Simulation study of effective pumping speed of divertor pumping system for CFETR with COMSOL Multiphysics

In this study, COMSOL Multiphysics is used in the numerical analysis of a neutral gas in the divertor pumping system of the China Fusion Engineering Test Reactor (CFETR). The slip boundary condition modified Navier–Stokes equation and angular coefficient methods are used for simulation. The corresponding divertor inlet pressures are 1 Pa under plasma discharge and 1×10−5Pa at the pumping limit. Additionally, the throughput and flow conductance of the divertor pumping system are calculated. The effective pumping speed (EPS) of a single cryopump in a vacuum chamber is also computed. Results indicate that the EPS values of the single cryopump from the divertor inlet are 33.35 and 16.91 m3/s, corresponding to the divertor inlet pressures of 1 and 1×10−5Pa, respectively. By comparing the simulation results with those of the direct simulation Monte Carlo and test particle Monte Carlo methods, the feasibility of COMSOL Multiphysics was verified with a maximum error of less than 5%. This study provides technical support to the subsequent optimization of CFETR divertor pumping channels and EPS evaluation.