Simulation and experimental study of an indigenously designed and constructed THGEM-based microdosimeter for dose-equivalent measurement |
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| Affiliation: | 1. Radiation Applications Research School, Nuclear Science and Technology Research Institute, AEOI, P.O.Box: 11365-3486, Tehran, Iran;2. Physics and Accelerators Research School, Nuclear Science and Technology Research Institute, AEOI, P.O.Box: 11365-3486, Tehran, Iran;1. Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Spain;2. Servicio de Radiofísica, Hospital Universitario Virgen Macarena, Sevilla, Spain;3. Politecnico di Milano, Dipartimento di Ingegneria Nuclear, Milano, Italy;4. Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare (INFN), Italy;5. Instituto de Física, Pontificia Universidad Católica de Chile, Santiago, Chile;6. Departamento de Física de Partículas, Universidad de Santiago, Spain;1. Departamento de Fisiología Médica y Biofísica, Universidad de Sevilla, Spain;2. Servicio de Radiofísica, Hospital Universitario Virgen Macarena, Sevilla, Spain;3. Politecnico di Milano, Dipartimento di Ingegneria Nuclear, Milano, Italy;4. Laboratori Nazionali di Frascati, Istituto Nazionale di Fisica Nucleare (INFN), Italy;5. Instituto de Física, Pontificia Universidad Católica de Chile, Santiago, Chile;1. Czech Metrology Institute, Okružní 31, 638 00, Brno, Czech Republic;2. Proton Therapy Center Praha, Budínova 1a, 180 00, Praha 8, Czech Republic;1. School of Physics (A28), The University of Sydney, NSW 2006, Australia;2. West German Proton Therapy Centre Essen, Hufeland Straße 55, D-45147 Essen, Germany;1. Department of Medical Imaging and Radiological Sciences, College of Medicine, Chang Gung University, Kweishan Taoyuan 333, Taiwan;2. Institute for Radiological Research, Chang Gung University/Chang Gung Memorial Hospital at Linkou, Kweishan Taoyuan 333, Taiwan;3. Proton and Radiation Therapy Center, Chang Gung Memorial Hospital at Linkou, Kweishan Taoyuan 333, Taiwan |
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| Abstract: | Most of the GEM/THGEM-based microdosimetric detectors presented in the literature simulate 2 μm of tissue which results in a flat neutron dose-equivalent response in the MeV region. The objective of this work was to introduce a neutron microdosimeter with a more extended flat response. In this regard, a THGEM-based microdosimeter with plexiglas walls, simulating 1 μm of tissue was designed and constructed. Its performance was investigated by both simulation and experimentation to determine the microdosimetric quantity of “lineal energy”.In the simulation study, lineal energy distribution, mean quality factor and dose-equivalent response of the microdosimeter for eleven neutron energies from 10 keV to 14 MeV, along with the energy spectrum of 241Am-Be neutrons, were calculated by the Geant4 simulation toolkit. Obtained lineal energy distributions were compatible with the distributions determined by a Rossi counter. Also, the mean quality factors agreed well with the values reported by the ICRU report 40 which confirmed tissue equivalent behavior of the microdosimeter. They were different from the effective quality factor values within 15% between 20 keV and 14 MeV. This led to a flat dose-equivalent response with 20% difference from a median value of 0.82 in the above energy range which was an improvement compared with other THGEM-based detectors, simulating 2 μm of tissue. In spite of the satisfactory determination of the dose-equivalent, the microdosimeter had low detection sensitivity.In the experimental study, the measured lineal energy distribution of 241Am-Be neutrons was in agreement with the simulated distribution. Further, the measured mean quality factor and dose-equivalent differed by 1.5% and 3.5%, respectively, from the calculated values. Finally, it could be concluded that the investigated microdosimeter reliably determined the desired dose-equivalent value of each neutron field with every energy spectrum lying between 20 keV and 14 MeV. |
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| Keywords: | Dose-equivalent response Geant4 toolkit Neutron THGEM-based microdosimeter Wide energy spectrum |
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