bluuebunny/crossref_metadata_2025 huggingface dataset:
Apparatus for Mechanical Loss Measurements in Low Loss Materials at Audio Frequencies and Low Temperatures
Authors: Scott W. W. , MacCrone R. K.
Published: February 2004

A new apparatus for measuring mechanical loss in low loss materials at low temperatures is decribed. The method has several advantages over existing techniques. Using this apparatus, losses as low as 2×10−6 with a resolution of 10−7 have been reproducibly measured at 4.2°K in TiO2 (rutile).
Hydrostatic Ring Test for High Precision Strain Measurements
Authors: Moberly John W. , Goggin William R. , Sedlacek Rudolf
Published: February 2004

A technique for measuring plastic strains at low stress levels is described. The system has a capability of recording residual plastic strains of less than 5×10−8. The test sample is a thin-walled right circular ring, which is stressed by applying known hydrostatic pressure on the inner wall. This results in a tangential tensile stress throughout the ring; the strain is simply the ratio of change in diameter to original diameter. The strain is measured by capacitance transducers. Materials that are often thought to behave in a perfectly elastic manner to stress levels of 10 kg/mm2 and higher are found to experience plastic deformation at loads as low as 0.35 kg/mm2 when tested with this high sensitivity system.
Nondestructive Thickness Measurement in Thin Sections of Germanium
Authors: Mittleman S. D. , Bess L.
Published: February 2004

A system for performing infrared absorption measurements using a laser source is described which allows the accurate determination of thicknesses of thin sections of germanium in the range of 4 to 10 μ. The advantages in the use of a laser in lieu of a polychromatic source are (1) only two calibration points need be made, (2) output power of the radiation source need not be regulated, and (3) small areas may be measured using only simple optics. The overall accuracy of the system yields an error less than 6%.
Calibration of Differential Pressure Indicators at High System Pressures
Authors: Richardson H. P. , Gordon John L. , Cummins David , Guereca R. A.
Published: February 2004

A technique and apparatus are described for accurately (±0.01%) calibrating differential pressure indicators beyond the normal operating range of available high pressure manometers.
Measurement of One-Dimensional Lagrangian Motion of Water Waves
Authors: Wells Donald R.
Published: February 2004

A system is described which is capable of measuring the water particle motion on the bed of a water wave tank. Heretofore gravity wave observations have been performed in the Eulerian or fixed frame of reference in which the apparatus is immersed in the water and fixed to the tank. This system described here utilizes an optical sensor which tracks a water particle tagged by an almost neutrally buoyant sphere moving horizontally on the tank bottom in response to the wave forces. A series of photocells senses the shadow of the moving sphere through a glass-walled flume. The photocells drive transistor switches which provide voltage levels appropriate to each position in the tank and data are then recorded on paper tape where they can be read off manually. This system was designed specifically to study the wave-induced water velocity on the bottom in shallow water in a model tank with implications for the the erosion of sand offshore of natural beaches.
Destructive Hydrogen Target Tests at the Princeton-Pennsylvania Accelerator
Authors: Jankowicz R.
Published: February 2004

The PPA standard hydrogen target system was tested for a catastrophic failure of the target flask. Two tests were performed. In the second test, the size of the vacuum housing surrounding the target flask was reduced. The resulting pressures, effect on the Mylar windows, and a single phase analysis of the gas flow are discussed.
Automatic Real Time Air Monitoring of 85Kr Utilizing the 4096 Memory of a Multiparameter Analyzer
Authors: Ludwick J. D. , Lashock J. J. , Connally R. E. , Nickola P. W.
Published: February 2004

A noble gas atmospheric monitoring field grid system in which 85Kr is used as a tracer has been designed, constructed and implemented for studying atmospheric transport and diffusion. This system has demonstrated its usefulness in the quantitative measurement of the transport and diffusion of both continuous and true puff-type radioactive gas releases on a real-time basis. Small fluctuations in the air concentrations of the tracer are determined by using integrating times of as little as 1 sec. The system consists of a large group of field detectors which relay their information to a 4096 address memory. The memory is presently programmed to accept information from 64 detectors. Information is accumulated in groups of 64 time channels and these groups are automatically stepped by the programmer. A time interval selector allows automatic advance of the stepping process at a slow or fast rate allowing the desired differential data accumulation. The memory is read out on magnetic tape and the equipment is ready for the next field test 35 sec after completion of a tracer field test.
Energy Resolution and Focusing in Inelastic Scattering Experiments
Authors: Stedman R.
Published: February 2004

In elastic scattering experiments, it is appropriate to consider the scattering pattern in the space of momentum and energy transfers, and a proper treatment of resolution takes account of momentum and energy together, both as regards the correlation of momentum and energy increments in the beams of incident and scattered particles and as regards the structure of the cross section under observation. A description is given of the calculation of resolution widths in measurements on a phonon dispersion surface with a three-axis crystal spectrometer, and of the manner in which the two main contributions to the energy resolution width may be minimized by focusing— which involves a suitable choice of the monochromator and analyser crystals, the beam path, and the incident and scattered energies. Focusing usually improves resolution markedly without loss of intensity, and often with a gain in the peak intensity of a recorded resonance. An experimental illustration is given. Cases where focusing entails loss of intensity are discussed in connection with intensity formulas.
Curve Tracer That Frees Diode Characteristics of Internal Resistance
Authors: Pankove J. I. , Berkeyheiser J. E.
Published: February 2004

