bluuebunny/crossref_metadata_2025 huggingface dataset:
Overview of the advanced photon source (invited)
Authors: Moncton D. E. , Crosbie E. , Shenoy G. K.
Published: July 2002

The Advanced Photon Source planned for construction at Argonne National Laboratory is based on a low-emittance storage-ring operated at 7 GeV and capable of providing tunable undulator radiation from 4 to 40 keV (using the first and the third harmonics). A technical description of the accelerator facility and the storage ring is presented in this overview, along with a brief summary of the characteristics of radiation that will be available from the insertion devices. Various plans for user access to this national user facility are also given.
Three-crystal spectrometer for 150-keV synchrotron radiation
Authors: Hastings J. B. , Siddons D. P. , Berman L. E. , Schneider J. R.
Published: July 2002

A triple-axis spectrometer for high-energy (≳150 keV) synchrotron radiation has been constructed and characterized. The reciprocal space resolution function of this instrument has been measured using perfect silicon crystals as monochromator, sample, and analyzer. It was found to have dimensions of 1.0×10−5 Å−1 and 2.3×10−4 Å−1 in the directions perpendicular and parallel to the momentum transfer Q, respectively, comparable to those achievable using standard 8-keV triple-axis instruments. The large penetration depths of high-energy x-ray photons, combined with the high instrumental resolution, opens new possibilities in the study of truly bulk condensed matter systems.
X-ray imaging arrays for impurity transport studies on the Texas Experimental Tokamak
Authors: Wenzel Kevin W. , Petrasso Richard D.
Published: July 2002

Three multichannel soft x-ray imaging arrays are used for impurity transport studies on the Texas Experimental Tokamak. The entire system has a total of 92 broadband x-ray detectors that view the plasma at the same toroidal location from three different poloidal angles: Array A is a 40-channel vertically viewing set of silicon surface barrier diodes (SBDs); array B is a 40-channel horizontally viewing set of SBDs; and array C is a 12-channel set of p-intrinsic-n (p-i-n) detectors viewing the plasma from 45° above the horizontal plane. Array B is absolutely calibrated; array A is relatively calibrated in situ; and array C is cross-calibrated relative to array B. In this article we describe the primary components of the system: (1) the specific x-ray diodes used for the arrays and their spectral sensitivities; (2) the corresponding electronics necessary for data acquisition; and (3) the vacuum system for the arrays. Furthermore, we describe a novel krypton edge absorption filter which discriminates between the resonance line radiation of He-like and H-like aluminum injected into TEXT plasmas.
Low-noise FET amplifier for dc SQUID
Authors: Pallottino Giovanni V. , Lupi Tito
Published: July 2002

We report on the design, characterization, and operation of a low-noise FET-input differential amplifier, which is used as second stage for a dc SQUID in the electronic instrumentation of the gravitational wave detector of the Rome group at CERN. The 3-dB bandwidth of the amplifier is from 10 kHz to 1.5 MHz. At the SQUID modulation frequency of 70 kHz the voltage noise is 0.5 nV/(Hz)1/2, the current noise is 35 fA/(Hz)1/2.
Simple cryogenic infrared window
Authors: Hartemink M. , Godfried H. P.
Published: July 2002

A simple, cheap technique is reported that allows materials with both large and small thermal expansion coefficients to be mounted as windows in low temperature cryostats while at the same time avoiding thermal stresses. The construction may be thermally cycled many times with no change in its properties. It can hold differential pressures of at least 1 atm for a 1-in.-diam window. This technique seems to be particularly useful for applications where the use of soft materials cannot be avoided (e.g., ZnSe in the infrared).
A plasma source for mirror physics simulation experiments
Authors: Vandegrift Guy , Donahue Kathy , Velat Deb
Published: July 2002

A low density, cold lithium plasma source with cross field injection operates with neutral gas density sufficiently low for studies that simulate certain low frequency waves in a mirror fusion reactor.
Computer-controlled system for the real-time measurements of membrane potential, internal and external pH’s, delta pH, proton fluxes, and O2 concentration
Authors: Hendler Richard W.
Published: July 2002

The construction of sturdy ion-selective electrodes for tetraphenyl phosphonium ion (TPP+), and salicylate is described. Instrumentation and procedures are presented for real-time studies of membrane potentials and pH gradients that form across the membranes of organelles that are capable of transducing metabolic or radiant energy into an electrochemical potential for protons. The system is based on input signals from a TPP+-selective electrode, fluorescence from a pH-sensitive dye, a pH electrode, and an O2 electrode. A microcomputer is used to perform extensive computations based on the raw input data and to display various aspects of the progress of an experiment both on a CRT monitor and a recorder.
A novel target manipulation technique used in generating bare metal cluster ions for catalytic research
Authors: Gangopadhyay Pritha , Lisy James M.
Published: July 2002

A novel method of target manipulation for laser vaporization of metals has been described. The simplicity of fabrication offers a number of advantages over existing techniques. The yield of stable clusters M+x, x=1 to 8 is quite good and mass selection using a Wien (E×B) mass filter has been achieved. Examples of Nb, Co, and Mn mass spectra are presented.
A protection circuit for side window photomultiplier tubes
Authors: Hartley P. E. , Wagner S.
Published: July 2002

