bluuebunny/crossref_metadata_2025 huggingface dataset:
X-ray absorption spectroscopy of liquid surface
Authors: Watanabe Iwao , Tanida Hajime , Kawauchi Sigehiro , Harada Makoto , Nomura Masaharu
Published: July 2002

An apparatus has been constructed for x-ray absorption spectroscopy of elements at air/aqueous solution interface. Its surface sensitivity is gained from glancing incidence of synchrotron radiation under total reflection condition. The absorption is detected by total conversion He ion-yield method. This apparatus was operated at the beam line 7C of Photon Factory, where the incident photon beam comes from a sagittal focus double-crystal monochromator via a 70-cm-long bent mirror. The mirror focuses the beam vertically and changes the beam direction downward by 1 mrad to irradiate solution surface. The essential requirement of this technique, ripple-free liquid surface at accurate position, was attained by introducing a trough on a floating boat, continuous surface level monitoring, and an automatic Z-stage control. The x-ray absorption edge jump demonstrated that surface concentration of bromide ion follows the Langmuir type adsorption for tetraalkylammonuim bromide solution. By comparing the jump values for surface-active and -inactive bromide salt solutions, the detecting depth of the present technique was determined to be 8.8 nm. An extended x-ray absorption fine structure analysis of bromide ion segregated to the surface by stearyltrimethylammonium cation indicated that its solvation structure is different from that of bulk.
The performance of a microchannel-plate-based position sensitive detection system
Authors: Waterhouse D. K. , Williams J. F.
Published: July 2002

The characteristics and calibration of a microchannel-plate-based resistive-anode position-sensitive detector (PSD) are reported. Factors affecting the spatial uniformity of the fast rise-time timing signals and the position-dependent performance are discussed. When two such detectors are used for (e,2e) coincidence measurements, the detection efficiency of the PSDs must be uniform to within 5% for reliable quantitative comparisons of data acquired on different sections of the PSD. The relative efficiency in coincidence mode reflects the single detector efficiency uniformity. Such an apparatus was used to measure argon triple differential cross sections (TDCS) to determine the validity of the distorted wave Born approximation (DWBA) quantum scattering model. Relative to the argon 3s TDCS, the simultaneously acquired 3p TDCS is smaller than the DWBA prediction by a factor of 1.15±0.05.
In situ calibration of microchannel-plate-based x-ray pinhole camera for observation of magnetically trapped plasma
Authors: Kikuchi Y. , Kiwamoto Y. , Takahashi T. , Saito T. , Tatematsu Y. , Abe H. , Kajiwara K. , Yamaguchi N. , Tamano T.
Published: July 2002

The electronic amplification gain of a microchannel plate (MCP), as employed for detector and image amplifier of an x-ray pinhole camera, tends to decrease as the output current increases, posing problems both in quantitative analyses and in construction of a three-dimensional emissivity distribution. We report that the output-current dependent MCP gain is described in a simple empirical formula that is determined by an in situ calibration experiment using a steady-state low-temperature discharge plasma. We examine the validity of the formula affirmatively in correcting raw data of x-ray images of magnetically trapped hot plasma. It is also demonstrated that the correction leads to a three-dimensional distribution of soft x-ray emissivity in a quadrupole-mirror-trapped hot plasma that is consistent with other indirect measurements.
A tri-arc system for growing high-purity crystals of metallic materials
Authors: Fort D.
Published: July 2002

A tri-arc Czochralski crystal growth system, for preparing high-purity crystals of metallic materials, is described. To improve the environmental cleanliness within the chamber beyond that found in conventional tri-arc systems, the equipment is built to ultra-high-vacuum standards (although actual operation in vacuum is not possible) so that leaks into the system and degassing of contaminating gases from the chamber walls during growth are minimized. Crystal growths of the intermetallic compounds TiAl and HoCo 2 are illustrated.
Hydrogen gas detection via photothermal deflection measurement
Authors: Kalli Kyriacos , Othonos Andreas , Christofides Constantinos
Published: July 2002

A study of a thermal wave hydrogen sensor interrogated via transverse optical beam deflection spectroscopy is presented. The sensor is a thin film polyvinylidene fluoride film coated with a thin palladium layer. The sensitivity to hydrogen results from thermal boundary condition changes at the gas–film interface and depends upon the thermophysical properties of the gas. A simple one-dimensional model is developed to qualitatively and semi-quantitatively describe the experimental results and it shows good agreement with the experiment. Concentrations of 0.1% hydrogen in the presence of a balanced air mixture and at room temperature were measured for this sensor and they indicate possible sensitivities approaching 100 ppm.
A noise-rejecting current amplifier for surface atmospheric ion flux measurements
Authors: Harrison R. G.
Published: July 2002

Large area electrodes are required to determine atmospheric charge fluxes at the earth’s surface. These also act as antennas for power line hum, swamping the small atmospheric electric signals. A battery-powered head-amplifier resolving 0.025 pA is described here, which uses active compensation to substantially cancel the interference, allowing the atmospheric charge fluxes to be resolved in the presence of the interference. The overall response is nominally −100 mV/pA, with 30 dB of 50 Hz rejection. The head amplifier can drive a low impedance line.
Propagation constant in a cylindrical waveguide containing a magnetoactive plasma with small transverse dimensions
Authors: Gutiérrez-Tapia C. , Arzate-Plata N.
Published: July 2002

