Recent Progress in High Resolution 2D Imaging Measurements of Reconnection Heating during Merging Plasma Startup in TS-3*)

Abstract

We present recent results from high resolution 2D imaging measurement of reconnection heating during central solenoid (CS)-free merging startup of spherical tokamak plasmas in TS-3 using an ultra-high resolution 2D ion Doppler tomography and in-situ 2D magnetic probe arrays. The new high-resolution 2D ion Doppler tomography diagnostic has successfully resolved the formation of fine structure during magnetic reconnection and it has been found that magnetic reconnection increases the ion temperature inside a current sheet as well as in the downstream region of an outflow jet. The maximum ion temperature is obtained during a current sheet ejection event and the double peak structure of ion heating becomes clearer after the end of reconnection. The maximum ion heating increases with the reconnecting magnetic field. The high temperature region in the downstream typically propagates vertically along a closed flux surface and MAST-like fine structure formation has successfully been reproduced in this laboratory experiment for the first time.