bluuebunny/crossref_metadata_2025 huggingface dataset:
X-pinch plasma conditions from time resolved x-ray spectroscopy
Authors: Shelkovenko T. A. , Pikuz S. A. , Skobelev I. Yu. , Sinars D. B. , Chandler K. M. , Mitchell M. D. , Hammer D. A.
Published: March 2003

X-pinch plasmas, produced by exploding two or more 10–50 μm metal wires that cross and touch in the middle in the form of an X, have been successfully developed as point sources of soft x rays for radiography. However, the parameters of the x-ray source as a function of time, space and wavelength band are not well understood. To determine the X-pinch plasma characteristics, time-resolved x-ray spectra produced by two- and multiwire X pinches made from different wire materials were recorded using an x-ray streak camera. A spherically bent mica crystal spectrograph was used with a ∼10 ps time resolution x-ray streak camera in a slitless configuration. Some spectra were dominated by continuum and others by line radiation, and observed spectral features varied on time scales ranging from 10 to 1000 ps, depending on the wire material. Electron temperatures and densities in Ti X pinches were estimated from line ratios based upon collisional-radiative calculations, and from the time delay between the appearance of He-like and H-like Ti lines, respectively, indicating peak values of ∼2.5 keV and ∼2×1023/cm3. Results are presented that demonstrate the necessity for 10–100 ps time-resolution spectral data to obtain plasma conditions from micropinch x rays.
X-ray spectral diagnostics of neon photoionization experiments on the Z-machine
Authors: Cohen David H. , MacFarlane Joseph J. , Bailey James E. , Liedahl Duane A.
Published: March 2003

We report on an initial spectroscopic study of low-density, x-ray photoionized neon with x-ray spectroscopy. These experiments, carried out on the Z-machine at Sandia, are optimized to produce a gradient-free, collisionless plasma, and to explore issues related to the rapid x-ray photoionization of relatively cold, low-density plasmas. The initial experiments used time-integrated absorption spectroscopy, backlit by the pinch radiation, to determine the ionization balance in the gas cell. Future experiments will use time-resolved spectroscopy in both absorption and emission. The emission spectra are expected to be similar to those seen from photoionized astrophysical sources, such as x-ray binaries. Indeed, in addition to addressing basic plasma and atomic physics issues, these experiments are designed to help the astrophysical community better understand the new, high-resolution spectra being produced by the Chandra and XMM-Newton telescopes, and to benchmark spectral synthesis codes.
High-Z 0.9–1.0 MA X-pinch as a possible backlighter in 50–100 keV and sub-keV-10 keV spectral regions and a powerful soft x-ray source for surface modification research
Authors: Kantsyrev V. L. , Fedin D. A. , Shlyaptseva A. S. , Hansen S. B. , Ouart N. , Chamberlain D.
Published: March 2003

The presence of collimated 1.5–2.0 MeV electron beams in 0.9–1.0 MA high-Z X-pinch plasmas leads to the generation of an anisotropic hard x-ray radiation (more than 50–100 keV) in the crossing point of the wires, with a 1–2 mm size source and a time duration of 100–150 ns. The side-on measured electron temperature is higher than the end-on. Introducing of a synchrotron radiation in a side-on direction is used for the explanation of the phenomenon. The new results of time-resolved 0.16–10 keV x-ray imaging and spectroscopic study of the development of jets and hot spots in X-pinches are presented. The plasma parameters varied significantly for consecutive x-ray bursts (hot spots) during the same X-pinch discharge. A minimum duration of x-ray pulses was 1.1 ns. The x-ray energy output was up to 10–11 kJ, and a maximum power can reach up to 3×1011 W. The X-pinch coupled with the x-ray glass-capillary converter for collecting and focusing of x rays can generate soft x-ray energy density up to (1–10) J/cm2, and the flux density up to (1–5)×109 W/cm2. The 1 MA X-pinch can be used as a possible hard and soft x-ray backlighter and a soft x-ray source for material science and microelectronics research.
Analysis of high current X-pinch structure in keV and sub-keV regions
Authors: Fedin D. A. , Kantsyrev V. L. , Shlyaptseva A. S. , Hansen S. B. , Ouart N.
Published: March 2003

The complex measurements with spectral, temporal, and spatial resolution are very important in studies of properties of radiation from hot dense plasmas (Te up to 1.5 keV, Ne up to 1022 cm−3) generated by a pulse-powered Z-pinch machine with Imax∼0.9–1.0 MA and a current risetime of 100 ns. Plasma radiation from Ti, Fe, Mo or W X-pinches has been studied. The analysis and comparison of 1D TGS images in a spectral region 20–80 Å with time-integrated and time-resolved images from pinhole cameras show differences in sizes and positions of images depending on the wavelength. A comparison of these data with data obtained from absolutely calibrated PCD, XRD, and the bolometer shows the input of radiation from this spectral range into the total yield. The temporal behavior and spatial structure were found to be different in keV and sub-keV regions along an anode–cathode gap.
Applications of advanced theoretical x-ray L-shell spectroscopy to various plasma and collision experiments
Authors: Hansen S. B. , Shlyaptseva A. S. , Kantsyrev V. L. , Fedin D. A. , Ouart N. D. , Safronova U. I. , Fournier K. B.
Published: March 2003

