Filippo Falezza

This article details a comprehensive Geant4 simulation based on an analytical approach to the PrimaryGenerator class. Rather than simulating the interaction of 241Am α decay with 9Be through the in-built Geant4 physics list, this simulation uses the differential cross sections of the 9Be(α,n)12C reaction to directly produce neutrons and 12C ions while simultaneously increasing computational efficiency. The advantage of this is the ability to generate Doppler broadened 4.4 MeV and 3.2 MeV γ rays from 12C decay and hence the verification of the excited states ratio per neutron emission. Each stage of the simulation has been verified against commonly accepted results, including the mass distribution of the 241Am fission fragments. The features of the emerging neutron spectrum have been compared to commonly accepted data, confirming the validity of the simulation. The source term and the simulation template are made publicly available in conjunction with this article. Although not extensively verified, the 239PuBe neutron source has also been implemented, making it a straightforward framework for implementing further sources.