Abstract:

Compton plateau in the  ¹³⁷Cs γray spectrum measured by a NaI(Tl) detector was studied via the KleinNishina formula of Compton scattering differential cross section, which is deduced from the Dirac formula of quantum mechanics, and   the MCNP simulation program also. There is distinct difference between the theoretical calculation and the experimental result, which is found to come from both the photon secondary effect in the scintillation crystal and the spectrum widening. By correction of these two effects, the MCNP simulation result is in  very good agreement with the experimental data.

Key words: γ spectrum, NaI(Tl) detector, Compton plateau, differential cross section, MCNP program