Plasmoid and blob structure of current sheet in TS-6 torus plasma merging experiment

We made 2D high-resolution magnetic field measurement of current sheets using the print circuit board (PCB) probe arrays in TS-6 merging tokamak experiment[1]. Each PCB coil is composed of a two-sided spiral coil circuit pattern (5mm×3mm) with a line width of 0.05 mm. The spatial resolution is as high as 5mm around X-point. We found multiple magnetic islands or blobs from one to three in the current sheet. These plasmoids tend to be formed when the guide field ratio Bt/Brec is over 4. The maximum plasmoid size increases with the guide field strength (0.1<Bt<0.2[T], Bt/Brec=3~8 ). [1] M. Akimitsu, Y. Ono, Q. Cao, H. Tanabe, “High-Resolution 2D Magnetic Field Measurement of Magnetic Reconnection Using Printed-Circuit Board Coils",Plasma and Fusion Research (2018)