bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact response of a shorted guard-ring quartz gauge between 20 and 26 kilobar
Authors: Hayes D. B. , Gupta Y. M.
Published: February 2004

Shorted guard-ring quartz gauges 1.27 cm diam and 0.32 cm thick with a 0.36 cm inner electrode exhibit an effective piezoelectric current coefficient of k = (1.89 + 0.0107σ)×10−8 C/cm2/kilobar within a precision of ±1%, when subjected to step impact loading between 20 and 26 kilobar. Data confirm that the effective charge-collecting area of the inner electrode includes half the area of the insulating gap. Increase of current with time is observed to be approximately three times that observed for shunted gauges. Unequal potential between inner and outer electrodes has no measurable influence on gauge response for the applications considered here. A comparison of present data with previous studies indicates that shorted guard-ring quartz gauges do not display the same degree of universality as shunted quartz gauges.
Technique for measurement of elastic constants by laser energy deposition
Authors: Calder C. A. , Wilcox W. W.
Published: February 2004

A convenient experimental arrangement for the measurement of elastic material constants from specimens of circular or rectangular rods is presented. An ultrasonic pulse technique is applied using very short stress pulses produced by laser energy absorption from a Q-switched ruby laser.
Simple moving film semicylindrical x-ray camera
Authors: Ito Taisuke
Published: February 2004

A moving-film semicylindrical x-ray camera with 100 mm radius was constructed. The camera moves in the direction of the axis of the semicylinder and allows 15 independent exposures for equatorial reflections on one film (43×240 mm in size). The exposed sections, each having 1.9 mm width, are arranged in a precisely parallel way with a fine (0.1 mm) unexposed zone between neighboring sections. These facilitate direct measurement and comparison of the reflection angles and intensities. Three photographs taken with this camera are shown. Two of these were obtained at high pressures (8 kilobars) by mounting a high pressure diffraction cell on the camera.
Balloon-borne radiosonde for the measurement of the atmospheric thermal structure coefficient
Authors: Barletti R. , Lemmetti P. , Paterno L.
Published: February 2004

The characteristics and operational limits of a balloon-borne radiosonde working up to 20 000 m for the measurement of the atmospheric thermal structure coefficient CT2 are described. The knowledge of CT2 profile up to 20 000 m gives information about the optical quality of the atmosphere with respect to high resolution astronomical observations. The radiosondes were launched during a research campaign carried out at Tenerife, Canary Islands in connection with the European JOSO (Joint Organisation for Solar Observations) project.
A collimator for soft x rays
Authors: Wriston Robert S.
Published: February 2004

A novel collimator is described which makes use of eight identical plates having holes located randomly. A holder aligns the plates so that on-axis x rays pass through the same hole in each successive plate. Off-axis x rays are attenuated by a factor of T8(=2×10−4), where T is the transmission of a single plate. The angular response measured at 8.34 Å was 15′ wide at half maximum and had wings because of the overlapping of the holes. The design has the advantage that it defines one unique direction rather than several, as is the case when regular hole patterns are used.
Error analysis and adjustment of the LEED goniometer
Authors: Aberdam D. , Baudoing R. , De Bersuder L.
Published: February 2004

We describe the error analysis and the adjustment procedure which are necessary to achieve the setting and determination of angular coordinates of the electron beams in the LEED goniometer described in the preceeding paper. Our goal is to obtain the best possible accuracy, particularly to allow LEED data reduction experiments.
A comparison of temperature measurement of oxygen in the 0–0 and 0–1 rotational bands using laser Raman spectroscopy
Authors: Hickman R. S. , Liang Louis
Published: February 2004

Rotational temperatures in pure oxygen at 1 atm, ranging from 243 to 343 K, and in air at room temperature have been measured from the 0–1 rotation-vibration Raman spectra of oxygen inside a laser cavity. The spectral temperatures obtained from the 0–1 transition are compared with those obtained from pure rotational spectra. Spectra obtained at different data collection rates are discussed. It is found that accurate temperature determination in pure oxygen is entirely feasible with an absolute accuracy of 3–8 K. The application of this technique in fluid mechanics is discussed.
Measurement of the linear electric field effect in EPR using the spin echo method
Authors: Mims W. B.
Published: February 2004

An apparatus is described which is designed to measure the linear electric field effect in EPR for amorphous samples such as those which are often encountered in biophysical studies. The apparatus is based on the electron spin echo method. It is capable of measuring g shifts ≃ 10−9 cm/V for samples with phase memory times ≃ 1 μsec. A brief general description of the electron spin echo apparatus is given, special attention being paid to those parts of the system developed specifically for the purpose of measuring the linear electric field effect. The influence of electric field homogeneity and of the pulse timing parameters on the measurements has been investigated in detail.
Precise calibration method for time-to-amplitude converter
Authors: Littman Michael G.
Published: February 2004

Accurate calibration of systems using time-to-amplitude converters can be difficult and time consuming. A simple and quick method for calibrating such systems is described. The method has wide operating range and high precision and uses equipment which is commonly available in the laboratory.
Control of fluid feed pressures in colloid sources at high potentials
Authors: Hepburn J. D. , Vermeulen F. E. , Chute F. S.
Published: February 2004

