bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanical Analog Computer for Solving the Axial Equations of Motion during Bunching in Linear Electron Accelerators
Authors: Demos P. T.
Published: February 2005

A mechanical analog computer is described which is suitable for the exploratory study of linear accelerator designs in the bunching region, at least in problems of the kind encountered in electron accelerators, where bunching is accomplished in comparatively short intervals and with relatively few phase oscillations. Particle phase is observed directly from a resolver; and particle momentum, particle velocity, and accelerating wave phase velocity are observed simultaneously as linear magnitudes whose relative change during calculation provides useful intuitive guidance in the choice of accelerator parameters. Some calculations are reported which were made with a rough apparatus capable of ∼5% accuracy.
Versatile and Sensitive Vibrating-Sample Magnetometer
Authors: Foner Simon
Published: February 2005

A vibrating-sample magnetometer, which measures the magnetic moment of a sample when it is vibrated perpendicularly to a uniform magnetizing field, is described. With this instrument, changes as small as 10−5 to 10−6 emu have been detected, and a stability of one part in 104 has been attained. In addition to permitting convenient measurements in the usual laboratory electromagnet, this instrument eliminates or minimizes many sources of error found in other methods. It is simple, inexpensive, and versatile, yet permits precision magnetic moment measurements to be made in a uniform magnetizing field as a function of temperature, magnetizing field, and crystallographic orientation. The mechanical design and detailed operating characteristics are presented. Applications and limitations of the method are outlined.
Low-Temperature Adiabatic Calorimeter with Automatic Shield Control
Authors: Cooper W. J. , Forsyth R. H. , Masi J. F. , Pabst R. E.
Published: February 2005

The design and operation of an adiabatic low-temperature calorimeter employing a somewhat different design of automatic shield control is described. Thermocouple difference is sensed by a dc μv amplifier, which is followed in the circuit by a recorder-controller and a Leeds & Northrup Series 60 (current adjusting type) control unit. The output of the latter is used to control the voltage across the shield heaters through a Westinghouse ``Magamp'' saturable reactor. This design has been used successfully with a conventional low-temperature adiabatic calorimeter (50-ml sample size). In most cases the recorder showed no variation from zero (±0.002°) during heating and equilibrating periods, while momentary disturbance at ``on'' and ``off'' was less than 0.05°.
Cryostat for Ferrimagnetic Resonance Experiments
Authors: Dillon J. F. , Geschwind S. , Jaccarino V. , Machalett A.
Published: February 2005

A cryostat is described consisting of a glass vacuum insulated inner vessel and a Styrofoam outer vessel. The inner Dewar narrows to a fine tip containing the sample at its lower extremity where it protrudes through the outer vessel, and extends into a microwave cavity.
Technique for Measurement of Specific Volume of Liquids at High Pressures and Temperatures
Authors: Cornish R. M. , Simon I.
Published: February 2005

A novel method is described for measuring specific volume of liquids at high temperatures and pressures. The displacement of the two ends of a continuous column of the liquid is measured. One end is maintained at high temperature and pressure while the other is at normal conditions.
Thermostat Control by Resistance Thermometer
Authors: Zwolenik James J. , Lind John E. , Fuoss Raymond M.
Published: February 2005

By intercepting on a selenium cell part of the light beam from the galvanometer in the bridge circuit of the resistance thermometer used to measure bath temperature, a signal is obtained which is used to trigger a photo-relay via a secondary galvanometer. The photo-relay controls the heating current in the thermostat. Design of the selenium cell mounting and accompanying circuits are described. The device holds a 50-gal thermostat to 25° within a hunting amplitude of 0.002°C.
Diffusion-Couple Analyzer for Use with the G.E. XRD Diffractometers
Authors: Cohen Jerome B.
Published: February 2005

Equipment is described to analyze diffusion couples and phase boundaries by means of x-ray absorption, in conjunction with the G.E. XRD diffractometers. Analysis may be carried out automatically with the system described here over a minimum distance of 14 μ. The equipment will not interfere with normal diffraction work over the range 0–106°2θ and, therefore, can be left fixed to the diffractometer when not in use.
Filament Furnace for Microscopy Studies at High Temperatures
Authors: Newkirk H. W. , Bates J. L.
Published: February 2005

A filament furnace is described which is suitable for heating gram quantities of materials to 3000°C under reduced pressures or in various atmospheres. A quartz window and shutter assembly permit the observation of the specimen during the heating cycle by long working distance microscopes.
Core Saturation Blocking Oscillator Control
Authors: Spinrad Robert
Published: February 2005

The parameters that control a blocking oscillator's pulse shape are reviewed. Limitations in previous techniques of pulse duration control are described. It is shown that the pulse duration may be determined either by tube (or transistor) saturation or by saturation of the transformer core material. The latter mode of operation is preferred because it confers stability against aging of tubes or transistors, variations of ambient temperature, and changes in loading. Design criteria for establishing either mode of operation are given. The means by which an externally applied magnetic bias can be used to control the pulse width over more than a 10:1 range are described. A blocking oscillator circuit designed according to the principles discussed is presented, along with specific performance data.
Some Liquids for Use in Large Bubble Chambers
Authors: Hahn B. , Riepe G. , Knudsen A. W.
Published: February 2005

