Carbon-metal brazing for divertor plates in fusion devices

摘要

A diverter unit, which consists of carbon armors brazed to a copper cooling channel, is under development for fusion devices. Isotropic graphite (IG-430U) and CFC (CX-2002U) are used for the armor, and a copper for the cooling tube. A technique named `dissolution and deposit of base metal' was employed for brazing. The reliability of the brazed components was evaluated both by a 4-point bending test and a thermal shock test. According to the results of the 4-point bending test under the temperature ranged from RT to 800$DGR@C in a vacuum, it was found that the strength of the brazed surface at RT was maintained up to the higher temperature, 600$DGR@C. A high heat load test has also been performed on the brazed sample in order to find out whether the samples meet the requirement of the diverter plates of LHD. Active Cooling Teststand (ACT:NIFS) with an electron beam power of 100 kW was used. In LHD, it is presumed that the maximum heat flux is 10 MW/m$+2$/. In addition, the surface temperature of the diverter has to be kept below 1200$DGR@C to avoid RES, by active cooling. The heat load test showed that the brazing components of CX-2002U (flat plate type CFC-Cu brazed) were stable at 1300$DGR@C under a heat flux of 10 MW/m$+2$/, when the flow velocity of cooling water was 6 m/s. No damage nor deterioration was found at the brazed zone after the heat load test.