bluuebunny/crossref_metadata_2025 huggingface dataset:
Line Shapes and Intensities for Disk Sources Used in an Homogeneous Magnetic Field Beta-Ray Spectrometer with New and Conventional Slit Geometries
Authors: Beard David B.
Published: February 2005

This paper is primarily concerned with the effect on the line profile shape and intensity of the angle φ, the angle made by the projection of the electron velocity vector on a plane perpendicular to the instrument axis at the source with the radius of the source point. Quantitative results are quoted for several geometries. The line profile, expected intensity, and optimum source size for a commonly used slit geometry utilizing an entrance slit for take-off angle selection is found to differ significantly from previously quoted results, the intensity for the same half-width for optimum source size being 46% of the earlier work. A new slit geometry consisting of an additional baffle near the source which restricts φ is discussed and is found to improve the expected intensity for the same line half-width by 24% for an optimized Hubert slit system which is already found in this paper to be 28% better than the best of previous slit geometries. Finally, a geometry which selects φ properly is shown to remove all dependence on source size from the resolution.
Schlieren Method for Mass Determinations in Microscopic Dimensions
Authors: Meyer-Arendt Jurgen R.
Published: February 2005

This paper discusses the principle and gives some formulas that can be used for computing from schlieren effects the refractive index, the mass concentration, and the anhydrous mass of microscopic particles like cells or cell constituents.
Continuously Indicating Precision Magnetometer
Authors: Green G. W. , Hanna R. C. , Waring S.
Published: February 2005

A flat coil is suspended in a magnetic field so that in equilibrium it is coplanar with the field and can oscillate about an axis in the plane of the coil perpendicular to the field. When an alternating current is passed through the coil the system behaves as an inductance in series with a condenser of capacity inversely proportional to the square of the magnetic field. The principle has been applied to the measurement of magnetic field. The instrument is capable of a precision of one part in 102 with simple auxiliary apparatus.

The application to a particle analyzing magnet is described. With some elaboration the magnetic field can be measured and stabilized to one part in 104 in the range 1–12 kilogauss.
Response of an Anthracene Scintillation Counter to 10–120 kev Electrons
Authors: Johnston L. W. , Birkhoff R. D. , Cheka J. S. , Hubbell H. H. , Saunders B. G.
Published: February 2005

Monoenergetic electrons from an electron accelerator were incident on a thin bare anthracene crystal centered on the photocathode of a RCA 6199 photomultiplier. A linear amplifier and single channel analyzer were used to obtain a pulse height distribution at each energy. The pulse height at the maximum of the distribution is a linear function of the incident electron energy with intercepts of 4.5 and 3.5 kev for 0.060- and 0.011-in. thick crystals, respectively. The pulse-height distribution could be fitted well with a Gaussian. The data indicate a linear relationship between the square of the full width of the pulse-height distribution at 1/e of the maximum and the electron energy. The average amount of electron energy absorbed in the crystal required to produce a photoelectron at the photocathode is 1.47±0.09 kev/photoelectron for the 0.060-in. crystal and 1.32±0.13 kev/photoelectron for the 0.011-in. crystal.
Precision Thermal-Conductivity Gas Analyzer Using Thermistors
Authors: Walker R. E. , Westenberg A. A.
Published: February 2005

The characteristics of a thermal-conductivity gas-analyzer unit employing thermistors as sensing elements are analyzed theoretically. It is shown that, as a consequence of the fact that thermistors have a negative temperature coefficient of resistance, the sensitivity of the instrument as a function of bridge current exhibits a maximum. The dependence of zero stability on current and cell temperature is approximately related to differences in resistance, temperature coefficient of resistance, and geometry of the reference and sample thermistors. An apparatus suitable for precise trace analyses is described and results obtained with it are presented. It is suggested that the widespread lack of faith in the inherent stability of thermistors for analysis applications is not justified, and has probably been due to insufficient care with current and temperature control.
Hermetic Seal for Ferrites
Authors: Iversen Arthur H.
Published: February 2005

The effects of moisture on the electrical properties of ferrites indicate that the electrical characteristics are adversely affected. The problem concerning the methods for the prevention of moisture absorption by the ferrite element has been solved by coating the surface of the ferrite with a thin layer of glass, thereby effecting a hermetic seal. It was found necessary, however, to first sinter a thin layer of finely ground ferrite surface to reduce porosity, which prevents the flowed glass from being absorbed into the porous ferrite. The glass seal has been shown to have good mechanical and thermal shock properties and yet has negligible effect on the electrical properties of the ferrite.
Coils for the Production of High-Intensity Pulsed Magnetic Fields
Authors: Foner Simon , Kolm Henry H.
Published: February 2005

The problem of producing extremely high magnetic fields is briefly reviewed in the light of modern technique. The design, performance, and application of a pulsed-field system capable of more than 750 000 gauss at room temperature is described. The coil comprises a suitably supported, machined, beryllium-copper, helix having an inside diameter of 316 in. and a length of about ½ in.; it is connected directly to a 2000 μf, 3 kv bank of surge capacitors by means of a triggered-spark gap. The discharge is oscillatory with a half-period of 120 μsec. Detailed design data and performance characteristics are presented for a large range of similarly constructed coils which afford increased volume and field uniformity at a sacrifice in field intensity. A coil providing transverse access to the field and one suitable for operation in liquid helium are also described. Characteristics of less durable coils constructed of a single strip of conductor are discussed. Brief comments on applications to a broad range of solid-state experiments and some inherent limitations are presented. Finally, the production of modulated pulsed fields, unidirectional fields, and the feasibility of extending the pulse duration are discussed.
Method for the Generation of Very Fast Light Pulses
Authors: Garbuny M. , Vogl T. P. , Hansen J. R.
Published: February 2005