A unique pressure converter for control of fluid feed pressure in a colloid source in a 100 kV accelerator dome is described. The pressure converter converts analog control pressures greater than one atmosphere absolute to fluid feed pressures near zero absolute pressure. A pressure calibration curve for the device is given.
The cracking of rubber O-rings by hydraulic fluids at high pressures
Authors: Whalley E. , Lavergne A.
Published: February 2004

Stretched rubber O-rings frequently crack when pressurized by low molecular weight fluids. This appears to be due to solvent induced crazing above the glass transition.
A phase-sensitive technique for measuring small birefringence changes
Authors: Serreze H. B. , Goldner R. B.
Published: February 2004

A phase-sensitive technique for detecting small changes in birefringence is described. Because the technique is essentially insensitive to light intensity fluctuations and drift, it is an improvement over a customary method for measuring changes in birefringence.
True centroid-sync used to cancel wander in a spot-image analyzer
Authors: Harris Robert W.
Published: February 2004

A method is described for analyzing the projected focal spot of a light beam spread by propagation through atmospheric turbulence. The degradation in the spot caused by the wander of its centroid is analyzed separately from the average spread of the intensity distribution about the centroid. The technique presented utilizes a unique analog circuit for measuring the time-centroid of the pulse which represents a one-dimensional scan of the light spot.
Removable interdigital electrodes for surface wave studies
Authors: Greenberg I. N. , Lipschultz F. P.
Published: February 2004

We have fabricated interdigital electrode structures on polished glass plaques. By placing the plaques next to the surface of a piezoelectric material and exciting the electrode of the transmitting plaque with pulsed rf energy of the appropriate frequency, good acoustic surface waves are received at a similar plaque at the opposite end of the sample. The plaque electrodes are fragile but reusable if handled with care.
Theory of a membrane-voltage clamp with discontinuous feedback through a pulsed current clamp
Authors: Brennecke R. , Lindemann B.
Published: February 2004

We present a voltage clamp (potentiostat) for biological membranes which works on a new principle. Its feedback loop contains a current clamp which drives a train of brief current pulses through the membrane (typically 8 μsec duration and 8 μsec intervals). In each interval between two current pulses, the difference between membrane voltage and command voltage is sampled and determines the amplitude of the next current pulse. Since the membrane capacitance acts as an analog store between current pulses, the membrane voltage oscillates near the desired value in a triangular waveform. It is independent of resistive voltage drops at electrodes or fluid layers developing in series to the membrane (or the electrode) to be clamped. The clamp does not tend to oscillate, in contrast to clamps with continuous feedback after compensation for series resistors. A precise measurement of membrane capacitance is possible.
A portable laser light-scattering probe for turbulent diffusion studies
Authors: Yang B. T. , Meroney R. N.
Published: February 2004

A new instrument has been devised, based on light scattering principles, to measure real-time concentration variation in a turbulent flow. Used for turbulent diffusion measurements in a wind tunnel boundary layer, it can also be utilized for other turbulent mixing studies as well. The instantaneous concentration was detected by means of a 5 mW He–Ne gas laser as a light source, dioctyl phthalate aerosols as tracer particles, fiber optics as the scattered light transmitter, and a photomultiplier as a scattered light sensor. The instrument was designed to be moved to any location in a wind tunnel to measure steady or unsteady diffusion processes.
Production of pulsed magnetic fields with a flat pulse top of 440 k0e and 1 msec duration
Authors: Dworschak G. , Haberey F. , Hildebrand P. , Kneller E. , Schreiber D.
Published: February 2004

A capacitance discharge unit for the production of pulsed magnetic fields up to 440 k0e is described. The pulse formed by a passive network has a field plateau of approximately 1 msec duration for a half-period of ∼ 3.5 msec and a field ripple of Δ H/H ≤ 1%. The unit occupies approximately 10 m2, the total weight is 600 kg. It can be produced at low cost.
A frequency modulator coupled to an electron multiplier
Authors: Muranaka T. , Kanayama M.
Published: February 2004

A frequency modulator coupled to an electron multiplier has been developed to extract and measure the output current which is small, floating at high voltage, and contains various frequencies starting from dc. The measurable input current range is from 1 × 10−9 to 3 × 10−7A and the cutoff frequency is about 2 kHz when using a 1 mΩ resistor for converting input current to voltage.
An anaerobic stopped-flow spectrophotometer
Authors: Michael D. , O'Donnell D. , Rees N. H.
Published: February 2004

A reliable, all-glass, stopped-flow apparatus is described in which extremely air-sensitive reactions can be studied under anaerobic conditions; it is also suitable for studying reactions involving oxygen in solution. The equipment can be used over the temperature range − 100 to + 100 °C.
An apparatus for the simultaneous measurement of reflectance, absorbtance, and transmittance
Authors: Thomason William H. , Macomber James D.
Published: February 2004

A simple apparatus for the accurate measurement of the angular dependence of the reflectance, absorbtance, and transmittance of objects illuminated by a cw laser is described. Beam profiles and divergences can also rapidly be determined.
Preparing polished crystal slices with high precision orientation
Authors: Mathiesen S. Ipsen , Gerward L. , Pedersen O.
Published: February 2004

