Cryosorption pumps create a vacuum by adsorbing gas at low temperature through porous solid adsorbents. The transmission probability of gas molecules and heat loads of cryosorption pumps are important factors affecting its performance. Herein, Molflow software based on the Monte Carlo principle is used to analyze the effects of the structural design of cryosorption pumps on transmission probability. The influence of structural design on radiation heat transfer is analyzed by ANSYS Steady-State Thermal software. This provides a reference for the design of a cryosorption pump to validate the prototype of a neutral beam injector for the China Engineering Fusion Experimental Reactor (CFETR).

The cryopump relies on the cryocondensation mechanism to create a clean, high-vacuum environment. Studying the heat and mass transfer mechanism and enhancing the performance of the cryopump are important because its heat and mass transfer performance directly affects the quality of the vacuum environment. This study proposes a systematic method for analyzing the mechanism influencing spatial changes, particle motion characteristics, and heat and mass transfer. This study identifies the key factors affecting the heat and mass transfer and investigates the influence of various factors in the vacuum chamber, liquid-nitrogen cooling area, and liquid-helium cooling area on the mass transfer performance. Next, the main source of heat load and the influence of spatial layout on the heat load are determined and a method for reducing the heat load is introduced. A cryopump designed based on these conclusions delivered a 33% higher pumping speed, a 35% shorter cooling time, and a better vacuum performance than the traditional cryopump in a simulation analysis. This study can provide guidance for the development of advanced cryopumps and instruct the design and operation of cryovacuum systems.

The neutral beam injector (NBI) generates a high-energy ion beam and neutralizes it, and then relies on drift transmission to inject the formed neutral beam into the fusion plasma to increase the plasma temperature and drive the plasma current. In order to better cooperate with the Experimental Advanced Superconductive Tokamak (EAST), part of the Chinese major national scientific and technological infrastructure, in carrying out long-pulse high-parameter physics experiments of 400 s and above, this paper considers the optimization of the current design and operation of the NBI beam line with a pulse width of 100 s. Based on an upgraded and optimized NBI vacuum chamber and the structure of the beam-line components, the gas-source characteristics under the layout design of the NBI system are analyzed and an NBI vacuum system that meets relevant needs is designed. Using Molflow software to simulate the transport process of gas molecules in the vacuum chamber, the pressure gradient in the vacuum chamber and the heat-load distribution of the low-temperature condensation surface are obtained. The results show that when the NBI system is dynamically balanced, the pressure of each vacuum chamber section is lower than the set value, thus meeting the performance requirements for the NBI vacuum system and providing a basis for subsequent implementation of the NBI vacuum system upgrade using engineering.