bluuebunny/crossref_metadata_2025 huggingface dataset:
Fractional-Millimicrosecond Oscilloscope System Utilizing Commerically Available Components
Authors: Winningstad C. Norman
Published: February 2005

Equipment for use with signal rise times slower than a millimicrosecond is readily available commercially. Recent advances in high-energy physics have directed attention toward research in the fractional-mμsec region. The fundamental tools for such research are pulse generators and oscilloscopes. Suitable pulse generators are commerically available, but suitable oscilloscope systems are not. There are two important factors that account for the lack of such oscilloscopes. One is that contemporary amplifiers are useless in the fractional-mμsec region. The second is that output timing in commonly used trigger circuits is too sensitive to changes in input amplitude.

This paper describes an internally synchronized oscilloscope system utilizing commercially available components, which provides less than 2% signal reflection at the sync takeoff point, and has less than 5×10−12 second of sweep-timing change per percent change in input amplitude (for amplitudes in excess of 30 trace widths).
Use of Freons in Bubble Chambers
Authors: Bugg David V.
Published: February 2005

The sensitive regions of several Freons in a bubble chamber have been determined. CF3Br, Freon 13B1, has been found to be sensitive at 30°C, at which temperature the equilibrium vapor pressure is only 264 psi. Because of its pleasant handling characteristics, and the fact that it can be used in any chamber designed for propane, it is suggested that it may find considerable use as a ``heavy'' liquid in large chambers. The time needed for bubbles to redissolve, and the difficulties implicit in the use of mixtures of liquids are discussed.
EPR Spectrometer of Very High Sensitivity
Authors: Misra Harihar
Published: February 2005

A recording electron paramagnetic resonance absorption spectrometer of very high sensitivity, operating at a wavelength of 3 cm, is described. It is of the reflection-cavity-in-magic-T-bridge type, using a superheterodyne receiver. Its special features are: (1) a two-cavity klystron oscillator with superior frequency stability and more available power; (2) a synchrodyne system to derive local oscillator power, thus avoiding the difficulty of tracking two independent oscillators; (3) a balanced magic-T mixer which considerably reduces the noise output; (4) a double-input low-noise intermediate frequency amplifier at 30 Mc; and (5) a tunable high-Q sample-carrying cavity with an almost identical cavity to balance it in the magic-T bridge. Arrangements for an oscilloscopic display of the absorption vs magnetic field and a continuous recording of the derivative of absorption vs magnetic field have been incorporated. Sensitivity of the microwave bridge system and of the spectrometer have been tested. About 1.1×10−11 mole of diphenyl picryl hydrazyl dissolved in purified benzene, which corresponded to approximately 1.06×10−14 mole of crystalline sample, has been detected by the spectrometer.
High-Speed Pulse Amplitude Discriminator
Authors: Farley F. J. M.
Published: February 2005

A circuit for pulse height discrimination in fast counting systems is described. Input pulses whose amplitude exceeds the threshold bias, adjustable from 1 to 21 volts, give rise to a positive output pulse of standard amplitude (6 volts), but length determined by the length of the input signal. Dead time is of order 20 mμsec and peaks 40 mμsec apart are handled independently.
Grating Vacuum Monochromator for the Spectral Range 1000–6500 A
Authors: Sluyters Th. J. M. , De Haas E.
Published: February 2005

In order to get information about the excitation processes in a discharge tube, a spectrograph has been built, which scans the range between the visible and the far ultraviolet. Using a Paschen-Runge mounting the spectrum has been detected with a cooled E.M.I. photomultiplier, which can move along the Rowland circle with a velocity of 0.1–12 A per second. At the wavelength of 2500 A, 0.6 A could be resolved.
Electrolytic Saw
Authors: Metzger M.
Published: February 2005

Strain-free cutting of metallic crystals at moderate rates can be obtained by localized electrochemical dissolution using a wire cathode. The width of the attacked zone is limited by applying a protective plastic film. Clean sharp cuts cannot generally be expected.
Mass Spectrometer Image Displacements due to Second-Order Aberrations
Authors: Robinson Charles F.
Published: February 2005

Second-order aberrations in mass spectrometers give rise to image broadening which is generally unsymmetrical about the optic axis, resulting in a net displacement of the image center from the optic axis. The net displacement depends on the properties of the mass resolving system and on the velocity and angular distribution in the ion beam. In the event different ionic species may possess either different mean kinetic energies or different energy distributions, the image shifts may differ appreciably, leading to small but appreciable errors in mass doublet measurements.
Glass Dewars for Optical Studies at Low Temperatures
Authors: Schoen L. J. , Kuentzel L. E. , Broida H. P.
Published: February 2005

All glass or predominantly glass vessels are well suited to spectroscopic or photochemical studies down to temperatures as low as 1.2°K. The choice of glass offers advantages of economy and simplicity in addition to allowing for a large degree of flexibility to be incorporated into a given design. A number of such Dewars are described and their relative merits discussed. It is shown that the heat leak arising from the optical arrangement is, in general, not serious.
Apparatus for Piezoresistance Measurement
Authors: Pollak Michael
Published: February 2005

