Simultaneous Measurements of Proton Ratio and Beam Divergence of Positive-Ion-Based Neutral Beam in the Large Helical Device

Abstract

A spectroscopy system was installed on the diagnostic neutral beam injector in LHD. The H_α lines spectrum emitted by full, half and one-third energy component are clearly observed, and the proton ratio and the beam divergence were estimated by the line intensity and the line width, respectively. The proton ratio of 85∼90 % is achieved in high arc power discharge. The beam divergence of them shows their minimum with the same perveance. It was experimentally confirmed that the spectroscopy system is useful for the monitor of the proton ratio and the divergence of the beam.