60 to 250 kV x rays and cobalt 60 and cesium 137

gamma rays with a variation in calibration factor of about 4% percent.

Another model, with a wall thickness of 0.25 mm, can be used to measure 60

to 250 kV x rays with a variation in calibration factor of about 3 percent.

For repeated calibrations, the range of calibration factors for any one quality of radiation is about 0.3 percent.

Recently a need has arisen for the calibration of instruments used by

medical institutions, research laboratories, and others for the measurement

of very soft x rays produced by 10 to 15 kV. Accordingly, a free-air chamber standard for the measurement of x rays produced by 10 to 60 kV was

constructed. Comparison with the NBS "low" energy standard, used for measurement of x rays generated by 20 to 100 kV, in their overlapping range gave an agreement, on the average, to 0.3 percent. The estimated

maximum inaccuracy is about 1 percent.

Radioactive Sources

Standards of Radioactivity. The sum of standards sold and calibra- tions performed exceeded 650. Radioactivity standards developed and pre- pared for distribution included tritiated ( hydrogen 3-labeled ) toluene, stron- tium 89, cerium 141, cesium 137-barium 137m (gamma-ray point source for gamma-ray spectroscopy), and americium 241. International comparisons were conducted of the radionuclides strontium-yttrium 90, americium 241,

and cobalt 60 (solid sources), distributed by the Bureau International des Poids et Mesures; cesium 137-barium 137m, distributed by the International

Atomic Energy Agency.

CONDUCTING

-.500- A h 12-

Cross section of NBS model of a portable ionization chamber for use in the

international standardization of radiation measurements by the International Bureau of Weights and Measures. The instrument measures 60 to 250 kV

x rays as well as cobalt-60 and cesium-127 gamma rays. (See page 97)

98
A new, precise method for diluting highly volatile liquids was used to prepare tritiated toluene which when compared with previously standardized tritiated water by liquid scintillation counting gave a standard deviation

of 0.1 percent.

Four radiochemical procedures, suitable for the determination of actinides

at the 0.1 MPC (maximum permissible concentration) level were evaluated

under the low-level radioactivity program, supported partly by the Atomic

Energy Commission. A new method of low-level radioisotope dilution analysis was developed and applied to cerium 144. Low-level intercomparisons

of cerium 144 in spinach (sponsored by the International Atomic Energy

Agency) and in radium 226 in water (sponsored by the Public Health Service) were carried out. Spectrometer for Neutron Source Studies. The energy range of greatest uncertainty in the use of neutron sources as standards is below 2 MeV,

where most spectrometers do not work or work poorly at best. A proton

recoil spectrometer using a methane proportional counter as radiator and a

silicon junction detector as the major energy detector is being developed.

Preliminary results indicate that the instrument will be useful down to at least 0.5 MeV, and will exhibit the low gamma sensitivity required for spectral

measurements of sources, such as the NBS standard Ra-Be(y,ft) source, having high gamma emission rates. Radiation Interactions with Nuclei

Fast Time-oj -Flight Measurements of Neutron Cross Sections. After

interaction with the nucleus under study, neutrons of differing energies are separated by measuring their flight times from target to detector. With one

technique (Mobley system) , the neutrons are produced in bursts and the time

of detection relative to the incident neutron burst is measured; with the other, a charged particle produced at the same time as the neutron is used as the time reference. A Mobley time compression magnet system installed on the Van de Graaff accelerator produced 0.8 microsecond proton pulses of about

360 microamperes. The charged particle technique was refined by improving

the time resolution to about 1 microsecond and developing n-y discrimination

compatible with fast time of flight. Nuclear Size Determinations from Coherent Neutral Meson Photoproduction. An extensive series of measurements on nuclear matter distributions by coherent 7r° photoproduction were completed for lithium, beryllium,

carbon, oxygen, magnesium, aluminum, silicon, sulfur, calcium, and copper. The nuclear matter radii were determined with an accuracy of about

0.2 X10 13 cm and agree well with nuclear size determinations by other

techniques, such as elastic electron scattering.

Nuclear Theory. A dynamic theory of the nuclear collective model was

developed in which the rotation-vibration model and the hydrodynamical

dipole-oscillation model are unified. A coupling between the dipole oscilla- tions and the quadrupole vibrations is introduced in the adiabatic approximation. The dipole oscillations act as a "driving force" for the quadrupole

vibrations and stabilize the nucleus in a non-axially symmetric equilibrium

99
Flask and sample container used for the new dilution technique developed for standardizing tritiated toluene. (See page 98)

shape. The dipole operator is established in terms of the collective coordinates, and the gamma absorption cross section is derived. Calculations are in progress to determine nuclear energy levels and wave

functions, according to the shell model, for nuclei with atomic weights be- tween 17 and 40. The computational difficulties are being reduced through

the application of group-theoretical methods involving the group SU8 . A

further test, through the study of elementary particle reactions, indicated large

violation of SU3 symmetry. This discrepancy could be accounted for by the presence of a large amount of octal symmetry braking (configuration inter- action) . A series of super resonances in the baryon resonance-meson systems were predicted as a result of this analysis.

100
Elementary Particle Theory. The role of unitary symmetry (SU3 ) in the classification and description of the various elementary particles was explored in detail. A particularly successful test was developed

in the form of a sum rule for trie cross sections of some 7r+ and K+ initiated processes. The difficult problem of comparing reactions

which involve projectiles of different incident energies and which have

a varied assortment of initial and final states was solved by a two-step

process. Satisfactory agreement was obtained between theory and experiment, and the assumption of unitary symmetry in strong interactions was

deemed valid. Photonuclear Cross Sections. The experimental program concentrated on measurement of the photoneutron yield cross section for light nuclei

( 10B, "B, 6Li, 7 Li, and 3 He). Although only a preliminary analysis of

the data for the boron and lithium isotopes was made, there appear to be

a number of previously unobserved significant and unexpected features

in the cross sections. Results of this experiment will contribute to the field of photonuclear reactions. Data obtained with a neutron detector in its early stages of development already shed considerable light on the dis- crepancies now existing in the magnitude of the photoneutron cross section. Detector for Photonuclear Reactions. One of the few systematic ex- perimental studies of the response characteristics of a 47r-neutron detector

of the type used throughout the world for measurements of photonuclear

cross sections was completed. Preliminary analysis of the data indicated

the probable source of the discrepancies that now exist in various measure- ments of photoneutron cross sections. The characteristics of semiconductor radiation detectors were investi- gated in detail to determine their usefulness in photonuclear reaction studies. Significant technological advances were made in extending the length of

silicon lithium-drift detectors. Measurement of the response of semiconductor radiation detectors as a function of temperature down to 4.2 °K

resulted in the discovery of an anomaly which may have interesting ther- mometry applications.

Nuclear Spectroscopy, New techniques allow beta-ray spectroscopy

with oriented nuclei to be accomplished with considerably higher resolu- tion than possible heretofore. These techniques were applied to the meas- urement of matrix elements in two forbidden beta-ray transitions in cerium

141. Extensive calculations related the experimental results on cerium 141

with theoretical predictions based on gage invariance principles.

New Linear Accelerator, Installation of the linear accelerator (Linac)

in the new Radiation Physics Laboratory at Gaithersburg, Md., began in April. Almost all major components of the accelerator are now in place,

with plumbing and interwiring well under way. Various subsystems being

installed include an inspection and warning system, a complex alarm, a remote TV monitoring system, a radiation monitoring system, and an

intercommunication and announcing system.

101
Magnet Testing Program. A magnet-testing program, utilizing heavy

ions produced by a 400 keV Van de GraafT accelerator to accurately simulate

electrons from the linac, made possible comparison of the actual behavior of magnetic components of the beam-handling system with the predicted per- formance. Elements tested to date are one 45° bending magnet, one set of

4-in. quadrupole magnets, and two sets of 2.5-in. quadrupole magnets. These

measurements, together with floating-wire and various magnetic field measurements, indicated substantial differences between the predicted and the

actual performance of magnets. Measurements of actual magnet performance, combined with computer calculations, served to define proper locations

for the magnetic elements of the beam-handling system necessary to insure

required system performance.

Target Chamber Design. Target chambers were designed that can with- stand the intense beam current and the high-radiation environment of the

linear accelerator. The radiation field makes it necessary to avoid the use of organic materials in the chamber construction, and the beam intensity has

necessitated both water cooling and target oscillation.

The NBS free-air chamber for measurement of 10 to 60 kV x rays was recently

developed to calibrate instruments used by medical institutes and research

laboratories. (See page 97)

102
Data-Handling System. An on-line data-handling system developed for use with the linear accelerator provides concurrent on-line processing of data

from several independent experiments. Several novel devices are included

to permit convenient real-time operator control of computer functions and to provide privacy of program by means of priority interrupt lines controlling

the sequence of operations. A family of building blocks is being developed

for the input of information. Surprisingly, the requirements of all nuclear

physics experiments projected for the facility can be met with only six dif- ferent blocks which feed information into the computer via a multiplex

register unit. The man-machine interface is made flexible by the use of two

decoding units, one for outgoing signals and one for sense-switch type in- formation to be used in computer control. The conventional computer out- put devices are supplemented in this system by direct analog, digital, graphic,

and scope output of data. This versatile system obviates costly specialpurpose analyzers that are subject to rapid obsolescence. Monitoring High-Intensity Electron Beams. The heat generated in beam

monitors by the high beam intensities of the linear accelerator poses a serious

problem. Cooling these monitors becomes essential, and is usually accomplished by circulating water systems. Beam monitors of various types under

development include secondary-emission monitors, Faraday-cage monitors,

and non-intercepting induction monitors. The major difficulties in all these are maintaining adequate insulation resistance in water-cooled systems and

keeping electrochemical potentials small and constant. At present, a secondary-emission monitor for beams up to 100 microamperes is built; a Faraday

cage for beams with up to 100 kilowatts of beam power is nearing completion;

and efforts continue to develop the non-intercepting induction monitor into a precise instrument.

Electron Scattering Program. One of the major experimental efforts on the linear accelerator will be an electron scattering program. The large

(30-in. radius of curvature) magnetic spectrometer for this program has

been constructed and will be delivered to NBS in the near future. The per- formance of this spectrometer as measured using a-particle sources is ex- tremely good.

Theory of Electron Scattering. When electrons scatter they radiate photons with consequent loss of energy. An understanding of these radiative

tails is essential for proper interpretation of these experiments. Calculation

of these radiative tails for both elastic and inelastic scattering has been made

exactly in Born approximation.

Accelerator Shielding Handbook. On July 1, 1964, NBS Handbook 97,

Shielding for High-Energy Electron Accelerator Installations, was issued. This handbook extends the recommendations of the National Committee

on Radiation Protection and Measurements for protection against the radiations from high-energy, high-power electron accelerators. In part, this handbook is an extension of NBS Handbook 55, Protection Against Beta- tron-Synchrotron Radiations Up to 100 Million Electron Volts, issued in 1954.

756-244 O—65 8 103
Since the publication of Handbook 55, high-energy accelerators, particularly of the linear type, have come into much wider use in research and in- dustry. Their applications in such areas as food processing and general

sterilization have generated radiation control problems not encountered with

earlier devices. Compilation and Evaluation of Data

Photonuclear Interactions. Under the auspices of the National Standard Reference Data System, a continuing project for the compilation and

evaluation of data in the field of photonuclear reactions (interactions of photons and electrons w

T ith the nucleus) was initiated. Work concentrated on abstracting the significant data in the field published during the last 10

years throughout the world and on building a complete file of reprints or copies of the relevant papers. The search of the literature published prior

to 1964 is essentially complete.

Electromagnetic Interactions. Improved tables were prepared pertaining to the stopping power and range of electrons at energies between 10

keV and 1,000 MeV. The tabulated information includes the mean energy

loss by collision with atomic electrons, the mean bremsstrahlung loss, the mean range, and the conversion of electron kinetic energy into bremsstrahlung energy. Data are also given on critical energies fat which the collision

loss equals the bremsstrahlung loss) and on electron positron differences in regard to energy loss and range. Two-variable proton stopping power and range tables were prepared as functions of the particle energy and of the mean excitation energy of the medium. These tables can be applied to any medium, as characterized by

its mean excitation energy, including protons: and. by simple scaling, also to other heavy charged particles.

A tabulation was made of the Vavilov distribution which describes energy

loss straggling of fast charged particles. The distribution is a generalization of the well-known Landau distribution, and applies to protons and mesons of moderate velocity traversing extremely thin targets, or to ex- tremely fast particles incident on targets of moderate thickness. Electromagnetic Cross-Section Theory. The Bethe-Heitler cross sec- tion with arbitrary form factor was integrated over all photon angles, with- out any approximation, for the case of elastic electron scattering. The re- sult was used to calculate the radiative tail due to the emission of real, hard

photons. This work was then extended to the case of inelastic electron

scattering in which the electron loses energy not only by radiation but also by exciting the nucleus. Methods for the measurement of the polarization of electrons, positrons,

and circularly polarized photons were investigated, with special emphasis on polarization-momentum correlation methods. The various physical processes taken into consideration include Mott, Mdller, Bhabha, and Compton scattering, two-quantum annihilation, single quantum positron annihilation, pair production, and bremsstrahlung.

104
More accurate predictions for the value of the attenuation coefficient for high-energy gamma rays were obtained by calculating the differential and

integral cross sections for pair production with the emission of a photon.

The total cross section for double Compton scattering was obtained also. In an investigation of elastic electron scattering by atoms, screening by

atomic electrons was shown to affect the cross section at both very small and

very large angles. For electron energies above approximately 200 keV, it has been possible to write the cross section as the product of two rather simple

factors, one depending only on the screening effect and the other, only on

the spin and relativistic effects. The cross section thus obtained is in good

agreement with results of previous exact numerical calculations which were

vastly more laborious.

Radiation Transport Theory

Charged Particles. Approximate methods were developed for calculat- ing differential and integral distributions of projected range, median ranges, and curves of ionization versus depth (Bragg curves) for protons traversing

thick absorbers. The analysis was used to extract the value of the mean

exictation energy of the medium from measured Bragg curves. The penetration and diffusion of electrons were studied by Monte Carlo

methods. Direct simulation of the physical scattering processes by random

sampling would be prohibitively expensive because of the enormous number

of collisions. Instead, the diffusion process is imitated by letting the elec- trons carry out a random walk, each step of which takes into account the

effects of many successive collisions. The calculational scheme is currently

being extended to include fluctuations of bremsstrahlung losses and the pro- duction of secondary knock-on electrons. The Monte Carlo techniques were

applied to the reflection and transmission of electrons by foils, energy dissipa- tion in unbounded and bounded media, and the determination of the slowingdown spectrum.

Electron transmission problems have recently gained increased practical significance in connection with the shielding of spacecraft against

Van Allen belt electrons. Detailed tabulations were made of the energy

spectra and angular distributions of electrons traversing sapphire foils used as protection for solar cells. The electron Monte Carlo programs were combined with conventional

gamma-ray Monte Carlo programs in a study of bremsstrahlung production

in thick targets. Attention focused on the energy region up to 10 MeV.

The output of these calculations includes the detailed angular distribution and angular spectrum of photons emerging in the forward and backward

directions from slabs of different thicknesses. Gamma Rays. The output of large cobalt 60 gamma-ray sources (spectral distribution, exposure) was studied by the Monte Carlo method, taking

into account scattering and absorption of radiation within the source, the source heading, and the collimator. These results were needed to establish the relation between the source strength in curies and the exposure

105
dose in roentgens for a given source-collimator configuration. They are

also used in estimating the difference of actual source spectrum (addition

of soft components) compared with the nominal 1.33 and 1.17 MeV spectral

lines as functions of the shape of the source, size of the irradiated field, and

source-detector distance. The problem of predicting dose rate and estimating the effectiveness of shielding from radiations resulting from nuclear explosions was the subject of an extensive literature review. Various existing calculations and

supporting experiments were summarized, and a set of approximately 500

references was catalogued as to source geometry and energy, absorber

material and configuration, type of data presented, and the method of calculation or experimental technique.

An engineering method was developed for calculating protection against

fallout radiation provided by various types of protective structures. This

work forms the basis of the procedures used by the Office of Civil Defense

in the National Shelter Survey and in current shelter engineering research. A new Monte Carlo method was developed for calculating the reflection and transmission of gamma rays by slabs. This method is the first to allow accurate and convenient determination of the spectrum and intensity of the emergent radiation for specific directions of incidence and emergence. Data

generated by this program were used to determine the amount of backscatter when a point-isotropic source and a point detector are placed in the vicinity of an air-concrete interface, and also to calculate the shielding of radiation

from a point-isotropic source by a shadow shield. Neutrons. Thermal neutron flux was studied near the boundary of a semi-infinite non-absorbing gas which scatters neutrons isotropically. Results indicate that the properties of the flux at the surface of a semi-infinite medium, integrated over all spectral energies, are insensitive to various of the scattering properties of the medium.

Monte Carlo data for neutron backscattering from concrete, aluminum,

iron, and water were analyzed and compared with the results of Chandrasekhar's theory of radiative transfer for the case of an isotropic single scattering law. The agreement is surprisingly good for non-hydrogenous materials,

but not for water. Mathematical expressions derived are suitable for a convenient representation of the energy spectrum and angular distribution

of the backscattered flux. These distributions were used in conjunction with an appropriate trans- port equation to describe the penetration of slow as well as fast neutrons through long, straight cylindrical ducts. The equation was solved numerically

for thermal neutrons in concrete with an assumed isotropic source at the duct

entrance.

106
2.1.11. RADIO STANDARDS

LABORATORY

The NBS Radio Standards Laboratory at Boulder, Colo., is responsible for providing the basis of the system of electromagnetic measurement in the United States and for coordinating this system with those of other countries. To do this the Laboratory conducts basic and applied research in the field of radio science. This research leads to the development and evaluation

of national standards for all important radio quantities, which are then

maintained as the national basis of electromagnetic measurements. At the same time extensive contact is maintained with other laboratories and with

industry to provide continual interchange on the developing state of the art. In addition to the national standards, the output of the Laboratory in- cludes calibration and broadcast services which furnish standards of radio

measurement to hundreds of industrial and government laboratories; accurate design data for radio materials; new measuring devices which the in- strument industry can produce; new theories which radio scientists can

exploit; and publications, consultation, and instruction to assist other lab- oratories in the solution of problems in this field. The unique competence of

the Laboratory in radio and microwave measurement is also used to explore

selected atomic and bulk properties of matter and to improve the determination of fundamental physical constants. Substantial interest has been expressed by other countries in NBS achieve- ments in radio science. NBS microwave measuring equipment, for example,

is now being duplicated by some European countries and interest in this has

been expressed by others. Also, as part of an exchange program between

the United States and Russia, three Russian metrologists visited the Radio

Standards Laboratory during January 1964. The Laboratory is continuing its efforts to assess accurately the national

needs for radio standards and then to establish the activities needed to satisfy these needs. Close contact is being maintained with industry, for example,

by a series of seminars in which selected speakers describe their measurment

needs or new developments in their field. Five such seminars were held dur- ing the past year, the presentations of which are receiving a detailed

analysis. Contact with both research and industry is stimulated by the biennial

Conference on Precision Electromagnetic Measurements. The fourth con- ference in this series, held at the Laboratory during June 1964, was attended

by more than 600 participants. Although the Conference is national in sponsorship, it receives international participation and is now firmly established as a significant forum for the interchange of ideas. This fact was recognized

recently in a formal charter signed by the three sponsoring organizations:

the National Bureau of Standards, the Institute of Electrical and Electronics

Engineers, and the U.S. National Committee of the International Scienific Radio Union.

107
As the needs of industry are discovered through seminars, conferences,

and personal contacts, this information is incorporated into the Laboratory's

long-range planning. The Laboratory capabilities are compared annually

with the needs of industry to set the goals for the program for the next 5 years. The Laboratory continued to develop an educational program for industrial and research personnel by offering a three-week course in electromagnetic

measurements and standards during July and August of 1963. It was at- tended by 153 scientists from the United States and 5 foreign countries,

representing industrial organizations, universities, and government laboratories. Since the course was well received, present plans are to offer it again

during the summer of 1965. Theoretical Physics. Theoretical work completed during the past year may provide the first successful calculation of properties of a plasma model

that is more realistic than the familiar electron-gas model. In this study, a new theory of the quantum statistics of multicomponent systems was applied

in calculating the thermodynamic properties of a fully ionized gas in thermal

equilibrium. The computations carry the expansions to a higher order than

done before, and obtain corrected lower-order terms. Recent developments in antenna theory emphasize the use of vectorial an- gular spectra and the "scattering matrix" description of radiating and receiv- ing systems. This approach seems well adapted to the formulation and

analysis of problems involving near-zone or Fresnel-zone interaction of an- tennas and led to results permitting electromagnetic field measurements with

arbitrary probes.

2.1.12. RADIO STANDARDS PHYSICS

The Bureau's program in radio standards physics emphasizes fundamental

research on the interaction of electromagnetic fields with matter. It is particularly concerned with research having application to radio standards, fre- quency standards, time scales, atomic and aggregate properties of matter, and

constants of physics. It also establishes standards of measurement in the areas of frequency, time, and radio materials, and disseminates these stand- ards to the general public. The program for electromagnetic standards is firmly linked to the requirements of both industrial and government laboratories. The staff provides a readily available consulting service to industry,

government agencies, and individuals. Frequency and Time Dissemination. Dr. Allen V. Astin, Director of the Bureau, dedicated the Bureau's two new standard frequency broadcast

stations, WWVL (20 kilohertz, kHz) and WWVB (60 kHz) , in August 1963. They are located near Fort Collins, Colo., about 50 miles northeast of Boulder.

The standards at the Boulder Laboratories directly control the carrier fre- quency of each of these stations by a 100-mile round-trip servo loop between

Boulder and the transmitters. This unique feature makes these transmissions

the most accurate and stable frequency transmissions in the world. The servo system removes phase perturbations caused by the controlling oscillator, the antenna system, and the transmitters. 108
The propagation characteristics of low radio frequencies enable station WWVB to provide excellent stability and coverage over the continental

United States. WWVL, still in the experimental stage, provides good sta- bility and coverage over much of the globe. The importance of these trans- missions is accented by the partial support provided by the National Aeronautics and Space Administration for the development and construction

of WWVL.

Additions were also made to the services offered by the shortwave stand- ards stations WWV (near Washington, D.C.) and WWVH (Hawaii). A

new announcing machine at WWV improved both the reliability and precision of the voice annoucements and made possible propagation forecasts every 5 minutes instead of only every 30 minutes. Another announcing

machine was installed at WWVH to enable this station to give voice an- nouncements for the first time.

Atomic Frequency Standard Research. The new cesium-beam fre- quency standard, NBS III, was evaluated and its accuracy found to be

±5X10~12

. The precision was found to be ±7X10-33 typically, attaining a value of ± 1.4 X 10~13 in the best cases. This frequency standard and two smaller cesium-beam devices provide

the basis for the NBS atomic time scale (NBS-A), and for a second time

scale maintained at a determined offset from NBS-A (presently 1.5 X10-8 sec). The second time scale is denoted NBS-UA, since it is essentially an

approximation to Universal Time derived from an atomic device. A uni- form time- and frequency-generating device maintaining the NBS-UA time

scale is now used to control the phase of transmitters of radio stations WWVL,

WWVB, and WWV.

Both atomic time scales are derived from the same system and use several high-precision quartz crystal oscillators, as well as a rubidium gas cell to interpolate between calibrations made with the U.S. Frequency Standard.

The reliability of this clock system was improved during the past year by

increased redundancy, and the precision improved from zhlXlO 11 to ±3X10-12

. The automatic data-handling capability of the frequency and

time standards was doubled and it is therefore now possible to compare two

secondary oscillators with the U.S. Frequency Standard simultaneously.

A hydrogen maser is being developed to study the effectiveness of such a

device as a frequency standard. Basic construction was completed during

the past year and stimulated emission observed. Present work is aimed at refining components to make possible self-sustained oscillations. International Comparison of Atomic Frequency Standards. The

international comparison of atomic frequency standards, begun in 1961, was continued using the very-low-frequency signals of GBR (16 kHz) at Rugby, England, and NBA (18 kHz) at Balboa, Canal Zone. The atomic

standards in England, France, Switzerland, and Canada agreed with those

at NBS to within 3 parts in 1010 in the worst case and to within 1 part in 1010 for the better ones. Hewlett Packard comparison of the Swiss and

NBS standards by means of portable commercial cesium beam units shows

109
Equipment used for the international comparison of atomic frequency standards using the VLF signals of Radio Stations GBR (England) and NBA (Canal Zone).

Such studies showed that atomic "clocks" in England, France, Switzerland, aVid Canada agreed with those at NBS Boulder to within 3 parts in 10 10

. (See page 109)

agreement within 1 part in 1011

. It is planned to extend this work to include

Japan, Australia, Sweden, and India during the coming year. Quantum Electronics. The Stark effect—the splitting of spectral lines by the application of an electric field to a material absorbing or emitting

radiation—offers the possibility of measuring high voltages with precision.

A completed apparatus based on this principle utilizes a Fabry-Perot

absorption cell and uses a rotational transition of methyl cyanide at 37 GHz.

A preliminary evaluation indicates that the precision obtained is of the order

of a few parts in 106 but the accuracy is not likely to be better than a few

parts in 104

. The present equipment operates with inputs under 5,000

volts, but if the method proves to be practical it will be useful primarily for measuring voltage ratios at about 100 kilovolts. Evaluation of the device

is continuing, with this application in mind. This project is supported

partially by ARPA.

Lasers are presently being used at NBS as a source of intense, coherent,

monochromatic optical radiation to investigate nonlinear optical properties

of materials. This is directed toward a better understanding of the characteristics of lasers and, eventually, the development of national measure- ment standards. 110
An ordinary ruby laser was used to observe stimulated Raman radiation

in benzene. A Q-switched, Raman-scattering laser was used to observe the double quantum absorption in anthracene crystals. It was also used to observe coherent Raman radiation from benzene in an optical resonator,

which was external to the optical resonator of the ruby laser. The axes of the two resonators were at a small angle to each other to permit them to resonate independently of each other. A symmetric-top molecule, CH3 CN, was studied by three-level maser spec- troscopy at 37 GHz. The molecule was subjected to radio-frequency energy

introduced into a Fabry-Perot type millimeter-wave resonator on a multiplewire grid placed between the reflectors. The results agreed approximately

with the theory of multiple quantum transitions. Other research in progress in the area of quantum electronics includes

measuring the velocity of gamma rays using the Mossbauer effect and measuring the fine structure separation in singly ionized helium. The latter will help in obtaining a better value for the fine structure constant. Radio and Microwave Materials. Research on electromagnetic materials is designed to improve understanding of the magnetic (primarily ferri- magnetic), dielectric, and conductive behavior of materials at radio and

microwave frequencies in terms of the atomic constitution and structure of matter. This research is intended also to improve and develop standards

and electromagnetic measuring techniques.

Magnetics. A study of the accuracy of ferrimagnetic resonance line width and gyromagnetic ratio measurements on ferrites and garnets at 1106

MHz revealed several anomalies and problems connected with disk-shaped

samples. In other experimentation an intermediate frequency attenuationsubstitution method was found to compare favorably with accurate frequencymeasuring techniques in plotting ferrimagnetic resonance curves. A knowledge of spin relaxation mechanisms in solids is vital to understanding magnetic resonance phenomena and to planning experiments in- volving photon and phonon masers. The staff is investigating these mechanisms and studying relaxation times and resonance line shapes with approach

to equilibrium, and the dependence of the mechanisms on external fields, frequency, and temperature. A paper completed during the year provides

exact equations for use in analyzing the approach to equilibrium in manybody systems. The theory of longitudinal spin-spin relaxation is now being

studied from both a thermodynamic and microscopic point of view.

Paramagnetic and antiferromagnetic crystals are being studied by magnetic

resonance techniques to improve our knowledge of the solid state and its interaction with electromagnetic radiation, as well as to collect basic information to apply these materials in the microwave and submicrowave region. A

useful ferric-ion electron paramagnetic resonance (EPR) spectrum was

obtained in these studies from a brown specimen of iron-doped quartz. It was thoroughly studied at /£-band frequencies and room temperature, and

the data were analyzed. Equipment was built for experiments in the field of electron-nuclear double resonance and on nuclear-spin transitions induced

111
in antiferromagnetic KMnF3 by ultrasonic modulation of the hyperfine

interaction. Research in the optical region of the -.electromagnetic spectrum included

studies of the fluorescence of manganese sensitized by cerium in single

crystals of calcium fluoride. The cerium absorbs ultraviolet photons and

transfers this energy to neighboring manganese ions; the managnese then

fluoresces in the visible region. This sensitization is believed to be due to an electron spin exchange process. With a sufficiently high ultraviolet in- tensity, the energy transfer to the manganese approaches saturation while

the quantum efficiency for cerium fluorescence increases. A simple physical

model was developed to explain this effect. From observations of the

fluorescence as a function of ultraviolet intensity one can estimate the number of lattice sites surrounding the cerium which can be sensitized. Materials Synthesis. Sometimes study of a fundamental process re- quires that materials of controlled composition be obtained. This is particularly important in experimentation on specimens of radio and microwave

material. Fairly large (3 to 4 mm) crystals of anyhdrous sulfates of some

transition metals were grown for studies of antiferromagnetic properties at low temperatures. Both pure and doped (with cobalt, chromium, and iron)

calcite crystals (1 to 2 mm) were grown for studies in electron paramagnetic

resonance.

Dielectrics. Three dielectric materials—fused silica, glass, and alu- mina—were evaluated in international comparison with Canada and England.

The three laboratories agreed within better than 1 percent for the real part of the permittivity, but disagreed more for the imaginary component, in the measurement of which accuracy is much more limited. A second round of measurements is in progress, with the expectation that closer agreement

will result. The international comparisons led to refinements in the standardization of the dielectric constants of the glass and the silica, standardized samples of which are now available for issue. For these the real part of the dielectric constant is specified to ±0.4 percent and the loss tangent to ±10 percent or ±0.0001, whichever is larger.

The results of a study on the effect of aging on certain dielectric materials are now being used in the design of precision coaxial connectors and terminals. Also, a system was modified to permit the precision measurement of

dielectric properties at several frequencies from 80 to 573 °K. Measure- ments on polycrystalline silver iodide by means of this system revealed a

correlation between the complex dielectric constant and the thermal expansion

coefficient, which becomes positive in the temperature interval 80 to 110

°K.

Both theoretical and experimental work on nonlinear dielectrics is being

started to develop better techniques for measuring the complex dielectric constant of materials at millimeter and submillimeter wavelengths.

Microwave Physics. Use of the higher radio waves—above about 100

GHz—is hampered by a lack of instruments to generate or detect these fre- 112
quencies. The staff developed a microwave spectrometer for use at such

frequencies and now is using it to study the properties of molecular oxygen,

transitions among the energy levels of which generate a spectrum above 60

GHz. The 119-GHz line could not be observed with the straight-line ab- sorption cell, but a spherical Fabry-Perot resonator now being tested is ex- pected to provide the necessary sensitivity.

Radiometry. Correlation radiometers are widely used to measure radio

noise despite the sizable discrepancies between the performance of radi- ometer circuits and the predictions of the usual idealized theory. During the past year the theory of the correlation radiometer has been further extended

to include the effects of amplifier gain fluctuations and of amplifiers with

different characteristics in the two channels of the instrument. Analysis allows

referring the sensitivity of a radiometer in which two noise sources are being compared to a second radiometer in which the output of the noise source

is compared to a continuous wave signal.

Microwave-Stimulated Transitions, A study of the interaction of microwave energy with excited free molecules resulted in the optical detec- tion of microwave transitions in the excited gaseous CN molecule and

observation of all 13 of the predicted absorption lines. A complete energylevel diagram of this rotational level was prepared by observation of the microwave transitions. A byproduct of this research was the development

of a compact and efficient microwave discharge cavity for use at 2450 MHz

in the dissociation of N2

. Interferometric Measurements, The past year was spent perfecting

techniques for measurement with the Michelson interferometer and searching

for the systematic errors in the system. Measurement of the velocity of

light at millimeter wavelengths with this interferometer reached the final stage.

A significant error was found to be created by reflections originating in the throat of the interferometer horn, near where the horn taper approaches

waveguide dimensions. Errors from this source were reduced by the design

of a new waveguide-to-horn transition which was electroformed in a smooth

curve, thus avoiding a discontinuity. Multiple reflections were further reduced by the use of matched phenolic plastic plugs of various thicknesses in the large end of the transition. It is now felt that averaging techniques can

eliminate any remaining errors due to multiple reflections. With these improvements it is possible to make measurements consistently with a pre- cision of about ±3 X 10-7

, or better. This work has recently been supported

partially by ARPA.

Brush-Cathode Plasma. A major reason for characteristics of plasmas

not being clearly understood is the general lack of fast, accurate, and con- venient diagnostic techniques. The development of such techniques is thwarted, in turn, by the enormous complexity of most plasmas. The recent NBS development of a new form of plasma—the brush-cathode plasma

which is both stable and uniform is a major achievement in this field. The negative glow associated with the brush cathode is particularly inter- 113
esting because it constitutes a well-behaved medium for a series of investgations in the field of plasma physics. The plasma in its normal condition is beam-generated and recombination-dominated.

Investigations of the brush-cathode discharge show that its negative

glow, and probably that of all other discharges, is an electron-beam-maintained

plasma. The beam energy is approximately equal to the cathode fall (200

to 5,000 volts at 1 torr) and the beam current is approximately equal to the discharge current. The high fields and potentials in the cathode region are measured with Langmuir probes and by observations of the linear Stark

shift and splitting in the transition. The fields in front of the cathode are found to be in the range 103 to 104 volts/cm by these means, to an agree- ment within 10 percent. Among other experiments now being conducted on the brush discharge are an investigation of possible laser action and a study of the scattering of light by the electrons in the ionized gas. Plasma Measurements. As a result of the development of the brush- cathode plasma, the diagnostic program now includes plasma investigations

using Langmuir probes, resonant probes, microwave interaction, and spectroscopic measurements. This program will also establish the reliability, compatibility, and useful ranges of these diagnostic tools in measuring electron

densities, electron temperatures, and collision frequencies.

Spectroscopic measurements are particularly important, under certain conditions making it possible to observe emission in the helium series 2s3S — nps P

Almost all laboratory produced plasmas are non-uniform and exhibit struc- tures caused by non-linear flow mechanisms (above). A recent NBS development of a new form of plasma—the brush-cathode plasma (below), which is both stable and uniform—presents a major achievement in this field. (See page 113)

114
up to the quantum number /i = 30. This series is used for measuring electron density and the electron temperature. The electron temperature is in the range 0.05 to 0.10 eV, spectroscopic measurements of which are in excellent agreement with Langmuir probe measurements. The electron density is in the range 1011 to 1014 cm-3

, similarly well-confirmed by measurements with

a microwave interferometer. These and other precision measurements can

only be made in a well-behaved medium, such as the brush-cathode plasma.

The series of instruments developed to study the brush-cathode plasma in- cludes: a microwave noise radiometer with a sensitivity of better than 10~15 watts for electron temperatures and rf emission measurements; a portable

interferometer operating at 8 mm Hg and used to measure electron density versus plasma current; a ring-shaped probe for use with a Faraday cage to eliminate the effects of secondary emission and metastable atoms in the plasma; and, presently under investigation, two new methods of determining

beam properties of a plasma.

Bounded Plasmas. Electromagnetic waves in bounded laboratory

plasmas were examined to find the effect of boundaries on waves traveling

longitudinally in a magnetoplasma, and to determine the resulting quantitative changes in the wave, compared with an infinite plane wave. A 5-inch

brush electrode discharge will be used in experiments to test some theories. 2.1.13. RADIO STANDARDS

ENGINEERING

The Bureau's program in radio standards engineering includes basic re- search on physical principles and fundamental engineering techniques having

applications in the field of precision electromagnetic measurements. This

research leads to the establishment, maintenance, continued improvement, and

international coordination of a comprehensive set of national standards and

precision measurement techniques for fundamental electromagnetic quantities in radio circuits. Dissemination is accomplished in large part through

calibration services, and information is distributed widely through publication, consultation, conference papers, invited talks, committee work with

technical societies, individual visits to other laboratories and the NBS-Air

Force Working Group visits to Air Force contractors. Low-Frequency Calibration. A new voltage calibration method,

which uses inductive voltage dividers to establish audio frequency voltage

ratios, is now the basis for calibrations on inductive voltage dividers at 400

and 1000 Hz. Multisection dividers are used, for which relative errors are

calculated at each tap and absolute measurements made at certain non-zeroerror taps. This information is combined to obtain accurate values of in- phase voltage ratio and phase angle at all taps. A service was begun for the calibration of multi-megohm resistors to 1010 ohms with an uncertainty of ±0.01 percent and to 1014 ohms with an uncertainty of ±1 percent. This system depends on a Wheatstone bridge

using high-quality wire-wound resistors in a wye-delta ratio circuit. All 115
This new culibration console for loop and dipole antennas at 30Hz to 1GHz

provides a significant improvement in NBS calibration services. (See page 119)

components are incorporated in a measurement console. Most of the research and development was completed for a new temperature-stabilized oil bath for saturated cells. Electronic circuits will control

oil temperature to within 0.001 °C of any temperature between 23 and 40 °C. The bath will be set to operate at a temperature of 28 °C. Agreement to within a few parts in 10 million was achieved between the NBS voltage standards at the Boulder and Washington laboratories in measuring the average electromotive force I emf ) of a Boulder traveling group

of saturated standard cells. It is expected that even better measurements

of emf will be obtained when the installation of a new standard cell comparator

in the Boulder Electronic Calibration Center is completed.

Improved voltage standards for a-c-d-c transfer measurements were built, using plug-in wire-wound resistors for changing from one voltage range to another. Corrections for these prototype standards, at frequencies between

20 Hz and 50 kHz, are less than ±0.001 percent. New current standards for a-c-d-c transfer are now being developed.

An experimental inductance bridge employing inductively coupled ratio arms was assembled to measure equivalent parallel inductance in terms of 116
capacitance and frequency. The measurements compare very favorably

with those by a precision Maxwell-Wein bridge at the 100 millihenry level. Further development is planned.

A study of the effects of oil circulation on the temperature of oil-cooled shunts was completed. As a result of this study, modifications were made

in the shunt oil bath that will provide better accuracies in reported values. A method for determining accurately the heating effects in master volt boxes was developed which will improve ratio accuracies. High-Frequency Standards. The Bureau completed a prototype noise

power comparator which compares power at 3 MHz from noise generators

having effective noise temperatures between 75 and 30,000 °K with an uncertainty of less than 0.5 percent. This prototype will serve as the pattern for comparators for calibrating noise factor instruments over a wide range of frequencies.

Electromagnetic Measurements. A special bolometer and resistance element combination was developed to eliminate dual bolometer error in radio frequency (rf) voltage measurement and has promise of yielding ac- curacies within 0.1 percent up to 500 MHz.

Electric-field standards were developed for the frequency range of 300 to 1,000 MHz. NBS now has electric-field standards covering the range of 30 to 1,000 MHz with an uncertainty of about 0.8 decibel (dB)

A thermal noise generator, cooled by liquid nitrogen, was constructed for use at 30 MHz. Its electrical and thermal characteristics are being evaluated

in preparation for its use as a working standard of noise power. Other

noise generators for operation at various temperatures are being constructed

with adjustable output impedances which essentially eliminate mismatch

errors. A special correlation detector was developed for use in 30-MHz attenuation- measuring systems, permitting simultaneous phase and amplitude nulling

in the measurement of complex insertion ratios. This precise detector achieves a sensitivity of 36 picovolts with a 30-second integration time,

which is only 17 percent greater than the theoretical limit. Performance

tests indicate the detector will aid in the development of insertion-ratio measuring systems by providing greatly increased range, accuracy, and

convenience.

A new calorimetric reference standard for rf power measurement in the frequency range 30 kHz to 1,000 MHz was completed and evaluated. The

accuracy of the standard is within 0.25 percent and the power range is 5

to 100 watts. This equipment augments other reference standards, which

extend downward in power level to 10 milliwatts. International comparison of rf power standards is proceeding on schedule; comparisons with the United Kingdom were completed in 1962 and with

Japan in 1963. Comparison measurements with Canadian transfer standards

are in progress. Two systems have been developed for the standardization and measure- ment of the peak voltage amplitude of short-duration, fast-rise, d-c, or uni- 117
directional pulses. The accuracy of both systems is within 0.2 percent in the range of 1 to 100 volts peak. These systems are expected to form the

basis of reference standards up to several thousand volts. A dual twin-T bridge circuit was developed to make resistance measure- ments directly in terms of capacitance and frequency up to a few hundred

megahertz. A model of this bridge, which operates at 1.5 MHz, is proving

useful not only in the determination of resistance and reflection coefficient standards, but also of the rf-d-c difference of thermoelements used in standards and for precise measurements of Q and loss. Construction of another model for use at 150 MHz was started. Evaluation of errors shows

that the bridge should be capable of measurements to a few parts per million, but present measurements are limited by mechanical problems in capacitance standards and instabilities in resistance to several hundred parts per million at 1.5 MHz.

A high-frequency ratio transformer bridge now under development demonstrated capabilities of a few parts per million at 1 MHz. It is being built for use with new high-frequency inductance standards and to increase the accuracy of high-frequency capacitance measurements by three-terminal

techniques.

X-band electron-beam power meter developed for application at very high powers. It is being used in a radar measurements standardization program for DOD. (See page 120)

118
An all-coaxial reflectometer was put into operation in the frequency range

of 0.1 to 1 GHz; the connectors, tuners, couplers, loads, and center-conductor

supports used in it are sufficiently precise to reduce measurement uncertainty to 0.1 percent. This, with the time domain reflectometer and as- sociated standards, is proving useful not only in the development of re- flection coefficient standards, but also in the design of high-precision coaxial

components, particularly connectors. An important task now well under way is the construction of an electro- dynamic ammeter for measurement of current in terms of mechanical properties and time. Operating at frequencies from about 0.1 to 1 GHz and to an

estimated accuracy of 0.1 percent, this instrument should be of considerable

value. It will be used not only as an accurate absolute standard of rf current, but also as a basis for establishing rf-d-c corrections for thermoelement

standards used in determining other quantities such as voltage, power, and

field strength, supplementing the impedance correction system now in use. High-Frequency Calibration, The Bureau made significant progress

in extending calibration services to greater powers and higher frequencies to meet the perennial need for growth in calibration capabilities. The highfrequency field-strength calibration services for horizontally polarized dipole antennas were expanded from 300 to 1,000 MHz; dipole antennas can now

be calibrated at any frequency from 30 to 1,000 MHz. The present calibra- tion uncertainty for this new service is approximately 12 percent—about

twice as good as the best previous measurements. The uncertainty in cali- bration at 150 to 300 MHz was slightly improved, and recent progress in evaluating measurement errors may result in further improvements in cali- bration uncertainty at all frequencies from 30 to 1,000 MHz. A recently

completed calibration console for loop and dipole antennas at 30 Hz to 1,000

MHz significantly reduces the time required to calibrate these antennas, there- by improving efficiency and reducing calibration costs. Improved standards for the calibration of ^-meters over the frequency

range of 50 kHz to 45 MHz were established by a statistical procedure for adjusting the values of the NBS standards. These procedures also yielded

improved tolerance limits for future calibrations. Significant progress was

also made toward the development of a coaxial reflectometer system for the measurement of VSWR at frequencies of 1.0, 2.0, 3.0, and 4.0 GHz. Slottedline calibration capabilities were improved by the addition of two new highprecision lines which extend calibration capabilities to the region of 8 GHz.

