bluuebunny/crossref_metadata_2025 huggingface dataset:
Surface diffraction beamline at ESRF
Authors: Ferrer S. , Comin F.
Published: July 2002

A brief description of the main components of the beamline is given. The source is a standard ESRF undulator. The first active optical element is a double-crystal monochromator cryogenically cooled and sagittally focusing. The end station consists in a six-circle diffractometer and in an ultra high vacuum system with a welded beryllium window that allows incidence and exit angles up to 45°. Preliminary measurements on a Ge(001) clean surface, show that the counting rates of reflections characteristic of the surface reconstruction are of the order of 105 s−1 for standard operating conditions.
Measurements of the impressed electric field inside a coaxial electron cyclotron resonance plasma source
Authors: Srivastava A. K. , Asmussen J.
Published: July 2002

The magnitude and spatial variation of the impressed electric-field patterns inside a compact electron cyclotron resonance ion/plasma source are experimentally measured for argon and nitrogen feed gases. This ECR plasma source consists of several components: a resonant coaxial coupling section, an evanescent circular waveguide section, coupling loop, and the ECR discharge load itself. The electric fields inside the coaxial and circular waveguide sections are measured as the operating pressure and input power and are varied from 0.2 to 2.0 mTorr and 100 to 170 W, respectively. The measured fields verify that a standing wave with a maximum of 20–40 kV/m exists inside the coaxial section of length l. For matched conditions the length of this section varies only slightly between 0.6 and 0.7λ as pressure, power, and gas type vary. However, the evanescent impedance-matching circular waveguide section of length d changes from 2.5 for argon to 3.2 cm for nitrogen, indicating that the gas type influences the plasma impedance. Field pattern measurements in the ECR section of the source demonstrate the presence of nonevanescent fields in the discharge region. Measured plasma loaded and unloaded quality factors varied from 220 to 1800, respectively, indicating that 87% of the net input power is coupled into the discharge load. Additional calculations of conductive wall losses show that about 6% of the input power is lost in the cavity walls, and the remaining 7% is lost in the coupling loop.
Magneto-optical measurements on mechanically stressed thin ferromagnetic films
Authors: Callegaro Luca , Puppin Ezio , Vannucchi Alessandro
Published: July 2002

We show that magneto-optical techniques provide a unique tool for magnetic measurements on thin ferromagnetic films stressed by external forces. Measurements have been conducted with a magneto-optical ellipsometer based on polarization modulation with a photoelastic birefringence modulator. We present data from Ni films evaporated onto glass substrates stressed by substrate bending. A strong dependence of remanence induction, coercive force, and cycle shape on direction and magnitude of the applied stress is observed.
X-ray supermirrors for BESSY II
Authors: Erko A. , Schäfers F. , Vidal B. , Yakshin A. , Pietsch U. , Mahler W.
Published: July 2002

X-ray multilayer supermirrors for the energy range up to 20 keV have been theoretically studied and experimentally measured with synchrotron radiation. A multilayer mirror with 50 W/Si bilayers with different thicknesses on the Si substrate has a smooth reflectivity of up to 32% in the whole energy range from 5 to 22 keV at a grazing incidence angle of 0.32° which is considerably larger than using total external reflection.
CO2 laser polarimeter for measurement of plasma current profile in Alcator C-Mod
Authors: Ma C. H. , Hutchinson D. P. , Richards R. K. , Irby J. , Luke T.
Published: July 2002

A multichannel infrared polarimeter system for measurement of the plasma current profile in Alcator C-Mod has been designed, constructed, and tested. The system utilizes a cw CO2 laser at a wavelength of 10.6 μm. An electro-optic polarization-modulation technique has been used to achieve the high sensitivity required for the measurement. The recent results of the measurements as well as the feasibility of its application on international thermonuclear experimental reactor are presented.
Design and construction of a microscope-based Raman system
Authors: LaPlant Fred , Ben-Amotz Dor
Published: July 2002

A relatively inexpensive micro-Raman system featuring confocal imaging, holographic optics, and CCD detection is described in detail. The construction of a confocal filter is discussed, along with the depth of field and spatial rejection expected. Limitations of the system such as low-frequency signal rejection by the holographic optics and wavelength calibration are also discussed. Spectra are shown giving examples of the capabilities of the system and the signal-to-noise ratio expected for typical liquid and solid samples.
Design aspects of a ruby-based fiber optic thermometer probe for use in the cryogenic region (≳77 K)
Authors: Hu Y. L. , Zhang Z. Y. , Grattan K. T. V. , Palmer A. W. , Meggitt B. T.
Published: July 2002

Research has been carried out showing that severe errors in the calibration of ruby fluorescence decay-time fiber optic thermometers, particularly in the cryogenic region (≳ 77 K), can occur if probes are not carefully designed to avoid fluorescence reabsorption effects. This effect is investigated and quantified.
A method of measuring surface permittivity by microwave dielectric analysis
Authors: Naito Satoru , Hoshi Masato , Mashimo Satoru
Published: July 2002

