Plasma and Fusion Research

Volume 17, 2401026 (2022)

Regular Articles

Chaotic Orbit of Low Energy Charged Particles in a Compact Dipole Magnetic Field Configuration
Haruhiko SAITOH and Itsuki TANIOKA
Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa, Chiba 277-8561, Japan
(Received 20 December 2021 / Accepted 21 January 2022 / Published 8 April 2022)

Abstract

Conditions for the emergence of chaotic orbit of low energy positrons are numerically calculated in a compact dipole trap for use in positron and electron-positron plasma experiments. Due to its relatively weak field strength and existence of magnetic null line near the confinement region, coupling between gyro and bounce motions is pronounced even for low energy particles in this trapping geometry. Breakdown of first and second adiabatic invariants and the resultant non-integrable chaotic motion are realized for positrons with kinetic energy below the order of 10 eV. This kinetic energy value is two orders of magnitude smaller than the threshold value for a chaotic orbit in the Ring Trap-1 (RT-1) experiment. The stochastic long orbit is potentially applicable for efficient injection and compression schemes of positrons in a compact levitated dipole experiment.

Keywords

orbit chaos, positron plasma, electron plasma, non-neutral plasma, levitated dipole experiment

DOI: 10.1585/pfr.17.2401026

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