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The Low Energy Electromagnetic package of the Geant4 toolkit incorporates a component for the simulation of atomic relaxation of elements with atomic number between 6 and 100. This process is triggered by the creation of a vacancy in the atomic shell occupancy as a result of an incident particle interaction with an atom of the target material. X-ray fluorescence and Auger electron emission result from the relaxation cascade. The availability of a model handling the atomic relaxation in Geant4 extends the applicability of the simulation toolkit to experimental use cases concerning the investigation of material properties through their characteristic X-ray or Auger emission. It is also relevant to precise simulation applications, like microdosimetry or the design and optimization of detectors based on nanotechnology. The key features of the software development process, the software architecture and design, and the implementation details of the physics model are described. [ABSTRACT FROM AUTHOR]

Auger emitting radioisotopes are of great interest in targeted radiotherapy because, once internalised in the tumour cells, they can deliver dose locally to the radiation sensitive targets, while not affecting surrounding cells. Geant4 is a Monte Carlo code widely used to characterise the physics mechanism at the basis of targeted radiotherapy. In this work, we benchmarked the modelling of the emission of Auger electrons in Geant4 deriving from the decay of 123I, 124I, 125I radionuclides against existing theoretical approaches. We also compared Geant4 against reference data in the case of 131Cs, which is of interest for brachytherapy. In the case of 125I and 131Cs, the simulation results are compared to experimental measurements as well. Good agreement was found between Geant4 and the reference data. As far as we know, this is the first study aimed to benchmark against experimental measurements the emission of Auger electrons in Geant4 for radiotherapy applications. • Auger electrons can deliver dose locally to the radiation sensitive targets. • The emission of Auger electrons in Geant4. • The Auger electrons are alternative channel to X-ray fluorescence. • Geant4 is extensively used in medical physics applications. • Geant4 in terms of emission of Auger electrons. [ABSTRACT FROM AUTHOR]