bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid electromechanical phase shifting in differential holography
Authors: Brehm Lawrence P.
Published: July 2002

Procedures for the rapid and precise control by electromechanical means of the reference beam phase shift during differential holography are described. Phase shift is created with the use of a piezoelectric ceramic translator that is driven by a two-step voltage pulse to minimize mechanical ringing. The resultant suppression of resonant vibration permits an order of magnitude reduction in the time interval between the exposures. The adjustment of the phase shift signal is assisted by use of feedback control arrangement to stabilize an interferometer.
Conversion and amplification of photomultiplier anode current in multiple-frequency phase fluorometry
Authors: Hädener K. , Bergamasco S. , Calzaferri G.
Published: July 2002

We have designed and built a low-cost current–voltage converter with a bandwidth larger than 200 MHz and a fixed ac insertion gain of 20 dB for use in multiple-frequency phase fluorometry (MFPF). We describe its application with the Hamamatsu R928 photomultiplier (PMT) and discuss problems of radio-frequency (rf) interference, signal-to-noise ratio (S/N), PMT nonlinearity, and overall frequency bandwidth. The separation of ac and dc signal paths introduces the possibility of direct determination of relative modulation in two simultaneous measurements. We demonstrate that systematic errors such as PMT nonlinearity can be completely eliminated in MFPF by an appropriate experimental procedure and report an accuracy of our dual-beam instrument of 5 ps.
High-resolution position-sensitive detector
Authors: Gao R. S. , Robert W. E. , Smith G. J. , Smith K. A. , Stebbings R. F.
Published: July 2002

This paper describes a position-sensitive detector for particles or photons which has a spatial resolution of about 15 μm. The active area is about 1.3 mm in diameter. This represents an improvement of conventional position-sensitive detection capability by about one order of magnitude and should be useful in spectrometry, spectroscopy, and atomic collision experiments.
Multipoint Thomson scattering measurements in a low-density plasma
Authors: Trost P. K. , Shohet J. L.
Published: July 2002

A multipoint Thomson scattering apparatus has been constructed to measure electron temperature and density at several spatial locations in a low-density toroidal plasma discharge. A multianode microchannel-plate photomultiplier tube detector is used to provide the multipoint capability of this device. This detector, along with a simple and efficient optical collection system, allows for low-density measurements. Critical for low-density operation is a low stray light level from the laser, which has been achieved through careful design of the laser beam handling optics. The plasma parameters in which this device operates are in a regime where Langmuir probes are the usual diagnostic method. The design of this device is presented, along with electron temperature and density profiles of an electron cyclotron heated plasma in the Interchangeable Module Stellarator. Comparison is made with Langmuir probe measurements of similar discharges. Discrepancies between these methods are seen, and are attributed to plasma perturbations by the probe.
Beam density fluctuation diagnostic
Authors: Heidbrink W. W.
Published: July 2002

The conceptual design of a neutral particle analyzer that is optimized for spatially resolved fluctuation measurements is described. Estimates indicate that a pair of these analyzers could detect fluctuations in beam-ion density associated with high β instabilities in the DIII–D tokamak.
Heteroepitaxial growth of smooth and continuous diamond thin films on silicon substrates via high quality silicon carbide buffer layers
Authors: Kawarada H. , Suesada T. , Nagasawa H.
Published: July 2002

Smooth and continuous diamond films have been heteroepitaxially grown on β-type silicon carbide (β-SiC) (001) surfaces. The smooth films can be obtained in the thickness of less than 6 μm which is the smallest in heteroepitaxial diamonds. The epitaxial growth is composed of three steps; (i) Bias enhanced nucleation on β-SiC (001) grown on silicon (001), (ii) 〈001〉 fast growth mode for the selection of epitaxially oriented particles, and (iii) 〈111〉 fast growth mode for the smoothing of (001) surface. High quality silicon carbide (001) surface is effective for oriented diamond nucleation. The winnowing process of oriented particles and the surface adjustment are due to the high surface energy of diamond.
Inelastic x-ray scattering with fluorescence coincidence detection using a pulsed synchrotron source
Authors: Marchetti Vincent , Franck Carl
Published: July 2002

We describe a system used to measure the spectrum of x rays scattered inelastically from K-shell electrons using a coincidence technique. The source of the x rays was a pulsed synchrotron source. We describe fast–slow coincidence logic adapted for use with a pulsed source of fluctuating intensity, describe in detail the background subtraction and statistical noise in the measurement, and present the results of measurements made with the system. The precautions used to avoid detector-to-detector scattering are also described. The combination of high source intensity and coarse time resolution (due to the pulsed nature of the source) put us in the regime for much of the scattered x-ray spectrum, in which the number of accidental coincidences greatly exceeded the number of true signal counts. We show that in this case significant reductions in statistical uncertainty may not be achieved by further increases in source intensity.
High precision alignment of x-ray transmission diffraction gratings
Authors: Hawryluk Andrew M. , Hill Sherry L.
Published: July 2002