This curve tracer measures the I-V characteristic of semiconductor diodes and, assuming an ideal rectifier, compensates for the internal resistance of the diode. The compensating resistance determines the internal resistance. Deviations from the ideal characteristic indicate that phenomena other than injection occur.
Simple Closed-Open-Closed Spectrograph Shutter for Exposure Times in the 10 μsec Range
Authors: Grasdalen G. L. , Huber Martin , Newsom G. H.
Published: February 2004

A frictionless closed-open-closed spectrograph shutter initially held in place by magnets and driven by an exploding wire is described. Measurements show that the peak transmission of the shutter is 100% and that the timing is reproducible to better than 1 μsec.
Temperature Measurements with Metal Ribbon High Temperature X-Ray Furnaces
Authors: Ostertag W. , Fischer G. R.
Published: February 2004

Improved temperature measurements have been made using thin thermocouple wire welded separately to the platinum ribbon of a high temperature x-ray diffractometer attachment. The tempera ure profile of the specimen stage has been determined in atmosphere as function of temperature, heater position, and heater geometry.
Radio Frequency Pulse Generators to Produce a 1.8 kG Rotating Field in a Plasma
Authors: Lietti A.
Published: February 2004

A circuit is described which produces a 2.17 MHz rotating magnetic field at the surface of a cylindrical hydrogen plasma column of 5 cm diam and 44 cm length. The field has a duration of 3.7 μsec. Line pulse generators are used. The spark gaps of the lines are triggered by a special ``synchronizer.'' With this device a number of generators can be connected in parallel in order to achieve higher power levels. Fields of 10–20 kG for application outside of plasma physics are possible.
Instrumentation for Ultrasonic Studies at Frequencies from 0.2 to 2.0 GHz
Authors: Hemphill R. B.
Published: February 2004

Instrumentation for ultrasonic pulse-echo experiments in the frequency range of 0.2 to 2.0 GHz is described. The apparatus includes a conventional pulsed rf transmitter, superheterodyne receiver, and tunable resonant cavity. Microwave diode switches are employed in single-ended operation of the equipment. A simple technique for the excitation of acoustic transducers with stripline is described. Additionally, a detection system is presented which utilizes correlation techniques for the recording of acoustic signals with an enhanced signal-to-noise ratio.
Alpha Particle Pressure Gauge for High Altitude Constant Level Balloon Flights
Authors: Howard R. L. , Nelson S. W. , Winckler J. R.
Published: February 2004

This paper describes an alpha particle pressure gauge designed for use on very high altitude constant level balloon flights. The instrument gives continuous readings from sea level to pressures less than 1 millibar with an accuracy in the 1–10 millibar range of a few tenths of a millibar. The instrument utilizes a sensitive electrometer measuring the ionization current due to a very weak polonium alpha particle source of less than 1 μCi in the form of nonreactive ceramic microspheres. The pressure is read out by the time interval between resets of the drifting electrometer in a form convenient for transmitting by radio telemetry. Temperature compensation in the electronic circuitry corrects for the gas law so that the instrument measures pressure independent of temperature to suitable accuracy between −25 and +25°C. The instrument has been tested on more than 50 balloon flights and gives reproducible and accurate results. The paper describes the complete physical and electronic operating principles and shows detailed drawings and photographs of the improved version sufficient to enable the experimenter to construct a copy. The instrument uses all solid state components and the size, weight, and power requirements are very small.
Analysis of Resistivity Measurements by the Eddy Current Decay Method
Authors: LePage J. , Bernalte A. , Lindholm D. A.
Published: February 2004

A systematic analysis is presented of the conditions in which the measurements of resistivities of metallic samples by the eddy current decay method give meaningful and accurate results. Coil sample geometry and material parameters are examined by means of equivalent circuits, and ways of extracting the desired information from the signal are discussed. We report selected measurements on critical parameters. A carefully designed and tested apparatus for the accurate determination of resistivity at room and helium temperatures with an operational logarithmic amplifier has been constructed. Most of the important conclusions of this study are displayed in graphical form to assist workers in the field.
Liquid Helium Cooled Stage with a Transverse Magnetic Field
Authors: Hörl Erwin M.
Published: February 2004

A stage for the observation of specimens in an electron microscope at liquid helium temperature is described. This stage is characterized by the addition of a transverse magnetic field in which the specimen is positioned. Provisions are made for tilting the specimen around two axes, which are perpendicular to each other.
Discharge Mechanism in Gases in the Subnanosecond Region
Authors: D'Alessio Juan T. , Lanza Hilda
Published: February 2004

