Radiative properties of puffed-gas mixtures: The case of optically thick plasmas composed of two elements with similar atomic numbers

Abstract

Using detailed atomic and radiative transfer calculations, we consider the K-shell radiative properties of optically thick plasmas composed of two different elements with nearly the same atomic number. A sodium-neon mixture is chosen for specificity, and the plasma conditions considered are similar to those achieved in puffed-gas or exploding-wire Z pinches. The emissivity of an individual K-shell line is parameterized in terms of an ‘‘ultimate’’ photon escape probability which is a function of both the single-flight photon escape probability and the collisional quenching probability. Holding the total ion density (sodium plus neon) constant, we have evaluated the total K-shell emissivity as a function of sodium-to-neon ratio. In contrast to the optically thin case the emitted K-shell power peaks at values of this ratio intermediate between pure neon and pure sodium. The opacity effects responsible for this phenomenon are analyzed using the escape parameterization.