bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal conduction normal to diamond-silicon boundaries
Authors: Goodson K. E. , Käding O. W. , Rösner M. , Zachai R.
Published: July 2002

Passive diamond layers fabricated using chemical vapor deposition can improve thermal conduction in electronic microstructures. The benefit of using diamond depends strongly on the thermal boundary resistance between active semiconducting regions, where heat is generated, and the diamond. Two independent experimental methods measure the total thermal resistance for conduction normal to 0.2, 0.5, and 2.6 μm thick diamond layers deposited on silicon, providing an upper bound for the effective silicon-diamond boundary resistance. The data agree with predictions that couple the local phonon scattering rate in the diamond to the grain size.
Metastable acceptor centers in boron implanted silicon
Authors: de Souza J. P. , Boudinov H.
Published: July 2002

The evolution of the electrical activation with the annealing time in B+ implanted (5.0×1014 cm−2, 50 keV) Si was studied as a function of the annealing temperature. Electrical activation yields of 15%–30% were observed after annealing for 2 s at temperatures above 550 °C. Prolonging the annealing time from 2 to 900 s we observed that the electrical activation evolves differently according to the temperature: (i) at 550 °C<T<700 °C it decreases toward an equilibrium level, (ii) at 700 °C<T<800 °C it decreases during the first minutes and subsequently increases again, and (iii) at temperatures <550 °C or T≳800 °C it increases continuously. In order to explain the carrier removal observed during annealing at 550–800 °C we proposed that metastable acceptor centers are formed during the B+ implantation and/or the initial period of the annealing time. Interaction of Si self-interstitial atoms with these centers leads to their neutralization and/or dissociation with consequent decreasing of the carrier concentration.
Plasma diagnostic requirements for Tokamak Fusion Core Experiment and International Tokamak Reactor (abstract)
Authors: Young K. M.
Published: July 2002

The preconceptual design phase of the Tokamak Fusion Core Experiment (TFCX) and Phase IIA of the International Tokamak Reactor (INTOR) workshop have included reassessment of the plasma diagnostic requirements for the large rf heated, neutron-generating plasmas in these devices. The three principal components of the work have been (i) to reassess the present level of diagnostic capability, (ii) to identify the diagnostics required for measurement before and during the burn phases of the two devices and (iii) to define a program of research and development activities of new or upgraded diagnostics. Both devices are expected to start operation in the early 1990’s; it is, therefore, necessary to set up development programs on U.S. tokamaks to evaluate fusion product measurements, and to establish capability of reliable, radiation-hardened instruments. The adequacy of the operational information available with very limited access through the shielding and structure of the tokamaks also must be determined. This paper describes the present plans for these programs.
X-ray spectroscopy diagnostics for the Tandem Mirror Experiment-Upgrade (abstract)
Authors: Silver E. H. , Clauser J. F. , Failor B. H.
Published: July 2002

We describe the x-ray diagnostics employed on the Tandem Mirror Experiment-Upgrade (TMX-U) to measure the x-ray emission from plasma locations where electron cyclotron radio frequency heating is applied. At each potential minimum of the TMX-U plasma, broadband spectra are obtained with NaI scintillation and cooled HPGe detectors that are coaligned to view the same plasma volume. The high-energy sensitivity of the NaI detector is necessary for studying x rays emitted by hot runaway electrons with energies exceeding 200 keV. The spectral response of the HPGe detector complements the NaI performance. Its higher resolution at energies below 100 keV is the key to determining what fraction of ECRH power is transferred to a bulk density of cooler (∼50 keV) mirror-confined electrons. X-ray spectra from the TMX-U end cell, where a potential peak produced by sloshing ions and ECRH create a localized plasma with Te ∼1.6 keV, will be measured with a Si(Li) detector. The geometrical configuration, shielding requirements, data handling systems, and recent results will be presented.
Tokamak Fusion Test Reactor horizontal high-resolution Bragg x-ray spectrometer (abstract)
Authors: Hill K. W. , Bitter M. , Tavernier M. , Diesso M. , von Goeler S. , Johnson G. , Johnson L. C. , Sauthoff N. R. , Schechtman N. , Sesnic S. , Tenney F. , Young K. M.
Published: July 2002

A bent quartz-crystal spectrometer of the Johann type with a spectral resolution of λ/Δλ= 10000–25000 is used on the Tokamak Fusion Test Reactor (TFTR) to determine central plasma parameters from the spectra of helium-like and lithium-like metal impurity ions (Ti, Cr, Fe, and Ni). The spectra are observed along a central radial chord and are recorded by a position-sensitive multiwire proportional counter with a spatial resolution of 250 μ. Standard delay-line time-difference readout is employed. The data are histogrammed and stored in 64 K of memory providing 128 time groups of 512-channel spectra. The central ion temperature and the toroidal plasma rotation are inferred from the Doppler broadening and Doppler shift of the Kα lines. The central electron temperature, the distribution of ionization states, and dielectronic recombination rates are obtained from satellite-to-resonance line ratios. The performance of the spectrometer is demonstrated by measurements of the Ti xxi Kα radiation.
Modeling diagnostics for neon-like systems (abstract)
Authors: Whitten B. L. , Hazi A. U.
Published: July 2002

