bluuebunny/crossref_metadata_2025 huggingface dataset:
H− beam emittance measurements for the Penning and the asymmetric, grooved magnetron surface-plasma sources
Authors: Smith H. Vernon , Allison Paul
Published: March 2003

Beam intensity and emittance measurements show that the H− beam from our Penning surface-plasma source (SPS) has twice the intensity and ten times the brightness of the H− beam from an asymmetric, grooved magnetron SPS. H− ion temperatures of 5 eV for the Penning SPS and 22 eV for the asymmetric, grooved magnetron are deduced by using a simple emittance theory and the present emittance measurements.
Simple radio-frequency apparatus for an X-band microtron
Authors: Spagnolo Bernardo
Published: March 2003

A simple rf apparatus for an X-band microtron is described. The efficiency of the apparatus is estimated and practical considerations on its stability and on the critical coupling between the resonator and the waveguide are given.
Low-temperature demountable joints connecting plastic and metal pipes
Authors: Isagawa Shigeru , Suzuki Shoji
Published: March 2003

A simple method of making a demountable joint between plastic and metal pipes is presented. The joint is helium leak tight even below the λ point.
Wall-less microwave cavity for optical detection of magnetic resonance
Authors: Lee K. M.
Published: March 2003

This paper describes a versatile TE011 cavity for 35-GHz optical detection of magnetic resonance (ODMR) spectroscopy. The cavity provides not only wide optical access but also a high Q factor. A novel design, including externally adjustable coupling and fine frequency tuning, allows quick and simple changing of samples and provides a facility to apply uniaxial stress.
Laser synchronizer for parametric frequency conversion systems
Authors: Schow F. L. , Riazi A. , Gandhi O. P. , Grow R. W.
Published: March 2003

A laser synchronization circuit, applicable to (optical) sum or difference frequency generation systems, is described. The laser synchronizer has yielded excellent results in preventing damage to the mixing crystal of an infrared-to-visible parametric upconverter.
Convenient low-temperature heat sink for electrical leads
Authors: McGrath W. R. , Richards P. L.
Published: March 2003

We describe a simple, efficient method for heat sinking electrical leads in a vacuum cryostat. This method employs commonly available materials. Thermal conductances as high as 20 mW/K with an electrical resistance greater than 109Ω have been measured.
Device for the construction of plane, noninductive, circular coils
Authors: Steinmann Ricardo G. , Bekeris Victoria I. , Beduz Carlos , Juri Luis
Published: March 2003

An apparatus for the construction of plane, noninductive, circular coils is described. These coils are very suitable as electrical heaters to establish a homogeneous heat flow through plane surfaces. Plane copper coils can be used as plane thermometers, where the electrical resistance of the wire is used as the thermophysical property.
Construction and performance of two indium superconducting switches
Authors: Bhattacharyya Bidyut , Gasparini Francis M.
Published: March 2003

We discuss the construction and performance of two indium superconducting thermal switches. We find that a satisfactory performance can be obtained with rather impure indium stock. Comparison with earlier data indicates our work to be the only one where the thermal conductivity of both the normal and superconducting state have been measured below 1.3 K.
Use of high mixing frequencies for rf generation and detection in a multinuclear and cross-polarization magic-angle-spinning NMR spectrometer
Authors: Gross S. , Zumbulyadis N.
Published: March 2003

Use of intermediate frequencies (IFs) above 100 MHz (rather than lower mixing frequencies) in a high-field multinuclear NMR spectrometer simplifies rf generation and detection, reduces rf filtering requirements, increases the frequency range of the rf synthesizers, and minimizes ’’spurious’’ responses. Simplified rf generation, gating, phase shifting, and detection electronics using 120- and 130-MHz IF’s are described for a 4.7-T (200 MHz 1H) NMR spectrometer designed for high-resolution, solid-state, and multinuclear experiments. The circuitry can be readily modified to function with the highest field (500 or 600 MHz 1H) solenoids available.
Active microwave delay line for reducing the dead time in electron-spin echo spectrometry
Authors: Narayana P. A. , Massoth Richard J. , Kevan Larry
Published: March 2003

A simple active microwave delay line to be used with an electron-spin echo spectrometer to reduce the dead time is described. The delay line employs a microwave amplifier and two PIN diode switches as its active components. Tests with a coal sample at room temperature show that the dead time could be reduced from 140 ns without to 60 ns with the active delay line.
Instrument to measure abundance ratios of transient mass species with a quadrupole mass spectrometer
Authors: Hamilton N. , Kelly J. W. , Struve H.
Published: March 2003

A mass-ratio control unit is described which extends the use of a quadrupole mass spectrometer to the measurement of abundance ratios of mass species whose quantities change rapidly with time. The principle used is to sample, alternately, each mass peak at the same time after the excitations or other perturbation process, has been initiated. The delay before sampling and the sampling period can be continuously and precisely varied over a range of 1–200. The design features low cost, generality of application, simplicity of use, and stable and reproducible performance.
High-resolution imaging with a two-dimensional resistive anode photon counter
Authors: Firmani C. , Ruiz E. , Carlson C. W. , Lampton M. , Paresce F.
Published: March 2003

