Study on in-situ carbon coating in JIPP T-IIU

The effectiveness of the in-situ carbon coating (carbonization) has been demonstrated to reduce the radiation loss by iron impurities during ICRF heating in the JIPP T-IIU tokamak. As a result of carbonization, the total radiation loss decreased down to one fifth of the RF power, which resulted in an increase in electrons and total stored energy compared with these conditions before carbonization. The thickness of the carbon layer was 300–900 A, and its toroidal uniformity was within a factor of 3, although only one anode and one gas-inlet were used. A thin carbide layer is formed between the C-film and the stainless steel substrate with carbonization at room temperature. The hydrogen concentration is 40–50 at.% in the carbon layer. Deposition of carbon was observed on window materials. The deposition rate was relatively less on electrical insulators compared to the deposition rate on metals.