The mechanisms of spark generation which produce luminous and electric pulses of the order of subnanoseconds in a gas at a high pressure are analyzed. The classical mechanisms, which account for regenerative processes initiated by the photons produced during the avalanches of electrons, cannot explain the generation of 1011 electrons in 0.3 nsec, which were experimentally detected when using our generator. In this work, the experimental results are interpreted by means of a model which considers the equilibrium surface shape of the liquid as the resultant of an increase in the field near the electrodes up to 109−1010 V/cm (the surface shape is determined by the super-imposed effect of the electric field and the surface tension). With a field of this magnitude, electrons are produced at the cathode in numbers large enough to explain the experimental results. In agreement with the model proposed, pulses of 10−10 sec duration can only be obtained with liquid electrodes in gases at a high pressure.
New Method for Measuring the Static Magnetic Susceptibility by Paramagnetic Resonance
Authors: Seehra Mohindar S.
Published: February 2004

This paper shows that large magnetic losses in a sample broaden the paramagnetic line in EPR without changing its g value. The expressions are derived for this ``extra line width'' for two experimental cases: (1) the oscillator frequency is stabilized to an external reference cavity; (2) the oscillator frequency is stabilized to the sample cavity. The ``extra line width'' is shown to be a simple monotonic function of the static magnetic susceptibility χ0, the Larmor frequency, the filling factor and the loaded Q of the cavity. From this, χ0 can be determined. The theory is compared with experiments on Cu(HCOO)2·4H2O and good agreement is obtained. The magnetic susceptibility of Cu(HCOO)2·4H2O is measured as a function of temperature by this technique. A weak broad maximum is observed around 70°K, in agreement with the results obtained by the usual methods.
Fast and Accurate Method for Measuring Photon Flux in the Range 2500–6000 Å
Authors: Yguerabide Juan
Published: February 2004

This paper presents a technique for fast and accurate measurement of photon flux from pulsed and steady state light sources over a wide range of wavelength and flux. The technique uses a 1P28 photomultiplier (PM) tube plus a solution of rhodamine B in ethylene glycol (RhB solution). The flux to be measured is absorbed by the rhodamine solution and the resultant rhodamine fluorescence is measured by the PM tube. The solution absorbs completely all photons below 6000 Å and fluoresces with constant fluorescence spectrum and fluorescence quantum efficiency for incident wavelengths from 6000 to at least 2500 Å. These properties of the RhB solution result in a PM tube-RhB solution detecting system with constant photon sensitivity from 6000 to 2500 Å. A large range of flux can be measured by adjusting the distance between the fluorescent solution and the PM tube so as to maintain the tube current within limits of stable operation. An RhB detector with a given distance between the RhB solution and the PM tube photocathode is useful over a 1000 to 1 flux range. Two RhB detectors described in this paper had solution-photocathode distances of 1 and 5.5 cm and operated in the ranges 2×1010 to 2×1013 photons/sec and 1.6×1012 to 1.6×1015 photons/sec. The lowest flux which can be detected (2×1010 photons/sec with the detectors here described) can be reduced by using special techniques for measuring noise and signal or by using red-sensitive photomultipliers. The RhB detector has excellent long time stability. Tests made with a tungsten-filament lamp showed constant sensitivity within ±2% over a period of more than two months. With the RhB detector photon flux measurements can be made in a few minutes with high precision. The detector can also be used for measuring relative fluxes with constant wavelength sensitivity. The RhB detector is compared with the potassium ferrioxalate actinometer, one of the most sensitive chemical actinometers presently available, and shown, where applicable, to be more sensitive and easier to use than the actinometer.
Low Energy Cosmic X-Ray Proportional Counter System
Authors: Cornell C. M. , Grader R. J. , Harri J. G. , Hill R. W. , Rumble R. P. , Salmi D. S.
Published: February 2004

A rocket-borne, thin window proportional counter system has been developed and used for several x-ray astronomy experiments in the range from 200 eV to 10 keV. The counter energy spread has been measured as 17% at 6 keV and varies approximately with the square root of the energy. The counter construction, gas system and pulse height preserving electronics are described.
Quadrupole Field in Circular Concave Electrodes
Authors: Hayashi Tomonao , Sakudo Noriyuki
Published: February 2004

The fields in circular concave electrodes with both infinitesimal and infinite thickness are analyzed by giving appropriate boundary conditions, and the optimum electrode angles for approximating the ideal quadrupole field best are obtained. These angles are 44° for infinitesimal thickness and 37° for infinite thickness. These results are verified by field plotting method. The realization of these electrodes is also discussed.
Method for Determining Charge Production in Semiconductors and Insulators
Authors: Matthews S. M. , Turiel I. , Furst M. , Kallmann H.
Published: February 2004

A method is described which allows separate determination of charge injection from an electrode into a semiconductor or insulator and separate determination of charge production in the bulk or at surfaces by thermal or radiative means. A basic part of the method is the use of a barrier layer of very high resistance at one or two surfaces of a material such as a crystal of CdS or anthracene. These barriers serve in this way as collecting capacitors for the charges. The amount of charge collected can be determined by quickly discharging these capacitors by light. By this method, in addition to determining very small rates of charge production, the total amount of charge made available in the sample by thermal charge production can be found. Radiative charge production in the presence or absence of external fields can also be determined.
Simple Method for the Automatic Recording of the Internal Magnetic Field
Authors: Asti G. , Conti F.
Published: February 2004

