bluuebunny/crossref_metadata_2025 huggingface dataset:
Absolute measurement of the diameter of a fused quartz hemisphere at 6 K
Authors: Tate J. , McIntyre D. H. , Cabrera B.
Published: July 2002

We have measured by interferometry the diameter of a fused-quartz hemispherical rotor to 200 nm, or an accuracy of 4 parts-per-million (ppm), at both room temperature and at liquid helium temperature. We placed the rotor in an optically contacted fused-quartz etalon, and used a continuous-wave dye laser to measure the lengths of the optical cavities. The laser frequency was referenced to Doppler-free absorption lines in molecular tellurium and molecular iodine. These measurements were done in order to determine the area of a superconducting ring used in a precision determination of h/me. Our results confirm earlier length measurements at room temperature performed by the National Bureau of Standards (NBS).
Rapid-tuning device for CO2 heterodyne detection lidar
Authors: Fox Jay A. , Gautier Cynthia R. , Ahl Jeffrey L.
Published: July 2002

A device for rapid-tuning cw, Q-switched lasers for a CO2 heterodyne detection lidar is presented. It is shown that it is possible to utilize galvanometer-driven mirrors to rapidly switch wavelengths over randomly selected lasing transitions in the 9–11 μm portion of the spectrum. Both a transmitter and a local oscillator are simultaneously switched between transitions while still achieving the frequency stability typically required for a coherent lidar system.
Measurement of residual stresses in films of unknown elastic modulus
Authors: Cuthrell R. E. , Gerstle F. P. , Mattox D. M.
Published: July 2002

In expressions of film stress, the term containing the film elastic modulus is negligibly small (with respect to other terms) when the ratio of substrate-to-film thickness is large, thus allowing the calculation of stress in films of unknown modulus. However, the consequent large radii of curvature require large-field-of-view interferometers. A Michelson interferometer capable of producing interferograms from 25-mm-diam samples was constructed using standard large precision optics. The large field of view compared to the usual 1-mm diameter allows determination of very large radii of curvature.
A trochoidal spectrometer for the analysis of low-energy inelastically backscattered electrons
Authors: Cloutier P. , Sanche L.
Published: July 2002

A spectrometer designed to study electrons which are scattered at 180° with respect to the direction of the incident beam from a gas or a solid surface target, has been constructed and tested. The instrument is capable of operating at very low impact energies (0.05–15 eV) with an absolute energy resolution of 18 meV full width at half-maximum (FWHM). The performance of this apparatus is demonstrated with vibrational energy-loss spectra of H2O and C6H6 molecules condensed on a polycrystalline platinum substrate held near a temperature of 80 K.
An image processing equipment for the inventory of micrometer sized shapes
Authors: Rosenbaum B. , Langevin Y. , Baron F. , Borg J. , Vassent B. , Bibring J-P. , Salvetat Ph.
Published: July 2002

We describe an image-processing equipment designed and built to meet the specific requirements of an astrophysical experiment, but having probably useful applications in other fields of science and technology. It locates and makes the inventory of specified micrometer-sized holes in thin metallic films. The data acquisition is made by a CCD camera looking at the film through an optical microscope. The information goes to a microcomputer through a special interface. The program and the electronics were designed for optimum acquisition speed, automatic operation, and minimum need for human intervention.
New experimental approach to the excess carrier transfer in semi-insulating GaAs based on time-resolved photovoltage
Authors: Hardalov Chavdar , Batovski Dobri , Dalakov Stefan
Published: July 2002

The photovoltage shows a very complicated behavior and could be considered as a new approach to the investigation of the excess carrier transfer in semi-insulating (SI) semiconductors. Both time-resolved short-circuit (SC) photovoltage and photocurrent at the same energies in the range 1.13–1.49 eV for SI GaAs were measured. The peculiarities of the photovoltage were explained in terms of hole transfer between EL2 deep center and a series of acceptor levels. The influence of the electrons and holes was distinguished, which is known to be impossible via conventional photocurrent measurements.
Phase shift moire apparatus for automatic 3D surface measurement
Authors: Dirckx J. J. J. , Decraemer W. F.
Published: July 2002

An instrument for automatic reconstruction of the surface of three-dimensional objects is described. The apparatus is based on phase-shifted shadow moire, a noncontacting optical metrological technique which we substantially improved by a new way of introducing the phase shift. The article includes details of construction and the ideas guiding the choice of component characteristics. Some typical measuring results are presented.
Coaxial cable attenuation in NMR sample coil circuits
Authors: MacLaughlin D. E.
Published: July 2002

An analysis is presented of the effect on power transfer and noise figure of attenuation in the radiofrequency coaxial cable (coax) between a NMR sample coil and the associated spectrometer. A matching network between the sample coil and the coax, which matches the coil to the coax characteristic impedance, is shown to decrease the noise temperature of the coax by a factor of the Q of the coil. In addition, the usual two-capacitor matching network, which provides a perfect match only if both capacitors are variable, is shown to yield an acceptably small mismatch over a wide range of frequencies even if one capacitor is fixed.
An x-ray gas position sensitive detector: Construction and characterization
Authors: Barbosa A. F. , Gabriel A. , Craievich A.
Published: July 2002

