Ion beam optics analysis and beam transmission simulation in the reflection magnet of the EAST NBI system

Abstract

Detailed trajectories of the residual ion passing through a reflection magnet, which is installed in the Experimental Advanced Superconducting Tokamak (EAST) neutral beam injector (NBI) system to remove the residual ion from the beam path, are reported. Monte Carlo simulation has been performed to obtain estimations of the beam density on the high heat flux elements of reflection magnet. On magnet pole shielding, there are three high beam power density regions, resulting from beam line focus and corresponding to the full energy, half energy and third energy. These high heat flux regions will bring a serious challenge for steady-state operation. The simulation result indicates that the re-ionization loss is about 2.43% and the magnet pole shielding encounters a problem of beam line focus, which should be taken seriously during the steady-state operation.

Conceptual Design of Neutral Beam Injection System for EAST

“…The non-neutralized ions in the beam are reflected into an ion dump by a 180 degree reflecting magnet [18] . The reflecting magnet made by hollow water-cooled electrical coils is installed in the second part of the vacuum vessel.…”