Plans for constructing rf bridges for calibration purposes were changed

slightly; bridges covering a range of frequencies are now deemed more

practical than bridges for fixed frequencies. The former are being constructed, and previously constructed bridges modified for broader frequency

application. Although this entails a sacrifice in convenience, fewer bridges

will be required, thus saving research and development expense. A continuous-wave power calibration service is now offered at power levels from 1 milliwatt to 100 watts at 500 MHz for coaxial rf calorimeters having

Type N connectors. Calibration uncertainty is ±1 to 2 percent, depending

756-244 0—65 9 119
upon the stability and standing-wave ratio of the calorimeter being calibrated. The attenuation calibration capability was substantially increased by rais- ing the upper frequency limit from 5.6 to 12 GHz. Improvements in a

reflectometer system increased measurement accuracy from 0.1 to 0.01 dB in 10 dB in the frequency range of 1 to 12 GHz. Phase shift calibration in the

0.2 to 12 GHz range was started and completion scheduled for early 1965. A program for coaxial attenuation measurements from 12 to 18 GHz was

started and completion is scheduled for the next fiscal year. A project to increase 30 MHz calibration accuracy from 0.005 to 0.001 dB in 10 dB was

begun, with completion scheduled for November 1964. A calibration console put into service for rf voltage measurements at 500

MHz covers a range from 0.2 to 7 volts at an accuracy of 5 percent. The

working standards used in this console consist of a set of frequency-compensated thermal voltage converters, which are calibrated in terms of the national reference standard. Microwave Standards. The international significance of NBS achieve- ments in microwave standards is demonstrated by such instruments as the NBS low-power calorimeter, which continues to attract visitors from around

the world. During the past 18 months three European countries have ex- pressed a desire to duplicate NBS microwave power-measuring equipment.

A water bath now being developed for the calorimeter will further narrow

the range of uncertainty of bolometer mount efficiencies. Thermal variations and gradients in the new bath remain under 0.00005 °C for room

temperature changes of ±1 °C over a period of hours, and still further improvement is expected.

A newly developed technique is used to transfer calibrations between power

meters of different input waveguide types or sizes. This technique makes it possible, for example, to calibrate a coaxial bolometer mount in terms of a rectangular waveguide standard. Work on microwave high-power standards was accelerated during the past

year, supported by ARPA. This led to stepped-up development of an electron- beam power meter, a frequency- and power-stabilized 200-watt microwave

source, and a high-power stirred-water calorimeter. Similar ARPA support

in the microwave noise standards program is permitting initial development

of cryogenic noise standards and measurement techniques.

The evaluation of precision coaxial connectors in cooperation with the

Institute of Electrical and Electronics Engineers continued with emphasis on procedures for investigating the proposed 7-millimeter connector over

the frequency range of 2 to 18 GHz.

Waveguide loss measurements are being made to narrow the limits of uncertainty in the value of the X-band national standard short circuit, using

both the X-band reflectometer and the microcalorimeter.

The 70-GHz reflectometer was improved by cophase-locking the signal gen- erator and the local oscillator to the Boulder Laboratories 100-kHz reference frequency and by using improved waveguide components. The instrument

is now being used to measure millimeter waveguide attenuation and to evalu- 120
These systems in WR137 and WR90 waveguides are the first of several calibra- tion systems which use the* impedance method to measure the efficiency of a bolometer unit. (See page 122)

ate millimeter waveguide connectors. Preliminary data on an electroformed

precision WR12 waveguide (60 to 90 GHz) showed the loss to be approximately 1 dB per foot. The measured coefficient of reflection from a UG387/U connector was 0.006 for a VSWR of 1.012.

Efforts to suppress leakage in reflectometer systems resulted in the de- velopment of gaskets of perforated and metallized fluorocarbon, which confined rf leakage to below a detectable amount. The gaskets are also ex- pected to provide adequate pressure seals. A single measurement system that will measure attenuation to ±0.005 dB

in 10 dB, phase shift to ±0.1° in 360°, and complex impedance to corresponding accuracies is under development. Its capabilities were used in a coaxial

waveguide system in the 1- to 2-GHz band. Refinements, including automatic

phasing, are being developed to simplify the measurement procedure. Also,

during the past year comparison of microwave impedance standards was made with the Swedish Standards Laboratory.

121
Microwave Calibration. Two European countries are presently duplicating the NBS microwave noise calibration system. NBS is already be- ginning an international comparison of microwave noise with these countries by making measurements on an interlaboratory standard which will be calibrated later by the other countries. The development of a new tube

mount improved interlaboratory and working standards and led to significant

improvements in the calibration of microwave noise sources. A power calibration system developed for WR137 waveguide is the first of several systems using the impedance method for measuring low-level con- tinuous wave (CW) power at frequencies less than 10 GHz. Calibration

services for additional waveguide sizes, at frequencies from 2.6 to 10 GHz,

will be announced soon. The calibration procedures using this method have

been considerably simplified during the developmental work, and further refinements are expected as the work progresses. Attenuation calibration systems using the modulated subcarrier method of measurement were completed and calibration services are now available for variable waveguide attenuators in WR90 and WR62 waveguide. This

method of attenuation measurement, developed by NBS, provides an improvement in measurement accuracy of one order of magnitude or better. Other attenuation calibration systems using this method are being developed

for additional waveguide sizes. A system to measure frequency stability of signal sources was completed,

and calibration services were announced for frequencies up to 500 MHz.

Additional capabilities now planned will provide similar calibration services extending into the microwave region.

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2.2. INSTITUTE FOR MATERIALS

RESEARCH

There is great demand and pressure everywhere for a more functional,

resourceful, and precise utilization of materials. To give substance to his complex and imaginative designs, the modern technologist draws upon a

far more extensive and varied inventory of materials, with a vastly broader

range of properties and performance, than was available to his predecessors

only a few decades ago. Any one equipment system embodies a host of

materials, each of which has its own specific function, and each of which

must also work harmoniously with all the others in order to carry out the

desired overall function. Also, materials are continually being required to perform, often with high precision, under environmental conditions of a

severity never before encountered—conditions of extreme heat or cold, pres- sure or vacuum, radiation, force and shock, and others. Since, in one way or another, materials are involved in all end items of our national output, any increase in basic knowledge of materials, any en- largement of our power to control, produce, and design materials for better performance, obviously will benefit productivity and utilization all along the

line.For many years the National Bureau of Standards has been active in the generation, collection, and dissemination of data on the properties of materials. It has developed methods for the preparation, purification, and

characterization of research materials in order that meaningful measure- ments of their properties might be made, it has developed precise methods

for making such measurements, and it has developed procedures for promoting uniformity of measurement in technology and industry.

Within the last year, in order to give maximum support to the national

materials effort, the Bureau has realined and refocused its programs dealing

with the structure and behavior of matter. All materials groups of the Bureau

are now concentrated in the recently formed NBS Institute for Materials

Research (IMR), permitting a strengthened and more closely coordinated

attack on the materials problems that have been traditionally a major NBS

responsibility. Specifically, this realinement is planned to give direct sup- port to one or more of the following NBS objectives

Preparation of Research Materials

Research materials are materials which have been prepared in such a manner as to have special characteristics, i.e., high purity, well-defined struc- tures or composition, specific properties, etc. Such materials are essential 123
for measurements of a meaningful nature. The development of methods for

their preparation, purification, and characterization is, therefore, a matter of utmost importance to the scientist and engineer concerned with the use of materials in a wide variety of environments. One of the primary objectives,

therefore, of this program is to produce new methodology for the preparation, purification, and characterization of such materials. The ability to prepare these materials is also essential to a number of NBS missions: (1) they are necessary as backup to the National Standard

Reference Data System both to make available material to verify research data entering the system and to provide new critical data; (2) they are the

basis of the Standard Reference Materials program; (3) they are essential

to NBS programs concerned with obtaining better understanding of the bulk

properties of materials in terms of their microscopic structure; and (4)

they are necesssary for defining basic physical standards that depend on a stable physical or chemical property of a material. Standard Reference Materials

The provision of these materials directly supports national science, tech- nology, industry, and commerce. Through this activity of long standing, more than 600 kinds of standard reference materials are prepared, certified, and distributed. These standard materials are certified either for chemical

composition or for a particular stable physical or chemical property. To

support this program a new Office of Standard Reference Materials has been

established. The staff of this Office will conduct studies of the needs for these materials in all areas of our technology and will be particularly con- cerned with determining where well-characterized materials should be used

to calibrate a measurement system.

The availability of standard reference materials is of tremendous importance to our economy in several ways. These reference materials allow a high degree of quality control throughout industry. Secondly, the use of

these materials provides a laboratory or industry with a self-calibration

ability which directly benefits both research and development activities as well as production and control activities, insuring better research and

engineering data and design. Finally, the most diffuse and possibly the

greatest benefit from the use of standard reference materials is the general

promotion of uniformity of measurement throughout the Nation.

Measurement of Bulk Properties of Materials

New measurement techniques for determining the properties and performance of materials are constantly required as our industrial technology de- mands that materials be used in new environments. The objectives of the IMR programs in this area are (1) to develop methods of measurement that have a wide degree of acceptance; (2) to acquire engineering data; (3) to define better the critical properties of materials which form the basis for developing methods for establishing criteria of performance; (4) to measure

124
and understand the stable properties of materials which are used to define standards of measurement; and (5) to understand the bulk properties of materials in terms of their microstructure.

Acquisition of Critical Data on Fundamental Physical and

Chemical Properties of Matter

A significant activity in the IMR program is the generation of highly

precise and critically evaluated data on the fundamental physical and

chemical properties of materials. Reliable data on materials properties

are essential to further the scientific and technological progress of the Nation.

In order to give direct support to these several Bureau objectives, the

Institute for Materials Research has been organized into six divisions. There

is, in addition, the Office of Standard Reference Materials, with its direct service responsibilities. The principal activities of the several divisions are developed in the following chapters.

2.2.1. ANALYTICAL CHEMISTRY

The analytical chemistry laboratories encompass some 30 different analytical competences from activation analysis and atomic absorption to vacuum

fusion and x-ray spectroscopy. These competences deal with research in analysis as well as awareness of the practical sample, be it service analysis or standard reference material. The laboratories are presently concentrating efforts in the areas of trace analysis and high-purity materials, in this way furnishing support for the broad materials program of the Institute of Materials Research. New

Inside view of clean room used in sample preparation for high sensitivity acti- vation analysis. All chemical procedures are conducted inside the glove boxes. (See page 126)

125
activities include inauguration of programs built around the electron microprobe and the spark source mass spectrograph. A considerable extension was also made of the programs in radio chemical analysis, including activa- tion analysis, Mossbauer spectrometry, and radiometric methods.

Activation Analysis Improved. An improvement in the sensitivity of an already highly sensitive analytical method called activation analysis was accomplished through the use of coincidence-counting techniques. The

technique discriminates among most of those radioisotopes that do not decay

by P-yi,-y2 in cascade. The decreased background results in an increase

by a factor of 1,000 in the sensitivity of the analysis for as many as 20

elements. Efforts are being made to combine the data handling and calcu- lating capability of high-speed digital computers with such physical dis- crimination techniques in order to broaden the scope of this analytical

method.

Improved Mossbauer Spectrometer. A very useful technique for the

structural analysis of a material utilizes a type of nuclear gamma-ray

resonant absorption commonly called the Mossbauer effect. A decisive im- provement in the design of a Mossbauer spectrometer eliminated many

precision and accuracy errors that exist in most spectrometers. A Doppler

motion-producing transducer was designed to eliminate drifts and distor- tions in the motion as well as to improve the reproducibility of the motion

to better than 0.1 percent. Current studies include application of the technique to the measurement of the quantity of an element in a sample.

Radioistopic Tracers Used for Analysis. The use of radioistopic

tracers for the analysis of small quantities of elements is relatively new. The method, which is called radioisotopic dilution, is based upon a measure- ment of the change in the specific activity (disintegrations per unit time

per unit weight of the element) of a radioisotope when an unknown amount

of the element being analyzed is added. Bureau personnel modified this method and developed a method of double radioisotopic dilution. Using

the Bureau method, sensitivities in the range of 0.1 microgram per gram

of sample for the analysis of such elements as silver, cobalt, and iron were

obtained. This technique allows any standard industrial laboratory to do

many trace analyses with existing laboratory equipment with only the addition of a radiation detector. Clean Room Constructed. The problem of handling very pure materials without contaminating them with foreign elements is a major one. To reduce contamination in high-sensitivity trace analysis, a clean room was

constructed at NBS. A clean room is a laboratory space in which consider- able effort is made to eliminate environmental contamination such as dust. Glove boxes are used in the clean room. The air which enters both the glove boxes and the room is passed through high-efficiency filters. The room

is used for sample preparation for high-sensitivity activation analysis.

Spark Source Mass Spectrograph Acquired. A commercial spark

source mass spectrograph, acquired during the past year, extends consider- ably the Bureau's capabilities in the general area of trace analysis of solids. 126
This type of instrument is particularly suitable for a fast survey of elements

present in a solid at the sub-part-per-million level, analysis of ultra-pure

solids for contaminants, and analysis of the surface of a solid. In present

work, well-characterized samples are being used to study the effect of in- strumental operating conditions on the reproducibility of analytical data. Single Reproducible Pulse Obtained with Laser Microprobe. A

critical study of excitation of spectra of solid materials by a high-energy

pulse of laser light was conducted. In this method the short-time pulse of a ruby laser is focused by a microscope on a very small area of the sample.

The energy produced by the laser is sufficient to volatilize any material at the point of focus. A high-voltage spark serves to excite the vapor jet, and

the resulting spectrum is photographed by a spectrograph in the usual way.

The problem was to obtain a reproducible spectrum so that quantitative

analysis of the sample could be made. The major causes for this lack of reproducibility were found to be variations in the energy of the laser pulse

and the irregular production of a train of several pulses. Equipment was

developed to measure the intensity and time duration of the pulses of light

from the laser and modifications were made in the laser system to obtain

optimum operation.

A single reproducible pulse is now obtained from each firing of the laser and this is being applied in quantitative analysis. With a single excitation, as little as 0.1 percent of an impurity was detected in a portion of sample

weighing 20 nanograms, giving an absolute sensitivity of 20 picograms.

X-Ray Spectrographic Analysis of Solutions. An x-ray fluorescence spectrographic method of analysis was developed and applied to the analysis

of brass standard reference materials in solution form. Careful design

of the analytical procedure minimized the effects of possible sources of error. Care is exercised to assure that all solutions are at the same acid concentration and contain the same weight of material per unit volume. The sample

cells are designed and filled in such a way that each solution is exposed

identically to the x-ray beam. Each sample is analyzed by reference to a

series of synthetic solution standards. A new standard is then prepared to have the same composition as the sample; a direct comparison of these two

nearly identical solutions provides additional verification of the accuracy

of the results. The data obtained compared well with the results of chemical

analyses of the same samples, but the x-ray method is considerably faster. Electron Probe Microanalyzer Extends Capabilities. The Bureau

acquired a commercial electron probe microanalyzer for the analysis of extremely small samples such as inclusions in alloys, minerals, and crystals. In this instrument, a beam of electrons is focused onto an area as small as one micron in diameter in order to excite the characteristic x-ray spectra of

the elements in the sample. The electron beam can be swept synchronously

with the display sweep of an oscilloscope in order to form an image of an

area of the sample being studied. This image can be made to represent

several aspects of the sample.

127
Quantitative spectrochemical analysis using a laser pulse and high-voltage spark

has resulted in as little as 0.1 percent of an impurity being detected with a single

firing. The laser pulse is focused on the block of metal by a microscope. The

laser energy volatilizes a small amount of sample which is then excited by a spark discharge between the two pointed carbon electrodes. (See page 127)

In one type of display, an image representing back-reflected electrons resembles what is seen through a high-power microscope but can also be

made to yield data on composition. Another image can be formed repre- senting the x-ray signal from a particular element in the sample, thus showing the distribution of that element. More complex displays are possible. For example, an attachment to the electron probe microanalyzer can display areas of the sample falling

within a certain range of concentrations for a particular element. The

sensitivity of detection depends on the nature of the sample and the element

being sought. Typically, the lower limit of detection will be between 0.01 and 0.1 percent, corresponding to a weight of material within the small focal spot of the order of a femtogram. The electron probe microanalyzer extends

considerably the capabilities of the Bureau in microanalysis.

Spectra Excited in Controlled Atmospheres. Two similar devices were developed for the excitation of atomic emission spectra in atmospheres

other than air. Although arc excitation in controlled atmospheres has

been known to improve sensitivity for several years, the advantage of spark

excitation in an argon atmosphere is a recent finding. The usual method of excitation in controlled atmospheres has been to enclose the electrodes in a 128
sealed chamber, with considerable time needed to analyze each sample.

The two new devices, however, allow the analyses to be performed as quickly

in controlled atmospheres as in air. The two devices, one for arc excitation and one for spark excitation, differ in design but both employ the principle of controlling the atmosphere in the

excitation zone by a gentle, tubular flow of gas around one of the electrodes. Spark excitation in an atmosphere of argon was shown to extend the applicability of spectrographic standard samples, since a single set of calibration curves can be applied to the analysis of several related alloys rather than

being useful for only a single alloy. Arc excitation in atmospheres of argon, helium, or mixtures of these gases with oxygen often permits a substantial improvement in the sensitivity of trace analysis compared with excitation in

air. Studies are presently under way of the complex physical and chemical

interactions between the sample, the discharge plasma, and the atmosphere in order to arrive at an understanding of the empirical observations of the effects of changing the gas in the excitation zone. Special Cast Iron Standards Prepared for the Malleable Research

Foundation. In view of previous successful work in the preparation of

eight NBS White Cast Iron Spectrochemical Standards, the Malleable Founders Society recently requested the NBS to aid them in the preparation of sev- eral special cast iron standards representative of the needs of this group. The first of these standards was prepared with special NBS equipment and

under the direction of NBS personnel in the foundry of the Naval Research

Laboratory. As the NBS cannot possibly provide all of the standards needed

by industrial laboratories, it concentrates efforts on those for use in critical areas of calibration, and encourages and assists outside groups such as the Malleable Research Foundation in the preparation of other standards. Errors in the Microscopical Measurement of Spheres Studied,

In chemical microscopical methods of quantitative analysis, final determination often depends upon the measurement of a volume. Although, it is as- sumed to be best for the final product to be in the form of transparent spheres, there is a long record of difficulties in the accurate microscopical measure- ment of the diameter of the spheres. A recent investigation disclosed that the problem originates chiefly in geometrical factors which influence the observer's selection of the position of focus. This error can be as large as 15

percent regardless of sphere size. This increased understanding made it possible to work out several methods by which these errors can be controlled. The accuracy now attained is limited only by the resolving power of the

optical system, or about 0.1 micron.

Thermodynamics of Solutions in Heavy Water, Renewed interest

is being taken in heavy water (or deuterium oxide) as a solvent, where the two hydrogen atoms of ordinary water are replaced by two atoms of deuterium, the heavier hydrogen isotope.

Corresponding to an acidity scale for solutions in ordinary water (the pH

Scale) , a pD scale for deuterium oxide solutions was established. Electro- motive force measurements were made over a temperature range using cells 129
with deuterium gas and silver-silver chloride electrodes and a solution of deuterium chloride in heavy water. From these measurements the standard

potential of the cell was derived. This was used used along with emf

measurements of a similar cell containing solutions of phosphate buffer to determine the acidity function (pD value) of the standard, equimolar (0.025

m) solution of KDL,P04 and Na2 DP04 in deuterium oxide. The pD value

at 25 °C is 7.429, compared with 6.865 for solutions in ordinary water. pH Standards in Partially Aqueous Media Investigated. Standard

buffer solutions are available to cover all the usual working range of the pH

scale in aqueous solutions. For many industrial and analytical purposes, however, water may not be a suitable solvent. Attention was therefore given

to methods of defining acidity scales in a solvent consisting of equal parts by

weight of water and methanol. Three buffer solutions—acetate, succinate,

and phosphate—in this solvent were investigated and pH values assigned to them over a range of both concentration and temperature.

Preconcentration Polarography. In this new analytical technique,

part of an unknown species is concentrated into a stationary mercury drop

electrode at a given potential, and then subsequently stripped out using

voltammetry with linearly varying potential. The method is being applied

to the determination of trace amounts of a number of elements in practical

samples.

Magnetic Densimeter Constructed. Densities of pure liquids and

solutions over a range of temperatures are needed for the interpretation of a wide variety of physical measurements, including dielectric constants, con- ductance, and thermodynamic properties of solutions. A magnetic dens- imeter was constructed which requires as little as 15 milliliters of liquid. A

magnetic float in the completely enclosed system is adjusted to buoyant

equilibrium by means of an external solenoid. An electrobalance provides a rapid and precise adjustment of the current supplied to the solenoid and per- mits the calibration of the instrument in reference to a 1-gram mass standard. Copper-Base and White Iron Standards Issued. Provisional certificates were issued during the year for four types of copper-base spectroscopic standards; free cutting brass, gilding metal, commercial bronze, and

aluminum brass. These are certified for copper, zinc, lead, iron, tin, nickel,

and phosphorus by chemical analysis. Manganese, silicon, aluminum, anti- mony, and arsenic were also determined in several standards. There are now

seven types of copper-base spectroscopic standards available, making a total of 36 samples.

Four new white iron spectroscopic standards are in preparation. The

homogeneity of these samples was checked by chemical analyses of carbon,

sulfur, phosphorus, and silicon. In addition, the minor elements tin, titan- ium, cobalt, aluminum, and arsenic were determined. Major elements will be determined at a later date. New Uranium and Plutonium Isotopic Standards Issued. A new

uranium isotopic standard (U-500) was certified in cooperation with the mass spectrometry laboratory. Synthetic standards at the 50-50 percent

130
level were prepared from highly purified uranium 235 and uranium 238

isotopes to evaluate the uranium 235 and uranium 238 content of the new

standard. The limits of uncertainty of the values obtained are believed

to be within ±0.1 percent of the amount present. A new series of uranium

233 "spikes" was prepared for all 16 uranium isotopic standards to obtain more accurate values for the uranium 234 and uranium 236 present. The

uncertainty of these values should be within ±0.25 percent. To obtain

better values for plutonium 241 in the new plutonium isotopic standard

(Standard Sample 948), americium 241 was removed by ion-exchange and

solutions of the americium-free plutonium were prepared for mass spectrometry. The procedure was tested using 1 microgram of plutonium.

High-Precision Coulometry. The research program for the development of very precise and accurate coulometric methods of analysis resulted in a new method for the determination of potassium dichromate. The dichromate is titrated with ferrous ions electro -generated at a platinum cathode

by constant-current coulometry. One-half gram samples may be analyzed

with a precision of a few thousandths of a percent. The new method per- mits the standardization of potassium dichromate, a most important chemical oxidizing reagent, with greater reliability than was previously possible.

Furthermore, its salient feature, the accurate electro-generation of the fer- rous ion, a versatile reducing agent, should find applications in other redox

titrations where high precision and accuracy are required.

Analysis and Purification Services Provided. Essential analytical

and purification services were provided to various research groups at NBS.

During the year 400 requests for such services were completed comprising

several thousand individual analyses and purifications. The analytical capabilities were extended by the acquisition of additional polarographic equipment which makes possible minor constituent and trace determinations

not readily accomplished by other means. A nuclear-magnetic-resonance

(NMR) spectrometer was acquired and a program concerned with analytical

applications of NMR was initiated; structural analyses and identifications of organic compounds are also provided as an analytical service. Development of methods of analysis is a byproduct of this service pro- gram. Methods published during the year include a new procedure for the determination of the precious metal rhodium in uranium alloys, and a method for the analysis of zirconia-yttria refractory materials. Advisory

and consultative service on analytical chemical problems to other Govern- ment agencies is also an ancillary aspect of this program.

2.2.2. POLYMERS

Research is carried out on the constitution and structure of both natural and synthetic polymers. Many of the successful applications of polymer

materials, such as rubber, plastics, cellulose, and collagen, depend on the

size, shape, distribution, and flexibility of their molecules and on the inter- actions of these molecules with each other. Hence, a better understanding

131
of the mechanisms involved in forming polymers is being sought to aid in the development of new materials and the efficient utilization of those now

available. Services are also provided to Government and industry in developing

and maintaining adequate measurement and materials standards. In this program, standard samples or reference materials having accurately known

properties are distributed to facilitate the calibration of measurement sys- stems, including instruments and test methods. These include the development of a series of standard polymers with precisely known molecular weight

distributions. The Department of Defense sponsors work in the development of fluoro- carbon polymers and in special techniques of polymerization; the National

Aeronautics and Space Administration assists in the study of polymer

stability; and the Advanced Research Projects Agency supports work on

the crystallization of polymers. The American Dental Association and the Federal dental services continue their support of a cooperative program to improve dental materials and equipment or to develop new ones for use

in restoring teeth. The Bureau also assists other Government agencies in developing standards and specifications for products made from polymers

and intended for Government use. Cooperative Intramolecular Transition Found in a Synthetic Polypeptide. Previous work at NBS and elsewhere has indicated that synthetic

poly-L-proline may exist in either of two forms, differing in crystallographic

structure as well as in other properties. Induced transformation between

these two forms was studied by measurement of the optical rotatory power of

dilute solutions of the peptide. The results, augmented by infrared spectro- scopy and crystallographic observations, led to the conclusion that the two

forms are configurationally homogeneous structures whose imide linkages are

respectively in either the cis- or £rari5-planar configuration, the transition be- tween them consisting of repeated cis-trans isomerizations along the back- bones of individual peptide chains. In contrast to the familiar helix-coil transitions observed in many polypeptides, the present system is a helix-helix transition. If the former is considered as the one-dimensional analog of melting, the latter is the analog of

solid-state transformations between different crystalline modifications of a

single substance. Of particular interest are (1) that the two forms are

helices of opposite sense, i.e., right- and left-handed, and (2) that the transi- tion between them is so abrupt as to suggest the existence of a cooperative

effect which, in the limit of a complete all-or-none mechanism, leads to a

first-order one-dimensional phase transition. Stress Found Proportional to Double Refraction in Amorphous

Polymers. Large polymer molecules characteristically have the ability to assume many conformations because of rotations of molecular segments

about the valence bonds. The elongation of these molecular chains forces

transitions to take place between the different conformations, and the in- crease in free energy of this process is responsible for a retractive force. 132
Not only are the chains stretched out, they also become partly oriented. If the chain bonds are optically anisotropic, this orientation should be directly related to double refraction of the chain.

For simple polymers, much is already known about their structural properties such as bond lengths, bond angles, and rotational angles for which the

potential energy is a minimum. To make calculations, however, for a rubberlike material that consists of many molecular chains crosslinked to one

another, it must be assumed that the intermolecular forces do not change

materially on stretching and that the only contributions to the elongation come from the intramolecular forces. Calculations based on these assumptions yielded a factor of proportionality between stress and double refraction

for an amorphous polyethylene sample. These results, in excellent agreeThe thickness and refractive index of adsorbed polymer film not more than

a few Angstroms thick can be measured by ellipsometric techniques, thus providing a better understanding of the constitution and structure of both

natural and synthetic polymers. (See page 135)

133
ment with published values in the literature, indicate that the supposed me- chanism underlying the stretching process is correct, and they also provide

a better understanding of the relationship between chain structure and elastic properties.

Polypropylene Crystals Studied. The formation mechanism of monoclinic spherulites of isotactic polypropylene was investigated. Specimens were crystallized from % percent solutions of the polymer in amyl acetate

in the temperature range 110 to 115 °C. An analysis of the resulting fine structures showed them to be dendritic crystals. Narrow (150 to 200 A),

diagonally oriented crystal branches were found to be lamellar when viewed

along the crystal plane. On the basis of these results, coupled with information on the molecular orientation in the crystals derived from another study,

it was concluded that the chain molecules in their constituent branches are regularly folded and that the extended interfold molecular segments are oriented preferentially parallel to the plane of the crystal and normal to its longer axis. Crystalline Polymers. A recent study of isotactic polypropylene

samples of varying degrees of crystallinity and morphology indicates that differences found among these materials depend almost entirely on the method of comparison. For example, when the various samples were compared at equivalent macroscopic strains, the resulting behavior was almost

independent of morphology and crystallinity. On the other hand, when they were compared at equivalent macroscopic stresses, the extent of relaxation

decreased uniformly as crystallinity increased. This behavior is explained on the basis that the crystalline polymer is a composite material consisting

of crystalline regions and some less perfectly ordered (amorphous) regions,

both of which may relax but to different extents. Thickening of Chain-Folded Crystals. Low-angle x-ray measure- ments were made on bulk polyethylene at various temperatures below the melting point while crystallization was occurring. As had been predicted

earlier on various grounds, it was found that the chain-folded lamellae slowly

thickened, for example, approximately doubling their initial thickness in a thousand minutes at 128 °C. This work is of significance in the explanation

of the melting and annealing behavior of crystalline polymers.

Lattice Parameters of a Copolymer. Recent measurements showed

that the lattice parameters of a copolymer of tetrafluoroethylene and hexafluoropropylene are larger than those of polytetrafluoroethylene at all temperatures between —196 and 25 °C. Thus the lattice of the copolymer is larger than that of polytetrafluoroethylene, even below the first-order transi- tion temperatures of about —50 °C in the former and between 15 and 30 °C

in the latter. It therefore appears that the larger size of the copolymer

lattice at room temperature is not the result of heating above the transition temperature where lattice parameters and thermal coefficients of expansion

increase. Instead, the results support the concept that the comonomer units are included in the lattice as point defects and thus enlarge the lattice. 134
Mechanism of Polymer Adsorption Investigated. Unlike small molecules, large polymer chain molecules may have only relative few of their segments adsorbed on a solid surface. These segments can then act as anchors for the rest of the molecule, which is in the shape of loops dangling

in the solution. Several theories have been advanced to describe this ar- rangement but the underlying assumptions have not been completely

satisfactory. Recent NBS work shows that low surface adsorption may be described

by a mathematical model virtually identical to the one used to describe

the helix-coil transition occurring in DNA (deoxyribonucleic acid), the well- known molecule of biological importance. Consequently, stiff chains should

be adsorbed with most of their segments in contact with the surface, and the loops should be sparse and short. Flexible chains should be adsorbed with

only a few anchoring segments, if the surface exerts weakly attractive forces,

and the loops should be large. For strongly attractive forces, flexible chains

should tend to flatten out at the surface. Experiments now under way to verify this theoretical work may provide a deeper insight into the mechanism

underlying polymer adsorportion.

Polymer Properties Statistically Calculated. A theoretical model,

based on the theory of absorbing Markov chains, was developed to calculate the various thermodynamic functions of a single polymer chain resulting from

intramolecular interactions. The idealization of a polymer chain as a Markov-type chain imposes a restriction on the type of intrachain interactions, so that only short-range interactions can be considered. Hence the new

model applies especially to extended polymer chains, with net repulsions be- tween its various elements, for example, polyelectrolytes or polymers in good

solvents. By use of the Monte Carlo technique, a computer program was designed

to calculate the stretching of model polymer chains resulting from the increase in the effective free volume of a single polymeric element. Compressibility of Natural Rubber. The specific volumes of unvul- canized natural rubber and of a peroxide-cured vulcanizate were measured

at pressures from 9.8 to 4900 X 104 newtons per square meter (N/m2

) at temperatures from 0 to 25 °C. Observations on mercury-filled dilatometers were made through a window in the pressure system. An empirical equation

representing the observations over the range investigated was found and

the constants evaluated. Calculations of values of compressibility (and its reciprocal, the bulk modulus), "internal pressure," bulk wave velocity, difference between specific heats, and several other physical properties were in reasonable agreement with those obtained by direct observation by

other workers.

Ultracentrifuge Used to Study Polymer Sedimentation. Information was obtained in recent ultracentrifuge experiments concerning the de- pendence of the sedimentation coefficient of polystyrene on concentration at temperatures around the theta point where the solution is thermodynamically

756-244 0—65 10 135
An electronic thermogravimetric balance used to detect changes in weight of coordination polymer samples as they are heated in a vacuum furnace (extreme

right). The measurements obtained are an indication of polymer thermal

stability. (See page 138)

ideal. The study showed that the concentration dependence does not dis- appear at the theta point but at a considerably lower temperature. This

behavior is attributed to a balancing of hydrodynamic and thermodynamic

interactions of the polymer molecules. The data were shown to be consistent with a recent theory predicting this behavior.

Heat of the Vulcanization Reaction. Quite a discrepancy exists in the literature as to the heat involved in the rubber-sulfur vulcanization

reaction. Earlier calorimetric work at NBS found heat to be liberated at

all concentrations of sulfur, but other investigators claim that no heat is liberated unless at least 7 or 8 percent of sulfur is reacted with the rubber. Recent experiments were conducted on the rubber-sulfur system with a

differential thermal analyzer, an extremely sensitive instrument to heat changes during a chemical reaction. The results give positive evidence that the vulcanization reaction is exothermic at all percentages of sulfur, verifying

the findings of the earlier NBS work.

136
Fluorine Chemistry. New highly or totally fluorinated aromatic monomers were synthesized for the purpose of preparing thermally stable polymers. One class, including such monomers as 2,3,4,5,6-pentafluorostyrene, a-hydroheptafluorostyrene, and perfluorostyrene, is designed to yield

polymers that have a pendent perfluorophenyl group along the polymer backbone. A second class, typified by p-hydroxyheptafluorotoluene, is designed

to incorporate a perfluorophenylene group in the polymer chain.

Efforts to prepare a material of high thermal stability and good elastomeric

properties were continued by the preparation and polymerization of perfluoropentadiene, the first completely fluorinated rubber to be reported.

Techniques and chemistry that will permit preparation of all terminal dienes

from C=4 to C = 24 were developed.

Polymer Stability to Radiation. A thermal conductivity cell sensitive to 0.01 mole percent of volatile products was used to study the decomposition of polytetrafluoroethylene exposed to ionizing radiation in a

flowing helium stream. Measurements were made in the temperature range

from 330 to 460 °C and at dose rates of from 0.2 to 10 megarads per hour.

The results of this work, together with thermochemical data, indicate a very high activation energy for polymer chain termination.

Techniques Devised to Study Polymer Oxidation. Two techniques were devised to measure the oxygen consumption of polymers as a function

of temperature. The first is a gas chromatographic approach which uses a molecular sieve to separate the various components in samples of the at- mosphere surrounding the polymer. Measurements of the relative amounts

of oxygen and nitrogen in samples of this atmosphere made at various time

intervals at a given temperature permit calculation of polymer oxygen con- sumption rate. Measurements at different temperatures give the apparent

activation energy for the reaction, which is indicative of polymer resistance

to oxidation.

Polarography is used in the second technique, permitting the investigator

to follow oxygen consumption directly and continuously. In this method, a commercial polarographic cell makes use of silver and gold electrodes and

a special diffusion membrane to obtain high selectivity for oxygen analysis.

Polymer Degradation. In a recent investigation, dextran triacetate was found to exhibit greater stability than dextran to gamma radiation. The

post-irradiative molecular weight drop in dextran was more rapid in the presence of moisture, indicating that some type of oxidative cleavage by

hydrogen peroxide is formed from the radiolysis of water. An insoluble crosslinked dextran, similar in appearance to chemically crosslinked dextran,

is formed at high concentrations and moderate dose rate in vacuum. The thermal decomposition of polystyrene in tetralin solution was also investigated between 253 and 297 °C. The percentage of material volatilized and the decrease in molecular weight were found to depend on concentration,

indicating that the scavenging effect of the tetralin is not complete under

these conditions. A rapid initial degradation, amounting to only 0.11 scis- sions per initial chain, was detected at the lower temperatures. An activation 137
energy of 25X 104 J/mole (60 kcal/mole) was obtained from the initial rates of the subsequent degradation. Hence, the rapid decrease of molecular

weight of polymeric materials cannot be based on the theory of "weak links"

in the molecular chain. Properties of Coordination Polymers. Coordination polymers

formed by the combination of 6«-bifunctional derivatives of 8-hydroxyquinoline with metal ions are an important new class of polymers having potential space applications. To obtain data on the properties of such polymers, an

organic ligand, 5,5'- [methylene- (p-phenylenenitrilomethylidyne) ] di-S- quinolinol was recently synthesized by the use of a SchifT-base bridging

group to link two 8hydroxyquinoline molecules. This ligand, when reacted with some first-row transition metal ions, yielded highly colored insoluble

coordination polymers having high thermal stability in vacuum. Data de- rived from the study on the relation between decomposition temperature and

the metal incorporated in the backbone of the polymer chain, coupled with

studies of molecular structure, will make it possible to explain and perhaps

control the behavior of these polymers.

Microradiography of Roofing Materials. Microradiography was re- cently used to determine the distribution of reinforcing materials in asphalt

films and mats, as well as the origin and development of failures in shingles

and other structures. The method not only reveals many details of the mechanism of deterioration; it is also often able to disclose intrinsic weaknesses in design or formulation before they become apparent by other methods of analysis.

Centrifugal Method for Measuring Tensile Strength of Dental

Amalgam. A centrifugal method of stressing specimens was developed.

It applies the Beams (University of Virginia) method of driving a rotor by

air. The stress (5) for any size specimen can be computed by the simple

formula S = 2rr2Df2L

2

. Hence, with density {D) and length (L) of a speci- men known, only the frequency of rotation (/) needs to be observed. With

this method, flow of a material under tensile stress can be determined at a constant rotation over a period of time. Tests made on dental amalgam

show tensile strengths of from 10X10* to 69X10° N/m2 (1,500 to 10,000

psi) in specimens ranging from 1 hour to 1 day old. Properties of Tooth Structure. A method developed for measuring

the shear strength of human tooth dentin requires the use of sectioned molars

parallel to the biting surface and a hardened steel punch with a diameter of 6.35 mm (0.250 in.). The maximum load the specimen supports divided

by the shear area (specimen thickness times punch circumference) gives the shear strength. The specimen thickness, between 0.26 and 1.14 mm (0.010

and 0.045 in.) , did not appear to be correlated with the average shear strength of 98±16X106 N/m2 (14,200±2,300 psi). However, the variance was

considerably smaller in data obtained on test specimens between 0.55 and

1.0 mm (0.021 and 0.039 in.) in thickness. The adsorption of gases is being used as a measure of the "inner surface

area," hence, the porosity of teeth. Measurements made on dentin samples

138
shortly after extraction of the teeth and then again after one year in cold

storage gave the same value of 10.5 square meters per gram. When the organic matter was extracted from these samples with ethylene diamine the area increased by more than an order of magnitude to 124 square meters per gram.

A proposed mechanism for the growth of tooth and bone crystallites was

developed and is being investigated. The crystallites are principally hydroxyapatite, Ca5 OH(P04 ) 3 . A unique feature of the mechanism is that the growth apparently involves the initial deposition of another crystalline cal- cium phosphate, octacalcium phosphate, Cas H2 (P04 ) 6 5H2 0. This departure

from the previously accepted growth mechanism introduces new factors which should lead to a better understanding of the beneficial effect of fluoride

in preventing caries. Rheological Behavior of Dental Amalgam. A study of the rheological behavior of dental amalgam (a mixture of mercury and powdered silver alloy used as the restorative material in about 75 percent of all dental fillings) was made by means of tensile creep tests. The tensile strain developed was

found to be a function not only of the applied stress but also of length of time of stress application. Amalgam was shown to exhibit (1) strain hardening; (2) elastic deformation; (3) retarded elastic deformation; and

(4) viscous deformation. The viscoelastic data obtained from the study

A new centrifugal method for measuring the tensile strength of dental amalgam

allows the flow of the material under stress to be determined over a period of

time. Insert shows top of rotor with specimen in place. (See page 138)

139
were used to calculate tensile stress-strain curves which agreed with those obtained experimentally at various stressing rates. Reinforcement of Dental Polymers. Polymer materials used to restore or fill teeth match natural teeth closely in appearance but have other

properties (such as a high coefficient of thermal expansion) that limit their usefulness. A study was made of the feasibility of employing fused

silica particles to reinforce dental polymers and to improve their properties. The results show that optimum conditions for reinforcement include

(1) use of a chemical coupling agent such an an organofunctional silane; (2) spherically shaped particles; (3) intermittent grading of particle sizes to reduce the amount of polymer; (4) fine particles to increase strength; and

(5) addition of certain glass powders to obtain visual and x-ray opacity.

Monomers having low polymerization shrinkage and other desirable features were produced for use with these powders. Compared with previously

existing dental filling resins, the resulting materials have an improved ther- mal expansion coefficient, compressive strength, and modulus of elasticity.

2.2.3. METALLURGY

The metallurgy program has two main parts, both aimed at solving problems important to the national economy. Mechanical characteristics and

resistance to corrosion are the two most important properties of metals,

which are used mainly as structural materials. The basic understanding of these two phenomena in metals is therefore emphasized.

Metallurgical research is focused on the mechanical properties of metals,

corrosion, metal crystal growth, and the physics of alloys. This work in- cludes studies of creep, fatigue, notch sensitivity, stress corrosion, nucleation and growth of oxide films, the kinetics of metal crystallization, elec- trolytic and vapor decomposition techniques for producing metal coatings,

and the electronic configurations in metals. The research stresses the re- lationships between the properties of metals and crystal defects and microstructures as observed by x-ray and electron diffraction, transmission and

replica electron microscopy, light microscopy, x-ray diffraction topography,

and electron probe microanalysis.

Analyses are made of the service failures of aircraft for the Bureau of Naval Weapons and the Civil Aeronautics Board. Consulting services on

corrosion are provided various agencies of the Department of Defense and the National Aeronautics and Space Administration. Critical evaluation of data on diffusion in metals is carried out and highly pure metal crystals are prepared. Various other metallurgical serv ices are provided to Government

agencies on request and in collaboration with other NBS Institutes. Effects of Notch Geometry Investigated at High Temperature.

The effects of notch geometry (depth, included angle, and root radius) upon

the tensile, stress-rupture, and creep properties of a high-strength titanium

alloy at temperatures up to 1200 °F were investigated. The strength of the

alloy was increased and ductility decreased with decrease in notch angle or
root radius and with increase in notch depth. Preliminary results in the creep and stress-rupture tests indicate that ductility increases with increase

in temperature and with a decrease in strain rate. The origin and propagation of fracture are affected by the notch geometry of the specimens and the

test temperature.

Precision Gage Block Materials. Several combinations of materials

and treatments yielded a gage-block dimensional stability better than

0.2 X10 6 in. /in. in a year, and a few combinations, better than 0.1 X 10"6 in./in. in a year. Additional observations were made on promising types

of experimental gage blocks now under investigation to establish their long term stability (see p. 60). New materials and treatments were investigated

to determine their suitability for inclusion in the gage-block program and

many were selected for test. Several factors that are believed to influence

stability are being studied in an effort to better understand and control the causes of instability.

Deformation of Metals Studied. The effect of multiaxial stresses in- duced by notches on the tensile deformation and fracture characteristics of

a 310 austenitic stainless steel were studied. Severe strain and work hardening in the highly stressed region near the root of the notch initiated a crack at relatively small average strain and at stresses considerably below

maximum load; these cracks then propagated slowly until final rapid frac- ture occurred at much larger strains. This mode of failure depends mainly

upon the radius at the root of the notch and not its depth. For this partic- ular steel, the minimum notch radius should be greater than 0.05 inch to avoid this type of crack initiation and growth.