A polishing procedure is described which utilizes a high precision Laue technique for crystal orientation. Crystal slices with their final polished surfaces parallel to a crystallographic plane within 0.02° can be prepared.
Rayleigh spectrometer
Authors: Shaya Steven A. , Han Charles C.-C. , Yu Hyuk
Published: February 2004

A versatile, self-contained, and inexpensive light scattering spectrometer has been constructed and calibrated. The data acquisition and subsequent spectral analysis by FFT are performed with an on-line minicomputer. Power spectra in the audio range (below 100 kHz) obtained by this direct FFT technique are found to have precision superior to any previously reported.
An automatic Toepler pump control
Authors: Moore H. E. , Frahm V. H.
Published: February 2004

A highly reliable Toepler pump control which makes use of photoconductive cells as mercury level sensors is described.
Simple refractory metal oven design of high temperature uniformity suitable for operation in ultrahigh vacuum
Authors: Osgood R. L. , Procik C. , Madjid A. H. , Anderson W. F.
Published: February 2004

The construction of a simple refractory metal oven of high temperature uniformity suitable for operation in ultrahigh vacuum is described. When made of tantalum the upper operating temperature limit is about 2700 K for oven lifetimes of about five hours. The uniformity differences in temperature over the entire oven can be less than 15 K at the maximum temperature. This high uniformity is made possible by allowing Joule heat to develop in the current leads to balance oven suspension heat losses. The attainable vacuum with a 50 liter/sec ion sputter pump is between 10−7 and 10−9 Torr in the incandescent range depending on the temperature.
A feedback pulse-lengthener circuit for the peak voltage measurement of a single shot pulse as narrow as 2.5 nsec
Authors: Uno Masami , Koike Ryuichi
Published: February 2004

A circuit capable of measuring the peak voltage of a single shot pulse as narrow as 2.5 nsec is described. The circuit uses a pulse-lengthener circuit that has an amplifier in its negative feedback path. The amplifier reduces the charging time constant of the pulse-lengthener circuit to improve its speed capability. The measurable peak voltage of a single shot pulse ranges from about +0.3 to +3.3 V. The meter deflection is held constant for easy readout by A/D and D/A converters until the A/D converter is reset.
Variable attenuator for TEA CO2 lasers
Authors: MacPherson R. W.
Published: February 2004

A compact gas cell uses propylene or propane to control the intensity of TEA CO2 lasers over a range of 1 to 10−4. Attenuation of megawatt pulses is smoothly and easily obtained without polarization effects and free of temporal or spatial distortion.
Pattern-generators and technique for electron-beam fabrication of submicron thin-film bridges for superconductivity studies
Authors: McCarthy S. L. , Stanko J.
Published: February 2004

A low-cost technique is discussed for fabricating bridges down to 0.12μ in width in aluminum using a conventional scanning electron microscope without a beam-blanking facility. A detailed discussion is also given of the bridge pattern generators for the rectangular and Anderson-Dayem geometries. The successful use of Shipley AZ-1350 as an electron resist is reported.
A transmission oscillator ultrasonic spectrometer
Authors: Conradi Mark S. , Miller J. G. , Heyman Joseph S.
Published: February 2004

A continuous wave ultrasonic instrument capable of measuring very small changes in acoustic attenuation and phase velocity is described. This transmission oscillator ultrasonic spectrometer (TOUS) exhibits high sensitivity because it oscillates marginally. In spite of this high sensitivity, the TOUS system is relatively simple, compact, and inexpensive. These features suggest that the TOUS is suitable not only for precise laboratory measurements of the physical properties of materials, but also for field applications in nondestructive testing.
A thin film thermopile for neutral particle beam measurements
Authors: Sharp L. E. , Holmes L. S. , Stott P. E. , Aldcroft D. A.
Published: February 2004

A simple design is described for a sensitive thin film thermopile (12 V W−1) which is suitable for measurements on low energy neutral beams in the range 300 eV-3keV. The device has been used as a secondary standard to calibrate fast response (τ ∼ 10−6 sec) neutral particle energy analyzers which incorporate gas stripping cells.
A double-modulation technique for obtaining high-resolution energy-differentiated electron transmission spectra
Authors: Schowengerdt F. D. , Golden D. E.
Published: February 2004

A method is described whereby high-resolution measurements of the derivative of the electron current transmitted through a gas may be made without the use of deflection or magnetic fields. The method consists of modulating a retarding element and the interaction region with signals which are 90° out of phase. It is shown that when the transmitted current is measured by a phase-sensitive detector which is referenced to twice the modulation frequency, the output signal is proportional to the derivative of the transmitted current and is characteristic of a monoenergetic beam. Results of performance tests on helium are presented and discussed. The tests show that the resolution is essentially equal to the average of the two modulation amplitudes. In the case of the 22S resonance in He−, a resolution of 29 meV with a signal-to-noise ratio of better than 400 has been obtained. Resolutions as good as 10 meV have been obtained with poorer signal-to-noise ratios.
Construction of a high power xenon ion laser
Authors: Harper Clinton D. , Gundersen Martin
Published: February 2004

