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Oct 2004

Volume 75, Issue 10, pp. 3091-4349

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back to top OPTICAL SYSTEMS, IR TO X-RAY

Characteristics of high energy Kα and Bremsstrahlung sources generated by short pulse petawatt lasers

H.-S. Park, N. Izumi, M. H. Key, J. A. Koch, O. L. Landen, P. K. Patel, T. W. Phillips, and B. B. Zhang

Rev. Sci. Instrum. 75, 4048 (2004); http://dx.doi.org/10.1063/1.1789596 (3 pages) | Cited 24 times

Online Publication Date: 12 October 2004

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We have measured the characteristics of high energy Kα sources created with the Vulcan Petawatt laser at RAL and the JanUSP laser at Lawrence Livermore National Laboratory. High energy x-ray backlighters will be essential for radiographing high energy-density experimental science targets for NIF projects especially to probe implosions and high areal density planar samples. Hard Kα x-ray photons are created through relativistic electron plasma interactions in the target material after irradiated by short pulse high intensity lasers. For our Vulcan experiment, we employed a CsI scintillator charge coupled device (CCD) camera for imaging and a CCD camera for single photon counting. We have directly measured the 22 keV Ag Kα source size using the RAL petawatt laser and performed knife-edge measurements of a 40 keV Sm Kα source using the JanUSP laser. The measured source sizes are both ∼ 60 μm full width half maximum. We have also measured the Ag Kα conversion efficiencies. At laser intensities of 1×1018 W/cm2 range, the conversion efficiency at 22 keV is ∼ 1×10−4.
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52.70.La X-ray and γ-ray measurements
52.38.Ph X-ray, γ-ray, and particle generation
52.40.Mj Particle beam interactions in plasmas
52.50.Dg Plasma sources

KB–PJX—A streaked imager based on a versatile x-ray microscope coupled to a high-current streak tube (invited)

O. V. Gotchev, P. A. Jaanimagi, J. P. Knauer, F. J. Marshall, and D. D. Meyerhofer,

Rev. Sci. Instrum. 75, 4063 (2004); http://dx.doi.org/10.1063/1.1786649 (6 pages) | Cited 3 times

Online Publication Date: 12 October 2004

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A re-entrant, highly adaptable, x-ray streaked imager has been developed for OMEGA to increase the sensitivity and spatial resolution in hydrodynamic-stability experiments. It is based on a four-mirror Kirkpatrick–Baez (KB) microscope, coupled to a high-current streak tube. The unique mechanical assembly of the KB optic allows a choice between single- or multi-image modes and one- or two-dimensional imaging. Currently, the optic uses an Ir coating at a grazing angle of 2.1°. The incidence angle has been optimized to maximize throughput in the chosen energy band, centered at 1.5 keV with a full width at half maximum of about 0.4 keV. A calculated resolution of better than 5 μm over the central 200 μm of the field of view was verified in inertial confinement fusion experiments. New multilayer mirror elements for high-energy or multiband imaging, take advantage of the flexible mechanical design. Some important features of the PJX streak tube are described.
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07.68.+m Photography, photographic instruments; xerography
41.50.+h X-ray beams and x-ray optics
42.79.Wc Optical coatings
52.70.La X-ray and γ-ray measurements
07.85.Tt X-ray microscopes

High definition imaging in the Mega Amp Spherical Torus spherical tokamak from soft x rays to infrared (invited)

P. G. Carolan, A. Patel, N. J. Conway, R. J. Akers, C. A. Bunting, G. F. Counsell, J. Dowling, M. R. Dunstan, A. Kirk, F. Lott, M. N. Price, M. R. Tournianski, and M. J. Walsh

Rev. Sci. Instrum. 75, 4069 (2004); http://dx.doi.org/10.1063/1.1789583 (8 pages) | Cited 2 times