K-shell spectroscopy is commonly used to diagnose laboratory plasmas, such as those produced in Z-pinches or laser targets. Neon-like systems are also of special interest because they produce the next simplest spectra, and because of applications to x-ray lasers. High-resolution spectroscopy and the acquisition of complex atomic physics data make it feasible to do diagnostics directly on neon-like systems. We present a model which calculates the 3-3 and 3-2 transitions of neon-like selenium. The ground state, n=3, and n=4 excited states are included explicitly; the n=5 through n=10 states are each lumped into one generic level. The model includes collisional and radiative transitions among these levels, and solves steady-state rate equations for the populations. The code includes graphics to plot line ratios and synthetic spectra. The model is analyzed for possible diagnostic use and is compared with experimental results.
Sequentially framing soft x-ray pinhole camera for tokamak plasma studies
Authors: Lieber A. J. , Snider R.
Published: July 2002

The x-ray camera techniques developed in laser fusion have been applied to view tokamak discharges in 1–3-keV light. The camera consists of an image intensifier fluor combination viewing the plasma tangentially through a pinhole. The resultant image is optically coupled to a standard CCD television camera for remote viewing. The first intensifier is gated so that the camera produces a sequence of photos every 16 ms of variable frame duration from 16 ms to 10 μs.
Ion energy analyzer for direct insertion in a dense hot ion plasma
Authors: Rhodes M. , Corbett J.
Published: July 2002

A retarding grid ion energy analyzer has been developed to measure ion temperature in the UCLA Toroidal Cusp Experiment. This device produces a moderately dense plasma (4×1013 cm−3 hydrogen, >1×1014 helium) with a highly energetic ion distribution. The probe and its associated drive circuitry has been developed with the following features: small size, high analyzing potential (0–500 V), fast single-shot distribution measurement (100 μs/sweep), and capable of direct plasma insertion. Design details and data for a variety of plasma parameters will be presented.
A beam probe spectroscopic technique for ion temperature and plasma rotation measurements
Authors: Goto Seiichi , Ito Yoshifumi , Ishimura Tsutomu
Published: July 2002

A compact and pulsed atomic-hydrogen beam source was constructed for the advanced spectroscopic technique of ion-temperature measurements. The mean energy and the equivalent current of the beam were ∼400 eV and ∼13 A/cm2. In this energy region, most of the charge-transferred neutrals in a hydrogen plasma are in the ground state and they emit spectral lines through an electron impact excitation process. The behavior of the neutrals generated by beam probing was analyzed by a Monte-Carlo simulation to study the relation between the temperatures of the plasma ions and the neutrals. The measured temperature of a plasma was 100 eV and its rotation energy 20 eV.
Microcomputer-controlled electrochemical system
Authors: Hagan D. , Spivey J. , Niculescu V. A.
Published: July 2002

A PET computer is used to control an electrochemical system incorporating a three−electrode potentiostat.
Data acquisition and instrument control system for ion flight time measurements in mass spectrometry
Authors: Stults J. T. , Myerholtz C. A. , Newcome B. H. , Enke C. G. , Holland J. F.
Published: July 2002

A microcomputer system is described that provides instrument control and data acquisition for ion flight time measurements in mass spectrometry. This system is designed specifically for time-resolved ion momentum spectrometry (TRIMS), a new mass spectrometry/mass spectrometry (MS/MS) technique that utilizes time-of-flight measurements in a magnetic sector instrument. The flexibility of the design, however, makes it applicable to many types of instruments that employ ion flight time measurements. The heart of the system is a digital boxcar integrator with 10-ns timing precision. The microcomputer has control of both the magnetic field and the sampled flight time. Software, written in forth, allows all standard MS/MS scans to be obtained, even those requiring complex linked scans of the magnetic field strength and the sampled flight time. Data that demonstrate the accuracy of these scans are shown for metastable decompositions of n decane.
Low-energy electron diffraction system using a position-sensitive detector
Authors: McRae E. G. , Malic R. A. , Kapilow D. A.
Published: July 2002

A low-energy electron diffraction (LEED) system using a position-sensitive detector is described. The design requirements for LEED observations are outlined. Most of these requirements are realized in a system incorporating a miniature, movable electron gun and a position-sensitive detector of the resistive anode type, interfaced to a computer. This system has been used to make 128×128 channel digital records of LED patterns. The speed of data acquisition is limited by the detector hardware and is 20 kHz. Records of good quality (0.1° instrumental angular resolving power) can be made by counting 5×105 electrons. Illustrative applications to silicon and tungsten crystal surfaces and prospects for improving the system are described.
Acoustic generation in crystalline silicon with femtosecond optical pulses
Authors: Wright O. B. , Gusev V. E.
Published: July 2002

Volume contraction in bulk silicon crystals is observed on excitation with femtosecond visible optical pulses. The surface deformation and generated acoustic strain are measured using detection based on both probe beam reflectivity changes and probe beam deflection. The contraction is explained by the dominant electronic contribution to the strain from excitation of electron-hole pairs, which swamps the thermoelastic expansion.
Self-flushing optical window to prevent collection of condensates
Authors: Crumley W. H. , Gole J. L.
Published: July 2002

