Hybrid simulations of FRC merging and compression

An improved understanding of FRC merging and stability in high acceleration and compression magnetic fields is needed to speed up the development of the pulsed fusion concept developed at Helion Energy. All previous theoretical and simulation work on FRC merging and compression was performed using 2D MHD models. Here the results of first 2D and 3D hybrid simulations (fluid electrons and full-orbit kinetic ions) of FRC translation, merging and compression are presented. Results of kinetic simulations, performed using the HYM code, are compared with MHD results. The comparison is then used to evaluate the importance of the ion kinetic effects. In cases without magnetic compression, both the MHD and hybrid simulations show a high sensitivity of the results to the initial parameters: FRC separation, velocity, the normalized separatrix radius and plasma viscosity, showing that FRCs with large elongation and separatrix radius either do not merge or merge partially, forming a doublet FRC. Application of mirror coil field at the FRC ends with increasing strength is shown to lead to fast and complete merging of the FRC in MHD and kinetic simulations.