bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Scanning Electron Diffraction System
Authors: Grigson C. W. B.
Published: February 2005

An improved transmission scanning electron diffraction system is described. It can make angular measurements comparable with those of photographic instruments, its intensity measurements can have an accuracy of ±0.2% for single traces, ±1% for complete frames, its sensitivity is sufficient to give clear intensity signals from specimens of average thickness equal to an atomic layer, its angular resolving power is 0.23 mrad. Important features of the system are a high productivity rate so that many specimens can be grown within the instrument and examined in a short time; the ability to record diffraction patterns continuously as films are grown by vacuum deposition with growth rate/vacuum values of up to 107 Å sec−1 Torr−1; and ability to scan diffraction patterns in two dimensions. Scan rates depend on the response speed of the X-Y recorder used and are 10–50 sec for a single trace, 20–60 min for an entire frame from a single crystal film. The design of the system is discussed and results from polycrystalline, grain-oriented, and growing films are given to demonstrate its versatility and performance.
Interferometer Technique for Measuring the Dynamic Mechanical Properties of Materials
Authors: Barker L. M. , Hollenbach R. E.
Published: February 2005

A new technique is described for measuring the position history of the free surface of an impacted specimen. Measurements can be made to 0.025 μ accuracy at free surface velocities up to 0.1 mm/μsec. Problems and possible solutions for monitoring higher velocities are indicated.
Electronic Integration Technique for Measuring Magnetization of Hysteretic Superconducting Materials
Authors: Fietz W. A.
Published: February 2005

A simple system capable of continuously recording complete magnetization curves for hysteretic superconductors is described. It allows the applied field to be cycled slowly in order to avoid transient effects in the specimen material. A voltage proportional to the differential susceptibility of the material is integrated by a chopper stabilized solid state amplifier, and plotted on an X-Y recorder as a function of applied field. The system is capable of recording magnetization curves over periods of 15 min with an over-all uncertainty of 5% or less.
Sensitivity Enhancement in Magnetic Resonance. I. Analysis of the Method of Time Averaging
Authors: Ernst R. R.
Published: February 2005

A theoretical analysis of the method of time averaging is made with special emphasis on the correlation effects caused by non-white noise. It is shown that only in special cases is the signal-to-noise ratio improved exactly according to the square root of the number of successive scans through the investigated spectrum. This is shown in detail for random noise with an exponential-cosine autocorrelation function. In the case of random noise with a pure exponential autocorrelation function, the deviation from the proportionality to the square root of the number of scans does not exceed a factor √2. If the frequency dependence of the power spectrum of the noise is given by |f|−λ, 0≤λ≤1, then the proportionality to the square root of the number of scans holds exactly. A peak in the noise power spectrum at a multiple of the repetition frequency of the scanning does affect the time averaging only if its width is smaller than the repetition frequency.
High dc Power, Solid State Switch for Pulsing an Arc Lamp
Authors: Alexander Thomas A. , Lawler Earl R. , Wilson Patrick W. , McDonald Richard I.
Published: February 2005

A high power, solid state device to switch direct current on and off for the controlled pulsing of a high intensity light source is described. Using 400 A (continuous rating) silicon controlled rectifiers, the switch has a design maximum power rating of 5000 A at 450 V for a 1 msec pulse.
Apparatus for the Simultaneous Determination of Young's Modulus and Shear Modulus at Temperatures between −190 and 600°C
Authors: Armstrong Philip E. , Dickinson James M.
Published: February 2005

An apparatus, based on thin-rod resonance techniques, has been used to determine both Young's and shear moduli as functions of temperature during a single experiment. The advantages of this method, its accuracy, and its limitations are discussed, along with the constructional details of the apparatus.
Generation and Detection of Subnanosecond Light Pulses: Application to Luminescence Studies
Authors: Yguerabide Juan
Published: February 2005

Techniques developed to study the kinetics of very fast luminescent systems are described. These techniques include lamps which generate subnanosecond light pulses and an instrument which measures their time characteristics. The lamps are of the gaseous discharge type. The conditions of gas pressure, capacitance, and gap width necessary to achieve fast light pulses have been established for several gases and mixtures of gases with oxygen. The experimental results indicate that high pressure (10 atm or larger) and minimum stray capacitance are required for lamps filled with pure gas. A lamp filled with hydrogen, and satisfying these requirements, yields light pulses with 0.35 nsec risetime and 0.5 nsec half-width. The time characteristics of the fast light pulses are not affected by gap width in the range 0.1–0.6 mm. Lamps containing a mixture of a gas and oxygen produce similar light pulses at total pressures much less than 10 atm. The instrument used to study subnanosecond light pulses employs a modified image converter tube. The image converter tube converts a light pulse into a photoelectron beam which is subsequently sampled by sweeping over an aperture. A complete intensity vs time curve is achieved by varying the time at which the sample is taken. The time resolution of the instrument is dependent on the sweep rate and the transit time spread of electrons in the image converter. Experimental and theoretical results indicate that the time resolution is around 0.1 nsec. The sweep is produced by a special circuit, consisting of a series of avalanche transistors, which generates sweep voltages around 600 V/nsec and can be triggered, with time jitter less than 0.2 nsec, by an electrical pulse as short as 1 nsec and amplitude of 0.8 V. This circuit makes it possible to measure the time characteristics of any light source for which a small electrical pulse can be generated simultaneous with the light pulse. A special detecting system which measures the intensity of the sample taken from the electron beam makes it possible to measure, with high precision, very low intensity sources. Thus, the time characteristics of a light pulse which produces less than one photoelectron per pulse at the photocathode of the image converter can be measured down to one decade of its peak intensity.
Technique for Preparing Laminated Pole Figure Samples
Authors: Leber Sam
Published: February 2005

