bluuebunny/crossref_metadata_2025 huggingface dataset:
Energy and spatial dependence of the electron detection efficiencies of single channel electron multipliers used in electron spectroscopy
Authors: Seah M. P. , Smith G. C.
Published: July 2002

Measurements for axially incident electrons are reported for the energy and spatial dependencies of the detection efficiency of a Philips X919BL single channel electron multiplier (CEM) in both the pulse counting and analog amplification modes. The behavior may be understood in terms of the general theory reported earlier.1 Essentially there are three regions to consider: the horn, the channel and the edge of the channel. In the pulse counting mode the difference in efficiencies between the channel and horn may reach a factor of two whereas in the analog mode the difference between the channel edge and the horn may reach a factor of five. The same behavior occurs when the CEM is used as the output stage of an electron spectrometer. The above variations may lead to (i) loss of efficiency in spectrometers, (ii) spectral distortion arising from the associated presence of stray magnetic fields, and (iii) irreproducibility of spectra from different regions of the sample surface, unless specific measures, such as larger horns, off-axis channels or lens defocusing, are used to eliminate them.
Equation-of-state measurements of low-density materials
Authors: Holmes N. C.
Published: July 2002

A precise optical method for determining the velocities of strong shock waves in low-density materials is described. Using an experiment on a polystyrene (CH) low-density microcellular material (LDMM), we also describe the analysis of the experimental data. Applications to the studies of other materials will be described.
Feedback system response in a scanning tunneling microscope
Authors: Jeon D. , Willis R. F.
Published: July 2002

The operation of a scanning tunneling microscope is based on a feedback using proportional and integral controller. By disturbing a z axis piezo artificially, the optimum feedback parameters for the critically damped response can be readily tuned thus dispensing with the need for exact analytical solutions.
Comment on ‘‘Digital parallel acquisition in frequency domain fluorometry’’ [Rev. Sci. Instrum. 6
, 2929 (1989)]
Authors: Alcala J. Ricardo
Published: July 2002

Feddersen et al. use pulsed cross-correlation techniques to obtain time resolved information of fluorescence decays employing frequency domain techniques. While the implementation is capable of acquiring phase and modulation data at several harmonic frequencies simultaneously it is considerably less sensitive than the traditional single-frequency technique. The nature of the pulsed cross-correlation technique used is reviewed.
Atomic force microscopy using ZnO whisker tip
Authors: Kado H. , Yokoyama K. , Tohda T.
Published: July 2002

We have developed an atomic force microscope (AFM) using a zinc oxide (ZnO) whisker crystal as a probing tip. The ZnO whisker crystal is tetrapodal in shape, with each leg having a length of 5–30 μm, a radius of curvature less than 10 nm, and a cone half angle of 1°–2°. Polyimide thin films rubbed with cloths as liquid-crystal aligning films were employed for AFM imaging. Due to the needle shape of the probing tip, the AFM was able to resolve the tiny grooves (3–5 nm deep, 60–80 nm apart) on these films more clearly than that using a conventional pyramidal tip. The new AFM will be available for precise evaluation of surfaces on which fine structures are microfabricated in nanometer scale.
Ion temperature measurements in tokamak plasmas by Rutherford scattering
Authors: van Blokland A. A. E. , Barbian E. P. , Donné A. J. H. , van der Grift A. F. , Grimbergen T. W. M. , Oyevaar Th. , Schüller F. C. , Tammen H. F. , van der Ven H. W. , Vijverberg T. F. , de Winter F. D. A. , Bertschinger G. , Cosler A. , Korten M.
Published: July 2002

A Rutherford scattering diagnostic has been applied at the TEXTOR tokamak to obtain spatially and temporally resolved information on the temperature of the bulk ions in the plasma. In the experimental setup, a helium atomic beam (30-keV, 12-mA equivalent current) passes vertically through the plasma core. A small part of the injected atoms is scattered elastically by the thermally moving plasma ions. The ion temperature in the scattering volume can be determined from the broadening of the energy spectrum of the scattered particles. Energy analysis of the scattered atoms is performed by a mass-selective time-of-flight analyzer detecting the particles at an observation angle which is selectable between 3° and 8°. Coincidence techniques have been successfully applied in this detector for rejection of background events triggered by detections of neutrons and gamma radiation. Ion temperature profiles were measured on a shot-to-shot basis by shifting the cross section of the diagnostic beam and the observational volume of the analyzer through the plasma. The ion temperatures measured in ohmic deuterium plasmas were found to be in reasonable agreement with those obtained from passive neutral particle analysis. Up to now, ion temperatures have been measured throughout the complete discharge with an accuracy of 8% and a time and space resolution of 100 ms and 0.10 m at a scattering angle of 7°. Deuteron density profiles could be deduced from the scattering yield measured at different radial positions in the plasma. The ratio of the isotopes, hydrogen and deuterium, was determined from their separate contributions to the spectrum of helium particles scattered on hydrogen and deuterium. Although theoretical predictions showed that the majority of the probing helium atoms loses one of its electrons during the elastic scattering process on multiply charged carbon and oxygen ions, contributions from impurities to the observed experimental spectrum are shown to appear dominant for impure plasmas.
A high rate preamplifier for use with a gas proportional counter
Authors: Jones A. O. , Smith A. D.
Published: July 2002