A method for controlling skin depth by microwave dielectric analysis using an open end cell is presented here. The correlation between the measured permittivity, the electric length of the cell, and the permittivity depth profile has been shown from time domain reflectometry measurements on a sample with known depth profile of permittivity. This skin depth controlling method is exceedingly useful for dielectric analysis of water in living organisms and related food products.
Heat capacity of silver paint
Authors: Dawson A. LeR. , Ryan D. H.
Published: July 2002

The heat capacity [CP(T)] of a silver loaded paint has been measured between 3 and 30 K. It is shown to be ideal for mounting small calorimeter samples for measurements above 1 K or where good thermal contact to the sample is essential.
Inversion of complex V(z) at high frequencies for acoustic microscopy
Authors: Duquesne J. Y.
Published: July 2002

We describe a phase-measuring acoustic microscope operating at high frequency. Both the phase and amplitude of the acoustic reflectance are found by inversion of the complex V(z) function at 300 MHz. Attenuation in the coupling fluid is considered and the focal point determination is discussed.
Design and performance of a high-temperature fluorescence cell for discharge and electron-beam excited gas mixtures
Authors: Tischler H. , Delaporte Ph. , Fontaine B. , Forestier B. , Sentis M.
Published: July 2002

The design and performance is described for a high-temperature cell appropriate for kinetic and spectroscopic studies on electron-beam or electrical-discharge excited species emitting in the vacuum ultraviolet. The experimental setup operates at temperatures up to 750 K for total gas mixture pressures of up to 5 bar. Particularly, the apparatus permits investigations on the emission spectra and their temporal behavior of ionic excimer molecules after excitation with these two most-common gas laser-excitation techniques. The comparison of the quantum efficiency for the production of the vacuum ultraviolet emissions with both excitation techniques, together with the possibility to perform optical gain measurements, will allow us to evaluate whether lasing for this new class of molecules can be achieved. The performance of the experimental device is presented by investigations on the second continua of the rare gas.
Quantitative measurement of analyte gases in a microwave spectrometer using a dynamic sampling method
Authors: Zhu Z. , Matthews I. P. , Samuel A. H.
Published: July 2002

This article reports quantitative measurement of concentrations of water vapor (absorption line at 22.235 GHz) and ethylene oxide (absorption line at 23.123 GHz) in different gas mixtures by means of a microwave spectrometer. The problem of absorption line broadening and the gas memory problem inherent in the quantitative analysis of gases using microwave molecular rotational spectroscopy have been solved. The line broadening problem was minimized by gas dilution with nitrogen and the gas memory problem was effectively reduced by means of a dynamic sampling method. Calibration of ethylene oxide with a dilution factor of 5 has demonstrated that the standard deviations of the calibration data were less than 4.2%. A typical ethylene oxide sterilization production cycle was chosen to monitor chamber ethylene oxide concentrations in the gas dwell phase and the repeatability of these real time measurements was 2.7%.
A 1–2 GHz pulsed and continuous wave electron paramagnetic resonance spectrometer
Authors: Quine Richard W. , Rinard George A. , Ghim Barnard T. , Eaton Sandra S. , Eaton Gareth R.
Published: July 2002

A microwave bridge has been constructed that performs three types of electron paramagnetic resonance experiments: continuous wave, pulsed saturation recovery, and pulsed electron spin echo. Switching between experiment types can be accomplished via front-panel switches without moving the sample. Design features and performance of the bridge and of a resonator used in testing the bridge are described. The bridge is constructed of coaxial components connected with semirigid cable. Particular attention has been paid to low-noise design of the preamplifier and stability of automatic frequency control circuits. The bridge incorporates a Smith chart display and phase adjustment meter for ease of tuning.
A 100 kV 10 A high-voltage pulse generator for plasma immersion ion implantation
Authors: Brutscher Jörg
Published: July 2002

The design of a high-voltage pulsing system for a plasma immersion ion implantation (PIII) facility is presented. A list of requirements, which have to be fulfilled by a high-voltage pulse generator to get best results and a optimum operation of the PIII system, is given. A simple electrical model of the plasma is presented which describes the plasma as a capacitive–resistive load. The model parameters are determined to fit experimental results. The requirements for the pulse generator can be fulfilled well using a pulse generator design which employs a hard tube switch. A pulse generator design is presented which is especially optimized for PIII systems. The hard tube control is especially optimized for obtaining voltage rise times as short as possible.
Design of sample holders for surface analysis of powders
Authors: Hellgardt K. , Chadwick D.
Published: July 2002

The handling, in situ treatment, and analysis of powdered samples under ultrahigh vacuum conditions can be quite difficult. New sample holder designs are presented which overcome most frequent problems associated with powders.
The multichannel triple-laser interferometer/polarimeter system at RTP (abstract)
Authors: Rommers J. H. , Donné A. J. H. , Karelse F. A. , Howard J.
Published: July 2002

A 19-channel combined interferometer and polarimeter system has recently become operational at the Rijnhuizen Tokamak Project (a=0.164 m, R=0.72 m, Btor⩽2.5 T, Ip⩽150 kA, plasma pulse duration ⩽500 ms), in order to determine the poloidal magnetic field and plasma density distribution simultaneously. The method is based on the separate propagation of two counter-rotating, circularly polarized probing waves, and enables high temporal resolution measurements of both the interferometric and the polarimetric phase change using only one detector per line of sight. In this article a thorough discussion of the (polarization-related) optical, electronic, and computational aspects of the system will be presented.
Electron temperature fluctuation measurements and techniques in the DIII-D tokamak
Authors: Rettig C. L. , Peebles W. A. , Lohr J. , Austin M. E.
Published: July 2002

