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Coupling Monte Carlo simulations with thermal analysis for correcting microdosimetric spectra from a novel micro-calorimeter

Fathi, Kamran, Galer, Sebastian, Kirkby, Karen, Palmans, H and Nisbet, Andrew (2017) Coupling Monte Carlo simulations with thermal analysis for correcting microdosimetric spectra from a novel micro-calorimeter Radiation Physics and Chemistry.

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Abstract

The high uncertainty in the Relative Biological Effectiveness (RBE) values of particle therapy beam, which are used in combination with the quantity absorbed dose in radiotherapy, together with the increase in the number of particle therapy centres worldwide necessitate a better understating of the biological effect of such modalities. The present novel study is part of performance testing and development of a micro-calorimeter based on Superconducting QUantum Interference Devices (SQUIDs). Unlike other microdosimetric detectors that are used for investigating the energy distribution, this detector provides a direct measurement of energy deposition at the micrometre scale, that can be used to improve our understanding of biological effects in particle therapy application, radiation protection and environmental dosimetry. Temperature rises of less than 1μK are detectable and when combined with the low specific heat capacity of the absorber at cryogenic temperature, extremely high energy deposition sensitivity of approximately 0.4 eV can be achieved. The detector consists of 3 layers: tissue equivalent (TE) absorber, superconducting (SC) absorber and silicon substrate. Ideally all energy would be absorbed in the TE absorber and heat rise in the superconducting layer would arise due to heat conduction from the TE layer. However, in practice direct particle absorption occurs in all 3 layers and must be corrected for. To investigate the thermal behaviour within the detector, and quantify any possible correction, particle tracks were simulated employing Geant4 (v9.6) Monte Carlo simulations. The track information was then passed to the COMSOL Multiphysics (Finite Element Method) software. The 3D heat transfer within each layer was then evaluated in a time-dependent model. For a statistically reliable outcome, the simulations had to be repeated for a large number of particles. An automated system has been developed that couples Geant4 Monte Carlo output to COMSOL for determining the expected distribution of proton tracks and their thermal contribution within the detector. The correction factor for a 3.8 MeV proton pencil beam was determined and applied to the expected spectra. The corrected microdosimetric spectra was shown to have a good agreement with the ideal spectra.

Item Type: Article
Subjects : Physics
Divisions : Faculty of Engineering and Physical Sciences > Physics
Authors :
NameEmailORCID
Fathi, Kamrank.fathi@surrey.ac.ukUNSPECIFIED
Galer, Sebastians.e.galer@surrey.ac.ukUNSPECIFIED
Kirkby, KarenK.Kirkby@surrey.ac.ukUNSPECIFIED
Palmans, HUNSPECIFIEDUNSPECIFIED
Nisbet, AndrewA.Nisbet@surrey.ac.ukUNSPECIFIED
Date : 2 August 2017
Identification Number : 10.1016/j.radphyschem.2017.02.055
Copyright Disclaimer : © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/).
Uncontrolled Keywords : Particle therapy; Calorimetry; Microdosimetry; Monte Carlo Simulations; Thermal analysis
Related URLs :
Depositing User : Symplectic Elements
Date Deposited : 02 May 2017 08:52
Last Modified : 25 Jul 2017 14:07
URI: http://epubs.surrey.ac.uk/id/eprint/814068

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