Development of RF heating in support of long pulse operation in WEST and future power plants

W—for tungsten—Environment in Steady-state Tokamak (WEST) is a superconducting tokamak with a full-tungsten environment and an actively cooled ITER-grade divertor. It is a unique European facility, offering crucial insights for the operation of future magnetic fusion devices with metallic environments in steady-state conditions. The heating and current drive in WEST is provided exclusively by radio-frequency (RF) systems, featuring dominant electron heating with negligible torque input. Recent WEST experiments have resulted in a new record of 1337 s pulse length and 2.6 GJ injected energy, using 2–3 MW of lower-hybrid current drive (LHCD). This achievement was facilitated by the use of an advanced LHCD monitoring system. An ITER-relevant use of the ion-cyclotron resonant heating (ICRH) antenna, such as wall conditioning with ICRH, has been evaluated during the three last WEST campaigns. ECWC is not considered today on WEST due to water leak risk due to high heat fluxes on the vacuum vessel wall. A new concept of ICRH system, the travelling wave array (TWA) antenna, is currently under design for WEST. Finally, a new electron-cyclotron heating system, featuring three 1 MW gyrotrons is under commissioning.