We describe a method for achieving high spatial resolution readout of individual photoelectron events using microchannel plates and a resistive anode. Specifically, we employ a clamped pair of microchannel plates (’’V geometry’’) followed by a gap and a clamped triplet of microchannel plates (’’Z geometry’’) in cascade, in order to achieve a high (3×107) stable electron gain. This high gain in turn allows the position determination of each photoelectron event with a very high signal-to-noise ratio, thereby giving a theoretical spatial resolution limited chiefly by the microchannel plate channel spacing rather than by the anode signal-to-noise ratio. Our first model of this detector is a windowless vacuum-ultraviolet image sensor, and demonstrates 500×500 pixel images (50 μm FWHM over a 25-mm circular field of view). Our spatial resolution is presently limited by the microchannel structure and by the error distribution in our analog pulse ratio electronics. High-current microchannel plates are employed to avoid serious gain variations with respect to changing count rate. Although our present detector hardware is a demountable assembly for laboratory experimentation, the mount design is compatible with planar, remotely-processed, proximity-focused photocathodes, and will shortly be evaluated as a sealed detector for echelle spectroscopy at visible wavelengths.
Microoptic double beam system for reflectance and absorption measurements at high pressure
Authors: Syassen K. , Sonnenschein R.
Published: March 2003

A microoptical double beam system for reflectance and absorption measurements from small samples (less than 100 μm size) in the spectral range of 0.5–5 eV is described. In conjunction with a diamond anvil high-pressure cell the system is particularly useful for optical reflectivity measurements at pressures up to 400 kbar. Examples are furnished illustrating the use of the system in high-pressure investigations of the stage two graphite intercalation compound C24SbCl5 and of solid oxygen. We briefly comment on Raman spectroscopy at high pressure.
Quality factors of a three-mode 50-kg gravitational radiation antenna at liquid helium temperature
Authors: Cosmelli C. , Richard J.-P.
Published: March 2003

A three-mode 50-kg gravitational radiation antenna has been tested in the temperature range 5–15 K. Acoustic losses in the Al–Nb system are estimated. Projections are made for the quality factor of each mode of a 1500-kg antenna. The fluctuations resulting from the thermal noise sources associated with the projected mechanical damping are estimated at 1.5×10−5 K in a system at 0.05 K.
Twin-slope method of measurement of specific heat and coating absorptance of solid materials
Authors: Hsieh C. K. , Wang X. A.
Published: March 2003

A twin-slope method has been developed to measure the specific heat and coating absorptance of solid materials. The method is comprised of measuring the temperature–time history of the sample when irradiated by a lamp that is commonly used in radiometry as the irradiance standard. Then by monitoring the heating and cooling rates of the sample at the identical sample temperature, the heat loss coefficient can be canceled out in the analysis. The method permits measurements of these properties independent of the loss coefficient, which also enables the test to be made even in a nonevacuated environment. As a demonstration to show the feasibility of the method, a copper and a paint sample are used for tests. The results are found to be good. A critique is also given in the paper to reveal the true strength and weakness of the method.
Simple vibrating sample magnetometer
Authors: Gerber J. A. , Burmester W. L. , Sellmyer D. J.
Published: March 2003

Design features of a simple and relatively inexpensive homemade vibrating sample magnetometer are described. These include signal electronics which employs an analog divider rather than the usual electromechanical feedback circuit, and a method for gas cleaning during sample changes allowing long experiments at liquid helium temperatures in a superconducting solenoid.
Design charts for Tesla-transformer-type relativistic electron beam generators
Authors: Matsuzawa Hidenori , Suganomata Shinji
Published: March 2003

The obtainable high voltage is more sensitive to the tuning between the primary and the secondary circuit than to the coupling between them. This is confirmed both numerically and experimentally. Fundamental designing charts and a simple diode chamber are presented.
Design and construction of a high-stability, low-noise power supply for use with high-resolution electron energy loss spectrometers
Authors: Katz J. E. , Davies P. W. , Crowell J. E. , Somorjai G. A.
Published: March 2003

The design and construction of a high-stability, low-noise power supply which provides potentials for the lens and analyzer elements of a 127° Ehrhardt-type high-resolution electron energy loss spectrometer (HREELS) is described. The supply incorporates a filament emission-control circuit and facilities for measuring electron beam current at each spectrometer element, thus facilitating optimal tuning of the spectrometer. Spectra obtained using this supply are shown to have a four-fold improvement in signal-to-noise ratio and a higher resolution of the vibrational loss features when compared with spectra taken using a previously existing supply based on passive potential divider networks.
Apparatus for high-resolution vibrational electron energy-loss spectroscopy of solid surfaces
Authors: Nishijima M. , Masuda S. , Kobayashi H. , Onchi M.
Published: March 2003

A high-resolution vibrational electron energy-loss spectrometer of 127°-cylindrical electrostatic deflection type has been constructed for surface studies. In the direct mode, an electron current at the collector entrance of 2.3×10−11 A is obtained with the energy spread (full width at half-maximum) of 60 cm−1 for electrons whose energy at the sample position is 5 eV. A ghost reduction slit is used to suppress spurious peaks due to the electron reflection from electrodes of the analyzer. Electron energy-loss spectroscopy can be combined in situ with low-energy electron diffraction, Auger electron spectroscopy, and thermal-desorption mass spectroscopy. Design and performance of the apparatus are reported. The vibrational spectrum of the Ni(110) (1×2)-H surface formed at room temperature is presented, and the location of hydrogen atoms on the surface is discussed.
Ultrahigh vacuum apparatus for combined low-energy electron diffraction, Auger spectroscopy, MeV ion scattering, and nuclear microanalysis
Authors: Sitter C. , Davies J. A. , Jackman T. E. , Norton P. R.
Published: March 2003

