bluuebunny/crossref_metadata_2025 huggingface dataset:
Simplified homodyne small-angle scattering technique which uses a diffraction pattern as local oscillator
Authors: Philipona R.
Published: July 2002

A CO2 laser small-angle scattering experiment has been set up and used for the investigation of plasma density fluctuations in a magnetized plasma. The local oscillator reference beam for homodyne mixing is produced by diffraction from a thin tungsten wire which lies in the main probe beam near the scattering center. The diffraction wire produces a diffraction pattern covering the scattering plane. An angular adjustment of one single mirror in the outgoing probe beam permits easy alignment of different scattering angles and scattering directions. Rayleigh scattering of ultrasonic waves has been used for testing and calibrating the scattering system. First results from plasma measurements are presented.
Multispecies coherent anti-Stokes Raman scattering instrument for turbulent combustion
Authors: Antcliff Richard R. , Jarrett Olin
Published: July 2002

A nonintrusive diagnostic system is described which permits simultaneous measurement of temperature, nitrogen number density, and oxygen number density in hostile combustion environments. This system is pumped by a 10-Hz neodymium YAG laser, and signals are detected with an intensified photodiode array and dual photomultipliers. The system utilizes a folded BOXCARS beam arrangement, two probe dye lasers, dynamic range expansion, polarization rejection of nonresonant background, and multiplexing of the signal beams.
Improved Lyman-alpha hygrometer for small-scale atmospheric turbulence measurements. Part II: The O2 filtering technique
Authors: Mestayer Patrice , Goutail Florence , Rebattet Claude
Published: July 2002

The detector of the IMST/SA-CNRS improved Lyman-alpha hygrometer is a solar-blind photomultiplier tube that ensures large signal-to-noise ratio and allows a miniaturization of the sampling volume. This PM tube has a relatively large spectral response and can detect, in addition to the Lyman-alpha line, hydrogen molecular transitions emitted by the discharge source between 120 and 180 nm. In order to avoid a spurious sensitivity to oxygen density fluctuations, an active filtering cell is added to absorb the undesired lines. The instrument sensitivity is calculated with the help of a two-gas, three-spectral-line UV-beam absorption model, fitted to calibration measurements. The technique of the active filtering associated with the three-line absorption model produces the following advantages: (1) reduced sensitivity to oxygen fluctuations, (2) a clear physical meaning to the model terms allowing the sensitivity computation in most conditions, (3) increased signal-to-noise ratio, and (4) in most conditions, improved sensitivity to water vapor compared to the monochromatic Lyman-alpha line.
Wide-band solids, rapid recovery, multinuclear transceiver/digitizer for a high-resolution NMR spectrometer
Authors: Claiborne T. C. , Cheng J. T. , Garber A. R. , Ellis P. D.
Published: July 2002

A transceiver which is capable of observation of spectral widths of 1.6 MHz has been constructed as an accessory to a Bruker WH-400 NMR spectrometer. This device permits observation of the NMR resonances of solid-state quadrupolar nuclei, which may contain frequency components more than 1 MHz away from their fundamental precession frequencies. The transceiver contains its own frequency generation section, which employs the host spectrometer’s master phase reference and synthesizer. The NMR signal undergoes image rejection mixing to an intermediate frequency above the observation band, and quadrature phase detection before final amplification with video speed operational amplifiers in the receiver section. Dual 8-bit, video speed digitizers feed the converted data to dual 16 kword deep buffers that can accept data at a rate of 4 Msamples/s. A slower data output rate is governed by the Bruker Aspect host computer. The noise figure of the device is 1.8 dB, with a sensitivity of at least −71 dBm and a recovery time of approximately 1 μs for linear amplification to resume after an excitation pulse.
Beam compression and beam multiplexing in a time-of-flight mass spectrometer
Authors: Riess I.
Published: July 2002

Two new methods for operating a time-of-flight mass spectrometer are suggested. The first is a beam compression method which allows separation of one kind of particle (one m/q ratio) at a time, from a beam continously emitted by an ion source. Due to the continuous operation of the source a corresponding increase in signal-to-noise ratio is expected. The second method is based on forming a multiplex beam by modulating a continuously emitted ion beam. The use of a time array detector enables the collection of the data. The algorithm of analysis is presented. This method should have the increased throughput advantage. An improvement in signal-to-noise ratio need not take place.
Semiautomated PVT facility for fluids and fluid mixtures
Authors: Linsky D. , Levelt Sengers J. M. H. , Davis H. A.
Published: July 2002

A manually operated Burnett apparatus has been converted into a semiautomated Burnett–isochoric PVT facility. An automated pressure injector with dedicated control logic nulls a sensitive differential pressure indicator. A microcomputer is used in setting the control temperature, monitoring equilibration, measuring temperature and pressure, processing the raw data, and storing the information. The quality of the apparatus is demonstrated by means of a low-density and a high-density isochore obtained for a geothermal working fluid mixture in one-phase, two-phase, and supercritical regimes, including a dew and a bubble point.
Nanosecond resistive high-voltage probes for transient ground rise measurement in gas-insulated switchgear. Part I: Newi probes with wire-wound resistors
Authors: Mitchel G. R. , Malewski R.
Published: July 2002