The University of Nevada, Reno has developed a collisional-radiative atomic kinetics model that has successfully described the spectra produced by widely different multicharged ion experiments. The application of the model to experiments that highlight the importance of particular kinetics effects, including time-dependence and non-Maxwellian electron distribution functions, will be presented. These experiments include ion beam collision and high-temperature femtosecond laser and X-pinch plasma experiments. Adequate descriptions of ion beam collision spectra and x-ray yield require time-dependent treatment of radiative cascades from high-n capture states. Spectra from plasmas with significant fractions of hot electrons, such as those produced by fs lasers and X-pinches, require calculation of hot electron effects on collisional rates. The kinetics model presented here extracts as much information as possible from advanced experimental diagnostics such as time- and space-resolved spectral measurements.
X-ray spectroscopy and spectropolarimetry of high energy density plasma complemented by LLNL electron beam ion trap experiments
Authors: Shlyaptseva A. S. , Fedin D. A. , Hamasha S. M. , Hansen S. B. , Harris C. , Kantsyrev V. L. , Neill P. , Ouart N. , Beiersdorfer P. , Safronova U. I.
Published: March 2003

X-ray spectra of high energy density (HED) Z-pinch plasmas have been analyzed by means of a comprehensive kinetic modeling. A new diagnostic, x-ray spectropolarimetry, was applied to study anisotropy of Z-pinch plasma. This diagnostic is based on theoretical modeling of polarization-dependent spectra measured simultaneously by spectrometers with different sensitivity to polarization. Specifically, K-shell emission from Ti X-pinches was recorded simultaneously with identical LiF crystal spectrometers with the dispersion plane perpendicular and parallel to the discharge axis. Spectroscopic results from seven Ti X-pinch shots have been analyzed. Similar K-shell Ti polarization-dependent spectra generated by a quasi-Maxwellian electron beam at the LLNL EBIT-II electron beam ion trap have been studied. Further, the EBIT-II M-shell W spectra have proved to be important in the development of M-shell diagnostics of HED Z-pinch plasma. The advantages provided by electron beam ion trap data in the interpretation of HED Z-pinch spectra will be presented.
Processing of multi-monochromatic x-ray images from indirect drive implosions at OMEGA
Authors: Welser L. A. , Mancini R. C. , Koch J. A. , Dalhed S. , Lee R. W. , Golovkin I. E. , Marshall F. , Delettrez J. , Klein L.
Published: March 2003

We report here on the processing of multi-monochromatic x-ray images recorded with the MMI instrument in a series of stable and low-convergence indirect-drive implosion experiments in which Ar-doped D2-filled plastic shells were imploded with the OMEGA laser system. MMI records numerous narrow-band x-ray images over a broad photon energy range. From these images, specific line- and continuum-based subimages can be extracted. A procedure for processing data from the array of images recorded by MMI was developed and implemented into a convenient interactive data language code. Data from narrow-band x-ray images are critical for diagnosing the spatial structure of ICF implosion cores.
An indirectly heated electron beam emitter assembly
Authors: Iqbal Munawar , Chaudhary Maqbool A. , Rafiq M. , Masud Khalid , Fazal-e-Aleem
Published: March 2003

A simple, high performance indirectly heated axial electron gun has been designed and fabricated. A 0.9-mm-thick and 15-mm-wide tantalum strip was used as a cathode with an emission length of 42 mm. An emission current of 600 mA was achieved at an input heater power of only 116 W. The gun is useful for laboratory experiments as well as welding, evaporation of refractory metals, and for linear accelerators.
New compact classical 40 kV Mott polarimeter
Authors: Petrov V. N. , Grebenshikov V. V. , Grachev B. D. , Kamochkin A. S.
Published: March 2003

A compact classical electron spin detector based on Mott scattering is described. This Mott polarimeter has an efficiency of ≈5.6×10−4, a maximum counting rate of 500 kcps and bulk size 15 cm×25 cm. The design of the polarimeter goes back to the classical Mott detector, operating from 100 to 120 kV but it can be combined with conventional analyzers due to its compactness. In this Mott polarimeter an electrostatic acceleration voltage up to 40 kV can be applied and the detectors are energy sensitive silicon diodes operated in reverse bias with variable discriminator threshold. The detectors with the amplifiers are floated on the top of acceleration voltage to allow a field-free travel of the electrons from the scattering gold foil to the detectors. Such features reduce the polarimeters sensitivity to slight motion or changes in the shape of the incoming beam.
Automatic system for directly measuring the dynamic viscosity of liquids
Authors: Molina C. , Victoria L. , Arenas A.
Published: March 2003

We present a variation of a method using an Ostwald viscosimeter to ascertain the dynamic viscosity of a liquid with errors of less than 2% and without the need to know the density of the problem liquid. It is simple and cheap, making it suitable for use in instrumentation laboratories and the classroom.
Utilization of background signal for inference of Zeff spatial profile in incoherent Thomson scattering diagnostic
Authors: Naito O. , Hatae T.
Published: March 2003

A simulation study on the feasibility of inferring the spatial profile of the effective ionic charge, Zeff, along with electron temperature and density in Thomson scattering diagnostic is presented. The background signal, which is usually discarded after being subtracted from the Thomson scattered signal, is used in the reconstruction procedure. If the contribution from line radiation to the background signal is by one order of magnitude smaller than that from bremsstrahlung, a fairly accurate Zeff profile can be reconstructed.
Resonant ultrasound spectroscopy in shear mode
Authors: Wang Y. C. , Lakes R. S.
Published: March 2003

