Proton decay experiment to determine the ultimate stability of matter. .Dr. Oscar Saavedra outside the door to the tunnel experiment with traffic streaming by. Oscar Saavedra, experimenter in the Mont Blanc Proton Decay group. The experiment consists of a 150-ton cube of iron sheets, interleaved with Geiger counter tubes. The cube has to be large enough to provide a mass of protons that will bring the probability of a decay event occurring within practical bounds, made difficult by the half life of the proton being 10 to the power 34 years. (1985).