In the development of detectors for use with synchrotron radiation, a serious limit to the maximum counting rate is frequently determined by the signal processing speed of the general purpose commercial electronic units that are often used. Therefore, in developing a high speed gas proportional counter for soft x-ray spectroscopy measurements, a major requirement has been for a high rate, low noise preamplifier. A crucial factor in meeting the required processing speed is the ability to separate out the fast electron pulse from the much slower, induced ion afterpulse and to reject the latter. In addition, all gas proportional counters suffer from occasional high voltage breakdown and so the circuit design must provide the sensitive front end of the preamplifier with sufficient transient protection. We present a design for a preamplifier circuit which offers a 30 MHz bandwidth and better than 2500 electrons rms noise. It features pulse shaping which permits the complete rejection of the ion afterpulse and an input protection circuit which has enabled the preamplifier to survive detector breakdown. The preamplifier has a measured gain of 0.6 μV per electron. The fast rise time of the preamplifier has allowed us to investigate the speed of the detector, a primary limitation of which is due to the electron diffusion rate within the counter. We describe an experiment conducted using this preamplifier to reduce the electron drift speed to <100 ns.
Improvements and recent performance of a double-crystal monochromator for a soft x-ray undulator at the Photon Factory
Authors: Kitajima Y. , Takata Y. , Toyoshima A. , Maezawa H.
Published: July 2002

A cooling system for the first crystal of a double-crystal monochromator for a 60-period soft x-ray undulator at the Photon Factory is newly designed and installed. In order to keep smooth movements of the original mechanism in a high-vacuum chamber, heat pipes and a liquid-metal bath are utilized. A fear for melting of an InSb crystal and the instability caused by warming of mechanisms have vanished and significantly improved energy resolution of 5000–8000 is achieved by Si crystals for high photon flux of about 1011 photons/s in a beam size of 3×3 mm2 at a sample position with the cooling system.
The use of polycarbonate in proportional counters
Authors: Trow Matthew , Smith Alan
Published: July 2002

Proportional counters are relatively sensitive to contamination through outgassing and the range of electrical insulators suitable for use in their manufacture is quite limited. Although small amounts of plastics such as polychlorotrifluoroethylene have been used as feedthroughs, ceramics are most commonly used when sealed counters with long lives are required. Ceramics have poor and widely scattered mechanical properties and the use of a more robust material is often highly desirable. Of particular interest is the use of polymers and this work examines polycarbonate in particular. To investigate its suitability in terms of outgassing a simple cylindrical, single anode proportional counter containing a large sample of polycarbonate was baked at ∼100 °C and filled with a CO2/Ar/Xe mixture (5:47.5:47.5 by pressure, respectively). Subsequent measurements of the counter indicated an increase in gain, which, after a second similar filling, was identified to be associated with a preferential loss of CO2 to the polycarbonate. The consequences of this result and the circumstances under which polycarbonate could be used on a large scale in the construction of proportional counters are discussed.
Long beam-lifetime operation at the SORTEC SR ring
Authors: Awaji N. , Kodaira M. , Kishimoto T. , Usami H. , Ohno M. , Tsuchidate H. , Iida T. , Tomimasu T.
Published: July 2002

With successful conditioning, the beam lifetime of the SORTEC SR ring extended over 50 h at our nominal beam current of 200 mA. The conditioning and the results are discussed from the point of (i) optimization of operating point, (ii) high vacuum, and (iii) effective removal of the produced ion.
Beryllium window and acoustic delay line design for x-ray lithography beam lines at the University of Wisconsin Center for X-ray Lithography
Authors: Brodsky E. L. , Hamilton W. , Wells G. , Cerrina F. , Corradini M.
Published: July 2002

X-ray lithography systems require sample chambers that can perform exposures in helium gas at atmospheric pressure. The interface between the experimental chamber and the beamline is critical for x-ray lithography and the storage ring. It must allow a high x-ray flux throughput while providing a vacuum barrier so that helium gas does not leak into the beam line and the storage ring. The beam line must also be designed to have protection in the case that a window does fail in order to minimize adverse effects to the ring and other systems. The details of the design for the vacuum system used on beam lines for the Center for X-ray Lithography at the University of Wisconsin Synchrotron Radiation Center 1-GeV electron storage ring are reported. Curved beryllium windows with a 1×5-cm2 aperture and 13 μm thick that have a leak rate less than 10−10 Torr ℓ/s have been successfully used at the experimental chamber beam-line interface. This thin flat beryllium foil is mounted in a curved housing with a wire seal to minimize helium leakage. The window assembly is designed and has been tested to withstand substantial overpressure before failure. If the beryllium window does fail, the beamline has an acoustic delay line that is designed to delay the incoming shock wave of helium gas so that a fast valve at the end of the beam line will close and minimize leakage of helium into the storage ring. The acoustic delay line is designed with baffles to slow the shock front and a secondary thin window to protect against molecular diffusion into the storage ring. The acoustic delay line has been tested to determine the effect of baffle design on delay of the shock wave. A theoretical model that provides a good description of the acoustic delay has also been developed.
X-ray lithography at the VEPP-3 storage ring
Authors: Artamonova L. D. , Gentselev A. N. , Deis G. A. , Krasnoperova A. A. , Mikhalyov E. V. , Prokopenko V. S. , Kulipanov G. N. , Mezentseva L. A. , Pindyurin V. F.
Published: July 2002

