Methods for dosimetric measurement and characterisation of laser-driven ion beams

Abstract

The work reported within this PhD thesis aims to address some of the technicalities surrounding dosimetry measurements of ultra-high pulse dose rate beams, in particular those generated through the mechanism of laser-driven acceleration. Early studies of irradiations performed with these beam modalities have indicated reductions in the normal tissue complication probability for similar levels of tumour control, highlighting the potential to offer marked improvements in such clinical applications. Novel strategies must be devised that are capable of performing accurate dosimetry measurements of these high-dose beams, especially given the harsh experimental environment created. A spectroscopic routine has been developed and reported that allows the characterisation of laser-driven proton beams through a deconvolution algorithm to derive the energy spectrum incident on a stack of radiochromic films. This tool has been tested through an experimental campaign carried out at Clatterbridge Cancer Centre, with an assessment of its accuracy performed through extensive Monte Carlo modelling. A novel strategy for dosimetry measurements of laser-driven proton beams has also been presented in this work. This is based on the use of a small portable graphite calorimeter developed at National Physical Laboratory, with the absorbed dose obtained through measurements of the radiation-induced temperature rise in the system. An experimental investigation was performed using the VULCAN PW laser system at Rutherford Appleton Laboratory, successfully demonstrating the proof of this principle in the first measurements of a calorimeter system to detect the absorbed dose of laser-driven beams. Through the methods developed for the characterisation and dosimetry of ultra-high dose rate laser-driven beams, suitable solutions are presented for accurate measurement of such modalities, whilst overcoming the challenges typically associated with this particle acceleration regime, in addition to unusable conventional detectors. These steps may represent important ones in the translation of this novel accelerating regime to the applications proposed.

Date of Award	Jul 2023
Original language	English
Awarding Institution	Queen's University Belfast
Supervisor	Marco Borghesi (Supervisor) & Satyabrata Kar (Supervisor)