bluuebunny/crossref_metadata_2025 huggingface dataset:
X-ray damage in optical coatings
Authors: Burkhalter P. G. , Ripin B. H. , Elton R. C. , Grun J. , Manka C. K. , Konnert J. H. , Burris H. R. , Newman D. A.
Published: July 2002

Thin film coatings are susceptible to high intensity x-ray damage. The PHAROS III laser was utilized to generate a point source of x-ray emission used to determine the damage threshold of AR-coated space optics. Thin filters coupled with magnets were used to shield the specimens from thermal radiation and plasma debris. Grids supporting the thin filters could be patterned into the coatings. The surface morphology of damaged specimens has been examined with SEM and AFM microscopes to determine the nature of the damage in multilayer AR coatings. Microscopic techniques were used to measure the depths of coating damage and edge sharpness in the patterned region.
Transient nonthermal electron cyclotron emission phenomena in high β TFTR plasmas
Authors: Taylor G. , Fredrickson E. , Janos A.
Published: July 2002

Intense bursts of nonthermal electron cyclotron emission (ECE), measured with a grating polychromator, have been observed to coincide with edge localized modes in TFTR H-mode plasmas. These bursts contain random 10–150 μs emission spikes. Similar nonthermal ECE bursts or spikes have been observed just before the thermal quench during major disruptions in high β TFTR plasmas. The recent installation of a second fast ECE grating polychromator system, at a different toroidal location, has provided additional data on this bursting phenomenon which suggests that the source of the nonthermal ECE may be highly anisotropic and/or poloidally localized on a helical flux surface.
X-ray sensitive charge-coupled device instrumentation for short and ultrashort pulse laser-produced plasma experiments
Authors: Dunn James , Young Bruce K. F. , Shiromizu Steven J.
Published: July 2002

We describe the use of x-ray sensitive charge-coupled device (CCD) detectors for measuring the 1–15 Å emission from high temperature plasmas produced at the L-Division JANUS and USP (pulse length∼100 fs) laser facilities. Instruments based upon commercially available video format cameras have been designed to replace x-ray film, as the two-dimensional recording medium, for imaging and x-ray spectroscopic applications. Used in conjunction with a high sensitivity x-ray pinhole camera, magnification 5–20, the CCD detectors can give spatial resolution approaching 5 μm and energy band information by the use of edge filters. A compact wavelength dispersive spectrometer equipped with the CCD detector and a flat Bragg crystal analyzer can record survey spectra.
Ultrafast x-ray streak camera for use in ultrashort laser-produced plasma research
Authors: Shepherd Ronnie , Booth Rex , Price Dwight , Bowers Mark , Swan Don , Bonlie Jim , Young Bruce , Dunn Jim , White Bill , Stewart Richard
Published: July 2002

In recent years there has been growing interest in energetic (≳100 eV), temporally short (<10 ps) x rays produced by ultrashort laser-produced plasmas. The detection and temporal dispersion of the x rays using x-ray streak cameras has been limited to a resolution of 2 ps, primarily due to the transit time dispersion of the electrons between the photocathode and the acceleration grid. The transit time spread of the electrons traveling from the photocathode to the acceleration grid is inversely proportional to the accelerating field. By increasing the field by a factor of 7, we have minimized the effects of transit time dispersion in the photocathode/accelerating grid region and produce an x-ray streak camera with subpicosecond temporal resolution (≊900 fs). The streak camera has been calibrated using a Michelson interferometer and 100 fs, 400 nm laser light. The characteristics of the streak camera, along with the most recent x-ray streak data will be presented.
PBFA II lithium beam characterization from inner-shell x-ray images
Authors: Moats A. R. , Derzon M. S. , Chandler G. A. , Dukart R. J. , Haill T. A.
Published: July 2002

The Particle Beam Fusion Accelerator (PBFA II) is now driving targets with ICF-relevant lithium ion beams. During the most recent lithium beam target series, time-integrated x-ray pinhole cameras viewed the ion-induced inner-shell x-ray fluorescence from the central gold cone target and a titanium-coated strip. Ion-beam profiles at a nominal 10-mm radius and fixed azimuthal direction were obtained from images of the Ti Kα fluorescence of a Ti-coated Al diagnostic wire. The gold cone gave us beam profiles at a nominal 3-mm radius and at all azimuthal angles from the Au Lα fluorescence. From these profiles, we obtained the ion-beam vertical focus position, the full width at half maximum, and the degree of azimuthal uniformity for the lithium target shots. For these initial results, beam steering problems were evident. Azimuthal uniformity was measured from the ion-beam footprint on the outer Au case (predominantly Au Lα) of the hohlraum target and was found to be in the same range (up to 30%) as for previous proton beam target series.
Bragg-diffraction x-ray spectrographs for the determination of T
e in 2–3-mm-sized laser-produced plasmas on NOVA
Authors: Failor B. H. , Hsing W. W. , Hockaday R. G. , Shepard T. D. , Klem D. E. , Kalantar D. H. , MacGowan B. J.
Published: July 2002

We have developed spectrographs to measure the electron temperature in gas-filled targets and low-density foams, and find it to nominally fall in the 2–4-keV range. The instrument we designed, built, and fielded can simultaneously record the Ti Heα and Cr Heα line emission. After compensating for the instrumental response, we can estimate the electron temperature from this line ratio to within ±15%.
Nitrogen depletion during oxidation in N2O
Authors: Saks N. S. , Ma D. I. , Fowler W. B.
Published: July 2002

