Lineshape response of plastic scintillator to pair production of 4.44 MeV gamma's

TL;DR

This study investigates how a plastic scintillator responds to 4.44 MeV gamma-rays from pair production, analyzing energy deposition and double-escape peaks to improve gamma-ray detection techniques.

Contribution

It presents the first detailed measurement of the lineshape response of a plastic scintillator to pair production at 4.44 MeV, including extraction of the double-escape peak amidst background.

Findings

Successful detection of the double-escape peak at 3.42 MeV

Demonstration of background suppression techniques

Insights into the scintillator's energy response at high gamma energies

Abstract

We measure the distribution of energy deposited in a 40x88 mm plastic scintillator by e+ e- pair production of 4.44 MeV gamma-rays. We observe the double-escape peak of 3.42 MeV from pair production by tagging 511 keV annihilation radiation in two high-Z scintillators. The source is a standard commercial neutron source using alpha-emitting 241Am encapsulated with 9Be, which has a reaction branch feeding the first Ipi=2+ state of 12C making the 4.44 MeV gamma-rays. We demonstrate the extraction of the double-escape peak from the large neutron-produced backgound, and explore some of the features and difficulties of this technique with our apparatus.