A method for measuring piezoresistance effects in semiconductors is described. The principal sources of error of the usual steady stress method, namely, drift of the temperature and the sample current, and semiconductor noise, are avoided by using a 29 cycle/second alternating stress. The method, because of high sensitivity, is particularly suitable for low resistivity material. It is, however, not applicable to materials with extremely high resistivity. The piezoresistance constants directly measured are adiabatic.
Pressure-Sensitive Diaphragm-Type Null Detector
Authors: White David , Hilsenrath Joseph
Published: February 2005

A high-sensitivity diaphragm-type null detector is described. The device, which is particularly suited to working with corrosive substances, has a high sensitivity, a reproducible null under ordinary operating conditions, and a small dead-space volume (approximately 0.01 cc). Pressure unbalance of 0.3 to 0.5 mm of Hg causes a thin (0.001 in.) metallic diaphragm to make or break electrical contact with an insulated probe. The above differentials are detectable at pressures of 200 atmospheres. The diaphragms require no special fabrication, and can withstand moderate overpressure on one side without affecting the diaphragm or its sensitivity.
High-Pressure Techniques
Authors: Warschauer D. M. , Paul William
Published: February 2005

This paper supplies information on hydrostatic pressure techniques up to 20 000 kg/cm2 under two headings. Under general pressure techniques, low temperature seals, experience with small diameter tubing, a pressure measuring bridge, and various tubing seals are described. Under optical techniques, optical windows of sapphire, germanium, and silicon, suitable pressure fluids, and a mechanism for moving samples inside a pressure vessel for use to 10 000 kg/cm2 are discussed.
Simultaneous Utilization of Magnetic Deflection and Coulomb Scattering in the Estimate of Particle Momenta
Authors: Kim Y. B.
Published: February 2005

The problem of estimating particle momenta under the simultaneous presence of magnetic deflection and Coulomb scattering is considered. This problem is of practical interest when nuclear emulsion plates are exposed under fields of multihundred kilogauss currently available from pulsed magnets. The estimation of momentum is separated into two parts, each utilizing the magnetic and the Coulomb effect, respectively. In this way one can fully utilize the numerous estimation techniques already developed and available in the literature for each of these two estimates. This separation, however, is carried out in such a way that the magnetic and the Coulomb estimate are statistically independent, and hence can be readily combined for an improved accuracy.
Pulsing of Photomultipliers
Authors: Farinelli U. , Malvano R.
Published: February 2005

Various ways of pulsing photomultipliers are investigated. Some drawbacks inherent to the conventional methods are pointed out; a new pulsing method is suggested and experimentally studied, which avoids these inconveniences.
Note on Accelerating Components in Particle Spectrometers
Authors: Mendlowitz H.
Published: February 2005

Some considerations on ``energy aberrations'' in electron spectrometers containing accelerating (decelerating) components are discussed with regard to their role in the measurement of the energies of electrons. Based on these considerations, design criteria are obtained for an electrostatic decelerating component for a given electron absorption spectrometer. The design criteria are derived by treating the problem of a charged particle in an electrostatic field by means of the Hamiltonian method in classical mechanics, and are found to be related to the curvature of the electrostatic field.
Use of a Constant Current Hot Wire for the Measurement of Extreme Temperatures
Authors: Hoenig Stuart A.
Published: February 2005

The theory of the constant-current hot-wire circuit for measurement of very high gas temperatures is developed and it is shown that such a system may be used above the melting point of the wire itself.
Response of a Liquid Scintillator to Fast Neutrons and γ Radiation
Authors: Hardy James E.
Published: February 2005

The response of a commercially available liquid scintillator to D(d,n)He3 neutrons and to γ radiation from several standard sources has been measured. It is found that the pulse height response to γ-ray energy is linear in the energy range 0.5 to 2.6 Mev, and that the fast neutron detection efficiency of a disk scintillator 5 cm thick is about 30% in the neutron energy range 2 to 3.5 Mev, and varies with neutron energy E as ξ(E)=0.146+0.45/E+0.82,where E is measured in Mev.
Resistance Thermometer Bridge for Measurement of Temperatures in the Liquid Helium Range
Authors: Blake C. , Chase C. E. , Maxwell E.
Published: February 2005

A 33-cps resistance thermometer bridge, suitable for precise temperature measurements in the liquid helium range, has been designed as a completely self-contained unit. The amplifier has a gain of 120 db, band width of 0.3 cps, and input impedance of 10 kohms. With a power dissipation of 2×10−8 watts in the thermometer, resistance changes of 0.1 ohm can be detected. For a typical resistance thermometer this corresponds to a temperature change of 4×10−6°K at 2°K. Other features include high rejection of line-frequency pickup, short recovery time after saturation, and a combination gain band-width control which shortens the response time during preliminary balancing operations.
Design of Regenerative Extractors for Synchrocyclotrons. I. Small-Amplitude Extraction
Authors: Stubbins Warren Fenton
Published: February 2005

The extraction of particles from the nonlinear magnetic field of a synchrocyclotron by a single magnetic perturbation is studied by use of a general approximation to the magnetic field and a calculation technique closely tied to the physical process. The analysis is useful for extraction amplitudes of several inches. Regenerator strengths are computed as an illustrative example.
Double Reflection X-Ray Camera
Authors: Fraenkel B. S.
Published: February 2005

