bluuebunny/crossref_metadata_2025 huggingface dataset:
High spatial and temporal resolution visible spectroscopy of the plasma edge in DIII-D
Authors: Gohil P. , Burrell K. H. , Groebner R. J. , Seraydarian R. P.
Published: July 2002

In DIII-D, visible spectroscopic measurements of the He ii 468.6 nm and C vi 529.2 nm Doppler broadened spectral lines, resulting from charge exchange recombination interactions between beam neutral atoms and plasma ions, are performed to determine ion temperatures, and toroidal and poloidal rotation velocities. The diagnostics system comprises 32 viewing chords spanning a typical minor radius of 63 cm across the midplane, of which 16 spatial chords span 11 cm of the plasma edge just within the separatrix. A temporal resolution of 260 μs per time slice can be obtained as a result of using MCP phosphors with short decay times and fast camera readout electronics. Results from this system will be used in radial electric field comparisons with theory at the L–H transition and ion transport analysis.
Improvement of the spherical mirror analyzer
Authors: Daimon Hiroshi , Ino Shozo
Published: July 2002

With the use of some obstacle rings and a set of retarding grids, the resolution of the prototype spherical mirror analyzer, which has been developed in a previous paper [H. Daimon, Rev. Sci. Instrum. 59, 545 (1988)], was improved. The uniformity of the resolution with respect to the emission angle was also achieved. Some examples of electron energy-loss spectra and XPS spectrum were presented.
Second order correction in cavity constitutive parameter measurements with application to anisotropic ferrites
Authors: Moore R. L. , Thompson M. C. , Robbins T. S.
Published: July 2002

An analysis is presented to calculate scalar permittivity and tensor permeability for ferrite materials from waveguide transmission cavity data. A correct measurement of the permittivity of ferrites and other high dielectric constant materials, requires an extension of current techniques to a second-order perturbational analysis. This second-order correction offsets an apparent frequency dependent dielectric behavior measured during a multimode cavity measurement. The analysis implies that dimensions of ferrite samples to be used in various waveguides (X-Ka bands) must be reduced to a near 0.015-in. cross-sections to eliminate a coupling of permittivity and permeability measurements.
Thrust stand for high-power electric propulsion devices
Authors: Haag T. W.
Published: July 2002

A thrust stand for use with magnetoplasmadynamic (MPD) thrusters operated at powers up to 250 kW steady state has been built and tested. The stand was based on an inverted pendulum configuration which resulted in large displacements and high resolution. Up to 50 mm of deflection was observed under a force of 5 N. This large range of displacement significantly reduced the effects of facility induced vibrations on thrust measurements. A remotely operated system was provided for in situ calibration of the thrust stand prior to and immediately after data were obtained. Calibrations showed that thrust measurements were linear and repeatable to within a fraction of 1%. Structural distortions of the vacuum facility due to pumpdown were detected with an inclinometer located in the thrust stand base. Slope deviations as small as 10 arcsec could be compensated using a remotely controlled leveling motor. Early problems with magnetically induced tares caused by the thruster discharge current were reduced by rerouting high-current cables to decrease stray fields. Tares due to discharge current were on the order of 26 mN at 3000 A, and those due to an applied field current were 63 mN at 1400 A. The thrust stand was used with a water-cooled, applied field, steady-state MPD device at power levels up to 125 kW. Hot thruster firings as long as 1 h were performed. By precisely maintaining a level thrust stand base, thermal drift was held to about 2% of the full scale reading over this period. The remaining thermal drift could be subtracted from the thrust measurement to further reduce systematic error. Tares caused by the applied magnetic field were similarly removed. By subtracting tabulated discharge current magnetic tares, thrust measurement uncertainty was reduced to approximately 2% of the measured value.
Production of a 95% proton yield beam in a semicylindrical plasma generator
Authors: Watanabe Kazuhiro , Araki Masanori , Dairaku Masayuki , Horiike Hiroshi , Ohara Yoshihiro , Okumura Yoshikazu , Paméla Jérôme , Tanaka Shigeru , Yokoyama Kenji
Published: July 2002

A high proton yield beam was produced in a semicylindrical multicusp plasma generator. The dimension of the cylinder is 34 cm in diameter and 129 cm in length, and the beam extraction area is 8 cm in width and 120 cm in length. A strongly linked magnetic field configuration was utilized to confine the primary electrons in the cylinder and prevent them from flowing into the beam extraction region. As a temporary test hydrogen ion beams were extracted from the central region of the plasma generator. Ion species in the beam were measured by a Doppler-shifted spectroscopy of Balmer-alpha light and found to be 95% at a beam current density of 175 mA/cm2 at the filling pressure of 0.4 Pa.
A reliable nonmagnetic liquid helium tight thermal feedthrough for a fiberglass Dewar
Authors: Hibbs A. D. , Cox D. W.
Published: July 2002

A method for making a leak tight cryogenic joint between a copper rod and a material of much lower thermal expansion has been developed. No materials of high magnetic susceptibility are present in the seal. The technique has been used to make high conductivity thermal connections to components in the vacuum space of a liquid helium Dewar made from G10 fiberglass.
Temperature measurement by means of semiconductor diode in pulse mode
Authors: Iskrenovic P. S. , Mitic D. B.
Published: July 2002

