bluuebunny/crossref_metadata_2025 huggingface dataset:
Teflon cell for electrical conductivity studies in molten fluorides
Authors: Elias A. M.
Published: July 2002

A novel conductivity cell for fluoride systems with a low melting point is reported. The instrument concerned is made of Teflon and has bright platinum electrodes. It may be used up to 170 °C. The value of the cell constant is 27.91±0.06 cm−1. The cell may be used with other values of the constant upon changing the capillary diameter of the horizontal cylindrical piece.
Erratum: Simple and reliable preionization technique using SiC ceramics and its application to a TEA CO2 laser for airborne DIAL [Rev. Sci. Instrum. 5
9, 880 (1988)]
Authors: Asai Kazuhiro , Itabe Toshikazu , Ishizu Mitsuo , Aruga Tadashi , Igarashi Takashi
Published: July 2002

Due to an editorial error, several co-authors names and addresses were inadvertently omitted. We apologize for any inconvenience this may have caused. The above listing has been corrected to include all of the authors.
Ultrahigh vacuum sample transfer device with broad temperature range
Authors: Drouhin H.-J. , Picard M. , Paget D.
Published: July 2002

The design of a sample transfer device for ultrahigh vacuum experiments is presented. In this device, the mobile sample holder has a wedge shape and can be attached to its place using a magnetic rod without delicate alignment. This device operates from close to nitrogen temperature to a temperature on the order of 700–800 °C.
Angular distribution measurement of fragment ions from a molecule using a new beamline consisting of a Grasshopper monochromator
Authors: Saito Norio , Suzuki Isao H. , Onuki Hideo , Nishi Morotake
Published: July 2002

Optical characteristics of a new beamline consisting of a premirror, a Grasshopper monochromator, and a refocusing mirror have been investigated. The intensity of the monochromatic soft x-ray was estimated to be about 108 photons/(s 100 mA) at 500 eV with the storage electron energy of 600 MeV and the minimum slit width. This slit width provides a resolution of about 500. Angular distributions of fragment ions from an inner-shell excited nitrogen molecule have been measured with a rotatable time-of-flight mass spectrometer by using this beamline.
Apparatus for measurements of PVT properties and their derivatives for fluids and fluid mixtures with a metal bellows as a variable-volume vessel
Authors: Kamimura T. , Iso A. , Higashi Y. , Uematsu M. , Watanabe K.
Published: July 2002

A new apparatus for measurements of PVT properties and their derivatives with a metal bellows was designed for fluids and fluid mixtures of a fixed composition for pressures up to 20 MPa in the range of temperatures from room-temperature condition to 473 K. The apparatus, procedures, and results of calibrations are described. The capabilities of the apparatus are illustrated by means of the vapor-pressure measurements for chlorodifluoromethane and the PVT measurements of sulfur hexafluoride. Temperatures were set and kept constant at the values desired within ±3 mK and pressures within ±2 kPa. It was shown that density derivatives with respect to pressure at constant temperature and those with respect to temperature at constant pressure may both obtain from the experimental results.
Simple high-speed circulating pump for gases
Authors: Hisham Mohamed W. M. , Benson Sidney W.
Published: July 2002

A high-speed, all-glass, and Teflon pump is described. It operates using a magnetic solenoid which is electronically controlled. This permits variable pumping speeds up to 150 cc/min. Design specifications and details of the electronic control circuit are given.
Erratum: Double-pulse Nd:glass laser system for Thomson scattering diagnosis of high-temperature plasmas [Rev. Sci. Instrum. 5
9, 1473 (1988)]
Authors: Dooling J. C. , York T. M.
Published: July 2002

Regarding the section on conversion efficiency on p. 1474 [Sec. II, part (5)], the reference to Eq. (2) in the text is in error and should in fact read, ‘‘Equation (1) provides...’’ Also, in Fig. 3 the reference to Eq. (2) should be a reference to Eq. (1). Finally, in Fig. 3, the reference to Eq. (3) in fact refers to the unnumbered expression for PDCE’ in the text on p. 1474, column 2.
A hyperbolic energy analyzer
Authors: Leal-Quiros Edbertho , Prelas Mark A.
Published: July 2002

The hyperbolic energy analyzer (HEA) is based on a novel diagnostic principle which uses a new type of electrostatic lens. The HEA has a pinhole aperture, a hyperbolic lens, and a long Faraday cup. The hyperboloid cones which make up the lens have a vertex angle of 70.53°. Each cone is held at a constant potential. The hyperbolic lens performs two functions: it focuses the ions in space and it selects the ion energy which is collected by the Faraday cup. The HEA measured electron and ion characteristics in the M4X (modified Missouri magnetic mirror experiment) and the results were confirmed with Langmuir probes and ion energy analyzers.
A new method for measuring phase shift in heterodyne interferometric measurement
Authors: Bi D. G. , Kubo S. , Nishizawa A. , Takahashi C. , Fujita J.
Published: July 2002

