bluuebunny/crossref_metadata_2025 huggingface dataset:
Flame Zone Spectroscopy of Solid Propellants
Authors: Rekers R. G. , Villars D. S.
Published: February 2005

The spectroscopy of burning solid propellants has been generally limited to a photographic integration of the various flame zones as the burning strand is consumed and the flame passes a spectrographic slit. A few instances have been reported in which separation of the spectral emission from the different zones of the flame has been attempted, but the results are deficient either through loss of resolution of the spectrograph system or shortness of exposure time. An automatic constant level device is reported which now permits the isolation and detailed exposure of a definite flame zone throughout the complete time of burning of a 72-inch length of strand. A discussion of the technique, illustrated with typical data on the degree of control, is presented. Typical absorption and emission spectrograms are given.
Storage and Transfer of Liquid Helium
Authors: Wexler Aaron
Published: February 2005

The performance of large, efficient storage containers for liquid helium is indicated, and liquid helium transfer techniques permitting correspondingly efficient use of the stored liquid are described.
Use of Proportional Counters in the Measurement of the Specific Ionization of Charged Particles
Authors: Igo G. , Eisberg R. M.
Published: February 2005

A method has been developed to obtain an accurate estimate of the mean ionization of energetic, heavy charged particles using a device which has small stopping power. A sample of the frequency distribution of energy losses in each of n identical proportional counters is obtained. This information is treated by selecting the smallest of the n pulses and using this smallest pulse to represent the mean ionization of the particle. The experimental results are compared with Landau's theory of the statistical fluctuations in the specific ionization of charged particles.
A Broadband, Low-Level, Error-Voltage Detector
Authors: Kuder M. L.
Published: February 2005

An error-signal detector is discussed which can resolve relatively small signals with unusual broadband response and zero drift stability. An rf chopper principle replaces the more conventional mechanical choppers which have very limited band width. Circuit and mechanical construction details are discussed. Experimental performance shows resolution to 1 millivolt with a band width of at least 1 megacycle. A zero-drift stability to 1 millivolt direct current is also readily attainable. Applications to high-speed multichannel sampling and mechanical servos are discussed.
Measurement of Two-Dimensional Fields. Part I: Theory
Authors: Elmore W. C. , Garrett M. W.
Published: February 2005

An arbitrary two-dimensional magnetic field may be uniquely specified by listing all coefficients of the power-series expansion of its complex potential function. An experimental procedure is described in which the first N coefficients are derived from an N-point harmonic analysis of the radial component of field or gradient, as measured with a dipole or quadrupole search coil at N equally spaced angular positions about an arbitrary longitudinal axis. The method may be refined by mounting two coils coaxially on a radial arm, so connected as to balance out the strongest component present and permit more accurate determination of the higher harmonics. With four coils, odd or even harmonics also may be suppressed. Analysis of the symmetry of various magnet pole structures shows that many of the coefficients vanish identically. Procedures are outlined for measuring with a quadrupole search coil the five independent elements of the magnetic gradient dyadic at a point in an unrestricted field. It is shown that in the fringing region at the ends of a long magnet gap the axial average of the transverse field can be treated as a two-dimensional field. It is correctly measured using line dipole or quadrupole search coils, whose design is prescribed. The procedure is identical with that for the two-dimensional case. A further extension of the same method to measurements made with the electrolytic tray analog increases greatly their speed and accuracy.
High-Intensity Ion Source for Cyclotrons
Authors: Livingston Robert S. , Jones Royce J.
Published: February 2005

The mechanical design features and operating characteristics of a hot-cathode arc-discharge type ion source are described. Proton currents of 500 milliamperes have been obtained under dc test conditions. A maximum current of 3 milliamperes of 22-Mev protons has been obtained with the source installed in the ORNL 86-inch cyclotron. Distinguishing features of the ion source are its arc chamber of carbon, its heavy tantalum filament heated with dc, and its use of a specially shaped accelerating electrode.
Stereoscopic Reprojection and Radius of Curvature Measurements of Cloud-Chamber Tracks
Authors: Emigh C. R.
Published: February 2005

A means of accurately and rapidly measuring the radii of curvature of many cloud-chamber tracks is described. The apparatus includes a photographing-reprojecting system and a curvature-measuring device. This device is capable of measuring radii of reprojected tracks in the range from 0.5 cm to 100 cm with the poorest accuracy of the order of 3 percent occurring at 100 cm.
A High Precision Electron-Diffraction Unit for Gases
Authors: Brockway L. O. , Bartell L. S.
Published: February 2005

An electron-diffraction unit incorporating a rotating sector has been developed which makes possible the accurate and objective measurement of the intensity of electrons diffracted by free atoms and molecules. The diffraction data afforded are sufficiently precise to permit the calculation of the distribution of electrons in atoms and the amplitude of vibration of atoms in molecules, as well as interatomic distances that are comparable in accuracy in suitable cases to those obtained by microwave spectroscopy. A description of the essential components of the unit is given together with some data on performance and discussion of the use of the apparatus.
Magnetic Measurement of Torque in a Rotating Shaft
Authors: Beth Richard A. , Meeks Wilkison W.
Published: February 2005