A bakable target manipulator/2-axis goniometer has been developed which permits high-precision MeV channeling studies and nuclear microanalyses to be performed over a wide temperature range (150–1000 K) under ultrahigh vacuum conditions (7×10−9 Pa). Design and performance features of the goniometer and target chamber and of the two-stage differentially pumped beam-line connection to a 2.5-MV Van de Graaff accelerator are discussed. A transmission Faraday cup in conjunction with a set of optically positioned standard targets enables the various ion beam analyses to be performed with an absolute accuracy of 1%–2%.
Self-extraction negative ion source
Authors: Leung K. N. , Ehlers K. W.
Published: March 2003

A large multicusp negative ion source has been constructed to generate H− or D− ions for high-energy neutral beam systems. With the presence of cesium, the source has produced a steady-state H− ion beam current greater than 1 A with an impurity level less than 1%. The vertical and horizontal profiles of the self-extracted beam have been measured with a gridded Faraday cup. The gas efficiency of the source and the electron component in the accelerated beam have been measured for two different pumping conditions.
Initiation of hot cathode arc discharges by electron confinement in Penning and magnetron configurations
Authors: Kovarik V. J. , Hershcovitch A. I. , Prelec K.
Published: March 2003

The paper describes a method to ignite hot cathode arc discharges by using ’’start-up’’ glow discharges in magnetron and Penning configuration. This method has been shown to provide the ignition of large, tantalum hollow cathode discharges even in a restricted space. It is simple, reliable, and requires lower voltages than some of the other methods.
Study of the characteristics of thermionic ionization detectors
Authors: Thompson D. C. , Stoicheff B. P.
Published: March 2003

Measurements of gain and noise in a thermionic detector (with an electrostatically shielded region) using Rb and K vapor are described. An approximate theory for space-charge limited operation is developed and found to agree with observations. Improvements in diode design are suggested.
Development of single-particle detectors for keV ions
Authors: Rinn Klaus , Müller Alfred , Eichenauer Horst , Salzborn Erhard
Published: March 2003

A series of three single-particle detectors for the detection of ions with keV energies has been built and investigated by experiment and by computer simulation. The incident ions hit a converter electrode and produce secondary electrons which are accelerated onto the funnel of a channel electron multiplier (CEM). Experimental information was obtained for secondary electron yields, γ, of slow multiply charged ions and the influence of γ on the detector efficiency ε is discussed. Efficiencies ε near unity have been achieved for ions incident on an effective area of more than 20 mm diameter. ε is greater than 90% for all ions and for count rates up to 3×104 s−1. The performance at higher count rates can probably be improved with a CEM of lower resistance.
Effects of perturbing magnetic fields on the performance of photoelectronic sensors
Authors: Coleman C. I.
Published: March 2003

Photoelectronic sensors are all susceptible, to a greater or lesser degree, to the influence of perturbing ambient magnetic fields. Theoretical and experimental results are presented for the effects of axial and transverse magnetic fields on the various types of image intensifiers (including microchannel plate devices), TV camera tubes, and photomultipliers. The most immediately apparent effects are image displacement and loss of focus; additionally, changes in gain and certain other more subtle effects may be encountered. Numerical and graphical or nomographic methods for determining the magnitudes of the major effects in the different electron-optical systems at various voltages are provided, and electrode supply tolerances may be obtained therefrom. The nomographs can also be used to derive the focus conditions for magnetically focused systems. Interpretations of previously unexplained phenomena in the behavior of microchannel plates are also presented.
Experimental system for studying the stimulated Cerenkov interaction
Authors: Kimura W. D. , Edighoffer J. A. , Piestrup M. A. , Wang D. Y. , Pantell R. H.
Published: March 2003

An experimental system has been developed in which momentum exchange between laser light and relativistic electrons is achieved using the stimulated Cerenkov interaction. The interaction occurs within a gas which retards the phase velocity of the light wave in order to allow wavevector matching with the electron velocity. Light at 1.06 μm from a 30-MW Nd:YAG laser intersects 50–100 MeV electrons at angles of 17–18 mrad in hydrogen or methane gases. A spectrometer magnet and scintillation detector system verifies the change of the electron beam energy spectrum in the presence of the laser and as a function of the refractive index of the gases. The electron beam transport, laser, gas cell, and detector systems are described. Experimental data obtained using this system are also given. Possible applications of this work include optical klystrons and laser-driven particle accelerators.
Modification of a cylindrical mirror analyzer for angle-resolved electron spectroscopy
Authors: Knapp J. A. , Lapeyre G. J. , Smith N. V. , Traum M. M.
Published: March 2003

A commercial double-pass cylindrical mirror analyzer has been modified for angle-resolved electron spectroscopy by insertion of an aperture-containing drum within the inner cylinder of the second stage. Three operating modes are possible; high angular resolution (±2°), low angular resolution (±6°), and complete retraction of the drum to permit normal angle integration. The gearing mechanism for rotation and translation of the drum is described, and the performance of the analyzer is discussed.
Containerless melting and solidification of materials with an aerodynamic levitation system
Authors: Oran W. A. , Berge L. H.
Published: March 2003

