bluuebunny/crossref_metadata_2025 huggingface dataset:
A multiple-beam, collective scattering technique for spatially resolved measurement of plasma turbulencea)
Authors: Spivey B. A. , Sverdrup L. H. , Lin S. H. , Trissel R. G. , Peebles W. A.
Published: July 2002

Collective Thomson scattering has long been utilized to study electrostatic turbulence in magnetic confinement fusion plasmas with a view to demonstrating a causal link to the observed anomolous transport of heat and particles. However, this goal has been severly hampered by the relatively poor spatial resolution available at the dominant turbulence wave numbers using standard experimental techniques. Good spatial resolution is necessary if adequate comparison of theory and experiment is to occur. The present paper describes the basic principles of a new technique utilizing simultaneous, multiple input beams, a detector array, and coherent tomographic inversion algorithm, which can substantially improve the available spatial resolution for these important measurements. The proposed multiple beam scattering diagnostic offers a spatial resolution of ∼10 cm at a fluctuation wave number of 5 cm−1 when the angular envelope of the beams is 0.1 rad. Optical designs suitable for implementing the multiple beam diagnostic on a large tokamak have been developed.
Source of low-energy hydrogen ions for measuring electron transfer in surface scattering experiments
Authors: Isenberg J. D. , Kwon H. J. , Seidl M.
Published: July 2002

We present the design and performance of a beamline which is the source of 5–50-eV protons for surface scattering experiments. The beamline also incorporates a collector for measuring total secondary ion and electron yields. The beam forming optics are built around a commercially available gas discharge ion gun and produce a mass-selected, energy-filtered beam. Results of computer ray tracing are included to illustrate the operation of the beam optics. Tests have produced 50-pA proton beams 3.5-mm wide at 5 eV with an energy spread of about 1 eV.
Continuously variable distortion-free attenuation of high-power transversely excited atmospheric CO2 laser pulses
Authors: Sakthivel P. , Mukherjee P.
Published: July 2002

A new technique for the continuously variable linear attenuation of high-power transversely excited atmospheric (TEA) CO2 laser pulses is reported. The use of a binary gas mixture comprising SF6 as the absorber and helium or argon as the buffer gas causes a significant enhancement in the saturation intensity, thereby allowing saturation-free attenuation of TEA CO2 laser pulses up to 1 MW/cm2. A linearly variable dynamic attenuation range of 0–30 dB, and continuously variable attenuation up to 60 dB in a 10-cm cell length, without spatial or temporal distortion in the attenuated beam is demonstrated.
Laser microprobe and resonance ionization mass spectrometry for the analysis of trace elements in solids
Authors: Hung Tuan-Yu , Su Ching-Shen
Published: July 2002

A laser microprobe and resonance ionization mass spectrometer (LAM/RIMS) has been designed and constructed by combining a newly designed simple laser microprobe (LAM) with a continuous-wave (cw) resonance ionization mass spectrometer, for the direct analysis of trace elements in solids. The LAM/RIMS has achieved a simultaneous record of the complete mass spectrum of a solid sample, and a three orders of magnitude enhancement in the detection signal of the selected trace elements in the solid, with precise spatial information, and without the need of sample preparation. A n-type silicon wafer containing an impurity of sodium in parts per billion order has been easily detected by applying a single shot of an ablation laser pulse and a cw resonance ionization laser. The result has also shown that the sensitivity of the LAM/RIMS for the analysis of selected trace elements is better than the Auger electron spectroscopy and is comparable to neutron activation analysis.
The electronic structure and energy level alignment of porphyrin/metal interfaces studied by ultraviolet photoelectron spectroscopy
Authors: Narioka S. , Ishii H. , Yoshimura D. , Sei M. , Ouchi Y. , Seki K. , Hasegawa S. , Miyazaki T. , Harima Y. , Yamashita K.
Published: July 2002

Electronic structures of 5, 10, 15, 20-zinctetraphenylporphyrin (ZnTPP)/metal (Au, Ag, Al, Mg) interfaces prepared in ultrahigh vacuum were investigated by ultraviolet photoelectron spectroscopy (UPS). We found that the electronic energy levels of ZnTPP align to the vacuum level of substrate metal, with a constant energy shift of vacuum levels across the interface. These findings cannot be explained by the simple models assuming vacuum level alignment at the interface. We also found that sample exposure to oxygen induces energy level shift in close relation with change of substrate work function at oxygen exposure.
Copper vapor laser drilling of copper, iron, and titanium foils in atmospheric pressure air and argon
Authors: Lash J. S. , Gilgenbach R. M.
Published: July 2002

