bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of absorption features in dense argon plasmas
Authors: Mancini R. C. , Hooper C. F.
Published: July 2002

We discuss the analysis of absorption features observed in a series of high-density implosion experiments in which Ar-filled microballoons were irradiated with high-energy laser pulses. The experimental spectrum shows the time evolution of an absorption feature in the core gas as the implosion achieves stagnation. While previous applications of absorption spectroscopy have mainly relied on estimates of the intensity of absorption features to infer plasma environmental conditions, here we propose to study quantitatively details of their shape. To this end, we have computed theoretical Stark-broadened line profiles and compared them with the experimental spectra. The temperature and density sensitivity are studied.
Evaluation of a multilayer mirror spectrometer in the 230–304 Å wavelength range
Authors: Regan S. P. , Zwicker A. P. , Finkenthal M. , Moos H. W. , Barbee Troy W.
Published: July 2002

The reflective properties of a flat Mo/Si multilayer mirror (MLM) optimized for the 230 Å<λ<304 Å range (2d=373.2 Å, N=25, 25 Å<Δλ<50 Å) have been measured. A near-normal incidence spectrometer using the MLM as the dispersive element, a beryllium foil as a light blocking filter, and a channel electron multiplier as the photodetector has been built. The interest in such a device is related to its possible application as a monitor of alpha particles by imaging the whole plasma using the Lyman series of He ii. In the laboratory experiment described here, the Lyman series of He ii, emitted from a Penning ionization discharge, were scanned with a θ-2θ goniometer. In parallel, high-resolution (Δλ≊1 Å) spectra were also recorded using a 1 m grazing incidence (GI) spectrometer. Comparisons are made between the high-resolution (GI) spectrum modeled to the bandpass of the MLM and the low-resolution (MLM) spectrum in the range of interest.
Ion contamination of x-ray pinhole camera images on PBFA II
Authors: Moats A. R. , Mehlhorn T. A.
Published: July 2002

Inner-shell x-ray pinhole cameras are an important diagnostic for time-averaged beam profile measurements on PBFA-II experiments which requires no shielding from the diode magnetic field. However, the same ions that create the inner-shell x rays can also Rutherford scatter and directly expose the x-ray film. A double image, due to this effect, has been observed in PBFA-II data. In this paper, we derive the expected film density due to these scattered ions relative to the film density from the ion-induced x-ray line radiation from titanium, aluminum, and gold targets. We then show that our calculated degree of ion contamination for a gold target Mα camera recently fielded on PBFA-II is consistent with the actual images observed−a phantom image tentatively identified as proton contamination with a film density of the same order of magnitude as the x-ray image. The amount of ion contamination is strongly dependent on the optical filtering used. For less heavily filtered cameras, we will show that this contamination will be less of a concern. We propose a different camera geometry for which this ion contamination will be a 5% effect in the titanium and aluminum Kα cameras, but may be a 16% effect in the gold Mα cameras.
A low-temperature sample mount for an inelastic electron scattering spectrometer
Authors: Tarrio C. , Schnatterly S. E. , Benitez E. L.
Published: July 2002

A continuously operable low-temperature (10–20 K) sample mount for a solid-state inelastic electron scattering spectrometer is described. The cooling is achieved by a closed-cycle gas phase He refrigerator. Because the entire sample chamber is at a potential of 300 kV, it must be isolated from ground, requiring computer automation for positioning, and insulating plumbing for the helium. The motion control has a detachable coupling that allows for complete thermal isolation from room temperature. Details and problems encountered in the design are described.
Layered synthetic microstructures for soft x-ray spectroscopy of magnetically confined plasmas (invited)
Authors: Moos W. , Zwicker A. P. , Regan S. P. , Finkenthal M.
Published: July 2002

With the recent advances in layered synthetic microstructure (LSM) technology, it is now possible to build a simple, high-throughput, near-normal incidence soft x-ray spectrometer as a diagnostic for magnetically confined plasmas. Such spectrometers could be used for radiative power loss measurements from intrinsic impurities, an impurity concentration monitor, or ion temperature measurements from Doppler broadening of high charge-state metallic impurities. LSMs have been developed as either flat or curved multilayer mirrors (MLMs) or as coatings for conventional gratings. Flat multilayer mirrors can have near-normal incidence reflectivities greater than 50% throughout the entire soft x-ray region with bandpasses that can be less than 4 Å. Coated gratings are being developed that will combine the high soft x-ray reflectivity of the LSM with the high resolution of the grating. Specific applications of LSMs as dispersive elements will be discussed. As an example, LSM-based low-resolution spectra of both a laboratory and tokamak plasma will be presented.
Variable frequency two-phase ac susceptometer for use in dc bias fields over the temperature range of 4.2 to 300 K
Authors: Koszegi L. , Foldeaki M. , Dunlap R. A.
Published: July 2002

A system has been designed and constructed in order to detect differential ac susceptibility as a function of temperature between 4.2 and 300 K. A dc bias field in the range of 0–50 kOe is provided by a superconducting magnet. The available ac field range is 0–1 Oe. Using the reference source of a PAR lock-in amplifier, the measurements can be carried out in a frequency range of 0.1–10 kHz. A differential amplifier circuit is used to accurately detect the susceptibility signal. As this provides both in-phase and out-of-phase compensating signals, both the real and imaginary components of the susceptibility can be detected even when using a single-phase lock-in amplifier. The circuit diagram and principle of operation as well as the calibration procedure and data processing methods are described in detail.
Micromachined submicrometer photodiode for scanning probe microscopy
Authors: Davis R. C. , Williams C. C. , Neuzil P.
Published: July 2002

