bluuebunny/crossref_metadata_2025 huggingface dataset:
Direct molecular-beam epitaxial growth of ZnTe(100) and CdZnTe(100)/ZnTe(100) on Si(100) substrates
Authors: de Lyon T. J. , Roth J. A. , Wu O. K. , Johnson S. M. , Cockrum C. A.
Published: July 2002

Epitaxial structures of ZnTe(100) and CdZnTe(100)/ZnTe(100) have been deposited by molecular-beam epitaxy onto Si(100) substrates misoriented from 0° to 8° towards the [011] direction. The films were characterized with x-ray diffraction, photoluminescence spectroscopy, optical microscopy, and stylus profilometry. Single-crystal CdZnTe(100) films comparable in structural quality to those obtained with growth on GaAs/Si composite substrates have been demonstrated on both 4° and 8° misoriented Si with the use of ZnTe buffer layers. X-ray rocking curves with FWHM less than 300 arcsec for ZnTe (400) and less than 160 arcsec for CdZnTe(400) have been obtained for as-grown films. Specular surface morphologies, superior to those obtained on GaAs/Si composite substrates, are also observed.
Prominent thermally stimulated current trap in low-temperature-grown molecular beam epitaxial GaAs
Authors: Fang Z.-Q. , Look D. C.
Published: July 2002

By far, the largest thermally stimulated current trap in molecular beam epitaxial GaAs grown at 200–250 °C is T5, with an activation energy of 0.27 eV and most likely related to VGa. After an anneal at 300–350 °C, another trap T6■ appears, with an activation energy of 0.14 eV and closely identified with VAs or the complex, VAs-AsGa. Proposed defect reactions in this As-rich material include VGa+AsAs→VAs-AsGa, and VGa+AsGa→VGa-AsGa.
Penetration depth, microwave surface resistance, and gap ratio in NbN and Ba1−xKxBiO3 thin films
Authors: Pambianchi M. S. , Anlage S. M. , Hellman E. S. , Hartford E. H. , Bruns M. , Lee S. Y.
Published: July 2002

We report values of the zero temperature magnetic penetration depth λ(0), microwave surface resistance Rs, and gap ratio 2Δ(0)/kBTc in technologically useful thin films of NbN and Ba1−xKxBiO3. A novel analysis technique was used to extract the absolute magnitude of λ(0) and 2Δ(0)/kBTc from shifts in resonant frequency of a parallel-plate resonator. For NbN and Ba1−xKxBiO3 values of λ(0)=3900±200 Å and 3300±200 Å were obtained, respectively. The gap ratios were found to be 2Δ(0)/kBTc=4.1±0.1 and 3.8±0.5, respectively, for Tc=16.3 K in NbN and Tc=17.2 K in Ba1−xKxBiO3. The surface resistance measurements on Ba1−xKxBiO3 represent the lowest values ever reported at microwave frequencies in this material.
Narrow bandwidth volume holographic optical filter operating at the Kr transition at 1547.82 nm
Authors: Leyva Victor , Rakuljic George A. , O’Conner Bruce
Published: July 2002

We describe and characterize a narrow bandwidth volume holographic optical filter operating at the Krypton transition line (1s2-2p8) at 1547.82 nm, which corresponds to the center wavelength of the proposed International Telecommunications Union wavelength standard. A reflectivity of 98% and a bandwidth full width at half-maximum of 0.18 nm are measured. The filter exhibits clean sideholes with a −20 dB optical response 0.5 nm away from the peak. The filter can be fabricated and operated with an absolute wavelength precision better than 0.005 nm.
Shear stresses in magnetorheological fluids: Role of magnetic saturation
Authors: Ginder J. M. , Davis L. C.
Published: July 2002

The interparticle forces and resulting shear stresses in a magnetorheological fluid are calculated. The field due to a linear chain of particles in a fixed average magnetic induction Bave is determined from a finite element analysis in which the nonlinearity and saturation of the particle magnetization are incorporated. The shear stresses are then computed from the field using Maxwell’s stress tensor. The stresses obtained for all but the lowest magnetic inductions are controlled by the saturation of the magnetization in the contact regions of each particle. Identifying the maximum shear stress as a function of shear strain with the yield stress gives values in agreement with results reported for typical fluids. For high magnetic inductions the yield stress plateaus due to the complete saturation of the particle magnetization; the stress scales as the square of the saturation magnetization in this regime.
Electron effective masses in 4H SiC
Authors: Son N. T. , Chen W. M. , Kordina O. , Konstantinov A. O. , Monemar B. , Janzén E. , Hofman D. M. , Volm D. , Drechsler M. , Meyer B. K.
Published: July 2002

Results from optically detected cyclotron resonance (ODCR) studies of electron effective masses in 4H SiC are reported. ODCR measurements were performed on high-purity n-type 4H SiC epitaxial layers grown by chemical vapor deposition at both X band (9.23 GHz) and Q band (35.05 GHz) microwave frequencies. Electron effective masses in 4H SiC were directly determined as m⊥*=0.42m0 and m∥*=0.29m0. A scattering time in the basal plane τ⊥≊4.3×10−11 s, and hence, the corresponding electron mobility μ⊥≊1.8×105 cm2/V s, was obtained from a fit of the ODCR line shape.
Finite difference computer simulation of two diverging electrostatic analyzers: The soft particle spectrometer and the spectrographic particle imager
Authors: Sablik M. J. , Winningham J. D. , Blevins V. A.
Published: July 2002

