The Research of Manufacturing for HL-2M Vacuum Vessel

The vacuum vessel (VV) is one of the main components of the HL-2M tokamak device. It is a thin-shell, all-welded torus made of Inconel 625 material. Maintaining the welding quality and controlling welding distortion are the main manufacturing difficulties. Welding, forming, and assembly are the research focus. This technical note describes the fundamental manufacturing research and development (R&D) and the actual manufacturing procedure of the HL-2M VV. Three stages of R&D work are carried out. The weldability of Inconel 625 plate is studied. Partial and full-scale mock-ups are made. By optimizing the manufacturing process, the HL-2M VV was completed in 2019, and the measurement data meet the design requirements. HL-2M has good vacuum performance, the total leak rate reaches 6.0 × 10⁻⁸ Pa·m³/s at room temperature, and the ultimate vacuum pressure reaches 2.4 × 10⁻⁶ Pa after baking up to 100°C.