Magnetic Island detection using dual tangential soft X-ray imaging system on magnetically confined devices*

Dual tangential soft X-ray imaging system was developed for the detection of the asymmetric deformation of the plasma, caused by the RMP application or the MHD instabilities. From the difference of the two images measured at different toroidal locations, deformation of the plasma can be visualized. This system successfully detected the islands-chain of the born-locked modes observed in DIII-D Tokamak [1] using the forward modelling. If the local deformation is determined only by the experimental data, this system is applicable to wider range of issues. Though this kind inverse problem can be not solved in general, it becomes possible if we assume that the perturbation is localized on the rational surfaces and aligned to the magnetic field line. The inverse problem of dual tangential SX system with appropriate regularization will be discussed.

[1] Xiaodi Du, et. al., “Direct Measurements of Internal Structures of Born-locked Modes and the Key Role in Triggering Tokamak Disruption”, this conference