A submicrometer photodiode probe with a sub-50 nanometer tip radius has been developed for optical surface characterization on a nanometer scale. The nanoprobe is built to detect subwavelength optical intensity variations in the near field of an illuminated surface. The probe consists of an Al–Si Schottky diode constructed near the end of a micromachined pyramidal silicon tip. The process for batch fabrication of the nanoprobes is described. Electrical and optical characterization measurements of the nanoprobe are presented. The diode has a submicrometer optically sensitive area with a 150 fW sensitivity.
A modified centrifugal apparatus for coexistence curve measurements−Polystyrene in methylcyclohexane
Authors: Chu Benjamin , Linliu Kung , Xie Ping , Ying Qicong , Wang Zhulun , Shook Jeffrey W.
Published: July 2002

A modified centrifuge has been developed. There are four advantages to this apparatus: (i) The presence of centrifugal acceleration permits the formation of the boundary between the two phases of a fluid system more quickly after phase separation, especially for viscous fluids such as polymer blends. (ii) The rotor is able to accommodate three samples. (iii) The formation of homogeneous solutions in the one phase region can be achieved within the constant temperature rotor which can be controlled to ±0.003 °C up to ≊300 °C. (iv) The phase separation temperature can be measured as a function of centrifugal acceleration up to 1500 gravity. By using the centrifugal apparatus, the coexistence curves of polystyrene in methylcyclohexane were measured. The results in terms of critical exponents and preexponential factors were in excellent agreement with the best literature values and thus confirmed the reliability of our apparatus.
An apparatus for in situ Raman spectroscopy of ion-irradiated frozen targets
Authors: Spinella F. , Baratta G. A. , Strazzulla G.
Published: July 2002

A novel experimental apparatus designed to study, using in situ Raman spectroscopy, chemical and structural modifications induced by ions impinging on frozen gases and solids at low temperatures (10–300 K) is described.
Automated system for resistance and critical current measurements
Authors: Wnuk J. J. , Eggenkamp P. J. T. , van der Linden P. J. E. , van der Steen H. J. L.
Published: July 2002

An apparatus is described for measuring the temperature and magnetic field dependencies of the resistance and critical current of high-temperature superconductors. The automated setup together with a set of inserts forms a universal system allowing for fast sample selection as well as for accurate complementary measurements at temperatures from 4.2 to 300 K and in high magnetic fields up to 30 T. Design details and low resistance measuring algorithm are presented and system peformance is discussed.
Photoionization mass spectrometer with a microscope laser desorption source
Authors: de Vries Mattanjah S. , Elloway Donald J. , Wendt H. Russel , Hunziker Heinrich E.
Published: July 2002

An apparatus is been described in which laser desorption, separate laser ionization, mass spectrometry, and microscopy are combined. An UV waveguide laser is focused on a sample, which is mounted on translation stages in vacuum. Desorbed neutral molecules are ionized above the surface by a second laser, and ions are extracted into a reflectron time of flight mass spectrometer. A spatial resolution of 1 μm is demonstrated, with a mass resolution of 2000 and a detection efficiency of 10−4.
Heat load and anticlastic effect compensation on an ESRF monochromator: An exhaustive ray-tracing study for a meridional-sagittal geometry
Authors: Zontone Federico , Comin Fabio
Published: July 2002

Undulators installed in third-generation synchrotron radiation facilities will provide photon beams with high brilliance and large power densities. The optical quality of these beams allows, in principle, the use of simpler optical systems for focusing and monochromatization. In practice the performance of the optical elements is the physical limit to the exploitation of these high brilliance beams. In double-crystal monochromators the bending of the first crystal due to the thermal load and the anticlastic effect on the sagittally bent second one are among the main sources of problems on the overall performances. Here we have considered a double-crystal monochromator with a meridionally bent first crystal followed by a sagittally focusing one. We show that this geometry offers correction either of thermal loads and anticlastic distortions, or minimization of the bandpass or tangential focusing. This can be particularly useful on the high-energy range and for sharp Bragg reflections.
Quasicontinuous gain in sol-gel derived CdS quantum dots
Authors: Butty J. , Hu Y. Z. , Peyghambarian N. , Kao Y. H. , Mackenzie J. D.
Published: July 2002

We report evidence for quasicontinuous optical gain in CdS quantum dots fabricated by the sol-gel process and embedded in glass. The gain spectra are obtained using the pump and probe technique and nanosecond (quasiresonant) excitation at 11 K. The dots are in the intermediate quantum confinement regime and the concentration of CdS is relatively high. The gain, which is spectrally broad, develops on the low energy side of the absorption band edge. The reason why the gain region is broad is not only the size distribution of the dots, but also the nature of the gain, which originates from the recombination of several excited levels between two and one electron-hole pairs states (i.e., biexciton to exciton). The maximum measured gain reaches 200 cm−1 at 11 K and 17 cm−1 at 170 K.
The undulator beamline at the SRS Daresbury
Authors: Mythen C. S. , van der Laan G. , Padmore H. A.
Published: July 2002