Gold transmission diffraction gratings used for x-ray spectroscopy must often be aligned rotationally to within submilliradian accuracy of an instrument axis. Currently, these gratings have a high line density (grating periods less than 300 nm) so conventional techniques (such as optical imaging or diffraction) which have been used previously to determine the grating orientation cannot work. Other techniques (such as polarization effects) give <1-mrad accuracy. We describe here a simple technique that allows one to produce an optically observable alignment mark that is oriented parallel to the grating direction within a few microradians. We ‘‘write’’ a line, ∼0.01-mm wide, directly on the grating by exposing an electron-beam-sensitive coating of polymethylmethacrylate (PMMA) on the grating while driving the grating through the beam of a scanning electron microscope (SEM). The direction of motion is made parallel to the grating lines by controlling the stage motion with a joystick while inspecting the grating in the SEM. Using the joystick, one can ‘‘follow’’ a single grating line from end to end. The SEM written line is made a permanent addition to the grating by ion-beam etching or gold microplating, and can later be used for in situ alignment verification. Our lines have been made parallel to the original grating lines to approximately ±5 μrad; this alignment can be extended to ±1 μrad. Standard optical techniques can be used to align the grating with respect to an arbitrary instrument axis. This technique works equally well with transmission and reflection gratings.
Simple, demountable, cryogenic, vacuum seal
Authors: Snell P. , Turkington R. R. , Harris-Lowe R.
Published: July 2002

In this note, we describe the fabrication of a simple, reliable, demountable, vacuum seal which can function in the presence of superfluid helium and withstand temperature cycling to room temperature.
Gating circuit for linear-focused photomultiplier
Authors: Schulman M. Bruce
Published: July 2002

A gating circuit is described which provides a cutoff efficiency of approximately 99% by pulsing the first dynode of an RCA C31034 type linear-focused photomultiplier by only 18 V. This is accomplished by utilizing a local minimum in the photomultiplier gain which occurs immediately before the sharp turn-on point. The circuit achieves the requirements of fast turn-on, variable gating duration, and minimal switching transients. The technique is especially suited to photon-counting applications in which stability of the anode baseline voltage is critical.
Electronics for microchannel photomultipliers in the LIDAR Thomson scattering diagnostic on JET
Authors: Bundgaard J. , Hansen K. B. , Weisberg K.-V.
Published: July 2002

The electronics for the microchannel plate photomultiplier tubes used in the LIDAR (Light Detection and Ranging) Thomson scattering diagnostic on the JET tokamak are described. It is shown how the microchannel plate photomultiplier tubes are gated with a very small coupling between gate signal and output, and how ≊300 V transient pulses with rise times of 230 ps are clipped to safe levels of ≊40 V.
Instrumentation and data acquisition for i
n s
i
t
u electrochemistry at the Daresbury SRS
Authors: Barlow N. , Brennan C. , Doyle S. E. , Greaves G. N. , Miller M. , Nahle A. H. , Roberts K. J. , Robinson J. , Sherwood J. N. , Walsh F. C.
Published: July 2002

X-ray diffraction and absorption spectroscopy provide complementary structural tools for the in situ characterization of electrode surfaces. To optimize surface sensitivity, techniques such as glancing angle scattering geometries and spectrum differencing can be employed while the application of synchrotron radiation allows the real-time collection of data. This paper outlines recent developments in in situ electrochemistry on the Daresbury SRS and describes an electrochemical cell for in situ x-ray studies, associated glancing angle instrumentation, together with computer hardware and software optimized for data acquisition using potential modulation techniques. Important fundamental and industrial applications are highlighted.
Spatial correction of solid-state semiconductor imaging detectors in x-ray range (abstract)
Authors: Fedotov M. G. , Kuper E. A. , Panchenko V. E. , Tiunov S. A.
Published: July 2002

The images which are obtained using solid-state semiconductor detectors (charge-coupled devices and photodiode arrays) in the x-ray region in the regime of integrating detectors with the accumulation of the charges of plural events in cells, have specific distortions caused by a diffusive propagation of photogenerated minority carriers. Due to the peculiarity in the corresponding point-spread function, these distortions do not worsen the geometrical resolution (i.e., at a sufficiently high frequency of the spatial discretization, any images, however close, of delta functions are distinguishable), but they turn out to be very significant for the determination of the configurations, sizes, and brightnesses of the objects. Thus, the elaboration of techniques for reconstruction of the initial undistorted images becomes an urgent problem. In this work we describe experimental results on the correction of the images obtained under various conditions. The correction was performed in digital form by a microcomputer using a fast Fourier transformation of the data of the image being processed and the measured point-spread function. In a series of cases, nonlinear adaptive filtering was performed to limit high-frequency noise. A comparative analysis has been made of the registration of x-ray images by detectors with a flat (epitaxial devices) and with tilted (the devices on the single-crystal substrate), but being corrected, modulation transfer function. A linear model with an additive noise and a theoretical Fourier transfer function is used. In addition, the feasibility of an on-line reconstruction of the images in the case of degeneracy of the transfer function at a grazing incidence of the radiation has been investigated.
Parameters of a high-sensitive x-ray imaging detector on the basis of an electro-optical image intensifier and an image vidicon (abstract)
Authors: Karpenko V. A. , Khil’chenko A. D. , Lysenko A. P. , Panchenko V. E.
Published: July 2002

