Development of the long-pulse ECRF system for JT-60SA

Improvements of the Electron Cyclotron Range of Frequency (ECRF) system in JT-60U and design works are underway towards steady-state operation in JT-60SA. Since the ECRF system in JT-60U was designed as a 5 s system, improvements in almost all the system are required to achieve the target pulse length of 100 s with a gyrotron output power of 1 MW for JT-60SA. The issues and present status of the design and development are summarized from a view point of requirements for obtaining long pulse ECRF system.