bluuebunny/crossref_metadata_2025 huggingface dataset:
Novel x-ray imaging methods at the Nova laser facility (invited)
Authors: Ress D. , DaSilva L. B. , London R. A. , Trebes J. E. , Lerche R. A. , Bradley D. K.
Published: July 2002

We are pursuing several novel x-ray imaging schemes to measure plasma parameters in inertial-confinement fusion experiments. This paper will concentrate principally on two quite successful approaches, the soft x-ray moiré deflectometer, and the annular (ring) coded-aperture microscope. The first scheme uses moiré deflectometry to measure the electron density within a plasma. When a beam of collimated light travels through a plasma, it is refracted by electron-density gradients. Moiré deflectometry is a scheme to measure the refraction, and thus provides a diagnostic of the line-integrated electron-density spatial profile. To use deflectometry with a high-density laser-produced plasma, we produced a probe beam with a soft x-ray laser (λ=15.5 nm). The short wavelength of the probe radiation allows us to measure the spatial profiles at densities up to critical (e.g., 4×1021 cm−3) in long scale-length (≳1 mm) plasmas. We use finely made one-dimensional rulings (10-μm pitch), a set of synthetic multilayer mirror optics, and a soft-x-ray sensitive CCD camera to achieve a spatial resolution of 6 μm. In the second scheme, a ring coded-aperture microscope (RAM) provides a large (factor of 5–10) improvement in signal-to-noise ratio over pinhole imaging when the source size is much less than the major diameter of the annular aperture. It is therefore very useful to image the cores of imploded laser-fusion capsules. We have obtained very high-quality (SNR≊100) time-integrated images of indirectly driven targets. By coupling ring apertures with x-ray framing cameras, we have also obtained high-quality (SNR≊50) time-resolved images of directly driven capsule cores. These images can be used to observe the symmetry of the drive and the hydrodynamics of the implosion. Recently, we also obtained high-quality images of short-pulse laser (0.6 ps) irradiations of Ta targets. The spatial resolution of the RAM has been investigated both experimentally and through diffraction calculations. The resolution is at least as small as the width of the annulus, and may be smaller under particular circumstances.
Synthesis of superhard carbon nitride composite coatings
Authors: Li Dong , Chu Xi , Cheng Shang-Cong , Lin Xi-Wei , Dravid Vinayak P. , Chung Yip-Wah , Wong Ming-Show , Sproul William D.
Published: July 2002

Crystalline carbon nitride/TiN composite coatings have been deposited using a dual-cathode magnetron sputtering system onto polished silicon and M2 steel substrates held at room temperature. We propose that TiN provides a lattice-matched structural template to seed the growth of carbon nitride crystallites. The resulting coatings are smooth, fully crystalline, with nanoindentation hardness in the range of 45–55 GPa. This hardness is in the low-end range of diamond films. Suggestions for better seeding materials to further improve the hardness are proposed.
Transverse-flow 50-kV trigatron switch for 100-pps burst-mode operation
Authors: Beverly R. E. , Campbell R. N.
Published: July 2002

An inexpensive, compact, three-electrode (trigatron) switch utilizing transverse gas flow was developed for burst-mode applications. The switch is cooled by adiabatic expansion from three built-in miniature nozzles and the interacting flow streams serve to sweep hot discharge gases from the electrode region. Tests demonstrated control of an average power of 100 kW for 10 s bursts at repetition rates up to 100 pulses per second (pps) while maintaining a hold-off voltage up to 50 kV. Under these conditions, the switch commuted currents up to 6 kA with a pulsewidth of 10 μs. The cost of operation is reduced by using oil-free and dry air at a supply pressure of 500–1000 kPa and a mass flow rate of 0.5–8 g/s. Minimum switch jitter is obtained using a rounded-tip trigger pin flush with the adjacent electrode and an optimum trigger voltage that causes breakdown first between the trigger pin and opposite electrode.
Design and construction of apparatus for characterization of gated field emitter array electron emission
Authors: Phillips Purobi M. , Hor Charles , Malsawma Lex , Jensen Kevin L. , Zaidman Ernest G.
Published: July 2002

An inchworm controlled microfabricated detector system with laser interferometric feedback has been developed to provide an absolute position characterization of the electron emission from gated field emitter arrays (FEAs) in an ultra-high-vacuum (UHV) environment with nanometric precision. The emission characteristics of single tip and multiple tip FEAs are required to provide comparison with theory and simulation in order for these to be predictably used as a reliable source of high current density for high frequency amplifiers and oscillators. In its present form, the instrumentation is used to determine the angular distribution of the field emitted electrons. The addition of a few components will allow the measurement of emittance of the FEAs for electron gun design. Angular distribution of the electrons is measured by means of a microfabricated detector which is manipulated within an UHV environment with nanometric precision. The absolute location of the detector (within 80 nm uncertainty) is determined via laser interferometry. The details of the instrumentation with some preliminary experimental results are shown.
Multiplexed single-photon counting. I. A time-correlated fluorescence lifetime camera
Authors: McLoskey David , Birch David J. S. , Sanderson Alan , Suhling Klaus , Welch E. , Hicks P. J.
Published: July 2002