A copper vapor laser (511 and 578 nm) is used to drill submillimeter diameter holes in 0.025–0.127 mm thick foils of copper, iron, and titanium. Foils are machined in atmospheric pressure air and argon. The laser is repetitively pulsed at 10 kHz with a per pulse energy of 0.5 mJ giving an average power of 5 W at the sample surface for a pulse width of 40 ns. A p-i-n photodiode and a photomultiplier tube detector are connected to a digital-display timing circuit that records the number of incident laser pulses used to drill through the sample. The number of pulses is converted to an average drilling time and can provide an estimate for the average laser energy used to drill the hole. Typical data for all three materials with a per-pulse fluence of 0.7 J/cm2 ranged from 0.1 to 500 s to produce holes of ∼0.3 mm diameter. Drilling times decreased in some cases by an order of magnitude when machining in air. This is attributed to the increased laser absorption of the metal-oxide layer formed in air and was especially noticeable with titanium. A continuous wave thermal model is used to compare experimental data as well as verify the thermal machining mechanism.
Low temperature magnetic force microscopy
Authors: Hug H. J. , Moser A. , Jung Th. , Fritz O. , Wadas A. , Parashikov I. , Güntherodt H.-J.
Published: July 2002

We have built a low temperature scanning force microscope which is able to measure contact and noncontact forces using the dc modes of force microscopy. We demonstrate the capabilities of our instrument on a magneto-optical disk at room temperature and at 77 K. Using a ferromagnetic thin film tip, the topography and the micromagnetic stray field of the sample is measured using the dc modes of force microscopy. The topographic and magnetic data are precisely correlated. The circular bit structure and the natural domain structure between the homogeneously magnetized bits is clearly visible. A lateral resolution below 100 nm and a force resolution of 10−12 N is reproducibly achieved.
A simple, rapid response vacuum furnace
Authors: Hyde T. A. , Sellers C. H.
Published: July 2002

This article presents a simple, lab scale, vacuum furnace design that features good temperature stability, rapid temperature response, and high-vacuum and high-temperature capabilities. The furnace was developed for applications such as in situ electrical resistivity measurements, precise heat treatment of small samples, and complex heat treatments.
Aluminosilicate sources of Cs+ ions
Authors: Ong P. P. , Tan T. L.
Published: July 2002

Synthetic cesium aluminosilicates in the form of β-eucryptite (Cs2O⋅Al2O3⋅2SiO2) and spodumene (Cs2O⋅Al2O3⋅4SiO2) were used to construct thermionic emitters of Cs+ ions. Total ion emission current and purity of ion emission of Cs+ ions for these two forms of aluminosilicates were studied and compared at four different material surface temperatures over 50 h of continuous heating. In addition, the ion emission characteristics were investigated for three other compositions of cesium aluminosilicates. It was revealed that as a Cs+ ion source, β-eucryptite gives the optimum ion emission at the temperature of 1100 °C.
Magnetic shielding of stray magnetic fields in the scanning electron microscope
Authors: Müllerová I. , Fišer J.
Published: July 2002

A stray magnetic field troubles all designers of electron microscopes. The influence of this field is most critical when an ultrahigh-vacuum low-voltage scanning microscope is to be designed. Transversal components of the stray magnetic field deflect the primary beam, but a stray field of the same value acting along the optical axis does not influence the primary beam significantly. We designed a shielding for our low-voltage scanning electron microscope which suppresses the influence of the transversal stray magnetic field by two orders but does not influence the field of the focusing lens. Therefore, unlike the full shielding of a small diameter, the segmental shielding proposed does not impair resolution.
Inward electrostatic precipitation of interplanetary particles
Authors: Rulison Aaron J. , Flagan Richard C. , Ahrens Thomas J.
Published: July 2002

An inward precipitator collects particles initially dispersed in a gas throughout either a cylindrical or spherical chamber onto a small central planchet. The instrument is effective for particle diameters greater than about 1 μm. One use is the collection of interplanetary dust particles which are stopped in a noble gas (xenon) by drag and ablation after perforating the wall of a thin-walled spacecraft-mounted chamber. First, the particles are positively charged for several seconds by the corona production of positive xenon ions from inward facing needles placed on the chamber wall. Then an electric field causes the particles to migrate toward the center of the instrument and onto the planchet. The collection time (of the order of hours for a 1 m radius spherical chamber) is greatly reduced by the use of optimally located screens which reapportion the electric field. Some of the electric field lines terminate on the wires of the screens so a fraction of the total number of particles in the chamber is lost. The operation of the instrument is demonstrated by experiments which show the migration of carbon soot particles with radius of approximately 1 μm in a 5-cm-diam cylindrical chamber with a single field enhancing screen toward a 3.2 mm central collection rod.
Space-charge compensation of electron beams by thermal ions and the production of highly charged ions in EBIS and EBIT
Authors: Becker R. , Kleinod M.
Published: July 2002

The space-charge compensation of electron beams by hot ions with a Boltzmann energy distribution has been investigated by solving Poisson’s equation. A unique relation is obtained between the degree of central compensation and the ion temperature: At high temperatures (as compared to the potential depression inside the beam) the compensation is low and the ions stay inside the electron beam only to a minor part, while at low ion temperatures, the beam is almost fully compensated. The potential difference between the beam axis and the surrounding tube is reduced by compensation, but when measured in terms of the temperature of compensating ions, it increases. This shall better confine the ions to the electron beam, the more complete the compensation. Increasing with the square of their charge state, trapped ions are heated by the ionizing beam electrons through small angle Coulomb collisions. For different ions with different charge states, the almost compensated electron beam acts as an energy filter, where the hotter ions are lost radially or axially. Therefore highly charged ions, which became ‘‘hot’’ by waiting for stepwise ionization, can be cooled by lower charged ones, which still are ‘‘cold.’’ This phenomenon has been called ‘‘evaporative cooling’’ in electron beam ion sources (EBIS) and traps (EBIT) and space-charge compensation of the electron beam is the driving physic for it.
Apparatus for efficient atomic level studies of alkali plasmas using sampling, probing, and spectroscopic methods
Authors: Svensson Robert , Lönn Benny , Holmlid Leif
Published: July 2002

