Pre-breakdown phase of coplanar dielectric barrier discharge in heliumTomáš Morávek, Jan Čech, Zdeněk Navrátil and Jozef Ráhel'Eur. Phys. J. Appl. Phys., 75 2 (2016) 24706DOI: https://doi.org/10.1051/epjap/2016150538