Development and testing of one-turn resistive structures of aluminum alloy vacuum vessel for reacting plasma experiment

R-tokamak is a low radioactive D-T experimental device now in the planning stage. The vacuum vessel has a D-shaped thick shell made of aluminum alloy. The development of toroidal one-turn resistive structures of the aluminum alloy vessel is one of the crucial design subjects for R-tokamak. There exist two possible ways to obtain toroidal one-turn resistive structures, i.e. insulating seal joints and bellows. This paper describes the results of the development and testing of these two types of one-turn resistive structures. As for the insulating seal joints, the authors have performed basic functional tests of the fiber-reinforced polyimide insulation and the anodized surface-layer insulation. In addition to doing the basic tests, they have proceeded to a trial fabrication of a one-fifth scale model of the D-shaped insulating seal joint. The model has shown a satisfactory vacuum leak tightness in a helium leak test conducted at room temperatures. As for the bellows, the authors have successfully fabricated the large, circular cross-section bellows made of aluminum alloy 5083, and also have performed trial fabrication of the D-shaped, reduced-size bellows as well as basic tests of the FRP (fiber-reinforced plastic) reinforcement of the bellows