Increased Relative Velocity due to Enhanced Magnetic Pressure Gradient for the Collision Experiment of High-Beta Plasmoids

The FAT-CM device at Nihon University has been modified to expand the experimental relative velocity range of the collisional merging of high-beta plasmoids. This experiment focuses on the ensuing collisionless shockwave that is generated. The relative velocity was increased by making modifications to enhance the magnetic pressure gradient at the exit from the formation regions of the device. The purpose of this modification is to increase the relative velocity up to similar to 1000 km/s at the collision of the plasmoids. This is selected to be comparable to the expansion speed of a supernova remnant that generates collisionless shocks. To generate collisionless shocks, the high-temperature and low density plasmoid generation technique is also required. After the modification, the relative velocity is nearly doubled, reaching up to 600 km/s by increasing the magnetic pressure gradient and reducing the mass of the plasmoid. The mean free path became longer than the length of a plasmoid due to increased ion temperature. The experimental range of the FAT-CM device has been expanded to the collisionless region successfully. (c) 2023 The Japan Society of Plasma Science and Nuclear Fusion Research