The paper deals with an x-ray lithography station at the VEPP-3 storage ring of the Institute of Nuclear Physics (Novosibirsk) and some recent results are reported. The utilization of rather high quantum energies is shown not to deteriorate the quality of x-ray replication. The presented work is an extension of the studies that were performed at VEPP-2M [E. S. Gluskin, A. A. Krasnopyorova, G. N. Kulipanov, V. P. Naz’mov, V. F. Pindyurin, A. N. Skrinsky, and V. V. Chesnokov, Nucl. Instrum. Methods 208, 393 (1983)].
Design of a compact storage ring for industrial research
Authors: Nakanishi T. , Okuda S. , Ikegami K. , Kodera I. , Matsuda T. , Nakagawa T. , Nakamura S. , Nakata S. , Tanaka H. , Tsukishima C. , Yamamoto S. , Yamada T. , Iwamoto M.
Published: July 2002

An 800-MeV compact storage ring is under construction for development of the technology of a compact ring and for research of x-ray lithography and material analysis. Synchrotron radiation with a critical wavelength of 0.65 nm is emitted from a pair of superconducting bending magnets. A straight section of the ring has only one quadrupole magnet to make the smaller ring. An injection efficiency with a single kicker magnet is optimized by computer simulation. The kicker field strength and an injection angle are determined. A beam tracking with a numerical integration method shows this ring has a sufficiently wide dynamic aperture of ‖x‖≂30 mm and ‖y‖≂50 mm at the center of the bending magnet, which has βxmin and βymax. A 1-GeV synchrotron is used as an injector, which has accelerated a beam up to 1 GeV.
The project of using a compact SR source at the Siberian microelectronic center
Authors: Sinyukov M. P. , Makarov O. A.
Published: July 2002

The project for the x-ray lithography facility using a compact storage ring SIBERIA-AS is considered. The SR source with 600-MeV electron energy and an orbit circumference of about 3 m has an ironless superconducting azimuthally symmetrical magnet. It allows us to install up to 15 SR beam lines. The scope of the project is further development of x-ray lithography, and new technologies in this area for development of scientific research: vacuum ultraviolet spectroscopy, photoinduced etching, photoelectron spectroscopy, and radiometry.
A VME-based photodiode array system for energy dispersive extended x-ray absorption fine structure
Authors: Derbyshire G. E. , Bogg D. , Dent A. J. , Farrow R. C. , Greaves G. N. , Helsby W. I. , Morrell C. , Ramsdale C. A. , Wells M. P.
Published: July 2002

A VME-based control and data acquisition system has been constructed for time resolved energy dispersive extended x-ray absorption fine structure. The system is discussed from initial concept to installation on the Daresbury SRS. The system performance is presented in detail together with examples of test data. Current operational characteristics are a 2-ms readout time for one scan of 512 pixels, at 16 bits resolution. Accumulation of 65 000 scans in a single frame and a total of 64 frames stored in memory. The system has been designed to run at rates of 0.2 ms per scan and a burst mode allowing 128 single scan frames to be accumulated.
Micropositioning in MAXIMUM: Photoemission microscopy with normal incident optics (abstract)
Authors: Ng W. , Wallace J. P. , Ray-Chandhuri A K. , Capasso C. , Cerrina F.
Published: July 2002

We discuss the two critical micropositioning systems implemented on the latest version of MAXIMUM at the Wisconsin Synchrotron Radiation Center. MAXIMUM is an undulator-based x-ray photoelectron microscope. The microscope utilizes a set of multilayer-coated normal incident Schwarzchild objective to produce a submicron focus spot. The sample is rastered across the spot and photoelectrons emitted from the sample are collected to form an image. The Schwarschild objective is mounted such that it is vibrationally isolated from the vacuum chamber. The two mirrors are mounted on a three axis flexural pivot stage actuated by inchworm motors. This system allows in situ fine alignment of the objective and it is totally decoupled from any vacuum forces. The inchworm motors will also act as clamps when the objective is aligned. The sample scanning is done by a flexural hinge stage actuated by an in-house design PZT stack. The stage has a range of 100 μm×100 μm×5 μm with a resolution of 100 Å. The system is totally UHV compatible. A laser interferometer is used for sample position feedback. This work was supported by NSF, DOE.
Sensitive x-ray imaging system
Authors: Panin A. M.
Published: July 2002

A sensitive imaging system for weak x-ray flux registration in a 1–25 keV band is presented. The system is based on a visible light intensifier and it is successfully used for x-ray spectroscopy of plasma sources. Performance of the system is described.
A microstrip detector with delay line readout
Authors: Barbosa A. F. , Riekel C. , Wattecamps P.
Published: July 2002

Principal limitations of position sensitive gasfilled detectors for x-ray synchrotron radiation applications are the counting rate and the positional resolution. Improvements in both areas are expected with microstrip technology. First results of a linear position sensitive microstrip detector with delay line readout are shown, and the possibility to achieve two-dimensional localization is evaluated.
A SPAN MCP detector for the SOHO Coronal Diagnostic Spectrometer
Authors: Breeveld Alice A. , Edgar Michael L. , Smith Alan , Lapington J. S. , Thomas Philip D.
Published: July 2002

