Time Resolved Spectroscopic Measurements of Electron Temperature and Ion Density in a High Repetition Rate Experiment

Many laboratory plasmas of interest are transient (<1 ms) and tenuous (<10¹⁵ cm-³) in nature, but measuring time-resolved temperatures and densities in this regime is challenging. The intensity ratios of spectral lines corresponding to successive ionization states are highly dependent on electron temperature, and Stark broadening is a well-established and reliable technique for determining density. However, these techniques are generally performed on steady-state plasmas, or time integrated to the point where valuable information is lost. We present a comparison between high-temporal resolution (~10 ns) spectroscopic data and a collisional-radiative model in order to characterize the evolution of the temperature and density of carbon ablated plasma in a regime where Thomson scattering and Langmuir probes prove challenging. A high repetition rate laser allows for individual time resolved spectral lines to be assembled into a highly resolved (~2 Å) composite spectrum for analysis.

This work was supported by the Defense Threat Reduction Agency, Lawrence Livermore National Security LLC, and the United States Department of Energy (DOE) under Contract No. DE-SC0017900.