Construction of a pulsed xenon ion laser, which has a combined peak power on all visible lines of over 80 kW is described. Design of the laser and the pulsing circuit is detailed, and the light pulse shape, peak power and electrical effieciency of the laser are discussed.
A circuit which predicts and diverts flashover from a long air gap
Authors: Jervis-Hunter G.
Published: February 2004

A fast, rugged, electronic circuit is described which predicts an impending switching surge flashover in a long air gap and diverts the discharge energy into a triggere'd bypass gap. Prediction is based on the amount of charge injected into the gap by the high voltage electrode. A protective gap could be designed which would operate only if the insulation being protected were about to fail. This could significantly improve the techniques of insulation coordination and has important implications for studies of the mechanisms of the long spark.
Electromechanical micromanipulator
Authors: Greer M. H. , Brockman W. H.
Published: February 2004

An inexpensive device useful for accurate positioning of electrodes, parts, tools, and other implements has been developed using audio speakers, linearly actuated potentiometers, and conventional power supplies. It is designed to have three independent orthogonal directions of motion; however, devices to control movement in one or two directions are also easily constructed.
Double probe measurement of electron thermal fluctuations in a plasma
Authors: el Shahid N. Abd , Deschamps P. , Gravier R. , Renaud C.
Published: February 2004

A new simple differential technique using two Langmuir probes yields an analog signal proportional to the local electron temperature fluctuations in a plasma, even in the presence of density and potential fluctuations. By externally driving a periodic change in the plasma temperature, it has been possible to check this technique and its accuracy and to enable calibration. This differential technique is used to measure the amplitude fluctuations in a turbulent collisionless drift wave spectrum present in a laboratory plasma.
A dual channel nitrogen laser useful for nanosecond excited state studies
Authors: Stephenson Paul B. , McDowell Vaughn P.
Published: February 2004

A two channel Blumlein excited N2 laser is described. The output of the laser consists of two pulses of approximately 250 kW peak power separated by 15 nsec. The laser is designed to study transient absorption spectra with characteristic lifetimes in the range of 20 nsec to several seconds.
High sensitivity gas flowmeter
Authors: Auriemma G. , Medici G. , Ubertini P.
Published: February 2004

This Note describes a very simple and inexpensive device for the measurement of gas flows in the range 0.1–10 cc/sec, employed by the authors to prepare gas mixtures used to fill proportional counters.
An improvement of a circularly polarized microwave cavity
Authors: Suematsu Hiroyoshi
Published: February 2004

A crossed-slits coupling iris is used for a reaction type cavity. A power ratio of the two opposite circular polarizations of more than 15:1 is obtained at 70 GHz.
Snap-action pneumatic valve for a gas gun
Authors: Miles A. W. , Pearson G. C.
Published: February 2004

The design of a snap-action pneumatic valve for a gas gun is presented and its operation described.
Computer-controlled double-grating spectrometer system for low light levels
Authors: Ushioda S. , Valdez J. B. , Ward W. H. , Evans A. R.
Published: February 2004

We have developed a computer-controlled double-grating spectrometer system designed for spectral analysis of low level light sources, in particular Raman scattering spectroscopy. This system incorporates a 16-bit minicomputer, a double-grating spectrometer, and various output devices. We have used this system for Raman spectroscopy of light scattering from opaque surfaces and found it valuable in the numerical analysis of weak spectra.
Rotating drum scanner-display system for digital image processing
Authors: Sandor Tamas , Cagliuso George
Published: February 2004

An electromechanical scanner-display system is described that as a scanner measures optical density in transparencies and as display device reconstructs the scanned image from digitally recorded optical density data. The instrument can accommodate image sizes up to 20×25 cm with maximum spatial resolution of 20 line pairs/mm. The optical density data are digitized into eight bits (256 levels) covering a range of 0–2.2 OD at a speed of 28 000 samples/sec. The display part of the system receives data digitized into 256 levels; out of these 95–105 can be distinguished at at output with statistical significance.
Autofrettaged high pressure chamber for use in inelastic neutron scattering
Authors: Blaschko Oskar , Ernst Gert
Published: February 2004

An autofrettaged high pressure aluminum chamber for pressures up to 3 kilobar for inelastic neutron scattering experiments has been designed and constructed. The autofrettage technique shows some advantages with respect to the simplicity and the flexibility of construction as compared with other methods.
A low cost sequencing and timing computer for the laboratory
Authors: Toms D. J.
Published: February 2004

A general purpose sequencing and timing computer with a program capacity of 100 instructions is described. Program storage is by means of a low cost shift register memory. Input, output, and branching instructions are provided, along with a novel instruction for the creation of ``DO'' loops. Complex pulse patterns with pulse durations ranging from 1 μsec to arbitrarily long times can be easily programmed. Up to eight external devices can be controlled without additional demultiplexing.
Separation of surface and bulk minority-carrier lifetimes in silicon
Authors: Carroll Kathleen A. , Casper Karl J.
Published: February 2004

One of the major problems in interpreting photoconductive lifetime measurements in silicon is the separation of the lifetime of carriers excited near the surface and that of carriers excited in the bulk of the crystal. This paper describes an experimental method of achieving this separation.
A temperature-jump apparatus for fluorescence measurements
Authors: Rigler Rudolf , Rabl Carl-Roland , Jovin Thomas M.
Published: February 2004

