A novel, cost-effective, multi-point Thomson scattering system on the Pegasus Toroidal Experiment (invited)

A novel, cost-effective, multi-point Thomson scattering system has been designed, implemented, and operated on the Pegasus Toroidal Experiment. Leveraging advances in Nd:YAG lasers, high-efficiency volume phase holographic transmission gratings, and increased quantum-efficiency Generation 3 image-intensified charge coupled device (ICCD) cameras, the system provides Thomson spectra at eight spatial locations for a single grating/camera pair. The on-board digitization of the ICCD camera enables easy modular expansion, evidenced by recent extension from 4 to 12 plasma/background spatial location pairs. Stray light is rejected using time-of-flight methods suited to gated ICCDs, and background light is blocked during detector readout by a fast shutter. This ∼10³ reduction in background light enables further expansion to up to 24 spatial locations. The implementation now provides single-shot T_e(R) for n_e > 5 × 10¹⁸ m^-3.