Operation and control of JT-60U ECRF system

This paper describes the operation and control for the 110 GHz ECRF system for JT-60U, which has started operation since March in 1999. This system is composed of a 1 MW gyrotron, its high voltage power supply, a transmission line about 60 m in length and a quasi-optical antenna using a steerable mirror. Key issues of the ECRF system are to drive the gyrotron stably and to control the local RF deposition profile in a plasma.