As an aid to the characterization of nominally condensible and/or high-temperature molecules using optical techniques, a self-flushing optical window operating at room temperature and requiring no external heating has been designed to prevent the collection of these condensates. The optical design allows the unobstructed transmittance of light into and out of several devices to which it is readily adopted.
Mass-separated negative-ion-beam deposition system
Authors: Ishikawa Junzo , Takeiri Yasuhiko , Takagi Toshinori
Published: July 2002

We developed a mass-separated negative-ion-beam deposition system to investigate the interactions between low-energy negative ions and solid surfaces and evaluated its usefulness as an advanced technique for film formation. The deposition system consists of an intense negative-ion source and a negative-ion-beam deceleration electrode system. In the new type of sputter negative-ion source, 0.74 mA of mass-separated C− ion beam was produced in a high vacuum. The negative-ion-beam deceleration electrode system has a new structure to suppress the divergent effect of the beam, where a lens and a deceleration gap are closely placed. This structure is also simpler than any of the positive-ion-beam deceleration systems because production of oppositely charged particles, i.e., positive ions that might be accelerated in the deceleration field, can be neglected. A decelerated negative C− ion current of several tens of μA in the range of a final energy of 10–100 eV and about 100 μA in the range of over 100 eV were obtained. In a deposition test, a carbon film with several thousand Å in thickness was obtained in a few hours at a final energy of about 24 eV.
Analytical study on the maximization of bremsstrahlung and K-series production efficiencies in flash x-ray tubes
Authors: Krehl P.
Published: July 2002

For a high-vacuum discharge flash x-ray tube, pulsed by an ideal transmission line, the important tube emission characteristics such as dose, maximum dose rate, discharge delay time, and pulse width are studied as functions of the line characteristics and the K-series excitation voltage. The tube is modeled by a time-varying ohmic resistor; transient tube voltage and current can be determined out of a closed-form solution. Basic matching rules are worked out in order to approach ideal operation for a given tube impedance-time profile. A parametric analysis reveals that with decreasing pulser impedance, there are increases in the bremsstrahlung and K-series radiation emissions, but that the pulse delay time and pulse width also increase, thus limiting applications to high-rate phenomena.
Experimental apparatus for photon/ion coincidence measurements of dielectronic recombination
Authors: Gardner L. D. , Kohl J. L. , Lafyatis G. P. , Young A. R. , Chutjian A.
Published: July 2002

An inclined beams apparatus for the measurement of absolute cross sections for dielectronic recombination between free electrons and singly or multiply charged ions is described. The collision products, a photon and a lower-charge-state ion, are detected in delayed coincidence. Measurements of dielectronic recombination in C3+ are described to illustrate the use of the apparatus and techniques. Verification of the calibrations and operation of the apparatus is demonstrated through measurements of charge transfer and electron impact excitation.
Vertical high-resolution Bragg x-ray spectrometer for the tokamak fusion test reactor
Authors: Bitter M. , Hill K. W. , Cohen S. , von Goeler S. , Hsuan H. , Johnson L. C. , Raftopoulos S. , Reale M. , Schechtman N. , Sesnic S. , Spinos F. , Timberlake J. , Weicher S. , Young N. , Young K. M.
Published: July 2002

A Bragg x-ray spectrometer of high spectral resolution (λ/Δλ=10 000–20 000) which accommodates three crystals and position-sensitive detectors in the Johann configuration has been installed in the diagnostic basement of the tokamak fusion test reactor (TFTR) for the measurement of radial ion temperature profiles. The ion temperature is derived from the Doppler broadening of Kα-resonance lines of metal impurity ions, e.g., Ti, Cr, Fe, and Ni, in the helium-like and hydrogen-like charge states. The x-ray diffraction plane is almost perpendicular to the magnetic axis, but slightly tilted by an angle of 3.8°, which makes it possible to measure poloidal and toroidal plasma rotation velocities of vΘ>5×103 m/s and vΦ>1×105 m/s, from the Doppler shift of spectral lines. Results obtained from the observation of TiXXl Kα-line spectra with a 220-silicon crystal of a 2d spacing of 3.8400 Å and a curvature radius of 11.05 m are reported.
Pulsed soft x-ray source for laser-plasma diagnostic calibrations
Authors: Bourgade J. L. , Cavailler C. , de Mascureau J. , Miquel J. L.
Published: July 2002

Improvement in laser-plasma analysis makes it necessary to perform accurate calibration in the soft x-ray range. For this purpose we have modified a plasma focus device (27 kJ, 40 kV, and 400 kA) in order to enhance its soft x-ray emission: A hollow anode is used to prevent hard x-ray bremsstrahlung emission, and a lot of filling gases are chosen for their characteristic lines in the keV and sub-keV range (Ne, Ar, O, N, and CH4). These emissions have been absolutely measured with an x-ray bolometer and can be used directly or indirectly (in the fluorescent mode: Mg Kα at 1.254 keV) for x-ray calibration of various diagnostics. Some detector calibrations in pulsed regime (10 ns) are presented [films, solid state Si doped p-intrinsic-n (PIN) diodes, and charge-coupled devices (CCD) arrays.]
High-intensity H− ion source with steady-state plasma injection
Authors: Hershcovitch A. I. , Kovarik V. J. , Prelec K.
Published: July 2002

