bluuebunny/crossref_metadata_2025 huggingface dataset:
High Temperature Furnace for X-Ray Diffraction of Liquid Metals
Authors: Joshi M. L.
Published: February 2005

The design of a high temperature electric furnace (maximum temperature 1300°C) using pyrolitic graphite both as a heating element and as a crucible for x-ray diffraction of liquid metals is described. The usefulness of the furnace for high temperature melting metals is demonstrated by obtaining an x-ray diffraction curve of molten copper in helium atmosphere.
Determination of the Relative Acoustic Gain in Semiconductors
Authors: Haydl William H.
Published: February 2005

A simple method for determining the relative acoustic gain in semiconductors is presented. It is not necessary to construct an acoustic wave amplifier, and the test should be applied to the crystal before the construction of such a device. If a high enough electric field is applied across the crystal, the current will oscillate under certain conditions. Strong current oscillations appear in materials with high acoustic gain, and in materials having low acoustic gain only very weak oscillations are observed. The ease with which the oscillations are obtained and their magnitude are a direct measure of the acoustic gain.
Multi-Channel Digital Program Generator for Simulating Charged Particle Penetration of Counter Telescopes
Authors: Weissman Richard
Published: February 2005

Simulation of charged particle penetration in solid state detectors has been accomplished by stimulating them with 2 μsec infrared light pulses. Infrared stimulators have been incorporated in the design of cosmic ray telescopes for space experiments and a program generator has been designed and built to provide programmed groups of stimulus pulses in which various coincidence and anticoincidence combinations can be set up in the detectors with a predetermined choice in each group of amplitude, repetition rate, and number of simulated events. The program generator and infrared pulsing circuits are described with consideration given to the logic design and circuitry employed. Other applications of the program generator are discussed, such as providing serial and parallel binary coded word groups, programmed sets of pulse trains, and/or time delays of fractions of a millisecond up to months in duration, control of or by computer data systems, and general purpose digital system testing.
Weak Ferromagnetic Gaussmeter
Authors: Shtrikman S. , Treves D.
Published: February 2005

A torque magnetometer GE type gaussmeter using weak ferromagnetic rotors is described. Such an instrument gives a reading essentially linear with fields up to 105 G. The actual torques are higher than those obtained with para- or diamagnetic rotors, even at 105 G. An experimental instrument was built, and found to yield a linear reading up to the highest field available, i.e., 25 kG.
Digitization and Integration of Low-Level Fluctuating Signals
Authors: Bradley E. F. , Wall B. H.
Published: February 2005

A method of producing time integrals of low level fluctuating electrical analogue signals is described, the integral accumulating directly on electromagnetic counters. Use of a galvanometer as the sensing element, and a simple mechanical digitizing system provide an economical solution to those applications which do not require the long term stability and versatility of expensive dc amplifiers and digital electronics.
New Mode of Operation of a Phase Sensitive Detector
Authors: Beers Yardley
Published: February 2005

The PS detector plays an important role in the instrumentation for spectroscopy and radio astronomy and in atomic frequency standards. Usually the phase sensitive detector is preceded by a narrow-band-pass amplifier centered on the reference frequency or one of its harmonics. Such a procedure discards useful information contained in the other harmonics. It is suggested that the narrow-band amplifier be replaced by a wide-band one and that the reference waveform be shaped to be identical with that of the desired signal. First order calculations show that this method gives slightly better sensitivity than the conventional one. Also, discrimination against coherent signals of other waveforms can be obtained. If a differentiating circuit is inserted into either the input or the reference circuit, the detector output is an odd function of the phase angle. Therefore, this arrangement can be used as a sensor for a servo system used to lock the phase of the reference oscillator to the signal.
Procedures and Apparatus for Zone Purification of the Alkali Halides
Authors: Warren R. W.
Published: February 2005

A simple apparatus and special techniques are described which have been used to purify and to grow single crystals of KCl and KBr. The measured inpurity content of such crystals is lower than that of commonly used, commercially available crystals by a large factor. Residual impurities have fractional concentrations, in most cases, of less than ten parts per billion. The techniques used, with appropriate modifications, can be employed for the growth of most of the other alkali halides.
Method for Measuring Small Nonlinearities of Electric Characteristics
Authors: Guldbrandsen T. , Meyer N. I. , Schjaer-Jakobsen J.
Published: February 2005

A method is described for measuring very small deviations from linearity in electric characteristics. The measurement is based on the harmonics generated by the nonlinear element when subjected to a sine wave signal. A special bridge circuit is used to balance out the undesired harmonics of the signal generator together with the first harmonic frequency. The set-up measures the small-signal value and the first and second derivative with respect to voltage. The detailed circuits are given for measuring nonlinearities in Ohmic and capacitive components. In the Ohmic case, a sensitivity in the measurement of the relative second order nonlinearity of about 5×10−8 is obtained. In the capacitive case, the sensitivity expressed in terms of the minimum measurable values of the derivatives is dC/dV = 1.5×10−17 F/V and d2C/dV2 = 2×10−16 F/V2.
Arc Image Furnace System for Electrical Conductivity and Thermal Expansion Measurements
Authors: Folweiler Robert C. , Schaffer Philip S.
Published: February 2005

