bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement and interpretation of electron cyclotron emission on JET (abstract)
Authors: Bartlett D. V. , Baker E. A. M. , Campbell D. J. , Costley A. E.
Published: July 2002

The first two channels of the JET electron cyclotron emission diagnostic have been in regular use for several months. A Michelson interferometer provides several hundred broadband spectral measurements (with time resolution 15 ms) on every plasma pulse. The second cyclotron harmonic in these spectra is used to deduce absolutely calibrated electron temperature profiles in the outer half of the plasma. Current measurements and their interpretation will be discussed, and the full diagnostic system, for the determination of two-dimensional profiles, will be described.
Detection of metal induced gap states in silicon
Authors: Railkar T. A. , Bhoraskar S. V.
Published: July 2002

An experimental technique involving the measurement of thermally stimulated exoelectron emission has been shown to be capable to detecting the surface states, caused by the presence of metal impurities, at the surface of silicon. The ionization energies of the surface states induced by the thermal diffusion of silver, gold, copper, and aluminum in silicon are estimated from this technique.
Second harmonic generation as a probe of antiphase domains in layered GaSe thin films on Si(111) substrates
Authors: Amzallag J. , Benisty H. , Debrus S. , May M. , Eddrief M. , Bourdon A. , Chevy A. , Piccioli N.
Published: July 2002

Second harmonic generation (SHG) at 1.064 μm reflected by thin films (20–60 nm) of layered GaSe epitaxially grown on Si(111) substrates is reported. Comparison with a theoretical calculation, taking into account all interfering waves, is made as a function of growth temperature, evidencing a large discrepancy at lower growth temperature. This discrepancy is attributed to the existence of antiphase domains whose nonlinear polarizations are opposite. Reflected SHG thus allows to probe the existence of an orientational disorder undetectable with electron or x-ray diffraction techniques.
High-power radio frequency generation in a hollow-cathode discharge
Authors: Arbel D. , Bar-Lev Z. , Felsteiner J. , Rosenberg A. , Slutsker Ya. Z.
Published: July 2002

High-power rf oscillations are obtained in a resistive load installed in the external electrical circuit of a low-pressure magnetic-field-free hollow-cathode discharge. These intense rf oscillations have been shown to be due to a collisionless instability of the cathode sheath. A very simple device based on this effect is shown to serve as a convenient and powerful rf oscillator. Typical results first achieved without any optimization, for frequencies of 20–30 MHz and load resistances of several tens of ohms, are as follows: power of about 5 kW and efficiency ∼25%.
Semiconductor preionized nitrogen laser
Authors: Rickwood K. R. , Serafetinides A. A.
Published: July 2002

The design and performance of semiconductively preionized nitrogen lasers employing optimized capacitor transfer excitation circuitry are described. These lasers of minimum complexity are capable of producing ultraviolet pulses of up to 1 mJ and 150 kW at efficiencies of more than 0.04%.
Large-area 200-ps gated microchannel plate detector
Authors: Eckart M. J. , Hanks R. L. , Kilkenny J. D. , Pasha R. , Wiedwald J. D. , Hares J. D.
Published: July 2002

Results are presented with a 15-mm-wide gated microchannel plate UV and x-ray detector. The active area is part of a 6-Ω transmission line driven by an electronically generated gate pulse. The microchannel plate is coated with CsI allowing tests with a frequency-quadrupoled, high-repetition-rate 1.05-μm laser. Results showing optical gate widths as short as 100 ps are presented.
Status of the University of Rochester tandem upgrade
Authors: Cross Clinton , Miller Thomas
Published: July 2002

The status of the University of Rochester tandem Van de Graaff accelerator upgrade is reviewed. The accelerator upgrade to 18 MV consists of extended tubes, shielded resistors, dead-section ion pumping, two rotating insulating power shaft systems to provide power to the dead sections and terminal, and a pelletron charging system to replace the charging belt. Control of many of the accelerator operating systems will be done by two IBM personal computers. The negative ion injector diffusion pump, isolation transformer, preacceleration high-voltage power supply, and high-voltage corona enclosure will all be replaced. Finally, the SF6 gas handling system will be improved with the addition of a second set of gas dryers and a larger recirculating pump.
High repetition long pulse XeCl laser with a coaxial ceramic pulse-forming line
Authors: Watanabe Shuntaro , Watanabe Masayoshi , Endoh Akira , Sato Tsukasa
Published: July 2002

A coaxial pulse-forming line using ceramic as a dielectric material has been developed for excitation of a long pulse XeCl laser. The dielectric constant of 1700 enabled a compact low-impedance pulse-forming line (PFL) with an electric transit time of 260 ns/m. A 200-ns optical pulse has been produced with an output energy of 240 mJ from a 2×2×28-cm3 active region. The use of a magnetic switch rather than a nontriggered rail gap improved dramatically the high repetition rate capability, jitter, and reproducibility of the optical pulse shape, which are essential for practical use. The jitter was within 2 ns and the fluctuation in the output energy was ±3%.
Magnetic monopole detector with sensitivity to extremely small magnetic charge
Authors: Fryberger D. , St. Lorant S. , Tillmann E. , Wolff A.
Published: July 2002

