Microscopy X-ray imaging enriched with small angle X-ray scattering for few nanometer resolution reveals shock waves and compression in intense short pulse laser irradiation of solids

Understanding how laser pulses compress solids into high-energy-density states requires diagnostics that simultaneously resolve macroscopic geometry and nanometer-scale structure. Here we present a combined X-ray imaging (XRM) and small-angle X-ray scattering (SAXS) approach that bridges this diagnostic gap. Using the Matter in Extreme Conditions end station at LCLS, we irradiated <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m1"> <mml:mrow> <mml:mn>25</mml:mn> <mml:mtext> </mml:mtext> <mml:mi>μ</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:math> copper wires with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m2"> <mml:mrow> <mml:mn>45</mml:mn> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">f</mml:mi> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m3"> <mml:mrow> <mml:mn>0.9</mml:mn> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">J</mml:mi> </mml:mrow> </mml:math> , <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m4"> <mml:mrow> <mml:mn>800</mml:mn> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">n</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:math> pulses at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m5"> <mml:mrow> <mml:mn>3.5</mml:mn> <mml:mo>×</mml:mo> <mml:mn>1</mml:mn> <mml:msup> <mml:mrow> <mml:mn>0</mml:mn> </mml:mrow> <mml:mrow> <mml:mn>19</mml:mn> </mml:mrow> </mml:msup> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">W</mml:mi> <mml:mo>/</mml:mo> <mml:mi mathvariant="normal">c</mml:mi> <mml:msup> <mml:mrow> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> <mml:mrow> <mml:mn mathvariant="normal">2</mml:mn> </mml:mrow> </mml:msup> </mml:mrow> </mml:math> while probing with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m6"> <mml:mrow> <mml:mn>8.2</mml:mn> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">k</mml:mi> <mml:mi mathvariant="normal">e</mml:mi> <mml:mi mathvariant="normal">V</mml:mi> </mml:mrow> </mml:math> XFEL pulses. XRM visualizes the evolution of ablation, compression, and inward-propagating fronts with <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m7"> <mml:mrow> <mml:mo>∼</mml:mo> <mml:mn>200</mml:mn> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">n</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> </mml:mrow> </mml:math> resolution, while SAXS quantifies their nanometer-scale sharpness via the time-resolved evolution of scattering streaks. The joint analysis reveals that an initially smooth compression steepens into a nanometer-sharp shock front after <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m8"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>t</mml:mi> </mml:mrow> <mml:mrow> <mml:mtext>sh</mml:mtext> </mml:mrow> </mml:msub> <mml:mo>≈</mml:mo> <mml:mrow> <mml:mo stretchy="false">(</mml:mo> <mml:mrow> <mml:mn>18</mml:mn> <mml:mo>±</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> <mml:mo stretchy="false">)</mml:mo> </mml:mrow> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">p</mml:mi> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> </mml:math> , consistent with an analytical steepening model and hydrodynamic simulations. The front reaches a velocity of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" id="m9"> <mml:mrow> <mml:msub> <mml:mrow> <mml:mi>c</mml:mi> </mml:mrow> <mml:mrow> <mml:mtext>sh</mml:mtext> </mml:mrow> </mml:msub> <mml:mo>≈</mml:mo> <mml:mn>25</mml:mn> <mml:mtext> </mml:mtext> <mml:mi mathvariant="normal">k</mml:mi> <mml:mi mathvariant="normal">m</mml:mi> <mml:mo>/</mml:mo> <mml:mi mathvariant="normal">s</mml:mi> </mml:mrow> </mml:math> and a lateral width of several tens of microns, demonstrating direct observation of shock formation and decay at solid density for the first time with few-nanometer precision. This integrated XRM–SAXS method establishes a quantitative, multi-scale diagnostic of laser-driven shocks in dense plasmas relevant to inertial confinement fusion, warm dense matter, and planetary physics.