An Acousto-Optic Technique for Measuring Cryogenic Flow

*† ‡ A novel, integrated cryogenic flow sensor design is presented in this paper along with experimental results using a surrogate fluid. This design is based on Bragg diffraction from an opto-acoustic grating induced in the flow. Diffraction changes resulting from the Doppler effect are used to estimate the fluid velocity without the need for back or forward scattering from the fluid. This sensor concept provides a robust alternative for use in harsh cryogenic environments, including low and zero gravity conditions, for liquid propellant feed systems and tankage.