8 - Calorimetry  pp. 230-272


By Claus Grupen and Boris Shwartz

Image View Previous Chapter Next Chapter

Most particles end their journey in calorimeters.


Methods of particle energy measurement in modern high energy physics have to cover a large dynamical range of more than 20 orders of magnitude in energy. Detection of extremely small energies (milli-electron-volts) is of great importance in astrophysics if one searches for the remnants of the Big Bang. At the other end of the spectrum, one measures cosmic-ray particles with energies of up to 1020 eV, which are presumably of extragalactic origin.

Calorimetric methods imply total absorption of the particle energy in a bulk of material followed by the measurement of the deposited energy. Let us take as an example a 10 GeV muon. Passing through material this particle loses its energy mainly by the ionisation of atoms while other contributions are negligible. To absorb all the energy of the muon one needs about 9m of iron or about 8m of lead. It is quite a big bulk of material!

On the other hand, high-energy photons, electrons and hadrons can interact with media producing secondary particles which leads to a shower development. Then the particle energy is deposited in the material much more efficiently. Thus calorimeters are most widely used in high energy physics to detect the electromagnetic and hadronic showers.