Slack-Quenching Effects Studied. Studies of the quantitative effect of slack quenching upon the mechanical properties of three steels of medium

hardenability (4140, 5140, and 8640) are in progress. It is generally be- lieved that the presence of a slack-quenched structure is detrimental to the optimum mechanical properties of steels. Preliminary data indicate that

this belief is generally valid; however, sometimes small amounts of slack- quenched structures have no detrimental effect and, under certain restrictive conditions, the presence of substantial amounts of these structures appear to improve mechanical properties.

Metal Fatigue. Present research is directed toward elucidating the effect of atmospheric environment on fatigue and the relationship between cracks and fatigue. A recent study of the effect of a fatigue crack on the strength

of an aluminum alloy used the beginning of gas evolution as an indicator of the inception of cracking. Cracked specimens show a fatigue strength of only about 40 percent of similarly stressed but uncracked specimens.

Nuclear Magnetic Resonance. Information can be obtained on the

electronic structure of alloys by analysis of nuclear magnetic resonance

linewidths, quadrupole effects, and Knight shifts of both the solvent and

solute nuclei in the same alloy. Hence, the nuclear magnetic resonances

of Pb207

, Bi209

, In115

, Hg199

, Sb121

, and Tl 205 in Pb-based primary solid 141
Notch geometry is extremely useful in studying the origin and propagation of metal fractures. Here, a tensile specimen of 310 stainless steel cracks under a true strain of 0.22 (left). Crack has grown under strain of 0.8 (right) just

prior to the rapid final fracture of the specimen. (See page 140)

solutions were studied in great detail. The Pb207 results showed that the change in Knight shift in composition is small in contrast to monovalent

and divalent systems. In the other work, no evidence of pronounced quadruple effects was obtained for the solutes in the alloys. Since both large

changes in Knight shift and large quadrupole effects in alloys have been

interpreted in terms of long-range charge oscillations around the solute atoms, it may be concluded that the charge oscillations in the Pb alloys are less effective than has been found in other cases. The existence of a nuclear magnetic resonance linewidth anomaly in lithium has long puzzled investigators. In a recent study, a multiple pulse

nuclear magnetic resonance technique was used to disclose that the anomaly

is an experimental one and it is associated with the diffusion effect in large

magnetic field gradients. These field gradients exist as a consequence of the bulk magnetic susceptibility of the lithium metal powder.

Highly Pure Metals and Alloys Prepared. During the preparation

of a series of lead-tin alloys, the tin in solid solution under nonequilibrium

conditions was retained long enough to make nuclear magnetic resonance measurements. The powdered samples were reheated and then quenched

in ice water. At the request of the NBS solid state physics laboratory, three gold-iron alloys with a small controlled addition of iron were prepared in the form of 10-mil wire for the study of magnetic ordering in dilute solid solutions of iron in gold. Iron-nickel alloys were also prepared for the Geological Survey and intermetallic compounds of niobium and iron for the Naval Research Laboratory.

142
Dislocations in Metals. An investigation of the nucleation of gold

deposited on cleaved zinc surfaces was completed. Decoration of surface

steps was observed in some cases, and the distribution of nuclei was found

to depend on substrate temperature. Observations of the nuclei were made

by transmission electron microscopy through the thin zinc substrate. Determination of the stacking fault energy in a series of dilute silver alloys was undertaken, and preliminary observations of dislocation structures in low stacking fault energy Ag(Sn) alloys were made.

Stacking Fault Theory Being Developed. The stacking fault energy

in many face-centered cubic (FCC) alloys is lowered by alloying; hence,

thermodynamic equilibrium requires some segregation of solute atoms in the stacking faults to lower the total free energy. In FCC crystals, a total dislocation may lower its energy by splitting into two partial dislocations connected by a stacking fault. Thus the separation between partial dis- locations is increased and the faulted area is enlarged. A general theory

is being developed to describe these phenomena. This theory may have important applications in the measurement of stacking fault energies by means of electron microscope observations of dislocations, and in theories of the mechanical properties of materials. Electron Probe Modified. The Bureau's electron probe microanalyzer was recently modified to make it a more versatile instrument. An increased

x-ray takeofT angle makes possible more accurate analysis of the light ele- ments. An improved light optics system was installed, together with an

enlarged specimen chamber. Facilities to perform Kossel line studies were added. New spectrometers are being built for the instrument so that quantitative microanalysis may be made of elements down to sodium and

ultimately down to carbon.

X-Ray Diffraction Studies. Residual microstrain measurements were made in individual grains of a deformed coarse-grained polycrystalline

aluminum specimen. By means of x-ray diffraction techniques employing

photographic film and a counter diffractometer, the effect of residual stresses upon the spacings between the planes of atoms within the metal grains was

observed. The existence of preferred orientations in electrodeposited cop- per samples was also observed.

Intermetallic structures of the niobium-tin system were studied on small

single crystals isolated from tin amalgams. Crystals isolated from amalgams

quenched from 1000 °C had the j3-W type structure and were found to be

ordered. Crystals isolated from 800 and 850 °C quenches consisted of Nb2 Sn

and had the CuMG2 type structure. Crystals of the Ni3 Sn4 type (monoclinic) and W5Si3 type (tetragonal) were also isolated in furnace cooled

amalgams. Isolated single crystals of Ag3 Sn were found to be of the Ni3 Ta

type structure, which requires doubling of the unit cell. Micrographic Analysis Performed by Computer. The Bureau's

experimental computer program for the automatic quantitative analysis of micrographs excited widespread interest during the year. A chromosome

matching program based on the NBS model is being developed elsewhere,

143
and NBS is studying nerve cell tissues by means of the technique. Micrographs are being prepared of photographic emulsions and ceramic materials

for computer measurement. The technique showed that excessive heat treatment of a niobium-tin alloy apparently caused inferior superconducting

properties to develop. An improved program for the NBS PILOT computer, now being completed, will respond to instructions given in normal

English sentences and will accept data obtained from grey-scale pictures up

to 20 X 24 cm in size. Polarization Technique for Measuring Corrosion Rates Applied

to Iron-Nickel Alloys. A polarization technique was used to study the corrosion of a series of iron-nickel alloys. The corrodent was Washington

city water containing 3 percent sodium chloride. Results thus far show a marked reduction in the corrosion rate of alloys containing 40 percent or more of nickel, with a further reduction in alloys containing 65 percent or more of nickel. When the nickel content is 80 percent, the corrosion rate is considerably less than 1 percent of that of the unalloyed iron exposed to the same corrodent. Surface Studies in Corrosion. The initial formation of oxygen films on iron surfaces was studied by means of elliptically polarized light. The

growth rates of the films were determined during the first fractions of seconds by measurements of film thickness and optical properties. The

first stage is an anodic process lasting about 0.2 to 0.4 seconds during

which no film growth is detected. This is followed by a rapid linear growth

and to different logarithmic growth processes. The latter stages of film growth are the results of the movement of metal ions through the film under

the driving force of an electric field. Steel Pilings Examined. Thirty-five steel piling structures in service

for from 5 to 50 years were inspected for the American Iron and Steel

Institute. They showed practically no damage below the water line. These

findings agree with those previously made, namely, that steel pilings driven

into the ground are not materially affected by corrosion, probably because

of the lack of oxygen under such "undisturbed soil" conditions. Stress Corrosion Cracking. The effect of the CI ion on the stress cor- rosion cracking of stainless steel, type 304, was investigated. The duration of the exposure periods to failure differed with specimens exposed to MgCL and LiCl, even though the CI ion, the stress, and the temperature of the corrodent were kept constant. Bubbling oxygen into the corrodent pro- foundly accelerated the corrosive attack. This result confirms earlier findings

which demonstrated the importance of the presence of oxygen in the initia- tion and propagation of stress corrosion cracks. Corrosion Failure of Electroplated Coatings. NBS and the American Electroplaters' Society are engaged in a joint study of the galvanic

effects associated with the corrosion failure of electroplated coatings. One

aspect of this work involves the electrolytic cell formed when a layer of metal is exposed at the base of a pit in an overlaying metallic coating. To

simulate a pit in a nickel coating on steel, a small hole was drilled in the 144
center of a sheet of nickel and an iron wire was cemented into the hole so

that one end of the wire was flush with the surface of the nickel. A lowresistance ammeter was connected between the nickel and iron wire and

the cell was exposed to a corrosive environment.

During a 1-year outdoor exposure, currents as great as iy2 microamperes were observed, though usually they were in the range of 10 to 100

nanoamperes. These values, corresponding to current densities of about

4 milliamperes per square centimeter (ma/cm2

) and 0.02 to 0.2 ma/cm2

, were converted to corrosion rates (depth) of 108 /Vday and 0.7 to 7 /x/day,

respectively. Dew, rain, and melting snow yielded similar currents and the larger currents were observed in warm weather.

Properties of Electrodeposited Copper, Measurements of the physical and mechanical properties of electrodeposited copper are in progress. The deposits are made from conventional copper sulfate-sulfuric acid solu- tions under a variety of conditions of temperature, current density, and

concentration of salt and acid. The results thus far show that tensile strength

increases with current density and decreases with increase in temperature

Transmission electron micrograph of extended dislocations in a stainless steel sample. The low stacking fault energy in this material permits observation of the faults (exhibiting interference fringe contrast) associated with the dislocations. Magnification 120,000. (See page 143)

145
or concentration of bath constituents. The stronger electrodeposits have

about the same strength as annealed wrought commercial copper but are not

as strong as hard-drawn commercial copper. Values of elongation of cop- per electrodeposits parallel their tensile strength values. Variations in in- ternal stress also parallel variations in tensile strength. The maximum inter- nal stress thus far found is not large enough to cause difficulty in engineering

applications of copper electrodeposits. This project is supported jointly by

NBS, the American Electroplaters' Society, and the International Copper

Research Association.

Chemical Deposition of Tungsten from the Vapor Phase. Some

time ago the Bureau developed a method of producing tungsten in the form

of thick coatings by passing tungsten hexafluoride (a gas) and hydrogen

over an object heated to about 650 °C. A rate of deposition of more than

25 microns per minute was obtained and smooth deposits up to 3 mm thick were produced. The process permits the production not only of coatings on

objects but also of complete items of tungsten. For the latter, a master of copper or nickel is first formed and then coated with the requisite thickness

of tungsten. The copper or nickel is then subsequently dissolved with nitric acid, which does not attack tungsten.

An investigation supported by the Air Force showed that the rate of deposition of tungsten increased with the concentration of tungsten hexafluoride,

and that an oxygen content equal to about 1 percent of the tungsten hexafluoride content had a noticeable effect in lowering the rate of tungsten

deposition. Hydrogen fluoride, a product of the reaction, inhibited deposition and in some instances stopped it altogether.

The hardness of the large columnar-grained material most commonly ob- tained was 42 Rockwell C, comparable to the hardness of commercial tungsten rod. The fine-grained material obtained in the presence of excess of tungsten hexafluoride had a hardness of 62 Rockwell C. Galvanostalametry. Efforts to devise means for extending electro- chemical investigations led to the development of a new technique called galvanostalametry, which is based on the tensile strength of liquids. This

little-known property of liquids is manifested upon suspension of a column

of liquid in a vertical glass tube terminating at the lower end in an evacuated

reservoir. When an indicator electrode is sealed at the top of the column

and an auxiliary electrode incorporated in the reservoir, the passage of a current which produces gas at the indicator electrode results in an abrupt fall of the metastable column.

Investigations showed that the critical electric charge required to drop

the column is a quantitative function of the electrolyte composition, elec- trode area, and other variables of the system. The method was used to study

oxygen and hydrogen overvoltages, to obtain information on the formation

rate of hydrogen and oxygen gases from their respective ions, and to deter- mine copper sulfate concentration.

Kinetic Equations for Diffusion in a Driving Force. When diffu- sion occurs by a vacancy mechanism, the individual atoms do not follow a 146
Study of mercury nucleation by electron field emission provides considerable

information on the mechanical properties of metals. (Left) Emission pattern

from clean tungsten tip. (Right) Pattern from same tip after nucleation of mercury crystallites (magnification 300,000). (See page 147)

random walk; hence, accurate kinetic equations for diffusion in a driving

force have been difficult to obtain. This difficulty was overcome by a consideration of planar diffusion along particular crystallographic directions and by use of effective jump frequencies. With this approach, accurate

kinetic equations having the same form as those of a one-dimensional random

walk were obtained. These equations can easily be modified to treat diffusion

in a driving force. Stacking Faults in High-Temperature Creep. Several studies are planned to investigate the influence of stacking fault energy on the mechanical

properties of face-centered cubic metals. The activation energy for hightemperature creep will be determined for a series of Cu-Ge alloys of varying

stacking fault energy. Electron microscope and etch pit studies will be made

to ascertain where the rate-controlling process for high-temperature creep occurs and the influence of stacking fault energy upon the mode of deformation. The extent of primary creep and the minimum temperature at which

the activation energy becomes that of self diffusion will also be determined.

Kinetics of Whisker Growth and Evaporation. In studies of the

kinetics of whisker growth from the vapor phase, it is assumed that growth

takes place by adsorbed atoms diffusing along the whisker surface and de- positing on the whisker tip at the growth step of an emerging screw dislocation. The partial differential equation describing the growth rate as a function of vapor pressure, evaporation time of adsorbed atoms, whisker

dimensions, and surface diffusion coefficient is complicated by a moving

boundary condition. A pair of implicit integral equations were therefore derived to permit numerical computation of the growth curve by the tech- nique of successive approximations. In addition, the asymptotic behavior of

the growth curve derived for long times was shown to be linear. Nucleation Studied by Electron Field Emission. The heterogeneous

nucleation of mercury onto tungsten field emitters is being studied by electron

field emission. Nuclei were observed at a substrate temperature of 100 °K

and at a mercury vapor pressure of 5 X 10"8 torr. The time required to form

147
the nuclei was measured and a critical coverage calculated. Nucleation time

is also being measured as a function of emitter temperature and vapor

pressure. Metal Single Crystals. In studies of the origin of defects in metal

single crystals grown from the melt, thin, tapered crystals of high-purity

aluminum were "pulled" at varying speeds and temperatures. X-ray topographs showed that the amounts of both dislocations and segregated impurities seem to decrease near the tip where the crystal diameter is less than 0.5 mm. 2.2.4. INORGANIC MATERIALS

The need for more precise information on the preparation and properties

of inorganic materials in modern technology is increasing rapidly, and the Bureau pursues an active program in these areas. Studies are under way on

the nature of the vapor phase of materials at high temperatures, the nature and properties of the vitreous state, inorganic synthesis, and on the basic

aspects of crystal nucleation and growth. Phase relations of oxides—particularly of the rare earths, bismuth and boron—magnetic properties of complex boron compounds, and the electron-spin-resonance of transition metal

complexes are subjects of further studies. Knowledge of the atomic arrangement of solids is fundamental in understanding the properties of materials. NBS programs include both the de- termination of key structures and the development of methods of measure- ment and instrumentation leading to increased speed and accuracy of struc- ture determinations and facilitate such studies under special conditions of temperature and pressure. There has been increased recognition of the profound effect that departure

from perfection in crystals has on their properties. The properties affected,

which include electrical resistance, dielectric loss, internal friction, and sin- terability are often of considerable commercial and scientific interest. NBS

is therefore actively studying the effects on these properties of both point

defects and dislocations. The Bureau is also active in programs of standardization, data production,

evaluation, and collection. Activity in these fields includes publication of accurate x-ray powder patterns for chemical analysis, compilation and

measurement of the melting points of refractory oxides, production of stand- ard glasses for viscosity measurements, collection of phase diagrams of in- organic materials, and production of bibliographies of high-temperature

research. Growth of Inorganic Compounds Investigated. The Bureau, sup- ported in part by the Advanced Research Projects Agency, was active in the study of methods of inorganic crystal growth. Various methods were in- volved because of the range of properties of the crystals and their intended

use.A high-frequency induction heater (45 to 90 MHz) was used successfully to melt the high-resistivity oxides Ti02 and NiO. Initial experiments, using

148
the direct-coupled rf power for floating-zone crystallization, yielded polycrystalline rods of NiO up to 5 inches in length. Refinements of technique

are currently being made in an effort to produce single crystals.

As a part of the program, an investigation is in progress to develop and

evaluate methods of growing highly perfect crystals at temperatures below

the melting point of the crystal not only to minimize physical lattice defects resulting from thermal agitation, but also to avoid problems resulting from

high vapor pressure, phase transformations, and incongruent melting. This

study involves the use of a narrow zone of solvent which is "sandwiched"

between a single-crystal seed and the polycrystalline source material. By

placing the "sandwich" in a suitable temperature gradient, the polycrystalline material dissolves at the hotter interface, migrates through the solvent,

and deposits on the seed. Thus far, a small amount of growth was obtained on a zinc oxide seed crystal using lead molybdate as a solvent. Single crystals of salts slightly soluble in water are being grown by slow

interdiffusion of the component ions in silica-gel medium. The following

substances were produced as single crystals up to 1 cm in their longest dimension: copper tartrate, calcium tartrate, calcium sulfate dihydrate, and lead

iodine. The diffusion of the reducing agent, hydroxylamine hydrochloride,

into silica gel containing copper sulfate forms both fernlike dendrites and

dendritic tetrahedra of metallic copper. The substitution of cupric chloride

in the same system gives tetrahedral single crystals of cuprous chloride up to 4 mm on edge. The silica gel method seems most applicable to materials

having solubilities of the order of 0.01 percent.

Dislocations in Nonmetallic Crystals Studied, Transmission elec- tron microscopy is being used to reveal dislocations in aluminum oxide,

quartz, and other nonmetallic materials for the first time. The relation be- tween etchpits and dislocations, and the interactions between dislocations are being studied. A high-temperature furnace within the electron microscope

is used to produce structural changes which are observed directly. The

climb of dislocations and the production of point defects by electron bombardment in aluminum oxide were demonstrated. The high-temperature

phase transformations of silica are also being studied. Crystals of High Perfection. The high physical perfection of large

single crystals of ammonium dihydrogen phosphate was demonstrated with

double crystal rocking curves and x-ray diffraction topographs. The crystals were grown from solutions of reagent-grade material, employing precisely controlled temperature programs. Careful sectioning of the crystals with a

string saw, followed by etch-polishing of the surfaces, produced specimens

whose diffraction characteristics are believed to approach those inherent

in the crystals as grown and are tentatively taken to be representative of the bulk crystal.

A pair of [110] sections give a rocking curve whose full width at half maximum is 2.8 seconds. Rough estimates indicate that this width is comparable to the theoretical value, which implies a neglible "mosaic spread."

The general uniformity of the diffraction topograph of these crystals shows

149
the absence of significant strain and indicates regions of 1 cnr or more to be

free of defect images.

Extensive defect-image patterns appear in the topographs taken on speci- mens not carefully prepared, on specimens purposely abused, and on single

crystals containing appreciable chromic ion impurity. Localized images

seen in the topographs are ascribed to emergent and non-emergent dis- locations. Point Defects Studied Using Internal Friction and Dielectric Loss. The effect of point defects (chemical impurities and vacancies) on refractory

crystals is under investigation. One method of study is to consider the symmetry of the crystal and to analyze the effects of reductions in this symmetry when the crystal is subjected to mechanical or electrical stress. This

approach permits all classes of crystals to be analyzed in a formal way for possible effects of point defects when the crystal is strained.

Determining the rates of vaporization of high-melting-point metals is necessary

in the development of thermionic generators of electric power. Here, a micro- balance apparatus is used in a very high vacuum to measure the rate of vaporization of tungsten at temperatures to 3000 °C. (See page 151)

150
For instance, in rutile, theory predicts that point defects should cause no

internal friction peak if stress is applied in the c direction. One peak should occur for isolated defects when specimens are strained in the a direction and

another peak should occur in this direction for paired defects. Also, one

peak, should occur for isolated defects when specimens are strained in the [110] direction; paired defects would not cause a peak in this direction. In

rutile specimens doped with Ni or Cr, no peaks occurred for those specimens

oriented in the c direction, in accordance with theory. With Ni as the dopant, two peaks were found for specimens oriented in the a direction and

only one peak for specimens oriented in the [110] direction. With Cr as the dopant, only one peak was found in both the a and [110] directions. From this, it may be concluded that Ni causes both isolated and paired

defects, while Cr causes only isolated defects. Crystal Structure Determined by X-Ray Diffraction. The study of the crystal structures of boron compounds revealed two new interesting structures in different fields of boron chemistry. The determination of the

structures of the isomorphous pair SrB4 07 and PbB4 07 resulted in a type of boron grouping not previously reported in anhydrous borates. All boron

atoms are intetrahedral coordination and the structure contains some oxygen

atoms shared by three tetrahedra. This structure and the previously reported

BaB4 07 , where the boron coordination is equally divided into triangular and

tetrahedral, show that concepts of predicting the ratio of triangular to tetra- hedral boron as a function of composition are not valid. Another interesting study was the first complete determination of a halogen

substituted boron hydride. The structure of iodopentaborane (B5 H8 I) was

determined at — 25 °C. The iodine is attached to the apex of the pentaborane

group, thus confirming nuclear magnetic resonance experiments.

Rate of Vaporization of High-Temperature Materials Investigated.

A program for the determination of the rate of vaporization of the highmelting-point metals useful in the development of thermionic generators of

electric power is being conducted at the Bureau with the support of the National Aeronautics and Space Administration. A microbalance operating in the very-high-vacuum region which permits measurements at temperatures

up to 3000 °C is used in this work.

The rate of vaporization, vapor pressure and heat of sublimation of tungsten, the most refractory of the elements, were determined during the year. The heat of sublimation from the (100) face of single-crystal tungsten was

found to be the same as that of the polycrystalline material, within experimental error. High-Temperature Mass Spectrometry. High-temperature mass

spectrometry is being used to investigate the vaporization of solid materials

and the chemical reactions of their vapors. In addition to the chemical

composition of the vapor species, Bureau scientists are determining their

partial pressures and heats of sublimation, the equilibrium constants and

heats of their reactions, and the heats of formation of any new vapor species

formed.

756-224 O—65 11 151
A complete study was made of the BeO-BeF2 system. The ternary gas

species Be2 OF2 was identified and its thermodynamic properties determined.

In addition, the heat of sublimation of BeF2 was measured. A study of the BeO-Al2 03 system, still in progress, showed the existence of the ternary gas species BeOAl.

This research is being supported by the Advanced Research Projects

Agency under its "Thermodynamics of the Light Elements" program.

Liquid-Liquid Phase Separation in Inorganic Oxides Studied.

The morphology of new phases, which form when a pressure or temperature change is imposed upon a homogeneous system, is generally a function of foreign surfaces which assist the nucleation process. A notable ex- ception is certain liquid-liquid phase separations, which apparently occur

without the aid of foreign surfaces resulting in liquid-liquid dispersions of extremely small particle size. These dispersions, by rapidly coalescing into larger units, elude further scientific examination. By choosing a highly

viscous system of molten oxides, which could quickly be cooled into glasses,

however, it was possible to arrest various stages of the coalescence-process.

The two phases are clearly visible, both forming an interconnected three- dimensional network.

Successive stages of the rearrangement process following the liquid-liquid

separation were investigated by electron microscopy and by nitrogen ad- sorption on one of the isolated phases. The kinetics of the process was also determined. A statistical theory explaining the network character of the phases was suggested and various theoretical models for rearrangements by

diffusive transport were calculated and compared with the experimental data. The results suggest an interface controlled bulk diffusion process. The

process was found to be Arrhenius having an activation energy of 1.67 X 105 joules/mole (40kcal/mole)

.

Boron Compounds Studied by Nuclear Resonance. The chemistry

of substituted derivatives of the lower boron hydrides was investigated as part of a program dealing with synthesis, properties, and reactions of in- organic compounds. The first known example of a partially fluorinated boron hydride species, difluoroborane (HBF2 ), was prepared and characterized. Synthesis of this compound indicates that derivatives of this type may

not be as inherently unstable as was supposed. Chemical and spectroscopic

properties of the new compound were studied to provide a better understanding of the effect of substitution on the reactivity of boron hydride derivatives. Measurements of high-resolution nuclear magnetic resonance (NMR)

spectra at low temperature were carried out for a number of boron compounds. These studies provide information about the structures of these compounds and may lead to a better understanding of the chemical bonding

in them.

Viscosity of Glasses Measured. A high-temperature rotating-cylinder

viscometer was modified so that the viscosity of molten glasses can be measured over the range 101 to 1010 poise. The method, based on room tem- perature calibration with standard viscosity oils, involves three different 152
I 1

Sodium borosilicate glass, heated below immiscibility temperature, separates

into two immiscible glassy phases. Electron micrograph shows preshadowed

carbon-replicas of fracture surface. (See page 152)

techniques in measuring the torque on the inner cylinder. Over the range

101 to 105 poise, the outer cylinder is rotated at a constant speed and the torque is measured on the inner cylinder with an electromagnetic torque

head by a null balance method. Over the range 104 5 to 107 5 poise, an

aperiodic method is used, wherein the inner cylinder is rotated through an

angle and time as it decays to its zero position. Finally, over the range of 106 5 to 1010 poise the inner cylinder is driven and timed through a specified

angle by means of the electromagnetic torque head. These techniques over- lap each other so that a continuous viscosity curve can be established for the

glass. With these new determinations the results of viscosity measurements

by the fiber elongation method on Standard Glass No. 710 were verified in the range of 108 to 1010 poise. Furthermore, precise viscosity measurements

in the range of 106 to 108 poise can now be made on many glasses where

none were possible before. This method also lends itself to viscosity meas- urements on glasses that cannot be drawn into rods (such as dehydrated

B203 glass) and measured by the fiber elongation method.

Mechanical Properties of Glass Studied at Elevated Temperatures,

Increased use of glass at elevated temperatures indicates a need of reliable information, not previously available, on the strength of glass under these conditions. The effect of temperature on the strength of several commercially available glasses was studied to supply this information.

The results indicated that the strength of glass in relation to temperature was apparently dependent upon composition. The modulus-of-rupture

153
values for annealed glass show that after a short-term exposure to elevated temperatures the glasses with the lower silica content decrease in strength

while the glasses with the higher silica content continually increase in strength from room temperature upwards. Heating for long periods of time

did not adversely affect the strength of annealed glass, and at the higher temperatures tended to strengthen the glass.

The modulus-of-rupture values obtained for the semi-tempered and tem- pered specimens gave results as expected: generally, the longer and higher

the specimens were heated, the lower were the modulus-of-rupture values. Young's modulus was also affected by temperatures. The same glasses that decrease in strength decrease in Young's modulus, while the glasses that continually increase in strength initially increase in Young's modulus.

Configurational Entropy is a Criterion for Glass Transformation. A new analysis of existing experimental data clarified the understanding of the conditions under which equilibrium supercooled liquids

change into glasses. Previous theories suggested that this change occurs when the free volume fraction of a material decreases to some critical value.

It is now indicated that an equally determining property is the configurational entropy of the material. This indication comes independently from

both molecular relaxation data and calorimetric data for supercooled liquids.

The relaxation data may be in the form of viscosity data, dielectric data,

dynamic mechanical properties, or creep or stress relaxation data. Both

types of evaluation indicate that when the equilibrium supercooled liquid

changes into a glass, the configurational entropy has decreased to about

0.8 entropy units per polymeric chain unit. This requires a polymeric

interpretation of the molecular structure of the glass forming material. The fact that configurational entropy is now indicated to be a critical property in glass transformation has stimulated re-examination of previous

theories and their possible relation to configurational entropy considerations.

Methane Crystals Formed. Experiments on low-temperature crystal- lization yielded single grains of methane as large as 8 mm X 5 mm X 5 mm

in a polycrystalline block. Thermal-etching techniques make possible nondestructive three-dimensional observation of the grains for spectroscopic,

solid state, and surface physics studies at low temperatures. Methane is the simplest molecular solid, next to the solidified rare gases, but in contrast to these, undergoes solid-solid phase-transitions. The experiments are aimed at elucidating the nucleation mechanism for such phase changes.

Metal Oxide Melting Point Standards Redetermined. A recent

critical compilation showed that the melting points for many of the more common and commercially important oxides are not known with any degree

of accuracy or reliability. In order to help rectify this situation, a program

was undertaken to redetermine the melting points of selected oxides and

to establish calibration standards. Because many oxides are susceptible to either reduction or oxidation upon

heating, it is necessary to study their melting behavior under carefully controlled environmental conditions. An induction furnace was constructed 154
Four sides of a methane crystal at 87 °K seen through liquid argon. The heavy

lines are grain boundaries on the back faces of the crystal and the lighter ones

are grain boundaries on the front faces. These crystals provide excellent sources for spectroscopic, solid state, and surface physics studies at low temperatures. (See page 154)

which permits the heating of oxide samples to 3000 °C in vacuum or inert atmosphere and to 2400 °C in an oxidizing environment. Either pure

tungsten or iridium crucibles serve as both the heating element (susceptor)

and as the blackbody for temperature measurement. Considerable atten- tion was given to the design of the susceptor-blackbody in order that a high degree of accuracy of temperature measurement can be achieved.

Theoretical calculations as well as experimental testing showed that the blackbody has an effective emirtance of 0.999 at 2000 °C. This small deviation fom a perfect radiator, which has an emirtance of 1.000, will cause an

error in measurement at 2000 °C of less than 0.25 °C. Because of various influencing factors, only a limited number of oxides

are considered suitable for use as melting point standards. At present,

the more promising materials include A12 03 , Y203 , and Sc2 03. The melting

point of high-purity single crystals of A12 03 (sapphire) in vacuo is now

being actively investigated.

Standard X-Ray Powder Diffraction Patterns, NBS, in cooperation

with the American Society for Testing and Materials and the American

Crystallographic Association, is actively engaged in a continuing program

for the further refinement and extension of the use of x-ray powder diffrac- tion patterns as a means of identifying and characterizing crystalline phases.

Cooperative work is in progress on the determination of intercomparative

intensities to extend the accuracy of quantitative analysis by this method, and

in the preparation and measurement of tungsten and silver samples for use as

internal calibration standards for spacings. The Bureau initiated a program

for the calculation of patterns of materials not readily available or too unstable for experimental study. During the year experimental work was com155
pleted on about 60 well -characterized inorganic compounds. Information on the (/-spacings, relative intensities, cell size, structure type, and density are being published.

Inorganic Materials Studied by Infrared Spectroscopy. Infrared

studies of B

10 and B11 substituted-anhydrous borates were carried out in the 2,000 to 300 cm-1 range. Spectral bands for all ortho-, pyro- and some

meta-borates could be assigned satisfactorily. From correlations between

spectra and structure it appears that boron in threefold or in fourfold co- ordination can be identified on the basis of the infrared spectrum alone. Triangularly coordinated boron is characterized by the presence of strong,

broad absorption ir the 1,100 to 1,300 cm-1 region. In addition, there is absorption in the 700 to 780 cm-1 region. Both of these characteristic bands

are strongly dependent on isotope mass and thus isotopic substitution can be

used to differentiate these bands from others occurring in these regions.

The most characteristic feature of tetrahedrally coordinated boron is the presence of strong, broad absorption in the 800 to 1,100 cm-1 region.

Also, absorption bands, which are not sensitive to isotope mass and there- fore can be distinguished from triangular boron, occur in the 700 to 800 cm-1 region.

These studies were used to predict that tetrahedral coordination of boron

occurs in SrB4 07

. This was confirmed by single-crystal x-ray diffraction

studies. 2.2.5. REACTOR RADIATIONS

During the past year the Reactor Radiations Division was created from the former Keactor Group. The new division continues with its responsibility

for the procurement, operation, and maintenance of the National Bureau of Standards Reactor facility, the NBSR, a high-flux, tank-type, heavy water moderated reactor using enriched fuel. The reactor has an eventual power

capacity of 20 megawatts, but will operate initially at 10 megawatts, with an

in-pile flux of 1014 neutrons per square centimeter per second. It will have

15 beam ports, and will be housed in a building providing 50,000 square

feet of usable laboratory space. The reactor is designed to meet the needs

of a number of Federal agencies and scientific institutions in the Washington

area, and thus has many unique features as a radiation source. Ground was

broken and construction started in the past year, with completion scheduled

for spring of 1965. The division has been supervising construction of the reactor with a

staff in offices established at the site. Preparations are under way for train- ing operators and generating technical specifications and further hazards

analyses in pursuit of an AEC operating license. The aim of the Reactor Radiations Division is to promote reactor- oriented

work of general significance to NBS and of particular significance to the

Institute for Materials Research. Staff competencies are being created in three scientific sections in the formative stage. By title, these are the Neutron- 156
Nuclear Physics, Neutron Solid-State Physics, and Radiation Effects Sections. They will not only generate work of their own, but will also embark with

other divisions on cooperative projects of mutual interest. Flux Standardization. The reactor facilities of the Argonne National

Lab ratory, the Brookhaven National Laboratory, and the Naval Research

Laboratory were utilized to begin several research and development pro- grams. An investigation is being made into the absolute measurement of neutron flux relative to thermal flux standardization. Glass beads containing

boron and an element that can be activated, for example, dysprosium, have

been made by NBS. These beads are to be activated in a neutron beam at the Graphite Reactor of the Brookhaven National Laboratory. If the neutron

current density of the beam is measured by absolute neutron counting, the

glass beads can be calibrated for measuring an unknown flux. Boron added

to the glass makes a bead that is essentially black to thermal neutrons. Research and development effort began on a fast neutron spectrometer

for reactor spectrum fast neutron flux standardization. The graphite reactor

at the Brookhaven National Laboratory is being used as the neutron source. A semiconductor He3 spectrometer is used for neutron measurements. The

system will ultimately assist radiation effects studies at NBS by characteriz- ing the fast flux spectra of the NBSR.

Molecular Motion. The research reactor, CP-5, at Argonne National

Laboratory was used by members of the NBS staff to study the molecular

motions in solids and liquids. Neutrons with energies of the order of or lower than the energies of the molecular motions to be studied were scattered from the sample, and their energy change was measured by a time-of-flight

spectrometer. The measurements provided direct information on the molecular binding in ammonium salts and on the motion of methyl groups in various compounds.

Lattice Vibrations. The lattice vibrations of gray tin (diamond struc- ture) and white tin (tetrahedral structure) were studied using the slow neutron facility at Brookhaven National Laboratory. The energies of the peaks in the phonon spectrum of gray tin are in good agreement with the corresponding peaks in silicon and germanium if the energies are scaled using the square root of the atomic mass. This implies that the interatomic

forces are of the same order of magnitude in the diamond structures

silicon, germanium, and gray tin. Neutron Moderation Study. Preliminary results were obtained in a second experiment at Argonne to measure the ability of various materials to moderate neutrons to subthermal energies. A large volume of heavy water

ice (D2 0) about 18 inches in diameter held at 22 °K was shown to be

quite effective. Neutron Optics. A study of the properties of several neutron optical

devices was undertaken at the Brookhaven National Laboratory Graphite

Research Reactor. These experiments centered mainly on the investigation

of the properties of curved totally reflecting pipes and curved totally reflect- ing soller collimators. 157
A neutron reflecting pipe in connection with reactor neutrons can be used

as a neutron conductor, a background suppressor, and a neutron filter. These properties were studied for both metal and glass pipes coated ( electroless) with nickel and installed in a beam hole at the Brookhaven Graphite

Reactor. In addition to their uses as neutron filters and background suppressors, curved totally reflecting soller collimators can be employed as order-removing devices when used in conjunction with a crystal monochromator. An

investigation is being conducted on the further use of these soller slits as magnetized cobalt-iron shims to obtain 100 percent polarized cold neutrons. Establishing Vacua, The establishment of high vacua in the intense radiation field of a reactor core is limited by poor conducting geometry (i.e., systems with a large length-to-diameter ratio), suitable reactor materials

(i.e., materials having low neutron absorption), and radiation-induced out- gassing. An investigation was made of the magnitude of the radiation- induced outgassing rate of a well-cleaned and baked 6061 aluminum system.

Measurements performed in both the NBS 31 kCi cobalt-60 gamma facility

and the Naval Research Laboratory's 1 megawatt reactor facility disclosed

that the phenomenon of radiation-induced outgassing was principally due to the gamma and its associated electron field, rather than to the fast neutron

field. The magnitude of the effect observed was 6X 10"11 torr liters/sec cm2 per watt/gram, which can be compared with the field free value for the sys- tem of 5X10"14 torr liters/sec cm2

. 2.2.6. CRYOGENICS

The Bureau's Cryogenic activities, centered at the Boulder Laboratories,

provide data on the bulk properties of materials in the environmental ex- treme of very low temperatures. Research is conducted at cryogenic temperatures to determine the physical properties of materials, the engineering

properties of systems, and to develop methods for measuring these properties. In addition, a national cryogenic data center is maintained where in- formation is collected and organized for use by other Government agencies,

industry, and the public.

An addition to the Cryogenics Laboratory Building has just been completed, increasing the space available by nearly 30,000 square feet. Research on properties of cryogenic fluids and measurement methodology, now

conducted in two temporary buildings, are being moved to the new addition. Viscosity of Parahydrogen Determined. The most advanced chemical and nuclear rockets use hydrogen as fuel or as monopropellant. Be- cause of these important applications, the thermodynamic and transport properties of hydrogen need to be known with higher accuracy and over wider

ranges of temperature and pressure. The Bureau is engaged in an extensive experimental program to determine these data, a major part of which

is supported by the National Aeronautics and Space Administration (NASA)

.

Previously pressure-volume-temperature and thermal properties were deter- 158
mined, and extensive provisional tables of thermodynamic functions were

published.

In the past year, measurements of viscosity were concluded covering the same pressure and temperature ranges as the previous work, up to about

3.4X107 newtons per square meter (N/m2

) (340 atm) and from 15 to 100 °K, thus including the liquid and gaseous phases and the critical region.

The viscosity was determined via the damping of a torsionally oscillating

piezoelectric quartz cylinder.

It is conventional to separate the viscosity into a low-pressure component

and a remainder, termed the "residual" viscosity. Some published correla- tions and extrapolations were based on the assumption that the low-pressure

component contains the entire effect of temperature on the viscosity, so that the residual viscosity is a pure function of density. The present data show

clearly that this is a gross oversimplification. Also, there is no evidence for an anomalous peak at the critical point, as was obtained for some other fluids by other experimental methods.

Solid-Vapor Equilibrium in the Hydrogen-Methane System.

Phase equilibrium studies of mixtures are of great practical value in designing fluid purification systems. In addition, provided the components have

widely different critical constants, condensed phase-gas equilibria lead to sensitive determination of the parameters for interaction of the unlike molecules. The hydrogen-methane system was investigated by measuring compositions

of gaseous mixtures of hydrogen and methane in equilibrium with solid methane at temperatures from 35 to 87 °K and pressures up to about

1.5 X 107 N/m2 (150 atm). Enhancement factors and cross virial coeffic- ients were derived. The data will be useful in designing hydrogen gas purifiers. In addition they can be used to evaluate various physical models for the

interaction forces between hydrogen and methane molecules. Mixtures of Solid and Liquid Hydrogen. Space vehicles fueled with

hydrogen in liquid form have required the development of new technology.

Although relatively high density at low pressures is accomplished by gas

liquefaction, problems exist with fluid behavior before, during, and after launch. Some of these problems are (a) short holding or storage time

caused by low heat of vaporization and temperature combined with minimal

insulation, (b) fluid temperature stratification resulting in pump cavitation problems, (c) sloshing of the liquid in such a manner to effect flight stability,

and (d) safety problems associated with the high vent rates before and

after launch. Further refrigeration of the liquid to form a "slush" or mixture of solid and liquid should eliminate or greatly reduce a number of these problems.

Under sponsorship of NASA, the Bureau is conducting a program on

"slush" hydrogen aimed towards an optimization of the concepts to be in- corporated in a space vehicle launch facility. The effort will be carried out on a laboratory scale with emphasis on the applicability to the ultimate large- scale requirement. Specific objectives are to evaluate, correlate and combine

159
all known applicable properties of slush hydrogen, to investigate production

methods, and to study flow characteristics. Instrumentation of the three- phase (single-component) system is a crucial portion of the program. A

study of the behavior of solid hydrogen crystals in the solid-liquid mixture

is also of great importance. The attainment of these objectives will assist in the establishment of standard specifications for instrumentation and pro- duction of flowable mixtures of solid and liquid hydrogen.

Superconductivity. The Atomic Energy Commission (AEC) is sup- porting Bureau work on thin film and high field superconductors. In thin

film experiments, careful sample alinement resulted in much better agree- ment with the Ginsburg-Landau theory than previous workers reported. This

supports the use of the theory, which rests on not too firm ground, in high

field superconducting problems. A parallel experiment to test another pre- diction of the theory on bulk superconducting niobium is well under way.

Finally, experiments are under way to deduce the topology of the Fermi sur- face of niobium from magnetoresistance measurements, and to relate this as

far as possible to the Class II superconducting behavior of this element. Metallurgy. Investigation showed that small changes in the elastic moduli observed in certain 300-series stainless steels are related to antiferro- magnetic transitions in these metals at about 40 °K. Based on this research,

consultation was given to interested groups in NASA and the Air Force who

are concerned about possible structural failures due to martensitic phase

transformations in stainless steels subject to high stresses at liquid hydrogen

temperatures.

Electronic Properties of Copper Investigated. Magnetoresistance

measurements indicate that the simple concept of a (scaler) electron mean

free path in copper, and presumably in other metals, must be abandoned in favor of more sophisticated analyses involving details of the electronic

structure. The theoretical implications of this advance are being investigated, and

related experimental work is beginning.

Aluminum Cryogenic Magnet Tested. The AEC is supporting an

investigation into the feasibility of generating strong magnetic fields at low

cost by using liquid hydrogen cooling of aluminum electromagnet windings.

Such a magnet was tested to burnout at 9.4 tesla (94,000 gauss) . It was

found that the cryogenic part of the system (heat transfer ratio, fluid flows, pressures, temperatures, and pumps) performed in accordance with en- gineering expectations. Additional measurements are necessary in order to be able to predict accurately the resistivity of the aluminum under stress at high fields and at the operating temperature.

Thermophysical Properties of Cryogenic Materials. With support

from NASA and the National Standard Reference Data System, the Cryogenic Data Center is critically evaluating and compiling data on the thermophysical

properties of materials from the scientific literature. The objective is to publish authoritative and comprehensive tables and graphs of data in a form

convenient to scientists and engineers studying cryogenic phenomena and

160
designing cryogenic systems. If the necessary data to complete a table are not available from the literature, values are computed from correlations based on theory and the properties of related materials. Extensive tables of the thermodynamic data for carbon monoxide were

completed together with a temperature-entropy diagram and a compressibility

factor diagram. A compilation of the dielectric constants of cryogenic fluids and an extensive bibliography of the thermophysical properties of argon were

also completed.

Temperature-entropy diagrams for helium and neon, and an enthalpyentropy diagram for helium were constructed and are now available. Also

available are interim reports with preliminary thermodynamic data tables for oxygen and argon. Further evaluation of these materials is in progress. In other work, a bibliography on the saturation properties (vapor pressure, saturation densities, latent heat, and specific heats at constant saturation) of cryogenic fluids was compiled and is in the process of publication. In addition, a collection of thermodynamic data for hydrogen in its various

phases and ortho-para modifications is being developed.