A new method is described for making composite samples for the x-ray diffraction, back reflection pole figure technique. Considerable savings, in material and machining costs, are realized by cutting strips, for lamination, at 45° to the rolling direction. The required reference surface is obtained, during lamination, by maintaining an angle of 54.7° between the strips and the surface developed by the cut edges. The advantages of the composite technique (better averaging, minimization of errors, and evaluation of random intensity from the pole figure data) are retained by this modification.
Improved Method for Measuring Small Volume Changes on Mixing
Authors: Levialdi Stefano , Wanke Enzo , Bianchi Umberto , Cuniberti Carla
Published: February 2005

An improved method is described for measuring small volume changes on mixing a polymer with a solvent. The change in volume, occurring in a special dilatometer, causes a shift of a mercury level inside a constant cross section capillary, whose external surface is silver coated. The capillary is thus acting as a cylindrical capacitor, any change in volume being converted into a capacitance change. To eliminate the influence of thermal fluctuations, the apparatus works as a differential set. The calibration is performed by producing a known thermal expansion of a given amount of solvent (contained in the dilatometer) whose expansion coefficient is known. The sensitivity achieved is better than 1 ppm.
Method for Determining the Peak Irradiance of an Optical Pump and Total Pump Energy That Is Incident Upon a Laser Crystal
Authors: Negrelli Thomas J.
Published: February 2005

A method has been developed for determining the peak irradiance of an optical pump and the total pump energy incident upon a laser crystal. Consideration is given to the variation of temperature within a copper cylindrical shell that is irradiated by an intense, short duration light pulse. A temperature distribution expression is derived which describes the variation of temperature with respect to time, at the innner wall of the shell. A copper, cylindrical shell was positioned within the helix of a xenon flash lamp and irradiated with light pulses of various intensities. The temperature rise of the inner surface was monitored with a fast response thermocouple and the temperature history displayed on an oscilloscope. The maximum temperature rise of the inner surface of the cylinder was used in conjunction with the derived temperature distribution expression and the peak irradiance and total incident energy determined.
Bakeable, Pulsed Gas Valve for Plasma Physics Experiments
Authors: Birdsall D. H. , Ping D. E.
Published: February 2005

A small, bakeable, magnetically actuated, pulsed gas valve has been constructed which overcomes many of the difficulties experienced with previous designs. Reproducible gas pulses of from 1 to 150 micron liters are readily attainable with the valve described.
Determination of Natural Tritium
Authors: Bainbridge A. E.
Published: February 2005

The experimental methods employed at the La Jolla Natural Tritium Laboratory, University of California, for the determination of natural tritium are briefly described. The method is to assay the electrolytically enriched sample as ethane gas in a proportional counter. An error of less than 4% is obtained for samples enriched by reducing the sample volume from 2 liters to 10 ml. It is found that the previous methods of calculating the electrolytic enrichment are not necessary nor are large volume reductions necessary for most applications. In the method adapted at La Jolla the enrichment in five electrolysed samples is determined by using a sixth spiked sample. In this way it is shown that the enrichment in the sixth sample is within 4% of the enrichment in the other five and can be quickly determined.
Rapid Determination of Electron Impact Ionization and Appearance Potentials
Authors: Martignoni Pasquale , Morgan Robert L. , Cason Charles
Published: February 2005

All manual controls of Fox's retarding potential difference (RPD) technique have been replaced by automatic electronic controls applied to a commercial time of flight mass spectrometer. The current difference ΔI between the electron energy voltage increments, is obtained from an electronic data processor and plotted as a function of the ionizing voltage. An ionization efficiency (IE) curve is obtained in 3.8 sec or less. The sensitivity of the system permits an IE curve to be obtained in the 10−8 Torr range. An empirical formula was required to correct the present systematic error. The error was found to be −3.67+0.834x−0.0306x2 for xenon, krypton, and argon, where x is the ionizing voltage of the data. This formula was used to correct the experimental water ionization potential (IP) to give 12.59±0.05 V. The spectroscopic water IP is 12.61 V.
Quantitative Coulometric Analyzer for Determining Dehydration Temperatures in Solids
Authors: Osgood J. H.
Published: February 2005

