Maximum entropy states of collisionless positron-electron plasma in a dipole magnetic field

Abstract

We are developing a positron-electron plasma trap based on a dipole magnetic field generated by a levitated superconducting magnet to investigate the physics of magnetized plasmas with mass symmetry as well as antimatter components. Such laboratory magnetosphere is deemed essential for the understanding of pair plasmas in astrophysical environments, such as magnetars and blackholes, and represents a novel technology with potential applications in antimatter confinement and development of coherent gamma-ray lasers. The design of the device requires a preemptive analysis of the achievable self-organized steady states. In this study, we construct a theoretical model describing maximum entropy states of a collisionless positron-electron plasma confined by a dipole magnetic field, and demonstrate efficient confinement of both species under a wide range of physical parameters by analysing the effect of the three adiabatic invariants on the phase space distribution function. The theory is verified by numerical evaluation of spatial density, electrostatic potential, and toroidal rotation velocity for each species in correspondence of the maximum entropy state.