Method and apparatus for measuring ice thickness on substrates using backscattering of gamma rays

摘要

The present invention provides a method and apparatus for in situ measuring thicknesses of ice buildup on airfoil. The method and device uses a probe including a radioactive 241Am gamma ray source producing 60 keV gamma ray photons which penetrate through the airfoil substrate and a photodetector mounted behind the source for detection of backscattered gamma rays. The probe is mounted on the interior of the airfoil and secondary radiation is backscattered within the ice layer and back through the airfoil substrate to the photodetector. The shape and density of the source holder in addition to the geometrical arrangement of the source and detector with respect to the airfoil substrate are used to block a substantial fraction of gamma rays backscattered in the airfoil substrate thereby favoring scattering in the ice layer over that in the airfoil material.