bluuebunny/crossref_metadata_2025 huggingface dataset:
The Glasgow 10 m prototype laser interferometric gravitational wave detector
Authors: Robertson D. I. , Morrison E. , Hough J. , Killbourn S. , Meers B. J. , Newton G. P. , Robertson N. A. , Strain K. A. , Ward H.
Published: July 2002

We present a description of the prototype interferometric gravitational wave detector at Glasgow. The detector, which has been under development for a number of years, consists of two perpendicular 10-m-long high finesse Fabry–Perot cavities formed between test masses hung as pendulums and is illuminated with a cw argon ion laser. The differential displacement sensitivity of the detector is ∼7×10−19 m/√Hz from 500 Hz → 3 kHz and is close to being limited by photoelectron shot noise in the detected photocurrent.
Superconductor imaging surface magnetometry
Authors: van Hulsteyn David B. , Petschek Albert G. , Flynn Edward R. , Overton William C.
Published: July 2002

The presence of superconducting surfaces in the vicinity of current sources may be interpreted in terms of image theory. This concept has both experimental and theoretical practicality. Experimentally, sensing coils for magnetic detection, when placed near such surfaces, perform in a gradiometric fashion. In order to explain this effect explicitly, a theoretical treatment of the magnetic fields in the presence of superconducting surfaces and coils is presented. Expressions are derived for planar and spherical geometries that approximate practical experimental situations. These expressions may be used to predict the expected gradiometric response of a coil as a function of the positions of the source and coil relative to the surface.
Optical luminescence spectroscopy with the scanning soft x-ray microscope at HASYLAB/DESY
Authors: Zhang H. , Föhlisch A. , Kunz C. , Moewes A. , Pretorius M. , Ranck A. , Sievers H. , Storjohann I. , Wedemeier V. , Voss J.
Published: July 2002

The first attempt to combine luminescence spectroscopy with scanning soft x-ray microscopy has been realized in our experiment. A new imaging luminescence spectrometer with a Schwarzschild objective was designed and built with a spectral resolution of 1.3 nm in the energy range of 1.6–6.5 eV for this purpose. Some luminescent ceramics have been investigated by using this spectrometer. A high contrast in luminescence micrographs is achieved due to the confocal arrangement of the Schwarzschild system and the microscope. The spectral and microstructural properties of these ceramics could be determined by means of luminescence microspectroscopy and spectromicroscopy.
Design and construction of a versatile scanning near-field optical microscope for fluorescence imaging of single molecules
Authors: Tarrach G. , Bopp M. A. , Zeisel D. , Meixner A. J.
Published: July 2002

A scanning near-field optical microscope (SNOM) for fluorescence imaging of single molecules requires efficient optical signal detection and background rejection combined with long-term stability and high spatial resolution. These requirements are dictated by the extremely low fluorescence signal of an individual dye molecule. We have built a SNOM that meets these requirements by combining a rigid and versatile near-field optical scanner with confocal detection optics. The relevant design parameters are discussed in detail. The near-field part of the microscope is based on a commercially available fiber aligner for coarse approaching the sample with respect to the tip. It also permits us to select a specific sample area in a range of 3 mm×3 mm with a nominal resolution of 10 nm. The tip–sample separation is probed by shear-force detection using a fiber-optical interferometer, which gives an excellent signal-to-noise ratio. The high versatility of this SNOM is demonstrated with measurements of a transparent dielectric grating and by imaging the fluorescence from individual rhodamine-6G molecules with a spatial resolution of ≊160 nm.
Nanoguitar: Oscillating string as force sensor
Authors: Stalder A. , Dürig U.
Published: July 2002

A force sensor is presented that makes use of an oscillating string. In a conventional scanning force microscopy setup comprising a tip and a sample consisting of a flexible cantilever beam, a string is attached to the free end of the beam along its deflection axis. Changes of the tip–sample interaction force modify the string tension and hence the resonance frequency of transverse oscillations. These oscillations can have amplitudes of the order of microns without causing noticeable wavering of the cantilever beam. This kind of sensor is particularly suitable for applications that require a stiff sensor. A prototype was built using a carbon fiber 5 μm in diameter and 4 mm in length, oscillating at 4 kHz. A force resolution of 2.5 nN was achieved in vacuum for a response time of 1 ms and a sensor stiffness of 160 N/m. For a conventional beam deflection sensor of equal stiffness this corresponds to a deflection sensitivity of 0.015 nm.
A high current H− radio frequency volume ion source
Authors: Saadatmand K. , Arbique G. , Hebert J. , Valicenti R. , Leung K. N.
Published: July 2002

The superconducting super collider rf-driven volume ion source routinely provided 35 kV, ≳30 mA H− beams with normalized rms emittances (εn-rms) <0.1 π mm mrad. The source was typically operated with a 100 μs beam pulse width at a 10 Hz repetition rate. To enhance H− output, the ion source was modified to accommodate a set of cesium dispensers so that a trace amount of cesium could be introduced into the plasma grid collar. A plasma grid heater element controls the temperature of the cesiated surfaces and the rate of cesium dispensation. Beam currents in excess of 100 mA and electron to H− current ratios close to one have been observed. Emittance measurements at 70 mA suggest a 20% increase over uncesiated emittance values. Improvements in the beam emittance are fully expected when the extraction optics are optimized. This enhanced, very reliable source is a strong candidate for high current H− accelerators.
Incorporation mechanism of N, Al, and B impurities in chemical vapor deposition of SiC
Authors: Kimoto Tsunenobu , Itoh Akira , Matsunami Hiroyuki
Published: July 2002