In a cylindrical shaft under pure torsion the principal stress lines are 45° helices around the axis, one for tension and the other for compression. These are also the directions of maximum and opposite permeability changes for a shaft of magnetostrictive material. Based on these ideas a magnetic torque measuring device has been devised and tested. It consists of an external magnetic yoke carrying a driving coil and pickup coils on each of several branches to detect the permeability changes in flux paths lying in or near the principal stress directions in the shaft. Linear response, good sensitivity and fair stability have been obtained with rotating shafts.
An Efficient Cryostat for Producing Temperatures Between 4° and 80°K: The Production of Liquid Hydrogen Targets Using Liquid Helium
Authors: Swenson C. A. , Stahl R. H.
Published: February 2005

The cooling of apparatus using liquid helium can be made a much more efficient process if the total heat content of the evaporating gas is used in addition to the latent heat of vaporization of the liquid. Two cryostats for use on very different problems which make use of this principle are described. The first cryostat was used to maintain temperatures between 4° and 80°K in an application with very high heat influxes. The second cryostat, made necessary by restrictions on the manufacture of liquid hydrogen, used liquid helium both to condense a liquid hydrogen cyclotron target, and to maintain the target at temperatures near 20°K.
Inexpensive Gamma Detector
Authors: Cone Donald R. , Garbellano David W.
Published: February 2005

A simple and inexpensive radiation detection device has been constructed sensitive to gamma fluxes in the range from a few to a few hundred roentgen per hour. Thus one can distinguish between dangerous and relatively safe radiation levels such as one might expect from radiological warfare, low level atomic blasts, or from ``rigged'' hydrogen bomb explosions.

A typical device consists of two gamma-activated crystals in a light-tight container which can be held close to one eye to exclude external light. A radium-activated phosphorescent material is included for light intensity comparison purposes. The more sensitive crystal can be discerned in a gamma radiation of a few R/hr, and its light output matches that of the fluorescent material at levels of 20 to 30 R/hr. The light from the less sensitive crystal matches that of the phosphorescent material at about 100 R/hr.
An Automatic System for the Study of Catalytic Reactions Involving Gases
Authors: Hannah K. W. , Joncich M. J. , Hackerman Norman
Published: February 2005

A automatic system, employing a metal bellows, was designed and constructed for the purpose of studying the catalytic combination of hydrogen and oxygen on a submerged catalyst in a stirred solution. The reaction was carried out under conditions of constant temperature, pressure, and volume. This system can be used to study the reaction for unlimited lengths of time; it is completely automatic, and can be used to study reaction rates quantitatively. It can be modified for the study of other reactions.
A Mass Spectrograph for the Analysis of Solids
Authors: Hannay N. B.
Published: February 2005

A double-focusing mass spectrograph for the analysis of low concentrations of impurities in solids has been developed. The instrument is of the Mattauch type and is designed for either photographic or electrical ion detection. The construction and performance of the instrument are discussed. Bulk concentrations below 0.1 part per million, and surface contaminants of less than 0.1 monolayer, can be detected in short exposures using a photographic plate.
Ultra-High Frequency Beam Analyzer
Authors: Bloom L. R. , VonFoerster H. M.
Published: February 2005

This paper describes a method for presenting on a fluorescent screen the time varying velocity and density modulation of an electron beam, modulated at a frequency of 3000 Mc, as it emerges from the cavities of a klystron, the wave guide in a traveling wave tube, or similar structures.

In order to deflect an electron beam at this frequency, each pair of the usual deflection plates is replaced by a two-wire transmission line, resonant at the beam modulating frequency. Under proper phase conditions a circular trace is obtained, where one complete revolution of the beam corresponds to exactly one complete cycle of events on the beam at the point of its deflection. Since electrons having different velocities will be deflected differently, a complete velocity and density picture of the beam at a given point of interest is obtained.

This is demonstrated by observing the bunching action in the drift region of a velocity modulated electron beam.
Absolute Water Flow Calorimeter for the Measurement of Intense Beams of Radiant Energy
Authors: Willoughby A. B.
Published: February 2005

A null instrument for the measurement of intense beams of radiant energy (from about 5 to 300 cal cm−2 sec−1) is described. The instrument utilizes two identical hollow blackbody receivers whose walls are provided with coils carrying a stream of cooling water. The inflowing water divides equally between each chamber. The temperature difference between the two outflows is determined by a differential thermopile. One of the chambers is exposed to the radiant energy beam, while the other chamber is heated electrically until a null is obtained on a galvanometer connected to the differential thermopile. It is shown that measurements of the electrical power dissipated in the chambers under null conditions and a measurement of the aperture areas of the chambers is sufficient to give the radiant flux density.
Liquid Scintillation Counting of Tritium and C14 Labeled Compounds
Authors: Rosenthal Donald J. , Anger Hal O.
Published: February 2005