A magnetic monopole detector with a sensitivity range down to extremely small magnetic charge is described. Backgrounds in the detector are discussed and representative background distributions are given. Appropriate steps to minimize these backgrounds are detailed. The region of sensitivity of the detector to magnetic monopoles in terms of monopole charge and monopole mass is given.
Automated pressure probe for measurement of water transport properties of higher plant cells
Authors: Cosgrove Daniel J. , Durachko Daniel M.
Published: July 2002

A computer-assisted instrument was constructed to measure the fundamental physical properties that regulate water transport at the cell level in plants. With this automated pressure probe, we measure a cell’s hydrostatic pressure by inserting an oil-filled glass capillary into the cell. The capillary is connected to a pressure sensor and to a plunger controlled by a stepper motor. At the capillary tip an interface forms between the cell sap and oil. The image of this interface is directed through a microscope to a video camera. The interface position is detected by a video processor sampling at 60 Hz and is regulated by a microcomputer which advances or retracts the plunger at rates up to 280 steps per second. To determine the hydraulic conductance of cell membranes, the computer carries out pressure-relaxation and pressure-clamp experiments. Pressure is recorded with a resolution of 0.02 bar and is regulated in pressure-clamp experiments at ±0.02 bar. The instrument measures the cell volumetric elastic modulus by injecting or removing small volumes from the cell while simultaneously measuring cell turgor pressure. This system was tested on the cells of pea seedlings and proved superior to the previous techniques, especially for pressure-clamp experiments and volumetric elastic modulus determinations.
Computer-controlled Raman spectrometer for time-resolved measurements in low-pressure gaseous samples
Authors: Mazur Eric
Published: July 2002

A spectrometer for measuring spontaneous Raman scattering in gaseous samples at pressures below 100 Pa (0.75 Torr) with nanosecond time resolution is presented. The apparatus was developed for studying intramolecular vibrational energy distributions in infrared multiphoton excited molecules and makes it possible to study the anti-Stokes Raman scattering from isolated molecules at pressures down to 14 Pa (110 mTorr). To achieve high sensitivity and time resolution simultaneously, spectral resolution (1 nm) is sacrificed. Because of the low level of the signals, the measurements are completely computer controlled. A detailed description of the apparatus, including the multichannel data-acquisition hardware and computer interface, is given.
Performance of a single-axis platform for balloon-borne remote sensing
Authors: Traub W. A. , Chance K. V. , Coyle L. M.
Published: July 2002

The balloon flight performance of the Mark I single-axis platform and telescope is presented. Three performance indicators are examined: inclinometer output, gyro output, and infrared detector signal. We find that the gondola itself experiences periodic angular disturbances with maximum amplitudes in the 0.1°–2.0° range, with peaks occurring at periods of about 1, 2, 7, 20, and 250 s. The 2- and 20-s oscillations are identified with simple and compound pendulum motions, while the 250-s oscillations are speculated to be caused by atmospheric waves. Maximum platform deviations from the horizontal are in the 0.002°–0.02° range, well within the 0.02° design goal, except in the 250-s regime where amplitudes are occasionally several times larger than the design goal because of horizontal atmospheric accelerations. We find that the system meets our basic goal of providing a stable pointing direction within an uncertainty which is much less than the 0.3° telescope beam diameter.
Measurement of salinity distributions in salt-stratified, double-diffusive systems by optical deflectometry
Authors: Bergman T. L. , Munoz D. R. , Incropera F. P. , Viskanta R.
Published: July 2002

Reliable salinity measurements in double-diffusive thermohaline solutions are necessary to understand relevant system behavior. An optical technique, which has previously been used to investigate solute diffusion in isothermal systems, is employed to measure the salinity distribution in a double-diffusive thermohaline system. The technique is verified by comparison with independent salinity measurements, and its use in a double-diffusive system reveals detailed salinity distribution information. When used with the shadowgraph method of flow visualization, the salinity measurement technique permits a more quantitative interpretation of the shadowgraphic results.
Adjustable speed and vibration-free hydraulic system for Langmuir–Blodgett films deposition
Authors: Munger G. , Lorrain L. , Gagné G. , Leblanc R. M.
Published: July 2002

Conventional apparatus for the dipping and raising of slides usually uses an electric motor with the slides fixed in a rigid holder. Most of the devices create a great deal of vibrations and this produces a nonuniform film deposition. We have used a new apparatus, which does not produce any vibrations of the slide, to build up Langmuir–Blodgett films. To move the slide, we employ a column of water and use the siphon principle, with speeds that can be varied between 3.0 and 120.0 mm min−1. An electronic circuit controls the automatic dipping and raising of the slide. A relay switches the solenoid valve to move the piston in the opposite direction. A machined Teflon trough and antivibration mount are used for the monolayer preparation. With this method, the deposition ratio usually obtained for the cadmium arachidate and chlorophyll a is 1.00±0.05. The absorption spectrum of multilayers of chlorophyll a give a linear relation between the absorbance at 680 nm and the number of layers up to 10. The nonlinear relation for the number of layers higher than 10 is explained by the presence of aggregates.
Effects of the gas flow rate and the circuit parameters of the spark gap side on characteristics of L
C inversion TE N2 laser
Authors: Saito Y. , Nomura A. , Kano T.
Published: July 2002

