bluuebunny/crossref_metadata_2025 huggingface dataset:
Computer Program to Facilitate Design of Wire Wound, Pulsed Field Coils
Authors: Segal Gail P.
Published: February 2005

This paper presents the formulas necessary to design wire wound, pulsed field coils to produce an initial time rate of change of magnetic field, Ḣ0≡Ḣ (t=0), the formulas being written in terms of the coil geometry, its wire size, and the applied voltage V. Since so many combinations of these parameters can result in the desired value of Ḣ0, the formulas for H and Ḣ0 were incorporated into a computer program to facilitate selection of the ``best combination'' of parameters. Economic or experimental constraints are easily handled by the program. The program is able to predict the performance of a pulsed field coil to an accuracy of better than 1%.
Extension of Scherzer's Theorem
Authors: Moses Ronald W.
Published: February 2005

A monochromatic, nonrelativistic system with electrostatic and/or magnetic quadrupole fields having common planes of optical symmetry is treated theoretically. It is proven that certain aperture aberration coefficients are positive definite when there is a real object and image in one or both of the optical symmetry planes. In a purely magnetic system which is doubly focusing and has a real object and image, all aperture aberration coefficients are positive definite. Conditions that imply nonzero aperture aberrations for systems with virtual objects and/or images are also given.
Generation of Cylindrically Symmetric Implosions
Authors: Bernstein David , Goettelman R. C.
Published: February 2005

An explosive configuration has been developed for going from a single initiation point to a cylindrically symmetric, converging detonation front. This technique utilizes the ``mousetrap'' concept but in a cylindrical geometry rather than the usual plane geometry. The mousetrap action results in the simultaneous initiation of the outer surface of an explosive cylinder 15.9 cm in diameter and 5 cm long. The breakout of the detonation front has been monitored as a function of axial position in a cylindrical hole 5 cm in diameter. The azimuthal simultaneity has been studied by monitoring the resultant collapse of a thin walled aluminum tube inside the explosive cylinder. Submicrosecond simultaneity was attained.
Sinusoidal Temperature Wave Generating System
Authors: Rigney D. A.
Published: February 2005

A method of generating and measuring sinusoidal temperature oscillations of variable amplitude is described, and typical applications are presented.
Mechanical System for Multiple Thin Film Deposition
Authors: Randlett M. R. , Stroberg E. H. , Chopra K. L.
Published: February 2005

A simple and versatile mechanical system, capable of allowing monitored deposition of sequential thin films on any one of the five substrates from any one of the five independent sources, and through any one of the five masks, is described. The vapor sources are moved by rotation. The substrates, masks, and the shutter are moved by sliding racks. All these movements are affected by one push-pull, rotary, and 60° cone feedthrough. Every component is easily removable for cleaning. The evaporation sources are shielded by removable chimneys. The electrical connection for resistive heating of the source is made by a uniquely designed roller bearing contact.
Large Aperture, High Efficiency Ion Detector
Authors: Gibbs Hyatt M. , Commins Eugene D.
Published: February 2005

A simple, highly efficient detector has been developed for negative ions that is similar to B. W. Ridley's for positive ions. The negative ions are accelerated to 10 keV, strike a Duralumin surface at 45° incident angle, and eject secondary electrons. These are in turn accelerated by 10 keV and focused crudely onto a plastic scintillator joined to an RCA 8575 photomultiplier tube. The detector has an entrance aperture of 5×5 cm, over which the sensitivity is uniform. The Duralumin surface requires no special preparation other than perfunctory initial cleaning, and the detector functions with excellent stability even in a rather poor vacuum (≈10−5 Torr). With appropriate voltage changes in the ion source the detector has been tested successfully for most of the positive alkali ions as well as the negative halogen ions F−, Cl−, Br−, and I−. The detector noise is a few counts per second at efficiencies exceeding 90% for all these ions, excluding grid losses.
Beam Steering with Quadrupole and with Rectangular Box Magnets
Authors: Draper James E.
Published: February 2005

The exact field configuration in the aperture of an asymmetrically excited electric or magnetic quadrupole lens is derived. The resulting effectiveness as a combined focusing and steering device for particle beams is analyzed, and the limitations are explored. Simple expressions are obtained for the steering effect. These results are compared to the effectiveness of a rectangular array of current sheets and iron as a steering device. The latter is shown to be superior in many cases.
Rocket Measurements of Faraday Rotation and Differential Absorption
Authors: Knoebel H. W. , Skaperdas D. O.
Published: February 2005

A system for high resolution measurements of Faraday rotation and differential absorption in the D region is described. Closed loop feedback between the rocket receiver and ground transmitter increases accuracy through the use of a null seeking technique which minimizes nonlinear receiver effects and transfers the differential absorption measurement to precision attenuators on the ground. Faraday rotation, which is superimposed on rocket roll, is separated from layer reflection, standing wave interference by increasing the effective roll rate through artificial rotation of the transmitter antenna produced by a 500 Hz difference frequency between the two oppositely polarized transmitted waves. Resolutions of 1° in Faraday rotation and 0.2 dB in differential absorption are obtained.
Elimination of Incoherent X Rays with Diffracted Beam Monochromators
Authors: Strong S. L. , Kaplow Roy
Published: February 2005