A linear x-ray gas position sensitive detector with delay line readout has been constructed. The detector is described, characterized, and used for detecting x-ray diffraction patterns from polycrystals.
Photon counting in x-ray diffraction
Authors: Gouhara K. , Omote K. , Yamada S. , Sakata M. , Uchikawa Y. , Kato N.
Published: July 2002

The photon counting method is proposed for the field of Å x-ray diffraction. For this purpose, a new memory device was developed. The photon distribution and the photon autocorrelation were measured, and high-intensity sources such as the rotating anode generator and the Photon Factory were characterized. It has been shown that the method is useful to investigate time-dependent phenomena on the time scale down to 10 μs.
Spatial distortions in solid-state semiconductor imagers in x-ray region (abstract)
Authors: Fedotov M. G. , Kuper E. A. , Panchenko V. E. , Tiunov S. A.
Published: July 2002

When detecting x-ray images by solid-state semiconductor imagers (charge-coupled devices, photodiode arrays) there arise specific distortions caused by the diffusion of minority photogenerated carriers in the semiconductor substrate. The mode and scale of the diffusion and, accordingly, of distortions which arise are determined by properties of both the detector and the image. In this paper, some aspects of the diffusion are experimentally studied and the results obtained are interpreted on the basis of a theoretical model obtained in definite approximations. The result of the theoretical model is presented as the Fourier transfer function of the time and spatial frequencies, normalized over the quantum efficiency. This function incorporates the following parameters: the diffusion length and diffusion factor for minority carriers, the depth of the depletion regions of sensitive cells, the thickness of the epitaxial layer (or the single-crystal substrate), the linear absorption coefficient of radiation for a semiconductor material, and the angle of incidence of the radiation on the device surface. For the corresponding point-spread function, among the properties illustrated experimentally are the peculiarity providing a good geometrical resolution, the formation of a ‘‘stepped’’ profile at the grazing incidence, the formation of the ‘‘halo’’ of the scattered charge. The results of the x-ray and optic measurements have also shown that diffusion from the passive (peripheral) regions, which determines, to a considerable extent, the applicability of linear imagers (lines) in high-resolution systems, contributes appreciably to the distortions. The authors have considered some ways of diminishing the distortions which are accessible to experimenters: diaphragming and oblique incidence of the radiation, and an increase of the depths of the depletion regions of the cells. In addition, the authors dwell briefly upon the influence of the diffusion on the quantum noise and the effect of spectra superimposition, the contribution of x-ray fluorescence and the photoelectron range to the distortions. As an illustration, the possibility of utilizing solid-state imaging detectors to x-ray tomography systems has been evaluated.
Multiframe digitization of x-ray (TV) images (abstract)
Authors: Karpenko V. A. , Khil’chenko A. D. , Lysenko A. P. , Panchenko V. E.
Published: July 2002

The work in progress deals with the experimental search for a technique of digitizing x-ray TV images. The small volume of the buffer memory of the analog-to-digital (A/D) converter (ADC) we have previously used to detect TV signals made it necessary to digitize only one line at a time of the television raster and also to make use of gating to gain the video information contained in the whole frame. This paper is devoted to multiframe digitizing. The recorder of video signals comprises a broadband 8-bit A/D converter, a buffer memory having 128K words and a control circuit which forms a necessary sequence of advance pulses for the A/D converter and the memory relative to the input frame and line sync pulses (FSP and LSP). The device provides recording of video signals corresponding to one or a few frames following one after another, or to their fragments. The control circuit is responsible for the separation of the required fragment of the TV image. When loading the limit registers, the following input parameters of the control circuit are set: the skipping of a definite number of lines after the next FSP, the number of the lines of recording inside a fragment, the frequency of the information lines inside a fragment, the delay in the start of the ADC conversion relative to the arrival of the LSP, the length of the information section of a line, and the frequency of taking the readouts in a line. In addition, among the instructions given are the number of frames of recording and the frequency of their sequence. Thus, the A/D converter operates only inside a given fragment of the TV image. The information is introduced into the memory in sequence, fragment by fragment, without skipping and is then extracted as samples according to the addresses needed for representation in the required form, and processing. The video signal recorder governs the shortest time of the ADC conversion per point of 250 ns. As before, among the apparatus used were an image vidicon with luminophor conversion of x-radiation to light, and a single-crystal x-ray diffraction scheme necessary to form dynamic test objects from x-ray lines dispersed in space (the projections of the linear focus of an x-ray tube).
Vertical x-ray stepper for synchrotron-based production lithography (abstract)
Authors: Cullmann E. , Kooper K. A.
Published: July 2002

The second generation SUSS XRS-200 stepper will be described. The development of this stepper was based on three years of experience with the first generation SUSS MAX-I steppers operated at the BESSY synchrotron ring in Berlin. These MAX-I steppers have been in use since 1984 in mask, resist, and source research and development. Circuits with sub-0.5-micron feature sizes were produced using the MAX-I. In contrast to the first generation stepper, the XRS-200 is designed for production volumes with fully automatic mask and wafer handling. With the production oriented XRS-200, gap setting is performed optically using a trinocular microscope. After coarse prealignment of each field, the maskholder and wafer chuck are clamped together. Fine alignment of mask to wafer is then performed, and the complete clamped unit is scanned through the horizontal stationary x-ray beam. Because the mask and wafer are scanned, the beamline end window need only be a few millimeters in height. With this design, a thinner end window can be used, thereby maximizing x-ray flux to the mask and wafer. The first of the XRS-200 series has been installed at BESSY. Initial alignment and exposure results will be presented.
Picosecond synchrotron radiation pulse radiolysis
Authors: Ogata Atsushi , Tagawa Seiichi
Published: July 2002