A simple circuit to protect side window photomultiplier tubes against damage from accidental exposure to intense light is described. The gain of the tube is reduced by a factor of at least 104 within 20 μs of overload and automatically returns to normal when the over exposure is removed. This is achieved by using high voltage transistor optocouplers to reduce the voltage between the photocathode and the first seven stages of the tube to zero. The circuit may be easily adapted to suit other types of photomultiplier.
An electronic Cranz–Schardin camera
Authors: Bretthauer B. , Meier G. E. A. , Stasicki B.
Published: July 2002

An electronic high-speed multiple-image camera based on the Cranz–Schardin principle has been developed. High-power LEDs are used as a light source. Frames are recorded by a system of eight CCDs and an eight channel image processor enabling a series of eight subsequent images at full-frame (512× 512) resolution or more images (up to 80) at a lower resolution. The maximum framing frequency is 10 MHz. The advantages upon the classical spark illumination and photographic techniques are mainly the precise electronic control, the immediate access to the frames, the on-line image processing and the low cost of the system. Examples of gas- and two-phase flow visualization are presented.
Control of charge trapping in a photorefractive polymer
Authors: Malliaras G. G. , Krasnikov V. V. , Bolink H. J. , Hadziioannou G.
Published: July 2002

Modification of the trap density of the photorefractive polymer composite poly(N-vinyl carbazole) (PVK), 2,4,7-trinitro-9-fluorenone (TNF) and N,N-diethyl-para-nitroaniline (EPNA) was achieved with the addition of 4-(diethylamino)benzaldehyde diphenylhydrazone (DEH). Measurements of the response time, the phase shift and the amplitude of the photorefractive grating are presented.
A novel technique for response function determination of shear sensitive cholesteric liquid crystals for boundary layer investigations
Authors: Parmar D. S.
Published: July 2002

A description of the design and setup of an experimental technique for measurement of the response function in shear sensitive liquid crystals has been reported. Utilizing the selective reflection characteristics of cholesteric liquid crystals, the method is capable of measuring the delay, rise, and relaxation times in response to a given dynamic shear stress as a function of the wavelength of the incident light. Application of a step input shear stress results in a liquid crystal time response that can be described as consisting of an initial delay, a shear induced helix deformation, and a relaxation to the initial state through diffusion processes. The method has been used for quantitative calibration of a shear sensitive liquid crystal by observing the peak in reflected light intensity, at a given wavelength, as a function of the shear stress. The selective reflection wavelength (λs) decreases linearly with an increase in shear stress (σ) and has a slope dλs/dσ≊10 nm/psi. The results suggest that in order to obtain quantitative information on the flow parameters over a test surface, three reflection spectra are required: one from a white surface and the other two from the liquid crystal surface one before and one in the presence of shear stress respectively. Free energy calculations for the elastic deformation of the liquid crystal suggest a time response of the liquid crystal for a step input in shear stress. Transport of the broken helix swarms has been suggested as a means for the helix relaxation to zero shear state even in presence of shear.
Summary of photon-beam stabilization at the Photon Factory
Authors: Kobayakawa Hisashi
Published: July 2002

The Photon Factory (PF) storage ring is a dedicated synchrotron radiation source. The stability of photon beams is the most important subject regarding such sources, since accurate positioning is especially required for sharply pointing undulator beams. A modification to increase the brightness by reducing the emittance of the circulating beams was carried out in 1987 at the PF ring. Though significant upgrades in the brightness have been obtained, many difficulties have simultaneously arisen, such as an increase of beam instabilities and photon-beam drifts. Stabilizing efforts have been carried out and great progress has been made: building distortion due to thermal stress, reduced to 1/6 by thermally insulating the roof.
X-ray, soft x-ray, and VUV beam position monitor
Authors: Karlin B. A. , Cowan P. L. , Woicik J. C.
Published: July 2002

An x-ray beam position monitor has been developed and is currently operational at the NIST beam line X-24A of the National Synchrotron Light Source. It was developed to accurately measure the vertical position of the synchrotron beam and to allow precise positioning of beam line optics. It is an area-type monitor positioned 5.6 m from the tangent point and precedes all beam line instrumentation. Vertical beam position is given by the differential photoemission current from two grids mounted on a Macor frame. The monitor also senses the total photon beam flux.
Self-tracking optical beam monitor
Authors: Miyahara Tsuneaki , Mitsuhashi Toshiyuki
Published: July 2002

A new optical beam monitor with a self-tracking system was constructed and tested at an undulator beam line of the Photon Factory. The monitor has a feedback system to receive a constant part of the radiation and gives a large range of linearity. The beam position is read out through a linear encoder to detect the self-tracking movement of a pair of photocathodes. The monitor except the feedback system is totally bakeable and UHV compatible and can be installed at a VUV or a soft x-ray beam line.
Recent experiments with liquid gallium cooling of crystal diffraction optics (abstract)a)
Authors: Smither R. K. , Lee W. , Macrander A. , Mills D. , Rogers S.
Published: July 2002

The x-ray beams for the next generation of synchrotrons will contain much more power (1–10 kW) than is available at present day facilities. Cooling the first optical components in these beam lines will require the best cooling technology that one can bring to bear. Argonne continues to pioneer the use of liquid metals as the cooling fluid and has adopted liquid gallium as the liquid metal of choice. Its low melting point, 29.7 °C and its very low vapor pressure make it an easy fluid to handle and its high thermal conductivity and heat capacity make it an excellent cooling fluid. A series of experiments were performed during April 1991 with the wiggler beam at the F2 station of the CHESS facility at Cornell to investigate the cooling of large areas of high power. Two types of cooling crystal geometries were tested, one where the cooling channels were core-drilled just below the surface of the crystal and a second where slots were cut into the crystal just below the surface with a diamond saw. Both crystals performed well with beam powers up to 1050 W and power densities of up to 14.5 W/mm2 at normal incidence.

