X-ray spectropolarimetry and hot electron effects on high-current X-pinch plasma spectra

Accurate K-and L-shell spectroscopic modeling of high-temperature and high-density X-pinch plasmas requires the consideration of anisotropic plasma characteristics: non-Maxwellian electron distribution functions and the polarization properties of X-ray lines. Experimental evidence for the existence of strong electron beams in X-pinch plasmas has motivated the development of a new tool, X-ray spectropolarimetry, for investigating the anisotropy of such plasmas. This diagnostic includes both space- and time-resolved X-ray spectroscopy and polarimetry and is based on theoretical modeling of X-ray line polarization-dependent spectra measured simultaneously by spectrometers with different sensitivities to polarization. Specifically, K-shell Ti and L-shell Mo X-ray spectra have been thoroughly modeled. Experimental spectra have been generated by Ti and Mo X-pinch plasmas produced at the Nevada Terawatt Facility. The detailed spectroscopic analysis of more than 20 shots with these X-pinches shows how X-ray spectropolarimetry complements the usual spectroscopic monitoring of z-pinch plasmas and demonstrates the importance of accounting for hot, non-Maxwellian electrons in plasma diagnostics.