Optimization of the gas flow in the neutralization region of EAST neutral beam injector

According to the problems encountered in the experiments of the EAST neutral beam test stand, the design of neutralizer of EAST neutral beam injector is suggested to modify to optimize the gas flow in the neutralization region. The modifications contain narrowing the slits between the neutralizer and the mounting flange hole, and rotating the gas injection angle from 90° to 60° in the neutralizer. In this paper, an adjusted Direct Simulation Monte Carlo (DSMC) code was used to estimate the modification. The results show that a little change of the slits width causes a large variation of gas target thickness, and the rotation of the gas injection angle can effectively reduce the gas density near the accelerator but with a little of decrease of target thickness.