Since the early 1980s a tandem system consisting of an electrostatically focused image intensifier and an image vidicon has found extensive applications to visualization of the images formed by weak fluxes of x radiation. We present the result of measurements of some parameters of this complex linear video signal shaper (LVSS). The test x-ray image—x-ray lines dispersed in space by a single-crystal diffraction scheme (the projections of the linear focus of an x-ray tube) is directed onto a commercial one-stage image intensifier with electrostatic image focusing whose fiber-optics input window is covered by a luminophor to convert x radiation to light. The outlet of the image intensifier is fiber-optically coupled to the input fiber glass window of the commercial image vidicon (silicon intensifier target tube with intensifier section). The measurements performed on the device for absolute calibration of x-ray imaging detectors and x-ray counters (see the report at this Conference) have shown that the use of this LVSS permits one to record threshold flux densities of monoenergetic photons which are more than one order of magnitude lower than with the use of the image vidicon alone. Measurements of the dependence of the threshold flux density on the photon energy have been made. For example, for 8 keV (Cukα), when using gadolinium oxysulphide as the luminophor the threshold flux density is 20 times lower than for the image vidicon alone, and achieves 105 cm−2 s−1. At such a high sensitivity, detection of small-scale details of images with low brightness and contrast requires taking account of the noise of the radiation being detected, which is caused by the fluctuations of the photon flux. This LVSS visualizes light flashes caused by single hard x-ray photons and β particles which are incident upon the luminophor settled on the inlet window of the image intensifier. Both the x-ray images of the test objects and the luminescent flashes caused by photons and fast electrons are represented in digital form (see the report on multiframe digitization x-ray images at this Conference).
The Adone wiggler x-ray lithography beamline
Authors: Burattini E. , Grilli A. , Balerna A. , Bernieri E. , Simeoni S. , Mencuccini C. , Qian-Hong Chen
Published: July 2002

A soft x-ray beamline, utilizing the radiation produced by the six-pole wiggler of the Adone storage ring, has been realized. The beamline allows the exposure of large area resists by means of a double-mirror scanning system or mechanically moving the wafer. The mechanical, geometrical, and spectral characteristics of the beamline will be described.
Performance of a dodecapole collision chamber for the study of ion–molecule reactions using synchrotron radiation
Authors: Suzuki Shinzo , Imamura Takashi , Koyano Inosuke , Okuno Kazuhiko
Published: July 2002

For the study of state selected ion–molecule reactions using synchrotron radiation, an apparatus incorporating a dodecapole collision chamber has been constructed. Its performance has been examined utilizing the Ne+ ions produced by photoionization of Ne at the 2P3/2 threshold. It has been confirmed that both the transmission of the primary ions and the collection efficiency for the secondary ions remain unchanged when the ion kinetic energy is varied over a wide range of interest. The ion–molecule reaction Ne++OCS has been studied using this apparatus, selecting the spin-orbit states of the reactant ion by the time-of-flight coincidence technique.
2.2-m Rowland-circle grazing-incidence monochromator
Authors: Watanabe M. , Sakai K. , Nakamura E. , Yamazaki J. , Matsudo O. , Fukui K. , Ishiguro E. , Mitani S.
Published: July 2002

A 2.2-m Rowland-circle grazing-incidence monochromator with a fixed entrance slit and a fixed grating, has been installed on the beamline BL8B1 at UVSOR, in which the axis of the monochromatized beam is unchanged for the wavelength scanning. Two gratings are interchangeable in vacuum. The designed useful region is 20–200 Å with a 2400/mm grating, but the actual useful region was 50–200 Å. At 100 Å, 1010/s output photons were obtained with a resolution of 10−3. The horizontal width of the beam at the sample position was about 5 mm, while the vertical width was between 0.5 and 3 mm.
High-resolution Czerny–Turner monochromator for application to undulators
Authors: Tondello G. , Zanini F.
Published: July 2002

A monochromator based on a Czerny–Turner configuration working in grazing incidence and using only plane or spherical surfaces is well suited for undulators. An advantage of this configuration is to have both entrance and exit slits fixed and to require only a rotation of the plane grating. The case treated, based on an undulator for ELETTRA, the ring planned for Trieste, working at a grazing angle of 3°, with a grating of 1200 lines/mm, shows resolutions up to 10 000 at 600 eV for 10-μm-wide slits; the spectral range is from 400 eV to 1 keV. Other values for grazing angles are possible in the same instrument, widening the spectral range.
200-MeV LINAC—injector of storage ring for HESYRL
Authors: Pei Y. J. , Wang D. F. , He D. H.
Published: July 2002

The 200-MeV electron linac at the Hefei National Synchrotron Radiation Laboratory (HESYRL) is described. It is not only an injector of the 800-MeV storage ring, but an electron accelerator used for nuclear physics experiments and some other applications as well. The main design parameters and measuring results of the LINAC are given. The linac is a travelling wave structure, operating at a frequency of 2856 MHz, constant impedance, in a 2/3π mode. Its total length is about 35 m. Five klystrons are used as rf power; each klystron will provide 15 MW. In November 1987, the machine was successfully commissioned and typical operating parameters are 220 MeV, and 50 mA with an energy spread of ±0.8%.
Observation of intracell avalanche amplification in charge-coupled devices (abstract)
Authors: Fedotov M. G. , Kuper E. A. , Panchenko V. E.
Published: July 2002