A method is described in which a visible or infrared light beam is repeatedly reflected between a rotating and stationary mirror system. The resulting sweep speed is proportional to the number of such reflections. Light pulses of 4×10−8 sec duration were measured. A considerable increase in the sweep speed appears feasible. Various applications of the system are mentioned.
Fast Gray Wedge Analyzer for High Input Rates
Authors: Flynn J. T. , Johnson F. A.
Published: February 2005

A fast gray wedge analyzer for operation at input pulse rates up to 107 per second has been designed and built. Circuits and operation of the instrument are described. Operation of the instrument depends on two trigger circuits which are initiated by the input pulse. Pulses of fixed amplitude (100 and 30 mμsec long) from the trigger circuits operate two gates, a pulse lengthener, a sweep, and an unblanking circuit. The combination of the two gates allows pulses separated by less than 15 mμsec to be resolved, and the instrument has a fixed deadtime of approximately 100 mμsec. Fast circuit recovery and high-duty cycle are achieved by driving trigger and pulse shaping circuits on both leading and trailing edges of pulses.
Wide-Range Thermal Convection Manometer
Authors: McMillan Juan A. , Buch Tomás
Published: February 2005

A pressure gauge covering both the Pirani and liquid manometer ranges, easily adaptable for continuous recording, has been devised and successfully operated. In the pressure range of the Pirani gauge, the working principle is that of the thermal conductivity at low pressures; at higher pressures, on the contrary, a convection stream takes place, which depends on pressure and determines temperature variations in the filament. Experimental results give maximum sensitivity in the range 0.5–5 torr and a reasonable sensitivity for pressures up to one atmosphere.
Current Integrator for Astronomical Photoelectric Photometry
Authors: Weitbrecht Robert H.
Published: February 2005

An integrator circuit is described, together with programmer and timer, which was constructed for measuring signal-current from a photomultiplier tube as used in astronomical photometry. At the end of a timed run, the voltage data are impressed upon a strip-chart pen recorder. The current-range of such instrument encompasses a span from 10−6 to 10−11 ampere, full scale, with stability and linearity. Furthermore, the design is such that, using a suitable programing circuit, any number of identical integrator units can be employed to measure a like number of separate phototube currents simultaneously over a given timed run; and afterwards the separate voltages are recorded in sequence upon the one recorder. This feature makes the herein described system very useful for simultaneous multicolor photoelectric photometry.
Barium Absorption Pumps for High-Vacuum Systems
Authors: Cloud Robert W. , Beckman Lars , Trump John G.
Published: February 2005

A simple high-vacuum pump which combines large areas of evaporated barium with a source of ionization is described. Though of moderate pumping speed this barium-ionization pump is capable of maintaining high vacuum in unoutgassed sealed-off systems even in the presence of organic sealing materials. Simplicity is achieved by use of externally applied heat for barium evaporation which may be performed initially or periodically as required. Data are presented which show the capabilities and limitations of such absorption systems. The similarity of this absorption process to that producing oxidation of metals in air is noted.
Electron Mobility in Boron Trimethyl
Authors: Ferguson G. A. , Jablonski F. E.
Published: February 2005

Boron trimethyl counters have operated successfully as neutron sensitive proportional counters. Differential pulse-height spectra for these counters show good resolution. The electron mobility in boron trimethyl is measured by the method of Nicholson in the X/P region from 0.8 to 7.0 v/cm/mm Hg. The data indicate a constant mobility above X/P=2.5 volts/cm/mm Hg but the mobility increases rapidly for lower values.
Low-Rate Neutron Dosimeter
Authors: Karp Ira L.
Published: February 2005

An instrument for monitoring of personnel in combined neutron and gamma radiation fields is shown to record the rem dose due to fast and slow neutrons and gamma rays. The instrument consists of a thermal neutron ionization chamber worn under the arm. The relative neutron to gamma response is trimmed by means of a gadolinium coating on the ionization chamber. The use of the human body as the moderator is discussed.
Method for Determining Thermal Conductivity at High Temperatures
Authors: Longmire C. L.
Published: February 2005

A method has been developed for determining thermal conductivity by measuring temperatures at the center of the faces of a rectangular rod which is heated electrically. Radiation of energy causes a difference in the temperatures of the short and long faces, and this difference is related to the thermal conductivity. The emissivity of the surface must be known. The method has been applied successfully by Dr. Ralph Muller, of the Los Alamos Scientific Laboratory, to the measurement of the thermal conductivity of graphite at temperatures near 2500°K, when other standard methods failed.
Single Crystal Goniometer for X-Ray and Neutron Diffraction
Authors: Barstad G. E. B. , Andresen A. F.
Published: February 2005