We report the operation of a new type of fluorescence lifetime imaging camera based on the time-correlated single-photon counting (TCSPC) technique. To the best of our knowledge the application-specific integrated circuit (ASIC) used in the camera is the first ASIC designed for the field of fluorescence. The ASIC also forms the basis for the first read-out system for single-photon timing array detectors and is capable of multiplexing and routing counts from up to sixteen detection channels, while preserving their timing characteristics with picosecond resolution. In conjunction with an array detector such as a multianode MCP-PM this ASIC allows multiple fluorescence decays to be routinely and simultaneously acquired using a single set of TCSPC timing electronics. To demonstrate one practical application of this technology, we have observed for the first time the spatial distribution of fluorescence lifetime contours through a strongly self-absorbing sample, and the effects observed demonstrate how differences in optical geometry can contribute to the lack of consistency between results obtained in different laboratories.
A fully integrated near-field optical, far-field optical, and normal-force scanned probe microscope
Authors: Lieberman Klony , Ben-Ami Nily , Lewis Aaron
Published: July 2002

We present a near-field scanning optical microscope (NSOM) which fully integrates near-field and far-field optics with scanned probe microscopy (SPM). The instrument incorporates a novel, flat scanning system that allows the NSOM/SPM head to be placed directly on the sample stage of any upright or inverted optical microscope and fully integrates the two microscopes. The near-field optical microscope that is designed around this flat scanner utilizes cantilevered optical force sensing probes that we have developed. Thus, the instrument can simultaneously image in a number of topographic and optical modes. The normal force sensing capability of our probes and microscope provides a significant advantage over straight optical fibers and the shear force detection techniques that are employed. The piezoelectric scanner incorporates X, Y, and Z scan ranges of over 40 μm into a flat stage less than 7 mm high. The scanning stage also provides for inertial translation of a sample over many millimeters. This completely and transparently integrates the technologies of near-field optics and other scanned probe microscopies with conventional far-field optical microscopy. Furthermore, the axial positioning capability of the flat scanner enhances the characteristics of the far-field microscope by allowing for three-dimensional optical sectioning that is required in techniques such as confocal imaging, nonlinear optical microscopies, and charge coupled device (CCD) imaging. Finally, the X, Y, and Z precision movements also have the potential for being used in optical tweezer applications.
Deep x-ray lithography for micromechanics and precision engineering (invited)
Authors: Guckel Henry
Published: July 2002

Micromechanics, an emerging technology for sensor and actuator fabrication, has a large market potential that has already been exploited in the sensor area. Progress in actuators, devices that modify their environment and are fundamentally three dimensional, has been much more modest and is suffering from the availability of a fabrication tool with the necessary attributes. If the tool is based on photoresist technology, requirements include very large structure heights: in the millimeter range, for mask-defined prismatic photoresist shapes with flanks that differ from 90 degrees by less than 15 arc-seconds. Photoresist procedures that lead to these results are very different from their counterparts in the microelectronic industry. Thus, application is based on precast sheets of polymethyl methacrylate, PMMA, and solvent bonding followed by precision fly-cutting. Exposure is based on well-collimated x-ray sources, synchrotrons, with flux densities that can deposit 1,600 Joules per cubic centimeter in a finite time at the correct photoresist depth. Since PMMA has an absorption length that varies with photon energy, it is 100 micrometer at 3000 eV and increases to 1 cm at 20,000 eV, beamline and exposure designs center on transmission filters that control the low energy portion of the synchrotron spectrum. Since exposure latitude is large, overexposure by a factor of 15 is allowed, beamline and exposure design are relatively simple. Experiments via the Wisconsin machine, Aladdin, and the Brookhaven 2.6-GeV ring are being used to study the effectiveness issue of manufacturing with synchrotron radiation. Actuator test vehicles are linear and rotational magnetic micromotors with force outputs in the milli-Newton range. High energy exposures have produced large parts with submicron precision that are finding applications in ink jet printing and precision injection molding procedures. Both device types are unique to x-ray assisted processing.
Large electromagnetic stop bands in metallodielectric photonic crystals
Authors: Brown E. R. , McMahon O. B.
Published: July 2002

An electromagnetic stop band spanning about one octave is observed in a periodic structure consisting of a face-centered-cubic Bravais lattice of metal spheres supported by a low-loss dielectric. The low-frequency edge of the stop band is consistent with the Mie condition for the metallic spheres, and the center frequency of the stop band is a function of the lattice constant and the support dielectric material. For example, a sample having a cubic lattice constant of 1.65 cm, 3/8 in. diam chrome spheres at each atomic core, and Teflon support dielectric displayed a lower band edge of approximately 5.2 GHz, an upper band edge of about 12.8 GHz, and a maximum rejection at the center of the band of roughly 20 dB.
Microgun-pumped blue lasers
Authors: Hervé D. , Accomo R. , Molva E. , Vanzetti L. , Paggel J. J. , Sorba L. , Franciosi A.
Published: July 2002