Cryogenic Literature Service. The Cryogenic Data Center's documentation unit searches the world literature for technical information perFermi surfaces of copper viewed along the (100) direction. The lines depict various electron orbits of importance in theoretical calculations.(See page 160)

161
tinent to the cryogenic engineering field and promotes an awareness of such

literature to the Bureau staff and the cryogenic industry. Over 6,000 ref- erences were noted and coded for entering into the Center's storage and

retrieval system. Additional mechanization (digital computer programming) to reduce the number of manual operations was accomplished, thus reducing unit costs and providing more capacity with existing facilities. More than 3,300 documents, of which about 1,300 are in microfilm, were

procured from world sources for the Bureau staff. The staff distributed an

estimated 18,000 items of NBS literature in response to some 1,900 requests.

Periodic announcements of available material and services were sent to ap- proximately 4,000 persons and institutions on the Center's mailing list. A weekly current awareness service was started in March in which about

100 new articles of interest to the Cryogenic field noted during the week

were listed and distributed to the Bureau staff. An expansion and improvement in the service is planned with the intent to make it more available to the public.

The documentation unit works closely with the Center's evaluation unit

in providing both literature-procurement services and bibliography retrieval. The evaluation unit is not only a primary user of these services, but is also a major contributor of information on cryogenic literature from their compilation programs and the associated literature searching on selected topics.

Measurement Methodology, Typical projects include investigating new thermometric materials; devising simpler calibration-correlation methods; and the modeling of transducer characteristics on analog and

digital computers. Research is performed upon those properties of materials, matter-matter and matter-energy interaction, which may lead to new

or improved measurement coefficients. Current examples include the study

of nuclear magnetic resonance techniques which may be applied to measure

the density or velocity of cryogenic fluids; pyroelectric phenomena for measuring small temperature differences; and the piezoresistivity of commercial

carbon composition resistors which may be used to measure pressure. An especially challenging task during the past year was the investigation of transducers for use in the extreme synergistic environment of combined

nuclear radiation and low temperatures. In this case, transducers must

operate from 20 to several thousand degrees Kelvin in a radiation field un- matched by any existing test reactor. Continuing programs include investigating means of measuring the density of flowing cryogens, studying the properties of semiconductors at low temperatures, analyzing the temperature dependence of pressure sensors, and determining the fraction solids in a mixture of liquid and solid hydrogen.

Fluid Flow and Heat Transfer, A study was completed on the pool

boiling of cryogenic fluids. This study compiled the experimental data

available and compared these data with correlations derived for fluids at higher temperatures. The more promising correlations were indicated and

graphical solutions using these correlations were presented. This will pro- 162
vide designers of a wide range of cryogenic systems with much-needed boil- ing heat transfer data. An analytical method was developed which will predict peak surge

pressures which are experienced when a cryogenic fluid is introduced into an ambient-temperature transfer line. It was determined experimentally

that these pressures may be several times the initial driving pressure for the

fluid. Therefore, this information is very necessary to ensure safe design for cryogenic systems. In many cryogenic systems, a conduit (tube, pipe) containing a cryogenic

fluid is exposed to a gas mixture (usually air) containing water vapor. In order to properly design such a system, one needs predictive expressions to determine data such as the heat transfer rates to the gas mixture and the rates of the frost formation on the conduit. An extensive experimental program

was carried out to determine these data and an analysis was completed using

a modification of rather conventional heat and mass transfer analogies which

shows reasonably good agreement with the experimental data.

163

2.3. INSTITUTE FOR APPLIED

TECHNOLOGY

The nation is currently faced with new demands to put technology to economic use—to create new markets, to compete with foreign industry, to apply technology to our public problems, create jobs, and put our technical resources to maximum use as well as to cope effectively with the social con- sequences of technical change.

Attention is also being called to certain gnawing social problems which

exceed in scope any one industry, company, or region of the country. These

include

—the control of air, land, and water pollution. —the inadequacy of our systems of land transportation (particularly in urban areas) and the unsolved problems of our nationwide transportation

system. —the inadequacy of our low- and middle-income housing. —the well-advertised pockets of poverty in the midst of plenty. —the problem, for much of the population, of adjusting to the constructive use of large quantities of leisure time. The National Bureau of Standards' concern with these problem areas, in ways appropriate to its resources and its traditions, is reflected in the pro- grams of the Institute for Applied Technology. This consists of four principal activities: —the dissemination of technical information. —the development of performance criteria. —the development of tools for the analysis of large-scale problems that cut across Government-industry lines. —analysis of problems associated with the introduction of new technology.

The Dissemination of Technical Information

The Federal Council for Science and Technology has established within

the Department of Commerce, building on the Office of Technical Services, in the Institute for Applied Technology, a Clearinghouse for Federal Scientific and Technical Information. Its scope includes the physical sciences, engineering, and related technology and it is meant to serve as a central point of contact in Government for industry and the technical community (paralleling the Library of Agriculture and the Library of Medicine, in their fields) . Its specific responsibilities are listed on page 167. 165
The Development of Performance Criteria

The National Bureau of Standards has a historical role in the development

of standards for industrial products as well as standards of measurement for physical quantities. There are few standards, mostly concerned with safety

and assigned by law in the public interest to the Department of Commerce

for which the Bureau has a responsibility to develop and promulgate the stand- ard itself. It cooperates fully with the private standards-producing bodies

industrial associations and professional societies, and groups such as ASTM

and ASA. Its role here is to serve as a technical resource to these private groups. It is available for expert and objective contribution to the development of methods of test, measurement, and criteria for the performance of

industrial materials, products and processes which lay the technical basis for industrial standards. The Institute will engage in the development of performance criteria in the fields of building, electronics, textiles, and information processing,

among others. In all these areas, it will identify projects of high priority

through industry's concern with the problem, as expressed in trade associations, professional societies, and private standards bodies. The Development of Tools for Analysis of Large-Scale

Problems

Many of our most serious technical and technical/economic problems are

so large as to cut across industry boundaries: they cannot be located wholly

in one industry or wholly in another. Many of these, in turn, cut across boundaries between industry and the Federal Government; both share a concern with them. Examples are to be found in

—urban and national transportation. —low-cost housing, for the military as well as for civilians. —man-machine systems for receiving, sorting, processing, storing, and

displaying data. In these cases, many industries join in production and service, and Govern- ment figures as user and purchaser as well as, on occasion, regulator. Because of the scope of these problems, as well as the fragmentation of some of the industries concerned with them, they are seldom considered as whole systems even though in many instances they are most effectively con- sidered in that way. Often, the very tools needed to treat them as systems

are missing. The Bureau has traditionally provided consultation to Government in its systems problems and in its use of new technology. Fre- quently in the past—as in the case of the early computer, SEAC—it has de- veloped tools for systems problems of interest to Government and industry

alike. The Institute for Applied Technology will continue to fill these functions, in a few areas of special competence.

166
The Analysis of Problems Associated with Introduction of New

Technology

The Institute's major objective—that of stimulating the application of

science and technology to national needs—requires an understanding of the problems and obstacles that keep science and technology from being applied

to needs, and of the sort of activity that would stimulate their application.

This means more concretely

—analysis of major problems of technical innovation, in industry and

Government alike. —analysis of the likely effects on new technology of programs currently

undertaken or planned within the Institute; e.g., in the areas of performance

by criteria, technical information, or systems analysis.

2.3.1. CLEARINGHOUSE FOR FEDERAL

SCIENTIFIC AND TECHNICAL

INFORMATION

The program of the Office of Technical Services (OTS) , established under

Public Law 776 (81st Congress) for the collection and distribution of Government research and development reports and translations of foreign tech- nical literature, was strengthened and broadened during fiscal year 1964.

On January 30, 1964, concurrent with the reorganization of NBS, control

of OTS was transferred from the Office of the Secretary of Commerce to the Bureau. Shortly thereafter, an interagency agreement under the auspices

of the Federal Council for Science and Technology, which was announced

by the White House on February 28, 1964, established within OTS the Clear- inghouse for Federal Scientific and Technical Information. The White

House announcement stated that the Clearinghouse will: (1) serve as the Federal agency through which unclassified and unlimited technical reports

and translations will be uniformly indexed and made available to the public;

(2) provide current awareness information concerning Government-sponsored research and development; (3) refer to appropriate specialized infor- mation centers requests for explicit scientific and engineering information; (4) establish links with the Smithsonian's Science Information

Exchange and the National Referral Center for Science and Technology at the Library of Congress.

Another significant development was the signing, on March 9, 1964, of an agreement between the Department of Defense and the Department of Commerce which provided that OTS will handle all processing and dis- tribution of unclassified and unlimited DOD reports, a function formerly

performed by the Defense Documentation Center (DDC) of the Defense

Supply Agency. The Clearinghouse began the complete processing of unclassified and unlimited to DOD reports in May for publication in DDC's

Technical Abstract Bulletin (TAB) and for distribution to authorized DOD

requesters. These same DOD reports appear in the U.S. Government Re756-224 0—65 12 167
Typical examples of the various methods used by the Clearinghouse for Federal

Scientific and Technical Information (formerly OTS) to disseminate information throughout industry and the technical community. Over 30,000 technical reports and foreign translations were processed into the Clearinghouse collec- tion last year. (See page 167)

search Reports (USGRR), a Clearinghouse publication, for distribution to the public domain. Prior to this agreement, OTS had been responsible for the announcement, reproduction, and sale of these documents to the general

public only. Processing of the documents by one agency serves all interested user communities and is designed to reduce the cost of such services. The purpose of the Clearinghouse is to make the results of science and

technology more readily available to industry, commerce, and the general

public and to reduce duplication and waste in Government technical infor- mation programs. The Clearinghouse services are designed to aid Govern- ment and industry to increase technological progress and to reduce duplication in research and development.

During the last quarter of fiscal year 1964, an integrated systems design

of the total Clearinghouse operation was developed to provide for efficient and reliable service as the workloads expand to higher levels. Shorter proc- 168
essing cycles, earlier announcement, and rapid request service are the goals

of this effort. Document Input Processing. The Clearinghouse receives technical

reports, bibliographic information, and translations of foreign technical

literature. These are derived primarily from the Atomic Energy Commission; Department of Commerce; Department of Defense; Federal Aviation

Agency; Department of Health, Education, and Welfare; Department of In- terior; National Aeronautics and Space Administration; and other Federal

agencies. A total of 30,000 titles was processed into the Clearinghouse col- lection during fiscal year 1964. This rate is expected to double in fiscal 1965. The Clearinghouse accepts from all Departments of the Government, and

from those non-Government agencies willing to participate, documents, magnetic tapes, punched cards, abstracts, catalog cards, and other bibliographic

records concerning federally sponsored research and development.

Cataloging is the instrument designed to facilitate the announcement and

location of materials collected by the Clearinghouse. After the material

is processed through descriptive cataloging and abstracting, it is prepared for announcement in journals, either in U.S. Government Research Reports or, in the case of foreign translations, in Technical Translations. These journals

are semi-monthly publications available by subscription from the Clearing- house. The Clearinghouse also announces Government-owned patents to the technical and industrial community through its Patent Abstract Series. Document and Information Request Processing. A primary re- sponsibility of the Clearinghouse is to provide its users with pertinent tech- nological information on its vast collection of reports and translations. Use

is made not only of the Clearinghouse catalogs, but also of the facilities of other Government agencies. Information is supplied in the form of bibliographies, answers to specific reference questions, identifications of documents, or referral to other proper sources. Requests for information

may be made by letter, telephone, teletype, or personal visit. Selective bib- liographies are prepared regularly on subjects of general interest. Fee

literature searches and subject searches are provided for research organizations, industrial firms, Government agencies, and others. In addition, the Clearinghouse has initiated plans for: —Central bibliographic control for Government-generated reports and

closely allied literature in the public domain. —Generation of a Government-wide index to this literature including access by subject, author, source, and number. —Repackaging of agency abstracts, indexes, and other bibliographic rec- ords in special consumer groups, e.g., textiles, machine tools, etc. —An expanded referral service. A new standard pricing schedule for the sale of reproduced copies of documents, whether printed by the offset reproduction method or produced

from microform, was developed in fiscal year 1964 for implementation dur- ing fiscal year 1965. Plans are also under way that provide for subscription

169
to an automatic distribution within selected subject categories. Clearinghouse sales include all forms of publications and bibliographic records such

as reports, translations, monographs, directories, reviews, indexes, bibliographies, announcements, journals, abstracts, and catalog cards. The Clear- inghouse cooperates closely with existing agency sales mechanisms to avoid unnecessary duplication of effort. For documents, both reproduced copies

and microform are available. Distribution of shelf stock is accomplished

within 24 hours of the receipt of requests; if reproduction is required, an

additional 3 days maximum is necessary. This service is designed to provide the fastest practical response to user requests. In its translations program, the Clearinghouse provided central directories and Clearinghouse services for technical translations of scientific and tech- nical literature in the Slavic, Oriental, and other unfamiliar languages. It produces a semi-monthly listing and index ( Technical Translations) to all translations made in the United States and abroad in English and in Western

languages.

2.3.2. WEIGHTS AND MEASURES

The control of weights and measures in the United States presents a unique situation in the governmental structure of this country because regulatory control has historically remained with the States, counties, and cities, even though fixing the standards of weights and measures is specified in the Constitution as a Congressional authority.

Such local control results in an obvious advantage—it allows problem

solutions to be patterned to local conditions. A disadvantage, however, is equally obvious—the possibility of more than 50 different systems of weights

and measures. To avoid this possibility, the Department of Commerce

and through it, the National Bureau of Standards—has been charged by

the Congress with the custody, maintenance, and development of the national standards of measurement, and with the provision of means and methods for making measurements consistent with those standards. To assist the State weights and measures programs, the Bureau tests and calibrates State standards and standard measuring apparatus and provides technical advisory services. To assure uniformity in weights and measures laws and

in methods of inspection, the Bureau extends general cooperation to State weights and measures officials. Thus the Bureau maintains an Office of Weights and Measures, which is responsible for (1) technical assistance to the States and to business and

industry in the area of measurements; (2) the design, construction, and

use of weights and measures standards and of instruments associated with

such standards ; ( 3 ) the training of weights and measures officials in the tech- nical aspects of their program; (4) technical assistance in the solution of

special measurement problems; (5) developing model laws and regulations;

(6) arranging national, State, and regional conferences; and (7) the col- lection, arrangement, and dissemination of technical data on measurement

units and systems.

170
Technical Services. At the request of the legislature of the State of

Mississippi, the only State that still had no comprehensive weights and measures law, an intensive survey of weights and measures conditions was con- ducted in that State. Seven representative cities were visited where tests of devices were conducted, test measurements of packaged commodities were

made, and general weights and measures conditions were observed. The

conditions revealed by the survey led directly, in March 1964, to the enact- ment by Mississippi of the National Conference on Weights and Measures

Model State Weights and Measures Law.

Studies of rental car and truck odometer accuracy continued through the

year. In cooperation with representatives of the automobile industry, detailed test procedures were developed, a single vehicle test speed and tire pressure were recommended, and tolerances were studied and revised. As

a result of NBS efforts in this area, odometers on all cars furnished to rental

fleets now comply with newly established tolerances and, eventually, all cars manufactured in the United States will more accurately register dis- tance traveled. The increasing production of packaged aerosol products has brought about

a concomitant need for accurate net content testing methods. Accordingly,

research has begun to determine test procedures that will be both usable by

weights and measures officials and workable for industry. The great variability in products packaged in aerosol containers presents a unique problem

of categorizing. This was solved by the establishment of five categories on

the basis of product characteristics. Testing within the first category, foam

Weighing aerosol cans during a research program to establish effective test pro- cedures for determining net content of aerosol products. (See page 171)

171
produ€ts (shaving cream, shampoos, etc.), was completed during the year, and definite procedures were prepared in draft form for review by industry

and State officials. Standards. As part of the Latin American standards program, trans- lations of U.S. weights and measures publications into Spanish and Portu- guese were completed. New State standard designs were revised to metric

denominations for use as national standards; a complete set of mass, length,

and capacity standards were procured; and plans are being considered by the Department of State to display these in Latin America (see p. 24)

.

Technical Training. Formal training schools were conducted in 11

States and field training on specific devices or package-checking methods was

provided in several others. In an effort to make technical training more easily available to a greater

number of weights and measures officials, a packaged series of audio-visual

self-training aids was devised. The first, on computing scales, is now avail- able and the script for a second has been written. With the assistance of the Office of Weights and Measures and of weights

and measures equipment manufacturers, a significant new educational pro- gram was established at the Alfred State University of New York. The new

Measurement Science curriculum is an attempt to answer at least partially the need for a college-level training course for weights and measures tech- nicians. Technical Information. Publications issued during the year include

Misc. Publ. 247, Weights and Measures Standards of the United States; Tech. Note 195, Report on Technical Investigation of Odometers; Tech. Note

196, Report of the Investigation of Slow-Flow Meters for Fuel Oil Distribution Systems; Handbook 98, Examination of Farm Milk Tanks; and several

articles in technical periodicals. Handbook 98 is the first of a series of

pocket-size handbooks that, in total, will succeed Handbook 45, Testing of Measuring Equipment.

National Conference. The 49th National Conference on Weights and

Measures held during the year broke all previous attendance records. Forty- one States, the District of Columbia, Puerto Rico, Canada, and England were

officially represented among a registered attendance of 633. A significant

accomplishment was the establishment by the Conference of package quantity

declaration standards. Consumer affairs received emphasis in the papers

presented. Other papers dealt with technical measurement matters, and such

subjects as weights and measures activities of other agencies of the Federal

Governmnt, and the reorganization of the National Bureau of Standards.

Federal-State Technical Services. During the year, an entirely new

program was established to assist the States in solving local and regional in- dustrial problems. As a part of this program, a National Conference on

State Science and Technology and similar regional conferences will be

organized.

172
As part of the Latin-American Standards Program, a new set of mass standards,

converted to metric units, has been designed and built. The set ranges from 30

kilograms down to one milligram. At right is a 30 kilogram precision one-arm

balance, also developed for this program. (See page 172)

2.3.3. ENGINEERING STANDARDS

An Office of Engineering Standards was established in recognition of the

basic importance of standards to the entire area of applied technology. The new Office brings together at NBS present activities of the Department of Commerce on commodity standards, technical standards coordination, and

international standards. The Office has also been assigned the responsibility for developing specifications for seat belts for use in motor vehicles. As

soon as these specifications are available, they will be promulgated by the Secretary of Commerce.

Commodity Standards. Technological information available at NBS

finds direct application in commodity standards for improving production

and marketing practices, and for enabling consumers to obtain products of recognized standard types, sizes, grades, and qualities. The Office of Commodity Standards cooperates with industries requesting assistance on stand- ards for their manufactured products . Two types of commodity standards

are published: "Commercial Standards" and "Simplified Practice Recommendations." For a list of both types made available in fiscal year 1964, see

p. 254. Commercial Standards give technical requirements for materials, construction, dimensions, tolerances, testing, grading, marking, or other details. The objectives are to define quality levels for products in accordance with the principal demands of the trade and to provide for close adherence to the 173
qualities thus denned. Uniform methods and practices are established for achieving and determining compliance.

Simplified Practice Recommendations are essentially lists of stock or

staple items in greatest demand. They make possible a choice, in accordance

with generally recognized trade practices, between "standard" items that are widely available from distributors' stocks, and "specials," which may

require factory orders and more costly production and handling methods.

Some recommendations give standard methods, such as methods of packaging.

The commodity standards activity began at NBS in 1921 as a program

of aid to business for general economic improvement. Transferred to an- other part of the Department in 1950 and returned to NBS in 1963, the present program embodies the experience of 43 years of close cooperation

with technical organizations, trade groups, purchasers, consumers, and pro- ducers on standards for more than 500 widely used manufactured products.

The method by which the standards are developed emphasizes their voluntary adoption by all of the above elements of the industry. The list of acceptors is published in the standard to show the extent of public support

for it. In addition, most standards include recommendations for certifica- tion and labeling to enable purchasers to identify the products that meet

the standard. Some industry groups employ commercial inspection and

testing programs, together with grade labeling, hallmarks, or certificates, for greater effectiveness in making their products more acceptable to con- sumers, through conformity to a commodity standard. Technical Standards Coordination, The Office of Technical Standards Coordination is responsible for coordinating the development and

revision of Federal Specifications work at NBS, serving as liaison between

NBS and other Government agencies engaged in standardization work,

and in providing information and copies of specifications to NBS and

outside sources upon request. During the past year, 550 proposed Federal

Specifications were reviewed by NBS personnel and comments transmitted

to the appropriate Government agencies. The specifications were reviewed

to determine technical accuracy and suitability for use by the Federal Government. The Bureau accepted responsibility for preparing and maintaining one

additional Federal Specification, making a total of 153 for which it now has

this responsibility. Complete files of over 4,000 Federal Specifications and

Standards were maintained as well as files of British and German Standards

and selected industry standards. Requests for information and specifications were received from NBS and Harry Diamond Laboratories personnel. Gov- ernment agencies including members of Congress, embassies and foreign

countries, and the public. These requests covered such subjects as Government, domestic, and foreign standardization, and problems of cross-referenc- ing standards of various countries. The Bureau's interest in engineering standards and test methods was

evidenced by the 1,400 committeeships held by NBS staff in 156 national

groups such as the American Society for Testing and Materials, the American

174
Standards Association, and the American Society of Mechanical Engineers.

Records for these activities as well as special committee reports to the Secre- tary of Commerce were maintained.

Standards for Developing Countries, NBS is concerned with two

types of standards for developing countries: (1) standards of weights and

measures; and (2) standard practices, including codes, specifications, and

methods of testing. Both categories of standards are essential for com- merce and trade and indispensable for industrial development.

During the year the Bureau procured (with funds from the Agency for International Development) a set of standards of mass, length, and volume

specially designed to serve as the national standards of developing countries. These standards and the accessory instruments for their use combine a high

degree of accuracy and permanence with unusually rugged construction and

practical utility. This equipment will be placed in a Latin American university where it will serve both as standards of measurement for the host country and for demonstration and training purposes for other countries

(see p. 24)

In the field of standard practices a number of standards that are widely

used in the United States were translated into Portuguese and Spanish, also with the support of the Agency for International Development. These in- cluded safety standards which were translated by contracts in Latin America

let by the Bureau of Labor Standards, and specifications, methods of test, and

manuals that were translated in cooperation with the University of Miami.

As in previous years the Bureau cooperated with the American Standards

Association in providing technical experts to serve on United States delegations to international meetings on standards. Noteworthy progress was made in a number of areas of standardization, particularly in the development of Pan American Standards for textiles, iron and steel, steel products

such as pipe and tube, cement, and concrete. 2.3.4. BUILDING RESEARCH

The diversity of problems in the field of building materials, construction,

and systems is such that research is required in physics, chemistry, and many

of the subdisciplines of engineering. These researches provide both data on

the performance characteristics of buildings and their components; and test methods for measuring these characteristics. The studies range from basic research to applications of the Bureau's competence to specific building problems. The development of test methods and laboratory reference materials

is often carried out in cooperation with interested laboratories of industry,

educational institutions, and other Government agencies. The information

developed is made available to the building industry and code-writing groups

as an aid to increased effectiveness in the use of building materials and

equipment.

An important service is that of consultation and advice to other Govern- ment agencies on building problems, and to other organizations in the 175
formulation of standards of value to the building industry. For example,

advice and assistance were furnished the Federal Aviation Agency in con- nection with studies they have conducted on the flammability of interior- finish materials for aircraft. Technical assistance was also provided to the U.S. Army Corps of Engineers regarding the selection of siding material

to be used to enclose the Vertical Assembly Building for the Saturn rocket

at Cape Kennedy, Fla. A member of the staff spent 3% weeks in South America, as the official American Standards Association representative, participating in the preparation of Pan American Standards for portland cement. In addition, meetings were held with standards organizations, universities, and cement manufacturers in Brazil, Uruguay, and Argentina.

Strength of Prestressed Concrete Beams Investigated, Prestressed concrete owes its remarkable properties to the fact that precompression in the concrete created by means of tensioned reinforcement counteracts tensile stresses which are developed in the structure under load. NBS is studying

the properties of a new system, dubbed "split-beam" by its originator at the Bureau of Yards and Docks. This system consists of a prestressed portion

of a beam in which tensile stresses are expected to develop under service

loads, and a subsequently cast nonprestressed portion in which only cornScale model (Vt actual size) of masonry block wall subjected to racking test. Spring-loaded yokes simulate the normal vertical load on the wall. This method

greatly simplifies the previous standard test procedure and applies forces more

nearly representative of the system encountered under service conditions. (See page 177)

176
pressive stresses are expected to develop under load. The two portions are bonded and become a monolithic beam. As the prestressing in the "splitbeam" system is confined to only a portion of the beam, a smaller tensioning

force is required, and considerable economies in the amount of steel can be

effected. The investigation at the Bureau was intended to determine how the twostage casting of the "split-beam" members affects their properties. The

results indicated that the resistance to flexure and shear of prestressed concrete was not affected adversely by the "split-beam" method of construction. Masonry Racking Test Simplified. The present standard racking

test for masonry consists of applying a horizontal force in the plane of and

at one top corner of a wall, while it is prevented from sliding by a suitable stop at the bottom, and from overturning. The test requires a massive self- contained loading frame sufficiently rigid to resist the system of forces in- volved in the test. In an effort to simplify the test procedure and to apply forces more nearly

representative of the system encountered under service conditions, a test procedure was developed in which the racking load was applied with a suit- able compressive testing machine, while a system of spring-loaded yokes

simulated normal vertical load along the top edge of the wall. The test pro- cedure was developed using quarter-scale models of concrete masonry units. By selecting proper proportions of mortar and suitable conditioning of the masonry units before and after fabrication of the wall models, racking fail- ures were obtained which were quite similar to those observed in prototypes.

It was found that application of relatively small boundary forces had a measurable effect on the racking strength of the models of masonry.

Models Used in Fire Research. In spite of the extensive qualitative

knowledge gained on the behavior of fires in buildings, it is highly desirable

to achieve a more exact understanding of the effects of different variables on

such fires. The high cost, in both time and money, involved in performance

of such studies with the use of full-size buildings or rooms made it desirable

to devise ways in which models can be effectively used for such purposes. The behavior of fires in enclosures of a simple type was studied. Variations were made in size of enclosure, size and shape of ventilation opening, and

fuel loading. Analyses of fuel consumption rate and decomposition gas product data suggest that models may be successfully used to predict the behavior of fires in larger enclosures. There is, however, a considerable

amount of additional work required before extensive use can be made of such

models.

Fire Performance of Partially Dried Plasters. An investigation was made of the influence of moisture content on the fire endurance of partially dried gypsum plaster specimens. This work is needed to furnish tech- nical information on the effect of fire testing building constructions before

moisture equilibrium with the ambient atmosphere is attained. The results show that when drying from both sides of the plaster specimen,

under quiescent ambient air conditions, a minimum of 15 to 20 days per inch

177
of plaster thickness is required for proper drying prior to test. The relation- ship between moisture content and fire endurance was not linear over the

full moisture range explored. It was observed that small changes in moisture

content near the equilibrium level had an unexpectedly large influence on fire endurance of such specimens.

Water Valves for Refrigerating Systems Studied. Refrigerantpressure-actuated regulating valves are the principal means used to control the flow of cooling water to the condensers of mechanical refrigerating and

air-conditioning systems. A laboratory study of several commercial makes

and sizes of these valves was carried out at the request of the U.S. Army

Natick Laboratories to identify the important performance characteristics and to provide information for specifications.

The investigation showed that the characteristics of importance included

the following: (1) the water-pressure drop through the valve at maximum

water flow rate; (2) the sensitivity of the valve in the working range of water

flow rate; (3) the tendency of the valve to leak water at low refrigerant con- densing pressures; (4) the decrease in sensitivity of the valve near the wide

open position; and (5) slack in the moving valve element between opening

and closing.

Thermal Properties of the Earth. Observed earth temperatures at 50

stations in the United States were tabulated for various depths ranging from

3 to 10 feet in most cases. Monthly averages covering several annual cycles are reported. A simple equation was fitted to the data for each station to develop design information on annual average earth temperature, the temperature variation from and lag behind average air temperature (at selected depths) based on the thermal properties of the earth, and the average temperature of the top 10-foot layer of earth for the month (August) when it was

likely to be a maximum.

Although the data were collected and analyzed under the sponsorship of the Office of Civil Defense to provide needed design information for environmental control in underground fallout shelters, they will have broad value. The need for collecting additional earth temperature data to cover adequately

the continental United States was revealed in the study.

Air Mixing Techniques Investigated. Methods for mixing moving

air streams that are nonhomogeneous, with respect to temperature and

humidity, are being investigated to provide greater accuracy in the testing of heating, air-conditioning, and refrigeration equipment that use air as a heat transfer medium. In a small apparatus designed for scale models,

chemical smoke is used to simulate temperature or humidity variations in an

air stream. The performance of a model mixer with smoke-laden air can be photographed or observed visually to assist in selection of the devices

which appear to merit more comprehensive measurement in a full-scale apparatus.

The full-scale apparatus provides a stream of air of known velocity and

measured inhomogeneity of temperature or humidity at the inlet to the mixing

apparatus. It provides for measurement of the uniformity of temperature or 178
Model apparatus designed to measure the effectiveness of air mixers such as this square-edged circular orifice. Smoke is used to allow the mixing process to be

observed visually. Mixers that show the greatest promise in the air-conditioning

and refrigeration field are then subjected to extensive testing on full size equip- ment. (See page 178)

humidity downstream of the device, and the scale and intensity of turbulence

produced by the mixer. Quantitative information on several mixers was

obtained and some of the better designs were introduced into testing stand- ards of the industry.

Asphalt Hardening with Reactive Oxidants. Asphalt is the most

widely used roofing material in the United States today. For this purpose,

asphalts are hardened by blowing with air at high temperatures (300 °C)

and at high flow rates. Recent research at the Bureau showed that, by replacing air with more

reactive oxidants, asphalts can be hardened at a much faster rate while using

temperatures 150 °C below those employed commercially, reduced gas flow

rates, and simple apparatus. Effective oxidants were pure oxygen, ozone- enriched air, ozone-enriched oxygen, nitrogen dioxide, nitric oxide and oxygen, and nitrogen dioxide excited with a short wavelength mercury arc. The

latter system required only 1/20 the reaction time needed with air to produce

the desired hardening.

The roofing-grade asphalts produced with these oxidants were more stable

to photochemical oxidation than were commercial asphalts from the same

asphalt flux . Building Codes and Safety Standards. Through membership in ASA

standards committees pertaining to building and construction safety, the Bureau assists in the development of needed national standards. Recent work was undertaken to aid in reorganization of ASA Project A. 112, Dimensional Standardization of Plumbing Equipment.

179
Measuring Thermal Conductivity of Materials. A new comparative

method for measuring the thermal conductivity of insulation and many other building materials was developed. This method is reliable, precise, and rela- tivelv simpler than the standard guarded hotplate method (ASTM C177).

Based on flow of heat in a conductive-disk hotplate, it requires only measure- ment of specimen thickness and a few steady-state temperatures.

A 12-inch diameter conductive-disk apparatus, made of a solid plate of low-conductivity metal, was constructed and compared with the XBS guarded

hotplate. The ease of calibration, the quality of the results, and the speed

with which they are obtained are all equal to or better than those for the standard test method. The demands on the operator's time are significantly

less.Moisture Condensation in the Insulation of Refrigerated Facilities. In many refrigerated structures, accumulations of ice or moisture develop

within the walls as a result of condensation of vapor coming from the warmer

side. These accumulations seriously reduce the insulating value, and often lead to deformations or physical injury to the structure. Corrective measures are usually difficult, and extremely expensive. Criteria which establish minimum properties of the vapor barrier, the insulation, and the interior

finish, if any. required to avoid moisture condensation were developed on an

analytical basis. It is hoped that with the criteria as a guide, designers of cold storage facilities can prevent difficulties in the future.

A newly developed comparative method for measuring the thermal conductivity of insulation and other building materials is more reliable, precise, and simpler

than the standard guarded hot-plate method. Here, the average thermal conductivity of two pieces of one-inch thick insulation is being determined. The

telescope is used to measure the thickness of the specimens under test conditions. (See page 180)

180
hong-Time Cement Test Program. Data collected from a long-time

study of the performance of portland cements are being analyzed by a digital

computer technique to find what correlations exist between the composition

of portland cement, performance criteria of cements as measured by laboratory tests, and the performance of concrete made with the cements. Some 200

different cements were studied in the program.

Some of the minor constituents, whose presence in the cement reflects the geographical source of the raw material, were found to have a definite in- fluence on the performance of the cement. Determination of these relation- ships will lead to future research on the manner in which certain minor constituents react with the major constituents to give the results observed, and

may lead to the deliberate addition of certain minor constituents to produce

improved cements. Thermal Emittance of Cavities. Before accurate heat transfer calcu- lations can be performed on building structures, the thermal emittance of the materials used in the construction must first be known. One of the most

accurate methods of measuring this property is to compare the energy radi- ated from a specimen to that from a blackbody cavity (isothermal enclosure)

at the same temperature.

Real blackbodies, because of the need for an opening, always provide less radiation than if the opening were not present. Theoretical expressions

derived to compute the "apparent emittance" of cavities with openings do not always predict the same apparent emittance.

Recently, experimental measurements were made at NBS to test the validity of the various expressions. This was done through use of a reflectance approach. Spectral reflectances were measured from 0.4 to 0.75 micron

for several cylindrical cavities of adjustable depth lined with different dif- fusely reflecting coatings. The resulting reflectances were converted to emittances by Kirchhoff's Law. Comparison of these experimentally deter- mined cavity emittances with those predicted by the analytical expressions

showed that two of these expressions gave excellent agreement. Therefore,

either one can be employed with assurance in emittance measurements in which shallow cylindrical cavities are used as the reference standard. Porcelain Enamel Institute Research Associateship Expanded.

The current emphasis of the recently expanded Porcelain Enamel Institute Associateship is on the development of standard test procedures for such

properties as weather resistance, alkali resistance and ease of cleaning. One

program recently initiated is an exposure test to evaluate the weather resist- ance of the new porcelain enamels for aluminum. Exposure sites are at Washington, D.C. ; Los Angeles, Calif. ; New York, N.Y. ; Montreal, Canada

and Kure Beach, N.C. Cement-to-Aggregate Bond Tested. The irregular shapes and coarse

surfaces of crushed stone and other concrete-aggregate materials make it very difficult to measure, to a satisfactory degree of precision, the effective surface area. As knowledge of surface area is essential to measurement

of the bond strength between cement and aggregate, smooth 14-inch-diameter

181
Exposing porcelain enamels on aluminum to determine their durability is part of a current NBS program to develop standard test procedures for such porcelain properties as weather resistance, alkali resistance, and ease of cleaning.

(See page 181)

spheres were used as aggregate in the development of a bond strength test method. The spheres were made of glass, steel, and two minerals frequently

used as concrete aggregates. The test method involves comparison between

the breaking strength of cement-aggregate bars and the strength of cement

bars without aggregate. Present concrete design practices with regard to strength are based solely on experience. It is hoped that the knowledge to be derived from this bond

strength test will contribute to the development of a rational, workable

theory on the strength of concrete. Such a theory would make possible fairly

precise design, with increased efficiency and economy in the utilization of materials. Granular Content of Sulfur Mortars Determined. The strength of sulfur mortars largely depends upon the ratio of the sulfur content to the granular materials. Many concrete-testing laboratories do not have the equipment or personnel needed to make determinations of this ratio by the ASTM carbon disulfide extraction technique. Therefore, a new method,

developed by the Cement and Concrete Reference Laboratory at NBS, which

is simpler and easier to perform, should be of interest to concrete testing

laboratories and to industry as well. 182
In this method, a sample of the sulfur mortar is crushed and ignited,

driving off the sulfur and leaving the granular materials. The ratio is deter- mined by comparing the weight of the crushed mortar to that of the residue. 2.3.5. INFORMATION TECHNOLOGY

The Information Technology Division (formerly the Data Processing Sys- tems Division) continues to serve as a central research and development

laboratory in the field of automatic information processing within the Government. In support of its responsibility to provide advice and assistance, not

only within the Bureau but also to other Government agencies, it conducts

investigations leading to the development and design of new technological

tools and techniques for more effective use of automation in processing

information. It responds to specific requests for technical assistance and

collaborates directly with the requesting agency in analyzing its operations

to design or improve its information processing system. With the expanding

use of information processing in Government and industry, the Information

Technology Division has of necessity continued to augment its staff competence through specialized training and to increase the versatility of its research facilities. The current program includes research and development activities using

basic knowledge of such diverse scientific disciplines as physics, chemistry,

electronic and mechanical engineering, linguistics, and the management sci* ences. Present activities include keeping up with new components and

appraising their applicability in nanosecond computer circuitry ; developing new techniques for the storage, processing, and retrieval of information; in- vestigating ways of assembling components into prototype devices and sys- tems; applying the techniques of communications and photogrammetry to information processing and control systems; developing automatic logging

and preprocessing systems for scientific experiments; studying the manmachine interface; and applying automatic information processing tech- niques to the decision-making and technical support functions. Research Information Center and Advisory Service on Information Processing (RICASIP) . The Research Information Center, which

has been sponsored jointly by the Bureau and the National Science Foundation since its inception in 1959, continued to maintain a file of the biblio- graphic references for information storage, selection, and retrieval, and for other areas of potentially applicable basic research. This collection now

numbers over 15,000 references. The data file supports surveys, studies,

and publications such as selected state-of-the-art reports and special bibliographies, as well as an index to the literature on legibility of alphanumeric

characters and symbols.

During the year RICASIP cosponsored a Symposium on Statistical Association Methods for Mechanized Documentation, which was attended by over 200 specialists. Papers and panel discussions were presented during the three-day meeting by 35 leading workers in the field. 756-224 0—65 13 183
Standardization Activities, Members of the staff participated in committees, subcommittees, and task groups of the American Standards Association, activities concerned with establishing standards related to computers

and information processing, data transmission, communications systems per- formance, character sets and data format, definition of controls, machine

indexing, abstracts, computer programming languages, and glossary termi- nology. A senior staff member served as the first chairman of the newly

formed ASA Information Processing Systems Standards Board and another

member of the staff was U.S. Delegate to the International Organization for Standardization Technical Committee on Computers and Information

Processing.

Processor Programming Research. Research continued on advanced

programming techniques to improve communications between people and

computers, between data acquisition devices and computers, and between

computers and devices which they control. Numerous models and diagrams representing populations, mazes, a manufacturing process, graphs, electronic circuits, and simple rectangular figures were studied. Ciphers which are acceptable to a computer were devised for each model or diagram considered. The requirements for manipulating these ciphers in a computer were studied and some subroutines for performing

these manipulations designed. The language for using these subroutines

is computer-independent, enabling the user to manipulate the subroutines by means of terms that are common to his special field. A trial language called SYNCRETIC was developed and existing research tool languages IPL-V,

COMIT, LISP, and SIMSCOPT were studied. Studies of Components and Materials. The study of new and exist- ing components continued as basic to developing faster, cheaper, more

reliable, and more efficient digital data-processing devices. Magnetic film materials in particular were studied and a survey of those having possible

applications in digital computer technology was prepared for publication.

A technique for measuring the ferromagnetic exchange constant of a magnetic

film with a conventional hysteresis loop tracer was developed by making

minor equipment modifications. The measurements that can now be made

should yield information that will aid in characterizing magnetic thin films. Specific efforts by two staff members were directed to maintaining current awareness of the latest components, devices, and circuit techniques, noting

progress in integrated circuits, discrete-component modules, planar-epitaxial

transistors, charge-control diodes, tunnel diodes, backward diodes, and hot- electron diodes. Anomalous temperature behavior in transistor-tunnel diode

circuits is being investigated.

Tunnel diodes and transistors were utilized in designing a binary counter capable of operation beyond 100 megapulses per second. A reset-set (R-S)

type of flip-flop was investigated for use in gating circuits for a shift register

capable of operating at more than 50 megapulses per second. Computer Input-Output Devices. Novel input and output devices for computers are being studied in terms of their effects on the computer-operator

184
interface. Particular attention was paid to computer operation with pictorial

inputs; means of generating displays of symbols, line drawings, and contours

and use of magnetic tape and photographic devices for transferring data

between man and the digital computer.

Technical Assistance for NBS Data Processing, New areas for the application of automatic data recording and processing were developed in collaboration with other laboratories of the Bureau to solve their data- handling problems. Some of the applications presented special data-logging

and preprocessing problems. Systems were devised for collecting data from

an automated infrared spectrophotometer (see p. 57), from crossed-beam

collision experiments simulating the upper atmosphere (see pp. 90 and 94),

and from infrasonic noise receivers (see p. 62)

Much of the equipment required for recording these data automatically was assembled from previously designed modules making use of standard cir- cuit cards. New modules designed and implemented during the year include

a digital magnetic tape transport, a ripple register, and an up-down counter

with built-in shift capability. The new circuit cards designed include a matrix

card, dual comparator, reed relay card, up-down counter, digital switch,

dual high-impedance amplifier, and a crystal oscillator. Some of the new

and previously developed modules were added to the on-shelf stock available

to Bureau laboratories on a short-term loan basis for assembly into their systems.

The information technology staff also furnished engineering assistance to the Bureau's high-energy radiation laboratory in planning and assembling

digital circuitry for processing the input to a computer-controlled data- logging system. Additional advisory services were furnished in planning

programs and procedures enabling the experimenters to intervene in the computer operation.

Automatic Indexing by SADSACT. A machine program for auto- matically assigning descriptors to technical articles was developed and is now being tested. The program, called SADSACT (Self-Assigned Descriptors from Self ^4nd Cited Titles) , "learns" associative links by inspection of previously formed pairs and then selects descriptors for words comprising new items. In the first step the program directs the machine in compiling a master

vocabulary, listing for each subject word all descriptors which occur with

it often enough to be significant. The machine does this by analyzing an

input "teaching sample," consisting of multiword entries paired with de- scriptors previously assigned by indexers. The computer reads in from punched cards the items for which descriptors are desired, searches the vocabulary for each word of each item, and sums the number of times each descriptor was found for each item. The

program then selects for each item the several descriptors found with greatest

frequency.

The program was tested after the machine was loaded with teaching samples

from a variety of subject fields which had been previously indexed at the 185
Defense Documentation Center. Test samples included scientific papers (for

each of which the title, abstract, and titles of references were included) and news items; the descriptors assigned were in substantial agreement with

previously made assignments. Further tests, on more homogeneous subject

matter, are now in progress under a grant from the Council on Library

Resources. Automation of Chemical Search Operations. The Bureau is engaged in continuing research, in collaboration with the Patent Office, on

methods of automating operations involved in processing patent applications. A large part of the patent application workload could be more readily

processed if the Patent Office had a speedy and sure way of automatically

searching its data on chemical compounds. The Bureau is working on this retrieval problem also for the Army Research Office, since retrieval of chemical information is essential to many research programs of the Department

of Defense. Automatic searching requires that chemical structures be represented in a manner capable of being encoded in digital form for computer manipulation. The Bureau's previous work in this area led to the development of HAYSTAQ, a computer program for searching chemical data by means of structure fragments encoded in digital form. Subsequent work at the Bureau, the Patent Office, and elsewhere produced notation systems for identi- fying whole structures. Much of the present work at the Bureau is devoted

to transforming the alphanumeric notations into a form that computer

programs can use directly.

Organic structures can be described by Hayvvard linear notations, the rules

An example of NBS assistance in solving information processing problems for other Government agencies is ACCESS. This high capacity, multipurpose, data- conversion and editing system was developed and built for the Office of Emergency Planning for handling resource-evaluation and status information.

