Recent results of boronization on EAST and HT-7 superconducting tokamak

The importance of wall conditionings for the reduction of the impurities in plasmas has been recognized in most tokamaks. Boronization associated with Ion Cyclotron Resonance Frequency discharge (ICRF boronization) has been developed on HT-7 superconducting tokamak since 1998, and now this boronization technique has become a routine method for wall conditioning on HT-7 and also on EAST. Carborane (C2B10H12) was used for the boronization and helium was usually provided as the auxiliary gas. However, after this kind boronization, lots of H2 released from the boron film make the controlling of the plasma density very difficulty. Recently, to reduce H2 content in the film, we change the auxiliary gas from He to D2 during the whole boronization procedure and find the release of H2 during plasma discharges was greatly reduced.