An infrared camera was used to measure the variation in the temperature of the top layer of the silicon crystals. For the core-drilled crystal the peak temperature measured at the center of the beam at a power density of 12.3 W/mm2 was 15 °C hotter than the crystal surface outside of the beam with a flow of liquid gallium of 2 gpm (gallons per minute) and was 10 °C with a flow of 4 gpm. The maximum distortion of the crystal surface distortion of the core drilled crystal was about ±2.0 arcsec for the 2 gpm case with a maximum power density of 10.9 W/mm2 and about 5% of the expected beam intensity was lost at peak power of 14.5 W/mm2. For the slotted crystal the peak temperature difference for a peak power of 10.9 W/mm2 was 3.5 and 2.0 °C for liquid gallium flows of 1 and 2 gpm, respectively. No intensity loss was measured for the maximum power density of 14.5 W/mm2. The fact that the peak temperature differences on the surface of both crystals was decreasing with increased flow of liquid gallium suggests that even higher power densities can be accommodated with higher flows of liquid gallium. This work is supported by the Department of Energy, BES-Materials Sciences, under Contract W-31-109-Eng-38.
Rapidly modulated variable-polarization crossed-undulator source
Authors: Green Michael A. , Kim Kwang-Je , Viccaro P. James , Gluskin Efim , Halbach Klaus , Savoy Roland , Trzeciak Walter S.
Published: July 2002

An integrated system to produce and utilize variable-polarization radiation from a crossed undulator source on the Aladdin storage ring is being designed in a multilaboratory collaboration. Brief discussions of the motivation and options available precede a description of the source. Comments on ongoing work are also presented.
Design study for an adjustable phase undulator
Authors: Carr Roger , Nuhn Heinz-Dieter
Published: July 2002

This is a presentation of the results of a design study for an adjustable phase undulator. Earlier work described the basic theory of these undulators, whose magnetic fields are adjusted by moving the rows of magnets longitudinally with respect to each other, while keeping the gap fixed. This paper explores further details of a proposed permanent magnet, phase adjustable, soft x-ray undulator that will be used to test theoretical and calculated performance predictions. We present the Hamiltonian mechanics of the electron-beam and numerical calculations of magnetic fields and trajectories of electrons, including end effects. We also discuss the trajectories of off-axis electrons, the vertical focusing effect, the effects of magnetic errors, and finite emittance effects on the x-ray spectrum.
Improvement of beam lifetime by optics modification at the Photon Factory storage ring (abstract)a)
Authors: Katoh M. , Hori Y. , Kitamura H. , Mitsuhashi T.
Published: July 2002

The vertical acceptance of the Photon Factory storage ring had been limited by a narrow vacuum chamber at an insertion device. To increase the acceptance, the vertical betatron function at the device was reduced. This modification resulted in an increase of the beam lifetime by a factor of 1.5 and enabled one to operate the ring continuously for 24 h without a beam injection. The effects of the optics modification on the beam lifetime, beam injection, betatron tune shifts produced by the insertion devices, and the brilliance of the synchrotron light are presented.
PSR-2000: The mode of low emittance operation, the program of synchrotron radiation investigations
Authors: Efimov S. V. , Gladkikh P. I. , Grigor’ev Yu. N. , Guk I. S. , Karnaukhov I. M. , Kononenko S. G. , Kozin V. P. , Mocheshnikov N. I. , Shcherbakov A. A. , Tarasenko A. S. , Trushkin N. A. , Zelinsky A. Yu. , Nagaenko M. G. , Severgin Yu. P.
Published: July 2002

The problems of optimizing the lattice of the Kharkov Pulse Stretcher Ring PSR-2000, intended for use as a source of synchrotron radiation, are considered. Calculations of the dynamic aperture in the presence of sextupole magnets that compensate the natural machine chromaticity are made with due account of the reference orbit corrections and magnetic field perturbations up to the third order. The program of synchrotron radiation investigations using the PSR-2000 as a base is also discussed.
A photoacoustic joulemeter for millimeter wave radiation
Authors: Blank M. , Casey J. A. , Kreischer K. E. , Temkin R. J.
Published: July 2002

A novel calorimeter for millimeter wave radiation based on the photoacoustic effect has been investigated. Single pulses from a 3-μs, 1-MW gyrotron operating between 135 and 150 GHz were measured. The joulemeter has both a slow time response (<500 Hz), due to gas expansion, and a fast time response (≳500 Hz), due to acoustic modes of the resonator and windows. The slow time response, which was more suitable for power and energy measurements, was compared with a calibrated thermopile detector and was found to be linear over the range of 0.15–3 J, with an error of less than ±5% near 3 J. The calorimeter was also tested with modes having different power distributions in space; the response was found to be independent of spatial power distribution. The joulemeter is a simple, rugged device that can be used in transmission or absorption mode. Use in transmission mode is attractive for basic research on high-power microwave sources.
Efficient magnetic focusing of low-energy ions (1–5 eV) onto solids for use in surface chemistry studies
Authors: Strongin D. R. , Mowlem J. K. , Lynn K. G. , Kong Y.
Published: July 2002

