Design concepts and initial experimental results of LHRF launcher in JT‐60

The phased array launchers of 4×8 waveguide for current drive and heating in JT‐60 have been constructed and have operated at a power level of ∼2 MW for a few seconds. The transmitted power densities have reached 4.1 KW/cm² and 2.1 KW/cm² for current drive and heating launchers, respectively, after only a few weeks conditioning. The coupling efficiency of 80∼85% has been obtained at the power level of a few MW into 1∼2 MA plasma and the coupling efficiency is explained well with Brambilla’s theory.