The design and performance of the undulator beamline 5U.1 at the SRS used for soft x-ray spectroscopy is reported and compared with the theoretical expectation of the intensity, resolution, and polarization. The beamline consists of a ten-period permanent magnet variable gap undulator followed by an entrance slitless plane grating monochromator. The energy region covered is from 0.1 to 1 keV. The design is similar to the SX700 but uses a spherical instead of an ellipsoidal focusing mirror. To eliminate the large horizontal beam width at the exit slit the beamline has been modified to include a post-focusing mirror. The spherical focusing mirror has been changed to one with a larger radius resulting in a decreased demagnification, thereby essentially eliminating primary coma. The monochromator contains an ion-etched and lamellar profile 1200-lines/mm plane grating of Pt-coated CVD SiC on a graphite substrate. The high flux of the undulator makes the beam line suitable for SEXAFS studies and for work involving soft x-ray fluorescence detection. The combination of high flux and high resolution is especially advantageous for atomic and molecular spectroscopy and to resolve the quasiatomic structures which are observed in localized 3d transition metal compounds.
YB66 as a new soft x-ray monochromator for synchrotron radiation (abstract)
Authors: Rek Z. , Wong Joe , Tanaka T. , Shimkaveg G. , Eckart M.
Published: July 2002

YB66, a complex binary semiconducting compound with a cubic crystal structure and a lattice parameter of 23.44 Å, is potentially a very good candidate for monochromatization of soft x-ray synchrotron radiation. The features such as: a large interatomic spacing, lack of absorption edges by the constituent elements in the region 1–2 keV, very narrow intrinsic rocking curves for (400) and (222) reflections and good thermal and mechanical properties make the material very useful. Using the known structure factors for the (400) and (222) reflections, having 2d values of 11.76 and 13.53 Å, respectively, their rocking curves have been calculated and are shown [J. Wang, G. Shimkaveg, W. Goldstein, M. Eckart, T. Tanaka, Z. Rek, H. Tompkins, Nucl. Instrum. Methods A 291, 243 (1990)] to be comparable to or better than that of beryl (101̄0). A novel indirect heating floating zone method for growing large size crystals was used by Tanaka and his coworkers in Japan [T. Tanaka, S. Otani, and Y. Ishizawa, J. Cryst. Growth 73, 31 (1985)]. Numerous modifications of this technique and double-zone passes were applied to reduce sub grain structure and lattice deformations. The crystalline perfection and absence of defects is critical to obtaining high energy resolution and good crystal reflectivity. Crystals large enough to accept 1 mrad of radiation, with growth direction [100] and [110] were grown. Rocking curve measurements, etch pit density, and x-ray white beam topography are used to characterize the quality of these crystals as a function of some critical growth parameters. Most crystals exhibit the existence of sub grain boundaries. Areas perfect enough were observed to give ∼ 0.5 eV energy resolution. Recent experiments in crystal growth, results of crystals characterization, and comparison with theoretical calculations will be discussed.
SX-visible photon beam lines 3B1A for lithography and 3B1B for biological spectroscopy at BSRL
Authors: Gu Xiangming , Xu Wenxuan , Cui Mingqi , Yi Futing , Wang Peiwei , Sheng Weifan , Wu Jianwu , Xian Dingchang
Published: July 2002

The photon beam lines from beam port 3B1 recently constructed at Beijing Synchrotron Radiation Laboratory (BSRL) are beam lines for soft x-ray lithography and VUV-visible spectroscopy alternately. The commissioning of these beam lines has been carried out under both the parasitic and dedicated modes of the storage ring Beijing electron-positron collider (BEPC). This article reports the status of these two beam lines as well as the comparison of the preliminary measurement results with the calculated synchrotron radiation spectra of these beam lines.
Current status of 10-m GIM for soft x-ray undulator at the Photon Factory
Authors: Yagishita A. , Masui S. , Toyoshima T. , Maezawa H. , Shigemasa E.
Published: July 2002

The current performance of a 10-m grazing incidence monochromator (GIM) is described. A resolution of 51, 95, and 220 meV (FWHM) has been achieved at 287, 401, and 867 eV, respectively, inferred from the linewidths for the K-shell resonances of gaseous CO, N2, and Ne. A photon flux of ≂1012 photons/s is obtainable at the first harmonic of undulator radiation with a 1200-ℓ /mm grating and 50-μm slit openings, which correspond to Δλ=0.04 Å.
A soft x-ray beam line (BL13C) at the Photon Factory with a CEM using undulator radiation
Authors: Matsubayashi N. , Shimada H. , Tanaka K. , Sato T. , Yoshimura Y. , Nishijima A.
Published: July 2002

A soft x-ray beam line which enables high resolution and high flux at the same time is being developed at the Photon Factory for advanced characterization of new functional materials. The beam line is designed based on a cylindrical element monochromator (CEM) concept using undulator radiation from a 27-pole multipole wiggler/undulator. The photon energy range of the beam line is 200–1000 eV which covers the core-level excitation energy of carbon, nitrogen, and oxygen. Ray tracing simulation shows that the resolving power (λ/Δλ) is over 12 000 at 30 Å with a throughput of 25% when the opening of the exit slit is 10 μm. The beam line will supply x rays which facilitate both x-ray absorption (XAS) and photoelectron (XPS) spectroscopic measurements with extremely high energy resolution.
X-ray characterization of lapped Si surfaces for coronary angiography with 311 reflection at 33.17 keV
Authors: Shiwaku Hideaki , Hyodo Kazuyuki , Wu Xiao-Jing , Horiuchi Shigeo , Ando Masami
Published: July 2002