A ``double-clamshell'' arc image furnace system has been successfully utilized in a practical arrangement for the measurement of thermal expansion and electrical conductivity under a controlled atmosphere. Maximum sample temperature of 2138°K has been achieved by using two 5000 W xenon arc lamps as energy sources. At 1500°K, a temperature gradient of 6°K/cm was measured along the furnace axis by thermocouples shielded with alumina, but without a sample in position. The thermal conductivity of a sample would reduce the gradient to less than 1°K/cm.
Field Modulation Techniques for Resolution Enhancement in ESR Spectroscopy
Authors: Glarum Sivert H.
Published: February 2005

Methods for reducing linewidths in electron spin resonance spectroscopy by 50–70% using complex magnetic field modulation waveforms are described. Results obtained using a field modulation line sharpener are presented to demonstrate the usefulness of such techniques.
Stable, Distributed-Dynode Electron Multiplier
Authors: Spindt C. A. , Shoulders K. R.
Published: February 2005

The development of a high gain, stable electron multiplier is described. The configuration investigated consists of two rectangular, continuous dynodes forming a plane-parallel channel. Details of strip preparation, film deposition, and experimental performance values are discussed.
Frequency Modulation of Large Cavities
Authors: Rajangam K. B. , Hai F. , MacKenzie K. R.
Published: February 2005

A model study is described in which a rotating capacitor is coupled to a large re-entrant cavity. The size and capacitive loading (∼500 pF) are such as to make modulation by ferrites or broadband amplifiers difficult and expensive. A nominal frequency range of 3 to 1 is achieved with a single-plate six-bladed rotor. On a possible fullscale cavity with a range of approximately 9 to 3 Mc, the data are scaled to a voltage of 5 kV peak for rf power requirements of 1 to 4.4 kW.
Equilibration of the Ice-Water Temperature Standard
Authors: Miksch Edmond S.
Published: February 2005

A test has been made of the accuracy with which an ice-water system establishes the equilibrium temperature. A device consisting of a bulb containing ice and water with provision for volumetric measurement is used as a thermometer. This was placed in the re-entrant well of a chamber similar to those used to establish the triple point. The temperature established by the well chamber was varied by varying the pressure of the water in it. It was found that when the temperature was made to differ from the equilibrium temperature of the thermometer by as little as 3×10−6°C, growth or melting occurred in the thermometer.
Precision (0.1°C) Vacuum Cryostat and Furnace for Mössbauer Experiments
Authors: Van Der Woude F. , Boom G.
Published: February 2005

The design of a small vacuum cryostat and furnace for a Mössbauer spectrometer is described. A regulating system for a 0.1°C temperature stability for periods of several days is given.
Proton Beam Technique for Measuring the Ion Density in a Plasma
Authors: Duclos Donald P.
Published: February 2005

A technique is described for obtaining localized measurements of the ion density in a plasma which is not affected by the presence of a magnetic field or the absence of thermodynamic equilibrium. The technique consists basically of exciting the ions with a proton beam and relating the measured absolute intensity of certain spectral lines to the ion density. Three requirements are discussed which must be satisfied in order to apply the method to a particular gas. The technique appears to be well suited to measuring the density of helium ions. The possible sources of error are examined and, for helium plasmas, none of the errors are large provided that the gas pressure is less than 1 mm Hg and the temperature is over 10 000°K. A preliminary experiment is described.
Versatile and Stable Recording Spectrofluorometer for the Measurement of Corrected Spectra
Authors: Rosen P. , Edelman G. M.
Published: February 2005

The design and performance of a versatile automatic recording spectrofluorometer are described. The instrument has a modular design and is capable of measuring fluorescence excitation and emission spectra, polarization of fluorescence, and phosphorescence spectra, each as a function of temperature and pH. Both right angle and frontal illumination may be used. A split beam optical system combined with an automatic gain control (AGC) amplifier assures long term stability and freedom from the effects of light source fluctuations. Corrected emission spectra in energy units are obtained automatically by the use of an adjustable function generator (Vernistat). A quantum counter used in conjunction with a second function generator and the AGC amplifier permits recording of true excitation spectra.
Improved Gradient Layer Animal Calorimeter
Authors: Quattrone Phillip D.
Published: February 2005

A rapidly responding gradient layer calorimetry system for experimental animals is described. Monitoring of radiant and evaporative components of heat loss is accomplished by separate heat exchange systems that employ thermoelectric heat flowmeters.

