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  • 1
    Electronic Resource
    Electronic Resource
    Fast lithium-beam spectroscopy of tokamak edge plasmas (1993)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 64 (1993), S. 2285-2292 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Plasma-wall interaction and impurity transport processes in the outermost region of magnetically confined hot plasmas (the so-called plasma edge) must be well understood for successful development of future thermonuclear fusion reactors. To this goal, sufficiently detailed edge plasma diagnostics are in great demand. By injecting a fast Li beam into the edge plasma region, a great number of information can be obtained with excellent space and time resolution. This so-called Li-beam plasma spectroscopy gives access not only to edge plasma density profiles from the collisionally excited Li atoms, but also to the impurity concentration and temperature profiles via line emission induced by electron capture from the injected Li atoms by the impurity ions. Full utilization of all capabilities requires a reliable data base for the atomic collision processes involving injected Li atoms and plasma constituents (i.e., electrons, hydrogen ions, and relevant impurities in their various charge states), since a precise modeling of Li beam attenuation and excited-state composition has to be made for evaluating desired plasma properties from the related spectroscopical measurements. The most recent methodical improvement permits a fully consistent determination of absolute edge plasma density profiles by measuring only relative LiI line emission profiles. This is of special interest for investigating rapid edge plasma density fluctuations in connection with, e.g., ELMs, L-H mode transition, turbulence or edge cooling by impurity injection. This paper describes the capabilities of Li-beam edge plasma spectroscopy by way of illustrative examples from measurements at the tokamak experiment TEXTOR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1144460
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  • 2
    Electronic Resource
    Electronic Resource
    Study of the power exhaust and the role of impurities in the Torus Experiment for Technological Oriented Research (TEXTOR) (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2272-2280 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Controlled application of radiating impurities in the boundary layer can help to solve the problem of power exhaust in a fusion reactor. Experiments in the Torus Experiment for Technological Oriented Research (TEXTOR) [J. Nucl. Mater. 145–147, 3 (1987)] are presented, which show that impurities with sufficiently high atomic number (≥10) are well suited for this purpose. Injection of neon, a gas recycled at the wall, enabled the establishment of a quasistationary radiating boundary layer, from which more than 90% of the input power was emitted. The required neon density was established by means of a feedback control for the neon influx, which was made possible by the toroidal pump limiter Advanced Limiter Technology (ALT-II) [J. Nucl. Mater. 162–164, 115 (1989)]. Alternatively, or in addition silicon was introduced as a condensing element—either by surface reactions from siliconized walls or by silane [SiH(D)4] injection—which revealed self-controlling mechanisms effective with changing plasma parameters. In neither case was a significant increase in central impurity concentration observed and good energy confinement time was maintained up to the highest plasma densities. Based on the information from various refined edge diagnostics, the underlying mechanisms for the buildup of a radiating plasma mantle and the interdependences of neon and silicon on other impurities are discussed. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871488
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  • 3
    Electronic Resource
    Electronic Resource
    Absolute concentrations of light impurity ions in tokamak discharges measured with lithium-beam-activated charge-exchange spectroscopy (1991)
    Springer
    Applied physics 52 (1991), S. 71-78 
    Details
    ISSN: 1432-0649
    Keywords: 52.70 ; 52.40M ; 34.70
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We demonstrate the application of Li-CXS (fast lithium-beam-activated charge exchange spectroscopy) for measuring spatially and temporally resolved impurity ion concentrations in the TEXTOR tokamak edge plasma. After briefly describing the method of Li-CXS and its capabilities, we present a model for attenuation and atomic state population of an injected Li beam due to collisional interactions with the background plasma particles, taking into account up to eight excited LiI states for considering stepwise excitation-ionization processes. Measured impurity radiation characteristics resulting from Li-activated CX of C q+ (q=5, 6) in ohmically heated TEXTOR plasmas are evaluated with the above model and lead to the corresponding impurity ion concentrations within the TEXTOR edge region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00357658
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  • 4
    Electronic Resource
    Electronic Resource
    An investigation of laser-induced fluorescence for measuring velocity distributions of neutral atoms using a CW dye laser (1984)
    Springer
    Applied physics 35 (1984), S. 83-93 
    Details
    ISSN: 1432-0649
    Keywords: 32.80 ; 42.60 ; 6.30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The velocity distribution of evaporated Zr atoms has been measured by means of laser-induced fluorescence using a cw dye laser by scanning the laser line across the Doppler-broadened absorption line profile of the atoms. It is shown that the experimental data can be explained on the basis of an excitation theory for a three-level system developed from basic principles. It was calculated that the probability for an atom to be in the excited state mainly depends on the radiation-power density of the laser and on the residence time of the atom in the exciting laser light. It was found that the laser frequency must be well stabilized in order to meet the assumptions in the excitation calculation. Otherwise deviations to the theoretical predictions appear in the experimental results due to the jitter of the dye laser.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00697427
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  • 5
    Electronic Resource
    Electronic Resource
    Bestimmung von Temperatur und Dichte eines Gleitfunkens aus der Bremsstrahlung im Infrarot (1965)
    Springer
    The European physical journal 186 (1965), S. 240-248 
    Details
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The absolute intensity of a vacuum sliding spark (length 2–10 cm, half cycle 0,8 μsec) has been measured in the spectral region between 0,4 and 3μ. From the long wavelength radiation emitted from an optically thick layer, one gets the temperature, from the short wavelength radiation emitted from an optically thin layer, one obtains the density. Using polyethylene as an insulator we reached a temperature of 4·105 °K at electron densities of 8·1018 cm−3 and current densities of 1.2·106 A/cm2. The temporal development of temperature and density has been determined. The maximum intensity at λ=0.43 μ was found to be 5·104 (7·1010 W/cm3 ster) as large as that of the positive crater of a properly driven carbon arc. At λ=3 μ this same parameter turned out to be 300 times as large (5·107 W/cm3 ster).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01380464
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