Wall Conditioning and Experience of the Carbon-Based First Wall in JT-60U

JT-60U has a variety of wall-conditioning methods such as baking of the vacuum vessel, helium Taylor discharge cleaning, helium glow discharge cleaning, tokamak discharge cleaning, and boronization. Using these wall-conditioning methods, the high-power operation of JT-60U has been successfully carried out with the carbon-based first wall. The material behavior of the carbon-based first wall has been investigated, and important knowledge was obtained on mechanical engineering and plasma surface interactions. In order to understand the tritium behavior in JT-60U, tritium retention in the first wall and tritium exhausted through the pumping system were measured. These results yield useful information on the tritium behavior in a future DT fusion machine.