bluuebunny/crossref_metadata_2025 huggingface dataset:
The integral six-color pyrometer: Linear dependence of the radiance temperature T
r on the wavelength lambda
Authors: Hoch Michael
Published: July 2002

The emissivity E of a radiating body as a function of wavelength can be expressed as (ln E)/C2=a+bL+cL2+dL3+eL4+ ... . In our first papers we assumed that the variation is linear; only two coefficients are needed. Later we developed ‘‘A New, General Method of Temperature Determination,’’ which consists of evaluating Te, the calculated blackbody temperature, using one, two, three, and four coefficients (with six wavelengths) in the equation for (ln E)/C2, as well as evaluating its error d′Te. The error is due to the uncertainty in the coefficients. The ‘‘correct’’ Te, called T*e, is obtained by averaging the Te’s, using the d′Te’s as weighting factors. We now have found that the radiance temperature Tr is a linear function of the wavelength over a large wavelength range: from 0.40 to 5.00 μm at low temperature and from 0.40 to 1.00 μm at high temperatures. In practical applications, one should use a wavelength range extending from 0.40 μm through the range where the radiation intensity is at its maximum. In the present paper we first summarize the earlier method and then present the ‘‘linear’’ method applied to data from the literature. We examined tungsten, aluminum alloy 2024, aluminum alloy 7075, titanium alloy Ti–6Al–4V, SiC, SiN, and silicon.
A driver for stable-frequency operation of laser diodes
Authors: Saunders P. , Kane D. M.
Published: July 2002

A driver for the stable-frequency operation of an AlGaAs laser diode is described. This consists of a constant current source with short-term fluctuations of ±8 μA and a drift of less than 2 μA in 10 h, in conjunction with a ±1 mdeg temperature controller. The current can be set to values up to 100 mA and a ramp current up to 20 mA can be added to this to allow frequency scanning of the laser. The laser linewidth is measured by heterodyning two such stabilized lasers and recording the beat note. This has a width of 27±7 MHz. The frequency drift is monitored by exciting the D2 transition of cesium and recording the change in absorbed power when a laser is tuned to the side of an absorption peak. The drift is measured to be 10 kHz/s over 5 h, and is attributed largely to temperature drift. In addition, the current circuit can be readily interfaced to a microcomputer for automatic control of the laser current without sacrificing stability.
Scan system for the sextupole-corrected scanning transmission electron microscopy
Authors: Ruan Shengyang , Kapp Oscar H.
Published: July 2002

A computer-controlled scan system has been completed for a sextupole-corrected high-resolution Scanning Transmission Electron Microscope. It is capable of driving 24 coils and 2 sextupoles in the microscope for beam scan, unscan, alignment, and correction of aberration. A PC-AT is employed to manage this system and control the system devices. By means of these devices the raster size, shape, rotation angle, and dc offset can be controlled by subroutines for image generation/transformation. Computer control provides numerous advantages for the management of such a complicated system making it possible to modify many parameters and invoke a new group of settings simultaneously. This provides convenience in microscope operation for such functions as change in magnification, selection of viewing area, locations of objects of interest and montage.
X-band low phase noise Gunn diode oscillator for EPR spectroscopy
Authors: Oles T. , Strangeway Robert A. , Luglio Juan , Froncisz W. , Hyde James S.
Published: July 2002

Two low phase-noise Gunn diode X-band oscillators intended for use in electron paramagnetic resonance (EPR) spectroscopy are described. In the first, a 250-mW MA49159 Gunn diode oscillator (M/A-COM, Burlington, MA) is mounted in a coaxial transmission line that is closely coupled to a TE011 transmission cavity that in turn is loosely coupled to the output transmission line. The output power is 50 mW and the phase noise is −145 dBc/Hz at 100 kHz offset. In the second, two such coaxial assemblies are used with 500-mW MA49110 diodes for increased power. The output power is 150 mW and the phase noise is −150 dBc/Hz at 100-kHz offset. These phase noise values are in the range of 24–29 dB better than the specification for a normal high quality klystron used in commercial spectrometers.
Madison symmetric torus far-infrared interferometer
Authors: Burns S. R. , Peebles W. A. , Holly D. , Lovell T.
Published: July 2002

A far-infrared (FIR) interferometer plasma density diagnostic has been installed on the Madison Symmetric Torus (MST) at the University of Wisconsin at Madison. This collaborative experiment between University of California at Los Angeles and the University of Wisconsin at Madison has been undertaken to study the physics of the reversed field pinch magnetic confinement configuration. The density profile will be measured via an 11 channel FIR Interferometer. Since MST does not possess slotted plasma viewing ports, each channel will have an individual 4-cm-diam port in the vacuum vessel wall. In order to provide sufficient spatial sampling while minimizing field perturbations, the ports are positioned along two radial arms (separated by 5°) with five ports along one arm and six along the other. The FIR system consists of a tunable twin-frequency FIR laser pumped by a tunable CO2 laser. The system will initially operate at 743 μm but can be discretely tuned from 185 to 1222 μm. This will allow the system to measure a wide range of density parameters. This paper will report and discuss the installation of the system and initial single-chord data from the interferometer.
Range and straggling effects on CR-39/range-filter ion energy measurements
Authors: Lapin S. N. , Cooper G. W. , Davis L. , Bailey J. E. , Stygar W. A. , Carlson A. , Reyes P.
Published: July 2002