A simple aerodynamic system which can heat, melt, cool, and solidify (in a containerless fashion) small, roughly spherical (diameter 1.5–4 mm) samples of materials is described. The principal components of the system are an aerodynamic levitation tube and an elliptical radiant heater. The materials processed, i.e., melted and resolidified, in the system include lead and an alkali borosilicate glass. The processing of a glass bead is described. In addition, the physical phenomena which may generate the levitation force in the tube are briefly discussed.
Two-wavelength infrared pyrometer for large and rapid temperature changes
Authors: Beckwith P. J. , Crane K. C. A.
Published: March 2003

A two-wavelength infrared pyrometer is described which is suitable for monitoring the rapid heating of materials by cw lasers or electron beams. Other existing two-wavelength pyrometers do not appear to have the combination of features required for this application, namely fast response, large dynamic range, and high sensitivity. With the present instrument a temperature range from 600 to 3000 K may be traversed in times of down to about 100 ms, with a spatial resolution of 1 mm, and with an accuracy of a few percent. The optical system includes a transparent chopper wheel on which a pattern of transmission filters has been vacuum deposited through masks. The electronic system combines a divider circuit with a fast-response automatic-gain-control loop. Results are given of the use of the pyrometer with laser-heated plates of aluminum and titanium.
Integrated multiple mixing chamber
Authors: Rosenbaum Ralph
Published: March 2003

The integrated multiple mixing chamber is a simple and novel component that replaces the conventional single mixing chamber in the He3 circulating dilution refrigerator. The chamber incorporates or ’’integrates’’ many mixing chambers in a single block of low thermal conducting material; the mixing chambers are interconnected in tandem by internal channels and by internal holes. Thermal isolation between adjacent mixing chambers is achieved through the Kapitza boundary resistance between the helium liquids and the walls of each mixing chamber, and through the low thermal conductance of the body material. Theoretically, the integrated chamber is expected to provide a reduction in temperature by a factor of three to ten over the minimum temperature of a single mixing chamber, depending upon the magnitude of the heat leaks and the He3 circulation rate. Experimentally, temperatures of 4.8 mK have been observed as compared to a 12 mK minimum temperature obtained in a single mixing chamber.
Modulation detection of fluorescence photobleaching recovery
Authors: Lanni Frederick , Ware B. R.
Published: March 2003

We have combined the simplicity of the periodic pattern method of photobleaching with the signal processing advantage of scanning detection. A periodic photobleaching pattern is produced in the sample by brief, intense illumination through a grating. The grating is then translated at constant speed through the reference beam to produce a moving pattern on the specimen. A modulation of fluorescence emission is produced as the bleached pattern and the illumination pattern fall into and out of phase. The resulting photocurrent contains an ac component whose frequency is determined by the spacing and velocity of the grating and whose amplitude relative to the dc component is determined by the extent of photobleaching. The decay constant of the ac component of the photocurrent is determined by the spacing of the grating and the diffusion coefficient of the labeled species. The major distinct advantages of the technique are: (1) the decay at the fundamental frequency is observed in real time, (2) adventitious photobleaching during the monitoring phase of the measurement does not perturb the determined parameters, (3) the measurement is insensitive to dc drift components, and (4) the measurement is insensitive to motion of the specimen. These substantial advantages are implemented by straightforward modifications in standard methodology.
Unitized paramagnetic salt thermometer
Authors: Abraham Bernard M.
Published: March 2003

The details of construction and assembly of a cerous magnesium nitrate (CMN) paramagnetic thermometer are presented. The thermometer is a small unit consisting of a primary, two secondaries, the salt pill, and thermal links. The thermometer calibration changes very little on successive coolings and is reliable to 35 mK. A typical calibration curve is also presented.
Multichannel recorder–display system based on an Apple II microcomputer
Authors: Lee Young H. , Park K. T.
Published: March 2003

An Apple II microcomputer-based system for recording, viewing, and plotting of multichannel analog signal is described. The system described is inexpensive and flexible and requires a minimum of interfacing effort.
Technique for direct phase demodulation in heterodyne interferometry
Authors: Jacobson A. R.
Published: March 2003

FM demodulation techniques have been applied to an existing heterodyne plasma interferometer. The direct phase readout so obtained is useful both for ambient density and for forward-scattering measurements.
Hybridized dead-weight piston gauge up to 1 GPa
Authors: Wiśniewski Roland
Published: March 2003

A hybridized dead-weight piston gauge consisting of a simple and a re-entrant piston-cylinder system is described. The device has an accuracy of 0.1% and can operate up to 1 GPa. The nominal diameter of the gauge piston is 2 mm, initial clearances 4 and 10 μm. The expression for effective area, experimental results confirming the idea of the gauge, and some meterological data determining their accuracy are given.
Low-frequency computerized lock-in amplifier
Authors: Toney Jeffrey H. , Demas J. N.
Published: March 2003

