Development of a Super-sonic Spheromak Merging Device for Magnetic Reconnection Experiments*

Super-sonic spheromak (Spk) merging experiments have been proposed to observe the magnetic reconnection process under super-sonic inflow conditions. Magnetic reconnection experiments have been mainly conducted by the Spk merging method. Despite simulation results indicating that the presence of a shockwave can accelerate the reconnection process [S. Zenitani et al., ApJL 894, L7 (2020)], its impact has not been satisfactorily assessed in previous experiments due to the relatively low merging speed of Spks, which is approximately 10 km/s. The newly-developed experimental apparatus consists of two magnetized coaxial plasma guns (MCPG) and a substantial transparent quartz chamber (~0.8 m in ID), equipped with coaxially arranged external magnetic field coils. Within the quartz chamber, two Spk-like plasmoids are formed and accelerated towards each other via the MCPGs, resulting in a collision and subsequent merge. This process is expected to achieve relative speeds ranging between 100 and 200 km/s. The merging process will be observed using an internal magnetic probe, fast-framing camera, and so on. The overview of the device and the initial results will be reported.