Pick-up coil systems suitable for magnetization measurements are shown to be useful also for the automatic recording of the internal magnetic field of an ellipsoidal specimen. The probe is made to operate in this way not with the need of special devices, but simply by properly changing the coil's position. The accuracy in the measurement is essentially limited by eddy current effects which cause distortion in the signal; it depends strongly on the geometry of the coils and of the sample, and on the differential susceptibility of the tested material. An open flux hysteresigraph that utilizes three coils is proposed as an application of this method and is shown to be particularly advantageous for hard materials.
Time Interval Multiplier for Shock Tube Studies
Authors: Duff Russell E. , Long James R. , Porter James R.
Published: February 2004

A relatively simple, solid state circuit is described which will generate a delayed output pulse that is related to the velocity of transit of a wave past two stations. The delay is a predetermined multiple k of the time interval between two input pulses. This time interval multiplier or proportional delay circuit is particularly useful in shock tube work where, for instance, a light source must be triggered when the shock wave is in a particular position and the shock velocity is not known precisely before the experiment. The maximum and minimum permissible times between the first and second input pulses in this circuit are 600 and 10 μsec, respectively. At the maximum interval, k can be adjusted between 1.5 and 0.07, and at the minimum interval, k can take values between 100 and 0.75.
Thermal Initiation Apparatus for High Energy Materials
Authors: Kendall Paul A. , Rosen Jerome M.
Published: February 2004

A thermal initiation apparatus is described for rapidly heating high energy materials to temperatures in the range of 300 to 1000°C. The time delays to explosion, which fall in the range of 0.05 to 5 msec, are measured as a function of the sample temperature. The sample is enclosed in stainless steel hypodermic needle tubing which is pulse heated by a capacitor discharge. A constant current source is used in monitoring the change in resistance of the heated stainless steel tubing. A number of important circuit features in use are described. Calibration methods and sample handling techniques are described. Representative thermal initiation data are reported.
Use of a Closed Cycle Helium Refrigerator for Mössbauer Studies
Authors: Wiggins J. W. , Oleson J. R. , Lee Y. K. , Walker J. C.
Published: February 2004

A closed cycle helium refrigerator has been used successfully to cool the target and absorber in Coulomb excitation Mössbauer studies. The refrigerator handles the appreciable power from the beam and may be used at any temperature above 20°K. The most severe problem of mechanical vibration has been solved.
Measurement and Control of Magnetic Field Homogeneity
Authors: Ernst Richard R.
Published: February 2004

Methods for the measurement and control of magnetic field homogeneity are described. They are designed for application in magnetic resonance spectroscopy. It is shown that field homogeneity can be described satisfactorily by properties of the observed spectral line shape only. Possible criteria include the moments, peak height, and signal energy of a typical resonance line. The moments are equivalent to the Lp norm of the magnetic field configuration. Only the second moment and related criteria allow the construction of a complete set of noninteracting shims which can be adjusted independently for any field configuration. The other moments may provide noninteracting control for certain simple field configurations only. For a resonance line with a sufficient natural width, peak height and energy can be related to the second moment and may also give noninteracting control. Iterative methods for automatic control by means of digital computers are described and applied to a high resolution nuclear magnetic resonance spectrometer.
A New ENDOR Cavity Configuration
Authors: Castner T. G. , Doyle A. M.
Published: February 2004

This paper reports a new microwave cavity-rf coil configuration for ENDOR experiments. It consists of a split rectangular cavity operated in the TE201 mode with two columns of multiple horizontal posts traversing the entire cavity and piercing the end walls. The posts are everywhere perpendicular to the microwave electric field and have a negligible effect on the cavity Q. The cavity is substantially widened in the direction which does not affect the cavity frequency in order to provide a good return path for the rf magnetic flux lines. The cavity can readily be adapted for the insertion of a cold finger Dewar. The merits and versatility of this configuration are considered.
Falling Sphere for Measuring Atmospheric Density
Authors: Haycock O. C. , Westlund C. D. , Pound E. F. , Woolley R. H.
Published: February 2004

An omnidirectional accelerometer for use in the rigid, 18 cm, falling sphere is described. The device permits measurements of transit time of a small ball, internal to the sphere, as it falls freely through a fixed distance. The transit time is related to drag acceleration on the spherical package and, therefore, to the density of the atmosphere. Operational and construction details are given and errors and limitations of the system are indicated.
Free Surface Velocity Measurement of an Impacted Projectile by Optical Doppler Shift
Authors: Johnson P. M. , Burgess T. J.
Published: February 2004

An optical technique for measuring the velocity of an accelerating, specularly reflecting surface from a position on the axis of motion has been successfully applied to a free surface velocity measurement of an impacted projectile in a pneumatic accelerator. The technique combines a laser light source, a surface tilt-insensitive, lensless optical configuration, and a Fabry-Perot spectrometer to obtain a velocity-time profile of the impacted projectile. The technique involves unique features in addition to surface tilt insensitivity. These include a mode matching scheme which permits the use of high power, multilongitudinal mode lasers where formerly a single frequency laser was required. Experimental results are presented and compared with independent accelerometer measurements.
Radial Heat Flow Thermal Conductivity Apparatus for Measurements on Sulfide and Telluride Melts
Authors: Williams R. K. , Veeraburus Manoo , Philbrook W. O.
Published: February 2004