X-ray characterization of lapped surfaces of Si monochromator crystals for coronary angiography was performed at 33.17 keV to find out its optimum condition to obtain highest integrated intensity and a reasonable energy resolution, such as materials, diffraction indices, asymmetrical factors, and states of crystal surfaces. Its integrated intensity and the full width at half maximum of Si 311 lapped by SiC ♯1200 abrasive was enhanced nine times and enlarged seven times as large as an etched one, respectively. These results meet the requirements for imaging in coronary angiography. Furthermore, from cross-sectional observation using the electron microscopy, it was found out that mechanical lapping by abrasives induced many cracks in the sample crystals. It is considered that the larger the particle size of the abrasive, the larger misorientation in the surface has occurred.
Magnetic Compton-profile experiments using circularly polarized hard x rays
Authors: Tanaka Y. , Sakai N. , Kawata H. , Iwazumi T.
Published: July 2002

The beamline NE-1A, constructed at the accumulation ring of the National Laboratory for High Energy Physics in Tsukuba has brought a remarkable progress in the magnetic Compton-profile experiment. Circularly polarized hard x rays emitted from an elliptical multipole wiggler are monochromatized and focused with a quasidoubly-bent Si monochromator. We report the methodological aspect of recent successful magnetic Compton-profile experiments with high statistical accuracy achieved by using a Ge solid-state detector having thirteen segments.
Evaluation of a new VUV/soft x-ray toroidal grating monochromator with a movable exit slit
Authors: Mancini D. C. , Bissen M. , Rioux D. , Patel R. , Rogers G. , Brodsky E. L. , Höchst H.
Published: July 2002

The performance of a toroidal grating monochromator can be significantly improved by compensating for the wavelength dependent defocusing aberration by means of a movable exit slit. Model calculations of a movable exit slit design show a resolving power that varies nearly linearly with wavelength over the scan range. The energy resolution follows the slope between two optimized resolution minima of a fixed slit TGM. The overall improvement in resolution due to the movable slit depends critically on the figure error of the toroid surface. The Al(LII,III) core edges provide a means to calibrate gratings and determine the resolution at 72.8 eV. A method is described for using the shift in core edge with exit slit position to enable final alignment of the exit slit motion providing stability of energy calibration of 2 meV over the scan range. Comparison of calculations and measured resolution suggests that slope errors remain the limiting factor in performance.
X-ray instrumentation for analysis of fluorescent and scattered radiation (invited)
Authors: Deslattes Richard D.
Published: July 2002

Application of high resolution instrumentation to the study of the near-threshold behavior of fluorescent and scattered radiation along with such properties as polarization and angular distribution has proven fertile. This article reviews some alternative strategies for improving the efficiency with which such secondary spectra can be registered.
The use of synchrotron x rays to exploit the Warren–Mavel fluorescence detection technique in studies of disordered systems
Authors: Bushnell-Wye G. , Finney J. L. , Turner J. , Huxley D. W. , Dore J. C.
Published: July 2002

Although the early structural studies of liquids and amorphous systems used x-ray diffraction, the advent of high flux reactor sources led to neutron diffraction becoming the preferred technique. There are several advantages: high scattering vector information is not form factor limited and, where isotopes exist, the variation in scattering length allows more detailed structural information to be extracted in many cases. However, the development of synchrotron radiation sources has generated renewed interest in x-ray measurements. High intensity is available at wavelengths short enough to give reasonable access to the high scattering vector region and, in theory, the tunability can be used to maximize anomalous scattering effects and so allow element specific scattering to be recorded. Another use of the tunability is for largely removing the Compton scattering which can often dominate the total scattered intensity and which contains no structural information. This technique requires a choice of incident photon energy such that the x rays scattered without energy loss excite fluorescence in a metal foil in the detection system while most of the Compton scattering has insufficient energy to do so. Hence, recording the fluorescence intensity effectively gives a measurement of the elastic scattering only. Whereas early experiments were limited by the available x-ray emission lines of conventional sources, synchrotron radiation can be tuned so that the incident energy is much closer to the absorption edge of the metal foil thus maximizing the efficiency of the technique. We demonstrate the power of this method and suggest where its application may continue to develop interest in x-ray experiments.
Refinement of time-resolved x-ray measurement system for studying the lattice deformation of silicon under pulsed Nd:YAG laser irradiation
Authors: Kojima S. , Maekawa I. , Kawado S. , Takahashi T. , Ishikawa T. , Kikuta S.
Published: July 2002

The time-resolved x-ray measurement system using the TAC technique and the MCS technique has been improved after the previous SRI conference. The improved TAC technique enables us to measure a time-resolved x-ray diffraction intensity distribution across a laser spot at any time after laser flashing with a time resolution of 25 ns under the multibunch operation of synchrotron radiation sources. Optical fiber delay units are developed for the MCS technique instead of ECL delay units to obtain long delay time for detective signals.
A beam expander facility for studying x-ray optics
Authors: Christensen F. E. , Hornstrup A. , Frederiksen P. , Nilsson C. , Grundso/e P. , O/rup P. , Jacobsen E. , Schnopper H. W. , Lewis R. , Hall C.
Published: July 2002

