Delphi detector at CERN: End view showing calorimeters and muon chambers

The energy of both charged and neutral particles can be measured with calorimeters. A calorimeter consists of several layers of a heavy material like lead or iron interleaved with layers of gas. The particle interacts in the heavy material giving rise to a shower of particles. The total number of particles produced is proportional to the energy of the original particle. The ionisation in the gas volumes between the heavy material measures the number of produced particles. The ionisation is collected on metal wires or pads as in the track detector.