We have completed a finite difference computer simulation of two diverging electrostatic analyzers. In both analyzers, the deflecting plates are cylindrical surfaces which flare out from each other like two arms of a hyperbola. The analyzers are the soft particle spectrometer (SPS) and the spectrographic particle imager (SPI), which correspond, respectively, to an energy spectrometer and an energy spectrograph. The simulation consists of two steps: (1) a finite difference computation of the electrostatic potential field inside the instrument; and (2) a ray-tracing computation in which many particles are ray traced through the instrument and statistics are gathered on the particles that make it to the collecting region. In both cases, the simulation is two-dimensional, restricted to the central plane of the instrument. This limitation turns out to be unimportant because the statistics acquired during simulation agree well with experimentally acquired statistics for each instrument. In the case of SPI, the computer simulation has been used to provide information on how variation of geometric parameters affects the quantities that describe a good spectrograph.
Radio frequency induction plasma generator 80-kV test stand operation
Authors: Goede H. , DiVergilio W. F. , Fosnight V. V. , Vella M. C. , Ehlers K. W. , Kippenhan D. , Pincosy P. A. , Pyle R. V.
Published: July 2002

Beam extraction tests at energies up to 80 kV were performed using a radio frequency induction (RFI) plasma generator hydrogen ion source. A 7×10-cm2, long pulse accelerator was operated with a 10×10-cm2 axial magnetic cusp bucket and a magnetic-filter bucket. Atomic fractions (up to 85% H+), plasma production efficiencies (≊0.6 A of beam per kW rf power), and beam divergence were at least as good as with arc plasmas in similar chambers. Potential advantages of the RFI plasma sources for large-scale applications are ease of operation, reliability, and extended service life.
Resolving the propagation direction of tokamak microturbulence via homodyne spectroscopy
Authors: Brower D. L. , Peebles W. A. , Luhmann N. C. , Ritz Ch. P. , Powers E. J.
Published: July 2002

A new homodyne spectroscopy technique [T. Tsukishima and O. Asada, Jpn. J. Appl. Phys. 17, 2059 (1978)] has been applied to tokamak microturbulence measurements in order to resolve the frequency spectra and wave propagation direction of low-frequency density fluctuations. Application of this method provides a high-resolution, inexpensive, and easily implemented alternative to the more technically demanding heterodyne detection schemes typically available. Comparison of heterodyne and the new homodyne spectroscopy results will be made.
Precision acoustic gas analyzer for binary mixtures
Authors: Polturak E. , Garrett S. L. , Lipson S. G.
Published: July 2002

We describe a cylindrical acoustic resonator which has been used for the determination of the molar concentration of a binary mixture of gases. We achieved an absolute accuracy better than 0.001 independent of the concentration or the type of gas. The practical factors limiting the accuracy are discussed in detail and their effect on the performance has been evaluated using gas samples prepared by precisely measured partial pressures. The device is routinely used to measure the concentration of 3He–4He mixtures.
Scintillation detector for escaping alphas and tritons in TFTR
Authors: Zweben S. J.
Published: July 2002

A diagnostic for escaping charged fusion products is presently being tested on tokamak fusion test reactor (TFTR). It consists of a 1×1-in. ZnS scintillator screen located inside a movable probe at the bottom of the TFTR vacuum vessel. The alphas or tritons hit the scintillator screen where they create visible light pulses which are fiber-optically coupled to photomultiplier tubes and/or an intensified video camera for recording and analysis.
Mass analyzed secondary ion microscopy
Authors: Bernius Mark T. , Morrison George H.
Published: July 2002

This paper reviews and critically assesses progress in the field of surface and near-surface imaging microscopies based on secondary ion mass spectrometry. The ion microscope performs a variety of analytical functions, including complete mass spectra and isotope ratios from areas on the submicron scale, and lateral distribution analysis using ion imaging, with high sensitivity for all elements of the periodic table. Recent developments have improved the ion microscope’s ability to image a specimen’s elemental morphology with spatial resolutions below 100 nm. Criteria for the quantitative evaluation of ion images and the instruments that produce them are reviewed within the framework of information-transmission theory. A complete and general description of the physical principles guiding the types of instrumentation available is thus presented, with emphasis on the accuracy and precision of an analytical measurement. Several directions for future developments are proposed.
Impulse excitation technique for dynamic flexural measurements at moderate temperature
Authors: Heritage Kevin , Frisby Clayton , Wolfenden Alan
Published: July 2002

The impulse excitation technique (IET), which is presently a precise and reliable technique for measuring dynamic moduli at room temperature, has been adapted to measure dynamic flexural modulus at temperatures in the range of 25° to 300 °C. This modified technique involves a sensitive microphone and electronics to record and analyze the sound waves emitted from a specimen vibrating in the fundamental flexural mode. The fundamental resonant frequency and geometry of the specimen are used to obtain the modulus. The location of the microphone relative to the specimen is critical and is a major factor once the specimen is placed within the heated environment. Problems were identified and solved, and test data for aluminum are presented to support the modification of the IET for use at elevated temperatures.
Response to ‘‘Comment on ’Mass analyzed secondary ion spectroscopy’’’ [Rev. Sci. Instrum. 5
9, 2508 (1988)]
Authors: Bernius Mark T. , Morrison George H.
Published: July 2002