The CR-39/range-filter technique measures ion energy by determining the maximum filter thickness which ions can penetrate. CR-39 located behind the filter records the ions. This method is used to measure peak voltage in pulsed power accelerators. We investigated range and straggling effects in this diagnostic by exposing it to 8- and 15-MeV protons for both Al and Ta filters. The range agreed with published values to better than ±6%. The range straggling decreased for higher incident ion energy and lower atomic number, as expected, although there were differences up to a factor of 1.7 between the experimental values and predictions. The dependence of the track diameter distribution on ion energy enabled us to establish a signature which is characteristic of ions which penetrate a filter, via straggling. These results can be used to evaluate the errors present when this diagnostic is used to measure accelerator voltage.
Detector array for measurement of high-frequency fluctuations in visible and near-UV emission from tokamaks
Authors: Hurwitz P. D. , Hall B. F. , Rowan William L.
Published: July 2002

We developed an imaging detector to measure high-frequency fluctuations in visible and near-UV emission from tokamaks. The detector is intended for the study of plasma turbulence, mhd phenomena, and edge-localized modes. Particularly in the first two applications, it will complement existing techniques by providing higher spatial resolution as well as measurement capability in otherwise inaccessible regions of the plasma. The device consists of an optical system, a linear array of 32 photodiodes, and an amplifier for each photodiode. The amplifiers have a transimpedance gain of 105–106 and the frequency response is flat to 100 kHz. Experience with this device has shown that optical imaging systems can be easily designed and tailored to a specific measurement because of the small size and close spacing of the individual light-sensitive elements. The device has been successfully tested on TEXT-U in measurements of Hα fluctuations.
Fast ECE correlation radiometry for fluctuation measurements in JET and PBX-M
Authors: Zolfaghari A. M. , Luckhardt S. , Woskov P. P. , Cohn D. R. , Jones S. , Kesner J. , Machuzak J. , Ramos J. J. , Bartlett D. V. , Costley A. E. , Cripwell P. , Porte L. , Smith R. J. , Kaita R.
Published: July 2002

We discuss the fluctuation characteristics expected from MHD modes including ballooning modes and show how they can be studied using measurements of ECE. A novel technique, ECE correlation radiometry, which enables the location and spatial structure of long wavelength (L≳0.1×a) MHD modes to be determined, is described. Measurements on JET with a 44-channel ECE heterodyne radiometer are presented and show the existence of high-frequency (high n number) MHD modes under high poloidal beta, pellet-enhanced performance (PEP) plasma conditions. Similar measurements are planned for PBX-M and the measurement system is described.
Calibration of the TFTR lost alpha diagnostic
Authors: Boivin R. L. , Lin Z. , Roquemore A. L. , Zweben S. J.
Published: July 2002

We present various aspects of the calibration of the TFTR lost alpha diagnostic. The diagnostic consists of four detectors, forming a poloidal array at the bottom of TFTR inside the vacuum vessel. The detector is composed of a ZnS(Ag) scintillator and a pair of collimating apertures which permit pitch angle, energy, and time resolution of the escaping flux of high-energy ions (MeV range). The first goal of this study was to establish the absolute calibration of the diagnostic for different particle types and energies. This enables us to compare for the first time, measured losses with loss calculations based on a first-orbit model. However, the factor of 2 uncertainty in the final calibration is still too large for full, quantitative comparisons of the data with the theory based on absolute flux measurements alone. We also present some of the aspects related to the detector’s resolution capabilities, its temperature dependence, and its time response.
Calibration of scintillation detectors for MeV charged fusion products
Authors: Tuszewski M. , Zweben S. J.
Published: July 2002

The light output of ZnS scintillators used to detect escaping fusion products in the TFTR Tokamak is studied with 3.5-MeV alpha and 3-MeV proton beams. The emitted light first increases linearly with beam current and then saturates. In all cases investigated, the saturations start at a fairly constant absorbed power density of about 1 mW/cm2. The scintillators have adequate time response up to 50–100 kHz.
Thickness and conductivity of metallic layers from eddy current measurements
Authors: Moulder John C. , Uzal Erol , Rose James H.
Published: July 2002

A robust method that uses eddy current measurements to determine the conductivity and thickness of uniform conductive layers is described. The method was tested by estimating the conductivity and thickness of aluminum and copper layers on various substrate metals, and the thickness and conductivity of free-standing foils of aluminum. The electrical impedance was measured for air-core and ferrite-core coils in the presence and absence of the layer for frequencies ranging from 1 kHz to 1 MHz. The thickness and conductivity of the metal layers were inferred by comparing the data taken with air-core coils to the exact theoretical solution of Dodd and Deeds [J. Appl. Phys. 39, 2829 (1968)] using a least-squares norm. The inferences were absolute in the sense that no calibration was used. We report experimental tests for eight different thicknesses of aluminum (20–500 μm) in free space and on four different substrates: Ti-6Al-4V, 304 stainless steel, copper, and 7075 aluminum, and for five different thicknesses of copper (100–500 μm) on 304 stainless steel. Both the thickness and conductivity could be determined accurately (typically within 10%) and simultaneously if the ratio of the layer thickness to the coil radius was between 0.20 and 0.50. For thinner samples either the thickness could be found if the conductivity were known, or vice versa.
Microwave discharge theory for the microwave ion source
Authors: Sun B. H.
Published: July 2002