Bent and ground LiF crystal monochromators, placed after the specimen in x-ray diffraction experiments can remove nearly all of the incoherent (Compton) component with Cu Kα or longer wavelengths and greatly reduce the incoherent component with shorter radiations. Efficiencies of 20 to 25% are readily attainable, allowing high geometrical resolution diffuse intensity analyses with specimens of low atomic number.
Combination Flash Photolysis-Flash Pyrolysis System
Authors: Petrella R. V. , Spink T. L. , Finlayson L. T.
Published: February 2005

A versatile flash photolysis/pyrolysis apparatus has been constructed. Timing circuit is off-the-shelf Tektronix pulse generators. Ignitron ``crowbar'' circuit fires a spectroscopic lamp. Flash pyrolysis of solids or liquids is now possible as well as conventional flash photolysis.
Two Pumps for Generating Pressures above 10 kbar
Authors: Daniels W. B.
Published: February 2005

This article describes a simple reciprocating hand pump for generating pressures to 13 kbar in oil, and an air driven reciprocating pump which has been used above 10 kbar. The hand pump incorporates a manganin pressure cell in its body, and has an output to 0.37 cm diam tubing so it constitutes a complete self-contained high pressure facility. The air driven pump has a sufficiently large pumping capacity to use together with a large gas-oil separator for generating high pressures in a gas system.
Calibration of Coulter Counters for Particles ∼1 μ in Diameter
Authors: Mercer W. B.
Published: February 2005

A linear relationship between particle volume and instrument response is confirmed for particles between 0.75 and 2.5 μ3, but this relationship may not hold for smaller particles. The implicit assumption of negligible surface conductance in derivations of this relationship is found acceptable for polystyrene spheres about 1 μ in diameter. A potential source of error in calibration is identified and allowed for. A relationship is developed between observed count and true count which allows coincident passage correction to be based on all available experimental points. The critical volume is found experimentally to be a function of particle volume.
Tandem Mass Spectrometer for Study of Ion-Molecule Reactions
Authors: Futrell Jean H. , Miller C. D.
Published: February 2005

An instrument for the study of ion-neutral interactions involving momentum transfer to the product ions has been constructed. It consists of a double focusing mass spectrometer which serves as an ion source for a collision chamber connected to a second double focusing mass spectrometer. This instrument provides both mass and energy resolution of the impacting ion beam and the in-line configuration maximizes collection of momentum transfer products, as from ion-molecule reactions. Ion beams of experimentally useful intensity are produced over the energy range 0.2 to 100 eV with an energy spread of 0.3 eV.
Continuous Horizontal Zone Refining Apparatus
Authors: Kennedy J. K. , Moates G. H.
Published: February 2005

A continuous horizontal zone refining system is described which can be easily assembled and eliminates most of the difficulties associated with the operation of existing continuous systems. The ability of this system to purify has been demonstrated by the purification of two solute-solvent systems. It is expected that this system will find application for the purification of a wide spectrum of organic compounds, inorganic salts, metals, and intermetallic compounds.
High Temperature Neutron Diffraction Furnace
Authors: Bowman M. G. , Hull D. E. , Witteman W. G. , Arnold G. P. , Bowman A. L.
Published: February 2005

An induction transformer furnace for a neutron diffractometer is described. This furnace has been used for the examination of refractory carbides by neutron diffraction at temperatures up to 2500°C.
Universal Capacitance Probe Liquid Level Measuring System
Authors: Dinkel John A.
Published: February 2005

A universal liquid level measuring system designed for most cryogenic installations is described. A number of remote measuring heads are used with a central indicator to enable one operator to scan or to continuously monitor liquid levels in a number of vessels. A coaxial probe immersed in the liquid measures the difference in dielectric constants between the liquid and gas phases of the media. The probe and its associated cable constitute the capacity in the tuned circuit of an oscillator, thus a change in liquid level is reflected as an oscillator frequency change. In the indicator unit, the error voltage required to phaselock a local oscillator to a probe oscillator is a function of the probe oscillator frequency. Results are given for a number of test level measurements made with N2 and 4He.
Total Absorption Gamma Ray Spectrometer System for Pulsed Beam n, n′ γ Measurements
Authors: Ashe John B. , Morgan Ira Lon , Hall J. D.
Published: February 2005

A gamma ray spectrometer that combines the techniques of neutron time-of-flight spectroscopy and gamma ray total absorption spectroscopy is described. Data on gamma ray pulse height resolution and photopeak efficiency are presented. Representative pulse height spectra from neutron inelastic scattering reactions are shown.
High Current Duoplasmatron Ion Source with Ferrite Permanent Magnets
Authors: Christensen L. J. , Zaharis E. J.
Published: February 2005

A duoplasmatron ion source capable of producing about 12 mA of hydrogen ions has been constructed and tested. The source uses ferrite permanent magnets and a low voltage, Pierce type extraction lens system.
Transverse Coherent Resistive Instabilities of Azimuthally Bunched Beams in Particle Accelerators
Authors: Courant Ernest D. , Sessler Andrew M.
Published: February 2005