A steady-state, radial heat flow apparatus for determining the thermal conductivities of sulfide and telluride melts is described. The apparatus was used in the temperature range 650–1000°C and data on silver-sulfur, silver-tellurium, and nickel-sulfur melts were obtained. The discussion emphasizes the experimental problems with vaporization, thermocouple stability, etc. A detailed analysis of possible convective heat transfer effects at Grashof-Prandtl numbers below 5000 is also presented.
Ruby Fluorescence as a Dosimeter for Pulsed, High Energy, Ionizing Radiation
Authors: Halpin J. J. , Wenzel R. F.
Published: February 2004

A convenient dosimeter for pulsed beams of high energy, ionizing radiation, of duration 300 μsec or less, is described. This dosimeter employs the R line (6943–6929 Å) fluorescence produced by ionizing radiation in low chromium concentration (∼0.001%) ruby single crystals. The fluorescent intensity of ruby is linear with dose where the dose delivered per pulse is as much as 105 rad (ruby). The advantages of this dosimeter are that the value for the integrated dose may be obtained immediately from suitable detection and recording devices, the dosimeter is reuseable without any treatment for cumulative doses up to 108 rad (ruby), and the dosimetric measurement can be made at a time sufficiently beyond the radiation pulse so as to avoid the radiation-induced detector noise.
Monitoring of Thin Film Growth by an Ultrasonic Interference Method
Authors: Lutsch A. G. K. , Wilk M. , Bierbaum P.
Published: February 2004

A better correlation between thickness values of a thin film grown on a substrate and on an auxiliary monitor is obtained by using the same substrate material in both cases. The velocity change of ultrasonic surface waves in the film and substrate is measured as a function of the film thickness by interference of the surface wave with a bulk (volume) wave in the substrate. Interference periods of 50–500 Å are measured and computed for Au, Ag, and Cu at 30 and 50 MHz; the values of the interference period could be decreased to a few tens of angstroms for frequencies above 100 MHz.
Remote Recording Shock Wave Detector and Gated Interval Timer
Authors: Hyland Robert N. , Bicknell Reid E. , Jones Donald L.
Published: February 2004

A general purpose, time interval counter, specifically applied to the measurement of shock wave arrival times, is designed and tested. The device consists of an integrated circuit oscillator gated into a counter. Time discriminations of 1 μsec or better are readily achieved. Total cost of the entire apparatus does not exceed $75.00, exclusive of labor.
Device for Converting Photographically Recorded Data to Computer-Compatible Magnetic Tape
Authors: Glass Ian S. , Richard Kenneth F.
Published: February 2004

This article describes a simple machine for automatically transferring counting rate data in the form of dashed trails on photographic film to computer-compatible magnetic tape. To ensure accurate registration of the film, a servo-controlled corrector is incorporated.
High Pressure pH Sensor for Oceanographic Applications
Authors: Ben-Yaakov S. , Kaplan I. R.
Published: February 2004

A high pressure pH sensor has been developed and tested in the laboratory to a pressure of 150 kg/cm2 and in the ocean to a depth of 270 m. The sensor is composed of specially designed glass membrane and reference electrodes. A pressure equalizing technique is used to prevent pressure gradients across the walls of the electrodes. Seawater buffer was used to calibrate the sensor for oceanographic application resulting in 0.02 pH units reproducibility.
Atomic Beam Source for the Energy Range of 0.2–45 eV
Authors: Politiek J. , Rol P. K. , Los J. , Ikelaar P. G.
Published: February 2004

An apparatus has been developed for producing an atomic beam of potassium in the energy range of 0.2 to 45 eV (1000–15 000 m/sec). The technique used here is cathode sputtering. With a velocity selector (spread, 6.7%; maximum rotational speed, 48 000 rpm), both the signal of a Pt-W detector and an energy independent one are measured as a function of the velocity of the beam particles.
Pressure Shock Technique for the Study of Chemical Relaxation
Authors: Hoffmann Heinz , Yeager Ernest
Published: February 2004

The pressure shock technique with a conductivity readout has been demonstrated to be a relatively simple means for the measurement of relaxation times from 1 μsec to several milliseconds in ionic systems involving association-dissociation processes.
Photomultiplier Radiometer for Detection of Radio Frequency, Intensity Modulated Light from Plasmas
Authors: Morris Glen J.
Published: February 2004

A photomultiplier radiometer is described which has been used successfully to detect radio frequency, intensity modulated light from both laboratory and astrophysical plasmas. A servo controlled, null balancing process is used to eliminate electronic instabilities in the receiver and to automatically compensate for changes in source light intensity. The basic sensitivity of the instrument in terms of photomultiplier parameters, percentage modulation, and receiver pre-detection and post-detection bandwidths is discussed.
Air Ion Apparatus
Authors: Bachman C. H. , Crandell M. E. , Hart F. X.
Published: February 2004