In situ doping characteristics of N, Al, and B in step-controlled epitaxy of SiC have been investigated. Clear C/Si ratio dependence was observed in the growth on (0001)Si faces. Doping efficiency of N decreased and those of Al and B increased under the C-rich condition, which agrees with a model proposed as ‘‘site-competition epitaxy.’’ However, doping efficiencies were almost independent of the C/Si ratio on (0001̄)C faces. Based on the results, the incorporation mechanism is discussed.
Intensity-dependent energy and line shape variation of donor–acceptor-pair bands in ZnSe:N at different compensation levels
Authors: Bäume P. , Gutowski J. , Wiesmann D. , Heitz R. , Hoffmann A. , Kurtz E. , Hommel D. , Landwehr G.
Published: July 2002

We show that energy position and line shape of donor–acceptor-pair luminescence bands in ZnSe:N/GaAs epilayers depend very sensitively on excitation density and compensation. A continuous development from structureless red-shifted broad to well structured donor–acceptor-pair (DAP) bands is observed for increasing excitation density. The red shift is explained by the fluctuating potential affecting the bands and impurity levels and is caused by random distribution of charged impurities in highly compensated samples. The shift is reduced when these charge fluctuations are diminished due to an increasing number of impurities being neutralized via light-induced carrier excitation. These effects have not been taken into account in previous work concerning doped II-VI materials; however, they have to be considered when evaluating the frequently used hypothesis of a deep donor in ZnSe:N as an explanation of low-energy broadband DAP emission. The influence of band fluctuations on the behavior of the DAP luminescence and excitation spectra is qualitatively discussed.
Adaptive silicon monochromators for high power insertion devices: Tests at CHESS, ESRF, and HASYLAB (abstract)
Authors: Quintana J. P. , Hart M. , Bilderback D. , Henderson C. , Setterston T. , White J. , Hausermann D. , Krumerey M. , Schulte-Schrepping H.
Published: July 2002

X-ray wigglers which produce tens of kilowatts of photon power within the white beam will soon become available as third-generation sources of synchrotron radiation. Insertion devices that produce several kilowatts already exist and we have used those at CHESS, ESRF, and HASYLAB to test and develop an adaptive 111 silicon water jet-cooled monochromator at up to 2 kW total incident beam power. This development of earlier work at the Brookhaven National Synchrotron Light Source uses the pressure in the water coolant to provide active compensation of the strain field in the thermal footprint, nulling its effect to within residual variations in the Bragg angle of only a few seconds of arc. The design is robust, vacuum compatible, and uses no moving mechanical parts.
One-dimensional focusing of synchrotron x-ray radiation with curved arrays of reflectors
Authors: Rode A. V. , Peele A. G. , Nugent K. A. , Johnson D. E. , Siddons D. P.
Published: July 2002

We present results of the experimental tests of various arrays of reflectors acting as x-ray optical elements. Planar reflectors were arranged in a vertical stack and aligned with a common center of curvature to create a focusing array with cylindrical curvature. The experiments were carried out using x-ray radiation in the spectral range 3.5–7 keV produced at beam line X-27C of the National Synchrotron Light Source at Brookhaven National Laboratory. The focal distribution had a width of 8 mm and a maximum intensity gain of 7.3, as measured with a 0.4 mm diameter pinhole. An x-ray beam splitter consisting of arrays of reflectors has also been designed and tested. The separation of x-ray beams is 40 mrad, and the intensity of each of the two beams is about 0.32 of the original x-ray beam.
Pendellösung suppression in the diffraction pattern of a set of thin perfect crystals in a Bonse–Hart camera
Authors: Sánchez del Río M. , Ferrero C. , Freund A. K.
Published: July 2002

In a Bonse–Hart camera, a set of two or more grooved (channel cut) perfect crystals are used to provide a very high angular resolution experiment. The resulting multireflection profiles can be calculated in a first approximation by the dynamical theory of diffraction, where usually only coherent scattering is considered. In addition, there is experimental evidence of incoherent Compton scattering (ICS) and thermal diffuse scattering (TDS) contributions. Such contributions are especially important when performing small angle scattering experiments where intensities in an interval of ten orders of magnitude are often recorded. We propose and analyze here the use of thin (a few micrometers) crystals for a Bonse–Hart camera in order to decrease the TDS and ICS components, thus to increase the performances of the device. However, using thin crystals causes the occurrence of interference (Pendellösung) fringes which degrades the instrument resolution. We study in this paper the possible elimination of Pendellösung fringes by angularly offsetting one or more crystals with respect to the others. Optimizing the offset value, the Pendellösung oscillations of the crystals interfere destructively, then significantly reducing their contribution to the total resolution function.
Reflectivities of chemical vapor deposition-diamond mirrors in the vacuum ultraviolet region
Authors: Sasano Tomohiko , Ishiguro Eiji , Mitani Shichiro , Tomimori Hiroshi
Published: July 2002

