The frequency of the EAST ECRH system is 140 GHz, and the X2 mode is used to heat and drive the plasma. The ECRH system is a high-power millimeter-wave system, which is mainly composed of 4 gyrotrons, high voltage power supplies, 4 waveguide transmission lines consisting of various evacuated corrugated waveguide components, a set of antenna with 4 independent channel launchers, interlock & control system, water & oil cooling system, auxiliary vacuum system, auxiliary low-temperature system, as shown in Fig. 1. The ECRH system is planned to use 4 long pulse gyrotrons as the microwave sources, each 2 gyrotrons are powered by a cathode high-voltage power supply, and each gyrotron is equipped with an independent anode high-voltage power supply. Each gyrotron is equipped with corresponding auxiliary systems such as a superconducting magnet, low-voltage power supplies, and a dummy load. The megawatt-level high-power microwave generated by the gyrotron is sent to the quasi-optical antenna located in the EAST M window through the evacuated corrugated waveguide transmission line, and then the high-power millimeter-wave is coupled to the plasma to achieve plasma heating and current driving. The interlock & control system monitors various operating data of the system in real-time, coordinates and directs the orderly operation of each subsystem according to the set parameters, and performs protection when the system fails. The water & oil cooling system is responsible for the cooling of all components in the system. The vacuum system ensures that the MOU and the corrugated waveguide are in a good vacuum.

Fig. 1. The schematic of the ECRH system.

The #1, #3 systems (using Russian Gycom gyrotrons) were put into EAST experiments in 2015 and 2018 respectively, and can achieve 0.9MW/100s long-pulse operation. After this round of upgrades, a new set of #2 system (using American CPI gyrotron) is added to the EAST ECRH system. At present, the simultaneous operation of three gyrotrons can provide a long-pulse high-power wave output of up to 1.38MW/200s. The poloidal adjustment range of the antenna is ∓5°~ ±25°. To avoid interference with the N-window ICRF, starting this year, the toroidal adjustment range of the antenna is limited to -10°~ +25°. The detailed parameters of the EAST ECRH system are shown in the table below.

Table 1 The parameters of the EAST ECRH system.