Reduction of RF sheaths potentials by compensation or suppression of parallel RF currents on ICRF antennae

Journal Article · Thu Nov 26 04:00:00 EST 2009 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.3273714· OSTI ID:21335692

Mendes, A; Colas, L; Vulliez, K; Argouarch, A ^[1]; Milanesio, D ^[2]

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1. CEA, IRFM, F-13108 Saint Paul-lez-Durance (France)
2. Department of Electronics, Politecnico di Torino, Turin (Italy)

Radio Frequency (RF) sheaths are suspected to limit the performance of present-day Ion Cyclotron Range of Frequencies (ICRF) antennae over long pulses and should be minimized in future Fusion devices. Within the simplest models, RF sheath effects are quantified by the integral V{sub RF} {integral}E{sub ||}{center_dot}dl where the parallel RF field E{sub ||} is linked with the slow wave. On 'long open field lines' with large toroidal extension on both sides of the antenna it was shown that V{sub RF} is excited by parallel RF currents j{sub ||} flowing on the antenna structure. We thus propose two ways to reduce |V{sub RF}| by acting on j{sub ||} on the antenna front face. The first method, more adapted for protruding antennae, consists in avoiding the j{sub ||} circulation on the antenna structure, by slotting the antenna frame on its horizontal edges and by cutting partially the Faraday screen rods. The second method, well suited for recessed antennae, consists in compensating j{sub ||} of opposite signs along long flux tubes, with parallelepiped antennae aligned with tilted flux tubes. The different concepts are assessed numerically on a 2-strap Tore Supra antenna phased [0, {pi}] using near RF fields from the antenna code TOPICA. Simulations stress the need to suppress all current paths for j{sub ||} to reduce substantially |V{sub RF}| over the whole antenna height.

• OSTI ID: 21335692
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 1187; ISSN APCPCS; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ANTENNAS
COMPUTERIZED SIMULATION
ICR HEATING
IONS
PLASMA
PLASMA CONFINEMENT
PLASMA SHEATH
PLASMA SIMULATION
POTENTIALS
PULSES
RADIOWAVE RADIATION
STRESSES
T CODES
TORE SUPRA TOKAMAK