A simple, low-cost, computerized, very low-frequency lock-in amplifier is described for signal-to-noise enhancement. This system is based on a low-cost digital multimeter connected to a microcomputer through an IEEE-488 interface. The system works with signals that can be modulated at ≃1 Hz. The signal-to-noise ratio, calculated in real time during data acquisition, can be used to terminate acquisition either after the desired signal-to-noise ratio is reached or after a specified number of samples has been averaged. The system is also suitable for eliminating large constant backgrounds on small signals. Possible applications include spectrophotometry, spectrofluorimetry, and ac calorimetry.
On arc prevention in glow discharge treatment
Authors: Brandt B.
Published: March 2003

A list of countermeasures against destructive arcing in glow discharge treatment of metal surfaces is given. A number of standard precautions is briefly reviewed and it is pointed out that one can provide an independent cathode thus taking the workpiece out of the electrical circuit. The workpiece has to be heated and the active species from the discharge have to diffuse to the workpiece. Large objects can be treated by several discharges.
Correction of Dasibi ozone measurements for the weak-line contribution
Authors: Hagemeyer J. R. , Ainsworth J. E.
Published: March 2003

Measurements made by means of the Dasibi UV-absorption ozone photometer are customarily converted to ozone number densities by assuming that it is only the absorption of the strong 253.65-nm mercury-vapor line which is measured by the Dasibi. Paur and Ellis (EPA-600/4-79-057, September 1979) have shown that the Dasibi also measures the absorption of a number of the very weak mercury-vapor lines in the vicinity of the 253.65-nm line and that as a result the calculated ozone number densities must be increased by (0.5±0.5) percent. We have made measurements which show the dependence of this weak-line correction upon the lamp current and the lamp-housing temperature of the Dasibi UV light source, and have reduced the uncertainty in the correction by an order of magnitude. The weak-line corrections range from 0.33% to 0.74%.
Field emission cathodes using commercial carbon fibers
Authors: Prohaska R. , Fisher A.
Published: March 2003

Field emission cathodes have been constructed using commercial carbon fiber products. Using carbon yarn, emission starts at 5–15 kV and 10–30 kV/cm. Current densities up to 10 A/cm2 are obtainable over 100 cm2. Felt and cloth of carbon fiber emit at 50 kV/cm and up, and allow current densities of 10–1000 A/cm2 over 10–100 cm2.
Versatile and user-friendly computer system for the CAMECA IMS-300 secondary ion mass spectrometer
Authors: Van Craen M. , Van Espen P. , Adams F.
Published: March 2003

A microcomputer using CAMAC as an interface was implemented on the CAMECA IMS-300 ion analyzer. The development of hardware and software resulted in a versatile system, allowing higher precision and accuracy of the ion intensity measurements, very accurate mass calibration, larger dynamic intensity range, and considerable improvement of detection limits compared with the original system. The hardware and software components used are described and examples of the advantages of the computer system over the analog recording mode are presented.
Reduction of gas flow into a hollow cathode ion source for a neutral beam injector
Authors: Tanaka Shigeru , Akiba Masato , Arakawa Yoshihiro , Horiike Hiroshi , Sakuraba Junji
Published: March 2003

Experimental studies have been made on the reduction of the gas flow rate into ion sources which utilize a hollow cathode. The electron emitter of the hollow cathode was a barium oxide impregnated porous tungsten tube. The hollow cathode was mounted to a circular or a rectangular bucket source and the following results were obtained. There was a tendency for the minimum gas flow rate for the stable source operation to decrease with increasing orifice diameter of the hollow cathode up to 10 mm. A molybdenum button with an appropriate diameter set in front of the orifice reduced the minimum gas flow rate to one half of that without button. An external magnetic field applied antiparallel to the field generated by the heater current stabilized the discharges and reduced the minimum gas flow rate to one half of that without field. Combination of the button and the antiparallel field reduced the minimum gas flow rate from the initial value (9.5 Torr 1/s) to 2.4 Torr 1/s. The reason for these effects was discussed on the basis of the theory for arc starvation.
Compact antiresonant ring mode-locking device
Authors: Vanherzeele H.
Published: March 2003

We present a compact and inexpensive monolithic prism assembly which can easily be substituted to one end mirror of a conventional laser. While offering all of the advantages of a conventional multielement antiresonant ring colliding pulse mode-locking setup, our device does not require more alignment than a single cavity mirror does.
Miniature pneumatic tensile stage for scanning electron microscopes
Authors: Hobbs S. Y.
Published: March 2003

A miniature tensile stage designed to operate at very low levels of vibration under fixed, variable, and cyclic loading conditions is described. The device, which can produce loads of up to 20 lbs, is suitable for carrying out tensile tests, creep and stress relaxation studies, and fatigue experiments in the scanning electron microscope.
High recovery voltage switch for interruption of large currents
Authors: Ford R. D. , Vitkovitsky Ihor M.
Published: March 2003

An opening switch for interrupting 50-KA currents in inertial–inductive storage systems has been developed. A switch arc voltage of 2 kV (3.3 kV/cm) has been obtained using explosive cutting of the current-carrying sheet. A single-gap switch interrupts a current of 7 kA per cm of sheet width in ∼10 μs. Recovery fields of up to 100 kV/cm were achieved at 2 kA/cm, at 35 μs after interruption. The switch is designed for long (∼1 s) current-carrying time associated with homopolar generator charging of inductors.
Fast determination of the field modulation amplitude of a saturation transfer electron paramagnetic resonance spectrometer at various field modulation frequencies
Authors: de Jager P. A. , Bremer H. J. L.
Published: March 2003