Calibration and test results with the equipment show the following: The response to energy input is linear in both the radiant heat exchange system (radiant calorimeter thermopile) and the circulating air heat exchange system (ventilatory calorimeter thermopile); the radiant calorimeter thermopile signal is independent of the location of the heat source in the chamber, and when referenced to a cold junction temperature of 20°C, it has a response of 0.0212 mV/g·cal/min; the ventilatory calorimeter thermopile has a response of 0.0159 mV/g cal/min when referenced to a cold junction temperature of 4°C; the automatic temperature control systems for the two thermopiles provide ±0.01°C control at their respective temperatures; the noise-to-signal ratio is less than 1% for the radiant calorimeter thermopile and less than 2% for the ventilatory calorimeter thermopile at thermal input levels comparable to those expected from the experimental animal.
Method of Producing a Fast Current Rise from Energy Storage Capacitors
Authors: Early H. C. , Martin F. J.
Published: February 2005

A rate of current rise of the order of 1013 A sec−1 can be produced by inexpensive capacitors used in conjunction with a special, low inductance fuse and spark gap. The capacitors are discharged through the fuse until the current reaches a near maximum value at which time the current is transferred from the fuse into a load inductance of about 1 nH. The spark gap isolates the load until the moment of current transfer.
Microfiber Stress-Strain Apparatus
Authors: Kelsey R. H. , Krock R. H.
Published: February 2005

A new testing device for whiskers or other fine fibers is described. Using a capacitive displacement sensing device and a commercially available bridge, it is capable of measuring strains below 0.1% in a fiber of 1 mm gauge length. Inherently free of frictional error, it permits incremental loading to the limit imposed by the analytical balance used as a loading device. Additional drive and sensing devices to make the drawing of the stress-strain curve completely automatic are proposed, and typical results are presented.
Focused-Beam Electron Bombardment Evaporator
Authors: Blackburn D. H. , Haller W.
Published: February 2005

A simple focused-beam electron bombardment evaporator was developed for the controlled vaporization of carbon and other refractory materials. An electrically isolated cylindrical shield deflects and focuses the electron beam, allowing a large anode to cathode distance. This avoids interference by gas conductance, resulting in a more efficient and stable bombardment process. A performance comparison is made between the described evaporator and a conventional carbon arc evaporator.
Correlation Study of a Thermistor Thermometer
Authors: Boël Michel , Erickson Burton
Published: February 2005

Using a thermistor in a dc bridge configuration, a relationship is developed between the bridge open-circuit output potential and the absolute temperature. This thermistor function accurately predicts temperature magnitudes and changes in temperature over large spans. The inflected shape of the bridge open-circuit output potential versus absolute temperature allows for an excellent linearization of the output potential over an appreciable temperature range. The function is completely determined by the temperature coefficient of resistance of the thermistor, by a characteristic bridge resistance ratio, and by the absolute temperature. The function has been programmed satisfactorily in FORTRAN IV.
Simplified Wedge Magnet Design Including Fringe Effects
Authors: Godlove Terry F. , Bendel Warren L.
Published: February 2005

The concept of replacing each magnet edge by a suitably located thin lens is used to develop a set of design formulas for the transverse focusing properties of uniform-field deflecting magnets. A brief comparison is given to recent work of Enge, who showed that the thin lens concept is a valid first order approximation. The formulas are applied to several examples, including a double focusing magnet with arbitrary deflection angle and ratio of gap to radius of curvature. Finally the method is used to study the transverse acceptance angle of a certain class of ``beam dump'' magnets.
Magnetic Flux Sensor
Authors: Zinke Otto H. , Jacovelli Paul B.
Published: February 2005

A device for measuring complex permeabilities, called a magnetic flux sensor, has been constructed from ferrite. Tests of the sensor which involve the imaginary part of the complex permeability are described in this paper. With a signal-to-null ratio of 2:1, the sensor can detect a change of resistance per unit resistance in metallic samples of 1.1×10−7, an electrical power absorption of 3.4×10−10 W, a radiant flux of 3.1×10−8 W/cm2, and a temperature change of 4.9×10−5°K. Construction of the sensor is also described.
Hot Thermistor Anemometer for Finite Amplitude Stability Measurements
Authors: Lambert R. B. , Snyder H. A. , Karlsson S. K. F.
Published: February 2005

A device similar to a hot wire anemometer has been developed in which the wire is replaced with a thermistor. Niiler has presented a theory of the response of the anemometer to velocity gradients. Experimental calibration curves are presented here to show that Niiler's model explains the operational characteristics quite satisfactorily. The associated electronic circuitry is described and the design considerations which determine the magnitudes of the various adjustable parameters are discussed. This anemometer has been used to detect the onset of the various modes of secondary flow, the amplitude of the disturbances, their wavelengths, and their drift velocities. Both velocity and temperature fields may be measured.
Simultaneous Velocity Selection of Crossed Molecular Beams
Authors: Colgate S. O. , Imeson T. C.
Published: February 2005

A metallic, horizontal disk mechanical velocity selector suitable for studying scattering at the intersection of two monoenergetic molecular beams has been constructed and tested. Principles of the design, construction, and operation are presented along with detailed calculations of the transmission characteristics for both narrow and divergent beams. The calculations are in good agreement with measurements of the transmitted intensities of beams of cesium atoms effusing from an oven at 405°K.
Simple Method to Determine an Accurate Refractive Index by an Interference Method
Authors: Ebina Astuko , Shionoya Shigeo
Published: February 2005

A simple method to obtain an accurate refractive index from an interference spectrum of a semiconductor was investigated, where the small change of the refractive index at the respective wavelengths of the transmission maxima was taken into consideration.
Self-Contained Transistorized AFC Circuit for a Klystron Power Supply
Authors: Berry J. E. , Benton A.
Published: February 2005

