Predicting the energetic and spectral characteristics of Z-pinch sources is a very
delicate task. Z-pinch plasmas conditions are spread across a wide range of parameter
space and often far from Local Thermodynamic Equilibrium (LTE). In
addition, the increasing optical depth of the plasma at stagnation can have a strong
influence on its own dynamics, suggesting that simultaneous solution of both the
magnetohydrodynamic (MHD) and radiative response is required. Unfortunately,
the estimation of the frequency and time dependent radiative properties of
Z-pinches
is computationally challenging and the recent improvements made to the
parallel architecture of the 3D resistive Eulerian MHD code GORGON have only
reinforced the strong emphasis already placed on optimizing the physics solvers
used in Z-pinch simulations.
To address these issues, we have developed a simple and fast pseudo NLTE
code based on a Screened Hydrogenic Model (SHM) that can be run in-line with
GORGON or as a post processing tool with synthetic spectra capabilities. Making
use of a computationally inexpensive modification of the Saha equation, this highly
optimized code has demonstrated a good ability to represent Non-LTE plasma
conditions. In order to handle the amount of data generated by the spectral
treatment of the billions of numerical cells constituting the simulation grids, an
original data structure derived from a self-balancing binary search tree has been
developed, enabling the use of Non-LTE DCA calculations in a large scale three
dimensional environment for the first time.
The implementation of this model is described in detail and comparisons with
a commercial package are offered. Results from Z-pinch simulations performed
with the new code are discussed and possible future improvements are presented