An experimental multipurpose alkali plasma device for atomic or molecular level studies of various plasma properties is described. The apparatus is built up around two or three electrodes which are mounted in a vacuum chamber, with the alkali vapor introduced through an array of laser-machined holes in one of the electrodes. There are no walls or insulating materials close to the electrodes, which could disturb the plasma or introduce contamination into it. The open and free position of the electrodes in the vacuum chamber permits many types of analyzing devices to be mounted inside the vacuum chamber in order to characterize the plasma, which in most cases has a pressure of the order of 1 mbar. Outside the plasma region, the pressure drops quickly to the background pressure of 10−6 mbar. The design easily permits probing experiments where for example a Langmuir probe is introduced directly into the plasma to determine the potential. The fundamental parameters, such as electrode temperatures, interelectrode distance, and alkali pressure, can easily be varied. The electrodes are easily interchangeable, which permits rapid testing of various electrode materials. The apparatus includes an electronic dc sweep and pulse system, which gives a wide range of possibilities to control the plasma. Besides the direct probing and characterization features of this apparatus, molecular beam methods are used to study the flux from the plasma region. Of special importance is the use of molecular beam sampling into a mass spectrometer. Large openings are used with differential pumping to minimize deexcitation of Rydberg species from the plasma to the mass spectrometer.
Use of a phase-sensitive detector for measuring losses in superconductors as a function of frequency
Authors: Jiang Hongbo , Bean Charles P.
Published: July 2002

We describe the design of a system that automatically measures losses in superconductors as a function of frequency. The method follows a suggestion by Gömöry who notes that, for a symmetric hysteresis loop, one can trace out the loop by measuring the output voltage of a phase-sensitive detector as a function of the phase angle between the applied field and the detector setting. We have measured the losses at 77 °K in aligned YBCO for frequencies from 10 Hz to 40 kHz with amplitudes of applied field up to 100 Oe. The usual method of measuring the in-phase component of dB/dt to determine the losses was also employed and we found that the two methods gave, within experimental error, identical results over the frequency range we have covered.
Rapid decompression of seeded melts for materials processing
Authors: Qiu Ning , Apfel Robert E.
Published: July 2002

A novel processing approach and experimental design to achieve as-cast bulk amorphous materials are investigated. By sudden decompression of a melt that is seeded with a volatile liquid, the dispersed ‘‘foaming’’ liquid vaporizes, taking its latent heat of vaporization from the melt, thereby homogeneously cooling the melt. Due to a high decompression rate, a sufficient cooling rate may be produced to yield an amorphous solid foam. The resulting ‘‘foam glass’’ is expected to be an open solid bulk structure that may possess glass properties and low density. These foam glass materials should be free of structural defects, and may have many potential applications. The ultimate goal for this form glass processing is to produce bulk amorphous metallic solids. This approach differs from other processes used in the production of metals with a porous structure. A description of the approach, the processing design and techniques, as well as some evaluation of foam processing with the organic p-terphenyl as a sample material are presented. Foam (p-terphenyl) is an open, porous, and yet interconnected structure, and can be made with a density as low as 12% of the original density of p-terphenyl. Extension of this principle to foam metallic glass processing is anticipated. Design of a more sophisticated apparatus for metal processing, currently in progress, is discussed.
A spectrometer for prompt mass identification of fragments from low-energy fission
Authors: Pearson C. J. , Varley B. J. , Phillips W. R. , Durell J. L.
Published: July 2002

A spectrometer for prompt mass identification of fragments from low-energy fission having a large effective solid angle of 35.2 msr is described. The mass identification is obtained by time-of-flight measurement using a pair of microchannel plate detectors and kinetic energy measurement using an axial ionization chamber. A mass resolution of 3.8 u at 100 u was obtained from experiments which observed coincidences between fragments and γ rays from a 252Cf spontaneous fission source.
Construction of a new imaging bandpass analyzer for a magnetic projection photoelectron microscope
Authors: Kim Changyoung , Pianetta Piero , Kelly Michael A.
Published: July 2002

An imaging bandpass analyzer consisting of two 90° spherical analyzers proposed earlier [C. Kim, P. L. King, P. Pianetta, M. A. Kelly, and C. A. Bryson, Rev. Sci. Instrum. 64, 1187 (1993)] has been combined with a magnetic projection photoelectron microscope and tested. The design and construction of a magnetic mesh to terminate the magnetic field from the microscope is described with an optical element to connect the microscope and the analyzer. An energy resolution of 2.6% of the pass energy and spatial resolution better than that of the imaging detector are obtained.
A variable radius mirror for imaging the exit slit of a spherical grating monochromator undulator beamline at the ALS
Authors: Warwick Tony , Howells Malcolm , Shlezinger Meir
Published: July 2002