A new instrument has been designed for the recording of chemical relaxation phenomena induced by a temperature jump, using changes in the nonpolarized and polarized emission of fluorescent molecules. The relative features of techniques for the measurements of light absorption and light emission are discussed specifically in regard to the signal-to-noise ratios of the measured signals and to problems related to the detection of polarized emission. Examples are given to demonstrate both the performance of the instrument as well as the usefulness of fluorescence measurements in chemical relaxation experiments.
Stabilized interferometer modifications
Authors: Cummins W. F.
Published: February 2004

The stabilized 70 GHz interferometer used for plasma density measurements on the 2XII experiment has been modified to increase its stability, linearity and dynamic range.
A 0.6 T omnidirectional superconducting magnet system
Authors: Wagner D. K.
Published: February 2004

The design and construction of a superconducting magnet system, producing a maximum magnetic field of 0.6 T with any desired direction, is described. The magnet consists of a pair of Helmholtz coils, which can be rotated about a fixed solenoid. The azimuthal angle of the field is selected manually by rotation of the Helmholtz coils, and the polar angle is selected electronically by adjusting the currents in the Helmholtz coils and solenoid appropriately. The latter is accomplished automatically by means of the associated power supply, which is described in detail. The accuracy of the magnet system is approximately 0.8 mT or ½% of the field magnitude, whichever is greater. This system has proved to be indispensable for studies of the rf size effect in pure metals at low temperatures. temperatures.
Pressure-resisting glass cell for high pressure, high resolution NMR measurement
Authors: Yamada Hiroaki
Published: February 2004

The technique of using a pressure-resisting glass cell for high resolution NMR measurement up to 2000 kg/cm2 has been established. The high pressure NMR experiment is shown to be safely conducted on the ordinary high resolution spectrometer. In this report, detailed illustration of the glass cell is described along with the explanation of the device to transmit the pressure, generated in the standard high pressure equipment, to the glass cell located in the high resolution NMR probe.
A pulsed EPR spectrometer
Authors: Huisjen Martin , Hyde James S.
Published: February 2004

A pulsed electron paramagnetic resonance spectrometer is described, and applications of the instrument to the determination of longitudinal relaxation times of dilute solutions of free radicals and of spin-labeled proteins using the saturation-recovery method are discussed. The spectrometer employs a bimodal cavity; the pumping and observing microwave powers are coherent; and all modulating frequencies, delays, and aperture widths are derived from a master clock. Free-induction-decay signals may be observed in such equipment, and special techniques are introduced to avoid interference of these signals with the saturation-recovery signals.
A Fourier transform spectrophotometer for astronomical applications, 700–10 000 cm−1
Authors: Ridgway Stephen T. , Capps R. W.
Published: February 2004

An FTS system has been constructed and operated in the range 700–10 000 cm−1. It has been used primarily for the observation of astronomical objects. Detector-noise-limited performance has been realized through the entire spectral range, and thermal background compensation has been achieved satisfactorily. Two features are emphasized: (1) the flexibility of the spectrometer in both spectral range and choice of resolution, and (2) the photometric quality.
A fast opening mechanical shutter system for flash photolysis experiments
Authors: Yatsiv S. , Ewing J. J.
Published: February 2004

A rotating disk mechanical shutter system has been developed to trigger flash photolysis experiments and prevent scattered light from blinding photomultipliers mounted on a monochromator. Trigger pulses are provided by He/Ne laser light passing through a pinhole in the disk. The monochromator entrance slit is exposed after a variable delay time by a slot in the disk. The system provides fast slit opening times (a few μsec), μsec jitter in delay times, and very high discrimination against unwanted light (rejecting unwanted signals ∼104 times the desired signal). The system is ideal for flash or laser photolysis experiments which must utilize very weak line sources as kinetic probes.
A technique for detecting critical loads in the scratch test for thin film adhesion
Authors: Greene J. E. , Woodhouse J. , Pestes M.
Published: February 2004

A new technique has been developed for detecting critical loads when using the scratch test to determine the adhesion of deposited thin films. In this technique, a 2μ diam 15 keV electron beam impinges upon the sample and the intensity of the induced x-radiation emission from the film and the substrate are monitored simultaneously and used to determine the applied normal load necessary to cause a diamond probe to cleanly strip off the film. Preliminary results are discussed using this technique to study the adhesion of rf sputtered TiC films on high speed steel substrates. Preheating of the substrate prior to deposition was shown to significantly increase the film adhesion.
Dipole approximation for vibrating sample magnetometers
Authors: Foiles C. L. , McDaniel T. W.
Published: February 2004

Standard procedures employed in the use and calibration of vibrating sample magnetometers rely upon the sample being a pure dipole. We have measured deviations from pure dipole behavior in right circular cylinders having a diameter to length ratio of ∼1 to 5. The nature of these deviations and their relation to coil geometry is discussed.
UHF spin-echo spectrometer for the study of impurities in ferromagnetic compounds by nuclear magnetic resonance
Authors: Khoi Le Dang , Veillet P.
Published: February 2004

