Creation and diagnosis of solid-density hot-dense matter with an X-ray free-electron laser

An international team of researchers headed by young Oxford physicist Sam Vinko created an unique state of matter by isochorically heating a thin aluminium foil using a tightly focused X-ray beam produced by the LCLS (Linac Coherent Light Source) free-electron laser in California. Solid-density plasmas at a temperature > 10⁶ K were produced under these irradiation conditions. By using the LCLS pulse, the authors have been able to study extremely well-defined hot-dense plasma states for the first time, with unprecedented detail. Detailed simulations of the X-ray-matter interaction process conducted with a radiative-collisional code further showed good qualitative agreement with the experimental results, providing additional insight into the evolution of the charge state distribution of the system, the electron density and temperature, and the timescales of collisional processes. These results should feed back into future high-intensity X-ray experiments involving dense samples, such as X-ray diffractive imaging of biological systems, material science investigations, and the study of matter in extreme conditions.

Nomarski (DIC – Differential Interference Contrast) images of ablation imprints created in lead tungstate (PbWO₄) by the focused beam of the X-ray free-electron laser LCLS built and operated at SLAC, Menlo Park, CA. The top-left inset contains a dependence of the ration of threshold and peak fluence f = E_th/E_pulse on the damaged area of the PbWO₄ surface, that serves to the determination of an effective area of the focused beam and other interaction parameters.

¹Department of Physics, Clarendon Laboratory,University of Oxford, Parks Road, Oxford OX1 3PU, UK
²Lawrence Berkeley National Laboratory,1 Cyclotron Road, CA 94720, USA
³Atomic and Molecular Data Unit, Nuclear Data Section, IAEA, P.O. Box 100, A-1400, Vienna, Austria
⁴Plasma Physics Department, AWE Aldermaston, Reading, UK
⁵Institute of Physics ASCR, Na Slovance 2, 18221 Prague 8, Czech Republic
⁶SLAC National Accelerator Laboratory,2575 Sand Hill Road, Menlo Park, CA 94025, USA
⁷Lawrence Livermore National Laboratory,7000 East Avenue, Livermore, CA 94550, USA
⁸Deutsches-Elektronensynchrotron DESY, Notkestrasse 85, 22603 Hamburg, Germany
⁹IOQ, Friedrich-Schiller-University, Jena,Max-Wien-Platz 1, 07743 Jena, Germany