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  • 1
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: In the reversed field experiment the electron temperature and density at the edge are measured from the intensity ratio of selected lines emitted by an atomic helium beam injected into the plasma. Helium is injected through a single microtube 30 mm long and with 150 μm of internal diameter. Four beam splitters allow three interference filters, coupled to linear array cameras or alternatively to photomultipliers, and a charge coupled device camera to observe the same beam volume. The application of photomultipliers as detectors has recently increased the time resolution of the diagnostic. This allows following the time evolution of edge density and temperature during nonstationary processes. Moreover, the enhanced time resolution increases the capability of the diagnostic to measure the edge electron temperature and density fluctuations, which are relevant to the edge electrostatic transport studies. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The conceptual feasibility of an active spectroscopic diagnostic on reversed field experiment (RFX) to measure the radial profiles of ion temperature, toroidal and poloidal drift velocities, and main impurity densities is examined. In particular a charge exchange recombination spectroscopy experiment is simulated for carbon and helium impurities. The motional Stark effect on the beam atoms injected into RFX is estimated as a means to measure the magnetic field pitch and intensity. A modulated beam injector (500 Hz) with 2 A of equivalent current and an energy of 50 keV/amu appears to be adequate to perform the measurements over a reasonable range of operational regimes. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The vacuum Czerny–Turner high-resolution spectrometer observing the plasma of the reversed-field-pinch device RFX has been absolutely calibrated in the spectral range 1215–7000 A(ring), in order to measure the emission spectrum in absolute units, with particular reference to the heliumlike carbon and oxygen ion lines. The source used to calibrate the spectrometer in the vacuum and near-ultraviolet region is a deuterium lamp; its spectral radiance was determined by comparison with the synchrotron radiation of the electron storage ring BESSY, in Berlin. A typical error of 35% has been estimated. In the visible a standard tungsten lamp has been used. The calibration has been transferred to an ultragrazing incidence XUV spectrometer by means of the branching-ratio technique, using the intensity ratio between the intercombination 1s2 1S–1s2p 3P0 and the 1s2s 3S–1s2p 3P0 transitions of carbon, nitrogen, and oxygen heliumlike ions. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The ultra-soft x-ray duochromator based on two multilayer mirrors installed on the reversed field pinch experiment (RFX) reversed field pinch is described. Built at the Budker Institute of Nuclear Physics of Novosibirsk, it has been designed to monitor the time behavior of the hydrogen and helium-like resonant transitions of carbon and oxygen, the main impurities in the RFX emission spectrum, with the possibility of scanning the wavelengths between 16 and 45 Å. The wavelengths can be independently selected for both the mirrors (made of Ni/C and Cr/C layers, respectively) via a aitch-theta–2aitch-theta mechanism, without breaking the vacuum. The detector is based on a scintillator layer deposited on the head of a photomultiplier. Vacuum ultraviolet and visible radiation is cut by means of thin metal films (Fe, Al, Cr) deposited on a mylar substrate and on the scintillator. The wavelength resolution (λ/Δλ) of 40 to 50 in the region of interest is provided by a Soller collimator and a precollimator stage placed in front of the mirror. The relatively large etendue allows one to perform observation in a wide range of experimental conditions. Sample results of the chordal observations are compared in absolute units with the predictions of a collisional–radiative one-dimensional impurity transport code. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 610-612 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The systems installed on the RFX reversed field pinch to study the impurity influxes are described. They comprise of telescope lenses, coupled through optical fibers and interference filters or spectrographs to photomultipliers for time-resolved analysis, and charge coupled device (CCD) cameras. The solutions adopted aim at giving an insight into the impurity production mechanisms in a situation characterized by largely asymmetric plasma–wall interactions. Main gas and various impurity influxes from the same area of the first wall are compared by means of very simple light splitters interposed between telescope lenses and narrow band filters. Four high-resolution CCD cameras also equipped with interference filters cover more than half of the first wall allowing detailed spatial studies of the impurity influx distributions. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: This paper describes the vacuum Czerny–Turner spectrometer with a 1.33 m focal length installed on the RFX fusion experiment. The optics are coated with MgF2 and the image intensifier, protected by a vacuum sealed MgF2 window, features a dual photocathode system, CsTe on one half and S20 on the other; thus the instrument covers efficiently the wide spectral range from the MgF2 limit to the near infrared. Sensitivity at short wavelengths is limited by the reflectance of mirrors and the transmittance of the MgF2 window. The detector is completed by a fast optical multichannel analyzer whose 1024 photodiodes can be read out in a time of 250 μs. The instrument can also be operated in a duochromator mode by deflecting the diffracted beam onto a second detector system, where two photomultipliers are applied to two exit slits, one fixed and the other remotely movable in such a way that the intensity ratios of two lines can be monitored for diagnostic purposes. Some examples of obtained spectra illustrating the instrument performance and comprising first results from the RFX plasma are presented.
    Type of Medium: Electronic Resource
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