A method is described that allows the efficient collection and focusing of ions, with kinetic energies between 1 and 5 eV, onto a nonmagnetic metal surface. Magnetic fields near the sample are used to focus the low-energy ions and typical currents achieved thus far exceed 100 nA/cm2 for 1-eV ion energies. The magnetic field of a magnet placed behind the sample significantly reduces the problem of transverse displacement of the ions due to beam divergence and space-charge effects. The magnetic field confines the particle to a circular orbit along the axial direction (cyclotron motion), while leaving the kinetic energy of the ion unaffected. We have utilized this method to interact Ar+ and CH+3 with 1-eV translational energy and 100 nA of current on a Pt surface.
The pursuit of brilliance−how and for what? (invited)
Authors: Hart Michael
Published: July 2002

Third generation synchrotron radiation sources are already under construction in several countries. As the logarithmic graph paper on which their main perceived attribute brilliance is displayed grows ever taller, it is useful to review in broad perspective the next steps. Interestingly, the nature of the scientific case for improved power and brilliance has not changed over three generations of synchrotron radiation sources and the needs of the scientific community will not be entirely satisfied even by the third generation sources.
Characteristics of the five-pole superconducting vertical wiggler at the Photon Factory
Authors: Ohmi Kazuhito , Nogami Takashi , Fukushima Yasuo , Katoh Masahiro , Yamakawa Tatsuya
Published: July 2002

A new superconducting vertical wiggler was installed in the 2.5 GeV KEK-PF ring in Sept. 1989 and has been operated as a generator of a synchrotron radiation since Oct. 1989. Characteristics of the wiggler are reported here. The wiggler has five magnet poles with a maximum field strength of 5 T along the beam orbit. The wiggler is operated in a permanent current mode and consumes liquid helium of 0.12±0.02 ℓ/h. An orbit distortion due to the decrease of the exciting current in the permanent current mode which comes from resistance of junctions between coils and PCSs is corrected by two normal steering magnets. The wiggler is operated continuously without supplying any current for a few weeks.
The new CHESS wiggler
Authors: Finkelstein K. D.
Published: July 2002

A 25-pole permanent magnet hybrid wiggler has been built at CHESS and installed on the CESR (Cornell Electron Storage Ring). This device has a magnetic period of 19.6 cm, a peak on-axis field of 1.2 T at the nominal operating gap of 4.0 cm, and a K parameter of 22. The wiggler has been designed to provide radiation for two new experimental stations with approximately four times the flux available from the present CHESS six-pole electromagnet wiggler. Under normal running conditions at 100 mA currents, the total power radiated should exceed 6 kW making this one of the highest flux x-ray sources below 1 Å critical wavelength. In this paper an overview of the development of the wiggler is given, including the unique features in its design and construction as well as results of measurements obtained on its magnetic and spectral properties.
SURF II: Characteristics, facilities, and plans
Authors: Madden R. P. , Canfield R. , Furst M. , Hamilton A. , Hughey L.
Published: July 2002

This facility report describes the Synchrotron Ultraviolet Radiation Facility (SURF II) operated by the National Institute of Standards and Technology, Gaithersburg, Maryland. SURF II is a 300-MeV electron storage ring which provides well characterized continuum radiation from the far infrared to the soft x-ray region with the critical wavelength at 17.4 nm. Brief descriptions are given of the user facilities, the characteristics of the synchrotron radiation, the main storage ring, the injector system and each of the operating beam lines, and associated instruments. Further description is given of expansion plans for additional beam lines.
The Stanford Synchrotron Radiation Laboratory: An update
Authors: Cantwell K. , Pianetta P.
Published: July 2002

The present status and future directions of scientific and machine development at the Stanford Synchrotron Radiation Laboratory (SSRL) are reviewed. A central focus is on the transformation of SPEAR into a fully dedicated synchrotron radiation source served by an independent 3-GeV booster injector synchrotron.
Influence of deposition conditions and film thickness on the 〈001〉 orientation of erbium films
Authors: Savaloni H. , Gu E. , Player M. A. , Marr G. V. , Munro I. H.
Published: July 2002

The influences of substrate temperature, deposition rate and film thickness on the structure of erbium films deposited on molybdenum substrates of surface roughness Rq=151 nm are investigated by energy-dispersive x-ray diffraction. This shows that erbium polycrystalline films grow preferentially in the 〈001〉 direction. The intensity ratio of the Er(002) peak to Er(101) increases with film thickness, in particular above 300 nm thickness. The influence of direction of the incident evaporated beam at 8.5° to the normal is also investigated and it is shown that at low substrate temperature the film orientation is offset, but at higher temperatures (Ts≥575 K) the film orientation becomes normal to the substrate. Such controllable preferred orientation may be of value in the fabrication of diffracting components for x-ray instrumentation.
Ultrahigh vacuum magnetic field modulation apparatus for magnetic-circular-dichroism studies in the vacuum ultraviolet region
Authors: Shidara Tetsuo , Koide Tsuneharu , Fukutani Hirohito
Published: July 2002