At present, in various imager devices, the phenomenon of avalanche amplification—in uniform MIS (metal-insulator-semiconductor) structures is extensively used. For these structures, the current is, as a rule, the output signal. The authors of this paper have previously made the supposition that an alternative approach can be feasible—to achieve the regime of avalanche amplification in MIS imagers dealing with electric charges, and in particular, to obtain intracell amplification in commercial charge-coupled devices (CCD) when detecting x-ray images. In this paper experiments in which the intracell avalanche amplification is obtained in a 1000-element commercial linear CCD imager are described. During direct detection of x rays and red optical radiation, no avalanche amplification takes place because of the peculiarities of the structure of the active regions of this device. However, in the blue spectral range there has been revealed, at room temperature, a stable uniform amplification of the order of 10, limited mainly by the multiplication of thermogenerated charges and, possibly, by a tunneling breakdown. At the temperature of liquid nitrogen, inner amplification factor roughly equal to 105–106 has been obtained in the active regions of the device and, hence, the observation of the signals from individual photogenerated carriers has become possible. The corresponding total amplification factor (of the order of 104) allows one to detect light fluxes in the blue spectral range, which are totally disguised by noise if the amplification is absent.

Such a high amplification factor in the optical region has made it possible to demonstrate the effectiveness of the avalanche regime at the temperature of liquid nitrogen when detecting x radiation, using its conversion to light on the luminophor. The amplification factor achieved is about 102. In conclusion, some peculiarities of the avalanche break-down of nonuniform MIS structures and, in particular, of in the active regions of the CCD under consideration have been analyzed. The structures, oriented to an effective avalanche amplification when detecting x-ray and optical radiation are discussed as well.
Four-circle diffractometry for surfaces (invited)
Authors: Robinson I. K.
Published: July 2002

Angle calculations for the four-circle diffractometer are usually made by the method of Busing and Levy [Acta Cryst. 22, 457 (1967)]. Here an additional mode of operation is described that allows control of the incident and exit angles at the sample surface. Experiences with this mode for surface crystallographic data collection are described.
A scanning tunneling microscope with a wide sampling range
Authors: Hipps K. W. , Fried Glenn , Fried Dale
Published: July 2002

Construction of a simple scanning tunneling microscope (STM) is described. This STM is suitable for atmospheric, controlled atmosphere, and high vacuum (but not UHV) work. This STM is especially well suited for determining surface topography on the 0.1 nm scale when images must be obtained over a wide sampling region (mm). Interchangeable piezo heads allow the STM to be used either for atomic resolution or for large (800×800 nm) area scans. Atomic resolution pictures of the graphite surface demonstrate that this design is suitable for use with structures smaller than 0.1 nm. An image of a thin film of Au, deposited on pyrex, is also presented.
Development of a fast scanning frequency meter for the K
a band
Authors: Otsuka Michio , Shimizu Masashi
Published: July 2002

A fast scanning frequency meter was developed for frequency measurements of microwaves generated in the pulsed gyrotron. The heterodyne technique, using a voltage controlled oscillator (VCO) as the local oscillator, was utilized in order to shorten the measuring time. The frequency coverage of this meter is in the range of 26.5–31.2 GHz. The minimum measuring time is 100 μs(10 kHz) with a measurement error of less than ±23 MHz.
X-windows-based user interface for data acquisition and display
Authors: Fredian T. W. , Stillerman J. A.
Published: July 2002

A Macintosh-like user interface for the MDS-Plus data acquisition system is being implemented using the DECwindows MIT/X interface. MDS-Plus is a model driven general purpose data acquisition system being developed collaboratively by the CMOD group at MIT Plasma Fusion Center, the RFX group at IGI-Padua, and the ZTH group at Los Alamos National Laboratory. The model is a hierarchical description of an experiment, including all of the tasks to be performed and the results of having performed them. The inherent complexity of this experimental model requires the users to specify fairly complicated descriptions of what they want the system to do. A ‘‘Point and Click’’ interface simplifies this by presenting to the user a coherent set of choices which are valid in the current context. We are implementing a set of tools for data acquisition and data analysis which use DECwindows to this end. They include a data displayer (Scope Replacement), an experiment model editor (Tree Editor), a timing system, and a waveform editor. These tools provide an easy to use interface to the MDS-Plus data acquisition system.
In situ density and temperature measurements of vibrationally excited hydrogen molecules in ion source plasmas
Authors: Stutzin G. C. , Young A. T. , Döbele H. F. , Schlachter A. S. , Leung K. N. , Kunkel W. B.
Published: July 2002

The role of highly vibrationally excited hydrogen molecules has been postulated to be of great importance in H− ion sources. However the the difficulty of making in situ measurements has led to a paucity of direct determinations of these species within the plasmas of these sources. Recently, vacuum-ultraviolet (VUV) laser absorption spectroscopy has been used to measure the H2 rovibrational populations up to v″=5 and J″=8 in a medium-power hydrogen plasma. This work extends those measurements to v″=8 and to J″=13. The populations of the vibrational levels still appear to be almost Boltzmann. The theoretically predicted plateau is not observed up to the detection limit. The dependence of several vibrational levels on discharge current and filling pressure is shown.
Analysis of microchannel plate response in relation to pulsed laser time-of-flight photoemission spectroscopy
Authors: Anacker D. C. , Erskine J. L.
Published: July 2002

