Non-LTE modeling of radiatively driven dense plasmas

Abstract

There are now several experimental facilities that use strong X-ray fields to produce plasmas with densities ranging from ∼1 to ∼103 g/cm3. Large laser facilities, such as the National Ignition Facility (NIF) and the Omega laser reach high densities with radiatively driven compression, short-pulse lasers such as XFELs produce solid density plasmas on very short timescales, and the Orion laser facility combines these methods. Despite the high densities, these plasmas can be very far from LTE, due to large radiation fields and/or short timescales, and simulations mostly use collisional-radiative (CR) modeling which has been adapted to handle these conditions. These dense plasmas present challenges to CR modeling. Ionization potential depression (IPD) has received much attention recently as researchers work to understand experimental results from LCLS and Orion [1,2]. However, incorporating IPD into a CR model is only one challenge presented by these conditions. Electron degeneracy and the extent of the state space can also play important roles in the plasma energetics and radiative properties, with effects evident in recent observations [3,4]. We discuss the computational issues associated with these phenomena and methods for handling them.