Online Publication Date: 12 October 2004

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The Mega Amp Spherical Torus (MAST) diagnostic needs are strongly influenced by physics goals that often require diagnostic integration and cross-mapping, especially in fine-scale investigations, such as transport barriers. Conversely, the unrivalled viewing access to the edge, scrape-off layer (SOL) and divertor regions, provided by the MAST open geometry, impacts on the physics program priorities. A supporting suite diagnostics, such as the high definition Thomson scattering systems, provide considerable added value in detailed data interpretation (e.g., bremsstrahlung emissivity in terms of Zeff). Thus, to exploit these advantages, an extensive set of high-resolution imaging diagnostics have been installed, encompassing soft x-rays, visible bremsstrahlung, charge exchange recognisation radiation, Dα from NBI, and edge plasma neutrals, and infrared (IR) from the divertor and wall regions. Plasma light collection optics provide near parallel illumination of narrow bandpass interference filters to give monochromatic images. One adaptation provides multiwavelength images; another accommodates smooth variation of wavelength across an image (e.g., for a range of Doppler shifts beam fast neutrals). Diagnostic synergy is enhanced by combining such diagnostics to common viewing optics which allow exact-mapping. Soft x-ray tangential imaging has been achieved by using a two dimensional charge coupled device detector in a pinhole camera. Finally, a fast IR camera monitors the power deposition on the first wall and divertor plates, important in quantifying power losses (e.g., ELMs, disruptions), and complemented by visible viewing of the SOL, and linear Dα cameras.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.55.Fa Tokamaks, spherical tokamaks
52.25.Fi Transport properties
52.40.Hf Plasma-material interactions; boundary layer effects
52.50.Gj Plasma heating by particle beams
52.25.Ya Neutrals in plasmas

High-speed optical diagnostic that uses interference filters to measure Doppler shifts

S. F. Paul, C. J. Cates, M. E. Mauel, D. A. Maurer, G. A. Navratil, R. M. Paul, T. S. Pedersen, and M. A. Shilov

Rev. Sci. Instrum. 75, 4077 (2004); http://dx.doi.org/10.1063/1.1790057 (5 pages) | Cited 7 times

Online Publication Date: 12 October 2004

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A high-speed, noninvasive velocity diagnostic has been developed for measuring plasma rotation. The Doppler shift is determined by employing two detectors that view line emission from the identical volume of plasma. Each detector views through an interference filter having a passband that varies linearly with wavelength. One detector views the plasma through a filter whose passband has a negative slope and the second detector views through one with a positive slope. Because each channel views the same volume of plasma, the ratio of the amplitudes is not sensitive to variations in plasma emission. With suitable knowledge of the filter characteristics and the relative gain, the Doppler shift is readily obtained in real time from the ratio of two channels without needing a low throughput spectrometer. The systematic errors—arising from temperature drifts, stability, and frequency response of the detectors and amplifiers, interference filter linearity, and ability to thoroughly homogenize the light from the fiber bundle—can be characterized well enough to obtain velocity data with ±1 km/s with a time resolution of 0.3 ms.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
52.25.-b Plasma properties
52.30.-q Plasma dynamics and flow
42.79.Ci Filters, zone plates, and polarizers
06.60.Jn High-speed techniques (microsecond to femtosecond)

Measurement of low frequency plasma fluctuations with a visible light detector in GAMMA 10

H. Higaki, M. Ichimura, K. Horinouchi, K. Nakagome, S. Kakimoto, Y. Yamaguchi, K. Ide, D. Inoue, H. Nagai, M. Yoshikawa, Y. Nakashima, and T. Cho

Rev. Sci. Instrum. 75, 4085 (2004); http://dx.doi.org/10.1063/1.1789263 (3 pages) | Cited 9 times

Online Publication Date: 12 October 2004

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Low frequency fluctuations of a plasma in the central cell of the GAMMA10 tandem mirror have been observed with electrostatic probes (ESPs) installed at the peripheral region of the plasma. Typical plasma parameters for a hot ion mode operation are ne ∼ 2×1012 cm−3, Ti ∼ 4 keV, Te ∼ 100 eV, B = 4 kG, and rp = 18 cm. Although the ESP is an effective tool to measure local plasma parameters and fluctuations, it can be damaged with the higher electron temperature. Here, a new visible light detector was introduced, which could measure the plasma fluctuations without contacting the plasma. The obtained results were compared with those of ESPs. It is found that the visible light detector is applicable when the electron temperature becomes much higher in the future experiment.
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52.70.Ds Electric and magnetic measurements
52.25.Gj Fluctuation and chaos phenomena
28.52.Av Theory, design, and computerized simulation
52.55.-s Magnetic confinement and equilibrium
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Absolute calibration of vacuum ultraviolet spectrograph system for plasma diagnostics

