Energy calibration of thin plastic scintillators using Compton scattered γ-rays

A practical method of using the Compton scattered photons for the energy calibration of thin plastic scintillators is described. The location of the Compton edge in the measured energy spectrum was obtained by matching this spectrum with the Monte Carlo simulated spectrum near the Compton maxima. The simulated spectrum was broadened by a Gaussian-type function. The γ-ray energy spectrum calculation was carried out by employing the MCNP4C simulation code. The natural degradation of the light yield within the scintillator was experimentally investigated and the observed non-uniform yield across the scintillator was taken into account in the simulation. A χ2 fit between the measured and the simulated γ-ray spectra provided the Compton edge positions for γ energies of 511, 662, 1173 and 1275 keV. The calibration approach can be simply applied to any thin organic scintillator with an arbitrary shape.