We present an enhancement of the resonant ultrasound spectroscopy method for the determination of elastic and viscoelastic properties. By using shear transducers rather than the usual compressional ones, signal strength for the fundamental is enhanced by one to three orders of magnitude. This enables simplified determination of shear modulus and damping tan δ with off-the-shelf electronics. Moreover, the polarization of the shear transducers can be used to identify modes of vibration.
Spatial-phase locking with shaped-beam lithography
Authors: Hartley John G. , Groves Timothy R. , Smith Henry I. , Mondol Mark K. , Goodberlet James G. , Schattenburg Mark L. , Ferrera Juan , Bernshteyn Alexandr
Published: March 2003

Spatial-phase-locked electron-beam lithography is a method of precisely locating pattern elements on a substrate by providing real-time feedback of the beam’s location by means of a fiducial grid located on the substrate surface. Previously, this technique has been demonstrated in Gaussian-beam systems, in one and two dimensions. In this note we propose a method of extending the spatial-phase-locking concept to a vector shaped-beam architecture. In the proposed method, an image of a screen grid is superimposed on the projected shape, and this grid image is dithered in X and Y to provide a periodic signal whose phase can be interpreted to determine the position of the projected shape relative to the fiducial grid.
Tests of a planar L-band orthomode transducer in circular waveguide
Authors: Engargiola G. , Plambeck R. L.
Published: March 2003

This note describes tests made of a planar L-band orthomode transducer consisting of four probes symmetrically arranged in a circular waveguide and two wideband baluns, made from back-to-back slotline-to-microstrip transitions. We designed this device to model at large scale (>50:1) the performance of a compact millimeter wave transducer for use in an astronomical receiver where probes and baluns are microfabricated with SiON thin-film dielectric deposited on a quartz substrate. In the L-band model, probes and baluns are printed on 0.010-in.-thick Duroid 6006, mounted on a 0.25-in.-thick piece of fiberglass and placed flush against the waveguide. Each pair of opposite probes is coupled through a balun to a 50 Ω microstrip output. Measurements show that, from 1.2 to 1.9 GHz, the orthomode transducer has an output return loss less than −18 dB and cross polarization less than −35 dB. It should be possible to scale this design to cover bands of high atmospheric transparency at 100, 230, or 345 GHz.
Orientation and direct current field dependent dielectric properties of bulk single crystal SrTiO3 at microwave frequencies
Authors: Eriksson A. , Deleniv A. , Gevorgian S.
Published: March 2003

The dielectric properties of bulk single crystal SrTiO3 (STO) are studied in the temperature range 30–300 K, under dc field 0–10 kV/cm at 1.0 kHz and in the frequency range 0.3–2.0 GHz. Two sets of circular disk shaped parallel plate resonators have been fabricated and tested experimentally. In the first set thin YBa2Cu3O7 films have been epitaxially grown on both surfaces of [100] STO disks. In the second set, three crystal orientations of SrTiO3 [100], [110], and [111] have been used to make parallel-plate resonators with evaporated Cu/Ti electrodes. No peculiarities in field dependent dielectric permittivity are detected for STO with smaller densities of impurities. For samples with larger impurity densities double loop hysteresis is observed in the dc field dependent permittivity. For all orientations the losses are minimum at temperatures about 50–55 K. The losses at microwave frequencies increase with the applied dc field regardless of the orientation of the STO crystal. At relatively high dc fields (depending on the temperature) the losses start decreasing slightly.
Giga- and terahertz frequency band detector based on an asymmetrically necked n-n+-GaAs planar structure
Authors: Suz̆iedelis A. , Gradauskas J. , As̆montas S. , Valus̆is G. , Roskos H. G.
Published: March 2003

We describe the concept of an asymmetrically shaped n-n+-planar GaAs diode whose operation is based on nonuniform free charge carrier heating effects. The detector was fabricated on thin elastic polyimide film and has been shown to have an operational bandwidth for detection ranging from 30 GHz up to 2.5 THz at room temperature. The voltage sensitivity of the detector is nearly independent of the frequency from 30 GHz up to 0.7 THz and is close to 0.3 V/W. In the upper section of the frequency range, 0.7–2.5 THz, the sensitivity is limited by the electron momentum relaxation time. The induced signal responds linearly to the incident power over the frequency range studied. It is shown that the performance of the detector can be explained well by a phenomenological theory.
Extending the pressure and temperature limits of hydrothermal diamond anvil cells
Authors: Burchard M. , Zaitsev A. M. , Maresch W. V.
Published: March 2003

A modified hydrothermal diamond anvil cell (HDAC) has been developed. The cell is designed primarily for use with anvils incorporating internal heaters, but also solves several technical problems limiting the pressures and temperatures that can be reached with conventional HDACs. The essential features of the cell are (i) the pressurizing mechanics ensure strictly parallel alignment and preclude accidental collision of the anvils, (ii) the mechanical anvil holders provide both robust fixation of the anvils without any glue and reliable electrical contacts with the anvil facets, (iii) the diamond anvils can be heated while the anvil backing plates and the holders remain comparatively cool, (iv) stable hydrothermal working conditions to at least 4.5 GPa and 1000 °C can be achieved during the course of sluggish reactions typical of geoscience research thrusts, and (v) large sample volumes are possible, such as diameters of 0.5 mm and heights of 0.1 mm for a 1 mm culet.
Direct measurement instrument for lattice spacing on regular crystalline surfaces using a scanning tunneling microscope and laser interferometry
Authors: Rerkkumsup Pongpun , Aketagawa Masato , Takada Koji , Watanabe Tomonori , Sadakata Shin
Published: March 2003