Solar and Heliospheric Observatory (SOHO) is a European Space Agency project scheduled for launch in 1995. Part of its payload will be a coronal diagnostic spectrometer that includes a grazing incidence spectrometer (GIS) with four detectors set at nonoverlapping wavelength ranges between 15.5 and 78.7 nm. The UV detectors are being developed at MSSL and consist of microchannel plate (MCP) stacks with one-dimensional SPAN anode readout. The dimensions of the sensitive area of each detector is 50×16 mm and it is required that 47-μm FWHM positional resolution is obtained in the 50 mm direction together with a throughput of 100 000 counts/s (random). The design of the detector system and readout electronics is described. A Monte Carlo PC based simulator has been developed to support the research program and permit an early optimization of various parameters.
Conceptual design of an adaptive x-ray mirror prototype for the ESRF
Authors: Susini J. , Marot G. , Zhang L. , Ravelet R. , Jagourel P.
Published: July 2002

Adaptive optics were proposed as a solution to heat load problems generated by powerful x-ray beams of next generation synchrotron radiation sources. A first adaptive x-ray mirror prototype is presently under design at the ESRF. This device, which is optimized for a wiggler beamline, is described here. It is composed of three main subsystems: the mirror body, the correction feedback loop including the actuators for the mechanical correction, and the optical setup for inspecting the mirror shape.
Band bending modified tunneling at metal/conjugated polymer interfaces
Authors: Ettedgui E. , Razafitrimo H. , Gao Y. , Hsieh B. R.
Published: July 2002

Metal/polymer interfaces play an important role in polymeric light-emitting diodes. Recent transport measurement studies by Parker promote a rigid band model with triangular barrier tunneling at the metal/polymer interface. This finding, however, stands in contradiction to the band bending and Schottky barrier formation observed using surface analytical techniques. We found that this apparent contradiction can be nicely reconciled if a modification of the tunneling model by band bending is included in the interpretation of the transport data. Band bending modified tunneling gives a clear physical picture of the tunneling process across the metal/polymer interface and is important for low field tunneling processes.
Design of soft x-ray plane-grating monochromator for CAMD
Authors: Morikawa E. , Scott J. D. , Poliakoff E. D. , Stockbauer R. L. , Saile V.
Published: July 2002

A plane-grating monochromator (PGM), the CAMD-PGM, designed for bending magnet radiation is described. In contrast with many other similar PGMs, the CAMD-PGM is equipped with an entrance slit. The wavelength range of 6–1500 Å is covered with two gratings (1220 and 360 gr/mm). The expected performance is a resolving power, λ/Δλ, of ∼2000 with the photon flux of ∼ 1010 photons/s at the photon wavelength of 10.0 Å. The beam spot size at the sample position is approximately 1×1 mm2. The monochromator is being constructed and will be installed in the summer of 1992.
New gas-phase experiment at the normal incidence beam line at MAX
Authors: Berg L.-E. , Erman P. , Källne E. , Sorensen S. L. , Sundström G.
Published: July 2002

We have recently started a new program to study ion fragments from photoionization and photodissociation processes, using synchrotron radiation at the normal incidence beam line at the electron storage ring MAX in Lund, Sweden. The experimental chamber is connected to the beam line via a simple arrangement consisting of a glass capillary with ∼25% transmission in the wavelength region 300–700 Å, leading through a differential pumping stage. This arrangement allows us to operate the target gas chamber at pressures of 1–3⋅10−5 Torr. The design and performance of this new experiment is presented as well as examples of the first results from experiments on diatomic molecules and noble gases. In particular, it has been possible to record ion spectra with sufficient resolution and intensity to permit a detailed line profile analysis of autoionization resonances.
A bend magnet facility for production and application of circularly polarized soft x rays at the Advanced Light Source (abstract)
Authors: Bustamante C. , Chen C. T. , Sette F. , Howells M. R. , Hunt A. J. , Kim K. J. , Kincaid B. M. , Maestre M. F. , Nygren D. R. , Wong M. , Snyder P. A. , Stern E. A.
Published: July 2002

The Advanced Light Source (ALS) is a synchrotron radiation facility based on a low-emittance, 1.5-GeV electron storage ring presently under construction at the Lawrence Berkeley Laboratory, U.S.A. Plans are under way to develop a polarized photon facility at the ALS, exploiting the natural polarization properties of the bend magnet synchrotron radiation. The radiation emitted in the plane of the storage ring is linearly polarized, while above and below the plane it is elliptically polarized. We will utilize these properties to obtain circularly polarized soft x rays. A participating research team (PRT A018) has been formed and is proceeding with the design of a high-resolution beamline in the soft x-ray energy region 100–1500 eV. Intense beams of monochromatic, tunable, pulsed, circularly polarized photons will become available. We will discuss the physical characteristics of this polarized soft x-ray source. New investigations in biology, materials science, physics, and chemistry will become accessible. Initial experiments using circularly polarized photons in the soft x-ray region are planned in the areas of differential scattering and absorption from chiral molecules and probing the electronic and magnetic properties of magnetic systems. This work was supported by the U.S. Department of Energy (DE-AC03-76SF00098).
A high-resolution spherical grating monochromator with a moveable entrance slit
Authors: Zanini F. , Di Fonzo S. , Melpignano P. , Jark W.
Published: July 2002