In case of temperature measurement utilizing forward-biased pn junction, a polarization current is necessary because it is what indicates the pn diode into an operating mode. Simultaneously, with the diode into the operating mode, the polarization current heats the pn junction and impedes measurement. The usual solution to this problem is to reduce the current through the diode. If the current is passed through the diode only at the moment of measurement and for a single brief impulse, the average current, as well as the amount of heat given off to the pn junction, is drastically reduced. The described pulsed-diode thermometer has an average relative error (within 20–100 °C range) of ΔT/T=0.25%.
Status of the development of insertion devices for ELETTRA
Authors: Diviacco B. , Bracco R. , Poloni C. , Walker R. P. , Zangrando D.
Published: July 2002

The status of the development of insertion devices for the 1.5–2-GeV synchrotron radiation source ELETTRA is described. Recent results achieved with a prototype pure permanent magnet undulator and the construction and performance of a prototype hybrid multipole wiggler are presented. The parameters and design of the first undulator that will be constructed for ELETTRA, U12.5, are also presented, and some details are given about the magnetic measurement system.
In situ optical diagnosis on hydrogenated amorphous silicon grown by vibration superimposed plasma chemical vapor deposition
Authors: Naito Nobuo , Takano Akihiro , Sumiya Masatomo , Kawasaki Masashi , Koinuma Hideomi
Published: July 2002

p-polarized 633 nm light reflection was in situ measured to detect a change, if any, in optical constants of hydrogenated amorphous silicon (a-Si:H) thin films by the application of 2 MHz ultrasonic vibration to the substrate during their plasma chemical vapor deposition (CVD). Although the vibration scarcely changed the hydrogen content in a-Si:H films under the reaction conditions of this study, it increased both the refractive index and absorption coefficient of a-Si:H. The results are attributable to the densification of amorphous network structure as well as to the increase of density of extended states in the valence and conduction bands. Films with improved photoconductivity were obtained by the ultrasonic vibration assisted plasma CVD.
A quarter waveplate for the polarization analysis close to the carbon K edge
Authors: Di Fonzo Silvia , Jark Werner
Published: July 2002

A recipe is presented for the optimization of quarter waveplates for the soft x-ray range constructed from multilayer transmission filters. The limitations are discussed in terms of state-of-the-art multilayer technology. A quarter waveplate with promising properties close to the carbon K-absorption edge is discussed in more detail for its polarizing and analyzing capabilities. Above this edge no further technologically possible device could be identified.
Construction and performance of BL28 of the Photon Factory for circularly polarized synchrotron radiation
Authors: Kagoshima Yasushi , Muto Sadatsugu , Miyahara Tsuneaki , Koide Tsuneharu , Yamamoto Shigeru , Kitamura Hideo
Published: July 2002

A branch beamline, BL28A, has been constructed for the application of circularly polarized vacuum ultraviolet radiation. The radiation can be obtained in the helical undulator operation mode of an insertion device, EMPW♯28, which is also cut for elliptically polarized hard x-ray radiation. T first harmonic of the helical undulator radiation can be tuned from 40 to 350 eV with its corresponding K value from 3 to 0.2. A monochromator working basically with constant deviation optics was installed, and has started its operation. A circularly polarized flux of ∼1010 photons/s has been achieved with energy resolution of around 500–1000 at the first harmonic peak. The circular polarization after the monochromator was estimated to be higher than 70% by comparing theory and experiment on the magnetic circular dichroism of nickel films in the 3p-3d excitation region. The design philosophy of the beamline and recent results on the performance tests are presented.
Laser diagnostics of edge plasmas and laser diagnostics of plasmas for industrial applications (invited)
Authors: Muraoka Katsunori , Honda Chikahisa , Uchino Kiichiro , Kajiwara Toshinori , Matsuo Keiji , Bowden Mark , Park Won Zoo , Hirakawa Yasuyuki , Tanaka Kenji , Maeda Mitsuo , Okada Tatsuo
Published: July 2002

In plasma physics, laser diagnostics were first developed to probe the core region of magnetically confined high-temperature plasmas, but the advent of various new lasers has turned out to be useful for edge plasma studies. The recent developments of various arc and glow discharges for industrial plasma applications have required measurement of the same quantities as in the edge plasma studies and expertise in the latter has been fully exploited for the former. The experience thus gained has then been used for the advantage in the studies of edge plasma behavior in high-temperature plasmas. The interplay of these two fields of plasma studies, where laser diagnostics of plasmas (which we call ‘‘laser-aided plasma diagnostics’’) is extensively used, is discussed.
Active control of beam trajectories for heavy ion beam probe on helical magnetic configurations
Authors: Fujisawa A. , Iguchi H. , Sasao M. , Hamada Y. , Fujita J.
Published: July 2002

Active control of beam trajectories using four sets of sweep plates is proposed for a heavy ion beam probe (HIBP) system on helical plasma, such as torsatron, stellarator, etc., in order to solve problems arising from the complicated beam trajectories in its nonaxisymmetrical magnetic field. By this method, a series of the probing beam trajectories giving a whole potential distribution can be managed to pass at a particular point (detector aperture) with the same angle. An equation is introduced as a guiding principle to simplify the optimization process of geometrical configuration of the HIBP system, which will be adjusted for different magnetic configurations by only changing the sweep plate voltages.
Hyper-resolution Brillouin–Rayleigh spectroscopy with an optical beating technique
Authors: Matsuoka T. , Sakai K. , Takagi K.
Published: July 2002

