Plasma spectroscopy of pulsed power driven Z-pinch plasmas

Over the years there has been a sustained interest in and fascination with Z-pinch plasmas. Whether the interest is in radiation source development, fusion plasmas, and hohlraum physics or basic research there exits an extensive bibliography of literature presenting a variety of claims regarding the performance of Z-pinch plasmas. In this paper we will study the dynamics of Z-pinch plasma loads and focus primarily on the production of soft x-ray radiation. Many of the issues and revelations are common to Z-pinch plasmas in general but the attention here will be focused on the loads radiative performance. For the cases investigated here the load is heated by a multi-terawatt pulsed power accelerator. A radiation hydrodynamic model self-consistently driven by a circuit describes the dynamic evolution of the massive Al multiwire load. Predictions are made for the K- and L-shell soft x-ray emission as a function of the ionization dynamic model. The ionization dynamic models are represented by 1) a time-dependent NonEquilibrium (NEQ) model, 2) a Collisional Radiative Equilibrium (CRE) model and 3) a Local Thermodynamic Equilibrium (LTE) model. For all three scenarios the radiation is treated I) in the free streaming optically thin approximation where the plasma is treated as a volume emitter and 2) in the optically thick regime where the opacity for the lines and continuum is calculated online and transported through the plasma. Each simulation is carried out independently to determine the sensitivity of the implosion dynamics to the ionization and radiation model, i.e., how it affects the radiative yield and emission spectra. Results will be presented for the L- and K-shell radiation yields and emission spectra representing the radiation intensity as a function of photon energy from 10 eV to 10 keV. The predictions from the Various ionization models will be compared and contrasted with experimental results wherever possible.