(Gamma transpOrt Utility, aPproximate but reversIbLe)
Goupil is a Monte Carlo transport engine designed for low-energy gamma-rays (0.1-3 MeV), typically emitted from radioactive isotopes. By using a backward transport algorithm, and making a few approximations, Goupil can significantly accelerate Monte Carlo simulations, resulting in computation time savings of up to 5 orders of magnitude in the air.
Documentation for Goupil can be found online at Read the Docs.
The Goupil library is under the GNU LGPLv3 license (see the provided COPYING and COPYING.LESSER files), except for examples and interfaces which are MIT-licensed.