A possible design for a spherical grating monochromator is based on the translation of the entrance slit in order to minimize the system aberrations during the wavelength scan. This configuration has been studied both analytically and by means of extended ray-tracing calculations and the design and performance of such a monochromator are discussed. In order to verify advantages and limitations of this solution a systematic comparison with a spherical grating monochromator with a moveable exit slit has been performed.
Trapping and probing of multiply charged Xe ions produced by synchrotron radiation
Authors: Sakurai M. , Kimura M. , Sekioka T. , Terasawa M. , Yamaoka H. , Niizeki T. , Awaya Y. , Hirayama T. , Yoda J. , Ogata A. , Ohtani S.
Published: July 2002

Multiply charged ions of Xe gases were produced through inner-shell photoionization by using synchrotron radiation, and were stored in an rf ion trap. The experimental apparatus for trapping and probing multiply charged ions is described, and results for the measurements on the mass spectra of trapped ions and lifetime of each charge state are presented.
Raytracing, chopper, and guideline for double-headed Dragon monochromators (invited)
Authors: Chen C. T.
Published: July 2002

The raytracing of the double-headed Dragon, a recently proposed monochromator for producing two simultaneous left and right circularly polarized soft x-ray beams, is presented. The energy resolution and wavelength of these two beams are confirmed to be identical, and the high performance of the original Dragon is found to be preserved in the double-headed configuration. A compact ultra-high vacuum compatible chopper for rapid alternation between left and right helicities is presented, and a guideline for collecting circularly polarized light from bending magnet sources is given.
Development of multipole wiggler as an intense circularly polarized x-ray source (invited)
Authors: Kitamura Hideo , Yamamoto Shigeru
Published: July 2002

There have been various ideas for generation of circularly polarized synchrotron radiation. Among them, this paper is concentrated on the novel multipole wiggler, elliptical multipole wiggler (EMPW), developed as an intense circularly polarized x-ray source at the National Laboratory for High Energy Physics. The EMPW has two jaws of magnet arrays. One jaw is coupled vertically and located along an electron beam axis to the other coupled horizontally with a phase difference of 1/4 magnetic period. In this article, spectral and technical performances of EMPW’s are described as compared with those of asymmetric wiggler.
An apparatus for studying sputter deposition with x rays
Authors: Payne A. P. , Clemens B. M. , Brennan S.
Published: July 2002

While electron-based structural probes have been extensively applied to low-pressure film growth techniques such as evaporation, similar studies on sputter deposition have been hindered by the relatively high gas pressure (1–10 mT) inherent to the technique. Because x rays scatter more weakly than electrons the absorption in the ambient is not significant and diffraction from the growing film can be observed if a sufficiently bright source of x rays is used. We have developed a chamber which combines features of an ultrahigh-vacuum sputter-deposition system with the goniometric adjustments and the x-ray windows of a scattering chamber. A description of its design and recent results are presented.
An in situ x-ray diffraction method for the structure of amorphous thin films using shallow angles of incidence
Authors: Burke T. M. , Huxley D. W. , Newport R. J. , Cernik R.
Published: July 2002

A technique for the structural characterization of thin amorphous films employing synchrotron radiation parallel beam x-ray optics at grazing angles of incidence is detailed. At incident angles near to the critical angle for total external reflection, sampling of specimens may be achieved via the evanescent mode. The parallel beam geometry allows the use of a technique in which a 2θ detector, incorporating a parallel plate collimator, scans diffraction data for a given incident angle. For a specified wavelength, the incident angle chosen will determine the penetration of the radiation into the sample (∼10–1000 Å). The data must be corrected for significant peak shifting resulting from x-ray refraction, as well as for the effects associated with conventional θ:2θ scans. Preliminary data resulting from the first application of this technique to amorphous hydrogenated silicon:carbon thin films, deposited onto crystalline silicon substrates, will be presented and discussed. Conventional θ:2θ powder diffraction data will also be presented as a comparative standard.
Monochromator on a synchrotron undulator source for liquid surface studies
Authors: Als-Nielsen J. , Freund A. K.
Published: July 2002

For liquid surface studies a monochromatic beam of relative bandwidth between 0.1% and 1% at a variable angle in the vertical plane between 0° and 10° is needed. The beam should be like a sheet some tens of μm thick and some mm wide, and as intense as possible. We discuss a monochromator made of a beryllium mosaic crystal using the (002) reflection in Laue geometry placed in undulator beams of DORIS III at the Hamburger Synchrotronstrahlungslabor and of the European Synchrotron Radiation Facility. An analysis of the diffraction properties in terms of mosaic spread, heat load, optical quality of the monochromatic beam, and, in particular, the expected flux, gives an optimum value of about 0.2 mrad for the mosaic spread. We show by experiments that presently available crystals a few hundred μm thick have the required quality and are capable of reflecting up to 45% of the useful x rays, in full agreement with diffraction theory including secondary extinction. Heat load experiments reported elsewhere in this conference prove that Be crystals can withstand high beam power density and that the thermal deformation is small compared to the mosaic spread. The results of the flux calculations are most encouraging: a gain of order 103 to 104 can be expected as compared to existing liquid surface spectrometers.
A new white beam single crystal and powder diffraction facility at the SRS
Authors: Clark Simon Martin
Published: July 2002