(See page 188)

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for which were originated at the Patent Office, and by Wiswesser notations,

both of which the Bureau is now studying. The original Hayward rules have been simplified for some complex structures and new rules devised to extend the notation to features not originally covered. Notations for de- scribing complex inorganic compounds are being developed by the Bureau

and the Patent Office. The Bureau is embodying algorithms (precise logical processes) in computer programs which automatically translate from the alphanumeric linear notations to HAYSTAQ-type "connection tables" encoded on an atom-to- atom basis, rather than by structure fragments.

In other work sponsored by the Patent Office the Bureau is studying by means of Boolean matrices the theory of files containing interrelated entries.

It is also developing techniques for the organization of very large files of

interrelated information, under sponsorship of the Army Research Office. Findings from both studies are expected to affect the manner chosen for the computer to store and process related data such as chemical structures, methods of manufacture, and biological activity.

Automatic Character Recognition. The Bureau continued a literature search and survey of equipment developments for recognizing printed

characters, sponsored by the Department of the Army. A corollary task was the development of a "syntactic analysis" technique for recognizing

the pictorial configurations of components of Chinese ideographs. A list of approximately 300 radicals and radical-like components and rules governing combinations have now been developed which account for more than 80

percent of the characters in common use. These rules were tested in a pre- liminary computer program using cases in which a machine recognition

scheme would not be able to decide between several alternatives. The method

facilitated error detection and in some situations error correction. Simulation of a Communications System. TELETRAF a computer

program capable of simulating portions of the Defense Communications System (DCS), was devised and used at NBS to render technical assistance to the Defense Communications Agency (DCA) . The DCS is a worldwide communications system, a composite of the separate long-line systems of three

Services, providing regular and emergency communications. A flexible method of evaluating potential sites and configurations is essential for the DCA to set up a system that is as catastrophe-proof as possible.

The Bureau also developed a computer program written to accept nuclear

attack data as input and produce a tape driving a plotter printing map overlays showing areas of possible destruction. These can be used to specify sys- tem features that probably would permit maintenance of a given grade of

service. They were used in experimentation with several vulnerabilitysimulation models.

Detection of Nuclear Events. The development of a data acquisition

and processing system for the detection of nuclear events in space was begun

under the sponsorship of the Advanced Research Projects Agency. The sys- tem will be used with a large number of geophysical sensors to study the 187
natural background for each variable and to determine useful discriminants.

The system design consists of a hybrid analog-digital system selecting sensor outputs occurring on a short time scale for recording by analog techniques.

Digital techniques will be employed where inter-sample intervals as large as

a millisecond can be tolerated. This system will use an on-line, computercentered digital data acquisition system, the operational requirements for which were established. The system will filter raw data to extract special events on a real-time basis, minimizing the volume of data retained for subsequent analysis.

Two data logging systems assembled from NBS modules will be used for data acquisition pending installation of the computer and will then be retained

as backup systems for use during routine maintenance of the computer.

ACCESS. An Automatic Computer Controlled Electronic Scanning

System (ACCESS) , a high-capacity, multipurpose data-conversion and editing

system, was completed and delivered to the Office of Emergency Planning.

This system, developed for handling resource-evaluation and status information, reads data from 16-mm microfilm of marked documents. It performs

such general-purpose computer tasks as code conversion, verification, editing,

summarizing, reorganizing, screening, storing, message preparation and

transmission, and control of input-output devices such as X-Y plotters,

magnetic tape units, and communication facilities. Its modular design

permits the system to be tailored to the requirement of various local, regional, or central data acquisition links within a complete organizational network.

The use of microfilm as a storage medium facilitates access to data by both man and machine without any intermediate conversion of data. This allows decision-making by men or by an electronic computer.

Completion of a set of routines for the central processor and scanner

diagnosis made possible experiments in which line drawings and map tracings were read by the computer-controlled scanner and digitized in the output

as X and Y coordinates. In this form they are suitable for automatic use, storage on magnetic tape, or plotting on an X-Y plotter. Good reproductions

of inked tracings of closed contours and geographic outlines were obtained

from the originals stored on 16-mm film. Global Space Information. A global-range information-processing

and control system for future orbital and space programs will require expansion of present capabilities. Such a system was planned for the Air Force to control instrumentation and data-handling equipment, to determine information-forwarding priority, to recognize the urgency of incoming information,

to make best use of available communications facilities, and to keep control

centers informed of information network status. Work on this project includes defining the problems of integrating the functions and facilities of military missile and space ranges in addition to studying computer languages, file manipulation, and generation of encoded

commands. The Bureau defined four elements of a range instrument control loop—central terminal logic and instrument control sequencer, station 188
terminal logic, site instrument control, and message composer—and started

their detailed functional design.

Naval Procurement Procedures. The Bureau assisted the Navy's

Bureau of Supplies and Accounts in developing data-handling techniques and

devices for an efficient system for procuring and distributing the thousands of items used within the Naval establishment. Present procedures at a Naval

supply center were surveyed and available input-output devices adaptable to the supply system examined; these included keyboards, printers, and card

printers and punches. Interface requirements for a future "real-time" supply

record system providing overall coordination of this Navy activity were

defined. Remote Inquiry Stations. A remote inquiry station was designed,

under joint sponsorship of the Patent Office and the Bureau, as a means of communication between human operators at various locations and a central data processor; a prototype model is now being fabricated. Such stations could be located within one building or separated by distances of hundreds

or thousands of miles to enable people to use the computer from wherever the information is required. By facilitating access to the computer such a development could multiply the usefulness of an information storage, search,

and retrieval system.

The Vigilometer. The Bureau completed the Vigilometer, a complex

device for presenting audio and visual stimuli to a subject and recording

his responses, and delivered it to the Army Personnel Research Office. It is

The Vigilometer is used in testing a subject's responses to various visual and

auditory stimuli. It was developed for the Army Personnel Research Office to measure attentiveness and fatigue thresholds. (See page 189)

189
now being used as a tool for research in vigilance and fatigue threshold determination. This system consists of five subject stations, each with five stimuli generators, and a central control console. Digital logic circuitry

under control of a prepunched paper tape program activates stimuli for any

time period up to eight hours. Responses are recorded by a column printer for analysis by the researchers. In other work for the Army Personnel Research Office, the Bureau applied

computer techniques to psychometric testing. It performed a design study on this means of overcoming many limitations in presently used printed

tests and answer sheets. Processing and Storing Microfilm. The Bureau continued to provide

technical advisory services to the Weather Bureau on transmitting and

processing photographic data acquired by weather satellites of the NIMBUS

series. The services included technical advice on storage of microfilmed

archival cloud analysis data. Three-Dimensional Information from Photographs. The Bureau

continued research on techniques for scanning aerial stereophotographic

information under the sponsorship of the Naval Training Device Center. The object of this program is to use the scanned information for automatically producing three-dimensional terrain information. Experimentation

with computer programming led to the development of techniques for computer recognition of conjugate points of an aerial stereophoto pair. This,

in turn, permits the determination of parallax and computation of X, Y, and

Z-axis information about the subject terrain. Management Data Processing. Advisory service was given also to the Internal Revenue Service in setting up and administering a comparative

study of the efficiencies of processing tax return information on three dif- ferent kinds of manually keyed machines. The study report compared per- formance on identical practice material using a 10-key adding machine, a 14-column (full bank) machine, and a keypunch-verify machine. The re- sults showed that the punch-and-verify process is significantly slower and no more accurate than either of the other two used in the experiment.

Computers in Management of Recreational Facilities. The Bureau

studied the feasibility of using automatic processing techniques in the devel- opment and management of a nationwide plan for outdoor recreation facilities at the request of the Bureau of Outdoor Recreation, Department of the

Interior. An inventory must be made of existing and potential recreation

areas, because of the need for planning future outdoor recreation facilities for the increasing population. The inventory will be used in an analysis

of present facilities and along with demand data (population and socio- economic factors, for example) will aid in projections for future recreation

needs. A computer program was written for maintaining a file of about

5,000 recreation areas of over 10 acres, from which current information and

statistical data on sites can be extracted. Members of the Bureau of Outdoor

Recreation staff were also given training in general computer techniques and

programming.

190
Automatic Data Processing for Public Housing Administration.

Technical assistance was continued to the Public Housing Administration

in data processing techniques and programming for tenancy reports. Local

housing authorities are required to submit reports about applicants and

present tenants in low-rent housing annually for review of tenant eligibility.

Computer programs were used in processing data on approximately 450,000

re-examinations and 12,000 new tenants. Survey of Federal Information-Storage Systems. The Bureau pre- pared case studies of Federal information storage, selection, and retrieval systems either in being or in planning. This was a preliminary in the design

of an improved information-handling system for domestic and international business figures in the Department of Commerce Office of Administration for Domestic and International Business. The information systems of the De- partment of State and the Small Business Administration were studied. Studies of systems currently in use in planning by the Central Intelligence

Agency, the Food and Drug Administration, and the Securities and Exchange

Commission are now in progress. Data-Handling Systems for the Office of Technical Services. The

Bureau concluded its work on the design of an information management

system for the Office of Technical Services for acquiring, advertising, and

disseminating reports on Government-sponsored research and development.

This included a computer program for the automated preparation of inte- grated cumulative indexes and a simple manual inventory and order-handling

system capable of the required performance for an increased number of documents.

Automatic Mail-Sorting Developments. The Bureau continued assist- ance to the Post Office Department in applying automatic data-handling tech- niques and equipment to the improvement of mail-sorting and routeselection operations. The manual sorting schemes now used at Washington,

D.C., were adapted for use with prototype codesort equipment by listing each

possible address (individually or in a group) on magnetic tape with bin as- signments. Final procedures were developed for updating these lists by

use of a computer.

Transportation network relationships were mathematically analyzed for finding the Post Office location having minimum transportation costs for

getting the mail to its patrons. The mathematical model and computer pro- gram written indicated that for a considerable area around the minimum

point the costs would be close to minimal.

A previous analysis of a buffer problem in matrix-type sorting machines was extended to a buffer which helps prevent overflow within a proposed

package-sorting machine. Buffer problems between stamp cancellation and

first sorting and the amount of storage capacity needed in a mail separator

machine also were investigated by use of computer simulations. The relative merit of reading addresses by optical character readers at- tached directly to sorting machines or operated separately was investigated.

191
Sorting systems are being developed for both configurations to determine

the comparative costs. The Bureau developed a model of a novel sorting concept involving a device called a director. The Post Office is using the model to evaluate the economic merits of the system. Its use would eliminate the cost of trans- ferring mail among machines within a sorting system, but would require

additional machinery.

A method for estimating the time required to process a letter through a

selected subsystem was developed. This is a statistical sampling procedure,

by use of which it can be determined if the time for a particular letter is greater or less than a predetermined time. It will be useful in time and

flow comparison studies. Technical advice was also given on human aspects of postal machinery

design and evaluation. Advice on such factors was specifically requested

in the conduct of three machine evaluation programs and in areas related

to man-machine interface. 2.3.6. INSTRUMENTATION

The Bureau is concerned with both the theory and practice of measurements; its practical work is aimed at improving both industrial technology

and the Bureau's own research programs. Since measurement precision

depends on the natural limitations of the method and the behavior of practical

instruments, both are being investigated to advance the measurement art. The Bureau maintains an extensive reference file of literature on instruments

and measurement methods to help disseminate measurement information and

avoid duplicating scientific research effort. The file is designed so that its data can be retrieved partly by mechanical means. Simple techniques insure

good coupling between the researcher and the file, so that the researcher is led quickly to relevant information.

Mechanical instrument activities include responsibility for the national

standards of humidity and for improvement in standard hygrometers and

humidity generators. Calibration methods are being developed for pressure an acceleration transducers, while other mechanical instruments are being

developed to meet specific Federal agency needs.

Electrical and electronic methods are widely used in modern instrumentation, even when the initial phenomenon being measured is not electrical in nature. Electronic methods were devised to investigate the characteristics of materials used in vacuum systems, as well as the characteristics and capabilities of electron devices themselves. Improved electronic instruments were

developed not only for use in Bureau research programs but also for use by

other Federal agencies.

Project FIST. The original object of Project FIST (Fault /solation by

Semi-Automatic Techniques), supported in part by the Navy Bureau

of Ships, was to develop techniques that would permit a relatively untrained

technician to locate faults in electronic equipment. Work has shown that 192
The distribution of current in a transistor can be "seen" by coating its active portion with a phosphor whose luminescence under ultraviolet irradiation de- creases as the temperature increases. Hot spots accompanying current flow become visible as dark areas. From left to right are transistors carrying no

current, high current, and current in the area of second breakdown, show as a dark spot. (See page 194)

this object can now be reached easily, and the goal has been expanded to include techniques that will produce diagnostic data, which the trained

technician can use to make maintenance decisions. The untrained technician will use good-bad indications from the generalpurpose test set and ignore other data that the test instrument can supply.

As he grows in competence he can use additional information from the test set to increase his effectiveness as an electronic maintenance technician.

In this way FIST will be more generally useful as a diagnostic tool and will counter prejudice which the technician might have against using a test in- strument permitting him to make no decisions. Precise Electrical Characterization of Semiconductors. Methods

and techniques are being studied, in a program supported by the Advanced

Research Projects Agency, to improve the fundamental accuracy with which

the electrical properties of semiconductors can be measured. These properties

include minority carrier lifetime, carrier mobilities, and resistivity at various

temperatures. In response to industry's most important need, the program

concentrated chiefly on room-temperature resistivity measurements of silicon by direct-current techniques in the 0.1 to 10 ohm-centimeter range. Three methods are of major interest: the four-point probe, the two-point

probe, and the van der Pauw technique. The van der Pauw technique has

the advantage that only one-dimensional measurement (thickness) of the sample is necessary. The two-point probe has the advantage of greater accuracy when used on a nonuniform sample. The four-point probe has the advantage of great convenience as a routine technique plus the ability to resolve resistive nonuniformities.

The Bureau study concentrated on the effects of sample surface finish and

probe material, the problems involved in sample nonuniformity, and the geometrical correction factors. Computing facilities available at the Bureau

were used extensively in this work. The ability of the four-point probe to detect nonuniformities was clarified and knowledge of four-point probe correction factors has been extended, enabling better comparison of four-point and

193
two-point probe measurements made on the same sample. The search for more uniform material on which to make comparative measurements led to study of samples doped by neutron irradiation and of samples doped with

boron or aluminum and grown by special techniques.

Second Breakdown. A study of the transistor operating mode known

as second breakdown, begun at the request of the semiconductor device in- dustry, was continued under sponsorship of the Rome Air Development

Center. The onset of second breakdown is marked by a decrease in collector junction voltage and a constriction of minority-carrier current in the base.

It was found that the mode appears above a threshold power level and has a

starting delay. Operation in this mode can damage the transistor, and its inadvertent onset causes circuit malfunction. Second breakdown, therefore,

is a matter of concern to both industry and its customers. The investigation of second breakdown led to a better understanding of

its characteristics. Temperature-sensitive phosphors with a short response time were used to display transient current distributions in transistors by means of the associated temperature distributions. The influence of structural

defects and base drive on the development of second breakdown is now bet- ter understood. It was found that the base current can control the fraction

of total current that flows through the current constricion and can so reduce

this fraction that the transistor will revert to a normal mode of operation.

The Bureau participated in meetings of the Joint Electron Device Engineering Council charged with specifying operating conditions under which

second breakdown does not occur. The Bureau also proposed a definition of second breakdown for adoption by the International Electrotechnical

Commission.

A cooperative program with industry is aimed at finding whether a rela- tion exists between the appearance of second breakdown and the existence

of strains, dislocations, and other imperfections in the transistor. Peak-Reading AC-DC Comparators as Laboratory Standards. An

ac-dc comparator was developed for the Bureau's Electricity Division as part

of a study of peak voltage measurements. Previous developments along these

lines at the Bureau include a differential thermocouple voltmeter for transfer measurements of audiofrequencies by comparison with direct current standards, with a repeatability of better than 20 parts per million (ppm). This

technique makes the comparison on a root-mean-square basis, but a sinus- oidal voltage can be specified as w7 ell by its average rectified value or its peak value. The average or peak measurement is often an easier one to make in the field. Audiofrequency generators recently became available with amplitude sta- bilities and total harmonic distortions of less than 100 ppm. These generators

make it worthwhile to investigate improvements in both average- and peakreading measurements. The essential feature of the new ac-dc comparator is a high-speed synchro- nous switch that samples the sinusoid voltage for a short interval in the region of its peak. The switch alternately samples a precise dc supply. The

194
two samples are compared by means of an oscilloscope; the visual comparison allows a precise value to be assigned to the peak of the ac waveform.

Preliminary results are repeatable to 20 ppm, using the thermal transfer technique as a standard. Additional noise reduction in the ac generators

might permit precisions of better than 10 ppm.

VHF Spectrum Analyzer. A spectrum analyzer was designed and

built for use in studies of the output power spectrum of a helium-neon laser

at the Bureau's atomic physics laboratories. Part of a laser's output radiation, at a wavelength of 1.15 micrometers, is intercepted by the cathode sur- face of a photomultiplier tube. The electrical output of the photomultiplier

consists in part of intermodulation difference-frequency components that correspond with the line separations of the laser's output spectrum. The

purpose of the analyzer is to examine these intermodulation components in

detail. The analyzer, a frequency-sweeping type, accepts inputs within a 5-MHz

range centered at either 150 MHz or 300 MHz. The swept bandwidth can

be selected in ranges from 200 Hz to 200 kHz with resolutions from 2 Hz

to 20 kHz. The amplitude-?;ersw.s-frequency spectral response is displayed on an oscilloscope.

FOSDIC Applications. The FOSDIC III equipment (Film Optical

Sensing Device for /nput to Computers) was developed in a joint effort with the Bureau of the Census for use in the Decennial Census of 1960. It has since been applied to many other projects for which NBS continues to supply consulting services. A recent large-scale project involved identifying the serial numbers on the mailing labels of questionnaires mailed back to the Government. The serial numbers were coded in binary form in an extra line of selected typewritten

characters on each label. By scanning the upper portions of the characters,

FOSDIC is able to derive the original number. In this manner, the returned

questionnaires can be checked off against a master list by machine.

FOSDIC was also used to scan the film records of instruments that measure the direction and speed of water currents. For this application, a special attachment was developed to allow the FOSDIC equipment to handle

motion-picture film. FOSDIC has been used experimentally to recognize handwritten characters. The machine can recognize all letters and numbers of a set of writ- ten characters if the writer accepts constraints on the style of character formation.

A new scanner, a transistor version of the scanner in FOSDIC III, was

completed and made an operating part of the ACCESS system (see p. 188).

In addition to its use for acquiring data from documents, it can be used for general-purpose scanning of patterns or line drawings.

The machine development sponsored by the Weather Bureau, FOSDIC IV, was completed and made ready for delivery to the National Weather Records

Center at Asheville, N.C. This machine scans microfilm copies of punched

tabulating cards, searching for selected data. Output can be on magnetic

195
tape or punched cards and can include part or all of the data on the input

films. Vacuum Physics. Many measurements in the very rarefied gas environment, including the calibration of gages and the measurement of throughput, depend on a detailed knowledge of mass transport through bounded

regions. However, the expressions for transport have been developed only

for limited geometries; only the long tube has had even moderate experimental study. It is desirable to test transport concepts to greater accuracy and at lower pressures than has been done before as a function of geometry,

surface condition, gas species, and temperature.

Substitution techniques are being studied as a method of precise measurement. A linear flow line was used for the purpose, and effects on its behavior

of various factors were investigated. These included flow stability, pump

behavior, ionization gage sensitivity, and temperature. Transient response

also was studied. Stability, sensitivity, and resolution of better than 0.1 percent at 10~5 torr were achieved, and the line was shown to be linear within these limits. The substitution procedure is independent of ionization gage pumping or other extraneous flows, provided they are constant during

the period of measurement. Ionization gage drift was examined and none

found until pressure changes greater than 2 percent were made at 10 r> torr. The relaxation effect of about 0.2 percent found under these conditions was

ascribed to sorption kinetics

196
2.4. CENTRAL RADIO PROPAGATION

LABORATORY

The Central Radio Propagation Laboratory (CRPL), located at Boulder,

Colo., has the primary responsibility in the U.S. Government for collecting,

analyzing, and disseminating information on the propagation of radio waves

at all frequencies along the surface of the earth, in the atmosphere, and in space. It also conducts scientific studies directed toward new techniques for the efficient use and conservation of the radio spectrum.

The radio-frequency spectrum, like other critical resources, is essential to our well-being but is limited in extent; it is not adequate to meet all conceivable future needs. We cannot enlarge the spectrum beyond its present

limits, but we can expand its usefulness through scientific research and de- velopment, and conserve it by planning and allocating it to more essential requirements.

CRPL is responsible for assisting administrative and operating activities of both Government and industry in the field of radio propagation. It does

this at the international level by active participation in the work of the Inter- national Scientific Radio Union (URSI), and from the International Radio

Consultative Committee (CCIR), the engineering organization of the Inter- national Telecommunications Union. Eighteen members of the CRPL staff were selected by the National Academy of Sciences to be members of the U.S. delegation to the General Assembly of URSI in Tokyo in 1963- Members of the CRPL staff direct the CCIR standards and international

allocation work in the LTnited States in the fields of radio systems, tropospheric

propagation, and ionospheric propagation. The work is coordinated in this country by the Department of State. Eight members of the CRPL staff were

selected to be delegates to the CCIR Plenary Assembly held in Geneva, Switzerland, in 1963. During the past year CRPL revised a chapter dealing with propagation and

technical factors in radio spectrum utilization in the book entitled Radio

Spectrum Conservation. The book was originally published in 1952 as a report of the Joint Technical Advisory Committee of the Institute of Radio

Engineers (the IRE, now merged into the IEEE) and the Electronic Industries Association. The revised chapter employs a systems approach by

frequency band, starting at the very lowest radio frequency used for tele- communication purposes and proceeding to higher frequencies.

Project HANDS, High-Altitude Nuclear Detection Studies, One of the most important of CRPL's present activities is HANDS, a project which

draws on the services and cooperation of the staffs of many groups in CRPL

197
and also in the Institute for Applied Technology. Project HANDS was

undertaken this year for the Advanced Research Projects Agency and is now in operation. Its purpose is the development and evaluation of methods

of detecting high altitude nuclear detonations by continuous monitoring.

A new building at the Table Mesa (Colo.) field station now houses the sensors being evaluated, data-processing equipment, and recording equipment.

These sensors measure phase and amplitude variations of radio waves re- ceived at steep and oblique incidences, ionospheric absorption of cosmic

radio noise, air fluorescence at 3914 A, and electromagnetic pulses.

Measurements of variation in magnetic field and infrasonic and acoustic disturbances, being obtained in other NBS programs, also will be used in

this program.

Present information indicates that a nuclear detonation can be most readily

recognized by means of the prompt effects produced by its x rays. Measure- ments of normal values and those incorporating solar disturbance effects are now being processed by an analog-to-digital converter and recorder

developed at the Washington measurements automation laboratories for

this program. The data are encoded on magnetic tape, which is processed

by a computer programmed to search for events of interest—those having

rapid rates of onset, higher-than-normal amplitude, or abnormally long

durations. A more elaborate system has been designed and will be placed in operation

when the new computer is received. Data from each sensor will be recorded

routinely every 5 seconds until an interesting event is detected by the on-line computer. The computer will then place the system into accelerated operation

to record more detailed data on all channels. Full-scale data acquisition is planned to begin in January 1965. IQSY—The International Years of the Quiet Sun. IQSY is a period during 1964 and 1965 which is characterized by a lull in solar radio

activity and hence permits studying phenomena which are obscured by

normal solar activity. Like the IGY (International Geophysical Year

1957-58) which occurred at a maximum of solar activity, the IQSY is being

conducted on an international basis. Scientists from more than 65 nations

are making measurements, under this coordinated program, in a variety of

disciplines concerned with solar and terrestrial physics. Measurements are being obtained from many of the IGY station locations and collected at many

of the IGY data centers. CRPL is operating World Data Center-A for Air- glow and Ionosphere and participating in the operation of World Data

Center-A for Solar Activity. The National Science Foundation is partially

supporting continued operation of these data centers. The success in some fields of the IQSY depends on making observations

when the desired types of solar and geophysical activity are taking place.

A listing of such periods, the "Abbreviated Calendar Record," is prepared by

the NBS Radio Warning Services from telegraphic reports and published

regularly in IQSY NOTES. It includes comments of the IQSY World Warning Agency, provided by the NBS North Atlantic Radio Warning Service at 198
Fort Belvoir, Va. This group also assigns designations to all satellites and

space probes for the international Committee on Space Research (COSPAR)

and distributes satellite launching and orbit data internationally.

IGY—The International Geophysical Year. CRPL continued to operate IGY World Data Center-A for Airglow and Ionosphere and the World Data Center-A for Solar Activity (in part), with financial assistance from the National Science Foundation. These data centers are not only

processing IQSY data, but are still occupied in cataloging, copying, and dis- tributing IGY data to scientific and technical groups. During 1964 approximately 3,500 "station-months" of data were examined

by CRPL staff and visiting scientists; about 9,000 station-months were supplied in response to requests; and 25 scientists from other groups visited the data center, staying an average of 5 days each. 2.4.1. IONOSPHERE RESEARCH AND

PROPAGATION

Since the time of Marconi's first transmission and reception of radio waves

across the Atlantic Ocean, reflection of radio waves by the ionosphere has

played a crucial role in long-distance communication, serving important

needs which land-line and submarine cable could not meet. In the future,

satellite relays, which do not depend upon ionospheric reflection, will un- doubtedly assume a large share of the burden, but communication engineers

realize that for many years yet to come the ionosphere will continue to play an important and exclusive role. Under the broad heading of Ionosphere

Research and Propagation, the Bureau conducts and coordinates studies of the ionosphere and its effect on the propagation of radio waves. The basic nature of ionospheric radio propagation is well understood; the main problem is to understand the processes responsible for the complexity and variability of the ionosphere and to learn to predict the ionosphere's net effect on radio waves. Vertical Soundings Research, The technique of vertical ionospheric

sounding, in which radio energy is transmitted straight up and the returned

energy monitored, is used extensively by the Bureau in studies of the ionosphere. Recently the Bureau launched a broad attack toward understanding the processes occurring at heights of 100 to 900 km, which are involved in the "continuity equations" for electrons and ions. This led to identification of the conditions—largely various ion composition ratios

under which the law of electron disappearance would approximate that observed in the ionosphere.

Study of electron density data from vertical soundings disclosed geo- graphic and seasonal variations in neutral composition of the atmosphere

which may be identified with large-scale circulation and mixing processes. In other work, ionization by electrons "dumped" from the Van Allen radia- tion belts was advanced as the cause of the puzzling persistence of the ionospheric F region during polar winters.

756-224 O—65 14
Plasma Resonances in the Ionosphere. Resonant oscillations of the ionospheric plasma excited by high-frequency radio pulses were observed

by topside ionospheric sounders carried aloft first in CRPL rocket tests and

later by the United States-Canadian topside sounder satellite, Alouette. Two years after first being observed, these resonances were correctly identi- fied as lying at the plasma frequency /y, the electron gyrofrequency fu

and its harmonics, and at a so-called hybrid frequency /r. These resonances are explained on the basis of existing theories of plasma

oscillations (simplified by the almost collisionless state of the upper

ionosphere) as involving electrostatic oscillations of the plasma with the

electric field of the electrons providing the restoring force. Resonances at and fn correspond to oscillations along the magnetic field and at fx and

nfx to those across the field. Oscillations at intermediate angles also are be- lieved to be excited, but to disperse away from the satellite too rapidly for observation.

An electron density probe utilizing the plasma resonances is being

developed in a program sponsored by the National Aeronautics and Space

Administration. Such a probe will be particularly useful at the very low

plasma densities in the magnetosphere and interplanetary space, where other kinds of probes encounter difficulties. Persistence of Solar Flare Activity at Fixed Longitudes, Solar

flares that emit sub-relativistic protons are observed to prefer certain loca- tions on the sun, at which new centers of intense activity break out repeatedly over the years. The pattern is related to previously recognized sunspot

clustering in certain solar longitudes. NBS is studying these characteristics for help in predicting solar proton events and understanding the solar processes responsible for the acceleration of particles and the formation of

flares. Active Dark Solar Filaments. Sudden changes in dark filaments on

the solar disk were found to be closely associated with bursts of radio noise

of centimeter wavelength. Such changes in the filaments (which would

appear as prominences at the limb of the sun) also occur at the time of solar

flares. The observed relation is interpreted to mean that a change in the magnetic field structure in the chromosphere near the flare is a necessary

condition for acceleration of the fast particles that excite the radio burst, as well as for the sudden changes shown by the filament. Noise Storms in the Solar Atmosphere. The apparent height of each

of about 30 solar noise storms was deduced by comparing its rate of travel across the solar disk (determined from published position measurements)

with the rate of travel of the solar surface. The heights ranged from onetenth to one solar radius above the photosphere. These estimates for indi- vidual storms in the solar corona give added insight into the emission and

propagation of the radio noise which often accompanies the ejection of solar

particles. Earlier analyses of combined data failed to produce the important

information provided by this study of individual storms. Study of the individual heights has led to a description of how intensity and change in 200
2007 U.T.-F1RST FLARE APPEARS 2022-FIRST FLARE EXPULSION BEGINS 2026-FLARE EXPELLED Solar flare and ejection that produced high-energy protons. These cosmic-ray

flares occur preferentially at certain longitudes on the sun. NBS is studying

these characteristics for help in predicting solar proton events and understanding solar processes. (High Altitude Observatory Photograph.) (See page 200)

position depend on storm height, and also to the discovery of a variation of average height during the solar activity cycle.

VLF Observations of Solar Flare Ionization in the D Region.

During most solar flares, new ionization is produced below the normal D

region over the sunlit hemisphere. The normal D region is thought to be

formed by ionization of the atmospheric constituents by solar Lyman-alpha

emission and cosmic rays, but this radiation is not adequate to explain the abnormal D region produced during a solar flare. Recent rocket and satellite observations during solar flares have given support to the suggestion

that the enhanced Z)-region ionization during solar flares is due to x rays. Recently the phase and amplitude variations of phase-stabilized VLF trans- missions over six long propagation paths were observed. This network

permitted variations occurring over approximately one quarter of the earth's ionosphere to be sampled and thus provided an excellent means for studying the effects of solar flare ionization over a large area of the ionosphere.

During 1961 multiple simultaneous observations of sudden phase anomalies

(SPA's) were made during some 30 solar flares. The observations indicate

that during a solar flare the mean change of reflection height on a sunlit path

is related in magnitude to the mean of the solar zenith angle along that path. Different flares, however, produce different curves of change of mean reflec- tion height versus mean solar zenith angle. This can be explained in terms

of the energy and intensity of the x rays producing the new reflecting region,

permitting deduction of energy flux and effective wavelength of the incident x rays in some cases.

It is expected that SPA observations, when interpreted in this way, will provide a useful alternative to the present method of classifying solar flares in terms of brightness and area. Effects of a Solar Eclipse on the D Region. The effects of solar radiation on ionization were investigated by means of VLF signals received

and recorded during the solar eclipse of 20 July 1963. Some of the signals

recorded were reflected from totally, or almost totally, eclipsed points in the D

region of the ionosphere. The observations indicate that the response of the D region to ionizing radiation was between 10 and 100 times faster than

indicated by earlier measurements of the effects of solar flares. Independent experimental evidence has indicated that the D-region ioniza- 201
tion is produced by two types of solar radiation: (1) the extreme ultraviolet radiation known as Lyman-alpha which comes from the visible disk of the sun, and (2) x rays which come from regions above active areas on the

visible surface. The results of the eclipse experiment are consistent with this evidence and indicate that the ionizing radiation does not necessarily reach

a minimum at the time of maximum optical eclipse, but may show variations

associated with the locations of the active x-ray-producing regions.

Effects of a Solar Eclipse in the F Region. Vertical incidence radio

soundings obtained at 22 locations across North America during the total eclipse of 20 July 1963 form the most extensive set of ionospheric observations

ever made during a solar eclipse. Analysis of the data showed a well-marked

and consistent geographical pattern of variation of f0F2 , the ordinary-wave

critical frequency of the F2 layer, with eclipse time. A series of maps of f0F2 for the North American area are being prepared for every 15 minutes during

the course of the eclipse. These maps should provide a useful reference for

testing theories of physical processes of the ionosphere.

Geomagnetic Pulsations in the 30 to 0.003 Hz Range. The

Bureau's ultra-low-frequency group has the mission, at frequencies between

30 and 0.003 Hz, to observe the electromagnetic field environment, to seek its geophysical source, and to understand propagation from distant natural

sources. New equipment includes a data-recording and analysis system for encoding ULF data on magnetic tape at an extremely slow (1 in./min) speed,

for rapid analysis when played back as signals in the kilohertz range. Ten new stations were established for observations at the magnetic pole, along

the auroral zone, at conjugate field points, at the equator, and along meridians.

Balloon-borne counters were used to record bremsstrahlung x rays at College, Alaska, in a study of the geomagnetic effects associated with 15

auroral zone precipitation events. The effects were interpreted by use of the derived total disturbance field variations and the line current electrojet tri- angulations. In many cases the rapid field fluctuations seemed to result from enhanced conductivity created by the particle precipitation into the region of the auroral electrojet.

The relationship of infrasonic pressure waves to ionospheric disturbances

and geomagnetic activity was investigated briefly. The result supported the proposition that the auroral region is a source of infrasonic pressure waves, probably arising from joule heating by the varying ionospheric electrojet.

The unique amplitude modulation and polarization for a class of natural

signals near 1 Hz was studied. The multiple elements of rising frequency

structure resulted in amplitude beating and a change in apparent polarization

of the locus of the magnetic flux density vector. Preliminary observations

indicated that the emissions propagate along magnetic field lines. Earth Conductivity Measurements. In measurements of ELF propagation in the ionosphere it is necessary to take into account the effect of the earth—its conductivity and the velocity of propagation through it. One

way of determining its conductivity is with the use of signals originating

naturally in lightning discharges. These signals, called atmospherics, are 202
very short in duration and contain energy over a wide band of frequencies,

extending from a few hertz to several megahertz.

The top of an electromagnetic wave front is tilted in the direction of propagation when observed near the surface of the earth. This tilt is pro- portional to the ratio of the horizontal to the vertical electric field in the

direction of propagation and is a function of the effective ground conductivity

at each frequency.

The conductivity of the earth was determined by recording atmospheric

signals received at a horizontal dipole and those received at a vertical monopole. The amplitude and phase spectra were used to determine tilt and from

it the earth's conductivity computed as a function of depth. The results of

this work indicated that the conductivity was 2X10-2 mhos/meter from the surface to a depth of 25 meters. Between 25 and 50 meters, the conductivity

increased to 10_1 mhos/meter, and then decreased to 10~3 mhos/meter below

Two-meter diameter antenna of 16,000 turns used for ultra-low-frequency

studies. This includes observations of the electromagnetic field environment,

seeking its geophysical source, and understanding propagation from distant natural sources. (See page 202)

203
50 meters. The maximum depth for determining conductivity under normal

conditions by means of atmospherics is about 2,000 meters. This technique can be employed with mobile recording units to determine

variations in earth conductivity for large areas. In this way it can be used

as an aid in prospecting, particularly in conjunction with seismic operations.

Magnetic Dip Coordinates. The use of "numerical mapping" in the preparation of the Bureau's monthly publication Ionospheric Predictions

(previously called Basic Radio Propagation Predictions) was inaugurated in January 1963. In using this technique, contours of critical frequency, or maximum usable frequency, are derived from mathematical mapping functions fitted to the observed data. Recent research showed that the mapping

accuracy can be substantially improved by the use of geomagnetic dip latitude,

based on the dip angle of the earth's magnetic field, instead of geographic

latitude. The use of magnetic dip latitude simplifies and makes more accurate

the mathematical representation because the ionosphere is strongly controlled by the earth's magnetic field. 2.4.2. TROPOSPHERE AND SPACE

TELECOMMUNICATIONS

Efficient use of the radio frequency spectrum is the aim of the CRPL pro- gram in troposphere and space telecommunications. Attaining this objective

requires a basic understanding of radio wave propagation, noise, and inter- ference. Also required is a basic understanding of the physics of the atmos- phere and detailed understanding of telecommunication systems. Present emphasis is on the development of theoretical and semi-empirical prediction

methods and their statistical comparison with samples of radio wave propagation and radio noise data; the resultant information is disseminated by

various types of publications and reports on consultative type programs. For example, several members of the CRPL staff performed work in support

of international technical groups, such as the Consultative Committee on

International Radio (CCIR) and the International Scientific Radio Union

(URSI).

Transmission Loss Prediction. Continuing work is directed to the development of formulas for estimating median transmission loss, long-term

power fading, phase interference fading, and service probability for propagation over irregular terrain and through a turbulent stratified atmosphere.

A recent completed report shows the theoretical diffraction loss over ridges,

cliffs, and bluffs. The last two represent discontinuities in electrical ground

constants as well as in the height of the surface of the earth. Computer programs for propagation over idealized inhomogeneous and

irregular terrain will provide estimates of transmission loss for a great

variety of terrain situations. Criteria were developed for applying certain engineering approximations to the diffraction attenuation over a double knife edge, and methods for evaluating multidimensional Fresnel integrals were improved for calculating diffraction loss over many knife edges.

204
Studies of Antenna Response, The response of standard antennas to specified electromagnetic fields is being studied, as is the response of selected antennas to standard plane wave fields. The propagation of waves through

a turbulent stratified atmosphere over irregular terrain at frequencies above

100 MHz can sometimes be described in terms of discrete plane waves. General engineering formulas for such cases were derived for calculating antenna beam orientation, polarization, and multipath coupling loss. Diffraction at Convex Surfaces, The theoretical solutions for diffrac- tion in parabolic and circular cylinders were extended to obtain general

engineering expressions which can be applied usefully to convex surfaces encountered in rough terrain. A tabulation was prepared of the Wait and

Fock formulations of the Airy functions that are encountered in the theory

of diffraction by convex surfaces. Radio Meteorology, The turbulence-related variation of the atmospheric refractive index, which is largely responsible for signal variations at VHF and higher frequencies, can now be readily studied with the micro- wave refractometer. The accuracy of this instrument is limited primarily

by the cavity used to sample the atmosphere under study. The conventional

microwave sampling cavity was evaluated, using water-flow and wind-tunnel

methods in conjunction with field sampling on a meteorological tower. These studies showed the cavities to be aspect-sensitive and also velocity- sensitive at low wind speeds. A new cavity was developed which has improved spatial resolution and practically no aspect sensitivity.

Measurements at the NBS Gunbarrel Hill, Colo., field station indicate that the microwave refractometer can be used to study the flux of water vapor

over short periods of time. A high correlation, for example, was found

between the variability of refractivity and the variability of absolute humidity near the ground for time intervals up to about 20 minutes.

Wide variations in propagation frequently occur over microwave relay

paths, due to fluctuations in the refractive index of the atmosphere and the radio wave absorption from rain. In a study of variability for the Army

Signal Corps, extensive weather data were obtained along radio paths be- tween Pikes Peak and Gunbarrel Hill, and between Cheyenne Mountain and

Karval, Colo. Detailed information on surface layer effects was obtained

at the Gunbarrel Hill meteorological tower, and airborne measurements of

refractivity were made several times daily along the entire radio path.

Mathematically tractable models of the absorptive properties of the atmos- phere are very useful in solving certain kinds of radio propagation problems.

A bi-exponential model of atmospheric water and oxygen absorption coeffi- cients as a function of height was developed for frequencies between 6 and

45 GHz and scale heights were determined for representative profiles. It was found that large deviations from the temperature model were nearly undetectable in changes of the brightness temperature if the water vapor

density was assumed to remain constant, but that small errors in estimating

the absorption coefficients would result in large errors in the computed

kinetic temperature. More accurate determinations of the line widths of 205
This radio-noise recording station at Ibadan, Nigeria, is one of a worldwide

network of noise recording stations. Radio noise data and prediction services

assist the telecommunications engineer in the design of facilities that promote

the best utilization of the electromagnetic spectrum. (See page 208)

oxygen at low pressures also were made during the year. A useful formula

for the scale height of oxygen absorption between 6 and 45 GHz was derived

in terms of surface temperature and the average atmospheric temperature

gradient.

Knife-Edge Diffraction Studies. During the past year propagation

studies using 4,300-meter-high Pikes Peak as a diffracting knife-edge were

continued with terminals for the path 223 km apart at Pueblo, Colo., and at the NBS Table Mesa field site. Continuous wave transmissions were used in the experiments. Horizontal and veitical space diversity at 751 MHz were

studied. High correlation coefficients between the signal envelopes were found for two antennas spaced vertically by 20 to 30 wavelengths, but coefficients close to zero were obtained with horizontal spacing of 250 wavelengths. Severe fading was observed at 9.2 GHz; at some times the field strength variations within an hour had an approximate range of 40 dB.

Observed overall median transmission loss values at 751 MHz agreed quite

well with calculations based on a "rounded knife-edge" model, but a value

calculated for the same model applied to 9.2 GHz was 13 dB greater than

the measured value. This discrepancy may be due to different effective radii of curvature for the two frequencies, caused by terrain features on the summit

of Pikes Peak.

Propagation Over Long Paths at SHF. Correlation between fading

at two frequencies, 9293 and 9430 MHz, was measured over exactly identical long line-of-sight paths to investigate the effect of path geometry and

206
meteorological conditions on the bandwidth of the medium. Meteorological

data were obtained from measurements made at the surface and on an instru- mented tower, radiosondes, radar, and an airborne refractometer. A 139-km

path from Pikes Peak to Gun Barrel Mill, Colo., with a beam-elevation angle

(from horizontal) of about 0.6°, was used in July and August, and a 113-km

path from Cheyenne Mountain to Karval, Colo., with a beam-elevation angle

of about 0.2°, was used in September. Both paths had a terrain clearance

equivalent to several Fresnel zones. Fading was more pronounced and the sample cross-correlation coefficient values generally less over the path with the smaller beam-elevation angle.

This confirms the assumption that propagation over line-of-sight paths is more

sensitive to the effects of horizontal stratification in the lower atmosphere

when beam-elevation angles are small. Surface-Satellite Communication Interference. In the event that space telecommunications services are assigned to frequencies shared with

surface systems, such as point-to-point microwave systems, isolation between

the systems must be provided. This could be provided by geographic separation and antenna discrimination.

Attenuation due to geographic separation can vary greatly with changes

in propagation parameters. One of the ways in which the point-to-point

microwave system can interefere with the space system is by scattering of

its signal at storm cells in its path. This scattering effect can be predicted

by correlation with weather radar data. The effectiveness of antenna discrimination against unwanted signals is being investigated through both theory and measurement. Under study are

possible decreases in the wanted signal due to beam or pattern orientation,

polarization changes, or phase interference from multipath propagation.