Design criteria for a N2 laser with LC inversion excitation circuit are theoretically and experimentally described. Lower resistance, depending on the spark gap pressure, gave higher energy, while the inductance was independent of it. Laser energy increased with higher gas flow rate and was saturated at rates over 10 l/min. Other experimental relationships between pulse width, gas flow rate, energy, and repetition rate are described. Typically, an energy of 4.6 mJ, a peak power of 700 kW, a pulse width of 6.6 ns, and an efficiency of 0.18% was obtained at a repetition rate of 0.4 pps, a gas flow rate 10 l/min, and a voltage of 15 kV. For a higher repetition rate of 10 pps the parameters were 3 mJ, 400 kW, 7.5 ns, and 0.12%, respectively.
Photopyroelectric thin-film instrumentation and impulse-response detection. Part III: Performance and signal recovery techniques
Authors: Power Joan F. , Mandelis Andreas
Published: July 2002

Frequency-modulation time-delay spectrometry (FM-TDS) was compared with stochastic excitation in photopyroelectric measurements on thin solid samples. These methods involve broadband signal excitation with simultaneous detection of all frequency components within the response bandwidth of the photothermal system. Fast signal recovery was achieved by FFT methods. Both FM-TDS and wideband random-noise excitation were found to yield high-quality, band-limited impulse-response information. Random noise measurements were found to be much less susceptible to distortions and nonlinearities in the excitation wave train. FM-TDS showed superior coherence and signal-to-noise ratio (SNR) to random methods. The results of this work demonstrate a photopyroelectric effect spectrometer capable of yielding fast, time-resolved information equivalent to the response of a pulsed laser, with low peak power. This important feature shows excellent potential for nondestructive thickness, thermal diffusivity, and thermal conductivity measurements on materials which are susceptible to optical damage.
Subnanosecond resistive high-voltage dividers for transient ground rise measurement in gas-insulated switchgear. Part II: Subnanosecond triple ladder
Authors: Melançon C. , Mitchel G. R.
Published: July 2002

This paper describes a resistive voltage divider with subnanosecond rise time for use up to 50 kV using a ‘‘triple ladder’’ of metal film resistors. Its low-voltage attenuators incorporate fast switching diodes for oscilloscope protection. The divider is used to measure fast transients generated by breakdown in SF6.
Hollow ballistic pendulum for plasma momentum measurements
Authors: Goncharov S. F. , Pashinin P. P. , Perov V. Y. , Serov R. V. , Yanovsky V. P.
Published: July 2002

A novel pendulum design—hollow ballistic pendulum—is suggested for plasma momentum measurements. It has an advantage over the pendula used earlier in laser plasma experiments of being insensitive to a momentum of matter evaporated and scattered by the pendulum wall exposed to the plasma, which usually exceeds plasma momentum to be measured. Simple expressions describing pendulum performance are derived, and requirements of shape and size are established. Using this kind of pendulum in experiments on laser acceleration of thin foils made it possible to measure the momentum of accelerated foil with an accuracy of about 10%.
Automatic colorimetric detector for traces of nitrogen dioxide in air
Authors: Punkkinen R. K.
Published: July 2002

A reliable and easy-to-operate detector has been developed for determining low concentrations of nitrogen dioxide in air. In the detector, the air sample is bubbled through a volume of 40 cm3 of Saltzman reagent, and the transmittance of light (550 nm) by the reagent is continuously measured by a built-in photometer. The output of the detector is a dc voltage proportional to the transmittance. The reagent is replaced every 12 h. The detection limit is about 1×10−10 by volume for 1-h measuring periods. After abrupt changes in the NO2 level, the rise and fall times of the readings (from 10% to 90% of the change) are about 5 min. A microcomputer can be used to control the system and to determine the nitrogen-dioxide concentrations automatically.
Apparatus for rapid thermal analysis studies of reluctant glass formers
Authors: Ethridge Edwin C. , Curreri Peter A.
Published: July 2002

An apparatus is described for performing rapid thermal analysis of milligram quantities of reluctant glass formers. Nucleation and crystallization kinetic analysis on samples cooled at very rapid cooling rates of 10 to 2500 °C s−1 is described. The apparatus utilizes focused heating of a sample contained on a fine thermocouple. The measured times and temperatures for nucleation of crystallization at various cooling rates and experimental conditions permit the construction of continuous cooling crystallization (CCC) boundaries and the determination of critical cooling rates for glass formation.
Variable bandpass filter with high rejection ratio for Raman scattering
Authors: Huang Yihe , Yu Peter Y.
Published: July 2002

A variable bandpass filter with a stray light rejection ratio as good as 10−8 is described. The applications of this filter in removing elastically scattered laser light from poor quality sample surfaces in Raman scattering are discussed.
Image bandpass filter in photoelectron spectromicroscopy
Authors: Turner D. W. , Plummer I. R. , Porter H. Q.
Published: July 2002

The design and construction of an imaging bandpass electron energy analyzer which operates in the intermediate magnetic field of a photoelectron spectromicroscope is described. Image electrons injected parallel to the magnetic field are guided, using crossed magnetic and nonuniform electrostatic fields, to a low-pass electron mirror and subsequently a high-pass retardation filter. The nonuniform electrostatic fields compensate for the energy-dependent dispersion of the crossed fields. A bandwidth-limited photoelectron image demonstrates the spatial integrity of the image after passage through the image bandpass filter. The performance of the device as an energy analyzer is assessed. An energy resolution of less than 30 meV is demonstrated and thermionic electron spectra are presented with electron energies ranging from 10 to 200 eV with a 250-meV bandwidth. Area-selected photoelectron spectra from Au and W show UPS and XPS performance of the device. In the case of Au, the spectrum was obtained from a 400-×400-nm area.
Design and performance of a rim-type chopper
Authors: Weaver Bradley D. , Frankl D. R.
Published: July 2002

