The ECRH antenna is coming back on WEST tokamak.
The WEST heating system requirements have evolved with the transformations of the tokamak, its new divertor and all-tungsten (W) environment. IRFM decided in 2021 to restart the former ECRH system previously used in Tore Supra to control W contamination and to increase of the RF power available to reach H-mode.
The new system is optimized with three 105 GHz gyrotrons (1MW/1000s) and the Tore Supra ECRH antenna is updated, in particular by adding a third steering mirror and by improving the reliability of the steering accuracy of the three lines. The summer 2023 was devoted to testing the antenna (calibration of beam position and environmental tests in a vacuum chamber so called TITAN) at temperatures of 70°C and 200°C. These tests demonstrated the reliability of the system in vacuum and temperature conditions of the tokamak (see image 1: antenna in the TITAN chamber).
The movement dynamic of the three mirrors will enable beam injection angles of ± 25° in the toroidal direction and ± 17° in the poloidal direction. The mirror limit for each channel of this antenna is 1 MW for a duration of 10 seconds.
The ECRH antenna was successfully installed in WEST on the 29th September (see image 2: ECRH antenna mounted in WEST) and will wait until the RF sources are ready in 2024-2025 to deliver its first MW into the plasma. In the meantime, its behaviour during the next experimental campaigns will be monitored using the diagnostics implemented, such as temperature sensors, tension sensor on the cables used to drive the mirrors. Mirror movement in the tokamak will be performed in order to check the reliability of the system.