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&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 (45.7×45.7 mm2) and a movable flat mirror which is placed at the input of the waveguide. Measurements were made in the range 0–10° 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° 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°. Transmission losses in the launcher waveguide over 0–10° 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&CD beam steering.