A single crystal goniometer intended both for x-ray and neutron diffraction analysis has been used in neutron diffraction work at the Kjeller reactor. The unique feature of this goniometer is a macromodel of the unit cell designed for easy orienting of the crystal. A special arrangement is provided for setting any plane in reflecting position without previously calculating the angles, and a set of three-dimensional data can be recorded on a counter moving in the horizontal plane.
Portable Liquid Density Instrument Employing Transistors
Authors: Hargens C. W.
Published: February 2005

A convenient electromechanical instrument has been developed to take the place of sets of sensitive hydrometers in measuring liquid densities. The range covered by the particular design is 0.8000 to 1.0000 and could be extended without impairing its accuracy. Temperature-controlled liquid samples of 100 cc are used. The instrument derives its sensitivity from a miniature differential transformer and associated transistor electronics. One of the primary advantages of the device is positiveness of reading.
Rotation Viscometer Directly Measuring the Ratio of the Shearing Stress to the Rate of Shear
Authors: Eisenberg H.
Published: February 2005

A rotation viscometer, directly measuring the ratio of the shearing stress to the rate of shear, is described in detail. The reading, for Newtonian liquids, is independent of the speed of rotation and, for non-Newtonian liquids, gives a direct indication of the dependence of the apparent viscosity on the rate of shear. The principle of the measurement is as follows: A slit, the width of which is proportional to the shearing stress, rotates together with the rotating cylinder of the viscometer; a narrow beam of light passes through this slit and falls on a photoelectric cell; the time of illumination of the photoelectric cell is proportional to the viscosity. The instrument may be used over a wide range of viscosities and rates of shear.
Automatic Frequency Control for a Marginal-Oscillator Magnetic Absorption Spectrometer
Authors: Nolle A. W. , Henneke H. L.
Published: February 2005

A closed-loop frequency-control circuit is added to an rf spectrometer of the Pound-Knight-Watkins type. Frequency variations are detected by a discriminator circuit operating at a heterodyne frequency of 175 kc/sec. Correction signals affect a saturable reactor which is added to the spectrometer. Frequency variations are reduced by factors of 5 to 11. Larger factors can be obtained without instability. The objects are (a) to reduce frequency drift due to physical changes of the coil surrounding the sample; (b) to reduce distortion of absorption line shape, due to frequency modulation arising from the dispersion component in magnetic resonance.
Focusing Procedures for Electrostatic Accelerators
Authors: Johnson C. H. , Judish J. P. , Snyder C. W.
Published: February 2005

Ion optics for Van de Graaff accelerators are reviewed in elementary terms of geometric optics with particular reference to the Oak Ridge 3-Mv accelerator. This machine produces well-focused beams of over 100 μa and pulsed peak currents of several hundred μa. The beam diameter measured at a distance of 2.7 tube lengths from the accelerator tube exit decreases from 0.26 in. at 0.38 Mv to 0.10 in. at 2.47 Mv. The beam divergence at 1.8 tube lengths from the exit is nearly constant, ≃2.8×10−3 rad. The system is analyzed in terms of five separate lenses: (1) einzel lens, (2) gap lens, (3) accelerator tube, (4) 90-degree analyzing magnet, and (5) strong-focusing lens. It is shown that the crossovers formed in the gap lens and near the exit of the analyzing magnet are of fundamental importance. Brief reference is made to the small energy spread, ≃0.025%, for the beams obtained from this accelerator in spite of the large control slit spacing demanded by a large crossover.
Production and Use of High Transient Magnetic Fields. II
Authors: Furth H. P. , Levine M. A. , Waniek R. W.
Published: February 2005

The transient containment of high magnetic energy densities in coils of various geometries is discussed. Inherent mechanical and thermal limitations are shown to apply to coils relying solely on the strength of materials. The usefulness of inertial effects is demonstrated. Instrumentation is described for producing 10 μsec range pulses of amplitude up to 1.6 megagauss in single-turn coils. Experimental observations document the appearance of ``saw effect'' and Kruskal-Schwarzschild instabilities at very high fields. The limitations characteristic of conventional coils can be overcome in force-free geometries. The appropriate mathematics is developed and illustrated with practical examples.
Use of Oxide Cathodes in Demountable Vacuum Systems
Authors: Haas George A. , Jensen John T.
Published: February 2005

A method is described whereby the life of an oxide cathode can be substantially increased when subjected to repeated air exposures. This is accomplished by preventing the hydrate formation, and consequently reducing flaking of the cathode coating. Further limitations to cathode life caused by the effects of poisoning are also discussed.
Fast Read-Out Chronotron System
Authors: Meunier Robert , Davidson Gilbert
Published: February 2005

A new electronic read-out system has been devised which enables one to obtain a fast answer from a chronotron to be used with accelerator beams of particles. It allows for an analysis of time delay with variable and continuous time intervals. The timing is pulse-height independent with an accuracy increasing for large pulses. The recovery time is in the range of one microsecond.

