Characterisation of a graphite calorimeter in scanned proton beams

• Main Author: Petrie, Lauren M.
• Other Authors: Regan, P. H. ; Palmans, H.
• Published: University of Surrey 2016
• Subjects: 539.7
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.701585

The NPL graphite proton calorimeter is used to measure the dose deposited from irradiation by proton beams. This thesis describes the first measurements carried out with the calorimeter in proton pencil beams as well as well as an analysis of the calorimeter data in scanned proton beams. In doing this analysis, a greater understanding of the response and heat flows within the calorimeter was achieved. These measurement results are compared to simulations carried out using COMSOL Multiphysics®, a finite-element simulation software package. A model of the calorimeter was built in TOPAS, a Monte Carlo platform which wraps and extends the GEANT-4 simulation toolkit. This model was used to calculate two correction factors: the gap correction factor, which increased with energy from 1.00064(08) at 60 MeV to 1.00359(15) at 230 MeV; and the volume averaging correction factor which was 0.99936(44) at 60 MeV and 1.00515(154) at 230 MeV. TOPAS was also used to build a model of the Clatterbridge beamline, producing Bragg peak and modulated depth-dose curves for the 62 MeV proton beam. This can be used for future, more detailed investigations and coupled TOPAS/COMSOL simulations.