High power experiments of remote steering launcher for electron cyclotron heating and current drive

High power (0.5 MW) radiation tests of a remote steering launcher for an electron cyclotron heating and current drive (EC H and CD) system were carried out to study the characteristic of the rf beam steering and transmission. The remote steering launcher consists of a 4.632 m corrugated square waveguide (45.7x45.7 mm2) and a movable flat mirror which is placed at the input of the waveguide. Measurements were made in the range 0-10 deg. at a frequency of 170 GHz. The measured radiation pattern is clearly a Gaussian-like distribution, which is in agreement with the theoretical prediction and the low power measurements. A steering capability of up to 10 deg. was experimentally confirmed. Transmission and radiation of 0.5 MW 3.0 s and 0.2 MW 10.0 s pulses were successfully demonstrated over a steering angle range of 0-10 deg. . Transmission losses in the launcher waveguide over 0-10 deg. were measured calorimetrically to be less than 5%. No arcing was observed during the experiments and no damage to the waveguide was found after the experiments were finished. We have confirmed that remote steering is a possible alternative scheme for EC H and CD beam steering