Upgraded actively cooled high-field-side belt limiter and its preliminary results in HT-7

The inner components of the HT-7 vacuum vessel, including the belt limiters, were upgraded before the 2008 spring campaign in order to improve the power exhaust capacity in the longer pulse discharge. The longest discharge duration had been extended from 306 s to over 399 s, which demonstrated that the upgrading in the HT-7 device was very successful. In addition, the maximum temperature on the surface of the high-field-side belt limiter in the long pulse operation was not more than 100 °C in the long pulse operation, while the relatively high temperature rise was about 50 °C. The simulation and the observation of the power deposition on the belt limiter have been carried out and these results showed that the power exhaust capacity of the belt limiter could afford the long operation. The heat flux pattern on the belt limiter needs further study.