bluuebunny/crossref_metadata_2025 huggingface dataset:
A personal computer-based nuclear magnetic resonance spectrometer
Authors: Job Constantin , Pearson Robert M. , Brown Michael F.
Published: July 2002

Nuclear magnetic resonance (NMR) spectroscopy using personal computer-based hardware has the potential of enabling the application of NMR methods to fields where conventional state of the art equipment is either impractical or too costly. With such a strategy for data acquisition and processing, disciplines including civil engineering, agriculture, geology, archaeology, and others have the possibility of utilizing magnetic resonance techniques within the laboratory or conducting applications directly in the field. Another aspect is the possibility of utilizing existing NMR magnets which may be in good condition but unused because of outdated or nonrepairable electronics. Moreover, NMR applications based on personal computer technology may open up teaching possibilities at the college or even secondary school level. The goal of developing such a personal computer (PC)-based NMR standard is facilitated by existing technologies including logic cell arrays, direct digital frequency synthesis, use of PC-based electrical engineering software tools to fabricate electronic circuits, and the use of permanent magnets based on neodymium-iron-boron alloy. Utilizing such an approach, we have been able to place essentially an entire NMR spectrometer console on two printed circuit boards, with the exception of the receiver and radio frequency power amplifier. Future upgrades to include the deuterium lock and the decoupler unit are readily envisioned. The continued development of such PC-based NMR spectrometers is expected to benefit from the fast growing, practical, and low cost personal computer market.
Multigap parallel-plate bracelet resonator frequency determination and applications
Authors: Gonord Patrick , Kan Siew , Leroy-Willig Anne , Wary Claire
Published: July 2002

A loop made from a length of transmission line with alternate electrical discontinuities (gaps) on the two conductors behaves as a resonator whose resonant frequency is a function of the transmission line parameters as well as its form and the number (n) of gaps. For a given loop diameter, one can thus design a wide range of resonant frequency by choice of n and the characteristic impedance Zc of the line. The analysis is illustrated by a parallel-plate transmission line resonator in the form of a bracelet. Experimental resonant frequencies obtained from resonators of various dimensions are in good agreement with calculated values. Two resonators were tested on a 3 T NMR imager: A 11 cm diameter 1H surface coil, yielding results comparable to those obtained from a lumped capacitor coil and a 13 cm diameter volume coil to perform in vivo muscle 13C spectroscopy without 1H decoupling.
Hyper-Rayleigh scattering in solution with tunable femtosecond continuous-wave laser source
Authors: Clays Koen , Persoons André
Published: July 2002

Hyper-Rayleigh scattering has been developed as a generally applicable technique for the determination of the first hyperpolarizability β of a wide class of molecules [Clays and Persoons, Rev. Sci. Instrum. 63, 3285 (1992)]. In this article, we show that it is possible to replace the low repetition rate, nanosecond pulse, Q-switched laser source and fast gated electronics by a self-mode-locked, femtosecond pulse, broadly tunable continuous-wave laser and phase-sensitive detection. This results in a faster and much simpler measurement procedure. The accuracy of the femtosecond hyper-Rayleigh scattering set-up was checked by measuring the first hyperpolarizability β of the octopolar molecule crystal violet in methanol [(450±100)×10−30 esu at 800 nm]. The sensitivity of the instrument allows concentration-dependence studies, down to the pure solvent.
High-intensity, heavy negative ion sources based on the sputter principle (invited)
Authors: Alton G. D.
Published: July 2002

Due to their ease of operation, simplicity, long lifetime, and wide range of species capabilities, negative ion sources predicated on the sputter principle are being used for an increasing number of diverse applications. Sources based on this technology have been developed which utilize either direct cesium-surface ionization, or a plasma seeded with cesium to form positive ion beams for sputtering sample materials from which negative ion beams are generated. This article will include a brief review of the fundamental processes underlying negative ion formation by the sputter technique, as well as describe a selected number of recent ion source developments which exemplify the state-of-the art of this technology.
Precision time counter for laser ranging to satellites
Authors: Kalisz J. , Pelka R. , Poniecki A.
Published: July 2002

A new design of the precision time counter for satellite laser ranging is described. The instrument features 3 ps incremental resolution within the measuring range up to 21.47 s, the short-term rms error below 30 ps, and the time drift within ±5 ps. To reject unwanted noise and other disturbing signals the programmable window discriminator has been employed. In order to achieve high accuracy and good long-term stability we used an automatic calibration based on the adaptive prediction. Further significant reduction of the measurement error has been achieved by self-correction of the nonlinearity error and robust estimation. Results from experimental tests are presented to demonstrate the performance of the instrument.
Design and fabrication of direct-feedback gradiometer: Axial gradiometer made of superconductive films and SQUIDs
Authors: Yokosawa Koichi , Kuriki Shinya
Published: July 2002

A new type of SQUID gradiometer, a direct-feedback gradiometer, is introduced in this paper. It is an axial gradiometer made of thin superconductive films. It consists of two magnetometers: a ‘‘cancellation magnetometer’’ and a ‘‘sensing magnetometer.’’ The feedback flux of the cancellation magnetometer is applied to both pickup coils of these magnetometers by connecting their feedback coils in a series. Environmental magnetic noise applied to the sensing magnetometer is cancelled by the magnetic flux measured by the cancellation magnetometer, when the two magnetometers are connected with normal conductive wires. The gradiometer has been fabricated and operated in a moderate magnetically shielded room. The capability to reduce environmental noise and thus to measure auditory evoked fields from the human brain has been confirmed.
Transfer function of a crossed wire pendulum isolation system
Authors: Kanda Nobuyuki , Barton Mark A. , Kuroda Kazuaki
Published: July 2002