A system of optical beating spectroscopy has been newly developed for hyper-resolution Brillouin scattering. Frequency resolution as high as 1 kHz was obtained, far beyond the limit of the classical Fabry–Perot interferometer which is commonly used in ordinary experiments. This system is useful over the frequency range from 104 to 109 Hz at present. Experiments for Rayleigh and/or Brillouin spectra were performed in water, toulene, and carbon disulfide to demonstrate the performance of this system.
Excitonic emissions from CuInSe2 on GaAs(001) grown by molecular beam epitaxy
Authors: Niki S. , Shibata H. , Fons P. J. , Yamada A. , Obara A. , Makita Y. , Kurafuji T. , Chichibu S. , Nakanishi H.
Published: July 2002

CuInSe2 epitaxial films grown on (001)-oriented GaAs substrates by molecular beam epitaxy have been characterized by means of low temperature photoluminescence spectroscopy at T=2–102 K. Distinct emission lines were observed near the band gap, and have been investigated further with varying sample temperature. An emission at 1.0386 eV (EX1) became broader with increasing sample temperature, and still remained up to T=102 K. A distinct, sharp emission at 1.0311 eV (IX1) which disappeared at a significantly lower temperature than the other peaks was observed only in films with weak donor-related emissions. We attribute such emissions to the ground-state free exciton [FEn=1] and exciton bound to neutral acceptor [A0,X], respectively. The band gap of CuInSe2 epitaxial films was also determined to be Eg=1.046 eV at 2 K using the reported exciton binding energy of Eex=7 meV.
dc Joule heating of amorphous metallic ribbons: Experimental aspects and model
Authors: Allia P. , Tiberto P. , Baricco M. , Vinai F.
Published: July 2002

A dc technique of Joule heating has been developed with the purpose of developing unconventional crystallization products in amorphous metallic ribbons. The thermal effects of a continuous current flow on Fe40Ni40B20 and Fe80Si10B10 amorphous ribbon strips are examined. The evolution of the temperature in samples submitted to different values of electrical current is followed by measuring the variations in the electrical resistance of the ribbon strips. A model of sample heating is developed and shown to predict both the steady-state temperature of the ribbon strips and the law of approach to the steady state. A number of experimental data, obtained from multiple-thermocouple measurements, x-ray diffractometry, and differential scanning calorimetry, support the model’s assumptions. The effect of fluctuations in the room-temperature resistance is discussed. The temperature behavior of samples submitted to free cooling after a Joule-heating treatment is considered.
Determination of zeta potential and pH of zero charge of oxides at high temperatures
Authors: Jayaweera P. , Hettiarachchi S.
Published: July 2002

High-temperature zeta potentials of oxides are important in understanding and preventing the deposition of corrosion products, particularly in nuclear power plants. They are also important in separation of minerals from coal/mineral aggregates and sol-gel processing of high-density advanced ceramics at supercritical temperatures. In this paper, a computer-interfaced experimental arrangement for the determination of high-temperature zeta potential via streaming potential measurements is described. Zeta potentials of oxides were calculated from the slopes of streaming potential versus differential pressure plots, avoiding any errors associated with the asymmetry of electrodes. The same measurement technique can be modified to determine the zeta potentials of solid conducting surfaces and coating materials. The oxides show the ability to retain a higher surface charge at high temperatures, presumably due to stronger acid/base dissociation of the surface hydroxyl groups. Consequently, the pH of zero charge of the oxides are shifted to lower values at higher temperatures as reported in the literature, indicating the importance of making these measurements at the desired temperature.
Use of the Stark effect to minimize residual electric fields in an experimental volume
Authors: Frey M. T. , Ling X. , Lindsay B. G. , Smith K. A. , Dunning F. B.
Published: July 2002

A technique based on the Stark effect is described that allows the residual electric field in a small experimental volume to be systematically reduced to ≲50 μV cm−1. Although developed initially to allow production of Rydberg atoms in states with very large values of principal quantum number n, it will also permit high resolution studies involving near threshold photoionization or very low-energy free electrons.
Gamma-ray focusing concentrators for astrophysical observations by crystal diffraction in Laue geometry
Authors: Melone S. , Francescangeli O. , Caciuffo R.
Published: July 2002

The diffraction and optical properties of several crystal concentrator configurations which could be adopted in hard x-ray astrophysical observations are discussed and compared in terms of effective area, focusing characteristics, and overall dimensions. First, a concentrator consisting of a set of circular rings covered with asymmetric mosaic crystals in Laue geometry is considered; focusing is achieved by an appropriate choice of the geometrical parameters and the asymmetry angles. Specific effective areas larger than 600 cm2 can be obtained in the energy range 120–190 keV by using Si (422) Bragg reflections in a device with a diameter of 2.5 m and a focal length of 13.5 m. Afterwards, a spherical-zone crystal concentrator is analyzed where asymmetric Laue geometry leads to focusing. With a focal length of 8 m and Si (422) reflections, the mean effective area in the energy range 100–300 keV is about 6500 times larger than the focal spot while the separation power of the concentrator is of the order of 10 arcsec. Finally, a concentrator consisting of several coaxial focusing paraboloids is analyzed. The surfaces of the paraboloids are covered by mosaic crystal tiles with lattice planes disposed normally to the meridians. By using Ge crystals with a mosaic width of ≊350 μrad and assuming a focal length f=10 m with a total aperture 2α=16 deg, it is possible to obtain effective areas larger than 1000 cm2 for energies smaller than about 150 keV. On the other hand, the ratio between the mean effective area and the size of the focal spot in the energy range 200–500 keV is higher than 10 000.
Inverse photoemission spectrometer using a BaF2 window for a low-pass filter
Authors: Sanada N. , Shimomura M. , Fukuda Y.
Published: July 2002