Several techniques for determining the level and characteristics of electron temperature fluctuations via measurements and analysis of electron cyclotron emission (ECE) have recently been proposed and demonstrated [S. Sattler and H. J. Hartfuss, Plasma Phys. Cont. Fus. 35, 1285 (1993) and G. Cima et al., Phys. Plasmas (1994)]. A technique relying on the correlation of ECE in orthogonal frequency bins but lying within the line broadening of the local emission spectrum is being pursued at DIII-D. Special concerns include the effect of large rotation in the discharges due to neutral beam injection and extremely low fluctuation levels in enhanced confinement regimes such as negative central shear discharges. An antenna design optimized for fluctuation studies is also being developed.
Detection of single photon ionization events using a contactless microwave technique
Authors: Tepper Gary , Losee Jon
Published: July 2002

For the first time, to the best of our knowledge, the electron-hole pairs generated in a material by a single photon ionization event have been detected using a microwave technique. The detection mechanism is based on the attenuation of a resonant electromagnetic wave and, unlike conventional particle detectors, does not rely on charge or scintillation light collection. The current technique has an inherent fast response (microwave frequency of 9 GHz) and is not affected by the problems associated with charge sweeping and/or light measurements. Experimental results for single high energy x-ray photons absorbed in high purity p-germanium are presented. The results demonstrate the potential for a new class of gamma/particle detectors and a useful method to study the kinetics of particle interactions in materials.
Use of charge-coupled device imagers for charged-particle spectroscopy
Authors: Burke B. E. , Petrasso R. D. , Li C. K. , Hotaling T. C.
Published: July 2002

We describe preliminary experiments designed to demonstrate the use of charge-coupled device (CCD) imagers as spectroscopic detectors of charged particles. A large-area front-illuminated imager made on p/p+ epitaxial material was irradiated with α particles with energies up to 5.5 MeV and protons up to 13 MeV. The charge per event agrees reasonably well with calculations that assume a collection zone comprising the p epilayer and the portion of the p+ substrate within a diffusion length of the p epilayer. The charge per event for these particles is relatively large, often exceeding the CCD well capacity in the case of α particles, and therefore some of the stressing requirements of other applications, such as low dark current and low read noise, are not essential in this case. The results indicate that CCD imagers are excellent candidates for applications such as charged-particle diagnostics of inertial confinement fusion implosions.
Measurements of neutron spectra from Nova targets
Authors: Chrien R. E. , Klare K. A. , Murphy T. J.
Published: July 2002

We have measured neutron spectra from targets on the Nova laser. The three basic classes of targets are (1) directly driven capsules with ablative or exploding pushers, (2) indirectly driven imploding capsules with various hohlraum drives, capsule thicknesses, capsule fill pressures, and hohlraum gas fills, and (3) gas-filled hohlraums containing deuterated gas mixtures. In many capsule implosions, the neutron spectra are significantly broader than predictions of fusion-reaction-weighted ion temperatures from simulations. For implosions of deuterated capsules filled with H2, the observed spectra are consistent with the predicted combination of thermal and motional broadening. For normal capsules filled with D2, we conjecture that implosion asymmetries may induce fluid motion within the compressed fuel which contributes to the measured spectral width, but not the fusion reactivity, and which is not included in the simulations.
The design of a second harmonic tangential array interferometer for C-Mod
Authors: Bretz N. , Jobes F. , Irby J.
Published: July 2002

A design for a tangential array interferometer for C-Mod operating at 1.06 and 0.53 μm is presented. This is a special type of two color interferometer in which a Nd:YAG laser is frequency doubled in a nonlinear crystal. Because the doubling efficiency is imperfect, two frequencies propagate collinearly through the plasma after which the 1.06 μm ray is doubled again mixing in the optical domain with the undoubled ray. The resulting interference is insensitive to path length but is affected by plasma dispersion in the usual way. A typical central fringe shift in C-Mod is expected to be 0.1–1.0, but the absolute and relative accuracy in nel measurements can be as high as in a conventional interferometer. This design uses a repetitively pulsed laser which is converted to a fan beam crossing the horizontal midplane. The chordal array is defined by internal retroreflectors on the C-Mod midplane which return the beam to the second doubler and a detector array. This interferometer design has beam diameters of a few millimeters and element spacings of a few centimeters, uses a repetitively pulsed, TEM00 Nd:YAG laser, fiber optic beam transport, commercial components, and a compact optical design which minimizes port space requirements. An optical system design is presented which is based on the performance of a tabletop prototype at Princeton Plasma Physics Laboratory.
Fabrication and characterization of Z-pinch foam targets
Authors: Antolak A. J. , Demiris A. , Derzon M. S. , Hrubesh L. W. , Louis H. , McNamara W. F. , Morse D. H. , Poco J. F.
Published: July 2002