We measured the vibrational transfer function of a newly proposed crossed wire pendulum in the frequency range 0.03–3 Hz. We confirmed that it behaves as a much longer simple pendulum of the same period as far as one dimensional movement of its center of mass is concerned. We conclude that the pendulum shows promise as a component in an ultra-low frequency anti-vibration system.
Solution to the high heat loads from undulators at third generation synchrotron sources: Cryogenic thin-crystal monochromators
Authors: Knapp G. S. , Beno M. A. , Rogers C. S. , Wiley C. L. , Cowan P. L.
Published: July 2002

We have developed a new design for a cryogenically cooled monochromator employing a thin-crystal strategy which is capable of handling the central-cone power of the advanced photon source’s undulator A at machine currents up to 300 mA. The key to the proposed design is to machine two opposing narrow channels in a large, indirectly cooled block of Si crystal, leaving a thin, ∼0.6-mm-thick strip of Si. The thin section absorbs only a fraction of the incident beam power so that the operating temperatures of the crystal are in the range where Si has both a very high thermal conductivity and a very small or slightly negative thermal expansion coefficient. The fact that the crystal is operated in the negative range of thermal expansion means that the crystal surface illuminated by the x-ray beam is always under tension and therefore will not buckle.
Simultaneous measurement of displacement current and absorption spectra of Langmuir film
Authors: Xu Xiaobin , Kubota Tohru , Iwamoto Mitsumasa
Published: July 2002

A Maxwell-displacement-current measuring system coupled with the system used for the measurement of absorption spectra of monolayers on a water surface has been developed. Using this system, the displacement current and the absorbance across monolayers of squarylium dye at the air/water surface were detected. It was found that the change in J aggregate in the monolayers with monolayer compression was detectable using the system.
Flash-type analog-to-digital converter using shaped superconducting film
Authors: Badri Narayana T. , Satyam M.
Published: July 2002

A flash-type analog-to-digital converter is conceived based on the property of critical current-density phenomena and shaping of superconducting films. This has been fabricated using high-TC yttrium barium copper oxide superconducting thick film and its function is demonstrated.
Relative calibration of photodiodes in the soft-x-ray spectral range
Authors: Anton M. , Dutch M. J. , Weisen H.
Published: July 2002

A method of obtaining a relative calibration of Si photodiodes for the spectral range of soft x rays (1–30 keV) is presented. A simple mathematical model of the p-n diode is adopted which allows the response to be described in terms of a small set of parameters. The diffusion length as well as the thickness of a dead layer below the front surface of the diodes are obtained from measurements of angular dependences of the photoinduced current. It is shown that a precise characterization of the diode response and an accurate relative calibration can be obtained using this method. However, it was found that the presence of a dead layer a few tenths of a micrometer thick can pose severe restrictions on the use of planar diode arrays in x-ray tomography systems where uniformity of response is crucial. The method has been applied to the diode arrays equipping the x-ray tomography system built for the TCV tokamak, a magnetic fusion research device.
Quantum-confined Stark effect in ZnSe/Zn1−xCdxSe quantum wells
Authors: Short S. W. , Xin S. H. , Yin A. , Luo H. , Dobrowolska M. , Furdyna J. K.
Published: July 2002

We report the observation of the quantum-confined Stark effect (QCSE) in the photoluminescence (PL) of ZnSe/ZnCdSe single quantum wells grown by molecular beam epitaxy. The electric field was applied via a reverse-biased Schottky barrier contact. Red shifts of the PL peak as large as 13 meV were detected, and accompanied by a dramatic reduction in the transition intensity, consistent with the QCSE. Even moderate applied voltages (∼5 V) were sufficient to completely quench the luminescence signal.
Development of an intense negative hydrogen ion source with an external magnetic filter
Authors: Takeiri Y. , Ando A. , Kaneko O. , Oka Y. , Tsumori K. , Akiyama R. , Asano E. , Kawamoto T. , Kuroda T. , Tanaka M. , Kawakami H.
Published: July 2002

An intense negative hydrogen ion source has been developed, which has a strong external magnetic filter field in the wide area of 35 cm×62 cm produced by a pair of permanent magnet rows located at 35.4 cm separation. The filter strength is 70 G in the center and the line-integrated filter strength is 850 G cm, which keeps the low electron temperature in the extraction region. Strong cusp magnetic field, 1.8 kG on the chamber surface, is generated for improvement of the plasma confinement. These resulted in the high arc efficiency at the low operational gas pressure. 16.2 A of H− ion current with the energy of 47 keV was obtained at the arc efficiency of 0.1 A/kW at the gas pressure of 3.8 mTorr in the cesium-mode operation. The magnetic field in the extraction gap is also strong, 450 G, for the electron suppression. The ratio of the extraction current to the negative ion current was less than 2.2 at the gas pressure of 3 mTorr. The two-stage acceleration was tested, and 13.6 A of H− ion beam was accelerated to 125 keV.
GeoCARS microfocusing Kirkpatrick–Baez mirror bender development
Authors: Yang B. X. , Rivers Mark , Schildkamp Wilfried , Eng Peter J.
Published: July 2002