The liquids C3F8, C4F10, SF6, C2ClF5, and CBrF3, and mixtures of SF6 with C2ClF5 have been found to possess a number of desirable properties for use in large bubble chambers, designed primarily for particle decay studies. These properties are relatively short radiation length, convenient operating pressure and temperature, chemical inertness, and nontoxicity. Some properties of TeF6 are also discussed.
Transistor Simulator
Authors: Lüscher J. , Döme P.
Published: February 2005

An apparatus allowing a straightforward determination of the π equivalent circuit of alloy junction transistors is described. The principle of measurement is based on the simulation of wave forms. The possibility of a simple determination of the equivalent circuit at any working point of the transistor enables a rapid evaluation of the current or voltage dependence of the circuit elements. The equipment, having an upper frequency limit of 10 Mc, can be used for transistors of much higher alpha cutoff frequencies, since for the measurements the common emitter configuration is chosen. Examples are given to demonstrate how some physical and dimensional values of the transistor can be calculated from the measured parameters.
Precision Thermometer System for the Liquid Helium Region
Authors: Sandlin B. J. , Thompson J. C.
Published: February 2005

A high-precision thermometer system has been developed using a carbon resistor (Allen-Bradley type) as the sensing element. The resistor is in the frequency determining circuit of a stabilized Wien bridge oscillator. Thus temperature changes are displayed as frequency shifts. The frequency is read directly from a Hewlett-Packard type 523B counter. When operated in the neighborhood of 100 kc at 4.2°K the sensitivity is approximately 50 kc/deg. This corresponds to a temperature resolution of 20 μdeg, when used with the above counter. Resolution can be improved by observing higher harmonics. The power input to the resistor is of the order of 10−2 μw. The time for a temperature measurement is 1 sec, and response times to changes are limited only by equilibrium in the thermometer. Absolute accuracy is essentially limited only by the determination of the helium vapor pressure during calibration.
Counter Telescope Efficiency Calculation for a Nonisotropic Neutron Source
Authors: Haddad E. , Warren John L.
Published: February 2005

The measurement of neutron cross sections with a counter telescope involves a calculation of the telescope efficiency. Past work has treated the case of an isotropic point source of neutrons. In the present work equations are derived for a nonisotropic point source of neutrons. The efficiency equations were evaluated by means of an IBM 704 computer for various experimental conditions and the results are presented in tables.
Instrument for Measuring Water Waves
Authors: Whittenbury C. G. , Huber E. A. , Newell G. S.
Published: February 2005

The variation of wave height is sensed by a probe whose capacitance is linearly dependent on wave height and controls the repetition rate of a blocking oscillator. The variation of repetition interval is converted into amplitude modulation at the recording site. The wide dynamic range (1000:1) of the electronic portion of the instrument permits the measurement of ripples with the same accuracy whether they are on calm or rough water. The dynamic range of the instrument is limited by the characteristics of the probe. The instrument requires no balancing, has a frequency range of 0 to 100 cps and a sensitivity which is adjustable. The maximum sensitivity used in the field was 8.0v/cm water displacement and the noise level at this sensitivity corresponds to 0.032 mm rms water displacement.
Reliable Optical Window for Cells Subjected to Widely Cycling Temperatures and Pressures
Authors: Waggener W. C. , Tripp A. M.
Published: February 2005

A new type of window has been designed for use in high-temperature aqueous solution spectrophotometer cells. The assembly employes a sapphire window and a separate spring-loaded Teflon seal which provide features of reliability, leaktightness, and safety not previously obtained.
Automatic Torque Balance for Magnetic Anisotropy Measurements
Authors: Penoyer R. F.
Published: February 2005

An automatic torque balance for the determination of magnetic anisotropy in ferromagnetic single crystals is described. The balance consists of a mechanical coupling between a solenoid suspended in a static magnetic field and a single crystal specimen. The torque produced by the specimen causes a minute motion of the solenoid, which is detected by means of a light beam-mirror-phototube network, and an automatically controlled current is fed back to the solenoid, establishing a torque equal and opposite to that produced. A voltage proportional to the feedback current, and thus the applied torque, is recorded on one axis of an X-Y recorder. The other axis is driven by a voltage governed by the direction of magnetic field in which the crystal is suspended. A method that automatically compensates for the deviation of magnetization from applied field direction in highly anisotropic crystals is described, and further advantages of the automatic balance over other systems are discussed.
Angular Correlation and Angular Distribution Attenuation Coefficients
Authors: Stanford A. L. , Rivers W. K.
Published: February 2005

Attenuation coefficients for angular correlation measurements and angular distribution measurements have been calculated for sodium iodide crystals of 1.5-in. diam and various heights. The crystals considered are right circular cylinders of heights 1.0, 1.25, and 1.5 in. Eleven photon energies in the range from 0.05 to 5.0 Mev were used. Attenuation coefficients for crystals of diameters other than 1.5 in. may be obtained from these results.
Improvements in the Microwave Propagation Method of Studying Decaying Gas Plasmas
Authors: Takeda Susumu , Holt E. Howard
Published: February 2005