This article describes the fabrication and characterization of targets produced for Z-pinch physics experiments. Low density foams with densities as low as 1 mg/cc were made. Targets fabricated include 1 cm×1 cm solid cylinders of SiO2 aerogels at various densities, 1 cm×1 cm solid cylinders of 10 mg/cc agar, and 10 mg/cc agar annuli with 10 mm o.d., 9 mm i.d., and 1 cm length. Target geometry and density uniformity were characterized by ion microtomography (IMT) which can nondestructively measure three-dimensional density variations to 1% with micron-scale resolution. The results of IMT measurements on several targets are reported and a discussion of factors affecting the quantitative microanalysis of these materials is presented.
Observations with a Mach probe on edge plasma of the CDX-U
Authors: Armstrong R. J. , Choe W. , Hwang Y. S. , Lo E. , Ono M.
Published: July 2002

Using a rotatable three-electrode Mach probe at the outer edge region of the plasma, preliminary observations indicate the existence of a toroidal rotation in the ion flow direction (of the toroidal current) with no comparable poloidal rotation. This rotation cannot be in the direction of the magnetic field, because of the large pitch of the local magnetic field.
Multiple view fan beam polarimetry on Tokamak devices
Authors: Geck W. R. , Domier C. W. , Luhmann, Jr. N. C.
Published: July 2002

A polarimeter diagnostic is under development which utilizes several fan beams to accumulate line integrated Faraday rotation data in a Tokamak plasma. The utilization of a fan beam configuration over that of conventional vertical view polarimeter systems significantly reduces access requirements. The high angular separation inherent in a fan beam implementation increases plasma coverage and eliminates the necessity of assumed plasma symmetries to generate high quality current density profiles. Codes have been developed to generate these high-resolution two-dimensional images of the plasma current profile from data collected at arbitrary positions and viewing angles.
Optically isolated current-to-voltage converter for an electron optics system
Authors: Band Alan , Unguris John
Published: July 2002

A simple, inexpensive, optically isolated current-to-voltage converter circuit has been developed for the measurement of bipolar currents in the range of 10 pA–1 μA on the biased elements of an electron optics system at voltages up to 3.5 kV. The design takes advantage of low-leakage, low-power complementary metal–oxide semiconductor operational amplifiers as well as linear optocouplers to create a low-noise battery-powered front end with an expected battery life of three years using a single 9 V lithium battery.
Los Alamos pinhole camera (LAPC): A new flexible x-ray pinhole camera
Authors: Oertel J. A. , Peterson C. G.
Published: July 2002

We have recently designed, built, and fielded a versatile, multichannel x-ray pinhole camera. The Los Alamos pinhole camera was designed to fit into any 6 in. manipulator (SIM) which is a standardized target chamber diagnostic tube. There are currently compatible SIMs available at the Trident, Omega, and NOVA laser systems. The camera uses nine pinholes in a 3×3 array to produce images at the film plane. The film housing is designed to hold multiple sheets of stacked x-ray film which also uses a dark slide to protect the film before exposure. Magnifications of 12, 8, 4, and 2X are selected by slip-on nose cones, which support pinholes, collimators, and blast shields. Individual channel filtering is provided by a 3×3 filter pack containing nine separate filter sub packs. Spatial resolution is limited by the pinhole diffraction limit and field of view is dependent on magnification and filter pack diameter.
A combined apparatus of scanning reflection electron microscope and scanning tunneling microscope
Authors: Maruno S. , Nakahara H. , Fujita S. , Watanabe H. , Kusumi Y. , Ichikawa M.
Published: July 2002

A scanning reflection electron microscope (SREM) combined with a scanning tunneling microscope (STM) has been developed for the purpose of nanoscale structure fabrication under ultrahigh vacuum conditions. A STM unit consists of a piezoelectric tube scanner and an inch runner for coarse and fine approach of a STM tip. A sample holder and the STM unit have six drive axes relative to an electron gun for simultaneous observation by SREM and STM. Energy-dispersive x-ray spectroscopy equipment is also installed for surface sensitive elemental analysis. It has been demonstrated that on a Si(111)7×7 surface atomic steps and 7×7 unit, cells can be observed in the SREM and STM images, respectively, and that surface elements with less than 1 ML thickness are detectable.
Interpretation of neutron time-of-flight signals from current-mode detectors
Authors: Murphy T. J. , Chrien R. E. , Klare K. A.
Published: July 2002

Neutron time-of-flight (nToF) signals from current-mode neutron detectors are often used to determine burn-averaged ion temperature from ICF targets because the spread of the neutron energy distribution is a function of the temperature of the reacting ions. The measured signal will, however, be a convolution of the actual neutron signal, the detector response, and the response of the recording system. In addition, scattered neutrons will arrive at the detector later than unscattered neutrons, further broadening the signal. The ion temperature derived from nToF data depends strongly on the functions used to fit the data or the methods utilized to unfold the neutron energy spectrum. A functional form based on known and measured properties of the detectors is used to fit the integral of the time-of-flight signal, allowing ion temperature derivations from targets with lower neutron yield than previously possible.
Measurements of ZEFF spatial profiles from bremsstrahlung emission in the visible and near infrared spectral region
Authors: Orsitto F. , Belforte M. R. , Borra M. , Brusadin A. , Giovannozzi E.
Published: July 2002

