bluuebunny/crossref_metadata_2025 huggingface dataset:
MBE grown CdTe photoconductor array detector for x-ray measurements
Authors: Yoo S. S. , Rodricks B. , Sivananthan S. , Faurie J. P. , Montano P. A.
Published: July 2002

A photoconductor array was made using molecular-beam epitaxy (MBE) grown CdTe. CdTe has been found to be an excellent material for high-energy photon detection. The objective is to develop an array detector with high efficiency and fast response toward x rays. There is considerable interest in the development of new x-ray detectors for use in the new synchrotron-radiation sources. Photoconductor arrays with gaps ranging from 5 to 50 μm between elements and 100 μm pitch size have been fabricated. The temporal response of the detectors was measured using 100 fs Ti:sapphire laser pulses. The temporal response of the photoconductor arrays is as fast as 21 ps rise time and 38 ps full width half maximum (FWHM). Spatial and energy responses were obtained using x rays from rotating anode (ANL) and synchrotron-radiation sources (NSLS, beam line X-18 B). The spatial resolution of the photoconductor obtained was 75 μm FWHM, for a 50 μm beam size. The best results were obtained for those arrays with the best crystal qualities. Linear response up to an energy of 15 keV was observed. Also observed was that a substantial number of x-ray photons were effectively absorbed within the MBE CdTe layer. The array detector did not show any evidence of radiation damage after x-ray exposures of several days. When the detector is cooled to 230 K the signal-to-noise ratio is improved by more than an order of magnitude. These results demonstrate that MBE grown CdTe is a suitable choice to meet the detector requirements for synchrotron-radiation applications.
Development of a proportional scintillation x-ray imaging chamber for synchrotron radiation experiments
Authors: Suzuki Masayo , Takahashi Tan , Awaya Yohko , Oura Masaki , Yamamoto Masaki , Uruga Tomoya , Mizogawa Tatsumi , Masuda Kimiaki
Published: July 2002

Proportional scintillation x-ray imaging chamber (PSXIC) is a new type of two-dimensional position-sensitive x-ray detector composed of a spherical drift chamber, a parallel plate avalanche counter, and an image-intensifier-associated charge coupled device camera. A prototype of PSXIC filled with xenon (97%)+triethylamine (3%) gaseous mixture has been stably operated under a high flux of x-ray irradiation. The spatial resolution the prototype can attain has been found better than 800 μm. The time-resolved imaging capability has also been examined by taking time-varying x-ray images of a test pattern with a time resolution of 1/30 s.
LNLS status report
Authors: Gonçalves da Silva C. E. T. , Rodrigues A. R. D. , Craievich A. F.
Published: July 2002

The Brazilian synchrotron light source consists of a 1.15 GeV electron storage ring with a 100 MeV injector. Most of their components have already been developed in-house and production has started. The increase of injection energy is being considered via a booster, for full energy, or by recirculating the beam in the LINAC (200 MeV) [R. H. Farias et al. (unpublished)]. An update of the production and characterization of the accelerators components and beamlines is presented.
Performance characterization of the Caltech compact torus injector
Authors: Loewenhardt P. K. , Brown M. R. , Yee J. , Bellan P. M.
Published: July 2002

A device is described which is designed to refuel tokamaks of major radius ≊1 m and magnetic field ≊1 T by the injection of a compact torus. The injector utilizes an acceleration stage which adds kinetic energy to the compact torus so that it can penetrate the tokamak magnetic field. The performance of the device was found to be optimized in an unexpected parameter regime. It is theorized that in this regime the accelerator takes part in the formation of the CT. A performance threshold with respect to accelerator current will be presented and methods of impurity reduction will be detailed.
Fast reciprocating probe system for local scrape-off layer measurements in front of the lower hybrid launcher on JT-60U
Authors: Asakura N. , Tsuji-Iio S. , Ikeda Y. , Neyatani Y. , Seki M.
Published: July 2002

A fast reciprocating probe system with a long drive shaft was incorporated into a multi-junction lower hybrid (LH) wave launcher on JT-60U in order to investigate an improved coupling mechanism of the radio frequency wave to the core plasma. The system has been operated reliably over a horizontal scan of 25 cm in 1.5 s using a compact pneumatic cylinder drive and springs. A double probe measurement provided the scrape-off layer plasma profile between the last closed flux surface and the first wall with the spatial resolution of 1−2 mm measured with a laser displacement gauge. The profiles of the electron density ne and temperature Te were in good agreement with those obtained with a triple probe method. During the LH wave injection with good coupling to the core plasma, an increase in the local Te was observed in front of the LH launcher mouth. The local ne was  (7−10)×1016 m−3, consistent values needed for the good coupling.
Nanosecond hard x-ray source for time resolved x-ray diffraction studies
Authors: Tomov I. V. , Chen P. , Rentzepis P. M.
Published: July 2002

We describe an optically driven x-ray diode which can generate nanosecond, hard x-ray pulses at a repetition rate of 300 Hz, with high stability and a synchronization capability of 1–2 ns. The system is suitable for nanosecond time resolved diffraction experiments. Using this system diffraction patterns from liquids and polycrystalline solids were recorded.
Fast algorithm for computing the Abel inversion integral in broadband reflectometry
Authors: Nunes Fernando D. , Leitão José M. N.
Published: July 2002