The distinctive features of the tuned spin-echo spectrometer described here are high sensitivity, high resolution, simple operation, and a frequency variation throughout the range 170–1700 MHz. In addition to magnetic structure and hyperfine interaction studies this apparatus is capable of detecting very small concentration of impurities in ferromagnetic compounds.
Differential photodiode detector for a shock tube laser schlieren system
Authors: Diebold Gerald , Santoro Robert
Published: February 2004

A fast photodiode recording system is described for use in a shock tube laser schlieren system. This device is relatively inexpensive, has a superior signal-to-noise ratio, is insensitive to ripple in the light source, and provides a convenient calibration correction for long term variations in laser intensity. Measurements of both relaxation and dissociation behind shock waves have been carried out using this device.
A circular streak camera tube
Authors: Kalibjian R. , McConaghy C. F. , Coleman L. W.
Published: February 2004

A circular streak camera tube has been developed. Initial application has resolved 6 psec laser pulses from a Nd:glass laser. The theoretical temporal resolution for this tube is estimated to be less than 2 psec.
Detecting near ultraviolet radiation in the presence of visible light
Authors: Bartlett D. F. , Groft J. , White M. G.
Published: February 2004

We describe a system which suppresses the detection of visible sodium vapor light by a factor of about 108 relative to near ultraviolet radiation.
A dropsonde for measuring vertical wind in thunderstorms
Authors: Bushnell R. H. , Glover V. M.
Published: February 2004

A special dropsonde system is described which measures vertical wind through the use of static and dynamic pressure measurements made while the dropsonde falls through a thunderstorm after having been dropped from an airplane at the top of the storm. The system allows ten dropsondes to be used simultaneously. It includes two ground stations which measure the positions of the dropsondes by a transponder method and receive the telemetered pressure measurements. Flight test results are given.
Fast self-compensating ellipsometer
Authors: Mathieu H. J. , McClure D. E. , Muller R. H.
Published: February 2004

A compensating automatic ellipsometer that employs Faraday rotators has been constructed. Speed of response and resolution superior to that of any similar instrument now in use have been achieved through novel Faraday solenoid designs, modulation with high frequency and large amplitude, and refinements in circuitry.
Compensation for limited dynamic range of recording instruments by use of an electronic compressor
Authors: Takeuchi K.
Published: February 2004

Due to the limited dynamic range of magnetic tape recorders, the recording of signals with large peak excursions compared to the average energy requires a choice between over-driving the recorder, or accepting a low signal-to-noise ratio. It is demonstrated that a simple and inexpensive limiter circuit can be successfully used to circumvent this problem. Pseudodata produced in the laboratory were recorded via such a circuit and the performance of the system was evaluated by comparing the calculated probability densities, third- and fourth-order moments, and spectra, of the original and recorded signals.
A high-speed testing machine for biaxial states of stress
Authors: Ohlson Nils-Gunnar
Published: February 2004

The possibility is demonstrated of designing a dynamic testing machine that works according to the principle of electromagnetic loading. The specimen can be subjected to a tensile force and a torsional moment at the same time. The amplitudes of the two loads are varied by changing the voltage of a capacitor battery. The time required to reach the load maximum is determined by the inductance of the electric circuit. It can be varied by shifting primary coils. The ratio between force and torque is varied by using secondary coils with different ratio between mass and moment of inertia. Since optical registration of all the variables measured has been used, electric disturbances from the loading system are eliminated. This machine has been successfully utilized for the determination of the yield surface for certain materials. It has also been used for fracture mechanics experiments at loading rates which exceed those of conventional toughness testing.
Preliminary results with saturable microchannel array plates
Authors: Timothy J. G.
Published: February 2004

Microchannel array plates with a performance comparable to that of a conventional channel electron multiplier have been obtained for the first time. These array plates employ an angled electrostatic field to inhibit the feedback of positive ions within the microchannels. Saturated output pulse height distributions with modal gain values in excess of 107 have been obtained and stable operation demonstrated over a range of ambient pressures from 1×10−7 to 8×10−5 Torr. However, a time-dependent reduction in the gain has been observed with these experimental plates because of the accumulation of charge on the insulating strips which are inserted in the wall of the microchannel to establish the angled electrostatic field.
A combination vacuum furnace-sample chamber for ion implantation
Authors: Doyle N. J. , Bogdon J. M. , Choyke W. J.
Published: February 2004

A vacuum furnace-sample chamber for ion implantation accelerators has been constructed in which bombardments can be performed at temperatures up to 800°C in a vacuum of <2×10−7 Torr. Construction details are given which permit accurate measurements of temperature and ion current.
Electrical performance of a liquid helium-cooled transformer
Authors: Prober D. E.
Published: February 2004

The noise performance of an audio-frequency transformer cooled in liquid helium and combined with a low-noise amplifier is reported. It is found that the transformer, modified for operation at low temperatures, behaves nearly as a noiseless transformer for low source impedances. The minimum noise temperature of the transformer-amplifier combination is 1.8 K for a 3 Ω source resistance. The bandwidth of the cooled transformer is similar to that obtained at room temperature.
A vacuum sample holder for an ion microprobe mass analyzer
Authors: McLaughlin J. F. , Cristy S. S.
Published: February 2004

