bluuebunny/crossref_metadata_2025 huggingface dataset:
Zn diffusion behavior in InGaAsP/InP capped mesa buried heterostructures
Authors: Swaminathan V. , Reynolds C. L. , Geva M.
Published: July 2002

A systematic study of the effects of Zn doping and diffusion in InGaAsP/InP capped mesa buried heterostructure lasers grown by metalorganic chemical vapor deposition was carried out. It consisted of varying the Zn doping of the p-InP cladding layer in the base epitaxial structure over the range (0.7–3.1)×1018 cm−3 and keeping the growth conditions in two subsequent regrowth steps the same. Secondary ion mass spectrometry was employed for a quantitative determination of the Zn depth profiles following regrowth using test sites on the 50 mm round wafers that contained the appropriate epitaxial layers. Clear evidence of Zn diffusion such as the penetration of Zn into the active layer and the presence of inflection points (accumulation and depletion of Zn near the p-n heterojunction) was illustrated in the depth profiles. It was observed that the diffusion of Zn during the third growth dominated the Zn profile in the base growth part of the p-InP layer and the final amount of Zn in this region was independent of the initial doping level. Above a Zn threshold level of ≊2.2×1018 cm−3, Zn diffusion increased significantly resulting in 5×1018/cm−3 or greater Zn in the active layer. The threshold for the onset of diffusion was found to be in accordance with the substitutional-interstitial diffusion of Zn.
Efficient excitation transfer in silicon studied by Fourier transform photoluminescence excitation spectroscopy
Authors: Singh Mandeep , Chen W. M. , Son N. T. , Monemar B.
Published: July 2002

Direct experimental evidence of excitation transfer in the recombination via deep defects in silicon is provided, by a novel approach of Fourier transform photoluminescence excitation spectroscopy. The 735 meV iron-related defect in Si is used as a model case. It is shown that this defect can be excited via two deep states of other centers that give rise to broad lines in the excitation spectrum at 976.3 and 1115.6 meV. The linewidths of these features infer extremely efficient transfer processes. Such an efficient excitation transfer is expected to play an important role in excitation and recombination processes in silicon.
Substrate selectivity in the formation of microcrystalline silicon: Mechanisms and technological consequences
Authors: Roca i Cabarrocas P. , Layadi N. , Heitz T. , Drévillon B. , Solomon I.
Published: July 2002

We report the results of an in situ spectroscopic ellipsometry study concerning the substrate dependence of the evolution of microcrystalline silicon films deposited by alternating amorphous silicon deposition and hydrogen plasma treatment. The evolution of the composition of the films during growth, up to thicknesses of ∼100 nm, indicates that besides etching, the diffusion of atomic hydrogen efficiently promotes the growth (and/or nucleation) of buried crystallites. Moreover, the evolution of the films strongly depends on the nature of the substrate. This substrate selectivity is discussed in terms of initial growth processes. The effect of the hydrogen plasma well below the film surface, which produces the thickness-dependent film composition, along with the substrate selectivity, may be of prime importance in technological applications of microcrystalline silicon.
Multikilohertz Pockels cell driver
Authors: Bado P. , Bouvier M.
Published: July 2002

We have developed a Pockels driver, based on field-effect transistors and a microwave tube. This system, capable of generating double voltage steps, operates reliably at repetition rates as high as 10 kHz.
Modification of a commercial 35-GHz EPR cavity
Authors: Iddings C. K.
Published: July 2002

The addition of a very simple sample positioning guide to this cavity raises the Q and makes it faster to use.
Poloidal magnetic field measurements on TEXT using the Zeeman current profile diagnostic (abstract)
Authors: West W. P. , Thomas D. M.
Published: July 2002

The Zeeman current-density profile diagnostic system installed on TEXT has observed the polarization shift of the π-line of the Zeeman split Li D lines due to the poloidal magnetic fields. The Li is injected into the plasma as a 95-keV neutral beam, and a cw dye laser is used to measure polarization shifts. The laser is tuned into resonance with the π-line and the polarization vector of the laser is rotated at 50-kHz using an electro-optic technique. The resulting 100-kHz laser-induced fluorescence signal is phase analyzed in order to observe the polarization shifts due to poloidal field. The Li beam intensity into the tokamak is approximately 1 mA and the dye laser intensity is 1 W at 3 GHz bandwidth. The diagnostic system and these early results will be discussed.
Single-crystal silicon high-Q torsional oscillators
Authors: Kleiman R. N. , Kaminsky G. K. , Reppy J. D. , Pindak R. , Bishop D. J.
Published: July 2002

We describe techniques for constructing single-crystal silicon high-Q torsional oscillators. The oscillators are fabricated by the high-precision micromachining of silicon using orientation-dependent etches. We describe methods for using these oscillators as very powerful probes of the mechanical properties of a variety of physical systems.
Device for handling cesium safely
Authors: Pepmiller P. L. , Loftus J. M.
Published: July 2002

A simple device has been designed and built to protect, warm, open, and dispense cesium (Cs) contained in glass vials. The device provides the user a larger margin of safety than most other commonly used methods, while being inexpensive and simple to operate.
Description and design for a remote-controlled glass–Teflon high-vacuum stopcock
Authors: Hutchinson Stewart
Published: July 2002