Described is an apparatus producing a ducted flow of air or gas which contains a controlled unipolar ion concentration. Included are flow regulators and a filter system that passes only particles smaller than 0.05 μ. Ionization is produced by a radioactive source. Control of ion concentration is best achieved by diluting the ionized flow with nonionized gas which has bypassed the ionizing unit. Electrical methods of controlling ion levels have also been examined. Ion concentrations up to about 106 ions/cm3 (1000 times ambient) are obtained with the radioactive sources presently in use.
Variable Temperature Dewar for Cathodoluminescence Studies
Authors: Knox W. P. , Cuthbert J. D.
Published: February 2004

We describe a single refrigerant, variable temperature Dewar employing the forced convection of cold gas to obtain sample temperatures in the range 12 to 300 K. Although the Dewar was developed for cathodoluminescence studies using 100 to 400 keV electrons, the design permits easy modification for other uses. The Dewar features quick cool-down time, the option of fast thermal cycling, the efficient removal of heat from small irregularly shaped samples mounted strain-free, the ability to change samples quickly at all temperatures, and thermometry isolated from the sample irradiation chamber.
Vapor Deposited Samples and Leads for High Pressure Measurements
Authors: Vaišnys J. Rimas
Published: February 2004

A method for making samples and leads for high pressure measurements by vacuum deposition is described. The technique has been used with Bridgman anvils to pressures above the bismuth III-IV transformation, and is particularly useful for measurements requiring many, precisely positioned, electrical contacts.
Economical, Single Scale, Ionization Gauge Pressure Readout System
Authors: Robertson John A. , Hendricks Charles D.
Published: February 2004

An inexpensive, single scale, vacuum readout system is described for use with either the Bayard-Alpert gauge or a standard triode ionization gauge. This readout system obviates a filament current regulator by performing a logarithmic solution to the defining relationship P=1/S·Ii/Ie. The described system indicates a constant pressure despite wide variations in gauge electron current and is suitable for both general laboratory monitoring and other applications where minimum weight and minimum power dissipation is required.
Lead Attachment to Silicon
Authors: Zucker M. J. , Traum M. M.
Published: February 2004

An earlier work describing the preparation of a soldered electrical contact to a silicon surface using a metal hydride flux has been extended to allow for the preparation of many such contacts, on both horizontal and vertical surfaces, with a single heating. A collodion film is used to keep the molten solder in intimate contact with the hydride and silicon during the heating process.
Pyroelectric Ceramics as Detectors of Fast Atomic Beams
Authors: Berkner Klaus H. , Myers Booth R. , Pyle Robert V.
Published: February 2004

A method for detecting fluxes of energetic atoms with pyroelectric ceramics is described. The detector consists of a commercially available, polarized lead zirconate-lead titanate (or barium titanate) disk which is silvered on both sides to provide electrical contact. The atoms are stopped in one of the silvered surfaces, and the resulting change in temperature gives rise to a pyroelectric signal. In our application the atomic beam is chopped, and the signal-to-noise ratio is increased by phase-sensitive amplification. Our detectors have been calibrated from 1.6×10−7 to 3×10−1 W, and are remarkably linear over this range.
Analysis of Ultrasonic Absorption Measurements in Liquids at High Pressure
Authors: Johnson Walter H. , Holton Gerald
Published: February 2004

A method, complete with error analysis, is given for determining the absorption coefficient for ultrasonic pulses and the loss at the mirror and crystal as a function of pressure. Results of the analysis are presented for distilled water and propanol. An expression for the pressure-dependent, mirror-crystal loss is derived and checked against the experimental values obtained. A second method is discussed for obtaining the absorption coefficient more directly from fewer measurements.
A Superconducting Gravimeter
Authors: Prothero W. A. , Goodkind J. M.
Published: February 2004

A gravimeter is constructed which uses the near perfect stability of superconducting persistent currents to make it a device with exceptional stability. A superconducting sphere is levitated in the magnetic field generated by two superconducting coils. Changes in gravitational or inertial forces in the vertical direction are measured as changes in the vertical position of the sphere or as changes in a feedback force, independent of the primary supporting force, which holds the sphere in a fixed position. In its present state of development the instrument produces data which, when compared to calculated earth tides, set an upper limit on the drift rate of ±6 parts in 109 of g/day. Several possible sources of drift are discussed.
Electron Gun for LEED Applications
Authors: Lee R. N.
Published: February 2004

An electron optical scheme has been developed for a low energy electron gun in which the focal properties are independent of final electron energy or beam current over a wide range of these variables. The scheme includes focus-independent provisions for pulsing the beam and regulating the current. Constructional details are given for typical guns and the performances of three guns are discussed. Beam currents in the microampere range were obtained for electron energies down to 4 eV, where the beam diameter was about 1.5 mm. Above 15 eV the beam diameters were less than 1 mm. At high energies, excellent focus properties were obtained by operating the final gun stage as an accelerating, rather than a decelerating, lens.
Measurement of Faraday Rotation in Megagauss Fields over the Continuous Visible Spectrum
Authors: Garn W. B. , Caird R. S. , Fowler C. M. , Thomson D. B.
Published: February 2004

