Fusion Science and Technology / Volume 51 / Number 2T / February 2007 / Pages 412-414
Technical Paper / Open Magnetic Systems for Plasma Confinement
Along the upgrade program of ECRH system in GAMMA10, the gyrotron of 500kW level at 28GHz has been developed. The first 500kW gyrotron delivered 500kW at the windows and contributed to produce high ion confining potential. During the operation, it is found that there were some points to be improved: 1) Saturation level of output is smaller than expected. 2) Body current is large. 3) Beam over current occurs frequently. The second gyrotron was redesigned to improve these three points for stable operation. The second one has been changed in the design of internal mode converter, the shape of structure in collector and the slope of internal top roof of the collector. As a Result of 3 improved points, the maximum output power increased from 516kW to 570 kW, body current decreased from 5mA to 2mA, and the rate of beam over current decreased from 7% to 4%.