Statistical methods for describing the response of an antenna in an arbitrary

orientation are being developed and measurements made using different frequencies and five different signal arrival directions. Over-Water Transmission Loss Measurements, Characteristics of over-water paths were studied by making simultaneous radio transmission

loss and meteorological measurements, in cooperation with the U.S. Air Force, on a 300-km path across a portion of the Gulf of Mexico. These measure- ments in a maritime temperate region show significant differences from

the large pool of data available for a continental temperature climate, especially in the long-term variability of hourly median signals. A study was made of the correlation between various observable and predictable meteorological conditions and the corresponding transmission loss values. Bandwidth of the Tropospheric Propagation Medium. The per- formance of transhorizon radio links using relatively large bandwidths is limited by intermodulation distortion caused by multiple scattering in the troposphere. A method of predicting the limiting bandwidth for a given

tropospheric scatter path is being sought to replace the empirical methods

on which present troposcatter-link design is largely based. 207
A measurement program, now completed under the sponsorship of the U.S. Air Force, was aimed at better understanding the relationship between

observed intermodulation distortion and the path bandwidth measured in terms of the correlation between discrete components of the transmitted

spectrum. The results, evaluated in terms of path length, antenna beam angles,

modulation index, and carrier frequency, offer considerable insight into the general problem of bandwidth prediction. New approaches to the problem

have been suggested as a result of this investigation.

Radio Noise Predictions. The basic objective of the CRPL radio noise

studies is to furnish the telecommunications engineer with information on

the interference environment relative to frequency, time, and location, so that design of terminal facilities will promote best utilization of the electromagnetic spectrum. To carry out this objective, the CCIR radio noise data were

completely revised by NBS in a report, World Distribution and Characteristics

of Atmospheric Radio Xoise. At the request of CCIR the correction data were combined with the original predictions in a program to make the complete

revision available for computer use. Information now available will make possible more accurate predictions

of not only average noise power, but also the expected deviation from the average power. Short-term variations of radio noise in the form of amplitude

probability distributions can be predicted by the use of these two parameters.

Development of the practical method of predicting noise by use of more

parameters makes possible more accurate predictions, supplanting the Gaussian noise model. The new prediction method has been applied, by means

of a computer program, to determining error rates for several types of binary

coded systems operating in the presence of atmospheric noise. One applica- tion was to the behavior of frequency-shift-keyed data transmission. This was extended to predict the reliability of the Minuteman radio launch control system operating in the presence of atmospheric radio noise. Radio noise information is still being obtained, for future revisions of the noise predictions, by operation of a worldwide network of noise record- ing stations. The longer term measurements being obtained will be needed

to determine the geographic dependence of the detailed structure of the

noise. Manmade Radio Noise and Transmission Loss Measurements.

Levels of manmade radio noise at some of the Minuteman missile sites were

checked by the CRPL mobile radio noise recorder to determine the degradation of the radio launch control system due to this noise and the rela- tive importance of manmade and atmospheric radio noise. Signal and noise were compared by recording noise and a stable signal from a transmitter

in the area simultaneously. By moving the mobile 500-watt transmitter, trans- mission loss measurements between sites and corresponding noise measure- ments were made. Not only transmission loss measurements, but also de- terminations of average ground conductivity were made, based on the trans- mission loss found. The effects of sky-wave interference, also, were studied

at distances out to about 240 km.

208
Early morning preparations prior to the launching of an infrared spectrometer.

The data from this instrument gave a water distribution profile of the atmosphere. Continuing efforts in this area will enlarge the knowledge and understanding of the absorption characteristics of the atmosphere. (See page 209)

Infrared Properties of the Atmosphere. A more thorough and exact understanding of the absorption characteristics of the atmosphere resulted from work on its infrared properties, supported by the Advanced Research

Projects Agency. Theoretical studies of the behavior of water vapor and

carbon dioxide in the infrared spectrum were analyzed in great detail and

excellent agreement with controlled laboratory experiments obtained.

Theoretical predictions can now be made with confidence. Continuing ef- fort in this area will enlarge the knowledge available on other infrared spectral regions of the major atmospheric absorption constituents. The experimental aspect of the program was successful in procuring

valuable data on atmospheric absorption due to water vapor. A highresolution grating vacuum spectrometer and a sunseeker were flown by bal- loon to an altitude of 30 km to record the solar spectrum and atmospheric

absorption spectrum at a wavelength of 35 microns. These data, when analyzed, give a water distribution profile of the atmosphere. The Office of Naval Research provided financial support for the instrument flights, and

the National Center for Atmospheric Research for the launch facilities. 209
Spectrum Analyzer. A data-reduction system for obtaining spectral

information by investigating preselected frequency bands was developed

for use in the data reduction facility. Signals to be analyzed are separated

into their component frequencies of interest in a parallel array of active bandpass filters. Outputs of the filters are individually squared and aver- aged and then recorded on a multichannel strip chart recorder. Running

records of the average power in up to eight frequency bands can be made

simultaneously on one chart in the range of 1 to 10,000 Hz. Center fre- quencies and Q of individual bandpass filters are adjustable. The system

is particularly useful for analyzing data with relatively smooth spectra,

where information about the response details of corner frequency and order

of rolloff is desired. Tracking Accuracy Research. During the past year an extensive research program was conducted, under sponsorship of the U.S. Air Force,

to determine the limitations due to atmospheric turbulence on microwave

tracking systems. A series of experiments was performed on the island of Maui, Hawaii, using Mt. Haleakala to simulate air-to-ground paths. Various

baseline configurations up to 1700 meters in length were used over 25-km

paths. Ranges and range differences were studied over periods of time up

to 7 days. Surface measurements of atmospheric conditions were made dur- ing radio observations to be examined for utility as predictors of radio conditions. Aircraft measurements of radio refractive index were made during

part of the experiments, as well as range measurements using commercial

microwave and optical geodetic instruments.

2.4.3. RADIO SYSTEMS

The Bureau's radio systems program provides technical information on

radio propagation factors affecting design and use of radio systems. The

emphasis of this work is on long-range radio transmission problems, and

methods of measurement, for radio communication, navigation, timing,

detection, and positioning systems. Radio wave propagation studies are

carried out for ionospheric, groundwave, and line-of-sight paths to define

the limitations, disturbances, and capacity of the transmission medium as a communication channel. The work is directed toward guidance of engineering practices, allocation and use of radio frequencies, and evaluation of sys- tem capabilities and limitations. The information is provided to meet the needs of Federal agencies and industry involved in radio telecommunication operation and regulation. Studies of information theory and coding,

modulation, and antenna design are directed toward improvement of the

reliability of systems and to the efficient utilization of the radio-frequency

spectrum. Consulting and advisory work is done in accordance with the needs of other Government, commercial, and scientific agencies.

Radio-Frequency Propagation Determination and Prediction

System. CRPL is the principal laboratory for development of a radio- frequency propagation determination and prediction system for the Navy

210
Bureau of Ships. The objective of the program is to increase naval highfrequency communication capability and high-frequency spectrum utiliza- tion as far as possible by assignment of optimum operating frequencies and

warning of expected ionospheric disturbances.

The frequency selection problems peculiar to the Navy, and techniques

for determining propagation and interference conditions were studied to provide information for the development of a system concept. Restrictions on system design imposed by operating procedures and interface require- ments with other systems were investigated to establish the limits for the

initial concept.

The system is expected to automate the selection of frequency assignments

and usage within the Navy by means of techniques for assigning the operating frequency of any communication circuit on a short time basis. Techniques for monitoring existing propagation conditions, providing short-term

(up to a few hours) predictions of expected conditions, and monitoring

interference and noise in the frequency channel will be incorporated.

Studies are also being carried out on means of improving ionospheric

disturbance warning capabilities and of using disturbance warning information in the naval system.

High-Frequency Ionospheric Radar, HF radar studies of ionospheric

irregularities were continued, supported in part by the Rome Air Development Center, with several improvements in the instrumentation. One of these was the conversion from a 500 rev/sec azimuth scan of the antenna,

at the Table Mesa field site, to a steerable-beam broadside array. This array

consists of 25 log periodic antennas forming a steerable beam for additional

flexibility in propagation studies. Operable between frequencies of 12 and

25 MHz and oriented toward 114° E of N, it was used on a 12-hour-per-day

schedule during several days of November and December 1963 at a frequency

of 17.6 MHz.

Ionospheric irregularities shown by backscatter records appeared mostly

to be in the form of long fronts moving perpendicularly to their long dimension. Practically all motion seemed to have a southerly component, with most irregularities moving in a generally southeast direction. Mean speeds

of about 600 km/hr were deduced. The irregularities give some indication

of changing direction or orientation during their transit across the scanning

beam. Some appear to be long curved fronts instead of linear ones; cur- vature might be expected for irregularities close to a generating source. Ray tracings were made of models of ionospheric irregularities for better understanding of the relationship between ionospheric configurations and the forms observed in backscattered signals. From studies thus far it appears

that modification of ionization densities of the order of 10 to 20 percent over

relatively small distances (a few tens of kilometers) is sufficient to provide

considerable focusing of backscattered signals. It also appears that irregularities in electron density are most effective at ionospheric heights slightly

below the reflection level in the ray path.

Fading studies of backscattered signals indicated that for F region back211
scattered propagation most of the amplitude power spectrum appears below

about 1 Hz and for E region below about 0.5 Hz. High speed motion of

irregularities can increase values of the F region-propagated fading spectrum

components. The high-frequency backscatter radar studies are supported in part by the U.S. Air Force. Further plans were formulated for construction of an HF radar facility

having an average power rating of 2 megawatts. Hie facility is being de- signed to be usable in a variety of experiments on HF propagation and

ionospheric physics. Initially, it will be used to continue and expand radar

studies which are now under way. Modulation Research, The characteristics of propagation media as

electrical networks or channels, and their relationship to system performance

is being studied in the modulation research program. Various classes of modulation and demodulation techniques are studied in work directed toward

improvement of performance on time-varying dispersive channels. An experimental program to obtain digital error distributions and their relationship to propagation conditions on a high-frequency communication

link was continued. The objective is to obtain data for optimum performance

design of error-detecting and error-correcting codes for such links. The

error distributions are valuable also in the design of adaptive modulation

and coding systems. The received digital sequences are being analyzed to determine the average error rate, the distribution of the spacings between

errors, and the autocorrelation function of the error pattern. In addition,

Directing a laser beam from Table Mountain (Boulder) toward Pikes Peak to determine beam fluctuations at long distances. The results of this program

should indicate the limitations imposed by the atmosphere on the use of lasers for telecommunications. (See page 216)

212
the distribution of the number of errors for various work lengths will be

determined. The first experiments used noncoherent frequency-shift keying.

Plans were formulated to investigate the effects of other modulation tech- niques, such as differentially-coherent phase-shift keying, and to obtain more

data for frequency-shift keying.

Theoretical studies of the performance of digital communications systems

included the computation of error probabilities. Digital errors were computed as functions of average signal-to-noise ratio for various modulation

and demodulation techniques and statistical signal-fading models, for both

Gaussian and atmospheric additive noise. The use of a flexible Gammafading model made it possible to represent a wide range of realistic fading

conditions. With moderate or severe fading conditions, the probabilities of error are nearly the same for both atmospheric noise and Gaussian noise;

for weak fading the probabilities of error can differ considerably between

the two noise conditions.

Theoretical studies of error-detecting and error-correcting codes in digital

communication systems have continued. Simpler decoding procedures were

sought, since the implementation difficulties of most codes seem to be related

to decoding. A simple decoding procedure was devised for the large family

of cyclic codes. A study was partially completed to arrive at a realistic comparison between the existing systems and higher performance alternatives. Operation was detailed to an extent including the intricacies of feedback control, synchronization, matching to teletypewriters, buffer storage, and other

practical features. HF Channel Characterization. Signal distortion and digital errors beyond the effects of additive noise are introduced by randomly-time-varying

amplitude and dispersion characteristics of propagation over HF ionospheric

links. The Bureau is studying the amplitude and phase correlation of received

signals, in work for the U.S. Navy, as a function of time and frequency

separation, using a large number of coherently generated signals. Such

statistical characterizations will be made for various distance and geographic

classes of HF communication paths likely to have unique characteristics. Multipath Microwave Transmission. Experimental microwave meas- urements were made between a mountaintop and several lower-elevation

receiving sites to determine the information rate or bandwidth limitations imposed by the atmosphere on satellite-to-earth communication systems at low elevation angles. This work is supported by the United States Air

Force. A transmitter on Cheyenne Mountain near Colorado Springs, Colo.,

transmitted one-nanosecond pulses at 10 GHz for the transit-time resolution

of path-length differences greater than 0.5 meter. Four lower-elevation

receiving sites provided propagation path elevation angles of 9.5°, 3.4°, 2.0°,

0.6°, used in determining the dependence of multipath propagation on path

elevation angle. Nearly 700 hours of measurements were made over the four

paths over an eight-month period, during which no time-separated multipath

propagation was observed. Some pulse fading observed on the two lowest- angle paths was caused by interference between multipath components and

213
had propagation time differentials of a small fraction of a nanosecond.

During all of the measurement time the bandwidth of the atmospheric medium, defined as the reciprocal of the propagation time differential, was

greater than several GHz. These results were obtained at altitudes above

1.5 km in a relatively dry climate. It is planned to continue the measure- ments for another four months to complete a year of observations.

Antenna Measurements and Research, Methods of determining antenna gain by measuring the transmission loss were extended, removing

the requirement for two identical antennas. A new technique is useful for measurement of three or more antennas, which do not have to be identical or have equal gains. The accuracy of final results can be estimated by comparing values obtained by pairing antennas in different combinations.

Measurements on several standard gain antennas, used for calibration of commercial antennas, gave results which were within 0.2 dB of each other. Experiments were carried out on the use of skint-range techniques for gain measurements and very promising results obtained. In these the antenna

being tested is raised well above ground, while the target transmitter antenna

is very close to the ground. The target transmitter antenna is positioned in such a way as to assure that its ground reflection does not illuminate the antenna being measured. The objective of this program is to develop improved techniques and instrumentation for the measurements of antenna

gain, radiation pattern, impedance and other characteristics. Antenna Aperture Synthesis. The principles of antenna aperture synthesis were applied in the past to field strength measurements to resolve the

field into several components differing in directions of arrival, polarization,

and phase. The field is probed over an area to simulate the effects of aperture

antennas. The methods of solution are readily applicable to linear scans, and during the past year were extended to apply to circular scans. Circular

scanning makes the technique more suitable for electromagnetic field sampling under practical conditions in the field. This work is supported

by the U.S. Air Force in connection with a study of methods for measure- ment and analysis of complex radio frequency fields. Frequency Utilization. Methods for predicting the performance of high-frequency sky-wave radio systems were improved by better statistical descriptions of propagation variations and the competing noise levels. Im- proved frequency utilization is made possible by better predictions of radio

system performance obtained by use of electronic computers.

Electronic computers were routinely used to improve Voice of America

international broadcast performance and to obtain optimum frequency

utilization in the NASA ground communication system. Computers made

possible improved prediction methods for planning data collection from a worldwide network of ocean buoys and revising frequency allocations. Elec- tronic computers were used also in estimating the extended range of HF

communications during the Appollo mission and in maintaining ground communications during mapping by the use of satellites. 214
Raising antenna at the South Pole Station for the detection of solar proton

events by VHF forward scatter observations. This program is a cooperative

effort by U.S., British, and Russian scientists. (See page 217)

Radiodetermination. The development of new techniques for more

precise determination of position and the transfer of time standards is a continuing program of the CRPL radiodetermination section, sponsored by

the U.S. Coast Guard. The Loran-C navigation system (using 100-kHz

pulses) has been used in these studies for" several years. A new study using

the Loran-C signals was initiated during the past year to measure the dis- persion of the groundwave pulse to determine the proper phase correction for propagation path. Dispersion represents dependence of velocity on wavelength and is an important effect for a high resolution system using wide-band

pulses.

Predictable system accuracy is usually limited by knowledge of the effec- tive conductivity of mixed paths. This limitation can be reduced by extract- ing the dispersion information from the distortion of the pulse shape. For

transmission paths with intervening land, it is estimated that the error in position prediction might be reduced by a factor of 10 by use of the dispersion correction. A technique for the transfer of time by means of VLF CW signals is being

explored in cooperation with the Radio Standards Laboratory, using the Fort Collins WWVL transmissions at 20 kHz. Two closely spaced signals are transmitted in a given time-phase relationship and the time-phase rela- tionship is observed at a distant receiver with respect to Loran-C time refer- ences. Experimental receiving equipment is under development and it is anticipated that field measurements will be started in January 1965. In

these measurements, Loran-C will be used as a time base and the phase

variations of the VLF signals will be measured relative to that base. Applied Electromagnetic Theory. Theoretical studies supplementing

experimental investigation of long-wave propagation have been carried out

756-224 0—65 15 215
under the sponsorship of NBS and defense agencies. These studies have

been principally directed toward greater understanding of the effects of the anistropy of the ionosphere and of ions on long-wave propagation.

The complete solution of the problem of low-frequency propagation be- tween the earth and the ionosphere for an idealized model can be written as

a series of integrals. The integrals are called wave hops because they reduce,

in the saddle point approximation, to the ray hops of geometric optics. Unfortunately, the approximation is inadequate near grazing incidence and in the shadow region. A computer program was prepared to find the electro- magnetic field in these regions by evaluating the wave hop integrals numerically for anisotropic models of the ionosphere. It is believed that the wave

hop theory can be extended to allow variation with distance of ionospheric

height and other parameters.

Classical magneto-ionic theory takes into account propagation in a pure

electron gas, including the effects of collisions with neutral particles. The

solution for propagation in a plasma with four constituents—electrons, positive and negative ions, and neutrals, including the effects of all twelve collision types—was reduced to a Booker-type quartic equation with modified coefficients. Given the coefficients of the quartic, the reflection from, and

transmission through, a stratified ion-electron plasma can be calculated in the conventional way; a computer program was written to do this. Laser Atmospheric Transmission Studies. The objective of this pro- gram was to investigate the propagation of coherent optical radiation through

the earth's atmosphere and, in particular, the limitations imposed by the medium on the use of this portion of the electromagnetic spectrum for tele- communication. During the year several measurements were made of the

effects of atmospheric turbulence on a tightly collimated laser beam operated

CW at a wavelength of 0.6328 microns. Over a 15-km path the beamspread was about 0.5 m and over a 144 km path between the Table Mesa field site and the top of Pikes Peak the beam spread to about 9 m.

Amplitude fluctuations varying in frequency from a fraction of a hertz

to several hundred hertz were observed on a single photocell placed in the beam. Longer term variations over periods of seconds to hours, in which

the beam shifted location over an area several times its diameter, were also observed. Measurements of this type will be continued under varying conditions of atmospheric stability.

Infrasonics Research. Terrestrial atmospheric pressure variations

propagated at sonic velocities in the frequency range 10"3 to 1 Hz are being

studied in the infrasonics program. Observations are being made at four

sites near Boulder and correlated with similar observations made by the NBS

infrasonics group in the Washington, D.C., area. It is known that on many

occasions infrasonic fluctuations occur at times of major ionospheric dis- turbances. Sources producing these events include severe earthquakes, major

volcanic action, and severe weather fronts producing tornadoes. Other

sources are long-lasting fixed events occuring only from September to March

and centered in the Pacific Northwest area (and during the Southern Hemi216
sphere summer in regions near the South American Anomaly), and events

associated with particle influx in the auroral zone producing ionospheric dis- turbances. Most of the infrasonic events observed fall into one of the above

categories with a fair degree of certainty.

The objective of this program is to investigate relationships, study

mechanisms, and determine if a correlation between infrasonic waves and

perturbations in radio waves exists. The project is related to the high

altitude nuclear detection and high frequency radar programs.

Solar Proton Event Detection. During the past year terminals were

set up in the Arctic and Antarctic for a number of radio paths in experiments on detection of solar proton events by VHF forward scatter observations.

The Antarctic paths include stations at Byrd, the South Pole, McMurdo,

Halley Bay, and Vostock. One of these is a British and another a Russian

station; the U.S. stations are supported primarily by the National Science

Foundation. The Arctic stations are at Frobisher Bay and Great Whale in Canada and Barrow, Anchorage, Annette Island, and Fairbanks in Alaska;

this work is supported by the National Aeronautics and Space Administration.

All of the stations except in Alaska are operated by the Bartol Research

Foundation.

The two detection networks are using a frequency of about 23 MHz in the ionospheric Z)-region forward scatter mode of propagation. The frequency

is lower than ordinarily associated with ionospheric forward scatter; it is being used to provide greater sensitivity during the low portion of the sunspot

cycle. A byproduct expected from this operation will be information on

the incidence of sporadic E at high latitudes. 2.4.4. UPPER ATMOSPHERE AND

SPACE PHYSICS

A variety of approaches is being used in seeking to understand the propagation of radio waves through the atmospheric medium. CRPL is accumulating

the basic information needed to use the medium most effectively. Methods

used include theoretical study, laboratory simulation, ground-based geophysical observation, and satellite observation.

Theoretical and Analytical Atmospheric Studies. A quantitative

investigation of ionization produced in the lower ionosphere by solar protons

has been started. The aim of the investigation is twofold: first, to compare

the calculations and observations of radio-wave absorption during polar-cap

absorption events, and second, to seek ways of measuring solar proton fluxes and spectra by purely ground-based techniques. The former should provide

important information on the properties of the lowest regions of the ionosphere. The latter provides information for monitoring and, it is hoped,

forecasting conditions in the near-space environment. Preliminary calculations indicate that measurements of radio-wave absorption at very high

geomagnetic latitudes can provide a reasonably accurate estimate of the

flux of solar protons with energy above about 5 MeV.

217
The propagation of solar protons from the sun to the earth was investi- gated theoretically using a model in which the initial rise of proton flux at the earth is controlled by diffusion of the protons through a thin region of

the solar atmosphere. Good agreement was found in comparing theoretical

results with observations of solar protons by the satellite Explorer XII beyond

the geomagnetic field, allowing a determination of diffusion coefficient for energetic protons in the solar atmosphere.

Computations of the theoretical shape of the outer boundary of the magnetosphere were completed. The results indicate boundary shapes and

magnetic field disturbances which are in agreemnt with data reported from

satellites. The magnetic field disturbances are of a magnitude to justify their inclusion as part of magnetic storm variations. Atmospheric Collision Processes. The analysis of many processes occuring in the upper atmosphere requires an accurate knowledge of the momentum transfer cross section between low-energy electrons and

atmospheric gases. The resonance absorption of microwave energy by a

slightly ionized gas in a magnetic field can be analyzed to yield this quantity.

The work done thus far includes an investigation of the effects on the shape

of the cyclotron resonance line of varied electron energy and the energy dependence of the collision frequency between electrons and the background

scattering particles. These calculations included resonance line shapes which

might be obtained in practice from experimentally determined collision frequencies for helium, argon, oxygen, and nitrogen. The change in broadening produced by very small concentrations of ions was computed.

The calculations of the present work show that the shape of the cyclotron resonance line is strongly affected by the energy dependence of the collision frequency and the distribution of electron energies. The line shape is in general less sensitive to realistic changes in energy distribution than to changes in the velocity dependence of the collision frequency.

The line shape may be sensitive to small variations in the collision frequency-energy relationship when it is a strong relationship. Complicated

Solar wind distortion of the geomagnetic field boundary. Such studies provide

better understanding of magnetic storm variations. (See page 217)

218
dependences can then often result in line shapes which are more Lorentzian

than would be calculated from an approximation to the dependence. Therefore the scientist must know the energy dependence of a collision frequency in order to obtain accurate average values for it from cyclotron resonance measurements. It was concluded from the calculations that accurate results for collision cross sections can be obtained from cyclotron resonance tech- niques only if detailed analysis is used in interpreting experimental data. Gas Discharge Afterglow. A program of gas discharge afterglow ex- periments was instituted to study the reaction processes of electrons, ions,

and unstable species at low thermal energies. The dependence of emission

intensities on electron temperature indicated that recombination of molecular ions is not likely to be a significant afterglow process in helium, in conditions under which it was previously assumed to dominate. Experimental

reports of dissociative recombination in helium were explained satisfactorily as three-body recombination involving two electrons and either the atomic

or molecular ion. Infrared Absorption by Charge Transfer. Infrared spectroscopy of weak charge-transfer complexes led to formulation of new mechanisms and

selection rules relating spectroscopic observations to molecular structure. The infrared absorption of an acceptor molecule vibrating in a complex

group was shown to be due to the variation of the molecule's vertical electron

affinity during vibration. Thus the intensity of a vibration band can be

related to the slope of the molecular negative ion potential curve at the molecular equilibrium internuclear distance. Nitric oxide in a solid krypton

matrix was shown to be capable of absorbing radiation by the charge-transfer processes postulated. Other small molecules and perhaps even atoms may

be able to absorb radiation, when in condensed phases, by this mechanism.

Jicamarca Radar Observatory, At the Jicamarca Radar Observatory,

located on the magnetic equator near Lima, Peru, studies are being made

of various features of the equatorial ionosphere with a powerful radar at 50

MHz. Its basic function is to study the distribution of electron density for heights up to 10,000 km by means of the incoherent scatter technique. Other

parameters of the ionosphere, such as electron and ion temperatures, are

also being measured.

The Jicamarca radar has been operating at full capability in incoherent

scatter studies since December 1962. Observations since that time have been

largely devoted to testing certain aspects of the incoherent scatter theory

and to refining the accuracy of measurement techniques.

Electron Density and Ionospheric Constituents. The incoherent

scatter theory predicts that radar can be used as a mass spectrometer to identify the ionized constituents of the upper atmosphere, but a series of attempts to observe this effect at Jicamarca was unsuccessful. This led to the discovery by theoreticians that the interaction of the ions themselves

renders the effect essentially unobservable under most conditions. As a con- sequence, the Jicamarca group faced uncertainty in electron density measure- 219
merits at heights where more than one kind of ion exists in significant

quantities.

The difficulty was solved by instrumenting the radar to measure electron density profiles by use of the Faraday effect. Profiles obtained by this technique are not subject to ambiguity due to ion mixtures, or to varying

electron/ion temperature ratio (Te/Ti). However, comparison of simul- taneous profile measurements by the radar and by the Alouette topside

sounder satellite (S-27) disclosed inaccuracies in measurements by one or both means. Most of the errors were corrected in recent radar observations, and the radar measurements now show excellent internal consistency. The observations yield information not only on electron density, at heights from 200 to approximately 10,000 km, but also on electron and ion composition and

temperature at heights from 200 to 1,200 km. Protons were found to be the major ionic constituent in the magnetosphere, outnumbering atomic oxygen

atoms at some heights and certain times of day. Ion temperatures ranged

from 800 to 1500 °K, with the higher temperatures occurring at greater

heights. As the observations continue, it will be possible to distinguish

whether helium occurs above Jicamarca in significant concentrations.

Synchrotron Radio Noise Measurements at Jicamarca. Observations of the decay of the synchrotron radio noise created by the July 9, 1962

nuclear explosion were being continued at Jicamarca. Continuous observation with a riometer at 30 MHz revealed a decay rate having a time constant T (in the amplitude proportionality expression 1/(1 + T) ) of approximately

40 days. The noise still present two years after the explosion is largely in- distinguishable from the sky background with this equipment, but at 50

MHz the synchrotron radiation can be distinguished by its linear polarization from the random polarization of the sky background. Synchroton noise

measurements at this frequency show a decay time constant of 50 to 60 days

but should continue to be measurable for several more years. Plasma Instability Research at Jicamarca, Radar measurements

combined with theoretical studies at Jicamarca show that acoustic-wave

plasma instabilities are generated in the equatorial E region by the flow

of the strong equatorial electrojet. These instabilities give rise to ionospheric wave irregularities which are primarily alined with wave fronts parallel to the lines of force of the earth's magnetic field. The strong radar echoes

from these irregularities bear characteristics typical of auroral radar echoes. The Jicamarca group believes that auroral radar returns arise from essentially the same phenomenon. Recent spectrum observations of the radar echoes at Jicamarca suggest that the irregularities are generated by several distinct modes of plasma instability, only one of which is thus far accurately explained

by theory. The new spectrum observations were made, with greater accuracy

than previously possible, by use of computing equipment assembled for the incoherent scatter observations.

Ionospheric Absorption at Conjugate Points. Since early 1963 a program of geophysical studies has been in progress at pairs of stations 220
The 22-acre antenna of the Jicamarca Radar Observatory near Lima, Peru. This radar, in full operation since December 1962, has recently been re- instrumented to measure electron density profiles using the Faraday effect. These instruments also provided information on electron and ion composition

and temperatures from 200 to 1200 km. (See page 219)

situated at opposite ends of selected lines of the earth's magnetic field. The new information provided by these continuing studies will add considerably

to our knowledge of auroral phenomena and the effects of energetic particles

at high latitude. Three such magnetically-conjugate pairs are in use, one

in the auroral zones and, one at subauroral latitudes, and the other at the polar caps. The three northern stations are in Canada (by arrangement with

various departments of the Canadian government) and the three southern

stations are maintained by the U.S. Antarctic Research Program.

The program includes the study of ionospheric absorption, measured with

riometers. The analysis completed thus far shows that the absorption is broadly similar at conjugate points, but that there are also certain differences. One point of similarity shows that fluctuations in the daytime absorption

(for periods of several minutes) are closely in phase at the conjugate points.

On the other hand, nighttime absorption often includes a slowly varying

antiphase component.

Airglow Arcs in the Tropics. Optical radiation at a wavelength of 6300 A is emitted from the upper atmosphere over the entire earth, due to the oxygen atom. In the auroral zone, it is a prominent feature, giving a reddish color to the upper part of many active auroral displays. In midlatitudes it is the principal spectroscopic feature of the so-called M-arcs,

which occur especially during the sunspot maximum.

Another manifestation of the emission has been under study for several years in the tropics, between the geomagnetic latitudes of about +20°

and —20°. The emission undergoes sporadic increases of intensity (as much

as ten times normal intensity, still well below visibility) over periods of one 221
to two hours. Studies of the entire sky indicate that the increase covers a

significant geographical region and often is oriented along magnetic parallels

approximately in an arc. Of particular interest is the fact that the increase

in optical radiation is directly correlated with a concurrent lowering of the F layer and an increase in its electron density. The phenomenon seems to be associated with the drift of ionization from high above the magnetic

equator down along the magnetic lines of force to the F region over latitudes of 15 to 20°. Model of Natural Sodium Abundance. The emission of the sodium

resonance doublet at 5890 and 5896 A from the upper atmosphere during

twilight is of considerable interest not only because it comes mainly from

the D region of the ionosphere, but also because this emission mechanism

is one that is well understood. There is no doubt that the emission process

is resonant scattering of sunlight. Observations of the intensity of this emission can be directly related to the concentration of free atomic sodium

in the atmosphere. Recent observations from several sites at latitudes from 65°N to 45°S were

assembled in a model of the atmospheric distribution of sodium. This model

considers both the chemical and ionic equilibria of sodium; its recombination coefficient for ionized sodium of 4X10-7 cm 3 sec

-1 reproduced, reason- ably satisfactorily, the observed seasonal and diurnal changes in sodium

abundance. The first tentative numerical solution exhibited agreement with

the observations. The recombination coefficient applied to ionized lithium

gives realistic results in this case also. During the development of the model, it became obvious that account must be taken of the pole-to-pole circulation of the atmosphere at D-region

heights. This circulation is clearly shown in the well-known "meteor wind"

measurements and is confirmed by the observations of lithium originating

in some thermonuclear explosions. Calculations are in progress to improve

the sodium model by using the observed wind velocities and numerically

integrating the chemi-ionic reaction equations.

Ionospheric Studies by Reception of Satellite Signal, CRPL scientists used signals from the satellite S-66 to chart the electron distribution below the satellite path. The electron density was found by determining

the signal polarities, and thereby the Faraday rotation imposed during transit on the linearly polarized satellite transmissions at two closely spaced

frequencies. Especially designed antennas, receivers, and recording devices were used at three receiving stations. The data must be recorded and ana- lyzed together to obtain values for the electron densities ; the values can then

be plotted on geographic charts. Analysis of the data required comparison of recordings from three sta- tions, located about 50 miles apart along a line parallel to the satellite's path. The data at two of the stations are transmitted to the principal ob- serving station at Table Mountain, Colo., over telephone lines, to simplify

obtaining accuracy in recording and time notation. This made it practical

to operate the two remote stations unattended; in design they are fully

222
transistorized, battery powered, and controlled from the Table Mountain

station by signals transmitted over the same lines as the data. Bottle-gaspowered thermoelectric converters will be added to keep the batteries charged

and permit unattended operation for long periods of time. The slow rate of Faraday rotation at the two frequencies, near 40 and

41 MHz, makes it necessary to use a scanning form of polarimeter to deter- mine the polarization plane at each frequency approximately once a second

at each station. This is done with fixed dipole antennas, oriented in a

cross and connected through a hybrid transformer to produce two orthogonal

circular polarization components. The phase difference between these two equal-amplitude components is a function of the polarization orienta- tion of the incoming waves. The rest of the receiver circuitry produces

output signals similar to those produced by an input from a mechanically

rotated dipole antenna. Built-in receiver circuitry permits insertion of syn- chronizing and calibration signals, including a test signal radiated from a small calibration antenna for a complete system check whenever desired. Two receivers are required at each station, one for each frequency, but the

rest of the system is sufficiently broadband for a single sequence of stages to treat similarly the two close-spaced frequencies.

The signals from the main station at Table Mountain are demodulated and

processed to produce oscilloscopic displays which are photographed simultaneously on continuously moving film. The audio-tone telemetry will be recorded on magnetic tape for permanent storage and further analysis

if desired. The output of the data analysis will be a map for each satellite pass of elec- tron distribution in the plane containing the satellite path and the three ground stations. Two or three satellite passes per day are expected to pro- duce records of quality sufficient for full analysis.

2.4.5. ELECTROMAGNETIC RESEARCH

A number of topics which can be generally classified as electromagnetic

research were studied by the Consultant on Radio Wave Propagation. This

work was supported by the Bureau, the Air Force Cambridge Research

Laboratories, the Department of Defense Advanced Research Projects Agency,

and the Navy BuShips in approximately equal amounts. Although the

studies are seemingly unrelated, the methods used have much in common

and some recent accomplishments are therefore reported together.

Mode Theory of the Propagation of VLF Radio Waves, The mode

theory was subjected to new treatment to exploit the essential two-dimensional

nature of wave propagation in the earth-ionosphere waveguide. It was shown that the usual working formulas of VLF mode theory can be derived

directly from orthogonality considerations, without resorting to erudite

arguments in the complex plane. Furthermore, the physical insight gained

by this novel development immediately suggested how the formulas can be generalized to an earth-ionosphere waveguide of nonuniform width.

223
Influence of the Lower Ionosphere on Propagation of VLF Waves.

Because of the great number of papers dealing with VLF radio propagation,

there appeared to be a need for consolidation of some of the recent theoretical data. Toward this end, the expected values of the attenuation and phase

velocity of the dominant modes in the frequency range from 8 to 30 kHz

were expressed in convenient graphical form. The results included the

effects of earth curvature, ground conductivity, and the gradient of the effec- tive conductivity of the lower ionosphere.

Effect of Ionospheric Perturbations at VLF. The effect of iono- spheric perturbations at VLF was calculated, taking into consideration many

factors affecting propagation. It was first assumed that the earth's magnetic

field could be neglected in treating the oblique reflections of radio waves from a continuously stratified ionized medium. The height profile of the

effective conductivity was taken to be a Gaussian curve superimposed on the undisturbed exponential form. The reflection coefficient was shown to be

influenced by the vertical location of the Gaussian perturbation, being in- creased in magnitude in some cases and decreased in other situations. In nearly all cases, insofar as phase was concerned, the presence of the perturbation corresponded to a lowering of the reflection height.

The same analytical method was also used to study the effect of a hyperbolic-type transition in which the effective conductivity is increased at all heights above a given level. These results, taken collectively, have applica- tion to the interpretation of VLF propagation data observed during solar

flares, magnetic disturbances, and high-altitude nuclear detonations.

Reflection Coefficients for a Lossy Magnetoplasma. Extensive

values were calculated for the reflection coefficient of a horizontally stratified ionized medium. The profiles of electron density and the collision frequencies were both taken to be exponential functions. The d-c magnetic field was

restricted to be horizontal and transverse to the direction of propagation. The

results were applied to the study of oblique reflection of VLF radio waves in the D layer of the ionosphere for propagation along the magnetic equator.

It was confirmed that the reflection coefficient was nonreciprocal in both

amplitude and phase. The magnitude of the reflection coefficient for a wide

range of the parameters was greater for west-to-east propagation than for

east-to-west propagation.

Diffraction Effects at VLF for a Localized Ionospheric Depression.

The effect of a localized ionospheric depression, such as can result from an

ionospheric disturbance, on the propagation of VLF waves in an earth-iono- sphere waveguide was studied. The depressions in the upper boundary of the waveguide cause the waveguide to be nonuniform in the vertical dimension. Calculations were carried out for depressions resulting from approximately rectangular disturbances and for the more realistic disk and bowl- type depressions. The results confirm what was previously suspected, that perturbations lying off a great circle radio path can produce appreciable

changes in the phase of the field at the receiver. The findings of this study

224
have application to waveguide propagation when localized electrons are "dumped" from radiation belts or nuclear explosions.

D-Layer Characteristics Studied by VLF Propagation, One of the most challenging problems in VLF research is obtaining information on the ionospheric D layer from data on the amplitude and phase of the signal from

a distant continuous wave transmitter. A previous approach has been by

comparison of observed attenuation versus frequency data with theoretical curves calculated for various assumed models. A better approach is being

used in the present study; measured data is inverted in such a way that the

characteristics of the medium are found rather than assumed. Theoretical

study has demonstrated that measured attenuation and phase data can be

used to determine the effective wave impedance of the lower ionosphere.

The consequences of this work, when completed, should be far-reaching in experimental studies of the D layer.

Microwave Models for VLF Propagation, CRPL, in collaboration

with the University of Colorado, is investigating the use of microwave models

as an analytical method for studying VLF radio propagation. The rectan- gular waveguide used has an inside thickness approximately equal, in wavelengths at 1 GHz, to the height of the ionosphere measured in wavelengths at 15 kHz. This being so, and since both waveguides have similar modal

equations and perturbations in the walls of each similarly affect propagation,

the microwave waveguide can be used, with suitable wall loading, to simulate

the electrical characteristics of the ionosphere.

Experimental studies were made of propagation in the waveguide with

several different wall perturbations. It was found that the wall perturbation causes the conversion of substantial amounts of energy from one of the propagating modes to others, as suggested by theory. It was found also that the effects of the perturbation are noticeable at great distances and that the amount of energy converted to various propagating modes is critically de- pendent upon the size and shape of the perturbation.

Impedance of a Monopole Antenna with a Radial-Wire Ground

System, The impedance of a vertical monopole located over the surface

of an imperfectly conducting earth and having a radial-wire ground system is an important parameter in designing low-frequency antennas. Extensive

calculations (carried out in collaboration with the University of Colorado)

based on previously developed theory show the antenna impedance to be a function of antenna height, top-loading, and number, size, and length of

radial wires, as well as of ground conductivity and permittivity. Some of these calculations have been checked experimentally, using microwave-model

techniques.

The Electromagnetic Field near a Wedge Apex, Numerical results for the structure of the field in the apex region of a wedge were obtained,

using the exact series solution for diffraction by a perfectly conducting

wedge. This provided insight into the nature of electromagnetic fields near

a surface discontinuity. The results provided some justification for the use 225
of approximate boundary conditions, which have been used previously in studying radio propagation over terrain features. Oblique Propagation of Groundtvaves Across a Coastline, In con- tinuing its study of the propagation of groundwaves over inhomogeneities,

the Bureau calculated the amplitude and phase changes of a groundwave

passing obliquely over a flat-lying and a sloping coast. In the first case, for both land and sea assumed to be smooth, level, and homogeneous, it was shown that the wave reflected at the discontinuity depended critically on

the angle of incidence, while the transmitted wave was only weakly de- pendent on it. The wave reflected at a beach sloping up with constant rise, on the other hand, can be quite significant and fundamentally different in character from a wave reflected at a flat-lying coastline. The influence of a finite transition zone on the electrical characteristics

at the land/sea boundary also has been studied in some detail. In general, it was found that the characteristics of the transition region will not produce

significant modifications of the transmitted field. However, the magnitude

of the reflected field for a flat-lying coast was greatly reduced as the width

of the transition zone was increased beyond about one-quarter wavelength.

Waves in Cold Plasma. A way of representing the composite magnetic

field resulting from a source and a nearby isotropic conducting cylinder,

surrounded by concentric stratums of plasma and generating a d-c magnetic

field alined with the cylindrical axis has been developed. Computation was

facilitated by transforming the harmonic series representation to a more

highly convergent form. The presence of the d-c magnetic field was found

to destroy the azimuthal symmetry usual in configurations of this type. The

situation is somewhat analagous to the propagation of radio waves in a

spherical earth-ionosphere system.

Sources in Plasma. Radiation from a finite source in a compressible

electron plasma was studied by means of a theoretical model, a perfectly

conducting sphere excited uniformly by an annular slot. In this configuration Maxwell's equations were separable, permitting it to be shown that a portion of the total power supplied by the source was radiated as an acoustic wr ave in the electron fluid. The influence of a concentric dielectric coating on

the sphere also was analyzed and found to have the effect of reducing the power "wasted" in electro-acoustic energy. The results have possible applica- tion to antennas for space vehicles. Related problems with various geo- metrical configurations also have been considered.

226
3. APPENDIXES

3.1. ORGANIZATION OF THE

NATIONAL BUREAU OF STANDARDS *

The Bureau is headed by a Director who is appointed with the advice

and consent of the Senate. The Director is assisted in the overall management of the Bureau by a Deputy Director. In addition, there are three Associate Directors and a Manager of the Boulder Laboratories who are

responsible for the planning and operation of various technical and administrative management services in support of the Bureau's technical programs.

