RF heated wall conditioning discharges in JT-60U

Abstract In series of experiments in 2000 and 2008, helium wall conditioning discharges by ECRF heating (ECH) were extensively studied in JT-60U with B T = 3.6 T and P ECRF ⩽ 2.5 MW. Homogeneous ECH conditioning discharges were reproducibly obtained by applying the horizontal field as large as 0.2% of B T . It was found that the horizontal field is effective to extend He plasma toward high field side from the fundamental resonant surfaces of ECH. The ECH wall conditioning discharge with P ECRF = 2.5 MW and t pulse = 1.5 s was applied after the plasma disruption with W = 3.3 MJ and the successful recovery of the current ramp-up with 0.5 V/m of ohmic electric field was obtained.