Influence of gas injection location and magnetic perturbations on ICRF antenna performance in ASDEX Upgrade
- Max-Planck-Institut für Plasmaphysik, EURATOM-Association, D-85748 (Germany)
- Max-Planck-Institut für Plasmaphysik, EURATOM-Association, D-85748, Germany and Department of Applied Physics, Gent University, 9000 Gent (Belgium)
- Euratom/CCFE Fusion Association, Culham Science Centre, Abingdon, OX14 3DB (United Kingdom)
- CEA, IRFM, 13108 Saint Paul-lez-Durance (France)
- Institute of Plasma Physics and Laser Microfusion, Association EURATOM-IPPLM, Warsaw (Poland)
In ASDEX Upgrade H-modes with H{sub 98}≈0.95, similar effect of the ICRF antenna loading improvement by local gas injection was observed as previously in L-modes. The antenna loading resistance R{sub a} between and during ELMs can increase by more than 25% after a switch-over from a deuterium rate of 7.5⋅10{sup 21} D/s injected from a toroidally remote location to the same amount of deuterium injected close to an antenna. However, in contrast to L-mode, this effect is small in H-mode when the valve downstream w.r.t. parallel plasma flows is used. In L-mode, a non-linearity of R{sub a} at P{sub ICRP}<30 kW is observed when using the gas valve integrated in antenna. Application of magnetic perturbations (MPs) in H-mode discharges leads to an increase of R{sub a}>30% with no effect of spectrum and phase of MPs on R{sub a} found so far. In the case ELMs are fully mitigated, the antenna loading is higher and steadier. In the case ELMs are not fully mitigated, the value of R{sub a} between ELMs is increased. Looking at the W source modification for the improved loading, the local gas injection is accompanied by decreased values of tungsten (W) influx Γ{sub W} from the limiters and its effective sputtering yield Y{sub w}, with the exception of the locations directly at the antenna gas valve. Application of MPs leads to increase of Γ{sub W} and Y{sub w} for some of the MP phases. With nitrogen seeding in the divertor, ICRF is routinely used to avoid impurity accumulation and that despite enhanced Γ{sub W} and Y{sub W} at the antenna limiters.
- OSTI ID:
- 22263865
- Journal Information:
- AIP Conference Proceedings, Vol. 1580, Issue 1; Conference: 20. topical conference on radiofrequency power in plasmas, Sorrento (Italy), 25-28 Jun 2013; Other Information: (c) 2014 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0094-243X
- Country of Publication:
- United States
- Language:
- English
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