Technical program activities are conducted in four major organizational

units known generally as Institutes. Each is headed by an Institute Director

who is responsible for the development and direction of research programs

and central national services essential to the fulfillment of a broad segment

of the Bureau's mission. These major organizational units are: (1) The Institute for Basic Standards, which includes 13 divisions (4

in Boulder, Colo.) , each serving a classical subject matter area of science and

engineering

(2) The Institute for Materials Research, which consists of 7 divisions

(1 in Boulder, Colo.), organized primarily by technical field; (3) The Institute for Applied Technology, which includes 12 industryoriented divisions; and

(4) The Central Radio Propagation Laboratory, which comprises a

series of four divisions located at Boulder, Colo. DIRECTOR

Allen V. Astin

DEPUTY DIRECTOR

I. C. SCHOONOVER OFFICE OF THE DIRECTOR

Assistants to the Director

G. E. Auman

C. N. COATES W. H. Gammon

Senior Research Fellows

C. ElSENHART

U. Fano

K. Shuler

J. R. Wait

Associate Director for Resources Planning

S. Silverman

Office of Public Information

A. V. Gentilini, Chief

*As of July 1, 1964. 227
ASSOCIATE DIRECTOR FOR ADMINISTRATION

R. S. Walleigh

Accounting

Administrative Services Budget and Management

Internal Audit

Patent Advisor

Personnel

Plant Supply

J. Seidenberg

H. P. Dalzeli

J. E. Skillington

H. F. Whittington

D. Robbins

G. R. Porter M. B. Goetz, Acting

G. B. Kefover

ASSOCIATE DIRECTOR FOR TECHNICAL SUPPORT

L. S. Taylor

Instrument Shops F. P. Brown

Technical Publications W. R. Tilley

Professional Development Vacant

Radiation Safety L. S. Taylor, Acting Research Information L. S. Taylor, Acting

Library Miss S. A. Jones MANAGER, BOULDER LABORATORIES

R. B. Scott

Consultant, Mathematics Group and Computation Facility Consultant, Mathematical Physics

Consultant, Statistics Communications Liaison Officer Executive Officer and Chief of Administrative Division Technical Information Officer Library

J. J. Sopka

E. H. Brown

E. L. Crow

A. Barnabei

S. W. J. Welch

J. R. Craddock

L. E. Leonard

INSTITUTE FOR BASIC STANDARDS

DIRECTOR

R. D. Huntoon

ASSOCIATE DIRECTOR, MEASUREMENT SERVICES

W. A. WlLDHACK

ASSISTANT TO THE DIRECTOR

H. L. Mason

OFFICE OF STANDARD REFERENCE DATA

ChiefThermodynamics & Transport Data Chemical Kinetics Information Systems

E. L. Brady

E. R. Johnson

S. A. ROSSMASSLER

F. L. Alt

APPLIED MATHEMATICS

Chief

Consultants

Numerical Analysis

Computation

Statistical Engineering Mathematical Physics

Operation Research

E. W. Cannon

H. Oser

Mrs. Ida Rhodes W. J. Youden

M. Newman

D. I. MlTTLEMAN

J. M. Cameron

W. H. Pell

A. J. Goldman

228
ELECTRICITY

Chief

Resistance and Reactance

Electrochemistry

Electrical Instruments Magnetic Measurements

Dielectrics High Voltage Absolute Electrical Measurements METROLOGY

Chief

Assistant Chief Technical Assistant Photometry and Colorimetry

Refractometry

Photographic Research Length

Engineering Metrology Mass and Volume

MECHANICS

Chief

Consultants Sound

Pressure and Vacuum

Fluid Mechanics

Engineering Mechanics

Rheology

Combustion Controls HEAT

Chief

Assistant Chief, Thermodynamics

Temperature Physics Heat Measurements

Cryogenic Physics

Equation of State

Statistical Physics

ATOMIC PHYSICS

Chief

Physical Science Administrator Spectroscopy

Infrared and Microwave Spectroscopy Far Ultraviolet Physics

Solid State Physics

Electron Physics

Atomic Physics Plasma Spectroscopy

PHYSICAL CHEMISTRY

Chief Consultants Chemical Kinetics Information Center

Theoretical Chemistry

Thermochemistry

Surface Chemistry

Organic Chemistry

Molecular Spectroscopy

Elementary Processes Mass Spectrometry Photo Chemistry and Radiation Chemistry

C. H. Page

C. Peterson W. J. Hamer

F. L. Hermach

I. L. Cooter

A. H. Scott

F. R. Kotter

F. K. Harris

A. G. McNish

D. B. Judd

D. V. Baker

L. E. Barbrow

F. E. Washer

C. S. McCamy

T. R. Young

I. H. Fullmer

P. E. Pontius

B. L. Wilson

J. M. Frankland

E. C. Lloyd

R. K. Cook

D. P. Johnson

G. B. Schubauer

L. K. Irwin

R. S. Marvin

F. R. Caldwell

R. P. Hudson

C. W. Beckett

J. F. Swindells

D. C. Ginnings

E. Ambler

J. Hilsenrath M. S. Green

K. G. Kessler

J. A. Suddeth W. C. Martin, Jr. D. R. Lide, Jr. R. P. Madden

H. P. R. Frederikse

J. A. Simpson

H. Boyne

W. L. Wiese

M. B. Wallenstein W. L. Clinton

E. J. Prosen

R. B. Parlin M. Krauss

D. D. Wagman

R. Klein

H. S. Isbell D. E. Mann

R. E. Ferguson

H. M. Rosenstock

J. R. McNesby

229
LABORATORY ASTROPHYSICS*

Chief L. M. Branscomb

RADIATION PHYSICS

Chief

Scientific Assistant Radiation Theory

Radiological Physics

ChiefX-ray Physics

Dosimetry

X-ray Standards Nuclear Physics Chief

Radioactivity Neutron Physics Photonuclear Physics Nuclear Spectroscopy

Accelerator Chief

Accelerator Engineering

Radiation Physics Instrumentation

Accelerator Physics

H. W. Koch

E. H. Eisenhower

H. A. Olsen

J. W. Motz

J. W. Motz

S. W. Smith

H. 0. Wyckoff

H. W. Koch

W. B. Mann

R. S. Caswell

E. G. Fuller

R. W. Hayward

J. E. Leiss

J. E. Leiss

L. Costrell

J. E. Leiss RADIO STANDARDS LABORATORY*

Chief

Assistant Chief for Program Evaluation and Development

Assistant Chief for Technical Planning and

Coordination

Scientific Consultant

J. M. Richardson

H. W. Lance

E. C. Wolzien

D. M. Kerns RADIO STANDARDS PHYSICS*

Chief

Assistant Chief

Consultant

Assistant Chief for Technical Planning and

Coordination Frequency-Time Dissemination Research Frequency-Time Broadcast Services Radio and Microwave Materials Atomic Frequency and Time Interval Standards Radio Plasma

Microwave Physics

Y. Beers

G. E. Hudson

P. F. Wacker

W. D. Goring

A. H. Morgan

D. H. Andrews

J. L. Dalke

R. C. Mockler

K. B. Persson

R. Zimmerer, Acting

RADIO STANDARDS ENGINEERING*

Chief

Assistant Chief for Technical Planning and

Coordination

Consultants

Coordinator, Calibration Services Low Frequency Calibration Services High Frequency Calibration Services High Frequency Electrical Standards High Frequency Impedance Standards Microwave Calibration Services Microwave Circuit Standards

F. D.

g. e. schafer

W.J.Anson

R. W. Beatty M. C. Selby W. F. Snyder

Weaver, Acting

K. R. Wendt

C. M. Allred

R. C. Powell

R. E. Larson M. B. Hall

^Located at Boulder, Colo. 230
INSTITUTE FOR MATERIALS RESEARCH

DIRECTOR

I. C. Schoonover, Acting

DEPUTY DIRECTOR

H. C. Allen, Jr., Acting

ASSISTANT TO THE DIRECTOR

P. H. Kratz OFFICE OF STANDARD REFERENCE MATERIALS

Chief W. W. Meinke

ANALYTICAL CHEMISTRY

Chief

Assistant Chief

Analytical Standards Coordinator

Associate

Assistant Radiochemical Analysis

Spectrochemical Analysis

Electrochemical Analysis

Quantitative Separations

Analysis and Purification R. A.

W. W. Meinke

R. G. Bates

J. L. Hague

R. E. Michaelis

T. W. Mears

J. R. Devoe

B. F. SCRIBNER

R. G. Bates

Paulson, Acting

J. K. Taylor

POLYMERS

Chief

Consultant

Consultant on Polymers

Consultant on Rubber

Macromolecules—Synthesis and Structure Polymer Chemistry

Polymer Physics

Polymer Characterization Dental Research

J. D. Hoffman

J. I. Lauritzen, Jr. S. G. Weissberg

L. A. Wood

D. McIntyre

L. A. Wall

E. Passaglia

. P. Bekkedahl W. T. Sweeney

Federal Standards and Specifications Laboratory

Chief Consultant on Leather

Consultant on Math Statistics Consultant on Paper

Consultant on Textiles Product Evaluation and Testing Procurement Systems

Evaluation Criteria Performance Research

R. B. Hobbs, Acting

J. R. Kanagy

J. Mandel

J. L. Harvey, Acting

H. F. Schiefer Vacant

Vacant

R. D. Stiehler Vacant METALLURGY

Chief

Assistant Chief

Special Assistant Consultant Engineering Metallurgy

Alloy Physics

Lattice Defects and Microstructures Corrosion Metal Physics

Electrolysis and Metal Deposition

Crystallization of Metals

L. M. Kushner

G. A. Ellinger

H. C. Burnett

L. Wyman

S. J. Rosenberg

L. H. Bennett

A. W. Ruff, Jr. G. A. Ellinger

R. E. Howard

A. Brenner

R. L. Parker

756-224 0—65 16 231
INORGANIC MATERIALS

Chief Technical Services Consultants

Inorganic Chemistry

Glass High Temperature Chemistry

Crystal Chemistry

Physical Properties

Crystallography

REACTOR RADIATIONS

Chief

H. Allen, Jr. C. B. Riecks

G. Gordon

E. R. Lippincott

T. D. Coyle

C. H. Hahner

Vacant

H. S. Peiser

J. B. Wachtman, Jr. H. F. McMurdie

C. 0. MUEIILIIAUSE CRYOGENICS*

Chief

Assistant Chief

Consultant Cryogenic Technical Services Cryogenic Data Center

Cryogenic Properties of Solids Properties of Cryogenic Fluids Cryogenic Systems

Cryogenic Metrology

Cryogenic Fluid Transport Processes

B. W. Birmingham

R. J. Corruccini

A. F. Schmidt W. A. Wilson

V. J. Johnson

R. H. Kropsciiot

R. J. Corruccini

D. B. Chelton

T. M. Flynn

R. V. Smith

INSTITUTE FOR APPLIED TECHNOLOGY

DIRECTOR

D. A. Schon

DEPUTY DIRECTOR

J. P. Ererhard

ASSISTANT TO THE DIRECTOR, INTERNATIONAL STANDARDS

A. T. McPherson

Consultant

Invention and Innovation

Technologist Research Assistant Domestic Technology Information Aid Technology Information OFFICE OF TECHNICAL SERVICES

Chief OFFICE OF INDUSTRIAL SERVICES

Chief OFFICE OF WEIGHTS AND MEASURES

Chief OFFICE OF ENGINEERING STANDARDS

Chief Commodity Standards

Technical Standards Coordination

J. L. SWEDOCK

D. V. Desimone

L. S. Hardland

Miss A. J. Kelly

E. A. Tietz Vacant

D. A. Schon

R. L. Stern

M. W. Jensen

A. S. Best

Miss J. Hartman

*Located at Boulder. Colo. 232
TECHNICAL DOCUMENTATION CENTER

Chief Deputy Chief

B. M. Fry W. W. Dunlop

Document Management

Chief Document Analysis and Services Chief Automated Systems and Services Chief Customer Relations Chief Plans and Development

Chief

Administrative Services Chief

Joint Publications Research Service Chief

P. W. Larson

Miss L. A. Hamrick

Vacant

J. E. Wheat

J. Harrington

J. L. Demarest

T. Miller

BUILDING RESEARCH

Chief

Special Assistant

Structural Engineering

Fire Research Mechanical Systems

Organic Building Materials Codes and Safety Standards Heat Transfer

Inorganic Building Materials

Metallic Building Materials

A. A. Bates

J. V. Ryan

D. Watstein

A. F. Robertson

P. R. ACHENBACH

W. W. Walton

A. A. Bates, Acting

H. E. Robinson

B. E. Foster

D. G. Moore

INDUSTRIAL EQUIPMENT TECHNOLOGY

Chief Vacant INFORMATION TECHNOLOGY

Chief Technical Assistant

Pilot Research Information Center Components and Techniques

Computer Technology Measurements Automation

Engineering Applications

Systems Analysis

S. N. Alexander

Miss M. R. Fox

J. P. Nigro

Miss M. E. Stevens

R. D. Elbourn

J. A. Cunningham

R. T. Moore

J. P. Nigro

S. N. Alexander, Acting

PERFORMANCE TEST DEVELOPMENT

Chief Vacant INSTRUMENTATION

Chief Engineering Electronics Electron Devices

Electronic Instrumentation Mechanical Instruments

Basic Instrumentation

G. F. Montgomery

G. Shapiro

C. P. Marsden

G. F. Montgomery, Acting

A. Wexler

J. Stern TRANSPORT SYSTEMS

Chief S. M. Breuning

TEXTILES AND APPAREL TECHNOLOGY CENTER

Chief Vacant 233
CENTRAL RADIO PROPAGATION LABORATORY*

DIRECTOR

C. G. Little DEPUTY DIRECTOR

J. W. Herbstreit

Consultants

Chief CRPL Liaison and Program Development

Consultant, Radio Wave Propagation

K. A. Norton

R. M. Gallet

A. G. Jean

A. H. Shapley

J.R. Wait

IONOSPHERE RESEARCH AND PROPAGATION

Chief

Assistant Chief

Assistant to Chief for Technical Planning and

Coordination

Consultants

Ultra Low Frequency Research Low Frequency and Very Low Frequency Research

Ionosphere Research

Prediction Services Sun-Earth Relationships

Field Engineering Radio Warning Services

Vertical Soundings Research

R. W.Knecht

T. N. Gautier

J. A. Kemper

L. R. Megill

H. H. Howe

W. H. Campbell

D. D. Crombie

K. Davies

Mrs. M Leftin

T. E. Van Zandt

H. G. Sellery

J. V. Lincoln

J. W. Wright

TROPOSPHERE AND SPACE TELECOMMUNICATIONS

Chief

Consultant

Consultant, Terminal Equipment

Data Reduction Instrumentation Radio Noise Tropospheric Measurements

Tropospheric Analysis

Spectrum Utilization Research Radio Meteorology Lower Atmosphere Physics

R. S. Kirby, Acting

D. M. Gates

E. F. Florman

W. E. Johnson W. Q. Crichlow

M. T. Decker

P. L. Rice

A. P. Barsis

B. R. Bean

M. C. Thompson. Jr. RADIO SYSTEMS

Chief

Assistant Chiefs Consultant Applied Electromagnetic TheoryHigh Frequency and Very High Frequency Research Frequency Utilization Modulation Research Antenna Research

Radiodetermination UPPER ATMOSPHERE AND SPACE PHYSICS

Chief

Assistant Chief

Assistant to Chief for Technical Planning and Coordination

Consultants

Upper Atmosphere and Plasma Physics

High Latitude Ionospheric Physics

Atmospheric Collision Processes Ionosphere and Exosphere Scatter Airglow and Aurora

Ionospheric Radio Astronomy

R. C. Kirby

D. W. Patterson W. F. Utlaut

G. W. Haydon

J. R. JOHLER

L. H. TVETEN

G. W. Haydon

C. Watterson

H. V. Cottony

G. Hefley

E. K. Smith, Jr. F. L. Taylor

S. S. Barnes

D. K. Bailey

G. C. Reid

R. J. Slutz Vacant

H. Chtvers

E. E. Ferguson

K. L. Bowles

F. E. Roach

R. S. Lawrence

'Located at Boulder, Colo. 234
FIELD ESTABLISHMENTS

Visual Landing Aids Field Laboratory Master Railway Track Scale Depot

Materials Testing Laboratories:

Areata, Calif. Clearing, 111. Denver, Colo.

Seattle, Wash.

Institute for Basic Standards Field Stations Radio Standards Laboratory Field Stations: Standard Frequency Station WWV

Standard Frequency Station WWVL-WWVB

Standard Frequency Station WWVH

Laboratory Astrophysics Division Field Station

Poor Man's Relief Mine, Four-Mile Canyon

Greenbelt, Md.

Fort Collins, Colo. Maui, Hawaii

Boulder, Colo.

Central Radio Propagation Laboratory Field Stations ALASKA

Adak**

Anchorage Barrow

College**

Cape Sarichef** ANTARCTICA

Byrd Station**

Eights Station** Pole Station** USNS ELTANIN (Floating Research Vessel) ** ARIZONA

Kitt Peak Observatory

AUSTRALIA

Cook**

Sydney**

BOLIVIA

La Paz** BRAZIL

Natal** Sao Jose Dos Campos**

CALIFORNIA

Lompoc PMR

CANADA

Baie St. Paul Cape Jones**

Frobisher Bay**

Great Whale River** CANARY ISLANDS**

CANTON ISLANDS**

CHILE

Concepcion**

Santiago**

COLOMBIA

Bogota**

COLORADO

Akron

Beulah

Brighton

Cheyenne Mountain

Erie

Fritz Peak

Green Mountain Mesa

Gunbarrel Hill Hanover

Haswell

Karval Kendrick Kolb

Lafayette Lee Hill North Boulder Rocky Flats Sunset Table Mountain

ECUADOR

Quito**

GREENLAND

Godhavn**

Narssarssuaq** Thule** HAWAII

Kauai (Kekaha)

Maui (Kealia Pond)

Maui (Puunene Airport)

ICELAND

Keflavik** Reykjavik**

ILLINOIS

Long Branch

INDIA New Delhi** JAPAN

Ohira**

KENYA

Nairobi** MALAGASAY

(MADAGASCAR)

Tananarive** MALAYA

Singapore**

MINNESOTA

Cedar Creek** MISSOURI

Warrensburg

MOROCCO

Rabat** NEBRASKA

Shickley

NEW JERSEY

Fort Monmouth**

NEW MEXICO

White Sands** NEW ZEALAND

Waimate**

NIGERIA

Kano**

Zaria** OKINAWA

Okuma**

Onna**

Contract or Mutual Cooperation

235
OKLAHOMA

Mangum

PANAMA CANAL

ZONE

Balboa** PERU

Lima**

Jicamarca Radio

Observatory

PHILIPPINE ISLANDS

Manila**

SOUTH AFRICA

Pretoria** Johannesburg**

SWEDEN

Enkoping**

VIRGINIA

Fort Belvoir Front Royal

Wallops Island WEST INDIES

Jamaica**

WYOMING

Bill

3.2. SUMMARY OF NBS STAFF

As of June 30, 1964

Washington Boulder Total

Total permanent staff 2, 675 1,230 3, 905 Other staff* 254 221 475

Total on rolls 2, 929 1,451 4, 380 Research associates and guest workers .... 140 37 177

Total on rolls at NBS 3, 069 1,488 4, 557

Professional staff:** Physicists 453 238 691 Chemists 295 9 304

Engineers 173 198 371 Mathematicians 52 52 114 Other 98 17 115 Total professional staff 1, 071 524 1,595

intermittent, consultants, students, teachers, postdoctoral fellows, and temporary

limited employees.

**Full-time permanent (excludes any under *).

3.3. FINANCIAL DATA ON NBS

PROGRAM

The activities of the National Bureau of Standards are financed from

three sources: from appropriations provided by the Congress; from pay- ments by other agencies for specific research and development tasks; and

from payments by industrial concerns, universities, research institutions, and

government agencies for specific calibration or testing services. The fol- lowing tabulation is a summary of the financial aspects of the Bureau pro- grams for 1964:

Contract or Mutual Cooperation.

236
Program and Source of Financing Obligations Incurred (Rounded)

Supported by NBS Appropriations:

Operating Programs:

Research & Technical Services. . . . Salaries and Expenses (Office of Technical Services)

Civilian Industrial Technology. . . . Special Foreign Currency Program

Subtotal

Construction and Facilities Program:

Plant and Facilities. . Construction of Facilities Subtotal Total NBS Appropriation.

Supported by Other Funds:

Research and Development Programs: Other Federal Agencies

Nongovernmental Sources

Subtotal

Calibrations, Testing, Standard Samples and Other Technical Services. . . Federal Clearinghouse

Reimbursable Administrative Services. Total Supported by Other

Funds

Total Program.

$28, 117, 000

987, 000

248, 000

657, 000

2, 027, 000

41, 245, 000

17, 693, 000

191, 000

$30, 009, 000

43, 272, 000

$73, 281, 000

17, 884, 000

5, 832, 000

1, 509, 000

809, 000

26, 034, 000

99, 315, 000

3.4. ADVISORY COMMITTEES

STATUTORY VISITING COMMITTEE

(Reports annually to Secretary of Commerce on NBS activities (Dates indicate expiration of appointment)

)

Dr. E. R. Piore, Vice President, Research & Engineering, International Business Machines Corporation (1967), Chairman

Mr. Crawford H. Greenwalt, President, E. I. du Pont de Nemours & Co. (1964) Professor Frederick Seitz, President, National Academy of Sciences (1966) Professor Charles H. Townes, Provost, Massachusetts Institute of Technology (1965) Dr. Elmer W. Engstrom, President, Radio Corporation of America (1968) TECHNICAL ADVISORY PANELS

Throughout the past year the Bureau's advisory input from the Nation's

scientific and technical community functioned with increasing vigor and

effectiveness. The National Academy of Sciences and National Research

Council, in cooperation with the leading scientific and technical societies,

increased the size and competence of the 18 NBS Advisory Panels to an

average of slightly over 10 members per panel and reviewed the work of every technical division. Every panel held at least one meeting either at 237
NBS Washington or the Boulder Laboratories. Most Panels visited throughout the laboratories in connection with their meetings. Panel members were

urged to critically evaluate the technical program in relation to overall national needs and to identify areas that should receive increased or de- creased emphasis hypothesizing a constant total level of support. Written

reports and recommendations have been received to date from 14 of the Panels and are being considered by the Institute Directors. In addition to the foregoing, the NBS Advisory Committee on Calibration and Measurement Services met at both Boulder and Washington and

made an unusually thorough critique of NBS calibration and measurement

service activities. The NBS Weights and Measures Advisory Committee

met immediately prior to the National Conference on Weights and Measures and served as an effective link between the Conference and the NBS.

Cooperating societies are: American Ceramic Society (ACerS) ; American Chemical Society (ACS) ; American Institute of Chemical Engineers (AIChE) ; Institute of Electrical and Electronic Engineers (IEEE) ; American Institute of Mining, Metallurgical, and Petroleum Engineers (AIME) ; American Institute of Physics (AIP) ; American

Society of Civil Engineers (ASCE) ; American Society of Mechanical Engineers

(ASME) ; and Conference Board of the Mathematical Sciences (CBMS).

Dr. Paul D. Foote, National Research Council, Executive Secretary Advisory Panel to Electricity Division

Prof. W. A. Lewis, Illinois Institute of Technology, Chairman (IEEE)

Dr. William G. Amey, Leeds & Northrup (IEEE)

Dr. Richard M. Bozorth, Short Hills, N.J. (AIP)

Dr. John Brainerd, University of Pennsylvania (IEEE)

Mr. Ivan G. Easton, General Radio Company (IEEE)

Prof. Henry B. Linford, Columhia University (ACS)

Mr. J. T. Lusignan, The Ohio Brass Company (IEEE)

Prof. M. B. Stout, University of Michigan (IEEE)

Prof. John G. Trump, Massachusetts Institute of Technology (AIP)

Advisory Panel to Metrology Division

Dr. Brian O'Brien, Pomfret, Conn., Chairman (AIP)

Dr. J. H. Werr, Eastman Kodak Company, Vice Chairman (AIP)

Prof. Isay A. Balinkin, University of Cincinnati (ACerS)

Dr. Alsoph H. Corwin, The Johns Hopkins University (ACS)

Mr. C. L. Crouch, Illuminating Engineering Society ( AL)

Mr. A. M. Dexter, Bausch & Lomb Incorporated (AL)

Dr. Rorert E. Hopkins, University of Rochester (AL)

Mr. Floyd W. Hough, American Geophysical Union (ASCE)

Dr. Elmer Hutchisson, American Institute of Physics (AIP). Mr. J. J. Moran, Kimble Glass Company (ACerS)

Mr. Louis Polk, Dayton, Ohio (ASME)

Prof. John Strong, The Johns Hopkins University (AIP)

Advisory Panel to Heat Division

Prof. Joseph E. Mayer, University of California, Chairman (ACS)

Prof. Henry A. Fairrank, Duke University (AIP)

Prof. H. R. Griem, University of Maryland (AIP)

Dr. Burgess H. Jennings, Northwestern University (ASME)

Prof. Joseph Kestin, Brown University (ASME)

Dr. P. G. Klemens, Westinghouse Research Laboratories (AIP)

Prof. Rorert S. Mulliken, University of Chicago (AIP)

Prof. John Ross, Brown University (ACS & AIP)

Dr. Charles Squire, Agriculture and Mechanical College of Texas (AIP)

Prof. Clayton A. Swenson, Iowa State University (AIP)

Prof. Edgar F. Westrum, Jr., University of Michigan (ACS)

238
Advisory Panel to Radiation Physics Division

Dr. A. 0. Hanson, University of Illinois, Chairman ( AIP)

Dr. John S. Blair, University of Washington (AIP)

Mr. Casimer J. Borkowski, Oak Ridge National Laboratory (AIP)

Dr. Robley D. Evans, Massachusetts Institute of Technology (AIP)

Dr. Harold A. Lamonds, Aerojet General Corporation (IEEE)

Dr. John S. Laughlin, Sloan-Kettering Institute for Cancer Research (AIP)

Dr. H. M. Parker, General Electric Company (AIP)

Prof. George T. Reynolds, Palmer Physical Laboratory (AIP)

Prof. Harald H. Rossi, Columbia University (AL)

Dr. Vance L. Sailor, Brookhaven National Laboratory (AIP)

Dr. Warren K. Sinclair, Argonne National Laboratory (AL)

Prof. Anthony Turkevich, University of Chicago (AL)

Advisory Panel to Analytical & Inorganic Chemistry Division

Dr. Charles E. White, University of Maryland, Chairman (ACS)

Prof. Clark E. Bricker, University of Kansas (ACS)

Dr. Norman D. Coggeshall, Gulf Research & Development Company (AIP)

Prof. W. D. Cooke, Cornell University (ACS)

Prof. George Morrison, Cornell University (ACS)

Prof. Charles N. Reilley, University of North Carolina (ACS)

Prof. L. B. Rogers, Purdue University (ACS)

Dr. James White, Oak Ridge National Laboratory (ACS)

Prof. George T. Austin, State College of Washington (AICE)

Advisory Panel to Mechanics Division

Prof. S. R. Beitler, American Society of Mechanical Engineering, Chairman

(ASME)

Prof. Lynn S. Beedle, Lehigh University (ASCE)

Prof. Arthur T. Ippen, Massachusetts Institute of Technology (ASCE)

Dean R. B. Lindsay, Brown University (AIP)

Dr. Harry F. Olson, Radio Corporation of America (AIP)

Prof. Jesse Ormondroyd, University of Michigan (ASME)

Dr. Milton Plesset, California Institute of Technology (AIP)

Dr. M. E. Shank, Pratt & Whitney Aircraft (ASME)

Advisory Panel to Polymers Division

Dr. C. G. Overberger, Polytechnic Institute of Brooklyn, Chairman (ACS)

Dr. Raymond F. Boyer, Dow Chemical Company (ACS)

Dr. J. H. Dillon, Textile Research Institute (AIP)

Dr. Milton Harris, Harris Research Laboratories, Inc. (ACS)

Dr. Frank C. McGrew, E. I. du Pont de Nemours & Co. (ACS)

Dr. Charles C. Price, University of Pennsylvania (ACS)

Dr. J. F. Downie Smith, Carrier Research & Development Company (ASME)

Dr. Charles Scott Venable, Wallingford, Pennsylvania (ACS)

Dr. C. M. Blair, Union Carbide Corporation (AICE)

Advisory Panel to Metallurgy Division

Mr. Francis L. LaQue, International Nickel Company, Chairman (ACS)

Dr. Robert H. Aborn, Millington, New Jersey (ASME)

Dr. W. A. Dean, Aluminum Company of America (AIME)

Dr. D. J. Dienes, Brookhaven National Laboratory (AIP)

Dr. Morris E. Fine, Northwestern University (AIME)

Mr. A. R. Lytle, National Academy of Sciences-National Research Council (AIME)

Dr. Oscar Marzke, United States Steel Corporation (AIME)

Prof. E. F. Osborn, Pennsylvania State University (ACerS)

Dr. Joseph A. Pask, University of California ( ACerS)

Dr. Albert J. Phillips, American Smelting & Refining Company (AIME)

Mr. J. H. Scaff, Bell Telephone Laboratories (AIME)

Prof. Robb M. Thomson, University of Illinois (AIP)

239
Advisory Panel to Inorganic Solids Division

Dr. Norbert J. Kreidl, Bausch & Lomb Optical Company, Chairman (ACerS)

Dr. Orson L. Anderson, Summit, New Jersey ( ACerS)

Dr. C. L. Babcock, Owens-Illinois Technical Center (ACerS)

Dr. Morris Berg, General Motors Corporation (ACerS)

Prof. C. Ernest Birchenall, University of Delaware ( AL)

Dr. Joseph E. Burke, General Electric Research Laboratory (ACerS)

Dr. James R. Johnson, Minnesota Mining & Manufacturing Company (ACerS)

Dr. Ralston Russell, Jr., the Ohio State University (ACerS)

Prof. Henry Taube, Stanford University (ACS)

Advisory Panel to Building Research Division

Dr. W. C. Hansen, Valparaiso, Indiana, Chairman (ACS)

Prof. Jesse H. Day. Ohio University (ACS)

Dr. Albert G. H. Dietz, Massachusetts Institute of Technology ( ASCE)

Dr. J. V. Fitzgerald, Tile Council of America, Inc. (ACerS)

Dr. Robert A. Hechtman, Planning Analysis & Design Corp. (ASCE)

Prof. James T. Lendrum, University of Florida ( AIA)

Dean Warren L. McCabe, Polytechnic Institute of Brooklyn ( AICE)

Dr. John S. Parkinson, Johns-Manville Products Corporation ( AIP)

Prof. E. R. Queer, The Pennsylvania State University ( AL)

Mr. Raymond C. Reese. Toledo, Ohio (ASCE)

Advisory Panel to Applied Mathematics Division

Prof. George E. Forsythe, Stanford University, Chairman (CBMS)

Prof. T. W. Anderson, Columbia University (CBMS)

Prof. Francis J. Anscombe, Yale University (AL)

Prof. Charles R. DePrima, California Institute of Technology (CBMS)

Prof. Joaquin B. Diaz, University of Maryland (CBMS)

Prof. William Feller, Princeton l^niversity (CBMS)

Dr. Ralph E. Gomory, International Business Machines Corporation (CBMS)

Dr. Alan J. Hoffman, International Business Machines Corporation (CBMS)

Dr. Alston S. Householder, Oak Ridge National Laboratory (CBMS)

Dr. Bernard 0. Koopman, Institute for Defense Analyses (CBMS)

Dr. J. P. LaSalle, Research Institute for Advanced Studies (CBMS)

Prof. Peter D. Lax, Institute of Mathematical Sciences (CBMS)

Dr. Elliott W. Montroll, Institute for Defense Analyses (CBMS)

Prof. R. D. RlCHTMYER, New York University (CBMS)

Dr. J. Barkley Rosser, University of Wisconsin (CBMS)

Prof. M. M. Schiffer, Stanford University (CBMS ) Prof. John Todd, California Institute of Technology (CBMS)

Advisory Panel to Data Processing Systems Division

Dr. Alston S. Householder, Oak Ridge National Laboratory, Chairman (CBMS)

Prof. George E. Forsythe, Stanford University (CBMS)

Dr. Alan J. Hoffman, International Business Machines Corp. (CBMS)

Mr. John C. McPherson, International Business Machines Corporation (IEEE)

Prof. Charles L. Miller, Massachusetts Institute of Technology (ASCE)

Mr. William Papian, Massachusetts Institute of Technology (IEEE)

Prof. Morris Rubinoff, University of Pennsylvania (IEEE)

Dr. Abraham Sinkov, Arizona State University (CBMS)

Advisory Panel to Atomic Physics Division and Joint Institute for Laboratory

Astrophysics

Prof. Peter Franken, University of Michigan, Chairman (AIP)

Dr. R. Grant Athay, University of Utah (AL)

Prof. W. R. Bennett, Jr., Yale University (AIP)

Dr. Bruce H. Billings, Pacific Palisades, California (AIP)

Prof. R. H. Dicke, Princeton University (AIP)

Dr. Wade L. Fite, University of Pittsburgh (AIP)

Dr. Leo Goldberg, Harvard College Observatory (AIP)

Prof. Jesse L. Greenstein, California Institute of Technology ( AL)

Prof. Vernon W. Hughes, Yale University (AIP)

Dr. R. L. Sproull, Advanced Research Projects Agency (AIP)

Prof. Gabriel Weinreich, University of Michigan (AIP)

Dr. M. Kent Wilson, Tufts University (ACS)

240
Advisory Panel to Instrumentation Division

Mr. R. W. Larson, General Electric Research Laboratories, Chairman (IEEE)

Dr. A. 0. Beckman, Beckman Instruments, Inc. (AL)

Mr. Ivan G. Easton, General Radio Company (IEEE)

Mr. William R. Hewlett, Hewlett-Packard Company (IEEE)

Dr. R. J. Jeffries, Data-Control Systems, Inc. (AL)

Colonel J. Z. Millar, Western Union Telegraph Company (IEEE)

Mr. Leon Podolsky, Sprague Electric Company (IEEE)

Dr. Richard C. Webb, Colorado Instruments, Inc. (IEEE)

Advisory Panel to Physical Chemistry Division

Prof. Henry Eyring, University of Utah, Chairman (ACS)

Dr. Paul Cross, Mellon Institute (ACS)

Dr. Benjamin P. Dailey, Columbia University (ACS)

Prof. Hans H. Jaffe, University of Cincinnati (ACS)

Dr. Joseph 0. Hirschfelder, University of Wisconsin (ACS)

Dr. Max S. Matheson, Argonne National Laboratory (ACS)

Dr. Daniel R. Stull, The Dow Chemical Company (ACS)

Advisory Panel to Cryogenic Engineering Division

Dr. Clyde McKinley, Air Products Incorporated, Chairman (AICE)

Dr. E. F. Hammel, University of California (AIP)

Prof. A. L. Hesselschwerdt, Massachusetts Institute of Technology (ASME)

Prof. Edward Lady, University of Michigan (ASME)

Dr. Hugh M. Long, Union Carbide Corporation (AIP)

Dr. Loyd B. Nesbitt, General Electric Laboratory (AIP)

Dr. David White, Ohio State University (ACS)

Advisory Panel to Central Radio Propagation Laboratory

Prof. Arthur H. Waynick, The Pennsylvania State University, Chairman (IEEE)

Mr. Stuart L. Bailey, Alexandria, Virginia (IEEE)

Dr. C. M. Crain, The Rand Corporation (IEEE)

Mr. Milton Greenberg, Geophysics Corporation of America (AL)

Dr. S. W. Herwald, Westinghouse Electric Corporation (IEEE)

Dr. F. S. Johnson, Graduate Research Center (AIP)

Dr. John M. Kelso, ACF Industries, Inc. (IEEE)

Prof. W. J. Ross, The Pennsylvania State University (IEEE)

Prof. John B. Smyth, The Pennsylvania State University (AIP) Dean George Town, Iowa State University (IEEE)

Dr. 0. G. Villard. Stanford University (IEEE)

Advisory Panel to Radio Standards Laboratory

Prof. Arthur A. Oliner, Polytechnic Institute of Brooklyn, Chairman (IEEE)

Dr. Sidney A. Bowhill, University of Illinois (IEEE)

Prof. Walter Gordy, Duke University (AIP)

Prof. E. L. Hahn, University of California (AIP)

Dr. E. W. Houghton, Bell Telephone Laboratories (IEEE)

Prof. E. C. Jordan, University of Illinois (IEEE)

Dr. R. Kompfner, Bell Telephone Laboratories (IEEE)

Prof. W. A. Lewis, Illinois Institute of Technology (IEEE)

Dr. Bernard M. Oliver, Hewlett-Packard Company (IEEE)

Prof. N. F. Ramsey, Harvard University (AIP)

Dr. John C. Simons, Jr., Weston, Massachusetts (IEEE)

Prof. M. W. P. Strandberg, Massachusetts Institute of Technology (AIP)

ADVISORY COMMITTEE ON ENGINEERING AND RELATED STANDARDS

(Members are nominated by the American Standards Association (ASA) and the American Society for Testing and Materials ( ASTM) ) Dr. I. C. Schoonover, National Bureau of Standards, Chairman

Mr. Roger E. Gay, American Standards Association (ASA)

Mr. Richard T. Kropf, Belding Heminway Company (ASTM)

Mr. John W. McNair, American Standards Association (ASA)

Mr. N. L. Mochel, Westinghouse Electric Corporation (ASTM)

Mr. Frank H. Roby, American Standards Association (ASA)

Mr. Alfred C. Webber, E. I. du Pont de Nemours, Inc. (ASTM)

241
ADVISORY COMMITTEE ON CALIBRATION AND MEASUREMENT

SERVICES

(Members are appointed on the basis of their broad personal knowledge of industrial measurement problems) Mr. W. A. Wildhack, National Bureau of Standards, Chairman

Mr. Joseph M. Aldrich, San Gabriel, California

Dr. William G. Amey, Leeds & Northrup Company

Mr. Ivan G. Easton, General Radio Company

Mr. Charles E. Johnson, The Boeing Company

Mr. E. C. Lloyd, National Bureau of Standards Mr. Sheldon C. Richardson, General Electric Company

Dr. George Sonneman, United Aircraft Corporate Systems Center Mr. Bruno Weinschel. Weinschel Engineering Mr. Charles E. White, Avco Research & Advanced Development Division Mr. L. B. Wilson, Sperry Gyroscope Company

WEIGHTS AND MEASURES ADVISORY COMMITTEE

(Members are nominated by the National Conference on Weights and Measures)

Mr. M. W. Jensen. National Bureau of Standards, Chairman

Miss Genevieve Blatt. Secretary of Internal Affairs, Commonwealth of Pennsylvania Mr. John Hoyt Chaloud. Ivorydale Technical Center Mr. C. G. Gehringer. The Hobart Manufacturing Company

Mr. Rollin E. Meek. State Board of Health, Indiana Mr. Arch W. Troelstri p, Stephens College Mr. Donald Malcolm Turnbull. City of Seattle. Comptrollers Department

3.5. AWARDS AND HONORS

Recognition of the Bureau's contributions to science and technology often takes the form of awards and honors from Government, academic, professional, and industrial groups. The following list reflects such recognition bestowed on Bureau staff members during fiscal year 1963. Recipient Award

Astin, Allen V. Rockefeller Public Service Award

Bates, A. Allan Stanton Walker Lecture Award from University of Maryland

Costrell, Louis Elected Fellow of Washington Academy of Sciences Diamond. Jacob J. Elected Fellow of Washington Academy of Sciences Landgrebe, Albert R. Superior Service Unit Award from Department of Agriculture

Logan, Hugh L. Burgess Memorial Awr ard by American Society of Metals Madden. Robert P. Elected Fellow of Optical Society of America

Malitson, Irving Elected Fellow of Optical Society of America Marton. Ladislaus Special Medal of University of Brussels Elected Honorary Member of Electron Microscopy

Society of France McCamy. Calvin S. Elected Fellow of Optical Society of America

Meijer. Paul Fellowship from John Simon Guggenheim Memorial

Foundation Ordway. Fred Elected Fellow of American Ceramic Society

Paffenbarger, George C. Elected to Honorary Membership in National Dental

Association 242
Passaglia, Elio

Scribner, Bourdon F. Sitterly, Charlotte M.

Smith, Jack C. Wachtman, John B., Jr. Wait, James R. Walker, Raymond F. Wyckoff, H. 0.

Elected Fellow of American Physical Society Elected to Executive Committee, American Physical

Society Division of High Polymer Physics

Elected to Membership in Society of Sigma Xi Annie Jump Cannon Centennial Medal from Wesley

College Elected Fellow of American Physical Society Elected Member of Textile Institute Elected Fellow of American Ceramic Society

Certificate of Service by Gordon Research Conference Arthur S. Flemming Award

Harry Diamond Memorial Prize Elected Fellow of American Ceramic Society

Medal from Radiological Society of North America

DEPARTMENT OF COMMERCE EXCEPTIONAL SERVICE AWARDS

(Gold Medal)

Recipient

Alexander, Samuel N. Allen, Harry C, Jr. Cook, Richard K. George, William D. (Deceased Feb. 12, 1963)

Little, C. Gordon

Richardson, John M.

Rosenberg, Samuel J.

Technical Area

Data Processing Molecular Spectroscopy

Acoustics Radio Standards Radio Propagation

Radio Standards Metallurgy

DEPARTMENT OF COMMERCE MERITORIOUS SERVICE AWARDS

(Silver Medal)

Recipient

Allred, Charles M.

Beehler, Roger E. Brauer, Gerhard M.

Cooper, John W.

Cox, Orson H.

Eisenstein, Julian C. French, Judson C. Graef, Alois N. Hardy, Robert C. Janes, Harris B. Megill, Lawrence R. Miller, Howard S. Ogburn, Fielding

Outman, Alice G. Powell, Robert C. Schafer, George E. Schweitzer, Walter G.

Joint Award

Codling, Keith

Madden, Robert P. Group Award

Simpson, John A. Kuyatt, Chris E. Mielczarek, Stanley R.

Technical Area High Frequency Measurements

Atomic Frequency and Time Interval Standards Dental Research

Absorption Spectra of Rare Gases

Concreting Materials

Solid State Physics Semiconductor Technology

Scientific Instruments Craftmanship

Viscosity Standards Radio Distance Measuring Techniques

Upper Atmosphere and Space Physics

Scientific Instruments Craftmanship

Electroplating Technology

Administrative Duties in Director's Office Radio and Electronic Measurements

Radio Standards Wavelength Standards Far Ultraviolet Physics

Far Ultraviolet Physics

3.6. EDUCATION, TRAINING, AND

UNIVERSITY LIAISON

A broad employee development program which is implemented primarily

through both the NBS Graduate School and nongovernment educational and

training facilities is available to all staff members. The program covers educational levels through postdoctoral research. The program is offered 243
at both the Boulder and Washington Laboratories; its primary objectives are

the increase of efficiency in the conduct of official assigned duties and the systematic preparation for increased responsibilities.

The Graduate School curriculum includes graduate and undergraduate

courses in the physical sciences, mathematics, and certain branches of engineering. Also, a series of scientific colloquia and seminars are led by re- search leaders from the Bureau staff and from other research centers. In

addition, general staff development courses, such as scientific German, practical metallurgy, and mathematical symbolism and terminology, are also

offered. Educational counseling is available, and employees may receive

thesis accreditation for research done at the Bureau.

Since the educational requirements of staff members are varied and

changing, the NBS Educational Committee determines course offerings on

the basis of periodic need surveys. The program is flexible, including both

NBS in-hours courses and NBS-university-sponsored out-of-hours courses. The Technician Career Program, established in 1960, offers a series of in-hours courses on the fundamentals of science and mathematics. The Program helps

increase job efficiency and offers educational opportunities to subprofessional

laboratory personnel. Since the establishment of the Washington educational program in 1908, 42 universities have awarded 308 graduate degrees

based partly on credits obtained or thesis work carried on under the NBS

Graduate School Program.

The Bureau has expanded the Graduate Program at Boulder through the establishment of a Joint-Course program and an Adjoint Professor plan

with the University of Colorado. Various graduate departments at both

the NBS Graduate School and the University offer courses simultaneously,

with benefits to both the Government and the University. Bureau staff members who teach the courses have the title of Adjoint Professor at the

University.

Nongovernment training, authorized by the Government Employees Training Act of 1958, falls into three major categories. These are:

1. Full-time (3 to 12 months) postdoctoral study and research assignments

at universities and research centers, both in this country and abroad.

2. Full-time (less than 3 months) attendance at institutes, seminars,

short concentrated courses, workshops, etc. Generally, these are offered through the educational facilities of major universities and industrial laboratories throughout the country.