Diamond mirrors have been fabricated by depositing a diamond thin film on a Si3N4 substrate by means of chemical vapor deposition (CVD). The reflectivities of the CVD diamond mirrors in the vacuum ultraviolet region from 30 to 2000 Å are reported and compared with those of SiC and gold-coated SiC mirrors measured in this work. The optical constants of the CVD diamond film are obtained from the reflectivities measured and also compared with those of a bulk crystal reported in the literature.
Parabolic focusing pyrolytic graphite x-ray monochromator (abstract)a)
Authors: Dolbnya I. P. , Zolotarev K. V. , Sheromov M. A. , Antonov A. A. , Grigoryeva I. G.
Published: July 2002

The results of the experimental testing of the parabolic focusing pyrolytic graphite x-ray monochromator (mono) on the wiggler (2 T) synchrotron radiation (SR) beamline of the VEPP-3 storage ring are presented. The monochromatization and the focusing of x radiation in both vertical and horizontal directions are provided by the optical properties of the parabolic surface of revolution of the properly shaped pyrolytic graphite crystal attached to the parabolic-machined brass support. A single crystal is a half of the parabolic surface 160 mm long and ∼19 mm minimal focus length. The sagittal radii are changed from 10 to 30 mm. The available photon energy range is 7–20 keV on the first harmonic of reflection. The second order of reflection still has a reasonably high intensity comparable with the intensity of the first one; due to this fact the energy range can be extended up to 40 keV. The change of the energy of the monochromatized x radiation is accomplished by the simple vertical shift of a mono; according to this shift the space location of the focal point is also vertically displaced. For the study the mono was placed at a distance of ∼16 m from the source point, so the accepted horizontal divergence of the ‘‘white’’ SR beam was ∼2 mrad. The mono was supplied with an In–Sn conical collimator to prevent parasitic scattering radiation and to avoid the possible undesirable characteristic emission x-ray lines in the working energy range mentioned above.

X-ray imaging of different cross sections (horizontal–vertical, horizontal–longitudinal, vertical–longitudinal) of the focal point space region was performed by the point-by-point scanning of a NaI(Tl) scintillation counter supplied by the pinhole collimator of ∼80 μm in diameter made in the lead disk screen of 2 mm thickness. The achieved size of the focal spot of ∼0.4 (horizontal)×0.7(vertical) mm2 is in a good agreement with theoretical expectations and preliminary computer modeling. In fact, the main role in an extending of the focal spot is the large angular mosaic spread (∼1° FWHM) of the graphite crystal used. The registration of Compton scattered radiation spectra from the acrylic cylinder of 5 mm diameter placed at the focus position by a Si(Li) liquid–nitrogen-cooled solid state detector was conducted to measure the behavior of spectra of monochromatic x radiation output with respect to the longitudinal location of the footprint of a primary SR beam on the parabolic surface of the graphite crystal. The possible applications of the presented mono for the construction of a ‘‘middle’’ space resolution class of SR based x-ray fluorescence microprobes and other usages such as powerful concentrators of x radiation are discussed and described.
Thermal bilayer monochromator crystal for a high resolution multiwavelength anomalous diffraction beamline at the European Synchrotron Radiation Facility
Authors: Ferrer Jean-Luc , Roth Michel , Fanchon Eric , Poupon Gilles , Saint-Lager Marie-Claire , Berar J.-F.
Published: July 2002

High intensity for diffraction experiments with high energy resolution, on an intense source like bending magnet at the European Synchrotron Radiation Facility, requires a strict control of the curvature of the optical elements placed in the beam for geometrical focusing and for wavelength monochromatization. Unwanted curvature of the first crystal of the monochromator can arise from the thermal load. Indeed, due to the size of the crystal, only cooling from the rear is conceivable. This induces a front-to-rear thermal gradient and, as a consequence, a strong spherical curvature. A new technique was developed for the CRG/D2AM beamline in order to control this effect. It was shown by calculation that this curvature can be exactly compensated, whatever the heat load power is, by the thermal expansion of a metallic layer coated at the rear of the crystal. First results confirm the predicted behavior and show how sensitive the technical problem of the fixation of this bilayer is on its cooling device.
Mirror concepts of the new wiggler and undulator beamlines at HASYLAB
Authors: Hahn U. , Gürtler P.
Published: July 2002

The mirror concept of the new HASYLAB bypass beamlines has as its main design goal the handling of the large radiation power of up to 7 kW from wigglers and undulators. The first optical element is a SiC-coated graphite mirror which acts as an energy low pass filter. The choice of the material, the cooling scheme, the mirrorchamber design, and the additional focusing mirrors are described.
Building a third generation source (invited)
Authors: Liu Yuen-Chung
Published: July 2002

Through a ten-year period of preparation work, from the feasibility study phase, the conceptual design phase, the engineering design phase, to construction, installation, and, finally, the commissioning phase, the Synchrotron Radiation Research Center (SRRC) celebrated the inauguration of its third generation synchrotron light source, the first of its kind in Taiwan as well as in Asia, on 16 October, 1993. In March 1994, the beam current achieved 450 mA, far exceeding the design goal of 200 mA. In April of the same year, the ring energy had been upgraded from 1.3 to 1.5 GeV. Three high-resolution vacuum ultraviolet photon beamlines were successfully commissioned. Synchrotron radiation experiments have been carried out. The following report will brief on the SRRC facility and concentrate mainly on constructing a successful source in lack of the needed accelerator expertise and experience in Taiwan.
Optimization of accelerator system performance at the National Synchrotron Light Source (invited)
Authors: Krinsky S.
Published: July 2002