The transverse electromagnetic coupling of bunches of particles with each other is investigated theoretically, and shown to incorporate the possibility (due to the effect of imperfectly conducting vacuum chamber walls) of coherent instability even when the longitudinal distance between bunches is much larger than the transverse dimensions of the vacuum tank. The modes of oscillation in which the bunches move rigidly are investigated; criteria for stability, and expressions for the small amplitude growth rates under unstable conditions are presented. The case of a single bunch is considered in detail and demonstrated to be stable (even in the absence of Landau damping) provided v lies between an integer and the next higher half-integer, where v is the number of transverse free betatron oscillations occurring in one revolution; for many bunches which are sensibly different in intensity (a criterion for this is presented), all modes are stable provided v satisfies the same restriction. For equally spaced bunches of equal numbers of particles, approximately half the modes are unstable without Landau damping. Numerical examples are presented covering some intermediate situations.
Three Dimensional Magnetically Supported Wind Tunnel Balance
Authors: Dancy William H. , Towler William R.
Published: February 2005

A three component, wind tunnel balance capable of magnetically suspending a test model in the center of a 25 cm diameter, high velocity, low density gas stream without the use of mechanical supports has been developed. Reaction forces experienced by the model are resolved into three mutually orthogonal components with one of these components being aligned with the axis of the tunnel. A complete description of the magnetic and electrical components of the balance is presented.
Merging Beams, A Different Approach to Collision Cross Section Measurements
Authors: Trujillo S. M. , Neynaber R. H. , Rothe Erhard W.
Published: February 2005

A different approach has been developed to measure two-body collision cross sections in the energy range from thermal to several hundred electron volts. Two molecular beams are merged and move in the same direction along a common axis. Ion-neutral reactions are discussed but the techniques could also be used for ion-ion and neutral-neutral collisions. Advantages of the merging beams technique over conventional beam-gas and crossed beam methods include accessibility (with good energy resolution) to the energy region from a few tenths of one to a few electron volts; the possibility of measuring cross sections for two general, labile species; and relative ease in collecting and detecting products for total reaction cross section measurements. The principles of the method and details of the instrument are discussed. A cross section for the resonant charge transfer of Ar was measured. Reasonable agreement with some previous measurements, and other tests, indicate that the basic principles of a merging beams technique are valid and that the apparatus performs satisfactorily.
Nonboiling Liquid Hydrogen Target
Authors: Jarmie Nelson
Published: February 2005

A thin 2 mm liquid hydrogen target is described. It operates at conditions away from the boiling curve and can therefore absorb considerable (200 mW) power from an accelerator beam without serious boiling. Construction and operation are discussed and several additional advantages are presented.
New Vibroscope Transducer
Authors: Stearn A. E.
Published: February 2005

A transducer system is described which enables the transverse frequency of resonance of strings to be determined with great precision. The theoretical discussion enables the magnitude of the output to be calculated, and a practical system used by the author is given. The excitation and detection of movement of the fiber is purely electrical, depending on the fact that a charged fiber vibrating with a small amplitude between two electrodes causes a charge movement at the electrode proportional to its displacement.
Modified Detection Arrangement for Scanning Electron Diffraction Instrument
Authors: Dove D. B. , Denbigh P. N.
Published: February 2005

Modifications to the detection arrangement of a scanning electron diffraction apparatus, described by Grigson [Rev. Sci. Instr. 36, 1587 (1965)], have been carried out to (i) permit rejection of inelastically scattered electrons, (ii) provide measurements of the main beam by Faraday cage, and (iii) provide high sensitivity measurements using a semiconductor detector and modulated beam.
Diffused Germanium Resistors for Thermometry in 20 to 70°K Range
Authors: Cohen B. G. , Tretola A. R. , Lilienthal R.
Published: February 2005

In studying the temperature variation of electrical conductivity of thin diffused layers in germanium, effects useful in thermometry have been found. For layers diffused with antimony in the range 3×1017 to 1×1018 cm−3, no impurity deionization is observed to temperatures as low as 13.9°K. Thus the variation of mobility in the layer determines the temperature dependence of resistivity. The mobility is observed to vary as μ=μ0Tn, with n close to unity in the range 20 to 70°K. This behavior makes such diffused resistors suitable for use as low temperature thermometers. By use of planar transistor technology n type resistors have been diffused into p type germanium. The resulting p-n junction electrically isolates but thermally connects the resistor and the substrate. Thus the resistance element can be conductively coupled to the system to be measured. Since the diffused resistor is typically only 1 μ thick, thermometers having 1000 Ω resistance at 60°K are readily obtainable and two wire measurement is satisfactory. Indication of a step change in temperature from 60 to 20°K is essentially completed in 20 msec. Data on the stability of indication and magnetoresistance effect are presented, and use between 2 and 20°K is discussed.
System for Orienting Balloon Payloads in Space
Authors: Derdeyn S. M. , Kniffen D. A.
Published: February 2005

An inexpensive system for orienting balloon payloads to allow a detector to view a fixed position on the celestial sphere is described. The basic system is a sun seeker with programmed motion to correct for earth rotation and wind drift, and to thereby provide relatively accurate orientation toward any desired direction on the celestial sphere. Two successful balloon flights have been flown utilizing this oriented platform, which can be used, with minor modifications, for a large number of applications.
Self-Modulating Derivative Densitometer
Authors: Aramu F. , Rucci A.
Published: February 2005