The incorporation of nitrogen in oxides has been studied after furnace oxidation in N2O at 900 °C. We observe that nitrogen is removed from the oxide bulk during oxidation in N2O, while simultaneously nitrogen is incorporated at the growing Si–SiO2 interface. This results suggests that nitrogen incorporation involves a dynamic equilibrium between competing processes which causes both nitrogen incorporation and depletion. A chemical model for nitrogen removal is proposed based on a reaction with NO. Reaction energies, estimated from semiempirical quantum-mechanical calculations, support the proposed model.
Improvements in the CHERS system for DT experiments on TFTR
Authors: Bush C. E. , Bell R. E. , Synakowski E. J.
Published: July 2002

Improvements in the charge exchange recombination spectroscopy (CHERS) system have resulted in accurate measurements of Ti and Vφ profiles during DT experiments. These include moving the spectrometer detector array and electronics farther away from the tokamak to a low neutron flux location. This relocation has also improved access to all components of the system. Also, a nonplasma-viewing calibration fiber system was added to monitor the change in fiber transmission due to the high flux DT neutrons. Narrow band filtered light transmitted through the calibration fiber is now used as a reference for the Vφ measurement. At a high neutron flux of ∼2.5×1018 neutrons/s (peak fusion power∼6.2 MW) with total yield of 1.3×1018 neutrons a modest 5% decrease in fiber transmission was observed. Corrections for transmission loss are made and Ti(r,t) and Vφ(r,t) profiles are automatically calculated within four minutes of every shot.
EX6AFS: A data acquisition system for high-speed dispersive EXAFS measurements implemented using object-oriented programming techniques
Authors: Jennings Guy , Lee Peter L.
Published: July 2002

In this paper we describe the design and implementation of a computerized data-acquisition system for high-speed energy-dispersive EXAFS experiments on the X6A beamline at the National Synchrotron Light Source. The acquisition system drives the stepper motors used to move the components of the experimental setup and controls the readout of the EXAFS spectra. The system runs on a Macintosh IIfx computer and is written entirely in the object-oriented language C++. Large segments of the system are implemented by means of commercial class libraries, specifically the MacApp application framework from Apple, the Rogue Wave class library, and the Hierarchical Data Format datafile format library from the National Center for Supercomputing Applications. This reduces the amount of code that must be written and enhances reliability. The system makes use of several advanced features of C++: Multiple inheritance allows the code to be decomposed into independent software components and the use of exception handling allows the system to be much more reliable in the event of unexpected errors. Object-oriented techniques allow the program to be extended easily as new requirements develop. All sections of the program related to a particular concept are located in a small set of source files. The program will also be used as a prototype for future software development plans for the Basic Energy Science Synchrotron Radiation Center Collaborative Access Team beamlines being designed and built at the Advanced Photon Source.
Spectroscopic analysis of Ar-doped laser-driven implosions
Authors: Haynes D. A. , Hooper C. F. , Mancini R. C. , Bradley D. K. , Delettrez J. , Epstein R. , Jaanimagi P. A.
Published: July 2002

In a series of experiments performed at the Laboratory for Laser Energetics plastic microballoons filled with DD and doped with small amounts of Ar were imploded using the Omega laser system. Time-resolved K-shell Ar spectra were simultaneously recorded using two spectrographs (SPEAXS and flat-crystal). We focus on the analysis of the He-β line and its associated Li-like satellites. The density and temperature sensitivity of this composite spectral feature has been studied previously [R. C. Mancini et al., Rev. Sci. Instrum. 63, 5119 (1992)]. Here, we use it as a diagnostic. Modeling results take into account the built-in density and temperature dependence characteristic of the level populations and broadening properties of these transitions; in addition, we also consider the effects of ion dynamics and opacity. To check the consistency of our analysis we include in the model the He-γ and Ly-β lines.
A universal pocket PIG ion source with a permanent magnet
Authors: Yu Jinxiang , Ren Xiaotang , Song Zhizhong
Published: July 2002

A universal pocket PIG ion source with a permanent magnet has been developed by our institute. Usually the source can produce single and multiple charged ions of gas or metal elements. At 20–30 kV extraction voltage, milliamperes of gas ions, and tens of μA of metal ions can be extracted with less than 50 W of discharge power consumption. And negative ions of some elements with larger electron affinity can be extracted directly from the source. Thus far, using LaB6 as a cathode, more than 50 μA of H−, about 1.4 mA of O−, and 1.8 mA of F− ions in total beam have been extracted at 15–20 kV extraction voltage. The power consumptions are less than 40, 50, and 100 W, respectively.
Performance of a high current H− radio frequency volume ion source
Authors: Saadatmand K. , Arbique G. , Hebert J. , Valicenti R. , Leung K. N.
Published: July 2002