Some improvements in measuring the transient values of the electron density in decaying gas plasmas by the propagation method are described. The electron density, as is known, can be calculated from measurements of phase shift and attenuation of a probing microwave signal propagated through the plasma. The increase of the detection sensitivity of very small phase shifts (X-band microwave) leads to at least a tenfold decrease in electron density measurement. Thus, in a ten-inch long discharge tube densities of 1011−108 cm−3 are measured, which is comparable to that by the cavity method at the same frequency.
Improved Diode for the Harmonic Generation of Millimeter and Submillimeter Waves
Authors: Ohl R. S. , Budenstein P. P. , Burrus C. A.
Published: February 2005

The only generally available source of monochromatic microwave energy in the shorter mm- and sub-mm-wave region is still some form of the point contact silicon diode harmonic generator, usually driven by a cw fundamental frequency source operating in the 8–12 mm wave region. It has been found experimentally that the performance and stability of diodes for this application can be greatly improved by bombarding the silicon surface with positive ions. Described here are the methods used for the bombarding and mounting of silicon for this harmonic generating application, the construction of two practical wave guide circuits, the operating conditions for the most successful use of the material, and finally, the measured high-frequency output is compared with that calculated on the basis of a simplified equivalent circuit for the harmonic generator.
Millimicrosecond Pulse Generator Capable of 10 Million Pulses Per Second
Authors: Nakamura Michiyuki
Published: February 2005

A compact, portable pulse generator with output pulses in the millimicrosecond region at high repetition rates is described. The generator has repetition rates of up to 107 pulses/sec, pulse rise times of less than 2.5 mμsec, and pulse widths adjustable from 2.5 to 25 mμsec. The output pulse is negative in polarity and is adjustable over an amplitude range of from 0 to 12 v into 125 ohms output impedance. The instrument has provisions for gating, single pulsing, and operation with drive from an external signal source.
Hall Effect Measurement in Semiconductor Rings
Authors: Pohl Robert G.
Published: February 2005

The Hall effect can be measured in a ring-shaped sample placed in an alternating magnetic field normal to the plane of the ring. The resultant circular electric field produces a current around the ring proportional to the time derivative of the magnetic field. This current interacts with the magnetic field, establishing a Hall voltage between the inner and outer radii of the annulus. For extrinsic semiconductors with single effective mass charge carriers, this Hall voltage is, in mks units, VH=μωB02(a2−b2) sin2ωt/8,where μ is the mobility, ω the field angular frequency, Bo the peak value of the magnetic field, a the inner radius, and b the outer radius. This technique eliminates voltages arising due to misaligned probes and end-effects in the conventional method. In addition, the measurement is independent of the conductivity for the case above. Experimental measurements on germanium, silicon, and indium antimonide rings yield mobility values in agreement with customary results.
Flip-Coil Target Positioner for Use with Accelerators
Authors: Stone Kenneth F. , Force Robert J.
Published: February 2005

A target positioner for use in the accelerating chamber of the Bevatron is described. This positioner has a rise time of 75-msec and equally fast drivedown. The mechanism has proven reliable to 106 cy between maintenance periods.
Cavity Resonators for Dielectric Spectroscopy of Compressed Gases
Authors: Bussey Howard E. , Birnbaum George
Published: February 2005

Convenient, tunable, sealed-off cavity resonators are described at frequencies of 1, 2, 9, and 24 kMc, for use with internal pressures up to 1000 psi. The modes of oscillation employed were TE01n, TE11n, and TM01 hybrid, all in a circular cylinder. A convenient method for sealing an iris, applicable over a wide-frequency range, is to insert a tapered Teflon plug. A Kovar-glass seal for coaxial lines is described that provides a good impedance match in a 50-ohm line. The measuring procedure is described. Accuracy of dielectric loss measurements was increased by calibrating the loss changes of the cavity arising from reresonating it upon admission of lossless gas.
Analysis of Single Crystal Pulse-Height Distributions
Authors: Childers H. M.
Published: February 2005

A method for analyzing the pulse-height distribution of a single NaI crystal gamma ray spectrometer is presented. The method consists in solving the matrix equation, P=KN(hv), for N(hv), the incident gamma ray spectrum in which P is the pulse-height distribution, and K is the sensitivity matrix of the detector. A procedure for obtaining the elements of K from curves obtainable from the pulse-height distributions produced by a few standard monoenergetic sources has been devised. Experimental results are presented which demonstrate the validity of the method.
Electronic Probability Generator
Authors: White Gerald M.
Published: February 2005

The investigation of nonstationary random processes arises in many models of control and learning systems. To aid in studying this class of systems, an electronic probability generator, EPI, was built. EPI can electronically ``flip'' a coin at a maximum rate of 500 times/sec. The probability of heads of this electronic coin can be varied from 0 to 1 and is a linear function of the input voltage. Graphs are presented to illustrate EPI's ability to generate independent events. EPI can also be used to generate sequences of heads and tails controlled by higher order probabilities. The only additional equipment required is an electronic switch.
Laue Spectrometer for Multichannel X-Ray Spectrochemical Analysis
Authors: Ladell J. , Spielberg N.
Published: February 2005