The application of the Hansen–Jablokow recursive technique is proposed for the numerical computation of the Abel inversion integral which is used in (O-mode) frequency-modulated broadband reflectometry to evaluate plasma density profiles. Compared to the usual numerical methods the recursive algorithm allows substantial time savings that can be important when processing massive amounts of data aiming to control the plasma in real time.
Characterization of a high-speed x-ray imager (abstract)a)
Authors: Ruggles L. E. , Spielman R. B. , Porter J. L. , Breeze S. P.
Published: July 2002

We are building a new time-resolving x-ray pinhole camera to image z pinches at the Saturn facility. The instrument is designed to have a spatial resolution of 64 μm for 2 keV photons, and a temporal resolution of 100 ps. The microchannel-plate-intensified detector will have nine, 20-mm-wide gold striplines. Each stripline will have an impedance of 5.55 Ω. We will present measurements of the temporal resolution of the detector, and describe new high-voltage gating circuitry designed to drive the low-impedance striplines.
Photoelectron spectroscopy for plasma x-ray measurements
Authors: Takahashi E. , Cho T. , Hirata M. , Kohagura J. , Sakamoto Y. , Yamaguchi N. , Tamano T. , Yagishita A. , Maezawa H.
Published: July 2002

A new x-ray spectrometer using the principle of a photoelectron spectroscopy method is developed for the purpose of the observations of plasma-electron temperatures in the range of a hundred of eV. X-ray photoelectron spectroscopy is a widely utilized method for surface-physics analyses; here, we employ a parallel-plate energy analyzer. This new type spectrometer is calibrated using synchrotron radiation from a 2.5 GeV positron storage ring at the Photon Factory (KEK). Theoretical calculations for photoelectron spectra from plasmas with various electron temperatures are carried out using the calibration data. This spectrometer is set up at the central cell of the GAMMA 10 tandem mirror for the measurements of potential-confined electron temperatures. Experimentally observed spectra are compared with the calculated spectra as well as the data from the other x-ray detection method.
A laser-induced fluorescence diagnostic for divertors
Authors: McChesney J. M. , Lippmann S. I. , Goldstein W. H. , Fournier K. B.
Published: July 2002

It is proposed that the technique of laser-induced fluorescence (LIF) be used to measure local ion velocity distributions in tokamak divertors. Recent theoretical work has indicated the existence of highly populated excited states of many partially stripped ions. These states are often connected to nearby levels by means of visible radiation, allowing useful LIF schemes to be devised. Passive spectroscopic measurements on DIII–D will be presented which verify some of the theoretical predictions. We considered ten Be-like and Mg-like ions and were able to identify over 150 LIF schemes. A possible laser system and experimental layout for the DIII–D tokamak will be presented.
Improvements in the CHERS system for DT experiments on TFTR (abstract)a)
Authors: Bush C. E. , Bell R. E. , Synakowski E. J.
Published: July 2002

Improvements in the charge exchange recombination spectroscopy (CHERS) system have resulted in accurate measurements of Ti and Vφ profiles during DT experiments. These include moving the spectrometer detector array and electronics farther away from the tokamak to a low neutron flux location. This relocation has also improved access to all components of the system. Also, a nonplasma-viewing calibration fiber system was added to monitor the change in fiber transmission due to the high flux DT neutrons. Narrow band filtered light transmitted through the calibration fiber is now used as a reference for the Vφ measurement. At a high neutron flux of ∼2.5×1018 neutrons/s (peak fusion power∼6.2 MW) with total yield of 1.3×1018 neutrons a modest 5% decrease in fiber transmission was observed. Corrections for transmission loss are made and Ti(r,t) and Vφ(r,t) profiles are automatically calculated within four minutes of every shot.
New data acquisition system for the JFT-2M tokamak
Authors: Matsuda T. , Hidekuma S. , Kojima M. , Suzuki M.
Published: July 2002

A new VAX-based data acquisition and analysis system for JFT-2M has been developed to handle various types of data flexibly. It consists of two main VAX4200 computers sharing data disks (2GB*2) with DSSI cluster and distributed VAXstations. One VAX computer acquires and stores CAMAC data. The other is used mainly for analyzing earlier data on data disks or a magneto-optical disk autochanger (0.6GB*56), where old data acquired by a previous system are also stored and utilized. Data acquisition software originally developed at NIFS was modified and localized for this system. It is characterized by centralized data management and network-wide expandability from a small VAXstation to cluster-wide VAXes. Presently, 3 MB of data for every shot are acquired, stored, and analyzed to obtain fast plasma and shape monitor outputs within 3 min.
PHiDAS: A two dimensional Langmuir probe array and high capacity CAMAC based data acquisition system
Authors: Lehmer R. D. , Gunner G. J. , Conn R. W.
Published: July 2002

An 8×8 array of Langmuir probes has been developed for measuring turbulent plasma parameters in tokamak edge plasmas. Fluctuations in plasma density ñ(r,θ,t) and floating potential φ̃f(r,θ,t) can be measured by the diagnostic, as well as the steady state (dc), profiles in n̄e(r,θ) and φ̄f(r,θ). The signal from each probe is processed by individual custom pre-amplifier circuits and the data from all probes are acquired simultaneously by a custom CAMAC based data acquisition system. This data acquisition system has 10 bit resolution with a maximum speed of 20 MS/s and has applications for various types of tokamak diagnostic arrays. Design considerations for the probe array and data acquisition system are discussed. Preliminary results from the probe array will be presented.
Development and characterization of silicon semiconductor x-ray detectors for plasma diagnostics
Authors: Cho T. , Hirata M. , Kohagura J. , Takahashi E. , Sakamoto Y. , Yatsu K. , Tamano T. , Miyoshi S. , Hirano K. , Yagishita A. , Maezawa H. , Saitoh Y. , Akamine T. , Sato K. , Inoue M. , Miyahara S. , Kondoh T. , Tanaka S.
Published: July 2002

