Influence of boronization on the plasma performance in TEXTOR
- 1 February 1989
- journal article
- Published by IOP Publishing in Plasma Physics and Controlled Fusion
- Vol. 31 (2) , 185-192
- https://doi.org/10.1088/0741-3335/31/2/004
Abstract
The plasma-facing surfaces of TEXTOR have recently been coated (plasma chemical deposition) by a thin layer of hydrogen-rich carbon and boron (ratio 1:1). The paper describes the improved plasma performance which resulted when this coating replaced the amorphous carbon (a-C:H) layer used before. The main differences were a pronounced reduction of the radiation losses, a decrease of Zeff from 1.4 to 1.2 and a significant change in the hydrogen recycling: the recycling coefficient was smaller than unity during current flat top at a wall temperature Tw=150 degrees C whereas this could only be achieved at Tw>or=300 degrees C with a-C:H. Density excursions during ICRH pulses were avoided even at a power level of more than 2 MW. Possible explanations for the reduction of the oxygen concentration and for the change in hydrogen recycling are suggested and discussed.Keywords
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