This note describes a method of opening and closing a glass–Teflon stopcock using a synchronous or stepping motor which can easily be modified to computer control.
Longitudinal CO2 laser operating directly at line voltage with hollow cathode discharge
Authors: Kukreja L. M. , Khare R. K. , Chatterjee U. K.
Published: July 2002

A different type of longitudinal CO2 laser is developed with multisegment hollow cathode discharge that sustains at low voltages. Operation of this laser is investigated with a 400-V peak ac source obtained directly from a three-phase line using inductive ballasts. Output laser pulses of 2 ms FWHM, 3-W peak power and repetition frequency of 100 Hz are obtained from an active length of about 45 cm at an operating pressure of 12 mbar (CO2:N2:He=1:1:10). The specific output power can be increased by improving cooling of the active medium.
Radiation diagnostics for x-ray laser experiments on Proto-II
Authors: Spielman R. B. , Dukart R. J. , Hammel B. A. , Hanson D. L. , Palmer M. A.
Published: July 2002

X-ray laser experiments on the Sandia Proto-II accelerator (10 TW, 40-ns FWHM, 0.125 Ω) use a wide array of radiation diagnostics. Precise x-ray measurements are difficult in the environment of a large pulsed power accelerator. Machine shock, EMP, and large x-ray fluences are significant problems. X-ray diodes and resistive bolometers provide excellent time-resolved information. Crystal and grazing-incidence grating spectrographs and x-ray pinhole cameras give time-integrated data. A recent major effort at Sandia has been the development of time-resolved x-ray pinhole cameras, crystal spectrographs, and grazing-incidence spectrographs. These diagnostics use microchannel plates or a scintillator and streak camera system to obtain time resolution. Precise alignment, nanosecond time resolution, and high spectral precision are all needed for successful x-ray laser experiments. We will present descriptions of the diagnostics and data taken on recent x-ray laser experiments. This work was supported by the U.S. DOE.
Arc facility for investigating non-local thermal equilibrium plasmas
Authors: Sedghinasab A. , Eddy T. L. , Murray R. T. , Larson A. V.
Published: July 2002

A high-pressure arc facility has been modified for computerized control and data acquisition to simplify measurements of non-local thermal equilibrium (non-LTE) plasmas. The instrumentation uses a 1-m monochrometer with programmable wavelength scanning system. Plasma self-absorption is determined via a concave back mirror and shutter. The raw data are corrected for absorption, zeroed, centered, and smoothed. The net line intensity is then determined and converted into the radial emission coefficient prior to feeding into LTE or non-LTE analysis programs. Sample graphs demonstrating the self-absorption correction technique and data reduction procedure are presented.
Operation of a multichannel tangential bolometer on PBX
Authors: Paul S. F. , Fonck R. J. , Schmidt G. L.
Published: July 2002

A compact 15-channel bolometer array that views plasma emission tangentially across the midplane has been installed on the PBX tokamak to supplement a 19-channel radially viewing poloidal array. By comparing these diagnostics, poloidal asymmetries in the emission profile can be determined. The detector array consists of 15 discrete 2-mm-diam thinistors, a mixed semiconductor material, which has a high temperature coefficient of resistance. Each active detector is operated in tandem with an identical blind detector in a Wheatstone bridge configuration. The variation in voltage owing to the change in resistance is amplified and stored on a CAMAC transient recorder. The detectors are sensitive to accumulated heat and software has been written to smooth and differentiate the signals so that instantaneous power can be calculated. In addition, the cooling time constants are determined in vacuo (3.1 s) so that the loss of heat from the detector during the course of a shot can be compensated. The detectors were relatively calibrated with a tungsten–halogen filament lamp and were found to vary by ±7%. The irradiance profiles are inverted and the power density is typically in the 0.1 to 0.5-W/cm3 range.
High-yield direct drive experiments at Nova
Authors: Lane S. M. , Cable M. D. , Prussin S. G. , Glendinning S. G. , Munro D. H. , Hatchett S. P. , Estabrook K. G. , Suter L. J. , Richardson M. C.
Published: July 2002

A series of direct drive implosions of D-T filled, glass microballoons has been initiated in an effort to produce intense neutron sources for diagnostics development. In particular, measurements such as neutron imaging, burn history using a neutron-sensitive streak camera, and fuel  ρr  by both neutron activation and neutron spectroscopy could be more easily tested with these simple targets than high-density targets that initially are not expected to produce such high yields. Targets with nominal dimensions of 1000×2 μm which contained D-T at 12–14 atm were imploded with 18 kJ of 0.35-μm light from the 10-beam Nova system. For pulse widths of 1 ns in either converging or diverging geometry, fusion yields in excess of 1013 have been obtained. The yields are comparable to those predicted from numerous 1-D model calculations in spite of the asymmetric illumination geometry of the driver. Work performed under the auspices of the U.S. DOE by Lawrence Livermore National Laboratory under contract number W-7405-ENG-48.
Neutral-particle densities outside the TMX-U plasma edge
Authors: Pickles W. L. , Jong R. A.
Published: July 2002

