Real-time Thomson scattering diagnostics and data processing for plasma control on LHD

Abstract Real-time measurement of the electron temperature and density is conducted in the Thomson scattering diagnostics on the Large Helical Device. The real-time data streaming is realized by the “RTRetrieve” system. It is operated with the repetition rate of 10 Hz and the delay time in the real-time Thomson scattering system is almost 50 ∼ 75 ms. The results of electron temperature and density by this real-time diagnostics are compared with the results by the usual processes which are made after the plasma discharge. The data are used as input for the plasma control system based on the data assimilation called ASTI (Assimilation System for Toroidal plasma Integrated simulation) in every 300 ms. The relation of the real-time Thomson scattering and the plasma control by ASTI is presented. Impact of the delay time on the ASTI based plasma control is analyzed in detail. This delay time is considered within the acceptable range.