A new method for analyzing the phase shift of probe beat in heterodyne interferometric measurement has been developed. The phase shift is obtained directly from the changes of the probe beat period without comparing with a reference beat. An electric circuit system has been designed according to this method of measurement, combined with a heterodyne interferometer of HCN laser or 4 mm microwave of line-integrated electron density of plasma in the compact helical system (CHS). The experimental results show that the method is effective. It simplifies the interferometric system and is free from the trouble of initial phase difference between the probe beat and reference. The minimum measurable phase shift is determined by the ratio of beat frequency to the counting clock frequency. The maximum measurable phase shift is infinite in principle.
Room temperature optical absorption characteristics of GaAs/AlGaAs multiple quantum well structures under external anisotropic strain
Authors: Huang Man-fang , Garmire Elsa , Partovi Afshin , Hong Minghwei
Published: July 2002

We report the room temperature anisotropic absorption characteristics of a GaAs/AlGaAs multiple quantum well structure under biaxial anisotropic strain that was achieved by bonding to an x-cut LiTaO3 substrate at 150 °C, with the [110] and [1■10] directions of the multiple quantum well along the y and z axes of LiTaO3, respectively. A stronger heavy hole excitonic feature can be observed when the polarization of the incident light is in the compression direction, which thus results in larger quantum confined Stark effect. An absorption coefficient change of 0.6 μm−1 was observed for an applied field of 7.4 V/μm. This change in absorption coefficient is 1.5 times the value obtainable from a multiple quantum well without strain.
Acoustic measurements of gas density
Authors: Shakkottai P. , Kwack E. Y. , Back L. H.
Published: July 2002

Density measurements can be made in a gas contained in an enclosure by measuring the sound pressure level at a receiver located near a dipole source driven at constant velocity amplitude at low frequencies. Analytical results are given in terms of geometrical parameters, wave numbers, and source type for simple model problems and compared with data available in a paper by Haran [Tech. Mess. 50, 43 (1983)].
A strain gage-variable area flowmeter
Authors: Guillaume D. W. , DeVries D.
Published: July 2002

This article presents a unique hybrid flowmeter that combines the turndown ratio/low resistance benefits of a variable area differential pressure flowmeter with the low component simplicity of a target flowmeter. The design attaches a single element strain gage to the flexural membrane suspended in a fluid flow passage, eliminating the need for force or pressure transducers. A prototype of the concept produced favorable results that conformed well to a theoretical model.
Fiber-optics Brillouin scattering spectrometer
Authors: Pakulski G. , Holuj F.
Published: July 2002

A simple and versatile spectrometer for obtaining Brillouin spectra from condensed matter is described. It utilizes optical fibers in the scattered light paths and is designed in such a way that alignment of the whole setup can be achieved and maintained easily. The spectrometer can automatically record spectra from two samples successively, where one of these samples can be used as a reference. A novel computer stabilization procedure which is able to maintain the finesse of the Fabry-Perot interferometer for long periods of time is also described.
1987 calibration of the TFTR neutron spectrometers
Authors: Barnes Cris W. , Strachan J. D.
Published: July 2002

The 3He neutron spectrometer used for measuring ion temperatures and the NE213 proton recoil spectrometer used for triton burnup measurements were absolutely calibrated for source strength measurements with DT and DD neutron generators placed inside the TFTR vacuum vessel. Details of the detector response and generator calibration are presented. The calibrated accuracy of the NE213 system to the DD neutron source strength is ±30%, to DT neutrons ±20%, and to the ratio ±20%. Background problems made the accuracy of the 3He system calibration ±70% for the DD peak. Strong affects of local attenuation were observed. For both systems the calibrated efficiencies were 10–100 times less than the unattenuated response, consistent with removal cross sections for the intervening material. The relatively high-energy threshold of these detectors resulted in insensitivity to scattered neutrons. Within the relative calibration uncertainties, the neutron source strengths from these systems are in agreement with the source strengths measured from the calibrated fission chamber system.
A symmetrical low temperature pressure transducer
Authors: Helvensteijn B. P. M. , VanSciver S. W.
Published: July 2002

The design and operating characteristics of a fully differential pressure transducer are described. The device is intended for use with He II heat transfer experiments where it operates in vacuum and at low temperatures (T<4.2 K). A movable electrode is attached to two sets of miniature bellows such that the electrode position is determined by the differential pressure across the device. The movable electrode is located between two fixed electrodes, thus forming a pair of variable capacitors. A dedicated charge amplifier is used to convert the pressure induced capacitance change to an ac output voltage. The sensitivity is roughly 5 μV/Pa. For the present application, the capacitor and electronics have acceptable performance, with a mean noise level of ±5 Pa.
Integraph mechanisms
Authors: Houtman H.
Published: July 2002

The principle common to mechanical integraphs in general is reviewed, with regard to many of those previously published. In addition, two novel integraph mechanisms are described in detail.
Compact resonator for low temperature NMR experiments
Authors: Nunes G.
Published: July 2002

We describe the design of a modified split-ring resonator, especially suited to low-temperature experiments, which enables cavities with dimensions of order 1 cm to resonate at frequencies as low as a few hundred megahertz.
Protection of laser power meters when used with pulsed laser beams of moderate waist and high peak-power
Authors: Damany H.
Published: July 2002

A simple and safe way is presented to protect power meters when dealing with moderate waist and high peak-power pulsed laser beams, such as Nd:YAG laser beams.
Identification and reduction of sources of error fields in layer-wound short solenoids
Authors: Nexsen William E.
Published: July 2002

