Fast Data Processing of a Polarimeter-Interferometer System on J-TEXT**supported by the National Magnetic Confinement Fusion Science Program of China (Nos. 2014GB106000, 2014GB106002, and 2014GB106003) and National Natural Science Foundation of China (Nos. 11275234, 11375237 and 11505238) and Scientific Research Grant of Hefei Science Center of CAS (No. 2015SRG-HSC010)

Abstract

A method of fast data processing has been developed to rapidly obtain evolution of the electron density profile for a multichannel polarimeter-interferometer system (POLARIS) on J-TEXT. Compared with the Abel inversion method, evolution of the density profile analyzed by this method can quickly offer important information. This method has the advantage of fast calculation speed with the order of ten milliseconds per normal shot and it is capable of processing up to 1 MHz sampled data, which is helpful for studying density sawtooth instability and the disruption between shots. In the duration of a flat-top plasma current of usual ohmic discharges on J-TEXT, shape factor u is ranged from 4 to 5. When the disruption of discharge happens, the density profile becomes peaked and the shape factor u typically decreases to 1.