The effect of phase front deformation on the growth of the filamentation instability in laser–plasma interactions

Abstract

Laser pulses of 0.9 kJ/1 ns/1053 nm were focused onto low- Z plastic targets in both spherical and planar geometry. The uniformity of the resulting plasma production was studied using x-ray pinhole imaging. Evidence is provided suggesting that thermal filamentation starts to occur for irradiances on the target of Iλ ^2 ⩾ 10 ^14 W cm ^−2 μ m ^2 , even on deployment of phase plates to improve the focal spot spatial uniformity. The experiments are supported by both analytical modelling and two-dimensional particle-in-cell simulations. The implications for the applications of laser–plasma interactions that require high degrees of uniform irradiation are discussed.