Matching to ELMy plasmas in the ICRF domain

An ICRF antenna coupled to the plasma presents a load impedance different from what the generator requires for optimal power transfer. The required matching must be able to accommodate changes in coupling impedance due to varying plasma conditions. The changes occur on a timescale varying between particle confinement time and MHD events. In ELMy plasmas, the latter can be as fast as 50 μs. Several methods are in use, but only a few can cope with this most challenging condition: hybrid couplers and conjugate-T. Hybrid couplers have been implemented on ASDEX Upgrade, Double-III-D and will be on JET, while Alcator C-mod, JET, Textor and Tore Supra have been outfitted with conjugate-T.