Ionization and temperature measurements in warm dense copper using x-ray absorption spectroscopy
T. Cordova, E. V. Marley, D. A. Chin, R. A. London, H. A. Scott, T. Döppner, F. N. Beg, F. Coppari, M. Millot, J. Emig, S. B. Hansen, P. M. Nilson, P. Sterne, M. J. MacDonald
公開日: 2025/9/16
Abstract
We detail experimental results inferring ionization and temperature for warm dense copper plasmas at several times solid density (15 to 25 g/cm$^3$) and temperatures of 10 to 21 eV. Experiments performed at the OMEGA Laser Facility generate uniform warm dense matter conditions via symmetric shock compression of a buried copper layer. The plasma is probed with a laser-generated x-ray source to collect the K-shell x-ray absorption spectrum. Fitting bound-bound absorption contributions from constituent charge states of copper provides an estimated $\overline{Z}$ of approximately 4 to 7 for these warm dense copper plasmas. We find that these partially ionized plasmas have K-edge shifts of 12 to 30 eV and bound-bound resonance 1s$\rightarrow$3p absorption shifts of 4 to 26 eV with respect to the cold K-edge. This study provides necessary experimental data to improve ionization and opacity models in the warm dense matter regime.