bluuebunny/crossref_metadata_2025 huggingface dataset:
Higher-order caustics and spectra of a Moellenstedt electron energy analyzer
Authors: Tian Renhe , Fink Manfred
Published: July 2002

First- and higher-order caustics and spectra of the Moellenstedt analyzer are computed. It is found that the higher-order caustics and spectra are due to multiple deflections of the electrons in the high chromatic aberration region of the Moellenstedt analyzer. These spectra consist of two parts: the caustic spectrum and noncaustic spectra, the so-called ‘‘ghost’’ spectra. The only reported ‘‘ghost’’ spectrum is reprodued by the calculation. Finally, the effects of changing the geometrical construction and the importance of determining the optimum operating point are discussed.
Ultrahigh-vacuum linear-rotary transfer mechanism utilizing a bakable self-lubricating bearing
Authors: Collet G. J. , Garwin E. L. , Kirby R. E.
Published: July 2002

An in vacuo translational-rotational motion based on a ball bearing package is described. Lubrication is accomplished by making the ball retainer from a solid dry lubricant, boron nitride (BN). This eliminates the need to separately coat the balls with lubricant prior to assembly; however, the balls are continuously coated while the bearing is in use.
High-stability bimorph scanning tunneling microscope
Authors: Blackford B. L. , Dahn D. C. , Jericho M. H.
Published: July 2002

A novel scanning tunneling microscope (STM) is described which is constructed almost entirely of aluminum and uses bimorph piezoelectric disks as the x,y,z drive elements. The design uses a simple, rugged tripod configuration for the fine motion drive arms. Coarse motion of the sample, which is mounted on an aluminum holder, is achieved by pushing or pulling, with a piezoelectric louse. Differential thermal expansion effects are avoided by design, to first order, and the resulting drift is ≤0.5 Å/min after only a short warm-up period. It is easy to build and operate, and has good immunity to mechanical vibrations. The frequency response is flat to 5 kHz. The x,y,z drive sensitivity is 8 Å/V and the range is ≥12000 Å. Some preliminary experimental results are presented, including atomic resolution images in air, of graphite and NbSe2.
Automatic ultrasonic measuring system using phase-sensitive detection
Authors: Iwasa Izumi , Koizumi Hirokazu , Suzuki Takayoshi
Published: July 2002

A new ultrasonic measuring system is developed that enables us to measure the changes in the sound velocity and attenuation in MHz frequency range simultaneously and automatically. The system utilizes a gated amplifier and a phase-sensitive detector (PSD) and is controlled by a personal computer. The unique feature of the system lies in the PSD with two double-balanced mixers that enables us to obtain simultaneously the sine and cosine components of the ultrasonic signal. The phase and amplitude of the signal are calculated from them by the personal computer and are then converted to changes in the velocity and attenuation, respectively. The performance of the PSD is tested. The system is suitable for measurements at low temperatures. The temperature dependences of the velocity and attenuation in ionic crystals are measured with this system.
Optimization of H− production from a small multicusp ion source
Authors: Leung K. N. , Hauck C. A. , Kunkel W. B. , Walther S. R.
Published: July 2002

A small multicusp source has been developed to generate volume-produced H− ion beams in pulsed operation. To obtain high H− current densities (J−>250 mA/cm2), this source requires relatively high gas pressure and high discharge power. Experiments have been conducted to improve the arc and gas efficiencies, the beam pulse shape, and the H− to electron ratio in the extracted beam by optimizing the filter magnetic field, the thickness and axial position of the extraction aperture in the plasma electrode, and by mixing xenon or other elements with hydrogen in the discharge. The biggest improvement is achieved by adding cesium to the source, resulting in a fivefold increase in the extractable H− current and a substantial drop in the e/H− ratio. In order to improve the lifetime of the cathode, both filament and coaxial type LaB6 cathodes have been developed and have been operated successfully in this H− source.
Apparatus for positron annihilation-induced Auger electron spectroscopy
Authors: Lei Chun , Mehl David , Koymen A. R. , Gotwald Fred , Jibaly M. , Weiss Alex
Published: July 2002

The apparatus used in the first direct measurement of energy spectra of positron annihilation-induced Auger electrons is described. The apparatus consists of a magnetically guided low-energy positron beam, a UHV surface preparation and characterization chamber, and an energy spectrometer. The spectrometer includes a trochoidal monochromator and a microchannel plate detector. A permanent magnet is mounted behind the sample to produce a field gradient which redirects the outgoing Auger electrons along the spectrometer axis. The combination of trochoidal monochromator and permanent magnet permits the measurement of the total kinetic energy of Auger electrons with an effective angular acceptance of ∼2π. The large angular acceptance and single particle detection capability of this spectrometer make it possible to perform Auger measurements using extremely low incident beam currents (∼10−15 A), and may make it useful in other low signal experiments. The spectrometer response function is modeled and compared to experimental results for different values of the magnetic field gradient.
Fabrication of layered metallic systems for perpendicular resistance measurements
Authors: Slaughter J. M. , Pratt W. P. , Schroeder P. A.
Published: July 2002