A magnetic field modulation apparatus has been designed and constructed for magnetic-circular-dichroism (MCD) studies beyond the LiF transmission cutoff in the vacuum-ultraviolet and soft x-ray regions. The magnet is a split-coil solenoid, immersed in liquid nitrogen in order to reduce its Ohmic loss, and can produce alternating magnetic fields of up to 5.5 kG rms at moderate frequencies (∼5 Hz). The clear bore of the magnet is 40 mm in diameter, enabling measurements in both reflection and transmission configurations. The entire apparatus is bakable up to 150 °C in order to make it ultrahigh-vacuum compatible. This apparatus, together with our recently developed triple-reflection circular polarizer, provides a powerful tool for detecting very small MCD signals (∼10−5) by a modulation technique, even on the existing beam lines.
Multidetection in ultraviolet angle-resolved photoemission
Authors: Leveque G. , Villachon-Renard Y. , Bonnet J.
Published: July 2002

We have tested at Super ACO (LURE) a new angular resolved photoemission device for the 12–30 eV energy range, using multidetection of photoelectrons: all electrons emitted in a plane are collected and focused onto a fluorescent screen in a coordinate grid directly related to (Ei, k∥). This multidetection provides a substantial diminution of the acquisition time. Ten seconds are needed to obtain a complete off-normal set of energy distribution curves (EDC). Real time visualization of the valence-band structure for one azimuthal plane is even possible. Digital image treatment is performed after the experiments, permitting an easier extraction of the characteristics of the bands and the emission structures.
Determining surface profile from sequential interference patterns from a long tracer profiler
Authors: Irick S. C.
Published: July 2002

The long trace profiler [P. Z. Takacs and S. Qian, U.S. Patent No. 4884697 (5 December, 1989)] is a slope-measuring instrument that was introduced several years ago. Development of this instrument continues at Lawrence Berkeley Laboratory in improving both hardware design and software algorithms for turning the raw interference data (a sequence of intensity patterns) into properly interpreted representations of surface slope and height. This report presents a mathematical model of the interference pattern and methods of extracting the slope and height profile from such patterns.
Apparatus with permanent magnet flipper for magnetic circular dichroism absorption measurements
Authors: Muto Sadatsugu , Kagoshima Yasushi , Miyahara Tsuneaki
Published: July 2002

An apparatus with permanent magnet flipper was designed and constructed to study magnetic circular dichroism (MCD) of various magnetic materials. The permanent magnet flipper is similar to a single period of undulator magnets but has two holes to allow the incident light to go through. The maximum magnetic field at the sample position is 1.2 T and its direction is switched by a linear motion of the magnet flipper. It was mounted in an ultrahigh vacuum chamber equipped with a vacuum evaporation system and a sample holder cooled to liquid nitrogen temperature. The MCD signal of Ni in the 3p-3d absorption region was successfully measured within an accuracy of 0.01%.
Generation of pseudorandom sequences for use in cross-correlation modulation
Authors: Koleske D. D. , Sibener S. J.
Published: July 2002

In this article we discuss how pseudorandom sequences are generated for use in cross-correlation modulation experiments and present means for generating all pseudorandom sequences (modulo-two) that have a maximum length of N=2n−1, with n=2–12. We explain the criteria that the pseudorandom sequences must satisfy, and find the set of recursion coefficients which are used to generate the pseudorandom sequences. These sets of recursion coefficients were calculated for n=2–16, with n=2–12 being explicitly presented in this article. We also explain how each set of recursion coefficients can be used to generate maximum length pseudorandom sequences of length sufficient for use in cross-correlation chopping.
Microtorquemeter for magnetization measurements on small superconducting samples
Authors: Qvarford M. , Heeck K. , Lensink J. G. , Wijngaarden R. J. , Griessen R.
Published: July 2002

A torquemeter with a noise level of ∼10−12 N m was developed and used for magnetization measurements (due to the Meissner–Ochsenfeld effect) on superconducting samples with a mass typically smaller than 10μg. The torquemeter consists of a very soft, thin metal beam, symmetrically placed between two capacitor plates, which are used for position measurement. Due to the symmetric setup electrostatic forces on the beam are largely compensated. A cheap but accurate electronic device replaces the conventional capacitance bridge and lock-in amplifier. Calibration of this kind of apparatus is discussed in some detail. Experiments are reported on a 6 μg lead disk and on small crystals of YBa2Cu3O7 and Nd2−xCexCuO4−δ.
The effect of a tapered aperture on x-ray diffraction from a sample with a pressure gradient: Studies on three samples with a maximum pressure of 560 GPa
Authors: Ruoff Arthur L. , Xia Hui , Xia Qing
Published: July 2002

X-ray diffraction patterns were obtained using a tapered lead aperture. A detailed analysis of the effect of the tapered aperture is given. Experimental studies include results on W (423 GPa), on Pt (440 GPa, obtained using type IIa diamonds), and Mo (560 GPa). These results extend earlier studies in which we achieved for the first time static pressures greater than the pressure at the center of the earth.
Elemental imaging of cartilage by scanning x-ray microscopy
Authors: Buckley C. J. , Foster G. F. , Burge R. E. , Ali S. Y. , Scotchford C. A. , Kirz J. , Rivers M. L.
Published: July 2002