An ac voltmeter is described for the determination of the field modulation amplitude at various frequencies. The accuracy is 5% from 1 to 200 kHz. This ac voltmeter is very useful in ST–EPR spectroscopy at various modulation frequencies because it eliminates the time-consuming calibration of the modulation amplitude.
Design and performance characteristics of a cw subsonic HF chemical laser with 120 W power output
Authors: Babarogić Z. , Belić I. , Mendaš I. , Trtica M.
Published: March 2003

The design and performance of a transverse flow cw subsonic HF chemical laser are presented. The laser provides up to 46 W (120 W) cw output power with argon (helium) as a diluent gas on a number of Pv(J) lines corresponding to v = 1→v = 0 and v = 2→v = 1 vibrational transitions of hydrogen fluoride. The measured values of electrical efficiency, chemical efficiency, and specific power with argon (helium) were 0.4% (0.8%), 1.2% (3.1%), and 13 J/g (66 J/g), respectively.
Measurement and control of subangstrom mirror displacement by acousto-optical technique
Authors: Wang C. P. , Varwig R. L. , Ackman P. J.
Published: March 2003

Control of laser mirror spacing and angular orientation is important for laser frequency and mode stability. A wave front sensor that employs acousto-optic modulation and optical heterodyning has been applied in conjunction with a servo-control loop to control mirror motion. The measurement and control of subangstrom mirror displacements are possible using this system. Experimental results are presented that indicate closed-loop control of mirror displacement to within 0.06 nm.
Pyroelectric-vidicon-aided infrared spectrometer for balloon experiments
Authors: Matsuzaki A. , Nakamura Y. , Itoh T.
Published: March 2003

A new type of IR spectrometer has been developed for balloon experiments on spectral measurement in the 2–5-μm region with a solar occultation method. The spectrometer is based on multichannel spectroscopy using a pyroelectric vidicon as the detecting sensor. In order to improve the spectral resolution and the dynamic range of the signal, the spectrum is divided into three spectra which are focused in parallel to each other on the target of the vidicon. The present spectrometer turns out to be applicable to a spacecraft-borne IR spectrometer.
High-power radio frequency irradiation system with automatic tuning
Authors: Butler Leslie G. , Reiner Carl , Brown Theodore L.
Published: March 2003

A high-power radio frequency irradiation system that can be tuned automatically is described. A rf magnetic field, H1, of up to 1.8 mT can be maintained over the frequency interval from 0.01 to 6.4 MHz with low harmonic distortion. The system is useful in a nuclear quadrupole double resonance spectrometer, and in other nuclear resonance experiments involving frequency sweeps.
Frequency-scanning marginal oscillator for ion cyclotron resonance spectroscopy
Authors: Kemper Paul R. , Bowers Michael T.
Published: March 2003

A number of ion cyclotron resonance applications have arisen in the past few years which require a frequency-scanned detection system. Since the traditional marginal oscillator detector has always been a fixed-frequency detector, alternative detection techniques such as bridge circuit detectors have become widely used. In this paper we present an alternative to the bridge detector, namely, a frequency-scanning marginal oscillator. Requirements and modifications necessary to convert a marginal oscillator to frequency scanning operation are discussed in detail and the necessary circuit diagrams presented. Finally, a theoretical comparison is made between bridge circuit and marginal oscillator sensitivities.
Characteristics of a gamma-ray detector using a bismuth germanate scintillator
Authors: Okajima Kenichi , Takami Katsumi , Ueda Ken , Kawaguchi Fumio
Published: March 2003

Characteristics of a gamma-ray detector that utilizes a 24×24×15-mm3 bismuth germanate (BGO) scintillator are measured. Fluorescent light output measured with a BGO crystal coupled to a R1306 photomultiplier (Hamamatsu TV) is found to be 15% that of a NaI(T1) scintillator for incident photons of a given energy. The FWHM of the time spectrum, measured with two BGO crystals coupled to R329-2 photomultipliers, is equal to 2.0 ns for a 68Ge–68Ga source at room temperature.
Portable precision dc voltage–current transfer standard for electrometer calibration
Authors: Landis G. , Godwin M.
Published: March 2003

A circuit design is presented for an instrument providing a highly stable and fully adjustable voltage and current in the range of 0–1.999 V or 0–199.9 mV and 10−11–10−15 A. This instrument is used to verify the calibration and performance of dc and vibrating reed electrometers and chart recorders on mass spectrometers of the USGS Isotope Laboratories in Denver.
Simple high-pressure magnetic pump
Authors: Ziger David H. , Eckert Charles A.
Published: March 2003

A simple high-pressure magnetic fluid circulation pump has been designed and built specifically for use in isothermal mixing experiments. Flow rates exceeding 10 cc/min at pressures up to 350 bars have been easily achieved.
Fabrication of extractor grids for neutral beam sources
Authors: Brouchous D. A. , Conrad J. R.
Published: March 2003