We analyze a ‘‘rim-type’’ chopper. The pulse duration can be varied at a fixed pulse repetition rate by changing the chopper-to-beam offset distance. Overall performance is discussed in terms of the transmission function, pulse length, and velocity-selection properties.
Ultranarrow bandwidth VUV-XUV laser system
Authors: Cromwell E. , Trickl T. , Lee Y. T. , Kung A. H.
Published: July 2002

An ultrahigh-brightness laser system has been developed to study the spectroscopy and dynamics of molecules and clusters in the vacuum ultraviolet (VUV) extreme ultraviolet (XUV) spectral region. The laser utilizes pulse amplification of a single-mode ring dye laser, frequency doubling, and four-wave mixing in a pulsed jet. Pulse energies of >100 mJ in the visible and >1011 photons/pulse in the VUV-XUV have been obtained. The bandwidth of the laser has been measured to be 91 MHz in the visible and 210 MHz in the XUV.
Self-filtering crystal monochromators for synchrotron x radiation
Authors: Cowan P. L. , Brennan S.
Published: July 2002

Monochromator crystal heating and radiation damage may be reduced significantly by reflecting much of the incident radiated power from the surface of the crystal. This requires strong Bragg diffraction of the monochromatized beam at grazing incidence angles. Examples of such cases are described, such as extremely asymmetric diffraction and grazing angle diffraction, which would permit continuously tunable x-ray energy. Additional benefits such as increased angular acceptance, variable beam cross section, adjustable bandpass, and increased flux for self-filtering monochromators are presented, and various considerations in implementation are discussed. Finally, the possibilities for exploiting the unused reflected x rays will be explored.
Optical constants of SiC mirrors produced by different methods for photons of 60–1000 eV
Authors: Yanagihara Mihiro , Cao Jianlin , Yamamoto Masaki , Namioka Takeshi , Sato Shigeru , Koide Tsuneharu , Takeda Shigekatsu , Iijima Akio
Published: July 2002

The optical constants of seven CVD-SiC mirrors produced by different processes and a sintered SiC mirror have been measured in the soft x-ray region by means of the reflectance method. Although they are different in the crystal structure, the optical constants of the CVD-SiC mirrors are almost independent of the samples over the measured 200–1000 eV range. But the optical constants of the sintered SiC differ from those of the CVD-SiC mirrors over the measured range of 60–1000 eV. The photon-energy dependence of the optical constants of CVD-SiC is represented in terms of power formulas above 300 eV.
The combined effect of random magnetic field errors and nonzero particle beam emittance on undulator spectral properties (abstract)
Authors: Viccaro P. J. , Alp E. E.
Published: July 2002

The very desirable spectral properties of transverse undulators as x-ray sources are very sensitive to both random magnetic field errors in the device and to nonzero particle beam emittance. Each of these factors can degrade the undulator performance and their effects must be realistically evaluated in order to accurately estimate the spectral characteristics of a given device. While both sources of degradation on undulator performance have been analyzed independently, no attempt has been made to investigate their combined effect. We have developed a code for calculating undulator-spectral properties which include both these effects. Results are given for typical undulators proposed for the 7-GeV Advanced Photon Source to be built at Argonne. The calculations indicate that present-day construction tolerances achieved for existing undulators will be more than adequate to achieve the desired spectral output of undulators proposed for the APS.
New Synchrotron Radiation Center beamlines at Aladdin
Authors: Pruett C. H. , Brodsky E. L. , Cole R. K. , Crossley S. L. , Crossley D. B. , Hansen R. W. C. , Nelson T. , Perkins F. K. , Rogers G. C. , Rosenberg R. A. , Wallace D. J. , Winter W. R. , Middleton F. H. , Filipponi A. , Zanini F.
Published: July 2002

In the past year, the Synchrotron Radiation Center (SRC) staff has installed five new beamlines at SRC. Three of these beamlines are ‘‘public’’ beamlines operated by SRC for experiments selected from peer-reviewed proposals. Fifty to seventy-five percent of the experimental time on the other two beamlines is managed by the SRC as a consequence of the SRC being a partner in participating research teams (PRTs). These new beamlines bring the number of VUV and soft x-ray research beamlines installed on Aladdin to 17 as of August 1988. Including two storage ring optical diagnostic ports, there will be 20 ports in use on Aladdin by the end of 1988.
The use of gradient sector magnets in Chasman-Green lattice (abstract)
Authors: Kato S.
Published: July 2002

The design of the next generation synchrotron radiation ring is based on a low-emittance storage ring with large numbers of zero-dispersion straight-section for insertion devices. As a candidate, the Chasman-Green lattice is likely to be the most promising to be investigated. In this paper, field gradients and edges which are not perpendicular to the optic axis are proposed to introduce the bending magnets for a low-emittance Chasman-Green lattice. The horizontal beam emittance of a large ring is generally expressed as1 (1) εx=Cqγθ3F(ψ)/Jx, where Cq=3.83×10−13 m, γ=Lorentz factor of the stored beam, θ=bending angle of a dipole magnet, F(ψ)=emittance form factor as a function of the betatron phase advance per half cell ψ, Jx=partition number of the horizontal betatron oscillation.

