Dynamics and attenuation of shock waves launched in liquid jets by X-ray laser pulses*

Chemical and biological experiments performed at X-ray laser facilities embed the samples in liquid microjets to enable rapid sequential X-ray probing of fresh samples. The absorption of intense X-ray laser pulses generates shock waves that travel along the liquid jets, and may damage samples in MHz repetition rate experiments. We imaged optically these shock waves and determined their properties up to ~40 ns of travel along liquid water microjets with 14 or 20 µm diameters. The shock pressure was evaluated from the shock velocity and was found to decay rapidly from peak pressures around 1 GPa to pressures below 100 MPa; the latter value still exceeds the Vickers hardness of lysozyme protein crystals. The reflection of the shock at the surface of the jets leads to cavitation and to the generation of additional pressure waves, leading to a complex shock structure that is related to, yet different from, the one observed in supersonic gas jets.