We have built a simple and high performance inverse photoemission spectrometer using a BaF2 window and a Cu–BeO electron multiplier with KBr as the photocathode for low- and high-pass filters, respectively. It is found that using the BaF2 low-pass filter improves the resolution by 0.2 eV to compare with SrF2. The intensity was reduced to a quarter of that with SrF2, although it is enough to obtain good inverse photoemission spectra.
Ultrahigh vacuum atomic force microscope using a pantograph inchworm mechanism
Authors: Hosaka Sumio , Honda Yukio , Hasewaga Tsuyoshi , Yamamoto Tatsuharu , Kondo Masayoshi
Published: July 2002

An ultrahigh vacuum atomic force microscope (UHV–AFM) with tunneling current detection has been developed. This microscope uses a new type of pantograph inchworm system. The features of the inchworm system are (i) operation of the clamp in normal clamping mode, (ii) an enlargement of the piezo device stroke for clamper stroke, and (iii) compact system for easy use. Our UHV–AFM has (i) six inchworm movements based on the new mechanism, and (ii) a sharp AFM probe whose tip is machined by a focused ion beam fabrication technique. UHV pressure experiments demonstrate that this system provides a contamination-free surface and can observe atomic resolution AFM images of MoS2 and silicon carbide.
Improved recursive convolution integral for the analysis of fluorescence decay data: Local approximation of the apparatus response function by a general polynomial
Authors: Večeř J. , Kowalczyk A. A. , Dale R. E.
Published: July 2002

An analytical solution of the recursion formula for convolution of a sum-of-exponentials fluorescence impulse (δ) response with an apparatus response (‘‘lamp’’) function approximated locally by a general polynomial of the nth degree is derived. The five lowest approximations are tested by comparison with properly simulated fluorescence evolution-and-decay data. These were obtained by analytical convolution of selected δ responses with an analytically defined apparatus function chosen closely to simulate typically observable flash-lamp apparatus functions, taking account of the integration within channels inherent in the experimental collection of both ‘‘lamp’’ and fluorescence response curves. A precise comparison of the recovery of various test theoretical mono- and sum-of-exponentials impulse-response parameters for the different approximations was attained by performing all calculations for both simulation and nonlinear least-squares optimization analysis in double precision. The results highlight the advantages of using local higher-order polynomial approximations under various circumstances. The improved time resolution in particular suggests more expedient regimes of data collection than heretofore possible.
Pulsed S-band electron spin resonance spectrometer
Authors: Hankiewicz Janusz H. , Stenland Christopher , Kevan Larry
Published: July 2002

A computer-controlled pulsed electron spin resonance spectrometer operating at S-band (2–4 GHz) is described. The instrument is designed for the study of weak interactions between paramagnetic centers and surrounding magnetic nuclei by electron spin-echo modulation techniques. The incorporation of loop-gap resonators gives good sensitivity and allows use over the full octave bandwidth range. Free-induction decay and electron spin-echo signals at room temperature and at liquid-helium temperature are shown in selected sample types. The expected increase of the electron spin-echo modulation depths relative to X band (∼9 GHz) frequencies is demonstrated for proton modulation.
A high-speed wide dynamic range time-to-digital converter
Authors: Lampton M. , Raffanti R.
Published: July 2002

We describe a time-to-digital converter able to measure intervals as great as 100 ns with a resolution of 4 ps rms. It achieves this large dynamic range by simultaneously sampling four sinusoidal wave forms (sine and cosine waves at 200 and 6.25 MHz) derived from a single quartz oscillator. Twelve-bit analog-to-digital conversion of the 200 MHz waves yields the high time resolution. Eight-bit conversion of the 6.25 MHz samples removes the cycle ambiguity of the 200 MHz data. The digital words are pipelined in a fully parallel data flow architecture. A first-in first-out stage in the pipeline derandomizes the random event arrival times. A subsequent stage in the pipeline uses an arctangent function to convert the sine and cosine pairs into linearized measures of event time. These are subtracted to yield start–stop time interval sizes for individual photoevents. The minimum start–stop interval is 50 ns, set primarily by the cycle time. Because the same processing is employed for the start and stop events, a large class of potential error and drift phenomena are eliminated. The digitizer provides an accurate way to decode the outputs of delay line detectors, offering high event throughput and extremely good long-term timing accuracy. As a side benefit, the pipeline data flow architecture permits simple breadboarding and low-throughput testing of the system stages with the arctangent work implemented in a personal computer. This arrangement is also very convenient for logging diagnostic evaluation data. The same front-end and data flow architecture is directly applicable to very high-speed applications where the event processing is implemented in a digital signal processor.
Performance of mass analyzed, low-energy, dual ion beam system for materials research
Authors: Al-Bayati A. H. , Marton D. , Todorov S. S. , Boyd K. J. , Rabalais J. W. , Armour D. G. , Gordon J. S. , Duller G.
Published: July 2002