This paper describes a 5-ns rise-time resistive voltage probe for use up to 150 kV. It is based on a wire-counterwound design and uses low-voltage arms incorporating fast switching diodes for oscilloscope protection. Much attention was paid to reducing inductance in the system through a compact layout, while still ensuring adequate dielectric insulation.
Measurements of electrical birefringence by using a transverse-field Pockels cell as a compensator
Authors: Mendicuti Francisco
Published: July 2002

An improved device for electrical birefringence measurements is described. The novel features of this apparatus include a new design of the Kerr cell and use of the Pockels cell as a compensator. These features show enhanced sensitivity and great improvement in reproducibility of results. A relationship between the intensity detected and the relative phase shifts in the Kerr and Pockels cells is determined by a matrix analysis of the amplitude of radiation passing through each optical element. Based on this analysis, a comparative study under different experimental configurations, as well as an evaluation of the effects of misalignments and methods to cancel the static birefringence, are made. From the results, the best experimental arrangement and procedure of measurement are deduced. Finally, the apparatus is checked by measuring Kerr constants (B) of several nearly isotropic solvents used for the study of polymers in solution.
Simplification in preparing fiber ends to attach small mirrors
Authors: Stone J.
Published: July 2002

A simplified way to make a good surface for contacting a mirror to an optical fiber by heating the fiber end is described. The technique causes the deposited core and cladding of a fiber made by the modified chemical vapor deposition method to bulge slightly, providing a pivoting surface for orienting the mirror. The method is applicable to the fabrication of high finesse fiber Fabry–Perot interferometers.
Asymmetric double Langmuir probe for fast and automatic measurements of plasma temperature
Authors: Uckan Taner
Published: July 2002

We present a fast technique for determining the plasma electron temperature Te automatically from the small signal application of the asymmetric double Langmuir probe when it is operated in the region where −1<eVa/Te<1. The method described here is based on simple time and rms averages of the probe current that results from a sinusoidally varying applied voltage Va.
Radiation-induced conductivity: The high-speed detection of photons and particles (invited) (abstract)
Authors: Kania D. R.
Published: July 2002

High-speed photoconductors have been used to detect photons from the infrared to gamma rays. Their technology has been extended to new materials and to the detection of particles (radiation-induced conductivity). The new materials include thin films of GaAs and diamond and bulk type IIa insulating diamond which complement previously tested material, bulk InP and GaAs. Thin films offer high speeds and discrimination against penetrating radiation. Insulating diamond is insensitive to visible light (scattered laser radiation). Both properties can be extremely valuable in a laser–plasma environment. In addition, these detectors have been used to detect 14-MeV neutron pulses from laser fusion experiments on the Nova laser. The thermonuclear burn rate and its temporal relationship to the driving laser pulse have been determined with 100-ps time resolution. This work was performed under the auspices of the U.S. DOE by the Lawrence Livermore National Laboratory under Contract No. W-7405-ENG-48.
XUV spectral observations with two-wavelength laser irradiation
Authors: Burkhalter P. G. , Apruzese J. P. , Seely J. F. , Brown C. M. , Newman D. A.
Published: July 2002

XUV diagnostic equipment was designed and utilized on the OMEGA target chamber at the University of Rochester to study high atomic number plasma generation by two-wavelength laser excitation. Spectral data were collected from silver tracer dot targets irradiated with 1/3 TW of 0.35-μm laser light of the multiple-beam OMEGA laser and the single synchronized 1.06-μm beam of the GDL laser for generating energetic electrons. XUV spectral data in the 30–300-Å region were obtained with both a 3-m grazing incidence spectrograph and a compact 1-m grazing incidence spectrograph designed for reentrant mounting in the OMEGA chamber. High-resolution x-ray spectra were acquired in the 3.6–4.2-Å region with a dual, flat-diffraction crystal spectrograph. A low-resolution x-ray spectrum of silver was recorded with a curved mica spectrograph. Some x-ray spectral lines appeared only when both OMEGA and GDL beams were used. These were identified as 2p–3s,3d transitions in F-like Ag xxxix. F-, Na-, and Mg-like lines were found in the grazing incidence spectra, with F-like lines appearing only with 1.06-μm irradiation.
Plasma profile fitting and alternate-view generation
Authors: Diesso M. , Hill K. , von Goeler S.
Published: July 2002

We present a method of using a plasma model to fit a given profile and using the model’s parameters to generate the profile seen along any alternate chord. We illustrate the method with a simple ‘‘linearly shifted circle’’ model in which it is assumed that the plasma cross sections are circles that are shifted along the major radius of the vacuum vessel as a linear function of their radii. Sample test results are provided.
Numerical simulation of an ECE diagnostic to measure magnetic fluctuations in fusion plasmas (abstract)
Authors: Thomas C. E. , Hanson G. R.
Published: July 2002

It has been previously suggested1 that crossed-sightline correlation of electron-cyclotron emission might be used to measure local fluctuations of the magnetic field in magnetically confined plasmas. Before implementing this idea in hardware, a computer (numerical) simulation of the diagnostic should reveal whether the idea has merit when applied to a less than ideal (realistic) experimental fusion device. A brief description of the proposed diagnostic, details of the simulation, and the results of numerical simulation as of the meeting date will be presented.
Asymmetric light scattering effects in tokamak plasmas
Authors: Doyle E. J. , Evans D. E.
Published: July 2002