Bendable metal mirrors have been implemented in two SGM undulator beamlines at the ALS. A piezoelectric actuator is employed to deform the mirror to image the SGM exit slit which moves longitudinally in the beamline as the grating rotates. The design and performance of these mirrors are discussed. Computed deformations and slope errors are compared to those found during optical metrology. The soft x-ray spot size produced at the experiment is shown.
Correlation of critical current and resistance fluctuations in bicrystal grain boundary Josephson junctions
Authors: Marx A. , Fath U. , Alff L. , Gross R.
Published: July 2002

We have performed a detailed analysis of the low frequency 1/f noise in  YBa2Cu3O7−δ   and  Bi2Sr2CaCu2O8+x grain boundary Josephson junctions (GBJs) fabricated on SrTiO3 bicrystal substrates. The normalized fluctuation of the critical current, δIc/Ic, and the normal resistance, δRn/Rn were found to be almost independent of temperature and the misorientation angle. Furthermore, the magnitude of the fluctuations is very similar for both high-Tc cuprates. Correlation experiments showed that the fluctuations of Ic and Rn are anti-correlated. Our analysis strongly suggests that the source of 1/f noise in high-Tc bicrystal GBJs are localized defect states in an insulating grain boundary barrier with fluctuating electron occupation. The effective charge trapping time within single traps was found to decay exponentially with increasing bias voltage.
Optimization design study for an elliptical wiggler at the Advanced Light Source
Authors: Marks S. , McKinney W. , Padmore H. , Young A.
Published: July 2002

This paper describes a design study with the objective of optimizing spectral performance of an elliptical wiggler to be installed at the Lawrence Berkeley Laboratory Advanced Light Source (ALS). This device is to produce circularly polarized radiation in the energy range of 50 eV–10 keV. A figure of merit, which is a function of flux density and degree of circular polarization, is introduced as the objective function for optimization. An optimum set point for a particular photon energy is characterized by values of peak vertical field, horizontal deflection parameter, and vertical aperture. Optimum performance is evaluated for the nominal ALS operating energy of 1.5 GeV.
Personal-computer-based control system for a 1.8 T hybrid wiggler
Authors: Quimby D. C. , Robinson K. E. , Jander D. R.
Published: July 2002

A control system has been developed for the 1.8 T wiggler to be delivered to the Synchrotron Radiation Research Center in Hsinchu, Taiwan. The system serves three major functions: gap monitoring and control, end-corrector adjustment and tracking, and interlock safety and monitoring. The end correctors are programmed with a gap-following feature for compensation of the electron trajectory in both transverse planes at all gaps. Software and hardware interlocks are provided for overtravel limits and protection against excessive variation in gap from end to end. The system is designed for stand-alone operation as well as for compatibility with the SRRC central control system. Because the wiggler controller is based on a personal computer and uses the LabVIEW programming language, it is readily adaptable for other wiggler or undulator applications.
Design and manufacture of a 10-T superconducting wiggler magnet at TERAS
Authors: Sugiyama S. , Ohgaki H. , Mikado T. , Yamada K. , Chiwaki M. , Suzuki R. , Sei N. , Ohdaira T. , Noguchi T. , Yamazaki T. , Isojima S. , Usami H. , Suzawa C. , Masuda T. , Keishi T. , Hosoda Y.
Published: July 2002

The 10-T wiggler is an iron-cored superconducting wiggler destined for Electrotechnical Laboratory’s 800-MeV electron storage ring to enhance the available radiation. The design and manufacturing contract for this magnet was started in April 1990 and was preceded by a feasibility study. The major features of the magnet are described in the article. Also, the effect of the superconducting wiggler with high magnetic field on the stored electron beam has been simulated.
Macromolecular crystallography station BL-18B at the Photon Factory
Authors: Watanabe Nobuhisa , Nakagawa Atsushi , Adachi Shinichi , Sakabe Noriyoshi
Published: July 2002

A new experimental station, BL-18B, has been constructed on a bending-magnet beamline at the Photon Factory. The branch beamline is equipped with a Pt-coated fused quartz bend cylindrical mirror of 1:1 focusing and a fixed-exit double-crystal monochromator. The mirror can focus an x-ray beam to about 0.4 mm (vertical) ×1.2 mm (horizontal). The monochromator consists of two kinds of flat crystals, usually Si(111) and Ge(220), mounted side by side on the goniometer, and those two crystals can be interchanged without opening the vacuum chamber. In addition to increasing the experimental time available to users of the Weissenberg camera, BL-18B provides a point focused white beam for the time-resolved Laue method. In order to allow more effective exposures using Weissenberg and Laue methods, a new multipurpose camera using large imaging plates, 400 mm×400 mm and 400 mm×800 mm, is being developed. A special scanner for the large imaging plate has also been developed. Response of the scanner was tested and the linearity between the incident x-ray photons and the measured intensity is confirmed from 1 to 1×105 photons per pixel.
Elliptical multipole wiggler facility at the Advanced Photon Source
Authors: Montano P. A. , Knapp G. S. , Jennings G. , Gluskin E. , Trakhtenberg E. , Vasserman I. B. , Ivanov P. M. , Frachon D. , Moog E. R. , Turner L. R. , Shenoy G. K. , Bedzyk M. J. , Ramanathan M. , Beno M. A. , Cowan P. L.
Published: July 2002