To satisfy the requirements of a negative-ion-based neutral beam line for future fusion applications, an H− ion source was developed using surface production of negative ions and a steady-state plasma injection from hollow cathode discharges. Steady-state and stable generation of H− ions on a negatively biased, cesiated converter has been achieved over periods of several hours; H− beam current pulses of 0.3-A amplitude with 1-s duration have been extracted over the same period, but steady-state operation of the extractor has not been achieved yet due to a lack of extractor cooling. The source meets some of the neutral beam line requirements, i.e., the obtained linear current density, background gas pressure, and the proven capability for steady-state H− ion generation.
New method of observing nonlinear waves in a plasma
Authors: Mori Ichiro
Published: July 2002

A new method for observing a nonlinear wave is proposed and illustrated with sample measurements. Observations are performed by using the time-of-flight method by counting the temporal upper hybrid wave packets which pass through the gap between two antennae. Two types of nonlinear waves were found in the experiment. One is outlined in the Korteweg de Vries equation by its behavior through the dispersion relation and the other behaves as a shock wave which represents the relaxing oscillation. The method of observation and the characteristics of the nonlinear waves are discussed circumstantially.
Mapping the quality of semiconductor wafers
Authors: Pankove J. I. , Berkeyheiser J. E.
Published: July 2002

A new instrument has been developed to map the photovoltaic response of a semiconductor to very penetrating sub-band-gap radiation (for silicon, λ=1.3 μm). The minority carrier density being nearly uniform throughout the thickness of the crystal, the photovoltaic response is dominated by the carrier diffusion length and thus reflects the quality of the material. A computer-controlled scan of the semiconductor presents a map of the gross quality of the specimen. The actual probe is a small transparent electrode (water) illuminated by an optical fiber carrying 1.3-μm light from an LED.
Quench detector circuit for superconductor testing
Authors: Dubé W. P. , Goodrich L. F.
Published: July 2002

A quench detector is a device that interrupts the flow of current through a superconductor in the event the superconductor reverts to the normal, resistive state. This new design has adjustable filtering and sensitivity. The input is well isolated from the output, eliminating any possible ground loop through the detector. It also has excellent noise immunity. A detector has operated with no false trips for more than two years, detecting hundreds of quenches.
X-ray anomalous scattering and EXAFS with a laboratory monochromator–diffractometer combination
Authors: Dreier P. , Rabe P.
Published: July 2002

A combination of a tunable focusing x-ray monochromator and a two-axis diffractometer designed for EXAFS and x-ray anomalous scattering experiments using a high-power rotating anode x-ray generator is described. The monochromator provides photon fluxes of 108–109 photons/s with the characteristic Kα and Lα emission lines of the x-ray target. An estimate of the relative magnitude of the difference anomalous scattering signal is given to determine the useful range of sample composition. Diffraction spectra of an aqueous 10-molal ZnCl2 solution at different photon energies (CuKα1, AuLα2, WLβ1, and AuLα1), the derived total and difference structure factors, and the corresponding radial distribution functions are shown as an example. The analysis of total and difference structure factors confirms a tetrahedral coordination of the zinc atoms in the solution.
Diode-array spectrometer (DAPS) for visible and near-IR absorption measurements with 10-ns time resolution
Authors: Sedlmair Josef , Ballard S. Gwyn , Mauzerall David C.
Published: July 2002

This paper describes a diode-array pulsed spectrometer (DAPS) that performs flash photolysis studies with a time resolution of 10 ns and a spectral resolution of 2.4 nm over a 600-nm wavelength window in the range of 350–1100 nm. It employs a 1024-element photodiode-array detector with high dynamic range and low noise. Laser-pumped fluorescent dye mixtures are used as a novel, stable light source which enable it to record spectra with a photolimited S/N ratio equivalent to 0.001 abs. units in a single shot. The measuring light distribution can be tailored so that a constant S/N ratio across a spectrum is attainable even in regions of high absorbance. Electrical artifacts from the actinic laser or other discharges do not interfere with the measurement and the effects of scattered actinic light and fluorescence from the sample are minimized. The instrument is simple to build, using mainly standard lab equipment, and easy to maintain and operate.
Measurement of small electrical forces using a torsion balance and capacitive position transducer
Authors: Winkler L. I.
Published: July 2002

A method for measuring the force arising from the attraction between a charged electrode and another electrode on which charges have been induced has been developed using a torsion balance operated in the ac mode far above the resonance frequency of the balance. The movement of the balance is sensed by a capacitive position transducer which uses two lock-in amplifiers to demodulate the position signal. The balance itself and the position transducer are described. The sensitivity of the position transducer is given, and results from three electrode geometries are discussed.
Simple and reliable system for gas flow regulation and measurement
Authors: Sanders William A. , Bogan Denis J. , Hand Clifford W.
Published: July 2002

An automatic regulation and measurement system for the delivery of gases at flow rates from about 0.01 to 1 cm3 (STP)/s is described. Flow measurement is based on the familiar direct method of determining pressure drop per unit time in a calibrated volume. The regulation and measurement functions are accomplished by simple electronic circuits. Pressure drop from the primary gas supply to the delivery point occurs in two stages. In the first stage, gas is admitted to the calibrated volume by a solenoid valve that can be opened for times as short as 10−3 s. In the second stage the gas flows through a needle valve to the delivery point. The pressure in the calibrated volume is measured by a transducer. The circuit reads the transducer output and regulates the pressure by controlling the frequency and duration of the solenoid valve opening. The fluctuations in delivered gas flow are typically ±0.5%, and could be made much smaller with modest effort. This sytem has several advantages over commercial ‘‘mass flow meters.’’ The relative (as opposed to absolute) error is constant. A single measurement of the ‘‘calibrated’’ volume suffices to calibrate the system for all gases. The gas is not exposed to heated filaments or thermistors.
Critical field index for passive coil stabilization of the spheromak shift instability
Authors: Goldenbaum G. C. , Hess R. A. , Shaw R. S.
Published: July 2002

