Molecular Dynamics Simulations of Temperature Relaxation in Non-Neutral Plasmas Relevant to Antimatter Experiments

TL;DR

This study uses molecular dynamics simulations to test a theoretical model of temperature relaxation in magnetized non-neutral plasmas, relevant to antimatter experiments, confirming the predicted multistep relaxation process.

Contribution

It extends previous models of temperature anisotropy relaxation to two-component systems in strongly magnetized plasmas relevant for antimatter trapping.

Findings

Simulation results support the theoretical multistep relaxation model.

Parallel temperature relaxes faster than perpendicular temperature.

The methods validate the use of Green-Kubo relations in this context.

Abstract

An important process for antimatter experiments is the cooling of particles in a Penning-Malmberg trap to experimentally useful temperatures. A non-neutral plasma of one species (e.g. antiprotons) can be collisionally cooled on another colder species (e.g. electrons). Modeling temperature relaxation in these devices is challenging from a plasma physics perspective because the particles are strongly magnetized (the gyrofrequency exceeds the plasma frequency). Recently, a theoretical model was proposed to describe the temperature evolution in these conditions, predicting a multistep relaxation process where temperatures parallel to the magnetic field relax much faster than perpendicular to it. Here, this model is tested using molecular dynamics simulations. Two analysis methods are applied: one based on an imposed temperature difference, and the other based on a Green-Kubo relation. The results of the simulations support the theoretical predictions. This work extends previous studies of temperature anisotropy relaxation in one-component non-neutral plasmas to the two-component systems relevant to trapped antimatter experiments.