THE CRYOPLANT FOR THE ITER NEUTRAL BEAM TEST FACILITY TO BE BUILT AT RFX IN PADOVA, ITALY

Abstract

The Neutral Beam Test Facility (NBTF), planned to be constructed in Padua (Italy), will constitute the prototype of the two Neutral Beam Injectors (NBI), which will be installed in the ITER plant (Cadarache‐France). The NBTF is composed of a 1 MV accelerator that can produce a 40 A deuteron pulsed neutral beam particles. The necessary vacuum needed in the accelerator is achieved by two large cryopumps, designed by FZK‐Karlsruhe, with radiation shields cooled between 65 K and 90 K and with cryopanels cooled by 4 bar supercritical helium (ScHe) between 4.5 K and 6.5 K. A new cryoplant facility will be installed with two large helium refrigerators: a Shield Refrigerator (SR), whose cooling capacity is up to 30 kW between 65 K and 90 K, and a helium Main Refrigerator (MR), whose equivalent cooling capacity is up to 800 W at 4.5 K. The cooling of the cryopanels is obtained with two (ScHe) 30 g/s pumps (one redundant), working in a closed cycle around 4 bar producing a pressure head of 100 mbar. Two heat exchangers are immersed in a buffer dewar connected to the MR. The MR and SR different operation modes are described in the paper, as well as the new cryoplant installation.