Laser-Driven X-ray Diagnostics for Heavy-Ion-Heated Matter

The study of matter at high-energy-density (HED) conditions is relevant to the understanding of compact astrophysical objects, and crucial for applications such as inertial confinement fusion. Producing such extreme states of matter in the laboratory, volumetric heating by intense pulses of heavy ions offers a novel approach (compared to more established drivers such as high-energy lasers), allowing to heat large sample volumes on the mm$^{3}$ scale, with small gradients, on comparably long time scales, and near thermal equilibrium. The future FAIR facility will provide powerful pulses of heavy-ions with unprecedented intensity, allowing to reach eV temperatures and Mbar pressures. The plasma physics collaboration HED@FAIR will exploit these unique capabilities for its HED science program.

State-of-the-art diagnostic techniques in HED science experiments often involve powerful laser-generated X-ray pulses, produced by high-intensity laser pulses, to probe the short-lived dense samples, and are consequently also envisaged to complement the experimental capabilities at FAIR. To this end, we have recently exploited the available infrastructure at GSI, which allows to use the ion bunches from the SIS18 heavy-ion synchrotron in combination with the ns-pulse of the high-energy laser facility PHELIX at the HHT cave, in order to demonstrate the feasibility of laser-driven X-ray diagnostics of heavy-ion-heated matter within the FAIR Phase-0 research program. We have commissioned and applied laser-driven X-rays for investigating heavy-ion heated matter through X-ray diffraction, X-ray Thomson scattering and X-ray absorption spectroscopy. This platform allows for the observation of phase changes induced by the heavy-ion beam and volumetric temperature measurements of the heated sample.

After giving an overview of the PHELIX facility and its capabilities, I will present first findings from our combined heavy-ion high-energy-laser experiments.