A new white beam single-crystal Laue diffraction (LD) and energy-dispersive powder diffraction (EDPD) facility has been constructed on station 9.7 of the SRS. This station receives radiation from a 5-T superconducting wiggler magnet with useful photon flux from 5 to 60 keV and a peak flux on the sample of 7×1011 photons/s/mm2 in a 0.1% bandwidth at 10 keV. The novel design of this facility allows rapid changeover between the two experiments without compromising either. Components have been built in a modular manner for ease of optimization for a particular set of data capture conditions.
A two-circle powder diffractometer for synchrotron radiation on Station 2.3 at the SRS
Authors: Collins S. P. , Cernik R. J. , Pattison P. , Bell A. M. T. , Fitch A. N.
Published: July 2002

The two-circle powder diffractometer on Station 8.3 at the SRS has recently been relocated to station 2.3, some half the distance from a dipole radiation source with the same nominal 1.2T field. The purpose of this paper is to detail the changes and modifications to the diffractometer operation.
Design of mirror and monochromator crystals for a high-resolution multiwavelength anomalous diffraction beam line on a bending magnet at the ESRF
Authors: Roth Michel , Ferrer Jean-Luc , Simon Jean-Paul , Geissler Erik
Published: July 2002

High intensity for diffraction experiments with high-energy resolution on an intense x-ray beam, like the bending magnet beam lines at the ESRF, requires a strict control of the curvature of the optical elements placed in the beam for geometrical focusing and for wavelength monochromatization. Unwanted curvatures can come from nonuniform and variable heating of the optical elements produced by the absorption of x rays. To design the CRG/D2AM beam line described in the accompanying paper, some new techniques were developed to control these effects based on geometrical, i.e., topological, considerations. (1) Cooling of the entrance mirror: longitudinal curvature can be strongly reduced by cooling the mirror from the sides (and not from the rear) and only near the reflecting surface (i.e., not over the whole lateral surface). The cooling can be achieved for instance with an isothermal liquid Ga eutectic bath. (2) Cooling of the first single-crystal Si monochromator: because of the size of the crystal, only cooling from the rear is conceivable in this case. It can be shown by calculation that the curvature due to the front-to-rear gradient can be exactly compensated by the thermal expansion of a metallic layer at the rear of the crystal, having a larger expansion coefficient than Si.
The first x-ray diffraction station at Beijing Synchrotron Radiation Laboratory, BEPC
Authors: Wang D. W. , Liu J. F. , Zhao Y. C. , Yang Y. L. , Liu D. S. , Xian D. C.
Published: July 2002

The first x-ray diffraction experimental station at Beijing Synchrotron Radiation Laboratory has been available for synchrotron radiation users in research. The station is located on the back-end of 4B9A, a beamline from a bending magnet. When the storage ring of BEPC operates in a dedicated mode (2.2 GeV), 4B9A provides a focused monochromatic x ray in between 4 and 12 keV. A four-circle diffractometer with a crystal analyzer is installed. Experimental processes such as apparatus alignment, monitoring of incident radiation, acquisition of diffracted intensities, and running of the monochromator, are controlled with a computer through CAMAC modules. In this article, instrumentation and performances of the station are outlined.
Thermal conductivity measurements using a short transient hot-strip method
Authors: Log Torgrim , Metallinou Monika M.
Published: July 2002

The transient hot-strip (THS) method has been modified to measure thermal conductivity of small test specimens. The conventional metal strip used simultaneously as the heater and the temperature sensor was substituted with a 50-Ω commercial temperature sensor (grid 5.85 mm×6.35 mm). The short transient hot-strip (STHS) method was tested on Pyrex 7740, stainless steel (NIST 1462 standard reference material), and aluminum to cover more than two orders of magnitude in thermal conductivity. The STHS method agreed with conventional measurement techniques within 3% in the thermal conductivity range 1–200 W m−1 K−1.
A technique for the study of ultrafast gas–solid reactions for residence times less than 100 ms
Authors: Raghunathan K. , Dastidar A. Ghosh , Fan L.-S.
Published: July 2002

An experimental technique for the study of short contact time gas–solid reactions is developed. The major components are a pulse powder feeder, an injection probe, and a collection probe. The feeder can inject small amounts of fine particles into the reactor as narrow pulses. The two probes also serve as optical solids monitors; an optical system consisting of fiber optic cables and miniature prisms is housed within each probe. With the combination of the two probes, residence time of the particles is determined directly and on-line using photometric principles. With a cold model entrained flow reactor, it is demonstrated that solids with residence times as low as 4 ms can be successfully sampled from the reactor, with the residence time calculated to within 5% error. Methods for rapid heating of the injected powder and rapid quenching of the reaction of the sampled solids are discussed.
Spectroscopic diagnosis of long-scale-length exploding-foil plasma in the presence of an intense radiation field
Authors: Shepard T. D. , Keane C. J. , Suter L. J. , Abdallah J.
Published: July 2002

An effective technique for measuring the local electron temperature and density of a laser-produced plasma involves analysis of the emission and/or absorption spectrum from an impurity dopant. However, when an intense high-energy radiation field is present the ionization balance, level population, and resulting spectrum produced by the impurity may be significantly perturbed. We are currently using several computer models to study the effects of such a radiation field for experimental conditions that could be obtained using the Nova laser facility, and are concentrating on the behavior of line intensity ratios that are typically used for density and temperature diagnosis. The goal of this work is to determine the feasibility of spectroscopic diagnosis when an intense high-energy radiation field is present.
High sensitivity bolometers development
Authors: Iborra E. , Sanz-Hervás A. , Rodríguez T. , Ochando M. A. , Navarro A. P.
Published: July 2002

