Modeling of DC potential structures induced by RF sheaths with transverse currents in front of ICRF antenna
- LPMIA, UMR CNRS 7040, Univ. Henri Poincare, Nancy 1, BP 239, 54506 Vandoeuvre Cedex (France)
- Association Euratom-CEA-DRFC, CEA Cadarache, 13108 St Paul les Durance (France)
RF heating is fully dependent on edge plasma conditions and particularly on convection of accelerated particles which can damage ICRH antennas (hot spots and impurity injection). These accelerated particle fluxes born in DC potential structures are induced by sheaths which rectify RF potentials. The potential map in front of antenna is not uniform so that transverse (to magnetic field) RF currents occur and can significantly modify the final DC potential map and thus convective flux distribution. The behavior of rectified potentials is investigated here for f = F{sub ci} and f>F{sub ci}, which was not yet achieved in our last works [1]. Therefore, a 2D fluid modeling including RF sheaths physics (parallel current) coupled with transverse RF currents has been built. The full description of the currents exhibits a maximum for frequencies around Fci, which can be explained by the fact that RF oscillation is capacitive at low frequency and inductive at high frequency. Both effects are present at frequencies around F{sub ci} and the DC peak potential appears for f = F{sub ci}/2. This is due to the rectification of the sinusoidal signal, which doubles the effective RF frequency radiated by the antenna. The theoretical DC peak value is 0.5 time the RF amplitude of the applied potential instead of 1/{pi} without transverse currents. For typical potential structures in front of ICRH antennas (centimetric wide and 1000 Volts peak potential), a factor between 0.4 and 0.45 can be expected according to 2D fiuid code results.
- OSTI ID:
- 21032762
- Journal Information:
- AIP Conference Proceedings, Vol. 933, Issue 1; Conference: 17. topical conference on radio frequency power in plasmas, Clearwater, FL (United States), 7-9 May 2007; Other Information: DOI: 10.1063/1.2800480; (c) 2007 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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