The main features of a self-modulating derivative densitometer as well as some typical results of the new method are reported. By comparing both derivative and nonderivative analysis of a spectrum conventionally recorded on a spectrographic plate, one can see that its detectability is increased by a factor much greater than 1. These experimental results are consistent with the gain to be expected by means of optical derivative spectroscopy.
Scattering Chamber for Study of Three-Body Reactions
Authors: Ehlers D. H. , Knowles H. B. , Pecka D. C. , Wise M. N.
Published: February 2005

A mechanically simple scattering chamber for heavy particle angular correlation studies has been designed and constructed. The chamber has provisions for controlling the motion of each of two solid state detectors. The lower detector possesses one degree of angular freedom in the horizontal plane, while the upper detector has two degrees of angular freedom and can be scanned continuously over the upper hemispherical surface. By means of external controls, the target can be tilted as well as rotated in order to accommodate to detector position.
Portable Battery Powered Instrument for Measuring Concentrations of Airborne Halogenated Hydrocarbon Compounds
Authors: Avera C. B.
Published: February 2005

A lightweight, portable instrument for detection and measurement of halogenated hydrocarbon concentrations in ambient air has been developed. The detection principle is a form of the Beilstein flame test, using propane as fuel. Sampling is accomplished by aspiration within the burner, eliminating the need for a motor driven sampling pump. Fuel delivery and sampling rates are automatically regulated. The optical system incorporates an interference filter and a photoconductor, and several solid state circuits have been developed for readout, two of which are described in the text. The instrument is battery operated and weighs about 4.5 kg.
Stress-Strain Properties of Plastics at High Strain Rates
Authors: Dannis M. L. , Watling R. E.
Published: February 2005

Apparatus of the falling weight type previously developed for tensile testing of rubbers at strain rates up to 14.5 m/sec has been made stiffer and more sensitive to accommodate plastics. Loads up to 225 kg and resolution to about 50 μsec have been achieved using a piezoelectric transducer. A modified ring specimen, the ``racetrack,'' is also required to attain high resolution and reduce errors associated with conventional slip in the grip. Transducer voltages are displayed on a 'scope and photographed using well-known procedures. These curves, when calibrated, are stress-strain curves, showing brittle and ductile failures. Elapsed times range from about 0.3 to 2 msec. Tensile fractures usually occur in the middle of the stressed legs, often in both legs simultaneously. Reproducible curves have been obtained from commercial plastics such as polyethylene, rigid vinyls, and polystyrene, from metallic alloys of aluminum and copper, and from elastomers such as tread rubbers.
Thin Liquid Sheets at Reduced Pressure and Applications in Nuclear Physics
Authors: Griffith J. A. R. , Burge E. J.
Published: February 2005

Thin sheets of flowing water, up to 10 cm2 and 0.01–0.05 cm thick, were produced and investigated under reduced ambient pressures down to the natural vapor pressure. Their behavior was well represented by Taylor's theory. Measurements were made of the sheet thickness, and a schlieren system was used to estimate thickness variations, which could be limited to about 1% over areas of a few cm2. Preliminary studies were also made with jets and sheets of liquid oxygen under reduced pressures. A practical water target is described for time of flight measurements on the reaction 16O(p,n)16F with 30 and 50 MeV protons. It is pointed out that such targets sometimes have advantages over gaseous, solid, and conventional liquid targets, particularly with regard to defined geometry, low background, single nuclear species, and ability to be used with high beam intensities.
Stopped Flow Apparatus Employing a Rapid Scanning Monochromator
Authors: Dye James L. , Feldman Larry H.
Published: February 2005

A stopped flow apparatus employing a rapid scanning monochromator is described. This system is thermostatted and uses Pyrex mixing cells. The monochromator permits rapid study of changes in the spectrum for suitable moderately fast reactions. The instrument is double beam and direct reading in absorbance units. Data are stored on an FM tape recorder and played back to an oscilloscope. Tests of the instrument's performance are given, and several possible applications are discussed.
Gyro-Orientation Determination Using Phosphorescent Materials
Authors: Tuffias Robert H.
Published: February 2005

The determination of the orientation of the spin axis of a spherical free gyroscope (i.e., electrostatic, low temperature, etc.) is usually performed optically by making use of some sort of pattern or marking on the rotor. This requires that the rotor have a preferred axis of rotation so that the relative orientation of the spin axis and pattern are known. This paper describes a method of ``attaching'' the pattern to the spin axis by making use of a phosphorescent coating on the rotor. This technique has the advantage of allowing the rotor to be manufactured as spherical as possible in order to eliminate torques caused by nonsphericity, while still having the capability of high accuracy readout.
Twin Liquid Metal Solution Calorimeter
Authors: Darby J. B. , Kleb R. , Kleppa O. J.
Published: February 2005