Microgun-pumped lasers, in which electron beam pumping is achieved via an array of low-voltage, field-emission microtips, were demonstrated in the blue and blue-green regions of the spectrum. The devices exploit graded index, separate confinement Zn1−xCdxSe/ZnSe heterostructures grown by molecular beam epitaxy on In1−xGaxAs(100) substrates. Lasing thresholds were in the 4–20 kW/cm2 range for temperatures between 83 and 225 K, and the device lifetime exceed several hours at a 12.5% duty cycle for a laser operating at 83 K and a wavelength of 478.4 nm.
Application of interferometry and Faraday rotation techniques for density measurements on the next generation of tokamaks
Authors: Snider R. T. , Carlstrom T. N. , Hodapp T. D. , Jobes F. C. , Peebles W. A.
Published: July 2002

The next generation of tokamaks present unique challenges to plasma diagnostic design due to the physical size of the devices and the radiation environment. The need for a density measurement for density feedback control for a prototype reactor such as ITER is well established and several proposals for line average measurements have been put forward. In this article, a design for a line average density diagnostic for ITER using collinear interferometry and Faraday rotation measurements will be presented. Plasma effects on both types of measurements and density resolution will be discussed along with the possibility of combining the information from the two collinear measurements to improve the reliability and quality of the density profile. Survivability of the plasma facing mirrors, in particular the surface flatness and surface roughness, are critical issues and preliminary analysis suggests these may limit the wavelength of probing beams. Thermal and stress analysis of the plasma facing mirrors will be presented along with a discussion of mirror material selection based on thermal, nuclear, and sputtering considerations.
Time-resolved, two-dimensional electron-temperature distribution of laser-imploded core plasmas
Authors: Heya M. , Nakasuji M. , Shiraga H. , Miyanaga N. , Azechi H. , Takabe H. , Yamanaka T. , Mima K.
Published: July 2002

We have developed a multichannel, multiimaging x-ray streak camera technique to measure two-dimensional electron-temperature distributions with a high temporal resolution by adding a multichannel spectrum selection capability to a multiimaging x-ray streak camera technique, and applied it to direct-drive implosion experiments with partially coherent light at Gekko-XII laser facility. It was found that electron-temperature distributions in the laser-imploded core plasmas of ICF targets had low-mode nonuniform structures changing with a temporal scale of 20 ps, and the abrupt drop of the electron temperature appeared in the deceleration phase. We have compared temporal profiles of the experimentally observed x-ray intensity and electron-temperature with those predicted by a one-dimensional hydrodynamic code “ILESTA” to investigate the hot spark heating in the core plasmas.
Dynamic behavior of cobalt granules with annealing treatment in ion-beam cosputtered Co22Ag78 granular film
Authors: Sang H. , Zhang S. Y. , Chen H. , Ni G. , Hong J. M. , Zhao X. N. , Jiang Z. S. , Du Y. W.
Published: July 2002

The dynamic behavior of ferromagnetic cobalt granules in ion-beam cosputtered Co22Ag78 samples under annealing treatment was examined by transmission electron microscopy (TEM), using a real-time video recording system. Cobalt granules about 10 nm in average size were embedded in a nonmagnetic silver matrix. It was observed that, in situ, the cobalt granules changed continually in shape and size with annealing temperature and time. We have estimated the changes of cobalt granule size from the results of TEM. The ferromagnetic resonance method was employed to study the evolution of the shapes of cobalt granules. It shows that cobalt granule shapes and sizes change mainly along the plane of the film during the process of annealing.
Time-of-flight neutral particle analyzer for Alcator C-Mod
Authors: Boivin R. L. , Koltonyuk M. , Munson C. P. , Mayo R. M.
Published: July 2002

A neutral particle analyzer, based on the time-of-flight technique is scheduled to be installed on the Alcator C-Mod tokamak. The instrument was originally designed and used in the ZT-40 experiment, and later, briefly used on the CTX experiment at Los Alamos National Laboratory. The design consists of a chopper wheel mounted on a turbomolecular pump, a ∼2 m long flight tube, a Cu–Be secondary electron emitting surface, and an electron multiplier, which together are used as the neutral particle detector. Among the changes introduced in the system from the original design, of particular interest is the location of the instrument. The instrument is mounted behind a magnetic-type neutral particle analyzer and shares the same line of sight. Both of them can be scanned, poloidally down to the X point and tangentially to R/R0=0.7. This will enable us to compare neutral flux through two different techniques with an overlap in energies from ∼0.5–4 keV, with the instrument capable of detecting neutral particles with energies as low as ∼20 eV. This should aid in characterizing neutral and ion behavior at the edge of the tokamak plasma, especially near the X point. We will also describe changes made to the controls for improved versatility and ease of operation.
Diagnostics for local spectroscopic measurements in the divertor region of the Alcator C-Mod and DIII-D tokamaks
Authors: May M. J. , Regan S. P. , Soukhanovskii V. A. , Finkenthal M. , Moos H. W. , Goetz J. A. , Lipschultz B. , Terry J. L. , West P. , Allen S. , Brooks N.
Published: July 2002