The physics of a shifting spheromak plasma inside a passive stabilization coil is examined. Criteria for the design of these coils are derived for various spheromak current distributions. For realistic coils and force-free plasmas a critical field index is derived, above which the coils are ineffective.
Rapid thermal annealing of low-temperature GaAs layers
Authors: Liliental-Weber Zuzanna , Lin X. W. , Washburn J. , Schaff W.
Published: July 2002

Electron microscopy studies of annealed GaAs layers grown by molecular beam epitaxy at low temperature (200 °C) were used to monitor growth of As precipitates. Ostwald ripening kinetics was used to deduce a migration enthalpy of 1.4±0.3 eV for the diffusion mediating defect. A conclusive picture of the dominant diffusion mechanism can be given, attributing this value to the migration enthalpy of gallium vacancies (VGa), which is well established by other experiments. The present studies indicate that growth of As precipitates is driven by supersaturation of VGa.
High-current, heavy atom beam system for plasma diagnostics
Authors: Moses K. G. , Quon B. H. , DiVergilio W. F.
Published: July 2002

This work describes the results of testing the heavy atom-beam source of the injected internal target technique (IT)2 diagnostic system. The (IT)2 device measures the localized electron density ne and the localized electron temperature Te of a hot electron plasma. The measurement of the spatial distribution of Te is afforded by the local enhancement of x-ray emission (bremsstrahlung) when a beam of high-atomic-number target atoms are injected into a hot electron plasma. Also, the intensity of the emission at the Kα energy of the injected target atoms is a measure of the hot electron density. The (IT)2 measurements require effective beam current densities of 15.0–50.0 mA/cm2 over 20.0–50.0-keV energy range. The beam system used in this work uses ≲2.0 kW of rf power at 2.83 MHz to generate a Xe plasma ion source. A total Xe atomic beam current of ∼15.0 mA at 20.0 keV with an angular divergence of <2.0° is produced after extraction, acceleration, and neutralization of the Xe ions. The ion optics of the beam source are not optimized and improved beam characteristics should be achievable.
Plasma measurements with the TMX-U E∥B end-loss-ion spectrometers
Authors: Foote J. H. , Wood B. E. , Brown M. D. , Curnow G. M.
Published: July 2002

Two E∥B end-loss-ion spectrometers (ELIS) are now making plasma measurements on tandem mirror experiment-upgrade (TMX-U). One instrument is mounted on each end of this open-ended tandem-mirror machine. These spectrometers observe plasma losses along magnetic-field lines. They operate reliably and with a minimum of attention during an experimental run. Their data, which are quickly acquired and analyzed, help guide the experimental sequence. The parallel electric and magnetic fields separate the end-loss ions according to mass (D+ and H+) and energy. Each spectrometer detects ions with an array of 128 flat collector plates that are made from copper-coated G10 epoxy fiberglass, normally used for printed-circuit boards. The ELIS diagnostic system produces a wealth of experimental information, including data on peak plasma potential, central-cell ion temperature, potentials in the thermal-barrier region, axial confinement and ion-end-loss plugging, energetic-electron losses, and hydrogen/deuterium concentrations.
Computerized video analysis of tethered bacteria
Authors: Berg Howard C. , Block Steven M. , Conley M. Patricia , Nathan Andrew R. , Power John N. , Wolfe Alan J.
Published: July 2002

When a flagellar filament of a bacterial cell such as Escherichia coli is fixed to a glass surface, the cell body spins alternately clockwise and counterclockwise at speeds of up to 15 Hz. In cells wild type for chemotaxis, reversals occur about once per second. A typical experiment on bacterial behavior involves data collected from as many as 30 such cells over periods of about an hour. A system is described that makes practical detailed analysis of such a large body of data. Microscopic fields, each containing many tethered cells, were recorded on VHS cassettes with a shuttered multiframe video camera. The tapes were played back through hardware that encoded information from successive images of a given cell and passed that information on to a minicomputer. This computer, following instructions provided in an editing session, identified intervals during which the cell was rotating clockwise, rotating counterclockwise, or remained stationary. Output files were generated listing the times at which transitions between these states occurred and the speeds of the cell averaged over successive time periods. This output was then combined with that from other cells and/or processed by various applications programs.
Carbon composition resistors for cryogenic thermometry
Authors: De Cosmo Vittorio , Gush Herbert , Halpern Mark , Leung Alex
Published: July 2002

Preparation of thermometers from carbon composition resistors to avoid large changes during repeated thermal cycling is discussed. Furthermore, it is found that the expression 1/(T)1/2 =A+B ln(R−R0)+C ln2(R−R0)+D ln3(R−!iR0) R−R0) provides a very good description of the thermometer temperature T as a function of device resistance R. Fitting accuracies of δT<1 mK at cryogenic temperatures are achieved. The value of R0 can be chosen so that the residual errors are not more than 10 K even up to room temperature.
Interferometer micrometer
Authors: Hartman Paul L.
Published: July 2002