We present development of microfocusing Kirkpatrick–Baez mirrors GeoSoilEnviroCARS. The mirror is made of single-crystal silicon and the desired elliptical shape is formed by elastic bending with a two-parameter bender. We present data from long trace profiler measurements of the bent shape, which verifies the design principle, and motivates a new bender design. We tested the re-engineered mirror bender focusing white radiation from a National Synchrotron Light Source bending magnet, achieving a 2.5 μm focus with a gain (using only one mirror) of 91.
A newly developed multilayer semiconductor x-ray detector for the observations of wide energy-range x rays
Authors: Hirata M. , Cho T. , Kohagura J. , Yatsu K. , Tamano T. , Miyoshi S. , Kondoh T. , Saitoh Y. , Sato K. , Miyahara S. , Hirano K. , Maezawa H.
Published: July 2002

For the purpose of the developments of wide-energy-range-sensitive x-ray detectors, we have designed and fabricated a new-type multilayer semiconductor x-ray detector. This new-type detector has been characterized using synchrotron radiation from a 2.5-GeV positron storage ring at the Photon Factory of the National Laboratory for High Energy Physics (KEK). This new detector is essentially composed of four layers of commercially available photodiodes. Each photodiode is made from a 300-μm thick, and a 10×10-mm square-shaped wafer. For the common affiliation of these individual photodiodes, the quantum efficiency normalized by the photon energy η/E begins to decrease at 8 keV, and then η/E decreases down to 26% at 20 keV. On the other hand, for our newly designed detector a flat response even in the 10–20-keV energy regime (beam line 15C at the Photon Factory) is observed, and even at 100 keV η/E<30% is still anticipated. This new x-ray detector has various advantages: (i) A compact, and (ii) outgas-free detector for a high-vacuum use, along with (iii) a high degree of immunity to ambient magnetic fields. Furthermore, (iv) the combination of the x-ray signal outputs from each detector layer provides information on the x-ray emitting electron energies. These properties are quite suitable for the use of the fusion-oriented plasma x-ray diagnostics under intense-magnetic field and high-vacuum conditions so as to interpret wide-band x-ray emitting electron-velocity distribution functions from the x-ray data.
Detection characteristics of an ultralow-energy measurable pure-germanium detector in the hundreds-eV photon-energy region
Authors: Kohagura J. , Cho T. , Hirata M. , Yatsu K. , Tamano T. , Ogasawara T. , Yagishita A. , Sekitani T. , Maezawa H.
Published: July 2002

In the energy range from 1 keV down to a few hundred eV, a newly developed ‘‘ultralow-energy measurable’’ pure-Ge detector for a pulse-height analysis and a current-mode observation has been characterized using synchrotron radiation monochromatized by a grasshopper monochromator at the Photon Factory of the National Laboratory for High Energy Physics (KEK). X-ray measurements in this low-energy region were previously tried out using several types of ‘‘windowless’’ Si(Li) detectors. These detectors, however, had trouble, including temporal variations in the quantum efficiencies because of their detector-surface deteriorations due to various impurities in vacuum chambers. Our pure-Ge detector has a 4000-Å thick polymer window metalized by a 1400-Å thick Al supported by a 100-μm apart Si-ribbed structure. However, for this liquid-nitrogen-cooled detector with the special window, its actual energy-response data are not available at this time. Therefore, the investigations of its characteristics are reported particularly for the purpose of the reliable x-ray observations in such a low-energy regime.
Vacuum ultraviolet high-resolution and high-flux beamline for the Aladdin storage ring
Authors: Reininger R. , Severson M. C. , Hansen R. W. C. , Winter W. R. , Green M. A. , Trzeciak W. S.
Published: July 2002

A new vacuum ultraviolet beamline for Aladdin based on an electromagnetic undulator and a 4 m normal incidence monochromator is described. The combination of the undulator, new optics, and an improved version of the currently operational monochromator is expected to deliver more than 3×1011 photons/s at a resolving power of 3×104 in the photon energy range 6–30 eV. At a lower resolving power of 104, more than 1011 photons/s will be available between 30 and 40 eV. Expecting a very high demand for the new beamline, two branches are planned to allow for time sharing.
Focusing characteristics of diamond crystal x-ray monochromators. An experimental and theoretical comparison (abstract)a)
Authors: Sánchez del Río M. , Grübel G. , Als-Nielson J. , Nielson M.
Published: July 2002

Perfect crystals in transmission (Laue) geometry can effectively be used for x-ray monochromators. Perfect Laue crystals show an interesting focusing effect when the incident beam is white and divergent. This focusing is highly dependent on the beam divergence and on the energy bandpass of the crystal. The aim of this work is to study whether this property can be used for focusing a synchrotron x-ray beam, and to obtain quantitatively the beam dimensions of the resulting monochromatic beam. We have experimentally measured the size of an undulator beam after diffraction from a diamond crystal in Laue geometry, and we analyzed and explained the results by comparison with ray tracing.
Novel adaptive directly water-cooled monochromator crystal for high heat load wiggler beamlines
Authors: Schulte-Schrepping H. , Materlik G. , Heuer J. , Teichmann T.
Published: July 2002