Design considerations, construction details, performance evaluation, and experimental tests of a time-of-flight photoelectron spectrometer utilizing a pulsed laser source are presented. The new spectrometer has been designed for heat transport and carrier dynamics studies of solid surfaces using femtosecond laser excitation. Special attention is directed to analysis of the dynamic range and linearity of the detector in order to obtain quantitative information from measured electron yields.
A piezoelectric-driven micropositioner with magnetic locking mechanism
Authors: Wu Sijia , Ng K.-W.
Published: July 2002

A micropositioner has been constructed with a piezoelectric tube and walking pads locked by magnets. These magnets were arranged in a special geometry to prevent slipping and trapping. The magnetic force created was large enough to operate the walker in any orientation. Tolerance of surface roughness was much higher than other similar types of micropositioners.
Electrocapillary parametric forcing of interfacial waves
Authors: Smart Ú. , Earnshaw J. C.
Published: July 2002

Standing waves have been parametrically excited on an interface between mercury and aqueous salt solutions by periodic electrical polarization of the interface. The waves obey the known dispersion relation for capillary-gravity waves. The variation of the interfacial tension with the bias voltage across the interface has been measured, and displays the expected quadratic dependence. Various aspects of the excitation mechanism are shown to be in accord with theoretical expectation.
Design and performance of a cylindrical reflection mirror analyzer for low energy ion scattering studies
Authors: Ku Yi-sha , Su Ching-shen
Published: July 2002

A compact cylindrical reflection mirror analyzer for low energy ion scattering spectrometer has been designed and constructed to be used in a vacuum thin film deposition system for in situ analysis of fresh-deposited films. The design of the energy analyzer is similar to that of the ellipsoidal mirror analyzer, consisting of an electrostatic reflection mirror of the cylindrical sector type with a mean radius of curvature of 4.0 cm and a sector angle of 70°, a high pass energy filter, and two slits. The performance of this analyzer has been tested by the scattering of Li+ ions with energies of 606, 707, and 807 eV, respectively, on Al, Ti, Co, Cu, and stainless steel samples at angles from 125° to 155°. An average energy resolution of (1)/(56) has been obtained at an energy band of 10 eV and primary ion energy of 800 eV. Better resolution is expected with a narrower energy band and a higher primary energy. In situ monitoring of thin Cu film deposited on Si substrate in Ar+ ion sputtering process has been done to show the feasibility of this system.
Output switch for a megavolt electron beam generator
Authors: Mathew J. , Golden J.
Published: July 2002

An improved gas output switch for a 12 Ω, 1.2 MV electron beam generator has been developed. The previous design used a cast epoxy switch housing with an embedded field shaper electrode. The original switch design was difficult to fabricate without defects in the casting, and several replacements failed during operation. The new design employs machined acrylic pieces instead of cast epoxy, and a glycol cavity surrounds the field shaper. Electric fields around the field shaper are therefore considerably lower. The present switch has demonstrated greater reliability and superior performance.
Pulsed relativistic electron beam of 3 ns produced by a velvet cathode
Authors: Zhang Qi , Xing Da , Ueda Ken-ichi , Takuma Hiroshi
Published: July 2002

A pulsed relativistic electron beam with a 3 ns duration was produced using Febetron 706 and electron beam tube with velvet cathode. Cathode current density of 7 kA/cm2 and lifetime of longer than 1000 shots were obtained.
Light amplification device using organic electroluminescent diode coupled with photoresponsive organic pigment film
Authors: Katsume Tadashi , Hiramoto Masahiro , Yokoyama Masaaki
Published: July 2002

An all-organic light amplification device was designed using organic electroluminescent diode coupled with photoresponsive organic perylene pigment film as an electron photoinjecting layer. Amplification gain of photon conversion from red to red reached 25-folds with the assistance of the large photocurrent multiplication in a perylene film. Moreover, optical switching behavior caused by the feedback of output light to the photoresponsive layer was observed. Since the spatial pattern of light was conserved, the present device has the potential to grow into new optoelectronic devices for optical image processing.
Diurnal deviation of the orbit circumference due to building distortion
Authors: Katsura T. , Kamiya Y. , Nakamura N. , Nakamura H. , Fujita Y.
Published: July 2002

Beam position stability was found to be largely affected by the distortion of the storage ring building, especially when the beam emittance was lowered. Building distortion in the horizontal direction was noticed as the diurnal deviation of the orbit circumference. The deviation was measured by reading the amount of rf frequency variation necessary to recover the horizontal central orbit. The deviation of the orbit circumference was interpreted to be induced from the ring floor expansion. Such diurnal expansion of the ring floor was evaluated by using a model simulation that dealt with the distortion of the ring building under thermal stress. To reduce such thermal stress, the rooftop of the building was insulated. The deviation of the ring circumference measured after insulation was reduced to one-half of that measured before. The simulation also gave the same amount of deviations as measured before and after insulation.
Diagnostic phosphors for photon beams at the ALS and APS
Authors: Shu Deming , Warwick Tony , Johnson Erik D.
Published: July 2002