Local measurements of line emission of either intrinsic or gas puffed impurities will be performed around and below the X point. Such spectroscopic measurements, together with divertor Thomson scattering and bolometric imaging will enable estimates of divertor impurity particle distributions and power losses. A proposed multilayer mirror (MLM) diagnostic mounted inside the tokamak vessel will measure XUV (100–200 Å) emission from impurities at multiple locations in the divertor region of the C-Mod tokamak. A prototype of this instrument measuring N V at 162.6 Å is scheduled to be installed on C-Mod with a single chordal view of the X point. A multichordal/multispectral device using MLMs and gratings has been designed for the DIII-D tokamak. The instrument will measure the resonance emission of C II to C VI from 40–2000 Å, thus enabling a more direct and reliable estimate of the impurity content in the divertor. At DIII-D, the device will be mounted on a port below the mid plane avoiding spectroscopic contamination from the core plasma.
High resolution threshold and pulsed field ionization photoelectron spectroscopy using multi-bunch synchrotron radiation
Authors: Hsu C.-W. , Evans M. , Ng C. Y. , Heimann P.
Published: July 2002

We have demonstrated a resolution of 0.8 meV [full width at half-maximum (FWHM)] for threshold photoelectron measurements using a steradiancy-type zero kinetic energy photoelectron (ZEKE-PE) analyzer and the high resolution monochromatized vacuum ultraviolet (VUV) undulator synchrotron radiation of the chemical dynamics beamline at the advanced light source (ALS). Using this high resolution ZEKE-PE energy analyzer to filter prompt electrons and by employing a proper voltage pulsing scheme adapted to the timing structure of the ALS, we have achieved a resolution of 0.5 meV (FWHM) for pulsed field ionization photoelectron (PFI-PE) measurements with little contamination from prompt photoelectrons produced from direct photoionization and autoionizing processes. The experiment scheme presented here is generally applicable to PFI-PE studies using multi-bunch VUV synchrotron radiation at other synchrotron radiation facilities.
Electronics for He-Ne-I2 stabilized laser with digital control
Authors: Lazar Josef , Čı́p Ondřej
Published: July 2002

The construction of He-Ne-I2 stabilized laser electronics with digital control by a PC computer is presented in this contribution. This system has been developed to work with a compact laser head as a wavelength standard for metrology of lengths. Due to its compact construction and portability it can be used in calibrations of laser interferometers in mechanical engineering and microelectronics. A novel approach to the design of a control is presented. Sensitive analog circuits are opto-coupled to a digital control communicating with a PC. All functions are accessible from keyboard, iodine spectrum and system diagnostic data are currently displayed. User friendly graphic interface allows easy hyperfine line selection and locking. The system was compared to the BIPM laser and showed a very good reproducibility.
Soft x-ray and bolometric tomography in RFX
Authors: Martin P. , Murari A. , Buffa A. , Marrelli L. , Baker W. , Gadani G. , Hemming O. , Manduchi G. , Parini A. , Taliercio C. , Hoffmann A. , Stasek G. , Wirth R.
Published: July 2002

The article presents the design and the first results of a new eight camera, soft x-ray (SXR) and bolometric tomography which has been installed in RFX, a large (R=2 m, a=0.46 m), high current reverse field pinch experiment operating in Padova. The main features of the diagnostic, which has been designed with standards compatible with the requirements of large fusion experiments, are: (a) it allows simultaneous reconstruction of both SXR and total radiation emissivity structures with high spatial and time resolution (bandwidth up to 200 kHz for SXR and 10 kHz for bolometry). Moreover, computer controlled remote actions which interchange up to five material filters in front of the detectors allow the exploration of different energy ranges; (b) it can be easily decoupled from the machine without breaking the main vacuum and can be operated during first wall baking up to 300 °C thanks to a cooling circuit; (c) the detection chain is designed to measure very low signals [in the order of 1 nA for SXR diodes and of 100 μV for bolometers]; (d) it is equipped with a VME based 1 MHz data acquisition system which allows on-line processing of a large amount of data. To accomplish these features the diagnostic consists of eight fully remotely controlled manipulators which can insert eight photocameras, carrying 78 top-rated Si SXR and 48 miniaturized metal film bolometric detectors in their operating positions. Initial results are presented.
Continuum x-ray source as a calibration system for charge coupled devices
Authors: Hashimotodani K. , Toneri T. , Kitamoto S. , Tsunemi H. , Hayashida K. , Miyata E. , Katayama K. , Kohomura T. , Asakura R. , Koyama K. , Yamamoto K. , Miyaguchi K. , Suzuki H.
Published: July 2002

We present x-ray spectra obtained by a charge coupled device (CCD) from an electron impacting x-ray source using several kinds of electron targets: Au, Al–bronze, Al, and pure Al. The x rays from the source are dispersed by a grating and the dispersed x rays are focused on the CCD. Owing to the fine spatial and moderate energy resolutions of the CCD, fine spectra with 2 eV energy resolution up to 2.2 keV are obtained. X rays from the pure Al target (99.999% purity) provide good continuum x rays except for Al K x rays. This continuum source is useful as a calibration source for low energy x-ray detectors.
Vapor volume fraction, flow regime, and vapor velocity inference using fluid conductivity measurements
Authors: Meftah Khaled , Ruggles Arthur E.
Published: July 2002