The form factor F(ψ) depends on the lattice structure and is expressed for the symmetrical cell as (2) F(ψ)=(1/ρθ3)(1/ρθ) ∫ρθ0(γη2 +2αηη′+βη′2)ds, where H=γη2+2αηη′+βη′2 is the Courant–Snyder dispersion invariant, ρ is the magnetic radius, α, β, γ are Twiss parameters and η, η′ are the dispersion function and the derivative with s the integral ranges over a bending magnet. We calculate, for examples, F(ψ) for a single lens approximation of equal focal length with ρ=25 and θ=π/32 radian. For the gradient magnet, the gradient parameter K is taken to be −0.05(1/m2) for example, where K is defined as (3) K=(1−n)/2, n=−(ρ/B)(dB/dx). The absolute value of K is restricted to be small to guarantee the damping of energy oscillation. For a nonperpendicular edge, the angle between the edge normal and the beam axis is chosen to be −0.255 radian, for example. The sign conversion is in the usual manner.2 The form factor F(ψ) is calculated as a function of Ψ for the two examples. Another factor to effect the emittance is the partition number Jx as seen in Eq. (1).

J x can be written as (4) Jx=1−Kρ2θ2/3, in the first-order calculation. A negative K has little effect to decrease the emittance in cooperation with F(ψ). The horizontal beam emittance is shown to be decreased by the reduction of the factor in two examples in cooperation with the increase of the horizontal damping partition number of the betatron oscillation.
Angular distributions of synchrotron radiation from a superconducting wiggler
Authors: Sugano T. , Taniguchi M. , Endo I. , Ohta T.
Published: July 2002

Angular distributions of radiation from a three-pole superconducting horizontal wiggler operated on a 1.5-GeV storage ring have been calculated in detail. The horizontal distribution of vertically integrated power exhibits a remarkable asymmetry when the radiation is observed at distances close to the center of the wiggler. The distribution exhibits a prominent dip in the forward direction, at a position where the radiation stems primarily from the main magnet, which is set at a maximum field of 4.40 T. The spectral flux at around 1–2 Å exhibits an effective angular spread of ±37 mrad. The central brilliance at 1 Å is 7×1012 photons/s mrad2 mm2 0.1% bandwidth for a current of 300 mA.
Compact pulsed laboratory synchrotron LIS-2
Authors: Kuznetsov A. S. , Tiit V. , Vilt E. , Pill K. , Haamer A. , Tammik A.-A. , Piilma M.
Published: July 2002

The construction of the compact pulsed synchrotron radiation source with a spectral range of 10–104 nm is reported. The design, injection method, and specifications of the SR source are described. The angular distribution of the σ and π components of SR has been investigated. The presence of asymmetry on the angular distribution of the π component has been established. This asymmetry is supposed to be connected with the interference radiation of the electron current with the coherent superradiation of electron-magnetic dipoles (spins).
Arc chamber deformation in small storage rings under pressure loads
Authors: Sharma S.
Published: July 2002

Bending deformations of small storage ring vacuum chambers under atmospheric pressure are described. Results from a finite element model are presented which show that bending deformations due to pressure forces on metal bellows and arc chambers can cause severe misalignments at the exit ports. The deformations are shown to be larger in arc chambers of small radii. The effect of using bellows load compensators and flexible supports to reduce the deformations in an existing storage ring by an order of magnitude is evaluated by analysis and compared to actual measurements.
Simple evaporation controller for thin-film deposition from a resistively heated boat
Authors: Scofield John H. , Bajuk Lou , Mohler William
Published: July 2002

A simple, inexpensive circuit is described for switching the current through a resistively heated evaporation boat during thin-film deposition. The circuit uses a silicon-controlled rectifier (SCR) to switch the 0–15-A current in the primary of a 2-kV A step-down transformer that supplies the 0–200-A current to an evaporation boat. The circuit is controlled by a 0–10 V-dc signal similar to that furnished by an Inficon XTC deposition-rate controller. This circuit may be assembled from a handful of parts for a cost of about $400, nearly one-tenth the cost of similar commercial units. Minimum construction is required, since the circuit is built around an off-the-shelf, self-contained SCR unit.
Characteristics of a surfatron driven ion source
Authors: Hajlaoui Y. , Pomathiod L. , Margot J. , Moisan M.
Published: July 2002

A small, lightweight ion source based on a surface-wave sustained plasma is investigated. Previously designed to be a 2 mA, 3 keV krypton ion launcher in an on board spacecraft experiment, its operation is extended to several common gases at various operating frequencies and extraction voltages. It is built around a fused silica discharge tube that has one end fitted with a two-grid extraction system. This tube is enclosed by a surface-wave launcher (surfatron) operated between 750 and 1000 MHz, and the discharge is sustained with only 35 W. The beam is neutralized by electrons emitted by a tungsten filament. Ion current densities extracted at a few kilovolts lie in the range 10–40 mA/cm2, depending upon the gas used. The largest ion current is obtained with hydrogen: 8.5 mA at 5 kV. Variations in the source performances with the gases used are analyzed using the ‘‘beam relative perveance’’ concept and the surfatron equivalent circuit model.
A 1.5–4 K detachable cold-sample transfer system: Application to inertially confined fusion with spin-polarized hydrogen fuels
Authors: Alexander N. , Barden J. , Fan Q. , Honig A.
Published: July 2002