An improved double reflection x-ray camera is described in which both the crystal and the film rotate simultaneously. It registers x-ray reflections from crystals in form of a line, and shows the double reflections on this line. Some examples of double reflections taken with this apparatus are shown.
Printing Register
Authors: Ford P. W.
Published: February 2005

A device is described which records and prints data which can be represented by the decimal system of numbers. The register section can be arranged to handle several groups of figures containing any number of digits and has a total capacity of 16 digits. The registers automatically return to zero before the beginning of each recording period.
Fast Sodium Iodide Spectrometer and Its Application to Millimicrosecond Time Measurement
Authors: Beghian L. E. , Kegel G. H. R. , Scharenberg R. P.
Published: February 2005

A scintillation counter using pure NaI cooled to liquid nitrogen temperature has been developed. The photopeaks of Co57 γ rays (122 kev) and Cs137 γ rays (662 kev) were found to have a full width at half-height of 33% and 14%, respectively. A 7-inch quartz light pipe was used between scintillator and photomultiplier. The decay time of the fluorescent light was found to be 27 mμsec. For fast time measurements a time-to-pulse-height converter has been constructed, which operates in the range from 0–100 mμsec. The converter was used in conjunction with two scintillation counters using plastic (Pilot B) scintillators. The time resolution for the detection of annihilation γ rays was found to be 2τ0 = 2.3 mμsec. With one plastic and the cooled NaI scintillator the time resolution was found to be 2τ0 = 2.7 mμsec. The possible factors contributing to the time resolution are discussed.
Drag Unit for the Artificial Generation of Turbulent Shear Flow
Authors: Elrod H. G.
Published: February 2005

This paper describes a device called a ``drag unit'' capable of generating turbulent shear flows of prescribed time-mean velocity distribution. The device can be used as a research tool to study features of turbulence or to ascertain the effects of flow nonuniformities. Typical experimental results are presented.
Production of a Square Temperature Wave in Filaments Operating at Low Temperatures
Authors: Klein Ralph , Simpson J. Arol
Published: February 2005

The problem of obtaining fast rising temperatures by resistance heating in a filament initially at low temperatures is examined. From a solution of the heat conduction equation the relationships, both steady state and transient, among temperature, heating current, and heating power are derived. These solutions are dependent on the initial temperature, the thermal properties of the filament, and its physical dimensions. For a typical filament the current-temperature curves are of the form i = F + (B/T) where B is negative for 77°K boundary temperature, zero for approximately 50°K, and positive below this temperature.

Experimental evidence taken with a 0.1-mm diam tungsten filament 2.5 cm long confirms these predictions.

A circuit capable of raising a filament from any temperature above 4.2°K to any desired temperature below 600°K in less than 0.3 sec is described.
Rapid High-Sensitivity Recording Thermometer
Authors: Stow Richard W.
Published: February 2005

The paper describes a rapid high-sensitivity thermistor thermometer including the circuit details for the activation of the thermistor bridge circuit and associated amplifier. Using a small bead thermistor housed in a hypodermic needle, the 95% response time is about 0.17 sec and noise levels as low as 2×104°C have been obtained.
Electron-Permeable Window for Cathode-Ray Tubes
Authors: Seehof Jerrold , Smithberg Stuart , Armstrong Melvin
Published: February 2005

An ultrathin window, permeable to low-energy electrons, has been developed for use with cathode-ray tubes and associated devices. This window, some 70 μin. thick, has the ability to withstand greater than 1-atmos pressure differential and, at the same time, allow a 15-kv electron beam to penetrate it. Window structures are composed of a ¼-in. square matrix (80-mesh nickel screen) supported bentonite clay film. It is expected that larger area configurations can be developed. The films are relatively gas-tight and are insensitive to temperatures of at least 400°C.
Extended Range Distributed Amplifier Design
Authors: Eichholz John J. , Nelson Carl F. , Weiss Gerhard T.
Published: February 2005

A distributed amplifier employing a straight wire transmission line is described. The amplifier has a gain of 15±3 db from 10 to 400 Mc, and input and output impedances of 50 Ω. Detailed electrical and mechanical design considerations are included.
Concerning Amidol Development of Nuclear Emulsions
Authors: Fatzer G. D.
Published: February 2005

A lowering of the development temperature introduces development defects which are characterized by the partial or total destruction of the developed image and by a deep coloration of the emulsion. These defects are eliminated by increasing the sodium sulfite concentration of the developer. Up to now contrast in nuclear emulsions has been evaluated subjectively by the experimenter; this forbids any comparison of the results obtained in different laboratories.

This paper shows that to develop reliably at low temperatures with the usual developers, it becomes necessary to increase the ratio (Na2SO3)/(Amidol). For development temperatures of 10–15°C the concentration ratio needs to be 70% greater than the ones commonly used.