Mass analyzed low-energy ion beams delivered into a UHV growth chamber have enormous potential for novel materials studies. However, there are significant practical problems in the production of useful ion fluxes at energies down to a few electron volts. Many of these problems have been investigated during the testing of a unique new instrument. This instrument consists of a dual source, mass analyzed, low-energy, ion beam system attached to an ultrahigh-vacuum (UHV) deposition chamber which houses equipment for in situ Auger electron spectroscopy and reflection high-energy electron diffraction analysis of the deposited material. A second UHV chamber, connected to the deposition chamber by means of a vacuum lock and sample transfer device, houses equipment for in situ low-energy electron diffraction and time-of-flight scattering and recoiling spectrometry. The instrument is briefly described herein and data are presented to illustrate the effects of various parameters on the performance of the ion beam. The parameters considered are beam line pressure, field penetration, electromagnetic fringing fields, retarding lens configuration, and ion arrival energy at the target (from 5 eV to 10 keV). The effects of these parameters on the energy spread and profile of the beam, ion-beam flux on target for various species, high-energy neutral atom content and electron content of the beam, and target chamber pressure are discussed. Examples showing the utilization of the instrument for (1) synthesis of the metastable binary compound carbon nitride, (2) deposition of ultrathin Al/Si multilayers, and (3) studying the growth mechanism of Si thin films, are presented. The prospects for materials research, film deposition, surface modification, and ion/surface chemistry studies using such an instrument are assessed.
The Beijing metal vapor vacuum arc ion source program
Authors: Huixing Zhang , Xiaoji Zhang , Fengsheng Zhou , Shenji Zhang , Qiang Li , Zhuen Han
Published: July 2002

Work on metal vapor vacuum arc (MEVVA) ion source development was initiated at the Institute of Low Energy Nuclear Physics, Beijing Normal University, in 1988. MEVVA ion sources I, II, IIA, and III have been designed, fabricated, and tested, and an ion implantation facility with three MEVVA ion sources has been developed and is now undergoing testing. Here the status of the MEVVA ion source research and development program is described.
Self-starting femtosecond pulse generation from a Ti:sapphire laser synchronously pumped by a pointing-stabilized mode-locked Nd:YAG laser
Authors: Siders Craig W. , Gaul Erhard W. , Downer Michael C. , Babine Alexei , Stepanov Andrey
Published: July 2002

We have constructed a self-starting Kerr-lens mode-locked Ti:sapphire laser pumped synchronously by a mode-locked, LBO-doubled Nd:YAG laser. Using a home-built beam-pointing stabilizer, beam wander of the 532 nm pump is reduced by a factor of 25, thus enabling long term operation of TEM00 nearly transform limited pulses with amplitude, repetition rate, and pulsewidth fluctuations comparable to or better than those of Ar-pumped Ti:Al2O3 lasers. Interferometric autocorrelation using second harmonic in reflection from GaAs yielded a pulse width of 30 fs, limited by the dispersion of wide bandwidth cavity optics which permit tunability from 0.7 to 1.0 μm.
Audio-frequency discharge cleaning system for the SINP tokamak using single turn primary
Authors: Ranjan P. , Hui A. K. , Chowdhury S. , Paul R. K. , Basu S. , Bhattacharya P. S. , Bal A. , Ray R. , Majumdar S. K. , Mukhopadhyay N. K.
Published: July 2002

Taking advantage of the iron core of the Saha Institute of Nuclear Physics (SINP) tokamak, a single turn primary coil was used to generate low power ohmically excited audio-frequency hydrogen plasma to clean the SINP tokamak vacuum vessel of adsorbed gases. This scheme allowed us to easily use available low voltage power transistors and other existing power supply components to generate audio-frequency voltage. Using this scheme the discharge cleaning system was tested successfully in a short period of 2–3 months. The system has been utilized to carry out initial discharge cleaning of the vessel as well as daily cleaning to achieve full designed parameters of our tokamak.
Beam extraction from a large vacuum-immersed negative-ion source
Authors: Takeiri Y. , Oka Y. , Kaneko O. , Ando A. , Tsumori K. , Akiyama R. , Kawamoto T. , Kuroda T.
Published: July 2002

A large vacuum-immersed negative-ion source has been investigated for the development of the neutral beam injection system in a large helical device. The structure of the vacuum-immersed source is compact and light because it is free from atmospheric pressure. Therefore, this is very advantageous for a large-scaled ion source. Moreover, since the grids of the accelerator are supported by post insulators, enhanced pumping of gaps between grids is expected, leading to a reduction of stripping loss of negative ions. The gas pressure distribution between grids was calculated and the stripping loss of H− ions was estimated and the effectiveness of the vacuum-immersed source structure was confirmed. The gas temperature effect of the gas pressure distribution is also considered by using a Monte Carlo code.
A pulsed supersonic molecular beam with high rotational temperatures
Authors: Häger J. , Zech S. , Glatzer D. , Fink M. , Walther H.
Published: July 2002

The construction and operation of a novel high temperature pulsed quartz nozzle employed for the generation of rotationally excited supersonic molecular beams are reported herein. At high stagnation pressures (≳ 1 bar) the NO molecules in the beam pulse exhibit a translational and rotational behavior identical to heated continuous nozzles (Trot<50 K; Ekin≊7/2 kTN). At reduced stagnation pressures (10 mbar–1 bar) the rotational temperatures of the beam molecules are increased substantially (up to Trot≊700 K) accompanied by a translational behavior, which can be characterized by a small Mach number. The design has produced the rotationally hottest supersonic beam ever prepared in the pulsed mode.
Critical viewpoints on the methods of realizing the metal freezing points of the ITS-90
Authors: Ma C. K.
Published: July 2002

