Transition radiation is produced by relativistic charged particles when they cross the interface of two media of different dielectric constants. The total energy loss of a charge particle on the transition depends on its Lorentz factor γ = E / mc² and mostly directed forward, peaking at an angle of the order of 1 / γ relative to the particle's path. The intensity of the emitted radiation is roughly proportional to the particle's energy E.

The characteristics of this electromagnetic radiation makes it suitable for particle discrimination, particularly of electrons and hadrons in the momentum range between 1GeV / c and 100GeV / c. The transition radiation photons produced by electrons have wavelengths in the X-ray range, with energies typically in the range from 5 to 15keV. However, the number of produced photons per interface crossing is very small: for particles with , about 0.8 X-ray photons are detected. Usually several layers of alternating materials or composites are used to collect enough transition radiation photons for an adequate measurement --- for example, one layer of inert material followed by one layer of detector (e.g. microstrip gas chamber ), and so on.

See also

External links

• Article on transition radiation: http://rkb.home.cern.ch/rkb/PH14pp/node194.html