A study of track and fog grain properties is carried out. It is shown that at a given temperature the mean gap length is practically independent of the development parameters. The optimum conditions at 14°C are determined with the help of a new quantity termed ``track visibility'' (K), a track to fog signal, and defined by K=blob length×track grain diameter/fog density×(fog grain diameter)2.
Generator of Nanosecond Light Pulses for Phototube Testing
Authors: Kerns Quentin A. , Kirsten Frederick A. , Cox Gerald C.
Published: February 2005

This mercury-capsule light-pulse generator was developed to test and evaluate the high-speed features of multiplier phototubes and low-level image tubes. Light pulses and electrical trigger pulses are generated simultaneously in an arc discharge at a usual repetition rate of 60 per second. The electrical pulse is used as a time reference for the light pulse. The time required for both the light and the electrical pulse to rise from 10 to 90% of peak amplitude is less than 5×10−10 sec. The light pulse rises to a maximum and falls to 50% peak amplitude in less than 1.5×10−9 sec. The electrical pulse power available is large. Time resolution of 10−10 sec is typical of measurements made with conventional fast oscilloscopes, while elaboration of technique permits relative time measurements that are better in some cases by at least three orders of magnitude. The light is emitted from a region a few mils in diameter, and thus may often be considered to come from a point source. An S4 photosurface subtending 0.1 sterad at the light source emits photoelectrically about 107 electrons per sterad per pulse. For convenience, three decoupled electrical output channels are provided, together with a Polaroid attenuator for the light pulse.
High-Temperature Pressure-Vacuum Furnace
Authors: Lodding William , Hammell Laurence
Published: February 2005

A simple high-temperature pressure-vacuum furnace using a recrystallized alumina tube as the vessel with external resistance windings is described. Temperatures to 1900°C can be used in both strongly reducing and oxidizing atmospheres. Pressures to 28 atoms at 1200°C were obtained and no water cooling was required. Differential thermal analysis with continuous gas analysis of reaction products is made possible.
Double Crystal X-Ray Monochromator-Collimator
Authors: Williamson Robert S. , Fankuchen I.
Published: February 2005

A pair of crystals mounted so as to have perpendicular planes of incidence is used to produce a collimated monochromatic x-ray beam. The design permits simple adjustment of the final beam inclination.
Specimen Holder for Controlled Deformation in the Elmiskop
Authors: Fisher R. M.
Published: February 2005

A specimen holder has been constructed to permit controlled deformation of thin metal films in the Siemens Elmiskop. The design details are described and the performance is illustrated.
On the High-Temperature Compatibility of Cesium Gas with Some Dielectrics
Authors: Wagner Paul , Coriell Sam R.
Published: February 2005

Eight refractory dielectrics were exposed, under controlled conditions, to cesium gas at temperatures as high as 1475°C. The apparatus designed for this work and results of this investigation are discussed.
Millimicrosecond Discriminator
Authors: Swift David F. , Perez-Mendez Victor
Published: February 2005

A discriminator circuit for use with millimicrosecond counting equipment is described here. The circuit utilizes a diode voltage comparator which drives a secondary-emission tube univibrator after amplification. Two shaped outputs are provided: one, of short duration, for use with 10-Mc scalers, and another longer pulse for microsecond scalers.

The main characteristics of this unit are its good response to pulses as short as 3 m μsec and the fast recovery time, which is less than 0.1 μsec at the fast output.
Absolute Method of Measuring Magnetic Susceptibility
Authors: Thorpe Arthur , Senftle Frank E.
Published: February 2005

An absolute method of standardization and measurement of the magnetic susceptibility of small samples is presented which can be applied to most techniques based on the Faraday method. The fact that the susceptibility is a function of the area under the curve of sample displacement versus distance of the magnet from the sample, offers a simple method of measuring the susceptibility without recourse to a standard sample. Typical results on a few substances are compared with reported values, and an error of less than 2% can be achieved.
Analog Integrator for EPR Spectra
Authors: Schwenker R. P.
Published: February 2005

An electromechanical analog integrator for obtaining a continuous time integral of varying voltage is described. It is suited for applications where integrating times of greater than one minute are encountered. Particular consideration is given to its applicability to magnetic resonance data reduction.
Precision Capacitor Divider Method for Measuring High Voltages
Authors: Larson H. V. , Myers I. T.
Published: February 2005

A high-precision capacitor divider method for measuring the voltage on the terminal of a 2-Mv Van de Graaff accelerator is described. Calibration of the system was done using the Be(γ,n) threshold reaction. Linearity was tested using a total beam calorimeter and a beam current integrator.
Automatic Recording Film Balance System
Authors: Trurnit H. J. , Lauer W. E.
Published: February 2005

An automatic recording film balance system is described. It consists of a film trough and two pendulum type balances with pressure ranges of 0–400 (800) millidynes/cm and 0–40 (80) dynes/cm, respectively. Each balance is connected to a float when in operation (Langmuir type balance) and the sensing element in both cases is a linear variable differential transformer, the iron core of which is connected to the pendulum. The transformer signal after amplification drives the pen motor of a strip chart recorder. Special features like a constant pressure device together with auxiliary instruments such as a second X-Y recorder, an automatic dipping device for film transfer, a volta potential meter and a slit viscosimeter permit the automatic recording of the following functions: (dFdA)T, (dAdT)F, (dFdT)A, (dFdt)T, A, (dAdt)T, F, (AwAs)T, F, (dVdF)T, and (dηdF)T.F=film pressure, A=film area, T=temperature, t=time, Aw/As=deposition ratio, η=film viscosity, and V=volta potential. Test and performance data are presented.
External Beam Current Monitor for Linear Accelerators
Authors: Bess L. , Ovadia J. , Valassis J.
Published: February 2005