The x-ray energy responses of silicon semiconductor detectors, including surface-barrier and photodiode-type detectors, have been investigated, using synchrotron radiation from a 2.5 GeV positron storage ring at the Photon Factory (KEK) in order to study the fundamental physics mechanism of the output signals. These studies are essential to obtain the principles of the future designs of plasma x-ray detectors, as well as of their plasma data analyses. The characterization experiments and their physics interpretations were made using (i) a group of fully depleted detectors and (ii) another group of partially depleted detectors characterized by obviously different depletion-layer thicknesses and minority-carrier diffusion lengths, but with the same wafer thickness. Both results are well interpreted by our newly proposed formula for a semiconductor x-ray-detector response. The importance of these investigations for the plasma x-ray diagnostics is highlighted by significant errors for the estimation of plasma-electron temperatures when the commonly utilized conventional theory is employed for the plasma data analyses.
Heterodyne reflectometer for phase and time delay measurements in W7-AS
Authors: Hirsch M. , Geist T. , Hartfuss H. J. , Estrada T. , Sanchez J.
Published: July 2002

A broadband heterodyne reflectometer operating in the frequency range 75–110 GHz in extraordinary mode polarization, is used at the W7-AS stellarator for density profile and density fluctuation studies. The system allows for broadband operation and permits unambiguous determination of the phase delay independent of the amplitude fluctuations in the reflected beam. The system uses two different gauss beam optics for both signal launch and detection with a slim beam waist of about 2 cm at the relevant plasma location. An amplitude modulation system has been incorporated operating at 133 MHz modulation frequency sharing with the phase sensitive system the main oscillators, antennas, and the receiver front end. AM detection is accomplished in the IF part by synchronous detection after recovery of the carrier by narrowband filtering. Time delay measurements can be done simultaneously with the carrier phase determination. The main purpose of the diagnostic in AM mode is fast edge density profile monitoring, conventional carrier phase detection is used for density fluctuation measurements and planned correlation studies. The agreement between the WKB approximation and the 1 D full wave numerical solutions for the W7-AS parameters and geometry guarantees the good localization of the measurements and permits the estimation of density fluctuation level from the measured phase fluctuations. Density fluctuation studies have been carried out in NBI and ECRH (L- and H-mode) plasmas. Fluctuation levels and spectral characteristics have been analyzed. In addition 2D effects possibly due to rotating turbulent structures have been observed.
High-intensity, neutral beam for beam-spectroscopy diagnostics
Authors: Bartsch R. R. , Davis H. A. , Henins I. , Greenly J. B.
Published: July 2002

Performance evaluation of a gas-puff neutralizer utilizing the hydrogen component of a flashover-anode, magnetized ion diode is described. A 200 cm2 source provides kiloamperes of ion flow into an annular channel 300 cm2 in cross section, 0.5 m long, into which the neutralizing H2 cloud is injected. Up to ∼50% of the H+ ion beam which flows through the cell in the absence of neutralizing gas can be converted to atomic hydrogen at the energies useful for beam spectroscopy. The detectors utilized in neutral flow measurements are also described.
The TEXT neutral lithium beam edge density diagnostic
Authors: Howald A. M. , McChesney J. M. , West W. P.
Published: July 2002

A fast neutral lithium beam has been installed on the TEXT tokamak for beam emission spectroscopy studies of the edge plasma electron-density profile. The diagnostic was recently upgraded from ten to twenty spatial channels, each of which has two detectors, one to measure lithium beam signal and one to monitor plasma background light. The spatial resolution is 6 mm, and the temporal resolution is designed to be as high as 10 ms for studies of transient events including plasma density fluctuations. Initial results are presented from the ten-channel system: Edge electron densities unfolded from the LiI (2 s 2S–2 p 2P) 670.8 nm emission profile have the same general time dependence as the line-averaged density measured by microwave interferometry.
A double pendulum plasma thrust balance and thrust measurement at a tandem mirror exhaust
Authors: Yang T. F. , Liu Ping , Chang-Díaz F. R. , Lander Harvey , Childs R. A. , Becker H. D. , Fairfax S. A.
Published: July 2002