A compact cold-transfer apparatus for engaging and retrieving samples at liquid-helium temperatures (1.5–4 K), maintaining the samples at such temperatures for periods of hours, and subsequently inserting them in diverse apparatuses followed by disengagement, is described. The properties of several thermal radiation-insulating shrouds, necessary for very low sample temperatures, are presented. The immediate intended application is transportable target shells containing highly spin-polarized deuterons in solid HD or D2 for inertially confined fusion experiments. The system is also valuable for unpolarized high-density fusion fuels, as well as for other applications which are discussed.
Gearless two-crystal x-ray spectrometer for chemical state analysis
Authors: Konishi Tokuzo , Nishihagi Kazuo , Taniguchi Kazuo
Published: July 2002

A two-crystal spectrometer for chemical state analysis of high-resolution x-ray fluorescence spectra employs ball-screw and slide mechanisms rather than gears to obtain a 2θ scanning range of 40°–147° and a Δ2θ scanning step of 10−4 deg under vacuum, and a 2θ resolution of 10−4 deg in determination of an intercrystal angle with encoder-based measurement and servomechanical control of position. The spectrometer, although simple in structure, is a powerful instrument for chemical state analysis, as demonstrated by its high resolution, stability, and repeatability in determination of the Kα lines of first transition metals, aluminum, silicon, and sulfur with Si(220), ADP(101), InSb(111), and Ge(111) as analyzer crystal, respectively.
Fast neutral beam ion source coupled to a Fourier transform ion cyclotron resonance mass spectrometer
Authors: Hill Nicholas C. , Limbach Patrick A. , Shomo Ronald E. , Marshall Alan G. , Appelhans Anthony D. , Delmore James E.
Published: July 2002

The coupling of an autoneutralizing SF−6 fast ion-beam gun to a Fourier transform ion cyclotron resonance (FT/ICR) mass spectrometer is described. The fast neutral beam provides for secondary-ion-type FT/ICR mass analysis [e.g., production of abundant pseudomolecular (M+H)+ ions] of involatile samples without the need for external ion injection, since ions are formed at the entrance to the ICR ion trap. The design, construction, and testing of the hybrid instrument are described. The feasibility of the experiment (for both broadband and high-resolution FT/ICR positive-ion mass spectra) is demonstrated with tetra-butylammonium bromide and a Tylenol■ sample. The ability to analyze high molecular weight polymers with high mass resolution is demonstrated for Teflon■. All of the advantages of the fast neutral beam ion source previously demonstrated with quadrupole mass analysis are preserved, and the additional advantages of FT/ICR mass analysis (e.g., high mass resolving power, ion trapping) are retained.
A simple and reusable metal sample holder for hydrogen permeation experiments
Authors: Ito Yoshiro , Sakai Hisahiro
Published: July 2002

A simple and reusable metal sample holder for a hydrogen permeation experiment was made of two standard conflat flanges and gaskets of copper and aluminum.
Optimized conversion dynode positioning for a sector mass spectrometer operated in normal, linked scan, or low accelerating voltage modes
Authors: Savickas Philip J.
Published: July 2002

The simple, correct positioning of the conversion dynode in a common sector type of mass spectrometer has been shown to increase the signal obtained in a variety of experiments by a factor of at least 3–5. In addition, with incorrect positioning, small vibrations of 6.8 μm are suggested to lead to 10% signal fluctuations. No degradation of any instrument performance has been observed with the changes made to allow optimization of the position of the conversion dynode. Details of the procedure necessary to implement this technique are given. The benefits of increasing the conversion dynode potential from 5 to 10 kV, for enhanced sensitivity and its effect on conversion dynode positioning, are also discussed. Careful positioning of the conversion dynode in a sector type mass spectrometer yields several advantages. The enhancement is best applied in low accelerating voltage or linked scan modes of operation.
A MOSFET transmission-line high-power electron-nuclear double-resonance spectrometer
Authors: Colligiani A. , Romanenghi G.
Published: July 2002

In the apparatus we are going to describe, since our ultimate aim was its broadband behavior, a very large irradiating rf field up to 80 G can be obtained from 1.0 to 50 MHz on the sample inside the microwave cavity. A mean power of 300 W was attained by suitably combining four homemade rf amplifiers. Two Motorola MRF 174 metal-oxide-semiconductor field-effect transistors (MOSFET) were used in each of the amplifiers. Broadband behavior was achieved, while retaining the principle already used of stepping down the rf amplifier output impedance, by introducing into the spectrometer a flat transmission line with the correct characteristics. Examples of electron-nuclear double-resonance (ENDOR) spectra are reported and compared with those obtained on an earlier spectrometer.
Surface acoustic-wave device for measuring rate of gas flow
Authors: Brace J. G. , Sanfelippo T. S. , Joshi S. G.
Published: July 2002

The use of a surface acoustic wave (SAW) device for measuring rate of gas flow is described. A delay-line stabilized SAW oscillator is heated above the ambient by using a novel approach in which radio frequency (rf) energy is converted to heat via acoustic dissipation. This ‘‘self-heating’’ arrangement eliminates the need for a separate heater and associated circuitry. Convective cooling caused by gas flow results in a change in the substrate temperature and thereby the oscillator frequency. The frequency of a 75-MHz oscillator fabricated on a 128° rotated Y-cut, X-propagating lithium niobate substrate is found to vary by more than 55 kHz for variation in flow rate from 0 to 500 cm3/min. A dual-oscillator configuration is implemented to provide temperature compensation and a convenient low-frequency output corresponding to flow rate. Adequate flow-sensing response is achieved with only modest (15 mW) oscillator loop power.
Insertion devices for the new generation of synchrotron sources: A review (invited)
Authors: Elleaume Pascal
Published: July 2002

