R&D progress of 1 MV power supply system for ITER

A DC 1 MV insulating transformer mock-up has been successfully developed for the ITER Neutral Beam Injector. The transformer has a newly developed composite bushing consisting of a small condenser bushing and fiber reinforced plastic (FRP) tube. The transformer mock-up has successfully fulfilled the ITER requirement of DC 1.2 MV for 3600 s insulation. In a development the high-voltage (HV) bushing, vacuum insulation characteristics of the multi-layer cylindrical electrodes have been investigated. As a result, it has been clarified that the voltage holding of multi-gap and meter-class electrode depends on the surface area of the electrode. Based on this result, dimensions and locations of the screen for the ITER HV bushing has been designed to realize a stable insulation of 1 MV in vacuum.