A completely self-contained AFC circuit for klystron power supplies used with reflection cavity type EPR spectrometers is described. No internal modifications to the klystron power supply are required and the entire AFC circuit is enclosed in a single unit containing an oscillator, ac preamplifier, phase detector, and feedback elements. The circuit has an open loop gain versus frequency characteristic which makes it particularly advantageous for use with klystron power supplies which generate 60 cps or other low frequency noise and which may, in addition, have a considerable amount of drift.
Electron Beam Probing of Plasmas
Authors: Harp R. S. , Cannara A. B. , Crawford F. W. , Kino G. S.
Published: February 2005

Measurement of static and dynamic electric fields in plasmas presents considerable experimental difficulties, particularly in regions such as sheaths, where the fields vary rapidly in space and common techniques such as the use of probes are not applicable. An extremely powerful approach is to employ an electron beam probe. This technique is a very old one which in recent years has passed through several stages of refinement. The authors review the previous work and describe in detail a system suitable for measuring accurately dc and rf fields up to several hundred Mc in low pressure discharges. The apparatus has been used to make a wide variety of measurements of plasma properties, and the associated techniques that have been developed are presented. These include methods of plasma production and of precision measurement of rf fields in amplitude and phase.
Electrical Phase Shift Multiplier
Authors: Noble Frank W. , Cook Peter Wm.
Published: February 2005

The sensitivity and resolution of a given phasemeter can be improved at least one hundred times by connecting a phase shift multiplier between the phasemeter and the signal sources. The multiplier has been used to improve the sensitivity of an ultrasonic detector for gas chromatography. It should find applications in other fields where measurement of extremely small phase shifts is required.
Ultrahigh Frequency Nuclear Magnetic Resonance Spectrometer
Authors: Jefferts K. B. , Jones E. D.
Published: February 2005

A spectrometer designed for operation between 600 and 700 Mc with samples at very low temperatures is described. The basic design is applicable between about 200 and 1000 Mc.
Simple Device for Stretching Test Pieces under High Hydrostatic Pressures
Authors: Brandes Marek , Szlachcic Henryk
Published: February 2005

Constructional requirements for devices used for stretching specimens under high hydrostatic pressure have been discussed. The construction of the device allows purely axial stretching of high strength steel specimens whose diameter reached ⅓ of the inner diameter of the pressure chamber itself. The device can be used for testing the strength of materials in all cases in which the stretching is carried out in a chamber of limited dimensions.
Automatic Pole Figure Plotter
Authors: Eichhorn Robert M.
Published: February 2005

A simple recording apparatus has been developed which automatically plots preferred orientation information obtained by x-ray diffraction in pole figure from. It is used with spiral scanning, counter tube, preferred orientation x-ray goniometers. The apparatus consists of an X-Y recorder, a spiral time base signal generator, and an encoder which translates variations in diffraction intensity into corresponding variations in the character of a spiral trace plotted by the recorder. Pole figures of cold rolled aluminum foil, automatically recorded with no corrections, are presented.
Superconducting Pseudo-Helmholtz Coil
Authors: Sampson W. B. , Kruger P. Gerald
Published: February 2005

Measurements of the field distribution along the axis of a Nb3Sn superconducting pseudo-Helmholtz coil, or ``split pair,'' are presented for various spacings between the two coils. The results agree well with the classically calculated field distribution and no current degradation effects that could be attributed to the multiple coil arrangement were observed. A maximum field of 58 kG was obtained in the region between the coils with the fields adding and a maximum field gradient of 26 kG/cm achieved with the coils powered in opposition.
NMR Calibration and Hysteresis Effects of Superconducting Magnets
Authors: Maxfield B. W. , Merrill J. R.
Published: February 2005

This paper reports a convenient method of absolute calibration for low homogeneity, superconducting solenoids for fields up to 85 kG. The method utilizes nuclear magnetic resonances of hydrogen and aluminum nuclei at rf frequencies up to 95 Mc. The NMR samples are in a liquid helium bath at the end of cables 1 m or more in length. Some measurements of hysteresis in an uncorrected superconducting solenoid are also reported.
Design of Efficient Flux Concentrators for Pulsed High Magnetic Fields
Authors: Wilson M. N. , Srivastava K. D.
Published: February 2005

The design of flux concentrators to produce pulsed high magnetic fields is discussed with special attention to the problem of energy transfer efficiency. A flux concentrator is described which produces a peak field of 300 kG in a cylindrical volume 2.0 cm in diameter and 3.5 cm in length. Energy storage is by means of a 440 μF capacitor bank and the pulse length is 120 μsec.
Design of High Field Magnet Coils for Long Pulses
Authors: Gersdorf R. , Muller F. A. , Roeland L. W.
Published: February 2005

Magnet coils are investigated which can produce magnetic fields of 15–40 MA/m (200–500 kOe) during working times of the order of 0.1 sec. These fields are suited for measurements in highly conducting materials. The coils are precooled to 20°K or 77°K and the Joule heat is not removed during the pulse. In Sec. I the thermal limitations of this method are reviewed. Plots are given for the optimum dimensions and current densities for coils producing a specified field during a specified time, minimizing the necessary power supply. Details of a magnet constructed along these lines are given. The maximum field produced by this coil, 16 MA/m (200 kOe) during 0.3 sec, however, proved to be determined by mechanical instabilities. These problems are reviewed in Sec. II. Calculations of the Lorentz force and the internal stresses resulting from it were carried out taking the elastic and plastic properties of copper and insulation into account. It is shown theoretically that a magnet stable to 35 MA/m (440 kOe) can be built from hard drawn copper if a reinforcing steel cylinder is used at a certain radius inside the coil.
Simple Data Display System for Fast Scanning Mass Spectrometer
Authors: Marsden D. G. H. , Forst W. , Feng K. K. , Park K.
Published: February 2005

