uranium was chosen as an absorber so that the calorimeter would be compensating. electrons and photons deposit energy differently from hadrons, but in a compensating calorimeter the response (e) for an electromagnetic cascade is equal to the response (h) for a hadronic cascade of the same energy (i.e. ). in the zeus calorimeter neutral pions interacted with uranium atoms to produce slow moving neutrons which were captured by the scintillator and increased the hadronic signal. another advantage of using uranium as the absorber was that the natural radioactivity allowed the calorimeter's sensitivity to be conveniently monitored.