Some tests have been made of phosphors for photon beam diagnosis. Plasma-sprayed coatings were checked for damage and decay during a period of several ampere hours of irradiation from the x-ray ring at the National Synchrotron Light Source. Surface temperatures were measured and extrapolated to give an indication of the temperatures expected in more powerful photon beams. Based on our findings we have chosen plasma-sprayed coatings of europium-doped yttrium oxide as the best candidate for use on masks and flags in ‘‘white’’ photon beams of the new facilities.
Study of spherical aberrations for the design of ESRF beam lines
Authors: Förstner G. , Krisch M. , Susini J.
Published: July 2002

The calculation of the spherical aberration, which has been given only in the case of a point source up to now, is extended to the case of source of finite size. It is shown that the real size of the image can be well described by a convolution of the ideal size of the image and the aberrations involved. The expression for an optimum magnification is developed yielding the smallest possible image size for a given optical system in the case of a cylindrical mirror. Calculations are presented for different ESRF sources and the results are compared to simulations performed by the ray-tracing code SHADOW.
Synchrotron radiation of electrons in the edge magnetic fields of storage rings
Authors: Bashmakov Yu. A.
Published: July 2002

The radiation of electrons in magnets with linear gaps is investigated. Typical spatial distribution of the magnetic field is discussed. The characteristic parametrization of this distribution is given. The law of the electron motion in such a field and the form of the electromagnetic field pulses arising at this motion is considered. The domain of the radiation generation is investigated. It is shown that in inhomogeneous edge field the radiation pulses are formed in the region with appreciable longitudinal dimension. Results of the numerical calculation of the angular and spectral distributions are given and the comparison with experimental data is carried out. Due to their higher intensity in the more longer wavelength spectral region in comparison with the standard synchrotron radiation from bending magnet this radiation can be useful in solving a number of applied problems.
The U5.0 Undulator for the Advanced Light Source
Authors: Hoyer E. , Chin J. , Halbach K. , Hassenzahl W. V. , Humphries D. , Kincaid B. , Lancaster H. , Plate D.
Published: July 2002

The U5.0 Undulator, an 89 period, 5 cm period length, 4.6 m long insertion device has been designed, is being fabricated, and is scheduled for completion in early 1992. This undulator will be the first high brightness source, in the 50 to 1,500 eV range, for the Advanced Light Source at the Lawrence Berkeley Laboratory. A hybrid magnetic configuration using Nd–Fe–B permanent magnet material and vanadium permendur poles has been selected to achieve the field quality needed to meet performance requirements. The magnetic structure is modular with each half consisting of five assembly sections, which provide the periodic structure, and end structures, for entrance and exit correction, mounted on a steel backing beam. Each assembly section consists of 35 half-period pole assemblies bolted to a mount. The required 0.837 T effective peak field at a 1.4 cm gap has been verified with model measurements. Vertical field integral correction is accomplished with the end structures, each having an arrangement of permanent magnet rotors which will be adjusted to minimize electron beam missteering over the undulator operating field range. To reduce the effect of environmental fields, the steel backing beams are connected through parallel, low-reluctance, Ni–Fe hinges. The magnetic structure is connected through four rollernuts to the drive system that provides gap adjustment with an arrangement of roller screws, chain drives, a gear reduction unit, and a stepper motor driven by a closed loop control system. Magnetic structure and drive system support are from a 2.4 m high structure which includes a support base with four vertical supports. The vacuum chamber design is a two-piece machined and welded 5083-H321 aluminum construction of 5.1 m length. Pumping is with a combination of ion, titanium sublimation pump and nonevaporable getter pumps. Magnetic design, subsystem design, and fabrication progress are presented.
A shear sensitive monomer-polymer liquid crystal system for wind tunnel applications
Authors: Parmar D. S. , Singh Jag J. , Eftekhari Abe
Published: July 2002

Characteristics of a liquid crystal system, comprised of a shear sensitive cholesteric monomer liquid crystal thin-film coated on a liquid crystal polymer substrate, are described. The system provides stable Grandjean texture, a desirable feature for shear stress measurements using selective reflection from the monomer liquid crystal helix structure. Impingement of gas or air flow on the monomer liquid crystal free surface changes the wavelength of the selective reflection for an incident white light from red towards blue with increase in the rate of gas flow. The contrast of the selectively reflected light improves considerably by providing a thin (∼5 μm) black coating at the monomer-polymer interface. The coating thickness is such that the steric interactions are still sufficiently strong to maintain Grandjean texture. For a small angle of incidence (∼15°) of a monochromatic light, the measurement of the reflected light intensity normal to the monomer-polymer liquid crystal interface enables us to determine the wavelength (λs) for selective reflection as a function of the gas flow differential pressure (Δp) applied in the plane of the interface. In the range of the Δp (0–100 mmHg) used in the present studies, the variation of λs with Δp is linear with a slope ∼2 nm/mmHg. Furthermore, the shear stress effects are reversible unlike for monomer liquid crystal−metal systems used so far for flow visualization on wind-tunnel model surfaces. Thus the present system offers a suitable method for direct on-line measurement of shear stress field from measurement of λs for an incident white light.
The present status of the Synchrotron Radiation Laboratory of the Institute for Solid State Physics of The University of Tokyo
Authors: Ishii T.
Published: July 2002