Quantitative Coulometric analyses for water yield are made during thermal dehydration of rock materials and other solids. An electrolytic hygrometer cell is utilized to quantitatively measure the evolved water from a solid at known temperature as it is uniformly heated to a maximum of 1200°C. By reduction of total exposed adsorbing surface area in the retort and in the electrolytic cell coupling system, the lag between the dehydration event in the sample and cell response has been reduced to a very few seconds, thus permitting direct correlation between sample temperature and hygrometer cell current. The rapid cell response permits the resolution of discrete dehydration events and defines the temperature range through which they occur. Specific temperature-desorption data gained with this instrument have been very helpful in gaining an understanding of the modes of constitution of water in silicates.
Magnetogalvanic Measurements to 60 000 Bar
Authors: Vaišnys J. R. , Kirk R. S.
Published: February 2005

Bridgman anvils have been adapted for Hall effect measurements, thus extending the pressure range of such measurements considerably. Multiple probes are introduced into the high pressure cavity by using an epoxide adhesive. Magnetic fields are produced axially: the anvils are used as pole faces. Samples are embedded in silver chloride to decrease nonhydrostatic effects. The technique is demonstrated by measurements performed with bismuth and tellurium. Problems of calibration are discussed.
Recording High Shear Viscometer for Measurement at Shear Rates Near 106 Sec−1
Authors: Porter Roger S. , Klaver Rudolph F. , Johnson Julian F.
Published: February 2005

An improved recording rotational high shear viscometer has been developed. The instrument employs concentric steel cylinders with unusually narrow and precisely defined shear clearances. Both shear rate and stress are continuously and independently recorded. Improved cylinders and other additional features have led to accurate viscosity measurements at shear rates from 5×102 to 2×106 sec−1. The temperature range is −20 to +150°C with a viscosity range which varies inversely with the desired shear rate for measurement. The shear rate range and the upper limit, 2×106 sec−1, exceed all previous reports of measurement at defined conditions in a homogeneous, isothermal shear field.
High Efficiency Source for Metal Ions
Authors: Magnuson G. D. , Carlston C. E. , Mahadevan P. , Comeaux A. R.
Published: February 2005

An ion source is described which produces beams of ions of both high and low vapor pressure materials. The source has the following characteristics which make it suitable for accelerator applications or laboratory ion beam experiments where the large size and complexity of isotope separator ion sources would be a disadvantage: (1) small size, (2) simplicity of construction and operation, (3) long filament life, (4) high charge utilization efficiency, (5) wide operating temperature range, (6) relatively modest power requirement, (7) ability to operate efficiently on either gas or solids. The source operates by electron bombardment ionization of the vapor of the charge material. The vapor is obtained by heating the charge to a sufficiently high temperature to achieve the proper source operating pressure. A unique feature of this source is the combination of the discharge chamber and charge container into one chamber. The operating temperature range of the source is from approximately 300 to about 1600°C. Beams of Zn+, Al+, Cu+, Ag+, Au+, and Fe+ ions have been produced which contain but a small percentage of impurity ions. The charge material in all these cases has been the pure metal.
Determination of Recoilless Fractions from Mössbauer Scattering
Authors: Debrunner P. , Morrison R. J.
Published: February 2005

The intensity of the recoilless and nonrecoilless resonant scattering of Mössbauer gamma rays for single line Lorentzian energy distributions is calculated. The scattered intensities are expressed in terms of a scattering function which contains the parameters of the scatterer. This scattering function has been evaluated for a wide range of values of the recoilless fraction, electronic absorption, thickness, and linewidth of the scatterer. It can be used to determine source and scatterer recoilless fractions from the total scattered intensities. If the recoilless fraction is sufficiently large the recoilless and the nonrecoilless part of the resonantly scattered intensity can be determined, with the aid of numerical calculations given, from a measurement of the transmission of the scattered gamma rays through a resonant absorber. The ratio of the recoilless to the nonrecoilless part of the resonantly scattered intensity does not depend very sensitively upon the properties of the source and can be used to determine unambiguously the recoilless fraction of the scatterer.
Locked rf Spectrometer for Nuclear Quadrupole Resonance
Authors: Volpicelli Richard J. , Rao B. D. Nageswara , Baldeschwieler John D.
Published: February 2005

A technique is described for locking a rf spectrometer to a pure quadrupole resonance signal. Since the quadrupole resonance frequency of a nucleus in a solid can be quite sensitive to changes in temperature and pressure, a quadrupole resonance signal is of potential interest in the measurement of these variables. The application of a locked rf spectrometer as a precise nuclear resonance thermometer is evaluated using the 35Cl resonance of KClO3 powder. The precision of this device as a thermometer is about ±0.002°K, and the system is capable of tracking a temperature change of at least 2°K/min. The locked quadrupole spectrometer appears to have promise as an absolute temperature standard.
Pulse Pattern Generator for Transient NMR Experiments
Authors: Favret A. G. , Meister R.
Published: February 2005

A pulse pattern generator for transient NMR experiments has been built using commercially available solid state circuit modules. The generator provides stable pulse widths and delays from a few microseconds to several seconds. By replacing a single blank module the logic can be changed from a Carr-Purcell T2 sequence to a T1 sequence of pulse pairs with systematically increasing delay between pulses. The 90 and 180° pulse widths are accurately preserved in the change over. A variety of gating pulses are available to synchronize oscilloscopes or to activate circuits for suppressing the ring following a transmitted pulse.
Technique for Calibration of a Dynamic Rheological Shear Apparatus
Authors: Miles D. O. , Knollman G. C. , Hamamoto A. S.
Published: February 2005