This article is about physical foundation of the microwave plasma ion source. The expressions to describe some physical regulations are given. The results show that the source is operated in the optimum state under the condition of electron cyclotron resonance (ωz=ω). This theory can also be applied to the microwave plasma cathode.
A novel hollow cathode device for the detection of trace elements in coal ash
Authors: Collett W. L. , Mahajan S. M. , Ventrice C. A.
Published: July 2002

The hollow cathode plume technique of spectroscopic analysis (HCP) is extended for the detection of trace elements such as arsenic, zinc, cadmium, lead, etc. in coal ash. Introducing a conical inner contour along with internal cooling of the hollow cathode, provides sufficient enhancement of spectral line intensity for the detection of small amounts of trace elements. Using the HCP technique on a coal ash sample supplied by NIST, the relative concentration of As to Zn was found to be within 2% of that obtained by NIST using independent techniques. Although the quantitative determination of the various trace elements in coal ash was beyond the scope of this initial study, ongoing work will establish the general viability of the technique.
A technique for eliminating white phosphorus deposits in vapor phase epitaxy systems
Authors: Wilt D. M. , Hoffman R. W.
Published: July 2002

A technique of heating the exhaust lines is described whereby phosphorus in the exhaust portion of an organometallic vapor phase epitaxy reactor is encouraged to deposit in the red form rather than the pyrophoric white form. This technique is simple, effective, and does not hinder or limit the conditions under which the reactor may be operated.
Rejection of stochastic background noise in low-level pulsed light scattering experiments
Authors: Wang Jyhpyng , Mazur Eric
Published: July 2002

We present an electronic scheme for reducing stochastic noise in the detection of low-level light signals in experiments where the signal coincides in time with a probe laser pulse. This scheme has been applied successfully in Raman experiments to reject the noise generated by afterpulsing in photomultiplier tubes as well as by unwanted laser-induced fluorescence.
Scanning instrumentation for measuring magnetic field trapping in high T
c superconductors
Authors: Sisk R. C. , Helton A. J.
Published: July 2002

Computerized scanning instrumentation measures and displays trapped magnetic fields across the surface of high Tc superconductors at 77 K. Data are acquired in the form of a raster scan image utilizing stepping motor stages for positioning and a cryogenic Hall probe for magnetic field readout. Flat areas up to 45 mm in diameter are scanned with 0.5-mm resolution and displayed as false color images.
Miniature diamond-anvil cell for electrical transport measurements in high magnetic fields
Authors: Tozer S. W.
Published: July 2002

The combination of high magnetic fields and high pressures offers many interesting avenues of exploration to the physics community. To facilitate these measurements, we have developed a diamond-anvil cell, cryogenic loader, and goniometer system which allow us to orient a pressurized sample with respect to a magnetic field while in a cryogenic environment. The cell, reported in this paper, has provisions for eight micro–mini triax cables which allow one to perform a variety of electrical transport measurements including studies of anisotropic materials. Optical access, f/3, is provided through the diamonds for pressure calibration and any variety of optical studies. The cell, constructed entirely of BeCu, can rotate freely in a cryostat with an inner diameter greater than 20.3 mm while keeping the pressurized sample space within the central 1-cm3 sphere of magnetic homogeneity typical of most magnets. Using this cell, we have monitored the second harmonic in the nonlinear optical material KTP to 7.3 GPa and observed the pressure-induced first-order phase transition at 5.77 GPa using 0.95-mm culets and liquid helium as a pressure medium.
Computer-controlled float zone crystal growth
Authors: Chan Y. T. , Mailloux P. A.
Published: July 2002

A PC-based computer control system to automate a high-temperature float zone growth of titanium carbide is reported. The control strategy of the computer control system relies on the relations derived from a combination of empirical relations and results from detailed mathematical analysis of the physical transports of the entire float zone assembly. A system control computer program was written to establish real-time determination of the size of the molten zone from a thermal image, control parameters from established relationships, and collected processed data to achieve control objectives. We found that the developed computer control allows the growth process to be operated nearer the stability limit. Any slight variations in growth conditions can be corrected in time to avoid any instability growth, which otherwise cannot be adjusted via manual control.
A particle bed heater for creating a clear, high-temperature, high-pressure gas flow
Authors: Birk Avi , McQuaid Michael J. , Bliesener Gary G.
Published: July 2002