We report on a study of the error fields of a set of layer-wound short solenoids of the type used in high-current electron linear-induction accelerators. These error fields are mainly caused by the azimuthal variation of the winding pitch angle. The conventional winding pattern design tends to concentrate the error fields in a dipole component perpendicular to the solenoid axis. Compounding the problem are smaller contributions due to the asymmetric coil feeds and conductor crossovers from one layer to the next. We have constructed and tested a prototype quadrufilar solenoidal magnet which utilizes symmetry to cancel the effects of current leads and crossovers and which, in the absence of winding errors, should have an intrinsically straight magnetic axis. This design tends to concentrate the error field in the much less harmful octapole component. Measurements of the dipole error field yield a value of the order of one milliradian for the quadrufilar magnet as compared with about six milliradians for the conventional ETA-II magnets and twelve milliradians for the ATA magnets. Several approaches for improvement are suggested. The improved cooling of the quadrufilar design allows dc operation at fields almost three times higher than the conventional magnets.
Fast estimation of the variance of a narrowband process
Authors: Astone P. , Bonifazi P. , Pallottino G. V.
Published: July 2002

We report on the estimation of the variance of a narrowband stationary random process in the presence of wideband observation noise. The aim is to reduce the measurement time required to obtain accurate estimates. We discuss the solution based on the Wiener-Kolmogoroff optimum filter and propose a simple suboptimal technique using an analog differentiator. Computer simulations as well as experimental results on the Brownian motion of a cryogenic gravitational wave detector with high quality factor confirm the theoretical prediction that the variance of a narrowband process can be determined in a time smaller than the correlation time of the process.
Code for time-resolved x-ray pulse analysis at high count rates for short tokamak discharges
Authors: Vega J.
Published: July 2002

The measurement of soft x-ray spectrum in fusion plasmas allows for information on the nature of electron distribution, identification of impurity contents, calculation of electron temperature, estimation of Zeff, etc. All these measurements can be performed with a semiconductor detector. By amplifying the signal and using it as input to a multichannel analyzer (MCA), the spectrum is obtained. This kind of measurement does not have the desirable property of temporal resolution unless several detection chains are used or a special hardware is developed. In this paper, a method is presented to reach that type of resolution. This method requires only one measurement chain and the substitution of the MCA for a digitizer and mass storage. The digitized signal is stored in a computer, which will be the input for the several codes developed with the purpose of performing all the tasks of an MCA. These codes allow any number of time windows, of any length, along the digitized signal. Furthermore, in this way, it is possible to process one signal several times with different input parameters. Results in the TJ-I Tokamak (R0=0.3 m; a=0.1 m; BT<1.9 T; IP<70 kA) are shown.
Diagnostic method for measuring voltages induced in the PBX-M stabilizing shell
Authors: Kugel H. W. , Okabayashi M. , Schweitzer S.
Published: July 2002

Measurements were performed to characterize the voltages induced in the PBX-M passive plate stabilizing shell during high-β plasmas. The design, calibration, and testing procedures are discussed. The initial measurements found that the largest induced voltages were observed at plasma startup and at the plasma current disruption and exhibited characteristics depending on operating conditions. The highest voltages observed have been at disruption and were less than 2 kV.
Five-chord high-resolution x-ray spectrometer for Alcator C-Mod
Authors: Rice J. E. , Marmar E. S.
Published: July 2002

A five-spectrometer array has been designed to provide high-wavelength resolution x-ray spectra from the Alcator C-Mod plasma. Each independently scannable von Hamos type spectrometer consists of a variable entrance slit, quartz crystal, and position sensitive proportional counter, and has 3 cm spatial resolution with a resolving power of 4000. The wavelength range of each spectrometer is from 2.8 to 4.0 Å, which covers the complete Rydberg series of helium- and hydrogen-like argon. Wavelengths are remotely selectable, with 120 mÅ covered at any one setting. The array will provide single shot ion temperature profiles by measuring the Doppler broadening of the resonance lines of argon. Five proportional counters have been fabricated and all five spectrometers have been constructed. Calibration spectra using cadmium and scandium anode sources have been obtained, and measured performance characteristics are presented.
High Z x-ray spectroscopy of laser-imploded capsules
Authors: Hammel B. A. , Bell P. , Keane C. J. , Lee R. W. , Lewis C. L. S.
Published: July 2002

X-ray spectroscopy is a valuable tool for diagnosing laser-imploded capsules. Using a compact spectrometer/streak camera, which fits down a 6-in.-diam tube, we routinely perform time-resolved measurements of deuterium-filled capsules, seeded with Ar, on implosions driven by the NOVA laser. Future high performance targets will preclude the use of Ar as a diagnostic; we are pursuing spectral diagnostics at higher proton energy (Ne-like Xe) and have performed a series of direct drive implosions of capsules filled with Xe, and with Kr, to help validate line broadening models for Ne-like ions. We will discuss the details of the instrument and these experiments.
Universal curves for optical-matrix elements of strained quantum wells
Authors: Chang Chih-Sheng , Chuang S. L.
Published: July 2002

Strain and quantum size effects on the optical matrix elements for both TE and TM polarizations of strained quantum wells are studied theoretically including the spin-orbit coupling. A set of universal curves for the polarization dependent optical matrix elements as a function of strain is shown. These curves will be very helpful for a quick estimate of the optical matrix elements including the effects of the spin–orbit splitoff band for modeling the optical gain and absorption using strained quantum wells.
Repetitive flash x-ray generator utilizing a simple diode with a new type of energy-selective function
Authors: Sato E. , Kimura S. , Kawasaki S. , Isobe H. , Takahashi K. , Tamakawa Y. , Yanagisawa T.
Published: July 2002

