The inelastic cross section, and hence the nuclear interaction length, is a function of both the energy and type of incoming particle. The interaction length of dense materials is much greater than the radiation length. Fluctuations in the amount of energy deposited are largely due to the variable fraction of the shower which is converted into an electromagnetic shower, by the production of fast neutral pions and their subsequent rapid decay into energetic photons. If the calorimeter plates are made of depleted uranium, slow neutrons from the hadronic shower induce fission, and fission products give an increased signal in the detector medium. Compensation can also be achieved by making the absorber plates sufficiently thin that a substantial fraction of the slow nuclear products reach the detector regions.
Most practical calorimeters are combined electromagnetic and hadronic detectors.
Because the nuclear interaction length is so much bigger than the radiation length, most hadrons pass through the electromagnetic front compartment and interact in the hadronic part behind. BBQ sheets are used to read out the scintillator with photomultipliers behind the module. In this way, modules can be stacked next to each other with minimal dead space between. Other Calorimeter Designs Barium Fluoride crystals can be used in an electromagnetic calorimeter. For a calorimeter to provide accurate energy measurements, more is needed than a good intrinsic energy resolution.