M. Yoshikawa, Y. Kubota, T. Kobayashi, M. Saito, N. Numada, Y. Nakashima, T. Cho, H. Koguchi, Y. Yagi, and N. Yamaguchi

Rev. Sci. Instrum. 75, 4088 (2004); http://dx.doi.org/10.1063/1.1789264 (3 pages)

Online Publication Date: 12 October 2004

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A space- and time-resolving vacuum ultraviolet (VUV) spectrograph system has been applied to diagnose impurity ions behavior in plasmas produced in the tandem mirror GAMMA 10 and the reversed field pinch TPE-RX. We have carried out ray tracing calculations for obtaining the characteristics of the VUV spectrograph and calibration experiments to measure the absolute sensitivities of the VUV spectrograph system for the wavelength range from 100 to 1100 Å. By changing the incident angle, 50.6°–51.4°, to the spectrograph whose nominal incident angle is 51°, we can change the observing spectral range of the VUV spectrograph. In this article, we show the ray tracing calculation results and absolute sensitivities when the angle of incidence into the VUV spectrograph is changed, and the results of VUV spectroscopic measurement in both GAMMA 10 and TPE-RX plasmas.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Vy Impurities in plasmas
52.58.Lq Z-pinches, plasma focus, and other pinch devices
28.52.Av Theory, design, and computerized simulation
52.55.-s Magnetic confinement and equilibrium

Laser-induced fluorescence measurements of three plasma species with a tunable diode laser

Amy M. Keesee, Earl E. Scime, and Robert F. Boivin

Rev. Sci. Instrum. 75, 4091 (2004); http://dx.doi.org/10.1063/1.1787166 (3 pages) | Cited 20 times

Online Publication Date: 12 October 2004

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Recently, we demonstrated that a single, tunable, low-power, diode laser can be used for laser-induced fluorescence (LIF) measurements of both argon ions and helium neutrals. We have now identified a third fluorescence scheme, for neutral argon atoms, accessible with the same tunable diode laser. Fluorescence measurements of a heated iodine cell are used to monitor the wavelength of the laser during the LIF measurement.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)

Diagnostic system of Hα emission on neutral beam injection experiments in the GAMMA10 central cell

Y. Higashizono, Y. Nakashima, T. Ohki, Y. Kubota, M. Yoshikawa, M. K. Islam, K. Watanabe, T. Ogita, T. Kobayashi, R. Murakami, M. Yamada, T. Cho, M. Shoji, and S. Kobayashi

Rev. Sci. Instrum. 75, 4094 (2004); http://dx.doi.org/10.1063/1.1789581 (3 pages) | Cited 1 time

Online Publication Date: 12 October 2004

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We newly designed and installed a Hα line-emission detector in order to examine neutral particle transport around the beam line of NBI in the central cell of the GAMMA10 tandem mirror. The Hα detector consists of a Hα interference filter, a lens, an optical fiber, and a photomultiplier. The detector is absolutely calibrated using a standard lamp. The Hα detector is located at the angle of 24° to the beam line, which enabled us to directly view the Hα emission due to neutral beam injection (NBI). In standard hot-ion mode plasmas, we measured the Hα line emission in the case of NBI. The Hα line emission during NBI strongly increased by 550% on the beam line compared with that before NBI. Moreover, it was found that hydrogen recycling played an important role in the neutral transport around the beam line. This diagnostic system is confirmed to be considerably helpful for examining the detailed behavior of the neutral particles related to NBI for the first time.
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52.70.Nc Particle measurements
52.50.Gj Plasma heating by particle beams
52.25.Fi Transport properties
28.52.Av Theory, design, and computerized simulation
52.55.-s Magnetic confinement and equilibrium
52.25.Ya Neutrals in plasmas
52.25.Tx Emission, absorption, and scattering of particles

Zeff from spectroscopic bremsstrahlung measurements at ASDEX Upgrade and JET

H. Meister, R. Fischer, L. D. Horton, C. F. Maggi, D. Nishijima, C. Giroud, K.-D. Zastrow, and B. Zaniol

Rev. Sci. Instrum. 75, 4097 (2004); http://dx.doi.org/10.1063/1.1787167 (3 pages) | Cited 9 times