A device is described for coupling a micrometer to a Michelson interferometer, which allows determination of the thickness of an opaque plate to usual machine shop accuracy and the uniformity of thickness to within a wavelength of light.
Space-resolved determination of electron temperature from x-ray continuum radiation
Authors: Sato Masumi
Published: July 2002

A method to obtain the electron temperature Te in plasmas from the chordal measurement of x-ray continuum radiation is described. The maximum value of Te along the line of observation can be derived from the slope of ln E1/2I vs E plot, where I is the chordal x-ray intensity and E is photon energy. The method is applied to obtain the value of Te from the soft x-ray measurement on ST tokamak.
Experimental tests of a toroidal electrostatic analyzer
Authors: Young D. T. , Ghielmetti A. G. , Shelley E. G. , Marshall J. A. , Burch J. L. , Booker T. L.
Published: July 2002

A toroidal electrostatic analyzer of a design suitable for space plasma instrumentation has been constructed and tested. Experimental results are compared with second-order ion optical theory and are in good agreement. Verifying the ion optics of the toroid was simplified by use of a position-sensing microchannel-plate detector mounted on a positioning system with three translational degrees of freedom located at the toroid exit. The toroidal analyzer described here is the first optical element in a fully toroidal mass spectrograph intended for analysis of kilovolt magnetospheric plasmas.
Compensating calorimeter for absorption measurements of transparent materials for IR optics
Authors: Gafni G. , Eliahu A. , Galron H.
Published: July 2002

A new method for the measurement of absorption coefficients of IR transparent materials is described. The method does not require thermal insulation and the measurement is made with the sample at room temperature. A heat pump removes the heat generated by absorption and keeps the sample temperature constant. The amount of heat removed is estimated from a calibration graph. The new method was used to measure the absorption coefficient of optical germanium.
Computer-controlled Cauchois-type x-ray spectrometer
Authors: André J. M. , Kefi M. , Avila A. , Couillaux P. , Bonnelle C.
Published: July 2002

A laboratory x-ray spectrometer designed for routine analysis in the 15–60-keV spectral range is described. It consists of a 40-cm bent-crystal transmission spectrometer in the Cauchois geometry, controlled by a microcomputer. The choice of the crystal analyzer and of the detection system is discussed. The instrument is well suited for large spectral range x-ray absorption and emission spectroscopy (XAS, XES) and x-ray source diagnostics.
Cryogenically cooled K-band high electron mobility transistor receiver for radio astronomical observation
Authors: Kasuga T. , Kawabe R. , Ishiguro M. , Yamada K. , Kurihara H. , Niori M. , Hirachi Y.
Published: July 2002

A K-band receiver using cooled high-electron mobility-transistor (HEMT) amplifiers was developed at the Nobeyama Radio Observatory (NRO). Remarkable reduction of receiver noise temperature Trec was obtained when it was cooled down to cryogenic temperature. The lowest Trec of 75 K was obtained at 23.4 GHz. This low noise characteristic reveals that the cooled HEMT amplifier is promising as a sensitive receiver for radio astronomical observations.
Circuit for simultaneous measurements of particle sizing interferometer signal characteristics
Authors: Son Jung-Young , Giel Thomas V.
Published: July 2002

Particle sizing interferometer (PSI) signal characteristics, including visibility, peak intensity, number of Doppler signal cycles, and pedestal intensity, are examined for simultaneous use in particle sizing. Requirements are defined for circuitry which can simultaneously measure these characteristics and can be implemented in an existing PSI signal processor. The circuitry was implemented and tested using a rotating wheel and latex spheres. The experimental results confirm circuit reliability.
Small diamond anvil high-pressure cell for infrared spectroscopy of gas and liquid
Authors: Dahan N. , Couty R. , Seijas A.
Published: July 2002

A small diamond anvil cell (DAC) for pressure (6 GPa) and temperature (90–500 K) infrared spectroscopy is described. The purpose of this equipment is to investigate phase diagrams of fluids. Infrared spectra of freon (CHF2Cl+C2ClF3) in the liquid and solid phases are given here to illustrate the capability of this apparatus.
Translation stage for a scanning x-ray optical interferometer
Authors: Becker P. , Seyfried P. , Siegert H.
Published: July 2002

A translation stage is described which allows rectilinear displacements of up to 200 μm with a load of 20 N. Lateral deviations from the rectilinear movement do not exceed a few nanometers. Tilts are reduced to a few nanoradians. By means of a piezoelectric drive, slow continuous motion with vibration amplitudes below 0.1 nm is achieved. Residual tilting errors due to machining tolerances and nonideal coupling of the drive are reduced to nrad levels by magnetic compensation elements which are remote controlled.
Fourier transform wavemeter
Authors: Junttila M-L. , Ståhlberg B. , Kyrö E. , Veijola T. , Kauppinen J.
Published: July 2002

We describe a scanning Michelson interferometer and utilization of fast Fourier transformation in laser wavelength determination. The Fourier transformation method is demonstrated to be particularly powerful in cw multimode (diode) laser investigations and in cw single-mode laser long-term frequency stability measurements. An uncertainty less than 10−7 can be concluded from comparisons of a two-mode polarization stabilized 543-nm He–Ne laser with an iodine stabilized 633-nm He–Ne laser.
Observations on the velocity scaling of thermistor dynamic response functions
Authors: Hill Kenneth D.
Published: July 2002