Neutral molecular densities just outside the plasma edge are measured at 11 axial locations in tandem mirror experiment-upgrade (TMX-U). These densities are time dependent and vary greatly with different modes of TMX-U plasma operation. The densities are low in the ion-cyclotron resonance heated central cell because of plasma pumping. The density is high in the plug near the sloshing-ion turning point. These densities are measured with a combination of new retractable, and fixed, magnetically unshielded Bayard–Alpert gauges that can be oriented to provide calibrated operation in the high (7 kG) TMX-U magnetic fields. The role of the neutral density in simultaneously fueling and charge exchanging away the plug density is modeled using smoke, a Fokke–Planck code.
Probes for edge plasma studies of TFTR (invited)
Authors: Manos D. M. , Budny R. V. , Kilpatrick S. , Stangeby P. , Zweben S.
Published: July 2002

Tokamak fusion test reactor (TFTR) probes are designed to study the interaction of the plasma with material surfaces such as the wall and limiters, and to study the transport of particles and energy between the core and edge. Present probe heads have evolved from prototypes in Princeton large torus (PLT), poloidal divertor experiment (PDX) [Princeton BETA experiment (PBX)], and the initial phase of TFTR operation. The newest heads are capable of making several simultaneous measurements and include Langmuir probes, heat flux probes, magnetic coils, rotating calorimeter fast ion probes, and sample exposure specimens. This paper describes these probe heads and presents some of the data they and their prototypes have acquired. The paper emphasizes measurement of transient plasma effects such as fast ion loss during auxiliary heating, the evolution of the edge plasma during heating, compression, and free expansion, and fluctuations in the edge plasma.
X-ray diagnostics for magnetic fusion (invited)
Authors: Silver E. H.
Published: July 2002

Current research efforts in magnetic fusion strongly depend upon information gained from x-ray observations of the confined plasma. Spectroscopic measurements make it possible to determine plasma temperature, density, electron energy distribution, ionization state, impurity content, and plasma velocity. X-ray imaging provides estimates of the spatial distribution of a few of these parameters, facilitates temporal studies of plasma size and shape, and indicates MHD activity. Diagnosing plasma properties in tokamaks and tandem mirrors has resulted in the development of a variety of sophisticated spectroscopy and imaging instrumentation. All share standard x-ray detection techniques and are either dispersive or nondispersive devices. To achieve optimal performance, these systems are individually tailored to specific operating regimes. Criteria such as energy, temporal and spatial resolution, plasma lifetime, x-ray emission bandwidth, system throughput, and the effects of the non-x-ray background influence the diagnostic design. X-ray diagnostics have been reviewed on numerous occasions in the context of tokamak plasmas heated by either neutral beams or lower hybrid waves. This report will focus on diagnosing tandem mirror plasmas. Detector requirements and limitations, recent instrument development and performance, and up-to-date x-ray measurements will be discussed. This work was performed for the U.S. DOE by Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48.
Dither-free stabilization of CH3OH pumping sources
Authors: Bennett C. A. , Patterson J. D. , Hutchinson D. P.
Published: July 2002

A dither-free stabilization scheme was reported recently1 in which the optical transmission through an absorption cell filled with CH2F2 provided an error signal necessary to stabilize the 214-μm line of CH2F2. Measurements have indicated that this technique is difficult to apply to the 119-μm line of CH3OH due to a lack of contrast in the absorption features of CH3OH over the tuning range of the pump. Efforts to find a nonlasant gas with the required absorption features and to develop a similar technique based on the photoacoustic technique will be described. This research was supported by the Office of Fusion Energy, U.S. DOE, under Contract No. DE-AC05-84OR21400 with Martin Marietta Energy Systems, Inc.
Poloidal rotation in Alcator C
Authors: Benjamin R. D. , Terry J. L. , Moos H. W.
Published: July 2002

The poloidal rotation velocity in the edge region of ohmically heated Alcator C plasmas was measured using the Doppler shift of impurity emission lines. The measurements were made using a high-resolution, photon counting detector, sensitive to wavelengths from ∼1200 to ∼2000 Å, mounted in the exit plane of a 1-m Ebert–Fastie spectrometer. The transitions used were the 2s2p 1P01–2p2 1D2 at 1371.292 Å in O v and 2s 2S1/2–2p 2P01/2 at 1242.804 Å in N v, both of which exist near the limiter radius in Alcator C. The measured rotation velocity is ∼4.1×105 ±2.1×105 cm/s at n̄e∼1.7×1014 cm−3 in the direction of the electron diamagnetic drift and is ∼1.4×105 ±2.5×105 cm/s at n̄e∼2.3×1014 cm−3 in the ion diamagnetic drift direction, although the error bars associated with this last measurement do not preclude the possibility of zero rotation or rotation in the electron diamagnetic drift direction.
Magnetic-fusion data analysis at Los Alamos
Authors: Klare K. A.
Published: July 2002

dad is a versatile, easy-to-use, easy-to-modify set of programs for data analysis and display. The physicist simply calls a program by its name and a few numbers, which will tell the device, shot, or operation needed. Each command invokes a separately compiled program. This allows each experimenter to write commands to display model calculations or particular devices. Typical displays include: raw and normalized signals, or derived results such as phase-modulation detection, Thomson scattering nonlinear fits, wall temperatures from thermocouple conversions, and ion temperatures from Doppler broadening of spectral lines. Multiple-device and multiple-shot displays of single-channel or quadrature signals show progressions otherwise hard to find. Some programs have three-dimensional displays with contour or surface plots. The shots available on disk and device settings during data recording can be listed; analysis parameters may be shown or set. One number can define a whole series of commands. The other data display (odd) is a calculatorlike program to quickly process data and graph results for user needs that have not been reduced to a standard program. These programs use a shared library on Prime and VAX computers.
Experiences with delta compression of data produced by DIII
Authors: Henline P. A.
Published: July 2002