The time-honored method for realizing the freezing point tf of a metal (in practice necessarily a dilute alloy) is that of continuous, slow freezing where the plateau temperature (which is the result of solidifying material’s being so pure that its phase-transition temperature is observably constant) is measured. The freezing point being an equilibrium temperature, Ancsin considers this method to be inappropriate in principle: equilibrium between the solid and liquid phases cannot be achieved while the solid is being cooled to dispose of the releasing latent heat and while it is accreting at the expense of the liquid. In place of the continuous freezing method he has employed the pulse-heating method (in which the sample is allowed to approach equilibrium after each heat pulse) in his study of Ag; his measurements suggest that freezing can produce non-negligible errors. Here we examine both methods and conclude that the freezing method, employing an inside solid–liquid interface thermally isolated by an outside interface, can provide realizations of the highest accuracy; in either method, perturbation, by inducing solid–liquid phase transition continuously or intermittently, is essential for detecting equilibrium thermally. The respective merits and disadvantages of these two methods and also of the inner-melt method are discussed. We conclude that in a freezing-point measurement what is being measured is in effect the however minutely varying phase transition, and nonconstitutional equilibrium, temperature ti at the solid–liquid interface. The objective is then to measure the ti that is the best measure of tf, which is, normally, the plateau temperature.
Analysis of response times for digital rate meter algorithms
Authors: Koturović A. M. , Arandjelović V. Dj.
Published: July 2002

An analysis of the response times of linear and exponential response digital rate meter algorithms to sudden changes in count rate is presented. Expressions defining minimum and maximum response times relative to changes in count rate that do not coincide with the beginning of the measurement interval are derived. Criteria for specifying the measurement interval for a desired response time are then obtained. General equations relating sampling time parameters and response times of digital rate meter algorithms are presented which form a foundation for analysis of digital implementations of classical analog rate meter circuitry.
Low noise wideband accelerometer using an inductive displacement sensor
Authors: Braccini S. , Bradaschia C. , Del Fabbro R. , Di Virgilio A. , Ferrante I. , Fidecaro F. , Flaminio R. , Gennai A. , Giassi A. , Giazotto A. , Gorini G. , Losurdo G. , Morganti M. , Palla F. , Paoletti F. , Passuello D. , Poggiani R. , Torelli G. , Zhang Z.
Published: July 2002

A wideband (dc to 500 Hz) low noise accelerometer has been developed. It makes use of a suspended mass whose displacement relative to the supporting structure is sensed by a linear variable differential transformer. It works both in horizontal and in vertical direction. The electronics is connected to the mechanical structure through 12 m long cables. The spectral sensitivity is 7×10−10 (m/s2)/√Hz below 6 Hz. The accelerometer will be used to perform an inertial damping of the resonances of the suspension of the mirrors in VIRGO, an interferometric antenna for gravitational waves detection.
Small-bore (1.8-mm), high-firing-rate (10-Hz) version of a repeating pneumatic hydrogen pellet injector
Authors: Combs S. K. , Foust C. R. , Milora S. L.
Published: July 2002

Repeating pneumatic pellet injectors developed at the Oak Ridge National Laboratory (ORNL) were used for plasma fueling experiments on the Tokamak Fusion Test Reactor (TFTR) and the Joint European Torus (JET). For plasma fueling on the DIII–D tokamak, a small-bore (1.8-mm) injector has been developed and tested in the laboratory at pellet rates of up to 10 Hz and speeds of ≤1 km/s (for pulse lengths of up to 15 s). This performance represents the smallest pellet size and highest repetition rate demonstrated with an ORNL repeating pneumatic pellet injector. The design has been incorporated in the three-barrel injector that was previously used on JET; the injection system, equipped with nominal pellet sizes of 1.8-, 2.7-, and 4.0-mm diameter, has been installed on DIII–D and will be used in future plasma fueling experiments.
Support systems for optics in the experiment stations at the Advanced Photon Source
Authors: Barraza J. , Shu D. , Kuzay T. M.
Published: July 2002

Support systems have been designed for optics in the experiment stations of the Advanced Photon Source at Argonne National Laboratory. These systems utilize modular precision positioning slides and stages arranged in 3-point kinematic mount fashion for optimum mechanical stability. Through the use of novel configurations, these systems can achieve large linear motions, six degree-of-freedom motion, and large load capacities without sacrificing valuable experimental station space. This paper will discuss the designs and specifications of the positioning systems developed.
Design and performance of the high-flux/high-brightness x-ray wiggler beamline BW2 at HASYLAB
Authors: Drube W. , Schulte-Schrepping H. , Schmidt H.-G. , Treusch R. , Materlik G.
Published: July 2002

The wiggler beamline BW2 at HASYLAB provides an intense monochromatic photon beam in the x-ray range from 2.02 to 33.5 keV for a diversity of experimental x-ray techniques such as surface diffraction, photoemission, absorption, microtomography, standing waves, etc. The beamline layout and its overall performance are described.
Construction and performance of beamline NE1B for circularly polarized soft x rays in the TRISTAN accumulation ring
Authors: Kagoshima Y. , Miyahara T. , Yamamoto S. , Kitamura H. , Muto S. , Park S.-Y. , Wang J.-D.
Published: July 2002