An array of conductivity sensors is presented that infers the vapor volume fraction, flow regime, and vapor velocity in a two-phase flow. The frequency response of the sensors is up to 40 Hz, which allows for dynamic signal processing to ascertain flow characteristics additional to the time average vapor volume fraction, such as the vapor velocity and flow regime. The sensor array, associated driving circuitry, and signal processing techniques are presented, and the performance of the array is evaluated for an air–water flow at one atmosphere and a steam water flow at 0.095 MPa.
New procedure for presenting data by integrated or differentiated smooth graphs
Authors: Wirbeleit F. , Niklas J. R.
Published: July 2002

A new algorithm for presenting data by integrated or differentiated smooth graphs was found while looking for a fast and flexible procedure for presenting experimental data by smooth graphs based on different line shape functions. The algorithm to be presented is applicable at data points that are both widely separated and scattered within the same set, as well as data of a higher dimensional frame.
Controllable fabrication of bent near-field optical fiber probes by electric arc heating
Authors: Lin H.-N. , Lewlomphaisarl U. , Chen S. H. , Lee L. J. , Tsai Din Ping
Published: July 2002

We describe the construction of a high voltage electric arc puller for controllable fabrication of bent near-field optical fiber probes. Various probes with bent angles ranging from 30° to 75° and bent lengths between 600 and 900 μm were successfully produced. The tip diameters achieved are between 100 and 200 nm. These bent type probes can be made into cantilevered probes that can be used for any dynamic mode atomic force microscope, and make the construction of a scanning near-field optical microscope easily attainable.
Micromachined silicon torsional resonator for magnetic anisotropy measurement
Authors: Morillo Jaime , Su Quanmin , Panchapakesan Balaji , Wuttig Manfred , Novotny Donald
Published: July 2002

A novel method for measuring the out-of-plane magnetic anisotropy of thin films has been developed using the existing techniques of silicon micromachining. The torsion pendulum, which is commonly used to measure the perpendicular magnetic anisotropy energy constant, Ku, is modified into a single crystal silicon high Q torsional resonator. This article describes the principle of a silicon torsional resonator, the experimental procedure for measuring magnetic anisotropy, and the results. The theoretical values of Ku for Terfenol-D and Metglas® thin films were compared to the experimentally determined values and found to be within the error limits which for Metglas©, better than 1%. The agreement is poorer, 5%–15%, for amorphous stressed Terfenol-D, since its magneto-elastic energy is less accurately known. The results show that this is a viable method for measuring the magnetic anisotropy.
Compact glow discharge x-ray tube
Authors: Tsuji Kouichi , Wagatsuma Kazuaki
Published: July 2002

We have developed a compact glow discharge x-ray tube (diameter: 10 mm, length: 20 mm), which is composed of a hollow anode tube, a cathode plate, and a thin film target. This glow discharge device was operated with an Al thin film target at a discharge voltage of 2.0 kV at a discharge current of 0.1 mA and at a He pressure of approximately 0.2 Torr, which was used as the discharge gas. The characteristic x rays of Al Kα are produced by bombardment of electrons emitted from the cathode surface. The strong x-ray emission intensity, which depended on the operating voltage and the gas pressure, was obtained throughout the discharge time of 1.5 h.
Characterization of a semiconductor detector and its application for ion diagnostics using a novel ion energy spectrometer
Authors: Sakamoto Y. , Cho T. , Hirata M. , Kohagura J. , Sasuga T. , Nishizawa Y. , Numakura T. , Minami R. , Nakashima Y. , Tamano T. , Yatsu K. , Miyoshi S.
Published: July 2002

Semiconductor ion detectors are developed and characterized for the purpose of the use for high-output and wide-energy-sensitive upgraded ion diagnostics. In particular, the theoretical basis for the simulation of the semiconductor ion-energy response along with its experimental verification using monoenergetic ion beams is investigated. High-output-current semiconductor signals ranging from one to three orders of magnitude larger than those from widely employed commercially available silicon-surface-barrier detectors are attained in the ion-energy region above 0.2 keV. These data are found to be well fitted by the developed simulation results. In order to observe ion signals alone under the complicated condition of the simultaneous incidence of ions, electrons, and x rays, we develop an upgraded electrostatic ion-energy spectrometer, having specific structures with obliquely positioned multiple grids. The combination of the installation of such a low-ion-energy-sensitive semiconductor detector and this novel-structured ion spectrometer provides a new electrostatic large-output and low-energy-sensitive ion spectrometer having no signal disturbances from the other plasma species and giving no perturbations to ambient plasma-confining magnetic fields. Accordingly, this novel compact-sized electrostatic ion spectrometer using a single-channel semiconductor collector provides temporal-evolution data on ion-energy spectra during a single plasma shot alone; therefore, this spectrometer is usefully applicable to the opportunities of the observations of ion parameters in both divertor and hot-core regions.
TJ-II data retrieving by means of a client/server model
Authors: Vega J. , Sánchez E. , Crémy C. , Portas A. , Dulya C. M. , Nilsson J.
Published: July 2002

