As an important component of Negative ion based Neutral Beam Injector (NNBI). the cryopump mainly provides a suitable vacuum environment for beam generation and transmission. In the paper. Liquid nitrogen (LN2) pipe structure models of two cryopumps were established for simulation and experimental studies. https://www.roneverhart.com/Christmas-Ornament-Ice-Ball-Molds-Design-Set-Options/