A liquid scintillation counter suitable for measuring H3 and C14 activities is described. A photomultiplier tube with a high sensitivity and signal-to-noise ratio is used, and is cooled to −10°C to further reduce the tube noise background. The phototube is mounted in a chassis containing its preamplifier, and the pulses are then led to a high-stability amplifier scaler. The radioactive materials are dissolved in aliquots of a xylene solution containing p-terphenyl (1.9 g/liter) and diphenylhexatriene (0.020 g/liter). Substances which quench the scintillations or color the scintillator solution cannot be counted by this method. A minimum of 4.3×10−10 curie of H3, or 1.8×10−11 curie of C14 may be measured by the counter.
A Chrono-Interferometer for Measuring Gas Density during Transient Flows
Authors: Curtis C. W. , Emrich R. J. , Mack John
Published: February 2005

An interferometer for measuring gas density as a function of time during a transient flow is described. This is an absolute instrument capable of measuring density changes over an approximate range from 10−2 to 10−5 g/cm3. Since the instrument requires only small optical components, it is relatively simple and inexpensive to construct.
A Scintillation Detector for Fast Neutrons
Authors: Seagondollar L. W. , Esch K. A. , Cartwright L. M.
Published: February 2005

A fast neutron detector has been prepared by suspending ZnS phosphor powder in ``Bio-Plastic''. The detector can be easily prepared using only simple laboratory equipment. In the presence of the gamma rays from a Ra-Be source, the neutrons from the source can be counted using this detector with about one percent efficiency.
A Multiple-Wire Proportional Counter for Fast Neutron Detection
Authors: Sun C. R. , Richardson J. Reginald
Published: February 2005

A cylindrical chamber, 8.5 in. in length and 8.5 in. in diameter, containing two sets of parallel multiple-wire grids has been built and operated as a proportional counter for fast neutron detection. The collecting wires are 0.001 in. in diameter. Filled with pure CH4 at about atmospheric pressure and operated at 3400 v, it serves to detect neutrons up to 10 Mev, with an average efficiency of 0.17 percent. The energy distribution of neutrons from 0.3 to 3 Mev can be estimated. The multiple-wire counter is completely insensitive to gamma radiation under these operating conditions. This instrument has been used to make a survey of fast neutrons around the U. C. L. A. cyclotron. At higher pressures the instrument can presumably be used to measure neutron spectra of higher energy.
A Pulsed Magnetic Extractor for Removing the Electron Beam from a Betatron
Authors: Foote R. S. , Petree Ben
Published: February 2005

The electron beam of the National Bureau of Standards betatron has been removed by the use of a pulsed magnetic extractor. The electrons were spiraled outward into the extractor that had created a sharp step magnetic field canceling the betatron guiding field for 19° of azimuth. This step magnetic field was produced by a current pulse flowing in an array of parallel wires. The removed beam was well focused. Initial testing up to 24 Mev showed that about 60 percent of the accelerated electrons were extracted in the beam.
Ultra-Speed Transient Dynamic Analyzer for Mechanics and Ballistics
Authors: Lindsay John C. , Masket A. Victor
Published: February 2005

A photoelectronic apparatus has been developed which makes possible the continuous simultaneous measurement of the depth of penetration, the speed, and the deceleration of a nondeforming small-caliber projectile dring armor penetration. The basic operating principle of the apparatus is to have the flight path of the projectile pass perpendicularly through a thin parallel light beam of uniform intensity which activates a vacuum-type phototube. The output of the phototube is proportional to position or the depth of penetration under appropriate geometry. A voltage signal derived from the phototube circuit is preamplified and differentiated to give voltage signals proportional to speed and deceleration. Permanent records of the signals are made by photography of cathode-ray tube traces and analyzed. The apparatus is capable of measuring real transient accelerations or decelerations as great as 108 ft/sec2 (3×109 cm/sec2) with average error of 2 percent. Possible applications of the system to mechanical problems as an accelerometer, speed, and displacement measuring device are indicated.
A Breakdown Cell for Measuring the Dielectric Strength of Solids at 100 Megacycles
Authors: Frisco L. J. , Chapman J. J.
Published: February 2005

A liquid-filled cell for measuring the dielectric strength of solids at 100 megacycles is described. The cell consists of a high-voltage resonant circuit and a built-in voltage measurement probe. The calibration of the voltage measurement network is fully discussed.
Two Types of Regulators and the Precision Control of Helium Bath Temperature
Authors: Sommers H. S.
Published: February 2005

A pneumatic and an electronic regulator for helium bath temperature are described. The pneumatic regulator, an automatic pressure regulating valve with large throughput, gives a simple controller suitable for regulation to a millidegree for temperatures above 1.4°K. The electronic control uses a carbon resistor for the thermometer and a heater inside the bath for the control element. Its regulation is an order of magnitude better, and it is usable at all achievable temperatures. Its theoretical analysis, circuit diagram, construction and operating details, and performance are described. Included are some general remarks and results concerning temperature regulation in He-I and at the lambda point.
A Rapid and Sensitive Recording Spectrophotometer for the Visible and Ultraviolet Region. I. Description and Performance
Authors: Yang Chia-Chih , Legallais Victor
Published: February 2005

