The Monte Carlo simulation of a 1MW neutral beam injector on RFX-mod

Summary form only given. The MW level TPE-RX Neutral Beam Injector is planned to be installed on the RFX-mod Reverse Field Pinch (RFP) experiment. The main purpose is to study the behavior of the fast ions, which in the helical equilibrium of the RFP have been seen to feature very long confinement times. Despite the many differences in several aspects, the use of a NBI on RFX has to face similar problems as the ITER NBI on ITER in both cases for instance, the stray poloidal magnetic field generated by the machine, has an impact on the transmission of the neutral beam heating power. To properly integrate the TPE-RX injector on RFX-mod, a 3D Monte Carlo simulation of the injector has been carried out. The code simulates the charged and neutral particle trajectories from the acceleration grids of the beam source up to the RFP plasma. The simulation includes the interactions between the accelerated beam and the background gas, particularly in the neutralization stage, and the effect of the magnetic field produced by RFX and by the Residual Ion Dump. The simulation has allowed to estimate the neutralizer and Residual Ion Dump (RID) efficiency and specifications, the geometry of the beam duct between the injector and RFX-mod and the necessary degree of magnetic screening.