An instrument for direct measurement of the lattice spacing on regular crystalline surfaces, which incorporates a scanning tunneling microscope (STM) and a phase modulation homodyne interferometer (PMHI), was developed. Our aim was to verify the applicability of the length measurement method in which the lattice spacing on the crystalline surface obtained with the STM is used as a fine scale and the optical interference fringe, i.e., wavelength λ, of the PMHI is used as a coarse scale. The instrument consists of a STM head with a YZ axes tip scanner, a precise X-axis sample stage with flexure springs, and the PMHI with a four-path differential configuration. Combining the movements of the YZ-axes tip scanner and the X-axis sample stage, the instrument can perform long atomic STM imaging of the crystalline surface along the X axis, which is also the fast scanning axis for eliminating thermal drift. The relative displacement of the X-axis sample stage between optical interference dark fringes (=null points) of the PMHI, which is λ/16 times the integer value in the design, can be measured with a resolution of 10 pm or less using the phase modulation technique. The lattice spacing on a highly oriented pyrolytic graphite (HOPG) crystalline surface was measured by comparing the number of atoms in the atomic STM image of 100 nm length with the optical fringes of the PMHI. The mean and expanded uncertainty (k=2) of the lattice spacing between α sites of the HOPG surface were 0.246 nm and 7 pm, respectively. The mean value was very close to that reported by Park and Quate [Sang-II Park and C. F. Quate, Appl. Phys. Lett. 48, 112 (1986)]. The experimental results also show the feasibility of realizing length measurement using the lattice spacing on the crystalline surface and the PMHI.
Portable tremor monitor system for real-time full-wave monitoring and analysis
Authors: Yang Meng-Hsiang , Sheu Yung-Hoh , Shih Yuan-Hsing , Young M. S.
Published: March 2003

Tremors, which occur anytime during the daily 24 h cycle, may be missed if monitoring is performed on a short-term basis. Improving this situation requires long-term ambulatory recording capability. There are traditionally two methods for long-term recording of tremors: one is the analog recorder, which is both heavy and inconvenient when transferring data to a PC system; the other is the Actigraph, in which only movement counts are recorded, such data being incomplete. Thus, for long-term and continuous tremor monitoring, this study presents a wrist-worn portable system that can save an entire 24 h tremor wave form in an expansible compact flash memory card. With a rechargeable battery and USB interface, the system has two modes: (1) the monitoring mode while connected to a host computer allows confirmation of system operation, calibration of accelerometers, and immediate display of data on a PC screen and (2) the collecting mode saves data during daily activity on the compact flash memory card within the device. After collection, data are accessed to a host computer for processing. Analysis based on complete tremor wave form including tremor frequency and intensity of 24 h data is expected to allow improved understanding and treatment of tremors.
Combined force and photonic probe microscope with single molecule sensitivity
Authors: Noy Aleksandr , Huser Thomas R.
Published: March 2003

Direct integration of atomic force microscopy (AFM) imaging with single molecule optical detection promises to combine the resolving power of AFM with the chemical identification capabilities of optical techniques. We present a straightforward experimental approach to achieving such integration. Our design allows simultaneous acquisition of topographical images and optical images with single molecule sensitivity at any region of the optical spectrum. We describe an instrument that combines atomic force microscopy and scanning confocal optical microscopy in a single multifunctional setup that maximizes the use of commercially available parts. To build this instrument we replaced the built-in piezoscanner of a commercial optical microscope–AFM platform with an external scanner that translates the sample. We also added a simple circuit to the setup that modulates the AFM head laser and synchronizes collection of the AFM and optical data in interleave scanning mode. Finally, we demonstrate the technique’s identification capabilities using a model system of dye-labeled beads.
Compton scattering and photoluminescence for x-ray imaging
Authors: Wootton A. J. , Ryutov D. D.
Published: March 2003

Experiments with high-intensity, submillimeter diameter, pulsed x-ray beams that will be generated by the planned Linac Coherent Light Source will require nonperturbing imaging of such beams. Two approaches to solving this problem are proposed: Compton scattering off a thin solid foil and photoluminescence induced in a thin gas jet. The first would be efficient for x-ray energies above a few keV, whereas the second can be used to detect lower-energy beams, below ∼1 keV. Spatial resolution of the time-integrated images would be ∼10 μm for the first technique and ∼60 μm for the second technique. The minimum number of x-ray quanta needed for reaching this spatial resolution is ∼10.11 The imaging does not introduce significant perturbations to the beam. A set of design equations and constraints is provided.
Mass sensing of adsorbed molecules in sub-picogram sample with ultrathin silicon resonator
Authors: Ono Takahito , Li Xinxin , Miyashita Hidetoshi , Esashi Masayoshi
Published: March 2003

Ultrathin single-crystalline silicon cantilevers with a thickness of 170 nm as a resonating sensor are applied to mass sensing. The hydrogen storage capacity of a small amount of carbon nanotubes (CNTs), which were mounted on an ultrathin resonator by a manipulator, is measured from the resonant frequency change. The resonator is annealed in ultrahigh vacuum to clean the surface and increase the quality factor, and exposed to oxygen gas to oxidize the surface for long-term stability. The resonator can be electrostatically actuated, and the vibration is measured by a laser Doppler vibrometer in ultrahigh vacuum. The mass of the CNTs is determined by the difference of resonant frequencies before and after mounting the CNTs, and the hydrogen storage capacity is determined from the frequency change after exposure to high-pressure hydrogen as well. The obtained hydrogen storage capacitance is 1.6%–6.0%. The available mass resolution and the achieved stability of the resonance of the 170-nm-thick resonator are below 10−18 g and 5 Hz/days, respectively.
Unpinned interface Fermi-level in Schottky contacts to n-GaAs capped with low-temperature-grown GaAs; experiments and modeling using defect state distributions
Authors: Lodha Saurabh , Janes David B. , Chen Nien-Po
Published: March 2003

