The High Voltage Deck 1 and Bushing for the ITER Neutral Beam Injector: Integrated design and installation in MITICA experiment

Abstract

MITICA is the full scale prototype of the ITER Heating Neutral Beam (HNB) currently under construction at the Neutral Beam Test Facility in Padova (Italy). In the ITER HNB, negative ions (H−/D−) are produced in the Ion Source (IS) polarized to ground at −1012 kV, then extracted and accelerated to ground at 1 MeV energy and finally neutralized. The complex power supply system feeding the IS includes two non-standard equipment, beyond the current industrial standard for insulation voltage level (-1 MVdc) and dimensions: 1) the High Voltage Deck1 (HVD1), a large air insulated Faraday cage (12.5 m (L) x 8.4 m (W) x 9.6 m (H)) hosting the IS power supplies and diagnostics; 2) the High Voltage Bushing Assembly (HVBA), a -1 MVdc air to SF6 Bushing which interfaces the HVD1 with the SF6 insulated Transmission Line (TL) connecting the Acceleration Grid Power Supply system with the IS, carrying inside its High Voltage electrode all IS power and diagnostics conductors. The HVD1 and HVBA are installed inside a large HV hall. The main design choices leading to the final hall layout, integrating the HV experimental equipment and the conventional building plants assuring the necessary clearance required by such very high electric insulation level, are presented. Moreover, the paper reports on the manufacturing design developed by the supplier, the factory type tests to validate the design of the HVD1, the factory tests carried out on the HVBA and the on-site installation, commissioning and testing activities.