A main drawback of bolometers is their low responsivity resulting in very poor time and/or spatial resolutions. Improvement of detectors responsivity would serve to solve this problem and bolometers could be useful in studies of fast-developing phenomena in plasmas. We are searching for the development of new detectors based on a standard multilayer design and having as sensitive material amorphous germanium. The chosen detector structure is rigid substrate (low conductivity glass)/interdigitated electrodes (Ti-Au defined by photo- lithographic techniques)/resistor layer (amorphous oxygen-doped germanium evaporated by electron beam)/insulation layer (photo-CVD deposited Si3N4)/absorber foil (evaporated + electrolytic gold layers). The detector performance has been compared with pyroelectric detectors and germanium bolometers in the TJ-I tokamak under the same experimental conditions. Also, the design and construction of monolithic miniaturized detector arrays, based on this concept, are in progress.
Nuclear radiation effects in fused SiO2 lightguides
Authors: Ramsey A. T. , Hill K. W.
Published: July 2002

High purity fused silica fibers are widely used in controlled fusion research to conduct visible light (down to about 4000 Å) away from the hostile environment of the tokamak. These fibers are not totally radiation immune, however. We see both luminescence and loss of transmission induced by radiation at the present levels of D–D fusion yields on Tokamak Fusion Test Reactor (TFTR). The luminescence shows spectral structure and is brightest near the widely used Hα–Dα wavelength of 6562 Å. The induced opacity has both transient (time scale of seconds) and permanent components. Extrapolation to D–T plasmas, which are planned for TFTR, yields levels of both luminescence and opacity which range from annoying to fatal if current practices are continued.
PROPX an x-ray manipulation program
Authors: Kyrala G. A.
Published: July 2002

An interactive microcomputer program that performs some manipulations on an input x-ray spectrum is introduced and described. The program is used to calculate the effect of absorption by filters, transmission through filters, responsivity of photocathodes, responsivity of absorptive detectors, folding of responses, plotting of cross sections, and calculation, as a function of electron temperature, of the response due to a bremsstrahlung spectrum. Fluorescence from the targets is not included. Two different x-ray libraries are offered, one covers the x-ray range 30–10 000 eV with 288 energy points, and the other covers the energy range 10 eV–1 MeV with 250 energy points per decade.
Diagnostics for investigation of magnetic reconnection in sawtooth crash on TFTR
Authors: Yamada M. , Nagayama Y. , Davis W. , Fredrickson E. , Janos A. , Levinton F.
Published: July 2002

Magnetic reconnection phenomena are documented by a set of noninvasive fast diagnostics during the crash phase of sawtooth oscillations. The electron cyclotron emission diagnostic system provides the highest resolution for measuring time evolution of electron temperature profile during a typical Tokamak Fusion Test Reactor fast sawtooth crash. The x-ray tomography also contains fast time scale information of the electron temperature profile and additionally the impurity concentration. Just before the crash, a shrinking circular hot peak and growing crescent-shaped flat island appear in the inside of the inversion radius on a bird’s-eye view of the electron temperature profile. The electron temperature gradient inside the inversion radius diminishes to nearly zero after the crash. Concomitantly, q(r) profile [q(r)=local safety factor] is measured by the motional stark effect (MSE) diagnostics to verify a magnetic field line reconnection during the sawtooth oscillation. Initial MSE data indicate that central q values increases by 5%–10% during the sawtooth crash phase even when the pressure gradient diminishes inside the q=1 region.
The UCLA frequency tunable correlation reflectometer system on DIII-D
Authors: Rhodes T. L. , Peebles W. A. , Doyle E. J.
Published: July 2002

A broadband tunable (∼50–75 GHz) correlation reflectometer system is installed and operational on the DIII-D tokamak. The same launch and receive horns are utilized for the two probing frequencies ensuring that they sample the same path within the plasma. Very wide band IF electronics allow the separation frequency to be continuously tuned over the range 100 MHz→10 GHz corresponding to a maximum spatial separation of ∼7 cm. Sweeping the separation frequency during the plasma shot produces multiple spatial points (≳10) on a single discharge reducing shot to shot reproducibility problems and increasing the spatial resolution. A description of the microwave system, laboratory tests, and representative data from a tokamak discharge are presented. Difficulties with the method and some possible resolutions are discussed.
Development of technology and techniques for reflectometry
Authors: Domier C. W. , Chung E. , Doyle E. J. , Liu H.-X. L. , Lapidus A. , Luhmann N. C. , Peebles W. A. , Qin X.-H. , Rhodes T. L. , Sjogren L.
Published: July 2002

Development efforts are directed at advanced reflectometry systems for next generation tokamaks such as ITER. Laboratory tests have been successfully completed for a pulsed radar reflectometer (τ≂200 ps) to be tested on DIII-D. In addition, there exists a need for sources and components beyond those commercially available. Monolithic quasi-optical spatial power combined arrays of solid state devices will provide continuous, watt level swept source coverage up to 200 GHz as well as electronically controlled beam steering, focusing, and modulation. Studies are also underway to address the feasibility of instantaneous profile coverage using monolithic impulse generators (τ≂1–3 ps) comprised of spatially combined nonlinear transmission lines, employing novel quantum barrier varactors.
A comparison of Langmuir probe techniques for measuring temperature fluctuations
Authors: Lin H. , Li G. X. , Bengtson Roger D. , Ritz Ch. P. , Tsui H. Y. W.
Published: July 2002