The experimental observation of spatially asymmetric scattering on the TOSCA tokamak has led to the identification of two distinct mechanisms responsible for such effects. The first is the influence of the plasma interaction length L on the scattered field (volume effect). When L is small, the plasma behaves like a thin phase grating and equal-amplitude positive and negative diffraction orders are generated (Raman–Nath scattering). As L increases, however, the scattering takes on three-dimensional properties similar to x-ray diffraction from a crystal; only one diffraction order can occur, and then only if the Bragg condition is satisfied (Bragg scattering). The second effect occurs whenever the scattering volume is large enough to contain counterpropagating waves. In this case, constructive/destructive interference can affect the measured intensity of the scattered light.
Measurements of density fluctuations using a simplified CO2 laser forward scattering technique
Authors: Philipona R. , Küttel O.
Published: July 2002

Coherent and fully turbulent modes of electron density fluctuations in a cylindrical magnetized plasma are investigated using a new simplified CO2 laser forward scattering technique. In our small-angle scattering system a diffraction pattern is used as local oscillator for homodyne photomixing. Self-excited density fluctuations ñ(K, ω) of a He plasma have been measured in the parameter range 3 cm−1≤K≤24 cm−1 and 20 kHz≤ω/2π≤500 kHz.
Measurements of neutral density profiles on the TEXT tokamak
Authors: Boedo J. A. , Bengtson Roger D. , Ouroua A. , Valanju P. M.
Published: July 2002

Neutral density profiles are measured in the outer third of the plasma of the TEXT tokamak in conjunction with ion temperature measurements using the far line wings of a Hα profile. The advantage of this technique is that it does not require a radial inversion of the data to obtain a measure of the local neutral density. The ion temperature profiles are compared with the results from a neutral particle analyzer, and the neutral profiles with the results of a numerical code which solves a system of coupled linear equations describing particle transport from a neutral source.
Visible and VUV spectroscopic diagnostics on Heliotron E
Authors: Kondo K. , Zushi H. , Nishimura S. , Kaneko H. , Sato M. , Sudo S. , Sano F. , Mutoh T. , Motojima O. , Obiki T. , Iiyoshi A. , Uo K.
Published: July 2002

Diagnostic applications of visible and VUV spectroscopic techniques, as applied to the currentless Heliotron E plasma device, are described. Visible spectroscopy has been used to measure (i) ion temperature, (ii) proton-to-electron density ratio, (iii) Zeff by charge exchange recombination from an intense neutral beam, (iv) radial electric field by poloidal rotation velocity measurement, and (v) electron density around an ablating pellet by a Stark profile. VUV spectroscopy has been used to investigate emission spectra due to multiply ionized impurity species. This information is used to measure the densities of these species, and to learn about the transport of these particles. Recently, a flat-field survey spectrometer has been constructed and used to study the emission spectra due to metallic impurities in ICRF-heated plasmas.
Optical time-domain reflectometer for ICF burn dynamics (abstract)
Authors: Kislev H. , Miley G.
Published: July 2002

A new ultrafast all-optical sensor for studies of ICF burn dynamics is described. The sensor measures the change in reflectivity at the interface between two glass plates. The front plate uses uranium-oxide doped silica while the rear plate uses pure silica with an index matching coating. Neutron-induced fissions preferentially change the refractive index of the front plate and the resulting mismatch is measured with a probe laser. A threshold neutron yield requirement of 2×109 is estimated for a sensor with 30 wt. % U-238 doping located 2 mm from the target. A time resolution <20 ps is predicted. Further properties and construction details will be presented.
Apparatus for direct measurement of ash fusion and sintering behavior at elevated temperatures and pressures
Authors: Khan M. Rashid
Published: July 2002

Ash fusion, sintering, and deposition may impose serious operational difficulties in conventional and advanced coal-combustion systems. Conventional ash fusion techniques (e.g., ASTM methods) determine the qualitative behavior of ash samples at atmospheric pressure. Presently, there is no known available technique that can measure the behavior of coal ash at elevated temperatures and pressures. In the literature, methods based on electrical resistance or shrinkage of coal ash have been reported at atmospheric pressure (elevated temperatures) conditions. A high-pressure microdilatometer (HPMD) has been developed to investigate ash fusion and sintering behavior at elevated pressures and temperatures by the simultaneous measurement of the temperature of initial contraction and electrical resistivity of samples. This novel technique facilitates the measurement of ash properties over a wide range of temperature, pressure, and gas atmosphere (oxidizing, reducing, or inert). The operating principle of the HPMD includes measuring the temperature at which there is a significant ‘‘shift’’ in the electrical resistivity (and/or sample volume) that represents ash sintering and fusion. Sintering occurs through the formation of solid-state, particle-to-particle ‘‘necks’’ or the appearance of a molten phase, which allows a path for electrical conductance. The ability to perform both resistivity and shrinkage measurements simultaneously or independently at elevated pressures makes the HPMD truly unique. The HPMD can also be used to investigate the swelling and softening behavior of pyrolyzing coal at elevated pressures and relatively rapid heating rates. The HPMD can provide insights into the sintering/fusion of coal ash or coal swelling at a range of conditions: (a) the influences of various gas atmospheres can be investigated, (b) the effects of pressure can be studied, (c) different temperature/heating rate schemes can be used (constant rates, isothermal holds below or above the sintering temperature, etc.), and (d) studies can be performed to investigate the influence of increased heating rate at elevated pressures (which were not performed previously) on coal swelling and plasticity.

