| Neutral beam injection (NBI) is one of three kinds of commonly used plasma heating methods on Tokamak. It has the advantage of simple principle and high power input, and it has become the main heating method in some large-scale nuclear fusion equipment. In order to reduce the re-ionization of neutral particle beam that come out from the neutralization chamber as far as possible, the dynamic vacuum within the drift pipe connected to Tokamak must be maintained highly. Therefore, a low temperature liquid helium vapour pump has been laid within the drift pipe of the NBI system to maintain continual vacuum by using the condensation of hydrogen and its isotope in the beam. This pump is situated within the drift pipe between the main vacuum chamber of the neutral beam injector and Tokamak.This article briefly introduces the neutral beam injection system in Institute of Plasma Physics, Chinese Academy of Sciences, and makes the analysis and computation that aimed at the heat load the cold pump endured when it worked. A numerical solution of the cold plate is also obtained. Through ANSYS simulation for the low temperature matrix of the cold pump, a reliable temperature field distribution map is also drawn. Finally, by taking the experiment as the basis, the vacuum and low temperature condition in the drift pipe is examined to determine whether it can satisfy the request of Tokamak experiment. |