The construction and the fundamental studies of a repetitive flash x-ray generator having a simple diode with an energy-selective function are described. This generator consisted of the following components: a constant high-voltage power supply, a high-voltage pulser, a repetitive high-energy impulse switching system, a turbo molecular pump, and a flash x-ray tube. The circuit of this pulser employed a modified two-stage surge Marx generator with a capacity during main discharge of 425pF. The x-ray tube was of the demountable-diode type which was connected to the turbo molecular pump and consisted of the following major devices: a rod-shaped anode tip made of tungsten, a disk cathode made of graphite, an aluminum filter, and a tube body made of glass. Two condensers inside of the pulser were charged from 40 to 60 kV, and the output voltage was about 1.9 times the charging voltage. The peak tube voltage was primarily determined by the anode-cathode (A-C) space, and the peak tube current was less than 0.6 kA. The peak tube voltage slightly increased when the charging voltage was increased, but the amount of change rate was small. Thus, the maximum photon energy could be easily controlled by varying the A-C space. The pulse width ranged from 40 to 100 ns, and the x-ray intensity was less than 1.0 μC/kg at 0.3 m per pulse. The repetitive frequency was less than 50 Hz, and the effective focal spot size was determined by the diameter of the anode tip and ranged from 0.5 to 3.0 mm in diameter.
New frequency-domain electric birefringence spectrometer using an advanced digital lock-in technique
Authors: Ookubo Norio
Published: July 2002

We have developed a frequency-domain electric birefringence spectrometer to measure stationary birefringence Δndc and alternating one Δn2ω induced by an applied sinusoidal electric field with an angular frequency ω. The new spectrometer is based on (1) the optimization of birefringence detection S/N ratio by taking into account the effects of optical noise, shot noise, optical leakage, and parasitic birefringence, (2) the electric field modulation technique, and (3) the advanced digital lock-in technique for further S/N enhancement. The electric field amplitude modulation at an angular frequency Ω shifts Δndc and Δn2ω signals to locate Ω and 2ω±Ω, which are demodulated with sinusoidal reference waves at Ω and 2ω and retrieved by digital data accumulation, i.e., the advanced digital lock-in technique. These techniques ensure the signal detection with extremely narrow bandwidth by removing the adverse effects of odd harmonic noises, drift, and 1/f noise in the measurement system. The detection sensitivity of 10−9 rad in a wide range of ω is accessible.
Autonulling ac bridge for accurate measurement of small impedance variations using MOS components
Authors: Bey Paul P. , Levine Michael D. , Yonce David J. , Fare Thomas L.
Published: July 2002

A self-contained prototype of an autonulling ac bridge based on phase-sensitive detection is discussed. The bridge nulling circuit uses an analog feedback network to establish a stable null for a wide range of resistive and capacitive values and requires minimal supporting hardware. Changes in resistance and capacitance in one arm of the bridge are compensated independently using a discrete voltage-variable resistor and capacitor in the alternate arm for nulling. The feedback voltage to the discrete control elements can be used to transduce signals from pressure, temperature, or chemical sensors. This bridge is especially well suited for microfabrication and is readily compatible with silicon-based sensors. It offers high noise rejection due to the phase-sensitive measurement taken differentially across the bridge nodes. State-space analysis is used to demonstrate the stability of this feedback network design.
A new scheme for lidar Doppler detection on the intermediate frequency at increased laser instability
Authors: Stoyanov D. V. , Bratanov B. M. , Angelova M. D.
Published: July 2002

A new scheme for Doppler lidar detection by frequency shifted tracking of the reference frequency is described. The main advantages of the scheme are wide tolerable range of the laser instabilities (in principle more than 100 MHz), easy wideband tuning of the tracking frequency, one analog output by A/D converter with a sampling rate of only several times higher then the maximum expected Doppler frequency. It is shown how to account for the chirp history. The use of frequency synthesis for Doppler detection in wide frequency band of laser instabilities is considered.
Compact supersonic molecular beam source with a liquid nitrogen trap
Authors: Nonaka Hidehiko , Shimizu Takashi , Arai Kazuo
Published: July 2002

A compact supersonic molecular beam source was developed that has a liquid nitrogen trap to cryogenically pump the gas and is small enough in size to install in conventional molecular beam epitaxy (MBE) systems. With the source, well-collimated molecular beams of N2O and NO2 whose flux densities are ∼1016 molecules cm−2 s−1 are generated. The effectiveness of the source was proved in the preparation of oxide superconducting thin films by MBE with an NO2 beam where as-grown superconducting films were obtained in high vacuum of ≤10−5 Pa.
Local lattice distortion relating to phosphorus antisite defect in phosphorus-ion-implanted GaP layer
Authors: Kuriyama K. , Kato Takashi , Tajima Satoru , Kato Tomoharu , Takeda Sin-ichi
Published: July 2002