With delay-line clipped coincidence pulses from two photomultipliers being fed into a 12-channel chronotron with a 30-mμsec range, a time resolution with half-width at half maximum of 1.2 mμsec was readily obtained. Using only 4 channels, with a range of 10 mμsec, a half-width at half maximum of 6×10−10 sec was observed. A simplified version with only three channels has made a useful fast coincidence circuit.
Forty-Megacycle Scaler
Authors: Nakamura Michiyuki
Published: February 2005

A fast scaler is described that employs a fast flip-flop circuit of unique design. With techniques applied to fast trigger circuits, this flip-flop circuit has been triggered at a rate higher than 50 megacycles per second and has a double-pulse resolution of 20 millimicroseconds. A 40-megacycle scaler, with a scale of eight and employing this fast flip-flop as a basic element, has been built at this Laboratory.
Instrument to Measure Fluorescence Lifetimes in the Millimicrosecond Region
Authors: Brody Seymour Steven
Published: February 2005

An instrument to measure fluorescence lifetimes of the order of millimicroseconds is described. It utilizes a hydrogen flash lamp and high-speed oscilloscope. The fluorescence decay is displayed on the oscilloscope, and using the method of moments the observed fluorescence is corrected for the response of the lamp and the detection equipment. The instrument was used to study the primary photochemical processes of photosynthesis. Measured lifetimes are given for the various photosynthetic pigments (in vitro), some organic dyes, and chlorophyll fluorescence in algae. With this instrument it has been possible to measure the delayed energy transfer in living systems.
Millimicrosecond Duration Light Source
Authors: Malmberg J. H.
Published: February 2005

A simple circuit utilizing a hydrogen flash tube is described. The duration of the pulses of light is equal to or less than one millimicrosecond.
Dosimeter for High-Energy Neutrons
Authors: Baranov P. S. , Goldanskii V. I. , Roganov V. S.
Published: February 2005

A neutron detector with a threshold at 20.6 Mev is described which is based on the C12(n,2n)C11 reaction in liquid organic scintillators.

The efficiency of the detector is almost independent of neutron energy from ∼40 Mev to ∼400 Mev. The detector can be used to measure with an error of 6% high-energy neutron fluxes in the tolerance range (20–50 n/cm2 sec).
New Technique for Measuring Rotational Hysteresis in Ferromagnetic Materials
Authors: Kelly Joseph M.
Published: February 2005

A new experimental technique for measuring rotational hysteresis losses over the frequency range 3 to 30 cps is described. A sample disk of ferromagnetic material is mounted on a top. The top is caused to spin about a vertical axis normal to the plane of the disk and of the magnetic field provided by an electromagnet. After removal of the driving force, the top dissipates its stored energy in losses in the sample and in bearing and windage losses. The bearing and windage losses are obtained by also performing the experiment in a magnetic field-free region. The rate of change of rotational energy of the top is determined by measuring the angular velocity of the top as a function of time.
Point-Focusing Two-Crystal X-Ray Monochromator for X-Ray Diffraction
Authors: Furnas Thomas C.
Published: February 2005

Crystal monochromators can provide the exceptionally fine collimation requisite for the study of small-angle diffraction phenomena. To obtain sufficient intensity and contrast it is necessary not only to bend the crystal but also to use two crystals in tandem with their focal circles mutually orthogonal.

The apparatus described uses the x-ray ``weak window'' line source to illuminate the (200) planes of mica in transmission and the (101̄1) planes of a cylindrically ground, polished, and etched quartz crystal in reflection. Symmetrical couple mounts were used to minimize aberrations. The camera essentially isolates the Kα1 component and consequently reduces diffuse background and general radiation artifacts as shown by pertinent applications to collagen and feather keratin. Although operating in air and using exposure times comparable (50–250 hr) to those encountered with aperture-collimated systems, the camera has resolved the central first order of the 640-A macroperiod of collagen fibers and is capable of resolving consecutive orders of spacings as high as ca 3800 A.

The Johansson, Johann, and Cauchois geometries are illustrated in a new manner to show the importance of weak and large sources of x-rays, to demonstrate the focal pattern characteristic of two-crystal point-focusing arrangements, and to show why mosaic crystals are incapable of the fine focus required.
Method of Radioassay of Volatile Compounds
Authors: Herber Rolfe H.
Published: February 2005

A rapid, convenient, and reproducible method has been developed for the radioassay of volatile materials labeled with beta emitters of more than 0.15-Mev energy. The sensitive detection element is a thin-walled aluminum G. M. tube sealed into an annular jacket and attached directly to a high-vacuum manifold. Analysis data for SiCl436 is presented, and application of the method to several tracer problems is suggested.
Ionization Gauges for Measuring Pressures up to the Millimeter Range
Authors: Schulz G. J. , Phelps A. V.
Published: February 2005

By designing an ionization gauge such that the electron paths are short and well-defined and that the collection efficiency of the ion collector is near unity, one can extend the range of ionization gauges to pressures of the order of a millimeter of mercury. Several specific tube constructions are proposed and the characteristics of the gauges are discussed.
General Purpose Immersion Cryostat
Authors: Fuschillo N. , Krautkopf D. W.
Published: February 2005

A cryostat is described for temperature control from 300° to − 150°C. Novel features of this apparatus include a combined heating-cooling thermal exchange coil, good temperature homogeneity over the experimental volume combined with simplicity in design and ease of demountability and maintenance. By using other bath liquids the range of the cryostat can be extended to higher and lower temperatures.
Millimicrosecond Pulses in the Millimeter Wave Region
Authors: Burrus C. A.
Published: February 2005

