Parallax diagnostics of radiation source geometric dilution for iron opacity experiments

TL;DR

This study uses parallax measurements from spectrometers to analyze how the geometric dilution of radiation affects the heating and opacity of iron samples in high-energy density experiments, improving understanding of plasma conditions.

Contribution

It introduces a parallax-based diagnostic method to accurately determine source-to-sample distance effects in iron opacity experiments.

Findings

Sample temperature decreases with increased source-to-sample distance.

Parallax measurements reveal the importance of geometric effects on sample heating.

The method improves accuracy in interpreting opacity measurements.

Abstract

Experimental tests are in progress to evaluate the accuracy of the modeled iron opacity at solar interior conditions [J.E. Bailey et al., Phys. Plasmas 16, 058101 (2009)]. The iron sample is placed on top of the Sandia National Laboratories z-pinch dynamic hohlraum (ZPDH) radiation source. The samples are heated to 150 - 200 eV electron temperatures and 7e21 - 4e22 e/cc electron densities by the ZPDH radiation and backlit at its stagnation [T. Nagayama et al., Phys. Plasmas 21, 056502 (2014)]. The backlighter attenuated by the heated sample plasma is measured by four spectrometers along +/- 9 degree with respect to the z-pinch axis to infer the sample iron opacity. Here we describe measurements of the source-to-sample distance that exploit the parallax of spectrometers that view the half-moon-shaped sample from +/-9 degree. The measured sample temperature decreases with increased source-to-sample distance. This distance must be taken into account for understanding the sample heating.