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Author(s):
V.S. Voitsenya, S. Masuzaki, O. Motojima, N. Noda and N. Ohyabu
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Title:
On the Use of CX Atom Analyzer for Study Characteristics of Ion Component in a LHD Divertor Plasma
Date of publication:
Dec. 1996
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Key words:
divertor plasma, ion-atom converter, particle reflection, chopper, time-of-flight atom analyzer, charge exchange atoms
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Abstract:
In this paper the analysis was provided for the possibility to use the charge exchange atom analyzer using the ion reflection phenomena on solid surtfaces for measuring the characteristics of the ion component of a divertor plasma in LHD. As an ion-atom converter the target plate made of refractory metal (Ta or W) is proposed to be used. This target plate can withstand the energy flux transported by the divertor plasma during LHD pulse: ~ 10MW/m^2 for ~ 2s with water cooling. The particle brightness of such target is much higher than the one of a gas target with a reasonable value of molecular hydrogen density (10^14cm^-3). The efficiency of W-made ion reflected atom converter is rather high, 40-65% in the incident ion energy range 50-1000eV, however the energy reflection coefficient is lower for these energies: ~ 20-40eV. Beside, the appearing the carbon or boron film on the target surface can lead to the decrease of ion-atom conversion efficiency. In such conditions the use of a time-of-flight (t-o-f) atom analyzer has some advantages as compare to the device with the gas stripping cell for charge exchange atom-ion conversion and electrostatic analysis of the ion energy distribution. In this paper we give the short description of energy component of the scheme with t-o-f atom analyzer in use, and the estimation of atom fluxes into the direction of atom analyzer with metal and gas targets.
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