The dynamic response of thermistor temperature sensors is known to be sensitive to the relative velocity between the sensor and the surrounding fluid on both theoretical and experimental grounds. The majority of the experimental investigations derive empirical velocity scaling relationships which have little basis in theory. We have determined that the dynamic response of a particular fast response thermistor scales with the square root of velocity, in accordance with the predictions of the boundary layer theory, over a speed range of 0.5–2 m/s with water as the working fluid.
Automated, small sample-size adiabatic calorimeter
Authors: Van Oort Michiel J. M. , White Mary Anne
Published: July 2002

An automated adiabatic calorimeter with an internal volume of 5 cm3, operable over the temperature range from 30 to 380 K is described. One of the main advantages of this calorimeter over others in use is the much abbreviated down time during sample changes, due to interchangeable sample vessels that fit into the heater/thermometer assembly. This calorimeter was tested by measuring the heat capacity of benzoic acid, and the results agreed with the literature values to within 0.5%.
Sample cell to measure the electromigration of tritium in metals
Authors: Rajan K. Govinda , Lässer R.
Published: July 2002

The features of a cell with which the electromigration of tritium in metals can be conveniently measured are described. The concentration profile due to the electromigration is monitored by a resistometric technique. The main requirements incorporated in the design of the cell are good thermal homogeneity and stability around the specimens, possibility of housing many samples in one run so as to generate more data during the long waiting times, and the safe containment of the radioactive tritiated samples. The cell has been used up to 300 °C. Results on the electromigration of tritium in niobium are presented to demonstrate the cell performance.
Measurements of fuse and resistor characteristics for multimegajoule capacitor bank application
Authors: McDonald K. F. , Smith T. , Golden J. , Floyd L. , Conley B.
Published: July 2002

Experimental tests have been conducted on commercially available fuses and resistors under fast high-voltage pulsed (10-μs) conditions to determine their ability to protect capacitor bank components during faults. Currents in the resistors ranged from 20 to 40 kA per resistor. The experimental results for the fuses have been compared to the manufacturer’s data for minimum melt and maximum let-through action integrals and to exploding bridge wire computer models.
Frequency response of thin-film thermometers: A critical review
Authors: Hill Kenneth D. , Woods Donald J.
Published: July 2002

The dynamic response of the platinum thin-film thermometer has been investigated. Our experimental results indicate that details of the probe form significantly affect the velocity scaling relationship for these probes. In particular, the theoretical relationship appears appropriate for probes with hemispherical tips with the thin film in the stagnation region, whereas the conical-tip probes in common usage deviate from the theory and require an empirical scaling relationship.
Instrument for measuring laser-beam profiles
Authors: Letalick Dietmar , Renhorn Ingmar
Published: July 2002

A simple single-element instrument for measuring laser-beam profiles is described. The laser beam is deflected by a self-resonant scanner and transmitted through a pinhole or a variable slit. Correction factors for various relative sizes of pinholes and slits are also given.
Response of piezoelectric bimorphs as a function of temperature
Authors: Tritt T. M. , Gillespie D. J. , Kamm G. N. , Ehrlich A. C.
Published: July 2002

The temperature dependence of the response of piezoelectric ‘‘bimorphs’’ ■ (■ Registered trademark of Vernitron Corp., Bedford, OH) has been studied. This response is markedly decreased as temperature is decreased. Since the bimorphs are voltage limited, the amount of motion available is thus reduced as the temperature is lowered. This effect is important in the design specifications for the use of bimorphs at low temperatures.
Volumetric determination of adsorption of helium over some zeolites with a temperature-compensated, differential tensimeter having symmetrical design
Authors: Suzuki Isao , Kakimoto Kazuhiko , Oki Shoichi
Published: July 2002

Amounts of adsorption of helium over some zeolites were determined ranging from 77 to 673 K with a temperature-compensated, differential tensimeter having symmetrical design. The amount of adsorption of helium was determined by measuring an increase in apparent dead space between the sample adsorption cell containing the sample and the reference adsorption cell containing several glass rods on the assumption that the amount adsorbed of helium at 673 K was negligibly small, the temperature of the adsorption cells being changed after each determination. Discussion has been made of the errors caused by the adsorption of helium to the determination of the density of solids when helium is used as the dilatometric fluid, and the determination of the surface areas of solids based upon the adsorption of nitrogen with a conventional volumetric adsorption apparatus.
dc amplifier with auto-zeroing of thermal drift
Authors: Freire R. C. S. , Abignoli M. , Lima A. M. N. , Deep G. S.
Published: July 2002

A dc strain-gauge bridge amplifier configuration with automatic compensation of thermal drift using common operational amplifiers is presented. The amplifier operation is divided into two steps: one of auto-zeroing and other of amplification of the input signal. The zeroing of the input signal is achieved by switching the bridge excitation to zero periodically at a frequency of about 100 Hz, thus limiting the maximum frequency of the input signal to about 8 Hz. With a gain of 5000, the output voltage drift of the amplifier is measured to be about 1 mV for a temperature change of 40 °C.
Four-hundred-picosecond single-photon timing with commercially available avalanche photodiodes
Authors: Lacaita A. , Cova S. , Ghioni M.
Published: July 2002