Low-temperature-grown GaAs (LTG:GaAs) has been used as a cap layer in ex situ, low-resistance contact structures to n-GaAs, indicating that a chemically stable surface with well-controlled electrical properties can be realized using this cap. Recently, capacitance–voltage (C–V) measurements on Schottky contacts have provided a direct indication of an unpinned interface Fermi-level in structures consisting of n-GaAs layers capped with thin layers of LTG:GaAs. This article describes experimental and modeling efforts to describe the near-interface energy band and Fermi-level behavior at metal/LTG:GaAs/n-GaAs interfaces. The C–V data are summarized, and the results of current–voltage measurements are presented to corroborate the initial observations. In simulation of the energy barrier, the defect bands in as-grown LTG:GaAs, for both unintentionally and Be-doped material, were described by models obtained by fitting to experimental data from scanning tunneling spectroscopy and other techniques. The near-interface energy band structure for the Schottky contacts to the LTG:GaAs-capped n-GaAs was computed by solving Poisson’s equation using the resulting midgap state distribution model in the LTG:GaAs layer. This approach allows an accurate determination of the interface barrier height, φb, from measured C–V data and accounts for the net charge and state densities in the cap layer. The results of measurements using metals of different work functions and possible interpretations in terms of interface Fermi-level pinning models are presented.
Calibration and sensitivity of the infrared imaging video bolometer
Authors: Peterson B. J. , Kostrioukov A. Yu. , Ashikawa N. , Osakabe M. , Sudo S.
Published: March 2003

The infrared (IR) imaging video bolometer (IRVB) is an imaging bolometer which uses a large (9 cm×9 cm) thin (1 μm) gold foil and an IR camera to provide images of radiation from the plasma. Calibration of the IRVB using a lamp has been performed to compensate for any nonuniformities in the foil’s thickness and its thermal properties due to blackening of the foil with graphite to improve the IR emissivity. This calibration revealed close to expected values for the calibration coefficient proportional to the product of the thermal conductivity and the foil thickness in the central region of the foil, while these values were anomalously high near the foil edge. The calibration coefficient proportional to the thermal diffusivity is a factor of 2 smaller than the expected value at the center and drops further at the edge of the foil. Using a derived expression for the IRVB noise equivalent power, a sensitivity comparison shows the IRVB using current IR technologies to be ∼200 times less sensitive than an equivalent conventional resistive bolometer operating under ideal conditions.
Measurements of poloidal rotation velocity using cross-correlation spectroscopy in the H-1 heliac
Authors: Shats M. G. , Punzmann H. , Xia H. , Solomon W. M.
Published: March 2003

A correlation spectroscopy diagnostic [M.G. Shats and J. Howard, Fusion Eng. Des. 34–35, 271 (1997)] measures fluctuation spectra and local fluctuation intensities in a radiation-dominated plasma, such as the low-temperature plasma in the H-1 heliac (Te<50 eV, ne<2×1018 m−3). When the fluctuation coherence lengths in the poloidal and radial directions are shorter than the plasma radius, the cross-correlation function of the two crossed-sightline fluctuating intensities contains information about the fluctuations amplitude and their phase in the intersection volume. The optical setup on the H-1 heliac uses two nearly orthogonal views to image 20 optical fibers arranged into two linear arrays in the plasma poloidal cross section. A matrix of 10×10 cross-correlation functions is then analyzed to determine the poloidal phase velocity of the fluctuations, poloidal and radial correlation lengths, and the radial profiles of the fluctuations intensity. The results on the poloidal propagation velocity measured using the cross-correlation technique (time delay of the cross-correlation functions) are compared with the poloidal velocity measured using poloidally separated probes in the plasma. Both velocities are found to be in good agreement and also agree well with the E×B drift velocity in this plasma.
Multichannel visible spectroscopy diagnostic for particle transport studies in the H-1 heliac
Authors: Punzmann H. , Shats M. G. , Solomon W. M. , Xia H.
Published: March 2003

A multichannel spectroscopy diagnostic has been developed to study cross-field particle transport in the radiation-dominated low-temperature plasmas (Te<100 eV) in the H-1 heliac. The optical setup covers the full plasma minor radius in the poloidal plane collecting light from ten parallel chords arranged tangentially to the flux surfaces. The light collected from the plasma is coupled into optical fibers and through interference filters into photomultipliers. Two such ten-fiber arrays are aligned parallel to one another to allow the simultaneous monitoring of two different spectral lines. The net radial electron particle flux is determined from the continuity equation by integrating over the ionization source term in the steady-state partially ionized plasma. The diagnostic measures the neutral line intensities and their ratios (in case of helium using the line ratio technique) and also measures excited neutral and ion spectral lines (in case of the argon plasma transport studies). A comparative analysis of the radial particle transport in the low- and high-confinement regimes is presented.
Island divertor spectroscopy at the Wendelstein W7-AS stellarator
Authors: König R. , Ramasubramanian N. , McCormick K. , Grigull P. , Gadelmeier F. , Wenzel U. , Schweer B. , Brix M.
Published: March 2003

