Radiation transport for R-Z modeling of Z-pinches: Validating and optimizing ray tracing methods with Monte Carlo solutions

Summary form only given. Radiation, mostly soft X-rays, plays a critical role in the dynamical evolution as well as in the diagnosis of Z-pinches. Detailed MHD modeling is an important tool in gaining basic physical insight into their behavior and in guiding experiments and load design. With radiation dominating the energy budget, it is therefore important to employ the most realistic treatment of radiation generation and transport as is feasible when weighing overall computational demands of the model against available resources. The present work is focused on extending practical yet accurate numerical methods for radiation transport from the one-dimensional to the two-dimensional regime, subject to a self-consistent coupling with detailed configuration atomic models. Our approach is based on equal weight quadratures , and can describe transport in spectral lines by using either a frequency grid or a line-profile-averaged attenuation function . The criterion for validation of our calculations is agreement with the results of Ref. 3 for test cases that best reflect the optical depths and ratios of collisional to radiative rates (the "quenching ratio") that are encountered in Z-pinches. We present comparisons for optical depths that vary from less than unity to 100, and for quenching ratios of 0.01 and 0.1. th Excellent agreement is obtained for 8 order quadrature, and th acceptable agreement for 4 order. Use of the attenuation function rather than the frequency grid is far more efficient and will sacrifice little or nothing in accurate energy transport when line overlap and/or line-continuum interaction can be neglected.