Fast electron penetration in laser-irradiated solids F.Y. Khattak, E. Garcia Saiz, P. Gibbon, A. Karmakar, T.W.J. Dzelzainis, C.L.S. Lewis, A.P.L. Robinson, M. Zepf and D. Riley Eur. Phys. J. D, 66 11 (2012) 298 Published online: 04 December 2012 DOI: 10.1140/epjd/e2012-30253-7