The performance of large area directly cooled monochromator crystals at high-power wiggler beamlines is degraded by the heat load from insertion devices and by the pressure of the cooling agent. Based on the experience gained with directly water-cooled crystals at HASYLAB, a new adaptive crystal with remotely controlled crystal bender was built. A characterization of the first new Si(111) crystal under different heat load conditions up to 850 W is presented.
Chromatic aberration of an asymmetrically cut curved crystal due to the dynamical diffraction effect
Authors: Takeshita Kunikazu
Published: July 2002

For the case of an asymmetrically cut curved crystal, x rays having different wavelengths with the same incident angle are reflected toward slightly different directions because of the dynamical diffraction effect. This causes a broadening of the focal spot size even for a point source when an asymmetrically cut crystal is used to obtain demagnified images of the synchrotron radiation sources. This broadening is estimated to be 0.7 mm even for a point source with the optics being currently used on the small angle scattering beam line BL-15A at the Photon Factory. It is important to take this effect into account in the designing of a demagnifying optics using an asymmetrically cut curved crystal.
At-wavelength metrology of 13 nm lithography imaging optics
Authors: Tan Zhengquan , MacDowell A. A. , La Fontaine B. , Bjorkholm J. E. , Tennant D. , Taylor D. , Himel M. , Freeman R. R. , Waskiewicz W. K. , Windt D. L. , Spector S. , Ray-Chaudhuri A. K. , Stulen R. H. , Ng W. , Cerrina F.
Published: July 2002

The development of an extreme ultraviolet (EUV) interferometer for testing EUV lithography optics operating at a wavelength of 13 nm using the U13U undulator beam line at the National Synchrotron Light Source is presented. The design and implementation of phase-measuring, lateral-shearing interferometry and a knife edge test will be described.
Radiometry laboratory of Physikalisch-Technische Bundesanstalt at BESSY
Authors: Ulm G. , Wende B.
Published: July 2002

The Physikalisch-Technische Bundesanstalt (PTB), the German national institute of metrology, operates a radiometry laboratory at the electron storage ring BESSY. Now, after more than ten years of BESSY operation, six experimental stations on four beamlines optimized for radiometric calibrations and characterization of optical components are in use. The calculable undispersed spectral photon flux of the primary radiation standard BESSY with relative uncertainties of below 0.4% is used in a broad spectral range from 1 eV to 15 keV for the calibration of energy-dispersive detectors and of monochromator-detector systems at one beamline and for the calibration of radiation sources in the spectral range from 3 eV to 1.8 keV at three experimental stations equipped with monochromators. Monochromatized synchrotron radiation, with emphasis placed on high spectral purity, is provided at three stations covering the spectral range from 3 eV to about 1.5 keV for detector calibrations and for reflectometry. Brief descriptions of the beamlines, experimental stations, and associated instruments are given. Furthermore, examples of recent radiometric calibrations and investigations and an outlook on radiometry at the future storage ring BESSY II are presented.
A finite element analysis of room-temperature silicon crystals for the advanced photon source bending-magnet and insertion-device beams (abstract)a)
Authors: Assoufid Lahsen , Lee Wah-Keat , Mills Dennis M.
Published: July 2002

In this paper, the results of a series of thermal and distortion finite element analyses performed on room-temperature silicon for the three standard APS sources, namely, the bending magnet, wiggler A, and undulator A, are reported. The modeling was performed with the silicon cooled directly with water or liquid gallium through rectangular channels.
First results of SRC’s new high-energy resolution variable line density grating monochromator beamline: HERMON
Authors: Bissen M. , Fisher M. , Rogers G. , Eisert D. , Kleman K. , Nelson T. , Mason B. , Middleton F. , Höchst H.
Published: July 2002

A new high-resolution soft x-ray beamline utilizing a variable line density grating has been constructed and tested at SRC. In addition to normal grating rotation, the grating housing mechanism allows a translation of the grating. This additional motion of the grating can be used in such a way that grating aberration effects such as defocus, coma, and spherical aberrations are minimized over the entire scan range. In order to achieve the theoretical resolving power of 105–5000 over the photon energy range of 280–1150 eV, extreme care had to be exercised in positioning and controlling the grating scan angle (<0.12 arcsec) and focus drive position (<10 μm). Using a spherical grating with a figure error of <0.2 arcsec and 10 μm slits, we were able to experimentally reproduce our theoretical predicted energy resolution over a wide energy range. We present photoabsorption data of the K-shell edges and associated Rydberg states of Ne, O2, and CO. The high-resolution monochromator unveils structures which were previously not seen or only poorly resolved. A quantitative data analysis of the Ne absorption peak shows the intrinsic lifetime broadening of the Ne 1s state agrees well with theoretical estimates.
The high-energy monochromator for the ALOISA beamline at Elettra
Authors: Busetto E. , Lausi A. , Bernstorff S.
Published: July 2002