We are studying the resistivity of layered metal systems in a direction perpendicular to the layers (ρperp). The techniques for measuring the very small resistances involved are briefly reviewed, and the system for producing samples with the appropriate geometry is discussed in detail. The samples are produced by sputtering in an ultrahigh vacuum compatible system that permits mask changing without breaking the vacuum. As an example, we give results illustrating the Cooper pair-breaking effects of thin layers of Co in a system consisting of consecutive layers of Nb–Co–Ag–Co–Nb.
Multilayer mirrors as power filters in insertion device beamlines
Authors: Kortright J. B. , DiGennaro R. S.
Published: July 2002

The power-filtering capabilities of multilayer bandpass x-ray mirrors relative to total reflection low-pass mirrors are presented. Results are based on calculations assuming proposed wiggler sources on the upcoming generation of low-energy (1.5 GeV) and high-energy (7.0 GeV) synchrotron radiation sources. Results show that multilayers outperform total reflection mirrors in terms of reduction in reflected power by roughly an order of magnitude, with relatively small increases in total absorbed power and power density over total reflection mirrors, and with comparable reflected flux values. Various aspects of this potential application of multilayer x-ray optics are discussed.
Electrostatic analyzer and optics for low-energy electron spectroscopy
Authors: Boumsellek S. , Tuan Vu Ngoc , Esaulov V. A.
Published: July 2002

A 45° parallel-plate electrostatic energy analyzer and associated optics, which were designed for low-energy electron spectroscopy, are described. Results of some computer simulations and some typical electron energy spectra obtained with this system are presented.
Magnetically insulated helium ion diode
Authors: Wessel F. J. , Heidbrink W. W. , Drum S. , Hoang K. , Layton P.
Published: July 2002

A gas-puff magnetically insulated ion diode is under development as a pulsed source of high-energy alpha particles for magnetic fusion experiments. The diode is patterned after the Cornell gas-puff diode [J. B. Greenly, M. Ueda, G. D. Rondeau, and D. A. Hammer, J. Appl. Phys. 63, 1872 (1988)], but with modifications to accomodate higher voltages (<1 MeV) and operation in helium. The diode is designed to yield current densities approaching 200 A/cm2 one meter downstream from the source; in our first test of the new source, a helium beam was obtained.
Low cost data acquisition system for transport characterization of high-T
c superconductors
Authors: Tessler Leandro R.
Published: July 2002

A low cost microcomputer-based data-acquisition system designed specifically to perform transport characterization of high-Tc superconductors is presented. It can measure the temperature dependence of both the resistance and the critical current. It utilizes the four-point ac in-phase method to eliminate the effects of lead and contact resistance and thermal voltages. Some of the advantages of this method over dc methods are pointed out. The system is implemented on a PC (IBM or compatible) through the IEEE-488 interface. The temperature is controlled by the system with resolution and accuracy of 0.1 and ±0.5 K, respectively, which are the limits of the platinum thermometer used. Voltages in the sample can be measured with a resolution better than 5 nV. The system can be easily modified to measure the critical current dependence on an applied magnetic field.
Spinning glass cell for high-pressure high-resolution NMR measurements
Authors: Yamada H. , Nakatsuka M. , Yamochi H. , Sawamura M. , Sera A.
Published: July 2002

A full description of the rotatable high-pressure glass cell method for the NMR measurements is presented. This simple device eliminates the use of massive high-pressure apparatus such as the oil pump, the Bourdon gauge, and the high-pressure tubing and valves in performing the high-pressure experiments. This system also demonstrates capability of realizing an extremely high-resolution level in the NMR measurements at high pressure otherwise not easily attainable.
A rocking beam electrostatic balance for the measurement of small forces
Authors: Miller G. L. , Griffith J. E. , Wagner E. R. , Grigg D. A.
Published: July 2002

There exists interest in the measurement of small forces for applications such as microtopography of semiconductor devices and atomic force microscopy. A new method is introduced here in which a small silicon beam, that is acted on by the external force of interest, has its position sensed by an rf phase shift technique. The position information in turn is fed back via electrostatic forces to continuously rebalance the beam about its central support. This force-feedback approach provides high sensitivity, submillisecond response, inherent force calibration, and electronically controlled stiffness.
Cuprous oxide manometer for high-pressure magnetic resonance experiments
Authors: Reyes A. P. , Ahrens E. T. , Heffner R. H. , Hammel P. C. , Thompson J. D.
Published: July 2002

We present a manometer designed to measure pressures of 1–20 kbar in temperatures between 4–300 K in cylinder-piston type chambers, with an accuracy of ∼100 bar. The manometer is based on pressure-dependent zero-field 63Cu nuclear quadrupole resonance frequency corresponding to ‖±3/2〉↔‖±1/2〉 transition in Cu2O. The nuclear quadrupole resonance frequency νQ varies linearly with pressure and its temperature dependence is adequately explained by a model of lattice vibrational modes in O—Cu—O bonds. This manometer is particularly convenient for zero or high-field magnetic resonance experiments.
Very low current amplifier for computerized data acquisition systems in noisy environments
Authors: Buksh P. A.
Published: July 2002

A routine requirement in experiments on synchrotron light sources is the measurement of the currents generated by photoemission. Accurate recording of such low level signals is often problematic due to electronically noisy environments and the distance between the data acquisition computer and the experiment. We present the design of a low current amplifier whose small size enables it to be mounted directly onto the experimental chamber. The device generates a frequency output proportional to its input signal. This method of frequency transmission ensures a high level of noise immunity and permits the use of standard counting electronics. Multiple devices may be driven from a common clock, derived from the counter clock, thus eliminating errors due to clock frequency drift.
Manufacture of three-dimensional microdevices using synchrotron radiation (invited)
Authors: Münchmeyer D. , Langen J.
Published: July 2002

