Speaker: Claudiu A. Stan, Rutgers University-Newark
Program Description:
Shock wave trains in liquid jets are a counterpart of the long-known Mach patterns in supersonic gas jets, but were only discovered recently during XFEL ablation experiments, and have a surprisingly rich physics. As in the gas case, the shock trains form through oblique shock reflections, but also exhibit unique cavitation phenomena, and realize a system where a maximal intensity sound is generated, with sound pressure levels above 270 dB in water. Since it was later found that the trains can also be generated via optical ablation of liquid jets, they could become a versatile tool to study cavitation in liquids and shock damage in soft matter.
The shock trains can affect megahertz serial experiments at XFELs by damaging samples before they reach the beam, and may impact data acquisition at EuXFEL. Using a XFEL pump-probe setup at LCLS, we simulated the shock conditions expected at EuXFEL, and recorded diffraction from previously shocked lysozyme and hemoglobin crystals. For both samples, the diffraction quality degraded, indicating damage to the crystalline lattice; for lysozyme, a 40 MPa pressure damage threshold could be estimated. Additionally, the structure of hemoglobin changed after shocks. We estimated that shock damage for lysozyme may occur only at the maximum EuXFEL pulse rate of 4.5 MHz, but other samples may be affected at lower rates, and it remains important to rapidly diagnose and detect shock damage.