To evaluate the performance of a high current H− rf-driven volume ion source, the Superconducting Super Collider ion source was modified to accommodate a set of cesium dispensers so that a trace amount of cesium could be introduced into the plasma grid collar. A plasma grid heater element controls the temperature of the cesiated surfaces and the rate of cesium dispensation. With this modification, beam currents in excess of 100 mA and electron to H− current ratios close to one have been observed. In contrast, the uncesiated source provided 30 mA of H− beam with an e/H− ratio ≥25. In both cases the source was operated with a 100 μs beam pulse width at a 10 Hz repetition rate, and an extraction voltage of 35 kV. This cesium enhanced source is a strong candidate for use in high current H− accelerators.
Multicharged metallic ion production for accelerators (invited)
Authors: Wolf B. H.
Published: July 2002

Various methods of metal ion production are presented with respect to multiply charged ion production. Depending on the ion source one or the other method is more commonly used. PIG ion sources for high charge states use mostly the sputtering technique for metal ions. ECR ion sources use oven techniques or direct evaporation by the plasma and also chemical compounds. Mevva ion sources use the vacuum arc and laser ion sources the laser power for evaporation and simultaneously multiple ionizing the metal atoms. Design details will be discussed in connection with these ion sources.
Atomic magnetic resonance based current source
Authors: Shifrin V. Ya , Kim C. G. , Park P. G.
Published: July 2002

A current of 1 A has been stabilized by locking the magnetic resonance frequency of Cs atoms placed at the center of a solenoid. Two auxiliary windings are used to obtain at the center of the solenoid a field uniformity better than 0.5 ppm in a 2 cm radius sphere, in agreement with the calculations. The variations of the external field and the effect of temperature changes are compensated for by two auxiliary feedback systems using a flux gate magnetometer and an adjustment of the locking frequency, respectively. The current fluctuation, including the noise of the current measuring system is 0.1 ppm and the current drift for 6 h is less than 0.2 ppm.
Development of an electron-beam ion source for a relativistic heavy-ion collider preinjector
Authors: Beebe E. , Alessi J. , Hershcovitch A. , Kponou A. , Prelec K. , Schmieder R. W.
Published: July 2002

At Brookhaven National Laboratory (BNL), an electron-beam ion source (EBIS) is operational as a test bed for development of a high current EBIS for relativistic heavy-ion collider (RHIC). Previously, the goal of most EBIS research has been to produce bare or nearly bare nuclei. At BNL, the EBIS is required to produce only medium charge states of heavy ions, e.g., Au35+, since there is further stripping at higher energies. The BNL effort is directed at reaching intensities of interest to RHIC, approximately 3×109 particles/pulse, which will require an EBIS electron beam on the order of 10 A. Initial tests using a 1 mm LaB6 cathode have produced electron beam currents up to the design value of 110 mA. A 2 mm LaB6 cathode has been installed and in a first run has produced currents up to 350 mA. This source has so far produced charge states up to Ar16+ using neutral gas injection, and up to Tl50+ using external ion injection. Results of these studies and ion injection trials are presented.
Ion implanted Bragg–Fresnel lens
Authors: Souvorov A. , Snigirev A. , Snigireva I. , Aristova E.
Published: July 2002

We have investigated the feasibility of widening the bandpath of the Bragg–Fresnel optical element through the use of ion implantation. The focusing properties of Bragg–Fresnel lenses (BFLs) were studied as a function of the implantation dose and energy. An enhancement of the focus intensity of up to 15% was found, which is less than expected. Due to the complicated scattering of the low energy ions inside the micrometer- and submicrometer-sized crystal features that make up the BFL relief, the implantation technology destroys the peripheral zones of the BFL more than it increases the intensity in the focus. Nevertheless we believe that high energy implantation can be successfully used to modify the BFL reflectivity, especially in the case of nearly backscattering reflection.
Femtosecond synchronization of two passively mode-locked Ti:sapphire lasers
Authors: Crooker S. A. , Betz F. D. , Levy J. , Awschalom D. D.
Published: July 2002

We describe a method of reducing the timing jitter between two passively mode-locked femtosecond titanium:sapphire laser systems, enabling femtosecond-resolved measurements with independently tunable pump and probe wavelengths. The scheme supplements a commercially available system (Coherent Synchrolock) which locks two Ti:sapphire lasers to a master clock. By selecting only those pulses which are temporally coincident within a user-specified range, a timing jitter reduction between the two lasers from ∼3 ps to <200 fs FWHM can be achieved, as measured by optical cross correlation. The timing jitter between the lasers is easily varied, allowing optimization of the tradeoff between temporal resolution and throughput depending on experimental needs.
Composition profile of an AlGaAs epilayer on a V-grooved substrate grown by low-pressure metalorganic vapor phase epitaxy
Authors: Pan Wugen , Yaguchi Hiroyuki , Onabe Kentaro , Ito Ryoichi , Shiraki Yasuhiro
Published: July 2002

A composition distribution of an AlxGa1−xAs epilayer on a V-grooved substrate grown by low-pressure metalorganic vapor phase epitaxy is described. The aluminum (Al) content of an AlxGa1−xAs epilayer on a V-grooved substrate is found to be on the order of x(111)A≳xtop(100)≳xedge-facet ≳xbottom-intersection by using spectrally and spatially resolved low temperature cathodoluminescence (CL) measurements. The composition difference between (111)A surfaces and bottom intersections is as much as 30%. The resulting spontaneous vertical quantum wells and spontaneous waveguides in the bottom intersections are expected to be applicable in low-threshold current laser devices.
Simple emittance measurement of H− beams for neutral beam injectors in magnetic fusion
Authors: Guharay S. K. , Tsumori K. , Hamabe M. , Takeiri Y. , Kaneko O. , Kuroda T.
Published: July 2002