Two references in our review article were in error; we regret the oversight. The technical points of disagreement are discussed, and a table comparing the University of Chicago scanning ion microprobe and the Cornell stigmatic ion microscope is provided to clarify one by R. Levi-Setti [Rev. Sci. Instrum. 59, xxx (1988)].
Design and application of a computer-controlled confocal scanning differential polarization microscope
Authors: Juang Ching-Bo , Finzi Laura , Bustamante Carlos J.
Published: July 2002

Based on the confocal scanning and differential polarization imaging technique, a computer-controlled confocal scanning differential polarization microscope has been built. This system possesses extensive image processing capability that provides digitized regular and/or differential polarization images. This microscope combines the advantages of the confocal design and the extended electronic sensitivity of polarization modulated instrumentation to achieve the measurement of an anisotropy ratio as small as 10−5. In this paper, the basic theory and the instrument are described. In addition, some samples are used to test the actual performance of the system, and it is found that the system provides high resolution (0.3 μm at wavelength 546 nm), reduced depth of field, and high signal-to-noise ratio (83 dB at 10-ms integration time) images. Finally, some biological applications are shown.
Multiprocessor system with parallel and pipelined architecture for a STEM quadrant detector
Authors: Epstein Avi
Published: July 2002

An integer processing unit board has been developed. The unit was designed to allow implementation of parallel and pipelined multiprocessor systems. This unit is the basic building block for a fast pipeline and parallel processing system needed to compute images from data produced by a 128-channel silicon detector array in a scanning transmission electron microscope. Systems consisting of 4, 6, and 16 such integer processing units were considered, and the performances of these configurations were evaluated.
Composite antennas for low-frequency gravitational radiation
Authors: Nagashima Y. , Owa S. , Tsubono K. , Hirakawa H.
Published: July 2002

Four types of composite torsion antennas for low-frequency gravitational radiation have been developed and tested at low temperature. They exhibited high quality factors comparable with that of a single-piece antenna. These experiments suggest a large-scale composite antenna may be built and retain a high quality factor.
γ-ray diagnostic for the CIT
Authors: Petrasso R. D. , Fiore C. L. , Li Chi-Kang
Published: July 2002

We have examined the feasibility of a fusion γ-ray diagnostic for the Compact Ignition Tokamak (CIT), which is expected to produce 1020 (d, t) fusion reactions per second. Gamma rays at 16.7 MeV are produced by the t(d, γ)He5 fusion reaction. A Monte Carlo coupled neutron–photon transport code is used to model the expected γ-ray spectrum incident upon a Compton spectrometer backed by a Čerenkov detector. The results indicate that a signal of ∼3×104 counts/s and a signal-to-noise ratio of ∼30 can be achieved.
Wide range magnetic electron spectrograph
Authors: Coplan M. A. , Wang L.-J. , Moore J. H. , Hoffman R. A.
Published: July 2002

An electron spectrograph is described that covers electron energies from 400 eV to 200 keV with an energy resolution of 10%. This overlaps the range of electrostatic deflection devices at low energy and solid state detectors at high energy. The spectrograph uses magnetic deflection of the electrons to achieve energy separation and images the full range of energies on a single plane. The magnetic circuit uses the fringing field of two axially located magnets to attain the large energy range. Six separate electron beams can be dispersed in the field, each entering the circuit from a different angle. This is a particular advantage when measuring plasma electron three-dimensional velocity distributions. The angular response of the instrument is particularly favorable and the stray magnetic field is sufficiently low to meet spacecraft requirements. Compared with electrostatic deflection devices, the spectrograph is particularly advantageous for measuring high energy electron plasma velocity distribution functions with fast time resolution at modest energy resolution.
Multichannel HCN laser interferometer for electron density measurements of the JIPP T-IIU tokamak
Authors: Kawahata Kazuo , Haba Kiichiro , Fujita Junji , Okajima Shigeki
Published: July 2002

A six-channel HCN laser interferometer system has been developed for the measurement of the electron density profile in the JIPP T-IIU tokamak. The fringe shift of the probe beam is directly read out using a reference beam, the frequency of which is Doppler shifted by 50 kHz with a rotating grating. The optical configuration is of the Michelson interferometer type, of which reflecting mirrors are directly attached on the wall of the vacuum vessel. An effective area of the optical window is only φ40 mm. This optical configuration enables us to make the electron density profile measurements by the multichannel laser interferometer with a single small optical window.
Discrimination between particle and radiation losses by using a time-of-flight type neutral particle energy analyzer
Authors: Tsuboi F. , Ichimura M. , Yamaguchi N. , Inutake M. , Adachi S. , Hattori K. , Mase A. , Nakashima Y. , Miyoshi S.
Published: July 2002

A time-of-flight type neutral particle energy analyzer can discriminate between neutral particle loss and radiation loss from a plasma by use of the difference between their times of flight. The energy distribution of hydrogen atoms which are emitted from the plasma can be estimated from the time evolution of the detector signal. The energy distribution of radiated photons can be obtained by using several filters which transmit different ranges of the photon energy. With this method the ratio of the particle and radiation losses emitted from the same plasma volume and within the same detector solid angle can be obtained.
Two-dimensional x-ray photoelectron diffraction measurements by a retarding field-type analyzer
Authors: Kanayama S. , Owari M. , Nakamura E. , Nihei Y.
Published: July 2002