The local lattice distortion relating to the phosphorus antisite defect (PGa) in the P+-ion-implanted GaP layer was studied using Rutherford backscattering (RBS), photoacoustic (PA), Raman scattering, and photoluminescence (PL) methods. The displacement fraction due to the excess phosphorus in 800 °C annealed samples is estimated to be ∼2×1020/cm3 by RBS channeling measurements. The slight reduction of the LO-TO phonon frequency splitting of the annealed P+-ion-implanted GaP with respect to the unimplanted one indicates the presence of PGa, corresponding to x=0.0084 of Ga1−xP1+x. This is consistent with the displacement fraction estimated by RBS. A PL emission relating to PGa is observed at 716 mm (1.73 eV).
Numerical simulation of ion beam related problems (invited)
Authors: Spädtke P.
Published: July 2002

The extraction of ions from a plasma source has been investigated by computer simulation for many years. The development of these computer codes started from the simulation of electron guns. The extraction of plasma ion sources for positive ion sources was optimized soon after. Now ion sources with magnetic fields can be simulated (electron cyclotron resonance or PIG sources) and even three component plasmas (for example, H− sources) can be modeled. The necessary computing time for these codes has shrunk from hours to minutes and even seconds on modern main frames. Different computer codes and the applied techniques are presented. The programs are demonstrated using several examples.
In situ tip exchange for an ultrahigh vacuum scanning tunneling microscope using dual-axes piezoelectric micropositioners
Authors: Osaka F. , Kato T.
Published: July 2002

We have constructed an in situ tip-exchangeable ultrahigh vacuum scanning tunneling microscope (UHV–STM). The STM has dual-axes piezoelectric micropositioners, and a damaged tip can be exchanged in situ for a new tip by moving the two micropositioners alternately. We have demonstrated that our tip-exchange method has great advantages of reliability, accuracy, simplicity, and ease of operation. These advantages have been shown to result from extremely high mechanical resolutions of these micropositioners. From the measured STM image of a GaInAs/InP multiquantum well (110) cleaved surface it has been demonstrated that the constructed tip-exchangeable STM works stably with an atomic resolution under UHV.
Analyzing noisy spectral line shapes
Authors: Filuk Alex B. , Bailey James E.
Published: July 2002

In many situations it is necessary to analyze spectral line shapes where the data contain significant amounts of noise or statistical fluctuations. Our visible spectroscopy measurements exploring ion diode physics on the PBFA II accelerator typically result in noisy spectra because the harsh environment limits the number of photons collected. The spectral line profiles include contributions from Doppler (Ti∼1–3 keV), Stark (ne∼1017 cm−3), and instrument broadening, as well as from Stark shifting (E∼3–10 MV/cm) and Zeeman splitting (B∼2–10 T). We extract a range of parameters (e.g., ion temperature from Doppler broadening) that fit the data by determining a range of fits that are consistent with the uncertainty due to the noise in the data. The range of fits is generated by a Monte Carlo technique. This method effectively distinguishes between actual spectral features and artifacts due to noise. It provides not only estimates of physical parameters, but also their uncertainties. We evaluated the technique over a range of signal-to-noise ratios and found that it works well for our application.
Phase locking and frequency locking of a 140 GHz klystron and a 280 GHz carcinotron
Authors: Sprehn Daryl W. , Rettig Curtis L. , Luhmann Neville C.
Published: July 2002

A phase and frequency-locked loop to synchronize two microwave tube oscillators for a high density plasma collective scattering diagnostic has been designed, assembled, and tested. A Varian (VRT2121A16) reflex klystron was down converted by mixing with the eighth harmonic of a 17.437 GHz phase-locked Gunn oscillator, and the resulting baseband was used to lock the klystron phase to a 200 MHz crystal. The down-converted 140 GHz klystron frequency spectrum shows a linewidth <50 Hz and sideband power <50 dB below the carrier (dBc). Frequency locking of a Thomson CSF TH4224S 280 GHz carcinotron was performed and the klystron was then down converted by the stabilized carcinotron and phase locked to the 200 MHz crystal. The klystron would track the frequency excursions of the carcinotron when the system was perturbed by direct modulation with frequencies of up to 10 MHz and remained locked as long as modulation sidebands were kept <15 dBc. The locked states of both configurations show 3 to 4 orders of magnitude improvement in short and long term stability over the unlocked states.
Neutron transport studies for the Ignitor neutron diagnostics
Authors: Rollet S. , Batistoni P.
Published: July 2002

As a preliminary step for the project of the neutron diagnostics in the Ignitor tokamak, the overall neutron field in the device has been calculated with the help of the MCNP code, which solves, with the Monte Carlo method, neutron and photon transport problems in arbitrary three-dimensional geometries. The poloidal distribution of the fluxes on the first wall and the related energy spectra have been calculated to estimate the backscattered contribution to signals at spectrometers and collimated detectors for measurements with spatial resolution in the plasma. The average fluxes on the top and the lateral cryostat surfaces and the local fluxes on the equatorial plane outside the cryostat wall are also calculated in order to determine the neutron counters characteristics and expected performances.
Operating experiences with the TFTR escaping alpha detectors
Authors: Zweben S. J. , Boivin R. , Darrow D. , Loesser D. , Medley S. S. , McSmith M. , Owens D. K. , Ulrickson M.
Published: July 2002