A method is described for calibrating a type of rheological shear apparatus previously discussed in the literature. The technique is based on the use of precision elastic rings whose compliance can be predicted theoretically, and thus avoids the use of standards whose viscoelastic properties vary with frequency, temperature, pressure, age, etc. Applicability of the method presented here is foreseen in calibrating rheological systems other than the sinusoidal shear equipment for which the technique has been developed and proved.
Printed-Circuit Modular Instrumentation System
Authors: Barna Arpad , Marshall J. Howard , Torzewski Daniel F.
Published: February 2005

A transistorized modular instrumentation system for handling photomultiplier signals from scintillation and/or Čerenkov counters in high energy physics experiments is described. The experimenter has available a multiplicity of operations, such as coincidence determination, gating, amplitude discrimination, multiplexing, mixing, amplification, and pulse-height analysis. System design considerations emphasize direct interchangeability of modules to minimize calibration procedures. Particular emphasis has been placed on the stability and linearity of the amplifying, gating, and mixing circuits, so that 1% pulse-height resolution may be meaningfully achieved. High speed coincidence and gating circuits are available, in which ``pile-up'' effects have been minimized to allow operation at counting rates of up to 10 Mc. In experiments where manual data reduction is feasible, the outputs of the system are displayed via scalers and/or commercial pulse-height analyzers; in more complex experiments, the outputs may be further processed through a digital computer.
Time Resolution of Photomultiplier Systems
Authors: Hyman L. G.
Published: February 2005

Results on the ability of a photomultiplier system to resolve time differences are presented in graphic form. The results are presented in parametric form and hence may be applied to a wide variety of scintillator-photomultiplier combinations, provided the system is reasonably approximated by the model used in this work. In addition to the usual effects included (scintillator lifetime, pulse shape, transit time spread), the model includes the effects of finite risetime in the scintillation process.
Automatic Torsion Pendulum for the Continuous Recording of Internal Friction at Constant Amplitude and Very Low Frequencies
Authors: Salvi A. , Dautreppe D. , Friess E.
Published: February 2005

A torsion pendulum of the inverted type is maintained in oscillation at constant amplitude by means of an electric device. The mechanical oscillation gives rise to a frequency modulation which is detected in an original demodulator. The signal is amplified and used to supply two driving coils acting on small permanent magnets mounted on the inertia member. The amplifier is controlled by an error signal coming from the comparison of the amplifier input signal and a reference. An example of record showing internal-friction peaks in neutron irradiated iron is shown.
Improved NMR Probe for Magnetic Field Measurements
Authors: Pierce W. L. , Hicks J. C.
Published: February 2005

A small, simple, transistorized, marginal-oscillator type nuclear magnetic resonance (NMR) spectrometer has been developed for high resolution mapping of magnetic fields in relatively inaccessible locations, such as the interior of superconducting solenoids. With a probe volume of 8×10−6 liter, the device is able to give magnetic flux-density measurements to an accuracy of 2 parts in 106 with a spatial resolution of about 1 mm. Remote operation of all controls adds considerably to its versatility.
Improved Dilatometer
Authors: Hyde Garrett R. , Domingues Louis P. , Furlong LeRoy R.
Published: February 2005

Several improvements in the differential-transformer-type of dilatometer have been made. Unwanted differential expansion and mechanical hysteresis have been minimized by proper design of the sample holder and transformer mount. High sensitivity in temperature control together with linearity in the rate of heating have been produced by substituting a programmable reference-voltage controller for the conventional control system. Furthermore, replacing the sample does not require disassembling the sample holder. Operation from 25 to 1700°C is fully automatic.
Furnace for Molten Salt Measurements on the Cary Model 14-H Spectrophotometer up to 1450°C
Authors: Boston Charles R. , Smith G. Pedro
Published: February 2005

A resistance-heated furnace is described which may be used with the Cary model 14-H spectrophotometer for measuring the absorption spectra of liquid systems at temperatures up to 1450°C. The furnace accommodates a 10-mm-square absorption cell and has a platinum liner to contain accidental release of corrosive liquids. The heating element is made of Pt-20% Rh alloy.
Some Characteristics of the VECO 32A8 Thermistor Operating in a Self-Heated Condition
Authors: Pharo Lawrence C.
Published: February 2005