It can also be applied to other fossil fuels such as oil shale or carbonaceous materials (e.g., graphite) to measure their electrical conductivity or expansion and contraction behavior at ambient or elevated pressures and temperatures. The HPMD allows researchers to gather novel data and thereby facilitate a fundamental understanding of the behavior of coal or coal ash at actual processing conditions.
Programmable interface for Transputer-based data acquisition and control
Authors: Fornili S. L. , La Gattuta G. , Lapis M.
Published: July 2002

A circuit is described which can interface instrumentation with cost-effective Transputer-based systems. Four control lines, 12-bit A/D conversion at programmable sample time, and accessibility to concurrent computing are provided.
Quantitative microtomography
Authors: Engelke K. , Lohmann M. , Dix W.-R. , Graeff W.
Published: July 2002

The performance of a system for quantitave microtomography with synchrotron radiation is described with regard to the spatial resolving power. The experimental setup consists of a double-crystal monochromator, a monitor in front of a sample stage and a line scan detector which is built up of two photodiode arrays (Reticon RL1024SF), which are cooled by Peltier elements to increase the dynamic range. We present the modulation transfer function of the detector and several monitor configurations. So far a spatial resolution of 100 μm has been achieved.
Instrumentation for the photoacoustic EXAFS method
Authors: Masujima T. , Kawata H. , Kataoka M. , Shiwaku H. , Yoshida H. , Imai H. , Toyoda T. , Sano T. , Nomura M. , Iida A. , Kobayashi K. , Ando M.
Published: July 2002

The instrumentation for the photoacoustic EXAFS experiment detailed here is under development at the Photon Factory. In the experimental setup, simultaneous detection of the absorption spectra in addition to the photoacoustic measurement was useful for confirmation of this phenomena and for data correction. The current detection limit of this system is not sufficient for application to a wide variety of samples. Several ways for improvement of the quality of the spectra were carried out and the results were discussed.
Diffractometer for synchrotron radiation structural studies of high temperature melts
Authors: Marumo F. , Morikawa H. , Shimizugawa Y. , Tokonami M. , Miyake M. , Ohsumi K. , Sasaki S.
Published: July 2002

A diffractometer has been constructed for structural studies of high-temperature melt with synchrotron radiation. It was designed to measure diffracted intensities from the free surface of a molten sample by scanning a scintillation counter with a fixed glancing angle of the incident beam. In order to heat samples up to 1500 °C, a small electric furnace is attached to the diffractometer. It carries a hemicircular (100 mm in diameter) cover, which has a window for the passage of x rays. The window is covered with a Kapton film. The sample container made of 30 Rh-Pt is mounted at the center of the furnace. A test measurement was performed on GeO2. Monochromatic beams with λ=1.32 A and its second harmonics were taken out of synchrotron radiation by a β-alumina crystal (d002=11.3 A) and used as incident beams. To partial scattering curves obtained with λ and λ/2 were combined to a single curve after correction for absorption. The radial distribution function obtained from these data is in good agreement with that previously reported which was derived from diffraction data collected on a conventional diffractometer.
Station for studying solid-state chemical reactions by Laue method
Authors: Gaponov Yu. A. , Lyakhov N. Z. , Tolochko B. P. , Baru S. E. , Savinov G. A. , Sheromov M. A.
Published: July 2002

A station for studying the solid-state chemical reactions by the in situ Laue method using synchrotron radiation is described. A two-dimensional position sensitive x-ray detector is used as the registration device. In the reaction chamber the sample is kept at the controlled temperature and under the pressure of air atmosphere (or vacuum). The possibility of investigating the kinetic and space regularities during the solid-state chemical reactions are shown on the example of crystalhydrate dehydration in vacuum.
Station on the SR beam of the VEPP-3 storage ring for the study of macromolecular crystal structure (abstract)
Authors: Popov A. N. , Antson A. A. , Bondarenko K. P. , Belyaev V. V. , Harutunyan E. G. , Kheiker D. M. , Sheromov M. A. , Mytnytchenko S. V.
Published: July 2002

The station designed to speed up the collection of integral intensity data from protein and virus crystals is constructed on the SR beam of the VEPP-3 storage ring. A flat triangular Si crystal cut at 8° relative to the (111) plane is used to monochromatize the radiation. The monochromator is placed on the automatic goniometer which allows us to obtain the necessary energy of radiation, to make the adjusting turns and displacements, and to bend the crystal in order to achieve focusing in the horizontal plane. All the mechanical drive units are supplied with position sensors based on multiturn potentiometers.

