Numerical modeling of an ITER type Cryopump

The present article is focused on the computational investigation of a 2D axisymmetric complex geometry of a model cryopump by the Direct Simulation Monte Carlo (DSMC) method. Since the flow close to the cryopanels can be assumed free molecular due to low pressures, the capture coefficient of the cryopanels can be estimated by applying the Test Particle Monte Carlo method. Then, this information can be used as input data to the corresponding DSMC simulations. The macroscopic parameters of practical interest as the bulk velocity, the pressure and the temperature in the whole flow field have been calculated as functions of the incoming gas throughput and of the pump inlet valve position. The importance of these calculations is based on the fact that it can provide information for quantities which are not accessible for measurement during pump operation and that it can be used for prediction of the pump behavior. This paper describes a post-operational investigation of a built pump and is thought as a proof-of-principle test to include this approach in the design process of a future pump development. Finally, the presented code could be further developed and benchmarked towards the control of the final pump as installed in ITER.