Gamma - when is pair production dominant

[lavster]

hi,
am i right in saying that for gamma rays of energies above 10MeV, the main interaction mechanism is pair production? and this is independent on energy? (or is it compton scattering for example?)
thanks

 

[Mirin]

While pair production is possible for photon energies of 1.022 MeV or higher, it is not usually dominant until the incident photon energy is, very generally, about 5 MeV.

The incident photon energy which dominantly results in pair production depends on the element/medium being considered. Here are two pictures, for lead and air, illustrating my point.

As you can see, pair production is the predominant mechanism of interaction between photons and electrons for energies at about 5 Mev in lead, and at about 10 MeV in air (when considering the photoelectric effect, Compton scattering, and pair production).

EDIT: Sorry, got carried away. A more concise answer: For photons with energies above 10 MeV, pair production is the most dominant interaction mechanism for most elements. The type of interaction depends on energy AND atomic number.