The design and operation of a twin liquid metal solution calorimeter of the Calvet type for use up to 1173°K is described. The calorimeter is well-suited for the study of alloys containing transition elements. A means of automatically recording the data is described. The satisfactory performance of the calorimeter has been demonstrated by a determination of the heats of solution of the noble metals and of palladium in liquid tin at 698°K. The results are in good agreement with existing data.
Microwave Bridge Measurement of Plasma Frequency
Authors: Lutz B. C. , Lindsay P. D. , Roemer L. E.
Published: February 2005

A simple method for determination of plasma frequency is described, utilizing the cutoff effect of a plasma near electron cyclotron resonance. This determination can be made visually or by use of a microwave bridge.
Specimen Holder for Deuteron Irradiation Experiments in Metals Between 4°K and Room Temperature
Authors: Herschbach K.
Published: February 2005

A specimen holder which permits annealing experiments to be carried out after deuteron bombardment at liquid He temperature is described. Utilizing the heat capacity of He gas results in lower He consumption and improved temperature regulation. For any temperature between 15 and 300°K, the temperature regulation is ±0.01°K or better. Details of the mounting of specimens are included in this report.
Gamma-Ray Pulse Dosimeter
Authors: Furuta Yutaka , Kinbara Seturo
Published: February 2005

A gamma-ray dosimeter, which has a response expressible in roentgens and high sensitivity with a small active volume, is described. The major parts of this dosimeter (gamma-ray pulse dosimeter) are a scintillation counter using an organic scintillator and an electronic integrator, with special care to reduce the counting loss. This dosimeter is sensitive to x or gamma rays with energies above 50 keV, and has an air equivalent response for energies above 200 keV with maximum response at 80 keV (+14%). A linear temperature dependence (0.5%/°C) is obtained under 40°C.
Low Cost Automatic Quartz Dilatometer
Authors: Wagner Paul , Gonzales Alfred L. , Minor Robb C. , Armstrong Philip E.
Published: February 2005

A fully automatic fused quartz dilatometer for operation in the temperature interval 25–700°C has been designed and built. Use of an unbonded strain gauge as the measurement transducer has resulted in a system of great simplicity, high precision, and very low cost. Details of the design and operation of the dilatometer are discussed.
Symmetry Properties of Beam Handling Magnet Systems
Authors: Herrera J. C. , Bliamptis E. E.
Published: February 2005

Matrix methods are used to analyze particle beam handling magnet systems composed of a primary system followed by a symmetrical replica of itself. There are three such combinations, i.e., the primary system M followed by its reflection MR, the system M followed by its antireflection MA, and the system M followed by the flipped over replica of itself MF. Explicit conditions are imposed on the primary system which due to the over-all symmetry result in desirable beam transport properties for the complete system.
High Speed Magnetically Operated Particle or Light Shutter
Authors: Kuswa Glenn
Published: February 2005

A shutter that can close five openings 0.635×5.84 cm to straight trajectory particles 240 μsec after it is pulsed, and remain closed for 1 msec, has been tested in a vacuum and in air. Driving energy is stored in a 15 μF capacitor. The shutter is intended to stop directed residual gas molecules of pulsed plasma guns from entering regions in which plasma properties are being studied.
Pulse Height Defect and Energy Dispersion in Semiconductor Detectors
Authors: Haines Eldon L. , Whitehead A. Bruce
Published: February 2005

We have calculated the contributions of the atomic (screened Coulombic) scattering process to the pulse height defect and energy dispersion observed when heavy ions expend their energies in semiconductor detectors. Atomic scattering appears to account qualitatively for the pulse height defect observed for most heavy ions in both silicon and germanium detectors. Atomic scattering also contributes substantially to the energy dispersion.
Highly Accurate Nonspherical Reflectors for the Millimeter and Submillimeter Wavelength Region
Authors: Rivers W. K. , Sheppard A. P.
Published: February 2005

A method of fabricating nonspherical reflectors for the millimeter and submillimeter wave region with a precision greater than that afforded by normal machining techniques yet less costly than optical grinding has been devised. The heart of the technique lies in bonding a thin foil of aluminum to a slip cast fused silica mold with epoxy cement. Both paraboloidal and prolate spheriodal reflectors have been built. The surface of a 30.5 cm paraboloidal reflector fabricated by this method has been found to vary by no more than ±12 μ which was the limit of resolution of the longitudinal aberration test used for checking the finished surface.
Optical Lever System Application to a Quartz Bourdon Tube Pressure Measuring System
Authors: Stratton Gilbert S. , Catalano Edward
Published: February 2005

An optical lever system for the null measurement of large angular displacements is described. The minimum resolution is 0.0002°. The over-all size is 15×15×10 cm, which includes light source, optics, and detector system. The optical lever system is used as a modification in a commercially available quartz Bourdon tube pressure gauge. Performance data for the lever and for the entire pressure measuring system are presented.
Simple High Temperature Compression Testing Apparatus
Authors: O'Boyle D. R. , Mack D. J.
Published: February 2005

A simple, inexpensive test fixture has been designed for use with a commercial tensile test machine for compression testing above room temperature either in vacuum or in an inert atmosphere. A unique seal design was incorporated into the apparatus which reduces dynamic seal friction sensed by the load cell to a minimum. The apparatus has been used for compression testing from room temperature to 1000°C and works well over a wide range of strain rates.
Design Considerations for a Kossel Microdiffraction Camera
Authors: Vieth D. L. , Yakowitz H.
Published: February 2005

