A Novel Metrology Standard for Synchrotron Produced Monochromatic X-ray Beams

Abstract

Purpose: X-ray beams produced using synchrotrons have unique properties that are of interest to radiotherapy investigations and the characterization of radiation detectors. To facilitate the use of synchrotron produced photons in such investigations, this project aims to determine the absorbed dose to water at depth for synchrotronproduced monochromatic x-ray beams with a standard uncertainty less than 1 %, significantly lower than current methods. Methods:The absorbed dose to water at a depth of 2 cm, D w, 2cm , was evaluated using a purpose built novel aluminum calorimeter design. Finite element modeling and radiation transport simulations were performed to refine the design, calculate correction factors, and assess influence quantities. Two iterations of the design were constructed to test calorimeter operation and a comparison of the quantity air kerma, using a secondary microDiamond detector, was performed. Results:The combined standard uncertainty in the determination of absorbed dose to water was estimated to be 0.89 %, and was found to be constant for monochromatic energies investigated (80 keV to 140 keV). No dependence on calorimeter design was observed and the comparison with the microDiamond detector showed agreement in the determination of air kerma rate at the 1.5 % level, providing confidence in the new calorimeter standard.Conclusions: This new calorimeter has been shown to accurately determine absorbed dose to water in synchrotron-produced x-ray beams with a substantially lower uncertainty compared to current methods. Routine operation has also been demonstrated, providing a new high-accuracy dosimetric tool for users of synchrotron beams, initially in Canada but potentially at sites worldwide. i Statement of OriginalityThis thesis summarizes the author's research over the course of his doctoral studies.The work has been published in the peer-reviewed papers and conference presentations listed below. This project was completed under the supervision of Dr. MalcolmMcEwen, where he has provided guidance throughout the project and provided comments on the published thesis and peer-reviewed papers. The author performed all of the measurements, design, computational work, analysis of the results and prepared the manuscript. Peer-reviewed papers I. El Gamal I, Dessureault J, McEwen MR. A novel calorimeter for synchrotron produced monochromatic x-ray beams. Med Phys. 2023.