An electron current monitor for linear accelerators has been developed. Its sensing element was a toroidal coil through which the beam passes undisturbed. With appropriate electronic circuity this permitted the true shape of the current pulse to be viewed and also provided an indication of the average beam current on a meter. The average beam current that could be measured ranged from 3×10−8 to 3×10−6 amp. Furthermore, the use of the current monitor greatly simplified the process of initially obtaining yield from the machine.
Time Analyzer Utilizing the Argonne Type 256-Channel Pulse-Height Analyzer
Authors: Whalen J. F. , Meadows J. W. , Nelson C. H.
Published: February 2005

A time analyzer has been designed which is capable of utilizing the memory of any multichannel analyzer which employs pulse height to time conversion or any similar instrument. The circuit described here has been specifically adapted for use with the Argonne type 256-channel analyzer. Channel widths from 1 μsec to >38 μsec are possible with a minimum dead time of 38 μsec.
Linearly Biased Track Counting in Cross-Section Determinations
Authors: Crawford Frank S.
Published: February 2005

In determining the average number n̄ of tracks per bubble chamber picture, for purposes of determining cross sections, one usually cannot count all tracks, but counts tracks in only some of the pictures, selected at random. An alternative procedure is described here in which the pictures are not selected at random, but are those which contain the ``interesting events.'' The average of 1/n over this ``linearly biased'' sample equals 1/n̄, where n̄ is the desired average over a random sample.

The linear-bias method has some advantages that are complementary to those of the usual random method.
Simplified Logarithmic Radiation Meter Using Noise
Authors: Cohn Charles Erwin
Published: February 2005

A logarithmic radiation meter has been developed which uses an ac-coupled logarithmic voltmeter to measure the random noise from a photomultiplier detector. A range of four decades has been obtained.
Probability Density Measurement with an Electrode Mounted in the Face of a Cathode-Ray Tube
Authors: Lien Hwachii
Published: February 2005

A small electrode mounted inside the face of a cathode-ray tube gives a ``window'' comparable to its own dimensions when the bias voltages are set so that secondary electron emission current dominates. Under these conditions the device can be used for measurement of probability densities of random signals.
Pulse-Height Analyzer for Neuro-Physiological Applications
Authors: Littauer R. M. , Walcott C.
Published: February 2005

A five-channel differential pulse-height analyzer is described, designed specifically for the observation of action potentials in nerve fibers. By measurement of the pulse amplitudes, it is possible to follow the activity of one or more single nerve fibers continuously.
Handling of Extremely Thin Wollaston Wires
Authors: Bomelburg Herbert J.
Published: February 2005

A reliable method of etching and mounting Wollaston wires is described. The method involves attaching one end of the wire to a specially prepared ceramic tube, dipping the pendant portion of the wire into an etching solution, and then after etching is completed, attaching the loose end of the wire to the ceramic tube, and finally, firing the tube and mounted wire to 1000°F. The thinnest wires handled by this method had diameters of 0.5 μ and lengths of 2 mm.
Submicrosecond High-Intensity Light Source
Authors: Bagley Charles H.
Published: February 2005

A short duration (1 or 2×10−8 second) high-intensity explosive light source, that may be used in the laboratory, has been proved experimentally. The charge, weighing 4.8 grams, yields a luminosity estimated in the neighborhood of 8×107 lumens. Pictures of high-speed shocks in air, transparent solids, and metal jets have been taken using this lighting system.
Solar Proton Stream Forms with a Laboratory Model
Authors: Bennett Willard H.
Published: February 2005

A laboratory tube has been developed which produces scale models of the forms assumed by streams of charged particles in the earth's dipole magnetic field. The forms are unexpectedly intricate and complicated, as are also the contacts on the earth's surface. Photographs of some representative stream forms and contacts are presented. The tube has served as an analog computer for stream forms and contacts and, in addition, has revealed the importance of the generation of ring currents of charged particles scattered into Störmer's periodic orbits. The same techniques can be applied in studies of stream forms in high-energy accelerators and in other complicated kinds of magnetic fields.
Transistorized, Crystal-Controlled Marginal Oscillator
Authors: Garwin R. L. , Patlach A. M. , Reich H. A.
Published: February 2005

A simple, crystal-controlled, transistorized marginal oscillator magnetometer has been built. It is self-contained except for an oscilloscope and modulation power supply. Circuit and construction details are given.
Technique for Measurement of Cross-Spectral Density of Two Random Functions
Authors: Uberoi Mahinder S. , Gilbert Elmer G.
Published: February 2005

The cross-spectral density of two functions may be determined by using two selective filters which have identical impulse responses except for a relative phase difference which should be 0° and 90° for the measurement of cosine and sine components, respectively. A technique is developed which is quite accurate and requires a minimum of special equipment. The operation of the system is checked by measuring the cross-spectral density of two functions whose statistical properties are known.
Measuring Device for Diffraction Patterns
Authors: Columbe Maynard J.
Published: February 2005

A device for accurate measurement of diffraction patterns is described in detail. The accuracy of measurement is better than 0.01%. In addition, this device is useful for viewing photographic negatives and can also be used for other kinds of measurements.
Helium Temperatures from Vapor Pressure Measurements
Authors: Hoare F. E. , Zimmerman J. E.
Published: February 2005