A review is made of the principal characteristics of the undulators and wigglers for the new generation of synchrotron sources. The main characteristics of the radiation are summarized followed by the effect on the stored electron beam. The technology of IDs is presented. Finally exotic IDs designed to produce circularly polarized radiation are discussed.
The measurement of magnetostriction constants of thin films using planar microwave devices and ferromagnetic resonance
Authors: Bushnell S. E. , Nowak W. B. , Oliver S. A. , Vittoria C.
Published: July 2002

In this paper we introduce a new technique for measuring the saturation magnetostriction constant (λs) for isotropic polycrystalline thin films. The technique makes use of nonresonant planar microwave structures together with a novel stressing mechanism to induce a shift in the resonant field of a magnetic thin film as measured by a ferromagnetic resonance (FMR) experiment. Measurement of the shift induced by a uniaxial stress allows for determination of λs via a magnetic resonance analysis. Either a slotline device or coplanar waveguide (CPW) was used as the source of the microwave excitation field depending upon the orientation of the dc magnetic field. To evaluate the technique, polycrystalline Ni films of thickness of 637 nm were sputtered onto glass substrates at room temperature for comparison with the literature. Using a 50-Ω CPW, FMR measurements at 9 GHz revealed an average value of λs of −36×10−6 a value in agreement with those previously reported. The technique provides increased flexibility over other FRM techniques as it is wideband and directly accessible.
Noncontact charge measurement
Authors: Lin Kuan-Chan , Wang Taylor G.
Published: July 2002

A novel method and system for measuring a static charge field in a noncontact manner has been developed. This system is based on the principle of reciprocal motion of a grounded conductor near a point charge. Experiments were done to characterize this new system and are in good agreement with the theoretical prediction. This system exhibits extremely good linearity with respect to the input electric field and has a resolution of better than 10 V/m, which is about two to three orders of magnitude in sensitivity higher than the one being used. The high sensitivity of this apparatus makes the system feasible for use at a safe distance in various applications where static charge must be monitored.
Construction of an inexpensive dc plasma jet for diamond deposition using commercially available components
Authors: Cerio F. M. , Weimer W. A.
Published: July 2002

A dc plasma jet reactor system, constructed from commercially available components, is described. Parameters for the chemical vapor deposition of high quality diamond are given. Diamond films were synthesized on Mo, Si, Cu, and stainless-steel substrates and characterized by optical microscopy and Raman spectroscopy.
A low-energy reactive-ion gun using an ECR ion source and acceleration-deceleration system
Authors: Tanaka Tohru , Maruo Tesuya , Higashi Yasuhiro , Homma Yoshikazu
Published: July 2002

A low-energy reactive-ion gun has been developed as a sputtering gun for high-depth-resolution analysis. It consists of an electron cyclotron resonance ion source and an acceleration-deceleration system. The current density, the energy distribution, and the amount of impurity particles were measured to characterize the ion gun. The current density was estimated by measuring the ion current and the beam diameter for various ion beams. The maximum ion current density at 100 eV is 8.42 μA/cm2, and this means that it takes 19 s to sputter atoms on the monolayer of 1015 atoms/cm2 assuming that each ion sputters an atom. The energy width calculated from the full width at half maximum of the energy distribution was very narrow, 2 eV for the 15-eV beam. The neutralization efficiencies evaluated by measuring secondary-ion emission under bombardment by only neutral particles were 2.9, 0.5, and 0.33 for 1000-eV Ar+, O2+, and BF2+, respectively. This order corresponds to the decreasing ionization potentials of the ion species.
Measurement of magnetic surfaces on the Compact Auburn Torsatron
Authors: Henderson Mark A. , Gandy Rex F. , Hanson James D. , Knowlton Stephen F. , Swanson D. G.
Published: July 2002

The magnetic flux surfaces of the Compact Auburn Torsatron have been experimentally mapped in a variety of magnetic configurations. The magnetic surface mapping was done using the phosphor screen technique. The results are compared with an extensive computer model in order to validate the design coil structure and determine what modifications are needed to correct any minor winding errors. In initial field mapping experiments, a large up–down asymmetry was identified in the vacuum magnetic surfaces. A set of mapping studies was used to characterize the error through addition of terms to the coil winding law. The error was corrected with the use of a radial trim coil.
Efficient long pulse TE-CO2 laser using magnetic-spiker sustainer excitation
Authors: Bhadani P. K. , Harrison R. G.
Published: July 2002

Long pulse operation of a multijoule transverse-electric-CO2 laser using a magnetic-spiker sustainer excitation in conjunction with a pulse forming network is described. The laser has produced 4.5 J in a 5 μs long pulse at a high efficiency of ∼10% from an active discharge volume of 416 cm3. The overall system is simple and reliable.
Moderate resolution x-ray reflectivity
Authors: Shindler J. D. , Suter R. M.
Published: July 2002

