Achievement of the H-mode with a screenless ICRF antenna in ASDEX Upgrade
- Max-Planck-Institut fuer Plasmaphysik, Euratom Association, D-85748 Garching (Germany)
The removal of the Faraday screen from one of the four ICRF antennas in ASDEX Upgrade and the achievement of the H-mode with that antenna alone allowed for the first time H-mode specific effects of screenless antenna operation to be analyzed in a divertor tokamak. Only in particular cases could small but consistent differences be seen as compared to an antenna with screen. The threshold power is marginally ({lt}10{percent}) higher for a screenless antenna. In the power range that has been reached with only one ICRF antenna (up to 1.3 MW, ELMy and ELM-free conditions, but still near the threshold), there is a slight difference in quality of the H-mode, reflected in a lower edge electron temperature and a lower total plasma energy for the antenna without screen ({minus}10{percent}). The screenless antenna was also operated in combination with neutral beam injection (type I ELMs) and under CDH conditions (small type III ELMs, detached divertor) with no significant differences to an antenna with screen. Only modulation experiments allowed to detect a minimal difference ({lt}5{percent}) in plasma stored energy under reversed field conditions, i.e. when the Faraday screen is misaligned to the magnetic field by about 30{degree}, in favour of the antenna with screen. {copyright} {ital 1996 American Institute of Physics.}
- OSTI ID:
- 285218
- Report Number(s):
- CONF-9505105-; ISSN 0094-243X; TRN: 96:023789
- Journal Information:
- AIP Conference Proceedings, Vol. 355, Issue 1; Conference: 11. topical conference on radio frequency in plasmas, Palm Springs, CA (United States), 17-19 May 1995; Other Information: PBD: Feb 1996
- Country of Publication:
- United States
- Language:
- English
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