Monte Carlo Simulation for the Beam Deflection in the EAST Neutralizer Due to Stray Magnetic Field

Efficient operation of the gas neutralizer is important to the neutral beam injection (NBI) system, which forms part of the auxiliary heating systems for Experimental Advanced Superconducting Tokamak (EAST). The particle transport through the beamline of the EAST NBI system was investigated by the recently developed numerical simulation code based on the Monte Carlo treatment of collisions. This paper reports the simulation results on the ion beam transport through the EAST neutralizer and the beam deflections in the neutralizer due to the EAST stray magnetic field. The results show that the current design of the magnetic shield for the EAST neutralizer is able to meet the requirement. The relations of the optimal neutralizer thickness to the beam energy and the corresponding fractional power carried by each particle species are also given.