A method for making use of the Laue diffraction technique rather than the Bragg symmetric technique in the design of multichannel x-ray spectrochemical analysis instruments is described. The method uses only one analyzing crystal, but with individual detectors for simultaneous registration of the relative amounts of the elements in the sample to be analyzed. Thus a compact instrument with no moving parts, which may often be designed so as to reduce spectral interferences, is possible. The method is compared with other well-known methods and some experimental tests of the principle are described.
Use of Oxide-Coated Cathodes in High Current Electron Accelerators
Authors: Davidson G. , Ozaki S. , Weinstein R.
Published: February 2005

An investigation has been made of the possibility of using an oxide-coated cathode as an electron source for the M.I.T. 320-Mev electron synchrotron. A button cathode originally designed by Sperry Gyroscope Company was redesigned slightly to meet our specifications. With this new cathode, we have obtained an average lifetime of 330 hrs, operated at peak-pulsed current of 200 ma in vacuums as poor as about 10−5 mm Hg. This represents a factor of about 20 improvement in lifetime-current product over directly heated cathodes.
Energy Loss Spectra for Gamma Rays in NaI
Authors: Miller W. F. , Snow William J.
Published: February 2005

Energy loss spectra for gamma rays incident on sodium-iodide crystals have been calculated by the Monte Carlo method. The calculations have been carried out for point sources, disk sources, and broad parallel beams of monoenergetic gamma rays varying in energy from 0.279 to 8 Mev. The crystals considered were right circular cylinders varying from small crystals of height and diameter one inch to large crystals of height and diameter 6 inches. Also calculated simultaneously with the energy loss spectra were the efficiencies and total absorption fractions.
Efficient Flash Photolysis System
Authors: Charlson R. J. , Harrison Halstead , Hardwick R.
Published: February 2005

A flash tube of annular design, improved flash circuitry, and a photomultiplier enabler circuit are described. Results obtained with this apparatus indicate that the system quickly delivers a large number of photons into an absorption cell (viz., ∼6×1016 photons/cc with about 5 μsec 1/e time and 50 μsec total decay time) and is thus suited for studies of fast photochemical kinetics.
Fast Coincidence Circuit for Slow Pulses
Authors: Draper J. E. , Fleischer A. A.
Published: February 2005

A circuit is described which permits the timing of slow pulses (e.g., 300-mμsec rise time) to good precision (e.g., ±3 mμsec) over a wide range of pulse heights (e.g., 6 v to 120 v) and at high counting rates (average separation ≳4 μsec. This is useful particularly in coincidence spectroscopy with NaI(Tl) scintillators.
Simple Technique to Control the Stray Field of Electrolytic Cells
Authors: Schwan Herman P. , Maczuk J.
Published: February 2005

A technique is outlined to control the stray field of electrolytic cells in a predictable and simple manner. The technique is particularly useful in biological impedance work and in determinations of the dielectric constant of solutions of high conductivity. It is based on a plot of the apparent dielectric constant as a function of electrode distance. In a logarithmic presentation the apparent dielectric constant appears as the sum of the true dielectric constant and two linear functions, representative of electrode polarization and stray field component. A few examples are given to illustrate the technique and its limitations.
Analog Computer for Charged Particle Trajectories
Authors: Good Robert H. , Piccioni Oreste
Published: February 2005

An analog computer has been applied to the problem of tracing the trajectories of a beam of charged particles such as is produced by high energy accelerators. The electrical circuit involved employs analogs for both quadrupole magnets and bending magnets, and thus it facilitates the determination of both the focal properties and the dispersion characteristics of the magnets; an accuracy as good as 2% has been attained for some of the calculations made with the present instrument.
Use of Bubble Chambers for Experiments with High Energy Gamma-Ray Beams
Authors: Guerriero L. , Mark Hans , Pless I. A. , Rosenson L. , Shapira Y. , Tuchman A. , Yamamoto R. K.
Published: February 2005

Visual particle detection methods have been used with high energy bremsstrahlung beams of low intensity. A method for obtaining a substantial increase in the gamma-ray beam intensity which can be passed through a 9-in. propane bubble chamber is described. The beam is collimated and then led through a hollow tube passing through the middle of the bubble chamber. It was found that use of a ``beam tube'' increases the number of events observed per picture by a factor between five and ten over the number found with no beam tube. The 300-Mev bremsstrahlung beam of the MIT synchrotron beam was used for these experiments. Advantages and limitations of the beam tube method are discussed.
Analysis of a Magnetic Resonance Spectrometer
Authors: Goldsborough J. P. , Mandel M.
Published: February 2005

This paper analyzes an electron paramagnetic resonance microwave bridge spectrometer, and expressions are given for the relation between the signal and the imaginary part of the magnetic susceptibility. From these the conditions for maximum signal are obtained. The analysis is also applicable to many other types of magnetic resonance spectrometers.
Transistorized Coincidence Circuit for π-e Experiment
Authors: Miller R. H.
Published: February 2005

