Analysis of radiation energy transport in high-temperature media: Application to ICF targets simulation and diagnosis

Previous calculations on the dynamics of inertial confinement fusion (ICF) targets subject to irradiation show that radiation plays a major role in the ignition phase of these targets, because at some hundred electron volts it becomes the dominant energy transport mechanism over electron + supra-thermal particle conduction. Correspondingly, the several kilo-electron-volts of thermal radiation originating from the hot zones of the reacting fusion fuel plays a role no less important in the process of burn propagation. A major problem in the analysis of radiation energy transport in dense, high-temperature media (typical of ICF systems) is the strong nonlinear character of the temperature-dependent radiation source term, even under the assumption of local thermodynamic equilibrium. In the cases in which local thermodynamic equilibrium (LTE) cannot be assumed, the radiation field itself, including its detailed frequency dependence, influences to a critical extent the transport medium optical properties and emission dynamics. Consequently, the nonlinear character of the problem is significantly strengthened, thus needing a detailed rather that average-based treatment. The PLANCKY code solves the radiation transport equation in a multigroup framework for the energy (frequency) variable of the radiation-specific intensity with angular dependence taken into account through a discrete ordinates treatment. 7 refs., 1 fig