Effects of Vacuum Impedance Changes on Mitl Flow Using 3D Electromagnetic Pic Simulations

Vacuum impedance changes in Magnetically Insulated Transmission Line (MITL) flow has been shown via simulation to have profound impact on MITL flow patterns. Using 3D Unstructured Time Domain Electromagnetics (UTDEM) Particle-In-Cell (PIC) simulation software (part of the EMPHASIS code suite), the addition of an expansion chamber, an increase and successive decrease of outer anode radius, into an extreme aspect (1) >r) cylindrical MITL geometry causes radially symmetric current vortex formation in the expansion chamber. Characteristics of these vortices have been studied as the transmission line impedance profile changes; specifically, the threshold impedance for vortex formation and vortex dynamics. The impedance change is caused by a radius change, either by step change or a linear transition. The effects of adding only a simple diffuser section (radial A-K gap increases in the direction of flow) and only a simple baffle section (radial A-K gap decreases in the direction of flow) are reported. Once vortex formation is achieved, the threshold radius step and gradient at which steady state flow is eventually attainable is reported. Additionally, the time under constant potential needed to reach steady state flow is reported.