For the purpose of measuring the plasma momentum flux in a plasma system, a highly sensitive and precision balance has been developed. It can measure a force, an impulse, or thrust as low as 0.1 mN free of mechanical noise, electrical and magnetic pickups. The double pendulum system consists of two parallel conducting plates. One or both of the plates can be suspended by needles. The needle suspended plate (or plates) can swing freely with negligible friction because of the sharp points of the needles. When one of the plates is impacted by an impulse it will swing relatively to the fixed plate or other movable plate. The capacitance between the plates changes as a result of such a motion. The change of capacitance as a function of time is recorded as an oscillating voltage signal. The amplitude of such a voltage signal is proportional to the impacting force or impulse. The proportional factor can be calibrated. The forces can thus be read out from the recorded value of the voltage. The equation of motion for the pendulum system has been solved analytically. The circuit equation for the electronic measurement system has been formulated and solved numerically. Using this balance the thrust at the exhaust of a Tandem Mirror plasma thruster has been measured. The analytical solution of the overall characteristics agrees greatly with the measurement.
An all solid-state near-infrared time-correlated single photon counting instrument for dynamic lifetime measurements in DNA sequencing applications
Authors: Legendre Benjamin L. , Williams Daryl C. , Soper Steven A. , Erdmann Rainer , Ortmann Uwe , Enderlein Joerg
Published: July 2002

We have constructed a simple, all solid-state, time-correlated single photon counting device for collecting decay profiles of chromophores attached to DNA fragments moving through a capillary tube filled with a sieving gel under the influence of an applied electric field (capillary electrophoresis). The major components of the instrument consist of an actively pulsed GaAlAs diode laser (λexcitation=780 nm; τp<200 ps; repetition rate=80 MHz; average power=5.0 mW), single photon avalanche diode (dark count rate <50 cps; quantum efficiency=65% at 800 nm) and a PC board containing a constant fraction discriminator, time-to-amplitude converter, and an analog-to-digital converter (maximum processing count rate=3×106 cps). The instrument possessed a response function of approximately 275 ps (full width at half-maximum), adequate for measuring fluorescence lifetimes in the subnanosecond regime. To demonstrate the utility and the sensitivity of the instrument, dynamic measurements of fluorescence lifetimes for near-IR dye-labeled DNA fragments were measured during capillary electrophoresis for the identification of the dye-labeled nucleotide bases via temporal discrimination. The results indicated that in a two-dye experiment, in which only two of the four constituent bases which comprise DNA were labeled with unique fluorescent probes, the characteristic lifetime of the probe could be used to readily identify the terminal nucleotide base. Decay profiles were constructed from roughly 17 500 photoelectrons accumulated over a 2 s counting interval at a loading level of approximately 6.2×10−21 mol (3900 molecules) of DNA per electrophoretic band. The lifetimes of the two labeling dyes were determined to be 669 ps (±42 ps) and 528 ps (±68 ps).
Radiation shielding and personal protection at synchrotron radiation sources (invited, abstract)
Authors: Rauchas T.
Published: July 2002

The workshop provided a forum for synchrotron facility designers and operators to discuss the following topics: aspects of shielding of high-energy synchrotron radiation facilities, radiation backgrounds, personnel protection systems, and aspects of implementation of the DOE Accelerator Safety Order. The workshop format consisted of presented papers with adequate time provided for discussion groups and round-table discussions.
A Fabry-Perot interferometer for sub-meV x-ray energy resolution (invited)
Authors: Caticha A. , Aliberti K. , Caticha-Ellis S.
Published: July 2002

The optical theory of Fabry-Perot interferometers (FPIs) for x rays using dynamically diffracting thin perfect crystals as reflectors is developed. Application to a device using high diffraction orders in silicon crystals of thickness of the order of 100 μm or more shows that energy resolutions of the order of a tenth of a meV are achievable. The effect that various features, such as gap and mirror thickness, lattice mismatches, etc., have on the FPI resonances is studied.
Modular data acquisition system and its use in gas-filled detector readout at ESRF
Authors: Sever F. , Epaud F. , Poncet F. , Grave M. , Rey-Bakaikoa V.
Published: July 2002

Since 1992, 18 ESRF beamlines are open to users. Although the data acquisition requirements vary a lot from one beamline to another, we are trying to implement a modular data acquisition system architecture that would fit with the maximum number of acquisition projects at ESRF. Common to all of these systems are large acquisition memories and the requirement to visualize the data during an acquisition run and to transfer them quickly after the run to safe storage. We developed a general memory API handling the acquisition memory and its organization and another library that provides calls for transferring the data over TCP/IP sockets. Interesting utility programs using these libraries are the ‘online display’ program and the ‘data transfer’ program. The data transfer program as well as an acquisition control program rely on our well-established ‘device server model’, which was originally designed for the machine control system and then successfully reused in beamline control systems. In the second half of this paper, the acquisition system for a 2D gas-filled detector is presented, which is one of the first concrete examples using the proposed modular data acquisition architecture.
Elliptically polarizing undulator beamlines at the Advanced Light Source
Authors: Young A. T. , Hoyer E. , Marks S. , Martynov V. , Padmore H.A. , Plate D. , Schlueter R.
Published: July 2002

Circular polarization insertion devices and beamlines at the Advanced Light Source are described. The facility will consist of multiple undulators feeding two independent beamlines, one optimized for microscopy and the other for spectroscopy. The energy range of the beamlines will go from below 100 eV to 1800 eV, enabling studies of the magnetically important L2,3 edges of transition metals and the M4,5 edges of rare earths.
Fluorescence dynamics of biological systems using synchrotron radiation (invited)
Authors: Gratton Enrico , Mantulin William W. , Weber Gregorio , Royer Catherine A. , Jameson David M. , Reininger R. , Hansen R.W.C.
Published: July 2002