A novel emittance meter is developed using the pepper-pot method. Kapton foils are used to detect intensity distributions of small beamlets at the ‘‘image’’ plane of the pepperpot. Emittance of H− beams for the neutral beam injector of the large helical device has been measured. The normalized emittance (95%) of a 6 mA H− beam with an emission current density of about 10 mA/cm2 is ∼0.59 mm mrad. The present system is simple, and it eliminates many complexities of the existing schemes.
Test of an apparatus for thermal conductivity measurements of superconducting coil blocks and materials at cryogenic temperatures
Authors: Broggi F. , Rossi L.
Published: July 2002

The thermal conductivity of a superconducting coil in the transverse (with respect to the current flow) direction is one of the most important parameters in determining the stability of a coil and the quench velocity, i.e., the growth rate of the resistive zone. The complexity and the number of materials involved in a superconducting coil wound with NbTi and Nb3Sn conductor make the direct measurement of the thermal conductivity very useful. The design and the calibration of an apparatus for measurements of thermal conductivity at cryogenic temperatures of NbTi and Nb3Sn coil blocks and of Bi2Sr2CaCu2O8 rod are presented. Two different methods to determine the thermal conductivity curves from measured values, the derivative approximation method and the thermal conductivity integral, are discussed and compared.
Effects of horizontal injection angle displacement on energy measurements with parallel plate energy analyzer
Authors: Fujisawa A. , Iguchi H. , Lee S. , Hamada Y.
Published: July 2002

A formula including correction due to change of beam injection angle is derived for measurements of beam energy using parallel plate energy analyzers. The formula is mainly aimed for potential measurements in high temperature plasma with heavy ion beam probes, and an example is presented to demonstrate the usage of the formula.
System for electron paramagnetic resonance measurements at high pressure and low temperature
Authors: Huang Ke , Decker D. L. , Nelson H. M. , Barnett J. D.
Published: July 2002

Major improvements have been made on the sensitive high pressure electron paramagnetic resonance (EPR) system developed previously in 1978 at this laboratory. These changes allow low temperature measurements and provide a more stable signal. The high pressure EPR cell is placed inside a vacuum chamber to provide thermal isolation, so that the system may be cooled by a closed cycle refrigerator to temperatures between 45 and 60 K, depending on the energy input to the modulation coil. The combination of high pressure and low temperature greatly expands the thermodynamic range over which EPR measurements can be made. An improved and effective method of forming a conductive surface to define the microwave cavity is presented. This method successfully avoids the deterioration of the sapphire’s polished surface which causes premature breaking of the sapphire high pressure anvil, and therefore significantly improves the reliability of the system at high pressure. Other modifications to the system, such as the microwave coupling method, the modulation coil, and selecting of a hydrostatic pressure fluid, are discussed. EPR measurements on BaTiO3 have been made at temperatures ranging from 233 to 353 K and pressures from 0 to 4.4 GPa. High quality signals can be realized in the entire pressure and temperature range.
Performance of a precise infrared shadow sensor thermometer
Authors: Fan Shuhua , Wu Shuchao , Luo Jun
Published: July 2002

This article presents the construction and performance of a new type of temperature sensor, which can resolve temperature changes of the order of 10−4 °C in the range of 0.1 °C. Measured with the new temperature sensor, the daily change of temperature in our underground laboratory is less than 0.0034 °C.
Absolute displacement measurement by using the synthesized modulation index of a frequency-modulated interferometer
Authors: Chang Lih-Wuu , Lee Ching-Ting , Chien Pie-Yau
Published: July 2002

A novel absolute displacement measurement by using a heterodyne interferometer, with a frequency-modulated laser diode has been successfully implemented. In this signal processing scheme, the synthesized modulation index of a phase-modulated interferometer is used for measuring the displacement, which is independent of the variation of the modulation frequency. The error induced from the intensity modulation in the laser diode can be eliminated.
Real time measurement of current and voltage in discharge pumped KrF* excimer lasers
Authors: Onkels E. D. , Seelig W.
Published: July 2002

An advanced measurement method for the dynamic current voltage characteristics of fast transversely excited atmosphere excimer laser discharges is presented. In contrast to well-known numerical techniques, inductive components are eliminated from the measured discharge gap voltage directly during operation of the laser by means of a fast video amplifier circuit. Comparison of experimental data obtained from a laboratory KrF* excimer laser with theoretical data shows that the achieved resolution is sufficiently high to reveal actual halogen donor concentration and arcing in the discharge.
Brookhaven National Laboratory electron beam test stand
Authors: Pikin A. , Alessi J. , Beebe E. , Kponou A. , Prelec K. , Snydstrup L.
Published: July 2002

