  In this letter we report for the first time the possibility of visualizing an
atomizing spray by simultaneously recording X-ray absorption and 2- photon
laser-induced fluorescence imaging. This unique illumination/detection scheme
was made possible thanks 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 (approximately 10 mJ)is
employed to form a light sheet and to induce 2-photon fluorescence from 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. The combination of these two highly complementary techniques, both
in the visible and in the soft X-ray regime, is very promising for the future
characterization of challenging spray systems as well as for further
understanding the physics of liquid atomization.