Future innovative microdevices and microsystems require manufacturing processes which allow a high degree of freedom in the geometrical design of the microstructure, a broad spectrum of materials, and a favorable potential for mass production at low costs. These requirements are met by the LIGA process, which uses synchrotron radiation lithography to produce extremely precise masters of three-dimensional microstructures and subsequent electroforming and moulding processes to produce microdevices from metals, polymers, and ceramics. In this article, the basic process principles, its physical and technological limits, and some specific applications such as sensors for automotive purposes, infrared optical components, optical demultiplexers, and fiber-chip coupling elements for optical communication systems, micronozzles and valves, electrical microconnectors, or moving microdevices are discussed.
Development of superconducting compact storage rings for technical purposes in the USSR (invited)
Authors: Kulipanov G. N. , Mezentsev N. A. , Morgunov L. G. , Sadjaev V. V. , Shkaruba V. A. , Sukhanov S. V. , Vobly P. D.
Published: July 2002

The work on the creation of compact storage rings, superconducting rectangular magnet-based synchrotron radiation (SR) sources produced jointly with the Association VACUUMMASHPRIBOR (Moscow) for technology and research purposes is described. The tests of a pilot model and the current status of work on SIBERIA-SM and a stand for storage rings are reported. Also presented are the results of calculations concerning the field distribution and the dynamic aperture in the storage ring. New projects of SR sources, a 1.2-GeV storage ring for micromechanics and a 2.4-GeV storage ring, both having superconducting and warm magnets in their structure, are discussed.
Reduction imaging with soft x rays for projection lithography
Authors: MacDowell A. A. , Bjorkholm J. E. , Bokor J. , Eichner L. , Freeman R. R. , Pastalan J. Z. , Szeto L. H. , Tennant D. M. , Wood O. R. , Jewell T. E. , Mansfield W. M. , Waskiewicz W. K. , White D. L. , Windt D. L.
Published: July 2002

It has been shown that it is possible to produce near diffraction limited images with soft x rays of wavelength 13.8 nm using normal incidence Si/Mo-multilayered coated optics. Initial experiments with a 20X reduction Schwarzschild optic produced features as small as 50 nm. It is considered that soft x-ray projection lithography may be a likely candidate for the future generation of lithographic tools needed to produce 0.1-μm features for integrated circuits around the turn of the century.
Injection turn measurement of the superconducting ring, Super-ALIS
Authors: Hosokawa Teruo , Nakajima Masayuki , Yamada Kouji
Published: July 2002

A novel method of measuring injection turns by using the burst beam generation function of the injection linac is discussed. This generating system and its performance are outlined, and they are used to measure the injection turns of the superconducting compact storage ring, Super-ALIS. The number of injection turns of Super-ALIS is 14.
A versatile environmental chamber at the Beijing Synchrotron Radiation Laboratory
Authors: Jiang Jianhua , Zhao Jiyong
Published: July 2002

A versatile environmental chamber at the Beijing Synchrotron Radiation Laboratory (BSRL) is described. This facility has been used for in situ x-ray topographic studies of the structural imperfection in the solids. As an example the investigating result of the domain boundaries and their evolution with temperature in KNbO3 crystal is given.
First operation of the medical research facility at the NSLS for coronary angiography
Authors: Thomlinson W. , Gmür N. , Chapman D. , Garrett R. , Lazarz N. , Moulin H. , Thompson A. C. , Zeman H. D. , Brown G. S. , Morrison J. , Reiser P. , Padmanabahn V. , Ong L. , Green S. , Giacomini J. , Gordon H. , Rubenstein E.
Published: July 2002

The Synchrotron Medical Research Facility (SMERF) at the National Synchrotron Light Source has been completed and is operational for human coronary angiography experiments. The imaging system and hardware have been brought to SMERF from the Stanford Synchrotron Radiation Laboratory where prior studies were carried out. SMERF consists of a suite of rooms at the end of the high-field superconducting wiggler X17 beam line and is classified as an Ambulatory Health Care Facility. Since October of 1990 the coronary arteries of five patients have been imaged. Continuously improving image quality has shown that a large part of both the right coronary artery and the left anterior descending coronary artery can be imaged following a venous injection of contrast agent.
An MBE growth facility for real-time in situ synchrotron x-ray topography studies of strained-layer III–V epitaxial materials
Authors: Whitehouse C. R. , Barnett S. J. , Soley D. E. J. , Quarrell J. , Aldridge S. J. , Cullis A. G. , Emeny M. T. , Johnson A. D. , Clarke G. F. , Lamb W. , Tanner B. K. , Cottrell S. , Lunn B. , Hogg C. , Hagston W.
Published: July 2002

This paper describes a unique combined UHV MBE growth x-ray topography facility designed to allow the first real-time synchrotron radiation x-ray topography study of strained-layer III–V growth processes. This system will enable unambiguous determination of dislocation nucleation and multiplication processes as a function of controlled variations in growth conditions, and also during post-growth thermal processing. The planned experiments have placed very stringent demands upon the engineering design of the system, and design details regarding the growth chamber; sample manipulator, x-ray optics, and real-time imaging systems are described. Results obtained during a feasibility study are also presented.
X-ray area detector based on CCD readout for diffraction study (abstract)
Authors: Amemiya Y. , Kishimoto S. , Suzuki M. , Ohnishi Y.
Published: July 2002

