Antenna plasma interaction and harmonic generation on Alfvèn wave heating
Additional plasma heating by Alfvèn waves (AWH) has been studied on TCA for some years. Although considerable agreement between fundamental wave and coupling phenomena has been observed, the heating results have always been poor and difficult to interpret. Only recently has energy deposition within the plasma been shown to be determined mostly by the density rise and ohmic effects and not by Alfvèn resonant absorption within the plasma. In TCA, the standard AWH antennae are unshielded and are in direct contact with the plasma scrape-off layer (SOL) in the shadow of the limiter. In this paper is tested the hypothesis that a Langmuir current (resistive and capacitive) referred to as the default current, flows from the antennae to the plasma on application of RF potential and the parasitic power deposited at the plasma SOL interface is estimated. Experimental results presented form the first stage of a study of the plasma-antenna parasitic interaction during AWH in TCA. The results demonstrate that it is physically feasible to obtain a direct measurement of the power dissipated by the default current at the antenna-SOL interface. Measurement indicates that 20-30 kWs is delivered to the SOL in the particular case of the asymmetrically excited antenna when grounded directly at the machine earth.
Bibliographic Reference: Paper presented: 16th European Conference on Controlled Fusion and Plasma Physics, Venezia (IT), March 13-17, 1989
Availability: Available from (1) as Paper EN 34429 ORA
Record Number: 198910536 / Last updated on: 1994-12-01
Original language: en
Available languages: en