Primary results of the upgraded actively cooled limiter system of HT-7

In order to achieve long pulse high performance plasma discharges, the actively cooled limiter system on HT-7 tokamak was upgraded in the end of 2003. High heat flux toroidal limiters based on copper alloy heat sink structures with bolt linking concept have been developed in order to enable a large increase of power extraction capacity. In the first plasma operation with the new limiter system, very promising results had been obtained (31 MJ of injected and removed power during 237 s discharge) in 2004. Repeated long plasma discharges were easily obtained. Low temperature of the graphite tiles, and low impurity level was observed during long plasma operation. In a long-term plasma operation, most tiles were only lightly eroded.