Probing multiphase flows with x-ray near-field speckles

Multiphase flows of simple and complex fluids are of great fundamental and practical interests due to their multitude of applications. However, multiphase flows are also often difficult to study optically because of intense multiple light scattering from the phase boundaries in the flow, such as liquid/gas interfaces. X-rays are highly penetrable in a multiphase flow because of the weak interaction between x-rays and materials. X-ray near-field speckles can be generated readily when x-rays pass through the flow. The x-rays do not need to be completely coherent. A partial or local coherence is sufficient to produce significant intensity fluctuation in the transmitted beam that can used to probe both morphology and dynamics. Combined with ultrafast imaging, x-ray near-field speckles and their spatiotemporal correlations have been proven powerful to interrogate multiphase flows highly transient and far from equilibrium.