Online Publication Date: 12 October 2004

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The effective ionic charge Zeff is a means to assess the impurity content of a fusion plasma. It can be derived from measurements of bremsstrahlung intensity. These have been extended at ASDEX Upgrade by the usage of the sight lines for the charge exchange recombination diagnostic. Together with a previously installed sight line array, it is now possible to routinely determine the bremsstrahlung intensity over the whole minor radius purely from spectroscopic measurements. In a tokamak where the plasma facing components are made up of various materials, this is necessary to check if measurements are contaminated by line radiation. The bremsstrahlung background of the respective spectra is determined using Bayesian probability theory, giving consistent and improved error statistics. Using the information for electron temperature and density profiles, the Zeff profile is determined by an integrated method. The same approach to assess the Zeff profile has been demonstrated to be successful also at the JET tokamak.
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52.55.Fa Tokamaks, spherical tokamaks
52.25.Vy Impurities in plasmas
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
28.52.Lf Components and instrumentation

Novel Doppler laser radar for diagnostics in fusion reactors

Madhavan Menon and Anthony Slotwinski

Rev. Sci. Instrum. 75, 4100 (2004); http://dx.doi.org/10.1063/1.1789582 (3 pages) | Cited 2 times

Online Publication Date: 12 October 2004

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We describe the development of a novel Doppler laser radar (DOLAR) for remote measurement of flow velocity (0–10 m/s) and film thickness of liquid metal walls, currently being studied for their superior heat handling and self-healing characteristics. Small fluctuations in flow velocity( ∼ mm/s) and flow thickness ( ∼ 50 μm) that may arise during plasma discharges can also be measured. The DOLAR is also designed for non intrusive mapping of features of plasma-facing solid surfaces with very high precision ( ∼ 50 μm). It can also measure the motion of structural components of a fusion reactor during plasma discharges and during plasma disruptions. The device utilizes frequency modulation laser radar principles for precision range measurements. Compensation of Doppler frequency shift is used to measure flow velocity. The DOLAR probe head is designed with acousto-optic and piezoelectric devices for operation in the harsh fusion environment.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.70.Ds Electric and magnetic measurements
52.30.-q Plasma dynamics and flow
52.25.Gj Fluctuation and chaos phenomena
52.80.-s Electric discharges
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)
42.60.Fc Modulation, tuning, and mode locking

Three-dimensional laser-induced fluorescence measurements in a helicon plasma

R. Hardin, X. Sun, and E. E. Scime

Rev. Sci. Instrum. 75, 4103 (2004); http://dx.doi.org/10.1063/1.1787168 (3 pages) | Cited 9 times

Online Publication Date: 12 October 2004

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We describe a three-dimensional (3D) laser-induced fluorescence (LIF) diagnostic for argon ions in a helicon plasma source. With three different laser injection orientations at a single spatial location, LIF measurements are performed to determine the 3D ion temperature and the 3D ion flow vector. The measurement process is then repeated at multiple locations in a cross section of the plasma column to create a two-dimensional (2D) map of the 3D ion flow, the ion temperature, and metastable ion density. Scanning in the 2D plane is accomplished by mounting the injection and collection optics on stepping motor driven stages.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.50.Dg Plasma sources
52.25.-b Plasma properties
52.30.-q Plasma dynamics and flow

Analysis of visible light images from a fast-gated intensified charge coupled device camera during flux rope interaction and magnetic reconnection

E. Hemsing, I. Furno, T. Intrator, and D. Wei

Rev. Sci. Instrum. 75, 4106 (2004); http://dx.doi.org/10.1063/1.1787169 (3 pages) | Cited 3 times

Online Publication Date: 12 October 2004

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We present the experimental setup and analysis of visible light images from a fast double-gated intensified charge coupled device (CCD) camera currently being used on the reconnection scaling experiment (RSX) at the Los Alamos National Laboratory. In RSX, externally driven free-boundary flux ropes are generated for magnetic reconnection studies in collisional plasma. Time-resolved images of flux rope interaction on submicrosecond time scales are achieved through the use of a microchannel plate intensified CCD camera and are shown to be consistent with probe measurements of plasma pressure and magnetic structure. High experimental repeatability allows plasma evolution to be displayed and measured from images taken over hundreds of RSX discharges to elucidate flux rope interaction dynamics. Peak-intensity fit algorithms extrapolate rope separation and two-dimensional rope velocities from images in agreement with probe data. First glimpses of two flux ropes that twist and merge are presented.
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52.70.Ds Electric and magnetic measurements
07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
42.79.Pw Imaging detectors and sensors
52.25.Fi Transport properties