Two-dimensional x-ray photoelectron diffraction (XPED) patterns of Ga3d and As3d photoelectrons from GaAs(001) were rapidly measured by using a retarding field-type electron energy analyzer and a synchrotron radiation x-ray source. In the raw images of photoelectrons obtained with this analyzer, clear XPED patterns were not observed, for most of the contrast was caused by moiré patterns of the four-grid electrodes. In order to obtain net XPED contrast, it is necessary to remove such instrumental functions. For this purpose, three techniques were applied: First, to perform pixel-by-pixel division between an image from a single-crystal sample and one from a polycrystalline sample. Second, to restore the XPED pattern by arithmetic treatments from two images measured before and after sample rotation. Third, to perform pixel-by-pixel division between an image from the crystal-state sample and one from the amorphous state, where the samples of two different states were obtained from the same sample before and after annealing without changing its position. In the case of GaAs, clear XPED patterns of Ga3d and As3d were obtained only by the third technique. The resultant patterns agreed well with calculated XPED patterns.
Development of a grazing incidence ultrasoft x-ray monochromator for radiation biology studies (abstract)
Authors: Kobayashi K. , Hieda K. , Maezawa H. , Ito T. , Naito T.
Published: July 2002

Irradiation experiments on biological samples with monochromatic ultrasoft x-rays are inevitable in elucidating the initial process in radiobiological phenomena. However, intense light sources with continuous spectra in this wavelength region have not been available until recently. Synchrotron radiation is the best light source for the study because of its intense, continuous emission spectrum. The purpose of the project is to develop a grazing incidence ultrasoft x-ray monochromator for radiation biology studies using synchrotron radiation as a light source. The following characteristics are required in the monochromator, namely, (1) high throughput with moderate resolution; (2) wide beam area with uniform intensity; (3) little contamination of higher order lights; and (4) easy operation and maintenance. Considering the above requirements, a plane-grating type monochromator (PGM) is adopted. The monochromator consists of two premirrors (M1 and M2), a plane grating (1200 ℓ/mm), a concave focusing mirror (r=12 m) and an exit slit. Two premirrors with different incident angles can be used interchangeably to eliminate higher order lights in the desired wavelength region. Wavelength of 30–70 A is available when M1 is used and 80–250 A when M2 is used. Expected wavelength resolution is 1% when the width of exit slit is 300 μm. All vacuum chambers accommodating these optical elements are bakable in order to attain ultrahigh vacuum. Wavelength is controlled by a microcomputer system equipped with a stepping motor and an encoder. This monochromator will be installed at beamline 12C at the Photon Factory, National Laboratory for High Energy Physics, and will be open to outside users in radiation biology by the end of 1988.
Very low-emittance 1.3-GeV storage ring
Authors: Wakuta Y. , Watanabe Y. , Yamada K. , Kumabe I.
Published: July 2002

A very low-emittance 1.3-GeV storage ring has been designed. Modified TBA lattice is used in order to achieve as low emittance as possible and the beam tracking is also carried out to find lattice parameters, which make the dynamic aperture as large as possible. High-emittance operation is also considered for obtaining large irradiation fields. Moreover, a high-gain single-pass FEL undulator which lases around 1000 Å is to be installed. For the biochemical and medical applications, a 5-T wiggler will be inserted in one of four of 6-m-long straight sections. The obtained emittance is ∼1.6×10−8 π mrad and the circumference of the storage ring is 126.0 m.
High pressure–high temperature research using high energy synchrotron radiation at the TRISTAN accumulation ring (invited)
Authors: Kikegawa T. , Shimomura O. , Iwasaki H. , Sato S. , Mikuni A. , Iida A. , Kamiya N.
Published: July 2002

High energy synchrotron radiation emitted from the bending magnet of the TRISTAN accumulation ring (6.5 GeV) at the National Laboratory for High Energy Physics has been used for the high pressure–high temperature diffraction experiments using a multianvil press system, MAX80. Owing to the specific features of high energy synchroton radiation, significant improvements have been brought to the high pressure research. The wide energy range of diffraction spectrum leads to an increase in the number of observable diffraction peaks in an energy-dispersive method, resulting in an increase in the accuracy of the measurements of the lattice and thermal parameters. Due to the high penetrating power of radiation, diffraction patterns can be taken in a short time from materials containing heavy elements or materials surrounded by a metal foil. Typical examples of high pressure–high temperature experiments with high energy synchrotron radiation are also described.
Scanning x-ray stepper for synchrotron radiation
Authors: Cullmann E. , Vach W. , Cooper K.
Published: July 2002

With the SUSS XRS 200 a synchrotron compatible stepper is available which combines high positional accuracy and high throughput using the scanning exposure method. With 1 s each for exposure, alignment, and stepping time, 20 6-in. wafers/h can be processed with the smallest stepfield size of 26×26 mm. The excellent linewidth control, irrespective of topography and surface characteristics, with a large gap and exposure dose window, show the capability of x-ray lithography to be used as the next generation production lithography method. The SUSS XRS-200 provides the user with a tool to take full advantage of this wide process latitude and make production of sub-half-micron features an economical operation.
Influence of an electron-beam injection on ion charge state distribution in an ECR source at 2.45 GHz
Authors: Dougar-Jabon V. D. , Golovanivsky K. S. , Kondratov B. A. , Kushnarenko V. D.
Published: July 2002