At the ALOISA beamline the photon energy range 0.25 to 8 keV will be provided by switching between a plane mirror/grating monochromator and a crystal monochromator sharing the same beamline mirror optics. All dispersing elements are used in a collimated beam, which is focused downstream by means of vertically mounted mirrors. It is shown that the variations in the geometry of the light spot at the sample remain within acceptable limits over the requested energy range even if a simple nonfixed-exit ‘‘channel-cut’’ crystal is used. The crystal will have an inclined cut which allows to spread the power load delivered by the wiggler source sufficiently over the first reflecting crystal surface to allow for simple back-side cooling. In addition a new type of power filter has been designed based on a rotating, water-cooled Be disk. This design reduces the effective absorbed power density in the filter by two orders of magnitude with respect to commonly used static multifoil solutions, resulting in a cool, clean, UHV-compatible device.
Distortions of the exit beam from asymmetric and inclined double-crystal synchrotron radiation monochromators (abstract)a)
Authors: Hrdý Jaromír , Busetto Edoardo , Bernstorff Sigrid
Published: July 2002

The vertical divergence of a photon beam impinging onto a double-crystal monochromator with asymmetric crystals, and the horizontal divergence in an inclined double-crystal monochromator, cause an optical distortion of the exit beam. The consequence of this distortion is that a real point-like source is transformed into a virtual source which has a finite vertical dimension. This may manifest itself on the size of the focus when using conventional focusing optics after the monochromator. For some real sources the height of the corresponding virtual sources are estimated, and it is shown that this effect is more serious in the case of the inclined monochromator. The beam distortions are confirmed also by raytracing simulations.
The combination of a VUV Fourier-transform spectrometer and synchrotron radiation
Authors: Yoshino K. , Smith P. L. , Parkinson W. H. , Thorne A. P. , Ito K.
Published: July 2002

Current research on the Earth’s upper atmosphere requires molecular parameters of unprecedented detail and accuracy. For example, state-of-the-art models of the vacuum-ultraviolet (VUV) absorbing properties of the atmosphere call for absorption cross sections with details on the scale of the Doppler linewidths. As a consequence, spectroscopic data at resolving powers of the order of 106 are needed. Current particular needs are for ultra-high-resolution absorption cross-section data for some bands of NO and O2 in the 170–185 nm spectral region. To meet these requirements, an existing, portable, VUV Fourier-transform (FT) spectrometer will be moved to a synchrotron-radiation facility (Photon Factory, KEK, Japan) and VUV photoabsorption cross sections of NO and O2 will be measured. It has been demonstrated so far with emission line sources that the FT spectrometer will perform to ≤139 nm. Extension of work on absorption measurements to shorter wavelengths and with ultrahigh resolution requires an improved light source. Synchrotron radiation from a storage ring facility is the best alternative.
Thermal effects of undulator radiation on Si optics for a plane grating monochromator
Authors: Jensen B. N. , Mancini D. C. , Nyholm R.
Published: July 2002

Insertion devices on the third-generation 1.5 GeV electron storage ring MAX II will subject the grazing incidence mirrors and gratings of new soft x-ray beamlines to high thermal loads. These thermal loads will cause distortion in the optical surfaces which can be reduced to acceptable levels by the proper choice of substrate material and cooling. A finite element analysis of the temperature variation and thermal distortions is carried out for Si plane mirrors and gratings under thermal load from the 66 mm period undulator planned for MAX II. The energy dependence of the reflectivity for Au-coated mirrors is taken into account. The minimum cooling requirements are determined for each of these optical components in the beamline. The effect of the final induced figure errors on the performance of a plane grating monochromator are discussed.
Phase-space description of synchrotron radiation optics (invited) (abstract)
Authors: Kim Kwang-Je
Published: July 2002

A study of the optics of synchrotron radiation in a fundamental level is important in view of the recent progress in synchrotron radiation research utilizing high brightness radiation from insertion devices, especially undulators, in low emittance storage rings. Important problems in synchrotron radiation optics are; How the strength of the various synchrotron radiation sources can be characterized in a manner independent from the optical transport system. How do the coherence properties of the synchrotron radiation differ from other sources such as lasers? How does radiation propagate through optical elements? What is the role of electron beam emittance in these respects, etc.? In this paper we review a theoretical formalism which can be a basis of a systematic study of synchrotron radiation optics. The approach, which will be called ‘‘The Phase Space Method of Synchrotron Radiation Optics,’’ starts from the Wigner distribution of electric fields and is a generalization of the phase space method of geometric optics to physical optics.
Performance of a high resolution, high flux density SGM undulator beamline at the ALS (invited)
Authors: Warwick Tony , Heimann Phil , Mossessian Dmitri , McKinney Wayne , Padmore Howard
Published: July 2002

The performance of ALS beamline 7.0 is described. This is an integrated system for delivering radiation from a 5 cm period undulator to spectroscopy and microscopy experiments across the range of photon energies from 60 to 1200 eV. The beamline is engineered to deliver the highest possible flux, with negligible deformation of the optic surfaces due to heating. Two experiment stations are served with rapid interchangeability. The measured operational parameters, the resolution and flux delivered, and the refocus of the light into a small spot at the experiment are all discussed.
Development of a second generation scanning photoemission microscope with a zone plate generated microprobe at the National Synchrotron Light Source
Authors: Ko Cheng-Hao , Kirz Janos , Ade Harald , Johnson Erik , Hulbert Steven , Anderson Erik
Published: July 2002