A special purpose coincidence circuit with millimicrosecond resolution time is described which illustrates the simplicity that can be achieved with transistorized circuits. The circuit performs all the logical operations of three simultaneous experiments to measure the branching ratio to the electronic mode of pion decay. Performance data under operating conditions on the cyclotron are given.
Determination of Flame Velocities in Gaseous Predetonation
Authors: Hecht G. J. , Laderman A. J. , Stern R. A. , Oppenheim A. K.
Published: February 2005

The application of ionization gap or ``pin'' probes to measure flame velocities during the development of detonation is presented. Probe construction and circuit techniques are described which, despite the widely varying character of the ionization signals in this region, yield timing precision of 2% or less for hydrogen-oxygen mixtures. Analysis of the ionization probe circuit permits the identification of the probe signal with the ionization levels encountered in the various waves generated during the development of detonation. In this manner it is possible to differentiate between shocks, flames, and detonation waves and to determine the axial flame velocity profile.
Use of Silicon p-n Junction Detectors in Studies of Nuclear Reactions Induced by Heavy Ions
Authors: Larsh Almon E. , Gordon Glen E. , Sikkeland Torbjo/rn
Published: February 2005

Experiments in which silicon p-n junctions have been used as detectors of fission fragments and elastically scattered heavy ions are described. The curve of pulse height versus energy for carbon particles is linear and passes through the origin. Points for Cf252 fission fragments and alpha particles fall on the curve determined by the carbon-particle points. This result implies that the energy required for electron-hole pair formation is the same for the three types of particles. Also, no ``ionization defect'' is observed for the fission fragments. Some other possible uses for the detectors of this type are suggested.
A Simple Field Detector for a Dc Permeameter
Authors: Adams Charles Q.
Published: February 2005

A two-core flux-gate magnetometer is employed in a simple balanced bridge circuit as the dc field detector of a single strip permeameter. The sensitive magnetometer and simple bridge circuit eliminated the necessity of the complex filter and selective amplifier used in earlier systems and allows operation independent of oscillator frequency stability. The H-measuring system is designed to measure fields from 1 moe to about 10 oe with a sensitivity of ≈25 μa/moe. Economy and simplicity of construction, circuitry, and operation are its chief advantages.
Erroneous Readings of Large Magnitude in a Bayard-Alpert Ionization Gauge and their Probable Cause
Authors: Barnes George
Published: February 2005

Experimental work is described in which pressure fluctuations as great as two orders of magnitude as recorded by a new type of cold-cathode vacuum gauge were undetected by a Bayard-Alpert ionization gauge. It is shown that the Bayard-Alpert gauge measures the pressure inside its electron-accelerating grid only and not that within the remainder of the evacuated system. Operation of the heated filament of this gauge within a glass tube or near glass parts gives rise to sodium, potassium, and other low ionization-potential materials throughout the vacuum system but in spite of being a major source of contamination, the Bayard-Alpert gauge does not detect the presence of these substances. This is because such low ionization-potential materials are photoionized by the light from the heated filament and cannot penetrate the positively charged electron-accelerating grid in order to be detected. Some other effects related to the phenomenon are discussed.
Some Considerations on Luminescent Fiber Chambers and Intensifier Screens
Authors: Reiffel L. , Kapany N. S.
Published: February 2005

Factors affecting the performance of filamentary scintillators are considered. Experimental data on light attenuation for both plastic scintillator filaments and thin-wall glass tubing liquid scintillators are presented. A theoretical interpretation which satisfactorily accounts for the performance of luminescent filaments in terms of bulk properties and surface reflection losses is given and permits quantitative evaluation of surface losses for various materials. While plastic scintillator fibers are mechanically convenient, it is suggested that liquid-filled fibers will prove more consistent and stable in their properties. Comments on the utility of arrays of fibers as particle track imaging devices and as image intensifier screens are included.
Self-Diffusion Measurements in Liquids by the Spin-Echo Technique
Authors: Woessner D. E.
Published: February 2005

A new method for spin-echo self-diffusion measurements is presented. The magnetic field gradient, instead of the rf pulse interval, is varied; hence, the oscilloscope sweep and pulser settings need not be changed during measurements. Requirements on H1 are discussed.
Crossed Electric and Magnetic Field Multichannel Ion Analyzer
Authors: Bailey L. Evan
Published: February 2005

A multichannel mass and energy analyzer using crossed electric and magnetic fields for ion separation has been constructed to analyze plasmas produced in conjunction with a magnetic mirror machine. Ions are piped between the strong magnetic field of the mirror machine and the weaker magnetic field of the analyzer by auxiliary magnetic coils, and they enter the analyzer traveling in a direction nearly parallel to the magnetic field. There, the ions are accelerated by the electric field and assume cycloid-like trajectories in the plane perpendicular to the magnetic field. The ions are collected by detectors located at the top of the cycloid. The amplitude of the cycloid is determined by the e/m of the ion; the distance traversed parallel to the magnetic field before collection is proportional to the velocity of the ion.
Simple Logarithmic Dc Amplifier
Authors: East L. V. , Parker W. E.
Published: February 2005