Measurement of plasma radiation (i.e., breusstrahlung) in the infrared (IR) range (λ=933, 978 nm), at six lines of sight from z=−20 cm to z=8 cm above the equatorial plane, using the detection system of the Frascati Tokamak Upgrade (FTU) Thomson scattering system (TSS) are reported. The agreement of IR with visible (λ=540 nm) bremsstrahlung intensity S, [S=photons/(m2 sr nm s)] measurements is within 20%–30% and depends upon the absolute calibration of both systems. The intensity is equal S(z)=〈ZeffGn2/Te1/2〉, where 〈⋅〉 means average on a line of sight. For determining the Zeff the Gaunt factor(G) is needed, and analysis the Born–Elwert formula is used. The Zeff spatial profiles (i.e., Zeff(r)), are determined using the plasma temperature (Te) and density (ne) measured by the TSS and the Abel inverted intensity profiles, determined using the plasma radiation S(z) measured from six horizontal chords. Zeff(r) behavior in a variety of FTU discharges is presented.
Calibration of a time-resolving spectrometer in the 100–800 eV spectral region (abstract)
Authors: Ruggles L. E. , Porter, Jr. J. L. , Bartlett R.
Published: July 2002

We are calibrating a new time-resolving x-ray spectrometer used to diagnose z-pinch driven hohlraums at the Saturn Facility. The instrument uses a 5000 lines/mm transmission grating dispersing element and has an array of silicon photodiodes and a gated microchannel-plate detector for recording spectra. The diodes are located every 50 eV from 100 to 850 eV (E/ΔE=10) and have subnanosecond temporal and near-theoretical quantum efficiency. The microchannel-plate detector uses a 6.25 Ω gold stripline to record both a 5 ns frame of continuous spectrum and shadows of each silicon diode in the spectrum. This poster describes measurements of the spectral sensitivity of the instrument, including relative grating order efficiencies, microchannel-plate detector efficiency, and absolute sensitivity and time response of the silicon diodes.
Application of high-resolution, high-sensitivity spectrometry in the extreme ultraviolet wavelength range for diagnostics of single and double electron capture processes in He2++He and Ar8++He collisions
Authors: Bruch R. , Kantsyrev V. , Golovkina V. , Shlyaptseva A. , Golovkin I. , Phaneuf R. , Schneider D.
Published: July 2002

We have applied a new, more efficient diagnostic technique for studies of extreme ultraviolet (EUV) radiation from multicharged ions interacting with He gas. Following single and double electron capture and one electron capture plus target-ion excitation in He2++He and Ar8++He collisions, the subsequent emitted EUV photons are analyzed with a high-resolution 2.2 m grazing incidence monochromator in conjunction with a new type of glass capillary converter (GCC) specifically designed for the EUV wavelength region. This new optical device images a horizontal cylindrical ion beam segment onto the vertical entrance slit of the monochromator. With this new imaging technique a spectral intensity enhancement of about 10 has been achieved over a distance of about 60 cm. By further optimizing this method an enhancement of the flux density of EUV radiation of about 20–30 is expected. As prototype examples, new advanced EUV spectra arising from He2++He and Ar8++He collisions are presented and discussed.
Threshold bubble chamber for measurement of knock-on DT neutron tails from magnetic and inertial confinement experiments
Authors: Fisher R. K. , Zaveryaev V. S. , Trusillo S. V.
Published: July 2002

We propose a new “threshold” bubble chamber detector for measurement of knock-on neutron tails. These energetic neutrons result from fusion reactions involving energetic fuel ions created by alpha knock-on collisions in tokamak and other magnetic confinement experiments, and by both alpha and neutron knock-on collisions in inertial confinement fusion (ICF) experiments. The energy spectrum of these neutrons will yield information on the alpha population and energy distribution in tokamaks, and on alpha target physics and ρR measurements in ICF experiments. The bubble chamber should only detect neutrons with energies above a selectable threshold energy controlled by the bubble chamber pressure. The bubble chamber threshold mechanism, detection efficiency, and proposed applications to the International Thermonuclear Experimental Reactor and National Ignition Facility experiments will be discussed.
Acceleration of particles using an elastic wave impulse
Authors: Liu Shi-Rong , Miao Zhen-Kui , Yu Qi-Lian
Published: July 2002

A method for accelerating particles which can be used in delivering genes into living cells is described. By inducing a one-dimensional elastic strain wave impulse in a fixed solid plate, the micron particles adhered to the center of the plate’s free surface can be accelerated to a velocity up to a few tens of meters per second. Two schemes have been devised in which the impulsive waves were generated by mechanical collision and by a piezoelectric transducer, respectively. Their principles are outlined and the initial velocities of particles are analyzed. The collision scheme has been tested experimentally for a long period and proved to be efficient in plant gene transfer. The particle velocities were measured in a range of 43–82 m/s, which agreed well with the results of the theoretical approximation. The initial velocity of particles accelerated by the piezoelectric transmitter may be controlled by changing the driving voltage. The apparatus for accelerating particles using an elastic wave impulse features tightly static sealing of the sample chamber and minimization of the aerodynamic effect caused by particle acceleration.
Investigation of nonthermal particle effects on ionization dynamics in high current density ion beam transport experiments
Authors: Chung H. K. , MacFarlane J. J. , Wang P. , Moses G. A. , Bailey J. E. , Olson C. L. , Welch D. R.
Published: July 2002