A review of the perturbation theory to calculate the wave propagation constant for a waveguide containing a plasma cylinder of small radius on its axis is presented. The wave propagation constant is important for implementing some diagnostic techniques. In the present paper, this constant for a column of a cold, magnetoactive plasma of small radius is calculated, assuming that the distribution of electron density in the plasma is a parabolic function of the radius, and it is shown that this result simplifies the determination of the average plasma density. Moreover, it is shown that for the particular case of an H11 mode, the result obtained at the electron cyclotron resonance, can be used to gauge the waveguide as well as to describe a simplified model of the plasma heating in an electron cyclotron resonance plasma source.
Production of intense beams of highly charged metallic ions from RIKEN 18 GHz electron cyclotron resonance ion source
Authors: Nakagawa T. , Ärje J. , Miyazawa Y. , Hemmi M. , Chiba T. , Inabe N. , Kase M. , Kageyama T. , Kamigaito O. , Kidera M. , Goto A. , Yano Y.
Published: July 2002

We successfully produced intense beams of highly charged metallic ions from various kinds of organic metallic compounds by the metal ions from volatile compounds method and solid materials in RIKEN 18 GHz electron cyclotron resonance ion source (ECRIS) (e.g., 135 eμA of Fe11+, 80 eμA of Fe13+, 10 eμA of Os29+, and 1 eμA of Os37+). Using this ECRIS the ion confinement time of highly charged ions was determined under the pulsed mode operation.
Status of the laser ion source at the Leuven isotope separator online
Authors: Kudryavtsev Yuri , Franchoo Serge , Gentens Johnny , Huyse Mark , Raabe Riccardo , Reusen Ils , Van Duppen Piet , Van den Bergh Paul , Vermeeren Ludo , Wöhr Andreas
Published: July 2002

An online laser ion source has been used at the Leuven isotope separator online for the production of pure beams of exotic nuclei. The operational principle of the ion source is based on the element-selective multistep laser resonance ionization of nuclear reaction products thermalized and neutralized in a high-pressure noble gas. A number of improvements has been carried out to obtain stable and reproducible operation. The ion source has been optimized for the production of beams of exotic nuclei, created in proton-induced fission reactions. The efficiency of the ion source has been improved by incorporating the sextupole ion guide to separate laser-produced ions from the gas jet and to transport them to the acceleration stage of the mass separator. A gas purification system has been installed to purify the noble gas down to ppb level. High selectivity and efficiency of the ion source allowed to collect nuclear spectroscopic information for the neutron deficient Ni54 and neutron-rich Ni68–74 isotopes.
Development of 18 GHz electron cyclotron resonance ion source with high-voltage extraction configuration
Authors: Kitagawa A. , Muramatsu M. , Yamada S. , Okada T. , Yamamoto M. , Uno K. , Biri S. , Vamosi J. , Zhou X. H.
Published: July 2002

An 18 GHz ECR ion source with high-voltage extraction configuration (NIRS-HEC) has been developed for the Heavy Ion Medical Accelerator in Chiba (HIMAC), National Institute of Radiological Sciences (NIRS). NIRS-HEC has a high extraction voltage of up to 60 kV in order to reduce the unwanted space charge effects at the extraction region. NIRS-HEC also has a strong magnetic field. A radial size of the plasma chamber is made as small as 40 mm, so that a sextupole field strength of 11 kG and an axial field strength of 12 kG are easily obtained. The experimental data show that a high extraction voltage is effective to realize the high beam intensity when the extraction current density is high. It is consistent with the computer calculations of the FUGUN code and TRAPCAD code.
Dual chamber PIG ion source with plasma transport by crossed E×B fields
Authors: Bogomolov S. L. , Kutner V. B.
Published: July 2002

The results of investigations of the dual chamber PIG ion source with plasma transport by crossed E×B fields are presented. The aim of the experiments was to study the possibility of ion production in the PIG source in two stages: plasma production in the first chamber and further ionization in the second chamber. The experiments on beam extraction from both chambers by two independent extracting electrodes have shown that the current extracted from the second chamber is determined mainly by the plasma flux from the first chamber. The charge state distribution of ions extracted from the second chamber is shifted to higher charge states comparing with that measured for the first chamber.
Design of a parallel-plate energy spread analyzer
Authors: Yuan D. , Kuo T. , Cojocaru G. , Jayamanna K. , Mcdonald M. , Schmor P. , Yin Y.
Published: July 2002

A 45° parallel-plate energy spread analyzer has been designed and built for the ISAC project at TRIUMF. It features an energy resolution of ⩽0.04% and a spectrometer constant of k=1.29. Nineteen 0.1 mm by 10 mm metal guard frames with 1 MΩ resistors are used to equalize the electric field in the analyzer to an order of ⩽0.5%. Electric field simulation is done by a code POISSON. This article describes the design of the analyzer. Preliminary experimental results are also presented.
Development of the radio frequency driven H- ion source for the National Spallation Neutron Source
Authors: Leitner M. A. , Gough R. A. , Leung K. N. , Rickard M. L. , Scott P. K. , Wengrow A. B. , Williams M. D. , Wutte D. C.
Published: July 2002