There is an active program of accelerator development at the National Synchrotron Light Source (NSLS) aimed at improving reliability, stability, and brightness. Work is primarily focused on providing improved performance for the NSLS user community, however, important elements of our work have a generic character and should be of value to other synchrotron radiation facilities. In particular, we have successfully operated a small gap undulator with a full vertical beam aperture of only 3.8 mm, with no degradation of beam lifetime. This provides strong support for the belief that small gap, short period devices will play an important role in the future.
ESCA microscopy beamline at ELETTRA
Authors: Casalis L. , Jark W. , Kiskinova M. , Lonza D. , Melpignano P. , Morris D. , Rosei R. , Savoia A. , Abrami A. , Fava C. , Furlan P. , Pugliese R. , Vivoda D. , Sandrin G. , Wei F.-Q. , Contarini S. , DeAngelis L. , Gariazzo C. , Nataletti P. , Morrison G. R.
Published: July 2002

The article describes the ESCA microscopy beamline dedicated to high spatial resolution quantitative and qualitative analysis on surfaces and interfaces. The scanning microscope is constructed to work both in transmission and photoemission within the photon energy range from 200 to 1200 eV with a spatial resolution of ∼0.1 μm. A Fresnel zone plate demagnifies the photon beam to submicrometer dimensions with 109–1010 photons/s in the focus spot. A photodiode and a hemispherical electron energy analyzer are used as detectors for recording the transmitted x-rays and emitted photoelectrons, respectively. The operation modes in photoemission give the opportunity to obtain conventional energy distribution curve spectra from a microspot or a two-dimensional micrograph of the spatial distribution and local concentration of a selected element as the sample is mechanically scanned. For conductive specimen topography measurements of a selected surface area probed by SPEM are possible using a scanning tunnelling microscope. The first test images of a zone plate and an e-beam written specimen with 1 μm2 Au squares on Si have shown a spatial resolution better than 0.2 μm.
Differential-phase reflectometry for edge profile measurements on Tokamak fusion test reactor
Authors: Hanson G. R. , Wilgen J. B. , Bigelow T. S. , Collazo I. , England A. C. , Murakami M. , Rasmussen D. A. , Wilson J. R.
Published: July 2002

Edge electron density profile measurements, including the scrape-off layer, have been made during ion cyclotron range of frequency (ICRF) heating with the two-frequency differential-phase reflectometer installed on an ICRF antenna on the Tokamak fusion test reactor (TFTR). This system probes the plasma using the extraordinary mode with two signals swept from 90 to 118 GHz, while maintaining a fixed-difference frequency of 125 MHz. The extraordinary mode is used to obtain density profiles in the range of 1×1011–3×1013 cm−3 in high-field (4.5–4.9 T) full-size (R0=2.62 m, a=0.96 m) TFTR plasmas. The reflectometer launcher is located in an ICRF antenna and views the plasma through a small penetration in the center of the Faraday shield. A 26-m-long overmoded waveguide run connects the launcher to the reflectometer microwave electronics. Profile measurements made with this reflectometer system will be presented along with a discussion of the characteristics of this differential phase reflectometer and data analysis.
Initial operation of the two-dimensional far-infrared scattering/interferometry system on TEXT-Upgrade
Authors: Brower D. L. , Jiang Y.
Published: July 2002

The UCLA far-infrared scattering/interferometry system on TEXT-Upgrade has recently been modified to include a two-dimensional capability. Along with the vertically viewing system, a horizontal view has been added. For interferometric measurements of the plasma density profile, the vertical view consists of a 45 cm array while the horizontal view array spans 15 cm. Density profiles for Text-Upgrade plasmas will be presented. For collective scattering measurements of electron density fluctuations, cross correlation of scattered signals from the two orthogonal views at the same wave vector will be examined. Finite cross coherence may be used to spatially localize the fluctuation measurements.
X-ray lasers for high density plasma diagnostics (invited)
Authors: Da Silva L. B. , Barbee T. W. , Cauble R. , Celliers P. , Harder J. , Lee H. R. , London R. A. , Matthews D. L. , Mrowka S. , Moreno J. C. , Ress D. , Trebes J. E. , Wan A. , Weber F.
Published: July 2002

Collisionally pumped soft x-ray lasers now operate over a wavelength range extending from 35 to 300 Å. These well-characterized sources have high peak brightness (GeV blackbody temperature) and narrow bandwidth making them ideal for x-ray imaging and interferometry. We will describe experiments which have used the yttrium neon-like x-ray laser operating at 155 Å to probe plasmas at electron densities exceeding 4×1021 cm−3. The short pulse duration of this x-ray laser (∼150 ps) has made it possible to image directly driven thin foils with 1–2 μm spatial resolution. Advances in multilayer mirrors and beam splitters have now also made it possible to develop x-ray laser interferometers. We will describe initial experiments to probe plasmas relevant to ICF using x-ray laser interferometry. The progress in the development of short pulse x-ray lasers (∼30 ps) which are ultimately necessary to extend x-ray laser diagnostic techniques to higher densities will also be presented.
Thomson scattering system on FTU tokamak: Calibration, operation, results (abstract)a)
Authors: Orsitto F. , Brusadin A. , Giovannozzi E. , Santi D. , Bartiromo R. , Pizzolati P.
Published: July 2002

