Hello, I am working on a project that is attempting to use GM tubes to detect low levels of radiation emitted from food or other objects. Currently I am trying to find the efficiency of these tubes to beta and gamma radiation. I wanted to get a pure beta and pure gamma source but I was only able to get a Na22 source and a Cs137 source. These both emit beta and gamma. Is it possible to use these to determine the efficeincy of the tubes to beta and gamma separately? I know I could block the beta with a piece of metal, giving the gamma only, then subtract that from the total to get beta, but how do I calculate how much of each radiation type is being emitted?? Thanks for any help!!