A system for the generation, amplification, and detection of extremely short, monochromatic pulses in the 5–6 mm region is briefly described. The pulses are 3 mμsec wide at the base, with a peak power of a few milliwatts at 55 kMc/sec; they may be viewed on a commercially available oscilloscope.
Automatic Spectrometer Using Interference Filters
Authors: Rohner E. , Strutt M. J. O.
Published: February 2005

A new automatic spectrometer is described, based on the use of interference filters. It yields spectra of light sources, reflecting surfaces and filters well within one second. It may be adjusted for obtaining integral spectral values and color coordinates of the above objects within one second.
Response of Radiosonde Thermistors
Authors: Badgley Franklin I.
Published: February 2005

The lag coefficient of a thermometer of cylindrical shape is shown to be approximately proportional to the one-half power of its diameter and inversely proportional to the one-half power of the product of ventilation speed and density of the environmental air. This leads to estimated lag coefficients on the order of twenty-five seconds for radiosonde thermistors near their useful ceiling which in turn implies that radiation errors of one to several degrees may be expected in radiosonde temperature measurements at high altitudes.
Beam Stacking Experiments in an Electron Model FFAG Accelerator
Authors: Terwilliger K. M. , Jones L. W. , Pruett C. H.
Published: February 2005

A number of experiments are described which test the interactions of particles with rf accelerating voltages in an FFAG acclerator. The experiments confirm predictions of a theory of Symon and Sessler and demonstrate the feasibility of ``stacking'' successively accelerated groups of particles with a density close to that of a single group.
Drift Velocities of Electrons in Some Commonly Used Counting Gases
Authors: Bortner T. E. , Hurst G. S. , Stone W. G.
Published: February 2005

The original method of Stevenson has been used to develop an apparatus capable of yielding high precision for the drift velocities of electrons moving in an electric field. Measurements have been made of the electron drift velocity in argon, nitrogen, methane, carbon dioxide, ethylene, cyclopropane, and a few mixtures of some of these gases. The results for argon and nitrogen agree with those of Nielsen.
Precision of the Geodimeter as Affected by the Speed of Light in Air
Authors: Williams D. T. , Williams John R.
Published: February 2005

The Geodimeter has been analyzed as to limitations on its precision in range measurement imposed by uncertainties in the velocity of propagation of light in the atmosphere. The instrument has been found elsewhere to be somewhat more consistent than the best current value of the velocity of light in vacuo, that is, to about one part in 3 million. On the basis of the analysis reported here, routine measurements to one part in 106 are concluded to be warranted, as far as propagational errors are concerned, up to ranges of about 100 km. Higher precisions, up to 1 in 107, are concluded to be attainable.
Feedback Controlled Heat Conductivity Gauge for Measuring Pressure in Vacuum Systems
Authors: Leck J. H. , Martin C. S.
Published: February 2005

This paper describes a simple feedback circuit for the hot wire Pirani gauge. This gauge is used for measurement at low pressures where the heat conducted away from a thin hot wire is a function of the gas pressure. The wire is included in a Wheatstone bridge circuit which serves both to heat the wire and to measure its temperature. In the circuit described here the heat input is adjusted automatically so as to keep the wire temperature approximately constant over a wide range of pressure changes. This is achieved by supplying the power from a magnetic amplifier which is controlled by the wire temperature, a fall in temperature increasing and a rise in temperature decreasing the power supply.

In this way pressure measurements can be made over the range zero to 3 mm Hg with wire temperatures of the order of 50 to 100°C by using either the feedback signal or the power output from the amplifier to give a measure of the pressure.
Comparison Type Nephelometer
Authors: Wright William Finley
Published: February 2005

A comparison type nephelometer has been designed and constructed with which turbidities are measured by both absorption and scattering of light. The especially designed cells permit accurate measurement of small changes in intensity of either transmitted or scattered light over a wide range of intensities. A single light source with a sector scanner alternately illuminates two separate optical paths for simultaneous comparison of two cells, one of which may be a standard. The intensities of the two optical paths can be varied independently for comparison measurements. A light integrating sphere with phototube assembly furnishes a single photoreceiver for the two optical paths. One such sphere compares the transmitted beams, another, the scattered beams. The reproducibility of resetting in the normal operating range is two parts in ten thousand. The apparatus will operate over a range of more than five density units. When making series of measurements, it was found possible to make and record readings for different cells every 15 sec. The apparatus was used successfully for two years in bacteriological, silica gel, and colorimetry studies. A slight modification permits measurement of the depolarization of the scattered light as well as the usual Tyndall scattering. This depolarization is measured for both polarized and unpolarized incident light, thus characterizing the size and optical anisotropy of the particles or scattering centers.
Mercury Vapor Jet Target and Stripper
Authors: Beringer Robert , Rall Waldo
Published: February 2005

A supersonic mercury vapor jet has been developed for use in stripping electrons from a beam of heavy ions. The required surface densities (2 to 20 μg/cm2) were obtained with the apparatus described. The increase in pressure caused by the jet was less than 3×10−7 mm Hg at the end of a 10-in. beam tube.
Propane Bubble Chamber in a High Magnetic Field
Authors: Oswald Larry O.
Published: February 2005

A liquid propane chamber 3.25 by 6.5 by 13 in., operating in a magnetic field of 22 000 gauss, is described. A simple compact dark-field type of illumination is used; this is discussed. For personnel and equipment safety a secondary pressure vessel is incorporated in the design. Special reference is given to some of the construction and design problems.