An x-ray area detector based on charged coupled device (CCD) readout has been designed and constructed for diffraction studies. Incident x-rays are converted to visible photons by a phosphor screen [Y2O2S or CsI(Na)] which is attached via fiber optic to the input surface of the demagnifying image intensifier with a 4:1 demagnification. The intensified visible image created on the output phosphor screen of the image intensifier is viewed through a 1:1 optical lens system by the cooled CCD (Thomson:THX31156) which has 1024×1024 pixels (pixel size: 19 μm×19 μm). The detector system should have the following characteristics: active area: 100 mm in diameter, spatial resolution: 0.1 mm×0.1 mm, detective quantum efficiency (DQE): about 70% for 8 keV, dynamic range: more than 104, readout time: 4 s. Nonuniformity of response due to the image intensifier is corrected by software. The CCD is cooled to −30° to −40° to reduce the dark current. The background noise level of the detector system corresponds to less than 10 x-ray photons per pixel. Detailed hardware and software configuration and measured performance of the system will be described. The system will be applied to small-angle x-ray scattering (SAXS) and protein crystallography.
A high-energy double-crystal fixed exit monochromator for the X17 superconducting wiggler beam line at the NSLS
Authors: Garrett R. F. , Dilmanian F. A. , Oversluizen T. , Lenhard A. , Berman L. E. , Chapman L. D. , Stoeber W.
Published: July 2002

A high-energy double-crystal x-ray monochromator has been constructed for use on the X-17 beam line at the National Synchrotron Light Source (NSLS). Its design is based on the ‘‘boomerang’’ right angle linkage, and features a fixed exit beam, a cooled first crystal, and an energy range of 8–92 keV. The entire mechanism is UHV compatible. The design is described and performance details, obtained in testing at the X17 beam line, are presented.
The high-flux beamline at the ESRF
Authors: Bösecke Peter
Published: July 2002

The high-flux beamline at the ESRF will be one of the first beamlines and will be available to users at the start of ESRF operation in 1994. It will provide a highly monochromatic photon flux with very low divergence through a small sample. The brilliance of the photon beam will be much higher than at existing sources. The optics is optimized for ultrasmall angle x-ray scattering experiments and biological macromolecular crystallography at 12 keV. This corresponds to a wavelength of about 0.1 nm. An undulator with a period of 46 mm and a maximum deflection parameter K of 2.08 has been chosen as an insertion device. The optics will consist of a cryogenically cooled Si(111) double monochromator followed by a double focusing mirror. In this paper the planned setup of the beamline is described. The optical properties have been studied with the ray-tracing program shadow.
Full polarization measurement of synchrotron radiation with use of soft x-ray multilayers
Authors: Kimura Hiroaki , Yamamoto Masaki , Yanagihara Mihiro , Maehara Takumi , Namioka Takeshi
Published: July 2002

Using two Ru/Si multilayers as a phase shifter and an analyzer, we have measured the state of polarization for 12.8-nm synchrotron radiation (SR) of the beam line 11A at the Photon Factory. It has been found that the state of polarization depends largely on the vertical inclination angle of the first mirror of the beam line. From the phase information, we have determined parameters of the polarization ellipse including handedness.
Study of different SX-700 monochromator designs for the undulator beamline (BL51) at MAX-lab
Authors: Aksela S. , Kivimäki A. , Nyholm R. , Svensson S.
Published: July 2002

Different designs of the SX-700 plane grating monochromator have been investigated for the undulator beamline (51) by using analytical considerations and carrying out ray tracing calculations. The most important modifications of the original design are those where the ellipsoidal focusing mirror has been replaced by a plane elliptical or by a spherical mirror. A significant advantage of the spherical mirror is essentially better figure accuracies (±0.2 arcsec). This is partly compensated by the introduced coma aberration which, however, can be made small with rather long exit arm lengths (5–6 m). If the slope errors of the plane elliptical mirror can be made as small as 0.5 arcsec, the differences in the ultimate resolution are small between the plane elliptical and spherical designs and then the source size is the main factor.
Construction of focusing soft x-ray beamline BL1A at the UVSOR
Authors: Hiraya Atsunari , Horigome Toshio , Okada Norio , Mizutani Nobuo , Sakai Kusuo , Matsudo Osamu , Hasumoto Masami , Fukui Kazutoshi , Watanabe Makoto
Published: July 2002

A focusing soft x-ray beam line equipped with a focusing premirror and a double crystal monochromator (DXM) has been constructed at BL1A in the UVSOR. An elliptically bent cylindrical mirror was used as the focusing premirror in order to attain both horizontal and vertical focusing at the sample position. Ray tracing shows that the size and shape of the focused spot at sample position with an elliptically bent cylindrical mirror is almost the same as that of an ellipsoidal mirror. Measured spot size of the monochromatic x-ray beam at the sample position was about 2 mm wide and 1 mm high, which is in good agreement with the result of ray tracing. Monochromatic x rays were observed up to 4 keV even after reflection by a platinum coated premirror with grazing angle of 1°.
Negative-ion formation from positive ion by two-electron transfer from an alkali-metal target
Authors: Hayakawa S. , Matsumoto A. , Yoshioka M. , Sugiura T.
Published: July 2002