A logarithmic dc amplifier circuit is described using a type 12AU7A dual triode. The amplifier output follows the equation E0=9.00−2 log10Ei with an accuracy of 2% or better for positive input voltages from 5 to 500 v. The circuit parameters may be easily adjusted to compensate for tube aging and differences in characteristics between individual tubes. Output voltage drift is low and relatively independent of filament voltage drift.
New Thermoluminescent Dosimeter
Authors: Schulman James H. , Attix Frank H. , West Edward J. , Ginther Robert J.
Published: February 2005

A simple dosimeter design is described in which a thermoluminescent phosphor is mounted on an electrically heatable support in an evacuated or gas-filled envelope. With CaF2:Mn as the phosphor, the device detects gamma-ray doses in the milliroentgen range and is linear in response up to at least 2×105 r. Dose readings can be made in less than a minute with simple instrumentation requiring no darkroom facilities. The dosimeter may be reused many times. The response is independent of dose rate at least over the range 10 mr/min to 7000 r/min. With suitable tin shields the response is independent of energy over the range 40 kev to 1.25 Mev. The advantages of this device for monitoring of personnel in health physics operations are pointed out.
Measurement of Betatron Oscillation Frequencies in the Cosmotron
Authors: Barton M. Q.
Published: February 2005

Coherent betatron oscillations are excited by an impulse magnetic field in one straight section of the cosmotron. The resulting oscillations can be observed using a communications receiver connected to the radial position induction electrodes.
Modified Double Slit Interferometer for Shock Wave Investigations
Authors: Markstein George H.
Published: February 2005

The possibility of applying the Rayleigh double slit interferometer for shock wave investigations has been explored. In common with Rayleigh interferometers currently used for diffusion, electrophoresis, and ultracentrifuge studies, the instrument adapted for the present application contained a cylinder lens for bringing the interference fringes and the test section into simultaneous focus at the camera image plane. However, in contrast to previous applications, it was found desirable in the present work to let the light paths through both slits traverse the test section. This arrangement required a modification which consisted of tilting the axis of the cylinder lens, and the light source slit, with respect to the conventional orientation parallel to the refractive index gradient. Conditions under which a useful interferogram is obtained with this instrument are derived, and results of preliminary experiments are presented. Compared with the Mach-Zehnder interferometer, the double slit instrument has the advantages of greater simplicity and ease of adjustment, lower cost, and offers the possibility of combining the interferometer with an inclined slit schlieren system.
Accumulating Digitizer System
Authors: Fields Thomas H. , Findley Robert W.
Published: February 2005

A system is described for digital measurement and automatic recording of linear or angular position. An adding-subtracting scaler is used to accumulate pulses generated by the digitizing element. Several of the major components are commercially available. The performance of the system as used for coordinate measurements on bubble chamber photographs is discussed.
Device for Generating a Low Temperature, Highly Ionized Cesium Plasma
Authors: Rynn Nathan , D'Angelo Nicola
Published: February 2005

A device for generating a linear, highly ionized, low temperature cesium plasma is described. The plasma is generated by having the output of cesium atomic beam ovens impinge on hot tungsten plates placed at both ends of a cylindrical vacuum chamber. The walls of the chamber are cooled so that neutral cesium condenses on them. The theory of the device, designated as the Q machine, is presented and some experimental results given. The maximum density achieved was 2×1012/cm3, with an estimated fractional ionization of 99%, and a confining field of 5900 gauss.
High-Resolution NMR Spectrometer with the Radio Frequency Controlled by the Magnetic Field
Authors: Freeman R. , Pound R. V.
Published: February 2005

A practical spectrometer for the observation of high-resolution proton magnetic resonance spectra at 30 Mc is described. Field modulation is imposed in such a way that ``sideband'' responses are observed, and this enables lock-in detection to be used, giving increased stability to the baseline of the records. Spectra are displayed by slowly sweeping the modulation frequency and thus are calibrated directly in frequency. The radio-frequency source is a proton controlled super-regenerative oscillator, whose frequency follows variations of the electromagnet field. This reduces the effects of field drift and instability, allowing relatively slow scanning speeds to be used in recording the spectra.
Apparatus for Direct Observation of Low-Energy Electron Diffraction Patterns
Authors: Scheibner E. J. , Germer L. H. , Hartman C. D.
Published: February 2005

An apparatus for the observation of low-energy electron diffraction patterns on a fluorescent screen is described. The diffracted electrons pass through a pair of grids and then are accelerated by a potential difference of the order of 103 v to excite the fluorescent screen. The equipment is designed for high vacuum, and pressures below 2×10−10 mm Hg have been maintained. Different gases can be introduced at low controlled pressures (10−9 to 10−7 mm Hg), and diffraction patterns produced by adsorbed layers can be photographed and studied. Typical diffraction patterns from a clean (111) face of a nickel crystal and from oxygen adsorbed upon this face are reproduced here.
Apparatus for Applying Liquids in Small Droplets to Animals
Authors: Buckholz E. E. , McPhail M. K.
Published: February 2005