The use of circularly polarized radiation is advantageous for the study of magnetic materials using x-ray scattering techniques. The APS is an ideal source of x-ray radiation for such studies. We present a description of the elliptical multipole wiggler (EMW) [S. Yamamoto, H. Kawata, H. Kitamura, and M. Ando, Phys. Rev. Lett. 62, 2672 (1989)] to be constructed at the APS. This device has been chosen for reasons of tunability and special polarization properties. This insertion device is capable of producing circularly polarized x rays on axis. The EMW period will be λu=16 cm, the number of full strength poles in the hybrid structure is 31, and the device length is 2.8 m. The hybrid magnetic structure produces a peak vertical magnetic field with Ky=14 and the electromagnet provides horizontal magnetic field with Kx=1–2. The frequency of the horizontal field change is up to 10 Hz. The beamline will consist of three stations operating in tandem with only one station receiving x rays at any one time. The three stations have three distinct functions, namely Compton scattering, magnetic scattering, and surface scattering. Special considerations will be made to insure the proper control of the polarization when using circular polarized light. The design of the elliptical multipole wiggler beam line will follow an approach very close to that developed by Kawata et al. [Rev. Sci. Instrum. 60, 1885 (1989)]. Our objective is to obtain a high photon flux with energies above 40 keV and well characterized polarization.
Performance of the elliptically polarizing undulator on SPEAR
Authors: Carr R. , Kortright J. B. , Rice M. , Lidia S.
Published: July 2002

This is a description of the first tests of the elliptically polarizing undulator (EPU) on the SPEAR storage ring at SSRL. The EPU is the first device of its type; it is capable of producing vertically and horizontally plane-polarized light, and right and left circularly polarized light in the 500–1000 eV range. Tests of the EPU were done to characterize its effect on the electron beam in SPEAR. Even at minimum gap, motion of the EPU magnets to vary the polarization of the output radiation caused negligible changes in the tune or the steering of the electron beam, even with no compensation of the steering trim coils. Also measured was the polarization of x rays generated by the EPU using a newly developed multilayer polarimeter built to be efficient in the EPU’s energy range. The EPU produces nearly 100% plane and circularly polarized x rays. Using left and right circularly polarized radiation, tests of magnetic circular dichroism on magnetic multilayers were also performed.
Accelerator plan for a light-source study at the TRISTAN MR
Authors: Kamada Susumu , Fukuma Hitoshi , Ogata Atsushi , Isawa Masahiro , Nakamura Norio , Sakanaka Shogo , Tobiyama Makoto , Ohmi Kazuhito , Kanazawa Ken-ichi , Kubo Tadashi , Egawa Kazumi , Mitsuhashi Toshiyuki , Mimashi Toshihiro , Kobayashi Masanori , Katsura Tomotaro
Published: July 2002

A three-month operation with a beam is scheduled for the autumn of 1995 at the TRISTAN MR for the sake of light-source development and research programs using it. The lattice will be modified so as to enable the installation of an undulator 5.4 m long and achieve a very low-emittance beam of 5 nm at 10 GeV. The emittance damping wigglers will enhance the radiation-damping rate, which will stabilize the coherent beam instabilities as well as reduce the emittance more. A considerable number of accelerating cavities will be removed from the ring in order to minimize the impedance of the higher-order modes of the cavities that may cause coupled-bunch instabilities and limit the intensity of the stored beam. For the stability of the light beam, a local feedback system will be applied to the electron orbit in the MR. The beam emittance will be measured by detecting the angular distribution of the Compton scattering of laser photons from the beam electrons. To measure the beam emittance in an independent way, visible synchrotron light from a bending magnet and 100 keV x rays from an undulator will be utilized.
Optics of a high power wiggler beamline at the European Synchrotron Radiation Facility
Authors: Krumrey M. , Kvick Å. , Schwegle W.
Published: July 2002

The materials science beamline (BL2) at the European Synchrotron Radiation Facility (ESRF) can provide monochromatic or white radiation in the energy range from 7 to 100 keV. The source is a multipole wiggler with a maximum critical energy of 29 keV, producing a radiant power of up to 5 kW. The main optical elements are an adaptive mirror, a monochromator with a liquid nitrogen cooled first crystal followed by a sagittally bent second crystal, and a second mirror including a bender for vertical focusing. The general layout as well as the performance of the beamline optics during the commissioning phase of the ESRF are presented.
Transient and steady state thermal and stress analysis of an insertion device beam shutter at the Advanced Photon Source
Authors: Ruan Yifei , Meron Mati
Published: July 2002

This article describes a conceptual design of an ultrahigh vacuum beam shutter for an insertion device beamline at the Advanced Photon Source. Various aspects of the design such as geometry, cooling arrangement, and material selection are optimized based on thermal and stress finite element analysis. The goal of the optimization is to assure survivability while maintaining a reasonably compact physical size.
Undulator test of a Bragg reflection elliptical polarizer at ∼7.1 keV
Authors: Shastri S. D. , Finkelstein K. D. , Shen Qun , Batterman B. W. , Walko D. A.
Published: July 2002

