(a) Sideview images of a water jet at various delays after interception by a FLASH FEL pulse. (b) Plot of the evolution of the gap size in the first 50 ns after the FLASH FEL pulse hit the jet (solid circles) and the fit of a logarithmic function to the data (dashed line). The jet was flowing at a rate of 6.7 µl min−1 (helium mass-flow rate Qg = 2.6 mg min−1) with a diameter djet = 3.1 µm and velocity vjet = 60 m s−1. The dose deposited into the jet was approximately 30 MGy. Note that the position of the gap in the jet varies as a result of nozzle vibrations; the frames shown here are among those with the largest jet gaps recorded. The scale bar in the first panel of (a) is 20 µm and X-rays are incident from the left.