Preliminary results of beam component measurement on EAST NBI testbed using Doppler shift spectroscopy

Doppler shift spectroscopy was established to support the development of the first neutral beam injection system (NBI) on the Experimental Advanced Superconducting Tokamak (EAST). The individual fraction of different beam energy components was determined via measuring the intensity of Doppler-shifted Hα lines emitted by different ions. The ion source was a filament-driven bucket type with four multi-slit rectangular accelerating grids. The ratios of different ions were monitored both in the vertical and horizontal directions to provide detailed information over the beam cross-section. Distorted Gaussian line shape resulting from partially accelerated ions was carefully treated by applying the modified Uhlemann et al. model. Typical spectroscopic experimental results were presented to illustrate the performance of the ion source for optimizing the operation regime of the ion sources.