The detailed study of the performance of full scale x-ray optics often requires the illumination of large areas. This paper describes a beam expander facility at the Daresbury Synchrotron Radiation Facility. It combines monochromatization and beam expansion in one dimension. The beam expansion is obtained from an extremely asymmetric reflection in a large single crystal of Si. An expansion of a factor of 50 was obtained in one dimension. The expanded beam of ∼85 mm is limited only by the crystal size. The facility is installed in a 12-m-long hutch. A specific application, in which a high throughput x-ray telescope will be studied, is described in detail.
Development of ultrasmall-angle scattering for studies of colloidal systems (abstract)a)
Authors: North A. N. , Rigden J. S. , Mackie A. R.
Published: July 2002

Ultrasmall-angle x-ray scattering (USAXS) using the Bonse–Hart twin-crystal diffractometer system1 on a synchrotron radiation source (SRS) is being developed as a technique for studying the structure of colloidal dispersions and other inhomogeneous materials with features in the size range 500 Å to 1 μm. The use of well-characterized colloidal samples in this range highlights the problems which must be resolved in order to obtain reliable data from the system. This paper addresses the specific problems of attenuation, absorption, detector dead time, and smearing for the USAXS configuration. The system has been used to study a variety of materials and some previously unobserved features have been found in the scattering profile of a colloidal latex. This serves to indicate the value of the improved system in the field of colloidal science.
The high-resolution powder diffraction station PO DI STA is ‘‘running’’ at Adone
Authors: Burattini E. , Simeoni S. , Cappuccio G. , Maistrelli P.
Published: July 2002

At the end of February 1991, a ‘‘triple-axis’’ high-resolution diffractometer for on powder sample measurements with synchrotron radiation was put in operation on the Adone wiggler line BX1 at Frascati. The diffractometer is based on a Seifert goniometer, designed according to our specifications. During the project, particular attention was paid in assuring the highest reliability together with great flexibility in the use. In fact, the diffractometer can also be used in a ‘‘medium resolution’’ configuration. For preliminary alignment and data collection, it is possible to operate with a traditional x-ray tube, too. The alignment procedure of the diffractometer to the x-ray beam is very easy. Powder samples can be measured both on the flat holder and on the capillary. An IBM PC computer is used for the instrument actuation and preliminary on-line data collection, while a large software package has been developed for the data analysis performed by a Macintosh IIcx. The instrument performance has been tested with a standard Si sample and quartz and Ni oxide samples. For the two possible resolution configurations, a test on a NiO sample gave FWHM values of 0.16° and 0.04°, respectively, for the [012] peak.
Angle-dispersive powder-diffraction techniques for crystal structure refinement at high pressure
Authors: Nelmes R. J. , Hatton P. D. , McMahon M. I. , Piltz R. O. , Crain J. , Cernik R. J. , Bushnell-Wye G.
Published: July 2002

An imaging-plate system designed for the full Rietveld refinement of crystal structures at high pressure is described. Emphasis is given to techniques that have been developed to obtain data free from contaminating diffraction peaks. Initial results from studies of III–V semiconductors and La2CuO4 are given.
Design and performance of a focused beam line for surface x-ray diffraction
Authors: Norris C. , Finney M. S. , Clark G. F. , Baker G. , Moore P. R. , van Silfhout R.
Published: July 2002

Focusing optics have been installed on the 5.0 T Wiggler beam line of the SRS at Daresbury Laboratory for use with x-ray diffraction measurements of surfaces and interfaces. A significant increase in the flux has been achieved without excessive degradation of the resolution in the vertical plane. The full width at half-maximum of the focused image compares well with the predictions of ray tracing analysis.
Economical x-ray area detector for focusing and alignment purposes
Authors: Chu Benjamin , Rousseau Jean , Gao Tong
Published: July 2002

We developed a two-dimensional x-ray detector for x-ray beam profile analysis. The detector was built from commercially available parts, which included a low-cost 8-bit CCD camera, and a zoom lens coupled to a close-up lens, to which was attached a fiber-optic faceplate coated with (Gd2O2S:Tb) phosphor to a surface density of (10 mg/cm2). Testing of the detector unit has shown good linearity of response to the incident x-ray intensity (within ±4%), and good spatial linearity. The advantages of this detector lie mainly in its compactness, its ease of maneuverability, and the fact that it can be remotely controlled by a PC/AT computer at a reasonable cost (∼$1000 without the PC/AT).
New chemistry for selective reactive ion etching of InGaAs and InP over InAlAs in SiCl4/SiF4/HBr plasmas
Authors: Murad S. K. , Beaumont S. P. , Wilkinson C. D. W.
Published: July 2002

