Code Verificaton of Magneticly Insulated Transmisson Lines (MITL) for Power Flow Applications

Time-independent solutions to electron flows in MITLs have been known for many years1. The motivation behind these calculations was to understand experiments by predicting the integrated qualities such as flow current, anode current, cathode current, and voltage. In the process of verifying Finite Element electromagnetic Particle-in-Cell codes developed at Sandia, EMPHASIS and EMPIRE, it was found that these global quantities were very close to the theoretical results for coarse meshing. This is consistent with earlier codes used for the original designs of HERMES, Saturn, and Z2. However, looking at spatial profiles (charge density, current density, velocity, electric and magnetic fields) a finer mesh was required for good comparison to theory. These details matter to the quality of the electron beam for many applications and surface plasma formation. This work focuses on showing the order of convergence for the spatial profiles for MITL flow as a function of the element count, time step, and number of macroparticles used. Most importantly, the impact of the algorithms used for the Space Charge Limited (SCL) emission boundary are examined3, The purpose of this verification is to have increased confidence in the predictive capability of these codes for improved Z power flow designs, High Power Microwave (HPM) sources, and advanced bremsstrahlung accelerators.