Year

2022

Degree Name

Doctor of Philosophy

Department

School of Physics

Abstract

The goal of this project is to further develop, improve and validate the Geant4 physics component modelling atomic de-excitation. Geant4 is one of the most used general-purpose Monte Carlo codes for modelling the interactions of particles in matter used in radiation physics, in applications spanning from high energy physics to space, environment and bio-medical sciences. This project is motivated by the ongoing effort to improve the physics model of Geant4, to meet the requirements of a very diverse user community.

Geant4 is capable of simulating the radiative (X-ray) and non-radiative (Auger electron) relaxation processes of singly ionised atoms. The first release of an atomic de-excitation module is dated in 1999 and further improved. The Low Energy Electromagnetic package’s first release included a basic functional implementation of X-ray fluorescence emission, which was initially associated with parameterized model implementations of the photoelectric and electron impact ionisation processes. It was then extended to describe Auger electron emission.

In this thesis, I developed a state-of-the-art X-ray fluorescence data library in Geant4, calculated using the Hartree-Fock method, which is widely recognised as a more realistic model than the Hartree-Slater model used in the default Geant4 data libraries (based on the EADL, developed at Lawrence Livermore National Laboratory, California, US). In addition, I implemented in Geant4 PIXE ionisation cross sections for proton and α particles calculated by Cohen et al. based on ECPSSR method. The new Geant4 data libraries, called here G4–ANSTO, have been released for the first time in Geant4 11.0, in December 2021.

FoR codes (2008)

0299 OTHER PHYSICAL SCIENCES

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.