Study on ion energy distribution in low-frequency oscillation time scale of Hall thrusters Liqiu Wei, Wenbo Li, Yongjie Ding, Liang Han, Daren Yu and Yong Cao Eur. Phys. J. Plus, 132 11 (2017) 452 Published online: 03 November 2017 DOI: 10.1140/epjp/i2017-11714-3