Avalanche photodiodes biased above the breakdown voltage are an interesting alternative to photomultiplier tubes in time-correlated single-photon counting. The characteristics and performance of a commercially available device (RCA C30921S) have been investigated. The time resolution is found to improve as the excess bias above the breakdown voltage is increased. Full width at half-maximum values down to 400 ps have been measured with the detector cooled at −40 °C, and down to 460 ps at room temperature. The best results were obtained with an active quenching circuit, suitable for operation with excess bias voltage up to 40 V; at room temperature, fast gated operation was used for attaining optimum performance. Experimental data on the statistical behavior of the avalanche current pulses in these devices are reported and discussed.
Double-crystal spectrometer for laboratory EXAFS spectroscopy
Authors: Tohji Kazuyuki , Udagawa Yasuo , Kawasaki Tsutomu , Mieno Kimitoshi
Published: July 2002

A double-crystal x-ray spectrometer designed for in-laboratory EXAFS (extended x-ray absorption fine structure) study is described. By the use of two curved crystals with different structure factors such as Ge(220) and Ge(111), reflections other than the desired order are virtually eliminated and monochromatic as well as intense x-ray flux can be obtained by applying higher voltage to the x-ray generator. As a result, data of very high quality can be collected in a short period by measuring the incident and the transmitted beam intensity simultaneously. It can cover a wide spectral range (7–26 keV) and is especially useful in the high-energy region, where the laboratory EXAFS system previously reported has some difficulties.
High-pressure probe and cryostat for pulsed NMR in a cryomagnet
Authors: Peereboom P. W. E. , Prins K. O. , Trappeniers N. J.
Published: July 2002

The construction of a probe suitable for pulsed NMR for the investigation of fluids and solids at hydrostatic pressures up to 3 kbar is reported. The probe fits in a cryostat constructed inside the room-temperature bore of a superconducting magnet. The temperature can be controlled in the range from 80 to 380 K. The apparatus has been used successfully in a NMR study of self-diffusion in gaseous and liquid xenon, using 129Xe and 131Xe spin echoes at 75 and 22 MHz, respectively.
Robotic work station for microscale synthetic chemistry: On-line absorption spectroscopy, quantitative automated thin-layer chromatography, and multiple reactions in parallel
Authors: Lindsey Jonathan S. , Corkan L. Andrew , Erb David , Powers Gary J.
Published: July 2002

A robotic work station has been constructed for automatically initiating and monitoring microscale chemical reactions. The work station consists of a robot with a general-purpose arm and interchangeable special-purpose hands, a carousel of seven reaction vessels, a series of stations for performing quantitative automated thin-layer chromatography (TLC), an on-line multichannel absorption spectrophotometer, sensors for verification, syringes and pumps for sample and solvent delivery, a supervisory computer for real-time data acquisition and process control, and a graphics terminal for data display. The controlling software is menu-driven and contains a scheduling algorithm that permits multiple reactions to be performed simultaneously. The automated TLC process is performed in four stages (plate dispensing, sample application, plate development, and plate densitometry), and samples are moved sequentially among these stations by the robot. The partial autonomy of these separate stations permits distributed sample processing. Four TLC plates are processed simultaneously with interleaving segmented schedules, giving a 160% increase in TLC sample throughput. The workstation can be applied to yield optimizations of synthetic reactions and to the exploration of synthetic reaction spaces. The capabilities of the workstation are demonstrated in the two-step synthesis of tetraphenylporphyrin from benzaldehyde and pyrrole in 1 h at room temperature. Kinetic data are obtained from a single-batch reaction concerning the consumption of benzaldehyde, the side reactions forming dipyrrylmethenes, and the formation of tetraphenylporphyrin.
Automated search for supernova explosions
Authors: Kare Jordin T. , Burns M. Shane , Crawford Frank S. , Friedman Peter G. , Muller Richard A. , Pennypacker Carlton R. , Perlmutter Saul , Treffers Richard , Williams Roger
Published: July 2002

We describe the design and construction of a new search for supernovae, based on the use of current computer and detector technology. This search uses a computer-controlled telescope and charge coupled device (CCD) detector to collect images of hundreds of galaxies per night of observation, and a dedicated minicomputer to process these images in real time. The search system has a detection threshold of 17th visual magnitude, discovered its first supernova on 18 May 1986, and at this writing has found three additional supernovae. The system currently is being upgraded with an improved detector and a more powerful computer. At full speed and sensitivity, the system will be able to search 2500 galaxies per night with a limiting magnitude of 19 or fainter.
Control electronics for atomic force microscopy
Authors: Marti O. , Gould S. , Hansma P. K.
Published: July 2002

The control electronics for the atomic force microscope (AFM) are described. The set of electronic devices described here allow convenient operation of an atomic force microscope. The key device is the force controller, which automates the otherwise tedious and time-consuming readjustment of the force to a preset value by controlling two gated feedback loops. The preset value of the force can be easily changed by simply turning a potentiometer. This automated system allows us to obtain reliable data, with known forces, despite piezoelectric creep and thermal drift in the force determining mechanical setup. The electronic devices and concepts presented here work for AFMs that use tunneling, capacitance measurements, or optical interference to sense small deflections of the spring.