To examine two-electron transfer producing negative ions from positive ions, an apparatus using an alkali-metal target has been developed. Positive ions formed by electron impact in an ion source collided with alkali-metal vapor in a target chamber. Negative ions formed by two-electron transfer have been analyzed with a single-focusing mass spectrometer. Precursor positive ions and product negative ions have been identified from the apparent masses in the negative-ion spectra. Using the target density dependence of the negative-ion intensity, the processes of negative-ion formation were determined to be double-electron transfer in one collision or successive single-electron transfer in two collisions. The cross section of these processes has been estimated from the peak area of positive- and negative-ion spectra and the target density evaluated using the vapor-pressure curve as a function of the temperature of the alkali-metal cell. A cross section for He−-ion formation in the Cs target with successive single-electron transfer have been evaluated to be 1.40×10−30±0.2 cm4 at a collision energy of 2.0 keV, which showed the fair agreement with the values reported by Donnally and Thoeming [Phys. Rev. 159, 87 (1967)]. The double-electron transfer cross section for C2−-ion formation from a C2+ ion with a Cs target has been evaluated as 7.03×10−18±0.1 cm2 at 3.0 keV. For O−-ion formation from O2+ ions, four broad peaks were observed due to the kinetic energy releases at dissociation which were 7.3, 3.4, 1.1, and 0.014 eV at full width at half maximum. Since the kinetic energy releases of the broad peaks corresponded with those by Peterson and Bae [Phys. Rev. A 30, 2807 (1984)], the peak extents have been explained as the dissociations of the excited neutral formed from exothermic neutralization. This two-electron transfer from an alkali-metal target offers a good advantage for the determination of the dissociation mechanism for excited neutral particles by means of the negative-ion detection method.
Pulsed supersonic source producing clusters with an adjustable vibrational temperature
Authors: Bucher J. P. , Douglass D. C. , Bloomfield L. A.
Published: July 2002

We report the construction and operation of a novel cluster source that produces clusters with well-defined vibrational temperatures. Clusters seeded in He gas are thermalized in a cavity before undergoing a weak supersonic expansion. This weak expansion does not affect their vibrational temperature. An optimized source design ensures a high cluster density in the beam. The vibrational temperature is measured by studying the magnetic deflection of superparamagnetic clusters. We show that thermal equilibrium with the source temperature is achieved for long residence times of the clusters in the cavity. A closed-cycle helium refrigerator coupled to the source body controls the source temperature. Under these conditions, cluster vibrational temperatures from 58 to 300 K are currently obtained.
Development of a geometry-compensated neutron time-of-flight detector for ICF applications with approximately 200 ps time response
Authors: Murphy T. J. , Lerche R. A.
Published: July 2002

Current-mode neutron time-of-flight detectors are used on Nova for neutron yield, ion temperature, and neutron emission time measurements. Currently used detectors are limited by the time response of the microchannel plate photomultiplier tubes used with the scintillators, scintillator decay time, scintillator thickness, and oscilloscope response time. A change in the geometry of the scintillator allows one to take advantage of the increased time resolution made possible by more advanced transient recorders and microchannel plate photomultiplier tubes. A prototype detector has been designed to incorporate these changes, and could potentially yield time resolution of less than 150 ps. Experimental results are presented demonstrating an ion temperature measurement of a direct-drive DT implosion on Nova.
Alpha particle diagnostics using impurity pellet injection (invited)
Authors: Fisher R. K. , McChesney J. M. , Howald A. W. , Parks P. B. , Snipes J. A. , Terry J. L. , Marmar E. S. , Zweben S. J. , Medley S. S.
Published: July 2002

We have proposed using impurity pellet injection to measure the energy distribution of the fast confined alpha particles in a reacting plasma [R. K. Fisher et al., Fusion Technol. 13, 536 (1988)]. The ablation cloud surrounding the injected pellet is thick enough that an equilibrium fraction F∞0(E) of the incident alphas should be neutralized as they pass through the cloud. By observing neutrals created in the large spatial region of the cloud which is expected to be dominated by the heliumlike ionization state, e.g., Li+ ions, we can determine the incident alpha distribution dnHe2+/dE from the measured energy distribution of neutral helium atoms dnHe0/dE using dnHe0/dE = dnHe2+/dE⋅F∞0 (E,Li+). Initial experiments were performed on the Texas Experimental Tokamak (TEXT) in which we compared pellet penetration with our impurity pellet ablation model [P. B. Parks et al., Nucl. Fusion 28, 477 (1988)], and measured the spatial distribution of various ionization states in carbon pellet clouds [R. K. Fisher et al., Rev. Sci. Instrum. 61, 3196 (1990)]. Experiments have recently begun on the Tokamak Fusion Test Reactor (TFTR) with the goal of measuring the alpha particle energy distribution during D–T operation in 1993–94. A series of preliminary experiments are planned to test the diagnostic concept. The first experiments will observe neutrals from beam-injected deuterium ions and the high energy 3He tail produced during ion cyclotron (ICH) minority heating on TFTR interacting with the cloud. We will also monitor by line radiation the charge state distributions in lithium, boron, and carbon clouds. Later experiments are planned to measure the energy distribution of the 3.7 MeV alphas created by 3He–D reactions during ICH minority heating. Observations of 3.7 MeV alphas should allow single-particle alpha physics to be studied now and result in a fully tested diagnostic prior to D–T operation of TFTR.
Cooled low-noise preamplifier for a bolometer
Authors: Gush H. P. , Halpern M. , Knotek S.
Published: July 2002

