Stability analysis of a proton-beam driven fast ignition by using Nyquist criteria A. Ghasemizad, S. Yaghoubi and S. Khoshbinfar Eur. Phys. J. Plus, 129 7 (2014) 145 Published online: 08 July 2014 DOI: 10.1140/epjp/i2014-14145-8