It is found that the temperature at any point below the surface of a helium bath, as deduced from pressure measurements over the surface corrected for hydrostatic head, does not agree with the temperature obtained using a vapor pressure bulb, the helium bath pressure invariably indicating a lower temperature, except below the λ point. The discrepancy can be reduced but not eliminated by employing a heater at the bottom of the bath to provide a copious supply of vapor bubbles throughout the bath. A sharp temperature gradient at the surface of the bath is indicated. Below the λ point no discrepancy is observed.
Automatic Cloud Chamber for Gas Discharge Studies
Authors: Allen K. R. , Phillips K.
Published: February 2005

A large volume expansion chamber (25-cm diameter, 25 cm deep) was constructed to investigate prebreakdown ionization processes in gaseous discharge. A homogeneous field electrode system was mounted within the chamber and provision was made for irradiation of the cathode. The chamber could be operated automatically at pressures from 40 to 68 cm Hg with a recycling time of about 5 min. Associated circuits for the production of millimicrosecond pulses up to 70 kvp are described. Some preliminary photographs of point-plane breakdown and of electron avalanches in a homogeneous field electrode system are shown.
Coefficient of Thermal Expansion of Barium Titanate
Authors: Keyston J. R. G. , Macpherson J. D. , Guptill E. W.
Published: February 2005

A method is presented for the determination of the coefficient of thermal expansion of solids, particularly in the low-temperature region. The method is based on the measurement of the resonant frequency of one or more modes of a microwave cavity made of the material for which the coefficient of expansion is required. A change in length of 5 parts in 106 can be detected. This accuracy is primarily determined by the Q of the resonant cavity. Measurements of the thermal expansion of copper and barium titanate are presented over the temperature range of −200 to +100°C and the former is compared with observations made by other techniques.
Bridge for Measuring the Impedance of Metal Microelectrodes
Authors: Gesteland R. C. , Howland Bradford
Published: February 2005

This note describes an ac bridge for measuring the series components of high-impedance metal-liquid interfaces. The real and imaginary components of the impedance may vary over a wide range. All frequency-independent residual error-introducing elements in the measuring circuit may be balanced out through a single square-wave initial balance step. This allows accurate, direct-reading measurement of the unknown. The bridge design is based upon superposition of frequency-independent bridge circuits.
Momentum Kicks for Particles Crossing a Gap at an Angle
Authors: Van Bladel J.
Published: February 2005

Formulas are derived for the longitudinal and lateral momentum kicks to which a particle is subjected upon crossing an accelerating gap. The angle ε between the particle's trajectory and the axis of the accelerator tube is assumed to be small, and terms of order higher than the first in ε are neglected in the formulas.
Electric System for Random Selection of Two Alternate Circuits
Authors: Lion J. R. , Lion K. S.
Published: February 2005

Description of an electric system which randomly closes one of two alternate circuits. The system is based upon the coincidence of two timing events of different origin. The sign of the coincidence signal varies at random and causes one of two thyratrons to fire. A statistical analysis shows that for 339 succeeding operations of the instrument the maximum deviation from complete randomness and independence of succeeding events is about 2%, the average deviation about 1%.
Simple Pulsed Neutron Source Based on Crossed-Field Trapping
Authors: Gow James D. , Ruby Lawrence
Published: February 2005

A simple pulsed neutron source has been constructed which consists of an anode formed by a cylindrical-shell permanent magnet and of two disk cathodes. One of the cathodes forms the neutron-producing target and the device is exhausted adjacent to the other. In operation, the anode is pulsed positive at 140 kv for 1 μsec at up to 200 pulses per sec. Continuous operation has also been achieved in a slightly different configuration. Ions are produced adjacent to the anode in a toroidal trapping region which exists as a result of the crossed electric and magnetic fields. The ionization is enhanced by the action of electrons reflecting through the inside of the magnetic shell. As a consequence of this trapping, large fluxes of soft x-rays are created which may be injurious to personnel.
Rotating-Disk Function Generator for Analog Computers
Authors: Young Mary Ellen , Alexander W. Merle , Schwetman Herbert D.
Published: February 2005

A simple device for the production of varying potentials which represent four functions of the form f(t) = at, f(t)+at+b sinωt, f(t) = at2+b, and f(t) = a for (50 msec≤t≤100 msec) and a rate of operation of 5 cps is described. It makes use of a rotating disk of variable radius to control the light incident upon the cathode of a photomultiplier tube. The accuracy of the functions is about 4%, with the exception that near points of discontinuity, maximum errors of 4 to 10% were observed. The method of preparing the disk, use of the functions in the solution of linear, ordinary differential equations, and an analysis of the error are presented.
Use of Operational Amplifiers in Precision Current Regulators
Authors: Eklund Karl
Published: February 2005

The design and construction of precision current regulators is simplified by the use of commercially available operational amplifiers. Their method of use is described and an example is given of a regulator used with an electron spectrometer, where the regulation obtained was 0.01%. It is felt that the use of operational amplifiers offers a great convenience to the physics laboratory.
Use of Operational Amplifiers in Accelerator Beam Control Systems
Authors: Eklund Karl
Published: February 2005