Calculation of edge toroidal current density distributions from DIII-D lithium beam measurements using Ampère’s law

D. M. Thomas, A. W. Leonard, and H. W. Mueller

Rev. Sci. Instrum. 75, 4109 (2004); http://dx.doi.org/10.1063/1.1787146 (3 pages) | Cited 6 times

Online Publication Date: 12 October 2004

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The local edge current density j(r) is a parameter of basic importance in understanding the stability of high performance tokamaks, as well as the dynamics of edge localized mode behavior. On DIII-D, the lithium beam polarimetry diagnostic provides precise measurements of the local magnetic field projection along the field of view at 32 radial locations in the plasma edge. Using these measurements, the known spatial calibration and a minimal amount of information about the magnetic field shape from equilibrium reconstructions, Ampères law may be used to provide a straightforward parameterization for the edge toroidal current density in terms of the measured magnetic field and its radial derivative. This approach is relatively insensitive to errors in the reconstruction and is simple to apply.
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52.70.Ds Electric and magnetic measurements
52.55.Fa Tokamaks, spherical tokamaks
52.40.Hf Plasma-material interactions; boundary layer effects
52.25.-b Plasma properties

Near infrared spectroscopy of the divertor region in the Alcator C-Mod tokamak

I. Furno and G. A. Wurden

Rev. Sci. Instrum. 75, 4112 (2004); http://dx.doi.org/10.1063/1.1787147 (3 pages) | Cited 1 time

Online Publication Date: 12 October 2004

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A new system for near infrared spectroscopic measurements (1.2–2.6 μm) is designed for the Alcator C-Mod tokamak. These measurements will provide a new window into understanding the physics of detached and∕or high radiating plasmas. The system, located on top of the Alcator C-Mod concrete igloo, will view a 30×30 cm2 region of the lower divertor by means of a re-entrant 5 m long ZnSe based periscope. A McPherson 218 spectrometer will disperse the light that will then be detected by a thermoelectrically cooled InGaAs, 256-element linear image sensor. The signals from each pixel will be digitized by a 16-bit, 333 kHz analog∕digital board and then transmitted over optical link to a personal computer (PC) located in Alcator C-Mod control room. The PC will remotely control the system and store the data in the MDSplus database.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.55.Fa Tokamaks, spherical tokamaks

Development of the megahertz planar laser-induced fluorescence diagnostic for plasma turbulence visualization

Aleksey Kuritsyn and Fred M. Levinton

Rev. Sci. Instrum. 75, 4115 (2004); http://dx.doi.org/10.1063/1.1787148 (3 pages)

Online Publication Date: 12 October 2004

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A megahertz laser-induced fluorescence-based diagnostic system for measuring ion density fluctuations in two spatial dimensions is described. Well resolved spatial and temporal two-dimensional (2D) images of turbulent structures will be useful in understanding ion turbulence in magnetically confined plasmas which is a key factor in the performance of fusion experimental devices. A sheet beam of a megahertz repetition rate tunable Alexandrite laser is used to excite ion emission from argon plasma. The fluorescence emitted from the plane of the laser beam is detected with a narrow band interference filter and intensified ultrafast charge coupled device camera providing 2D images of relative ion density fluctuations every microsecond. It is expected that the edge plasma on fusion devices will be accessible to this technique.
Show PACS
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.50.Jm Plasma production and heating by laser beams (laser-foil, laser-cluster, etc.)
52.35.Ra Plasma turbulence
52.55.-s Magnetic confinement and equilibrium
52.25.Gj Fluctuation and chaos phenomena

Beam emission spectroscopy measurement for density fluctuations in compact helical system

Tetsutarou Oishi, Satoru Tanaka, Shinichiro Kado, Mikirou Yoshinuma, Katsumi Ida, and Shoichi Okamura

Rev. Sci. Instrum. 75, 4118 (2004); http://dx.doi.org/10.1063/1.1794846 (3 pages) | Cited 12 times

