P 351 - A prototype secondary standard calorimeter for dosimetry of conventional and ultra-high dose rate protons

Aylward, Jack; Bass, Graham; Taylor, Michael; MacKay, Ranald; Kirkby, Karen; Thomas, Russell

Abstract

Ionisation chambers are commonly used as secondary standard detectors, however these are less suited for ultra-high
dose rates (UHDR), or FLASH dosimetry, because of collection inefficiency due to ion recombination. Calorimetry shows
promise for UHDR: it is suited for irradiations of high dose of short duration to minimise heat loss from the detector core
during the measurement. A low-cost secondary standard calorimeter has recently been developed at the UK’s National
Physical Laboratory (NPL) and has been tested in x-ray and electron beams, including at UHDR electrons [1]. This work tests
the feasibility of the calorimeter, and characterises the response, in conventional dose rate and UHDR Pencil Beam
Scanning (PBS) protons. A 245 MeV PBS gaussian proton beam (rx 5 4.6 mm, ry 5 6.6 mm) was used to characterise the
calorimeter at a reference depth of 2 cm in water. The linearity of dose response was assessed up to 60 Gy. Dose rate
dependence was assessed up to 110 Gy/s corresponding to a maximum nozzle current of 56.4 nA. Repeatability was
assessed for a 10 3 10 cm scanned field. Repeatability was measured to be 0.67% and 1.93% at conventional and UHDR
respectively (one standard deviation). Conclusion: The suitability of a low-cost calorimeter as a secondary standard detector
of conventional and UHDR protons is presented.

• Presentation Conference Type: Conference Abstract
• Conference Name: Annual Conference of the Particle Therapy Cooperative Group
• Start Date: Jun 10, 2023
• End Date: Jun 16, 2023
• Acceptance Date: Apr 1, 2023
• Online Publication Date: Nov 3, 2023
• Publication Date: 2023-11
• Deposit Date: Sep 24, 2024
• Journal: International Journal of Particle Therapy
• Print ISSN: 2331-5180
• Electronic ISSN: 2331-5180
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 10
• Issue: 2
• Pages: 393
• DOI: https://doi.org/10.14338/ijpt-23-ptcog61-10.2
• Public URL: https://uwe-repository.worktribe.com/output/12908393