A brief summary of the operation of the propane chamber in the 6.2-Bev neutron beam is given.
Energy Modulation for Particle Accelerators
Authors: Cranberg L. , Aiello W. P. , Beauchamp R. K. , Lang H. J. , Levin J. S.
Published: February 2005

The energy of an electrostatic accelerator is modulated over a range of 50 kev by applying an alternating potential of 50-kv amplitude to an insulated target at a frequency of 10 cps. A sample of the modulating voltage and the signals from a nuclear detector are fed to a so-called ``function sampler,'' which furnishes an output pulse whose height is proportional to the instantaneous value of the target voltage. Analysis of the pulse-height spectrum by means of a 100-channel analyzer then affords a presentation of the spectrum of nuclear events as a function of accelerator energy over a 50-kev range, each channel of the analyzer corresponding to an energy width of 500 ev. Advantages of this system are discussed for high resolution work with an electrostatic accelerator.
Measurement of Fast Neutron Total Cross Sections
Authors: Cranberg L. , Beauchamp R. K. , Levin J. S.
Published: February 2005

A system is described for measuring high resolution (e.g., 1 kev) total neutron cross sections at high counting rate in the range above 50-kev neutron energy using as a neutron detector a thick proton recoil detector. The pulsed-beam time-of-flight technique is used to identify the neutrons of interest, which are produced in the target of an electrostatic accelerator. Energy modulation of the accelerator makes it possible to make observations at 100 energy points simultaneously. Illustrative results are given on the 585-kev resonance in sulfur and on aluminum in the neighborhood of 585 kev. The gain in speed of taking data over conventional systems is greater than a factor of 100.
Precise Nuclear Resonance Thermometer
Authors: Benedek G. B. , Kushida T.
Published: February 2005

The properties of a thermometer based upon the temperature variation of the pure quadrupole resonance frequency (ν0) of the Cl35 nucleus in granular KClO3 have been investigated. In the range ∼10°K<T <300°K, the thermometer has a very high sensitivity, being better than ±0.002° at 273°K and ±0.004° at 77°K. The accuracy at 20°K is estimated as at least ±0.02°. The thermometer is exactly reproducible if care is taken that the KClO3 is of high chemical purity. No hysteresis effects were observed. Establishment of the thermometer requires a single precise determination of the ν0 versus temperature curve using the fundamental temperature standards to measure the temperature.
Principle for Null Determination of Magnetization and Its Application to Cryogenic Measurements
Authors: Arrott Anthony , Goldman J. E.
Published: February 2005

A principle of measurement of magnetization is described which uses a sample in a uniform magnetic field such that the sample does not affect the uniformity of the field and the sample itself is uniformly magnetized. The measurement is absolute in that it requires only a measurement of a current and dimensions. The method uses a cylindrical specimen on which a small pitch fine wire coil is wound. The proper current through the coil required to restore the uniformity of the field in all space gives a direct measurement of the magnetization. Uniformity of the field is detected by an induction technique. The method is suitable for most magnetic measurements but in the case of strongly ferromagnetic materials and superconductors requires currents in the coil that are too large. This principle has been incorporated in an apparatus for measurements of magnetizations from liquid helium temperatures to room temperature.
Medium-Energy Neutron Time-of-Flight Spectrometer
Authors: Grismore R. , Parkinson W. C.
Published: February 2005

A neutron time-of-flight spectrometer developed for the 1- to 20-Mev region is described. The instrument makes use of the phase bunching of deuterons in the Michigan 42-inch cyclotron and an external beam pulsing system to provide isolated bursts of neutrons of 4-mμsec time duration. Flight times are measured with an improved version of the chronotron capable of a precision of ±3×10−10 sec. The energy spread for a 5-meter flight path varies from 3.5% at 0.5 Mev to 10% at 20 Mev. The available neutron flux permits an improvement of at least a factor of three by lengthening the flight path. The Be9(d,n) thick target and the O16(d,n) thin target spectra are discussed.
Ultra-High-Speed Flash Cinemicrograph
Authors: Courtney-Pratt J. S. , Huggins Charles M.
Published: February 2005

The principles of Cranz-Schardin flash cinematography are described. This method uses up to thirty separate lenses and air sparks to produce an equivalent number of ``still'' photographs. The framing rate and exposure times are determined by the characteristics of the light sources; framing rates of over one million per second have been reported. A modified version of the Cranz-Schardin camera which uses only one microscope objective lens and eight air sparks to produce eight micrographs is described. The performance to be expected and some possible applications are discussed.
Low Temperature Mixing Calorimeter for Liquids
Authors: Jeener J.
Published: February 2005

A technique is described for measuring the heat of mixing, excess volume, specific heat, and other thermodynamic properties of liquid systems at low temperature (e.g., CO, CH4, A, Kr). Experiments are carried out at constant pressure, without any vapor phase in the calorimetric vessel.
Compensation of the Earth's Magnetic Field
Authors: Scott G. G.
Published: February 2005