The Frascati tokamak upgrade (FTU) Thomson scattering system is employed for the measurement of the electron temperature and density spatial profiles along the vertical torus diameter in 19 spatial points up to ten times in a single plasma discharge with a spatial resolution ranging from 2 cm in the central region to 4 cm in the plasma edge. The radiation source is a Nd:YLF laser at 1053 nm. The scattered radiation is collected by two objectives: the first looks at the plasma center, the second at the plasma edge. Bundles of optical fibers in the focal plane of the objectives carry the scattered light from the tokamak hall to a set of 19 interference filter polychromators, whose transmission is 70% and the rejection of the stray light at the laser wavelength is 1/107. The detectors are avalanche photodiodes with a NEP of the order of 10−13 W/(Hz)1/2 at 1053 nm. The absolute calibration for the electron density measurement has been carried out by Raman scattering on hydrogen and deuterium. Examples of temporal evolution of Te and ne spatial profiles are presented for ohmic plasma heating, lower hybrid current drive, and pellet injection experiment. A comparison between scattering data with interferometer for the density measurement, and ECE for the electron temperature shows agreement between the diagnostics. The system is controlled by two computers: a real-time computer for the laser settings, while the detection system parameters and data acquisition are managed using CAMAC by the data acquisition system of FTU.
Photon recycling system for multiposition tangential Thomson scattering
Authors: Barth C. J. , Chu C. C. , Donné A. J. H.
Published: July 2002

Multiposition tangential Thomson scattering makes it possible to measure the profiles of the local drift velocity and current density of a tokamak plasma. To achieve a reasonably small observational error (20%) a high photon yield is required. In this paper we propose an optical system to increase the photon yield by about a factor of 7. Photons from a pulsed ruby laser are captured in a ring cavity by means of an electro-optical switch. The trapped laser beam recirculates about 14 times through the sampling volume which is part of the cavity, increasing the laser energy of 25 J to an effective energy of about 140 J.
The visible, imaging diode arrays on Alcator C-Mod
Authors: Terry J. L. , Snipes J. A. , Kurz C.
Published: July 2002

A set of multichord, absolutely calibrated viewing arrays has been used to measure the distributions of H/D and C+2 emissions. A total of 227 chordal views are available, with the chords separated at the plasma by ∼1 cm typically. The chord brightness profiles have been combined and inverted (without recourse to symmetry assumptions) to yield local volume emission rates. Because of the thickness of the superstructure surrounding Alcator C-Mod, the views are from points re-entrant to the vacuum vessel. All but one of the arrays employ 64-channel, linear diode arrays, which are read out serially, thus requiring only one digitizer channel per array. Variable frame rates (∼1 Hz to ∼3.5 kHz) result in an extremely large dynamic range for these detectors. A 35-channel diode array which is read out in parallel and can track fast events like ELMs or pellets is also in use.
X-ray optical analyses with x-ray absorption package (XRAP)
Authors: Wang Zhibi , Kuzay Tuncer M. , Grace Thomas , Dejus Roger
Published: July 2002

XRAP is a computer code developed for analysis of optical elements in synchrotron radiation facilities that can generate BM (bending magnet) and ID (insertion device) spectra and calculate their absorption in media, such as variable thickness windows/filters and crystals, and provide a finite difference engine for fast but sophisticated thermal and stress analyses for optical elements, such as filters and windows. After a thermal stress analyses, XRAP performs a buckling check. For complex geometries, an interface is provided directly to a finite element code. XRAP features a user-friendly graphical interface that is based on the X-window system.
Proposed experiment to investigate use of heated optical fibers for tokamak diagnostics during D-T discharges
Authors: Tighe W. , Morgan P. , Adler H. , Cylinder D. , Griscom D. , Johnson D. , Palladino D. , Ramsey A.
Published: July 2002

A JET/TFTR study to investigate attenuation and luminescence effects due to neutron irradiation of optical fibers that have been heated to 400 °C is described. A significant improvement in fiber behavior due to temperature annealing is expected which may be relevant in fiber-related, tokamak diagnostics exposed to high neutron flux. Results show that an unheated fiber shows ≳20% transmission loss while an identical, heated fiber only ∼1%. Experimental details are presented.
Optical metrology facility at the ESRF
Authors: Susini J. , Baker R. , Vivo A.
Published: July 2002

Regarding x-ray mirror design and fabrication, the unique properties of the ESRF source push specifications far beyond the obtainable limits of current technology. In order to keep control of the high quality of optical beamline components, interferometric based metrology capabilities are mandatory. This paper describes the ESRF metrology facility in which four complementary systems permit complete analysis of the quality of x-ray optical components.
An apparatus for multiparametric studies of ion–surface collisions
Authors: Esaulov V. A. , Grizzi O. , Guillemot L. , Huels M. , Lacombe S. , Tuan Vu Ngoc
Published: July 2002

