INITIAL ICRF COUPLING AND HEATING EXPERIMENTS ON ALCATOR C-MOD

Initial ICRF coupling studies were performed successfully on the Alcat or C-Mod tokamak with all-metallic first wall, using a radially movabl e single-current-strap (monopole) antenna. The plasma loading is 10-40 times the vacuum loading, which is sufficient to inject 2 MW of r.f. power through one two-strap (dipole) antenna. The observed loading is consistent with predictions of full-wave calculations. Up to 1 MW of r .f. power (antenna power density of greater than or similar to 10 MW m (-2)) has been injected into the C-Mod plasma without serious impurity problems. Definite signs of both ion and electron heating were observ ed at power levels of 0.4 MW and higher (P-RF/P-OH greater than or sim ilar to 0.3) in the D(H) minority heating regime. High-power heating e xperiments with 4 MW of source power and two dipole antennas began in May 1994.