A preamplifier has been built for use within a cryogenic system operating at a temperature of 2 K. The input stage is a 2N6483 JFET operating near 100 K. The equivalent input noise is less than 8 nV/Hz1/2 at a frequency of 10 Hz.
Time-resolved Fourier transform spectroscopy with 0.25 cm−1 spectral and <10−7 s time resolution in the visible region
Authors: Hartland Gregory V. , Xie Wei , Dai Hai-Lung , Simon Arno , Anderson Michael J.
Published: July 2002

The development of a new time-resolved Fourier transform spectrometer that is capable of 0.25 cm−1 spectral resolution and better than 10−7 s temporal resolution in the visible is reported. The time-resolved capability of the spectrometer is achieved by coupling a step-scan interferometer to a transient digitizer/laser system. The operation of the spectrometer is described in detail, and scattered light and laser-induced fluorescence spectra from an I2 gas cell are presented to demonstrate the temporal and spectral resolution of the spectrometer.
A complete characterization of x-ray polarization state by combination of single and multiple Bragg reflections
Authors: Shen Qun , Finkelstein K. D.
Published: July 2002

We present a simple method for complete determination of the x-ray polarization state, using just one Bragg reflection from a single-crystal analyzer. For the linear polarization components P1 and P2, we show that the usual method of using a 90° Bragg reflection can be extended to using any Bragg reflection with 2θ≠90°. For circular component P3, we use the intensity modulation profile in an azimuthal rotation caused by the phase-sensitive interference around a multiple-beam Bragg reflection. The combination of the two measurements allows a straightforward complete determination of x-ray polarization, including an unpolarized component, in a broad applicable energy range.
Compact stand-alone atomic force microscope
Authors: van der Werf Kees. O. , Putman Constant A. J. , de Grooth Bart G. , Segerink Frans B. , Schipper Eric H. , van Hulst Niek F. , Greve Jan
Published: July 2002

A stand-alone atomic force microscope (AFM) featuring large scan, friction measurement, atomic resolution, and liquid operation, has been developed. Cantilever displacements are measured using the optical beam deflection method. The laser diode and focusing lens are positioned inside the piezo tube and the cantilever at the end of the piezo tube. Because the laser beam stays on the cantilever during scanning, the scan range is solely determined by the characteristics of the piezo tube. In our case 30×30×9.5 μm3 (xyz). The optical beam deflection detection method allows simultaneous measurement of height displacements and torsion (induced by lateral forces) of the cantilever. AFM images of dried lymphocytes reveal features in the torsion images, which are only faintly visible in the normal height images. A new way of detecting the nonlinear behavior of the piezo tube is described. With this information the piezo scan is linearized. The nonlinearity in a 30-μm scan is reduced from 40% to about 1%, as is illustrated with images of a compact disk. The stand-alone AFM can be combined with a (confocal) inverted microscope, yielding a versatile setup for biological applications.
Fourier-transform spectrophotometer for time-resolved emission measurements using a 100-point transient digitizer
Authors: Preses Jack M. , Hall Gregory E. , Muckerman James T. , Sears Trevor J. , Weston Ralph E. , Guyot Christian , Hanson Jonathan C. , Flynn George W. , Bernstein Herbert J.
Published: July 2002

An infrared time-resolved Fourier-transform emission spectrophotometer has been constructed and its use has been demonstrated. The instrument is based on a commercial interferometer combined with a CAMAC-based data acquisition system. The use of a transient digitizer permits acquisition of a single interferogram point at 100 time intervals following a single photoexcitation. The instrument operates in the ‘‘smooth scan’’ mode. The combination of this mode of operation with the use of a transient digitizer provides great time efficiency for data acquisition because there is no mirror settling time at each optical retardation. Complete interferograms free from the artifacts associated with assembly of interferograms arising from multiple scans are available after each mirror scan. The maximum resolution of the present instrument is 0.1 cm−1, limited only by data storage considerations; the maximum resolution of the commercial interferometer is 0.02 cm−1 (with apodization) and could be utilized with long scans. The shortest time that can be resolved by the instrument, currently ∼1–2 μs, is limited only by the infrared detector/preamplifier combination. The longest time interval which is permitted between successive photochemical or photophysical events (nominally 3.16 ms) is limited by the slowest scan velocity of the moving mirror, (0.01 cm/s). Usable data can be acquired from 10 to 50 mirror scans, where acquisition, storage, and coaddition of a single 1 cm−1 resolution scan takes ∼5 min.
Time-resolved exciton luminescence in GaN grown by metalorganic chemical vapor deposition
Authors: Shan W. , Xie X. C. , Song J. J. , Goldenberg B.
Published: July 2002

We report the results of time-resolved studies on the exciton radiative decay in single-crystal GaN films grown by metalorganic chemical vapor deposition. Time-resolved photoluminescence (PL) measurements were performed on the samples at various temperatures from 10 to 320 K. The well-resolved near-band-edge luminescence features associated with free excitons and bound excitons in the GaN allow us to unambiguously determine their decay times. We found that the nonradiative recombination processes play an important role and dominate the decay of exciton population. The processes depend on the density of defects and impurities in the GaN samples.
A new collimator design for energetic neutral atom instruments
Authors: Gruntman Michael A.
Published: July 2002