We demonstrate that x-ray reflectivity data covering eight decades of intensity can be obtained from a rotating anode source. Our moderate resolution configuration uses a bent graphite monochromator in contrast to the usual high resolution measurement which uses a silicon or germanium monochromator. Illustrative data show that moderate resolution is appropriate for probing a wide variety of surfaces and films. The availability in our configuration of roughly 100 times the incident intensity of a high resolution experiment using a laboratory source allows measurements over a broader angular range which in turn allows us to probe short length scale details of interface structure and tightens the constraints on models of interface structure. Both specular and diffuse scattering signals are accessible. A discussion of reciprocal space resolution explains why there is almost no difference in effective resolutions in the measurement of diffuse scattering.
ac detection of the superconducting transition using voltage controlled circuit
Authors: Tinchev S. S.
Published: July 2002

An eddy-current apparatus for measurement of the superconducting transition of high-Tc films has been developed. It uses a LC resonant circuit driven by a voltage controlled oscillator. The system is ideally suited for nondestructive screening of many high-Tc films. High-Tc films deposited on both sides of a substrate can be investigated successfully.
Single-frequency method for the determination of interface state density
Authors: Tolpadi Amita , Srivastava R. S.
Published: July 2002

The single-frequency method of Hill and Coleman [Solid-State Electron. 23, 987 (1980)] for the evaluation of interface state density has been modified to provide more accurate information about the interface state density. Interface state density obtained by this method has been found to be in good agreement with the interface state density obtained from Nicollian–Goetzberger’s conductance method.
An ECH beam monitor for the Texas Experimental Tokamak
Authors: Roberts D. R.
Published: July 2002

A compact poloidal array of ten receiving antennae has been installed on the high-field wall (x=+30 cm) of the Texas Experimental Tokamak (TEXT) opposite the electron cyclotron heating (ECH) microwave launch port (x=−45 cm, 60 GHz, 200 kW). Both these antennae and the launching structure are oriented to couple to the ordinary mode in plasma. The array serves as a diagnostic of the unabsorbed, first-pass ECH microwave power, which includes both power refracted by the equilibrium plasma density gradients and power scattered by density fluctuations. Each antenna has a Δθy=13° poloidal and Δθz=32° toroidal half-power beam width, corresponding to 12-dB gain. For refraction studies, interchannel and intrachannel poloidal resolutions are Δy=3.5 and 2.5 cm, respectively, at the array aperture surface. For scattering studies, the wave number selectivity extends from k⊥=0±2.5 cm−1 to k⊥=7±2.5 cm−1.
Modulational sources, sideband correlations and nonstationary interference for waves scattered from random mediaa)
Authors: Nazikian Raffi
Published: July 2002

For the small angle scattering of coherent plane waves from inhomogeneous random media, the three-dimensional mean square distribution of random fluctuations may be recovered from the interferometric detection of the nonstationary modulational structure of the scattered field. Modulational properties of coherent waves scattered from random media are related to nonlocal correlations in the double sideband structure of the scattered field. To second order, such correlations may be expressed in terms of a suitably generalized spectral coherence function for analytic fields.
Magnetic imaging of moat-guarded superconducting electronic circuits
Authors: Jeffery Mark , Van Duzer T. , Kirtley J. R. , Ketchen M. B.
Published: July 2002

Superconducting electronic circuits surrounded by various configurations of holes in the superconducting ground plane have been imaged using a high resolution scanning superconducting quantum interference device (SQUID) microscope. These data demonstrate that in the weak field limit continuous moats trap flux more effectively to protect the circuits than small holes in the same configuration.
A technique for measuring radiation-induced infrared absorption in optical materials located in or near a nuclear reactor
Authors: Brannon P. J.
Published: July 2002

A technique for measuring radiation-induced absorption in optical materials located in a nuclear reactor is given. This technique uses optical fibers to couple a probe beam into the reactor volume and requires a minimum of effort to facilitate. Reactor vibrations have a minimal effect on the optical alignment and, consequently, accurate absorption measurements can be made. The technique is illustrated by measurements of radiation-induced absorption in infrasil silica at 1.06, 1.73, and 2.03 μm.
New ac microammeter for leakage current measurement of biomedical equipment
Authors: Branca F. P. , Del Prete Z. , Marinozzi F.
Published: July 2002

A new inexpensive current probe for on-line leakage current measurement of biomedical devices in hospital environment is described. The prototype is designed to detect and measure leakage currents on the ground wire of the device’s power cord so that its integrity can be monitored in real time. Realized with a sensing coil specially matched to a low-noise op amp, this probe adds only negligible impedance on the monitored ground lines. From this preliminary study about the device’s metrological performances, a sensitivity of 10 nArms for a current range 1–500 μArms has emerged, together with a mean linearity error of 0.03% and a frequency response flat within 1% of gain from 50 to 2000 Hz.
Fabrication and characterization of diamond film thermistors
Authors: Miyata Koichi , Saito Kimitsugu , Nishimura Kozo , Kobashi Koji
Published: July 2002

Diamond film thermistors were fabricated from polycrystalline diamond films grown on sintered Si3N4 by microwave plasma chemical vapor deposition. An undoped diamond layer and a zigzag or rectangular pattern of B-doped semiconducting diamond were successively deposited by a selected-area deposition technique. For ohmic electrodes, a Ti/Au bilayer was used. The resistance-temperature characteristics were measured from room temperature to 300 °C. It was found that the temperature coefficient of a diamond film thermistor with a B-doped diamond layer grown using 0.1 ppm B2H6 as dopant gas was higher than those of platinum resistive temperature detectors and SiC film thermistors.