The design and operation of a compact, lightweight particle bed heater for rapidly loading (≤1 s) a 1000 cm3 test chamber with clear, high-temperature (100≤T≤600 °C), high-pressure (10≤P≤50 MPa) gas is described. The device facilitates the design of short duration (≤10 s) experiments where visualization of dynamic systems at such conditions are desired. The heater has enabled visualization of reactive spray phenomena in our laboratory, and its performance in this application is summarized.
Signal analysis of fluctuations in toroidal fusion plasmas
Authors: Bell J. D. , Harris J. H. , Dunlap J. L. , Crocker N. A. , Paré V. K.
Published: July 2002

Spectral-based signal-processing techniques for characterizing fluctuation data from plasma discharges in the Advanced Toroidal Facility fusion experiment are described. The analysis process moves from wave form display and spectral analysis of single discharges to coherence filtering and database techniques for identifying coherent fluctuations. These analysis techniques are used to distill large volumes of spectral data from many signals per discharge (for many discharges) into simple forms suitable for comparison with the global variation of plasma parameters.
Threshold current temperature dependence of GaInP/(AlyGa1−y)InP 670 nm quantum well lasers
Authors: Smowton P. M. , Blood P.
Published: July 2002

The temperature dependence of threshold current of (AlyGa1−y)InP/GaInP quantum well lasers (y=0.3, 0.4, and 0.5) has been investigated and used to characterize thermally activated loss mechanisms above room temperature. We show good agreement between activation energies measured by Arrhenius analysis and those expected for the loss of electrons from the well to the X-conduction band minima in the barrier. Our analysis uses measured band gaps of the actual structures, avoiding assumptions about the alloy compositions, spontaneous emission data to subtract radiative and other direct gap processes, and recent band gap data for this alloy system. This provides convincing experimental confirmation of the loss of electrons from the indirect minima as the preferred process causing the rise in current at high temperature in these lasers.
Low-current temperature compensated bipolar log-ratio amplifier
Authors: Acharya Y. B. , Tikekar S. G.
Published: July 2002

Numerous instrumentation applications can benefit from the use of logarithmic or exponential signal processing technique. A temperature-compensated bipolar log-ratio amplifier has been designed for measurements of currents of both polarity in the current range 10−11–10−5 A. This amplifier finds its usefulness in signal compression, especially in space-borne instrumentation for the study of various atmospheric parameters, such as electron temperature, where currents of both polarity having large dynamic range are to be measured. Temperature compensation is achieved in the temperature range −10 to +70 °C.
Time-resolved electric field measurements in a 15 kHz helium glow discharge
Authors: Preppernau B. L. , Ganguly B. N.
Published: July 2002

Time-resolved electric field profile measurements were made in a driven 15 kHz parallel plate helium glow discharge using optogalvanic spectroscopy. Electric field values in the sheath region were determined from the energy splitting of the helium Rydberg state Stark manifolds due to the local applied electric field as a function of position and phase. The measured field values in the cathode sheath region range from about 800 to 300 V/cm; the measurement accuracy of electric field values are ±25 V/cm. The line of sight laser probe measurements have a spatial resolution of 200 μm and a temporal accuracy of better than 1% of the driving cycle. The low driving frequency allows for a comparison with the dc discharge approximation. The spatial electric field profile is identical to a dc discharge operating at the same peak current and voltage values and the temporal field profile is symmetric about the current wave form extremum.
Full temperature calibration from 4 to 300 K of the voltage response of piezoelectric tube scanner PZT-5A for use in scanning tunneling microscopes
Authors: Vandervoort K. G. , Zasadzinski R. K. , Galicia G. G. , Crabtree G. W.
Published: July 2002

We have calibrated the displacement/voltage (Å/V) response of our piezoelectric scanning tube (PZT-5A) by imaging graphite at over 40 temperatures between 4 and 300 K. We have also calibrated the (Å/V) response as a function of voltage up to 220 V at room temperature, imaging a gold-plated diffraction grating. We find that the temperature dependence of the (Å/V) response is linear to within 10% and is reduced by a factor of 5.5 on decreasing temperature from 300 to 4.2 K. The near linearity with temperature of the (Å/V) response makes the PZT-5A lead zirconate titanate composition a convenient choice for low temperature scanning tunneling microscope piezo tube elements.
A new technique to obtain a fast thermocouple sensor for thermal diffusivity measurements in an extended temperature range
Authors: Calzona V. , Cimberle M. R. , Ferdeghini C. , Grasso G. , Putti M. , Siri A. S.
Published: July 2002

An improved ac method to measure the thermal diffusivity in an extended temperature range is presented. The basic idea is to solder thermocouple wires directly on the sample, so that the sample itself acts as a thermocouple junction and the relaxation time for the temperature measurement becomes negligible. This new technique allows one to measure smaller samples and to increase the frequency of measurement so that the thermal losses could in principle be completely neglected. Finally, by the particular geometry a concurrent measurement of the electrical resistivity is obtained.
Ultrahigh vacuum compatible cooling and vibration isolation stage
Authors: Stalder A. , Dürig U.
Published: July 2002

A scheme is described that resolves the problem of coupling sensitive equipment to a heat exchanger while retaining excellent isolation against vibrations in an ultrahigh vacuum environment.
Fast-rise, large-volume, 1.7-kG magnetic-field coil
Authors: Weidman D. J. , Rhee M. J. , Schneider R. F.
Published: July 2002