The main purpose of the electron beam test stand (EBTS) project at the Brookhaven National Laboratory is to build a versatile device to develop technologies that are relevant for a high intensity electron beam ion source (EBIS) and to study the physics of ion confinement in a trap. The EBTS will have all the main attributes of EBIS: a 1-m-long, 5 T superconducting solenoid, electron gun, drift tube structure, electron collector, vacuum system, ion injection system, appropriate control, and instrumentation. Therefore it can be considered a short prototype of an EBIS for a relativistic heavy ion collider. The drift tube structure will be mounted in a vacuum tube inside a “warm” bore of a superconducting solenoid, it will be at room temperature, and its design will employ ultrahigh vacuum technology to reach the 10−10 Torr level. The first gun to be tested will be a 10 A electron gun with high emission density and magnetic compression of the electron beam.
Micropulsed ion source via self-sputtering avalanche
Authors: Riyopoulos Spilios
Published: July 2002

In the proposed pulsed ion source, a steady-state sputtering avalanche sustained by secondary ions locked in phase with an ac voltage applied between plates creates high current bunches with energy monochromaticity and ion purity. In a two-surface cascade, the average current exhibits a Child–Langmuir-like scaling, due to the dynamical constraints on the normalized ac voltage. A single-surface cascade, using a bending magnetic field, operates with unconstrained voltage and exhibits much lower heat load for given current, as well as the ability for average current in excess of the Child–Langmuir limit. The pulsed source is particularly attractive for ion beams of solid materials with high vaporization temperature.
Physical dependence of the sensitivity and room-temperature stability of AuxGe1−x thin film resistive thermometers on annealing conditions
Authors: Fortune Nathanael A. , Graf Michael J. , Murata Keizo
Published: July 2002

The reported nearly constant temperature sensitivity of appropriately annealed polycrystalline AuxGe1−x thin films at cryogenic temperatures would appear to make them promising materials for low mass, rapid thermal response resistive thermometers, but their adoption has been limited by difficulties in fabrication and uncertainties in annealing. In this work, we present a method of fabrication and annealing which allows control of the two most important parameters for these films: the room-temperature resistivity ρRT and the temperature sensitivity η(T), where η≡−d ln R/d ln T. We find that the dependence of ρRT on total anneal duration t for x≈0.18 is given by ρRT=ρ∞[1−Aexp(−t/τ)], where the limiting room-temperature resistivity ρ∞, the annealing coefficient A, and relaxation time τ are annealing temperature dependent parameters. The dependence of ρRT and temperature calibration ρ(T) on anneal duration can be minimized by annealing above 250 °C. Like ρRT, the sensitivity η(T) also depends on annealing temperature, with higher annealing temperatures corresponding to lower cryogenic sensitivities. In all cases η(T) can be well described by a polynomial expansion in ln T from room temperature down to at least 2 K.
New apparatus for the precise temperature control in He3 refrigerator
Authors: Kato Kiyonori , Yoshida Hisashi , Suzui Mitsukazu
Published: July 2002

A new, simple, and low cost apparatus was developed to control the temperature in the very low-temperature region (0.3–3.3 K) using a He3 refrigerator. A low temperature was obtained by controlling the He3 vapor pressure. The apparatus consists of a set of valves, an automated microvalve, a manually operated auxiliary valve, a controller including a one-board microcomputer, and a set of pressure transducers. The temperature was easily controlled by this apparatus. The temperature stability was 0.95% at 1.04 K by controlling the He3 vapor pressure. The temperature drift was typically 0.02 K at 0.85 K.
Factors governing the discharge of electrostatic mirror formations in the scanning electron microscope
Authors: Wong W. K. , Thong J. T. L. , Phang J. C. H.
Published: July 2002

Two primary parameters for an automated electrostatic mirror discharge technique are studied, namely the discharge voltage and the discharge current. It was found that using discharge voltages corresponding to the σ>1 region and near the first crossover point of a sample’s total yield curve gave the optimum discharge rate for the technique. Also, using discharge currents larger than the scanning current was shown to improve the rate of discharge. These optimizations ensure the feasibility of this technique as a discharge tool where repeated high and low beam voltage switching in the scanning electron microscope is needed.
Battery-operated atomic force microscope
Authors: Furman Burford J. , Christman Joseph , Kearny Michael , Wojcik Frank , Tortonese Marco
Published: July 2002

The design of a battery-operated atomic force microscope (AFM) using a piezoresistive cantilever is described. The AFM is designed so that all power to drive the scanning tube and detection electronics comes from a self-contained battery. The prototype AFM uses a 6 V, Ni–Cd, camcorder battery, however, any battery that supplies between 6 and 12 V may be used. Scanner control and data acquisition are implemented using commercially available software running on an external computer. The prototype AFM achieves a scan area of 53 by 53 μm, consumes 1.8 W of power, and can scan continuously for about 7 h on a single battery charge.
Gain of windowless electron multipliers 226EM and EMI 9643/2B for highly charged Ta ions
Authors: Krása J. , Woryna E. , Stöckli M. P. , Winecki S. , Walch B. P.
Published: July 2002

The gain of windowless electron multipliers 226EM and EMI 9643/2B with BeCu dynodes was measured for Taq+ ions (12⩽q⩽49) with kinetic energies ranging from 8 to 164 keV/q. A Faraday cup was used as a standard ion-current detector. The comparison of the anode current of an electron multiplier (EM) with the Faraday cup current initiated by impact of ions indicates effects of their charge state as well as the velocity for response of both the EMs. The current gain of both the EMs has been found to monotonously increase with increasing charge state for ion energy per charge up to 24 keV/q but has a minimum for higher energy. The analog particle gain derived from the measured current gain increases with increasing charge state for all the accelerating voltages applied. The analog particle gain of 226EM increases with increasing ion energy per charge for q less than ∼27 but decreases with ion energy for higher q. For EMI 9643/2B the particle gain increases with increasing velocity up to charge state 49 where it becomes approximately independent of its velocity.
Last results of the continuous-wave high-intensity light ion source at CEA-Saclay
Authors: Gobin R. , France A. , Beauvais P.-Y. , Delferrière O. , De Menezes D. , Ferdinand R.
Published: July 2002

