Assessment of Gradient Effects on Soft X-ray Spectral Measurements on the Z Machine

Accurate assessment of temperature, density, magnetic field, opacity, etc. can be complicated by a spatial gradient or rapid temporal variation, among other factors. The Z Pinch Dynamic Hohlraum (ZPDH) radially emits X-rays that are used for backlighting and for heating a plastic (CH)-tamped sub-micron-radially-thick magnesium sodium-flouride (MgNaF) foil. Simulations were performed over a range of temperature and density values to match observed absorption spectra and thereby determine experimental plasma parameters. Impurity-oxygen lines were included, using our recently developed isoelectronic line-ratio technique for soft x-ray absorption spectra as a temperature diagnostic on Z [Lane, et al., ICHEDS 2017] to overcome previous discrepancies between theoretical and experimental results.