A one-turn coil of 20 cm diameter and 30 cm length produces a field up to 1.7 kG with a rise time of 30 ns. The rate of rise of field, nearly 6 T/μs, is faster than for any other coil of this size. Powering the coil is a transformer-charged pulse-forming line machine operating at up to 28 kA, 280 kV without deleterious arcing. The field is uniform to 5% over the coil length, focusing an electron beam passing along its axis.
A detection scheme for zero-kinetic-energy photoelectron spectroscopy with multibunch synchrotron radiation
Authors: Waterstradt Eckhard , Jung Rolf , Dietrich Hans-Jörg , Müller-Dethlefs Klaus
Published: July 2002

A detection scheme for zero-kinetic-energy photoelectron spectroscopy (ZEKE spectroscopy) adapted to the time structure of multibunch vacuum ultraviolet synchrotron radiation from BESSY is described. A resolution of 50 cm−1 (6 meV) is achieved at high stored ring currents providing high photon flux and resolution for one-photon ZEKE spectroscopy and electron-ion coincidence measurements.
Double-crystal high-resolution x-ray spectroscopy of laser-produced plasmas
Authors: He H. , Wark J. S. , Foerster E. , Uschmann I. , Renner O. , Kopecky M. , Blyth W.
Published: July 2002

A double-crystal x-ray spectrometer (DCS) has been used to obtain high-resolution x-ray spectra of laser-produced plasmas. The DCS has a high dispersion, and thus can obtain highly resolved spectra in circumstances where the resolution of a conventional single-crystal Bragg spectrometer at comparable source-to-detector distances would be limited by the source size. In addition the DCS also yields unit-magnification one-dimensional spatial resolution in the direction perpendicular to the spectral direction. The instrument produces two spectra symmetrically disposed about a central wavelength, which makes it especially useful for measuring spectral line shifts. Analysis of the spectra from hydrogenic aluminium and helium-like chlorine indicates a resolving power (λ/Δλ) greater than 2500 and a spatial resolution better than 30 μm.
Doing double-crystal diffraction experiments with a conventional four-circle diffractometer
Authors: Chao W. K. , Gao E. Z. , Wong H. K.
Published: July 2002

A simple attachment has been built to convert a conventional four-circle diffractometer to a double-crystal diffractometer. This modification allows us to do high-resolution structural studies at high/low temperatures.
Implementation of a position sensitive detection system in a scattered electron-Auger electron coincidence experiment
Authors: Johnson P. M. , Beames S. D. , Bell S. , Lohmann B.
Published: July 2002

A coincidence data acquisition system, incorporating a position sensitive detector and a custom-built data acquisition card installed in an IBM-PC 486 computer, has been implemented in a coincidence experiment in which scattered electrons and Auger electrons are detected in coincidence. Three analog-to-digital converters (ADCs) are used to digitize all the timing and energy information, and custom-designed and written control software is used to accumulate the data, display it in real time, and store it in expanded memory. The new system has ben used to measure the energy and angular distribution of Auger electrons ejected from argon after electron impact ionization.
Vacuum arc ion source for the ITEP RFQ accelerator
Authors: Batalin V. A. , Volkov J. N. , Kulevoy T. V. , Petrenko S. V.
Published: July 2002

A version of vacuum arc ion source has been developed and constructed at the Institute for Theoretical and Experimental Physics, Moscow, for use with a heavy ion radio frequency quadrupole linac. The source is operated in a pulsed mode with a pulse length from 5 to 120 μs and a repetition rate of from 1/8 to 1 pps. The injection voltage is up to 90 kV depending on the kind of ions being used, and the beam current at the injector output is up to 500 mA. The results described in this article were made at a beam current of from 10 to 100 mA. In order to obtain ions having a charge-to-mass ratio of about 1/60, metals such as Cu, Mo, Ta, W, and Pb were used as the cathode material. Volt-ampere characteristics and charge state distributions were measured. The charge state spectral variation was investigated throughout the arc current pulse duration as well as the dependence of the mean charge state of the beam ions on the melting point of the cathode material.
The study of a 2.45 GHz plasma source as a plasma generator for the SCECR electron cyclotron resonance ion source
Authors: Srivastava A. K. , Asmussen J. , Antaya T. , Harrison K.
Published: July 2002

The 2.45 GHz plasma source is a multicusp electron cyclotron resonance source with a tuned single mode microwave cavity. This is a bright plasma source with a well characterized operating mode and plasma parameters [A. K. Srivastava, et al., Rev. Sci. Instrum. 63, 2556 (1992); A. K. Srivastava and J. Asmussen, J. Vac. Sci. Technol. A 11, 1307 (1993)]. The superconducting electron cyclotron resonance (SCECR) is a fully superconducting, hexapole stabilized tandem mirror ion source with a multimode microwave cavity. It is a high charge state ion source with extensive beam diagnostics [T. A. Antaya, Nucl. Instrum. Methods B 40/41, 1024 (1989)]. The coupling of these two sources permits a number of fundamental studies important to both classes of ion sources. The 2.4 GHz plasma source will be used to study the effects of ion or electron (or both) density enhancement on the charge state distribution, total extracted current, and ion energy distributions of the SCECR. The SCECR in turn will be used as a test stand to measure directly the ion distribution and beam characteristics of the 2.45 GHz plasma source. The first results with this hybrid ion source will be presented at this conference.
High current H− ion production in cesium seeded large ion sources
Authors: Tsumori K. , Ando A. , Takeiri Y. , Kaneko O. , Oka Y. , Okuyama T. , Kojima H. , Yamashita Y. , Kawamoto T. , Akiyama R. , Kuroda T.
Published: July 2002

