Fully Electro-magnetic Relativistic Drift-Kinetic Formulation in Particle-in-Cell Code*

The drift-kinetic treatment is a reduced-physics model for magnetized plasmas in which particles are advanced along their guiding center and cyclotron oscillations are effectively removed by time-averaging the actual particle orbit over a cyclotron period. The drift-kinetic model applied to magnetically insulated transmission lines (MITLs) was initially described in a recent paper by Evstatiev and Hess*, in which displacement current was neglected. We have implemented a fully electromagnetic version, including diamagnetic current corrections for dense plasmas, of the original model into the hybrid-PIC code Chicago. The model was originally limited to 2D rz cylindrical coordinates with the magnetic field in the azimuthal direction, but the model has been extended to 2D and 3D Cartesian coordinates. The model also allows for relativistic particles. We briefly describe the model, its implementation into Chicago, and present results from the test problems in the Evstatiev and Hess paper. We then demonstrate results for a realistic inner MITL geometry of the Sandia National Laboratories’ Z machine.  There is reasonable agreement between fully-kinetic and drift kinetic treatments. There is also significant increase in permissible timestep when using the drift-kinetic treatment as the requirement to resolve to the cyclotron period is lifted.

*E. G. Evstatiev and M. H. Hess, Efficient kinetic particle simulations of space charge limited emission in magnetically insulated transmission lines using reduced physics models, Phys. Rev. Accel. Beams 26, 090403 (2023).