A method of using operational amplifiers in beam control systems is described. A basic preamplifier is used with various output stages to control beam energy and position by magnetic and electrostatic means. The use of commercially available operational amplifiers provides great advantages in simplifying design, construction, and maintenance.
Redundant Circuitry for Reliability in Low-Level Counting
Authors: Burke W. H.
Published: February 2005

This paper describes a system of redundant counting circuitry which has been used for about two years in carbon-14 dating. The use of this circuitry enables the operator to know when a measured counting rate is unreliable because of electronic trouble, either steady or intermittent. It also enables him to continue taking reliable data despite most intermittent troubles and aids in locating them.
Design and Performance of a Hot Cathode Magnetically Collimated Arc Discharge Ion Source
Authors: Abele Manlio , Meckbach Wolfgang
Published: February 2005

A hot cathode arc discharge type ion source is described. The discharge is collimated in an axial magnetic field and the ion beam is extracted axially. The maximum total ion current of the source, tested with hydrogen, is 42 ma. The extraction system allows focusing of almost 100% of this current. The limiting factor of the maximum ion current is analyzed. Although strong arc discharges could allow the extraction of higher ion currents, space charge spreading causes the ion beam to hit the front surface of the extracting electrode. Secondary electrons, released there, are focused back into the arc chamber producing instabilities of the source. A convenient means of regulation or modulation of the beam current is described. A magnetic analysis of the extracted beam shows about 34% atomic ion current.
Use of a Direct Current Amplifier and Recorder to Balance a Mueller Resistance Bridge
Authors: Armstrong George T. , Wong P. K. , Krieger L. A.
Published: February 2005

By taking corrective action for electrical noise resulting from alternating current pickup and induced electrostatic charges, it has been possible to use a commercially available high gain dc amplifier and a recorder to balance a G-3 Mueller resistance bridge. Noise levels below 0.01 μv peak to peak were observed with a response time of approximately five seconds. Using a 25-ohm platinum resistance thermometer and 1-ma thermometer current, a precision of 0.0001°C was obtained in temperature measurement. The permanent and continuous record provided offers advantages over the ordinary optical galvanometer for the observation of time-dependent phenomena and the study of sources of error.
X-Ray Absorption Coefficients and Geometrical Collimation of the Beam
Authors: Parratt L. G. , Porteus J. O. , Schnopper H. W. , Watanabe T.
Published: February 2005

In recent years, in order to achieve high angular collimation of an intense x-ray beam in a measurement of an absorption coefficient, most investigators have used the action of a high-resolving-power monochromator to provide the collimation. In this case, if the absorber exhibits small-angle scattering (including multiple scattering) of significant intensity in a scattering cone as large as a few seconds of arc, the value of the coefficient depends upon the absorber position with respect to the monochromator. A few measurements are reported with a two-crystal spectrometer to illustrate the points discussed.
Rapid-Opening Mechanical Gate Valve
Authors: Denardo B. P. , Charters A. C.
Published: February 2005

The design of a rapid-opening mechanical gate valve is revealed. Its operation and construction details are discussed, along with results of operational tests. In use, a port whose diameter is 1¼ in. can be completely opened in about 0.6 msec from the time a signal is fed to the valve unit.
Measurement of Nuclear Isomeric Half-Lives in the Range from One Microsecond to Ten Milliseconds
Authors: Lindstrom I. E. , Crasemann Bernd
Published: February 2005

Relatively simple and accurate delayed-coincidence apparatus for the measurement of isomeric half-lives in the millisecond range is described. Practical aspects of the statistics of delayed-coincidence counting are discussed. Half-life measurements of Ta181m (17.83±0.10 μsec) and Y88m (300.5±5.0 μsec) are described.
Mass Sensitive Detector for Relativistic Electrons
Authors: Marshall L.
Published: February 2005

A mass sensitive detector for relativistic particles is proposed whose mass sensitivity increases with increasing particle energy. The counter detects synchrotron radiation emitted by relativistic particles as they travel through a high-intensity magnetic field. The power emitted in synchrotron radiation varies inversely as the rest mass to the fourth power, and the frequency of the spectral region in which the main power is emitted varies inversely as the rest mass cubed. In 50-cm path of a presently practicable magnetic field, 105 gauss, an electron of 1 Bev emits on the average 10 photons with a total energy of 68 kev, each of about 7 kev. This radiation when converted to visible radiation in NaI crystals is detectable by photomultipliers. In application to cosmic rays, with a steady-state magnetic field, the counter enables specific recognition of electrons of ≥1 Bev.
Wire-Rod Spark Counters in Air
Authors: Daddi Lino , De Franceschi Luciano
Published: February 2005

The operating characteristics of the Rosenblum type spark counters in air are examined. A qualitative interpretation of the experimental data is given.