A system of diffracting perfect crystals for the generation of variable, elliptically polarized x rays was tested at the Cornell High Energy Synchrotron Source under the conditions of a standard undulator source. The phase retarding optical component was a 4-bounce, Ge(220) Bragg reflection channel-cut crystal. The full polarization state of the output beam, including the circular polarization purity P3, was determined using the multiple-beam Bragg diffraction technique. In addition to measuring the optics’ efficiency, the ability to scan the system in energy, while frequently reversing the circular helicity, was demonstrated at the vicinity of the Fe K edge at 7.1 keV. The setup was applied to a circular magnetic x-ray dichroism measurement.
Quadrupole trap control circuit for laser desorption mass spectrometry of levitated microparticles
Authors: Yang Mo , Whitten William B. , Ramsey J. Michael
Published: July 2002

An electronic control system for laser desorption mass spectrometry of a levitated single microparticle in a quadrupole trap is described. This circuit provides appropriate low-frequency ac and dc voltages for microparticle levitation and switches them to ground prior to laser desorption, enabling the trap to store and mass analyze the laser-desorbed ions.
Analytical compensation of stray capacitance effect in Kelvin probe measurements
Authors: Hadjadj A. , Cabarrocas P. Roca i , Equer B.
Published: July 2002

The Kelvin probe is a very sensitive technique for surface studies. The contact potential (CP) value measured by this method is related to the work function of the material under study. In order to use this technique in a plasma enhanced chemical vapor deposition reactor to investigate in situ the electronic properties of semiconductors and devices during their growth, we need to take into account the variations of the apparent values of the CP, with the mean probe-to-sample distance, due to stray capacitance. In this article, we describe a simple method to compensate analytically the stray capacitance contribution in order to obtain the true values of the CP. We have used a simple model based on the assumption of a constant stray capacitance contribution, which allows the formulation of an analytical expression of the difference between the apparent and true values of the CP. We show that, in the configuration in which the vibrating plate of the Kelvin capacitor is grounded and in the case of low modulation, it is possible to estimate the distance between the Kelvin capacitor plates and then to correct the apparent values of the CP within 10 mV. We have verified the good agreement of this model with our experimental results and justified the assumption of a single stray capacity term.
A threading tool for hard materials
Authors: Brown Kyle A. , Ho W.
Published: July 2002

A simple threading method suitable for difficult-to-machine materials is described. The instrument consists of two mating threaded brass pieces. A hole through both pieces accommodates a rod or tube to be threaded. Set screws in the male brass piece are used to force coincident rotation. The pitch of the threads is reproduced on the rod by screwing the male piece in and out while a rotating diamond abrasive wheel cuts the groove.
Increase in velocimeter depth of focus through astigmatism
Authors: Erskine David J.
Published: July 2002

Frequently, velocimeter targets are illuminated by a laser beam passing through a hole in a mirror. This mirror is responsible for diverting returning light from a target lens to a velocity interferometer system for any reflector. This mirror is often a significant distance from the target lens. Consequently, at certain target focus positions the returning light is strongly vignetted by the hole, causing a loss of signal. This note finds that the loss of signal can be prevented and that the useful depth can be greatly increased by attaching a cylindrical lens to the target lens.
A video-enhanced plate method for simultaneous measurements of surface tension and contact angle
Authors: Tsay Ruey-Yug , Yan Shaw-Chern , Lin Shi-Yow
Published: July 2002

The assumption of zero contact angle of the Wilhelmy plate method causes error for the surface pressure-area characteristics of some spread monolayers. To avoid this problem, a video-enhanced plate method is developed to monitor the dynamic surface tension and contact angle simultaneously. According to this method, the profile of the air–water interface adjacent to a flat plate is captured by an image digitization technique. The surface tension and contact angle are obtained from the best fit between the edge coordinates of the captured image and a theoretical equation derived from the Young–Laplace equation. Preliminary results show satisfactory agreement between the curve of the air–water interface obtained from experimental data and the theoretical curve for obtained values of surface tension and contact angle. Twenty tests for pure water at 25 °C give an average surface tension 72.0±0.2 mN/m, which confirms the accuracy of this method. A preliminary dynamic test also indicates that the effect of the contact angle in the Wilhelmy method can be corrected by dividing the apparent surface tension obtained from the Wilhelmy method by the cosine of contact angle measured by the present method.
New double beam spectrophotometer for microsamples. Application to hydrostatic pressure experiments
Authors: Moral B. Amaya , Rodríguez Fernando
Published: July 2002

This article describes a new double beam spectrophotometer specially conceived for optical absorption measurements on low-absorbing microsamples. The available long-working distance makes this apparatus attractive for use on samples placed in special environments such as heating stages, biological cells, and particularly hydrostatic pressure cells. Its performance has been tested in optical absorption measurements for different Mn2+ and Cu2+ complexes. We applied the instrument for investigating the electronic spectrum of Cu2+ doped (CH3CH2NH3)2CdCl4 crystals under hydrostatic pressure using a Sapphire anvil cell. A salient feature of this work is the enormous redshift (1400 cm−1) experienced by the first Cl−→Cu2+ charge transfer band at 26 kbar. We briefly comment on the origin of this shift.
Experimental comparison of a helium electron polarimeter with a calibrated high-precision Mott detector
Authors: Fischer T. , Kessler J.
Published: July 2002