Light ion inertial fusion experiments require the presence of a moderate density background gas in the transport region to provide charge and current neutralization for a high current density ion beam. In this article, we investigate the effects of nonthermal particles such as beam ions or non-Maxwellian electron distributions on the ionization dynamics of the background gas. In particular, we focus on the case of Li beams being transported in an argon gas. Nonthermal particles as well as thermal electrons are included in time-dependent collisional-radiative calculations to determine time-dependent atomic level populations and charge state distributions in a beam-produced plasma. We also briefly discuss the effects of beam ions and energetic electrons on the visible and vacuum ultraviolet (VUV) spectral regions. It is found that the mean charge state of the gas, and hence the electron density, is significantly increased by collisions with energetic particles. This higher ionization significantly impacts the VUV spectral region, where numerous resonance lines occur. On the other hand, the visible spectrum tends to be less affected because the closely spaced excited states are populated by lower energy thermal electrons.
Operation of flush-mounted probes in the TdeV tokamak
Authors: Gunn J. P. , Boucher C. , Desroches D. , Robert A.
Published: July 2002

An array of 16 flush-mounted probes (FMPs) has been installed in the outboard divertor plate of TdeV, giving a radial resolution of 3.3 mm at the plasma strike point. Extensive use during an aggressive, 14-month experimental campaign has yielded a massive data base, as well as a better understanding of the level of precision required in the fabrication of FMPs. We will report on the technical performance of the FMP array, and present examples of measurements which illustrate the usefulness and reliability of this diagnostic.
Method to characterize the vibrational response of a beetle type scanning tunneling microscope
Authors: Behler Stefan , Rose Mark K. , Ogletree D. Frank , Salmeron Miquel
Published: July 2002

We describe a method for analyzing the external vibrations and intrinsic mechanical resonances affecting scanning probe microscopes by using the microscope as an accelerometer. We show that clear correlations can be established between the frequencies of mechanical vibrational modes and the frequencies of peaks in the tunnel current noise power spectrum. When this method is applied to our “beetle” type scanning tunneling microscope (STM), we find unexpected low frequency “rattling resonances” in the 500–1700 Hz range that depend on the exact lateral position of the STM, in addition to the expected mechanical resonances of the STM above 4 kHz which are in good agreement with theoretical estimates. We believe that these rattling resonances may be a general problem for scanning probe microscopes that use some type of kinetic motion for coarse positioning.
Wide field of view, ultracompact static Fourier-transform spectrometer
Authors: Steers D. , Patterson B. A. , Sibbett W. , Padgett M. J.
Published: July 2002

The development of a novel static Fourier-transform spectrometer based on two Wollaston prisms, two polarizers, and a compact two-dimensional detector array is described. The wavelength calibration is fixed by the geometry of the prisms and the detector array and is therefore inherently stable. The Wollaston prisms are fabricated from materials with opposite sign of birefringence which gives a significantly increased field of view compared with existing Wollaston prism based Fourier-transform spectrometers. The spectrometer operates in the visible region of the spectrum, has a resolution of 350 cm−1, an aperture of 6×4.6 mm, and a field of view of ±10°. The optical assembly is interfaced to a laptop computer resulting in a rugged, portable instrument with no moving parts.
Calibration of direct nuclear activation diagnostics for measuring intense proton, lithium, and fluorine beams
Authors: Ruiz C. L. , Cooper G. W. , Chambers G. , Schmidlapp F. A.
Published: July 2002

In the light-ion-beam fusion program at Sandia National Laboratories an intense lithium beam is being developed to drive inertial confinement fusion targets. Since beam purity is an important issue, direct nuclear activation diagnostics based on the thick target yields of the reactions 7Li(p,n) 7Be, 10B(p,α) 7Be, 19F(7Li,d) 24Na, and 11B(19F,2p) 28Mg have been developed to measure the proton, lithium, and fluorine content of the beam. The specific target materials chosen for this work are LiF and BN. To calibrate these diagnostics, a Van de Graaff accelerator was used to measure the thick target yields as a function of ion energy for each of the ion and target material combinations. Each target material was also irradiated by carbon ions to assess the importance of any possible competing reactions. The results of these calibration studies are presented.
SID: An automated diagnostic inserter system for inertial confinement fusion experiments (abstract)
Authors: Bourgade J. L. , Reverdin C. , Bailleux D. , Chaigneau F. , Charet M. , Desenne D. , Le Breton J. P. , Renaudin P. , Mens A. , Schirmann D.
Published: July 2002

