Experimental observation of direct ion heating/acceleration during merging formation of an FRC

A novel merging formation of a field reversed configuration (FRC) has been developed in the TS-3 merging experiment, leading to a new scenario of FRC slow formation, heating and current amplification. Two force free spheromaks with opposing toroidal fields were merged in the axial direction to form a high β FRC with an ion temperature of up to 200 eV. A central OH coil was used to amplify the FRC by a factor of 2-3. This unique relaxation from the force free (β approx = 0.05-0.1) spheromaks to the high β(β approx = 0.7-1) FRC is attributed to direct conversion of toroidal magnetic energy to ion thermal energy through their counter-helicity reconnection. (author). 15 refs, 7 figs