This paper reviews the operating experiences obtained with a set of scintillator-based escaping fast ion detectors which have been used successfully for several years on the TFTR tokamak. There have been several operational problems which need to be resolved before these detectors are used to measure 3.5 MeV DT alphas in 1993. The main problem has been overheating by edge plasma heat flux for large major radius plasmas, when the detectors were not shadowed by the adjacent limiter. Other problems have been due to runaway electron-induced x-ray flux and scintillator and foil damage.
Relativistic detuning limit on energy in electron cyclotron resonance x-ray source
Authors: Kumar Ashwani , Baskaran R.
Published: July 2002

In this paper, a detailed theoretical analysis of electron acceleration in a TE111 cylindrical resonant cavity used as a cyclotron resonance accelerator is presented. The relativistic detuning limit on energy is found to depend critically on the externally applied dc magnetic field. The optimum value of the magnetic field, for a given operating frequency, electric field, and the cavity dimensions, is calculated. The cavity dimensions are optimized to get maximum peak-to-peak electric field so that higher electron energy can be obtained. It is also shown that most of the electrons, depending on the time of emission, end up in two accelerating bunches.
An electron beam ion source for laboratory experiments
Authors: Beebe E. N. , Kostroun V. O.
Published: July 2002

The design and properties of an electron beam ion source (EBIS) capable of producing low-energy, highly charged ions such as Ar16+ and Xe30+ are described. The source, to be used in laboratory experiments in atomic and surface physics, utilizes a conventional, 0.42-T solenoid and an externally launched electron beam. Ultrahigh vacuum in the ionization region is created by a distributed sputter-ion pump. The source design is relatively simple, and the source is small and easy to operate. The concept of a saturated electron beam is introduced in order to explain the observed argon and xenon ion charge state evolution. Very high ion charge states can be produced by confining ions for times up to 1 s in an electron beam in which the degree of space-charge neutralization by ions is determined by potentials applied to the drift tubes.
Plasma diagnosis related to ion sources (invited)
Authors: Girard A.
Published: July 2002

The different kinds of ion sources have been most commonly classified according to the extracted beam parameters: ion charge state, energy and current, and beam quality. We adopt here a somewhat different approach: ion sources are usually plasma sources where each component (ionic as well as electronic) plays an important role. This article deals with the experimental techniques which can be used to get information on the plasma state of an ion source. In Section II the interest of the different plasma parameters is discussed. Section III describes a few well-known techniques of plasma diagnostics; examples of their applications on ion sources or related devices are given and limitations of these existing techniques are discussed. Section IV presents some of the work that is needed to get a more accurate description of the plasma.
Pyroelectric detector for particle beams
Authors: Viehl A. , Kanyo M. , van der Hart A. , Schelten J.
Published: July 2002

For ion beams used for ion beam etching and sputtering in electronic device technology and for monitoring plasma wall interactions, a pyroelectric detector has been developed to measure the current density of neutralized ions and the fraction of the total beam which is neutralized. The pyroelectrically induced charges due to beam heating of a PVDF film and the deposited charge from the ion beam are measured with a charge sensitive and current sensitive amplifier, respectively. The pyroelectric detector has a sensitivity of 1000 V/W and 1/e response time of 2 s. Beam current densities in the range 0.01–100 μA/cm2 of 1 keV particle energy can be measured.
Noncontact flash method for measuring thermal expansion of foil specimens
Authors: Heng Wang , Guanhu He , Benlian Zhou , Xin Chen , Wuming Liu
Published: July 2002

A noncontact flash method for measuring thermal expansion of foil materials has been developed using laser-pulse thermal-conductivity equipment (H. Guanhu, Proceedings of the 1st Asian Thermophysical Properties Conference, 1986, p. 331), which is usually used for measuring thermal diffusivity, specific heat, and thermal conductivity. The automatic measurement of thermal expansion of foil materials can be realized if some low-cost accessories are simply added to the thermal-conductivity equipment. Thermal expansion of pure copper was measured to check the validity of this new method, and that of constantan foil with thickness 5 μm was also measured.
An innovative, simple design for a computer-controlled, three-dimensional plasma probe drive system
Authors: Braught G. , Pfister H. , Wachtel J.
Published: July 2002

A simple design for a fully computer-controlled, three-dimensionally movable probe position system is described. Particular attention is given to the constraints of a plasma environment. A novel spring joint eliminates the need for ball bearings, universal joints, telescoping parts, etc., and thus avoids the potential risk of cold welding. The new probe drive is external to the plasma device, user-friendly and robust, and it provides for high spatial resolution. The computer control system is flexible with respect to computing platform and application development environment.
Use of capacitance diaphragm gauges at pressures down to 10−6 Torr
Authors: Straub H. C. , Renault P. , Lindsay B. G. , Smith K. A. , Stebbings R. F.
Published: July 2002

The useful range of a capacitance diaphragm gauge is extended down to 1×10−6 Torr with an uncertainty of ±10−7 Torr using computer-based averaging. Gauge linearity is measured by observing the deflection of the diaphragm by the force of gravity. Precise pressure increments are generated by tilting the gauge through a range of accurately measured angles. By this procedure the gauge is observed to be linear to within ±1% plus 10−7 Torr between 1×10−6 and 8×10−3 Torr. Additionally, the deflection of the center of the diaphragm per unit pressure is found to be 2×10−5 m Torr−1.
Donors bound to X valleys in type-II GaAs–AlAs quantum well structures
Authors: Weber Gerald
Published: July 2002