The high-intensity light ion source (SILHI) is designed to be a prototype source for high power linear accelerators. The goal is to produce a 100 mA proton or a 140 mA deuteron ion beams at 95 keV with rms normalized emittance lower than 0.2 π mm mrad. A 108 mA total beam (J=215 mA/cm2) was extracted in April 1997 (85% H+, 12% H2+, and 3% H3+ fractions) with two electron cyclotron resonance (ECR) zones located at both plasma chamber extremities simultaneously. First beam measurements indicate a 0.17 π mm mrad rms normalized emittance for a 80 mA proton beam at 80 keV. In these conditions, a 96% availability was obtained during an 8 h working day. An intermediate electrode is placed in the accelerator gap to minimize emittance distortions as shown by simulations. Beam analysis were made as a function of the intermediate electrode voltage, the gas flow, the magnetic field, and the 2.45 GHz rf power. First rf plasma coupling observations indicated that the magnetron was too highly coupled with the load (plasma chamber). By adding a second circulator and locking the oscillator with an external signal, this dependence was decreased. Measurements then clearly show that the output spectrum is completely independent of the load phasing. All these results will be presented.
Production of metallic ions with an ECRIS at GANIL
Authors: Bex L. , Flambard J. L. , Dupuis M. , Lehérissier P. , Rataud J. P.
Published: July 2002

A summary of recent and future developments in metallic ion production with an electron cyclotron resonance ion source (ECRIS) at GANIL is presented. Multicharged metallic ions are routinely produced with an ECRIS (ECR4 14 GHz) and accelerated for nuclear and atomic physics experiments. We present the various methods which have been used to generate these multicharged metallic ions. The accelerator requires stable beams for periods of weeks. The results obtained recently by direct ion plasma sputtering of Ni, Nb, and U samples are remarkable and stable beams from these metals have been delivered continuously for weeks. A pulsed EXCIMER laser, injecting a beam axially through the extraction hole of the ECRIS, has been tested for ablation on a rotating uranium target for uranium beam production. The metal ions from volatile compounds technique using volatile compounds has been also tested with ferrocene [Fe(C5H5)2] to produce multicharged Fe ions. We plan to install a third high voltage platform using an ECRIS totally built with permanent magnets.
Development of high power ion sources for fusion (invited)
Authors: Ohara Y.
Published: July 2002

Recent progress and development activities regarding high power ion sources for fusion researches are reviewed. High power positive ion sources, which have progressed in the 1980s, played important roles in fusion research. Most of the ion sources developed for major neutral beam injection (NBI) systems are a large area magnetic multipole type with tungsten cathode, and produce tens of amperes of positive hydrogen/deuterium/tritium ion beams at the energy around 100 keV. The NBI systems based on these ion sources delivered tens of MW neutral beams to the plasmas, and contributed to produce high temperature plasmas in the break-even condition in the tokamak type fusion devices. Meanwhile, R and D of high current negative ion sources were carried out for a high energy NBI system to be utilized not only for plasma heating, but also for the steady state operation and stable plasma control in the fusion burning plasmas. In the 1990s, rapid progress of high current negative ion sources has been made. Particularly, a cesiated magnetic filter source with high plasma confinement has, for the first time, produced a multi-ampere negative ion beam stably in the conditions required for the negative-ion-based NBI systems, namely high negative ion current density, low operating pressure, low extracted electron current, and good beamlet optics. Based on this progress, a 500 keV 10 MW NBI system has been developed for JT-60U at the Japan Atomic Energy Research Institute, and construction of a 180 keV 15 MW NBI system is carried on at the National Institute for Fusion Science in Japan. The same type of negative ion source is applied to the design of a 1 MeV NBI system for the International Thermonuclear Experimental Reactor (ITER).
Stripping of ion beams by multiple passes through a plasma medium
Authors: Dougar Jabon V. D. , Vivas F. A. , Chacon Velasco A. J. , Umnov A. M.
Published: July 2002

A method to increase the charge state of multicharged ions is explored. The method is based on stripping, during multiple passes, of an initially low charge-state ion beam through a plasma medium with energetic electrons heated at the electron cyclotron resonance. The key feature of the system is a magnetic recirculating line which has a built-in stripping chamber and a system of entrance-exit apertures. The recirculating line comprises a magnetic low-loss ion guide which delivers ions being passed through the stripping chamber to its entrance. As a stripping medium, a hydrogen plasma confined in a magnetic trap of cusp configuration is proposed. To model the conversion of initially injected ions with charge state ζ=1 to higher states, basic parameters of the stripping chamber can be estimated as follows: microwave frequency: 14.4 GHz; effective plasma length 10–30 cm; gas pressure: 1×10−5 Torr. Results of numerical calculation of the proposed stripping process show that an increase of ion charge is possible with acceptable deterioration of ion beam characteristics. Conversion efficiency, for example, for Pd103 from ζ=1 to ζ=5 for these parameters is about 80%.
Simulation of 10 A electron-beam formation and collection for a high current electron-beam ion source
Authors: Kponou A. , Beebe E. , Pikin A. , Kuznetsov G. , Batazova M. , Tiunov M.
Published: July 2002