The amount of data collected for each tokamak experimental shot is rapidly increasing. This is caused by many factors, including more diagnostic experiments, reduced cost of electronics hardware (especially memory), and longer plasma duration. The design goal for the DIII-D tokamak is 25 Mbytes of data per shot. In order to store the shot data as one logical unit, the delta compression algorithm, as it was implemented at ORNL by E. Blair, is being used. Statistics on compression factors, times, and general usage will be presented for actual DIII data. Data for 8-, 10-, and 12-bit digitizers will be highlighted since this hardware is common to most sites.
ECE diagnostic for the TARA tandem mirror machine using a fast-scanning Michelson interferometer
Authors: Guharay S. K. , Boyd D. A. , Ellis R. F.
Published: July 2002

This ECE (electron cyclotron emission) diagnostic utilizes a fast-scanning Michelson interferometer to determine two parameters, the temperature and the loss cone angle, of the distribution function of the hot electrons (T≳100 keV) generated in the axisymmetric plug plasma of the TARA tandem mirror device. The radiation transport system employs a lens relay and a low-pass grating filter in order to transmit the synchrotron radiation over a spectral range of 2.9–18.6 cm−1. This enables us to study the emitted radiation spectrum up to the 40th harmonic of the electron–cyclotron frequency in the plug plasma (B=5 kG). Details of the design principles and the development of the diagnostic at TARA will be presented.
Electron cyclotron measurements with the fast-scanning heterodyne radiometer on the tokamak fusion test reactor
Authors: Taylor G. , Efthimion P. C. , McCarthy M. P. , Fredd E. , Cutler R. C.
Published: July 2002

Three fast-scanning heterodyne receivers, swept between 75 and 110, 110 and 170, and 170 and 210 GHz have measured electron cyclotron emission on the horizontal midplane of the tokamak fusion test reactor (TFTR) plasma. A second-harmonic microwave mixer in the 170–210-GHz receiver allows the use of a 75–110-GHz backward wave oscillator as a swept local oscillator. Electron temperature profile evolution data with a time resolution of 2 ms and a profile acquisition rate of 250 Hz will be presented for gas-fueled and pellet-fueled ohmic and neutral beam heated plasmas with toroidal fields up to 5.2 T. Recent results from a new swept-mode absolute calibration technique which can improve the accuracy and data collection efficiency during in situ calibration will also be presented.
Flexible, real-time, data-collection and analysis system and its utilization in a basic plasma physics experiment (invited)
Authors: Gekelman W. , Xu L.
Published: July 2002

A CAMAC-based LSI microcomputer coupled to a VAX minicomputer with a high (200 kbyte/s) transfer rate network make possible real-time data processing and control of a data-intensive plasma physics experiment. The system is constructed out of reliable, commercially available components. Most of the network software is written in fortran and is easy to maintain and modify. A description of its four software layers and illustrations of the type of experiments it has been used on are presented.
PLT data acquisition and analysis system
Authors: Murphy J. A. , Gibney T. R.
Published: July 2002

The data acquisition and analysis system for PLT (Princeton Large Torus) is being moved from a DEC-10 to a VAX 11/785. Most of the major diagnostics are currently running on the VAX, with approximately 1 Mbyte of data being taken each shot. The system uses the MIT model data system (MDS) for acquisition and archival of data and the PPPL event-controlled scheduler (ECS) for scheduling. The analysis programs use the MDS data retrieval subroutines which deliver correctly calibrated results to the user program.
TFTR data management system
Authors: Randerson L. , Chu J. , Ludescher C. , Malsbury J. , Stark W.
Published: July 2002

Developments in the tokamak fusion test reactor (TFTR) data-management system supporting data acquisition and off-line physics data reduction are described. Data from monitor points, timing channels, transient recorder channels, and other devices are acquired and stored for use by on-line tasks. Files are transferred off line automatically. A configuration utility determines data acquired and files transferred. An event system driven by file arrival activates off-line reduction processes. A post-run process transfers files not shipped during runs. Files are archived to tape and are retrievable by digraph and shot number. Automatic skimming based on most recent access, file type, shot numbers, and user-set protections maintains the files required for post-run data reduction.
Application of coincidence techniques to fusion product measurements
Authors: Murphy T. J. , Heidbrink W. W. , Strachan J. D.
Published: July 2002

Measurement of two products of a fusion reaction in coincidence is proposed. Possible detector arrays and sample count rates have been evaluated for reactions in the Fontenay-aux-Roses tokamak (TFR) and the Texas experimental tokamak (TEXT) and in the tokamak fusion test reactor (TFTR) neutral beam lines. The count rates indicate that this method is feasible on existing devices.
Thin-film nonlinear optical diode
Authors: Tocci Michael D. , Bloemer Mark J. , Scalora Michael , Dowling Jonathan P. , Bowden Charles M.
Published: July 2002

We present results of a theoretical investigation into a nonlinear thin-film multilayer device that exhibits passive anisotropic optical transmission—the analogue of the electronic diode. This optical diode is a nonlinear, asymmetric, distributed Bragg reflector. Material parameters for a nonlinear polymer (polydiacetylene 9-BCMU) and rutile are used in alternating layers to model a realistic device. The diode exhibits more than five times as much transmittance in one direction as in the opposite direction. It has a thickness of only 2 μm and is polarization insensitive.
New high-resolution conductance bridge for tunneling spectroscopy
Authors: Christanell R. , Smoliner J.
Published: July 2002