A double-beam recording spectrophotometer has been developed for rapidly obtaining spectra of labile intermediates in biochemical reactions. Light from a monochromator is split into two beams by a chopping mirror and then the ratio of light intensities in two optical paths is measured. This ratio is expressed as percent absorption or converted electronically into units of optical density. Results are recorded on a linear wavelength scale at a maximum rate of 6 mμ per second. A servo system corrects the nonlinearity of the wavelength scale of the quartz monochromator. The noise level corresponds to a change of optical density of 10−4 at 400 mμ with a spectral interval of 3 mμ. The over-all accuracy on standard solutions (National Bureau of Standards) is about 2 percent. The air-against-air zero absorption line varies only 0.004 in optical density from 210 to 650 mμ.
A Rapid and Sensitive Recording Spectrophotometer for the Visible and Ultraviolet Region. II. Electronic Circuits
Authors: Yang Chia-Chih
Published: February 2005

The electronic photometer of a recording spectrophotometer is described in detail. Sources of error of the circuit and experimental measurements of the inherent noise of the system are discussed. A segmented diode circuit is described for converting data in absorption to units of optical density with an accuracy of better than 1 percent. The electronic circuit of the servo system to correct the nonlinearity of the wavelength scale is also described.
Frictional Adhesion of Metal to Glass, Quartz, and Ceramic Surfaces
Authors: Belser Richard B.
Published: February 2005

In 1947 W. A. Wooster and G. L. McDonald reported that titanium would adhere by frictional contact to glass, certain mineral, and ceramic surfaces. In order to explore this property further small disks of a number of different metals, mounted separately on one-eighth-inch shafts driven by a high-speed hand-grinder, were applied to glass, quartz, and ceramic surfaces. By suitably varying the rpm of the motor and the pressure of application, the metal of the disks could be made to adhere securely to such surfaces. At higher rpm erosion of the glass surfaces usually occurred. Variations of the technique of application allowed either the metallic coating or the cutting of glass. Some of the metals tested were titanium, zirconium, aluminum, magnesium, gold, silver, copper, iron, nickel, cobalt, cadmium, zinc, and lead.
A Copper Resistance Temperature Scale
Authors: Dauphinee T. M. , Preston-Thomas H.
Published: February 2005

Fine commercial copper wire, attached with Formel varnish to a copper base, has sufficiently stable and reproducible resistance temperature characteristics to be used as a resistance thermometer in the temperature range 20°–320°K. Excellent thermal contact is achieved by this construction; hence, unusually large heat inputs to the thermometer can be tolerated. Resistance and temperature coefficient of resistance are tabulated and limitations of accuracy discussed.
A Thermostatic Chamber for the Measurement of Light Scattering from Solids at Elevated Temperatures
Authors: Keane John J. , Stein Richard S.
Published: February 2005

A chamber is described which, in conjunction with a Zimm type light scattering apparatus, may be used to determine the angular dependency of the scattering from polymer films at temperatures between 30°C and 200°C at scattering angles between 10° and 70° from the incident beam. The temperature is maintained by circulating heated air. The use of this chamber is illustrated with a series of measurements of scattering from a polythene film.
Differential Conductance Manometer
Authors: Pappenheimer J. R.
Published: February 2005

The conductance manometer is designed to measure and record rapid changes of pressure in liquid systems. The manometer is symmetrical with respect to its moving member and is liquid filled throughout; it is therefore specially adapted to the measurement of differential pressures. Sensitive instruments with natural frequencies ranging from 60 to 500 cps have been used for recording differential pressures in the circulatory and respiratory systems, for flow measurements, for the rapid determination of colloid osmotic pressures, and for other applications involving extremely small volume displacements.
Effect of Cold Worked Surfaces upon Ultrasonic Echoes in Single Crystal Specimens of Lead
Authors: Kammer E. W.
Published: February 2005

Some techniques for measuring the velocity of sound in single-crystal materials utilize multiple internal reflections of an ultrasonic pulse between two plane parallel surfaces of the specimen. If a thin layer of cold worked material is present at these surfaces, it is possible for the initial pulse to be distorted upon successive reflections in a way which would make the apparent transit time too short. The characteristic distortion of the initial pulse is shown in an unrectified oscillogram and consists of a forerunner pulse with a dominant frequency controlled by the thickness of the cold worked layer. Velocity determinations based on the arrival time of this forerunner will be too high. In the example considered the error amounts to about ½ percent for cold worked surface layers approximately 0.005 in. thick.
Decay Times of Some Organic Scintillators
Authors: Swank R. K. , Buck W. L.
Published: February 2005

The luminescence decay times of a number of organic crystal, liquid, and plastic scintillators are reported. The scintillators were excited by pulses of x-radiation of 7.5-kev quantum energy. The dimensions of the specimens are given, although the effect of specimen size on decay time was not investigated.
Adiabatic Calorimeter for Use with Condensable Gases and Gas-Solid Systems between 10 and 150°K
Authors: Pace E. L. , Pierce Louis , Dennis Kent S.
Published: February 2005