The fabrication of tungsten wires for use in extractor grids on neutral beam ion sources is described. The tungsten wires are machined from 0.152-cm-diam tungsten wires into triangular wires by a three-step grinding process. These grid wires have been used in the neutral beam sources for Phaedrus (6 keV beams) and for the Wisconsin Levitated Octupole (15 keV beams). The beam angular divergence is comparable to that obtained from commercially supplied grid wires.
APACHE: A low-background hard x-ray spectrometer for 10.6-μm laser fusion experiments
Authors: Priedhorsky W. , Lier D.
Published: March 2003

We describe a ten-channel hard x-ray spectrometer, named APACHE, which is used to diagnose target x-ray spectra at the HELIOS 10.6-μm laser fusion facility. Each channel consists of a filter, scintillator, and photodiode detector. Spectral bands are defined by filtration, and the choice of scintillator type and thickness. This scheme of channel definition gives broad spectral response channels, but it also yields large signals at the detector. This allows the use of insensitive photodiodes as detectors, reducing the effect of penetrating background. The two scintillators used, cesium fluoride and a lead-loaded plastic scintillator (NE142), have time responses of a few nanoseconds. The system is thus unable to resolve the 1-ns laser pulse, but is useful in isolating the target signal from laser electron beam, and possible target neutron, backgrounds. Cesium fluoride has a low scintillation response for hν⩽100 keV, and is used for higher-energy channels; NE142, which is self-absorbing in thick sections, is used for low-energy channels. Both scintillators have been shown to be stable over a time scale of months. Because of the broad spectral response functions, the channel signals are fit to an exponential spectrum. Very good fits are obtained by this method. The APACHE results are corroborated by an independent thermoluminescent dosimeter system. A fast detector is used to provide ∼400 ps time resolution in a separated broad high-energy channel (named CYCLOPS). The agreement of the fast signal with that predicted from the APACHE spectrum demonstrates that APACHE measures the prompt hard x-ray signal. A linear relation is found between fastest ion velocity and APACHE kTH, providing an additional check of APACHE results. The APACHE system has proved convenient to field and free of background, and is a standard diagnostic at the HELIOS facility. We routinely measure hard x-ray yields of tens of joules from laser shots on high-Z targets.
Scalings for a traveling mirror adiabatic magnetic compressor
Authors: Bellan P. M.
Published: March 2003

Detailed practical scaling relations for a traveling mirror adiabatic magnetic compressor are derived, and an example is given of how this technique could be used to translate, compress, and heat the Los Alamos FRX-C reversed field theta pinch plasma.
High-pressure stopped-flow apparatus for the study of fast reactions in solution
Authors: Ishihara Koji , Funahashi Shigenobu , Tanaka Motoharu
Published: March 2003

A high-pressure stopped-flow apparatus with spectrophotometric detection has been exploited, which enables one to follow fast reactions in various media at pressure up to 2000 kg cm−2. The rate of the following reactions was successfully measured at various pressures: (1) reaction of nickel (II) nitrate with 1-(2-pyridylazo)-2-naphthol in glacial acetic acid and (2) reaction of nickel (II) perchlorate with isoquinoline in N,N-dimethylformamide. The apparatus allows the measurement of activation volumes for reactions with half-lives longer than several milliseconds.
Stress distribution in cylindrical windows for optical high-pressure cells
Authors: Alt H. C. , Kalus J.
Published: March 2003

Calculations are described of the stress distribution in optical high-pressure windows consisting of a transparent cylinder which is supported by a plug bearing a hole as optical aperture. The method based on an extension of Love’s strain function, the Galerkin vector, takes advantage of the axisymmetry of the arrangement, thus allowing very economic computations. The results apply to homogeneous, isotropic materials in the linear-elastic region. Critical stress concentrations exist at the unsupported area, as the radial stress component will most probably become positive there and near the edge of the support where the maximum shear stress occurs. It is shown that, in general, thickness to diameter ratios greater than 0.5 will not improve the pressure resistance of the window significantly.
Electron spectrometer for spin-polarized angle- and energy-resolved photoemission from ferromagnets
Authors: Kisker E. , Clauberg R. , Gudat W.
Published: March 2003

An electron spectrometer allowing energy- and angle-resolved spin-polarized photoemission from ferromagnets is described. The system is designed for use with samples magnetized perpendicular to the photoelectron extraction direction (transverse magnetization geometry) and a Mott detector (100 keV) for the spin-polarization measurements. It transforms the emitting spot at the magnetic photocathode to a parallel beam which matches the size of the apertures of the Mott detector, resulting in a high efficiency. Angle selection is achieved despite initial acceleration of the photoelectrons. Energy resolution is obtained with a 90° spherical deflector connected to the Mott detector whose apertures act as the spectrometer exit slits. The performance of the setup is demonstrated by measurements with an evaporated iron film and a neon resonance lamp as light source. Sample geometries for use with the transverse magnetization configuration are discussed.
Microprocessor-based unit for measurement of spectroscopic splitting factors (g values) in electron paramagnetic resonance spectroscopy
Authors: Wormald D. I. , Sagstuen E. , Vistnes A. I.
Published: March 2003

A g-value processor has been constructed for use with an electron paramagnetic resonance spectrometer, to calculate and display g values and place g markers on the chart recorder. It is also used to control the magnetic field and signal averager, for amplitude measurements at field positions determined by two g values. The device is based on a 6504 8-bit microprocessor and is operated from a 4×4 keypad. It includes a system for magnetic field measurement and control which counts the resonant frequency signal from a nuclear magnetic resonance gaussmeter and it is provided with the IEEE 488 interface in order to read a microwave frequency counter.
High-temperature NMR probe
Authors: Aurora T. S. , Day S. M.
Published: March 2003

