IMPURITY SOURCES IN TEXTOR
The deuterium, oxygen and carbon fluxes from the main limiter and the deuterium fluxes from the wall are measured in TEXTOR for an "all carbon" surrounding as a function of central density ne, of applied ICRHpower and of different wall conditions (carbonization). For this purpose, emission spectroscopy both with filter systems and spectrometers has been used. It is found that a major release mechanism for light impurities is via the formation of molecules. Oxygen seems to enter the discharge from the liner via OD containing molecules, whereas the limiter acts as the main carbon source by the release of hydrocarbons as indicated by the observed CD band spectra. Both oxygen and carbon fluxes are reduced by about a factor of two after a fresh carbonization. Above a certain critical density the plasma detaches from the limiter and forms a stable discharge with a radiation cooled boundary layer and with a major fraction of particles now reaching the wall instead of the limiter. The critical density rises with decreasing impurity fluxes or with increasing heating powers.
Bibliographic Reference: JOURNAL OF NUCLEAR MATERIALS, NOS. 145-147 (1987), PP. 574-579
Record Number: 1989126004400 / Last updated on: 1988-02-01
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