A description of a low temperature adiabatic calorimeter for use in the 10 to 150°K range is given. Its construction is described in detail concerning the features in which it differs from calorimeters previously described in the literature. These features have resulted in an improved performance and precision. At 30°K, its precision was better than 0.1 percent, while at temperatures above 50°K, a precision of 0.03 percent or better is indicated. At the lowest temperatures, an uncertainty of 1 percent exists, largely the result of the decreasing sensitivity of the platinum resistance thermometer.
A Microwave Microcalorimeter
Authors: Macpherson Alan C. , Kerns David M.
Published: February 2005

This paper gives a brief account of a calorimeter developed at the National Bureau of Standards for the measurement of microwave power with relatively high accuracy (better than 1 percent) and at low (milliwatt) power levels. The calorimeter is identifiable as an electrically (dc) calibrated, aneroid micro-calorimeter of the Joule twin type. A bolometer mount assembly serves as a wave-guide termination for the absorption of microwave power and constitutes the calorimetric body whose temperature rise is observed. This arrangement enables the use of a novel indirect measurement technique and tends to insure calorimetric equivalence of dc and rf heating. The equivalence error is investigated with the aid of heat flow analysis and auxiliary experiments, and an upper bound for the error is assigned.
Recording High-Sensitivity Paramagnetic Resonance Spectrometer
Authors: Hirshon Jack M. , Fraenkel George K.
Published: February 2005

A high-sensitivity, automatic recording paramagnetic resonance absorption spectrometer operating at a wavelength of 3.2 cm is described. The spectrometer is of the crystal-heterodyne type employing a local-oscillator and a magic tee bridge with a reflection cavity. Automatic frequency control of the signal and local-oscillator klystrons is provided to eliminate anomalous dispersion and to reduce frequency fluctuations. The output signal can be presented as a trace of the paramagnetic absorption versus magnetic field on a continuous strip recorder, as a pattern on an oscilloscope of absorption versus magnetic field for either visual observation or photographic recording, or as a continuous recorder trace of the derivative of absorption versus magnetic field. Provision is made for calibration of the magnetic field by means of the proton magnetic resonance absorption. Approximately 2×10−11 mole of 1, 1-diphenyl-2-picryl hydrazyl can be detected with the spectrometer.
Geometric Efficiency of Cylindrical Counters
Authors: Goldemberg José
Published: February 2005

Counting experiments were made with cylindrical counters fitted with geometry ``definers'' in order to ascertain whether it is possible to find an area of constant sensitivity in these counters. These measurements are similar to those made by Gleason et al. with end-window counters. It is possible to achieve this result by means of a careful choice of the dimensions of these definers. The definers also allow a great simplification of the calculation of counter efficiency for a point source. We present a formula for sources placed in any position with respect to the counter. This formula is compared with experiment and the agreement is found to be good. A comparison of absolute beta counting between one of our cylindrical counters (with definer) and an end-window counter (with definer) is made. The agreement obtained is satisfactory.
Measurement of Time Varying Optical Absorption
Authors: Phelps A. V. , Pack J. L.
Published: February 2005

Time sampling techniques have been applied to the study of optical absorption transients. The method is described in terms of its use for the study of the decay of the concentration of metastable atoms following a pulsed discharge. Light from a capillary source is passed through the discharge tube. The transmitted intensity of one of the spectral lines which is absorbed by the metastable atoms is measured using an interference filter and a gated photomultiplier. The photomultiplier gate occurs at twice the discharge frequency so that alternate pulses of the photomultiplier output are reduced by absorption. The component of the photomultiplier output at the discharge frequency is proportional to the absorption and can be measured with a narrow band amplifier and synchronous detector. Since the time resolution of the system is determined by the width of the photomultiplier gate, the response of the synchronous detector can be made slow enough to average the absorption signal over many decay periods. Fluctuations in the number of electrons leaving the cathode of the photomultiplier limit the useful sensitivity of the present system to approximately two parts in 104. This represents a hundredfold improvement in sensitivity over that available with previous techniques. The results of some studies of helium metastables are presented in order to illustrate the detail which can be obtained with this technique.
Booster Cryostat for Temperatures down to 0.74°K
Authors: Atkins K. R. , Edwards M. H. , Pullan G. T.
Published: February 2005

The cryostat produces temperatures down to 0.74°K by pumping on a liquid helium bath with a large diffusion pump. A shielding pot containing liquid helium at 2°K reduces heat influxes to the main bath and plays a very important role in reducing the pressure drop arising from viscous flow of the gas up the helium Dewar. The low temperature region is visible and the experimental apparatus is easily accessible merely by removing two glass Dewars.
Double Diffracting X-Ray Spectrometer for Study of Irradiated Materials
Authors: Cummings W. V. , Kaulitz D. C. , Sanderson M. J.
Published: February 2005

A double diffracting x-ray spectrometer has been developed which will be used to study the crystallographic features of irradiated materials. The design features of this instrument include: (1) a mechanism to support and align the x-ray tube as it rotates on a conventional goniometer; (2) a remotely controlled sample holder to position and rotate radioactive samples; (3) a mechanism to adjust the position of a curved aluminum crystal which is placed in the second diffracting position in such a way that it focuses the diffracted x-rays into the detector; and (4) sufficient lead shielding between the sample and detector to absorb the radiation emanating from the sample in order that such radiation will not influence the detector. Preliminary tests of the instrument have shown that the design features reduce the background radiation originating from the sample to a very low level, and that no serious loss in diffracted x-ray intensities results from the double-crystal arrangement.
The Stanford Mark II Linear Accelerator
Authors: Post R. F. , Shiren N. S.
Published: February 2005