A system is described for producing a highly homogeneous, variable, and directable magnetic field. This system, which was used in gyromagnetic ratio experiments, was directed against the earth's magnetic field to obtain very nearly a field free space. Horizontal fields in this working space were held to less than 0.01% of the earth's horizontal component.
Cryostats and Mechanical Stage for Nuclear Magnetic Resonance Studies
Authors: Mulay L. N.
Published: February 2005

Cryostats for use with liquid helium and other coolants providing temperatures in the range 77° to 600°K constant to within ±1° are described. These are designed to provide a self-contained probe with the facility of interchanging different radio-frequency coils. The rf coil is so mounted that it keeps the sample free from condensation of moisture at low temperatures and facilitates changing of samples without disturbing its position in the homogeneous region of the magnetic field. A mechanical stage which locates this region and clamps the probe in this position is also described. It reproduces this setting quickly and is particularly useful for high resolution studies. A new method of setting up the mechanical stage with the cryostat, the magnet, and the oscillator provides a compact assembly with considerable ease in their operation and allows the use of a very short coaxial cable (about 6 in.) for connecting the rf coil to the oscillator. This considerably improves the signal-to-noise ratio.
Improved Method to Measure the Thickness of Thin Films with a Photoelectric Ellipsometer
Authors: Rothen A.
Published: February 2005

This article describes the advantages of a photoelectric ellipsometer over a visual instrument for the measurement of the thickness of films from 1 A up to many thousand A. Experimental curves are given showing the unambiguous correlation between film thickness and position of two rotating elements, a λ/4 plate and an analyzing Nicol prism.
High Stability Nuclear Magnetic Resonance Spectrograph
Authors: Baker Edward B. , Burd L. W.
Published: February 2005

An NMR spectrograph using an electromagnet is superstabilized by a feedback loop which uses the error signal from a secondary nuclear resonance probe to control the oscillator driving frequency. Field fluctuations thus produce such frequency variations as to preserve the Larmor condition for both short and very long times. The same oscillator is used for the measurement probe and thus also the Larmor condition is preserved in the sample being measured. Means are provided for sweeping frequency to produce precalibrated spectra of high precision at various magnifications and scale shifts with a very convenient and rapid setup procedure. Frequency scales are directly related to graph paper markings. Improved temperature control of the magnet and a reproducible precycling recipe also contribute to an unusually high degree of stability and reliability of day-to-day operation.
Preparation of High-Sensitivity Cadmium Sulfide Cells for Gamma-Ray Detection
Authors: Hollander Lewis E.
Published: February 2005

Single synthetic CdS crystals 3×4×10 mm, having dark conductivities from 10−9 to 10−10 ohm−1 cm−1, were prepared for gamma-ray detection. In a 50 r/hr Co60 field the conductivity increased to 10−6 ohm−1 cm−1. The crystals were grown in a static system at 930±5°C. Indium electrodes were applied by an ultrasonic soldering technique. The effect of constant excitation from radium to reduce the crystal rise time is illustrated. The time response and spectrographic analysis of crystals and commercial CdS powders is presented.
X-Ray Powder Diffraction Assembly for Studies at Elevated Temperatures and High Gas Pressures
Authors: Goon Edward J. , Mason John T. , Gibb Thomas R. P.
Published: February 2005

A high temperature-high pressure assembly has been designed to be used with a Straumanis-type powder camera and a modified oscillatory attachment. The assembly consists of a small resistance furnace with a cooling shield and a specimen holder. The furnace is capable of heating the sample to a maximum temperature of 500°C and the temperature of the sample can be controlled to within ±1°C. The specimen holder, which is constructed from beryllium and Monel metal, has withstood hydrogen gas pressures above 600 psi at 500°C. The apparatus has been applied to the structural study of the system: uranium-uranium hydride-hydrogen gas. The lattice parameter of uranium hydride (β-tungsten structure) is reported for the temperature range, 25°C to 500°C, with an accuracy of ±0.001 A.
Cell for the Determination of Pressure Coefficients of Dielectric Constant and Loss of Liquids and Solids to 10 000 psi
Authors: McCall D. W.
Published: February 2005

A cell is described in which one can measure pressure coefficients of the dielectric constant and loss of liquids and solids to 10 000 psi. Data are reported for the liquids benzene, dioxane, and toluene to illustrate the use of the cell. Data are also reported for polyethylene-5% butyl rubber to illustrate the use of the cell for the measurement of solids.
Some Design Data for a Nonmagnetic Radio-Frequency Mass Spectrometer
Authors: Dekleva J. , Ribarič M.
Published: February 2005

The current efficiency and the half-width of the resonance curve in a radio-frequency mass spectrometer are discussed in relation to the energy gain in the one-, two-, and three-stage tube. Both quantities are calculated and measured for two different analyzing systems; in the first case with a retarding barrier and secondly with a deflecting field. The measurements show that there is, instead of the theoretical relation between the resolving power (r.p.) and current efficiency, r.p.∼Emax−1 with a retarding field as an analyzer, a less useful one, r.p.∼Emax−1/5. But in the case with a deflecting field as an analyzer the theoretical relation between the resolving power and the current efficiency, r.p.∼Emax−½, and the measured relationship are the same.
Techniques and Equipment Utilized in Low-Temperature Reactor Irradiations
Authors: Coltman R. R. , Blewitt T. H. , Noggle T. S.
Published: February 2005