The present status of the Synchrotron Radiation Laboratory of the Institute for Solid-State Physics of The University of Tokyo is described. Explanation is made mostly for the beam lines of SOR-RING as well as the new beam lines built in the Photon Factory ring. A short history of the laboratory is also given.
Plans for the Swiss Light Source (SLS) at PSI
Authors: Abela R. , Joho W. , Milton S. , Rivkin L.
Published: July 2002

The feasibility of constructing an intense VUV to x-ray synchrotron light Kurchatov Institute. A status report is given on the SIBERIA. (AIP) source at the Paul Scherrer Institute (PSI) is being investigated. Under study is a machine design with very flexible parameters and which is capable of providing very low emittance and short pulse lengths.
Inelastic electron tunneling spectrometer for complete calibrated measurements of any two or four terminal junctions
Authors: Gauvin Serge , Leblanc Roger M.
Published: July 2002

The conventional tunneling spectrometer gives the uncalibrated second derivative d2V/dI2 versus applied voltage (V) of the junction current-voltage curve (I-V). However, the calibrated second derivative d2I/dV2 is more useful for accurate comparison with theory and can be applied to negative resistance devices. We report here a single electronic instrument for calibrated measurements of all relevant tunneling junction parameters, i.e., dynamic conductance (G), dynamic capacitance (C), current-voltage curve, and its first and second calibrated derivatives. Moreover, it can measure the derivative of the dynamic capacitance (dC/dV) versus applied potential, which is useful for various types of semiconductor devices. This design is versatile enough to find many laboratory applications where current-voltage curves are of interest. The circuit, based on a simple design, is accurate to 1% and allows spectral acquisition in about 15 min.
FEL sources: Present status and future prospects (invited)
Authors: Poole M. W.
Published: July 2002

FEL development has now reached the stage where user facilities are being planned and a number of these are already in operation or very near to completion. All such facilities so far provide sources of infrared radiation and the next step will be to extend this to the ultraviolet and beyond. An elementary introduction to the operating principles and main characteristics of FELs is given, with the emphasis on practical schemes that can be envisaged. Existing FEL sources will be reviewed and progress in the development to shorter operating wavelengths discussed.
Extended x-ray absorption fine structure studies of structure and short-range order in C-Er bilayer and Er/C multilayer films
Authors: Player M. A. , Marr G. V. , Gu E. , Savaloni H. , Munro I. H.
Published: July 2002

Glancing angle extended x-ray absorption fine structure (EXAFS) has been applied to study structure, diffusion, and short-range order in ultrahigh vacuum evaporated C-Er bilayer and Er/C multilayer films, which provide a model for the influence of microstructure in x-ray multilayer reflectors. A lack of crystallinity in the C-Er bilayers and Er/C multilayers is indicated by x-ray diffraction. EXAFS spectra of C-Er bilayers and Er/C multilayers are substantially different from that of a 6000-Å erbium film, which shows local structure similar to pure erbium. For bilayers and multilayers a local ErC2-like environment has been found, even though only a small concentration of carbon is thought to have diffused into erbium layers. It is possible that carbon diffusion and Er—C bond formation prevent the crystallization of locally ordered hcp erbium metal clusters. That low Z atoms can diffuse into the high Z metal layers and change their structure appears to be a common feature for x-ray multilayer mirrors.
Scanning tunneling microscope as a high sensitivity radiation detector
Authors: Hasan Z. , Andsager D. , Saltz D. , Cartwright K. , Nayfeh M. H.
Published: July 2002

We present measurements on the effect of laser radiation impinging on the tunneling gap of a scanning tunneling microscope, causing a modulation of the tunneling gap. We have measured variations in the tunneling current equivalent to microscopic expansions that are as small as 0.03 Å, of the order of vibration of individual molecules. The process has also been used for recording the absorption spectrum of an alexandrite crystal.
Development of a sodium z-pinch load for use on the Saturn accelerator
Authors: Porter J. L. , Spielman R. B. , Vargas M. F. , Matzen M. K.
Published: July 2002

A reliable sodium wire-array z-pinch load has been developed for use on the Saturn accelerator. This load routinely produces implosions with ≥200 GW of power in the heliumlike sodium 1s2–1s2p 1P1 line at 11 Å. Our best shots have used a 12.5-mm-diam, 20-mm-long annular array of 16 75-μm-diam pure sodium wires. This load will allow us to test predictions of gain in the sodium/neon resonant photoexcitation x-ray laser system.
A fully automated scanning ratio calorimeter for use in adsorption studies
Authors: Lysek Mark , Day Peter , LaMadrid Marissa , Goodstein David
Published: July 2002

This article describes a scanning ratio calorimeter that has been developed for studying multilayer adsorbed films. The scanning technique presented is able to accumulate highly precise data much more quickly than other calorimetric techniques. The rms noise in the total heat capacity of the sample cell is 0.02% at 70 K and 0.04% at 120 K for scan rates of 2 K/h. Sources of error in the heat capacity measurement are analyzed in detail. The calorimeter is completely automated and can be operated continuously using a personal computer.
A wide wavelength range spectrometer (1150–8000 Å) for the RFX reversed field pinch experiment
Authors: Carraro L. , Puiatti M. E. , Scarin P. , Valisa M.
Published: July 2002