A precision apparatus for applying liquid in uniform droplets to test surfaces has been described. The mean diameter of the droplets can be varied from 0.045 to 0.450 mm.
Magnetically Driven Fast-Acting Valve for Gas Injection into High Vacua
Authors: Gorowitz B. , Moses K. , Gloersen P.
Published: February 2005

A description is given of a valve suitable for use in studies involving the acceleration of plasmas into regions of high vacua. Valve opening durations of less than 60 μsec may be attained, and amounts of gas lower than 0.01 cc STP may be introduced. Valve performance characteristics and measuring techniques are discussed.
Betatron Energy Calibration by Magnetic Field Measurement
Authors: Penfold A. S. , Garwin E. L.
Published: February 2005

The technical features of a system for the determination and control of the operating energy of a 100-Mev betatron are described. The system is based on a determination of the magnetic field at the tip of the x-ray target at the instant of x-ray production. It is believed that an accuracy of 0.25% was obtained.
Thin-Heater Thermal Conductivity Apparatus
Authors: Hager Nathaniel E.
Published: February 2005

Apparatus is described for measuring the thermal conductivity of insulating materials. A constant current is passed through a rectangular sheet of stainless steel foil in such a manner that the rate of generation of heat per unit area can be computed from electrical measurements. Identical sample slabs are placed against opposite sides of the heater, and the combination is enclosed in a plastic film and immersed in a bath having constant and uniform temperature. When thermal equilibrium is reached, the temperature drops across the central portions of the sample slabs are measured with differential thermocouples. The elementary one-dimensional form of the Fourier heat transfer equation is used to compute the thermal conductivity from the observed quantities. In preliminary tests with representative insulating materials equilibrium is reached within 15 min. It is estimated that the apparatus is capable of giving measurements accurate to within 2%, and experimental results are not inconsistent with this estimate. Thermal conductivity values are reported for polystyrene and a cork-rubber composition at mean temperatures ranging from liquid nitrogen temperature up to room temperature. Differential thermocouple techniques are discussed. The characteristics of the apparatus make it especially suitable for academic laboratory instruction and for low-temperature measurement.
Automatic Device for Recording Experimental Results Directly on Teleprinter Tape
Authors: Winn M. M. , Ogilvie K. W.
Published: February 2005

A device is described which will record the results of counting experiments directly on teleprinter tape at predetermined intervals.
Large Proportional Counter Spectrometer for the Study of Radioactive Samples with Low Specific Activity
Authors: Holloway J. T. , Lu D. C. , Zaffarano D. J.
Published: February 2005

The design and construction of a cylindrical proportional counter 36 in. long, 12 in. i.d. is described, and its performance as a spectrometer for studying soft radiations from radioactive samples of low specific activity is given. The counter tank is operated in an axial magnetic field of 2500 gauss to constrain beta rays to helical paths. A line width of 3.4% (ΔE/E) is obtained for 625-kev electrons from a Cs137 source mounted on a thin film placed within the tank. Simple theory would predict 2.2%. Beta spectra are readily obtained with sources having total activities less than 10 mμC.
Frequency Control of an Oscillator by Nuclear Magnetic Resonance
Authors: Pound R. V. , Freeman R.
Published: February 2005

A simple super-regenerative oscillator that produces a coherent signal at the magnetic resonance frequency of a sample in its coil is described in theory and in practice. A cw oscillator is phase locked to the super-regenerative oscillator and the signal which results follows variations in the frequency of magnetic resonance, owing to variations of the field, within less than 5 parts in 103; the signal produced is adequately monochromatic and stable enough to be used for magnetic resonance experiments with high resolution. The requirements for time and temperature stabilization of the magnet are very greatly relaxed.
Compact Pulsed Generator of Fast Neutrons
Authors: Hawkins P. O. , Sutton R. W.
Published: February 2005

A study of the factors influencing the design of pulsed neutron generators is made. By using the reaction between tritium and deuterium, peak rates of 1013/sec should be obtainable from quite small sources.

A method of keeping the pressure of deuterium gas substantially constant at the working pressure was evolved. This enabled a ``sealed-off'' and hence portable source to be made.

The development of a fast neutron generator or neutron tube based on these considerations is described. This was capable of producing neutrons at a rate of 5×1012/sec at a voltage of 100 kv. The tube was suitable for operation at pulse lengths of 20 μsec, and the neutron content of each pulse was 108. No difficulty was experienced in operating at 1 pulse/sec, and higher pulse repetition frequencies may be possible.
Theory of a High-Resolution Beta-Ray Spectrometer with High Luminosity
Authors: Daniel H.
Published: February 2005

Second-order perturbation theory has been used to calculate the electron orbits in a ``flat'' beta-ray spectrometer with an azimuth-independent magnetic field having a symmetry plane. Abandoning first-order z focusing, it is possible to obtain a much higher resolution at a given transmission compared with the usual π√2 instrument. The resolution depends, in the lowest power, only on fourth-order terms of the radial and axial emission angles. The resolution does not depend on the first power of the source height. The focusing principle is applicable for a set of angles θ, and the dispersion increases strongly with increasing angle. Several examples are discussed.
Direct Reading Resistance Thermometer Bridge. Part II
Authors: Dauphinee T. M. , Kirby C. G. M. , Preston-Thomas H.
Published: February 2005