We have been developing an instrument that combines the techniques of x-ray photoelectron spectroscopy and zone plate microfocusing to perform spectromicroscopy. The X1A undulator provides a bright photon source in the soft x-ray range with a high degree of spatial coherence (a requirement for zone plate focusing). A spherical grating monochromator selects the desired photon energy in the 280–800 eV range. A Fresnel zone plate focuses the beam to a small spot. Photoelectron spectra can be acquired from the small irradiated area with an electron energy analyzer. With the beam focused on the surface and the sample mechanically scanned, element-specific or chemical-state-specific images of the surface can be obtained.
Measurement of thermoelectric power using metal opposed anvil cells up to 100 kbar
Authors: Ferdin Bimal T. , Jaya N. Victor , Anbukumaran K. , Natarajan S.
Published: July 2002

In this paper we describe the design of a simple Bridgman opposed anvil cell to measure the thermoelectric power of solids as a function of pressure up to 100 kbar. The anvils are made of EN-24 alloy steel hardened to RC55.
A new apparatus for surface x-ray absorption and diffraction studies using synchrotron radiation
Authors: Oyanagi H. , Owen I. , Grimshaw M. , Head P. , Martini M. , Saito M.
Published: July 2002

A new apparatus for structural studies of surfaces and buried interfaces using synchrotron radiation was built and tested at the 27-pole wiggler station BL13B of the Photon Factory. The apparatus was designed to combine x-ray absorption fine structure (XAFS), x-ray standing wave (XSW), and surface x-ray diffraction techniques in the same ultrahigh vacuum (UHV) chamber. The apparatus features a seven-element Si(Li) solid-state detector array for a fluorescence yield measurement and a high precision eight-axis goniometer in the UHV chamber with a base pressure of 1×10−10 Torr. For the same sample mounted on the in-vacuum goniometer, vertically or horizontally polarized surface-sensitive XAFS, surface x-ray diffraction, and XSW can be measured. As a performance test, the structure of Ge overlayers on Si(001) was studied by polarized surface-sensitive XAFS. The results show that the apparatus can probe the local structure of adatoms with ∼0.1 monolayer sensitivity.
Spectroscopic measurement of impurity transport coefficients and penetration efficiencies in Alcator C-Mod plasmas
Authors: Graf M. A. , Rice J. E. , Terry J. L. , Marmar E. S. , Goetz J. A. , McCracken G. M. , Bombarda F. , May M. J.
Published: July 2002

Impurity transport coefficients and the penetration efficiencies of intrinsic and injected impurities through the separatrix of diverted Alcator C-Mod discharges have been measured using x-ray and vacuum ultraviolet (VUV) spectroscopic diagnostics. The dominant low Z intrinsic impurity in C-Mod is carbon which is found to be present in concentrations of less than 0.5%. Molybdenum, from the plasma facing components, is the dominant high Z impurity and is typically found in concentrations of about 0.02%. Trace amounts of medium and high Z nonrecycling impurities can be injected at the midplane using the laser blow-off technique and calibrated amounts of recycling, gaseous impurities can be introduced through fast valves either at the midplane or at various locations in the divertor chamber. A five chord crystal x-ray spectrometer array with high spectral resolution is used to provide spatial profiles of high charge state impurities. An absolutely calibrated, grazing incidence VUV spectrograph with high time resolution and a broad spectral range allows for the simultaneous measurement of many impurity lines. Various filtered soft x-ray diode arrays allow for spatial reconstructions of plasma emissivity. The observed brightnesses and emissivities from a number of impurity lines are used together with the mist transport code and a collisional-radiative atomic physics model to determine charge state density profiles and impurity transport coefficients. Comparisons of the deduced impurity content with the measured Zeff and total radiated power of the plasma are made.
Active silicon x-ray filter for measuring electron temperature
Authors: Snider R. T.
Published: July 2002

Silicon diodes are commonly used for x-ray measurements in the soft-x-ray region between a few hundred eV and 20 keV. Recent work by Cho et al. [J. Appl. Phys. 72, 8 (1992)] has shown that the charge collecting region in an underbiased silicon detector is the depletion depth plus some contribution from a region near the depleted region due to charge diffusion. The depletion depth can be fully characterized as a function of the applied bias voltage and is roughly proportional to the square root of the bias voltage. We propose a technique to exploit this effect to use the silicon within the detector as an actively controlled x-ray filter. With reasonable silicon manufacturing methods, a silicon diode detector can be constructed in which the sensitivity of the collected charge to the impinging photon energy spectrum can be changed dynamically in the visible to above the 20-keV range. This type of detector could be used to measure the electron temperature in, for example, a tokamak plasma by sweeping the applied bias voltage during a plasma discharge. The detector samples different parts of the energy spectrum during the bias sweep, and the data collected contains enough information to determine the electron temperature. Benefits and limitations of this technique are discussed along with comparisons to similar methods for measuring electron temperature and other applications of an active silicon x-ray filter.
Application of a three sample volume S(k,ω) estimate to optical measurements of turbulence on TEXT
Authors: Hurwitz P. D. , Rowan William L.
Published: July 2002