A selective reactive ion etching process which etches InP and InGaAs, but not InAlAs, using a mixture of SiCl4/SiF4/HBr gases has been developed. Optical emission spectroscopy shows that the dominant emitting species in the plasma are HBr+, Br, and Br2, with a weaker emission from SiBr and SiHBr. We believe that the bromosilanes or chlorosilanes of the form (SiHxBry,SiHxCly) are responsible for the etching of these In-containing compounds by the formation of indium bromosilanes and indium chlorosilanes. Using a flow rate ratio of SiCl4/HBr of 7/15 sccm, a pressure of 100 mTorr and with dc bias of 80 V, an etch rate of InGaAs and InAlAs as high as 100 nm/min at room temperature was achieved with good surface morphology. The addition of SiF4 suppresses the etching of InAlAs and the selectivity obtained can be changed by varying the proportion of SiF4. At a flow rate ratio (SiCl4:SiF4:HBr) of 5/6/20 sccm, dc bias of ≤70 V and a pressure of 150 mTorr, the selectivity obtained is extraordinarily high (≳600:1) for this material system.
High energy x-ray imaging diagnostic on Nova
Authors: Remington B. A. , Hammel B. A. , Landen O. L. , Pasha R. A.
Published: July 2002

We have developed a diagnostic suitable for high photon energy (∼7 keV) time resolved one-dimensional x-ray imaging on Nova. This diagnostic uses a 12 μm wide, 750 μm long imaging slit mounted on a 20× magnification snout which is coupled to an x-ray streak camera of variable streak speed. The diagnostic fits into retractable manipulators on the ten-beam chamber at Nova. In situ backlit grid experiments using a large-area backlighter give a spatial resolution full width at half-maximum of about 15 μm with high brightness.
Multichannel interferometry using high-order rotating diffraction gratings
Authors: Howard John , Warr George B. , Dodds Peter
Published: July 2002

We report the successful construction and operation of a far-infrared (337 μm) interferometer based on a multiple-order diffraction grating wheel. On reflection from the wheel circumference, the incident laser beam is diffracted into a number (∼12) of approximately equal intensity high-order beams. Since the Doppler offset of the beams is proportional to the diffraction order, information encoded by the spatially distinct beams is multiplexed in the frequency domain. This allows simultaneous multichannel phase shift information to be obtained using only a single detector.
Ultrafast photoconductive detectors for burn time and bang time measurements on Phebus
Authors: Garçonnet J-P. , Bourgade J-L. , Nail M. , Schirmann D. , Cuzin M.
Published: July 2002

To study deuterium-tritium mixture implosion conditions on laser fusion experiments, we developed very high-speed photoconductive devices. The targets are irradiated by the 1.3-ns, 5-kJ blue light of the two beams of the Phebus laser. The neutron yield is a few 1010/4π. Some neutron sensitivity measurement results are presented on neutron-damaged GaAs and diamond. These devices are able to measure the time behavior of the thermonuclear neutron burst. So, we have measured the burn time and the bang time on direct drive experiments with 100 ps as accuracy.
PIXE x rays: From Z=4 to Z=92
Authors: Li C. K. , Wenzel K. W. , Petrasso R. D. , Lo D. H. , Coleman J. W. , Lierzer J. R. , Hsieh E. , Bernat T.
Published: July 2002

A high-intensity, charged-particle-induced x-ray (PIXE) source has been developed for the purpose of characterizing x-ray detectors and optics, and measuring filter transmissions. With energetic proton beams up to 165 keV, intense line x radiations (0.5 Å≤λ≤111 Å) have been generated from the K, L, M, and N shells of elements 4≤Z≤92. The PIXE spectrum has orders-of-magnitude lower background continuum than a conventional electron beam or radioactive α-fluorescence source [C. K. Li, R. D. Petrasso, K. W. Wenzel et al. (to be published)].
High count rate time-of-flight spectrometer for DD fusion neutrons
Authors: Gorini G. , Källne J.
Published: July 2002

The basic factors setting the performance limits of the time-of-flight (TOF) spectrometer for 2.5-MeV neutrons as used for tokamak plasma diagnostics are analyzed. Special scintillator designs are proposed for best performance. Examples of diagnostic uses of the TOF spectrometer are also given.
Saturation recovery electron paramagnetic resonance spectrometer
Authors: Quine Richard W. , Eaton Sandra S. , Eaton Gareth R.
Published: July 2002

A versatile saturation recovery accessory based on a small, special-purpose timing controller and an efficient mix of coaxial and waveguide microwave components has been added to a commercial electron paramagnetic resonance (EPR) spectrometer. The spectrometer was designed for study of the spin lattice relaxation time of transition metals and free radicals over a wide temperature range, such as are of interest in materials science and metallobiochemistry. A microprocessor-based timing system was designed to provide a wide dynamic range with a simple user interface. Waveguide phase shifters and rotary vane attenuators were used for their precision and resetability, while coaxial components were used where their superior performance could be exploited. Sensitivity is provided by a low-noise GaAs field-effect transistor (FET) microwave preamplifier and a double-balanced mixer (DBM) detector. A biphase modulator (±180° phase shifter) on the lo side of the DBM provided efficient addition/subtraction of successive recovery curves, obviating slow data transfer to a computer prior to the arithmetic operations. Because the system is designed for the study of inherently broad spectra, it does not use the magnetic field step modulation of some prior spectrometers. In addition, although most EPR spectrometers have been designed with a phase shifter in the reference arm, we have found it more convenient to keep the reference arm phase constant and adjust the phases of the pump and observe arms of this three-arm bridge spectrometer. The saturation recovery system described here could be implemented on any commercial EPR spectrometer with only minor modifications.
Electron paramagnetic resonance spectrometer for three-dimensional in vivo imaging at very low frequency
Authors: Alecci M. , Della Penna S. , Sotgiu A. , Testa L. , Vannucci I.
Published: July 2002