A very simple display device is described that makes use of two independent time bases provided by some types of oscilloscopes. The device consists essentially of a diode gate driven from the oscilloscope by means of some rather simple associated circuitry. The ion beam signal is chopped, or sampled, peak after peak, smoothed by an RC filter, and displayed by means of a pen recorder, a recording galvanometer, or another oscilloscope. Most of the statistical fluctuation in peak height is thus eliminated.
X Ray Luminescence Sample Compartment with Automatic Shutter
Authors: Bodi Lewis J. , Cosgrove James F. , McIntosh Gardiner
Published: February 2005

A sample compartment is described which, with a standard x-ray generator, allows routine observation of phosphor response to x rays. A unique feature is an automatic shutter which permits safe sample transfer while the x-ray tube is excited. Some experimental results are provided.
Apparatus for High Pressure, High Temperature Studies of Oxide Materials
Authors: Van Hook H. J.
Published: February 2005

A platinum-rhodium wound furnace built into a pressure vessel is described for investigation of phase equilibria at 1200–1700°C under oxygen pressures of up to 100 atm. The apparatus is designed for quenching small samples under pressure with a minimum of pressure seals to be broken for sample introduction and removal. Heat transfer at high pressure from the hot zone to the vessel wall limits the pressure-temperature conditions obtainable within the power loading limits of the resistance wire.
Optics of the Integrating Schlieren Instrument
Authors: De Boer P. C. T.
Published: February 2005

An analysis is presented of the optics encountered in the integrating schleiren arrangement as first described by Resler and Scheibe. Expressions have been developed for the signal which will be received on the phototube, both for the instrumentation using an inclined knife edge and for that with a vertical knife edge. Attention is given to the conditions which must be satisfied to guarantee that the response of the phototube shall be proportional to the difference in refractive index at the beginning and the end of the test section. A simple method is described for calibrating the density scale; the method involves displacing the knife edge over a known distance and measuring the resulting signal. The influence of certain diffraction phenomena on the measurements is briefly discussed, and it is concluded that Fresnel diffraction occurring in the edges of the light beam is one of the factors determining the resolving power. Another factor important for the resolving power is the divergence of the incident light. In comparing the various possible positions of the knife edge, it is concluded that the inclined knife edge, besides allowing operation over a wide range of density gradients, has the advantage of giving a linearity of response which suffers little from diffraction effects. The advantage of the vertical knife edge is the very high sensitivity which can be obtained.
Nonpolarizing Electrode System for Dielectric Measurements on Soda-Glass
Authors: Chakravorty D. , Cross L. E.
Published: February 2005

An experimental cell for making dielectric measurements on small soda glass samples with sodium amalgam electrodes is described. The cell allows a properly guarded nonblocking measurement of the dielectric properties on samples of 1.3 cm diameter. The performance is illustrated by a very brief description of measurements on glasses of composition 1.5 Na2O, 0.5 Al2O3, 5 SiO2.
Short Duration 2500 J Flash Photolysis Apparatus Controlled by an Ignitron
Authors: Clerc M. Michel
Published: February 2005

A versatile, easily constructed flash photolysis apparatus has been built using a high performance ignitron as the firing system.
Lithium-Drifted Position Sensitive Detector
Authors: Ludwig E. J.
Published: February 2005

An attempt has been made to produce position sensitive detectors with depletion depths of several millimeters by lithium drifting. The technique used involves evaporating a thin metallic layer onto the side opposite the lithium diffusion to provide a uniform resistive sheet. Detectors measuring 8×28 mm were tested with 5.5 MeV α particles and 4.2 MeV protons and exhibited energy spreads of 2–3.5% uncooled and 1–2% when cooled. The position linearity plot of the detectors indicated that the particle position could be determined to within 0.3 mm.
Focused Slow Ion Beam for Study of Electron Ejection from Solids
Authors: Hagstrum H. D. , Pretzer D. D. , Takeishi Y.
Published: February 2005

This paper reports advances in the operation of the ion lens system used in studies of electron ejection by slow ions which make it possible to conduct the experiment with ion energies as low as 4 eV. Ejected electrons may be retarded by as much as 20 eV in the presence of this beam. Significant differences in electron kinetic energy distributions for ion energies differing by as little as 1 eV in the lower energy range are observed. Electrode arrangements and circuit innovations including amplifier calibration and negative feedback stabilization of the ion beam are discussed. Criteria for proper lens performance are given and experimental data illustrating the meeting of these criteria are presented. Examples of lens failure are also shown.
Micromachining Electron Optic Apertures in Clear Fused Quartz
Authors: Blahnik Carl E.
Published: February 2005