This article discusses pulse radiolysis using synchrotron radiation from the TRISTAN accelerators, the accumulation ring (AR) and the main ring (MR). They provide intense radiation, the energy of which goes up to the γ-ray region, and a pulse length below 50 ps, which could be below 10 ps. The time separation between neighboring bunches is 1.25 μs at the AR and 5 μs at the MR. These features should make it possible to detect reactive intermediates in radiation-induced reactions in the time span from picoseconds to microseconds. Possible applications of the picosecond synchrotron radiation pulse radiolysis are introduced. They include studies of radiation effect on resist materials, on radiation sensitive materials, biological systems, and reaction from selected states such as Rydberg state, inner-shell excited states, and multi-ionized states.
Fabrication of 57Fe/Fe multilayers (abstract)
Authors: Kikuta S. , Zhang X. , Yoda Y. , Izumi K. , Ishikawa T.
Published: July 2002

Synchrotron radiation can furnish Mössbauer radiation sources with higher brightness compared with conventional radioactive γ-ray sources when nuclear resonant Bragg scattering of synchrotron radiation is utilized. So far the observation of nuclear resonant Bragg scattering has been successfully carried out using single crystals containing 57Fe isotope at INP, HASYLAB, and BNL. We intend to use 57Fe/Fe multilayers instead of the crystals as a nuclear scatterer. In order to observe nuclear resonant scattering it is necessary to suppress Thomson electronic scattering which makes a huge background noise. In the case of the multilayer containing 57Fe and 56Fe only, nuclear resonant Bragg scattering can be observed in the absence of electronic Bragg scattering. Computation of the reflected intensities from a multilayer was made by the method analogous to that used in the design of a multilayer interference filter for a visible ray. Multilayers were fabricated by depositing alternate layers of 57Fe and 56Fe with designed layer thicknesses of 8 and 12 Å, respectively. As substrates, quartz glass plates and quartz crystal plates were used. The substrates were cooled by liquid nitrogen. The structure of the multilayer was characterized by Mössbauer γ-ray diffraction. The 14.4-keV γ-rays from 57Co source were used. A rocking curve has a peak, when measured under the resonance condition. The Bragg angle of the peak coincide well with that calculated from the designed spacings. From these facts it is concluded that the peak corresponds to nuclear resonant Bragg scattering.
SHADOW: New developments (abstract)
Authors: Lai B. , Chapman K. , Runkle P. , Cerrina F.
Published: July 2002

We report on extensions that have been implemented in SHADOW,1 our x-ray and synchrotron sources modeling program. New types of sources have been implemented: (a) undulators are now part of the gallery of sources; (b) an optimization module has been implemented for systems with high losses. For the ray-tracing module, we have now implemented zone plates optical systems. Several new analysis programs have been implemented, as well as a new user’s interface. Two modules, PLOTXY and SYSPLOT, in particular, have been extended and improved. PLOTXY can now plot the wave-front surface directly, while SYSPLOT can generate a realistic layout of the optical system. Work is currently in progress on the implementation of asymmetric crystal diffraction and effect of roughness on image formation. A first version of the User’s Guide has also been written and will be presented at the meeting
Construction of a multipole wiggler, MPW♯13, at the Photon Factory
Authors: Sasaki Shigeki , Yamamoto Shigeru , Shioya Tatsuro , Kitamura Hideo
Published: July 2002

An insertion device, MPW♯13, which can be operated in both wiggler and undulator modes, is presently under construction at the Photon Factory (PF). When installed in the PF storage ring, this device will produce wiggler radiation in the hard x-ray region, and also undulator radiation in the vacuum-ultraviolet (VUV) and soft x-ray regions. The wiggler structure employs 27 magnetic poles with a period length of 18 cm. The maximum peak field of the device of 1.5 T is attained via the hybrid configuration of its magnetic poles. Calculations of the spectral brilliance of the device exhibits the following features: in the wiggler mode, the brilliance at 10 keV will exceed that of the PF bending magnet radiation by a factor of 30; and in the undulator mode it will be between 10 and 100 times higher, from 10 eV to 1 keV, utilizing up to the fifth harmonic.
HESYRL: Recent status
Authors: Bao Zhong-Mou
Published: July 2002

The 200-MeV linac injector was completed in October 1987 and commissioned to the designed targets. The 800-MeV storage ring is expected to complete the installation by the end of 1988. Five beamlines and experimental stations, which are under construction, are described.
Suppression of beam instabilities induced by accelerating cavities
Authors: Kobayakawa Hisashi , Izawa Masaaki , Sakanaka Shogo , Tokumoto Shuichi
Published: July 2002