The flexibility and nonintrusive nature of spectroscopic measurements can complement results from Langmuir probes by extending fluctuation measurements to otherwise inaccessible regions of the plasma. On TEXT, studies of fluctuations in Hα light using a photodiode array (PDA) detector [Hurwitz et al., Rev. Sci. Instrum. 63, 4614 (1992)] have yielded estimates for fluctuation characteristics that are in qualitative agreement with those from probes. The most obvious limitation of this spectroscopic diagnostic is its extended radial viewing volume which overlaps the naturally occurring velocity shear layer just inside the last closed flux surface (LCFS). We present here a three sample volume estimate for the spectral density function S(k,ω) which models the PDA signal as consisting of two modes in k space corresponding to the contributions from inside and outside of the shear layer. This method aids in the radial localization of the PDA measurement and may be applied to other diagnostics as well.
New techniques of magnetic surface measurement on the compact Auburn torsatron
Authors: Lin H. , Gandy R. F. , Hart B. M. , Hartwell G. J. , Knowlton S. F. , Owens M. , Sasser G. , Schneider T. A. , Thomas E. , Voorhees S. B.
Published: July 2002

Torsatron and stellarator plasma devices rely on magnetic surface mapping to verify the detailed vacuum magnetic field structure. Two new techniques of magnetic surface mapping are under development on the compact Auburn torsatron. The first is a fast-rotating fluorescent wire (FRFW) system. Compared with the usual fluorescent screen, fluorescent rod, or the capacitive point probe techniques, the FRFW system has the advantage of greatly increasing the number of detectable toroidal transits and of minimizing surface mapping time. The second technique is a resistive wire system which provides an alternative fast-field mapping method.
Infrared laser interferometric thermometry: Extension to batch processing environments
Authors: Saenger K. L.
Published: July 2002

Infrared laser interferometric thermometry (IRLIT) is a noncontact technique for measuring the temperature of single semiconductor substrates (with polished front and back surfaces) from thermally induced changes in wafer thickness and refractive index. It is suggested that IRLIT can be extended to a batch processing environment by making use of antireflection coatings for all but the wafer(s) of interest. This concept is tested with an IRLIT measurement of the temperature of a bare Si wafer sandwiched between several AR-coated Si wafers stacked on a hotplate. The data for this generic wafer arrangement confirm the applicability of IRLIT to situations such as temperature measurement of selected-position wafers in fully loaded boats during heating or cooling in a tube furnace.
A soft x-ray spectrometer for resonant inverse photoemission
Authors: Weibel P. , Grioni M. , Hêche C. , Baer Y.
Published: July 2002

We describe the concept and the performances of a new tunable soft x-ray inverse photoemission (IPES) spectrometer. The instrument is based on a variable-geometry Bragg spectrograph, and it can be operated with minor modifications over a wide range of photon energies (600<hν<4000 eV). It was originally designed for IPES measurements of cerium compounds at the Ce M5(3d5/2→4f,hν=883 eV) absorption edge, where the Ce 4f IPES cross section is resonantly enhanced. Such resonant IPES (RIPES) spectra, now routinely performed by this instrument, are 10–100 times more sensitive to the Ce 4f states than conventional x-ray bremsstrahlung spectra, with a comparable energy resolution (ΔE∼600 meV). We plan to exploit the wide tunability of the spectrometer to perform RIPES measurements of other correlated materials, namely at the Cu L2,3(2p→d,hν=930 and 950 eV) edge in the high-Tc superconductors.
Cross collimation: A new scheme for grating monochromator alignment (abstract)
Authors: Xu Z. , Hulbert S. L. , McNulty I.
Published: July 2002

A simple scheme for precision alignment of grating monochromators is presented. The achievable resolution and limitations of the scheme are also discussed. By requiring each of two laser beams to be normal to the grating surface and collinear with the reflected beam from the other laser, the grating surface normal can be accurately made orthogonal to the monochromator spindle axis (roll adjustment). With the lasers set 150° apart and 5 m away from the grating, the alignment resolution of the roll axis is of the order of 2 arcsec. The grating grooves and the monochromator spindle axis can be made parallel (yaw adjustment) then by aligning all the diffracted beams of different orders (including zeroth order). A screen 5 m away from the grating yields a yaw resolution of the order of 10 arcsec. This scheme has been used to align the monochromators at X13A and U13U beamlines at the National Synchrotron Light Source. This research was supported by the U.S. Department of Energy, BES Materials Sciences, under Contracts No. W-31-109-ENG-38 and No. DE-AC02-76CH00016.
Multipurpose monochromator for the Basic Energy Science Synchrotron Radiation Center Collaborative Access Team beamlines at the Advanced Photon Source x-ray facility
Authors: Ramanathan M. , Beno M. A. , Knapp G. S. , Jennings G. , Cowan P. L. , Montano P. A.
Published: July 2002

The Basic Energy Science Synchrotron Radiation Center (BESSRC) Collaborative Access Team (CAT) will construct x-ray beamlines at two sectors of the Advanced Photon Source facility. In most of the beamlines the first optical element will be a monochromator, so that a standard design for this critical component is advantageous. The monochromator is a double-crystal, fixed exit scheme with a constant offset designed for ultrahigh vacuum windowless operation. In this design, the crystals are mounted on a turntable with the first crystal at the center of rotation. Mechanical linkages are used to correctly position the second crystal and maintain a constant offset. The main drive for the rotary motion is provided by a vacuum compatible Huber goniometer isolated from the main vacuum chamber. The design of the monochromator is such that it can accommodate water, gallium, or liquid-nitrogen cooling for the crystal optics.
Analysis methods for fast impurity ion dynamics data
Authors: Hartog D. J. Den , Almagri A. F. , Prager S. C. , Fonck R. J.
Published: July 2002