A new type of collimator design is described for energetic neutral atom instruments for space research applications. The collimator consists of annular entrance and exit slits with charged particle deflection plates between them. This configuration allows one to meet three seemingly contradicting requirements of compact design, efficient rejection of the incoming ions, and a large field of view.
A modified ultrasonic interferometer for sound velocity measurements in molten metals and alloys
Authors: Nasch Ph. M. , Manghnani M. H. , Secco R. A.
Published: July 2002

An ultrasonic interferometer has been developed for measuring compressional wave velocity (VP) and attenuation (or conversely, quality factor QP) in molten Fe, Fe-Ni, Fe-Ni-S, and Fe-Ni-Si alloys. Results for pure molten Fe are presented. A radio frequency (rf) induction technique is used for heating that allows a ±1 K temperature stability at 1973 K. The effects of the electromagnetic field interaction with the molten conductive metal are discussed in terms of applicability to VP and QP measurements. Considerations of acoustic impedance and thermal absorption are presented to discuss the high-temperature use of polycrystalline Al2O3 buffer rods for velocity and attenuation measurements. Viscoelastic theories, when applied to pure molten Fe, predict an extremely small acoustic coefficient of attenuation. Suggestions are made to circumvent the experimental difficulties encountered in attenuation measurements.
A photon counter and pulse train generator interface for a personal computer in pulse optically detected magnetic resonance
Authors: Granger B. E. , Nishimura A. M.
Published: July 2002

The decay of coherently prepared excited triplet state can be observed by pulse optically detected magnetic resonance (ODMR). Analysis of this data yields important information about the various relaxation pathways open to a molecule in a given environment. Pulse ODMR requires shorter pulses with higher resolution than those used in pulse nuclear magnetic resonance. Programmable pulse train generators are commercially available, but they can be costly. In this article, a fully programmable photon counter-pulse train generator interface is described which has the required resolution and speed. The interface cards occupy two slots of a personal computer and are based on advanced Shottky transistor–transistor logic series of logic circuits. This inexpensive, yet highly flexible apparatus for use in pulse ODMR, can be adapted for other applications, such as pulse magnetic resonance and photon counting. In addition, the modular design allows easy expansion to multichannel pulse or photon counting and to the generation of even the most imaginative pulse sequences.
Five new experimental stations at the SRS Daresbury from a 6 T superconducting wiggler magnet
Authors: Bilsborrow R. L. , Bliss N. , Bordas J. , Cernik R. J. , Clark G. F. , Clark S. M. , Collins S. P. , Dobson B. R. , Fell B. D. , Grant A. F. , Harris N. W. , Smith W. , Towns-Andrews E.
Published: July 2002

Daresbury Laboratory is currently completing the construction and commissioning of five new experimental research stations utilizing high flux hard x-ray radiation from a 6 T superconducting wiggler magnet. The broad areas of science covered by the new stations and the novel features are presented.
Performance of Beamline 4W1C for x-ray diffuse scattering station at Beijing Synchrotron Radiation Facility
Authors: Jiang X. , Zheng W. , Wu J. , Jing Y. , Liu G.
Published: July 2002

Bent triangular Si crystals with an oblique-cut angle 12.16° are used on the beamline 4W1C at Beijing Synchrotron Radiation Facility, to select monochromatic x-rays and to focus the beam in the horizontal direction. The downstream Pt-coated reflective mirror is bent as a cylindroid focuses the beam vertically. Double-focused monochromatic x rays are available on the diffuse scattering station. Specifications of the beamline with the Si (220) monochromator were measured as follows: size of the focus spot—0.5 mm (horizontal)×0.3 mm (vertical), maximum x-ray density—1.6×109 photons/s mm2, and energy resolution of the monochromatic beam—4.4×10−4.
Simultaneous resolution of spectral and temporal properties of UV and visible fluorescence using single-photon counting with a position-sensitive detector
Authors: Kelly Lisa A. , Trunk John G. , Polewski Krzysztof , Sutherland John C.
Published: July 2002

A new fluorescence spectrometer has been assembled at the U9B beamline of the National Synchrotron Light Source to allow simultaneous multiwavelength and time-resolved fluorescence detection, as well as spatial imaging of the sample fluorescence. The spectrometer employs monochromatized, tunable UV and visible excitation light from a synchrotron bending magnet and an imaging spectrograph equipped with a single-photon sensitive emission detector. The detector is comprised of microchannel plates in series, with a resistive anode for encoding the position of the photon-derived current. The centroid position of the photon-induced electron cascade is derived in a position analyzer from the four signals measured at the corners of the resistive anode. Spectral information is obtained by dispersing the fluorescence spectrum across one dimension of the detector photocathode. Timing information is obtained by monitoring the voltage divider circuit at the last MCP detector. The signal from the MCP is used as a ‘‘start’’ signal to perform a time-correlated single photon counting experiment. The analog signal representing the position, and hence wavelength, is digitized concomitantly with the start/stop time difference and stored in the two-dimensional histogramming memory of a multiparameter analyzer.
Results obtained using the pellet charge exchange diagnostic on TFTR
Authors: McChesney J. M. , Duong H. H. , Fisher R. K. , Khudoleev A. V. , Mansfield D. K. , Medley S. S. , Parks P. B. , Petrov M. P. , Roquemore A. L.
Published: July 2002