The theoretical and experimental studies described in this paper have shown that a VECO type 32A8 thermistor operating with an internal temperature of 0.578°C above ambient in still water can measure temperature changes of the surrounding water at least as small as 0.021°C. Since the increase in sensitivity of the thermistor is proportional to the increase in bridge voltage, the 4-V bridge voltage required to attain the 0.578°C internal temperature represents an increase in measurement sensitivity by a factor of at least 10. The maximum usable bridge voltage was not determined. Measurement of the time constant of the 32A8 thermistor indicates that if this thermistor is used to measure small temperature variations, there is probably an optimum bridge voltage for the greatest frequency response to be achieved and the frequency response seems to increase as the temperature fluctuation of the surrounding medium decreases in amplitude. A 10% velocity turbulence field was assumed for a typical self-heated bead type thermistor probe operating in water with an average relative velocity of 51.5 cm/sec (1 knot). The noise level at the output of the thermistor bridge circuit due to the turbulence was calculated from a measured curve and shown to represent a temperature variation of approximately 0.002°C; this value compares closely to the theoretical value of 0.0012°C. The self-heated 32A8 thermistor is very sensitive to water velocity changes below 10.3 cm/sec (0.2 knots).
Use of a Large Gap Spark Chamber in an Intense Beam of Particles
Authors: Knasel T. M. , Walker J. K. , Wong M.
Published: February 2005

An application is considered where a beam of charged particles is passed through a large gap spark chamber. It is shown that the use of helium gas contained in a thin plastic bag in the region of the beam can reduce the efficiency of the spark chamber, in that region, to as little as 10−6 or less. The efficiency for track detection outside this region is maintained at 100% with the use of a gas mixture of 89% neon, 10% helium, and 1% argon.
Differential Heat Capacity Calorimeter for Polymer Transition Studies
Authors: Gill S. J. , Beck K.
Published: February 2005

A differential-heat-capacity calorimeter suitable for measuring the heats of thermally induced transition reactions of polymer solutions is described. The sensitivity of the calorimeter is such that an effect of 0.200 calories can be measured with a precision of ±1% on top of a large amount of heat (approximately 300 cal) needed to raise the temperature of the calorimeter 10°C.
Automatic Optical Density Integrator
Authors: Deutsch Sid
Published: February 2005

An instrument for the automatic integration of amino acid chromatograms is described. Translation of the optical density from logarithmic to linear digital units is accomplished via a logarithmic potentiometer and voltage-to-frequency converter. Cycles are counted in a decade counter and the accumulated total is printed out when each curve ends. The chromatogram baseline is continuously corrected to compensate for drift. The operator can select any one or any combination of photocells for integration. The equipment features 11.6-sec-holding circuits and a high gain amplifier in which a signal whose period is 40 min long is sampled at a 0.25-cps rate and is synchronously detected with a relay.
Conversion of the Bausch & Lomb Dual Grating Spectrograph for the Direct Reading of Nonuniform Line Profiles
Authors: Cremers Clifford J.
Published: February 2005

A description is given for the modification of the Bausch & Lomb dual grating spectrograph so that it may be used to directly measure longitudinal spectral line profiles with fixed phototube detectors. These measurements are often necessary in plasma diagnostics. The modified instrument has a single, compact, out of the way drive system that tilts the grating. This allows any number of lines to be recorded simultaneously. The time for scanning a cross section in the radiating source is on the order of 30 sec.
High Efficiency, Low Background GM Counter
Authors: Landis V. J. , Jensen R. C.
Published: February 2005

A gas flow, GM counter having a low background, a 4π counting configuration, and a convenient sample changing arranagement has been constructed and tested. The counter consists of two disk-shaped detectors hinged so that the sample is completely enclosed by the detector windows. The beta counting efficiency is about 94% for a weightless sample. The counting characteristics, stability, and configurational efficiency are comparable to conventional designs. The relative figure of merit of the counter is such that, within a given time period, two to four times as many samples can be counted to the same statistical accuracy as was possible with 2π type counters.
Amplitude and Decay Rate Analysis of Low Level Exponentially Decaying Radio-Frequency Signals
Authors: Berg Howard C.
Published: February 2005

A method is described which allows routine measurements of the relative amplitudes and absolute decay rates of low level exponentially decaying radio-frequency signals to be made to within an accuracy of 1%. The signals are converted to audio frequency, narrow banded, rectified, and integrated over two successive periods of time. The theory of the measurement, which is given in detail, shows how the analysis can be made in the presence of noise which is white over a frequency bandwidth large compared to the inverse decay times. The general features of the circuits are described, and a schematic is given for a nearly ideal full-wave linear rectifier.
Magnetic Field of Noncylindrical Coils
Authors: Grant W. J. C. , Strandberg M. W. P.
Published: February 2005

An exact calculation is presented for the magnetic field produced by a pair of rectangular coils. The calculation is not based on approximations tailored for the central region of the configuration. For current sheets of rectangular cross section, we obtain a closed analytical expression for the fields which is exactly valid for all points on the principal coordinate planes, and for all possible combinations of coil parameters. The calculation is extended to sources of arbitrary thickness by numerical integration. Detailed numerical application is made to the calculation of field homogeneity in the central region of the configuration.
Automatic Phase-Measuring System for an 8-mm Carrier Wave and its 4-mm Harmonic
Authors: Lisitano G.
Published: February 2005