Techniques and apparatus for producing holes as small as 0.05 mm in diameter with optical quality in clear fused quartz disks are described. The realizable tolerances in roundness, concentricity, and surface finish are sufficiently high to yield apertures for an electrostatic electron optical system that requires no axial alignment after initial assembly or repeated high temperature vacuum bakeout.
Thermoelectric Control Apparatus for the Fabrication of Thick Lithium-Drifted Germanium Detectors
Authors: Palms John M. , Greenwood Arthur H.
Published: February 2005

Lithium-drifted germanium radiation detectors have been fabricated utilizing thermoelectric cooler-heater modules to provide temperature stabilization during the drifting period. The thermoelectric modules provide rapid temperature control determined by the diode bias current. The control loop system is able to provide fast response because, contrary to a conventional oven heater and cold sink arrangement, one no longer has to balance a variable heat source with a constant heat sink. Power levels required for proper control have also been substantially reduced. The detector control unit incorporating a novel differential thermoelectric power circuit is described. The apparatus enables drifting to take place uniformly across the crystal. Depletion depths of 7 mm in crystals with an area up to 8 cm2 have been obtained. Linewidth of 5.4 keV for 54Mn has been achieved. The detailed technique of diode fabrication and typical detector characteristics are presented.
Variable High Voltage Pulse Generator
Authors: Ruben M. J.
Published: February 2005

A high voltage pulse generator is described which delivers into a capacitive load square voltage pulses of an amplitude from 0 to 1 kV, controlled by the setting of a variable HV supply. The pulse polarity is positive, with the base at ground potential, and its width can be varied from 1 μsec to 1 msec. The repetition rate can be varied up to 104 sec−1, provided that consecutive pulses are spaced at least 70 μsec. The rise and fall rates are better than 5 kV/μsec at maximum load. Overshoots of 2% are allowed and the droop at maximum width is negligible.
Recording Creep Tester for Soft Polymeric Materials
Authors: Penn Robert W. , Fulmer Glenn E.
Published: February 2005

An apparatus to measure tensile creep of soft polymeric materials has been designed and tested. This servo-controlled device permits recording the length of a plastic sample as a function of time from approximately 1 sec after loading. Length changes up to 20 cm can be determined to a precision of ±0.0012 cm. The instrument is stable to ±0.0012 cm over periods of several hours.
Technique for the Deposition of Macromolecular Samples in Field Emission and Field Ion Microscopy
Authors: Abbott Robert C.
Published: February 2005

The technique involves the freezing on the microscope tip of a droplet of solution containing the subject molecules, followed by freeze drying. Alternate hypotheses concerning the delivery mechanism during freeze drying, and thus estimates of required specimen concentrations in solution, are evaluated by comparing them with experimental results obtained for copper phthalocyanine (10 mg/ml), transfer RNA (1 mg/ml), and light meromyosin (10−3 mg/ml).
27.6 cm Internal Diameter Superconducting Magnet
Authors: Stekly Z. J. J. , Lucas E. J. , De Winter T. A. , Laverick C.
Published: February 2005

The design construction and testing of a 27.6 cm bore superconducting magnet are described. The magnet was operated at 32 800 G at an average current of 10 A and a stored energy level of 300 000 J during a 9 day test.
Rotating Steel Mirrors—Failure and Success
Authors: Brixner Berlyn
Published: February 2005

Four main causes of rotating steel mirror failure—excessive vibration, excessive speed, hydrogen embrittlement, and defective steel—are discussed and illustrated. Performance characteristics are given for a successful, 10 000 rps, 25×38 mm mirror drive.
Low Level Second Harmonic Detection System
Authors: Thomas D. E. , Rowell J. M.
Published: February 2005

A second harmonic detection system suitable for detailed study of current-voltage characteristics, particularly tunneling characteristics of superconductor and semiconductor junctions, is described. The system is capable of detecting second harmonic voltage changes as low as 10−9 V which allows the fundamental signal level to be ≤kT at a junction temperature of 1°K. A selection-rejection impedance transformation reactance network which is the heart of the system is described. The quantitative relationships between second harmonic voltage and second derivative of current with respect to voltage are given. The capabilities of the system are illustrated by a photograph of an X-Y recorder tracing of second harmonic voltage vs dc bias voltage for an Al-I-Pb tunnel junction.
Simultaneous Measurements of Optical Transmission and Reflection in Thin Films
Authors: Váradi P. F. , Suffredini J. R.
Published: February 2005

A monochromator modification was developed which makes simultaneous measurements of the optical transmission and reflection of thin films deposited in vacuum. The measurements can be made with light incident from either the substrate of the film or from the vacuum interface. The instrument is capable of working in the 0.4 to 2.30 μ wavelength range. The measuring system, sample design, and experimental errors are discussed.
Design and Performance of a Low Attenuation Electromagnetic Shock Tube
Authors: Smy P. R.
Published: February 2005