In order to provide an accurate, repeatable reentrant plasma diagnostic support, an in-vacuum automated robotic diagnostic inserter (SID) was designed, built, and tested for the Phebus French laser facility. The SID system allows us to change quickly and accurately a diagnostic required for a new experiment. The other advantage of this new system is that the detector can be placed closer to the plasma (<0.5 m) and consequently the sensitivity of the corresponding diagnostic to x-ray photons or neutrons is increased. That permits more accurate measurements in present inertial confinement fusion (ICF) experiments (larger magnification ratio imaging systems with better spectral resolution). The SID has three major components: (i) a mobile platform which carries the diagnostic itself, (ii) a vacuum chamber, and (iii) an accurate mechanical guide system inside the target chamber. The repeatability of the diagnostic repositioning is at least ±10 μm over a travel range of 220 mm. Two main diagnostics are today in operation: a time grated x-ray imaging system and a high resolution crystal spectrograph. A detailed description of the main features of our SID and of two experimental results (implosion core formation imaging and spectra of x-ray argon filled microballoon) will be presented.
Miniature, high-resolution, quadrupole mass-spectrometer array
Authors: Orient O. J. , Chutjian A. , Garkanian V.
Published: July 2002

A miniature quadrupole mass spectrometer array consisting of 16 rods in a 4×4 array is reported. Each rod is 25 mm in length and 2 mm in diameter. The ionizer is of a miniature Nier-type design, and the detector is a channel-type electron multiplier. Operating frequencies are 5.3, 7.1, and 12.9 MHz. The mass range demonstrated herein is 1–300 u; and the resolution of the system is 0.1–0.5 u (full width at half-maximum), or m/Δm=600. The present sensitivity is calculated and measured to be approximately 1×1012 counts/Torr s.
A comparison of the oscillating mirror and Bragg resonance pictures of fluctuation reflectometry in one-dimensional plasmas (abstract)
Authors: Chou Albert E. , Afeyan Bedros B. , Luhmann Neville C.
Published: July 2002

We have computed the amplitude and phase responses of microwaves scattered from fluctuation wave packets that stream down a density gradient. At various wavelengths and packet sizes and shapes, the dominant scattered signal is either due to reflection from the critical surface or due to Bragg resonance scattering from below the critical density. Depending on the amplitude and wavelength of the fluctuation, one or both of these mechanisms might play a role. The delineation of their relative importance is carried out. Comparisons are made to previous studies within and beyond the Born approximation.1,2 The motivation for this work is a series of well-controlled experiments carried out by the plasma diagnostics group at UC Davis. We will show comparisons of our numerical results, using their experimental parameters, with their measurements of scattered microwave amplitude and phase.3
One- and two-dimensional simulations of ultra-short-pulse reflectometry (abstract)
Authors: Cohen Bruce I. , Kaiser Thomas B. , Garrison John C.
Published: July 2002

Ultra-short-pulse reflectometry is studied by means of the numerical integration of one- and two-dimensional full-wave equations for ordinary and extraordinary modes propagating in a plasma. The numerical calculations illustrate the use of the reflection of ultra-short-pulse microwaves as an effective probe of the density or magnetic profile in the presence of density or magnetic fluctuations in the plasma. Bragg resonance effects can be identified in the reflected signals, which give information on fluctuations. It is also demonstrated that ultra-short-pulse reflectometry can be used to perform correlation reflectometry measurements in which correlation lengths for density fluctuations are deduced from the observed cross-correlation function of phase shifts as a function of frequency.
Thirty-five centimeter diameter radio frequency ion-beam source
Authors: Kanarov V. , Hayes A. V. , Yevtukhov R. , Vidinsky B. , Navy A.
Published: July 2002

A 35 cm diam inductively coupled rf ion source and its applications for material processing is described. This is the largest commercial rf ion-beam source presently available for ion-beam etching and deposition. It has been used to generate beams of different ions (Ne+, Ar+, Kr+, Xe+, O2+, Cl2+, CH4+,…) at 50–1000 eV of ion energy and corresponding beam currents of 0.15–1.5 A. A presentation of the ion source operation characteristics, along with performance results for various etching and deposition applications are given. Etch uniformities of less than 3% for etch diameters of up to 250 mm are obtained. Etch rates in excess of 100 nm/min for NiFe or silicon dioxide are achievable.
Calculation of Thomson scattering of intense lasers from electron beams at different interaction angles
Authors: Zheng Xiaochao , Ruan Cunjun , Shang Rencheng , Deng Jingkang
Published: July 2002

Recently there has been considerable interest in the Thomson scattering of intense laser from relativistic electron beams, and a new kind of x-ray source named laser synchrotron source (LSS) has been discussed based on this mechanism which is expected to have extremely good performances. In order to verify this theory, an experiment is going to be carried out by our group using a frequency-doubled yttrium–aluminum–garnet laser and a 25 MeV electron beam generated by the accelerator in the Applied Department of the Institute of High-Energy Physics. In this article some theoretical results have been calculated for this experiment, including the scattered x-ray’s wavelength and intensity distribution. The results at 180° and 90° have been given and the 180° result should be very close to the experimental geometry of 178.5°. In Sec. III, figures of the spatial distribution of x-ray are drawn. The future of LSS is prospected finally in Sec. IV.
Influence of the acousto-optic effect on laser Doppler anemometry signals
Authors: Jack Susan H. , Hann David B. , Greated Clive A.
Published: July 2002