Comparative electron polarization measurement with a helium electron polarimeter and a high-precision Mott detector are presented. For these measurements the helium electron polarimeter was calibrated according to theory, whereas the Mott detector was calibrated independently with an improved auxiliary-target method. The comparison of the experimental results reveals various problems inherent in helium electron polarimetry, such as poor efficiency and problems occurring in precise light polarization measurements. At present, a high-precision Mott detector is therefore clearly superior to a helium polarimeter with respect to efficiency and accuracy.
Systematic corrections in Bragg x-ray diffraction of flat and curved crystals
Authors: Chantler C. T. , Deslattes R. D.
Published: July 2002

Measurements of spectral wavelengths in Bragg diffraction from crystals often require refractive index corrections to allow a detailed comparison of experiment with theory. These corrections are typically 100–300 ppm in the x-ray regime, and simple estimates may sometimes be accurate to 5% or better. The inadequacies of these estimates are discussed. Even with a possibly improved index of refraction estimate, this correction is insufficient since additional systematics in the diffraction process occur at or above this level. For example, asymmetries of diffraction profiles with π-polarized radiation or due to three-beam diffraction can approach the magnitude of refractive index corrections for flat or curved crystals. The depth of penetration of the x-ray field inside curved crystals, the shift of the mean angle to the diffracting planes, and lateral shifts around the crystal surface are rarely considered but can dominate over refractive index corrections, particularly for high-order diffraction or medium-energy x rays. Shifts and nonlinearities arise when diffracting surfaces lie off the Rowland circle, and exhibit strong and rapidly varying angular dependencies. Johann geometries with the source located on the Rowland circle should be avoided to minimize profile truncation shifts from crystal ranges or minimum grazing angles, and to avoid extreme scaling corrections. Other significant shifts are identified and illustrated, with functional relations provided to allow an estimation of related magnitudes. The central concerns of this paper are the effects on flat crystal diffraction and curved crystal diffraction in the Johann geometry, with a source and crystal of variable dimensions and location. Experiments often interpolate or extrapolate from calibration lines, so dependencies upon the diffracting angle are as important as the magnitude of the corrections. These dependencies are presented in formulas and graphs.
X13A: A versatile soft x-ray undulator beamline
Authors: Xu Z. , McNulty I. , Randall K. J. , Yang L. , Gluskin E. , Johnson E. D. , Oversluizen T.
Published: July 2002

The undulator based beamline X13A at the National Synchrotron Light Source has been commissioned recently. The X13 undulator has an 8 cm period, and its first harmonic is in the energy range of 200–700 eV at the nominal ring energy of 2.5 GeV. The beamline uses horizontally deflecting optics. It consists of a SiC plane mirror, a water cooled entrance slit, a spherical grating, and two fixed exit slits. A flux of more than 1012 photons/s at 450 eV has been measured at X13A with an aluminum-oxide photodiode with a 200 μm entrance slit, a 500 μm exit slit, and a ring current of 242 mA. A VF3 absorption spectrum recorded at X13A shows the monochromator resolving power is at least 1000 at ∼500 eV with 30 μm entrance and exit slits, in agreement with calculations. The X13A beamline will be used for x-ray coherence studies, spectroscopy, and multilayer reflectivity measurements as well as for x-ray instrumentation diagnostics.
Uniform beam profiles of 5 cm convex gridded ion beam source
Authors: Koh S. K. , Song S. K. , Choi W. K. , Jung H.-J. , Gontcharov L.
Published: July 2002

A Kaufman-type 5 cm convex gridded ion-beam source is characterized in terms of angle-resolved ion-beam current density and beam uniformity at various discharge currents, electromagnet currents, and acceleration potentials.
Phase errors and predicted spectral performance of a prototype undulator
Authors: Dejus Roger J. , Vasserman Isaac , Moog Elizabeth R. , Gluskin Efim
Published: July 2002

A prototype undulator (3.3 cm period, permanent-magnet hybrid device) has been used to study different magnetic end configurations and shimming techniques for straightening the beam trajectory. Field distributions obtained by Hall-probe measurements were analyzed in terms of trajectory, phase errors, and on-axis brightness for the purpose of correlating predicted spectral intensity with the calculated phase errors. An rms phase error of less than 3° is found and 87% of the ideal value of the on-axis brightness for the third harmonic (nominal gap is 11.5 mm and derived effective K is 2.25) is predicted. The gap dependence of the phase errors and spectral brightness was also analyzed and it was found that the rms phase error remains small at all gap settings.
High-speed surface temperature measurements on plasma facing materials for fusion applications
Authors: Araki Masanori , Kobayashi Masanobu
Published: July 2002