The ion source for the 1 MW National Spallation Neutron Source (NSNS) is required to provide 35 mA of H- beam current (1 ms pulses at 60 Hz) at 65 keV with a normalized root-mean-square emittance of <0.2 pi mm mrad. The same ion source should be able to produce 70 mA of H- at 6% duty factor when the NSNS is upgraded to 2 MW of power. For this application, a radio-frequency driven, magnetically filtered multicusp source is being developed at Lawrence Berkeley National Laboratory. The design of this R and D ion source, which is equipped with a cesium dispenser-collar, a fast ion beam prechopper (rise times <100 ns) and a strong permanent-magnet insert for electron deflection, will be presented.
Design aspects of a compact, single-frequency, permanent-magnet electron cyclotron resonance ion source with a large uniformly distributed resonant plasma volume
Authors: Liu Y. , Alton G. D. , Mills G. D. , Reed C. A. , Haynes D. L.
Published: July 2002

A compact, all-permanent-magnet, single-frequency electron cyclotron resonance (ECR) ion source with a large uniformly distributed ECR plasma volume has been designed and is presently under construction at the Oak Ridge National Laboratory. The central region of the field is designed to achieve a flat field (constant mod-B) which extends over the length of the central field region along the axis of symmetry and radially outward to form a uniformly distributed ECR plasma “volume.” The magnetic field design strongly contrasts with those used in conventional ECR ion sources where the central field regions are approximately parabolic and the resulting ECR zones are “surfaces.” The plasma confinement magnetic field mirror has a mirror ratio Bmax/BECR of slightly greater than 2. The source is designed to operate at a nominal rf frequency of 6 GHz. The central flat magnetic field region can be easily adjusted by mechanical means to tune the source to the resonant conditions within the limits of 5.5–6.8 GHz. The rf injection system is broadband to ensure excitation of transverse electric modes so that the rf power is largely concentrated in the resonant plasma volume which lies along and surrounds the axis of symmetry of the source. Because of the much larger ECR zone, the probability for absorption of microwave power is dramatically increased, thereby increasing the probability for acceleration of electrons, the electron temperature of the plasma, and, consequently, the “hot” electron population within the plasma volume of the source. The creation of an ECR “volume” rather than a “surface” is commensurate with higher charge states and higher beam intensities within a particular charge state. The source has also been designed so that it can be easily converted into a conventional magnetic field geometry source so that comparisons of the performances of the “volume” and “surface” forms of the source can be easily made. The design features of the source and rf injection system will be described in detail in this article.
Absolute calibration of a flat field spectrometer in the wavelength range 10–70 Å
Authors: Saemann A. , Eidmann K.
Published: July 2002

We characterize an x-ray spectrometer in the wavelength range 10–70 Å. The instrument has been designed for the study of the soft x-ray emission from plasmas generated with intense sub-ps laser pulses. It uses a flat field reflection grating with 2400 lines per mm as dispersing element and an x-ray charged coupled device (CCD) as detector. The sensitivity of the spectrometer and CCD detector has been absolutely calibrated by means of a ns-laser generated gold plasma of well known x-ray conversion efficiency. The calibration procedure is explained in detail. Finally, we present examples of spectra emitted by a sub-ps laser plasma. From the spectra follows a resolving power of 150–350 and a low conversion efficiency into the second diffraction order of the flat field grating of only a few %. The measured frequency averaged total conversion of laser energy into x-ray energy emitted into 2π is in the range of 2.4×10−4 up to 6.2×10−3 depending on the material of the solid targets.
The simple spot-welding apparatus
Authors: Hiraoka Takeshi
Published: July 2002

A simple spot-welding apparatus has been developed for the fabrication of stable electrodes used in the measurement of transport properties in condensed matter physics. The apparatus is especially suited for the use of brittle and small sized samples of rare-earth intermetallic compounds (REICs). The spot welding is made by a sharp pulse (150 A and several μs), generated by the precise time generation IC in a capacitor discharge circuit, to avoid breaking the sample. Stable electrodes of six 15 μ Au wires can be made on a REIC sample with length less than 1 mm.
Apparatus for the laser-optical measurement of stress in thin films: Results on CuNi
Authors: Brückner W. , Griessmann H.
Published: July 2002

Dedicated to the investigation of the temperature dependence of mechanical stress in thin films (up to 700 °C in vacuum), a sensitive apparatus has been built up to measure the substrate curvature of a beam-shaped sample by deflection of a splitted laser beam from both ends. The measuring sensivity is about 0.1 MPa for a typical film thickness of 1000 nm. The long-term value over 24 h is about ±0.5 MPa due to ambient-temperature drifts. The determination of absolute stress magnitudes is possible by comparative measurements between the measuring bending beam and a reference one before and after film deposition or film removal. Investigations on sputtered Cu0.57Ni0.42Mn0.01 films have shown that (1) the stress relaxes above 300 °C and remains nearly constant between 430 and 550 °C during the first heating, (2) a hysteresis behavior occurs during the repeated cycles, and (3) the stress at room temperature increases a little with the cycle number.
Hermetic holder for x-ray powder diffraction of air-sensitive differential scanning calorimetry samples
Authors: Lexa Dusan
Published: July 2002