A cryostat used in hole No. 12 of the graphite reactor at Oak Ridge National Laboratory is described in detail. The cryostat which is made almost entirely of aluminum is supplied with cold helium gas from an Arthur D. Little helium refrigerator. Bombardments have been made in the cryostat at temperatures as low as 15°K for periods as long as two weeks. A discussion of the equilibrium temperature attained by a specimen in the cryostat is given taking into account the reactor gamma ray heating effects. A method for measuring stored energy and specific heats of materials bombarded in the cryostat utilizing gamma ray heating is described. A method for pulse annealing specimens at low temperatures employing the discharge of the energy stored in a bank of condensers is also described. Relatively sharp and quite reproducible thermal pulses can be obtained with this method (which is also suitable for use in the laboratory). The hazard of cryogenic devices in high radiation fields is discussed. It is believed that when air is allowed to condense on a cold surface in the presence of intense ionizing radiations, a hazardous condition results.
Monoenergetic Absorption Peaks Obtained with a Scintillation Spectrometer
Authors: Haskins J. Richard
Published: February 2005

The effect of finite channel width in distorting intensities of monoenergetic lines in a scintillation spectrometer is considered. It is found that peak area divided by channel width gives the rate of monoenergetic absorptions in the crystal. A correction to intensities proportional to the square root of the pulse height is not applicable.
Preparation of Large Plastic Scintillators
Authors: Clark G. W. , Scherb F. , Smith W. B.
Published: February 2005

A process is described for the manufacture of disks of plastic scintillators weighing over 100 kg and composed of polystyrene (∼99%), p-terphenyl (∼1%), and POPOP (∼0.03%). The design and performance of two large plastic scintillation detectors for cosmic rays are discussed.
Gravity Anomaly Simulator
Authors: Gerrard J. A. F. , Strickland L. , Wade A. L. , Reynolds H. K.
Published: February 2005

An instrument that will simulate the anomalous gravity effects of a subsurface body, having a density differing from that of its surroundings, is described. The device makes use of the similarity between the gravity equation and Lambert's cosine θ law, and enables the geophysicist to synthesize the anomaly producing body in a time much shorter than that required for conventional computational methods. The accuracy that can be expected is ±5% of the maximum anomaly within limitations noted in the paper.
Microwave Triode Oscillators
Authors: Andrews C. L.
Published: February 2005

Coaxial and rectangular wave-guide oscillators are described which yield frequencies of 4 to 6 kilomega-cycles per second. A metal cap fitted around the anode end of the tube confines the anode grid cavity entirely inside the tube. Studies of efficiency indicate that the upper limit in frequency of the GL-6299 tube is imposed by the circuit inside the tube and not by the electronics of the tube.
Acoustic Air Pump
Authors: Dauphinee T. M.
Published: February 2005

An air circulating pump that works on the principle of acoustic wind is described. The pump will move up to 700 l/min of air when powered at 60 cps by a 4-in. loudspeaker. The speaker diaphragm is the only moving part and could be protected by inert material when it is desired to seal in and circulate corrosive gases. Alternating current pickup from the speaker is so small as to be negligible in most instances.
Contribution to the Floating Zone Refining of Silicon
Authors: Buehler E.
Published: February 2005

A floating zone refining apparatus for silicon, which can operate unattended, has been assembled to assist in the production of high purity material for research purposes. Features of this equipment are a simple mechanical drive, a switching panel to recycle the apparatus, and a self-stabilizing rf heating circuit to maintain constant zone length. Silicon containing less than 1 part per billion of electrically active impurities (resistivity of 16 000 ohm cm and lifetime of 1.2 milliseconds) has been prepared. The effect of many-pass refinings on the diameter of the sample is discussed. Surface tension effects on material transport are significant.
Automatic Adiabatic Calorimeter Shield Control
Authors: Zabetakis M. G. , Craig R. S. , Sterrett K. F.
Published: February 2005

An automatic adiabatic calorimeter shield control has been built and operated successfully for approximately 700 hours. It has been used with an existent low temperature (10 to 300°K) intermittently heated calorimeter in runs of up to 100 hours duration. Each control unit consists essentially of a difference thermocouple, high sensitivity taut suspension galvanometer, a set of four photomultiplier tubes, a relay servo mechanism, a reversible ac motor and gear train and two ON-OFF control relays. The observed behavior of the control and the internal consistency of the data obtained during its use indicate that the precision with which it controls the shield temperature is comparable with that obtainable from a trained human operator.
Automatic Bridge Balance for Nuclear Spin Resonance Spectrometer
Authors: Collins R. L.
Published: February 2005

Troublesome changes of the bridge balance in a twin-T nuclear resonance bridge have been eliminated by the application of a voltage-sensitive condenser. A small amplitude, high-frequency modulation voltage applied to the condenser senses any deviation from balance, and a servo loop provides a dc correction voltage which maintains the bridge balance. No apparent deterioration of the spectrum results from modulation of the bridge.