Identification of m=2 competent mode of complex magneto-hydro-dynamics activities during internal soft disruption based on singular value decomposition and tomography of soft-X-ray emission on the HT-7 tokamak

In this paper,the singular value decomposition(SVD) method as a filter is applied before the tomographic inversion of soft-X-ray emission.Series of ’filtered’ signals including specific chronos and topos are obtained.(Here,chronos and topos are the decomposed spatial vectors and the decomposed temporal vectors,respectively).Given specific magnetic flux function with coupling m = 1 and m = 2 modes,the line-integrated soft-X-ray signals at all chords have been obtained.Then m = 1 and m = 2 modes have been identified by tomography of simulated ’filtered’ signals extracted by the SVD method.Finaly,using the experimental line-integrated soft-X-ray signals,m = 2 competent mode of complex magnetohydrodynamics(MHD) activities during internal soft disruption is observed.This result demonstrates that m = 2 mode plays an important role in internal disruption(Here,m is the poloidal mode number).     

Observation of Runaway Electrons with Soft X-Ray Camera on HT-7 Tokamak

The runaway electron phenomenon caused by dis- ruptions is one of the challenging conditions on the ITER Tokamak, which may destroy the vacuum ves- sel. To avoid runaway electrons hitting the fist wall, there must be some monitor systems which can pro- vide position information of the runaway electron beam. Hard x-ray camera is the most conventional di- agnostic system to monitor the runaway electrons. While there is no hard x-ray camera working for the entire ITER operation phase even for D-D phase of ITER, there must be some systems playing the role of observation of the runaway electrons. In this case, with some international experiences from other Toka- mak devices, the soft x-ray camera can share the role of runaway electron observation. On JET and some other Tokamak devices, the runaway electron current generated by disruption has been observed by the soft x-ray camera system.