This paper describes a measuring system which automatically displays the phase variation of two different electromagnetic waves radiated together in the measuring channel. The two waves are an 8-mm carrier wave and its second harmonic 4-mm wave. The latter is produced by distortion of the carrier signal before its entrance into the measuring channel. The carrier wave is sawtooth frequency modulated. By using a long reference path a low frequency sinusoidal interference signal is produced for both waves. Tuned amplification does not affect the phase information of the interference signal and the high sensitivity needed for the second harmonic detection is achieved by biasing of the detector crystals. The drive power may be as low as 10 mW and the phase measurement is to large extent independent of amplitude variation for both waves.
3He Cryostat with Adsorption Pumping
Authors: Mate C. F. , Harris-Lowe R. , Davis W. L. , Daunt J. G.
Published: February 2005

A 3He cryostat is described in which temperatures down to 0.3°K have been obtained by pumping the 3He refrigerant bath with activated charcoal at a temperature of 1.3°K. The performance characteristics of the adsorption pump are described in some detail, and a discussion is given of the extent to which the speed, adsorptive capacity, and cooling requirements of such a pumping system can be predicted by calculation.
Lorentz Force Calibrator for Magnetogasdynamic Interaction Coils
Authors: Savic P. , Guty V.
Published: February 2005

A device is described which measures the Lorentz force of any magnet coil with radial fringe component due to the axial motion of a metallic slug. The first method uses the effect of this force on the logarithmic decrement of a mass-spring system; in the second a feedback circuit effects self-excited oscillations, the Lorentz force being measured by its effect on the loop gain necessary to maintain a given oscillation amplitude.
Low Energy Charged-Particle Detection Using the Continuous-Channel Electron Multiplier
Authors: Evans D. S.
Published: February 2005

It has been found to be possible to operate the continuous-channel electron multiplier, a recently developed type of windowless electron multiplier, in a gain saturated mode such that single, charged particles entering the input mouth of the channel will initiate output pulses whose amplitude and shape are both uniform and independent of the character of the excitation radiation. By suitable design of the channel this saturated pulse can be made stable against changes in such operating conditions as ambient pressure and applied voltage. When operated in this mode, the efficiency of the channel for the detection of electrons over the energy range 250 eV to 10 keV is estimated to be greater than 50%.
Longitudinal Resistive Instabilities of Intense Coasting Beams in Particle Accelerators
Authors: Neil V. Kelvin , Sessler Andrew M.
Published: February 2005

The effect of finite resistance in the vacuum-tank walls on the longitudinal stability of an intense beam of particles in an accelerator is investigated theoretically. We show that even if the particle frequency is an increasing function of particle energy, the wall resistance can render the beam unstable against longitudinal bunching. In the absence of frequency spread in the unperturbed beam, the instability occurs with a growth rate that is proportional to (N/σ)½, where N is the number of particles in the beam and σ is the conductivity of the surface material. By means of the Vlasov equation a criterion for beam stability is obtained. In the limit of highly conducting walls the criterion involves the frequency spread in the unperturbed beam, the number of particles N, the beam energy, geometrical properties of the accelerator, but not the conductivity σ. A numerical example presented indicates that certain observations of beam behavior in the MURA 40 MeV electron accelerator may be related to the phenomenon we investigated.
Apparatus for X-Ray Diffraction Studies of Liquids
Authors: Rodriguez S. E. , Caputi R. W. , Pings C. J.
Published: February 2005

A sample enclosure compatible with the Norelco goniometer permits x-ray diffraction measurements on liquids confined under their own vapor pressure or an inert gas. Diffraction is in reflection-type geometry using a free liquid surface. The prototype, made of plastic, has been operated between 0 and 50°C.
Logarithmic Pulse Amplifier
Authors: Lunsford James S.
Published: February 2005

A solid state logarithmic pulse amplifier has been developed primarily for use in single shot large dynamic range experiments. It has a risetime of less than 100 nsec, a logarithmic range of 3 decades, and a usable range of greater than 4 decades. A temperature control circuit is used to maintain critical transistors at a constant temperature to achieve a thermal stability of approximately 2% referred to the input for a 10°C ambient temperature change.
Digital Time-Interval Analyzer
Authors: Hohenberger M. , Lindeman H.
Published: February 2005

A digital time-interval analyzer is described, which records the number of intervals between successive events of a duration less than a certain time T with great precision. The range of T lies between 10 and 1000 μsec. The application of the analyzer to the measurement of the resolving time of a scintillation counter arrangement is described.
Modified Dauphinee Thermocouple Comparator Circuit for Adiabatic Calorimetry
Authors: Stansbury E. E. , Nauman E. B. , Brooks C. R.
Published: February 2005

A modified Dauphinee thermocouple circuit has been used to isolate the thermocouples in the circuitry of an adiabatic calorimeter. The system eliminates direct electrical connection between thermocouples to be welded to a common ground. The variation in the difference in the emf between two thermocouples at the same temperature is less than ±0.2 μV. A calorimeter using the Dauphinee circuit has been used to determine specific heats of metals up to 700°C with a reproducibility, over a wide range of heating rates, of better than ±0.5%.
Vacuum-Jacketed Hydrofluoric Acid Solution Calorimeter
Authors: Robie Richard A.
Published: February 2005