The design and performance of a hermetic holder for the preservation of air-sensitive differential scanning calorimetry samples during powder x-ray diffraction are described. The holder was developed specifically for the Perkin–Elmer DSC-2C type samples to be analyzed in a Rigaku D/max-2400V diffractometer. It could, however, easily be modified for use with a variety of diffractometers and larger samples. This holder provides simplicity of operation superior to previous holders at a fraction of the cost of environmental chambers.
On the recovery of a spark gap in a fast discharge circuit
Authors: Biswas D. J. , Nilaya J. P. , Chatterjee U. K.
Published: July 2002

We have shown theoretically that the maximum repetition rate attainable with a switch for both resistive and resonant charging is independent of the value of energy transferred through the switch in case of a very fast discharge. Experimental confirmation of this has been achieved with a resistively charged 20 kV pulse generator (C was varied from ≅5 to 35 nF) switched by a spark gap into a load whose resistance varied from few ohms to a kΩ.
Frequency stabilization of a radio frequency excited CO2 laser using the optogalvanic effect
Authors: Choi Jong-Woon , Chung Young-Boong , Strzelec Marek , Kopica Mirek
Published: July 2002

Frequency stabilization of a rf excited CO2 laser on the peak of the Doppler broadened gain curve using the optogalvanic effect generated from the laser itself is achieved. The optogalvanic signal is directly coupled from a rf discharge chamber via a capacitor into a detector and a lock-in stabilizer. The frequency stability is estimated to be better then 3×10−8.
Electrostatic cage “Stark barrel” for rapidly switching a uniform electric field through arbitrary angles
Authors: Horn J. L. , Homan D. M. , Hwang C. S. , Fuqua W. L. , MacAdam K. B.
Published: July 2002

A cylindrical arrangement of electrodes, together with control electronics, is described that provides uniform electric fields over cm3 volumes in a vacuum, whose angle and magnitude can be switched on a μs time scale. Full 360° field rotation is achieved, and the device allows access for particle or light beams from all sides. Both numerical and analytic descriptions of the general fields are given. Extension to full three-dimensional field control and other variations are described. The device, which was originally designed for crossed-beam collision experiments with keV energy ions and laser-excited Rydberg atoms in field-directed Stark states or coherent-elliptic states, may be more generally useful in atom trapping and cold collisions or in materials and surface science.
Liquid helium transfer using a mass-flow controller
Authors: Fujii Yusaku , Miki Yukinobu , Shiota Fuyuhiko , Watanabe Ritsu
Published: July 2002

An automated liquid helium transfer method using a mass-flow controller, by means of which an empty cryostat at room temperature can be filled with liquid helium without thermal shock, has been developed. Before liquid helium collection is initiated, mass flow is controlled to be constant. After the start of liquid helium collection, mass flow is controlled so that the differential pressure of the empty cryostat against the storage Dewar containing the liquid helium is of the proper value to overcome the height difference due to the transfer tube. A mass-flow controller, a vacuum pump, a differential pressure sensor, a liquid helium level sensor and a computer with suitable software are required to replace the conventional manual transfer by this method.
A Thomson scattering diagnostic for measurements in the divertor region of TCV
Authors: Behn R. , Rommers J. H. , Pitts R. A. , Pietrzyk Z. A. , Chavan R. , Marletaz B.
Published: July 2002

For future divertor studies on TCV measurements of electron temperature and density and their spatial gradients along open flux surfaces will be of major interest. A Thomson scattering system is proposed for this purpose, which takes advantage of the good access via horizontal ports on three vertical levels. The modular design of the existing Thomson scattering diagnostic on TCV offers the possibility to modify it for simultaneous measurements in the main plasma and in the divertor region using the same laser. Arranging for a second passage of the laser beam at a radial position shifted towards the inside, measurements can be made along the open flux surfaces between the X point and the outer divertor strike point. The optical system is designed to share the camera lens with the existing system. After installation of additional fiber bundles and another set of filter spectrometers, the system will be capable of measuring temperature and density at ten selected locations in the divertor zone with a resolution in the vertical direction of 15 mm. Using numerical simulations, a set of interference filters has been selected to cover the range from 100 to 5 eV.
Electronic signal regulator for constant resolution inelastic electron tunneling spectroscopy
Authors: Seman T. R. , Mallik R. R.
Published: July 2002

A relatively simple and inexpensive ac signal regulator is described which facilitates constant resolution inelastic electron tunneling spectroscopy (IETS). Constant resolution is achieved by maintaining an approximately constant ac modulation voltage across IET junctions during spectral scans. The regulator circuit is based upon a field-effect transistor optoisolator with appropriate feedback control acting as a voltage comparator. It is modular in design and can easily be added in the signal path of existing IET spectrometers. A complete schematic diagram of the circuit is provided as well as a discussion on the theory of operation. IET spectra obtained from tunnel junctions with various degrees of nonlinear conductance-voltage behavior are presented with, and without, the circuit. Analysis of these spectra shows that the regulator increases the spectrometer’s signal-to-noise ratio, produces no distortion and, in the case of severely nonlinear junctions, reveals spectral features at mid to high bias, which are otherwise difficult or impossible to detect. Additionally, the regulator offers approximately an order of magnitude increase in data acquisition rate over software algorithms for maintaining constant resolution via IEEE-488 control of spectrometer instrumentation. Our results suggest that such a modular analog regulator would be a valuable addition to IET spectrometers, especially for workers wishing to investigate severely nonlinear IET junctions.
Nanometer-scale patterning and individual current-controlled lithography using multiple scanning probes
Authors: Wilder Kathryn , Soh Hyongsok T. , Atalar Abdullah , Quate Calvin F.
Published: July 2002