The characteristics of a large negative-ion source with external filter is investigated for the neutral-beam injection system in a large helical device. The magnetic cusp field is set up at almost the same strength as that in our well optimized 1/3 ion source with rod-type magnetic filter. An H− ion current of 5.2 A is extracted from the ion source with Cs seeding. The H− current corresponds to 19.7 mA/cm2, and the value is comparable to the current density obtained using the 1/3 scaled ion source with a rod-type magnetic filter at the same extraction voltage. In low operating pressure, the ion source with the external filter has a better performance on the extraction of H− ions.
Method for making electrical contacts to hard and reactive intermetallic compounds
Authors: Walker I. R.
Published: July 2002

A method is described for making electrical contacts to metallic materials which, because of their hardness and reactivity, can be very difficult to attach leads to using other techniques. These metals, including some of the heavy fermion materials, form inert and tightly bonded oxide layers which hinder the use of ordinary soldering methods. It has been found that a simple modification to an ordinary soldering iron, involving the replacement of the standard copper tip with one made of tungsten carbide, enables these oxide layers to be penetrated and electrical contact to be made without the use of flux. The size of the resulting contacts can be very small and their electrical resistance very low. Other, less viable, techniques for making contacts are also discussed, and a means of holding samples in place during soldering is described.
Dynamic analysis of piezoelectric elements
Authors: Yang Shengyuan , Huang Wenhao
Published: July 2002

A general model is presented for dynamic analysis of piezoelectric elements. The detailed solution of the model is given for the first time. The previous research results are some specific cases to our model and can be deduced from our model. Using this model, one can analyze precisely the dynamic response of the mechanical system driven by piezoelectric elements. As an example, the dynamic response of the widely used scanning probe microscope scanner is calculated. The method to deal with structure damping in the piezoelectric material is also discussed and we get different results from the previous results.
Apparatus for measuring time-resolved light scattering profiles from supercritical polymer solutions undergoing phase separation under high pressure
Authors: Kojima Junichi , Nakayama Yoshiaki , Takenaka Mikihito , Hashimoto Takeji
Published: July 2002

A light scattering instrument was constructed to investigate the phase diagram and the dynamics of phase separation processes for supercritical polymer solutions. The instrument has the following features: (i) the light scattering cell withstands pressure over 34.3 MPa and temperature up to 573 K, (ii) viscous solutions such as a polymer solution can be easily handled, (iii) a rapid incremental or decremental pressure change as small as 0.01 MPa can be precisely controlled, and (iv) the angular distribution of the scattered intensity can be continuously measured over a wide angular range (0°–30°) at 100 scans/s. The phase diagram of polypropylene/trichlorofluoromethane was measured with the instrument. Some preliminary experimental results for the dynamics of the phase separation of the system are also presented.
A method for preparation of Pt–Ir tips for the scanning tunneling microscope
Authors: Weinstein Vladimir , Slutzky Michael , Arenshtam Aleksandre , Ben-Jacob Eshel
Published: July 2002

A method for preparation of Pt–Ir tips using alternating currents at frequency of 400 Hz is presented. Interpretation of the etching process and discussion on the quality of the prepared tips are reported.
The vacuum ultraviolet scanning photoelectron microscope at MAX-LAB
Authors: Johansson U. , Nyholm R. , Törnevik C. , Flodström A.
Published: July 2002

The performance of a scanning photoelectron microscope at the MAX I storage ring in Lund is presented. The microscope utilizes undulator radiation in the energy range 15–150 eV and is comprised of a plane-grating monochromator with a Kirkpatrick–Baez objective and a gracing incidence ellipsoidal focusing mirror. The instrument with its high photon flux, 109–1010 photons/s, and narrow bandwidth, better than 0.2 eV, is excellently suited for high-resolution core-level spectroscopy and imaging of samples with lateral inhomogeneties in the micrometer range.
The transient internal probe: A novel method for measuring internal magnetic field profilesa)
Authors: Bohnet M. A. , Galambos J. P. , Jarboe T. R. , Mattick A. T. , Spanjers G. G.
Published: July 2002

The transient internal probe (TIP) diagnostic is designed to permit internal magnetic field measurements in hot, high density plasmas. A small probe is fired through the plasma at high velocities and magnetic field measurements are accomplished using Faraday rotation within the Verdet glass probe. Magnetic field resolution of ±40 G and spatial resolution of 5 mm have been achieved. System frequency response is 10 MHz. Ablative effects are avoided by minimizing both the probe size and the time the probe spends in the plasma. A two-stage light-gas gun is used to accelerate the probe (held by a sabot) to 2.2 km/s. The sabot is removed using gas dynamic forces and a gas interface system prevents the helium muzzle gas from entering the plasma chamber. Work is underway to integrate the TIP diagnostic with laboratory plasma experiments.
An optical fiber interface circuit for high electrical insulation between a personal computer and a measurement system
Authors: Boella G. , Senepa L.
Published: July 2002