The single stage multicharged ion ECR source supplimented with a La-B electron gun is investigated. The magnetic system of the source consists of Sm-Co hexapole and two solenoids which create mirror configuration. The argon plasma production chamber is a TE111 mode cavity fed with a 600-W oscillator of 2.45 GHz. The source performance was found to be independent of the gun bias potential if the gun was located in a magnetic throat. It was observed that the injection of the cold electron beam (15 mA) at the pressure of 0.008 mTorr shifted the mean ion charge from 1.3 to 1.8 and increased the currents of ions in states Z=3 and Z=4 by a factor of 2.5–3.0. For a low-frequency source, the application of an electron gun allows for the generation of middle charged ions.
Project of an ECR source with a stripping stage
Authors: Dougar-Jabon V. D. , Umnov A. M.
Published: July 2002

A two-stage cascade device is proposed for generating heavy completely stripped atoms. The first stage of an ECR source of 10-GHz type is to produce ions in high charge states. In the second, electrons emitted by an electron gun and a plasma of residual gas are heated under synchrotron gyromagnetic autoresonance (SGA) regime. Such a created SGA plasma under certain conditions might be negatively charged. Ions transported from the first stage into SGA plasma are trapped by an electrostatic pit where they experience further stripping under collisions with energetic electrons. Parameters of the second stage are defined. Computer simulation of ionizing processes shows that for obtaining 1×107 completely stripped argon atoms one should inject 9×109 ions in the state Z=+15 during 36 ms into the second stage where the 10-GHz microwave field accelerates the electrons up to an energy of 200 keV. The residual gas pressure is taken to equal 1×10−8 Torr.
The Frankfurt ECR-RFQ facility
Authors: Stiebing K. E. , Hofmann D. , Schmidt-Böcking H. , Bethge K. , Streitz H. , Fröhlich O. , Schempp A. , Klein H. , Zschornack G. , Lyneis C.
Published: July 2002

An ion beam facility for high-intensity beams of highly charged ions in the energy range between 1 and 200 keV/u has been funded and will be installed in 1992 at the Institut für Kernphysik, Frankfurt am Main, Germany. The facility is based on a 14.6 GHz ECR ion source and a variable-energy RFQ as postaccelerator. The facility is intended for atomic-physics and materials research.
Investigation of an injector with an arc multicharged ion source
Authors: Biri S. , Bogomolov S. L. , Kutner V. B. , Tretyakov Yu. P.
Published: July 2002

An injector with a PIG ion source has been designed for the axial injection system of the U-200 cyclotron. An accel-decel electrode system and Wien filter are used for extraction of the ion beam. Some results of computer simulations of the ion trajectories in such an ion optical system and the experimental results of the ion beam formation and transport are presented.
Performance of a low-duty pulsed Penning source for the medical synchrotron facility at NIRS
Authors: Sato Y. , Ogawa H. , Yamada S. , Yamada T. , Kohno T. , Kitagawa A. , Sato K. , Itano A. , Kanazawa M. , Takada E. , Noda K. , Sudou M. , Hirao Y.
Published: July 2002

A low-duty pulsed Penning source has been developed for the injector of the medical synchrotron facility at NIRS. The repetition rate is 1 Hz, with a duty factor of 4×10−4. The lifetime of the cathodes has been evaluated to be longer than two months, and that of the filament (cw) longer than one week. The intensity of multiply charged ions was increased by a factor of 10 compared with that obtained under dc operation. The reliability and stability were also improved. The results concerning the performance and some improvements of the source are discussed.
DIONÉ status report
Authors: Courtois A. , Faure J. , Gobin R. , Leroy P. A. , Visentin B. , Zupranski P.
Published: July 2002

The SATURNE synchrotron facility is equipped with an EBIS source for heavy ion nuclear-physics experiments. SATURNE is accelerating either conventional heavy ions as Kr30+ or polarized 6Li3+ produced in two external ion sources, injected and stripped inside DIONÉ. In this paper, the DIONÉ last performances will be given and recent developments as well: evaporative cooling experiments and the main options for a new EBIS project: RHÉA.
Studies of negative ion formation and interaction with a laser beam
Authors: Berkovits D. , Boaretto E. , Paul M. , Hollos G.
Published: July 2002

An experimental system composed of a standard negative ion source and an Nd:YAG laser is used to study the formation of negative ions by laser impact and the interaction of the laser with the negative ion beam. Using a Q-switched Nd:YAG laser (about 107 W/cm2) impinging on the solid FeS sample of a Cs-sputter source, pulses of negative ions of sulphur with a peak intensity of 3 mA and a width of 150 ns were observed. The time structure of the pulses is measured and shows a complex behavior, not yet fully understood. The same experimental system is used to analyze the production of rare negative ions in the lanthanide and actinide regions and to study their interaction with a laser beam. Cross sections for photodetachment in La− and Th− are measured.
Numerical study on production processes of vibrationally excited molecules in hydrogen negative ion sources
Authors: Fukumasa Osamu , Mutou Kouji , Naitou Hiroshi
Published: July 2002

Production processes of vibrationally excited hydrogen molecules and their effects on H− production are studied theoretically by using a set of particle balance equations in a steady-state hydrogen plasma. For vibrational excitation, three processes, i.e., fast-electron collisional excitation, neutralization of moleculer ions, and atom-surface recombination, are taken into account. Enhancement of vibrational excitation including vibrational distribution and H− production is obtained as a function of three different excitation processes.
BNL volume H− source
Authors: Prelec K. , Alessi J. G.
Published: July 2002