A method is described for making Faraday rotation measurements simultaneously over most of the visible spectrum at magnetic fields in the megagauss range. The fields are produced by explosive-driven magnetic flux compression systems and typically reach 1.2 MG in a few tens of microseconds. The optical train consists of an explosive white light source, polarizer, sample, analyzer, and a sweeping image spectrograph. The technique is applicable to solid or liquid samples. Verdet coefficients are given for LiF, H2O, and fused quartz over the wave-length range from about 4000 to 6300 Å. The coefficients generally agree to within ±2% with previously published values except for fused quartz for which the present values are somewhat higher at the short wavelength end.
Method of Orienting Single Crystals for ESR Measurements
Authors: Palaia Frank L. , Haase Oswald , Marinkas Paul L.
Published: February 2004

A method has been developed that permits accurate orientation of lattice directions in small single crystals with respect to the applied magnetic field in electron spin resonance (ESR) experiments. The technique is particularly useful when used with the Varian ESR spectrometers, for which many of the standard methods are unsuitable. An x-ray diffractometer and an autocollimating telescope are used to allow orientation of a given lattice direction parallel to the field with an accuracy of ±0.1°.
Direct Access 3He Cryostat
Authors: Halpern T. , Fritzsche H.
Published: February 2004

Details of the design and construction of a 3He cryostat in which the experimental chamber can be reached directly from the outside are described. Main features of the system are (i) the use of a copper-to-copper conical joint to lock thermally at 1.2 K the structural and electrical parts that will reach the low temperature experimental chamber, and (ii) the use of epoxied joints that can be easily opened to allow for the use of different geometries. This avoids the magnetic flux trapping associated with the presence of superconductive solder in the low temperature region. The refrigerator is capable of operating down to 0.32 K for at least 10 h as a one shot system and to 0.41 K with continuous circulation of the 3He.
Unattended Controller for a Frequency Synthesizer
Authors: Cairns F. V. , Shepertycki T. H.
Published: February 2004

An electronic controller, made of integrated circuits and inexpensive silicon controlled rectifiers, has been designed as a coupler or interface between a card reader and a frequency synthesizer to permit sequential selection of one of the 5×109 frequencies available from the frequency synthesizer. Because it was designed for unattended operation under clock control, a lamp display for monitoring was included and effects of impulsive interference were investigated.
Multiple-Image Objective System for a Rotating-Mirror Camera
Authors: Gardner S. D.
Published: February 2004

An optical system is described that produces multiple images on a streak camera slit plane. The apparatus is made up of several identical optical objectives. Each objective, consisting of a pair of collimating lenses and a pair of Dove prisms, serves to form an image that can be arbitrarily positioned and oriented at the camera slit plane. The instrument was designed primarily to record the progress of a nonplanar shock wave or detonation wave along several nonparallel paths. When used with suitable short-duration object illumination, it is also capable of recording framing pictures of a dynamic event. Two applications of the instrument are described.
Instrumentation for the Digital Recording of the de Haas-van Alphen Effect in Impulsive Magnetic Fields
Authors: Panousis P. T. , Gold A. V.
Published: February 2004

A high-speed digital recording system has been developed for studying the de Haas-van Alphen (dHvA) effect (and related phenomena) in impulsive magnetic fields. The data obtained during each pulse are stored in a small memory, from which they can be recovered at leisure and analyzed by computer. Use of this digital recording instrumentation has resulted in a substantial improvement in the reliability of the values of the dHvA frequencies as determined in impulsive fields, and has also led to an enormous saving in the time required for data reduction and analysis. The calibration of the magnetic field is also discussed.
An Ion Ejection Technique for the Study of Ion-Molecule Reactions with Ion Cyclotron Resonance Spectroscopy
Authors: Beauchamp J. L. , Armstrong John T.
Published: February 2004

A novel technique involving a straightforward modification of an ion cyclotron resonance spectrometer has been developed which utilizes the excitation of the characteristic oscillatory motion of the ions, due to the trapping field, for ejecting ions from the cyclotron resonance cell. By pulsing the rf ejection field and referencing the detection system to the pulsing frequency, a spectrum of ions whose number density is modulated by the pulsed ejection field is obtained. This is directly applicable in studying ion-molecule reactions for the determination of product ion distributions, even when other processes, such as direct ionization or concurrent ion-molecule reactions, contribute to product ions of interest.
Simultaneous, Local Measurement of Two Magnetic Field Components and the Sum of Their Squares
Authors: Jones I. R. , Peiry J.-M. , Cocq D.
Published: February 2004

An apparatus is described which is capable of measuring simultaneously the local amplitudes of two magnetic field components, their squares, and the sum of their squares. It consists of a two-coil magnetic probe and a voltage signal squaring circuit. Details of the construction and calibration of the apparatus are given and an application of the complete system is briefly outlined.
Characteristics of Composite Carbon Resistors Used for Measuring Accelerator Terminal Voltages
Authors: Stevenson F. R. , Gauntner D. J.
Published: February 2004

