Code for AmBe simulation

Americium-Beryllium (AmBe) sources are commonly used in industry and research applications. Existing simulations fail to match all the expected features of the AmBe neutron spectrum from reliable underlying data, and also lack the generation of carbon ions and fission fragments that appearexperimentally.
This article details a comprehensive Geant4 simulation based on an analytical approach to the PrimaryGenerator class. Rather than simulating the interaction of 241 Am α decay with 9 Be through the in-built Geant4 physics list, this simulation uses the differential cross sections of the 9Be(α, n)12 C reaction to directly produce neutrons and 12 C ions while simultaneously increasing computational efficiency. Each stage of the simulation has been verified against commonly accepted results, including the mass distribution of the 241 Am 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 239 PuBe neutron source has also been implemented, making it a straightforward framework for implementing further sources.