The island divertor concept, which is regarded as being the natural concept for low shear advanced stellarators like W7-AS and W7-X, has for the first time been put to a realistic test in the present experimental campaign of W7-AS. A large number of diagnostics, specifically geared towards the diagnosis of island divertor plasmas, have been installed in the course of the last two years. This report will introduce some of the newly installed active and passive spectroscopy based divertor diagnostics.
Investigation of proton rotation measurements using hydrogen line wings in the TJ-II stellarator
Authors: Zurro B. , Baciero A. , McCarthy K. J. , Tribaldos V. ,   TJ-II Team
Published: March 2003

In this article we investigate the feasibility of measuring proton rotation using spectral line emission from excited fast neutrals created from inner core plasma protons via charge exchange transfer reactions. After outlining the experimental method and discussing it with regard to the TJ-II stellarator device, we present representative results obtained in plasmas created and maintained by electron cyclotron resonance heating. Finally, we outline the current limitations of this method and its potential.
Coherence-imaging approach to time-resolved charge-exchange recombination spectroscopy in high-temperature plasma
Authors: Howard J. , Carraro L. , Puiatti M. E. , Sattin F. , Scarin P. , Valisa M. , Zaniol B. , König R. , Chung J.
Published: March 2003

A coherence-based, or interferometric approach to spectral analysis of charge-exchange recombination (CXR) emission radiation from high-temperature plasma probed or heated using energetic neutral beams, offers a number of advantages over wavelength-domain instruments. The spectral-line shift and broadening are obtained from measurements of the spectral coherence at a given fixed time delay. The coherence is monitored by first approximately isolating the spectral line of interest using an interference filter and subsequently imaging the spectral scene using a field-widened electro-optic path-delay-modulated polarization interferometer. Interferometers have the advantage of high-light throughput (no slit aperture). Moreover, because the spectral information is encoded at harmonics of the electro-optic modulation frequency, a single detector suffices to capture the spectral information, thereby opening the possibility for time-resolved two-dimensional spectral imaging. When unwanted spectral features are passed by the interference filter, the interpretation of the coherence phase and amplitude images can become ambiguous. By modulating the particle beam source, however, we show that coherence imaging using a single-delay modulatable interferometer can distinguish and characterize the Doppler-broadened CXR emission component against a significant background of continuum and intrinsic radiation, or pollution from nearby spectral features.
Diagnosis of edge localized mode evolution in DIII-D using fast-gated CID and infrared cameras
Authors: Groth M. , Fenstermacher M. E. , Lasnier C. J. , Hernandez R. , Moller J. M. , Sturz R. A.
Published: March 2003

The tangentially viewing visible and vertically viewing infrared camera systems on DIII-D were upgraded to permit emission measurements during edge localized modes (ELMs) with integration times as short as 1 and 100 μs, respectively. The visible system was used to obtain two-dimensional poloidal profiles of CIII (465 nm) and Dα (656.3 nm) emission with 20 μs integration during various stages of ELM events in the lower DIII-D divertor. The infrared system was used to measure the heat flux to the divertor targets at 10 kHz with 100 μs exposure. Upgrades to the data processing and storage systems permitted efficient comparison of the temporal evolution of these measurements.
The Filterscope
Authors: Colchin R. J. , Hillis D. L. , Maingi R. , Klepper C. C. , Brooks N. H.
Published: March 2003

The filterscope is a diagnostic for monitoring visible light emission from plasmas. Light from a plasma is conducted to the filterscope via optical fibers. This light is split into multiple paths, and optical bandpass filters in each path pass the light from visible wavelengths, including Dα, Dβ and various impurities. The filtered light is then detected by compact photomultipliers and the resulting data digitized and stored. Because of the large number of data channels employed, the filters and electronics are designed to be compact. Measured light intensities are absolutely calibrated. Filterscopes are presently employed on the DIII-D, the National Spherical Torus Experiment, and the Current Drive Experiment-Upgrade tokamak plasma devices.
High dispersion spectrometer for time resolved Doppler measurements of impurity lines emitted during ISTTOK tokamak discharges
Authors: Gomes R. B. , Varandas C. A. F. , Cabral J. A. C. , Sokolova E. , Cortes S. Reyes
Published: March 2003

A high dispersion, multichannel, visible spectrometer has been developed for the ISTTOK tokamak, aiming at measuring the evolution of both the edge ion temperature and plasma poloidal velocity, by analysis of a CIII spectral line. It is based on a double monochromator configuration with two high ruling densities (2700 l/mm) and 1 m focal length concave diffraction gratings, a commercial double microchannel plate image intensifier, a fast (f/#=1) relay lens built with two high diameter condensers in a back-to-back configuration, and a 2048 element photodiode charge coupled device optical multichannel analyzer. Laboratory tests have shown that a high dispersion has been achieved (≈1.65 Å/mm), while keeping good temporal resolution (5 ms). Typical values measured for ion temperature (from Doppler broadening) were Ti≅25 eV while for poloidal velocity (from Doppler shift) vθ≅6 km/s.
Diagnostic exploitation of complex heavy elements in tokamak plasmas
Authors: O’Mullane M. G. , Summers H. P. , Whiteford A. D. , Barnsley R. , Coffey I. H. , Counsell G. , Loch S. , EFDA-JET Work Program Contributors to the
Published: March 2003