Online Publication Date: 12 October 2004

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A system of beam emission spectroscopy (BES) which has been proposed as a method for the measurement of long wavelength plasma density fluctuations has been applied to compact helical system (CHS). Spatial channels of BES consist of 16 optical fibers with object lenses focused on the plasma minor radius in CHS. Spatial resolution which corresponds to the width of a sightline and the spatial pitch between sightlines are 1.0 and 1.1 cm on the imaging surface, respectively. The hydrogen neutral beam for heating with the acceleration voltage of about 28 keV is used for the probe beam. The avalanche photodiode detectors combined with a 100 kHz low-pass filter are used as photon detectors. The temporal evolution of the inverse density scale length Ln−1 and the density fluctuation were measured simultaneously at the edge region where the beam attenuation was negligible. As an initial result, the rapid increase of the local plasma density gradient near the plasma edge accompanied by a coherent-like density fluctuation of several kilohertz was detected by using this system when the edge particle transport barrier was formed. Measuring the density fluctuations at the inner regions considering the beam profile, its attenuation, and normalized radii of the sightlines with finite beta shift will be a subject of study in the future.
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52.70.Nc Particle measurements
52.40.Hf Plasma-material interactions; boundary layer effects
52.50.Gj Plasma heating by particle beams
52.25.Gj Fluctuation and chaos phenomena
52.25.Fi Transport properties

Measurement technique of electric field using ultraviolet/visible spectroscopy in cylindrical plasmas

T. Kobayashi, M. Yoshikawa, Y. Kubota, M. Saito, M. Numada, K. Ishii, and T. Cho

Rev. Sci. Instrum. 75, 4121 (2004); http://dx.doi.org/10.1063/1.1789584 (3 pages) | Cited 2 times

Online Publication Date: 12 October 2004

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The rotation of impurity ion has been measured using ultraviolet (UV) visible spectroscopy in the cylindrical fusion plasma GAMMA 10 to investigate diamagnetic drift and E×B drift. The electric field is estimated with the plasma rotation and E×B drift analysis. Since the detected signal is the line integrated emission, the parametric Abel inversion technique has been developed. In the method, a density profile of impurity ion was assumed. Recently, we can obtain the density profile using collisional–radiative model (CRM) calculation. Then the electric field is obtained independently of that assumption. We present the measurement technique of the electric field using UV/visible spectroscopy and CRM calculation. The experimental result in GAMMA 10 is that consistent with the result of the neutral beam probe measurement.
Show PACS
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Vy Impurities in plasmas
52.30.-q Plasma dynamics and flow
28.52.Av Theory, design, and computerized simulation
52.55.-s Magnetic confinement and equilibrium
52.35.Qz Microinstabilities (ion-acoustic, two-stream, loss-cone, beam-plasma, drift, ion- or electron-cyclotron, etc.)

Multiplexing thermography for International Thermonuclear Experimental Reactor divertor targets

K. Itami, T. Sugie, G. Vayakis, and C. Walker

Rev. Sci. Instrum. 75, 4124 (2004); http://dx.doi.org/10.1063/1.1789585 (5 pages) | Cited 4 times

Online Publication Date: 12 October 2004

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The concept of multiplexing thermography is applied to the design of the divertor thermography system for International Thermonuclear Experimental Reactor (ITER). The combination of the front mirror with multiellipticity and a Czerney–Turner spectrometer with a 0.2 mm pitched multichannel detector enables a spatial resolution of 3 mm and a time resolution of 20 μs above a target temperature of 300 °C to be achieved. This should be sufficient to measure ELM heat fluxes to the targets in ITER. To satisfy the measurement requirement, it is very important to keep an accurate alignment around the optical axis against movement of the vessel during the plasma discharges. Several key engineering problems, such as the survivability of components against mirror coating by redeposited divertor material, remain to be solved. Potential solutions have been identified.
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52.55.Fa Tokamaks, spherical tokamaks
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
42.79.Pw Imaging detectors and sensors
07.57.Ty Infrared spectrometers, auxiliary equipment, and techniques
52.40.Hf Plasma-material interactions; boundary layer effects
52.80.-s Electric discharges

Multichannel and multicolour infrared thermography in Tore Supra

R. Reichle, C. Pocheau, C. Balorin, E. Delchambre, C. Desgrange, D. Guilhem, S. Henry, P. Messina, and H. Roche

Rev. Sci. Instrum. 75, 4129 (2004); http://dx.doi.org/10.1063/1.1789586 (4 pages) | Cited 4 times