A simple four-terminal conductance bridge circuit, which provides high-resolution measurements of the current–voltage characteristics, dI/dV and d2I/dV2, as well as capacitance and dC/dV measurements, is presented. Current measurements in the wide range 1 nA–10 mA are possible and modulation voltages down to 1 μV can be used to achieve high resolution. The circuit has been used successfully for tunneling spectroscopy on GaAs–GaAlAs field effect transistor structures.
New inelastic electron tunneling spectrometer with an absolute peak intensity
Authors: Horiuchi Tsutomu , Ebisawa Fumihiro , Tabei Hisao
Published: July 2002

A new inelastic electron tunneling spectrometer with an absolute peak intensity is described. A smoothed second differential calculation is directly applied to high precision (7.5 digits) tunneling current-voltage data measured with Al/AlOx/Benzoic Acid/Pb tunnel junctions at 4.2 K. Interpolation and accumulation in addition to the above calculation permit high resolution and high signal-to-noise ratio inelastic electron tunneling (IET) spectra with absolute intensities. The half width at half maximum is 22 cm−1 and signal-to-noise ratio is more than 26 at 1598 cm−1 at the smoothing parameter M=19. The absolute peak intensities of tunnel junctions doped with solutions of different concentrations are measured easily and simply with this new method. The absolute peak intensities increase with an increase in both the solution concentration and dipping time. This method shows promise as a quantitative surface analytic system.
Directional load-cell anemometric probe
Authors: Vallascas Rinaldo , Porcu Gian Franco
Published: July 2002

A load-cell anemometric sensor is presented for simultaneous measurement of flow rates and flow direction of a fluid. The tests were carried out in steady flow conditions with air temperature of 28.5±0.5 °C, flow-rate range of 10–20 m/s and a pressure of 101.1 kPa.
Relaxation behavior of a hot-film anemometer under imposed bias flow
Authors: Dubbelday Pieter S.
Published: July 2002

The response of a hot-film anemometer to vertical hydroacoustic particle motion is influenced by free convection, which acts as a bias flow. At this low flow speed the output is proportional to particle displacement for a wide range of parameters. While investigating the response of the anemometer to hydroacoustic motion under an imposed bias flow, it was found that a relaxation-type transition takes place from dependence on particle speed to dependence on displacement. The relevant time constant is the residence time of the fluid particle near the sensor. This effect deserves consideration in interpretation of turbulence measurements in liquids.
Linear rotary differential capacitance transducer
Authors: Peters Randall D.
Published: July 2002

A linear sensor of the differential capacitance type, possessing more than 120 dB dynamic range, has been developed. The electrical equivalent circuit is that of a symmetric bridge, whose four capacitor elements derive from two semicircular segments each of a rotor and a stator. When driven at a constant excitation voltage, and configured with a differential amplifier and synchronous detector; the sensor output is proportional to the angular displacement, from the nominal position, of the rotor compared to the stator.
Interfacing the IBM PC compatible for simultaneous photon-counting and wavelength scanning
Authors: Warner Doug W. , Wells Fred V.
Published: July 2002

The simultaneous photon-counting and wavelength scanning by IBM compatible computers is described. Real-time photon counting is accomplished using the EG&G Ortec ACE-MCS interface board while the monochromator scan is simultaneously driven by a DCC5 multifunction counter-timer interface board. Count rates of up to 100 MHz are achieved.
Combined apparatus for x-ray photoelectron spectroscopy and extended x-ray absorption fine structure method using synchrotron radiation
Authors: Matsubayashi N. , Kojima I. , Kurahashi M. , Nishijima A. , Itoh A. , Utaka T.
Published: July 2002

A combined apparatus for Synchrotron Radiation (SR) was designed and developed in order to analyze the structure and properties of the solid surface. Two kinds of analyses; x-ray photoelectron spectroscopy (XPS) and x-ray absorption spectroscopy (XAS), are available using a 180° hemispherical electrostatic analyzer and/or other detection systems. High resolution XPS spectra were achieved with high signal-to-background ratio over a wide electron energy range up to 2600 eV using a monochromatized x ray (2600 eV) from SR. XAS spectra were obtained in two modes of total electron yield and Auger electron yield. The two modes described are complementary.
A 77-K cold stage for Raman microprobes and optical microscopy
Authors: Loppnow Glen R. , Mathies Richard A.
Published: July 2002

A 77-K cold stage has been developed for spectroscopic measurements in an optical microscope. This stage eliminates fogging of the optical windows observed in an earlier design by adding vacuum jackets around the liquid nitrogen transfer lines and by maximizing the sample-to-environment distance without sacrificing optical imaging power. Increased maneuverability of the cold stage is achieved by using flexible stainless-steel liquid-nitrogen transfer lines. In our application, the sample in the cold stage is illuminated with a focused laser beam and vibrational resonance Raman scattering spectra are recorded. We have used this Raman microprobe system to measure the Raman scattering from a variety of individual rod photoreceptor cells. This work has provided new information about the mechanism of wavelength regulation in color vision.
A simple alkali metal ion gun
Authors: Beck Scott T. , Warner Doug W. , Garland Ben A. , Wells Fred V.
Published: July 2002