The database of the TJ-II flexible heliac is centralized in a Unix server. This computer also commands the on-line processes related to data acquisition during TJ-II discharges: programming of measurement systems, connectivity with control systems, data visualization, and computations. The server has to provide access to the data so that signal analysis can be performed by local users or even from remote hosts. Data retrieving is accomplished by means of a client/server architecture in which two data servers are permanently running in the background of the Unix computer. One of them serves data requests from local clients and the other one sends data to remote clients. The communication protocol in both cases has been developed by using TCP/IP and Berkeley sockets. The client part consists of a set of routines (FORTRAN and C callable), which, in a transparent way, provide connectivity with the servers. This structure allows access to TJ-II data exactly in the same way from any computer, hiding not only specific aspects of the database, but hardware architecture of the server computer as well. In addition, the remote access makes it possible to distribute computations and to reduce the load on the Unix server from analysis and visualization tasks. At present, this software is running in four different environments: the Unix server itself, various types of Unix workstations, a CRAY J90 and a CRAY T3E. Finally, due to the fact that visualization is essential for TJ-II data analysis, a powerful and a very flexible visualization tool has been developed. It is a point and click application based on X Window/Motif. Data access is carried out through the client/server processes mentioned above and the software runs in the client computer.
High resolution emission and absorption spectroscopy for erosion product analysis in boundary plasmas
Authors: Jentschke H. , Hirsch K. , Klenge S. , Schumacher U.
Published: July 2002

The highly resolved spectra of the silicon multiplet around 251 nm are studied for plasmas in front of a C/C-SiC target interacting with a nearly cylindrically symmetric low temperature plasma jet. The erosion rates from this target are deduced from the silicon density distribution, which is determined from the line intensity ratios and details of the line profiles. Under the conditions of the plasma parameters in this plasma-target interaction experiment these spectral line parameters depend on the optical depths of the emitting and absorbing silicon atoms along the line of sight. The spectral line central branching ratios of lines with quite different products of absorption oscillator strength and statistical weight are most sensitive to the optical depth. In the case of high plasma jet currents the density of the eroded silicon is found to reach values of up to 5×1018 m−3 in agreement with gravimetric measurements.
An optimized multifoil soft x-ray spectrometer for the determination of the electron temperature with high time resolution
Authors: Murari A. , Franz P. , Zabeo L. , Bartiromo R. , Carraro L. , Gadani G. , Marrelli L. , Martin P. , Pasqualotto R. , Valisa M.
Published: July 2002

In RFX a monitor for the measurement of the on-axis electron temperature with high temporal resolution has been designed and operated during the last experimental campaigns. It consists of four soft x-ray (SXR) diodes which observe the plasma through four beryllium filters of different thickness. In this article the main design issues are presented. The measured values of the temperature, computed both with the standard double foil method and with a fit of all the available signals, are reported, correlated with the main plasma parameters and briefly compared with the results of other diagnostics. The main causes of systematic error, the effect of the noise and the reliability of the results in various plasma conditions have been investigated. Dynamic evaluations of the temperature up to a maximum bandwidth of 5 kHz are described, confirming the potentialities of the technique to follow fast phenomena. Possible improvements of the diagnostic and future developments are also pointed out.
Advance in diagnostics for high temperature plasmas based on the analytical result for the ion dynamical broadening of hydrogen spectral lines (abstract)
Authors: Oks E.
Published: July 2002

It is well known that the ion dynamics is very important for Stark broadening of spectral lines in high-temperature plasmas. However, it was usually assumed that with the increase of the plasma density N and/or of the principal quantum number n of the upper level of the radiator, the ionic contribution to the impact width (ICIW) tends to zero. In distinction to that paradigm, by finding an analytical result for the ion dynamical broadening of hydrogen spectral lines, we show here that with the increase of N and/or n, the ICIW does not decrease. Moreover, for practically important ranges of T, N, and n, this “residual” ICIW, being virtually independent of n, can be comparable to the standard electron impact width. This novel result leads to: (1) a substantial revision of the past diagnostic conclusions for a variety of high-temperature plasma experiments; (2) a much better possibility to deduce from experimental, Stark-broadened line profiles not only the plasma density but also the plasma temperature; (3) a significant enhancement of the accuracy of N and T obtained from experimental line profiles. The consequences are especially important for tokamak plasmas, where the diagnostics based on experimental profiles of high Balmer and Paschen lines is frequently used.
Estimation method of a separatrix profile of field-reduced configuration plasma with the deconvolution concept
Authors: Yamanaka Koji , Suzuki Yukihisa , Kitano Katsuhisa , Ito Shoji , Okada Shigefumi , Goto Seiichi
Published: July 2002

A method to analyze the separatrix profile of a field-reversed configuration is presented that is based on a multichannel excluded flux measurement. In the method, the plasma current is represented by current filaments. This current code includes all the magnetic sources (e.g., a vacuum conducting vessel, coils for the confinement field, search coils, and coils for additional fields) as inputs to estimate the separatrix profile. With the aid of a numerically calculated function, experimental data are deconvolved to determine the current filament. The influence of measurement error included in the raw data of the calculated profiles is also discussed.
Fielding of the on-axis diagnostic package at Z
Authors: Hurst M. J. , Nash T. J. , Derzon M. , Kellogg J. W. , Torres J. , McGurn J. , Seaman J. , Jobe D. , Lazier S. E.
Published: July 2002