A conventional Arndt-Wonacott rotation camera is used to collect structure information. The station also includes an optical bench which can turn about the axis coinciding with that of the monochromator, and a set of slits to cut the background and to form the beam. The ionization camera serves to adjust the monochromator and to monitor the beam.
Optical constants of superthin gold films for soft x rays
Authors: Yanagihara Mihiro , Cao Jianlin , Yamamoto Masaki , Arai Akira , Nakayama Shigeru , Mizuide Tamaki , Namioka Takeshi
Published: July 2002

The optical constants, δ=1−n and k, of superthin gold films have been determined from the reflectance data obtained in the soft x-ray region of 60–900 eV. The gold films were prepared to various thicknesses, d=39–270 Å, by ion-beam sputtering (IBS) and electron-beam evaporation (EB). A plane-parallel slab model with due consideration for the surface and the interfacial roughness was used to analyze the data by least-squares curve fitting. The optical constants derived for the IBS samples definitely show variations in the vicinity of d=100 Å. It is also found that δ of the 201-Å-thick IBS film is smaller by about 7% than that of the 211-Å-thick EB film.
Soft x-ray undulator for the U5 beamline at NSLS
Authors: Viccaro P. J. , Shenoy G. K. , Kim S. H. , Bader S. D.
Published: July 2002

The magnetic structure and spectral properties of a 7.5-cm, 30-period hybrid undulator are described. The device will be installed at the U5 port of the VUV storge ring at Brookhaven National Laboratory and will be a tunable source of very high brillance soft x-ray radiation over the range of 13 to approximately 150 eV.
Optimization of undulator design for high brightness sources (abstract)
Authors: Rowen M.
Published: July 2002

The properties of transverse undulators are systematically reviewed and the criteria for optimizing both the undulator and the electron beam parameters at the insertion device are discussed. To achieve high brightness, and coherence, the maximum number of undulator periods are desired. It is assumed the undulator is not divided into sections, separated by focussing quadrupoles, there for the length and minimum gap of the device is limited by the beam emittance and β function. A reduction of the period length corresponds to an increase in the energy first harmonic, thus to keep the same spectral output the operating beam energy is decreased, the emittance goes as E2 in a storage ring, until reduced damping and other factors start to dominate. Using conventional technologies, permanent magnet, hybrid and micropole undulators, the maximum magnetic deflection parameter K, and, therefore, flux, is limited at short period lengths even at small gaps. The optimization of undulator design, β function and beam energy for high brightness at a given wavelength is presented.
Breakdown of alumina rf windows
Authors: Saito Y. , Matuda N. , Anami S. , Baba H. , Kinbara A. , Horikoshi G. , Tanaka J.
Published: July 2002

The breakdown of alumina rf windows being used in high-power rf systems of accelerators has been investigated. The puncture and the thermal fracture often taking place in s-band pulsed rf systems and in UHF cw rf systems, respectively, are found to be induced by alumina surface heating due to an electron multipactor bombardment accompanied by a luminescence of alumina. It is ascertained that TiN coatings on the alumina window suppress the multipactor, and that the window duration for breakdown is dependent on the microstruture of the alumina ceramic.
Finite element analysis of electromagnetic field for multidimensional rf cavities
Authors: Ye G.-W. , Miyauchi Y. , Yagawa G. , Yoshimura S.
Published: July 2002

A new finite element code, resonance analysis system for Maxwell’s equation (RAMAX), has been developed for the numerical analysis of electromagnetic fields of multidimensional resonance frequency (rf) cavities. The penalty function method is used to deal with both the divergence-free condition and the boundary condition. The present code is able to analyze 2D (x-y,r-z) waveguide problems, 2.5D [x-y-(z), r-z-(r)] and 3D cavity resonator problems. In this article, the formulation and the features of the code are described. Several numerical examples of 2D, 2.5D, and 3D problems are also presented to demonstrate the accuracy and efficiency of the code.
Measurement of bunch lengthening in TERAS
Authors: Sugiyama S. , Yamazaki T. , Noguchi T. , Nakamura T. , Mikado T. , Chiwaki M. , Suzuki R. , Tomimasu T. , Sato S. , Usami H.
Published: July 2002

The bunch length was measured by using a highly sensitive streak camera with a time resolution of 2 ps. It was found that fine structures appeared in the electron bunch shape and that the shapes of electron bunches were described by a Gaussian distribution on the average. The dependence of bunch length on beam current was measured for an electron beam of 607 MeV. The bunch length was well represented by a power function of beam current with an exponent of 0.197 at currents lower than 35 mA or 0.30 at high currents. The experimental results suggest that the longitudinal coupled-bunch beam instability takes place at low beam currents and the turbulent instability dominates at high currents. It was also found from the three-dimensional bunch shape measurements that the bunch shape tended to blow up at high currents.
Mössbauer isomer shift measurements without mechanical tuning
Authors: Sinor T. W. , Reittinger P. W. , Collins C. B.
Published: July 2002

A technique is described which demonstrates how a frequency modulation spectrometer (FMS) can be used to measure the isomer shift of ferromagnetic absorbers without mechanical tuning. As an example, the isomer shift of an iron sample relative to a 57Co source in a Pd matrix was measured and found to be −(0.1869±0.003) mm/s compared to the literature value of −(0.185±0.02) mm/s.
Experimental apparatus for production, cooling, and storing multiply charged ions for charge-transfer measurements
Authors: Kwong V. H. S. , Gibbons T. T. , Fang Z. , Jiang J. , Knocke H. , Jiang Y. , Ruger B. , Huang S. , Braganza E. , Clark W. , Gardner L. D.
Published: July 2002