A requirement for electron storage rings for the synchrotron radiation experiments is that circulating beam is very stable. In particular, for small emittance machines, obtaining a high-quality beam is the most important subject. Though the rf-accelerating cavities are essential for the storage rings, sometimes they cause serious beam instabilities, and lead to a current limit and an emittance growth. The Photon Factory storage ring (KEK) is a dedicated synchrotron radiation source. There are four single-cell cavities in the ring. Beam instabilities arising from the cavities have been investigated. The resonant frequencies of these cavities were trimmed by choosing the proper length of blank-flanges attached to the cavity ports, to avoid the conditions unstable for all existing coupled-bunch instabilities. Reduction of the instabilities was remarkable.
Stabilization of synchrotron radiation beam at HASYLAB (invited)
Authors: Brefeld W.
Published: July 2002

At DORIS II/HASYLAB a vertical beam position control system is in regular operation. It controls the position and angle of a photon beam simultaneously, and can stabilize beam movements up to frequencies of 0.1 Hz. To suppress beam vibrations up to 50 Hz and above, a prototype beam stabilization system for these frequencies was built and tested successfully. The present beam oscillations at the HASYLAB beamlines are explained, the quality of the beam position control system and the results of the prototype test are presented.
Determination of the magnitudes and signs of flow parameters by hot-wire anemometry. Part II. Measurements using a triple hot-wire probe
Authors: Acrivlellis Michael
Published: July 2002

This article deals with the determination of the magnitude and sign of the three components of the instantaneous velocity vector from the output signals of a triple-sensor hot-wire probe. All three sensors lie in the same plane with a given angular orientation. Measurements with this triple probe are performed with the wire plane inclined at an angle of about 45° to the main transport direction of the fluid, thus ensuring high sensitivity of the probe and the determination of the three components of the instantaneous velocity of the flow in magnitude and sense. Furthermore, the region of applicability and the accuracy of the values of the flow parameters of the method are discussed.
Liquid helium level meter by audio-sound detection
Authors: Kato Kiyonori
Published: July 2002

A new audible-liquid-helium level detector using the thermal oscillations of helium gas has been developed. A liquid level can be easily detected by a clear sound change of a vibrating plastic film which is fixed on top of a stainless-steel tube. This level meter is very simple, but more convenient and economical compared with commercial electronic types of level meters.
Low emittance and positron storage operation at the Photon Factory (invited)
Authors: Huke Kazuo
Published: July 2002

The Photon Factory ring has been successfully in operation with a lower horizontal emittance of 127-nm rad since February 1987. It was previously 404-nm rad. There have been many kinds of beam instabilities and the closed orbit distortions observed. These causes have been studied diagnostically in order to find a solution. Positron storage has also been achieved as the next step. In positron storage, the two-stream instability caused by ion trapping has completely disappeared and the abrupt decrease of the beam lifetime presumably due to dust trapping has not been observed since.
Operational experience of NSLS storage rings (invited) (abstract)
Authors: Krinsky S.
Published: July 2002

We review the operating experience at the National Synchrotron Light Source on the VUV and x-ray storage rings, with particular consideration given to achieved current and lifetime, transverse bunch dimensions, and orbit stability. The status of the Phase II upgrade will be discussed, as will the operation of the presently installed insertion devices.
ESRF x-ray synchrotron radiation source (invited)
Authors: Laclare Jean-Louis
Published: July 2002

The European Synchrotron Radiation Facility (ESRF) will be one of the most performant low-emittance synchrotron radiation sources covering the x-ray domain. Construction of the facility in Grenoble started in January 1988 with the following target specifications: first priority to insertion devices; in general, capacity to produce brilliances in the 1018 to 1019 photons/(s mm2 mrad2 0.1% bandwidth) range from undulators; in particular, capacity to produce a brilliance larger than 1×1018 in the fundamental of an undulator at 14.4 keV; high flexibility of the lattice to accommodate wigglers and undulators; stability of the beam greater than one tenth of the rms dimensions; beam lifetime greater than 8 h; capability of providing bending magnet sources at 10 and 20 keV. The source will be completed by mid 1993. The governments of France, Federal Republic of Germany, Italy, United Kingdom, Spain, Switzerland, Denmark, Finland, Norway, and Sweden are contributing to the financing.
Wisconsin x-ray lithography program (invited)
Authors: Wells G. M. , Chen G. , White V. , Wallace J. , Cerrina F. , Lien Neil
Published: July 2002

The facilities and research activities of the University of Wisconsin’s Center for X-ray Lithography (CXrL) are outlined. We discuss recent modifications to the two x-ray lithography beamlines operated by CXrL at the Aladdin storage ring. Ongoing research in various aspects of x-ray lithography, including photoresist characterization, mask stability and distortion studies, and modeling of the x-ray lithography process are summarized. We present plans for the expansion of the CXrL research facilities.
Synchrotron radiation lithography system in an atmospheric environment (invited)
Authors: Okada K. , Kouno E. , Nomura E. , Suzuki K. , Fujii K. , Tanaka Y. , Iwata J. , Kawase Y.
Published: July 2002