The paper describes an electron paramagnetic resonance apparatus for spectroscopy and imaging at very low frequency (283 MHz). The bridge operates in a reflection cavity homodyne configuration and can be used on a very broad frequency range. The sample cavity is a one loop-two gap resonator and accepts samples up to 5 cm in diameter and 10 cm long. These sample dimensions make the apparatus suitable for observing living samples such as rats. For the main field and gradients the apparatus uses a newly designed multipolar magnet that can provide the main field and gradients for 2D image reconstruction. The third gradient is obtained by coils mounted in the bore of the magnet. Tests on peroxilamine disulfonate samples have shown micromolar sensitivity. The minimum spatial resolution is limited by the sample linewidth and by the signal/noise. In living samples the toxicity of nitroxide radicals restricts the maximum label concentrations to values of the order of 10−4 M, and the resolution seems to be limited by sensitivity to fractions of cm3.
The Hamburg Synchrotron Radiation Laboratory (HASYLAB)
Authors:   HASYLAB
Published: July 2002

HASYLAB is situated at the storage ring DORIS. Existng experimental stations at HASYLAB are summerized. Brief information concerning the source and optical, system, energy range and other operating parameters is given. (AIP)
High-pressure, high-temperature two-chamber cell with changeable path lengths for accurate measurements of absorption coefficient
Authors: Gorbaty Yu. E. , Bondarenko G. V.
Published: July 2002

A cell with two sample chambers arranged in sequence is designed to provide accurate absorption coefficients for the components of binary fluid systems at high pressures and temperatures. Once primed, the cell allows one to obtain results over the whole range of temperature and pressure required without disassembly and refilling. The method eliminates or at least diminishes most of the possible errors automatically.
Optical interferometer for gas bubble vibration measurements with Angstrom sensitivity
Authors: Rovati Luigi , Lago Paolo , Corti Mario , Gomarasca Carlo
Published: July 2002

An optical interferometer which measures the radial pulsations of gas bubbles in liquids with Angstrom sensitivity is described. The gas–liquid interfaces act as mirrors. The interferometer, intrinsically differential, is insensitive to the overall movement of the bubble and to vibrations of the optical components. Examples of the resonance behavior of oxygen bubbles in water are given.
Enhancement of H− production in an rf-driven multicusp source
Authors: Leung K. N. , Bachman D. A. , McDonald D. S.
Published: July 2002

An rf-driven multicusp source has been operated in pulsed mode to generate H− ions that are formed by volume processes. A total H− current of approximately 40 mA has been extracted from a 5.6-mm-diam aperture with rf input power higher than 50 kW. Attempts have been made to enhance the H− beam current by introducing a small quantity of cesium vapor into the source chamber. It is found that the H− output current can be increased by a factor larger than 3 if some cesium is applied in the collar around the exit aperture. Electron current can be reduced by cesium deposition on the chamber walls. A simple cesium delivery system fabricated from small dispensers has been operated very successfully with the clean rf induction discharge.
Theory and operation of a three-gate time-of-flight velocity analyzer
Authors: Martus K. E. , Orient O. J. , Hodges R. R. , Chutjian A.
Published: July 2002

Theoretical considerations and test results are presented for a new-type velocity analyzer for incident fast neutral particles, positive ions, and negative ions. Velocity analysis is carried out by means of a pulsed, three-gate time-of-flight (TOF) technique capable of eliminating alias velocities (harmonics) to sixth order. In addition the design and operation are presented of a four-element ion lens system, with small spherical and chromatic aberrations, suitable for interfacing a large-diameter ion beam from the TOF section with a subsequent mass analyzer.
The electron-beam furnace: A new facility for materials science research
Authors: Stenzel Ch. , Braun M. , Krass C. , Mayer H.-G.
Published: July 2002

The development and the test results of an electron-beam furnace for the later utilization in a microgravitational environment are reported. By just varying the deflection pattern by means of the electron-optical components two reference profiles, a gradient profile with a maximum slope of 220 K/cm, and a hot zone profile with a zone temperature of 1520 K could be established and maintained. A beam power of 550 W had to be applied to a sample made of massive Ta for the gradient profile, for creating a hot zone profile an input power of only 250 W onto a sample with a ceramic core was sufficient. A continuous pyrometric measurement system with a high local and time resolution has been realized. By temperature sensing of the sample with this system an intrinsic feature of electron-beam heating could be directly observed, the sharply localized energy deposition at the sample surface.
Highly oriented pyrolytic graphite as a reference surface for optically stimulated electron emission surface quality monitors
Authors: Baseman Robert J. , Batchelder J. Samuel
Published: July 2002

Optically stimulated electron emission (OSEE) measurements may be used to monitor a variety of surface properties. To take full advantage of the potential of such measurements, well-defined reference surfaces are required to serve as calibration standards and for use in comparative studies. Here we describe the use of freshly cleaved highly oriented pyrolytic graphite as a reference surface. With the most elementary protocol of peeling the surface with adhesive tape, surfaces with OSEE currents varying by ±3.5% may be produced. By taking into account sample thickness changes with repeated use, variations should be reduced to on the order of ±1% routinely.
Dual-beam, double-pass absorption spectroscopy of shocked materials
Authors: Holmes N. C.
Published: July 2002