A novel method is described that combines the production of ions by laser ablation with an ion-trap technique for the measurement of thermal-energy charge-transfer rates of multiply charged ions and neutrals. The charge-transfer rate is determined by measuring the rate of loss of stored ions from the trap. Verification of the calibration of the apparatus is demonstrated through investigation of charge transfer of N2 and N2+, which has been studied by another group. We also have made the first measurement on the thermal-energy charge-transfer coefficient of Ar and W2+. The rate coefficient is 0.99(0.22)×10−11 cm3 s−1.
Melting of NaCl in a heater as a simple temperature monitor at high pressure
Authors: Mishima O. , Nagashima T. , Ohsawa T. , Yamaoka S.
Published: July 2002

A simple method to monitor the temperature in a high pressure apparatus has been developed. In this, a small amount of NaCl placed in the graphite heater of a pressurized furnace assembly melted when the heater temperature was increased and this caused an abrupt change in the heater resistance. This effect could be used to measure the sample temperature in a high-pressure experiment and to calibrate the temperature as a function of electric power. The method was used successfully to attain a better control of temperature in growing crystals of cubic boron nitride under high-pressure high-temperature conditions.
Detection of new superconductors using phase-spread alloy films
Authors: Lederman D. , Vier D. C. , Mendoza D. , Santamaría J. , Schultz S. , Schuller Ivan K.
Published: July 2002

We describe an effective method for discovery of new superconductors, which combines phase-spread alloy thin film preparation with a magnetic field modulated (MFM) microwave absorption technique. The MFM technique can detect superconductivity in YBa2Cu3O7−δ volumes as small as 5×10−11 cm3. As an illustration, PrxGd1−xBa2Cu3O7−δ thin films with varying x were simultaneously grown on the same substrate using a phase-spread alloy technique. The onset temperature determined from the microwave absorption agrees with resistivity, Auger spectroscopy, and energy-dispersive x-ray microanalysis data. When phase-spread Lax(NiB)1−xNy films (0<x<1) were grown at several different N partial pressures and temperatures, no superconductivity was detected except that of pure La. In contrast, superconductivity was detected in Yx(NiB)1−xCy films grown on MgO.
Beryllium gaskets suitable for pressures up to 10 GPa
Authors: Macavei J. , Schulz H.
Published: July 2002

A systematic study of the possibility of using beryllium gaskets in diamond-anvil pressure cells was carried out. Six different Be-BeO alloys were tested and treated in different ways in order to obtain Be gaskets suitable for pressures up to 10 GPa. The beryllium quality, the shape of the diamond anvils, the thickness of the gasket, the diameter of the sample chamber, and the depth of the gasket preindentation determine the highest obtainable pressure and its stability.
A combination spectrophotometer for measuring electronic absorption, natural circular dichroism, and magnetic circular dichroism spectra
Authors: Policke Timothy A. , Schreiner Anton F. , Trexler Jack W. , Knopp James A.
Published: July 2002

The design, construction, and evaluation of a combination spectrometer for measuring electronic absorption (EA), natural circular dichroism (CD), and magnetic circular dichroism (MCD) are described. Around the optical components of a JASCO ORD/UV-5 spectropolarimeter, a new EA/CD/MCD instrument was built with the realized intentions of increasing sensitivity and upgrading the analog tube type circuitry to a solid-state digitally, computer-controlled spectrophotometer. It is a flexible, dynamic, and user-controllable system, interfaced to an Apple II Plus computer, for studying instrument and signal parameters. The monochromator (M), photoelastic modulator (PEM), photomultiplier tube applied voltage (PMHV), and photomultiplier tube dc output current (PMdc) are under complete and independent software control. Our system has two unique aspects for obtaining the circular dichroism. First, the ac signal is measured with a voltage-to-frequency (V/f) converter; and, second, both the ac and the dc are independently recorded and their ratio is digitally calculated. This design has several advantages which include the elimination of voltage divider integrated circuits or division electronics, a wide dynamic range, a greater precision of ac values at low percentages of full scale, and the capability of continuous integration over long time periods. Also, both types of spectra, EA and CD or MCD, are obtained from the current output of the PM. This paper not only describes the design of the instrument for obtaining the two types of spectra but also compares four methods of obtaining the circular dichroism. Sensitivities of ∼1×10−7ΔA units are achievable as determined by measuring CD spectra of the well-known enantiomer (+)−[Co(en)3]3+.
A microcomputer-controlled linear heater
Authors: Schuck Vern , Rahimi Saeid
Published: July 2002

In this note the circuits and principles of operation of a relatively simple and inexpensive linear temperature ramp generator are described. The upper-temperature limit and the heating rate are controlled by an Apple II microcomputer. The temperature versus time is displayed on the screen and may be plotted by an x-y plotter.
Determination of thin-film optical constants with an automatic reflectance and transmittance goniometer
Authors: Bader G. , Ashrit P. V. , Elouatik S. , Girouard F. E. , Truong Vo-Van
Published: July 2002

An automatic goniometer has been built in order to simultaneously measure the reflectance and transmittance of films at different angles of incidence of the incoming light. The angle can be varied from 7° to 83° and the incident light can be either s or p polarized. Following a minimization procedure, optical constants for the deposited films can be accurately determined. Results for Nb2O5, WO3, LiBO2 are presented and the precision of the method is discussed.
Near-infrared spark source excitation for fluorescence lifetime measurements
Authors: Birch D. J. S. , Hungerford G. , Imhof R. E.
Published: July 2002

