Shahryar Malekie; Seyed Musa Safdari; Sedigheh Kashian; Morteza Akbari
Abstract
Polycarbonate-bismuth oxide composite has been used as a beta-ray sensor in the previous works. Calculation of two main quantities namely stopping power and range of electrons in this material can be useful to evaluate the optimal thickness of the sensor. Thus, in this study, the range of electrons and ...
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Polycarbonate-bismuth oxide composite has been used as a beta-ray sensor in the previous works. Calculation of two main quantities namely stopping power and range of electrons in this material can be useful to evaluate the optimal thickness of the sensor. Thus, in this study, the range of electrons and stopping power of polycarbonate/bismuth oxide composite for several pure beta-emitters were estimated using the ESTAR program. Simulation findings indicated that the amount of concentration of the heavy metal oxide particles into the composite is an important factor to determine the range and stopping power of the electrons. Also, in the experimental phase, the response of the 50 wt% nanocomposite with thickness of 1 mm against the beta-rays of the P-32 source at the average energy of 695 keV in different activities was measured using an electrometer at a constant voltage of 800 V. Results showed that the response of the sample ranging from 4 to 6 mCi was linear with R2= 0.9757.
Shahryar Malekie; Sedigheh Kashian; Seyed Musa Safdari; Morteza Akbari; Arjang Shahvar
Abstract
In this experimental work, Polycarbonate/Bismuth Oxide (PC-Bi2O3) nanocomposites were prepared in various concentrations of 0, 10, 30, and 50 wt% with thicknesses of 1 mm and irradiated by a pure beta-emitter source of Sr-90. To fabricate the electrodes, copper sheets with thickness of 100 µm were ...
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In this experimental work, Polycarbonate/Bismuth Oxide (PC-Bi2O3) nanocomposites were prepared in various concentrations of 0, 10, 30, and 50 wt% with thicknesses of 1 mm and irradiated by a pure beta-emitter source of Sr-90. To fabricate the electrodes, copper sheets with thickness of 100 µm were attached to the top and bottom surfaces of the samples using the silver paste. Then, electric current as the dosimetry response, was measured at various dose rates ranging from 30-102 mSv.h-1 at a fixed voltage of 400 V using an electrometer. Results showed that increasing the Bi2O3 wt% led to improvement in the dosimetry response linearly at various dose rates. Also, the amounts of sensitivities for the samples of 0, 10, 30, and 50 wt% were measured as 20.3, 19.8, 28.6, and 36.7 nC.mSv-1.cm-3, respectively. Regarding the mechanism of beta interaction with a polymer-heavy metal oxide nanocomposite, the Bremsstrahlung radiation can be considered as a dominant effect.
Amir Veiskarami; Mahdi Sadeghi; Dariush Sardari; Shahryar Malekie
Abstract
Collision of protons with background gas and beamline wall in proton therapy causes the creation of secondary particles, e.g. neutrons, which results in more difficulties in curing the tumors. In the present simulation-based study, the optimum diameter of ...
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Collision of protons with background gas and beamline wall in proton therapy causes the creation of secondary particles, e.g. neutrons, which results in more difficulties in curing the tumors. In the present simulation-based study, the optimum diameter of proton beamline was determined to minimize the production of secondary particles in the presence of electric field with the magnitude of 50 kV/m, perpendicular equal magnetic fields of 0.7 T, and background gas of argon under Bounce boundary conditions via finite element method. The results showed that the optimum diameter of the beamline for minimization of the secondary particles in the spot scanning proton therapy in the aforementioned conditions was 7 mm. Also, the values of drift velocities of protons were plotted in different time steps of 10 ns to 50 ns for the optimized size of the beamline. Due to few interactions of forwarding particles with background gas, the results showed that the forwarding particles in the propagation direction have greater velocities than those of rear particles. The results can be used in spot scanning proton therapy for curing the localized cancers.