An easily constructed alkali-metal-ion gun with a large metal-zeolite reservoir is described. The gun provides ion-beam currents from 100 eV to 5 keV in excess of 10 μA with a wide range of focal lengths. The ion trajectories of the extraction, acceleration, and focusing have been computed using the program simion. A versatile three-electrode extraction geometry that provides ion trajectories which emulate the planar diode is described.
Determination of the local current density by means of tangential Thomson scattering: Experimental setup, feasibility test, and preliminary observations
Authors: Barth C. J.
Published: July 2002

The local current density is one of the most important and most difficult parameters to be determined in a thermonuclear plasma. An experimental setup to measure the local electron drift velocity and thus, the current density, by means of tangential Thomson scattering, is presented. The drift velocity of the plasma causes a small wavelength shift of the scattered spectrum, which will be proportional to the local current density if toroidal ion rotation can be neglected. The ratio between the drift velocity and the mean thermal electron velocity is small, typically ∼0.05. A 20-channel high transmission polychromator has been constructed to observe the electron temperature and density within an accuracy of 1% and the drift velocity within 20% at a plasma density ne≊5×1019 m−3 and a laser energy of 7 J. A feasibility test on radial scattering shows that there is good agreement between the accuracy obtained from quantum statistics and observations, respectively. The high transmission and relatively high resolution of the polychromator enable the observation of irregularities in the velocity distribution which should be taken into account in the determination of the drift velocity. Preliminary observations in the tangential direction demonstrate the possibility to determine the drift velocity by a single laser shot. At ne ≊6×1019 m−3 and a laser energy of 3.5 J in the scattering volume a wavelength shift of −2.5±0.5 nm has been recorded corresponding to jφ≊1×107 A/m2.
Anisotropic conductivity of silver thin films grown on silicon (100) vicinal surfaces
Authors: López-Ríos T. , Briggs A. , Guillet S. , Baro A. M. , Luna M.
Published: July 2002

The electrical conductivity between 4 and 300 K of Ag thin films (up to 30 nm grown at room temperature on Si(100) vicinal surfaces has been measured and their morphology imaged with an atomic force microscope. A noticeable anisotropy of the resistivity of the films which is related to the structure of the films has been found.
High-resolution time-of-flight methods for studies on ionic fragmentation of molecules
Authors: Ueda K. , Shigemasa E. , Sato Y. , Yagashita A. , Sasaki T. , Hayaishi T.
Published: July 2002

The design and operation of the time-of-flight (TOF) mass spectrometer developed for ionic photofragmentation studies of molecules is described. Characteristics are summarized for three different operation modes of the TOF spectrometer; a pulse mode, a photoelectron–photoion coincidence mode, and a photoion–photoion coincidence mode. Experimental results for SiH4 are demonstrated as an example for the performance of the apparatus.
Photoreflectance optimization: A comparison between monochromator and glass filters for photoluminescence and laser light elimination
Authors: Giordana Adriana , Glosser R.
Published: July 2002

This article evaluates a photoreflectance apparatus in which unwanted photoluminescence and laser light are separated from the signal by a monochromator placed in front of the detector as compared to separation by the more commonly used glass filters. We present results from the application of both techniques to the study of the 3.4- and 4.3-eV structures in both bulk silicon and silicon films on sapphire, the 1.4-eV structure in GaAs, and the 1.8-eV structure of Al0.33Ga0.77As. The replacement of glass filters with a second monochromator, in addition to allowing a better rejection of spurious light, extends the range of wavelengths in which a satisfactory photoreflectance signal can be obtained and permits observation of a signal closer to the modulating laser line. On the other hand the use of glass filters can be preferable for high laser power, for weak signals in regions of low grating efficiency, or merely for economical reasons.
Two powder quenching devices with high cooling rates
Authors: Riemersma A. J. , Manuputy R. J. D. , Schlatter H. , Moolhuyzen W. F. , Rik R. , Lo Cascio D. M. R. , Loeff P. I.
Published: July 2002

Two devices for rapid quenching of powders are described. One of the devices, based on conventional resistance heating, is designed for application at temperatures up to 1200 °C and inert atmospheres. The other apparatus uses an rf coil as heating source and can be used at higher temperatures. The estimated quenching speed for both devices, is about 5×104 K/s. Examples of experiments are given to illustrate the performance of the devices.
Design and implementation of an inexpensive target scanner for the growth of thin films by the laser-ablation process
Authors: Rao A. M. , Moodera J. S.
Published: July 2002

The design of a target scanner that is inexpensive and easy to construct is described. Our target scanner system does not require an expensive personal computer to raster the laser beam uniformily over the target material, unlike the computer driven target scanners that are currently being used in the thin-film industry. The main components of our target scanner comprise a bidirectional motor, a two-position switch, and a standard optical mirror mount.
A versatile soft x-ray appearance potential spectrometer
Authors: Padalia B. D. , Shinde P. S. , Korgaonkar A. V. , Carvalho W. C. J.
Published: July 2002