We describe a new method for performing dual-beam, double-pass absorption spectroscopic studies of shocked fluids and solids at ultrahigh pressures. This method can provide high time and spectral resolution of the opacity of shocked materials. It uses a multichannel fiber-optic-coupled system. Two kinds of detectors are used: photomultipliers provide high time resolution in a set of narrow wavelength bands, and a gated, intensified, linear diode-array detector yields a ‘‘snapshot’’ spectrum with high resolution. Applications to the study of shock-induced chemical reactions are described. We briefly describe related applications using this method and apparatus.
Distinction between multicharged ion species with equal q/m
Authors: Aumayr F. , Kurz H. , Winter HP. , Schneider D. , Briere M. A. , McDonald J. W.
Published: July 2002

We present a new technique for selective, highly sensitive, absolute detection of different multiply charged ion species with equal charge-to-mass ratios in mixed multicharged ion beams. This is achieved by exploiting the statistics of potential electron emission as induced by the ion beams on a clean metal surface. The applicability of the method is illustrated by way of different practical examples.
Simple arrangement for liquid-droplet experiments due to morphology-dependent resonances
Authors: Taniguchi Hiroshi , Tomisawa Humihiro
Published: July 2002

The arrangement for simple and inexpensive experiments based on the morphology-dependent resonances (MDR) is presented which allows a method of making liquid droplets with stable diameters and efficient light emission from the droplets. The lasing and Raman scattering characteristics due to MDR with this arrangement are also described.
Tracing fast changing temperature on laser-pulsed metal surfaces by micropyrometry
Authors: Schäfer B. , Bostanjoglo O.
Published: July 2002

The surface temperature of pulse laser heated tungsten targets was determined by a high-speed micropyrometric method. Using a blue line of the heat radiation, a temporal/spatial resolution of 2 ns/10 μm is achieved. Temperatures were traced in the range from 2800 K to the boiling point of tungsten at about 6000 K. The accuracy is about 5%–10% because of uncertain values of the spectral emissivity. However, the accuracy of radiance temperature is limited only by the photon shot noise. Numerical calculations of the one-dimensional heat equation are in satisfactory agreement with the experimental results. If melting occurs, thermocapillary flow reduces the spatial resolution from the Abbe limit to about 10 μm.
Tunneling probes for metrological applications using a long-range profilometer
Authors: Liu X. , Smith S. T. , Chetwynd D. G.
Published: July 2002

The construction of a long-range tunneling profilometer based on a ‘‘Nanostep’’ slideway is reported. This profilometer has potential capability of measuring surface profiles over a complete traverse of 50 mm horizontally and 15 μm vertically. Its characteristics have been investigated over both long and short scanning ranges. Results are presented of a series of repeat measurements over 1.4-mm traces on a gold-coated silicon wafer. A repeatability of better than 0.2 nm is obtained and surface features of a few nanometers have been resolved laterally. Anomalies in the characteristic of tunneling current with the bias voltage are discussed in terms of surface contaminants and physical contact between tip and sample. Some problems in the application of STM in nanometric metrology are also discussed.
Microwave cavity spectrometer for process monitoring of ethylene oxide sterilization
Authors: Zhu Z. , Gibson C. , Samuel A. H. , Matthews I. P.
Published: July 2002

This article reports a novel and simple cavity spectrometer for process monitoring of ethylene oxide sterilization, in which the source frequency, cavity resonant frequency, and gas absorption center frequency are asynchronous with respect to each other, thus, enabling sophisticated signal enhancement techniques to be employed without the need to engage the Stark effect. The operation of the device is such that the source frequency sweeps across a given range (F1 to F2) which contains one of the absorption peaks of the analyte gas (gases) of interest while the cavity resonant frequency Fr is oscillated within the profile of the absorption peak. Signal enhancement is achieved by adding a relatively small magnitude/high-frequency ‘‘dither’’ signal to the source frequency sweep pattern. The salient information of the gas absorption due to the oscillation of the resonant frequency of the cavity is carried by the ‘‘dither’’ signal and amplified and extracted by a series of tuned amplifiers and demodulators. Although the device is still at the initial design stage, a working prototype has been constructed in order to test the feasibility of the novel asynchronous modulation technique. This was achieved by successfully demonstrating that the device operates in an expected manner to within a standard error of 8.3%. It is believed that this error largely results from mechanical components. The significance of this error is greatly reduced when the spectrometer is operated in a large signal scanning mode as is the case when we apply the ‘‘power saturation’’ technique to measure the concentration of ethylene oxide in the resonant cavity. This measurement showed that there is a good linear correlation between the output signal and the concentration of ethylene oxide gas (to within a standard error of 4%).
Development of a real time visualization system for the shape of a tokamak plasma cross section
Authors: Hara S. , Takeuchi K. , Abe M. , Otsuka M.
Published: July 2002

A real time visualization system for the shape of a tokamak plasma cross section has been developed by using Versa Module Europebus (VME)-standardized modules. Digital signal processors (DSPs) are used in parallel for magnetic analysis. A fast and high resolution graphics control processor is adopted for part of the display system. Fast shape identification methods are presented in which tabulated Green’s functions are utilized. The analysis errors are evaluated with Hitachi tokamak 2 (HT-2) experimental data. The plasma shape is visualized in real time with the cycle time of 30 ms. When this system is applied to the International Thermonuclear Experimental Reactor (ITER), the estimated cycle time for visualizing the plasma shape is 40 ms.