Online Publication Date: 12 October 2004

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An imaging spectrometer using a sapphire prism as dispersing element has been conceived at Tore Supra for the spectral range of 1–4 μm. It measures simultaneously at various wavelengths the temperature on distributed high heat-flux elements under plasma impact with 36 optical fibers, four of which are ZrF4 fibers. It employs an InSb focal plane array detector (256∗320 pixels) behind a silicon filter and a ZnS window yielding a dynamic range of 200–1500 °C with 20 ms temporal resolution. The fiber transmission and the spatial variation of gain and background of the camera are calibrated using a light source with integrating sphere. With a blackbody source one determines the nonlinearity of the average gain and controls its stability during operation. The spectral dispersion of about 24 nm/pixel is determined with interference filters and controlled with a spectral lamp. The measurements at various wavelengths allow to determine the temperature distribution in the field of view.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.55.Fa Tokamaks, spherical tokamaks
52.25.-b Plasma properties

Plasma radiometry with 30 chord resolution for fast transients in the DIII-D tokamak

D. S. Gray, E. M. Hollmann, S. C. Luckhardt, J. Chalfant, L. Chousal, R. Hernandez, E. Jones, and A. G. Kellman

Rev. Sci. Instrum. 75, 4133 (2004); http://dx.doi.org/10.1063/1.1787149 (3 pages) | Cited 6 times

Online Publication Date: 13 October 2004

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A diagnostic capable of providing time resolved measurements of plasma radiated power during disruptions and other fast transients, e.g., edge localized modes has been employed in the DIII-D tokamak. The radiation is detected with absolute extreme ultraviolet (AXUV) photodiode arrays. Thirty chords from a single port provide measurements from a full slice of the plasma at one toroidal location. The analog bandwidth is up to 1 MHz for the brightest events, i.e., disruptions. Active cooling of the diode arrays prevents damage during high temperature vessel baking. Effective responsivity values of 0.12–0.18 A/W are taken from previous work on the application of AXUV diodes in DIII-D. The total radiated energy in disruptions typically agrees with bolometer measurements within about 12%.
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52.55.Fa Tokamaks, spherical tokamaks
52.70.Kz Optical (ultraviolet, visible, infrared) measurements
07.60.Dq Photometers, radiometers, and colorimeters

Charge exchange spectroscopy by Fabry–Pérot spectrometer in W7-AS

M. Yoshinuma, K. Ida, and J. Baldzuhn

Rev. Sci. Instrum. 75, 4136 (2004); http://dx.doi.org/10.1063/1.1789587 (3 pages) | Cited 2 times

Online Publication Date: 13 October 2004

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Charge exchange spectroscopy using a Fabry–Pérot spectrometer has been developed to study the dynamic of ion temperature and radial electric field in plasmas. A charge coupled device detecter with 80×80 pixels was used to gain the spectral resolution of the charge exchange spectroscopy system. This Fabry–Pérot charge exchange spectroscopy system has been applied to measure the ion temperature using the charge exchange line of carbon impurity with a time resolution of 5 ms for high density quasisteady discharges in W7-AS. The cold component due to the charge exchange reaction between the carbon impurity and thermal neutrals is subtracted from the change emission with the beam modulation technique
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52.50.Gj Plasma heating by particle beams
52.25.Vy Impurities in plasmas
52.25.Ya Neutrals in plasmas
52.80.-s Electric discharges

AXUV bolometer and Lyman-α camera systems on the TCV tokamak

A. W. Degeling, H. Weisen, A. Zabolotsky, B. P. Duval, R. A. Pitts, M. Wischmeier, P. Lavanchy, Ph. Marmillod, and G. Pochon

Rev. Sci. Instrum. 75, 4139 (2004); http://dx.doi.org/10.1063/1.1787131 (3 pages) | Cited 7 times