When laser Doppler anemometry (LDA) is used to measure sound fields in water it is important to take into account the refractive index variations in the water due to the sound wave. These have the effect of creating a phase difference between the two laser beams in the LDA setup so that when they intersect they create moving fringes. In some situations this acousto-optic effect can dominate over the movement of the particles due to the sound wave, thereby influencing the Doppler signal. This article determines in which situations the acousto-optic effect can be ignored and in which situations it has a dominant effect. Theoretical expressions are derived for the magnitude of the acousto-optic effect on the LDA signal in terms of the distance of the laser beam propagation and acoustic wave number. The results show that varying the value of the wave number, the distance the laser beams have traveled in the direction perpendicular to the optical axis, or the angle of the sound wave, has an effect on the amplitude, yamp, of the fringe movement. For low wave number values, an angle of 0, ±π from the optic axis (y direction) corresponds to the situation in which the laser beams have been affected to the same degree by refractive index changes in the water and thus the path difference is zero and the value of yamp is a minimum. A maximum value of yamp is obtained for an angle of ±π/2 from the y direction for low wave number values. It is shown that the ratio of the acousto-optic effect to the amplitude of the particle movement due to the sound wave varies as the square of both the acoustic wave number and the distance of the laser beam propagation for low wave number values. An equation for the apparent motion of the particles in the fringes is determined and is used to show that the acousto-optic effect dominates as the value of the wave number and the distance of propagation of the beams increases. Also, for very low wave numbers and short distances, the acousto-optic effect is negligible. This is because at low wave numbers, corresponding to low sound frequencies, the refractive index gradients, and hence the phase changes along the lengths of the laser beams, are small.
Reduction of vibrational noise from continuously filled 1 K pots
Authors: Lawes G. , Zassenhaus G. M. , Koch S. , Smith E. N. , Reppy J. D. , Parpia J. M.
Published: July 2002

We have examined the vibrational noise originating from 1.3 K pumped helium chambers (1 K pots) that are continuously filled from the 4.2 K bath through an impedance. The noise can be largely eliminated by either heating the pot or by heating the impedance directly. Noise in 1 K pots has detrimental consequences for the operation of audio frequency torsional oscillators and for high precision thermometry.
Measurements of laser-hole boring into overdense plasmas using x-ray laser refractometry (invited)
Authors: Kodama R. , Takahashi K. , Tanaka K. A. , Kato Y. , Murai K. , Weber F. , Barbee T. W. , DaSilva L. B.
Published: July 2002

We developed a 19.6 nm laser x-ray laser grid-image refractometer (XRL-GIR) to diagnose laser-hole boring into overdense plasmas. The XRL-GIR was optimized to measure two-dimensional electron density perturbation on a scale of a few tens of μm in underdense plasmas. Electron density profiles of laser-produced plasmas were obtained for 1020–1022 cm−3 with the XRL-GIR and for 1019–1020 cm−3 from an ultraviolet interferometer, the profiles of which were compared with those from hydrodynamic simulation. By using this XRL-GIR, we directly observed laser channeling into overdense plasmas accompanied by a bow shock wave showing a Mach cone ascribed to supersonic propagation of the channel front.
Low frequency fluctuations measured by probes in the GAMMA10 tandem mirror
Authors: Tanaka S. , Ichimura M. , Takayama S. , Inutake M. , Kanazawa S. , Nakamura M. , Ishikawa E. , Satake C. , Motegi S. , Saito T. , Hojo H. , Mase A. , Ishii K. , Tamano T. , Yatsu K.
Published: July 2002

In the limited regions of operation of the GAMMA10 tandem mirror, a saturation or a reduction of the stored energy in the central cell is sometimes observed. By using electrostatic and magnetic probes, the low frequency (<1 MHz) fluctuations are studied in relation to plasma parameters. Dominant fluctuations are identified to be flute type and drift type modes. Magnetic fluctuations, of which frequency is much lower than the ion cyclotron frequency, are newly observed.
Design of a beamline for soft and deep lithography on third generation synchrotron radiation source
Authors: Di Fabrizio E. , Nucara A. , Gentili M. , Cingolani R.
Published: July 2002

ELETTRA is a third generation synchrotron radiation source. The energy spectrum allows the design of beamlines suitable for x-ray lithography from soft to hard x-ray wavelengths. An appropriate lithographic window for micro- and nanofabrication can be obtained by a combination of selected filters and mirrors. As the beamline is interfaced to a vertical x-ray stepper, a uniformity in the beam intensity better than 3% (3σ) in the horizontal direction has to be reached. The present beamline is designed by taking into account the main factors which can affect the beam quality, namely, thermal loading on mirrors and filters, slope errors, and surface roughness of the mirrors. The resulting lithographic resolution at soft x-ray wavelengths is better than 100 nm.
Measurements of thermal effusivity of liquids using a conventional photoacoustic cell
Authors: Balderas-López J. A. , Gutiérrez-Juárez G. , Jaime-Fonseca M. R. , Sánchez-Sinencio Feliciano
Published: July 2002

In this article, we present a new photoacoustic technique, based on the conventional photoacoustic configuration, to characterize the thermal effusivity of liquid samples. This new technique is applicable for all kind of liquid samples, including the nontransparent ones. In order to show the usefulness of this new technique, we measured the thermal effusivity of a variety of liquid samples including: distilled water, ethanol, methanol, chloroform, glycerol, and car oil. The comparison with literature values shows a remarkable agreement. Also, we show measurements of the thermal effusivity of acetone in distilled water mixtures, showing the graphical dependence of this thermal property with the concentration of one of the components.