Scanning probe lithography (SPL) is capable of sub-30-nm-patterning resolution and nanometer-scale alignment registration, suggesting it might provide a solution to the semiconductor industry’s lithography challenges. However, SPL throughput is significantly lower than conventional lithography techniques. Low throughput most limits the widespread use of SPL for high resolution patterning applications. This article addresses the speed constraints for reliable patterning of organic resists. Electrons field emitted from a sharp probe tip are used to expose the resist. Finite tip-sample capacitance limits the bandwidth of current-controlled lithography in which the tip-sample voltage bias is varied to maintain a fixed emission current during exposure. We have introduced a capacitance compensation scheme to ensure continuous resist exposure of SAL601 polymer resist at scan speeds up to 1 mm/s. We also demonstrate parallel resist exposure with two tips, where the emission current from each tip is individually controlled. Simultaneous patterning with multiple tips may make SPL a viable technology for high resolution lithography.
Miniaturized scintillation technique for protein solubility determinations
Authors: Feeling-Taylor Angela R. , Banish R. Michael , Elison Hirsch Rhoda , Vekilov Peter G.
Published: July 2002

We have developed a miniaturized (volume of crystallizing solution ∼100 μl) technique for the determination of protein solubility as a function of temperature. After nucleation, crystals are detected by the light they scatter. Then the temperature at which a solution with the initial concentration is in equilibrium with the crystals is sought by stepwise, equilibrium dissolution of the crystals. The approach to solubility from the side of dissolution provides for higher accuracy of the determinations. The method was used to determine the temperature dependence of the solubility of human hemoglobin (Hb) C, for which high-resolution x-ray crystallography data are needed to understand the structural basis for the drastically different in vivo aggregation/crystallization behavior of β6 Hb mutants.
Simple method to reduce the dead time of multichannel analyzers
Authors: Puzović J. M. , Aničin I. V.
Published: July 2002

A method to reduce the dead time of multichannel analyzers which uses multiple sample-and-hold circuits in the input circuitry of the analyzer’s analog-digital converter is proposed. Due to the exponential distribution of time intervals between successive pulses, the dead time is greatly reduced with even a small number of sample-and-hold circuits. The effects of the method are analyzed and discussed by means of Monte Carlo simulations.
Construction of the multilayered-mirror monochromator beam line for the study of synchrotron radiation stimulated process
Authors: Mekaru Harutaka , Tsusaka Yoshiyuki , Miyamae Takayuki , Kinoshita Toyohiko , Urisu Tsuneo , Masui Shin , Toyota Eijiro , Takenaka Hisataka
Published: July 2002

A multilayered-mirror (MLM) monochromator beam line designed specially for synchrotron radiation (SR) stimulated process experiments has been constructed for the first time. The beam line was designed by the criteria; a beam spot size on the sample surface ⩾3×3 mm2, a density of total irradiated photons ⩾1018 photons/cm2 (for an irradiation time of a few tens of minutes to a few hours), and low-energy background ⩽1% of the output. The performance of the beam line was evaluated by measuring the transmitted photon flux of an Al filter around the Al L2,3 absorption edge and by measuring the photoemission spectra of Ta using the output beam as an excitation light source. The Al thin film deposition was successfully demonstrated by using the monochromatized output beam. We conclude that this MLM monochromator performs sufficiently well to study the excitation energy dependence in SR-stimulated processes.
Microwave-induced acoustic imaging of biological tissues
Authors: Wang Lihong V. , Zhao Xuemei , Sun Haitao , Ku Geng
Published: July 2002

We present tomographic imaging of biological tissues by use of microwave-induced acoustic signal. It was demonstrated that the acoustic signal was proportional to the intensity of the incident microwave and was related to the absorption property of microwave in the medium. Pulsed microwave radiation was used to illuminate the samples. Absorbed microwave energy caused thermoelastic expansion that radiated acoustic waves. A focused ultrasonic transducer detected the time-resolved acoustic signals. Each acoustic signal was converted into a one-dimensional image. A linear scanning of the ultrasonic transducer yielded multiple one-dimensional images, which formed a two-dimensional image. The imaging contrast is based on the difference in the dielectric constants among biological tissues. Because of the large contrast in microwave absorption among different tissue types, microwave-induced acoustic tomography could potentially provide a new modality for detecting early-stage cancers.
Frequency stabilized distributed feedback laser diode system at 1.323 μm using the modulated Zeeman effect
Authors: Schwarze Craig R. , Rentz Julia H.
Published: July 2002

We present the design of a highly stable, compact system that achieves the frequency stabilization of a distributed feedback laser diode to an excited-state argon transition at 1.323 μm. The argon atomic reference is generated in a miniature hollow cathode lamp. A small a/c magnetic field is used to Zeeman split the transition and both right- and left-circularly polarized light are used to generate the error discriminant signal and cancel laser relative intensity noise. The output does not contain any frequency modulated components and has been measured to have long-term frequency stability of better than 8×10−11 (20 kHz) with the Allan Variance technique.
Calibration of single-mode content of semiconductor diode laser emission
Authors: Dinklage A. , Solyman Samir , Wilke C.
Published: July 2002

