Hybrid simulations of FRC merging and compression

TL;DR

This paper presents novel 2D hybrid simulations combining fluid electrons and kinetic ions to study FRC merging and compression, revealing the effects of initial parameters and magnetic fields on the merging process.

Contribution

It introduces the first hybrid simulation results for FRC merging, comparing them with MHD models, and explores the impact of axial magnetic compression on merging behavior.

Findings

High sensitivity of merging outcomes to initial parameters.

Magnetic compression enhances merging speed and completeness.

Hybrid simulations align with MHD results under certain conditions.

Abstract

An improved understanding of Field Reversed Configuration (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. The results of novel 2D hybrid simulations (fluid electrons and full-orbit kinetic ions) of FRC merging and compression are presented. Results of kinetic and MHD simulations, computed using the HYM code, are compared and analyzed. In cases without axial magnetic compression, both the MHD and hybrid simulations show a high sensitivity to the initial parameters (i.e. FRC separation, velocity, 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 a mirror coil field at the FRC ends with increasing strength is shown to lead to fast and complete merging of the FRCs in MHD and kinetic simulations.