Electron-density scaling of conversion efficiency of laser energy into L-shell X-rays

Journal article

Laser-Produced plasmas at subcritical densities have proven to be efficient sources for X-ray production. In this context, we obtain experimental results from Kr and Xe gas-filled targets that were irradiated by the OMEGA (Laboratory for Laser Energetics, University of Rochester) laser. Nearly 40% of the laser energy was converted into X-rays in the L-shell-photon-energy range (≥ 1.6 keV) by a Kr-filled target. The conversion efficiency measurements were correlated with time-resolved plasma-temperature measurements done by means of a Thomson-scattering diagnostic. The measured range of temperatures, between 2-3.5 keV, is in good agreement with LASNEX radiation-hydrodynamics simulations. X-ray-cooling rates and charge-state distributions were computed using detailed atomic data from the HULLAC suite of codes. X-ray yields predicted by the cooling-rate calculations are compared to measured spectra, and good agreement is found for predictions made with highly-detailed atomic models. We find that X-ray conversion efficiency in Kr-filled targets is a strong function of temperature, and has an optimum density near 15% of the laser's critical density. © 2005 Elsevier Ltd. All rights reserved.

Authors: Fournier, K; Constantin, C; Back, C; Suter, L; Chung, H

• Publication status: Published
• Journal: JOURNAL OF QUANTITATIVE SPECTROSCOPY and RADIATIVE TRANSFER
• Volume: 99
• Issue: 1-3
• Pages: 186-198
• Publication date: 2006-01-01
• DOI: 10.1016/j.jqsrt.2005.04.008
• ISSN: 0022-4073
• Language: English
• Keywords: underdense radiator; laser plasma; X-ray conversion efficiency