Accurate modeling of thermal radiative transfer problems in the X-ray regime is an important and difficult task. One of the main challenges is the presence of absorption and re-emission, which causes a strong nonlinear interaction between radiation and host media. Recently, we have developed moment-based acceleration (or high-order/low-order, HOLO) algorithm [1] that enables implicit treatment of the absorption-emission physics via a discretely consistent low-order (LO) system. Thus far, we have only considered ``two-temperature'' (radiation/electron) equations.
In many radiative transfer (high-energy density physics) problems, however, it is necessary to model a ``three-temperature'' system, where the radiation, ion, and electron energies are separately treated. There are several recent studies that extend linearized two-temperature algorithms to include three-temperature effects [2,3]. However, these linearized algorithms must explicitly treat a portion of the ion-electron energy coupling, adversely affecting their stability [3]. Because of the availability of the implicit LO system, a HOLO algorithm can incorporate three-temperature effects seamlessly, without modifying the original HO transport solver. In this work, we present an extension of the HOLO algorithm to three-temperature thermal radiative transfer and demonstrate the advantages and applicability of the method.