In future burning plasma experiments, a promising method for the diagnosis of first wall erosion is to detect the onset of emission from nonintrinsic materials embedded in the plasma facing components as they are revealed and enter the confined plasma. Likely high Z species were introduced into the Joint European Torus plasmas by laser ablation. Results from targets of single species (W and Hf) and dual species (W/Hf composite) are presented. The composite target experiment has shown that it is possible to distinguish reliably between emission from near neighbor heavy elements, even with instrument resolutions of Δλ/λ∼0.001. Forward prediction to power plant conditions necessitates a model of the complex spectra and a system for generating the required atomic data and producing spectral feature emissivity coefficients is described. An important consideration is to enable exploration of different instrumentation so the spectral resolution of the compound features are tuned to the diagnostic capability.
Use of one dimensional Dα camera to measure edge electron density gradients
Authors: Tournianski M. R. , Carolan P. G. , Conway N. J. , Counsell G. F. , Arends E. , Walsh M. J.
Published: March 2003

One of the clearest signatures of the transitions from L- to H-mode plasmas is the steepening of the edge density gradient. A concomitant narrowing of the visible radiation, usually dominated by Balmer Dα emission, is generally observed. Typically, the Dα emissivity width is 4–6 cm for the L-mode, similar for ELMs, and 1–3 cm for H-mode MAST plasmas, comparable with typical edge ne scale lengths. A means of extracting electron densities from this narrowing of the radial Dα emissivity profile was pioneered on the START device and developed further on MAST. It takes advantage of the near insensitivity to electron temperature of both the ionization and emission rates of hydrogen at temperatures well in excess of the ionization potential (13.6 eV). The Dα emissivity profile is obtained from spatial inversion of line-of-sight integrated intensities recorded by a linear camera (Δt=125 μs, 256 pixels). The 300 point Thomson scattering diagnostic has been used as a yardstick in comparing experimental data from a wide range of edge density gradients and a range of edge temperatures in checking the models validity and assumptions.
High-resolution spectroscopic diagnostic for divertor and scrape-off layer neutral and impurity emission measurements in the National Spherical Torus Experiment
Authors: Soukhanovskii V. A. , Roquemore A. L. , Skinner C. H. , Menard J. , Kugel H. W. , Johnson D. , Maingi R. , Sabbagh S. , Paoletti F.
Published: March 2003

The National Spherical Torus Experiment boundary physics program presently focuses on edge power and particle flow optimization and control in β⩾25% long pulse L- and H-mode plasmas with high harmonic fast wave heating power up to 6 MW and neutral beam injection power up to 5 MW, with the emphasis on the edge physics implications resulting from the low aspect ratio geometry. To address the particle flux measurements in the divertor and plasma scrape-off layer (SOL), two spectrally filtered one-dimensional charge coupled device cameras have been fielded. The cameras utilize 2048 pixel 12-bit Dalsa CL-C6 arrays, f=85 mm lenses, and Δλ=1.5 nm bandpass interference filters. Both cameras provide mm spatial resolution, sub-ms temporal resolution and are spatially and photometrically calibrated. Midplane SOL and divertor brightness profiles of C III and deuterium species have been obtained in the L- and H-mode phases of center stack limited and diverted plasmas. The equilibria reconstructed by the EFIT code are found in agreement with the optical and infra-red measurements. In–out asymmetries in divertor recycling and carbon fluxes have been observed in L- and H-mode plasmas. The analysis of neutral recycling and impurity fluxes using the two-dimensional multifluid code UEDGE is in progress.
Highly efficient time-of-flight spectrometer for studying low-energy secondary emission from dielectrics: Secondary-electron emission from LiF film
Authors: Samarin S. N. , Artamonov O. M. , Waterhouse D. K. , Kirschner J. , Morozov A. , Williams J. F.
Published: March 2003

A highly efficient time-of-flight electron spectrometer is described. An incident electron current of the order of 10−14 A makes it suitable for studying secondary emission from dielectric surfaces. A microchannel plate position-sensitive detector allows flight distance correction while keeping a large acceptance angle. Measured energy distribution curves of secondary electrons generated from a LiF film by 19–31 eV incident electrons demonstrate good energy resolution and reveal reproducible and stable emission features at 2.6±0.3 eV, 7.2±0.3 eV, and 10.3±0.3 eV.
Microfabricated oscillator for radio-frequency microscopy with integrated magnetic field concentrator
Authors: May T. , Il’ichev E. , Meyer H.-G. , Grajcar M.
Published: March 2003

We present a lithographically manufactured chip with niobium thin-film pancake coils, and a washerlike structure above this coil for focusing flux. Due to a wide range of coupling coefficients, various samples can be investigated in flip-chip or on-chip configuration, with the aim of evaluating the superconducting current-phase relation. With this, structures with dimensions in the order of 10 μm were coupled to the resonance circuit with coupling coefficients from 10−3 up to 0.9. Resonance frequencies in the 10 MHz range and quality factors of about 500 were obtained with external capacitors. Furthermore, the chip is designed to facilitate the manufacture of superconducting qubits in the center of the coil. This offers the possibility of combining on one chip novel technologies for fabricating superconducting qubits along with high-quality tank circuits for studying the qubits.
Real-time plasma rotation diagnostic for measuring small Doppler shifts
Authors: Paul S. F.
Published: March 2003

