Modeling magnetic fields for TREX drive cylinder using COMSOL

The Terrestrial Reconnection EXperiment (TREX) at Wisconsin Plasma Physics Laboratory (WiPPL) [1] aims to explore the kinetic collisionless regime of magnetic reconnection. The drive cylinder geometry induces an anisotropic electron distribution in the reconnection region. Lundquist numbers up to S = 10⁵ are accessed by reducing the overall inductance of the power supply and applying a rapidly increasing voltage to the drive coils such that the experimental runtime (<10 μs) is comparable to the collisional time of the plasma (1 μs). Compared to TREX’s previous 4-coil configuration [2], we estimate that the drive cylinder reconnection current layer will be up to a factor of 2 longer, achieving a maximum system size of L/d_i ≈ 20, and we expect to increase the reconnection electric field tenfold. Based on a multi-coil model to approximate the boundary conditions of the cylinder, we expect that the field interior to the cylinder will be straighter throughout the volume. The drive cylinder will be modeled using COMSOL to confirm the validity of this approximation. COMSOL uses a finite-element method to more realistically model the geometry and numerically solve Maxwell’s equations with the appropriate boundary conditions and time dependence of the coil current.