Multipulse Thomson scattering system for the National Spherical Torus

The back scattering geometry chosen for the multipulse Thomson scattering system (MPTS) on the National Spherical Torus provides the sensitivity, the outer edge spatial resolution, and the profile capability to satisfy project requirements. The system is based on Nd:YAG lasers and avalanche photodiode detectors chosen to allow high repetition rate measurements. The viewing window and the collection optics provide formidable engineering challenges environmentally, in the radiation links to the center stack, and geometrically, in the complex configuration of the fiber optics at the imaging plane. The optical engineering utilized the full range of capabilities of the OSLO program used in this design. The design features presented address the responses to the system requirements necessary to achieve successful implementation.