Self-generated electric fields in imploding capsules due to shock-front polarization

The generation of strong, self-generated electric fields in direct-drive, inertial-confinement-fusion capsules has been reported using 15 MeV proton radiography [1]. A model incorporating charge separation at a shock front [2] is shown to provide good agreement with the measured proton deflections. A simple proton deflectometry model is developed to further assess the origin of the fields and the sensitivity to thickness of the annular field-generating region in an imploding capsule. The strength of the field in a polarized shock front is calculated to be $\approx $10$^{10}$ V/m or higher, and is competitive with the criterion for runaway electron generation. Collisional particle-in-cell simulations of a shock front are performed to gauge such kinetic effects and their potential role on shock-front broadening. \\[4pt] [1] J.R. Rygg \textit{et al}., Science \textbf{319}, 1223 (2008); C.K. Li \textit{et al}., PRL \textbf{100}, 225001 (2008). \\[0pt] [2] Ya. Zel'dovich and Yu. Raizer, \textit{Physics of Shock Waves} (Dover, Mineola NY, 2002), p. 522.