A versatile soft x-ray appearance potential spectrometer with UHV and several other facilities has been designed and constructed using HAMAMATSU-make Cu-BeO photoelectron multiplier for the detection of soft x rays. Salient features of the design and construction aspects of the instrument and its performance are discussed.
A thermal phase-locked loop for frequency stabilization of internal-mirror He-Ne lasers (λ=0.633 μm)
Authors: Chien Pie-Yau , Pan Ci-Ling
Published: July 2002

A new servo circuit based on the thermal phase-locked loop (TPLL) has been developed for frequency stabilization of internal-mirror He-Ne laser. A feedback signal proportional to the fluctuation in the frequency of the laser is down-converted through a voltage-controlled oscillator (VCO) and compared in a phase/frequency circuit with that of a frequency reference. The detected phase difference then drives a heater wrapped around the laser tube for tuning the laser cavity length. The frequency stability achieved is ±1.0×10−9 over a period of several hours.
Application of the flush mounted hot film gauge for measuring blast wave surface shear
Authors: Batt R. G. , Magony G. A. , Cohen L. M.
Published: July 2002

Use is made of the fast response capability of the hot film shear gauge to perform unique shock tube and field test blast wave surface shear measurements. Mean flow turbulent calibration data are presented from three different test facilities: a low speed wind tunnel, a high pressure pipe facility, and a laboratory scale shock tube. Favorable agreement in calibration data between the three facilities is demonstrated. The good correlation in calibration results validates the ‘‘established’’ formulation procedure and provides a unique verification of available shock tube shear data. Measurements of ground shear under clean wall, i.e., nondusty, flow conditions are reported for blast waves created by high explosive detonations under large scale field test conditions. Satisfactory scaling of results in terms of event yield and overpressure location is demonstrated.
Milliwatt mixer for small fluid samples
Authors: Berg Robert F. , De Luca Nicholas P.
Published: July 2002

Mixing without excessive heating is sometimes needed for temperature-sensitive fluids. We modified an inexpensive low-frequency electronic filter based on a mechanical resonator to produce a compact (16 mm) and low-power (1–3 mW) mixer for low viscosity fluids. Tests made in air and methanol at room temperature and in fluoroform near its critical point are compared against the predictions of an electromechanical model.
An x-y-z stage for scanning proximity microscopes using elastic elements
Authors: McCord M. A.
Published: July 2002

A stage design is presented that allows coarse motion of the sample in an STM-type instrument. The stage utilizes the bending motion of springs driven by micrometers to achieve coarse motion in x, y, and z, and has no sliding parts other than the micrometers themselves. The design is compact, precise, and has excellent vibration and thermal drift characteristics.
A fast capacitive-RC hybrid probe for high power voltage pulse measurement
Authors: Saw S. H. , Wong C. S. , Lee S.
Published: July 2002

A simple and reliable capacitive-RC hybrid probe, designed for voltage measurement of fast pulse discharge systems, is presented. Further, besides its power handling capacity, it can be easily adapted to suit other pulse discharge systems.
A sensitive resistivity probe of high temperature phase transformations
Authors: Holzer J. C. , Summers G. , Majzoub E. H. , Kelton K. F.
Published: July 2002

A new apparatus for making in situ measurements of changes in the electrical resistivity accompanying phase transformations in metallic alloys is presented. Measurements can be made in vacuum or inert gas at annealing temperatures as high as 1500 K. The long-term thermal stability is better than ±0.3 K. The measurement circuit is stable to better than 0.01% over any time scale. This apparatus provides a relatively simple and inexpensive means for obtaining high temperature resistivity measurements on very brittle samples.
Viscosity measurement of an enclosed liquid using ultrasound
Authors: Hertz Thomas G. , Dymling Stephan O. , Lindström Kjell , Persson Hans W.
Published: July 2002

A novel method for noninvasive measurement of viscosity is proposed. The method is based on acoustic streaming, which can be induced by ultrasound in a liquid enclosed in a container. Measurements of the streaming velocity, obtained with wetted transducers at 10.4 MHz, show that it is inversely proportional to the viscosity of the liquid. Since the ultrasound Doppler technique can be used to measure flow velocities of enclosed liquids containing scatterers, the described method would appear to be well suited for the assessment of the viscosity or changes in the viscosity of such liquids enclosed in sealed containers. This opens up new possibilities in quality control of sterile packaged products such as milk and blood. Accuracy of the method in the reported experiments is found to be within ±6%.
High T
c superconducting levitation motor with a laser commutator. II
Authors: Weeks David E.
Published: July 2002

Significant improvements and extensions have been made to a high Tc superconducting levitation motor with an optical commutator. The primary extension is the development of a heat exchanger that permits high Tc superconductors to be cooled with liquid nitrogen to 77 K and below in vacuums of 10−5 Torr and less. This permits the levitation motor to be operated without the decelerating force of atmospheric drag. The result is an increase of nearly two orders of magnitude in the sustainable rotational frequency from a maximum of 10 s−1 at atmospheric pressure to 500 s−1 (30 000 rpm) at 10−5 Torr. The corresponding tangential velocity of the rotor arms increased from 3 m/s to 155 m/s. Angular frequencies between 100 s−1 and 200 s−1 have been sustained for periods exceeding 6 h. Measurements and analysis of rotor deceleration as a function of pressure and time are presented. Other improvements are discussed.
Silicon photodiode detector for a glancing-emergence-angle EXAFS technique
Authors: Brewe D. L. , Bouldin C. E. , Pease D. M. , Budnick J. I. , Tan Z.
Published: July 2002

