Local gas injection has recently been tested as a tool to improve coupling of ion cyclotron range of frequency (ICRF) waves to tokamak plasmas, which relies on the tunnelling of the fast wave between the antenna structure and the cut-off layer within the plasma. It is found that antenna loading resistance is substantially increased when using a local gas inlet at a deuterium gas injection rate of 5 × 1021 el s−1 or higher, and that the proximity of the gas inlet to the antenna is the key factor to optimize the improvement in coupling due to gas injection.
Experimental analysis of the ICRF waves coupling in EAST