ECH microwave measurement using in-vessel thermocouple array on JT-60SA

The in-vessel first wall made up of inertially cooled graphite tiles supported on stainless steel pedestals was installed in the vacuum vessel to protect the in-vessel components from the plasma and injected electron cyclotron eating (ECH) microwave in the integrated commissioning phase of JT-60SA. Sixteen thermocouples were installed in the inboard first wall, which is one of the in-vessel first walls, to measure and control the temperature of both graphite tiles and their pedestals during plasma experiments and ECH microwave injection in the vacuum vessel. We observed the increase in temperature obtained from thermocouples when the microwave was injected into the vacuum vessel without plasmas during ECH conditioning. According to the thermal analysis, the ECH microwave directly heats the sheath of the thermocouple of the pedestal. The estimated heat fluxes due to the microwave are 70 kW/m2 and 21 kW/m2 for the graphite tile and pedestal, respectively, when the injection power and frequency of the gyrotron are 470 kW and 110 GHz. The observed profile of the increasing temperature obtained from thermocouples during ECH microwave injection indicates that the microwave reflects at the inboard first wall and propagates to the opposite side of the torus. The thermocouple measurement can be usefully measured the stray microwaves.