Online Publication Date: 13 October 2004

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A set of seven twin slit cameras, each containing two 20-element linear absolute extreme ultraviolet photodiode arrays, has been installed on the Tokamak à Configuration Variable. One array in each camera will operate as a bolometer and the second as a Lyman-alpha (Lα) emission monitor for estimating the recycled neutral flux. The camera configuration was optimized by simulations of tomographic reconstructions of the expected Lα emission. The diagnostic will provide spatial and temporal resolution (10 μs) of the radiated power and the Lα emission that is considerably higher than previously achieved. This optimism is justified by extensive experience with prototype systems, which include first measurements of Lα light from the divertor.
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07.57.Kp Bolometers; infrared, submillimeter wave, microwave, and radiowave receivers and detectors
52.55.Fa Tokamaks, spherical tokamaks
07.68.+m Photography, photographic instruments; xerography
52.70.Kz Optical (ultraviolet, visible, infrared) measurements

Measurement of impurity emission profiles in CHS Plasma using AXUV photodiode arrays and VUV bandpass filters

C. Suzuki, B. J. Peterson, and K. Ida

Rev. Sci. Instrum. 75, 4142 (2004); http://dx.doi.org/10.1063/1.1787132 (3 pages) | Cited 3 times

Online Publication Date: 13 October 2004

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We have designed a compact and low-cost diagnostic system for spatiotemporal distributions of specific vacuum ultraviolet (VUV) emission lines from impurities in Compact Helical System (CHS) plasmas. The system consists of 20 channel absolute extreme ultraviolet photodiode arrays combined with interchangeable thin foil filters which have passbands in the VUV region. A compact mounting module which contains all the components including an in-vacuum preamplifier for immediate current–voltage conversion has been designed and successfully fabricated. A preliminary measurement with a single module using an aluminum foil filter has been carried out for monitoring the behavior of oxygen impurity in CHS, and initial results have been obtained. Two identical modules equipped with Versa Module European bus-based analog-digital converters will be available for future tomographic measurements.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.25.Vy Impurities in plasmas
52.25.Fi Transport properties

Versatile multiwavelength imaging diagnostic in the MAST spherical tokamak

A. Patel, P. G. Carolan, N. J. Conway, C. A. Bunting, and R. J. Akers

Rev. Sci. Instrum. 75, 4145 (2004); http://dx.doi.org/10.1063/1.1789608 (4 pages) | Cited 4 times

Online Publication Date: 13 October 2004

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Spectral imaging diagnostics that view the full plasma cross section are used on MAST with sensor resolutions and frame rates of up to 256×512 chords and 130 Hz, respectively. The incident and solid angles of filter illumination are fully controllable. Image splitting and spectral selection with separate filters are performed in the telecentric region of the optics, whereas quasicontinuous polychromatic selection is achieved with a single filter in the convergent region. The versatility is investigated in exploiting the diagnostic techniques facilitated by neutral beam injection. Three color image dissection, detection of impurity charge exchange emission and Balmer-alpha beam emission are demonstrated. In another application it has been possible to use a single narrow band filter to image the spatially varying Doppler shifted emission from an inclined neutral beam even though the spatial variation well exceeds the filter bandwidth.
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52.70.Nc Particle measurements
52.55.Fa Tokamaks, spherical tokamaks
52.50.Gj Plasma heating by particle beams
52.25.Ya Neutrals in plasmas
52.25.Vy Impurities in plasmas

Ultraviolet imaging of a magneto–plasmadynamic thruster

G. Spizzo, P. Franz, G. Gadani, L. Marrelli, P. Martin, F. Paganucci, and P. Rossetti

Rev. Sci. Instrum. 75, 4149 (2004); http://dx.doi.org/10.1063/1.1789588 (3 pages) | Cited 2 times

Online Publication Date: 13 October 2004

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We present a project of an imaging system of a plasma produced by a magneto–plasmadynamic (MPD) thruster for space applications, in the ultraviolet range. This system consists of four detectors placed outside the thruster (5 cm from the anode surface), plus nine arrays of ultraviolet (UV)-enhanced photodiodes, viewing the plasma at three different axial positions (z = 3.5,8.0, and 12.5 cm from the cathode tip) obtained carving directly their lodgings in the cylindrical structure of the anode, in between anode and cathode. We used single UDT455 UV/LN detectors with low noise, built-in amplifiers. The system allows the imaging of m = 1 helical instabilities which limit the MPD thrust efficiency.
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52.70.Kz Optical (ultraviolet, visible, infrared) measurements
52.30.Cv Magnetohydrodynamics (including electron magnetohydrodynamics)
52.50.-b Plasma production and heating
52.35.Py Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.)
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