This paper describes the design and tests of an ultrahigh vacuum apparatus built for the study of particle surface interactions, with emphasis on ion scattering experiments. The system was designed to provide facilities for angle resolved electron spectroscopy, ion scattering spectroscopy (ISS), Auger electron spectroscopy (AES), and ultraviolet photoelectron spectroscopy (UPS). It has provisions for photon spectroscopy and fixed angle time-of-flight (TOF) scattering and recoiling spectrometry. Mass selected ion beams in the energy range from a few eV to a few keV can be produced in a continuous or pulsed mode. Two independent, parallel plate tandem electrostatic analyzers, which can rotate around the sample are employed. The angular range spanned is analysis-type dependent and varies from 0° to 135°. One of the analyzers was designed for low energy secondary electron spectroscopy (0–100 eV) and the other one for ISS and AES measurements in the energy range from a few eV to 5 keV. The system disposes of a Czerny–Turner monochromator for optical spectroscopy in the visible. TOF analysis can be performed for 7° and 38° scattering angles and a flight length of 2.2 m. Alternatively, a large area detector set at 20 cm from the collision center allows TOF and charge fraction measurements over an angular range from 0° to 110°. We describe various tests of the different components of the apparatus and some results of experiments on ion scattering.
Laser ion source for the Leuven Isotope Separator On-Line
Authors: Kudryavtsev Yu. A. , Andrzejewski J. , Bijnens N. , Franchoo S. , Huyse M. , Piechaczek A. , Szerypo J. , Reusen I. , Van Duppen P. , Vermeeren L. , Wauters J. , Wöhr A.
Published: July 2002

An on-line laser ion source has been developed and coupled to an on-line isotope separator for the production of isotopically and isobarically pure beams of radioactive ions. It is based on element-selective resonant laser ionization of nuclear reaction products thermalized and neutralized in a high-pressure noble gas after their recoil out of the target. Pure beams of 54,55Ni and 54Co, produced in a light-ion-induced fusion-evaporation reaction, and of 113Rh, produced in a proton-induced fission of 238U, were obtained. A preliminary efficiency of the ion source of ∼6% for fusion reactions and of ∼0.2% for fission reactions has been obtained. A selectivity of the ion source of 300 for fusion and 50 for fission reactions limited by the evacuation of non-neutralized reaction products has been achieved.
Simple transmission infrared cell made of Swagelok for in situ infrared spectroscopic studies of heterogeneous catalysis
Authors: Komiyama Masaharu , Obi Yoko
Published: July 2002

A transmission infrared (IR) cell of a very simple design for in situ study of heterogeneous catalysis is constructed using commercially available parts. The cell design is based on the use of Swagelok unions, and the use of custom-built parts is minimized. The use of a sheathed thermocouple as an internal local heater of the sample eliminated the window cooling lines up to 300 °C sample temperatures, making the cell design very simple and also resulting in short heating and cooling time of the sample. The usefulness of the cell in studying heterogeneous catalysis is demonstrated in the in situ observation of catalytic NOx removal.
Ultrahigh vacuum scanning force/scanning tunneling microscope: Application to high-resolution imaging of Si(111)7×7
Authors: Olsson L. , Wigren R. , Erlandsson R.
Published: July 2002

We present a combined scanning force/scanning tunneling microscope (SFM/STM) operating in ultrahigh vacuum using a fiber-optic laser interferometer to detect the lever deflection. As force microscope it operates in ac and dc mode with commercial (Si, Si3N4) or individually made (W) cantilevers. Samples and cantilevers can be inserted without breaking the vacuum using a load-lock system. The force sensor includes a novel three-dimensional micropositioner based on the piezoelectric slider principle. The system includes standard surface analytical techniques (low-energy electron diffraction/Auger, prepared for x-ray photoelectron spectroscopy) and is equipped for mass spectroscopic detection of reaction products from catalytic surfaces at elevated temperature. Tips are cleaned in situ using electron bombardment. By using tungsten cantilevers with a high spring constant (k=100–200 N/m), it is possible to switch directly between STM and SFM operation. As reference surface we have used the Si(111)7×7 reconstruction, prepared by in situ flashing to 1150 °C, which is imaged at atomic resolution using STM as well as ac-mode SFM.
Quantitative analysis of nonlinear microwave surface impedance from non-Lorentzian resonances of high Q resonators
Authors: Jacobs T. , Willemsen Balam A. , Sridhar S.
Published: July 2002

A method of analyzing the response of nonlinear high Q resonant circuits, such as superconducting microwave cavities, is presented. The method enables one to extract the nonlinear surface impedance, Zs(Hrf), from the complex transmission amplitude, S21(f), as frequency, f, is swept across the resonance. Sensitivity to small changes in the microwave field strength (ΔHrf<1 mOe) can thus be obtained.
Development of an extended path length supersonic slit source for the study of highly corrosive environments
Authors: Grantier David R. , Gole James L.
Published: July 2002