A voltage divider board composed of 1152, 22 MΩ composite carbon resistors used to measure the terminal voltage of a 3 MeV Dynamitron was investigated. The board was calibrated in situ using the 9Be and D photoneutron threshold reactions and a magnetic analyzer. The present calibration of the divider board which was made after over 5 years of extensive accelerator usage agrees within 2% with the original factory calibration. The linear temperature coefficient of resistance was measured to be +(0.85±0.10)×10−3/°C in the range 25 to 35°C. The divider board resistance decreased linearly with voltage (−1.1×10−5%/V) up to 2 MeV which corresponds to 1750 V on each resistor. The results show that composite carbon resistors and the techniques described can be applied with confidence to the measurement of high voltage.
Reconstruction of Fiducial Marks and Cameras Utilizing Simultaneously All the Photographs Available
Authors: Negri Pietro
Published: February 2004

We describe in this paper a program to calculate a posteriori the coordinates of a set of points photographed by n cameras, together with the positions and orientations of the cameras, also not known a priori. The coordinates of the cameras are obtained by an unique fit, requiring the points measured on the pictures to be images of true points, existing somewhere in space. The coordinates of the points photographed are then easily obtained.
Synthesized Plasma Generator
Authors: Rajangam K. B. , Page J. O. , MacKenzie K. R.
Published: February 2004

A cesium plasma with a useful volume of 3 by 15 cm is produced inside a hot cylindrical tantalum cavity at temperatures around 1400 K. Ions are produced by contact ionization at the wall while electrons are obtained from an internal filament. The plasma potential determines the energy of the electrons, and this can be varied such that the electron-ion temperature ratio ranges from 1 to 2.4. In the vicinity of 1011 ions/cc the background noise is about the same as found in Q machines.
Simple Instrument for Two-Level Control of Liquid Nitrogen in Dewars
Authors: Alon Yosef
Published: February 2004

An instrument for automatic topping-up of liquid nitrogen in Dewars is described, featuring small diameter (5 mm) splash-proof level sensors on flexible leads. A 9 W flow-controlling solenoid valve is directly driven by a reliable, low power circuit, which requires no readjustments. Standard, inexpensive components are used throughout.
Processing Nuclear Emulsions for X-Ray and γ-Ray Spectrographs
Authors: Saunders Bernard G.
Published: February 2004

A technique is described for processing thick nuclear research emulsions used for recording x-ray or γ-ray spectral lines. The procedure is simpler than that employed when processing emulsions for nuclear tracks, yet low distortion is achieved.
Collection Efficiency of Continuous Dynode Electron Multiple Arrays
Authors: Burroughs E. G.
Published: February 2004

The ratio of incident electrons to electrons which participate in the multiplication process for continuous dynode electron multiplier arrays has been experimentally determined. For an array which had a geometrical transmission of 50%, it was found that 75% of the incident electron current reached the multiplication section of the array tubes. Of this percentage, 50% were considered to be initial electrons and the remaining 25% reflected or secondary electrons from the top electrode.
Nonrelativistic Nuclear Reaction Kinematic Crossover Angles
Authors: Warshaw Stephen I.
Published: February 2004

A nonrelativistic expression relating the bombarding energy to the laboratory angle at which the energies of reaction products from two dissimilar nuclear reactions coincide is derived and discussed. Applications to accelerator beam energy measurement, detector angular calibration, and nuclear reaction experiment planning are considered.
Device Which Separates Minute Particles According to Electronically Sensed Volume
Authors: Fulwyler Mack J. , Glascock Robert B. , Hiebert Richard D. , Johnson Norman M.
Published: February 2004

A device has been developed that is able to fractionate a mixture of microscopic particles according to small differences in their volume. A dilute suspension of the particles passes through a sensor within which the volume of each particle is electronically measured. Subsequently the suspension emerges into the air as a liquid jet. This jet is caused to break into a large number of individual droplets, thereby isolating the suspended particles. Droplets containing particles of the desired volume ranges are electronically charged and electrostatically deflected into suitable receptacles. The apparatus is described in considerable detail with illustrative application to polystyrene spheres and to human white blood cells.
SiO2(Quartz), MgO, PbF2, and Bi as Low-Pass Neutron Velocity Filters
Authors: Holmryd Sten , Connor Donald
Published: February 2004

We have measured the transmission of monochromatic slow neutrons over the wavelength range 1–5 Å for monocrystalline and polycrystalline samples of SiO2(quartz), MgO, PbF2, and Bi at 83 K and 300 K. These materials were selected as apparently suitable for use as neutron ``low-pass'' velocity filters; SiO2 and Bi have already been used in this manner at several laboratories. Single crystals of MgO cooled to 83 K are remarkably transparent to thermal neutrons; more than 70% of the incident 2 Å neutrons are transmitted by a 15 cm sample whose transmission for 1–2 MeV neutrons is about 0.01. SiO2 is nearly as transparent, in agreement with several earlier measurements by other workers. A comparison of our measurements on Bi with other reported work shows that neutron transmission is low and quite variable from sample to sample for neutron wavelengths in the range 1–2 Å but fairly high for all samples at wavelengths >4 Å (∼50% for a 15 cm sample). For the latter wavelength range, we find slowly cooled Bi castings, in which large grains have developed, to be about as transparent as (nominally) monocrystalline samples. A single crystal of PbF2 exhibited higher transmission in the range 1–3.5 Å than did any Bi sample. The theoretical basis for the neutron filtering action of crystalline materials is briefly discussed.