The atmospheric environmental exposure system for synchrotron radiation (SR) lithography has been integrated using the Photon Factory storage ring (2.5 GeV). The system, composed of a highly reliable beamline, an SR extracting chamber and a prototype SR stepper, aims at attaining higher accuracy and throughput. Based on a fail-safe mechanism notion, a double-vacuum protection system, in which two sets of a fast closing valve and acoustic delay line are installed in the main beamline and branch beamline, respectively, has been organized. Vacuum breakdown tests indicated that any vacuum breakdown, a beryllium (Be) window rupture in the worst case, exerts little influence on the storage ring ultrahigh vacuum. The SR extracting chamber, equipped with a Be window and an extraction window, is filled with helium at atmospheric pressure. Particularly, the 50-μm-thick, 35-mm-diam Be window, vacuum-sealed by a Viton O-ring, was preliminarily employed and, so far, has operated successfully, giving a 25-mm square exposure area. In terms of practical availability and simplicity, the SR stepper in an atmospheric environment has been constructed. A novel differential mode linear Fresnel zone plate alignment method, which can detect an alignment error between a mask and a wafer during exposure, was developed.
Compact high repetition rate magnetically switched transverse, electric, atmospheric CO2 laser
Authors: Sylvan A. , Spiers G. D. , Johnstone A. , Harrison R. G.
Published: July 2002

A corona preionized compact transverse, electric, atmospheric CO2 laser providing an average optical output of 18 W from a 4.6-cm3 discharge volume is reported. The laser was driven at pulse rates up to 1 kHz by an all solid-state exciter circuit which has produced>109 pulses.
An experimental system for symmetric capacitive rf discharge studies
Authors: Godyak V. A. , Piejak R. B. , Alexandrovich B. M.
Published: July 2002

An experimental system has been designed and built to comprehensively study the electrical and plasma characteristics in symmetric capacitively coupled rf discharges at low gas pressures. Descriptions of the system concept, the discharge chamber, the vacuum-gas control system, and the rf matching and electrical measurement system are presented together with some results of electrical measurements carried out in an argon discharge at 13.56 MHz. The system has been specifically designed to facilitate external discharge parameter measurements and probe measurements and to be compatible with a wide variety of other diagnostics. External electrical measurements and probe measurements within the discharge show that it is an ideal vehicle to study low-pressure rf discharge physics. Measurements from this system should be comparable to one-dimensional rf symmetric capacitive discharge theories and may help to verify them. Although only a few results are given here, the system has been operated reliably over a wide range of gas pressures and should give reproducible and accurate results for discharge electrical characteristics and plasma parameters over a wide range of driving frequency and gas components.
Apple II direct memory access interface to acquire neutron scattering time of flight spectra
Authors: Cilloco F. , Ippoliti A. , Sacchetti F.
Published: July 2002

A data acquisition system designed to acquire time of flight spectra in neutron scattering experiments is described. The system is completely hardware, so that even employing a relatively slow clock (1 MHz) it is adequate to work at 300 kHz with no loss of information.
Nonlinear grating interaction in photorefractive Bi12SiO20
Authors: Buchhave Preben , Andersen Peter E. , Petersen Paul Michael , Vasnetsov Mikhail
Published: July 2002

Recently significant crosstalk has been observed in a multibeam experiment in which gratings were previously thought to be independent. In this letter, it is shown that the crosstalk is due to a coherent nonlinear combination of the primary gratings, which causes additional peaks to occur in the diffraction pattern and changes the diffraction efficiency of the primary gratings explaining the apparent crosstalk. It is shown that the effect can be derived from the band transport model when all the terms in the expression for the generation of charge carriers are retained. Results are presented for a configuration consisting of a reference beam and two object beams and show experimental results that confirm the model.
Vibrating membrane elastometer for reliable measurement of mechanical properties of metallic films
Authors: Fartash A. , Schuller Ivan K. , Grimsditch M.
Published: July 2002

We describe an apparatus for measuring the biaxial mechanical properties of metallic films. A circular knife-edge support forms a drum-head geometry over which the film to be studied is stretched. The film’s tension is obtained from the frequency of its membrane modes, and its strain by using an optical technique. The biaxial modulus is obtained from the ratio of tension and strain. An electronic detection system is developed that regeneratively locks to the film’s resonant frequency. The system is also capable of measuring the film’s damping when the lock is switched off.
Nanometer-scale recording on chalcogenide films with an atomic force microscope
Authors: Kado H. , Tohda T.
Published: July 2002

A nanometer-scale recording technique has been demonstrated on an amorphous GeSb2Te4 film with an atomic force microscope (AFM). Data are recorded by locally changing the electrical property of the film with a conductive AFM probe. The conductance of the film is able to be increased more than one hundred times by applying a pulse voltage between the probe and the film. The recorded data are read by detecting the change of the conductance with the probe. The simultaneous measurement of the topographic and conductance images with the AFM shows that the surface topography of the recorded regions is not changed during the recording process. The smallest recorded region is 10 nm in diameter, which corresponds to a data storage density of 1 Tbit/cm2.
An electro-optical sensor for surface displacement measurements of compliant coatings
Authors: Adair Desmond , Madigosky Walter M. , Mease Norman E.
Published: July 2002

Compliant coatings are now being used in many engineering applications, chiefly in relation to sound absorption and noise shielding. Another, though still controversial, application is their use in the reduction of skin friction drag of moving vessels. The design of a compliant coating to realize the latter goal or to achieve optimum sound absorption is complex and requires the determination of the surface motion characteristics resulting from the hydrodynamic forces [D. M. Bushnell, J. N. Hefner, and R. L. Ash, Phys. Fluids 20, 531 (1977)].
Picosecond time-resolved absorption spectrometer using a streak camera
Authors: Ito T. , Hiramatsu M. , Hosoda M. , Tsuchiya Y.
Published: July 2002