A Kossel microdiffraction camera has been adapted to the National Bureau of Standards electron probe microanalyzer. Design criteria for a Kossel camera are discussed and evaluated. The details of their adaption to the National Bureau of Standards Kossel microdiffraction camera are given. The major features adopted were (1) transmission camera, (2) inclusion of microgoniometric capabilities, (3) film cassette in air rather than vacuum, and (4) source to film distance adjustable between 5 and 11 cm. Transmission pseudo-Kossel patterns of an aluminum crystal obtained with Cu radiation are presented to illustrate the capabilities of the camera.
Wide Temperature Range Adiabatic Calorimeter
Authors: Karasz F. E. , O'Reilly J. M.
Published: February 2005

An adiabatic calorimeter with automatic shield control is described which has been used for the measurement of heat capacities and transition heats in the range 15 to 600°K. The apparatus was designed specifically for the study of bulk polymers. Over most of the temperature range a precision of better than ±0.2% may be attained.
Use of ``On Line'' Computer for Mössbauer Experiments
Authors: Goodman R. H. , Richardson J. E.
Published: February 2005

The application of a small general purpose computer as an ``on line'' data acquisition device for Mössbauer effect experiments is described. A method of conversion from analog to digital information and an outline of the computer program are given. The performance of the system is demonstrated by a Mössbauer spectrum of iron sulphide (pyrite). The extension of these techniques to other experiments is briefly considered.
Variable Brewster Angle Flat Used as Gas Laser Gain Control
Authors: Schleusener Stuart A. , Read Alvin A.
Published: February 2005

A method is described which allows making photoextinction measurements with a sensitivity of 0.01%. The procedure involves inserting test media directly into the cavity of a 6328 Å He-Ne gas laser and detecting transmission losses by measuring laser output changes with a photomultiplier. Calibration is accomplished by using a very thin variable Brewster angle flat within the cavity.
Energy Monitor for Electron Beams
Authors: Okabe Shigeru , Tabata Tatsuo , Tsumori Kunihiko
Published: February 2005

An energy monitor for electron beams has been developed which makes use of the elastic scattering of electrons caused by a foil placed in the beam path. The scattered electrons are magnetically analyzed and detected by measuring the direct current from a plastic scintillator. During use of the beam the sweep of the magnetic field is repeated automatically, and the energy spectrum is displayed on a storage oscilloscope. Performance of the monitor constructed for a 15 MeV linear electron accelerator is presented.
Flexural Fatigue Machine for High Temperature Operation at Resonance in Vacuum
Authors: Achter M. R. , Smith H. H. , Riley R. J. , Stegman R. L.
Published: February 2005

A resonance type reversed bending, high temperature fatigue machine for operation at constant bending amplitude in vacuum has been developed. The vibration frequency is maintained at resonance by means of a feedback circuit employing a capacitance pickup. Another circuit maintains a constant amplitude of vibration. As fatigue cracks are developed, the resonant frequency decreases. Curves of resonant frequency versus time at 800°C for materials of high damping, such as type 316 stainless steel, and for materials of low damping, such as Inconel X, illustrate the development of fatigue damage.
Influence of Collection Efficiency on Omegatron Measurements
Authors: Marklund Ingvar , Danielsson Hans
Published: February 2005

A simple omegatron, without guard rings and side plates, for measuring partial pressures has been studied. The factors influencing the collected ion and electron currents are discussed. Deviations and variations in omegatron collection efficiency are eliminated by using partial pressure ratios and the ionization gauge reading corrected for the gas mixture. Curves of ion versus electron currents are obtained. Possible effects from a hot tungsten filament are investigated. Fragmentation pattern and principal ion production are measured and discussed. The omegatron sensitivity is a function of secondary electron emission from the electron collector. Only one characteristic peak of each gas is necessary for residual gas analysis, when the fragmentation pattern is known.
Cylindrically Symmetric Plasma Source
Authors: Knopp C. F. , Cambel Ali Bulent
Published: February 2005

A wall stabilized arc constrained to operate within a transparent tube is described. The device produces a plasma column of true cylindrical symmetry, justifying a one dimensional analysis of energy transfer within the column. Axial temperatures in excess of 12 000°K have been achieved in argon.
Reliable Sample Changer for Mass Spectrometer
Authors: Christie W. H. , Cameron A. E.
Published: February 2005

A sample changing device for a mass spectrometer is described. Five filaments are mounted on a wheel which is adapted to be rotated by suitable drive mechanism through the vacuum wall. Reliable wiping electrical contact is made to the filament lugs by means of stationary blades, spring loaded with tungsten wire helices.
Aperture Correction in Fabry-Perot Interferometer Measurements
Authors: Bruce C. F.
Published: February 2005