We have constructed a silicon photodiode detector for use with a glancing-emergence-angle (GEA) geometry useful for obtaining fluorescence EXAFS spectra from thick specimens with concentrated absorbing species. We present a description of the detector and the results of tests, including dark-noise tests, EXAFS spectra from a standard sample, and a comparison to an ion chamber also in the GEA configuration. Data obtained from the two detectors are comparable in quality, making the diode detector a preferable choice for this application due to factors such as simplicity of construction and compact size. The diodes also have potential for significant further improvement in the quality of the signal due to their high quantum efficiency if the dark noise can be reduced. We present suggestions for achieving this in future generations of the detector.
Detailed structural calculation and mechanical measurement of the insertion device support structure for ELETTRA
Authors: Poloni C.
Published: July 2002

Structural calculations made during the design and testing of the insertion device (ID) carriage for ELETTRA are presented pointing out the differences obtained between different modeling approaches. The calculations are compared with a set of measurements that prove the validity and need of a detailed numerical model in order to predict the performance of such structures. The effects of thermal gradients are also considered. The results of a series of measurements made in order to assess the mechanical performances of the insertion device carriage are also presented.
Up-to-date information on the status of HESYRL
Authors: Zhongmou Bao
Published: July 2002

The recent status of HESYRL SR facility and the established beam lines and station are described concisely in this paper.
Status of the UVSOR Facility−1991
Authors: Watanabe M. , Isoyama G. , Kamada M. , Kimura K.
Published: July 2002

At the UVSOR Facility, a 750-MeV storage ring has been operated with an initial current of 200 mA. It has two undulators and a superconducting wiggler. A computer control system with two VAXs was introduced. The bunch length at the single-bunch operation was studied. A gain measurement for free electron laser study was successfully done. The number of beam lines is 19. By the use of these beam lines, about 140 programs have been accomplished in the fiscal year 1990. Among them, a photoelectron coincidence study on Xe atoms, a Te 4d absorption study in p- and n-type SnTe, and a photostimulated desorption study of Na atoms from sodium halides are demonstrated as topics. The Department of Vacuum Ultraviolet Photoscience has been newly approved at IMS to impel the researches by using UVSOR.
The Daresbury Synchrotron Radiation Source
Authors: West J. B.
Published: July 2002

The experimental programs at the 2-Gev electron storage ring at Daresbury is discussed. The users of the Synchrotron Radiatin Source (SRS) are from U.K. and Europe. A considerable amount of medical research is performed at the SRS. (AIP)
A new apparatus for electron–ion coincidence studies
Authors: Shigemasa E. , Koizumi T. , Itoh Y. , Hayaishi T. , Okuno K. , Danjo A. , Sato Y. , Yagishita A.
Published: July 2002

Design and operation of a new apparatus for electron–ion coincidence studies is described. For ionic fragmentation of inner-shell excited molecules, the degree of decomposition of the molecule depends on where valence two holes are created by a subsequent Auger decay. Auger electron–photoion coincidence (AEPICO) measurements are indispensable for studying the ionic fragmentations of the core-excited molecules, because these measurements can define the fragmentation products produced from a certain Auger final state. Experimental results for SiF4 are demonstrated as an example for the performance of the apparatus.
Infrared synchrotron radiation instrumentation and applications
Authors: Williams Gwyn P.
Published: July 2002

Infrared synchrotron radiation (IRSR) in the wavelength range from 1 μm to ∼1 cm has now been used quite extensively both in Japan at UVSOR, Okasaki and in the United States at the NSLS, Brookhaven, following an earlier program at the first infrared beamline at Daresbury in England. Elsewhere around the world, several new beamlines are under construction or planned−including a new facility at Daresbury (UK), and those at Lund (Sweden), SuperACO (France), ADONE (Italy), and the ALS (USA). The use of IRSR poses many new challenges, none the least of which is the fact that the radiation covers four decades of energy and is also very divergent and subject to diffraction. However the advantages are particularly significant due to the 1000-fold increase in brightness available over conventional sources in a region where detectors become a limiting factor. In addition, IRSR is also highly spatially coherent allowing the possibility of a new class of interferometers based on wave front division. We will discuss this and other instrumentation issues as they critically relate to experiments. The applications discussed will be in the areas of surface vibrational spectroscopy, both in ultrahigh vacuum and in electrochemical cells, and in areas which use the pulsed nature of the source both for fast response studies and for pump-probe studies.
The Advanced Light Source at Lawrence Berkeley Laboratory
Authors: Robinson A. L. , Perera R. C. C. , Schlachter A. S.
Published: July 2002

The Advanced Light Source (ALS) at the Lawrence Berkeley Laboratory (LBL), scheduled to be operational in the spring of 1993 as a U.S. Department of Energy national user facility, will be a next-generation source of soft x-ray and ultraviolet (XUV) synchrotron radiation. Undulators will provide the world’s brightest synchrotron radiation at photon energies from below 10 eV to above 2 keV; wiggler and bend-magnet radiation will extend the spectral coverage with high fluxes above 10 keV. These capabilities will support an extensive research program in a broad spectrum of scientific and technological areas in which XUV radiation is used to study and manipulate matter in all its varied gaseous, liquid, and solid forms. The ALS will also serve those interested in developing the fabrication technology for microstructures and nanostructures, as well as for characterizing them.