This paper describes the vacuum Czerny–Turner spectrometer with a 1.33 m focal length installed on the RFX fusion experiment. The optics are coated with MgF2 and the image intensifier, protected by a vacuum sealed MgF2 window, features a dual photocathode system, CsTe on one half and S20 on the other; thus the instrument covers efficiently the wide spectral range from the MgF2 limit to the near infrared. Sensitivity at short wavelengths is limited by the reflectance of mirrors and the transmittance of the MgF2 window. The detector is completed by a fast optical multichannel analyzer whose 1024 photodiodes can be read out in a time of 250 μs. The instrument can also be operated in a duochromator mode by deflecting the diffracted beam onto a second detector system, where two photomultipliers are applied to two exit slits, one fixed and the other remotely movable in such a way that the intensity ratios of two lines can be monitored for diagnostic purposes. Some examples of obtained spectra illustrating the instrument performance and comprising first results from the RFX plasma are presented.
Multiple-angle, time-resolved spectroscopy of scattered light from laser-produced plasmas (abstract)
Authors: Bradley K. S. , Batha S. H. , Drake R. P. , Montgomery D. S.
Published: July 2002

A new instrument at the NOVA laser facility has been developed to measure absolute levels of scattered light at up to seven angles simultaneously from laser-produced plasmas. The multiple-angle time-resolving spectrometer (MATRS) both temporally (t=120 ps) and spectrally (λ=1 Å) resolves light scattered from the plasma at or near the laser wavelength. MATRS has been used to study parametric instabilities in plasmas pertinent to laser fusion. Measurement of the angular dependence of the scattered light from these processes will provide a clear test of convective theory. This work was performed under the auspices of the U. S. Department of Energy by the Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48.
Spatial coherence diagnostic for laboratory x-ray lasers (abstract)
Authors: Trebes James E. , Nugent Keith , Mrowka Stan , Barbee Troy
Published: July 2002

A spatial coherence diagnostic for measuring the spatial coherence of laboratory x-ray lasers has been developed. The x-ray laser beam illuminates a uniformly redundant array of slits, producing a partially coherent diffraction pattern which can be analyzed to yield the complex coherence factor for the x-ray laser beam from a single x-ray laser pulse. Measurements using x-ray lasers at LLNL will be presented and discussed in detail. Results from experiments conducted in collaboration with the Rutherford x-ray laser consortium to improve the spatial coherence of x-ray lasers will also be discussed. A definition of a highly spatially coherent x-ray laser based on simple physical arguments will be given. This work was performed under the auspices of the U. S. Department of Energy by Lawrence Livermore National Laboratory under contract No. W-7405-ENG-48.
Diagnostics for the study of helium exhaust in DIII-D (abstract)
Authors: Wade M. , Finkenthal D. , Hillis D. , Klepper C. , West W. P. , Seraydarian R. , Gohil P. , Burrell K. H.
Published: July 2002

Recent studies have shown that fairly weak dilution of the D-T fuel mixture by the thermal alpha particle population may quench ignition in ITER. The alpha particle exhaust issue is not well understood experimentally, especially in H mode. On DIII-D, a large set of diagnostics for studying alpha particle thermalization and exhaust are being developed. Helium density profiles in the core plasma are inferred from data obtained by the existing DIII-D charge-exchange recombination spectroscopy system which has 32 chords that span the plasma cross section and has been absolutely calibrated so that absolute emission intensities can be inferred from the measured data. Relative chord-to-chord intensity calibrations have been made by injecting neutral beams into neutral gas with no magnetic fields. A multifiber system viewing the divertor floor has been absolutely calibrated to measure the hydrogen and helium recycling profile across the divertor floor. Other diagnostics in development include a Penning discharge gauge to measure helium partial pressure under the divertor baffle in DIII-D. Preliminary measurements from these diagnostics will be presented. This work supported by U.S. Department of Energy (DOE) Contract DE-AC03-89ER51114 and by appointment to the DOE Fusion Energy Postdoctoral Research Program administered by Oak Ridge Associated Universities.
General purpose high-resolution x-ray crystal spectrometer (abstract)
Authors: Barnsley R. , Abbey A. , Dunn J. , Lea S. , Peacock N. J.
Published: July 2002

This spectrometer was designed to give access to a wide range of Bragg angles and crystal focal lengths while using the Rowland circle radius as a free parameter. Stability is achieved using a rigid beam or ‘‘Rowland chord,’’ which provides a reference axis for all the critical alignments, the chord length being variable between about 0.2 and 5 m. Crystals of size up to 100×30×0.5 mm can be accommodated in a novel four-pillar jig, (λ/δλ) is typically 104 in the wavelength range from 0.1 to 1.3 nm, depending on the crystal. Various detectors have been used, including photographic film, multiwire gas proportional counters and large area CCD detectors, the latter having a 2-D spatial resolution of 22.5 μm (1152×1242 pixels, 26×28 mm2), a quantum efficiency greater than 20% between 0.7 and 12 keV and an energy resolution of about 150 eV. By sacrificing energy resolution, a one-dimensional mode with on-chip binning allows ∼ms time resolution of spectra from high flux sources such as tokamaks and synchrotrons. Results presented include photographic spectra from tokamak, beam foil and laser produced sources, and CCD spectra from tokamak and standard electron-beam excitation laboratory sources.