PROMT: A multiposition Thomson‐scattering system for RTP

PROMT is a system for multiposition Thomson scattering in use at the Rijnhuizen Tokamak Project tokamak. Light from a ruby laser is scattered by the free electrons in the plasma and is collected along a vertical chord of 180 mm. Electron temperature and density profiles can be measured resolving up to 36 spatial elements. Scattered light is spectrally analyzed by a Littrow polychromator and subsequently detected with an intensified charge coupled device camera. At densities of 2×1019 m−3 electron temperatures in the range of 50 eV–3 keV can be measured with an accuracy of ∼5%.