Various aspects of the design of a low attenuation electromagnetic shock tube are discussed. The driver gas is nitrogen at atmospheric pressure and is separated from the driven gas by a thin Mylar diaphragm. Particular attention is paid to matching electromechanically the shock tube driver to the energizing capacitor bank. These considerations may increase the uniformity of flow behind the shock wave as well as improve the efficiency of the shock tube. A simple criterion is evolved in terms of the various shock tube parameters, which states that the driver gas should be ejected as a single body during the first discharge of the capacitor bank. The construction of the shock tube is described. Measured shock velocities in air and argon for different capacitor voltages and downstream gas pressures are given and are compared with the velocities predicted by the simple theory. It is concluded that the shock driving mechanism is predominantly electromagnetic in nature but that at low downstream gas pressures (≤ 1 mm Hg) this mechanism is augmented by the wave action which accompanies Joule heating of the driver gas.
External Beam Extraction Rate Control for the Cosmotron Accelerator
Authors: Cottingham J. G. , Kovarik V. J. , Pellegrin J. L.
Published: February 2005

The delivery rate of the external proton beam from the Cosmotron is made more uniform by a feedback system acting on the internal orbit center. This improves the experimental statistics and makes more efficient use of available beams.
Growth of Single Crystals and Bicrystals of Alkali Halides
Authors: Fuschillo N. , Nelson C. E. , Gimpl M. L.
Published: February 2005

Techniques are described for the growth of large (6.3 cm2 by 15 cm) single crystals and bicrystals of NaCl. Grain boundaries from 2 to 45° mismatch across the interface were grown for pure tilt and pure twist misorientation in NaCl by the Czochralski technique. The method of crystal growth and the techniques required for good control of the misorientation and the planarity of the grain boundary are described. Similar techniques can be applied to KCl, LiF, and CsBr. The tilt grain boundaries of the NaCl bicrystals were found to be strong mechanically and not easily cleaved apart. The twist grain boundaries were very weak mechanically, especially at mismatch angles greater than 20°. Techniques and results for growing long thin single crystals of NaCl which have great flexibility and for observing the substructure of the growing interface of a single crystal are described.
Mössbauer Spectrometer using a Piezoelectric Bar in Resonant Oscillation
Authors: Gerson Robert , Denno William S.
Published: February 2005

A Mössbauer velocity spectrometer has been constructed using a bar of piezoelectric ceramic (lead titanate zirconate) as the source of the Doppler-shift velocity. The bar was driven electrically at its longitudinal resonant frequency (22 kHz for a bar 7 cm long and 0.6×0.6 cm cross section), the resonant condition permitting the attainment of higher velocities than had previously been obtained with piezoelectric drives. The piezoelectric is driven with about 1 V of excitation to display the Mössbauer spectrum for iron. This type of spectrometer may be useful for special purposes, as when its small size or ruggedness is necessary.
Measurement of the Dielectric Constant and Loss Tangent of Isotropic Films at Millimeter Wavelengths
Authors: Conklin G. E.
Published: February 2005

A technique for measuring the dielectric constant and loss tangent of isotropic films of electrical thickness less than about 60° has been developed. The method is adapted specifically to a cavity system constructed from 1.111 cm i.d. waveguide for use with the TE°01 mode from 50 to 60 Gc. The approximate limits on the measurable loss tangent of ordinary plastics by this technique are: 1×10−4≲tanδ≲1×10−1. Measurements at 55.2 Gc were made on three materials. The results are as follows:     Material ε2′ tanδ2Plexiglas2.550.0048General Electric varnish No. 12022.650.012Mylar film3.145̄0.0044
Direct-Reading Ratio-Sensitive Tristimulus Colorimeter
Authors: Schlotzer George
Published: February 2005

A direct-reading ratio-sensitive CIE tristimulus colorimeter employing photovoltaic cells is described. Its characteristics as a function of cell loading and cell illumination have been examined. The instrument is insensitive to large variations in light level provided there is no attendant color change. The ratio sensitive colorimeter is simpler to operate than the conventional current balance since the preliminary normalizing adjustment is eliminated. This property allows the ratio colorimeter to be used to continuously monitor color.
Laser Interferometer for Earth Strain Measurements
Authors: Vali V. , Krogstad R. S. , Moss R. W.
Published: February 2005

A laser interferometer for earth strain measurements has been constructed and is described. The apparatus is designed to measure displacements down to small fractions of the laser wavelength. Measurements of length change of the interferometer arm of 10 m length were obtained during normal microseismic activity and following a distant earthquake. Some representative results of this laser application are presented.
Evacuate-Back Fill Glove Box
Authors: Wanser R. , Uhlmann D. R.
Published: February 2005

A glove box is described whose chamber may be evacuated into the range of 10−6 mm Hg and subsequently back-filled with a dry gas. Essential features include caps for evacuating simultaneously both sides of the gloves and quick disconnecting fittings for ready accessibility to the box. Slight modification of design permits wide variation in box geometry.
Ultrasonic Treatment of Specimens in the Electron Microscope
Authors: Langenecker B.
Published: February 2005

A method and technical details are described for direct observation of effects of high amplitude ultrasonic stress waves on dislocations in metal crystals. The technique combines, for the first time, ultrasonic treatment at high acoustic energy densities (up to 109 ergs/cm3 at frequencies between 30 and 100 kc), observation of damping of stress waves, and electron microscopy. Results from this in situ technique allow fundamental refinement of present theories on ultrasonic activation of dislocation mechanisms.
Design and Adjustment of a 20 cm Mach-Zehnder Interferometer
Authors: Gebhart B. , Knowles C. P.
Published: February 2005