We calculate the binding energies of donors bound to X valleys in type-II GaAs–AlAs quantum well structures using an anisotropic variational method which enables us to take into account the effective mass anisotropy and quantum confinement. For a comparative study, we use two sets of effective masses obtained from different measurements [B. Rheinänder et al. Phys. Status Solidi B 49, K167 (1972) and M. Goiran et al., Physica B 177, 465 (1992)]. We show that the binding energies have a pronounced dependence with the effective mass, AlAs layer thickness, and impurity position.
Simulation study on ion extraction from electron cyclotron resonance ion sources
Authors: Fu S. , Kitagawa A. , Yamada S.
Published: July 2002

In order to study beam optics of NIRS-ECR ion source used in the HIMAC project, the EGUN code has been modified to make it capable of modeling ion extraction from a plasma. Two versions of the modified code are worked out with two different methods in which 1D and 2D sheath theories are used, respectively. Convergence problem of the strong nonlinear self-consistent equations is investigated. Simulations on NIRS-ECR ion source and HYPER-ECR ion source are presented in this paper, exhibiting an agreement with the experiment results.
Particle simulation on extraction of positive and negative ions from a volume source
Authors: Naitou Hiroshi , Fukumasa Osamu , Sakachou Kouji , Mutou Kouji
Published: July 2002

A two dimensional electrostatic particle simulation was done to study the extraction of positive (negative) ions from a volume plasma source. The simulation model is a rectangular system which consists of an extraction grid (left wall), a plasma grid, and a grounded wall (right wall). Upper and lower boundaries are connected by the periodic boundary condition. Full dynamics of charged particles are followed. Positive (negative) ions are extracted from the plasma region through a slit in the plasma grid to the extraction grid. Electrons are reflected by the magnetic filter and confined in the region to the right of the magnetic filter. Simulation results are compared with the Child–Langumuir law where the extracted ion current is proportional to the three-halves power of the potential of the extraction grid. In the case of the positive ion extraction, simulation results agree quite well with the Child–Langumuir law. Whereas, in the case of the negative ion extraction, simulation results agree with the law only for the lower value of extraction grid potential.
A plasma arc reactor for fullerene research
Authors: Anderson T. T. , Dyer P. L. , Dykes J. W. , Klavins P. , Anderson P. E. , Liu J. Z. , Shelton R. N.
Published: July 2002

A modified Krätschmer–Huffman reactor for the mass production of fullerenes is presented. Fullerene mass production is fundamental for the synthesis of higher and endohedral fullerenes. The reactor employs mechanisms for continuous graphite-rod feeding and in situ slag removal. Soot collects into a Soxhlet extraction thimble which serves as a fore-line vacuum pump filter, thereby easing fullerene separation from soot. Thermal gravimetric analysis (TGA) for yield determination is reported. This TGA method is faster and uses smaller samples than Soxhlet extraction methods which rely on aromatic solvents. Production of 10 g of soot per hour is readily achieved utilizing this reactor. Fullerene yields of 20% are attained routinely.
Thermal anemometry, current state, and future directions
Authors: Fingerson L. M.
Published: July 2002

The variation in heat transfer between a fine wire and the surrounding fluid has traditionally been the most accepted method for measuring the detailed movements of a flow fluid. This paper reviews the present understanding of thermal techniques as used in research and recent advancements of the technique. While the basic research sensor is still a fine wire, modern electronics has greatly simplified data analysis as well as established constant temperature operation of the sensor as the control method of choice. Film sensors have extended the use of thermal sensors to new applications. Comparisons with laser Doppler velocimeters help to identify experiments where thermal sensors still represent the best choice. The ability of modern electronics to easily address the typical nonlinear response of thermal sensors has resulted in increased use for commercial applications. While in these applications fast response can be a factor (e.g., fuel flow control in engines), generally only average flows are needed. As a result, calibration shifts due to deposits on the sensor surface when exposed to contaminated fluids can generally be reduced to acceptable levels by using larger sensors.
Low-temperature-processed (150–175 °C) Ge/Pd-based Ohmic contacts (ρc∼1×10−6 Ω cm2) to n-GaAs
Authors: Wang L. C. , Hao P. H. , Wu B. J.
Published: July 2002

We have developed low resistance (ρc∼1×10−6 Ω cm2) Ge/Pd-based (the Au/Ge/Pd and the Ag/Ge/Pd contacts) Ohmic contact schemes processed at temperatures 150–175 °C to n-GaAs (n∼1×1018 cm−3). The Ohmic contact formation mechanism can be rationalized in terms of the solid phase regrowth (SPR) principle and the interdiffusion between Au (or Ag) and Ge.
A solid state detector for soft energy extended x-ray absorption fine structure measurements
Authors: Smith A. D. , Derbyshire G. E. , Farrow R. C. , Sery A. , Raudorf T. W. , Martini M.
Published: July 2002

Following the success of solid state detector systems for extended x-ray absorption fine structure studies at high x-ray energies, there is now an increasing demand for similar devices capable of operating in the soft x-ray energy range below about 3 keV. Recent developments in sophisticated detector fabrication techniques now make the construction of specialized devices, suitable for high quality spectroscopy in this energy range, a practicable proposition. We present the results of extensive testing of a new detector developed specifically for use in the sub-3 keV energy range. We have measured energy resolutions of less than 125 eV full width at half maximum at sulfur and silicon Kα energies and the ability of the detector to achieve this resolution at the copper Lα line has also been shown. Finally we demonstrate the potential of this device in a study of trace dopants in bulk silicon based quantum dot glasses.
Compact active/adaptive x-ray mirror: Bimorph piezoelectric flexible mirror
Authors: Susini J. , Labergerie D. , Zhang L.
Published: July 2002