For the lifetime evaluation of plasma facing materials in fusion experimental machines, it is essential to investigate their surface behavior and their temperature responses during an off-normal event such as the plasma disruptions. An infrared thermometer with a sampling speed as fast as 1×10−6 s/data, namely, the high-speed infrared thermometer (HSIR), has been developed by the National Research Laboratory of Metrology in Japan. To evaluate an applicability of the newly developed HSIR on the surface temperature measurement of plasma facing materials, high heat flux beam irradiation experiments have been performed with three different materials under the surface heat fluxes up to 170 MW/m2 for 0.04 s in a hydrogen ion beam test facility at the Japan Atomic Energy Research Institute. As for the results, HSIR can be applicable for measuring the surface temperature responses of the armor tile materials with a little modification. It is also confirmed that surface temperatures measured with the HSIR thermometer show good agreement with the analytical results for stainless steel and carbon based materials at a temperature range of up to 2500 °C. However, for aluminum the HSIR could measure the temperature of the high dense vapor cloud which was produced during the heating due to lower melting temperature. Based on the result, a multichannel arrayed HSIR thermometer has been designed and fabricated.
Electrical single probe with an automatic positioner
Authors: López R. , Meléndez L. , Sánchez A. M. , Gaytán E. , Chávez E. , Valencia R. , Cruz G. , Olayo M. G. , Flores A.
Published: July 2002

An easy to assemble and inexpensive plasma diagnostic system is presented. An electrical single probe and its vacuum and electrical isolation arrangement, integrated to an automatic positioner device, has been constructed and tested in plasma environments. This system provides a more precise estimation of the probe electrode position than others previously proposed in the literature. To control the probe electrode position an electronic circuit based in a microcontroller device is used. This automatic positioner avoids the troubles related to a manual operation.
A system for measurement of sub-parts-per-trillion helium in solids
Authors: Takao Y. , Kanda Y.
Published: July 2002

A system for measurement of less than 1 ppt (parts per trillion) of helium contained in a solid within the range of mass between 100 mg and 1 g has been developed for the primary purpose of measuring neutron-induced helium production cross sections. The system consists of an apparatus based on ultrahigh vacuum techniques, computer codes to estimate suitable parameters for the given experimental conditions and to control data acquisition parts, and an appropriate routine of operation of the system. The system apparatus consists of a gas releaser, a mass spectrometer, and a standard helium supply. A sample containing helium is evaporated in the gas releaser and the gas is analyzed with the mass spectrometer after purifying it for helium to decrease background gases. The background of helium for a dummy sample of silicon is measured to be 0.04 ppt. The total uncertainty of the apparatus is 4.4% in the range of (0.5–5.0)×1010 He measurement.
A high precision micropositioner with five degrees of freedom based on an electromagnetic driving principle
Authors: Wang Wanjun , He Tian
Published: July 2002

A five degrees of freedom high precision micropositioner based on spring suspension and electromagnetic driving has been designed, constructed, and tested. The device consists of two parts: a moving part and a stationary part. The moving part, named as ‘‘motor’’, is formed with a rigid frame and three groups of coils fixed on it. The stationary part of the device, called ‘‘stator’’, includes a chassis and twelve U-shaped magnetic ‘‘shoes’’. The motor is attached to the stator with flat springs whose linear suspension allows it to move in all dimensions except the rotation around z axis. The coils have been laid out in such a way that fractions of them pass through the air gaps between the facing magnets in the magnetic shoes. When electrical currents are supplied to the coils, the resulting Lorenz forces drive the motor to move in the five degrees of freedom allowed by the spring suspension. Since the system is inherently stable and there is no mechanical friction, the open-loop resolutions of the device are found to be limited only by that of the 12-bit D/A board used. A closed-loop translation resolution of 0.3 μm has been achieved over a working space of 180 μm by 180 μm by 680 μm. A closed-loop rotation resolution of 2.73×10−6 rad has been achieved over a working space of 1.38×10−3 rad. Potentially the device can be used for high precision microprobing and testing, cellular biology, microsurgery, and testing of micromechanical devices in the fast developing MEMS area.
Infrared cell for supercritical fluid–polymer interactions
Authors: Kazarian Sergei G. , Vincent Michael F. , Eckert Charles A.
Published: July 2002

A novel high pressure cell for Fourier transform infrared studies of extraction, impregnation, partitioning, and interactions between supercritical fluids and polymers is presented. Two parallel optical paths through the cell permit the measurement of IR spectra of the supercritical fluid and the polymer sample under the same conditions without essential overlapping of the absorption bands studied. This cell has been applied to study the supercritical CO2 drying of poly(methyl methacrylate) using deuterated water to eliminate the overlap of the IR absorption bands of the stretching modes of water with the bands due to combination modes of CO2. The technique for attaining quantitative measurements of the partitioning of the solute between the supercritical fluid and polymer phases is described.
Physics of ion beam plasma and problems of intensive ion beam transportation (invited) (abstract)
Authors: Soloshenko I. A.
Published: July 2002

Studies considering the problem of intensive ion beam transportation on large distances are performed in the Institute of Physics, including three main aspects: (1) space charge compensation of a stationary steady state beam, (2) dynamic decompensation of a beam space charge resulting from the current modulation owing to ion source plasma instabilities, and (3) collective processes. The results presented show the summary of plasma studies regarding the positive ion beams in the absence of external fields. These results make possible the numerical simulations or the qualitative predictions of the main properties for the transported beams (boundary particles trajectories, spatial distributions of static and variable fields, emittance, etc.).