A vacuum sample holder designed to protect moisture-sensitive or air-sensitive materials from exposure prior to examination in the ion microprobe is described. The advantage of this piece of apparatus is that samples can be loaded in inert atmospheres and transported in vacuum to the ion microprobe for analysis without exposure to moisture or air.
An inexpensive vacuum operated tweezer
Authors: Henrichsen Roy E.
Published: February 2004

The construction of an inexpensive vacuum operated tweezer from a modified aquarium air pump and a disposable syringe is described.
An improved sample drive rod and sample holder for a P.A.R. Foner-type vibrating sample magnetometer
Authors: Drake Robert F. , Hatfield William E.
Published: February 2004

The lower section of the instrumented sample drive rod and the sample holder of a P.A.R. Foner-type vibrating sample magnetometer have been redesigned in order to simplify the disassembly of the rod for removal of the gallium arsenide diode sensor or for repair and to reduce by a significant amount the diamagnetic contribution of these components to the moments of powdered paramagnetic samples studied on the magnetometer.
Pulsed spectrophotometric chemical relaxation measurements
Authors: Olsen Steven L. , Holmes L. Paull , Eyring Edward M.
Published: February 2004

A pulsed power supply for a 450 W xenon arc lamp has been constructed that yields an intense 0.1–10 msec duration square wave flash of light. When combined with an auto-offset device the resulting system provides an intense monochromatic sampling beam for the detection of submicrosecond chemical relaxations in an electric field jump cell.
Application of a vibrating sample magnetometer to magnetic measurements under hydrostatic pressure
Authors: Guertin R. P. , Foner S.
Published: February 2004

A vibrating sample magnetometer has been adapted for use with nonmagnetic high hydrostatic pressure clamps of the type described by Wohlleben and Maple. With this apparatus, the magnetic moment of 0.2 cm3 samples can be measured vs temperature under the simultaneous influence of high magnetic fields (to ≃7 T) and high hydrostatic pressure (to ≃8 kilobar). The sensitivity of the apparatus is at present ≃2×10−3 emu, limited by the reproducibility from run to run of the background moment of the ≃40 g pressure clamp.
Raman spectroscopy under pressure using a diamond pressure vessel
Authors: Wong P. T. T. , Whalley E.
Published: February 2004

A transparent pressure vessel made of diamond has been used to study Raman spectra under pressure. It has the advantage that the relative displacement of the pressurizing pistons can be used to determine directly the change of density of the sample and to determine directly the Grüneisen parameter, and it can easily be heated or cooled over a wide temperature range by a gas stream. The relative displacement of the piston can also be used to identify the phase being examined, which is particularly valuable when a substance with a complicated phase diagram is being studied. The Raman spectra of the translational vibrations of ammonium fluoride II and of the rotational vibrations of anthracene have been studied using the cell.
A coupled laser scanning electron microscope system for investigating laser materials interactions
Authors: Magee Thomas J. , Krehl Peter , Hirschberg Kenneth , Terry Jan
Published: February 2004

This paper reports the development of a coupled laser scanning electron microscope system that enables a laser beam to be introduced into the microscope sample cavity and permits active-mode monitoring of surface modifications during or subsequent to laser pulsing. Instrumentation is also incorporated within the system design for measuring laser induced pressures and equivalent laser coupling coefficients in target materials.
Simple method for adiabatically sampling reactive gaseous systems for mass spectrometric analysis
Authors: Wyatt J. R. , DeCorpo J. J. , McDowell M. V. , Saalfeld F. E.
Published: February 2004

An understanding of the nature of the chemical processes occuring in dynamic, reactive, gaseous systems, such as hydrocarbon flames and chemical lasers, requires knowledge of the chemical species that actually exist in these systems. This paper reports the design and use of a flow-type reactor tube which is passed through the ion source of a mass spectrometer permitting the components of a reacting gas phase system to be extracted adiabatically through a 10 μ orifice into the ion source for analysis. The procedure for drilling this orifice with a focused CO2 laser is presented, together with data which indicate that the reactive species extracted from a flame zone are representative of those existing within the reactive system.
An original measurement of high-field effect on microwave conductivity of semiconductors
Authors: Vindevoghel J. , Leroy Y. , Bruneel C. , Zimmermann J.
Published: February 2004

We describe an original and easy method to measure the microwave conductivity of semiconductors as a function of frequency (up to 140 GHz) and high electric field. This method does not need impedance measurements of the semiconductor and is based on the comparison of thermal and high field effects; measurements are equally possible as a function of lattice temperature. It may be used with sufficiently low-doped semiconductor materials. In the case of silicon, measurements are possible for 1 <pDC<50 Ωcm. An example of results is given for 10 Ωcm n-Si at 300 K and for frequencies equal to 10, 35, and 70 GHz.
The use of a microchannel electron multiplier in spectroscopic instrumentation, involving frequent vacuum breaking
Authors: Rager J. P. , Renaud J. F.
Published: February 2004