We have developed a comprehensive diagnostic package for observing z-pinch radiation along the pinch axis on the Z accelerator. The instrumentation, fielded on the axial package, are x-ray diagnostics requiring direct lines of sight to the target. The diagnostics require vacuum access to the center of the accelerator. The environment is a hostile one, where we must deal with an intense, energetic photon flux (>100 keV) debris (e.g., bullets or shrapnel), and mechanical shock in order for the diagnostics to survive. In addition, practical constraints require the package be refurbished and utilized on a once a day shot schedule. In spite of this harsh environment, we have successfully fielded the diagnostic package with a high survivability of the data and the instruments. In this article, we describe the environment and issues related to the reentrant diagnostic package’s implementation and maintenance.
Design of the magnetic diagnostic for ITER
Authors: de Kock L. , Walker C. , Coccorese E. , Costley A. E. , Dremin M. , Gernhardt J. , Kasai S. , Senda I. , Shoji T. , Leuer J. , Snider R. , McCarthy P. , Portone A. , Stott P. , Young K.
Published: July 2002

The detailed design of the magnetic diagnostic for ITER is presented. The system consists of groups of pickup coils and flux loops on the vessel wall, the back plate, and the divertor. These sensors provide the measurements for the equilibrium reconstruction and the fluctuation analysis. The system is supplemented by Rogowski coils for halo current measurements and by a diamagnetic loop. The complete system meets the measurement requirements, matching those of contemporary large divertor tokamaks. The maximum radiation exposure is such that the sensors will survive for the lifetime of the ITER.
Diagnostic for fast charged particles at TEXTOR-94
Authors: Bonheure G. , Van Wassenhove G. , Vervier M. , Messiaen A.
Published: July 2002

A diagnostic for measuring the energy spectrum of fast charged particles has been developed at TEXTOR-94. It consists of a pair of solid state silicon passivated implanted planar silicon detectors which are actively water cooled. The detectors are mounted on a manipulator and are inserted into the vacuum vessel during plasma operation. The preamplifiers are located just behind the detectors. The noise level is strongly minimized by careful grounding and rf shielding. Collimators placed in front of the detectors allow to obtain radial and pitch angle-resolved measurements. Fast particles coming from the center of the plasma are detected by one detector. The second detector can be used as a background monitor or can provide an additional measurement at another position. Orbit calculations in a realistic magnetic field predict the detection efficiency. The calculated detection efficiency shows good agreement with our experiments. The stable temperature and excellent noise immunity of our system allow to measure the energy spectrum of the 3 MeV protons and 1 MeV tritons produced by the DD fusion reactions in discharges with different heating scenarios. High resolution energy spectra are even obtained in discharges heated with injection of deuterium in a deuterium plasma.
New concepts for x-ray spectroscopy of tokamak plasmas
Authors: Fraenkel Benjamin S. , Bitter Manfred
Published: July 2002

The throughput of Bragg crystal spectrometers with two-dimensionally curved crystals has been computed and is found to be much larger than the throughput of conventional Johann spectrometers with cylindrically bent crystals. Special attention was given to spectrometers with spherically and toroidally bent crystals which provide, in addition to a high throughput, good spectral and spatial resolution. These spectrometers should meet the growing diagnostic requirements for present and future large tokamaks.
Photoacoustic measurement of intracavity energy in pulsed lasers
Authors: Villagrán-Muniz M. , Zaragoza-Lemus A.
Published: July 2002

We show that the photoacoustic signals generated at the high reflection mirror of a pulsed laser depend linearly on the output energy. This allows us to measure acoustically the output energy, the tuning range, and the optimum temperature and concentration of a dye laser, with the advantage that there is no interference of the output beam, as is the case with optical measurements.
Low velocity boron micro-pellet injector for edge and core impurity transport measurements
Authors: Kugel H. W. , Gorman J. , Kaita R. , Munsat T. , Stutman D.
Published: July 2002

A simple low velocity boron micro-pellet injector has been under development for Current Drive Experiment Upgrade (CDX-U) spherical torus edge and core impurity transport measurements, and wall conditioning. The injector consists of 16 barrels on a rotatable turret. Each barrel can be loaded with boron powder particles of diameters ranging from 1 to 40 μm diameter in amounts ranging from less than 0.25 mg to more than 2 mg. A selected barrel is manually rotated into firing position using a vacuum precision rotary/linear motion feedthrough. A piezoelectric valve gas feed system triggered by CDX-U discharge timing is used to control H2 or D2 propellant gas at a cylinder pressure of 5.8×10−3  Pa (40 psi) or less. The injector barrel-to-CDX-U plasma edge distance is 0.47 m. Initial low mass injections of neutral boron beams were performed into CDX-U plasmas at a velocity of 23 m/s. Measurements were obtained with a filtered gated charge coupled device TV camera, bolometry, visible spectroscopy, and ultrasoft x-ray diagnostics. This work is in support of the present CDX-U research program and possible applications on National Spherical Torus Experiment.
A fiber-optic-based multichannel time-correlated single-photon-counting device with subnanosecond time resolution
Authors: Waddell Emanuel , Stryjewski Wieslaw J. , Soper Steven A.
Published: July 2002