An extended slit nozzle source, whose dimensions exceed previous designs by more than an order of magnitude and which maintains its structural integrity at temperatures in excess of 1100 K, has been designed to create an extended path length zone for the study of the interaction-reaction of corrosive reactants at high concentration. We facilitate the interaction of an increased number density of reactants when an expanding sodium flux (Nax≥1021/cm2 s) sheath formed from the slit nozzle is intersected by comparable halogen atom fluxes. The construction of the large scale dual oven systems necessary to carry out such experiments using both pure and seeded alkali expansions is outlined with emphasis on the fabrication of the extended slit nozzle source. The operation of this alkali source is considered as it creates a long path length high concentration cooperative environment which might be used to monitor exciplex formation, to develop a visible chemical laser oscillator, or to study the long range interaction of excited electronic states. The optical train necessary to probe this high temperature corrosive environment is also outlined.
Electrochemical cell for the preparation of porous silicon
Authors: Guerrero-Lemus R. , Moreno J. D. , Martínez-Duart J. M. , Corral J. L.
Published: July 2002

The design of a practical electrochemical cell to fabricate porous silicon layers (PSLs) is described. This cell is useful to rapidly produce PSLs without the need to prepare new electrochemical solutions. The cell is also adapted for the formation of PSLs in the dark or under illumination, with nitrogen flow in the solution. The special design of the silicon wafer support guarantees a homogeneous electrical contact and no solution infiltration into it.
Static light scattering instrument for rapid and time-resolved particle sizing in polymer and colloid solutions
Authors: Wright Lucille Smith , Chowdhury Aslam , Russo Paul
Published: July 2002

A static light scattering instrument capable of time-resolved intensity measurements for polymers and colloids in dilute solution is described. An optical multichannel analyzer reports, with an ultimate time resolution of 15 ms, the scattered intensity in any angular range spanning 40°. Data acquisition software allows for the rapid collection of intensity data in a timed sequence. This instrument is especially useful for following size changes in large (≳∼30 nm) polymers or colloids. The instrument has been applied successfully to study the interaction of an antimicrobial peptide, (KLAKKLA)3, with large unilamellar vesicles composed of dioleoylphosphatidylcholine (DOPC). For a 10:1 lipid to peptide ratio (KLAKKLA)3 induces a 20% increase in the average radius of a DOPC vesicle suspension. The interaction is complete within 5 min, but most of the change occurs in the first 200 s after peptide addition.
Two-conductor line model: Rapid inversion of eddy current data for foil thickness and conductivity determination
Authors: Ptchelintsev A. , de Halleux B.
Published: July 2002

An eddy current method based on the theoretical model of a two-conductor line placed over a plane conductive medium is described. We show the performance of the method in determining thickness and electrical conductivity of foils. The expressions for the vector potential and the coil electrical impedance are obtained in the case when the coil is placed over a thin foil. This theoretical model was applied to measurements of a conductive foil using rectangular coils with finite length-to-width ratio. Two rectangular coils with large length-to-width ratio were manufactured. Copper and aluminum foils having thicknesses 15–216 μm were studied experimentally in the frequency range 5–100 kHz. Theoretical values of the electrical impedance of the coils were compared to those measured. Agreement between theory and experiment was excellent. The method allows the determination of the thickness–conductivity product of a thin foil. Consequently, if the foil conductivity is known, we can find the thickness; and if the thickness is known the conductivity can be found. The inversion procedure, employing the Newton–Raphson method with two variables, namely the thickness–conductivity product and the coil lift-off, takes about 100 ms. Using a simplified formula for a very thin foil the inversion time can be further reduced. The formula gives an error in foil thickness determination of less than 2% when foils are thinner than 100 μm. The agreement between measured conductivity and thickness and those obtained by other techniques is good. The uncertainty of the conductivity and thickness measurement is typically better than 2%, and often ±1% is obtained. The integral relations obtained allow the use of a fast inversion procedure that considerably reduces the time of development of eddy current methods and probes. The excellent agreement between theoretical and experimental results strongly suggests that the model can be used with success in numerous other eddy current applications. With a medium accuracy the model can be applied for eddy current measurements using rectangular coils with a length-to-width ratio as low as 5.
Mean secondary electron yield of avalanche electrons in the channels of a microchannel plate detector
Authors: Funsten H. O. , Suszcynsky D. M. , Harper R. W.
Published: July 2002

By modeling the statistical evolution of an avalanche created by 20 keV protons impacting the input surface of a z-stack microchannel plate (MCP) detector, the mean secondary electron yield γC of avalanche electrons propagating through a MCP channel is measured to equal 1.37 for 760 V per MCP in the z stack. This value agrees with other studies that used MCP gain measurements to infer γC. The technique described here to measure γC is independent of gain saturation effects and simplifying assumptions used in the segmented dynode model, both of which can introduce errors when inferring γC through gain measurements.
A broad beam cold cathode Penning ionization gauge ion source for ion-beam-assisted deposition
Authors: Rao Yusheng , Wu Jiannan , Xu Taoguang
Published: July 2002

A broad beam cold cathode Penning ionization gauge ion source is developed for ion-beam-assisted deposition. The ion source is composed of several modules and it is 88 mm in diameter and 80 mm in height without any cooling system. The discharge voltage is 500 V. The multiaperture extracted ion beam diameter at the exit is 35 mm. It can be operated dc in oxygen, argon, nitrogen, and other gases. The ion energy can be adjusted from 50 to 1500 eV and the maximum extraction current density is above 200 μA/cm2. The extracted ion beam is matched to the arched rack in different vacuum coaters. Due to the small volume of the ion source, single or multiple sources can be installed according to the volume of the coaters.
A new scanning photoemission microscope for ELETTRA: SuperMAXIMUM
Authors: Welnak John T. , Solak H. , Wallace J. , Cerrina F. , Barbo F. , Bertolo M. , Bianco A. , Di Fonzo S. , Fontana S. , Jark W. , Mazzolini F. , Rosei R. , Savoia A. , Underwood J.H. , Margaritondo G.
Published: July 2002

