Spectroscopic studies of x-ray line polarization in HED plasmas illustrated using z-pinches

The studies of polarization properties of mid-Z_a High Energy Density (HED) plasmas are challenging and extremely important, because of, for example, its relevance to hot electron beam studies for Inertial Confinement Fusion (ICF) research. Such plasmas can be produced by high power lasers and Z-pinch generators. Plasma Polarization Spectroscopy (PPS) is able to provide more information about HED plasmas, including existence, directionality, and energy of particle beams, compared to traditional spectroscopy. In particular, such PPS studies with X-pinches on 1 MA Zebra at UNR have provided the evidence of anisotropy in Z-pinch plasmas in the form of electron beams [1, 2]. They involved the simultaneous measurement of X-ray polarization-dependent spectra by two spectrometers with different sensitivity to polarization and their modeling. The further development of such PPS studies for HED plasmas demands the comprehensive analysis of polarization properties of X-ray lines prominent in such plasmas. The present work reviews our previous results on x-ray line polarization of X-pinch plasmas and spectroscopically evaluates our recent results on K- and L-shell radiators from Z-pinch plasmas. It focuses on new theoretical predictions of polarization properties of x-ray K- and L-shell lines prominent in Z-pinch plasmas as well as in HED plasmas in general. The calculations of atomic characteristic and polarization data are performed using the FAC [3] and MZ [4] codes as well as theoretical approach from Ref. [5]. X-ray line polarization of both resonance lines and dielectronic satellite lines are considered. These results suggest the promising candidates for PPS of mid-Z_a HED plasmas which include the lines that have maximum values of polarization, the stronger dependence on the energy of electron beam, and that are almost non-polarized. In addition, the important depolarization effects in plasmas are estimated and discussed.