Elemental imaging via scanning transmission x-ray microscopy (STXM) and scanning fluorescence x-ray microscopy (SFXM) has been used to image calcium deposits in cartilage. In the case of STXM, 0.1 μm thick sections were imaged to investigate the proximity of calcium deposits in relation to chondrocyte cells. The resolution available was 0.5 μm, and field widths of up to 25 μm were used at this resolution. The resolution available in SFXM was 10 μm, and field widths of up to 2 mm were used at this resolution on 5-μm thick specimens. Together these techniques were used to map calcium deposits at the cellular level, and at the full tissue size level.
Development of a battery-operated portable synchronous luminescence spectrofluorometer
Authors: Alarie Jean Pierre , Vo-Dinh Tuan , Miller Gordon , Ericson M. Nance , Maddox S. Randall , Watts Wendi , Eastwood DeLyle , Lidberg Russ , Dominguez Martha
Published: July 2002

A battery-operated portable synchronous luminescence spectrofluorometer was developed for on-site analysis of groundwater or hazardous waste sites. The instrument is capable of either emission, excitation, or synchronous fluorescence measurements. The instrument is suited for trace analysis of important pollutants such as polyaromatic hydrocarbons, creosotes, and polychlorinated biphenyls in complex mixtures. The ability to perform synchronous luminescence measurements on these samples can reduce the complexity of fluorescence spectra and help in rapid field site characterization. A description of the instrumental components is given and an evaluation of the instrument using anthracene and several oil samples is provided to illustrate the usefulness of the instrument.
The scanning Kelvin microscope
Authors: Mäckel R. , Baumgärtner H. , Ren J.
Published: July 2002

This article describes a new instrument to monitor simultaneously the topography and the contact potential difference between the sample and the tip. This so-called scanning Kelvin microscope has a lateral resolution better than 5 μm. The control of distance between the Kelvin probe and the sample during the scan is realized using the ratio of two harmonics of the measured displacement current. The influence of the geometry of the Kelvin electrode on the time dependence and the frequency spectrum of the displacement current is discussed. Verification of the theory and a linescan across a test sample is shown.
A new method for sensitive and automatic measurements of sound velocity and attenuation
Authors: Frénois Christian
Published: July 2002

A new automatic method using the pulse-echo technique has been developed to sensitively measure ultrasonic wave velocity change and attenuation in liquids or solids. This method relies on two principal ideas: (i) All the frequencies (the ultrasonic frequency fus, the local oscillator flo, the mixed frequency fmx, and repetition rate frep) are derived from a single master oscillator. Therefore, they are commensurate, and there exists some relationship between their phases. (ii) A frequency down conversion results in a phase sensitivity enhanced by the conversion ratio fus/fmx. A computer-controlled apparatus has been built on this principle with phase-locked synthesizers working in the 10–2000 MHz range. An experiment performed on a diluted magnetic crystal shows that the sensitivity on the sound velocity is better than 5.0×10−9 at 1000 MHz. An intrinsic characterization of the sound velocity sensitivity may be defined as the measurement performed on a reference path length equal to an acoustic wavelength λ. This gives the sensitivity at 1000 MHz as (δV/V)λ=3.0×10−5. The method performs simultaneous amplitude measurements with an accuracy of ±0.01 dB and a dynamic range larger than 60 dB. The idea could also be used to improve the sensitivity of other measurements; for instance, that of dielectric constant or magnetic susceptibility.
Laser beam profiler in the vacuum ultraviolet spectral range using photostimulable phosphor
Authors: Katto Masahito , Matsumoto Ryusuke , Kurosawa Kou , Sasaki Wataru , Takigawa Yasuo , Okuda Masahiro
Published: July 2002

We propose and demonstrate the use of a photostimulable phosphor material, BaFBr:Eu2+, for recording two-dimensional intensity distributions within output beams of vacuum ultraviolet lasers. The sensitivity characteristics were measured not only for nanosecond pulsed radiation from KrF, ArF, and Ar2 excimer lasers but also for quasi-continuous-wave synchrotron radiation. We designed and constructed a laser beam profiler to record, read, and erase images in vacuum. The intensity distribution in the output beams from an Ar2 excimer laser was measured with it, and then the threshold gas pressure for obtaining the well collimated beams was found to be 22 kg/cm2. The intensity is not uniform in the beams but stronger in the peripheral part than in the central one.
Study of magnetic susceptibility processing in an increment of the total flux
Authors: Lisowski Michal/ , Nowak Józef
Published: July 2002

The relative increment of the total flux in a secondary coil is presented as a function of sample magnetic susceptibility, a demagnetization factor, and the secondary coil filling factor caused by the sample. The filling factor was defined and its basic properties were given. The relation between the filling factor and geometric parameters of a spherical sample coaxially placed in a cylindrical coil was determined. The calibration factors, used up to now, and the filling factor, were compared. It was shown, that if the demagnetization factor D→1 (in the case of a thin film placed perpendicular to the magnetic field), and the sample susceptibility χ≠−1, the magnetization susceptibility is not measurable, except in the case when χ=−1.
Susceptibility spectrum of a magnetic conducting sphere
Authors: Prados C. , del Real R. P. , Chen D.-X. , Li B.-Z. , Hernando A.
Published: July 2002

The frequency dependence of the complex ac susceptibility of a magnetic conducting sphere is derived. The resultant formulas can be used to determine electrical conductivity from ac susceptibility measurements, to calculate ac susceptibilities of standard samples for the calibration of ac susceptometers, and to analyze ac losses in materials research.
Determination of laser beam waist using photoionization time-of-flight mass spectrometer
Authors: Wang C. R. C. , Hsu C. C. , Liu W. Y. , Tsai W. C. , Tzeng W. B.
Published: July 2002