Two techniques are applied and the results compared in the edge plasma of TEXT-U to estimate temperature fluctuations. The first technique fits the measured current fluctuations from a double probe as a function of probe bias with several fitting functions to provide density, and temperature fluctuations but with no spectral information. The second method uses a triple-probe technique to measure density, temperature, and floating potential as a function of time. The two techniques are in agreement to within estimated error limits and find T̃/T≊0.4–0.5 ñ/n both in the scrape-off layer and in the main body of the plasma.
The Frascati Tokamak Upgrade Thomson scattering system: The optical and spectral analysis equipments
Authors: Pizzolati P. , Briccola M. , Garbi M. , Golinelli E. , Mezzetti S. , Giorgetti G. , Molesini G. , Bartiromo R. , Brusadin A. , Giovannozzi E. , Orsitto F. , Santi D. , Ferrario A. , Bassan M.
Published: July 2002

An overall view of the Frascati Tokamak Upgrade (F.T.U.) Thomson scattering system is illustrated and particular attention is paid to the optical and spectral analysis equipments. The system includes the laser source, the collection optics, a set of filter polychromators, all the electronic equipments necessary to collect the data relevant to the scattered light and to send them to the F.T.U. data acquisition system. The features of this system can be summarized as follows: rejection to laser wavelength: ≥107, laser energy: ≥5 J, overall optical efficiency: ≥40%, and capability of multiple time and space measurements on the Thomson scattered light.
Monochromator harmonic content measurements and calculations at energies above 20 keV
Authors: Chapman D. , Moulin H. , Garrett R. F.
Published: July 2002

Measurements of the harmonic content from single- and double-crystal silicon monochromators have been made in the 20- to 100-keV range at the X17 superconducting wiggler beam line at the NSLS. These measurements are compared with calculations which estimate the monochromatic beam harmonic content and the detection system efficiency with good agreement. At high photon energies (≳20 keV), the scattering of x rays from an amorphous scatterer is dominated by the inelastic Compton process. At large scattering angles this will completely overwhelm the more forward directed elastic scattering. The Compton x-ray energy shift is large enough to make the distinction between elastic and Compton scattering unambiguous when a spectrum is acquired with a solid-state detector. This shift, which is energy dependent, allows the measurement of the relative harmonic intensity in a way that is not affected by pulse pileup in the detector and electronics. The present measurements were done to assess the level of harmonic contamination from two monochromator systems both used on the X17 beam line: the single-crystal-type monochromator for the digital subtraction coronary angiography project; and the double-crystal monochromator being developed for the multiple energy computed tomography (MECT) project and the Materials Science program.
Investigation of radiation damage to biological specimens at water window wavelengths
Authors: Foster G. F. , Buckley C. J. , Bennett P. M. , Burge R. E.
Published: July 2002

This article reports the continuation of a series of experiments investigating the effects of soft x-ray radiation damage on the contractile elements of mammalian striated muscle (myofibrils), using their ability to contract as a functional assay. The myofibrils were exposed to 385 eV x rays. This energy is within the ‘‘water window’’ between the oxygen and carbon K edges, where the x-ray absorption coefficient of biological materials, such as protein, is about an order of magnitude greater than that for water. An exposure of 8×105 photons μm−1 was found to prevent contraction in the majority of myofibrils. Preliminary results indicate that it is possible to increase this exposure level by approximately 25% by adding the radioprotective dimethyl sulphoxide (DMSO), an OH radical scavenger to the myofibril buffer during irradiation. This suggests that OH radicals are important in the inactivation of myofibrils through irradiation.
Evaluation of a commercial, computer-operated heat flow meter apparatus
Authors: Graves Ronald S. , McElroy David L. , Kollie Thomas G.
Published: July 2002

A Holometrix, Inc., R-Matic model R-41 Heat Flow Meter Apparatus (HFMA) is evaluated by measurements on homogeneous materials and anisotropic composite materials. The former class of materials includes: foams, calcium silicate boards, fiberglass batts, and loose-fill fiberglass. Materials in the latter class are polystyrene with gas-filled panels and batts with powder-filled evacuated panels. Thermal models of the anisotropic composite materials allow design of composite test specimens and help in the interpretation of test results by computation of apparent thermal conductivities (k). The HFMA includes a dedicated computer for test control, data acquisition, and data analysis. Thus, the computer helps obtain the conditions needed to conduct accurate and repeatable steady-state tests to meet ASTM C 518 with minimum operator involvement. The k values from this HFMA and three other HFMAs (model R-20 and R-21 units) exhibit imprecisions of 2.2% (two standard deviations) for specimens of foam insulation. Such performance requires proper calibrations of good quality heat flux transducers and use of correct thermocouple thermometry practices. For six lots of fiberglass batt insulation, this HFMA and a HFMA model R-21 yield k values as a function of density with two standard deviations of 4.5%. Test results from this HFMA for three specimens of loose-fill fiberglass insulation provide k values as a function of density with two standard deviations of 5.1%. Because these levels of imprecision (2.2%–5.1%) include material differences, they illustrate the limits of error of the model R-41 HFMA.