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The energy leakage probability of charged particles from an ICF pellet has been estimated earlier using a small angle binary collision approximation for Coulomb scattering from electrons and ions. While this is the most predominant energy loss mechanism, elastic nuclear scattering is important for high density pellets at higher temperatures. In this paper, we generalize the calculation of energy leakage probability to include nuclear scattering, large angle Coulomb scattering and collective plasma effects. In general, these effects reduce the thermalization distance in the plasma and increase the fraction of energy deposited to ions. We also develop a simple approach for energy deposition by neutrons due to nuclear interaction with the ions. The same model is then used to re-evaluate the concept of internal tritium breeding in high density ICF pellets. It is found that tritium breeding improves significantly in comparison with earlier estimates.

a b s t r a c tNon-equilibrium radiation diffusion is an important mechanism of energy transport in inertial confinement fusion, astrophysical plasmas, furnaces and heat exchangers. In this paper, an analytical solution to the non-equilibrium Marshak diffusion problem in a planar slab and spherical shell of finite thickness is presented. Using Laplace transform method, the radiation and material energy densities are obtained as functions of space and time. The variation in integrated energy densities and leakage currents are also studied. In order to linearize the radiation transport and material energy equation, the heat capacity is assumed to be proportional to the cube of the material temperature and the opacity to be independent of temperature. The steady state energy densities show linear variation along the depth of the planar slab, whereas non-linear dependence is observed for the spherical shell. The analytical energy densities show good agreement with those obtained from finite difference method using small mesh width and time step. The benchmark results obtained in this work can be used to validate and verify non-equilibrium radiation diffusion computer codes in both planar and spherical geometry.