Conclusions on Rf Heating Contributions Presented at the Varenna International School of Plasma Physics 1977

Weynants, R.R.

doi:10.1016/b978-0-08-023426-7.50024-1

Cited by 1 publication

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“…Although in several recent experiments [2][3][4][5][6][7] this problem has been studied and, to some extent, overcome, there is no clear consensus as to the principal source of metal impurities or the dominant mechanism for their release. Impurity generation during ICRF heating involves the complex interactions between the scrape-off layer plasma, the RF fields, and the materials exposed to the scrape-off layer [8], namely the limiter, the walls and the ICRF antenna structure, which must be near the plasma to ensure good coupling. For an extension of ICRF heating to reactor level powers, further understanding of these interactions is needed in order to minimize the enhanced radiated power losses and impurity concentrations which persist in most of the current high power ICRF experiments.…”

Section: Introductionmentioning

confidence: 99%

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Impurity generation during ICRF heating experiments on Alcator C

et al. 1986

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Observations of impurity behavior are presented from ICRF heating experiments at 180 MHz performed over a variety of conditions on the Alcator C tokamak, using graphite limiters and stainless steel antenna Faraday shields. Spectroscopic observations revealed significant increases in metal impurity concentrations during the RF pulse, with iron levels increasing by as much as a factor of 12 at the highest RF powers (-350-400 kW). Analysis of the inferred iron source rates shows an approximately linear dependence on RF power up to 400 kW. with no clear dependence on resonance conditions or bulk plasma parameters.However, a sharp increase in the temperature in the limiter shadow region was observed during the ICRF pulse, which was well correlated with the iron influx rate. It is concluded from this and other evidence that physical sputtering of the Faraday shield due to an elevated sheath potential is the primary source of metal impurities during ICRF heating on Alcator C. The same process, occurring at the graphite limiter, is believed to be the dominant source of carbon and oxygen. Calculated sputtering yields obtained from an edge erosion code demonstrate the plausibility of this model.

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Section: Introductionmentioning

confidence: 99%

“…Impurity generation during ICRF heating involves the complex interactions between the scrape-off layer (SOL) plasma, the RF fields, and the materials exposed to the SOL [8]:…”

Section: Introduction Resonant Heating Of Fusion Plasmas Via Absorptimentioning

confidence: 99%