A picosecond time-resolved absorption spectrometer is described. The apparatus consisting of a probe light source, a polychromator, and a streak camera enables us to observe time-resolved absorption spectra in the range from picoseconds to several nanoseconds, with 50 ps time resolution. The probe light has the properties of a wide range continuum spectrum from UV to near IR and is of several tens of nanoseconds in duration. Using this apparatus, with only a single laser shot, we can observe transient absorption both temporal and spectral simultaneously. This apparatus is useful for studying the primary process of photochemical dynamics.
An improved capacitive divider probe for plasma potential measurements in the Phaedrus tokamak
Authors: Wang E. Y. , Diebold D. , Nonn P. , Pew J. , Li W. Q. , Probert P. , Breun R. , Majeski R. , Yan S. L. , Hershkowitz N.
Published: July 2002

High bandwidth capacitive probes are useful tools for potentials measurements in the tokamak scrape off layer. An improved capacitive divider probe design with very high frequency bandwidth is shown. The gain of this system is between 0 and −8 dB for frequencies from 0.1 Hz to more than 100 MHz, with the −3 dB point at approximately 40 MHz. The probe structure, circuits, performance, and experimental results from the Phaedrus-T tokamak are given.
Optimized Rutherford-scattering geometries for intense ion-beam diagnostics
Authors: Stygar W. A. , Mix L. P. , Leeper R. J.
Published: July 2002

Rutherford scattering is used routinely for diagnostic purposes to reduce the intensity of ion beams in inertial-confinement-fusion experiments. A limitation of the scattering technique is the strong dependence of the Rutherford cross section on the scattering angle [σ∝1/sin4(θs/2)] because the angular distribution of the beam ions is not precisely known and is difficult to measure. It is shown that this limitation can be overcome with the use of a thin scattering foil, and an analytic expression is derived that defines geometries for which the scattering probability is, to first order, independent of θs.
High-flux photon beam position monitor
Authors: Mitsuhashi T. , Ueda A. , Katsura T.
Published: July 2002

A high-flux photon beam position monitor for insertion devices was constructed and tested at the Photon Factory. The monitor comprises two pairs of water-cooled right-triangle electrodes placed in paralled at both horizontal edges of the beam. The monitor’s linear regions are 800 μm in the horizontal direction and more than 1200 μm in the vertical direction. The response of the monitor was also studied for various gap sizes of insertion devices.
Beam intensity measurement of BSRL 4W1B beamline
Authors: Shan Qiao , Yaning Xie , Yang Hai , Tiantou Hu , Shaojian Xia , Esheng Tang , Dingchang Xian
Published: July 2002

To better understand the state of BSRL, Beijing Synchrotron Radiation Laboratory XAFS station and the related beamline 4W1B, the monochromatic beam intensities available at the station have been measured. The synchrotron radiation intensity is too high to be recorded by an impulse-type detector and no integrating detector has energy resolution. Unfortunately, the ‘‘monochromatic’’ beam not only has fundamental components but also has high-order harmonics. To resolve these problems, an ion chamber is used to record the total intensity and an NaI(Tl) scintillation detector behind the chamber is used to measure the harmonics ratio, simultaneously. The chamber also acts as an attentuator to absorb most of the photons to meet the low counting rate limitations of NaI(Tl) detector. The result shows that this method is practicable. The maximum intensity available at our station is 1.14×107 photons/mA/s at the photon energy about 11 keV. The whole spectrum is reported below.
Electron beam measurements on the Daresbury SRS
Authors: Laundy David , Cummings Stewart
Published: July 2002

Two experiments which use hard x-ray synchrotron radiation have been carried out to allow us to monitor the electron beam on the Daresbury SRS. The beam spatial and angular vertical position and size was determined over a period of time when the SRS was operating normally. From these measurements, the position and angular stability of the electron beam during the measurement period was assessed and correlation of the beam emittance to the electron current was determined.
Correlation between measured undulatormagnetic fields and x-ray spectra (abstract)
Authors: Carr Roger , Kincaid Brian , Hassenzahl William
Published: July 2002

Electron storage ring insertion devices, especially undulators, are designed using ideal device theory, and the resulting x-ray spectra are reasonably close to predictions in most cases. However, there are magnetic field errors which result in nonideal x-ray spectra. These effects can be calculated theoretically, and may also be measured. We present a study based on an undulator whose magnetic fields and x-ray spectra we have measured carefully. We account for undulator spectral peak shapes due to the effects of magnet errors, finite emittance, and finite length, and compare experiment and theory.
SPring-8 prototype undulator
Authors: Sasaki Shigemi , Matsuki Nobuo , Takada Takeo
Published: July 2002

An undulator of wedged-pole-hybrid type was constructed as a prototype undulator for the SPring-8. This device has 33 mm magnetic period, 123 magnetic poles, and generates 5.87 kG peak magnetic field at the minimum gap position (13.5 mm). The magnetic field measurements were performed on this undulator. By using these data, expected undulator radiation intensity was computed including the effect of magnetic field error. The reductions of peak intensity due to the field error were observed for higher harmonics.
The Optics Laboratory of the ESRF (abstract)
Authors: Freund A. K. , Susini J. , Ziegler E.
Published: July 2002