A noninvasive velocity measurement has been developed for use in high-temperature plasma confinement devices, having particular use where multi-kilohertz measurement of plasma rotation is needed. The most interesting aspect of the technique is that the Doppler shift is determined from the ratio of the light intensity from two detectors rather than by resolving the emission line with a spectrometer. One detector views the plasma through an interference filter whose passband has a negative slope, and the other channel views the identical volume of plasma through a positive-slope filter. The signal ratio varies as the line is shifted across the passbands, but is not sensitive to changes in plasma emission. For interference filters with linear passbands, that is, constant slopes, the ratio is not sensitive to ion temperature, and the shifted wavelength reduces to a simple function of the signal ratio, the channels’ relative responsivity, and the two filters’ transmission curves. Filters with sharp passband slopes (100%–200% per nm) and ≈0.1% deviation from linearity have been fabricated. For an uncertainty in the signal ratio of ±1%, the expected error in the wavelength shift is ±0.001 nm (Δvφ≈±1 km/s).
Spectroscopic ion beam imaging for investigations into magnetic field mapping of a plasma
Authors: Demers D. R. , Schoch P. M. , Radke R. J. , Anderson J. K. , Craig D. , Hartog D. J. Den
Published: March 2003

The trajectory of an ion beam as it passes through a magnetically confined plasma is determined by the ion mass, energy, and charge state, and the magnetic field structure. In undergraduate physics laboratories, students use a measure of beam deflection in a well-defined magnetic field to determine the charge-to-mass ratio of a particle. The complementary analysis is equally valid; the field may be determined given a known charge-to-mass ratio. Additional complexity is introduced in a spatially nonuniform, time-varying magnetic field, such as that of a plasma. The technique of field mapping via spectral imaging is being developed with a heavy ion beam probe on the Madison Symmetric Torus. Technical issues, such as choice of wavelengths, optics, viewing geometry, and imaging hardware, are being addressed. Calculations indicate that beam emission is brighter than background bremsstrahlung for several transitions of interest. However, a wavelength region containing lines from the beam ions, but free of atomic lines from the plasma, remains to be identified.
Direct removal of edge-localized pollutant emission in a near-infrared bremsstrahlung measurement
Authors: Anderson J. K. , Andrew P. L. , Chapman B. E. , Craig D. , Den Hartog D. J.
Published: March 2003

Visible and near-infrared electron–ion bremsstrahlung measurements in fusion research devices, used to determine the effective ionic charge (Zeff), are often plagued by pollutant emission from the cool-edge region. The primary sources of visible and near-infrared non-bremsstrahlung continuum emission in the Madison Symmetric Torus arise from electron–neutral interactions, and the pollutant emission is hence directly proportional to the bulk neutral density. Simultaneously monitoring the total emission at 1040 nm and the neutral contaminant (via Dα emission) has enabled an extraction of the electron–ion bremsstrahlung and a measurement of Zeff at comparatively low electron density (1013 cm−3).
Spectroscopic system using image magnifying optics for plasma velocity and ion temperature measurement
Authors: Sakakita H. , Kiyama S. , Hirano Y. , Yagi Y. , Koguchi H. , Sekine S. , Shimada T. , Hirota I. , Maejima Y.
Published: March 2003

A spectroscopic system equipped with image magnifying optics has been developed for measuring a time-resolved plasma velocity at one discharge of a reversed-field-pinch plasma of the TPE-RX at National Institute of AIST. This spectroscopic system enables a simultaneous measurement from two different lines of sight, using two sets of quartz optical fiber bundles. This system provides a precise measurement of Doppler shift without the need for a calibration of the central location of a spectral line. Two fiber bundles are coupled to the entrance slit of a modified Czerny–Turner-type, 1-m-focal-length spectrometer with an 82×82 mm2 grating. In order to adjust the spectral image of the exit slit to each surface of two sets of one-dimensional detector arrays, an optical system equipped with a toroidal mirror, a cylindrical mirror, and splitting mirrors has been developed. The focal lengths of the toroidal mirror are selected for focusing vertically on the splitting mirror and horizontally (wavelength direction) on detectors. Plasma rotation and ion temperature for O V impurity ions (278.1 nm) are successfully measured at one plasma shot with a 25-μs time resolution in the TPE-RX.
H
α
measurements on hot-ion-mode plasmas in the minimum-B anchor cell of the GAMMA 10 tandem mirror
Authors: Nakashima Y. , Kobayashi S. , Aminaka H. , Fukasawa T. , Shoji M. , Ishimoto Y. , Kubota Y. , Yoshikawa M. , Kawamori E. , Ichimura M. , Islam M. K. , Yatsu K.
Published: March 2003

Results of Hα measurement in the GAMMA 10 tandem mirror are described, with a particular focus on the behavior of neutrals in the anchor minimum-B region. Recently a set of Hα line-emission detector arrays was designed and installed in the anchor-cell, where the shape of the magnetic flux tube becomes flat and the cross section of plasma is elongated elliptically. The detector consists of Hα interference filter, optical fiber, and photomultiplier with magnetic shield, and is absolutely calibrated by using a standard lamp. In standard ion-cyclotron-range-of-frequency heated, hot-ion-mode plasmas, detailed measurements of Hα line-emission form the central-cell to the anchor-cell were carried out, and the dependence of the Hα intensity on the quantity of gas puffing was investigated. The characteristic behavior of neutrals in the nonaxisymmetric anchor-cell is also discussed, based on the result of neutral transport simulation.