We have extended the range of excitation wavelengths from spark sources used in single photon timing fluorometry into the near infrared by means of the all-metal coaxial flashlamp filled with an argon-hydrogen gas mixture. At 750 nm this mixture gives ∼15 times the intensity available from pure hydrogen for a comparable pulse duration. Measurements are demonstrated by using the laser dye IR-140 in acetone, for which a fluorescence lifetime of 1.20 ns is recorded.
The use of aluminum alloy 5056 for high-Q mechanical oscillators at low temperatures
Authors: Adams P. W. , Xu Jing-chun
Published: July 2002

Measurements of the quality factor (Q) and period (P0) of two Al 5056 torsional oscillators are presented as a function of temperature from 0.02 to 1.2 K. The 5056 alloy is found to have Q’s of order 104 at room temperature and 107 below 4 K. In addition to having an extraordinary high Q, we also find that the temperature dependence of the reduced period, ΔP/P0, is extremely weak at low temperatures, making this material well suited for superfluid helium film studies. A technique for attaching thin dielectric substrates to the torsion member of one of the oscillators is also discussed.
High-speed diffractometer-reaction chamber using synchrotron radiation
Authors: Larson E. M. , Waide P. A. , Wong Joe
Published: July 2002

A high-speed diffractometer capable of recording diffraction patterns in the time scale of a few milliseconds using a synchrotron x-ray source is described. This instrument is designed to monitor fast, self-propagating high-temperature solid-state synthesis reactions in an inert atmosphere. A vertical θ-2θ geometry is employed to collect maximum scattering from the horizontally polarized synchrotron beam. The detector system consists of two silicon photodiode arrays each of which can be integrated in as little time as 4 ms with shorter time frames possible if some pixels are skipped. Operation of the detectors, transfer and storage of data, and movement of the motors are controlled by an IBM-AT computer. The design, construction, and subsequent testing and performance at the Brookhaven National Synchrotron Light Source are discussed in detail.
Guiding of a gun plasma by a permanent magnet octupole field
Authors: Barrett Christian , Robertson Scott
Published: July 2002

Plasma from a coaxial gun has been guided 1 m by a linear octupole magnetic field generated by an array of permanent magnets. Calorimetry indicates 30% efficiency. The technique is useful for removing the neutral gas component from the plasma.
Real-time, high-resolution optical beam position-sensing device
Authors: Toda Kohji , Yoshida Shinzo
Published: July 2002

An optical beam position-sensing device with real-time and high-resolution abilities is described using a Pb2CrO5 thin-film lateral photodetector. A high resolution of less than 5 nm in an effective measuring range of 16 μm is compatible with a real-time response of up to 10 kHz. Three parallel, planar gold electrodes evaporated on the film surface in a configuration with two narrow electrode gaps are essential for sensing the position of a light beam. Relationships between photocurrent and light beam position are examined under various combinations of the electrode configuration and beamwidths. The displacement deviation at the surface of the shaft of the rotating motor is measured for a demonstration of real-time and high-resolution position sensing.
Inexpensive, flexible sample transfer system
Authors: Chen Qibiao , Chevako P. , Onellion M.
Published: July 2002

A simple, inexpensive, and flexible sample transfer system is described. The system possesses the advantages of excellent base pressure and the flexibility to study thin films deposited in situ. We have applied the system to study thin-film magnetism with magnetic measurements utilizing optical techniques that require stable sample support.
A valve with seat-slope proportional to flow area at all poppet positions
Authors: Guillaume D. W. , DeVries D.
Published: July 2002

An adjustable gas-blending apparatus is hypothesized that would maintain a consistent mixture over a broad range of flowrates. The design equations for the unique valve seat required for such an apparatus are developed and solved numerically. An example seat is calculated and illustrated in table form. For preliminary study, a prototype is constructed and empirical data are presented which substantiate the design.
A simple heater for use in a thermoreflectance spectrometer
Authors: Ramírez-Flores G. , Lastras-Martínez A.
Published: July 2002

We present a simple heater for sample temperature modulation in a thermoreflectance spectrometer. The performance of the heater is evaluated by determining the band to band transition energies at the E1 and E1+Δ1 critical points of GaAs.
Calibration of a multichannel detector coupled to a high resolution spectrometer
Authors: Bradley Michael S. , Krech John H.
Published: July 2002

A straightforward method for frequency calibration of multichannel detectors coupled to high resolution spectrometers is presented. Comparison with literature data shows the method is reproducible and accurate.
Laser-induced fluorescence measurement of a 50-MeV hydrogen atom beam
Authors: Sander R. K. , Archuleta F. , Harker W. , Martinez R. , Quick C. R. , Reeder R. , Taylor D. J. , Brumwell F. , Hummer C.
Published: July 2002

Laser-induced fluorescence has been used to measure the velocity, direction, and divergence of a beam of neutral hydrogen atoms traveling at 50 MeV or one-third the speed of light. The beam was produced by neutralizing a negative hydrogen ion beam in a foil stripper, which generated a fraction of the atoms in the metastable 2s state. These metastables were measured by pumping the 2s to 3p transition with a flashlamp pumped dye laser at 623 nm and detecting fluorescence in the vacuum ultraviolet from the 3p to 1s ground-state transition.
Laser beam alignment devices for ultrashort pulses
Authors: MacFarlane D. L.
Published: July 2002

