Studies of ion leakage from a Penning trap induced by potential barrier closure

Abstract

This paper presents the details of intermittent ion leakage from a Penning trap during potential barrier closure [H. Himura et al., Phys. Plasmas 24, 102129 (2017)]. A high-energy tail arises in the distribution functions of parallel kinetic energies of the ions after they pass through the upstream potential barrier ϕiu. Correlation between ion leakage and the slew rate of ϕiu is clearly verified. The total number of ions leaking out during the initial leakage is approximately predictable by considering the axial profile of the potential well of the Penning trap. The axial oscillation of leftover ions in the potential well agrees with the (1,0) mode of spheroidal plasmas in Dubin's notation, herein referred to as “Dubin's (1,0) mode,” which strongly correlates with the intermittent ion leakage following the initial leakage.