In order to obtain low uncertainty levels in computer-controlled electrical precision measurements, the controlling system must not interfere with the measurement system. The optical interface described here provides the two systems with an insulation resistance higher than 1014 Ω using two optical fibers, which also allow the systems to be remotely located. The interface treats two dc voltage signals: one of them is used to drive the measuring system, and the other is the result of the measurement and can be read with a relative accuracy of 1×10−4. The interface can be used to automatically drive dc resistance bridges and will be applied to a cryogenic setup having a superconducting quantum interference device as a detector.
Improved Kelvin method for measuring contact potential differences between stepped gold surfaces in ultrahigh vacuum
Authors: Bellier J. P. , Lecoeur J. , Koehler C.
Published: July 2002

A new mechanical system and a convenient piezoelectric driven Kelvin probe for the measurement of the contact potential difference (CPD) under ultrahigh vacuum are described. Charging effects on CPD measures are discussed. The probe is small (2.2 mm diam) and allows cartography of the surface. The mechanical system is frictionless so the distance between the sample and the probe can be maintained constant and at a low value (≊20 μm). By elimination of charging effects, reliable and reproducible results can be obtained within ±10 mV. The system is tested on gold vicinal surfaces.
Measurement of microphone membrane displacement with an optical beam deflection technique
Authors: Benedetto Giuliana , Gavioso Roberto , Spagnolo Renato
Published: July 2002

Optical beam deflection is a simple and reliable method for the detection of small displacements. This paper describes its application to the measurement of the displacement of the membrane of a condenser microphone, where the displacement is induced by supplying an alternate voltage to the transducer terminals. A sensitive reconstruction of the dynamic deformation of a microphone membrane in a wide frequency range is obtained.
Analysis of two-dimensional temperature response during the measurement of thermal diffusivity of platelike samples by an ac calorimetric method
Authors: Yamane Tsuneyuki , Katayama Shin-ichiro , Todoki Minoru
Published: July 2002

A new method has been developed to estimate the two-dimensional periodic temperature response of platelike samples using the Fourier transform of the two-dimensional impulse response for the designated system. This method is applied to the case of thermal diffusivity measurements parallel to the sample surface using an ac calorimetric method. It is concluded from the theoretical consideration that the thermal system can be considered as a one-dimensional system except at the boundary of the heated and nonheated regions. The thermal system cannot be considered as a one-dimensional system near the boundary of the heated and nonheated regions since the ac temperature response changes transiently perpendicular to the sample surface.
A quasiparticle-trap-assisted transition-edge sensor for phonon-mediated particle detection
Authors: Irwin K. D. , Nam S. W. , Cabrera B. , Chugg B. , Young B. A.
Published: July 2002

We have demonstrated the operation of composite superconducting tungsten and aluminum transition-edge sensors which take advantage of quasiparticle trapping and electrothermal feedback. We call these devices W/Al QETs (quasiparticle-trap-assisted electrothermal feedback transition-edge sensors). The quasiparticle trapping mechanism makes it possible to instrument large surface areas without increasing sensor heat capacity, thus allowing larger absorbers and reducing phonon collection times. The sensor consists of a 30-nm-thick superconducting tungsten thin film with Tc∼80 mK deposited on a high-purity silicon substrate. The W film is patterned into 200 parallel lines segments, each 2 μm wide and 800 μm long. Eight superconducting aluminum thin film pads are electrically connected to each segment, and cover a much larger surface area than the W. When phonons from particle interactions in the silicon crystal impinge on an aluminum pad, Cooper pairs are broken, forming quasiparticles which diffuse to the tungsten lines where they are rapidly thermalized. The W film is voltage biased, and self-regulates in temperature within its superconducting transition region by electrothermal feedback. Heat deposited in the film causes a current pulse of ∼100 μs duration, which is measured with a series array of dc superconducting quantum interference devices. We have demonstrated an energy resolution of <350 eV full width at half-maximum for 6 keV x rays incident on the backside of a 1 cm×1 cm×1 mm (0.25 g) silicon absorber, the highest resolution that has been reported for a fast (<1 ms pulse duration) calorimetric detector with an absorber mass≳0.1 g. Applications of this technology include dark matter searches and neutrino detection.
Latch proof operation of a switch of a high repetition rate laser with dc resonant charging
Authors: Biswas D. J. , Nilaya J. P. , Chatterjee U. K.
Published: July 2002

We report on the operation of a high voltage high current switch in which command resonant charging capability is built in. Elimination of switch latch up problems do not require any extraneous and complex circuitry. The indigenously developed switch delivers power in excess of 3 kW into a dummy load typical of a TE laser at a pulse repetition rate of 200 Hz. The test on a real TEA CO2 laser load was, however, limited up to 50 Hz repetition rate beyond which the accumulation of dissociation products within the active volume led to arcing.
Diagnostics for a waste processing plasma arc furnace (invited) (abstract)a)
Authors: Woskov P. P.
Published: July 2002