The effect of the size of the small aperture which isolates the central portion of the interference fringe system in the photoelectric scanning Fabry-Perot interferometer has been investigated. The phase shift due to size of aperture is given accurately by Δ=Kθ2/2, where K is half the phase difference and θ the angular radius of the aperture, only if the diameter of the aperture is not greater than about one-eighth of the diameter of the first interference ring. This phase shift is equivalent to a length correction with the Fabry-Perot interferometer of θ2/4 per unit length. This simple relation cannot be used with larger apertures, and visibility considerations make the use of such apertures quite undesirable.
Apparatus for Measurement of Stress-Strain Properties of Filaments in Tension at High Temperatures
Authors: Smith W. H. , Bacon Roger
Published: February 2005

An apparatus is described which can make mechanical property measurements on single filaments at temperatures to 2500°C. It is a constant rate-of-strain machine which uses linear variable differential transformers (LVDT's) to measure filament tension and elongation. A split furnace, using graphite heating elements, completely surrounds the filament, which is cemented to graphite supporting rods with a carbonizable cement.
Instrument for Designing Uniform Field Spectrometers
Authors: Green A. E. S. , Berkley R. J.
Published: February 2005

A simple instrument is described which can be utilized to check the optical properties of uniform field magnetic spectrometers. It can also be used as an aid to determine the boundaries of the magnetic field required to achieve desired optical properties.
New Thermionic Emission Microscope
Authors: Eichen E. , Forgacs R. L. , Parafin B. A.
Published: February 2005

A new thermionic emission microscope has been designed and constructed. It is a two lens microscope having a combination electrostatic-electromagnetic objective lens and an electromagnetic projector lens. The microscope has a magnification range of 78 to 5600× and a resolution of about 500 Å which is independent of magnification. It is capable of operating at a vacuum of 10−8 Torr at 1600°C. A specimen temperature and control system has been incorporated which operates with an accuracy better than ±5°C. The microscope stage is so constructed that the specimen can be independently moved in the x, y, and z directions. The electron-optical axis is horizontal to facilitate the recording of data.
Simple Interferometric Manometer
Authors: Herskovitz S. B.
Published: February 2005

A device employing a Michelson interferometer as an optical refractometer has been used to measure gas pressure in the range of 10 Torr and above. The instrument is simple and its test cell bakeable and noncontaminating. With atmospheric gases, using visual fringe readout, an accuracy of ±1.0 Torr can be achieved over all pressure ranges. The linear relationship between pressure difference and interferometric fringe shift is developed. Effects of gas species, wavelength, and temperature, as well as methods of improving the accuracy, are discussed. Results for nine pure gases and several mixtures are presented.
Microwave Helicon Interferometry in Semiconductor Plasmas
Authors: Furdyna Jacek K.
Published: February 2005

A microwave interferometer bridge technique for the study of helicon wave propagation and related transmission phenomena in semiconductor plasmas is described. The bridge arrangement is in effect a microwave version of the classical Rayleigh refractometer. This approach has several important advantages over the conventionally used Fabry-Perot dimensional resonance technique, particularly where considerable damping is involved. In addition to high sensitivity, the bridge method allows reliable dispersion measurement even under conditions when less than one helicon period is observed. Furthermore, the interferometer bridge can also be used for quantitative investigation of the helicon damping processes. This latter aspect of the helicon problem, so far relatively unexplored in theory and experiment, is considered in some detail. Helicon experiments, performed on a variety of semiconductors at 35 Gc in the temperature range from 78 to 300°K in magnetic fields up to 100 kG, are used to illustrate the various features of the Rayleigh method. In addition, the influence of leakage, as well as a number of modifications of the bridge approach, are discussed.
Time Resolved Microwave Interferometry as Diagnostic Tool for Decaying Plasma Afterglows
Authors: Estin A. J. , Anderson M. M.
Published: February 2005

Two methods for obtaining time resolved electron density measurements with a microwave interferometer are described. Precision phase measurement techniques permit these methods to be used in weak afterglow plasmas with a high resolution such that decaying afterglow can be followed down to ωp/ω∼0.01 with a time resolution of 10 μsec.
Apparatus for Measurement of Piezoresistivity of Low Resistivity Materials
Authors: Drobish William E. , Bate R. T. , Einspruch Norman G.
Published: February 2005

This paper describes a highly sensitive system which has been used to measure seven of the eight independent components of the piezoresistivity tensor of bismuth. The apparatus employs a 35 Hz alternating stress with dc applied to the sample, and is capable of resolving piezoresistive voltages as small as 1 nV. The increased sensitivity, which is required for low resistivity materials, is obtained primarily by the suppression of noise. The signal-to-noise ratio was improved by a balanced connection of sample voltage directly to a low noise stepup transformer which was followed successively by a bandpass preamplifier, 60 Hz rejection filter, selective amplification, and phase detection at 35 Hz. Although common mode 35 Hz noise was reduced by the balanced configuration, further suppression was possible by active cancellation using a phase balanced bridge prior to the selective amplifier. The sensitivity achieved makes this system useful for precise piezoresistivity measurements on materials with resistivities as low as 10 μΩ cm.
Indium Ion Source
Authors: Daley Howard L. , Perel Julius , Vernon Richard H.
Published: February 2005

