Investigation of ion heating/transport process during high guide field reconnection using full-2D ultra high resolution ion Doppler tomography*

We present detailed full 2D imaging measurement of ion heating during high guide field merging/reconnection experiment in TS-3U. We have found two types of fine structure both around X-point and downstream under the influence of better toroidal confinement. The high temperature region around the X-point is affected by Hall current j_Hall from the decoupling of ions and electrons, the characteristic heating profile rotates poloidally toward j_Hall×B_t direction. This characteristic is clearer in high field side (B_t depends on major radius for tokamak) and with higher mass ratio (enhancement of j_Hall due to the larger scale length than current sheet width). While at the end of merging, ion heating downstream is surrounded by closed flux surface formed by reconnected field lines and forms another fine structure. The high temperature profile downstream propagates vertically and finally forms poloidally double-ring-like structure under the influence of better toroidal confinement. Higher guide field strongly suppresses perpendicular heat transport (χ_///χ_⏊∼2(ω_ciτ_ii)²>>10) and the double-peak ion temperature profile by outflow heating was transported to field line direction, finally forms hollow profile.