Modelling of Silicon in inertial confinement fusion conditions

In ICF experiments recently undertaken at the National Ignition Facility (NIF), the high-Z dopant in the capsule ablator material has been changed from Germanium to Silicon for some experiments [1]. In this paper two issues involving the modelling of Silicon in the ablator of an ICF capsule will be addressed. Firstly, we consider the differences between LTE and non-LTE modelling of Silicon in the prediction of the opacity and of the mean charge state. Secondly, the necessary size of the photon groups (or 'bins') used in the radiation transport modelling will be discussed, and radiative transport calculations with varying bin sizes will be presented in order to support the conclusions.