Presented is a report on the development of an electron-beam ion source (EBIS) for the relativistic heavy ion collider at Brookhaven National Laboratory (BNL) which requires operating with a 10 A electron beam. This is approximately an order of magnitude higher current than in any existing EBIS device. A test stand is presently being designed and constructed where EBIS components will be tested. It will be reported in a separate paper at this conference. The design of the 10 A electron gun, drift tubes, and electron collector requires extensive computer simulations. Calculations have been performed at Novosibirsk and BNL using two different programs, SAM and EGUN. Results of these simulations will be presented.
Deposition probe technique for the determination of film thickness uniformity
Authors: Bilek M. M. M. , Brown I. G.
Published: July 2002

We describe a quantitative method of measuring film thickness profiles as deposited by plasma beams. Film thickness profiles are usually closely related to the plasma density profile of the depositing beam. The technique relies on the deposition of a semiopaque film over a large area transparent medium in situ and thus is particularly suitable for plasma systems used for thin film deposition. A simple and fast technique for quantifying the optical density versus position in the deposited film using a scanner and image processing software is described. The ability to quantify the relative optical density between different deposition profiles makes this a powerful tool for the study of the effects of process parameters on plasma density profiles and for the optimization of deposition systems.
Design and performance of a portable 3He cryogenic system for ground based instrumentation
Authors: Verveer J. , Rando N. , Andersson S. , Gondoin P. , Peacock A. , Collaudin B.
Published: July 2002

The availability of compact cryogenic refrigerators is of importance for the development of both ground and space-borne instrumentation based on cryogenic detectors. In this article we report on the design and performance of a complete ground based cryogenic system consisting of a He3 cryosorption refrigerator, and designed to cool a 6×6 element detector array of tantalum based superconducting tunnel junctions (STJs). The refrigerator provides an operating temperature of 330 mK, with a hold time in excess of 7 h. The system is designed to be portable, to provide a very stable focal plane, and to minimize the use of magnetic materials. Such a system has been used to host the focal plane assembly of S-Cam, the first optical camera for ground based astronomy utilizing an array of STJs, recently installed at the William Herschel Telescope, in La Palma.
High-resolution temperature measurement of void dynamics induced by electromigration in aluminum metallization
Authors: Kondo Seiichi , Hinode Kenji
Published: July 2002

The local temperature of aluminum metallization is measured directly during electromigration. High resolution thermography is used to detect void dynamics induced by a dc current. In the vicinity of the growing area, infrared radiation pulses less than 0.5 s wide are observed concomitant with resistance pulses. Their amplitudes are found to correspond to a temperature increase of more than 200 °C, which locally exceeds the melting point of aluminum metallization. These pulses occur as a consequence of void movement. Healing of voids is discussed along with the results.
Investigation of etched silicon wafers for lobster-eye optics
Authors: Peele A. G.
Published: July 2002

We investigate some high aspect ratio etched silicon to determine its suitability as a lobster-eye optic. The major defects present leading to performance degradation are identified and tolerance goals are set for prospective candidates.
X-ray diagnostic applied to the study of shock wave propagation in foams
Authors: Batani D. , Koenig M. , Benuzzi A. , Boudenne J. M. , Cauchon G. , Hall T. , Nazarov W.
Published: July 2002

A new radiographic technique has been studied in order to analyze the continuous evolution of shock wave propagation in low density foams. The technique is based on a Bragg–Fresnel multilayer lens. Preliminary static results, obtained by imaging a grid of suitable size, are presented.
Measurements of thick target neutron yields and shielding studies using beams of He4, C12 and O16 at 155 MeV/nucleon from the K1200 cyclotron at the National Superconducting Cyclotron Laboratory
Authors: Britvich G. I. , Chumakov A. A. , Ronningen R. M. , Blue R. A. , Heilbronn L. H.
Published: July 2002

Measurements of neutrons from a thick target of Hevimet were made, using beams of He4, C12, and O16 ions at 155 MeV per nucleon. These measurements were made both inside and outside of thick concrete shielding, using Bonner-sphere techniques. Yields, spectra, and spectral integral quantities were obtained. The neutron yields were parameterized, and a Moyer-model approach was taken to estimate the dose-equivalent outside of the thick concrete shielding. The effect of local iron shielding, and the dose equivalent outside of iron roof shielding were also investigated. Finally, two methods to obtain neutron field integral values, the “reconstructed spectra” and “six-spheres” methods, were compared. The measurements and analyses should prove useful to other present or planned medium-energy heavy-ion accelerator facilities.
Improved calibrator for the evaluation of batch produced strain gauges in cryogenic environments
Authors: Huber W. H. , Hernandez L. M. , Goldman A. M.
Published: July 2002

