Progress on the design of the cryogenic plant for the ITER Neutral Beam Injector test facility in Padova

In the framework of the construction of the Test Facility for the ITER Neutral Beam Injector to be installed at Consorzio RFX in Padova (Italy), a cryosorption cryopump, designed by FZK, will be employed to guarantee the appropriate pressure range for the D2or H2 pulsed beam. The cryopanels that constitute the cryopump will be indirectly cooled by means of supercritical helium at temperatures ranging from 4.5 K to 6.5 K and at a pressure of 0.5 MPa. The thermal shields will be indirectly cooled by means of high pressure (>1.5 MPa) gas helium at temperatures from 65 K to 90 K. In order to provide the helium gas and the supercritical helium to the cryopump, a cryogenic plant has been further designed by RFX. The cryogenic plant consists of a Main Refrigerator to supply the supercritical helium, a Shield Refrigerator based on a Brayton cycle for the cooling of thermal shields, a Proximity Cryogenic System to provide the helium distribution and a Helium Recovery and Purification System to deliver pure helium to the refrigerators. The plant has been conceived to operate in several functioning modes according to the needs of the test facility: a cool-down operation, stand-by and NBI operation modes, a 100 K regeneration mode, a warm up operation to ambient temperature, and a 470 K regeneration mode. The full flexibility of the system has been pursued to assure its reliability and to chase unbroken operation. This paper presents the cryoplant design and the technical solutions adopted to optimize the system performances and its capability to implement all the required operative scenarios in a fully automatic mode.