Development of fast helium beam emission spectroscopy on MST

Emission from an energetic neutral helium beam has been investigated as a potential localized diagnostic for the plasma parameters. A collisional-radiative model in atomic data and analysis structure was used to estimate evolutions of the atomic level populations in the beam and the beam emission intensities. It has been found that singlet lines are insensitive to the local metastable fraction and thus have been chosen to construct line ratios. The T-e and n(e) dependences of the ratios were investigated and some have been found to be sensitive to the density, but no ratios show significant sensitivity to the temperature in the range of interest for Madison symmetric torus. The theoretically expected line ratios are compared with the experimental results. It is shown that local density measurements may be possible using the singlet line ratio technique.