13-point Thomson scattering system for JFT-2M plasma

A 13-point Thomson scattering system mounted on the JFT-2M tokamak routinely provides reproducible electron temperature and density data. Good performance has been achieved with the help of a large collecting lens (capable of gathering data over a vertical 60-cm long plasma volume), the automatic transfer of data from a 180-channel attenuator into the CPU, the use of high-pass optical filters and a large polarizer plate to reduce stray light, and a better matching of LED calibration signal intensities to those of the scattered signals. Peaked density profiles are measured in improved L-mode (IL) plasmas, in contrast to those observed during the H-mode phase. IL-mode is caused by the broad and high electron temperature. With pellet injection, peaked density profiles are again observed. (author)