Self-Consistent Non-LTE Radiation Transport in High Energy Density Plasmas*

Radiation transport in the high energy density regime produces changes in material conditions through the transport of significant energy in the form of radiation.  Strong coupling between radiation and matter requires a self-consistent computational approach, usually obtained with an implicit treatment.  Effective and efficient methods for providing an solution implicit in temperature and radiation field are available for physical systems under the assumption of local thermodynamic equilibrium (LTE), where the material response (at fixed density) can be fully characterized by an evolving temperature.  Many high energy density applications, particularly those with with high-Z materials, require a non-LTE treatment in which the material properties also depend on the radiation field.  Obtaining implicit solutions for these systems remains problematic.

 

We discuss methods for achieving full self-consistency for these non-LTE systems and present a radiation transport treatment which provides an implicit solution for material properties, temperature and radiation field.  The information needed to achieve consistency comes from the Linear Response Method¹, which uses coefficients describing the material response to radiation to provide a tabular approach to non-LTE atomic kinetics in the presence of a radiation field.  Using this information for radiation transport requires incorporating response coefficients over the full spectral regime into all aspects of the solution algorithm.  We discuss the resulting formulation and present progress towards an efficient implementation of this approach to non-LTE radiation transport.

 

[1] H.A. Scott, J.A. Harte, M.E. Foord, and D.T. Woods, Phys. Plasmas 29, 082703 (2022)