In parallel to the design and construction of new synchrotron radiation sources quite important efforts are required to upgrade existing and develop new x-ray optics that is capable of conditioning powerful x-ray beams with minimum losses of brilliance. In the context of these research and development activities a well equipped laboratory is absolutely vital. Such a laboratory must have capabilities to prepare, mount, transfer, align and test optical elements with the high precision that is typical for European Synchrotron Radiation Facility (ESRF) beamline instrumentation, for example, microroughness and slope error of mirrors down to 0.1 nm root mean square and μrad, respectively, and μm and μrad spatial and angular positioning. At ESRF the following facilities presently exist or are being installed: (i) a laboratory for single crystal orientation, cutting, grinding, polishing, and mounting, (ii) three interferometers for optical metrology of surfaces such as figure and finish, all in clean room and thermally stable environment, (iii) a three axis diffractometer for precise x-ray metrology of all kinds of optical elements up to 1-m long, also in clean room and stable environment, (iv) a multilayer fabrication facility featuring sputtering and plasma chemical vapor deposition with in situ x-ray diffraction and ellipsometry controls.
Design of front-end components for a high-power density beamline
Authors: Chen Q. H. , De Bona F. , Fava C. , Gambitta A. , Mazzolini F. , Sedmach A. , Savoia A.
Published: July 2002

A prototype front end for undulator beamlines to be installed on the storage ring Elettra is presented. Design criteria are briefly discussed, in particular for those components which have to withstand heavy heat load.
Design, construction, and characterization of an electromagnetic small period undulator
Authors: Gomes Paulo Alberto Paes , Rafael Fernando da Silva , Rodrigues Antonio Ricardo Dröher
Published: July 2002

In this work a new concept for the construction of small period electromagnetic insertion devices is presented. The construction of a pulsed undulator with 2 mm gap and 8 mm magnetic period is described, as well as its pulser. The magnetic measurement system is presented and the obtained data is compared with the calculated field. Finally, the possible application of this device for synchrotron radiation production in LINAC’s and a future cw superconducting version for storage rings is discussed.
Removal of superfluid helium films from surfaces below 0.1 K
Authors: Torii R. , Bandler S. R. , More T. , Porter F. S. , Lanou R. E. , Maris H. J. , Seidel G. M.
Published: July 2002

We have constructed an apparatus that is able to maintain a helium-free surface at low temperature (T≤0.1 K) in a cell containing superfluid helium. We discuss the considerations involved in the design of this device, and describe tests that we have made to confirm that a film-free surface has been produced.
The introduction of spurious modes in a hole-coupled Fabry-Pérot open resonator
Authors: Cook Jerry D. , Long Kenwyn J. , Heinen Vernon O. , Stankiewicz Norbert
Published: July 2002

A hemispherical open resonator has previously been used to make relative comparisons of the surface resistivity of metallic thin-film samples in the submillimeter wavelength region. This resonator is fed from a far-infrared laser via a small coupling hole in the center of the concave spherical mirror. The experimental arrangement, while desirable as a coupling geometry for monitoring weak emissions from the cavity, can lead to the introduction of spurious modes into the cavity. Sources of these modes are identified, and a simple alteration of the experimental apparatus to eliminate such modes is suggested.
Study of Schottky barriers on n-type GaN grown by low-pressure metalorganic chemical vapor deposition
Authors: Guo J. D. , Feng M. S. , Guo R. J. , Pan F. M. , Chang C. Y.
Published: July 2002

Schottky barriers on n-type GaN films grown by low-pressure metalorganic chemical vapor deposition are characterized and derived. A thin Pt or a Pd layer is deposited by electron-gun evaporation to form Schottky contacts in a vacuum below 1×10−6 Torr. The Schottky barrier heights of Pt on the n-GaN film are determined to be 1.04 and 1.03 eV by current–voltage (C–V) and current density–temperature (J–T) measurements, respectively. Also based on C–V and J–T measurements, the measured barrier height of Pd on n-GaN is 0.94 and 0.91 eV, respectively. Schottky characteristics of Pt and Pd observed in the experiment are compared with those of Au and Ti in previous reports.
Polarimetry of motional Stark effect and determination of current profiles in DIII-D (invited)
Authors: Wróblewski D. , Lao L. L.
Published: July 2002

The motional electric field E=v×B, where v is the velocity and B is the tokamak magnetic field, produces a strong Stark effect in spectral lines emitted by hydrogenic neutral beams. The tilt angle of the magnetic field line, a quantity related directly to the distribution of the plasma toroidal current, is deduced from a measurement of the direction of polarization of the Stark components. In the DIII-D tokamak, the Balmer-α line of deuterium emitted by one of the high-power heating beams is analyzed. A multichord polarimeter measures the magnetic field pitch angle at eight spatial locations covering ∼0.6 of the nominal plasma diameter at the midplane outboard side. The diagnostic offers 2–8-cm resolution in the major radius and 1-ms integration time. The accuracy of the measurement of the polarization direction necessary for an adequate reconstruction of the current profiles is obtained with the use of active polarizing elements which produce high-frequency intensity modulation with an amplitude related to the direction of linear polarization of the plasma radiation. The current profiles in highly shaped (noncircular) plasmas cannot be determined solely from the tilt angle measurements because they do not provide any information about the shape of magnetic surfaces. Thus, the polarization measurements are used in conjunction with a large set of external magnetic measurements (magnetic field and flux probes, diamagnetic loops, and Rogowski coils) by the magnetic field equilibrium code EFIT, and provide a constraint on the possible solutions for the current profile.
Aluminum K-shell line emission as a diagnostic in light ion beam fusion experiments
Authors: MacFarlane J. J. , Wang P. , Mehlhorn T. A. , Bailey J. , Dukart R. J.
Published: July 2002