Beamline BL-NE1B has been constructed at the 6.5-GeV TRISTAN accumulation ring (AR) for applications of circular polarization in the soft x-ray region. Circularly polarized soft x rays are produced by a helical undulator operation mode of an insertion device, EMPW♯NE1. The fundamental harmonic peak can be tuned from 0.25 to 2 keV. The NE1B beamline is equipped with a vertical-dispersion spherical-grating monochromator using the Rowland mounting. A monochromatized circularly polarized photon flux higher than ∼1011 photons/s has been obtained over an energy range from 0.25 to 1.25 keV with an energy resolution (E/ΔE) of around 1500–300. An energy resolution of about 5000 has been achieved at 400 eV with slit widths of 10 and 10 μm.
Development and application of x-ray phase retarders (invited)
Authors: Hirano Keiichi , Ishikawa Tetsuya , Kikuta Seishi
Published: July 2002

Transmission x-ray phase retarders (TXPRs) in both Bragg and Laue diffraction geometries were investigated at the Photon Factory. The TXPRs were used for polarization control of SR as well as for complete determination of the polarization state. A novel optics to produce high-quality circularly polarized x rays with high throughput at an x-ray beamline of SR facilities is discussed.
Fluorescent scanning x-ray tomography with synchrotron radiation
Authors: Takeda Tohoru , Maeda Toshikazu , Yuasa Tetsuya , Akatsuka Takao , Ito Tatsuo , Kishi Kenichi , Wu Jin , Kazama Masahiro , Hyodo Kazuyuki , Itai Yuji
Published: July 2002

Fluorescent scanning (FS) x-ray tomography was developed to detect nonradioactive tracer materials (iodine and gadolinium) in a living object. FS x-ray tomography consists of a silicon (111) channel cut monochromator, an x-ray shutter, an x-ray slit system and a collimator for detection, a scanning table for the target organ, and an x-ray detector with pure germanium. The minimal detectable dose of iodine in this experiment was 100 ng in a volume of 2 mm3 and a linear relationship was shown between the photon counts of a fluorescent x ray and the concentration of iodine contrast material. A FS x-ray tomographic image was clearly obtained with a phantom.
Performance of an infrared microspectrometer at the NSLS
Authors: Carr G. L. , Reffner J. A. , Williams G. P.
Published: July 2002

A facility to perform infrared microspectroscopy is under development at the NSLS of Brookhaven National Laboratory. The high brightness infrared light produced as synchrotron radiation makes a nearly ideal source for microspectroscopy. High quality spectra from 10 μm sized areas can be acquired in less than 1 min. A description of the installation, microspectroscopy performance, and an example application are presented.
Diffraction anomalous fine structure measurements by using an energy/angular ‘‘dispersive diffraction’’ experimental setup
Authors: Hodeau J. L. , Vacínová J. , Garreau Y. , Fontaine A. , Hagelstein M. , Elkaïm E. , Lauriat J. P. , Prat A. , Wolfers P.
Published: July 2002

DAFS (diffraction anomalous fine structure) measurements give intensity variations of x-ray Bragg reflections as the energy is tuned near an absorption edge of an atom of the sample. In this way, the long-range structural information contained in the diffraction peak is combined with the chemical and local structure selectivity of x-ray absorption spectroscopy. Generally, for such experiments diffraction intensities are measured using classical monochromatic optics. In this report, we propose a new energy/angular ‘‘dispersive diffraction’’ setup which allows a parallel intensity collection over the whole energy range. This method was demonstrated on a hexaferrite single crystal where intensity variations of eight Bragg reflections have been measured at the Fe K edge over a spectral range of 250 eV. The same DAFS measurements were performed using double-crystal optics and we compare both results. This experiment was done on a sample where, for all reflections, contributions of different Fe sites are mixed. An intensity analysis of these reflections, which was performed by a simultaneous refinement procedure of several reflections at all energies, is also given.
Force-balancing force sensor with an optical lever
Authors: Kato Nobuhiro , Suzuki Ippei , Kikuta Hisao , Iwata Koichi
Published: July 2002

Scanning force microscopes (SFMs) are sometimes used to obtain a force curve, which shows the force variation as a function of tip–sample distance. In the force curve measurement, if the spring constant of the force detecting lever is small, the measured force curve has discontinuity and is different from the true force curve. In this paper, we present a new type of force balancing force sensor built in SFM. This force sensor employs an optical lever for detecting the rotation of the lever and two electrostatic force actuators with transparent electrodes. This sensor has two operating modes; with and without feedback. In the feedback mode, the force detecting lever is balanced with the electrostatic force. This system has the effect of enlarging the effective spring constant of the whole sensor. In the nonfeedback mode, this sensor acts as an ordinary force sensor. By using this sensor in both modes we will show the effectiveness of the force feedback in force curve measurements.
Fusion reactor power and position control from neutron measurement analysis
Authors: Navarro A. P. , Ochando M. A. , Blázquez J. B.
Published: July 2002