A beamline for time-resolved fluorescence spectroscopy of biological systems is under construction at the Synchrotron Radiation Center. The fluorometer, operating in the frequency domain, will take advantage of the time structure of the synchrotron radiation light pulses to determine fluorescence lifetimes. Using frequency-domain techniques, the instrument can achieve an ultimate time resolution on the order of picoseconds. Preliminary experiments have shown that reducing the intensity of one of the fifteen electron bunches in the storage ring allows measurement of harmonic frequencies equivalent to the single-bunch mode. This mode of operation of the synchrotron significantly extends the range of lifetimes that can be measured. The wavelength range (encompassing the visible and ultraviolet), the range of measurable lifetimes, and the stability and reproducibility of the storage ring pulses should make this beamline a versatile tool for the investigation of the complex fluorescence decay of biological systems.
System for monitoring position of the photon beam in the new undulator beamline at SRC
Authors: Mossessian D.A. , Rogers G.C. , Bissen Mark , Severson M.C. , Reininger R.
Published: July 2002

A system of beam position monitors was developed for the plane grating monochromator (PGM) undulator beamline at the Synchrotron Radiation Center (SRC). Two monitors are located in the upstream section of the beamline providing the capability of measuring the transverse angular and spatial motion of the photon beam. The jaws of the entrance slit of the monochromator may also be used as monitors to detect changes in the vertical position of the source. Overall, the system allows measurements of the photon beam position and angle to be done with ∼10 μm and ∼3 μrad accuracy, respectively. The aperture of the monitors can be changed in both the vertical and horizontal direction. Thus, the beam motion can be measured with the highest possible resolution for any value of the undulator deflection parameter K. In addition, the design of the monitors provides the capability of mapping the angular power distribution of the photon beam. The first monitor was installed and successfully tested. The design of the system and results of test measurements are reported.
Design and performance of the ALS diagnostic beamline
Authors: Renner T. R. , Padmore H. A. , Keller R.
Published: July 2002

The design and operation of an imaging beamline at the Advanced Light Source used for providing diagnostic information on the electron beam for the accelerator and experimental groups is described. This system is based on a Kirkpatrick-Baez mirror pair and utilizes a carbon filter to give a bandpass in the soft x-ray region. The focused x-rays are viewed on a single-crystal scintillator through an optical microscope and the image recorded on a CCD camera. This system, together with other instruments to evaluate beam size, stability, and other time-dependent information, is described, data are presented, and the operation of the overall beamline is evaluated.
X-ray resonant magnetic scattering ellipsometer (abstract)
Authors: Xu Z. , Randall K. J. , Gluskin E. , Kao C.-C. , Johnson E. D. , Chen C.T.
Published: July 2002

It is very difficult to characterize the polarization of a synchrotron radiation source in the soft and/or intermediate x-ray energy region particularly from 1 to 2 keV. Conventional multilayer mirror or single-crystal polarimeters do not work over this energy region because their throughput (the reflectivities combined with the phase shift) becomes insignificant. In this paper, we present a new ellipsometer scheme that is able to fully characterize the polarization of synchrotron radiation sources in this energy region. It is based on the dichroic x-ray resonant ferromagnetic scattering that yields information on both the polarization of the x-ray and the material (element specific) dielectric-constant tensor [C.-C. Kao et al., Phys. Rev. B 50, 9599 (1994)] due to the interband ferromagnetic Kerr effect [B.R. Cooper, Phys. Rev. A 139, 1504 (1965)].
Millimeter-wave two-dimensional imaging array for the GAMMA 10 tandem mirror
Authors: Oyama N. , Mase A. , Tokuzawa T. , Imamura K. , Itakura A. , Tamano T. , Harada Y. , Mizuno K.
Published: July 2002

A millimeter-wave two-dimensional imaging array has been fabricated in order to diagnose the plug-cell plasma of the GAMMA 10 tandem mirror. The heterodyne system with two separate sources enables the measurement of density and electron cyclotron emission (ECE) in one plasma shot. The interferometer successfully measures the time evolution of the axial and radial line-density profiles with phase resolution less than 1/200 fringe and spatial resolution of 16 mm in the vertical direction and 5 mm in the horizontal one. It is shown that the Abel-inverted density profiles are changed due to the injection of electron-cyclotron-resonance heating at the plug/barrier cells and central cell. The axial and radial dependence of the second-harmonic ECE emitted from hot electrons produced in barrier region is observed simultaneously. The fluctuation spectra of the ECE signals are compared with those obtained from the far-forward scattering diagnostic system.
Characterization of new semiconductor detectors for x-ray tomography in the ASDEX Upgrade Tokamak and its generalized physics interpretations
Authors: Cho T. , Hirata M. , Kohagura J. , Kanke S. , Takahashi K. , Sakamoto Y. , Okamura T. , Yatsu K. , Tamano T. , Hirano K. , Maezawa H. , Tanaka S. , Bessenrodt-Weberpals M.
Published: July 2002

The energy response of a new semiconductor detector in the ASDEX Upgrade Tokamak for plasma x-ray tomography studies is characterized using synchrotron radiation from a 2.5 GeV positron storage ring at the National Institute for High Energy Physics in Japan. This international collaborating research clarifies a fairly good agreement between the x-ray energy response data and our recently proposed theoretical predictions for such a semiconductor x-ray-detector response. The x-ray response for several positions on the active area of the detector unit is studied; a good uniformity observed guarantees that the detector can employ any sized and shaped collimator for the x-ray tomography regardless of any correction factor coming from the response nonuniformity on the detector active area. Operational conditions of the detector for the ASDEX Upgrade plasma diagnostics are optimized using its capacitance measurements as a function of an applied bias as well as the numerical evaluations of the detector response; these are also directly verified by the synchrotron-radiation experiments.
Noise elimination method using a transmission line for the diagnostics of radio frequency plasma
Authors: Shimizu K. , Hallil A. , Amemiya H.
Published: July 2002

