SU-E-T-492: High Precision Cross Sections and Physics Models for Proton Interactions Below 20 MeV in Geant4

Abstract

Purpose: Geant4 is a Monte Carlo (MC) toolkit with an increasing use in the field of medical physics. Electromagnetic processes are well validated, but for hadronic interactions of charged particles at energies of the order of a few MeV, particularly for low Z materials, there are no physics models able to reproduce the experimental data. With the default version of Geant4, the cross sections and production of secondary particles for proton-nucleus interactions at an energy below 20 MeV are not satisfactory. In this study, a new physics package to simulate particles below 20 MeV has been added to Geant4. Methods: A new Geant4 package has been developed to simulate proton interactions below 20 MeV using the data on reaction cross sections and production of secondary particles contained in evaluated nuclear databases. The new package has been tested making use of the TENDL-2009 and TENDL-2012 databases to simulate the 18O(p,x) interactions for energies ranging from 4 MeV up to 20 MeV. For this particular reaction, we have also included in the database the accurate data that can be found in the IAEA medical database. Results: The obtained energy spectra of the secondary particles produced by the 18O(p,n) and 18O(p,gamma) reactions were compared with those calculated with the standard Geant4 physics, QGSP_BIC_HP, and also with suitable MCNPX calculations. The neutron and gamma production obtained with the new Geant4 package and TENDL/IAEA-libraries are significant from 4 MeV, while with the standard Geant4 physics there is no production of neutrons for energy below 8 MeV, while above 8 MeV the gamma and neutron production shows a wrong yield. Conclusion: A new high precision physics package with corresponding cross section libraries have been successfully added to the Geant4 MC toolkit for particle energies below 20 MeV, improving the accuracy and production rates of different secondaries.