Transition Radiation in Cerenkov Detectors

In connection with the use of gas Cerenkov detectors for the measurement of the energy of electron beams, it has been found necessary to take into consideration the modification of the radiation due to the end effects in the detector. Using electrons of energy in the range 26-29 MeV, observations have been made of radiation both below and above the Cerenkov threshold, the intensity and angular distribution of which are in good agreement with the transition radiation theory of Frank and Ginsburg and the theory of Cerenkov radiation as formulated by Tamm. The threshold technique as a method of measuring beam energy is considered in the light of the above investigations.