The vacuum and gas inlet systems for the RFX fusion experiment

RFX is a large fusion experiment under construction in Padova (Italy). The toroidal vacuum vessel, having a major radius of 2 m and a minor radius of 0.475 m, is built in Inconel 625, and its inner surface is completely covered by 2016 graphite tiles. The residual final pressure should be in the range of 10−9 mbar; to reach the required vacuum conditions, 12 uhv pumping groups are provided, each of them including one turbo pump (1000l s−1) and one cryogenic pump (1500l s−1). Six forevacuum pump systems, each including one roots pump (double stage) and one rotary pump, assure the regeneration of the cryogenic pumps and the forevacuum conditions for the turbo pumps. The gas inlet system is designed to supply H2 and D2 to the vessel in very high purity conditions or in a pre-defined mixture with impurities. The plant control system can work either in manual or automatic mode: in manual mode the system is handled from ‘local operation panels’, whereas in automatic mode it is controlled by a ‘Programmable Logic Controller’ (PLC) which is part of the overall control and monitoring system of the RFX experiment. The paper describes the design of the systems and evidences the main technical solutions that have been adopted.