Exploring Compton Scatter in Gamma Ray Detectors

In a Compton scatter, a part of the energy of an incident photon is transferred to a free electron and a new photon with reduced energy is generated. Compton scattered photons encode angle-dependent information that can be used for locating or imaging the photon source or deducing the linear polarization of the original photons. This work focuses on analyzing Compton scatters in two different detector setups, the first being a semiconductor (Ge) detector with segmented electrodes, the other a close-packed array of scintillation (CLYC) detectors.

The Ge detector is a double-sided strip detector that forms a 6 x 6 array of 5 mm x 5 mm pixels, allowing for position determination of interaction points and reconstruction of scattering events, either to analyze the scattering itself, or to recombine events back into a photopeak energy if Compton scattered photons end in a photoelectric capture.

CLYC is a novel scintillator capable of both neutron and gamma ray spectroscopy, with excellent pulse shape discrimination properties. Recently, new detectors of square geometry have been developed, which allow for modular packing. This work focuses on four 1” x 1” x 3” CLYC detectors arranged in a clover geometry, to evaluate polarization sensitivity and explore “add-back” algorithms to restore Compton events back into the photopeak.