Spectral radiance of single-mode semiconductor diode laser emission was investigated. The contribution of broadband and sideband emission was determined by absorption measurements at an optically thick absorption line. Essential single-mode operation was controlled by a Fabry–Perot interferometer. Since no additional dispersive elements are used, spatial displacement is avoided, which is essential for spatially resolved spectroscopy.
Reducing loss of a hole-coupled resonator for a free-electron laser with partially reflecting meshes
Authors: Shu Xiaojian , Wang Yuanzhang , Jiang Yunqing , Huo Yukun
Published: July 2002

We propose a method to reduce the loss of a hole-coupled resonator for a free-electron laser (FEL) oscillator. A mesh with a reflectivity of 50%–70%, which is quite easy to be produced, can be used to cover the hole. Both the extraction and diffraction losses can be reduced effectively to obtain higher net gain, which allows the FEL oscillator to be operated under worse conditions. These advantages and properties are confirmed by numerical simulations using a three-dimensional code with the parameters of a compact far-infrared FEL oscillator built at the China Academy of Engineering Physics. Furthermore, it can be used as a electron transparent mirror to make the FEL device more compact and less expensive.
A simplified GaAs polarized electron source
Authors: Al-Khateeb H. M. , Birdsey B. G. , Bowen T. C. , Green A. S. , Johnston M. E. , Gay T. J.
Published: July 2002

We report operational and construction details of a simplified GaAs polarized electron source. It is contained in a modified 4.63 in. Conflat four-way cross, and uses a single 56 ℓ/s turbomolecular pump. The design incorporates multiple cesiators to extend source lifetime, a new spring-clamp GaAs crystal mounting design to provide uniform crystal heating, and a very simple tubular 90° electrostatic deflector. We also discuss matters related to preparing, heat cleaning, and activating the GaAs crystal.
Ionization equilibria and efficiency for electron cyclotron resonance ion sources
Authors: Cavenago M.
Published: July 2002

Kinetic equilibria implications on the ionization efficiency ηi of electron cyclotron resonance (ECR) ion sources when used as a charge breeder are discussed. The ion density distribution n(i) where i is the ion charge state is here expressed by a properly factorized formula, which allows analytic consideration. Agreement with some numerical simulation is excellent. In the case of low ion recombination rates, a detailed solution is given, and some relevant approximation of ionization rate Si and ionization energies are proposed. A useful approximation log(Si)=a−(cs−k3)i is found, with a and cs mainly related to ionization energies and macroscopic plasma parameters, such as the hot electron density nh and temperature Th, while k3 is related to the ambipolar electrostatic potential. Formulas for the charge state at which efficiency is maximum and for the maximum value are written in detail.
Very broad vacuum arc ion and plasma sources with extended large area cathodes
Authors: Ryabchikov A. I. , Stepanov I. B. , Dektjarev S. V. , Lukonin E. I. , Shulepov I. A.
Published: July 2002

Two versions of vacuum arc sources for producing accelerated ion beams and plasma flows are described. The sources are distinguished by use of a dc vacuum arc discharge for plasma generation on the basis of a simple linear or coaxial plasma gun with extended large area (70 300 and 1500 cm2) cathodes and microparticle filtering system. The dc vacuum arc discharge combined with the diode extraction system enables us to use the single source for dc mode of plasma flow formation and repetitively pulsed mode of ion beam generation. Experimental and numerical results are presented on the repetitively pulsed accelerated ion beam formation in the vacuum arc sources with large area cathodes.
Improvement of microwave ion source for higher B+ ion current
Authors: Okada M. , Sakudo N. , Hayashi K. , Ikenaga N. , Okuji S. , Onogawa T. , Maesaka T. , Nishiyama Y. , Takahashi M. , Ito S. , Ito H.
Published: July 2002

Microwave ion sources have many advantages over dc-discharge ion sources, such as long lifetime and high current for most ion species. But B+ ion current has been the only disadvantage. Here we experimentally study how to get higher B+ ion current by optimizing the shape and volume of the source chamber as well as by increasing the secondary electron emissivity of the chamber wall. We carry out the experiment with regard to the maximum ion beam, lifetime, and dynamic range of the beam current for various ion species. Then, we compare the data with those of the Bernas-type ion source that has been widely used in semiconductor manufacturing factories. As a result of the improvement, the performance of all the above-mentioned aspects of the microwave ion source exceed those of the Bernas-type ion source.
Electron cyclotron resonance charge breeder (invited)
Authors: Sortais P. , Bruandet J. F. , Bouly J. L. , Chauvin N. , Curdy J. C. , Geller R. , Lamy T. , Sole P. , Vieux-Rochaz J. L.
Published: July 2002