A high-resolution spectrometer has been developed and used on the MST reversed-field pinch (RFP) to measure passively impurity ion temperatures and flow velocities with 10 μs temporal resolution. Such measurements of MHD-scale fluctuations are particularly relevant in the RFP because the flow velocity fluctuation-induced transport of current (the ‘‘MHD dynamo’’) may produce the magnetic field reversal characteristic of an RFP. This instrument will also be used to measure rapid changes in the equilibrium flow velocity, such as occur during locking and H-mode transition. The precision of measurements made to date is ≤0.6 km/s. We are developing accurate analysis techniques appropriate to the reduction of this fast ion dynamics data. Moment analysis and curve-fitting routines have been evaluated for noise sensitivity and robustness. Also presented is an analysis method which correctly separates the flux-surface average of the correlated fluctuations in u and B from the fluctuations due to rigid shifts of the plasma column.
Comment on ‘‘Modular digital boxcar for applications in pulsed laser spectroscopy’’ [Rev. Sci. Instrum. 66, 3057 (1995)]
Authors: Sloman A. W.
Published: July 2002

The performance of the digital boxcar could be substantially improved by redesigning it around currently available components. This would require and allow the authors to address well-known experimental problems not discussed in their paper. The description of the ‘‘digitally controlled delay line’’ appears to omit at least one component.
Quantitative detection of low energy positive and negative ions with a channel electron multiplier
Authors: Keller C. A. , Cooper B. H.
Published: July 2002

We have constructed ion optics which, when interfaced with a channel electron multiplier (CEM), make possible quantitative measurements of positive and negative ion fluxes. We describe the design and operation of a detection system using these optics and present a calibration of the CEM for low energy (0.2–8.7 keV) positive and negative oxygen ions.
Tensiometer for free standing smectic films
Authors: Eberhardt Matthias , Meyer Robert B.
Published: July 2002

We present the design of a machine which allows us to measure the surface tension of a free standing smectic film with an accuracy of 0.1 mN/m absolute and 0.01 mN/m relative. Our design makes it possible to measure the surface tension over a wide range of temperatures with minimal drift in the detector itself. The response time of our detector can be as small as 0.01 s which allows us to study dynamic processes involving the interaction between the film and the meniscus around the frame that supports the film. Our design is based on a rigid frame with a movable side suspended as a pendulum. The surface tension force on the movable side is opposed by a feedback system to stabilize the position of the movable side. The stabilizing force then is a measure of the surface tension. An optical system detects deflection of the movable side due to the surface tension force, and applies a restoring force by generating electric current in a coil which applies force to a permanent magnet attached to the pendulum arm. The feedback control includes an integrator stage to achieve finite force with negligible error in position. The device can be calibrated with a simple lever and weight scheme to simulate a surface tension force. The design elements that determine the stability and accuracy of the system are discussed.
Sensitive photothermal interferometric detection method for characterization of transparent plate samples
Authors: Li Bincheng , Deng Yanzhuo , Cheng Jieke
Published: July 2002

In this article, a recently developed, sensitive photothermal interferometric detection technique, in which an interference fringe pattern formed by overlapping two reflected probe beams from the front and rear surfaces of the sample was used to measure the photothermal signal, and its application for characterization of transparent (or partially transparent) plate samples were theoretically and experimentally investigated in detail. The theoretical descriptions of the intensity distribution of the interference fringe pattern and the photothermal signal with pulsed excitation were presented. Experiments were conducted with plate samples of optical glasses doped with heavy-metal ions and the results were compared with the theoretical ones. Good agreement between theoretical and experimental results demonstrated the proposed photothermal interferometric detection technique to be a sensitive photothermal method for the study of the thermophysical properties of transparent samples. Its applicability to weak absorption or spectroscopy measurement and microvolume trace analysis was also discussed.
Joulemeter for pulsed ruby laser
Authors: Breaban F. , Deffontaine A. , Bridoux M. , Depret D.
Published: July 2002

This article presents a joulemeter that permits us to measure the beam energy of a pulsed ruby laser from the HLS-3 holographic system at the recording photosensitive surface of the holographic plate. This is an inexpensive alternative to commercially obtainable energy measuring silicon detectors. The joulemeter contains a photodiode used in the photoconductive mode, an integrating circuit, and a buffer amplifier. The output signal is displayed on the screen of a digital storage oscilloscope. We have tested the joulemeter for different photodetectors. The best responsivity, 3 V/J, was obtained with the BPW21 photodetector. Its possible to measure the energy of a different pulsed laser, by using a photodetector adapted for the laser wavelength and to change the energy domain by changing the attenuators.
Measurement of the width of a wedge boundary using phase change of interference with partially coherent light
Authors: Kanai N.
Published: July 2002

In this article, the phase change of interference in the shadow region of a wedge-shaped object with partially coherent light is illustrated. It is shown that this phase change can be applied to the detection of the width of adjacent boundaries of small samples with partially coherent light.