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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. [ABSTRACT FROM AUTHOR]

Intermittent leakages of trapped ions from a Penning trap are clearly explained. Two mechanisms are revealed by considering both experimental and numerical results. The initial leakage is due to ions energized by the potential barrier that is just closing to form a positive potential well. The following leakage is induced by an axial average oscillation of the bulk of the trapped ions. Some individual bounce ions are pushed out of the potential barriers owing to the space potential of the bulk. [ABSTRACT FROM AUTHOR]