The volume H− ion source under development at Brookhaven is unique in that it has a toroidal plasma region, which feeds ions into the central extraction region through a conically shaped filter field. In pulsed operation, it produces 25 mA of H− in a 1 cm2 aperture, with an electron-to-H− ratio of ≊3. At 19 mA, a normalized, 90% emittance of 0.44 π mm mrad has been measured. Up to 50 mA has been extracted through a 1.87 cm2 aperture. Although not designed for steady state operation, up to 6 mA has been extracted dc. The addition of xenon to the discharge was found to improve the source output by 20%–70%. The circular magnetic cusp field geometry was found to be more favorable than radial cusp fields.
Low-energy injector design for SSC
Authors: Anderson O. A. , Chan C. F. , Leung K. N. , Soroka L. , Wells R. P.
Published: July 2002

An injector is being designed for SSC that will deliver 30 mA of H− at 35 keV, matched to the RFQ input. The H− ions are produced by a new rf-driven multicusp source that uses no cesium. The ions are extracted by a high-perveance accelerator designed to handle the large electron content of this type of source. The low-energy beam transport system (LEBT) uses electrostatic focusing; gas-neutralized magnetic focusing is ruled out because pulse lengths (7–35 μs) are shorter than plasma buildup times and because pulse intervals are longer than plasma decay times. Plasma buildup is prevented by the LEBT electric fields, so the system is noise free and stable. The advantages of electrostatic LEBTs were demonstrated by a previous design tested at LBL, which showed negligible emittance growth, confirming the results of computer modeling. The object of our new LEBT design is to preserve the emittance of the rf-driven source, which is less than 0.01 π mrad cm (normalized rms), and thereby produce a beam well within the SSC RFQ acceptance of 0.018 π mrad cm.
Influence of the rf excitation on the low energy broad ion beam characteristics (abstract)a)
Authors: Engemann J. , Korzec D. , Ningel K.-P. , Zrnc G.
Published: July 2002

Influence of the rf excitation in a capacitively coupled filamentless broad ion beam source with radial electrode configuration on the ion beam properties has been examined. Ion energy distribution was measured by use of a retarding field energy analyzer connected to a computer controlled data acquisition system. Influence of working conditions on the average ion energy and on the ion energy spread in the beam is described. Energy spread has typical values between 8 and 25 eV. Average ion energy can change due to variations of ion source working conditions (at constant extraction voltages) up to 60 eV. Increase of both the average ion energy and ion energy spread is observed with increasing rf power coupled to the plasma (20–100 W). This correlates to the increasing amplitude of plasma floating potential oscillation. Average ion energy decreases with increasing magnetic induction (0–75 mT) and with increasing pressure in the vacuum chamber (2×10−4–1.8×10−3 mbar) due to decreasing cathode oscillation amplitudes. Average ion energy decreases with increasing distance from the broad beam axis because of chromatical and spherical aberrations of the source extraction optics. Multiple peaks in the ion energy spectrum are observed. Their occurrence can be explained by charge exchange effects in the rf oscillating plasma sheath.
Operational characteristics of the ion source for the RFQ (abstract)
Authors: Thakur N. M. , Sethi R. C.
Published: July 2002

A high current, light ion duoplasmatron ion source was designed and has been brought into operation. This ion source has been designed to deliver up to a maximum of 20-mA light ion beam at an energy of 20 keV and will serve as an injector to the RFQ accelerator. The magnetic field mapping in the anode column region and studies of the filament characteristics have been carried out. The effects of the gas pressure, magnetic field, puller voltage, and screen voltage on the ion current have been studied to obtain the optimized values. The spatial beam distribution has been mapped in two orthogonal planes. So far the source has yielded about 12 mA of unanalyzed proton beam at an extraction voltage of 15 kV and arc current of 2.5 A. Tests at higher extraction voltages and the detailed beam emittance studies are being carried out.
Polarization of isotope separator beams at the Leuven Isotope Separator On Line
Authors: Vanderpoorten W. , Wouters J. , DeMoor P. , Schuurmans P. , Severijns N. , Vanneste L. , Vervier J.
Published: July 2002

A setup has been constructed which implements the techniques of grazing surface scattering and of the tilted foil method to produce nuclear polarized beams at the Leuven Isotope Separator On Line (LISOL), which is connected to the cyclotron Cyclone at Louvain-la-Neuve. This development makes it possible to use the intense radioactive ion beams (RIB), which will be available soon in the framework of the RIB−project at Louvain-la-Neuve, for polarization experiments. Especially solid state studies using polarized probe nuclei are envisaged in the beginning. First experiments to test the setup have been carried out and the results are very promising. The specific features of the setup are discussed together with the results of the test experiments.
Production of ions in open-ended region of coaxial-type microwave cavity
Authors: Yoshida Yoshikazu
Published: July 2002