Experiments are underway on TFTR to measure the confined alpha particle distribution functions using small low-Z pellets injected into the plasma [Fisher et al. Fusion Technol. 13, 536 (1988)]. Upon entering the plasma, the pellet ablates, forming a plasma ablation cloud, elongated in the magnetic field direction, that travels alongside the pellet. A small fraction of the fusion produced 3.5 MeV alpha particles incident on the cloud are converted to helium neutrals. By measuring the resultant helium neutrals escaping from the plasma by means of a mass and energy resolving charge exchange analyzer, the energy distribution of the alpha particles incident on the cloud can be inferred. Preliminary experiments to observe neutrals from the 100 to 1000 keV 3He tail produced during ICRF minority heating experiments were successful. However, no significant alpha particle signals have been observed during D-T operation on TFTR. We attribute this lack of signal to stochastic toroidal field ripple loss in the outer regions of the plasma. We are studying ways to improve the pellet penetration so that the pellet penetrates into the central regions of the plasma where ripple induced losses are small and the alpha population is high.
A multichannel monolithic Ge detector system for fluorescence x-ray absorption spectroscopy
Authors: Bucher J. J. , Allen P. G. , Edelstein N. M. , Shuh D. K. , Madden N. W. , Cork C. , Luke P. , Pehl D. , Malone D.
Published: July 2002

The construction and performance characteristics of a monolithic quad-pixel Ge detector designed specifically for fluorescence x-ray absorption spectroscopy (XAS) at synchrotron radiation sources is described. The detector semiconductor element has an active surface area of 4.0 cm2 that is electrically separated into four 1.0 cm2 pixels, with little interfacial dead volume. The spatial response of the array demonstrates that cross-talk between adjacent pixels is less than 10% for 5.9-keV photons that fall within 0.5 mm of the pixel boundaries. The detector electronics system utilizes preamplifiers built at LBNL with commercial Tennelec Model TC 244 amplifiers. Employing an 55Fe test source (Mn Kα , 5.9 keV), energy resolution of better than 200 eV is achieved with a 4 msec peaking time. At 0.5 msec peaking time, pulse pileup results in a 75% throughput efficiency for an incoming count rate of 100 kHz. Initial XAS fluorescence measurements at the beamline 4 wiggler end stations at SSRL show that the detector system has several advantages over commercially available x-ray spectrometers for low-concentration counting applications.
An elliptical wiggler beamline for the ALS
Authors: Martynov V. V. , McKinney W. R. , Padmore H.A.
Published: July 2002

A beamline for circularly polarized radiation produced by an elliptical wiggler has been designed at the ALS covering the broad energy range from 50 eV to 2000 eV. The rigorous theory of grating diffraction efficiency has been used to maximize transmitted flux. The nature of the elliptical wiggler insertion device creates a challenging optical problem due to the large source size in the vertical and horizontal directions. The requirement of high resolving power combined with the broad tuning range and high heat loads complicate the design. These problems have been solved by using cooled optics and a variable-included angle monochromator of the ‘‘constant length’’ type with high demagnification onto its entrance slit.
Amplitude modulated heterodyne reflectometer for density profile and density fluctuation profile measurements at W7-AS
Authors: Hirsch M. , Hartfuss H.-J. , Geist T. , de la Luna E.
Published: July 2002

A broadband heterodyne reflectometer operating in the frequency range 75–110 GHz in extraordinary mode polarization is used at the W7-AS stellarator for both fast density profile determination and density fluctuation studies. The probing signal is amplitude modulated at a frequency 133 MHz using the envelope phase for profile evaluation and the carrier phase to determine the fluctuation information simultaneously. Separate Gaussian beam optics for final signal launch and detection permits a beam waist of about 2 cm at the reflecting layer in the plasma. Amplitude modulated detection is accomplished in the intermediate frequency part by synchronous detection after recovery of the carrier by narrow-band filtering. Voltage controlled solid state oscillators followed by active frequency multiplication allow to scan the full frequency band within less than 1 ms. For typical W7-AS operation the accessible density range is 1×1019 to 6×1019 m−3 for on axis magnetic field of 2.5 T and 4.5×1019 to 10×1019 m−3 for 1.25 T, respectively. The probed radial positions range between 0.2<r/a<1.1 depending on plasma conditions (a≊17 cm).
Flowing afterglow apparatus for the study of ion–molecule reactions at high temperatures
Authors: Hierl Peter M. , Friedman Jeffrey F. , Miller Thomas M. , Dotan I. , Menendez-Barreto Melani , Seeley John V. , Williamson John S. , Dale Fred , Mundis Paul L. , Morris Robert A. , Paulson John F. , Viggiano A. A.
Published: July 2002

We describe two versions of a high temperature flowing afterglow apparatus. With a stainless steel flow tube wrapped with heating tape we have obtained data over the range 300–1300 K. In a version with a ceramic flow tube in a commercial furnace we have obtained data over the range 300–1600 K. The ceramic version is designed to take data up to 1800 K, but we have encountered experimental problems at the upper temperature range. The design modifications to a standard flowing afterglow needed to make measurements at elevated temperatures are described in detail, as are problems associated with operating at elevated temperatures. Samples of data are given.