An ion source that utilizes a continuously oxygenated porous tungsten surface to generate indium ions is described. Indium vapor supplied to the back of the tungsten ionizer from a reservoir percolates through to the front surface where the indium is evaporated as ions. An accel-decel electrode extraction system is used to increase the ion current capability of the source. The ionizer and reservoir are designed to operate at temperatures in excess of 1000°C and at voltages up to 20 keV. The peak ion current attained was 0.57 mA at an ion energy of 10 keV.
Field Ionization Detectors for Molecular Beams
Authors: Johnston Wilbur D. , King John G.
Published: February 2005

The operating principles of the field ionization microscope have been applied to the development of molecular beam detectors characterized by high geometrical resolving power, rapid time response, and unit detection efficiency for any beam substance. The detector described here has been in use for 10 months with beams of helium, argon, and nitrogen.
Heat Capacity of Copper
Authors: Ahlers Guenter
Published: February 2005

In order to establish the suitability of copper as a low temperature calorimetric standard, the heat capacities of four samples were measured between 1.3 and 20°K with a precision of 0.1%. All samples were at least 99.999% copper. One was a single crystal, one polycrystalline and annealed, one chill cast, and one polycrystalline and cold worked. The heat capacities of the annealed and chill cast samples differ by less than 0.1%. The heat capacity of the single crystal is 0.2% higher. The heat capacity of the cold worked sample is 0.7% higher at low temperatures and 0.3% higher above 10°K. It is concluded that high purity cast copper samples are excellent as low temperature calorimetric standards.
Direct Coupled, Full Wave Phase Sensitive Detector
Authors: Ryan David P.
Published: February 2005

A phase sensitive detector is described which allows full wave synchronous rectification of amplitude modulated waves without the use of transformers, diodes, capacitors, or mechanical choppers. This is accomplished by a new concept, shared load resistances. The resulting direct coupling allows the device to have a frequency response which is limited only by the transistors used. Further advantages of the detector are that it accepts a differential input signal and provides a single ended output signal suitable for analog computation, metering, writing or storage recording, and cathode ray tube observation. The detector output stage offers good load isolation and low output impedance.
Force Intensifier for Low Temperature Use
Authors: Towle Laird C. , Stajdohar Ralph E.
Published: February 2005

A hydraulic type of force intensifier which uses a solidified gas as the working medium has been developed for use at very low temperatures. It has been used to load an anvil type of high pressure cell with continuously variable pressures in the range up to 55 kbar at 77.4°K with minimal refrigerant consumption. The design and operating characteristics are discussed and suggestions for further utilization of this concept are presented. In its present form the system is potentially capable of generating pressures up to 100 kbar at 4.2°K with a liquid helium consumption of about 1 liter/h.
Ultracentrifuge Rotor Temperature Measurements and Control
Authors: Fabricant Steve J. , Windsor Alfred A. , Lindgren Frank T.
Published: February 2005

A radio telemetry system for use with analytic or preparative ultracentrifuge rotors is described. Capable of sustained high speed operation, this modulated FM system simultaneously transmits with precision both rotor speed and rotor temperature.
Leads Power in Calorimetry
Authors: Neighbor J. E.
Published: February 2005

In calorimetric studies, electrical power developed in the heater leads contributes to the warming of the specimen. An expression for this contribution is derived, without assumptions concerning the temperature dependence of electrical or thermal conductivity of the leads material. The expression reduces to half the total leads power in situations of practical importance.
Specific Heat Measurements in 1–10°K Range Using Continuous Warming Method
Authors: Cochran J. F. , Shiffman C. A. , Neighbor J. E.
Published: February 2005

We describe a system for measuring specific heats by a continuous warming method with accuracy at least as high as has been attained with the usual heat burst method. Using this system data can be obtained very rapidly, even by unskilled operators, and reduced to final form with straightforward analysis and small amounts of computer time. We analyze the method in terms of simple models which take into account uncertainties in the stray heat, thermal gradients in the specimen assembly, the effects of electrical noise and finite bandwidth in the thermometer circuits, and their relation to the measurement of small heat capacities. Data on lead, mercury, and gallium are presented which indicate that the models lead to fair estimates of the anticipated scatter once certain characteristics of the apparatus are known. The observed scatter varied from 0.3% for gallium, where electrical noise in the amplifiers was a dominant factor, to less than 0.1% for lead and mercury, where no single factor was conspicuous. In addition, completely independent measurements were reproducible to about 0.1%. In these experiments the measuring intervals were never greater than 1% of the absolute temperature.
Refrigerated Inlet Arrangement for Mass Spectrometric Studies of Unstable Species at Low Temperatures
Authors: McGee H. A. , Malone T. J. , Martin W. J.
Published: February 2005

A refrigerated mass spectrometer inlet apparatus is described which also functions as a multipurpose low temperature reactor and a rough separative device. The arrangement has proven to be a powerful tool in the study of the synthesis, reactivity, and energetics of compounds that are stable only at very low temperatures.
Method of Plotting Field and Current-Induced Phase Transition in Superconductors
Authors: Kolb Werner
Published: February 2005

A method is outlined to plot the dependence of the critical field of a superconductor on its critical current automatically on the screen of an oscilloscope. Critical field and current, respectively, control the X and Y input of the oscilloscope whereas the beam intensity is controlled by the voltage drop across the superconductor. Use of short current and field pulses eliminates disturbing thermal effects. The device is particularly useful for routine measurements on cryotron circuits.