Characteristics of a microwave planar magnetron ion source are described. This source, using a tuned coaxial-type cavity which excited the plasma at the end of the coaxial line, is able to produce a 100-mm-diameter by 20-mm-thick plasma disk that is well matched, stable, and allows continuous operation over a wide range of gas pressures. The isotropic microwave propagation from the surface of the magnetized plasma column to the center is one of the most effective coupling methods to obtain a high-density disk-like plasma. Argon ion current densities of 20–50 μA/cm2 have been obtained at energies ranging from a few to 70 eV. The beam uniformity is ±2% within a diameter of 5 cm. This new source has the potential to produce low-energy broad-beams.
Production of mixed metal–gas and pure metal ion beams with an electrodeless rf ion source in the low keV regime
Authors: Waldorf J. , Oechsner H.
Published: July 2002

Mixed metal–gas or even pure metal ion beams with current densities in the order of 1 mA cm−2 can be generated by electron beam evaporation of metals into the plasma chamber of an rf ion source operated in electron-cyclotron wave resonance. The operation principle of this novel ion beam source is described, and examples for the production of Ag+ and Cu+ beams with varying fractions of Ar+ ions are presented.
Electron temperature and plasma density of capacitive rf-discharges in noble gases
Authors: Wüst K.
Published: July 2002

Electrical discharges in He, Ne, Ar, and Kr at medium pressure (density of neutral atoms from 1021 to 1023 m−3), sustained by an rf electric field of 27.12 MHz, are investigated. Electron temperature and plasma density were measured with a Langmuir probe at 8, 13, and 20 W total discharge power. The plasma density was found to increase with the input power, whereas the electron temperature depends only weakly on the input power.
The rf-ion source ‘‘PRIS’’ with a metal ionizer chamber and a plasma embedded rf-coupling coil
Authors: Freisinger J. , Krempel-Hesse J. , Krumeich J. , Löb H. , Münz W. D. , Scharmann A.
Published: July 2002

The family of 10 cm diam ion sources PRIS is built for ion beam processing. It comprises two groups: The high energy version PRIS 10 HE and the low energy version PRIS 10 LE. The conventional rf-ion sources RIM 10 consist mainly of a quartz discharge chamber surrounded from an outside by a rf-induction coupling coil. In some cases, quartz cannot be used for manufacturing the discharge chamber (e.g., fragility of quartz, operating with condensible metal vapor). Therefore, in the PRIS sources, we replaced the quartz ionizer vessel by a metallic discharge chamber and put the rf antenna inside the discharge plasma. The performance data and the ion beam characteristics of PRIS are presented for argon and oxygen.
A simple, high efficiency, negative surface ionization source
Authors: Alton G. D.
Published: July 2002

A spherical-geometry, self-extraction negative ion source has been designed and fabricated. The source utilizes direct surface ionization to form negative ion beams resulting from interactions between high electron affinity gaseous elemental or molecular materials and a negatively biased, spherical-sector LaB6 surface ionizer maintained at ∼1300 K. The design features of this source and principles upon which the source is based are discussed in this report.
Negative metal ion and cluster source
Authors: Belykh S. F. , Evtukhov R. N. , Lysenko Ju. N. , Rasulev U. Kh.
Published: July 2002

Construction, characterization, and applications of a negative metal ion and cluster, M−n (n=1–3) source are described. The Au−n ions are produced by sputtering of a gold target during Cs+ bombardment. The Au− current was ∼ 10−6 A in the ion energy range of (3–25) keV. The Au− yield was an order of magnitude greater than the Au−2 yield. The value of the yield produced was dependent on an alkaline covering on the gold target. Alkaline coverage was varied by changing the target temperature and the Cs vapor stream. This source gives a possibility to produce both Au− and Au−n(n ≳ 1) ions under the same experimental conditions. The research results and applications of the source are presented.
Photoresonant plasma as an emitter of negative ions
Authors: Gorshkov O. A. , Rizakhanov R. N.
Published: July 2002

A new method of negative ion beam production is examined. We propose the use of the photoresonant plasma created in a mixture of an electronegative gas and alkaline metal vapor as an emitter of negative ions. It is shown theoretically that practical laser light power can provide the production of negative ion beams with intensities up to 10 mA/cm2. The attaching gases, for example, SF6, CCl4, CFCl3, etc. are considered as the main feed substance. These gases are usually used in up-to-date technologies. The expected advantages of such a method of negative ion beam generation are selective cleanliness of ion beam, low electron swarm, and absence of traditional discharge electrodes.
Effects of magnetic field on the output of duoplasmatron (abstract)
Authors: Öztarhan A.
Published: July 2002

The studies of three different duoplasmatrons differing in geometry and magnetic field structure showed that output was maximum when the intermediate electrode and anode pole pieces were saturated. One can also predict the total output by knowing the geometry and magnetic field configuration of duoplasmatron together with the running conditions.
High-current-density metal-ion implantation
Authors: Wilbur Paul J. , Wei Ronghua
Published: July 2002

Design features and preliminary performance data for an ion-implantation system that derives its broad, high-current-density beam directly from a steady, metal-plasma discharge in a high temperature graphite chamber are described. Metal vapor is supplied by drawing electron current to an anode-potential crucible to vaporize a pure metal in it. Argon used to start the discharge is turned off once sufficient metal vapor is present to sustain it. Extraction of metal-ion beams that are several centimeters in diameter at current densities ranging to several hundred μA/cm2 of titanium or copper onto targets 50 cm from the ion source is demonstrated. The system is simple, reliable, and easy to maintain.
Negative metal ion sources (invited)
Authors: Mori Yoshiharu
Published: July 2002

