Reconstruction of plasma shape and eddy current profile based on modified cauchy condition surface method in merging spherical tokamak

The spherical tokamak merging start-up is one of the central solenoid-free start-up method. For controlling the merging actively, it is essential to identify the plasma shapes during the merging process. In the present work, the modified Cauchy condition surface method is applied to demonstrate the reconstruction of the plasma boundary shapes as well as the eddy current profiles at three different representative phases in the merging start-up process (a. initial phase, b. merging phase, c. after merging). Profiles of magnetic flux and plasma boundary have been reconstructed accurately using noiseless magnetic sensor signals and reconstructed with a fairly good accuracy using sensor signals with 3% noise. The eddy current profile have been also reconstructed with a fairly accuracy.