Generation of electron high energy beams with a ring-like structure by a dual stage laser wakefield accelerator - Spesyvtsev,R; Brunetti,E; Vieux,G; Shahzad,M; Maitrallain,A; Yoffe,S; Ersfeld,B; Kornaszewski,A; Streeter,MJ; Finlay,O; Ma,Y; Kettle,B; et al. (SPIE-INT SOC OPTICAL ENGINEERING, 2019)