Simultaneous laser-driven x-ray and two-photon fluorescence imaging of atomizing sprays

• DOI: 10.1364/optica.378063
• Publication Date: 2019-12-24T14:30:10Z
• Authors: D. Guénot; K. Svendsen; J. Björklund Sven...; H. Ekerfelt; A. Persson; O. Lundh; E. Berrocal
• Keywords: Accelerator Physics (physics.acc-ph); Atom and Molecular Physics and Optics; 0103 physical sciences; Fluid Dynamics (physics.flu-dyn); FOS: Physical sciences; Physics - Accelerator Physics; Physics - Fluid Dynamics; 01 natural sciences; Physics - Optics; Optics (physics.optics)

In this Letter, we report for the first time, to the best of our knowledge, the possibility of visualizing an atomizing spray by simultaneously recording x-ray absorption and two-photon laser-induced fluorescence imaging. This unique illumination/detection scheme is made possible due to the use of soft x rays emitted from a laser-driven x-ray source. An 800 mJ laser pulse of 38 fs duration is used to generate an x-ray beam with up to

4 ×

10 8

photons ranging from 1 to 10 keV, allowing projection radiography of water jets generated by an automotive port fuel injector. In addition, a fraction of the laser pulse (

∼

10

m J

) is employed to form a light sheet and to induce two-photon fluorescence in a dye added to the water. The resulting high-contrast fluorescence images provide fine details of the spray structure, with reduced blur from multiple light scattering, while the integrated liquid mass is extracted from the x-ray radiography. In this proof of principle, we show that the combination of these two highly complementary techniques, in both the visible and soft x-ray regimes, is very promising for future characterization of challenging spray, as well as for further understanding of the physics of liquid atomization.