A filter using a transmission line formed by a cascade connection of inverted L-type networks has been developed to reject the distortion of the probe characteristics by rf (radio-frequency) noise. Each inverse L network consists of two coaxial cables with the same physical constant and length. The filter can remove discrete frequency components including the fundamental and harmonic components, the cut-off frequencies being determined by the distributed circuit constant and the length of the cables. By inserting different kinds of the network in cascade, many noise components associated with the rf frequency can be eliminated at the end section of the filter. Experiments have been performed in rf plasmas by inserting three kinds of inverted L networks with the frequency f (13.56 MHz), 2 f and 4f as the cut-off frequency. Distortion free probe characteristics have been obtained, from which accurate determination of plasma parameter such as the electron energy distribution is possible.
Narrow bandpass multilayer x-ray monochromator
Authors: Sammar A. , Krastev K. , André J.-M. , Barchewitz R. , Rivoira R.
Published: July 2002

We propose a method to reduce the bandpass of soft x-ray multilayer Bragg reflectors. It consists in etching down to the substrate a multilayer mirror having a large number of bilayers in order to get a lamellar grating with a multilayer bar width representing only 10%–30% of the grating period. The grating is used at the zeroth diffraction order. Once designed, this monochromator was tested with the Lα,β spectra of iron and copper.
Time-resolved measurement of single-electron tunneling in a Si single-electron transistor with satellite Si islands
Authors: Fujiwara A. , Takahashi Y. , Murase K. , Tabe M.
Published: July 2002

A Si single-electron transistor (SET) with satellite Si islands has been fabricated by pattern-dependent oxidation of cross-shaped Si wires on a separation by implanted oxygen (SIMOX) substrate. The oscillatory conductance-versus-gate voltage characteristics of the SET show hysteresis as a result of abrupt jumps in the conductance at high temperatures around 30 K. This phenomenon is attributed to the memory effect of a single electron that tunnels between the SET Si island and the satellite Si islands. Time-resolved measurements have clarified that the conductance jump is a Poisson process, which is clear evidence of the single-electron tunneling between the Si islands.
Investigations of forming metal-plasma flows filtered from microparticle fraction in vacuum arc evaporators
Authors: Ryabchikov A. I. , Stepanov I. B.
Published: July 2002

This article describes the processes of forming metal-plasma flows filtered from a microparticle fraction. The plasma filtering system (PFS) is a shutter electrode system lying at an angle with respect to the axis of the vacuum arc evaporator. The principle of operating the plasma filter is based on varying the path of traveling a plasma charged component when the positive near-electrode potential drop is formed. The neutral plasma component, at that, maintains the direction of its motion, and in case when the shutters of the PFS are optically opaque, it is accumulated on its walls. The dependence of efficiency of passing the plasma flow on the amount of the potential being formed, the angle of turning electrodes with respect to the direction of plasma spreading is considered for different designs of the plasma filters. The performance data of the device make it possible to achieve no-presence of the microparticle fraction in the structure of Ti coatings as well as reduction of the number of defects by two orders of magnitude in Al coatings with efficiency of passing the plasma flows by the filter up to 70%.
Estimate of cusp loss width in multicusp negative ion source
Authors: Morishita T. , Ogasawara M. , Hatayama A.
Published: July 2002

Expression of cusp loss width derived by Bosch and Merlino is applied to JAERI’s Kamaboko source. The width is related to the ambipolar diffusion coefficient across the cusp magnetic field. Electron–ion collision is found 1.2–7.4 times larger as compared with electron-neutral collision. Averaged cusp magnetic field in the diffusion coefficient is taken as a parameter in the simulation code for Kamaboko source. When the averaged magnetic field is 48 G, simulation results agree well with JAERI’s experiment in a wide range of pressure and arc power variation. The value of 48 G is reasonable from the consideration of confining the equation of ion source plasma. The obtained width is about 10 times the value evaluated by two times ion Larmor radius on the surface of cusp magnet.
Dissipation mechanisms in pendulums and their implications for gravitational wave interferometers
Authors: Huang Y. L. , Saulson Peter R.
Published: July 2002

We present a precise test of the dissipation dilution effect in the transverse wire mode quality factors in pendulums. Several excess loss mechanisms are diagnosed in detail, with special attention paid to dissipation from sliding friction.
Experimental results from the Brookhaven National Laboratory test electron beam ion source
Authors: Beebe E. , Alessi J. , Hershcovitch A. , Kponou A. , Pikin A. , Prelec K. , Stein P. , Schmieder R. W.
Published: July 2002

