Time-resolved X-ray Thomson Scattering and Fluorescence Spectroscopy for IFE Target Design

Understanding the behavior of polymer foams at high energy density conditions is crucial to advance inertial fusion energy research [1]. Here, we present data measuring the thermodynamic state of these materials at megabar pressures. At the Matter in Extreme Conditions Endstation of the Linac Coherent Light Source, we heat samples using an optical, high-intensity, femtosecond laser and dynamically probe them with ultra-short, coherent X-ray pulses of high peak brightness. Our data resolve the ultrafast response to laser heating with sub-ps resolution, measuring plasma temperatures exceeding 50 eV [2]. At the OMEGA laser facility, we study spherically converging implosions of foam shells. In both experiments, we field X-ray Thomson scattering measurements in forward and backward scattering geometries to capture both collective and non-collective electron behavior and determine the temperature of the sample. Simultaneously, X-ray fluorescence spectroscopy is used to measure the emission from a mid-Z dopant, providing complementary information on the plasma conditions. By combining these techniques, we obtain temporally resolved temperature measurements of the transient warm dense matter states and lay the foundation for future precision studies of laser-driven polymer foams wetted with liquid nuclear fuels.



References

[1] Fusion Energy Sciences Workshop on Inertial Fusion Energy, “Report of the Fusion Energy Sciences Workshop on Inertial Fusion Energy,” Tech. Rep. (U.S. Department of Energy, Office of Science, Fusion Energy Sciences, 2023).

[2] Martin, W. M., et al. "Characterizing laser-heated polymer foams with simultaneous x-ray fluorescence spectroscopy and Thomson scattering at the Matter in Extreme Conditions Endstation at LCLS." Physics of Plasmas 32.7 (2025).