A vacuum-jacketed metal calorimeter for determining heats of solution in aqueous HF was constructed. The reaction vessel was made of copper and was heavily gold plated. The calorimeter has a cooling constant of 0.6 cal-deg−1-min−1, approximately ¼ that of the air-jacketed calorimeters most commonly used with HF. It reaches equilibrium within 10 min after turning off the heater current. Measurements of the heat of solution of reagent grade KCl(−100 mesh dried 2 h at 200°C) at a mole ratio of 1 KCl to 200 H2O gave ΔH = 4198±11 cal at 25°C.
Helium Gas Scintillation
Authors: Esterling Robert J. , Lipman Norman H.
Published: February 2005

A gas scintillation counter is described which operates to 40 atm pressure. An attempt was made to maximize the scintillation light output in helium. Helium scintillation properties studied with this counter include the effect of various wall-coating materials, gas-purity effects, the linearity of pulse height with energy, and the variation of pulse height with pressure. With purified helium and for a given amount of energy deposited in the gas, the scintillation pulse height was found to increase with pressure P approximately according to the function kP/(1+KP), where k and K are proportionality constants. A semiquantitative argument is presented, explaining this pulse-height increase with pressure in terms of electron-ion recombination times in helium.
Retrieval of Microsecond Signals from Noise by Sampling and Averaging
Authors: Robinson J. D. , Yogi T.
Published: February 2005

A method is described for applying sampling to conventional digital averaging methods to increase bandwidth to 30 Mc. An oscilloscope and a sampling unit are used with a modified pulse-height analyzer. Results are shown for the application of the method to retrieve a weak, 1 μsec risetime infrared detector signal from noise. A simplified method that does not require a digital averaging device is also described. Extension of the time range for both methods is discussed.
Small Fringe-Field-Free Mass Spectrometer
Authors: Carette J. D. , Kerwin Larkin
Published: February 2005

A small low resolution mass spectrometer in the shape of a cylinder of over-all dimensions 8.6×4.5 cm is described. The use of an enveloping yoke shields the magnetic fringing field, making the spectrometer suitable for association with devices such as electron selectors. Small Alnico V pole pieces supply a field of 1800 G, which analyzes 40 eV mass 8 ions with a resolving power of 10×.
Temperature Transducer for Thermogravimetric Studies
Authors: Schnizlein J. G. , Brewer John , Fischer D. F.
Published: February 2005

An instrument has been designed to measure the temperature of a sample suspended in a thermobalance without interfering with the balance operation. Continuous and simultaneous temperature and weight records therefore can be obtained. The instrument uses the principle of a magnetic amplifier to sense a current caused by the potential generated by a thermocouple in the sample. A dc potential linear with temperature is recorded. Precision has been demonstrated to be better than 2°C up to 700°C. No measurable effect of the temperature transducer on weight recorded by the analytical balance was detected. Buoyancy and convection effects on weight are discussed.
Improved Apparatus for the Measurement of Atmospheric Electrical Conductivity
Authors: Gunn Ross
Published: February 2005

A new design for the measurement of the electrical conductivity of the atmosphere under severe conditions is described. The main features include novel means for minimizing the difficulties of maintaining a high insulation resistance not only for the central system, but for the polarizing batteries. The insulators are sapphire rods mounted in a side arm where the relative humidity is maintained at very low values by an external and isolated heater. The polarizing batteries are mounted inside a Faraday cage carried by the same insulators. Provisions are made to define accurately the electrical capacity of that part of the system exposed to the ambient ions so that this critical factor can be reliably measured. The apparatus is designed to minimize the loss of ions to the walls of the induction system by eddy diffusion.
Recycling Integrator for Measuring Nanoampere Currents
Authors: McQuaid James H.
Published: February 2005

A current-to-frequency converter for gamma MeV measurements is described. In this application a photo-multiplier tube is used as the current source. Currents as low as 10−9 A have been measured with a long term stability of 0.09 %/8h period. Extremely low leakage is achieved by the use of a field effect transistor at the input. The current to be measured is integrated and digitized. The output pulses are then fed to a frequency counter for digital readout.
National Bureau of Standards Gas Thermometer III. Constant Volume Valve
Authors: Anderson R. L. , Guildner L. A.
Published: February 2005

Special valves have been constructed to meet the constant volume requirements of a gas thermometry program. With a total volume inside the valve block less than 20 mm3, and that which is a part of the gas thermometer about 3 mm3, no change in excess of 0.005 mm3 is expected. This is achieved by extending the valve stem past the seat through a seal on the opposite side, so that the volume of stem pulled into the gas chamber is equal to the volume withdrawn when the valve is opened.
Optical Pyrometer Measurement of RF Power
Authors: Reed T. B. , Roddy J. T.
Published: February 2005

The power output of an RF generator coupled to a graphite cylinder can be conveniently measured by determining the equilibrium temperature of the cylinder with an optical pyrometer and using the blackbody formula to obtain the power radiated by the cylinder. This power was found to agree closely with the generator output measured with a conventional water-cooled calorimeter. Graphite, with a resistivity of about 10−3 Ω cm, easy machinability, and good blackbody characteristics, is an excellent dummy load for studying the output of RF generators to such relatively high resistivity loads as plasmas and semiconductors. The pyrometer method has also been used to determine the coupling efficiency of a generator as a function of the ratio of load diameter to coil diameter. Efficiencies of 27, 41, 59, and 63% were found for ratios of 0.46, 0.61, 0.77, and 0.92, respectively.
X-Band Waveguide Cell for Study of Microwave Propagation Through Magnetoplasma
Authors: Noon J. H. , Holt E. H. , Reynolds J. F.
Published: February 2005