The development of the Mark II electron linear accelerator, the second linear accelerator constructed at Stanford University, is described. Primarily intended to provide an intermediate milepost on the way toward the eventual construction of a 1-Bev machine, it was designed to be a prototype of one of the many sections of the larger accelerator. Electron energies up to nearly 40 Mev have been obtained, and peak beam currents of about 10 ma in 1-μsec pulses. The theoretical design and experimental testing procedures developed in constructing the loaded wave guide are outlined. A brief description of the auxiliary equipment, including a multi-megawatt klystron amplifier, is given. Operating characteristics of the accelerator are summarized. The machine has been in use since 1950 for experimentation in electron physics.
Precision Measurement of Detonation and Strong Shock Velocity in Gases
Authors: Knight Herbert T. , Duff Russell E.
Published: February 2005

A simple system is described for determining the velocity of detonation or strong shock waves, with temperatures above 3000°K, by using the conductivity behind the wave. Wave contact is made by two 36-mil wires set 0.1 inch apart in a Teflon plug mounted in the experimental tube. When a wave passes, signals are produced across a 30-K resistor in series with these wires and a 0.001 μf capacitor charged to 300 v. Any number of circuits may be paralleled across a single signal resistor if a diode is added to each circuit to prevent signal deterioration. The arrival time of a wave at a pin can be determined with an accuracy of almost 10−8 sec from an oscilloscope record of the signals. The principal advantages of this system are excellent space resolution and very simple basic circuitry. An amplifier is described which can be used with an individual pin circuit to fire a thyratron and extend the range of applicability of this system to waves with temperatures as low as 1000°K.
Isothermal Processing of Thick Nuclear Emulsions
Authors: Yagoda Herman
Published: February 2005

A method for the processing of thick nuclear emulsions is outlined which develops the tracks of singly charged particles at the minimum of ionization without resort to a hot stage. The developing agent is introduced into the thick layer by means of a series of solutions varying in pH from 4.7 to 7.2 and of increasing reducing power. Uniform depth development is secured by allowing the last solution to diffuse out of the emulsion into water at 5°C. The processes of fixation and washing are designed to avoid resolution of surface silver grains, and to keep lateral swelling at a minimum. Turbidity resulting from residual silver iodide is reduced by means of a buffered thiourea solution. Thick unsupported emulsions can be restored to approximately their original size by leaching the electrolytes from the gelatin with a series of graded alcohols. The isothermal cold processing reduces distortion and facilitates the microscopic study of preparations up to 2 mm thickness by minimizing danger of overdevelopment and production of excessive fog.
Miniature Bomb Calorimeter for the Determination of Heats of Combustion of Samples of the Order of 50 mg Mass
Authors: McEwan William S. , Anderson Carl M.
Published: February 2005

A new bomb calorimeter for the combustion of very small quantities of organic materials has been constructed. The use of a small sample size is particularly important when dealing with explosive materials which when used in larger quantities, may detonate enough to spatter material from the crucible or when using substances which are difficult to prepare and purify in larger amounts. This calorimeter has several unique design features including a light weight bomb, coaxial stirrer, and flame holding sample holder.
Direct Reading Analyzer for Short Time Intervals
Authors: O'Neill G. K.
Published: February 2005

A time-analyzer with nine 4.6 mμsec channels has been developed. It is based on the chronotron principle, but presents data directly on mechanical registers. The device is compact, stable, and easy to adjust. Variation of channel boundaries is less than 5×10−10 sec over long periods. Construction is such that changes in the time scale can be made, and even narrower channel widths should be possible. The principle is applicable to analyzers of more than nine channels.
Microbalance Assembly for Adsorption Studies at Low Temperatures
Authors: Bowers Raymond , Long Earl A.
Published: February 2005

A microbalance assembly is described, suitable for the measurement of adsorption isotherms at liquid helium temperatures by the gravimetric method. The design leaves the balance readily accessible and overcomes the two principal difficulties which are spurious mechanical disturbances and buoyancy effects.
Apparatus for Low-Frequency Dynamic Measurement on Polymeric Systems
Authors: Morrisson T. E. , Zapas L. J. , DeWitt T. W.
Published: February 2005

An apparatus is described for the measurement of the low-frequency (0.0003 to 2 cps) dynamic properties of solid and liquid polymers. It is basically a torsion pendulum driven in forced vibration by a low-frequency sinusoidal current. The current generator, which is a mechanically-driven potentiometer arrangement, is also briefly described. The treatment of data, calibration, and areas of usefulness of the instrument are discussed, and an example of the results of its application to a concentrated polymer solution is given.
Automatic Recording Torsional Magnetic Susceptibility Balance
Authors: Croft G. T. , Donahoe F. J. , Love W. F.
Published: February 2005

