A method to collect 3D measurement data regarding a working fluid in a system, e.g., a turbo-machine, including: arranging sources of beams proximate to a passage of the working fluid in or downstream of the turbo-machine such that beams from the sources are projected through the working fluid; detecting intensities of the beams after they pass through the working fluid, and generating at least a two dimensional (2D) representation of the working fluid based on the detected intensities of the beams.