A method for the determination of a focused laser beam waist via photoionization and retarding potential analysis is discussed. The focused laser beam was employed to photoionize gas phase clusters generated from a supersonic cluster source. It intersects the cluster beam at right angle in the first stage of the time-of-flight (TOF) acceleration lens assembly. With a simple modification on a laser-based TOF mass spectrometer, retarding fields were applied right in front of the microchannel plate ion detector to map out the kinetic energy distribution of the cluster ions. The size of the laser beam along the molecular beam axis in the ionization region can then be directly related to this energy distribution. In addition, this method manifests a sensitive probe (within 10 μm) to the laser beam position.
Relative secondary-electron yields from clean metals under fast-atom bombardment and angle-integrated UV-photoelectron spectra in a photoelectron spectromicroscope
Authors: Coath C. D. , Plummer I. R. , Turner D. W.
Published: July 2002

This article describes the construction and operation of a source of 2–5 keV argon atoms for use in the strong (1–7 T) B-field environment of a photoelectron spectromicroscope. The velocity spread of the atom beam has been determined from the time of flight. Atom-induced secondary-electron yield measurements on selected areas of various metallic elemental samples are described and the results show that yields differ by up to a factor of 4×103 between elements and trend towards lower yields with increasing atomic number. A number of ultraviolet photoelectron spectra of the fast-atom sputter-cleaned sample surfaces are also presented. These spectra are angle-integrated over the full 2π of electron-emission angles.
Measurement of time-resolved photoluminescence of semiconductors using correlational analysis
Authors: Baier T. , Walter T. , Mauckner G. , Schneider J. , Thonke K. , Sauer R.
Published: July 2002

We present a new method for measuring time-resolved photoluminescence on a time scale of microseconds and milliseconds using correlational analysis, and we demonstrate it to work on porous silicon and GaP:Fe. We modulate the pumping laser with a pseudorandom binary sequence which yields correlational properties similar to white noise. The photoluminescence decay is computed via cross correlation of the detector signal with the pumping sequence. The presented method is highly sensitive, simple in application, and inexpensive.
Material characterization using a frequency-doubling two-color interferometer
Authors: Matsumoto Hirokazu
Published: July 2002

A new characterization method of materials processed by ion beams or laser beams using a two-color interferometer with two frequency-doubling optical crystals is described, based on the dispersion property of the materials. Resolution of measurement is improved to an optical phase of 1° (subnanometers) by use of a heterodyne technique with acousto-optic modulators.
A 10-J electric-discharge-pumped phototriggered XeCl laser
Authors: Bychkov Yu. , Makarov M. , Suslov A. , Yastremsky A.
Published: July 2002

An electric-discharge-pumped XeCl laser using phototriggering by x rays is reported. A consistent input of the stored energy into the pumping discharge plasma has been realized. An output pulsed energy of about 10 J has been achieved in a ∼3-ℓ active volume with an efficiency ≳2%. High spatial uniformity of the laser radiation and a stable space discharge were observed. A stability analysis of the discharge pumping has been made for the XeCl laser in terms of the current-voltage characteristic model. The method for parametric optimization of such systems is described.
Triggering techniques for a compact Marx generator
Authors: Beverly R. E. , Campbell R. N.
Published: July 2002

Optically controlled, sequential breakdown of the spark-gap switches is a simple method for triggering compact Marx generators. Techniques for reliably initiating breakdown of the first switch are discussed. A 300-kV Marx generator for flash x-ray applications is described.
Simple shutter circuit for protecting microchannel plate photomultipliers from excess light exposure
Authors: Kauffman J. F. , Liu C. S.
Published: July 2002

A simple circuit is described which closes a shutter on the optical input of a photon counting detector when the photon count rate exceeds a preset level. The circuit utilizes common integrated circuits, and is designed to protect microchannel plate photomultipliers from excess light exposure.
Studies on the positive hydrogen ion production from a small multicusp source
Authors: Olivo M. , Mariani E. , Leung K. N.
Published: July 2002

An rf driven ion source has been developed and tested at LBL for positive hydrogen ion production. Studies of this new source on ion species and current densities for a dc arc discharge are made in the 60-kV PSI ion source test stand and the results compared with those obtained using the rf discharge. This source, using both discharge modes, will be installed in the PSI Cockcroft–Walton preinjector to increase the 870-keV dc proton beam intensity from the present 8–10 mA operation to about 25 mA.
Kyushu University polarized ion source
Authors: Wakuta Yoshihisa , Maehata Keisuke , Arima Hidehiko , Hirose Tomonori , Noda F. , Hichida Naoki , Sumita Jiro
Published: July 2002

A compact atomic-beam type of polarized ion source, under construction at Kyushu University, is described. Newly developed permanent sextupole magnets are used and their operational characteristics are measured precisely and analyzed. In order to optimize the strong magnetic field electron impact ionizer performances, a computer code has been developed which simulates the trajectories in the ionizing volume of the electrons and the positive ions produced. A method of optimizing the radio-frequency unit is proposed. This polarized ion source will be used for a variety of research, especially for the polarized fuel fusion reaction study.
Beam symmetry preservation through a dipole with zero pole face rotations and uniform field
Authors: Liu Hongxiu
Published: July 2002