This paper presents the details of circuitry and construction for a direct reading resistance thermometer which has been built utilizing the design criteria formulated in Part I. By using any standard 25.5Ω platinum resistance thermometer as a sensing element, the bridge gives subdivision of the temperature scale to 0.001°C between −50° and +700°C with an accuracy exclusive of that of the thermometer of about ±0.001°C. Methods are described that allow for variations of thermometer constants, for autocalibration of the bridge circuit, and for maintaining constant sensitivity by variation of the thermometer current. The bridge as described has performed satisfactorily for three years and has proved to be a useful and convenient laboratory tool.
Scintillation Type Mass Spectrometer Ion Detector
Authors: Daly N. R.
Published: February 2005

A new and relatively simple type of mass spectrometer ion detector is described. The positive ion is accelerated onto an aluminum surface releasing secondary electrons, and these in turn are accelerated onto an organic scintillator, viewed by a sealed-off photomultiplier. Counting methods are used to measure the ion beams. The detector has a low noise level, 4×10−20 amp, and the mass discrimination is small for ions in the high and low mass range.

Admission of air to the vacuum system does not affect the gain of the detector, since no activated surfaces are situated within the vacuum.

In the event of a fault occurring in the photomultiplier a new one can be substituted in a few minutes without letting air into the vacuum system.
Resistance Strip Magnetic Photomultiplier for the Extreme Ultraviolet
Authors: Heroux L. , Hinteregger H. E.
Published: February 2005

The performance of a windowless resistance strip magnetic multiplier for detection of extreme ultraviolet is described. The detector is characterized by a high spectral sensitivity for wavelengths below 1400 A and a low sensitivity to longer wavelength radiation. It is reproducible in spectral response and gain after exposure to air or after cleaning. A current gain of 108 can be realized with the multiplier for an over-all voltage of approximately 2000 v. The photomultiplier can be operated as a photoelectron counter with a well-defined counting plateau for pressures below 10−4 mm Hg. The background counting rate of the detector, at room temperature and typical operation in the plateau region, is less than 0.1 count/sec.
Studies of Ionization Parameters in Nuclear Emulsions
Authors: Blau M. , Bloch S. C. , Carter C. F. , Perlmutter A.
Published: February 2005

A semiautomatic instrument for ionization measurements in emulsion is described briefly. The instrument was used in the investigation of the various ionization parameters. Deviations from a purely exponential gap-length distribution were observed, a result found earlier by Cortini et al. This observation limits the usefulness of the mean gap length as a parameter. A new parameter based on the blob-length distribution, which is useful over the entire ionization range, is proposed. The relation of this parameter to grain density is discussed. It is shown that the behavior of the latter (determined from the blob-length distribution) as a function of restricted ionization loss seems to be in agreement with theoretical expectations, with the exception of the very dense region, where appropriate corrections are proposed.
Some Properties of a Graded Vacuum Spark Gap
Authors: Mather J. W. , Williams A. H.
Published: February 2005

A high power, low inductance vacuum spark gap combination (crowbar and main switch) is described which is capable of dc operation over a wide voltage range. The electrical properties are discussed in regard to shorting and multiple switch operation. The principal difficulty of vacuum spark gaps, the coating of the inner surface of the insulator with evaporated and sputtered electrode material, is absent in this design after conditioning. A mechanism to account for this, based on the establishment of a large number of nucleation centers on the insulating walls, is shown to be consistent with observation.
The Piezoresistive Effect and its Applications
Authors: Hollander Lewis E. , Vick Gerald L. , Diesel T. J.
Published: February 2005

Piezoresistivity, the change in resistivity with applied stress, offers a tool for analyzing the conduction mechanism in semiconductors and also offers potential transducer applications. A discussion of this effect in semiconductors and an analysis of the fourth-rank piezoresistive tensor for two crystal symmetries are presented. The magnitude of the effect in semicondictors is tabulated, including two materials, TiO2 and PbTe, which the authors have determined to be of considerable interest. The design of devices based on piezoresistivity is discussed and illustrated by working models.
Development of a Special Thermocouple for Measuring Transient Temperatures within a Solid Body
Authors: Clem Joseph D.
Published: February 2005

A special thermocouple was developed to measure transient temperatures at relatively large distances within the walls of uncooled rocket nozzles. The device, known as a thermoplug, was designed to cause a minimum disturbance of the temperature field. Results of limited experiments indicate the design to be adequate for the purpose for which it was developed. All development work was done using a homogeneous metallic nozzle, but the design could be adapted readily to nonmetallic or composite nozzle walls. The thermoplug may be fabricated in the laboratory and should be adaptable to many internal temperature measurements not connected with rocket propulsion units.
High Pressure Manometer
Authors: Reamer H. H. , Sage B. H.
Published: February 2005

A manometer which measures differential pressures involving a total head of as much as 1 atm with a precision of 0.002 in. Hg is described. The calibration of the manometer is relatively insensitive to pressure and does not involve any direct or indirect means of visual observation of the mercury-fluid interface. Application of the instrument is limited to fluids which do not react with mercury.