Modes of Energy Deposition in the Detector

If Compton scattering takes place, only a fraction of the photon energy is given to an electron. A scattered photon still exists carrying the rest of the energy. The energy of the electron is deposited in the detector. But what happens to the energy of the scattered photon  

The scattered photon may or may not interact again inside the detector. The probability of a second interaction depends on the size of the counter (Fig. 12.2), on the position of the first interaction, on the energy of the scattered photon, and on the material of which the detector is made. Unless the detector is infinite in size, there is always a chance that the scattered photon may escape, in which case a pulse will be formed with height proportional to an energy that is less than the energy of the incident photon. 

From the study of the Compton effect (Chap. 4), it is known that Compton electrons have an energy range from zero up to a maximum energy which is 

Scattered photon interacts inside this larger detector 

Sometimes the Compton interaction occurs very close to the surface of the detector or in the material of the protective cover surrounding the detector (Fig. 

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