It is shown that the cylindrical symmetry of a charged particle beam can be preserved precisely while it is bent through a single dipole with zero pole face rotations and uniform field, although in one plane the beam is freely drifting whereas in the other plane the beam is focused. The beam conditions at the entrance to the dipole are derived and cast into two analytic formulas. It is shown that symmetry preservation calls for matched beam optical functions (β,α), that is, matched orientation and amplitude of the beam phase space ellipses into the dipole. The beam conditioning at the entrance to the dipole is discussed and formulated. Some illustrative cases are calculated, and an example design is presented. Finally, it is proved that such a symmetric matched beam may be defined for any system with equal diagonal R-matrix elements, and the results are applied to another specific case of a parallel sided magnet.
Measurement of thermal diffusivity of thin films and foils using a laser scanning microscope
Authors: Kemp T. , Srinivas T. A. S. , Fettig R. , Ruppel W.
Published: July 2002

A novel method for measuring the thermal diffusivity of free-standing foils and thin films is described and has been used to measure the thermal diffusivity of gold and amorphous silicon foils. The method involves scanning the surface of the film using a sinusoidally modulated, finely focused laser beam and monitoring the thermovoltage developed at a fixed point on its surface. A thermal wave spreads out from the point where the laser spot irradiates the foil which depends only on the thermal properties of the film material and the modulation frequency. Measuring the phase of the thermovoltage, which in turn is generated due to the thermal wave, the thermal diffusivity of the films was determined. The experiments were performed in vacuum so that convective heat losses could be neglected. The thermal diffusivity of 100-nm-thick gold foils was found to be 1.17×10−4 m2/s and that of 200-nm-thick amorphous silicon foils was determined to be 0.062×10−4 m2/s.
Design consideration in an ultrafast scanning tunneling microscope
Authors: Botkin D. , Weiss S. , Ogletree D. F. , Beeman J. , Salmeron M. , Chemla D. S.
Published: July 2002

We describe an ultrafast scanning tunneling microscope (USTM) with picosecond temporal resolution. We present results of single-point ultrafast tunneling measurements and outline some of the methods and pitfalls in USTM. Ultimately, the technique has the potential to create picosecond scale movies of surface phenomena with atomic spatial resolution.
Simple window-compensation method for improving the signal-to-noise ratio in measurements of the magneto-optic Kerr effect in ultrathin films
Authors: Arnold C. S. , Venus D.
Published: July 2002

Measurements of the magneto-optical Kerr effect in magnetic ultrathin films in ultrahigh vacuum (UHV), have a signal-to-noise ratio (S/N) which is limited by the extinction ratio of the apparatus. Although polarizing crystals with excellent extinction characteristics are usually employed for in situ measurements of films grown in UHV, the net extinction ratio is degraded by optical windows, resulting in poor signal contrast and poor S/N. A simple procedure for cancelling the effects of the windows is to slightly, but precisely, misalign the initial linear light polarization state from S or P (with respect to the sample). This technique does not require compensators or any additional optical components and is capable of an extinction ratio of 3×10−7, allowing the rapid acquisition of high quality Kerr-effect hysteresis loops with a very simple apparatus. The dependence of the extinction ratio on the initial light polarization is investigated and explained in terms of a Jones matrix analysis. Correcting for the windows is interpreted as a phase shift from the film substrate balancing phase shifts from the optical windows. The technique is applied to the acquisition of hysteresis loops for 4 ML Fe/W(001) films and a substantial improvement in S/N is demonstrated.
Total reflection x-ray fluorescence spectroscopy using synchrotron radiation for wafer surface trace impurity analysis (invited)
Authors: Pianetta P. , Takaura N. , Brennan S. , Tompkins W. , Laderman S. S. , Fischer-Colbrie A. , Shimazaki A. , Miyazaki K. , Madden M. , Wherry D. C. , Kortright J. B.
Published: July 2002

Trace impurity analysis is essential for the development of competitive silicon circuit technologies. Current best methods for chemically identifying and quantifying surface and near-surface impurities include grazing incidence x-ray fluorescence techniques using rotating anode x-ray sources. To date, this method falls short of what is needed for future process generations. However, the work described here demonstrates that with the use of synchrotron radiation, total reflection x-ray fluorescence methods can be extended to meet projected needs of the silicon circuit industry until, at least, the year 2000. The present results represent over an order of magnitude improvement in detection limit over what has been reported previously. A double multilayer monochromator on a high flux wiggler beam line resulted in a detection limit for Ni of 3×108 atoms/cm2. This is to be compared with a detection limit of 5×109 atoms/cm2 obtained with a rotating anode system. This is due to the greatly improved signal to background in the case of the synchrotron. Furthermore, there is a path to improving the synchrotron case to reach a detection limit of 5×107 atoms/cm2.
Studies of He-like krypton for use in determining electron and ion temperatures in very-high-temperature plasmas
Authors: Widmann K. , Beiersdorfer P. , Decaux V. , Elliott S. R. , Knapp D. , Osterheld A. , Bitter M. , Smith A.
Published: July 2002

High-resolution measurements of the He-like Kr K-shell radiation are presented showing the direct excitation lines as well as Li- and Be-like dielectronic recombination lines appearing in the KLL resonance. The measurements were performed on the Electron Beam Ion Trap (EBIT) facility and motivated by the need for accurate atomic data of high-Z He-like K-shell transitions for diagnostic applications in determining the central ion and electron temperature of very-high-temperature plasmas produced in next-generation tokamaks, such as the International Thermonuclear Experimental Reactor (ITER).