The TCA tokamak is mainly dedicated to the study of additional heating by the absorption of Alfven Waves ( omega VM LS TH omega //c//i). RF waves are launched by the antennae to heat the plasma core. Unwanted edge dissipation can reduce the heating efficiency and may lead to spurious edge heating. A sufficiently large bias voltage of the antennae can decrease the RF impedance, as well as increase the strength of the wavefields. This observation indicates the presence of some parasitic loading, particularly evident at low power, and reduced above 50 kW. The loading stabilizes at bias voltages below minus 60 volts. The asymptotic loading is compared with numerically calculated values. The origin of these effects is discussed.
Proceedings of the 4th International Symposium on Heating in Toroidal Plasmas, Rome, Italy, 26 March 1984 / Heinz Knoepfel, and Elio Sindoni (eds.),
Vol. 1, pp. 193-199