Initially developed for radioactive ion beam production, the electron cyclotron resource (ECR) charge breeder shows that the beam injection of a primary beam inside an ECR ion source is a very general process for beam production. In this article we will review the latest results obtained on the ISN Grenoble test bench for the production of clockwise (CW) or pulsed metallic ion beams with the so-called “1+/n+” method. New results are given for CW operation where the efficiency is particularly optimized for application to multicharged radioactive ion production (for example, 3.5% for Zn1+→Zn9+, 4.2% for Pb1+→Pb24+, 5% for Rb1+→Rb15+). Different ion sources have been used to study the variation of the efficiency as a function of the energy of the 1+ primary beam. Charge state distributions are especially measured for Pb and Rb ions. A new mode of operation, the electron cyclotron resonance ion trap breeder/buncher, which permits the trapping and the bunching of the n+ ion beam is demonstrated and experimentally verified. The injection of a 400 nAeRb1+ ion beam leads to a 11.5 μAe peak current of the Rb15+ ion beam extracted during the first ms. The temporal evolution of the cumulated particle transformation and trapping efficiency is measured in the case of Rb15+. This new method shows that it is possible to modify the time structure of the injected beam, just by trapping the ions inside the plasma and re-extracting them by using the “afterglow pulsed mode.” It will also be shown that it is possible to produce “multi-charged metallic ions” by using a primary source for the dissociation of a complex molecule and then by injecting the low charge state beam inside the multicharged electron cyclotron resonance ion source. A preliminary example will be presented for the production of U26+ by injection of U3+ obtained from dissociation of UF6 gas.
Negative ion sources for high energy accelerators (invited)
Authors: Peters J.
Published: July 2002

Due to the development of reliable H− ion sources, charge-exchange injection into circular accelerators has become routine. For preacceleration of heavy ions tandem generators with a stripping foil are used in order to double the energy with the same high voltage. This article reviews recent developments in negative hydrogen ion sources. The underlying physics, operating parameters, and beam characteristics of selected sources will be described and compared.
Improvement of the lifetime of radio frequency antenna for plasma generation
Authors: Reijonen J. , Eardley M. , Gough R. , Keller R. , Leung K. , Thomae R. , Pickard D. , Williams M. D.
Published: July 2002

At Lawrence Berkeley National Laboratory different antenna protection schemes have been investigated for the radio frequency-driven multicusp ion source. It was found that the antenna lifetime can be greatly enhanced by an additional shielding, which consists of porcelain, quartz or boron nitride. Different antenna configurations and their influence on the plasma generation will be discussed. Antenna life time greater than 500 hours continuous wave operation has been demonstrated in hydrogen plasma using a novel quartz antenna design.
Development of a steady-state microwave ion source with large spherical electrodes for geometrical focusing
Authors: Kawakami T. , Shimada T. , Yonezawa T. , Ueda Y. , Nishikawa M.
Published: July 2002

A steady-state electron cyclotron resonance ion source with large spherical electrodes has been developed to study the plasma wall interaction, erosion mechanism, and hydrogen retention of first wall materials in a nuclear fusion reactor. Discharge characteristics of the ion source were studied in terms of microwave power, magnetic field configuration, and gas (H2) pressure. Ion saturation current density Jis of about 21 mA/cm2 near the electrodes (target value is 20 mA/cm2) was achieved with microwave power of 3.0 kW and magnetic field of 2.3 kG at an optimal gas pressure. The measurement of Jis was made by a Langmuir probe. It was found that the dependence of ion saturation current density on the magnetic field was different between high (>5 mTorr) and low (<5 mTorr) pressure. The change of the gas inlet position from the center of the plasma production chamber to near the microwave input window gave higher ion saturation current density.
Investigation of a radio frequency-driven multicusp ion source of the diagnostic neutral beam for the Hanbit device at Korea Basic Science Institute
Authors: Yang H. L. , Yoo S. J. , Hwang S. M. , Chung K. H.
Published: July 2002

A radio frequency-driven multicusp ion source has been fabricated and tested as a part of the development of a diagnostic neutral beam for the Hanbit magnetic mirror device [S. M. Hwang et al., Trans. Fusion Technol. 35, 99 (1999)]. Hydrogen plasma produced by a three-and-one-half turn antenna and rf power system with 2.5 kW, continuous wave (cw) 1.874 MHz was extracted through a single-aperture accel-decel system. The first results of the ion beam extraction experiments are described in this article.
Emittance improvement of the electron cyclotron resonance high intensity light ion source proton beam by gas injection in the low energy beam transport
Authors: Beauvais P-Y. , Ferdinand R. , Gobin R. , Lagniel J. M. , Leroy P.-A. , Celona L. , Ciavola G. , Gammino S. , Pottin B. , Sherman J.
Published: July 2002

SILHI is the ECR high intensity light ion source studied in France at C.E.A. Saclay. This is the source for the injector of the high intensity proton injector prototype developed by a CNRS-IN2P3 collaboration. 80 mA at 95 keV beams with a rms normalized r–r′ emittance lower than 0.3 π mm mrad and a proton fraction better than 85% are currently produced. Recently, it has been found that the injection in the low energy beam transport of a buffer gas had a strong effect on the emittance measured 1 m downstream of the focusing solenoid. By adding several gases (H2, N2, Ar, Kr), improvements as great as a factor of 3 have been observed. The emittance has been measured by means of an r–r′ emittance measurement unit equipped with a sampling hole and a wire profile monitor, both moving across the beam. Simultaneously, the space charge compensation factor is measured using a four-grid analyzer unit. In this article all results of these experiments are presented and discussed. A first explanation of the emittance reduction phenomenon and possible consequences on the injector operation is given.
Optimization of Cs deposition in the 1/3 scale hydrogen negative ion source for the large helical device-neutral beam injection system
Authors: Oka Y. , Takeiri Y. , Belchenko Yu. I. , Hamabe M. , Kaneko O. , Tsumori K. , Osakabe M. , Asano E. , Kawamoto T. , Akiyama R.
Published: July 2002

