McManus, M; Romano, F; Royle, G; Botnariuc, D; Shipley, D; Palmans, H; Subiel, A (2022) Determination of beam quality correction factors for the Roos plane-parallel ionisation chamber exposed to very high energy electron (VHEE) beams using Geant4. Physics in Medicine & Biology, 67 (6). 065011

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Abstract

Detailed characterisation of the Roos secondary standard plane-parallel ionisation chamber has been conducted in a novel 200 MeV Very High Energy Electron (VHEE) beam with reference to the standard 12 MeVelectron calibration beam used in our experimental work. Stopping-power-ratios and perturbation factors have been determined for both beams and used to calculated the beam quality correction factor using the Geant4 general purpose MCcode. These factors have been calculated for a variety of charged particle transport parameters available in Geant4 which were found to pass the Fano cavity test. Stopping-power-ratios for the 12 MeVelectron calibration beam quality were found to agree within uncertainties to that quoted by current dosimetry protocols. Perturbation factors were found to vary by up-to4%for the calibration beam depending on the parameter configuration, compared with only 0.8% for theVHEE beam. Beam quality correction factors were found to describe an approximately 10% lower dose than would be originally calculated if a beam quality correction were not accounted for. Moreover, results presented here largely resolve unphysical chamber measurements, such as collection efficiencies greater than 100%, and assist in the accurate determination of absorbed dose and ion recombination in secondary standard ionisation chambers.

Item Type:	Article
Keywords:	geant4, Monte Carlo, perturbation factors, beam quality correction, VHEE
Subjects:	Ionising Radiation > Radioactivity
Divisions:	Medical, Marine & Nuclear
Identification number/DOI:	10.1088/1361-6560/ac5a94
Last Modified:	04 Jul 2025 08:29
URI:	https://eprintspublications.npl.co.uk/id/eprint/9562