3. Part-time, job-related academic courses at local educational institutions,

generally in early evening classes. Four hundred and seventy-two staff members at Washington and Boulder were trained through non-Government facilities in 1964; 16 career scientists were selected for full-time research assignments at universities and research

centers. Participants in approved full-time non-Government training pro- grams receive full salary and expenses, including tuition, related fees, travel, and per diem, as well as transportation of family and household effects. 244
Short concentrated courses and training programs at universities and in industry were attended by 156 Washington and Boulder staff members. Three

hundred employees, mostly from technical divisions, attended job-related courses at local educational facilities. Another important area of Government-sponsored programs since the Training Act is the Inter-agency series of courses sponsored primarily by

the Civil Service Commission. One hundred and eighty-nine Bureau employees participated in a wide range of special courses with a sizable number

in the supervisory-management fields. The Bureau sponsors a student trainee summer program for college stu- dents majoring in the physical sciences, mathematics, and certain branches

of engineering. Each summer an integrated work-study program including

lectures, tours, demonstrations, supervised laboratory assignments, and professional counseling, is conducted. The program acquaints young people

interested in career scientific research opportunities with the work being done

at NBS. One of the purposes of the program is to help in preparing talented students for scientific careers. The students participating in the program come from schools throughout the country; many of the participants in the program are graduate students. In collaboration with the National Research Council, the Graduate School

offers postdoctoral resident research associateships to young scientific in- vestigators of unusual ability and promise of becoming creative leaders in basic research in the various branches of the physical and mathematical

sciences. While acquiring basic knowledge, they have opportunities to develop new scientific approaches and laboratory skills, and thus advance

scientific knowledge. Twenty new Research Associateships (tenable at both

the Washington and Boulder Laboratories) are open each year. During

1964 the following young men were selected and served : Walter Braun, John

M. Crissman, Richard A. Durst, Clyde K. Edmiston, Lewis J. Fetters, Fred

Gross, David L. Hogenboom, Marcel Holberstadt, Arthur Hyman, William

H. Kirchhoff, John E. Lagnese, Theodore E. Madey, Roland J. Miech, Raymond D. Mountain, Ralph D. Nelson, Jr., Paul Peyser, Mark Sharnoff, and

John T. Yates, Jr. Scientific staff meetings, held weekly from September through May, are

also included in the Bureau's educational program. The staff meetings are

of a less specialized nature than colloquia and seminars offered in the Graduate School program. They are open to all professional staff members

of the Bureau and to scientific personnel from neighboring laboratories. Visiting Scientists. The Bureau encourages distinguished scientists to spend their sabbatical years, summer vacations, or other extended periods at the Bureau. Such a program increases the Bureau's ties with the Nation's

universities and provides a continuing influx of new ideas into the Bureau's programs. To increase the flexibility and usefulness of the visiting scientist program, the Bureau is seeking legislation that will provide selective pro- cedures making it possible to reimburse visiting scientists for the necessary

travel and transportation of household effects. 245
The largest visiting scientist program at the Bureau is at the Joint Institute for Laboratory Astrophysics; during the past year 18 scientists were involved

in the JILA program. In other parts of the Bureau there were 30 visiting

scientists—9 in Washington and 21 in the Boulder Laboratories.

3.7. PUBLICATIONS* AND PATENTS

Publications in the Bureau's Series

Journal of Research. Contains full research papers, including laboratory data, experi- mental procedures, and theoretical and mathematical analyses. Advances in measure- ment standards and techniques . . . physical constants . . . properties of materials . . . instrumentation . . . radio propagation.

The Journal is published in four separate sections . . . A. Physics and Chemistry, issued six times a year. Annual subscription: Domestic,

$4; foreign, $4.75; single copy, 70 cents. B. Mathematics and Mathematical Physics, issued quarterly. Annual subscription:

Domestic, $2.25; foreign, $2.75; single copy, 75 cents. C. Engineering and Instrumentation, issued quarterly. Annual subscription: Domestic,

$2.25; foreign, $2.75; single copy, 75 cents. D. Radio Science (formerly Radio Propagation), issued monthly. Annual subscription: Domestic, $9; foreign, $11.50; single copy, $1.00. Volume 67A (Phy«. and Chem.), No. 4 (July-Aug. 1963) Symmetry splitting of equivalent sites in oxide crystals and related mechanical effects.

J. B. Wachtman, Jr., H. S. Peiser, and E. P. Levine. Relaxation modes for trapped crystal point defects. A. D. Franklin. A note on the galvanomagnetic and thermoelectric coefficients of tetragonal crystalline materials. W. C. Hernandez, Jr., and A. H. Kahn.

Photolytic behavior of silver iodide. G. Burley. Correlation of muscovite sheet mica on the basis of color, apparent optic angle, and

absorption spectrum. S. Ruthberg, M. W. Barnes, and R. H. Noyce.

Thermodynamic properties of magnesium oxide and beryllium oxide from 298 to 1,200 °K. A. C. Victor and T. B. Douglas. Heat exchange in adiabatic calorimeters. E. D. West.

Preparation of anhydrous single crystals of rare-earth halides. N. H. Kiess. A phase study of the system: oxalic acid/acetic acid/water; its significance in oxalic acid crystal growth. J. Strassburger and J. L. Torgesen. Wavelength calibrations in the far infrared (30 to 1000 microns). K. N. Rao, R. V. de Vore, and E. K. Plyler. On the fourth order Hamiltonian of an asymmetric rotor molecule of orthorhombic symmetry. W. B. Olson and H. C. Allen, Jr. Measurement of the thickness and refractive index of very thin films and the optical properties of surfaces by ellipsometry. F. L. McCrackin, E. Passaglia, R. R. Stromberg, and H. L. Steinberg. Color phenomena associated with energy transfer in afterglows and atomic flames. A. M. Bass and H. P. Broida. Volume 67A (Phys. and Chem.), No. 5 (Sept.-Oct. 1963) Reduction of space groups to subgroups by homogeneous strain. H. S. Peiser, J. B. Wachtman, Jr., and R. W. Dickson. High-temperature thermodynamic functions for zirconium and unsaturated zirconium

hydrides. T. B. Douglas. Heat of oxidation of aqueous sulfur dioxide with gaseous chlorine. W. H. Johnson and

J. R. Ambrose.

Thickness of adsorbed polystyrene layers by ellipsometry. R. R. Stromberg, E. Passaglia, and D. J. Tutas. Melting temperature and change of lamellar thickness with time for bulk polyethylene.

J. J. Weeks.

Precise coulometric titrations of ,potassium dichromate. G. Marinenko and J. K. Taylor. Publications for which a price is indicated are available by purchase from the Super- intendent of Documents, U.S. Government Printing Office, Washington, D.C., 20402 (for- eign postage, one-fourth additional). Reprints from outside journals and the NBS Journal

of Research may often be obtained directly from the authors. 246
Resolution limits of analyzers and oscillatory systems. E. L. R. Corliss. Synthesis, purification, and physical properties of seven twelve-carbon hydrocarbons.

T. W. Mears, C. L. Stanley, E. L. Compere, Jr., and F. L. Howard.

Reactions of polyflurobenzenes with nucleophilic reagents. JL. A. Wall, W. J. Pummer,

J. E. Fearn, and J. M. Antonucci. Volume 67A (Phys. and Chem.), No. 6 (Nov.-Dec. 1963)

Analysis of the spectrum of neutral atomic bromine (Br i) . J. L. Tech.

Matrices of spin-orbit interaction in the electron configuration np

2 n p and rip* n' p. J.L. Tech. A study of the gas-stabilized arc as an emission source for the measurement of oscillator strengths. Determination of some relative ^/-values for Fe I. M. Margoshes and B. F. Scribner. Tritium-labeled compounds. IX. Determination of isotope effects in reactions yielding

water-* from nonvolatile reactants. Oxidation of aldoses-/-* with iodine. H. S. Isbell and L. T. Sniegoski. Buffer solutions of potassium dihydrogen phosphate and sodium succinate at 25° C. M.

Paabo, R. G. Bates, and R. A. Robinson.

Recalibration of the NBS glass standards of spectral transmittance. H. J. Keegan, J. C.

Schleter, and M. A. Belknap. Thermal behavior of muscovite sheet mica. S. Ruthberg.

Absolute configuration and chemical topology. S. J. Tauber.

Reversibility of polyester adsorption on glass. R. R. Stromberg: and W. H. Grant. Chemical purity by dielectric cryometry. G. S. Ross and L. J. Frolen. Adsorption, desorption, resorption. W. V. Loebenstein. Color phenomena in polymer fracture. S. B. Newman and I. Wolock.

Volume 68A (Phys. and Chem.), No. 1 (Jan.-Feb. 1964)

Fast neutron dose measurements for a D-D source in water. W. B. Beverly and V.

Spiegel, Jr. X-ray spectrometric analysis of noble metal dental alloys. B. W. Mulligan, H. J. Caul,

S. D. Rasberry, and B. F. Scribner. The first spectrum of manganese, Mn I. M. A. Catalan, W. F. Meggers, and 0. Garcia- Riquelme.

Transition probabilities of forbidden lines. R. H. Garstang. Franck-Condon factors to hi^h vibrational quantum numbers ITT; CN. R. W. Nicholls. Infrared absorption spectrum of nitrous oxide (N2 0) from 1830 cm"1 to 2270 cm"1

. E. K. Plyler, E. D. Tidwell, and A. G. Maki. An absolute light scattering photometer: II. Direct determination of scattered light from solutions. D. Mclntvre. High pressure microscopy of the silver and cuprous halides. A. Van Valkenburg.

Lattice parameters and lattice energies of high-pressure polymorphs of some alkali halides. C. E. Weir and G. J. Piermarini. Calculation of the higher order dipole-dipole effect in paramagnetic crystals. P. H. E. Meijer. Second and third virial coefficients for hydrogen. R. D. Goodwin, D. E. Diller, H. M.

Roder, and L. A. Weber.

Heats of solution, transition, and formation of three crystalline forms of metaboric

acid. M. V. Kilday and E. J. Prosen. Volume 68A (Phys. and Chem.), No. 2 (Mar.-Apr. 1964)

Tritium-labeled compounds X. Isotope effects in the oxidation of aldoses-7-f with bro- mine. H. S. Isbell and L. T. Sniegoski. Thermal degradation of fractionated high and low molecular weight polyisobutylene. D. Mclntyre, J. H. O'Mara, and S. Straus. Ionization constants of the six dichloroanilines and the six dichlorophenols in aqueous

solution at 25° C. R. A. Robinson.

Stereoregularity in ionic polymerization of acenaphthylene. V. M. Story and G.

Canty.

Dielectric behavior of the film formed on mica cleaved in moist air. S. Ruthberg and

L. Frenkel. On the measurement of dielectric losses and surface conductivity of dielectrics in parallel plane test capacitors. L. Frenkel. Polymorphism of bismuth sesquioxide. I. Pure Bi203 . E. M. Levin and R. S. Roth. Polymorphism of bismuth sesquioxide. II. Effect of oxide additions on the poly- morphism of Bi;03 . E. M. Levin and R. S. Roth. Second spectrum of tungsten ( Wn) . D. D. Laun. 756-224 0—65 17 247
Volume 68A (Phys. and Chem.), No. 3 (May-Juno 1964)

Compressibility of natural rubber at pressures below 500 kg/cm2

. L. A. Wood and G. M. Martin. A copolymer with lamellar morphology. R. K. Eby.

Variation of glass temperature with pressure in polypropylene. E. Passaglia and G. M. Martin. Perfluorophenyl ether and related polymers. W. J. Pummer and L. A. Wall.

Cyclic polyhydroxy ketones II. xv/o-Trihydroxycyclohexenediolic acid and keto-inositols. A. J. Fatiadi and H. S. Isbell. Tritium-labeled compounds. XI. Mechanism for the oxidation of aldehydes and al- doses-/-i with sodium chlorite. H.S. Isbell and L. T. Sniegoski.

Medium effects on the dissociation of weak acids in methanol-water solvents. E. E. Sager, K. A. Robinson, and R. G. Bates.

Crystallization of anhydrous copper sulfate from sulfuric acid—ammonium sulfate mixtures. P. M. Gruzensky.

Detection of lattice deformation and recovery in epsilon phase silver-tin alloys. R. M.

Waterstrat and G. E. Hicho. Vapor pressures of ruthenium and osmium. N. J. Carrera, R. F. Walker, and E. R.

Plante. The 0-2 transition of CO in condensed oxygen, nitrogen, and argon. S. Abramowitz

and H. P. Broida. Volume 67B (Math, and Math. Phys.), No. 3 (July-Sept. 1963) Remarks on hypo-elasticity. C. Truesdell. Error bounds in the pointwise approximation of solutions of elastic plate problems.

J. H. Bramble and L. E. Payne.

Effect of error in measurement of elastic constants on the solutions of problems in classical elasticity. J. H. Bramble and L. E. Payne.

Eigenfunctions of the f configuration. J. C. Eisenstein. Zeroes of first derivatives of Bessel functions of the first kind, Jn '(x), 21 — n — 51, O^x^ 100. G. W. Morgenthaler and H. Reismann.

Volume 67B (Math, and Math. Phys.), No. 4 (Oct.-Dec. 1963) Zonal harmonic perturbations of an accurate reference orbit of an artificial satellite.

J. P. Vinti. Optimal periodic inspection programs for randomly failing equipment. G. H. Weiss. An analysis of pedestrian queueing. G. H. Weiss.

Solutions of the equation VIX +- Vx -\-Kx ne* = O. E. A. Kearsley. X On the graphs of finite idempotent Boolean relation matrices. D. Rosenblatt. Volume 68B (Math, and Math. Phys.), No. 1 (Jan.-Mar. 1964) A note on a generalized elliptic integral. G. H. Weiss. An asymptotic expansion for the multivariate normal distribution and Mills' ratio. H. Ruben.

Calculation of certain multiple generating functions. G. H. Weiss. Some infinite sums involving zeros of /o(x) • L. F. Epstein.

Optimal matchings and degree-constrained subgraphs. A. J. Goldman. - Effects of a distribution on gap acceptance functions on pedestrian queues. G. H.

Weiss. Gaussian wave functions for polyatomic molecules: integral formulas. M. Krauss. Volume 68B (Math, and Math. Phys.), No. 2 (Apr.-June 1964) Determinations based on duplication of readings. J. A. Speckman.

General application of Youden's rank sum test for outliers and tables of one-sided per- centage points. T. A. Willke. A generalization of Rennie's inequality. A. J. Goldman. On the asymptotic joint normality of quantiles from a multivariate distribution. L. Weiss.

Fitting y =fix when the variance depends onx. J. Van Dyke.

Existence of k-edge connected ordinary graphs with prescribed degrees. J. Edmonds.

Inequalities for solutions of mixed boundary value problems for elastic plates. J. H. Bramble and L. E. Payne. Volume 67C (Eng. and Instr.), No. 3, (July-Sept. 1963) Apparatus for the detection of piezoelectric coupling. L. Frenkel. Large aperture interferometers with small beam dividers. J. B. Saunders. 248
A far-infrared vacuum grating spectrometer. L. R. Blaine. Relation of emittance to other optical properties. J. C. Richmond.

Minimization of the arrestment error in one-pan, two-knife balance systems. H. A. Bowman and H. E. Aimer.

Determination of residual thiosulfate in processed film. C. I. Pope.

Drag compensation and measurement with manned satellites: feasibility study. R. M.

Langer and J. P. Vinti. Surface flame propagation on cellulosic materials exposed to thermal radiation. D. Gross and J. J. Loftus.

Parallel reversible permeability measurement techniques from 50 kc/s to 3 Gc/s. C. A. Hoer and R. D. Harrington. Volume 67C (Eng. and Instr.), No. 4 (Oct.-Dec. 1963)

Limitations on electron beam density of unipotential electron guns at low voltages. J. A. Simpson and C. E. Kuyatt. New radiofrequency mass spectrometer having high duty cycle. R. M. Mills. A power-series buildup factor formulation. Application to rectangular and off-axis disk

. source problems. J. H. Hubbell. An alinement interferometer. J.B.Saunders.

Determination of optical path difference for a photographic objective. F. E. Washer

and W. R. Darling.

Development of filters for a thermoelectric colorimeter. S. H. Emara and R. P. Teele. Application of air bearings to an electrodynamic vibration standard. T. Dimoff and

B. F. Payne.

Leak-resistant rotation seal for vacuum applications. F. L. Howard.

Studies on the tungsten-rhenium thermocouple to 2000 °C. D. B. Thomas.

Volume 68C (Eng. and Instr.), No. 1 (Jan.-Mar. 1964) A Fabry-Perot spectrometer for high-resolution spectroscopy and laser work. K. D. Mielenz, R. B. Stenhens, and K. F. Nefflen. A variable impedance power meter, and adjustable reflection coefficient standard. G. F. Engen.

A laser with a multihole diaphragm. T. Morokuma.

Principles of cryometric impurity determination as applied to samples of small sizes. C. P. Saylor and G. S. Ross. Reference tables for thermocouples of iridium-rhodium alloys versus iridium. G. F. Blackburn and F. R. Caldwell. Volume 68C (Eng. and Instr.), No. 2 (Apr.—June 1964) Fringe pattern of an oscillating Fabry-Perot interferometer. K. D. Mielenz. Interferometer for testing extended surfaces such as surface plates and precision ways. J. B. Saunders and J. V. McDermott.

Ferrimagnetic resonance in polycrystalline ferrite and garnet disks at L-band fre- quencies. W. E. Case, R. D. Harrington, and L. B. Schmidt. Changes in the influence of atmospheric humidity during fatigue of an aluminum

alloy. J. A. Bennett. The theory of a stable high-speed externally pressurized gas-lubricated bearing. H.

Sixsmith and W. A. Wilson.

Infrared spectra of asphalts: some aspects of the changes caused by photooxidation.

P. G. Campbell and J. R. Wright. Volume 67D (Radio Prop.), No. 3 (May-June 1963)

Effects of radio wave propagation through midlatitude 6300 A auroral arcs. J. R. Roach • Comparison of observed atmospheric radio refraction effects with values predicted

through the use of surface weather observations. B. R. Bean and G. D. Thayer.

Ionospheric scattering effects in long-distance propagation. H. A. Whale.

Concerning solutions of the VLF mode problem for an anisotropic curved ionosphere.

J. R. Wait. On the statistical theory of electromagnetic waves in a fluctuating medium (I). K.

Furutsu. Reception of skywave signals near a coastline. J. B. Andersen.

Analysis ?nd synthesis of nonuniform transmission lines or stratified layers. G. Latmiral, G. Franceschetti, and R. Vinciguerra. Resonant characteristics of a corrugated sphere. J. R. Wait and C. M. Jackson. Impedances of long antennas in air and in dissipative media. D. W. Gooch, C. W. Harrison, Jr., R. W. P. King, and T. T. Wu. 249
Reflection of VLF radio waves from an inhomogeneous ionosphere. Part I. Expomentially varying isotropic model. J. R. Wait and L. C. Walters. Volume 67D (Radio Prop.), No. 4 (July-Aug. 1963)

Influence of the lower ionosphere on propagation of VLF waves to great distances. J. R. Wait. Comments on a paper "Auroral Sporadic-^ Ionization" by R. D. Hunsucker and L. Owren. J. M. Bullen and G. A. M. King.

Reply to J. M. Bullen and G. A. M. King's "Comments on a paper 'Auroral Sporadic-^

Ionization' by Robert D. Hunsucker and Leif Owren." R. D. Hunsucker and L. Owren. Optimum reception pattern of the Beverage wave antenna at very low frequencies.

E. W. Seeley.

Effect of a dissipative medium of finite size on antenna measurement. K. Iizuka and

R. W. P. King. Some implications of aircraft interference patterns in troposcatter reception. J. A. Bradshaw.

Asymptotic behavior of the current on an infinite cylindrical antenna. K. S. Kunz. A dipole approximation of the backscattering from a conductor in a semi-infinite dis- sipative medium. M. B. Kraichman.

Small electric and magnetic antennas with cores of a lossy dielectric. J. Galejs. Volume 67D (Radio Prop.), No. 5 (Sept.-Oct. 1963)

Ionospheric VHF scattering near the magnetic equator during the International Geophysical Year. R. Cohen and K. L. Bowles. Radio pulse propagation by a reflection process at the lower ionosphere. J. R. Johler. Field of a horizontal magnetic dipole in the presence of a magnetoplasma halfspace. G. Tyras, A. Ishimaru, and H. M. Swarm.

Reflection of VLF radio waves from an inhomogeneous ionosphere. Part II. Perturbed

exponential model. J. R. Wait and L. C. Walters.

Collisional detachment and the formation of an ionospheric C region. E. T. Pierce. Magnetic torques and Coriolis effects on a magnetically suspended rotating sphere.

J. C. Keith. Radiation field characteristics of lightning discharges in the band 1 kc/s to 100 kc/s. W. L. Taylor.

Low-frequency radio propagation into a moderately rough sea. D. F. Winter. VLF superdirective loop arrays. E. W. Seeley. Curves of ground proximity loss for dipole antennas (a digest). L. E. Vogler and

J. L. Noble.

Observations and results from the "hiss recorder," an instrument to continuously observe

the VLF emissions. J. M. Watts, J. A. Koch, and R. M. Gallet. Volume 67D (Radio Prop.), No. 6 (Nov.-Dec. 1963) A radiometeorological study, part I. Existing radiometeorological parameters. J. A. Lane and B. R. Bean. A radiometeorological study, part II. An analysis of VHF field strength variations and

refractive index profiles. B. R. Bean, V. R. Frank, and J. A. Lane. A radiometeorological studv, part III. A new turbulence parameter. B. R. Bean, E. J. Dutton, J. A. Lane, and W. B. Sweezy.

Reflection of radio waves from undulating tropospheric layers. A. T. Waterman, Jr., and J. W. Strohbehn. Obiique propagation of groundwaves across a coastline—Part I. J. R. Wait. Oblique propagation of groundwaves across a coastline—Part II. J. R. Wait and C. M.

Jackson. On the index of refraction of air, the absorption and dispersion of centimeter waves by

gases. G. Boudouris. Translated from French bv G. W. Curtis. A numerical approach to the solution of radio diffraction problems. J. K. Hargreaves and S. Hargreaves.

Inversion of radiowave absorption data to establish ionospheric properties. I. Nondeviative absorption. A. D. Wheelon.

Radiation in a lossless maometo-ionic medium at frequencies high relative to the electron gyrofrequency. J. W. Marini. Radiation through cylindrical plasma sheaths. J. H. Harris. Chart for determining the effects of ionospheric tilts using an idealized model. T. A.

Croft and R. B. Fenwick.

Reflection of VLF radio waves from an inhomogeneous ionosphere. Part III. Exponential model with hyperbolic transition. J. R. Wait and L. C. Walters. Families of distributions for hourly median power and instantaneous power of received radio signals. M. M. Siddiqui and G. H. Weiss. 250
Statistical methods in radar astronomy. Determination of surface roughness. H. S. Hayre.

Electrical conductivity of the Great Lakes. L. H. Doherty.

Radio Sci. J. Res. NBS/USNC-URSI, Vol. 68D, No. 1 (Jan. 1964) Comparison of observed VLF attenuation rates and excitation factors with, theory. A. D. Watt and R. D. Croghan.

Field intensity measurements at 10.2 kc/s over reciprocal paths. J. C. Hanselman, C. J. Casselman, M. L. Tibbals, and J. E. Bickel. The propagation of VLF waves over distances between 1000 and 3000 km. B. Burgess. Some experimental results concerning nonreciprocal east-west VLF wave propagation.

B. Burgess. An experimental study of the phase stability of VLF signals. D. E. Hampton.

Some particular observations on diurnal phase variations of VLF transmission received

in Paris. B. Decaux and A. Gabry.

Periodic fading of VLF signals received over long paths during sunrise and sunset. D. D. Crombie.

Effects of wall perturbations in multimode waveguides. S. W. Maley and E. Bahar. VLF utilization at NASA satellite tracking stations. C. H. Looney, Jr. Long waves associated with disturbances produced in plasmas. H. Bremmer. Some remarks on the Watson transformation and mode theory. L. A. Berry. Concerning limitations and further corrections to geometric-optical theory for LF, VLF

propagation between the ionosphere and the ground. J. R. Johler. Some remarks on mode and ray theories of VLF radio propagation. J. R. Wait. Two-dimensional treatment of mode theory of the propagation of VLF radio waves.

J. R. Wait.

Reflection of electromagnetic waves from a lossy magnetoplasma. J. R. Wait and L. C. Walters. Propagation of ELF waves below an inhomogeneous anisotropic ionosphere. J. Galejs and R. V. Row. VLF propagation under the ionosphere in the lowest mode of horizontal polarization. H. A. Wheeler.

Propagation of VLF waves under disturbed conditions. B. Burgess. VLF disturbances caused by trapped beta-rays from the decay of neutrons produced in high-altitude nuclear explosions. A. J. Zmuda, B. W. Shaw, and C. R. Haave. VLF anomalies observed at State College, Pa., during the U.S. 1962 high-altitude nuclear

tests. C. F. Sechrist. Radio Sci. J. Res. NBS/USNC-URSI, Vol. 68D, No. 2 (Feb. 1964) Generation of an electromagnetic pulse by an expanding plasma in a conducting half- space. A. P. Stogryn and R. N. Ghose. Impedance of a monopole antenna with a radial-wave ground system on an imperfectly

conducting half-space, part II. S. W. Maley and R. J. King.

Capacitor type biconical antennas. J. Galejs. Simulated angular response patterns for transhorizon propagation. J. W. Strohbehn and

A. T. Waterman, Jr. Radio-star scintillations from ionospheric waves. J. W. Warwick.

Ionosonde studies of some chemical releases in the ionosphere. J. W. Wright.

Diurnal changes of transmission time in the Arctic propagation of VLF waves. W. T. Blackband.

Geometrical optics convergence coefficient for the whistler case. J. H. Crary. Comments on a paper, "Collisional Detachment and the Formation of an Ionospheric,"

by E. T. Pierce. H. R. Arnold. The quasi-longitudinal approximation in the generalized theory of radio wave absorption. R. F. Benson.

Diurnal phase variation of VLF waves at medium distances. H. Volland. Application of diffractions by convex surfaces to irregular terrain situations. H. T

Dougherty and L. J. Maloney.

Effect of lossy earth on antenna gain. R, J. Coe and W. L. Curtis. Propagation of radio waves with frequency 99.9 Mhz as a function of the vertical struc- ture of the atmosphere derived from daily radiosonde observations. G. P. A. Braam.

Radio Sci. J. Res. NBS/USNC-URSI, Vol. 68D, No. 3 (Mar. 1964) An interpretation of rapid changes in the phase of horizontally polarized VLF waves

recorded at night over a short path in the Southwestern United States. E. E. Gossard and M. R. Paulson. 251
Precise phase and amplitude measurements on VLF signals propagated through the Arctic zone. F. H. Reder, C. J. Abom, and G. M. R. Winkler. On the long term phase stability of the 19.8 kc/s signal transmitted from Hawaii, and

received at Boulder, Colorado. A. H. Brady.

Oblique propagation of groundwaves across a coastline—Part III. J. R. Wait. Impedance of a monopole antenna with a radial-wire ground system on an imperfectly

conducting half space—Part III. S. W. Maley and R. J. King.

A simplified theory of diffraction at an interface separating two dielectrics. J. Kane and

S. N. Karp.

Variational solution for the admittance of a long cylindrical antenna. R. A. Hurd. Admittance of annular slot antennas radiating into a plasma layer. J. Galejs.

Propagation of plasma waves in a "spoke-wheel" magnetic field. R. L. Liboff. An experimental investigation of signal strength in the area around a transmitter's anti- pode. R. M. Pipp and J. B. Webster.

Relationship between simultaneous geomagnetic and ionospheric oscillations. H. Rish- beth and 0. K. Garriott. Radio Sci. J. Res. NBS/USNC-URSI, Vol. 68D, No. 4 (Apr. 1964) Some basic microwave phase shift equations. R. W. Beatty. A light-modulated scattering technique for diffraction field measurements. A. M.

Vural and D. K. Cheng.

Radiation from an aperture in a coated plane. C. M. Knop and G. I. Cohn. Impedance of a cylindrical dipole having a sinusoidal current distribution in a homogeneous anisotropic ionosphere. W. S. Ament, J. C. Katzin, M. Katzin, and B. Y.-C. Koo.

Propagation of electromagnetic waves through a continuously varying stratified ani- sotropic medium. G. H. Price. Lunar semi-diurnal tides in h'F and their influence on transequatorial radio propagation. J. A. Thomas. Some statistical parameters related to the Nakagami-Rice probability distribution. W.

R. Burns. The U.S. National Committee Report for Commission 6 of URSI. Subcommission 6.3, Electromagnetics.

Radio Sci. J. Res. NBS/USNC, Vol. 68D, No. 5 (May 1964) URSI National Committee Report, XIV General Assembly, Tokyo, September 1963: Commission 1. Radio measurement methods and standards. Commission 2. Tropospheric radio propagation.

Commission 3. Ionospheric radio. Commission 4. Magnetospheric radio. Commission 5. Radio and radar astronomy. Commission 7. Radio electronics. Radio Sci. J. Res. NBS/USNC-URSI, Vol. 68D, No. 6 (June 1964)

Electrical properties of sea ice at 0.1 to 30 Mc/s. F. L. Wentworth and M. Cohn. ELF and VLF waves below aninhomogeneous anisotropic ionosphere. J. Galejs.

The effects of a small local change in phase velocity on the propagation of a VLF

radio signal. D. D. Crombie.

Auroral-zone absorption effects on an HF arctic propagation path. R. D. Hunsucker.

Amplitude-probability distribution of atmospheric radio noise. P. Beckmann. An approximate method for computing diffraction patterns caused by ionospheric irregularities. R. Gagnon.

Wave propagation in stratified random media. Y. M. Chen. Radar scattering from coated perfect conductors: application to the semi-infinite cone and use of exact eikonal. H. Uberall. Technical News Bulletin. This monthly publication summarizes the current research, development, and test activities of the Bureau. The articles are brief, with emphasis on the results of research and their significance, chosen for their importance to other

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Central Radio Propagation Laboratory Ionospheric Predictions: This is a monthly

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Abramowitz, S., Broida, H. P., v3 vibration in condensed oxygen, nitrogen, and argon,

J. Chem. Phys. 39, No. 9, 2383-2384 (Nov. 1, 1964)

.

Agy, V., Davies, K., Effects of magnetic disturbance as noted on oblique incidence iono- grams, AGARDograph 59, The Effect of Disturbances of Solar Origin on Communications, ed. G. J. Gassmann, pp. 167-176 (Pergamon Press Inc., London, England,

1963). Akima, H., Signal-to-noise characteristics of some typical systems and their comparisons,

Proc. Mountain States Navy Research and Development Clinic, Raton, N. Mex., Sept. 28-29, 1961, pp. A125-A130 (Raton, Communication and Electronics Foundation,

1963). Akima, H., The error rate in a multiple frequency shift system and the output signal noise ratio in a frequency modulation and pulse code modulation frequency shift system, Proc. IEE (London) III, No. 3, 547-555 (Mar. 1964). Akima, H., Theoretical studies on signal-to-noise characteristics of an FM system, IEE Trans. Space Electron. Telemetry SET-9, No. 4, 101-108 (Dec. 1963)

.

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.

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*For completeness, a few references to publications issued prior to July 1963 are included. 256
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Ambler, E., Dove, R. B., Kaeser, R. S., A He3 cryostat for performing experiments with

oriented nuclei (Proc. 1962 Cryogenic Engineering Conf.), Book, Advances in Cryogenic Engineering 8, Paper H-2, 443-445 (Plenum Press, Inc., New York, N.Y., 1963) . Andersen, H. C, Oppenheim, I., Shuler, K. E., Exact conditions for the preservation of a canonical distribution in a Markovian relaxation process, J. Math. Phys. 5, 522-536

(Apr. 1964). Andersen, K., Shuler, K. E., On the relaxation of the hard sphere Rayleigh and Lorentz

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Antonucci, J. M, Synthesis of perfluorostyrene and (2,2-difluorovinyl) perfluorobenzene

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Armstrong, G. T., Calorimetry (report on Calorimetry Conf.), Science 143, No. 3602, 158-163 (Jan. 10, 1963) ; Phys. Today 17, No. 2, 50-54 (Feb. 1964)

Armstrong, G. T., The calorimeter and its influence in the development of chemistry, J. Chem. Ed. 41, No. 6, 297-307 (June 1964)

Armstrong, G. T., Vapour pressure, Encyclopaedic Dictionary of Physics 7, 586-587

( Pergamon Press Inc., New York, N.Y., 1962 )

Ami, H. T., Discussion of paper on "Predicting compressive strength from the properties

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Ausloos, P., Gorden, R., Jr., Lias, S. G., Effect of pressure in the radiolysis and photolysis

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Ausloos, P., Lias, S. G., Gorden, R., Jr., Effect of additives on the ionic reaction mecha- nism in the radiolysis of methane, J. Chem. Phys. 39, No. 12, 3341-3348 (Feb. 1964).

Ausloos, P., Lias, S. G., Sandoval, I. B., The gas phase radiolysis of propane. The

effect of pressure and added inert gases, Discussions Faraday Soc. No. 36, 66-74

(Mar. 1964). Auterman, J. L., Remarks presented at panel discussion on modulation, Proc. Mountain

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Malitson, I. H., Refractive properties of barium fluoride, J. Opt. Soc. Am. 54, No. 5, 628-632 (May 1964).

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Megill, L. R., Carleton, N. P., Excitation by local electric fields in the aurora and airglow,

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Meshkov, S., Snow, G. A., Yodh, G. B., Comparison of a new SU3 prediction with ex- periment, Phys. Rev. Letters 12, No. 3, 87-92 (Jan. 20, 1964). 270
Meyer-Arendt, J. R., Frostbite: signs, prevention, and treatment, Trail and Timberline,

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Meyer-Arendt, J. R., Herrick, R. B., Emmanuel, C. B., Determination of optical thickness

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Michaelis, R. E., Summary of Sessions I and II of the Symposium on X-ray and Electron Probe Analysis, ASTM Spec. Tech. Publ. 349 (1963)

Mielenz, K. D., Note on "Interferometric measurement of vibration amplitudes," Appl.

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Mies, F. H., Effects of anharmonicity on vibrational energy transfer, J. Chem. Phys. 40,

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Madden, R. P., Codling, K., Recently discovered autoionizing states of krypton and xenon

in the X 380-600A, J. Opt. Soc. Am. 54, No. 2, 268-269 ( Feb. 1964)

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Madorsky, S. L., Thermal Degradation of Organic Polymers, Book, 315 pages (Inter- science Publ., Inc., New York, N.Y., 1964)

.

Maeda, H., Matsushita, S., Shirgaokar, M., Yashuhara, M., On the geomagnetic effect of the Starfish high-altitude nuclear explosion, J. Geophys. Res. 69, No. 5, 917-945

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Maienthal, E. J., Taylor, J. K., Separation and determination of zirconium in zirconia

yttria mixtures by precipitation with cupferron, Anal. Chem. 36, No. 7, 1286-1287

(June 1964). Maki, A. G., Blaine, L. R., Infrared spectra of HCN from 2000 to 3600 cm

-1

, J. Mol.

Spectry. 12, No. 1, 45-68 (Jan. 1, 1964)

.

Malitson, I. H., A redetermination of some optical properties of calcium fluoride, Appl. Opt. 2, No. 11, 1103-1107 (Nov. 1963).

Malitson, I. H., Refractive properties of barium fluoride, J. Opt. Soc. Am. 54, No. 5, 628-632 (May 1964).

Malitson, I. H., Cleek, G. W., Stavroudis, O. N., Sutton, L. E., Infrared dispersion of some oxide glasses, Appl. Opt. 2, No. 7, 741-747 (July 1963)

.

Mandel, J., Estimation of weighting factors in linear regression and analysis of vari- ance, Technometrics 6, No. 1, 1-25 (Feb. 1964)

.

Mandelkern, L., Canty, G., Diorio, A. F., The melting (contraction) and recrystalliza- tion of fibrous proteins in nonaqueous media, J. Phys. Chem. 67, No. 12, 2882-2884

(Dec. 1963). Mann, D. E., White, D., Seshadri, K. S., Dever, D. F., Linevsky, M. J., The infrared

spectra, structures and thermodynamics of gaseous LiO, Li2 0, and Li 2 02 , J. Chem.

Phys. 39, No. 10, 2463-2473 (Nov. 1963)

.

Mann, W. B., Medlock, R. W., Yura, O., A recalibration of the National Bureau of Standards tritiated water standard, Intern. J. Appl. Radiation Isotopes 15, No. 6, 351-361 (June 1964). Marcus, M., Mine, H., The Pvthagorean theorem in certain symmetry classes of tensors, Trans. Am. Math. Soc. 104, No. 3. 510-515 (Sept. 1962)

.

Marshak, H., Wagner, R., Miller, P. P., Tamura, T., The interaction of 350 keV

polarized neutrons with oriented Ho105 nuclei, Phys. Letters 10, No. 3, 316 (June

15,1964).

Martin, G. M., Mandelkern, L., The effect of hydrostatic pressure on the crystallization kinetics of natural rubber, J. Appl. Phys. 34, No. 8, 2312-2317 (Aug. 1963). Martin, W. C, Low energy levels of neutral cerium (Ce i), J. Opt. Soc. Am. 53, No. 9, 1047-1050 (Sept. 1963). Marton, L.. Marton, C, Characteristics energy losses of electrons in solids, book, Actions Chimiques et Biologiques des Radiations, Ch. IV, pp. 260-281 (Mason et C

le Editeurs, Paris, France, 1964). Mason, H. L., Analog simulation of zone melting, Instr. Control Systems 37, No. 1, 121-123 (Jan. 1964)

.

Matsushita, S., Ionospheric storms, Proc. URSI XlVth General Assembly, Tokyo,

Japan, Sept. 1963, XIII, 169-180 (1964). Maximon, L. C, Isabelle, D. B., Radiative tail in elastic electron scattering, Phys. Rev. Letters 133, No. 5B, 1344-1350 (Mar. 9, 1964)

.

Mazur, J., Statistical thermodynamics of the lattice model of a polymer molecule,

J. Chem. Phys. 40, No. 4, 1001-1007 (Feb. 1964). Mazur, J., Rubin, R. J., Coefficient of thermal expansion and Young's modulus for a one-dimensional model of a solid, Am. J. Phys. 34, No. 11, 835-836 (Nov. 1963). Meggers, W. F., Review of reviews of atomic spectroscopy, Appl. Opt. 2, No. 7, 657-663

(July 1963).

Megill, L. R., Carleton, N. P., Excitation by local electric fields in the aurora and airglow,

J. Geophys. Res. 69, No. 1, 101-122 (Jan. 1, 1964)

.

Mendlowitz, H., Transition array for d?d2p: vanadium, Astrophys. J. 138, No. 4, 1277-1296

(Nov. 15, 1963).

Merrill, R. G., Lawrence, R. S., Roper, N. J., Synoptic variations and vertical profiles of large-scale ionospheric irregularities, J. Geophys. Res. 68, No. 19, 5453-5459 (Oct. 1, 1963). Meshkov, S., Comparison of experimental reaction cross sections with various relations obtained from SU3 , Proc. Conf. Symmetry Principles at High Energy, Coral Gables,

Fla., Jan. 30, 1964, pp. 104-126 ( 1964)

.

Meshkov, S., Snow, G. A., Yodh, G. B., Comparison of a new SU3 prediction with ex- periment, Phys. Rev. Letters 12, No. 3, 87-92 (Jan. 20, 1964). 270
Meyer-Arendt, J. R., Frostbite: signs, prevention, and treatment, Trail and Timberline,

p. 3 (Jan. 1964). Meyer-Arendt, J. R., Herrick, R. B., Emmanuel, C. B., Determination of optical thickness

gradients from a far distance, J. Opt. Soc. Am. 53, 1344 (1963)

Meyerson, M. R., Pennington, W. A., Gage blocks of superior stability. II. Fully hard- ened steels. Am. Soc. Metals Trans. Quart. 57, No. 1, 3-25 (Mar. 1964)

Meyerson, M. R., Sola, M. S., Gage blocks of superior stability. III. The attainment

of ultrastability, Am. Soc. Metals Trans. Quart. 57, No. 1, 164-185 (Mar. 1964).

Michaelis, R. E., Report of Committee E-2 on Emission Spectroscopy, Am. Soc. Testing Mater. Proc. 63, 456 (1963).

Michaelis, R. E., Report on standard samples, reference samples, and high-purity materials for spectrochemical analysis, ASTM Spec. Tech. Publ. 58—E (1963)

Michaelis, R. E., Suggested practices for establishing sampling and sample preparation

techniques in spectrochemical analysis, book, Methods for Emission Spectrochemical

Analysis, 4th ed., pp. 256-259 (American Society for Testing Materials, Phila., Pa., Feb. 1964).

Michaelis, R. E., Summary of Sessions I and II of the Symposium on X-ray and Electron Probe Analysis, ASTM Spec. Tech. Publ. 349 (1963)

Mielenz, K. D., Note on "Interferometric measurement of vibration amplitudes," Appl.

Opt. 3,542 (Apr. 1964). Mies, F. H., Effects of anharmonicity on vibrational energy transfer, J. Chem. Phys. 40,

No. 2, 523-531 (Jan. 1964).

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.

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Wait, J. R., The theory of an antenna over an inhomogeneous ground plane, book,

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.

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.

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.

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.

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.

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.

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.

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Patents The following U.S. Patents have been granted to NBS inventors; assigned (or licensed as indicated) to the United States of America, as represented by the Secretary

of the department noted in parentheses:

Lloyd, Edward C; Johnson, Daniel P., and Hutton, Ulric O., No. 3,100,912, August 20, 1963. Dual-Wedge High-Pressure Apparatus. (Commerce)

Hefley, Gifford; Linfield, Robert F.; Davis, Thomas L., and Doherty, Robert H., No.

3,106,709, October 8, 1963. Atmospherics Direction Finding System. (Air Force)

Hogue, Ephraim W., No. 3,107,308, October 15, 1963. Transistorized Magnetic Amplifier and Amplifier-Complementer for Digital Computer Circuits. (Air Force)

Pummer, Walter J., and Wall, Leo A., No. 3,109,855, November 5, 1963. Tetrakis- [Pentafluorophenyl] -Silane and Method of Making the Same. (Navy)

Holt, Arthur W., No. 3,112,453, November 26, 1963. Diode Amplifier. (Navy)

Macurdy, Lloyd B., No. 3,112,808, December 3, 1963. Balance Beam. (Commerce)

Ruehrwein, Robert A., No. 3,113,914, December 10, 1963. Process for Making Ozone. (Army)

Stern, Joshua, No. 3,117,491, January 14, 1964. Information Retrieval Apparatus.

(Commerce)

Skramstad, Harold K., No. 3,119,928, January 28, 1964. Components for a Combined

Digital-Analog Differential Analyzer. ( Commerce

)

Cleek, Given W., No. 3,119,703, January 28, 1964. Infrared Transmitting Glasses. (Navy)

Hefley, Gifford; Linfield, Robert F.; Doherty, Robert H., and Berger, Earl L., No.

3,122.076, February 25, 1964. Intermittent Action Camera. (Air Force) Huntoon, Robert D., No. 3,123,821, March 3 1964. Proximity Fuse with Two Oscillators. (Army)

Hermach, Francis L. No. 3,124,747, March 10, 1964. Coaxial Thermal Voltage Converter. (Commerce)

Taylor, John K., and Smith, Stanley W., No. 3,131,348, April 28 1964. Coulometric Titra- tion Coulometer. (Commerce)

Jacobs, Robert B. ; Mullen, Lewis O. ; Van Gundy, Donald A. ; Richards, Robert J. and

Steward, Willis G., No. 3,137,143, June 16, 1964. Condensing Vacuum Insulation (Army)

281

U. S. GOVERNMENT PRINTING OFFICE :1965 O - 756-224






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