A fiber-optic-based multichannel time-correlated single-photon-counting device with subnanosecond time resolution was developed. A passively mode-locked Ti:sapphire laser provided the excitation source for 12 separate time-correlated single-photon counting channels in which three single-photon avalanche diode detectors were used to analyze the fluorescence from the channels. Single-mode optical fibers provided the conduit for the excitation light as well as the fluorescence emission. We determined that the excitation pulses undergo a temporal spread of 50 fs, a spectral spread of 0.2 nm, and remained nearly transform limited. The average instrument response function of each channel was determined to be 181 ps (full width at half maximum). The fluorescence lifetime of a representative near-infrared dye, aluminum tetrasulfonated naphthalocyanine, was determined to be 3.08 ns using this fiber-optic-based multichannel time-correlated single-photon-counting device.
Ultralow noise high gain transimpedance amplifier for characterizing the low frequency noise of infrared detectors
Authors: Howard R. M.
Published: July 2002

An ultralow noise transimpedance amplifier with a gain of 1010, a bandwidth greater than 10 kHz, and an input equivalent noise power spectral density of 1.7×10−30 A2/Hz (single sided) for frequencies less than 10 Hz and a level of 5×10−30 A2/Hz at 1 kHz is described. This level of performance is achieved with standard electronic devices, rather than batteries, powering the amplifier. Very good agreement between theoretical and experimental noise measurements is achieved due to careful measurement and modeling of the significant noise sources. It is shown that the noise level of the 1010 Ω feedback resistor increases with frequency and contributes a significant level of noise for frequencies in the kHz frequency range. The usefulness of the amplifier is demonstrated through measurement of the noise of a HgCdTe planar photovoltaic 3–5 μm mid-wavelength infrared detector cooled to 80 and 120 K.
Design and construction of a nanoelectrospray ion source for a triple quadrupole mass spectrometer
Authors: Troxler Heinz , Wetzel Erich , Kuster Thomas , Heizmann Claus W.
Published: July 2002

The design and construction of a nanoelectrospray ion source for a triple quadrupole mass spectrometer that is used for identification and analysis of minimum peptide amounts is described. This interface exhibits several improvements over commercially available devices: a new capillary holder that allows very simple loading and placement of the spray capillary, and a rotary stage that enables reproducible adjustment of the capillary’s angle at the orifice of the mass spectrometer. We also introduced a pressure-regulating system for fast and reproducible adjustment of the static backing air pressure onto the sample solution in the spray capillary. Furthermore, an electric safety circuit increases handling and operation safety of the nanoelectrospray interface.
On apparatus for studying catalysts and catalytic processes using neutron scattering
Authors: Turner J. F. C. , Done R. , Dreyer J. , David W. I. F. , Catlow C. R. A.
Published: July 2002

The design of a cell, built to investigate catalysis and catalytic processes, is reported. The cell is for use at ISIS spallation neutron source at the Rutherford Appleton Laboratory. It is required to operate in a dual manner either under gas flows of controlled composition at low pressure (ambient −5 bar) and at high vacuum (10−6 mbar working pressure). The temperature range of this cell is 4–1273 K. It will be used on a variety of instrument beam lines on ISIS. In use the cell is attached either to a furnace or cryofurnace center-stick assembly and gas is supplied from a gas circuit assembly.
A large-area plasma source excited by a tunable surface wave cavity
Authors: Wu T. J. , Kou C. S.
Published: July 2002

A large-area high-density microwave plasma is successfully generated at low pressure by a tunable surface wave cavity which consists of a 12 period vane-type slow wave structure. This cavity is operated in the π mode and resonant at 2.45 GHz. The plasma area is in excess of 50 cm×25 cm with a uniformity of ±10% at pressures less than 30 mTorr. A plasma surface wave has been excited so that a plasma density as high as 1.0×1012 cm−3 can be achieved at 30 mTorr for a microwave power of 2.0 kW. The plasma temperature is ∼1.5 eV and the plasma potential is ∼12 V. Above all, the number of the periods of the π-mode cavity can be increased without changing the resonance frequency and the distribution of the microwave fields such that this plasma source is easy to up-scaled.
Noise analysis of geometrically complex mechanical structures using the analogy between electrical circuits and mechanical systems
Authors: Yaralioglu G. G. , Atalar A.
Published: July 2002

Random fluctuations of displacement or velocity in mechanical systems can be calculated by using the analogy between electrical circuits and mechanical systems. The fluctuation-dissipation theorem expresses the relation between the generalized mechanical admittance and the noise in velocity. Similarly, correlation of mechanical noise can be calculated by using the generalized Nyquist theorem which states that the current noise correlation between two ports in an electrical circuit is dictated by the real part of the transadmittance. In this article, we will present the determination of the mechanical transadmittance and we will use the mechanical transadmittance to calculate the noise correlation on geometrically complex structures where it is not possible to approximate the noise by using the simple harmonic oscillator model. We will apply our method to atomic force microscope cantilevers by means of finite element method tools. The application of the noise correlation calculation method to rectangular cantilever beams shows some interesting results. We found that on the resonance frequencies, the correlation coefficient takes values 1 (full correlation) and −1 (anti-correlation) along the cantilever axis depending on the mode shapes of the structure.