At Brookhaven National Laboratory, an Electron Beam Ion Source (EBIS) is operational and has produced charge states such as N7+, Ar16+, and Xe26+ using neutral gas injection. Ions such as Na7+ and Tl41+ have been produced using external ion injection. The BNL EBIS effort is directed at reaching intensities of interest to RHIC, approximately 3×109 particles/pulse which will require EBIS electron beams on the order of 10 A. Pulsed electron beams up to 1.14 A have been produced using a 3 mm LaB6 cathode. Ion yields corresponding to 50% of the maximum trap capacity for electron beams up to 0.5 A have been obtained. The goal for the TestEBIS is to produce a uranium ion charge state distribution peaked at U45+ with 50% of the trap capacity for a 1 A electron beam.
Photoelastic measurement of anelasticity and its implications for gravitational wave interferometers
Authors: Beilby Mark A. , Saulson Peter R. , Abramovici Alex
Published: July 2002

We have developed a method to determine the internal friction over a wide range of frequencies in transparent materials such as fused silica. We measure the anelastic aftereffect, the relaxation of a sample after a steady stress is removed, by sensing the polarization of a beam of light that traverses the sample. The fractional relaxation of the sample on a given time scale is a direct measure of the anelastic loss angle of the material at the corresponding frequency. To date, we have achieved sensitivity to loss angles as small as 10−6. We discuss the relevance of these measurements for the design of interferometric detectors of gravitational waves.
Optimal operating conditions of the impulse diode thermometer
Authors: Iskrenović P. S. , Arsić M. Z.
Published: July 2002

Statistical analysis of experimental results obtained by implementing an impulse diode thermometer with a sensor at constant temperature yields the dependence of relative error in determining the voltage across the diode–sensor ends upon the voltages which figure as parameters. Very good agreement of the experimental results with analytically obtained estimates completely confirms both applied methods. In such a way uniquely determined operating conditions of the impulse diode thermometer with maximal resolution and minimal error are obtained.
A confocal fiber-coupled single-lens theta microscope
Authors: Swoger Jim , Lindek Steffen , Stefany Thomas , Haar Frank-Martin , Stelzer Ernst H. K.
Published: July 2002

A confocal theta microscope using a single water-immersion objective lens is described. The system is based on the Zeiss Axioplan universal microscope, such that the illumination light is coupled into, and the detected light out of, the microscope optics via optical fibers attached to the reflector slider of the microscope. Conventional wide-field, laser-scanning confocal, confocal theta, and 4Pi-confocal theta microscopy modes are available with the system. As the design can be easily adapted to other microscopes, objective lenses, and wavelengths, it allows confocal theta techniques to be implemented in many standard systems. The design constraints and specifications for the microscope are given, as well as a demonstration of its performance.
A device for recharging evaporation sources in ultrahigh vacuum systems
Authors: Fuenzalida V. M. , Grahmann C. R. , Herrera C.
Published: July 2002

We describe a device capable of recharging the evaporation sources of ultrahigh vacuum systems without breaking the vacuum. The device is operated through the same load lock used for the introduction of the substrates and is able to place grains of materials on resistively heated boats.
Comparison of the charge state distributions of electron cyclotron resonance ion sources working in high B mode at different frequencies
Authors: Gammino S. , Ciavola G.
Published: July 2002

The behavior of the two superconducting electron cyclotron resonance ion sources of Michigan State University-National Superconducting Cyclotron Laboratory and of INFN-Laboratori Nazionali del Sud, operating respectively at 6.4 and 14 GHz is compared in this note. The charge state distributions present a similar shape, when both the sources are optimized for the production of high charge state ions. The beam intensity is roughly proportional to the square of the frequency which may be explained by the difference in plasma density.
Infrared absorption measurement using the photothermal deflection effect of thallium bromide iodide (KRS-5): Examination of basic characteristics
Authors: Minato Hideyuki , Nishimoto Akio , Ishido Yosinari
Published: July 2002

An infrared absorption measurement technique based on the photothermal deflection effect of thallium bromide iodide (KRS-5) is proposed. The optical system for infrared absorption measurement by this technique consists of a crystal block of KRS-5, an XY axis translation stage, an off-axis parabolic reflector, a He–Ne laser, and a position sensitive detector. To estimate the sensitivity of the system, its typical frequency characteristics and the thermal diffusion length of a block of KRS-5 were measured. The thermal diffusion length was measured over the chopping frequency range of 5–15 Hz. The accuracy of the measured thermal diffusion length was compared with that theoretically calculated using the physical constants of the thermal conductivity, density, and specific heat. The measured results agreed well with those calculated theoretically within ±4 μm. We also analyzed the frequency characteristics for a carbon black sample and estimated the detection limit of absorption that is characteristic for some irradiance levels at the sample surface. The results suggested that our proposed technique is useful for infrared absorption measurement.
New instrument design of high pressure optical cell for biophysical and chemical research
Authors: Zhou Jack G. , Ostrow Alan , Koulas Spiros , Chong Parkson Lee-Gau
Published: July 2002

The use of high pressure as a research tool and as a special processing method in both biophiscochemical studies and industrial applications has shown great prospects. Most of the currently available high pressure optical cells only allow for observation of the optical properties of single samples, thus limiting the data that researchers can obtain. An innovative design which enables users to introduce a second component to the original sample, while both components are under high pressure, is presented in this article. It will allow researchers to observe initial molecular interactions at high pressure via fiberoptics and to record data. The design innovation which distinguishes the high pressure optical cell from existing models is the introduction of a laser-activated stopper system which separates two components prior to mixing. A complete structure and components design for the new cell is described. Computer-aided finite element analysis and optimization were conducted for the design. Some preliminary testing has been done to verify the design concept and to check its feasibility. A prototype of the pressure cell was built to further verify the structure and system setup and to explore new challenges.
Fast-responding thermionic chlorine analyzer for respiratory applications
Authors: Nodelman Vladislav , Ben-Jebria Abdellaziz , Ultman James S.
Published: July 2002