The design of a large Mach-Zehnder interferometer which uses fused silica flats in aluminum mounts and piezo-electric crystals for remote fine adjustment is discussed. In addition, an expedient method of alignment is given which allows the adjustment to fringes and to the white light fringe condition to be more conveniently and quickly accomplished.
Instrumentation for Fermi Surface Measurements Using Ultrasonics
Authors: Ketterson J. B. , Eckstein Y.
Published: February 2005

Three methods are described for enhancing specific oscillatory components of the magnetic field dependent attenuation coefficient of sound found in pure metals at liquid He temperatures. These oscillations are related to Fermi surface properties. Instrumentation suitable for these methods is described in detail. Some data taken with these techniques are shown. In addition, a description of the ultrasonic technique used is included.
Density Balance for Low Temperatures and Elevated Pressures
Authors: Grigor Anthony F. , Steele William A.
Published: February 2005

An electromagnetic balance for the measurement of fluid density at low temperature and elevated pressure is described. The balance is operated by balancing the changes in gravitational forces due to the buoyancy of a sphere immersed in the fluid against the electromagnetic force between a current carrying coil and a permanent magnet. The apparatus, which requires a relatively small amount of fluid, is capable of high precision and can be operated at any temperature below ambient and at pressures up to 80 atm.
Ionization Discrimination Properties of Spark Chambers
Authors: Grieder P. K. F.
Published: February 2005

Spark chamber behavior with respect to heavy and minimum ionizing particles is investigated in an attempt to find suitable gases and modes of operation that would permit ionization discrimination. Chambers having a gap of 10±0.05 mm and fillings of pure helium, pure argon, and helium-argon mixtures were analyzed. It was found that for the given modes of operation only argon-filled chambers show useful ionization discrimination properties, while chambers with pure helium fillings have practically none. The results obtained for helium-argon mixtures are better than those for pure helium but inferior to those obtained for pure argon fillings. Curves showing the chamber responses with respect to 210Po alpha and minimum ionizing particles are presented for helium and for argon filled chambers. The effect of gas contamination is discussed and some data are given.
Low Temperature System for Thermal Conductivity Measurements
Authors: Klein Miles V. , Caldwell R. F.
Published: February 2005

Germanium and platinum resistance thermometers are used with two metal Dewars over the temperature range from 1.2 to 300°K. A variable conductance helium exchange gas switch is employed together with automatic heating to maintain any desired temperature within this range. Two coupled potentiometric dc measuring circuits are used—one to measure and control the sample temperature, and the other to measure the temperature gradient. The performance of the system is discussed.
Accurate Resistance Measurement with Smith Bridge
Authors: Dekker H. , Mosselman C.
Published: February 2005

A commercial 6 decade Smith bridge has been improved by elimination of several types of disturbances. It is now possible to differentiate between temperatures which are less than 1.5×10−5°C apart.
Determination of Plasma Potentials and Ion Energies by Ion Extraction and Energy Analysis
Authors: Erickson C. W.
Published: February 2005

This paper describes the theory and operation of a new diagnostic tool for the extraction of ions from the main body of a confined plasma. The device, a magnetically shielding tube used in conjunction with an electrostatic energy analyzer and secondary electron detector, can be used for measuring ion energy distributions, plasma potential, and energy dependence of plasma ion lifetimes. Shielding properties and limitations of the device are also discussed.
Use of Probes to Measure Static Potential in High Vacuum Electron Devices
Authors: Lear W. Edward , Simpson Richard S.
Published: February 2005

Design factors are considered for the use of emitting and nonemitting metallic probes for measuring static potential in electron streams. Both unneutralized streams and those neutralized by positive ions in a field free drift space are considered. Experimental results are given for potential measurements in a cylindrical diode and in a beam type tube. Good agreement with theory is found for the radial potential distribution in the diode using either probe. The emitting probe gives best results but is more complex in construction and circuitry. Qualitative agreement with theory is found for axial and radial potential distribution in a neutralized cylindrical electron beam.
Automatic Unit for Thinning Transmission Electron Microscopy Specimens of Metals
Authors: Schoone R. D. , Fischione E. A.
Published: February 2005

A specimen holder and a polishing unit with an automatic shutoff were designed for thinning disks taken from preselected areas of large metallic specimens or from specimens with small cross sectional areas. Since the disk precisely fits the specimen holder of the microscope, a supporting grid is unnecessary and deformation from cutting and handling after thinning is eliminated. The automatic shutoff device greatly improves conditions for transmission by stopping the polishing current at the optimum time.
Arc-Image Stagnation-Flow Reactor for Measuring Kinetics of Gas-Solid Reactions from 2000 to 3000°K
Authors: Ladd Irwin R. , Wilson Harold W.
Published: February 2005

An arc-image stagnation-flow reactor has been developed to study the rates of gas-solid reactions between 2000 and 3000°K. Most refractory solids can be heated in this reactor to their melting points in a partial atmosphere of almost any gas except strong oxidizers such as fluorine. The standard deviation of a datum point, in the case of oxidation of tungsten by CO2 at 100 Torr, is 6% at 2500°K, corresponding to a temperature uncertainty of ±9°K.