A torsional magnetic susceptibility balance suitable for studying the de Haas-van Alphen effect has been developed in which the torque and magnetic field are recorded continuously while the magnet current is reduced automatically. The torque is recorded as a bucking current to a galvanometer suspension supporting the sample, and the magnetic field is obtained from a recording of the magnet current. A circuit for stabilizing the magnet current is also described.
Semi-Micro Calorimeter
Authors: Hutchinson Eric , Manchester Kenneth E.
Published: February 2005

To facilitate heats of wetting measurements, a metal calorimeter has been designed and constructed which employs a platinum resistance thermometer for temperature measurement and an evacuated dead space to minimize heat losses. Auxiliary circuits for the temperature bridge, and bath temperature control are shown. Initial measurements of the heats of solution of NaCl, both coarse and finely divided samples, indicate a precision of measurement of 0.08 percent. The surface energy of NaCl, calculated from these data, is 366 ergs/cm2.
Use of A37 to Determine Argon Behavior in Vacuum Systems
Authors: Carr Donald R. , Kulp J. Laurence
Published: February 2005

By employing A37 as a tracer it has been possible to show that quantities of argon as small as 10−9 cc can be circulated in a vacuum system containing furnaces, charcoal traps, electrical discharges, and stopcocks without measurable loss of argon. Further, it is shown that argon is not desorbed from charcoal at liquid air temperatures in appreciable quantities during prolonged evacuation.
High-Current Cockcroft-Walton Accelerator for Neutron Production
Authors: Peck R. A. , Eubank H. P.
Published: February 2005

The 200-kev deuteron accelerator described utilizes a water-cooled T-Zr film as a source of 14-Mev neutrons. High voltage is provided by a Cockcroft-Walton generator of six oil-filled stages, operated at 32 kc. An rf ion source provides up to 15 ma (90 percent deuterons), at least 10 ma of which can be focused on the target. A system of forced water cooling allows at least 5 ma (at 120 kev) to be used in bombarding the target foil without reaching a surface temperature of 100°C. Observed neutron yield is approximately 2×109 neutrons/sec ma from a target containing roughly one tritium atom per four of zirconium.
Mixing Machine of High Precision for Study of Rapid Reactions
Authors: Ruby W. R.
Published: February 2005

The mixing machine described was designed for use in the study of certain rapid reactions by the steady-state-of-flow method. This machine combines several features not previously described for a single machine. (1) It may be used for reactions whose range of half-reaction times varies from 6 milliseconds to 1.6 seconds. This wide range is obtained by varying syringe piston speed to change the velocity of flow and by inserting spacer units to increase the length of reaction path. (2) It give results of high precision when used with the ``chemical stop'' method. The combination of precision-machined syringes and sensitive sampling and timing mechanism gives data from which precise calculations of velocities of flow and reaction time can be made. (3) The combination of three separate mixing chambers with or without spacer units enables one to premix sensitive reagents, immediately before initiating the primary reaction. The performance of the machine was evaluated by measuring the rates of a first-order reaction using the steady-state-flow technique.
Phototube High-Intensity Gamma Survey Instrument
Authors: Koch G. E. , Gottfried H. L. , Lamb W. R. , Rhoads F. A. , Valdivia J.
Published: February 2005

Many portable gamma-radiation detection instruments employing either Geiger tubes or ionization chambers require collection potentials which are large compared to those needed for the operation of the other electronic components. This paper describes an instrument which uses a simple phototube-phosphor combination as the main detecting element with an inverted triode electrometer. It operates at potentials as low as 4½ volts at radiation intensities from 5 mr/hr to 500 r/hr.
New Shunt-Series Nanosecond Pulse Amplifier
Authors: Millard J. K.
Published: February 2005

A new shunt-series amplifier section was developed for fast rise time pulse amplifiers intended primarily for use with accelerator beam probes, solid state detectors, and fast ionization chambers. Design equations for the gain section were derived from a high frequency model and were validated by computer analysis and experimental results. Two amplifiers were built, with three gain sections cascaded in each. The gain of these amplifiers was 270 and 135, and the rise time was 1 and 0.9 nsec, respectively.
Apparatus for Determination of Interaction Virial Coefficients in Systems Containing Condensables
Authors: Knobler C. M.
Published: February 2005

An apparatus for the determination of interaction virial coefficients is described. The new design, which makes use of a pressure transducer, is a modification of a differential device previously employed for mixtures of the permanent gases. Dead space corrections have been completely eliminated and the technique is now applicable to a broad range of substances.
Multichannel Analyzer System for High Sensitivity Mass Spectrometry
Authors: White J. W.
Published: February 2005

A multichannel analyzer using time-amplitude conversion for time of flight mass spectrometry is described. This system extends the ultimate sensitivity of the Bendix mass spectrometer from about 10−8 mm to about 10−11 mm partial pressure of H2 in the source, while still retaining whole spectrum presentation. It is equally applicable to negative and positive ion pulses, and so greatly improves the flexibility of the spectrometer. Examples of mass spectra from low partial pressures of gas are given showing the signal to noise improvements up to 103 obtained for a minute's operation.
Pressure Pulse Detection by Frustrated Internal Reflection
Authors: Ahlborn Boye , Zuzak William W.
Published: February 2005

