The TFTR edge Thomson scattering system

The authors report on a system under construction which will provide measurements of TFTR plasma edge profiles of electron temperature and density. The edge diagnostic would make use of many of the components of the full profile systems now installed-the laser, the collection optics, the calibration and alignment hardware. It would sample signal from three adjacent fiber optic bundles of one of the two existing 76 bundle systems and send it to a spectrometer and detector which are optimized for low density, low temperature conditions. The choice of sampled positions is scannable from the inner wall to the outer wall at the horizontal midplane. Optically, the system will be able to resolve the resulting 10 cm profile into 20 spatial points and 20 spectral channels. The detector consists of a CCD intensified with an 18 mm third generation intensifier. Minimum detectable temperatures will range from 5 ev at the inner edge to 10 ev at the outer edge. With efficient background suppression the minimum density will be 5 x 1011/cm-3