A compact cesium deposition system was used for direct deposition of cesium atoms and ions onto the inner surface of the 1/3 scale hydrogen negative ion source for the large helical device-neutral beam injection (LHD-NBI), system. A small, well defined amount of cesium deposition in the range of 3–200 mg was tested. Negative ion extraction and acceleration were carried out both in the pure hydrogen operation mode and in the cesium mode. Single Cs deposition of 3–30 mg to the plasma chamber has produced temporary 2–5 times increases of H− yield, but the yield was decreased within several discharge pulses to the previous steady-state value. Two consecutive 30 mg depositions done within a 3–5 h/60 shot interval, produced a similar temporary increase of H− beam, but reached a large H− yield steady-state value. Deposition of larger 0.1–0.2 g Cs portions with a 20–120 h/150–270 shot interval improved the H− yield for a long (2–5 days) period of operation. Directed depositions of Cs to the various walls of the plasma chamber showed approximately the same H− increase. Deposition of 0.13 g Cs to a surface polluted by a water leak, produced a temporary increase, and a H− steady-state level similar to that from a single 30 mg cesium deposition. Deposition of 0.1 g with a cesium plasma produced one half the H− yield obtained by deposition of the same amount of cesium atoms. A higher steady-state H− current value and a smaller rate of H− yield decrease was recorded during the eight filament discharge operation, as compared to the 12 filament operation at the same discharge power.
Reduction in time jitter for free-running, nanosecond-pulsed, Xe lamp by supplementary illumination with blue light-emitting diode
Authors: Komatsu Toshiyuki , Iwata Tetsuo , Araki Tsutomu
Published: July 2002

We have found out a phenomenon that the large fluctuation in the repetitive frequency of emission from a free-running, nanosecond-pulsed, Xe lamp can be reduced markedly by illuminating the lamp electrodes with a light flux from a blue light-emitting diode. There was a wavelength dependency in the stabilization effect. The upper limit of the effective wavelength of the illumination light was around 750 nm, but no power dependency was observed between 0.5 and 3.0 mW. The reduction in the fluctuation was observed only for a Xe lamp manufactured by a specific maker, where materials with low work function elements were mixed in its cathode electrode for the purpose of improving standard direct current arc operation. In order to evaluate the fluctuation quantitatively, we have constructed a system for measuring time intervals between every pulsed emissions. Our conclusion is that the reduction in the fluctuation is due to photoelectrons emitted from the surface of the cathode electrode and thereby the breakdown voltage for discharge in the lamp was maintained at a fixed value.
Quantitative measurement of sliding friction dynamics at mesoscopic scales: The lateral force apparatus
Authors: Hendriks C. P. , Vellinga W. P.
Published: July 2002

We describe an apparatus designed to quantitatively measure friction dynamics at the mesoscopic scale. This lateral force apparatus, LFA, uses double parallel leaf springs in leaf-spring units as force transducers and two focus error detection optical heads, optical heads, to measure deflections. The design of the leaf-spring units is new. Normal spring constants are in the range of 20–4000 N/m, and lateral spring constants are 7–1000 N/m. The optical heads combine a 10 nm sensitivity with a useful range of about 100 μm. The proven range of normal forces is 400 nN–150 mN. The leaf-spring units transduce friction and normal forces independently. Absolute values of normal and friction forces are calibrated. Typical errors are less than 10%. The calibration is partly in situ, for the sensitivity of the optical heads, and partly ex situ for the normal and lateral spring constants of the leaf-spring units. There is minimal coupling between the deflection measurements in the lateral and normal directions. This coupling is also calibrated in situ. It is typically 1% and can be as low as 0.25%. This means that the displacements of the tip can be measured accurately in the sliding direction and normal to the surface. Together, these characteristics make the LFA, well suited for quantitative study of friction dynamics at mesoscopic scales. Furthermore the design of the leaf-spring unit allows exchange of tips which may be fabricated (e.g., etched) from wire material (d≈0.4 mm) and can have customized shapes, e.g., polished flat squares. The ability of the LFA to study friction dynamics is briefly illustrated by results of stick-slip measurements on soft polymer surfaces.
Elliptical x-ray microprobe mirrors by differential deposition
Authors: Ice Gene E. , Chung Jin-Seok , Tischler Jonathan Z. , Lunt Andrew , Assoufid Lahsen
Published: July 2002

A differential coating method is described for fabricating high-performance x-ray microfocusing mirrors. With this method, the figure of ultrasmooth spherical mirrors can be modified to produce elliptical surfaces with low roughness and low figure errors. Submicron focusing is demonstrated with prototype mirrors. The differential deposition method creates stiff monolithic mirrors which are compact, robust, and easy to cool and align. Prototype mirrors have demonstrated gains of more than 104 in beam intensity while maintaining submilliradian divergence on the sample. This method of producing elliptical mirrors is well matched to the requirements of an x-ray microdiffraction Kirkpatrick–Baez focusing system.