We describe two novel devices for optical beam alignment. One allows for a variable angle, fixed position of incidence upon a target. The other allows for a variable position, fixed angle of incidence upon a target. Cascaded together, these devices allow placement of a laser beam upon a sample with arbitrary angle and arbitrary position of incidence. These devices are particularly useful for experiments and applications involving ultrashort pulses since the time of flight through either of these devices is a constant independent of the angle of incidence and position of incidence.
A new coincidence technique for vacuum ultraviolet photoelectron spectroscopy of neutral clusters in a molecular beam
Authors: Rademann K. , Rech T. , Kaiser B. , Even U. , Hensel F.
Published: July 2002

The magnetic bottle photoelectron spectrometer principle has been employed for the study of neutral clusters in a seeded supersonic molecular beam. Mass selectivity is achieved by correlating each detached photoelectron to the cluster cation that is produced simultaneously. The necessary high detection probabilities for both particles, the photoelectron and the cluster ion, are achieved by time-of-flight spectrometers for both channels. The collection efficiency of the magnetic photoelectron spectrometer is increased to ≊80% of 4π by combining a permanent ring magnet, which produces an inhomogeneous field to parallelize the electron trajectories, with a 730-mm-long coil that guides the electrons by a weak, homogeneous field through the flight tube towards a scintillation detector. An advanced data acquisition electronics is described that is capable of recording and storing simultaneously photoelectron-photoion coincidence spectra of those neutral clusters that have sufficient intensity in the molecular beam.
Fiber optic temperature sensor based on the cross referencing between blackbody radiation and fluorescence lifetime
Authors: Zhang Zhiyi , Grattan K. T. V. , Palmer A. W.
Published: July 2002

A high-temperature optical sensor scheme, based on the cross referencing between a fluorescence lifetime measurement and a blackbody radiation measurement, has been developed. Results are presented indicating the value of this scheme over a wide sensing range and measurements are achieved from room temperature to 900 °C. The measurement resolution over the range and practical applications are discussed.
Low-noise preamplifier with input and feedback transformers for low source resistance sensors
Authors: Lepaisant J. , Lam Chok Sing M. , Bloyet D.
Published: July 2002

We describe the design, schematics, and performances of a very-low-noise, low-frequency preamplifier. It operates in the 5 Hz–100 kHz range and offers an input equivalent voltage noise density as low as 65 pV/√Hz; the current noise increases with frequency and settles to about 1.5 pA/√Hz at 100 kHz. The amplifier uses input and feedback signal transformers and operates in full differential mode; a −163 dB common-mode rejection ratio is achieved at line frequency. Design methodology is applicable to other ranges of frequencies.
A remote delivery tube with an integral Joule–Thompson valve for the helium liquefier
Authors: Jacob S. , Kasthurirengan S. , Karunanithi R. , Raguraman R.
Published: July 2002

Remote delivery tubes (RDTs) in Collins and similar types of helium liquefiers interconnect the liquefier with the storage dewar. In these liquefiers the Joule–Thompson (J–T) valve is separately situated in the liquefier cryostat. Therefore there is a regime of J–T heating during the initial cool down of the liquefier, since there is a time lag in reaching the inversion temperature for the J–T valve. The note describes the design, fabrication, and testing of a RDT with an integral J–T valve. A demountable copper cold seal working at a pressure of 15 bar was successfully tested. The J–T valve seat made of Cu-Cr-Zr alloy provided excellent sealing with the stainless-steel valve tip at liquid-helium temperatures. The testing of this RDT with integral J–T showed substantial reduction in cool down time for the liquefier as well as better control of the dewar pressures.
Lanthanum hexaboride filament in an x-ray generator of a laboratory extended x-ray absorption fine structure facility
Authors: Yao Takeshi
Published: July 2002

A lanthanum hexaboride filament was used in the x-ray generator of the laboratory extended x-ray absorption fine structure (EXAFS) facility. Both the number and the intensity of excitation lines were much smaller than those of tungsten. The property was excellent for EXAFS measurements.
Robust improvement in the signal-to-noise of a laser fluorosensor through selectively averaging signals
Authors: Wang H. , Hengstermann T. , Reuter R. , Willkomm R.
Published: July 2002

Signals acquired with a laser fluorosensor are composed of the fluorescence of the object and noises. The average of n signals theoretically has the signal-to-noise ratio (S/N) which is √n times higher than the S/N of the single signal, provided that the fluorescence remains constant from signal to signal and that the noises are independent of each other. In practice, the sources of noise in the signals are often correlated with each other, leading to S/N improvement below the theoretical one. In this paper a procedure is proposed and applied in a laser fluorosensor to obtain better S/N. It is shown that the average signal can have better S/N if the signals with the correlated noises are selectively discarded by averaging many signals. This procedure can be advanced for improving S/N of any multi sample averager.
A new-type antenna for continuous gravitational radiation
Authors: Suzuki T. , Akasaka N. , Ogawa Y. , Kudo N. , Morimoto K.
Published: July 2002

A new-type disk antenna has been developed to search for continuous gravitational waves emitted from millisecond and submillisecond pulsars. The antenna not only has a wide tunable range of the eigenfrequency that covers down to almost half of the original frequency of the quadrupole mode, but also is easily tuned to an objective frequency with an accuracy of 4×10−5 at 4.2 K. The mechanical quality factor has reached 3.0×107 at 4.2 K in an antenna made of Al5056.