A nuclear-magnetic-resonance probe has been developed to investigate the behavior of solid electrolytes at high temperatures. The probe will fit in a 44-mm-wide magnet pole gap while allowing orientational studies. The sample chamber may be evacuated to minimize oxidation. Sample temperatures in excess of 1100 K can be obtained with modest input power.
Dielectric relaxation measurements in the ultralow frequency region
Authors: Takeishi S. , Mashimo S.
Published: March 2003

Refinements in the dc transient current method are described for precision measurements of dielectric permittivity from 50 mHz down to 1 μHz. Relaxation increment, relaxation time, and distribution of the relaxation times for a test sample of poly(vinyl acetate) have been measured with satisfactory accuracy as judged by comparison with results from steady-state measurements. Convenient procedures for numerical Fourier transformation of the observed current are described to easily obtain the complex permittivity.
Automatic system for analysis of micromechanical properties
Authors: Etienne S. , Cavaille J. Y. , Perez J. , Point R. , Salvia M.
Published: March 2003

This paper gives a description of an automatic and programmable device especially designed for the analysis of the mechanical properties (dynamic modulus of elasticity, creep, and stress relaxation) of samples under light loads. This microprocessor-controlled device is a torsion pendulum operating in forced oscillations in the very low-frequency range (VLF : 10−5–1 Hz). Its characteristics are compared with those of other existing equipments and some typical results are presented in order to illustrate the operating range of this pendulum.
Electric field meter based on the breakdown of gases
Authors: Friedmann D. E. , Curzon F. L. , Feeley M. , Young Jeff F. , Auchinleck G.
Published: March 2003

A portable device for measuring low-frequency electric fields is described. The sensor for the device makes use of the breakdown of gas contained in a glass bulb. The shape of the bulb determines the directional properties of the sensor. A spherical bulb has a spatially isotropic sensitivity, whereas a cylindrical bulb responds, primarily, to the electric field component along its axis. The operation of the device with both types of sensor has been studied in electrical fields typical of high-voltage transmission lines and switch yards.
Technique for fabricating integrated optical devices in glasses by electric field enhanced ion diffusion
Authors: Persechini David L.
Published: March 2003

An apparatus is described for electric field enhanced ion exchange, with excellent electrode isolation. This apparatus has been successfully used to fabricate channel waveguides for fiber optics applications.
Conversational interfacing between a HP 9825 and a CBM 8032 (PET) via an IEEE-488 bus
Authors: Rouff M. , Vibet C. , Varoquaux E.
Published: March 2003

The interconnection of two data-acquisition systems controlled, respectively, by a Hewlett–Packard HP 9825 and a Commodore CBM 8032, via an IEEE-488 (GPIB) bus is described. The interface, whose schematics are given, solves the problems of compatibility between the two computers.
Grinding jig for mechanical thinning of gaskets for high-pressure cells
Authors: Sankara Sastry V. , Khanna Rita , Rajan K. Govinda
Published: March 2003

A simple grinding jig makes it possible to smoothly grind gaskets and discs to thicknesses of a few hundred microns.
Automatic liquid helium transfer system
Authors: Ihas G. G. , Spencer G. F. , Alexander P. W.
Published: March 2003

A simple system is described for automatic control of the liquid helium transferred to cool down a cryostat when using hydrogen exchange gas. The system not only frees personnel from tending to this (typically) 4 h task, but makes it impossible to collect liquid in the Dewar until the apparatus is sufficiently cold.
Simple differential lock-in amplifier for optical measurements
Authors: Riess I.
Published: March 2003

A lock-in amplifier for chopped optical signals is described. It is simple but effective. Its special features are: (a) The system reduces the effect on the experimental results of fluctuations in the light source intensity. (b) The locking in can be carried out with a chopper operating with a variable frequency. (c) A series of odd harmonics synchronous with the chopper can be chosen to be highly rejected. In particular, a signal due to pickup of the 3rd harmonics can be made small.
Double beam fluorescence lifetime spectrometer with subnanosecond resolution: Application to aqueous tryptophan
Authors: van Resandt R. W. Wijnaendts , Vogel R. H. , Provencher S. W.
Published: March 2003

An instrument capable of accurately measuring fluorescence lifetimes with subnanosecond resolution is described. The equipment consists of a mode-locked frequency doubled dye laser and a channel plate photomultiplier. The time dependence of the fluorescence is measured using the single photon counting technique. The apparatus response function which was found to be count rate dependent (FWHM = 150 ps at 10 kHz) is monitored simultaneously with the sample fluorescence with the same detection equipment by using a double beam and optical delay technique and a standard reference (p-terphenyl). With this technique, typical problems such as count rate and wavelength dependence of the time response of the channel plate photomultiplier are eliminated. The data are analyzed using a nonlinear least-squares procedure where the fluorescence of the reference is directly used to account for the time response of the instrument. The system is applied to the fluorescence decay of aqueous solutions of tryptophan excited at 295 nm and observed between 320 and 380 nm. The fluorescence decay can be described by a biexponential with 3.15 and 0.54 ns components, which are found to be independent of emission wavelength.