High power gyrotron development for fusion application

Recent progresses in gyrotron development and related technologies are presented. The gyrotron demonstrated ITER relevant parameters at 170 GHz (1 MW, 800 s, 55 %), and proved a reliability with long operation period. Recently, one hour operation was obtained at 0.8 MW with the efficiency of 57 %, and total output energy of 190 GJ was recorded with 2 years operation. On the other hand, a power increase of 110 GHz gyrotron up to 1.5 MW was demonstrated on the electron cyclotron heating and current drive system of JT-60U.