Local Enhanced Evaporation of Carbon Pellets in a Wendelstein 7-AS Stellarator

Timokhin, V.M.; Kuteev, B.V.; Sergeev, V. Yu.; Skokov, V.G.; Burhenn, R.
April 2004
Technical Physics Letters;Apr2004, Vol. 30 Issue 4, p298
Academic Journal
Experiments with second-harmonic electron cyclotron resonance plasma heating performed on a Wendelstein 7-AS stellarator revealed a new regime of the carbon pellet evaporation, whereby sharp peaks with the characteristic spatial width of a few millimeters appeared on the evaporation rate profile. The peaks were observed in a peripheral region of the plasma column for an electron density in the central region below and the heating power above the threshold values. The appearance of these peaks is correlated with the observation of a superthermal emission in the low-frequency part of the cyclotron radiation spectrum. The observed effect is related to the excitation of superthermal electrons by the cyclotron radiation of gyrotrons. The energy and density of the superthermal electron population are estimated at 30-50 kev and 1011-109 cm-3, respectively.


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