Energy Flow in the Super Alfvénic/Sonic Collisional Merging Process of Field-Reversed Configurations

Energy flow in the collisional merging process of a field-reversed configuration (FRC) was experimentally evaluated. Collisional merging formation of an FRC was carried out in the FAT-CM (FRC amplification via translation-collisional merging) device. In this experiment, the field-reversed theta-pinch formed FRC-like plasmoids are accelerated due to a magnetic pressure gradient. Then, two plasmoids collide at a relative speed of ∼300 km/s, which is faster than typical Alfvén and ion sound speeds (∼50 km/s) on the separatrix. The kinetic and internal energy of plasmoids before and after collision are estimated by simultaneous multi-point measurements combining magnetic probes and interferometers. The energy flow in the collisional merging process is compared to an experimental case with single plasmoid translation. This comparison indicates that the kinetic energy of two accelerated plasmoids regenerates back into the internal thermal energy of the FRC after merging. Moreover, density and neutron measurements suggest excitation of shockwaves. These results indicate that shock heating may become a channel for energy regeneration.