Monte Carlo calculation of the thermal radiation heat load of the ITER pre-production cryopump

Large-scale customized cryogenic pumps are employed to pump the ITER torus. The high performance of this kind of non-conventional cryopumps is achieved by the cryosorption of the gas load on the charcoal-coated panels working at 4.5 K. In order to avoid the direct thermal radiation, the 4.5 K pumping panels are installed inside a 80 K heat shielding system. In this paper, we will present the Monte Carlo simulation of the thermal radiation heat loads to the cryopanel circuit, the thermal shield circuit and the valve head when the pump is in stand-by, pumping and regeneration. The results are of great importance in the design of the ITER pre-production cryopump (PPC).