Maintaining the quality of our environment has become an important goal of society. As part of this goal new technologies are being sought to clean up hazardous waste sites and to treat ongoing waste streams. A 1 MW pilot scale dc graphite electrode plasma arc furnace (Mark II) has been constructed at MIT under a joint program among Pacific Northwest Laboratory (PNL), MIT, and Electro-Pyrolysis, Inc. (EPI)c) for the remediation of buried wastes in the DOE complex. A key part of this program is the development of new and improved diagnostics to study, monitor, and control the entire waste remediation process for the optimization of this technology and to safeguard the environment. Continuous, real time diagnostics are needed for a variety of the waste process parameters. These parameters include internal furnace temperatures, slag fill levels, trace metals content in the off-gas stream, off-gas molecular content, feed and slag characterization, and off-gas particulate size, density, and velocity distributions. Diagnostics are currently being tested at MIT for the first three parameters. An active millimeter-wave radiometer with a novel, rotatable graphite waveguide/mirror antenna system has been implemented on Mark II for the measurement of surface emission and emissivity which can be used to determine internal furnace temperatures and fill levels. A microwave torch plasma is being evaluated for use as a excitation source in the furnace off-gas stream for continuous atomic emission spectroscopy of trace metals. These diagnostics should find applicability not only to waste remediation, but also to other high temperature processes such as incinerators, power plants, and steel plants.
A new approach to internal disruption analysis with the five-camera soft-x-ray diagnostic on RTP
Authors: Tanzi C. P. , de Blank H. J. , Donné A. J. H.
Published: July 2002

A novel method is presented to analyze internal disruptions (sawteeth), observed with the five-camera soft-x-ray diagnostic at the Rijnhuizen Tokamak Project (RTP). Using four or five cameras, tomographic images with seven poloidal harmonics have been obtained throughout sawtooth crashes and precursor oscillations. The detection of cross-field transport and magnetic reconnection from the reconstructed tomographic images is complicated by the fact that (except during the final phase of the collapse) the time dependence is dominated by the m=1 ideal MHD displacement of the hot core in combination with plasma rotation. It is possible to define quantities, e.g., the plasma volume where the emissivity is within a certain range, whose change is only determined by cross-field transport or reconnection, and are not affected by displacement and rotation. The good spatial resolution of the 80-channel system enables us to compute these quantities with such an accuracy that their sensitivity to plasma rotation and MHD convection is small. Using this approach we find in the sawteeth studied so far that m=1 magnetic reconnection may take place, but affects less than half of the magnetic flux within the q=1 surface, thus ruling out complete reconnection as a mechanism for the final collapse of the hot core in these cases.
Interferometric measurement of the physical constants of laser dye solvents
Authors: Hassan G. E. , El-Kashef H. , El-Baradie B. Y. , El-Labban M.
Published: July 2002

The absolute value of refractive index and its variation with temperature of benzene and chloroform at He-Ne laser wavelength 6328 Å are measured. The measurements are carried out using laser interferometric technique. This technique is based on the shift of interference pattern when rotating the sample in one arm of a newly developed Mach–Zehnder interferometer. The refractive index shows a linear relationship with temperature in the range of interest. The thermal refractive index coefficients of benzene and chloroform are all negative. Applying Maxwell’s theory and Lorentz–Lorenz function, the obtained results are used for calculating the optical permittivity (or dielectric susceptibility) as a function of temperature and many other important related physical constants.
Measurement of temperature fluctuations from electron cyclotron emission
Authors: Watts Christopher , Gandy R. F. , Rempel T. D. , Cima G.
Published: July 2002

Radial scans of high-frequency electron temperature fluctuations T̃e,rms have been performed in TEXT-U ohmic discharges. The measurements were accomplished by using a technique correlating the electron cyclotron emission at two disjoint frequency bands emitted from essentially the same plasma volume. Focusing and defocusing the optics allows one to estimate the poloidal k spectrum of these fluctuations. Applying the analysis stroboscopically synchronized with the sawtooth oscillations it is shown that, in the central region of the plasma, sawteeth are the dominant contribution to low-frequency modes. Additionally, by adjusting the frequency of one of the bands, one can separate the two volumes and thus estimate the radial correlation length of T̃e,rms.
Results from the TFTR high-frequency toroidal Mirnov array for detection of modes in the Alfvén range of frequencies
Authors: Fredrickson E. , McGuire K. M. , Chang Z. Y.
Published: July 2002

Toroidal Alfvén eigenmodes and other Alfvénic modes have been predicted to be destabilized by the presence of a fusion α population in TFTR and future D-T machines, possibly resulting in significant loss of the fast α population. A new array of Mirnov coils has been added primarily for the measurement of moderate to high toroidal mode numbers. Initial measurements of the n number of ICRF generated toroidal Alfvén eigenmodes modes is presented. The array has also been used to measure the toroidal correlation length of the edge magnetic turbulence.