A metal X-band waveguide cell has been developed for studying microwave propagation through plasmas immersed in a longitudinal magnetic field. The cell consists of a length of circular waveguide mounted between turnstile junctions. Modification of these junctions permits the installation of discharge electrodes on the magnetic field axis. No glass cell is required. The discharge can be operated successfully at pressures in the range 0.25 to 1 Torr. Measurements of the changes in the amplitudes of the circular components of the wave polarization, due to the presence of a magnetoplasma in the cell, allow the electron density and electron collision frequency to be calculated.
Velocity Profile Determination for Flowing Blood
Authors: Bennett Leon , Gutstein William H. , Schneck Daniel
Published: February 2005

An apparatus for determining the local stream velocity in flowing blood is described. Neutral buoyancy pellets are employed as tracers. Direct x-ray photographs, obtained with an automatic indexing, multiple-exposure camera, provide time-displacement data of the ensuing tracer motion. This device is utilized in laboratory studies of boundary layer phenomena.
Mercury Pool for Precise Alignment of Instruments
Authors: Thekaekara Matthew P. , Appler Robert
Published: February 2005

A fixed direction to which angles measured by autocollimators can be referred is essential in many cases which involve precision measurement of angles. The normal to a mercury surface affords such a standard direction, since the normal is along the local gravity vector and the deviations of the local gravity vector about the direction of the earth center are within the limits of accuracy of most measurements. The high reflectance of the mercury surface makes it specially suitable for use with autocollimators. It has been shown that the loss of reflectance due to ripples which damp out too slowly, and oxidation which progresses with exposure to air, can be eliminated by pouring a film of transparent, highly viscous oil over the mercury.
Coincidence Corrections for Particle Size Determinations with the Coulter Counter
Authors: Princen L. H. , Kwolek W. F.
Published: February 2005

A new mathematical treatment has been given for coincidence corrections necessary in determining particle size distributions by means of a Coulter counter. The coincidence phenomenon has been divided into ``horizontal'' and ``vertical'' interactions, of which the latter is believed to predominate. Expressions are developed relating the observed count, the real number of particles, the mean diameter, and the standard deviation of a distribution. The resulting equations are rather complex, and although manual solution is not impossible, an electronic digital computer would decrease the time required.
High Resolution Dark Field Microscopy Using a Philips 100B Electron Microscope
Authors: Meakin J. D. , Cinquina L.
Published: February 2005

A simple modification to a Philips 100B electron microscope makes possible the production of dark field images without any loss of resolution. The method utilizes electrical tilting of the primary beam and permits rapid alternation between bright and dark field viewing.
Method for Measuring Energy Transfer from a Molecular Beam
Authors: McKeown D. , Fox M. G.
Published: February 2005

A method has been developed for measuring the transfer of energy from a molecular beam to a surface. The method makes use of temperature sensitive Y-cut quartz crystals. A crystal was placed in the beam and the energy transferred to its plating was determined by changes in its oscillating frequency. Crystals having a fundamental frequency of 10 Mc were used and an energy transfer rate of 50 μW could be detected. Results are given for the transfer of energy by Ar+ to an Au surface between 100 and 500 eV.
Incandescent Lamp as a Control System Element
Authors: Howarth Robert F.
Published: February 2005

Three tungsten-filament lamps have been investigated with particular attention given to determining the applicability of the standard linear transfer function concept to these basically nonlinear elements. The lamps cover a power range of from 14 mW to 14 W. They are the Kay L12–12 Pinlite, 12 mA at 1.2 V, the No. 47, 150 mA at 6 V, and the No. 94, 1.2 A at 12 V. The greatest range of operation linear to within 5% is determined from output luminous flux versus input voltage characteristics. Allowable flux variation about a dc bias point selected in the 5% linear range is found to be at least ±40%. Bode type amplitude-phase characteristics are measured for the three lamps. Conventional linear transfer functions are deduced from the Bode plots, linear approximations are constructed, and the resulting composite approximations are compared to the empirical characteristics and found to be satisfactory for design usage. Deviations from linear operation are investigated, and in the case of the lamp bias, found to impose some restrictions. An operating lamp control system designed on the basis of the above described work has been built and is discussed.
Optical Measurement of Switch Jitter
Authors: Oertel G. K. , Williams M. D.
Published: February 2005

An optical method is described for simultaneous monitoring of more than 100 luminous events on a single film record, e.g., the breakdown of spark gaps. A time resolution better than 1 nsec may be achieved. The system employs light pipes, an image converter streak camera, and a trigger delay generator, all commercially available items. Sample records of the breakdown of a sample of 16 spark gaps in a megajoule capacitor bank are shown; the time resolution is about 1 nsec.