Plasma Equilibrium in Diamagnetic Trap with Neutral Beam Injection

TL;DR

This paper develops a self-consistent theoretical model for plasma equilibrium in a diamagnetic trap with neutral beam injection, incorporating kinetic theory for hot ions and MHD for warm plasma, and provides numerical solutions for specific device configurations.

Contribution

It introduces a novel combined kinetic-MHD model for plasma equilibrium in diamagnetic traps with neutral beam injection, including effects of ion drag and non-adiabatic losses.

Findings

Numerical solutions for plasma equilibrium in a cylindrical diamagnetic bubble.

Equilibria examples corresponding to GDMT device configurations.

Analysis of the transition layer in diamagnetic bubbles.

Abstract

This paper presents a theoretical model of plasma equilibrium in the diamagnetic confinement mode in an axisymmetric mirror device with neutral beam injection. The hot ionic component is described within the framework of the kinetic theory, since the Larmor radius of the injected ions appears to be comparable to or even larger than the characteristic scale of the magnetic field inhomogeneity. The electron drag of the hot ions is taken into account, while the angular scattering due to ion-ion collisions is neglected. The background warm plasma, on the contrary, is considered to be in local thermal equilibrium, i.e. has a Maxwellian distribution function and is described in terms of magnetohydrodynamics. The density of the hot ions is assumed to be negligible compared to that of the warm plasma. Both the conventional gas-dynamic loss and the non-adiabatic loss specific to the diamagnetic confinement mode are taken into account. In this work, we do not consider the effects of the warm plasma rotation as well as the inhomogeneity of the electrostatic potential. A self-consistent theoretical model of the plasma equilibrium is constructed. In the case of the cylindrical bubble, this model is reduced to a simpler one. The numerical solutions in the limit of a thin transition layer of the diamagnetic bubble are found. Examples of the equilibria corresponding to the GDMT device are considered.