High brightness, third-generation synchrotrons allow diffraction-limited performance and large flux for scanning photoemission microscopes. A new microscope, SuperMAXIMUM, is being developed at the University of Wisconsin Center for X ray Lithography in collaboration with the Sincrotrone Trieste. The beamline, being built in Trieste, uses a variable angle spherical grating monochromator (VASGM). A combination of rotation of a plane mirror and rotation of the spherical grating keeps the slit positions and beam directions fixed. The microscope objectives are normal-incidence, multilayer-coated Schwarzschild objectives. The project, which is nearing completion, utilizes novel designs for optics alignment, sample rastering mechanics, and software control. We will discuss the project status, new designs, and techniques.
Application of microwave reflectometry to the measurement of fast magnetosonic waves in the Tokamak Fusion Test Reactor
Authors: Nazikian R. , Majeski R. , Mazzucato E. , McCarthy M. , Park H. K. , Phillips C. K. , Rogers J. H. , Schilling G. , Taylor G.
Published: July 2002

The application of microwave reflectometry to the study of fast magnetosonic waves in the Tokamak Fusion Test Reactor (TFTR) is investigated. Assuming the validity of geometric optics for reflectometer measurements, it is shown that linearity to the fast wave amplitude is restricted to very small density fluctuation levels (ñ/n<10−3). Beyond this level, both phase and amplitude ambiguities occur that makes interpretation difficult. Measurements of 30 MHz fast magnetosonic waves in the core of TFTR plasmas are presented.
Verification of unfold error estimates in the unfold operator code
Authors: Fehl D. L. , Biggs F.
Published: July 2002

Spectral unfolding is an inverse mathematical operation that attempts to obtain spectral source information from a set of response functions and data measurements. Several unfold algorithms have appeared over the past 30 years; among them is the unfold operator (UFO) code written at Sandia National Laboratories. In addition to an unfolded spectrum, the UFO code also estimates the unfold uncertainty (error) induced by estimated random uncertainties in the data. In UFO the unfold uncertainty is obtained from the error matrix. This built-in estimate has now been compared to error estimates obtained by running the code in a Monte Carlo fashion with prescribed data distributions (Gaussian deviates). In the test problem studied, data were simulated from an arbitrarily chosen blackbody spectrum (10 keV) and a set of overlapping response functions. The data were assumed to have an imprecision of 5% (standard deviation). One hundred random data sets were generated. The built-in estimate of unfold uncertainty agreed with the Monte Carlo estimate to within the statistical resolution of this relatively small sample size (95% confidence level). A possible 10% bias between the two methods was unresolved. The Monte Carlo technique is also useful in underdetermined problems, for which the error matrix method does not apply. UFO has been applied to the diagnosis of low energy x rays emitted by Z-pinch and ion-beam driven hohlraums.
Spectroscopic diagnosis of foam z-pinch plasmas on SATURN
Authors: Nash T. J. , Derzon M. S. , Allshouse G. , Deeney C. , Jobe D. , Seaman J. , Gilliland T. , McGurn J. , MacFarlane J. J. , Wang P.
Published: July 2002

Solid and annular silicon aerogel and agar foams were imploded on the SATURN accelerator to study plasma initiation, acceleration, and stagnation. SATURN delivers 7 MA with a 50 ns rise time to these foam loads. We fielded several spectroscopic diagnostics to measure plasma parameters throughout the z-pinch discharge. A spatially resolved single frame time-gated extreme ultraviolet spectrometer measured the extent of plasma ablation off the surface of the foam. A time integrated crystal spectrometer showed that characteristic K shell radiation of silicon in the aerogel and of sulfur and sodium impurities in the agar were attenuated when the foam loads were coated with a conductive layer of gold. A time-resolved pinhole camera showed that in general the quality of the pinch implosions was poor but improved with increasing efforts to improve current continuity such as prepulse and conductive coatings.
Properties of plasma radiation diagnostics
Authors: Idzorek G. C. , Oona H.
Published: July 2002

A number of diagnostics utilizing the radiation emitted from high-temperature plasmas have been developed at Los Alamos. Photoemissive x-ray diodes with photon energy bandpass filters provide time-resolved rough spectral data from about 6 eV to >10 keV photon energy. Filtered silicon photodiodes can be used down to 1 eV and offer the advantages of nominally flat response and ability to operate in poor vacuum conditions. Both types of diodes will provide a rough time-resolved spectrum and both are relatively inexpensive, reliable, and passive (i.e., no synchronization problems). For higher-energy resolution, bent crystal spectrographs are used in the x-ray region. With the addition of streak cameras or gated microchannel plates these systems provide data with high energy and high time resolution. To measure the total energy output, a thin foil bolometer is used that measures the change in foil resistance as it is heated by the plasma radiation. By combining these diagnostics into a complementary set good diagnostic information can be guaranteed on any plasma experiment.