To noninvasively determine the distribution of inhaled air pollutants in the intact human respiratory tract, a gas analyzer with a fast dynamic performance, small sampling flow, and high sensitivity is required. Such an analyzer was developed for chlorine (Cl2) by utilizing a commercially available transducer consisting of a thermionic catalytic source and a metallic collector. Operation of the transducer at 600–800 °C, an absolute pressure of 120 Torr, and a sampling flow rate of 0.6 ℓ/min resulted in a sensitivity of 3–5 pA/ppm Cl2, a minimum detection limit of 0.04 ppm, a response time of less than 100 ms, and signal-to-noise ratios of approximately 10 and 40 at Cl2 mole fractions of 0.1 and 1.0 ppm, respectively. The calibration was linear in the range of 0.3 to 4.0 ppm Cl2 and insensitive to variations in temperature, CO2 content, and humidity which exist in respired air during a breathing cycle.
Extruder system for high-throughput/steady-state hydrogen ice supply and application for pellet fueling of reactor-scale fusion experiments
Authors: Combs S. K. , Foust C. R. , Qualls A. L.
Published: July 2002

Pellet injection systems for the next-generation fusion devices, such as the proposed International Thermonuclear Experimental Reactor (ITER), will require feed systems capable of providing a continuous supply of hydrogen ice at high throughputs. A straightforward concept in which multiple extruder units operate in tandem has been under development at the Oak Ridge National Laboratory. A prototype with three large-volume extruder units has been fabricated and tested in the laboratory. In experiments, it was found that each extruder could provide volumetric ice flow rates of up to ∼1.3 cm3/s (for ∼10 s), which is sufficient for fueling fusion reactors at the gigawatt power level. With the three extruders of the prototype operating in sequence, a steady rate of ∼0.33 cm3/s was maintained for a duration of 1 h. Even steady-state rates approaching the full ITER design value (∼1 cm3/s) may be feasible with the prototype. However, additional extruder units (1–3) would facilitate operations at the higher throughputs and reduce the duty cycle of each unit. The prototype can easily accommodate steady-state pellet fueling of present large tokamaks or other near-term plasma experiments.
Highly efficient optically pumped NH3 laser with near diffraction limited output
Authors: Makowe J. , Boyarkin O. V. , Rizzo T. R.
Published: July 2002

We present the design of a highly efficient, pulsed ammonia laser which is optically pumped by a commercial TEA CO2 laser and is line tunable in the spectral range of 780–930 cm−1. The power, spectral, and temporal characteristics of the laser have been investigated for different configurations of the optical cavity. Using a stable resonator, the laser operates with an efficiency of 24% (940 mJ) in a multiline configuration and 16.5% on a single line. Changing the resonator to an unstable configuration produces a diffraction limited output on a single line with an efficiency of 13%. These output characteristics make this laser suitable for experiments in the field of infrared multiphoton dissociation.
X-ray diagnostics on WENDELSTEIN 7-AS
Authors: Weller A. , Görner C. , Gonda D.
Published: July 2002

The spatially and temporally resolved x-ray emission in the W7-AS stellarator is analyzed by three diagnostic systems. The first consists of two cameras using arrays of surface barrier diodes. A variety of absorber-foils can be used to change the spectral response of the system. This flexibility allows one to analyze impurities and magnetohydrodynamic (MHD) activity. The measurements are also used for the reconstruction of equilibrium parameters (e.g., Shafranov shift) and of the topology of MHD modes. The second system serves to monitor the electron temperature profile by using the two-foil method. Pairs of large ion-implanted Si diodes in combination with different foil combinations are used. In addition, the measurements provide routine informations about Zeff, plasma position and profile width. Finally, a compact camera system (ten cameras with planar pin-diode arrays and curved Be-foils, 320 viewing chords) inside the vacuum vessel allows one to obtain proper two-dimensional tomograms of the equilibrium flux surfaces and of mode structures without prior information. In addition to the camera systems spectral information is obtained from x-ray pulse height measurements with two Si(Li) detectors. These data are correlated with the x-ray profile measurements by an impurity radiation code. The contribution of x-ray measurements to the investigation of various physics issues is illustrated by selected examples.
X-ray spectrograph for quick turnaround measurement of z-pinch plasma parameters
Authors: Failor Bruce H. , Song Yuanxu , Yadlowsky Edward J. , Hazelton Robert C. , Moschella John J.
Published: July 2002

Our objective is to diagnose primarily Ar z-pinch plasmas with 1019<ne<1022 e/cm3 and 0.5<Te<2.0 keV at 0.2 mm spatial and 2 ns temporal resolutions. Our approach is to add Cl as a dopant, and use its He resonant to intercombination line ratio to estimate ne, and a He resonant to Li-like satellite line ratio to estimate Te. Ti is found from Doppler broadening. Because line brightness can be affected by high energy electrons in the tail of the distribution, we have measured the emission at polarizations both parallel and perpendicular to the applied electric field. We describe the spectrograph and the data obtained during experiments at the DECADE Module 2 facility at Maxwell Physics International.