K α satellite line emission from targets irradiated by intense light ion beams can be used to diagnose plasma temperatures and densities. The fluorescence lines are created as 2p electrons drop down to fill 1s vacancies that result from ion beam-induced ionizations. We present results from collisional-radiative equilibrium calculations for thin Al diagnostic layers to illustrate the dependence of the Kα emission spectrum on temperature, density, and layer thickness. We also discuss the effects of opacity on the spectrum and the contribution from Kα transitions involving excited states.
Tomographic wire-grid imaging of magnetic surfaces
Authors: Blackwell B. D. , Howard J. , Tumlos R. B.
Published: July 2002

We describe a new, fast, and accurate method for obtaining magnetic surface puncture plots by the use of a rotating grid of fine wires. Electrons launched from a small gun follow the magnetic field lines, and a fraction are intercepted by the wire grid. The current signals, chordal integrals of electron beam intensity, are inverted by an iterative pseudotomographic method to obtain an image of the electron beam density in the plane of the grid, that is, a puncture plot of the magnetic surface. The method is capable of high resolution while maintaining a high transparency to electrons, and is demonstrated on a small toroidal stellarator, the SHEILA heliac.
Source characteristics and design consideration for an iron-free variable-period/polarizing undulator for the UV/VUV range on SPEAR (abstract)
Authors: Tatchyn Roman
Published: July 2002

Insertion devices that are tuned by electrical period variation are particularly suited for the design of flexible polarized-light sources [R. Tatchyn, J. Appl. Phys. 65, 4107 (1989); R. Tatchyn and T. Cremer, IEEE Trans. Mag. 26, 3102 (1990)]. Important advantages vis-a-vis mechanical or hybrid variable field designs include: (1) significantly more rapid modulation of both polarization and energy, (2) an inherently larger set of polarization modulation capabilities and (3) polarization/energy modulation at continuously optimized values of K. In this paper we outline some of the general considerations that enter into the design of hysteresis-free variable-period/polarizing undulator structures and present the parameters of a recently-completed prototype design capable of generating intense levels of UV/VUV photon flux on SPEAR running at 3 GeV.
Specific heats of type E thermocouple wires
Authors: Chung M. , Brill J. W.
Published: July 2002

We report on the specific heats of type E thermocouple wires, constantan (55% Cu–45% Ni) and chromel (10% Cr–90% Ni), measured using ac calorimetry in the temperature range 18–290 K. Data were normalized to values at 200 K determined by differential scanning calorimetry. The constantan values are close to those of other Cu/Ni alloys, while this is the first reported low-temperature result for chromel.
Time-gated gain cell for frequency-stable, single-longitudinal-mode operation of a transverse, electric, atmospheric CO2 laser
Authors: Nordstrom R. J. , Berg L. J. , DeSimone A. F. , Sugimoto N.
Published: July 2002

A time-gated gain cell has been demonstrated as a method for producing single-longitudinal-mode output from a pulsed transverse, electric, atmospheric (TEA) carbon dioxide laser. The gain cell is operated as an oscillator during the time between the laser pulses and is rapidly dropped below threshold during the TEA pulse output to avoid degradation of the gain-switched spike in the laser pulse. Standard dither-stabilization techniques can be used during the time between the laser pulses (cw oscillation) to position the output coupler for single-mode operation and frequency stabilization while the gain cell is operated above threshold.
Optimization of photoinitiated impulse-enhanced electrically excited CO2 laser discharges by attachment control
Authors: Labun A. H. , Seguin H. J. J. , Capjack C. E.
Published: July 2002

Control of frequency and amplitude of the impulses used in photoinitiated, impulse-enhanced, electrically excited laser pumping determines the E/p value of the discharge. This occurs through the influence of these impulses on the processes of electron density decay and ion-electron recombination and dissociative attachment. The degree of attachment can be controlled through the use of high-frequency excitation (f≳10 kHz), while the relative importance of ion-electron recombination increases with increasing impulse potentials. The reduced electric field E/p can thus be varied by a factor of 3, while the anode fall potential Va can be reduced from 400 to 250 V. This technique appears amenable to providing fine variation and control of the laser output power. Possible applications in materials processing are pulse shaping and rapid power modulation (superpulsing).
Simple system for high-pressure FTIR measurements of supercritical fluid mixture
Authors: Yokoyama Chiaki , Kanno Yo-ichi , Takahashi Minoru , Ohtake Katsuto , Takahashi Shinji
Published: July 2002

A simple system for high-pressure FTIR measurements was designed and tested. This system can be applied to physicochemical measurements and in situ analysis of chemical reactions in supercritical fluids. The principle of the high-pressure IR optical cell proposed in this study was based on that of the cylindrical internal reflectance. This system was tested by measuring the IR spectra of supercritical CO2 and of naphthalene dissolved in supercritical CO2 .