Interactive optical design and realization of an optimized charge coupled device Thomson scattering system for the spherical tokamak START

A high resolution, multipoint Thomson scattering system has been successfully implemented on the START tokamak. It incorporates a low-divergence, 10–15 J Q-switched ruby laser system with a gated (GaAs) image intensifier (II) and a charge coupled device as the detection elements. It is designed to measure temperatures between 25 eV and 4 keV and densities from 3×1018 m−3 with high accuracy (∼2.5%). The spatial resolution is approximately 1.5 cm. An interactive design of the optics train has been used to ensure matching of the optics from light collection to light detection. Use of coherent fiber bundles allows a resolution down to about 2 mm.