The development of a membrane type pressure probe is reported in which the position of the membrane is recorded by frustrated internal reflection. The probe has a risetime of not more than 5 μsec, and records pulses of any length, as well as static pressure. It can have a static sensitivity of several volts per atm, and is relatively unaffected by electrical pickup noise. Examples for application are given, and the probe is compared with a piezo probe.
Harmonic Bridge for Measurement of Nonlinear Electric and Electrooptic Properties of Crystals
Authors: Fay Homer
Published: February 2005

A harmonic bridge circuit has been developed for measuring linear and nonlinear electric coefficients and quadratic electrooptic coefficients in high dielectric perovskite crystals. Third and fifth harmonic components are added to the fundamental audio-frequency driving voltage. The bridge is balanced when the charge or displacement of the crystal is sinusoidal. The harmonic content of the driving voltage may then be measured on a harmonic analyzer, from which measurements the electric coefficients of the crystal may be calculated. The same sinusoidal displacement may be used to display the electrically induced phase retardation intensity pattern on the oscilloscope. The effective electrooptic coefficients are readily determined from the oscillographs. The advantages of the harmonic bridge method are illustrated by measurements of the electric and electrooptic coefficients of a crystal of potassium tantalate niobate (KTN).
Spinning Arc Zone Heater
Authors: Warren Roger W.
Published: February 2005

A method is proposed and a device described for creating a hot zone which can be moved down a long tube in a controlled manner without the use of any moving parts. The heat source is an arc whose position can be controlled by small magnetic fields. The details and performance of the critical control circuit are discussed. Applications to the zone growth of crystals are apparent.
Automatically Controlled Adiabatic Reactor for Reaction Rate Studies
Authors: Dyne S. R. , Glasser D. , King R. P.
Published: February 2005

An apparatus is described for the measurement of the kinetics of fairly fast (half times 1–5 min), homogeneous, liquid chemical reactions, by recording the temperature-time curve in an adiabatic batch reactor. Adiabatic conditions are maintained by keeping the metal reactor as closely as possible at the same temperature as the reacting species by passing a heating current directly through the walls. Allowance is made for controller set point changes which accompany a temperature increase of the system. Specific heat determinations were carried out on water to test the ability of the control system to maintain adiabatic conditions. The operation of the apparatus is illustrated with kinetic measurements of the hydrolysis of acetic anhydride in dilute aqueous solutions.
Diminution of Sensitive Time of Spark Chambers
Authors: Cork Bruce , George Daniel R. , Rangaswamy T. N.
Published: February 2005

The sensitive time of a thin gap spark chamber immersed in a magnetic field was measured. The magnetic field was normal to the electric field of the chamber, and various amounts of Freon 12 (CCl2F2) were used to decrease the sensitive time. A concentration of 100 ppm Freon 12 was sufficient to make the sensitive time less than ½ μsec, with an efficiency of greater than 70% for delays of less than 300 nsec.
Preparation of Thin Sections by Ion Bombardment for Transmission Electron Microscopy
Authors: Hirthe W. M. , Melville A. T. , Wackman P. H.
Published: February 2005

The apparatus and technique for preparing thin sections of nonmetals suitable for transmission electron microscopy are described. The last stage of the thinning process involves bombardment with argon ions. The optimum operating conditions of the discharge tube were established for near stoichiometric rutile (TiO2), and the quality of the sections evaluated by observation at 100 kV in an electron microscope. Specimens having (001), (110), and (100) surfaces were successfully prepared, and no damage was in evidence as a result of the nature of the preparation. It is believed the technique can be extended to the preparation of thin sections suitable for transmission electron microscopy of metals, as well as other nonmetals.
Multiple Gas Selector System for Accelerator Ion Source
Authors: Evans Albert E. , Simons Donald G. , Brown Bernard
Published: February 2005

A means is described for remotely selecting one of four sources of gas for an rf ion source. The system consists of a specially designed five way ball valve connecting one of the gas sources to the ion source via a mechanical leak assembly. Provision is made for feedline roughout during source switchover.
High Field Zeeman Effect Measurements Using a Scanning Technique and Pulsed Fields
Authors: Maartense I.
Published: February 2005

A method is described for obtaining optical spectra of solids subjected to short duration pulsed magnetic fields of the order of 300 kOe. A spectral region is scanned repetitively every 28 μsec by a moving slit and detected photo-electrically, making it possible to measure wavelength and intensity changes of spectral features as a function of magnetic field. Provision is made for cooling the sample to liquid helium temperature. The Zeeman effect of the 7F0−5D2 transition of 3+Eu in europium tungstate is used as a demonstration of the technique.
Characteristics of Photoionization Plasma Source
Authors: Hyman Julius , MacKenzie K. R.
Published: February 2005

A new plasma source is described. A collimated beam of photons of 6 μsec duration generates a plasma by single quantum photoionization of a rarefied gas. A uniform plasma column with sharply defined initial boundaries is produced remote from the container walls and in the absence of currents or fields. At 90 cm from the photon source, plasma densities of 1010 cm3 are produced in argon at a pressure of 5 μ.