Simulation of neutral beam attenuation and its influence to beam emission spectroscopy diagnostic on HL-2A tokamak

Neutral beam (NB) attenuation and beam emission are important aspects for Beam Emission Spectroscopy diagnostic on magnetic confinement devices. In this article, we present the simulation of beam attenuation and beam emission in typical HL-2A discharge scenarios, i.e. Low mode (L-mode) and High mode (H-mode) discharges. Not only the NB attenuation, but also the plasma density and electron temperature determine the beam emission intensity. The pronounced beam emission peak ranges from rho = r/a = 0.7 to 0.9 in H-mode discharge, while it has a much lower and broader peak in L-mode discharge. 16 BES channels have been developed on HL-2A tokamak and the experimentally diagnosed data fit well with the simulation, showing not only the validation of this simulation but also the high performance of developed BES channels. And it provides a reference for the upgrading of a 64-channel BES system.