A very compact active x-ray mirror based on the properties of bimorph piezoelectric systems has been developed at the ESRF. The use of such a system as an x-ray focusing device has a number of advantages among which are compactness, low cost, and versatility. As a demonstrative test, a white focused beam of 35 μm has been obtained on an ESRF bending magnet beamline that corresponds to a demagnification of 1/18. A theoretical description of the system behavior is given, and compared with both finite element analysis and interferometric measurements. Examples of more advanced devices are discussed.
Multiple simultaneous time-resolved experimental techniques
Authors: Bras W. , Mant G. R. , Derbyshire G. E. , Bouch D. , Sheldon J. , Dings J. , Ryan A. J.
Published: July 2002

The desire to eliminate experimental artifacts due to the correlation of several independent time-resolved experiments has provided the impetus to attempt to perform several simultaneous experimental techniques on a single sample. The data acquisition system of an existing small angle x-ray scattering beam line has been adapted in order to accommodate the simultaneous operation of a second detector system in order to collect the wide angle x-ray scattering pattern. Electronic pulses received and/or generated by the data acquisition system enable control and communication with PC’s controlling the sample environment.
Thermal conductivity and diffusivity of free-standing silicon nitride thin films
Authors: Zhang Xiang , Grigoropoulos Costas P.
Published: July 2002

The thermal conductivity and diffusivity of free-standing silicon nitride (Si-N) films of 0.6 and 1.4 μm in thickness are measured. A new experimental technique, the amplitude method, is proposed and applied to measurement of the thin-film thermal diffusivity. The thermal diffusivity is determined by three independent experimental approaches: the phase-shift method, the amplitude method, and the heat-pulse method. Good agreement among the measured thermal diffusivities obtained by the three methods indicates the validity of the amplitude method. High-resolution electron microscopy studies show a large quantity of voids in the 1.4 μm Si-N films. In contrast, very few voids are found in the 0.6 μm films. This difference may be responsible for the measured lower conductivity of the 1.4 μm Si-N films as compared to the 0.6 μm thin films.
Zeeman absorption measurements of two-dimensional magnetic field structuresa)
Authors: Spanjers G. G. , Yadlowsky E. J. , Hazelton R. C. , Moschella J. J. , Settersten T. B.
Published: July 2002

A diagnostic technique is presented where polarization measurements of transmitted resonant laser light are used to determine the two-dimensional magnetic field profiles in a plasma. The diagnostic laser is propagated parallel to the magnetic field direction and resonant with circularly polarized transitions. Tuning the laser slightly off-resonance results in differing absorption coefficients for right and left circularly polarized light. Analysis of the transmitted light, combined with independent measurements of the resonant line profile, results in a measurement of the magnetic field. Spectral analysis of the Zeeman splitting has been commonly used to measure plasma magnetic fields, both in emission and absorption. The intensity comparison of the right and left circular components to measure relatively small magnetic fields has its origins in the astrophysics community. Here, the intensity comparison technique is used in conjunction with resonant absorption, and the information is stored using a high-speed framing camera. This results in a measurement of relatively small magnetic fields, with a high signal-to-noise ratio and two-dimensional spatial resolution.
Compact electron-accelerator system using laser-induced photoelectrons and DISKTRON electrostatic accelerator
Authors: Tanabe T. , Kawamura Y. , Li D. , Toyoda K.
Published: July 2002

A new type of relativistic electron acceleration facility is being developed by the Laser Science Research Group at The Institute of Physical and Chemical Research. It utilizes laser-induced photoelectrons accelerated by a compact DISKTRON electrostatic accelerator, which makes it possible to generate a controllable bright short-pulsed electron beam up to the energy of 1 MeV with a low emittance (<2×10−5 mrad) and high current density (∼500 A/cm2) without any guiding field. The characteristics of the entire facility and some of the key components are described in detail. The experimental results which confirm the possibilities of increasing quantum efficiency of metal photocathodes by geometric alteration are reported. Observation of laser undulator effects in the visible wavelength was demonstrated in the facility. The coming use of the system includes a far-infrared/submillimeter free-electron laser using a microwiggler and generation of extreme ultraviolet radiation by the laser undulator.
Apparatus for time-resolved measurements of acoustic birefringence in particle dispersions
Authors: Giardini M. E. , Cristiani I. , Piazza R. , Degiorgio V.
Published: July 2002

An apparatus for time-resolved measurements of the birefringence induced in a particle suspension by an acoustic wave pulse is described. Efficient acoustic coupling is obtained by operating near the transducer resonant frequency and by matching the acoustic impedances of the cell constituents. An almost-overdamped acoustic configuration can alternatively be employed whenever a faster response is needed. Careful design of the optical setup and of the detection unit minimize diffraction and stress-birefringence parasitic effects and yields a good responsivity at fairly low acoustic intensities. A test of the apparatus on a colloidal suspension of PTFE rodlike particles is presented and discussed.