A negative metal ion source using plasma sputtering was developed at KEK in 1988 and since then various types of plasma sputter negative metal ion source have been constructed so far at various institutes. In this paper, after theoretical understanding of the negative metal ion formation process on metal surface by plasma sputtering is briefly reviewed, then characteristics and performance of various types of plasma sputter negative ion source which have been developed so far are presented.
The ECR ion source at the TRIUMF isotope separator TISOL
Authors: Buchmann L. , Vincent J. , D’Auria J. , Dombsky M. , McNeely P. , Roy G.
Published: July 2002

The installation at the isotope separator TISOL of a single-staged ECR (electron cyclotron resonance) ion source has been completed. The source can now routinely deliver radioactive species extracted from the production target when bombarded by 500 MeV protons. Among the radioactive species detected so far are isotopes of He, C, N, O, Ne, Cl, Ar, Kr, and Xe in single- and multiple-charge states as well as as molecular species. The yields obtained exceed in many cases those of the isotope separator ISOLDE at CERN. For stable species the source has shown high efficiencies often exceeding 10%. Details of the source construction, the isotope separator TISOL, and the variation of source parameters under operational conditions will be discussed.
Ion beam assisted deposition with a duoplasmatron (abstract)a)
Authors: Ensinger W. , Barth M. , Martin H. , Schröer A. , Enders B. , Emmerich R. , Wolf G. K.
Published: July 2002

One of the recent applications of ion sources is their use for ion beam assisted deposition of thin films and coatings. This method combines a coating technique such as evaporation or sputtering with bombardment with ions in the keV energy range. The required ions with defined energy, flux, and impact angle are delivered from an ion source. An apparatus for ion beam assisted evaporation with a duoplasmatron ion source is described. The features of the duoplasmatron with respect to application for ion beam assisted deposition such as beam shape, uniformity and intensity, ion-to-neutral ratio, and focused and defocused mode are discussed.
Suppression of magnetic granularity by transport current in (Bi,Pb)2Sr2Ca2Cu3Ox tapes
Authors: Pashitski A. E. , Polyanskii A. , Gurevich A. , Parrell J. A. , Larbalestier D. C.
Published: July 2002

Using the magneto-optical technique, transport current flow in (Bi,Pb)2Sr2Ca2Cu3Ox (BSCCO) Ag-sheathed tapes has been imaged. For zero transport current, I, the magnetization currents display a pronounced macroscopic magnetic granularity (on a scale larger than the actual grain size) characterized by a percolative distribution of current loops. By applying I≊0.8Ic this granular behavior was largely replaced by a more uniform current flow. Due to the significant dependence of Ic on E in BSCCO, the extent to which the magnetic granularity is observed strongly depends on the magnetic prehistory and on the electric field E, whose characteristic values are very different for magnetization and transport measurements.
Diode laser for in situ transient measurements in explosively formed aerosol clouds
Authors: Labbé J. L. D. S. , Bardon M. F. , Sellens R. W.
Published: July 2002

A diode laser based system was developed to monitor the mean concentration of aerosol clouds formed by cylindrical liquid fuel-air explosive (FAE) devices. Characteristics of the aerosol clouds are first described to provide an understanding of the nature of the flow which led to the engineering design of the system used. This paper then concentrates on the construction and testing of this optical system, which was designed to carry out four simultaneous in situ light extinction measurements through FAE clouds. The results of a typical liquid fuel dispersion test are presented and discussed as an illustration of the characteristics of the optical system in this application.
A Hall probe technique for characterizing high-temperature superconductors
Authors: Zhang Jue , Sheldon P. , Ahrenkiel R. K.
Published: July 2002

Thin-film GaAs Hall probes were fabricated by molecular beam epitaxy technology. A contactless technique was developed to characterize thin-film, high-temperature superconducting (HTSC) materials. The Hall probes detected the ac magnetic flux penetration through the high-temperature superconducting materials. The Hall detector has advantages over the mutual inductance magnetic flux detector.
Infrared thermographic analysis of polymer composites during ballistic impact
Authors: Hsieh C. Y. , Nagarajan S. , Zee R. H.
Published: July 2002

Heat is deposited in a target material when it is impacted by a projectile. The feasibility of using an infrared thermographic system to measure the surface temperature profile of composite materials under ballistic impact was demonstrated. Three types of composites were used in this instrumentation study to illustrate the effectiveness and limitation of this technique. The resolution of temperature was found to be better than ±1 K. The total temperature rise in the materials during impact can be attributed to the deformation required to perforate the material as well as frictional heat produced between the projectile and the hole. The heat deposited was calculated based of the temperature profiles. The relative contribution of the frictional effect to the total energy absorption was evaluated using a sequential shot technique. Effects of material properties and impact parameters on the peak temperature and heat deposition were determined. Graphite and PE composites are more effective than Kevlar composite in dissipating heat during the ballistic impact penetration process due to their higher thermal conductivity. The correlation between heat dissipation and extent of damage in composites was also investigated.
Micropipetting device operating under surface vibration motion of piezoelectric ceramic vibrator
Authors: Toda K. , Matsuyama K. , Takamori M.
Published: July 2002

A micropipetting device incorporating an ultrasonic pump is described, in which vibration motion on the side surface of a cylindrical piezoelectric vibrator plays the key role. A core tube surrounded by three bearings mounted at the central part of the rotor operates essentially for the pump function. The tube-type pipetting device has the merits of transportation of a minute, highly precise amount of liquid because of the electrically controllable characteristics.