Benchmarking 2D T_e and n_e Measurements from Multi-Spectral Imaging of Helium in TCV's Divertor with 2D Thomson Scattering and Reciprocating Probe Measurements.

This talk presents results of experiments that benchmark 2D poloidal measurements of T_e and n_e  over the SOL using line ratios obtained from multi-spectral imaging of intrinsic He-I emission in TCV's divertor.  T_e and n_e are obtained by matching multiple emissivity line ratios to a collisional radiative model. For non-recombining plasmas, the T_e measurements showed very good agreement with those from Thomson scattering and reciprocating probes, while the agreement for the n_e measurements was fair.  Two multi-spectral cameras with fields of view tangent to the torus were used simultaneously. A camera in the lower divertor imaged He-I emission from 2 singlet transitions, 2 triplet transitions, and a He-II line. A second system imaged 2 singlet transitions, and a 3 transitions from a pupil 30 cm higher.  Single-null L-mode plasmas were observed for both He and D majority plasmas, for both B_T directions, and a range of core densities. The outer legs of the plasmas were nearly vertical allowing comparisons with 2D measurements from a vertical reciprocating probe and three Thomson scattering lasers.   Following this benchmarking, the multi-spectral measurements were compared against SOLPS-ITER, and acquired for several TCV discharges with different divertor configurations.