Plasma power and position are two important magnitudes to measure and control in the operation of a fusion reactor. Reactor diagnostics are extremely difficult by reason of the reduced access to the plasma and the need for systems with low sensitivity to radiation damage. Neutron detectors are already well developed and can be applied in reactors without any of the above-mentioned limitations. In this paper we consider two arrays of collimated neutron detectors around the plasma at a fixed toroidal location, in accordance with the ITER conceptual design, and deducing from the different momenta of the signal distribution, the fusion power and the displacement of the plasma. Sensitivity to the plasma turbulence has been studied. Neutron noise analysis techniques are applied to simulated oscillation modes to check the capability of this technique to detect and forecast such phenomena.
Measurements of DT and DD neutron yields by neutron activation on the Tokamak Fusion Test Reactor
Authors: Barnes Cris W. , Larson Alvin R. , LeMunyan G. , Loughlin M. J.
Published: July 2002

A variety of elemental foils have been activated by neutron fluence from the Tokamak Fusion Test Reactor under conditions with the DT neutron yield per shot ranging from 1012 to over 1018. Linear response over this large dynamic range is obtained by reducing the mass of the foils and increasing the cooling time, all while accepting greatly improved counting statistics. Effects on background gamma-ray lines from foil-capsule-material contaminants, and the resulting lower limits on activation foil mass, have been determined. DT neutron yields from dosimetry standard reactions on aluminum, chromium, iron, nickel, zirconium, and indium are in agreement within the ±9% (one-sigma) accuracy of the measurements; also agreeing are yields from silicon foils using the ACTL library cross section, while the ENDF/B-V library has too low a cross section. Use of the 115In(n,n′)115mIn reaction (0.42 times as sensitive to DT neutrons as DD neutrons) in conjunction with pure-DT reactions allows a determination of the DT/(DD+DT) ratio in trace tritium or low-power tritium beam experiments.
Absolute calibration of neutron counters on the Compact Helical System
Authors: Isobe M. , Osakabe M. , Sasao M. , Matsuoka K. , Fujita J.
Published: July 2002

A calibration experiment of the neutron counters of the Compact Helical System (CHS) has been carried out in order to determine the calibration factor which relates the neutron-counter output to the extended neutron source of a torus plasma. The instruments employed in the present experiment include a BF3 proportional counter, a 3He proportional counter, an NE213 organic liquid scintillator. The BF3 counter was installed at the center of the CHS torus and the other two detectors were installed outside the torus. A total of 64 toroidal angles along the magnetic axis of plasma were surveyed by the movement of a 252Cf neutron source. The poloidal cross section of the CHS plasma is elliptical in shape and rotates toroidally with the same period as that of the helical coil. The spatial distribution of 25 local point efficiencies in three poloidal cross sections with elongated orientations of 0°, 45°, and 90° were investigated in order to determine the influence of the plasma profile on the calibration factor. The shadow and scattering effects were clearly observed by the center counter when the source was located behind the helical coil. The calibration factor for the BF3 counter, obtained by averaging the point efficiencies over all the toroidal angles, was 3.6×10−4 counts per neutron, about several ten times greater than those of the counters located outside the torus. Details of the calibration setup and the analysis of experimental results are presented.
TORE SUPRA fast reciprocating radio frequency probe (abstract)a)
Authors: Thomas C. E. , Harris J. H. , Haste G. R. , Kwon M. , Goulding R. H. , Hoffman D. J. , Saoutic B. , Becoulet A. , Fraboulet D. , Beaumont B. , Kuus H. , Ladurelle L. , Pascal J. Y.
Published: July 2002

A fast reciprocating ion cyclotron range of frequencies (ICRF) probe was installed and operated on TORE SUPRA during 1992/1993. The body of the probe was originally used on the ATF experiment at Oak Ridge National Laboratory. The probe was adapted for use on TORE SUPRA, and mounted on one of the two fast reciprocating probe mounts. The probe consists of two orthogonal single-turn wire loops, mounted so that one loop senses toroidal rf magnetic fields and the other senses poloidal rf magnetic fields. The probe began operation in June, 1993. The probe active area is approximately 5 cm long by 2 cm, and the reciprocating mount has a slow stroke (5 cm/s) of 30 cm and a fast stroke (1.5 m/s) of about 10 cm. The probe was operated at distances from the plasma edge ranging from 30 to −5 cm (i.e., inside the last closed flux surface). The probe design, electronics, calibration, data acquisition, and data processing are discussed. First data from the probe are presented as a function of ICRF power, distance from the plasma, loop orientation, and other plasma parameters. Initial data show parametric instabilities do not play an important role for ICRF in the TORE SUPRA edge and scrape-off-layer (SOL) plasmas. Additionally it is observed that the probe signal has little or no dependence on position in the SOL/plasma edge.
Advances in reflectometric density profile measurements on the DIII-D tokamak (abstract)a)
Authors: Kim K. W. , Doyle E. J. , Peebles W. A. , Ejiri A. , Luhmann N. C. , Rettig C. L.
Published: July 2002

Significant improvements have been achieved in the accuracy and reliability of broadband frequency-swept (FM) reflectometer measurements on DIII-D. This has been achieved through several improvements, the most important of which has been the application of digital complex demodulation (CDM) analysis software, which can extract signal phase with subfringe accuracy. Using this new analysis technique, results from the broadband FM system look very promising: reflectometer measurements show excellent agreement with Thomson profiles in Ohmic and H-mode plasmas, and good agreement with Thomson data in L-mode. Clear resolution of the steep edge density profile in H-mode plasmas, where very small phase shifts are involved, confirm the accuracy of the system calibration and performance.