The advantages of the device (no background, absence of walls, detection of heavily ionizing particles only) and its disadvantages (limited reproducibility for some incidence directions, small sensitive volume), which limit its practical utilization, are reported.
Scintillation Spectrometer with an Anticoincidence Annulus of NaI(Tl)
Authors: Trail C. C. , Raboy Sol
Published: February 2005

In the scintillation spectrometer described, the main detecting crystal of NaI(Tl) is enveloped by a hollow cylinder of NaI(Tl) in anticoincidence with the main crystal. This system completely suppresses the peaks associated with the escape of the two quanta from the annihilation following pair production, and it reduces the Compton background by a factor of 7 for 4.43-Mev gamma rays and by a factor of 5 for those of 6.1 Mev.
Vacuum Adiabatic Heat Capacity Calorimeter
Authors: O'Neal H. Edward , Gregory N. W.
Published: February 2005

The design, operation, and performance of a constant heating adiabatic vacuum calorimeter, suitable for measurement of the heat capacities of corrosive, hygroscopic, easily oxidized, and slightly volatile materials in the temperature range from 50° to 460°C, are described. A sealed glass cell is used to protect the sample.
Semiautomatic Townsend Balance System
Authors: Garfinkel Samuel B.
Published: February 2005

A semiautomatic system has been developed for use with a Lindemann-Ryerson electrometer. The system measures ionization current in the National Bureau of Standards 4π γ-ionization chamber by the Townsend balance-of-charge method. Two minature semiconductor photocells, with associated electronic circuitry, are used for detecting deflections of the electrometer and for controlling the amount of compensating charge placed on the electrometer. In addition, the starting and stopping of an electronic clock is controlled by a third photocell. The system has an ultimate precision of about 0.02%.
Replica Method for Examining Surface Profiles
Authors: Young A. P. , Clegg B. H.
Published: February 2005

A nondestructive method for the light microscope examination of surface profiles by means of replicas has been developed. The method has been applied to the examination of the surfaces of gear teeth. Possible extension of the method to electron microscope examination of the profiles of nearly smooth surfaces is described.
Simple Method of Shunt Impedance Measurement
Authors: Dekleva J. , Robinson K. W.
Published: February 2005

A direct method for the measurement of the shunt impedance of high-Q resonant systems is described. The shunt impedance value is deduced from a set of normalized transmitted signals which are obtained by means of a perturbation technique. The sensitivity of the method is equal to that obtained from R/Q measurements but requires greatly simplified instrumentation and makes it possible to obtain results much more rapidly.
Use of a Silver Tube to Admit Oxygen to a Vacuum System
Authors: Whetten N. R. , Young J. R.
Published: February 2005

Oxygen admitted to a vacuum system through a silver tube has been analyzed with a mass spectrometer. The oxygen was found to be of high purity. A satisfactory silver tube assembly is described, and some advantages over other methods of admitting oxygen are discussed.
Extended Range Pirani Gauge
Authors: Smith Alan W.
Published: February 2005

A Pirani gauge has been developed which is useful from atmospheric pressure to 10−5 mm Hg. This gauge has two elements: a platinum ribbon active in the low-pressure region and a thermistor bead active in the high-pressure region. By a simple but unique electrical circuit, the sensitivity in the intermediate region is maintained at a high level. In any pressure region, the gauge has the optimum characteristics possible with a Pirani-type gauge.
Dynamic-Condenser Magnetic Fluxmeter
Authors: Burson S. B. , Martin D. W. , Schmid L. C.
Published: February 2005

This instrument was designed to measure and control the flux density between the poles of an iron-core electromagnet used in conjunction with a beta-ray spectrometer. A sensing coil, rotating at 1800 rpm, generates 0.115 v (rms) per gauss. A comparison signal, against which the emf of the coil is bucked, is generated electrostatically by a dynamic condenser. Its rotor plates are shaped to produce a sinusoidal wave form. The amplitude of the comparison signal is determined by a dc voltage applied between two stator sections which are juxtaposed on opposite sides of the rotor shaft. This voltage thus provides a measure of the field strength. An unbalanced condition results in the appearance of a 30-cps error signal at the stator sections (which are isolated with respect to ac). After amplification and synchronous rectification, this signal indicates the degree and phase of the imbalance. The motor speed is maintained constant by a precision 60-cps tuning fork. The stability of the fluxmeter is of the order of one part in 2500, as determined by the reproducibility of the positions of internal-conversion-electron lines from Bi207 and Cs137 sources.
Flux Concentrator for High-Intensity Pulsed Magnetic Fields
Authors: Kim Y. B. , Platner E. D.
Published: February 2005

Use of multiturn coil structure in the production of several hundred kilogauss pulsed fields is discussed with specific emphasis on coil life. The magnetic force that shortens the coil life is reduced by introducing a flux concentration device. Into the multiturn coil is inserted a rigid, slotted metal slug that generates induction current in such a way as to shift the magnetic flux from the multiturn to the central vacuum region and serves as a flux concentrator. Electromagnetically and mechanically this scheme is a convenient synthesis of the multiturn and single turn coils. The advantage of this scheme is most apparent for tape-wound coil structures, and a quantitative analysis of the flux pattern relevant to this coil system is given. An analog computer is employed in solving the time dependence of the field. The results are documented by experimental tests carried out with a 3000-μf, 4-kv capacitor bank.
Growth of Large Diameter Silicon and Germanium Crystals by the Teal-Little Method
Authors: Runyan W. R.
Published: February 2005

The equipment and techniques used to grow 6-in. diam silicon and germanium crystals are described, and the effect of spin, radiation, and mode of heating on crystal growth from a melt is discussed.