We have constructed a simple, improved apparatus for calibrating strain gauges down to liquid helium temperatures to permit an estimate of the repeatability and linearity of commercially available, batch produced, metal foil strain gauges. The apparatus is based upon an original design first proposed by McClintock [R. M. McClintock, Rev. Sci. Instrum. 30, 715 (1959)]. Calibrations performed on a particular batch produced metal foil strain gauge indicate that it behaved ideally at low temperatures. Although the gauge resistance was strongly temperature dependent, the gauge factor was virtually independent of temperature and did not display any detectable nonlinearity or hysteresis.
Setting up and time-resolution measurement of a radio-frequency-based streak camera
Authors: Aleksandrov A. V. , Dikansky N. S. , Guidi V. , Lamanna G. V. , Logatchov P. V. , Shiyankov S. V. , Tecchio L.
Published: July 2002

We have experimented with a radio-frequency-based streak camera. The basic idea behind the method consists of magnetic deflection of the electron beam imparted by a radio-frequency cavity. All the components of the camera were tested and the time resolution was measured to lie within the sub-ps domain. Further advantages of the method are simplification of triggering, weaker dependence on space-charge effect within the electron beam, high modularity, and ease of implementation.
Improvement of beam emittance of the CEA high intensity proton source SILHI
Authors: Gobin R. , Beauvais P.-Y. , Ferdinand R. , Leroy P.-A. , Celona L. , Ciavola G. , Gammino S.
Published: July 2002

The emittance of the intense proton beam extracted by the source SILHI at Commisariat à l’Energie Atomique (CEA)-Saclay is a key parameter for the design of the IPHI Project RFQ. This parameter has a relevant role even for the design of an intense proton source for the TRASCO project of Istituto Nazionale di Fisica Nucleare (INFN). The tests performed in the framework of CEA-INFN collaboration have been mainly devoted to a 75 mA beam emittance investigation injecting different gases in the beam line. The results show that the rms normalized emittance decreases up to a factor 3 while the beam losses induced by recombination are contained within 5%. Normalized emittance in r-r′ plane of about 0.1 π min mrad have been obtained using Ar and Kr.
Simulation and calibration of an open inductive sensor for pulsed field magnetization measurements
Authors: Weckhuysen L. , Vanacken J. , Trappeniers L. , Van Bael M. J. , Boon W. , Rosseel K. , Herlach F. , Moshchalkov V. V. , Bruynseraede Y.
Published: July 2002

The relation between the voltage induced in an open sensor and the magnetic moment of a sample during pulsed field magnetization measurements has been calculated. The calculation takes into account the size of a sample, its internal flux distribution, and its position with respect to the center of the sensor. It has been found that the behavior of the response signal with respect to the sample position is the same for homogeneously magnetized Ni samples and high temperature superconductors. Because of this universality, it is possible to calibrate the open sensor even in the case of an unfavorable sample geometry. The calculations have been experimentally verified by using Ni samples with different geometries. Our results can easily be extended to samples with an arbitrary local field distribution.
Novel scanning near-field optical microscope (SNOM)/scanning confocal optical microscope based on normal force distance regulation and bent etched fiber tips
Authors: Wolf J. F. , Hillner P. E. , Bilewicz R. , Kölsch P. , Rabe J. P.
Published: July 2002

We report on a unique combination of a novel scanning near-field optical microscope/scanning confocal optical microscope based on normal force distance regulation with bent etched fiber tips. The use of normal force detection makes all classic atomic force microscope operation modes such as contact mode and tapping mode accessible to scanning near-field optical microscopy (SNOM), thus allowing near-field optical imaging at sample distances unavailable to shear force regulated distance control. The SNOM laser light is pulsed or detected synchronously to the fiber tapping amplitude to illuminate the sample at a predetermined height above the sample. Bent etched fiber tips are used, whose fiber diameters are additionally etched down to yield resonant frequencies between 60 and 300 kHz, Q factors around 180 and spring constants in the range of 80–400 N/m. The typical roughness of the tip cone surfaces is shown to be due to etching in a meniscus. For the first time, simultaneously acquired constant gap width mode topography and constant height mode near-field optical images are presented, allowing topography induced contrast to be separated from true optical contrast such as absorption and fluorescence.
Dynamic behavior of a piezowalker, inertial and frictional configurations
Authors: Mariotto G. , D’Angelo M. , Shvets I. V.
Published: July 2002

We have examined two configurations of a piezowalker, the inertial and the frictional one, both of which are capable of moving samples with submicrometer steps over a distance of some millimeters. We demonstrated that, contrary to expectations, operation of the frictional walker in which six piezos shear one by one, is still dependent on inertial slip-stick action. We studied the dependence of the step size on the time delay between rising fronts applied to consecutive piezos and we found that the characteristic time associated with the minimum value of the step size is of the order of the time of a sound wave propagating along the rod between the piezos.
Ion energy spectra analyzers for magnetized plasma
Authors: Churkin I. N. , Volosov V. I. , Steshov A. G.
Published: July 2002

Ion energy spectra analyzers for investigation of plasma in an axial magnetic field are considered. These analyzers can measure the velocity spectra of the magnetized ion components of dense plasma. The small inlet hole method is used in presented analyzers for spatial separation of electron and ion flows. The construction and operating features of these analyzers are described. The described analyzers have been used for measurements of ion parameters of plasma flow with magnetized titanium ions generated by the universal plasma source. Experimental results are presented and discussed.