The use of microchannel electron multipliers in laboratory instrumentation as a detecting system coupled to an x-uv monochromator or spectrograph, or to a low energy particle spectrometer, corresponds to a particular class of operation in which the detectors are exposed to a very low average input current and to stringent operational conditions, imposed by the instrument concept. It is shown in this paper that frequent vacuum breakings in the system containing the multiplier are not harmful to the stability of its performance. The monitoring of the strip current vs the applied potential is shown to be the simplest and most efficient way of assessing the state of the detector, as, in this particular regime of operation, it is necessary to follow a precise operating procedure to limit spurious secondary effects correlated to the water vapor contamination of its emissive surface.
Reversibility of parameter changes of microchannel electron multipliers due to outgassing
Authors: Rager J. P. , Renaud J. F. , du Montcel V. Tezenas
Published: February 2004

The changes in the gain and strip current characteristics of a microchannel electron multiplier which are caused by outgassing due to ir baking were investigated. Baking at 200°C caused only reversible outgassing. Baking at 250°C for six hours produces irreversible changes. Detailed descriptions of the experimental set up and the controls performed during the baking are given.
Digital plasma density determining device
Authors: Holly D. J. , Lovell T. W. , Sprott J. C.
Published: February 2004

A device is described for measuring the time dependent, volume averaged density of a decaying plasma in a large multimode microwave cavity such as is typically used for plasma confinement studies. The technique consists of filling the cavity with microwave radiation and digitally counting the modes observed with a detector as the plasma decays. Since each mode corresponds statistically to a constant density increment, the density at a given time is proportional to the number of modes that appear as the density decays to zero. Experiments in a toroidal octopole show good agreement with density as measured by other methods.
An improved laser-schlieren system for the measurement of shock-wave velocity
Authors: Bander J. A. , Sanzone George
Published: February 2004

An improved laser-schlieren system for the measurement of shock-wave velocities has been developed which employs a single detector. Calibration of multiple detectors has been obviated. The system has been shown to yield, in addition to the shock-wave velocity, additional information on the arrival time of the contact surface. Shock-tube performance is compared to the predictions of Mirels' theories.
Apparatus for ice point of capsule platinum resistance thermometers
Authors: Martin Douglas L. , Snowdon Robert L.
Published: February 2004

A ``dip-stick'' for holding capsule type platinum thermometers during an ice point determination is described. It appears easy to obtain an ice point stable to ±0.0005°C over many hours.
Diffusion bonding of gold to gold
Authors: Ornellas Donald L. , Catalano Edward
Published: February 2004

Diffusion bonding of gold to gold was investigated at low pressures and temperatures. Mercury, indium, and gallium were the diffusing species; tests as a function of several surface finishes were made. Bonds that exceeded the yield point of gold were obtained with mercury.
Photomultiplier gate with gating times larger than a few microseconds
Authors: Yamashita Mikio
Published: February 2004

A photomultiplier gate based on pulsing the first dynode with two transistor switches in series-shunt connection is described. It provides a high cutoff efficiency with moderate switching speeds and has the advantage of simplicity and versatility.
Pulse technique for measuring intensity variations of continuous lights in comparison with reference scintillation flashes
Authors: Yamashita Mikio
Published: February 2004

A technique is described for measuring both a continuous light and reference scintillation flashes simultaneously by means of gated operation of a single photomultiplier tube. The technique enables us to measure intensity variations of continuous lights with very high accuracy.
A disk chopper for time-of-flight analysis of neutral particles
Authors: Ishimaru Hajime , Satoh Kohtaro
Published: February 2004

A disk chopper for time-of-flight analysis of fast neutral particles (νthermal∼107 cm/sec) is described. The open time of the disk chopper is of the order of 1 μsec, and the closed time is of the order of 100 μsec.
Windowless seal for photomultiplier tubes
Authors: Davis P. , Gingle A.R. , Knasel T.M.
Published: February 2004

Direct sealing of a photomultiplier to a vacuum system eleminates signal loss in an extra window.
High voltage probe for liquid immersion
Authors: Harris N. W.
Published: February 2004

A capacitive voltage divider for the measurement of very high voltage transients in liquid-filled transmission lines has been developed. The probe is suitable for pulse lengths in the range 10 nsec to 1 μsec, and peak voltages between 50 kV and 10 MV. The divider automatically compensates for changes in dielectric constant and loss.
Fast power ``crowbar'' system using a current transformer with extremely low leakage inductance
Authors: Kitagawa S. , Hirano K.
Published: February 2004

A power crowbar system for fast θ-pinch experiments is operated successfully. A current transformer with extremely low leakage inductance is used to reduce the effective impedance of series capacitor system. The leakage inductance of the transformer is reduced to 2 nH by employing a special arrangement of windings. It is demonstrated that a current of 40 kA, the rise time of which is 4 μsec, is maintained for 500 μsec.
A grinding jig for thin foil preparation
Authors: van der Kuur J. H.
Published: February 2004

A technique for the mechanical preparation stage of thin foil specimens is described.
Infinite-hold-time electronic ramp generator
Authors: Tyler Israel L. , Denenstein Arnold , Langenberg D. N.
Published: February 2004

We have designed and built an inexpensive electronic ramp generator which also incorporates the excellent hold-time characteristics of a mechanically operated ramp generator.