The detection efficiency of a gamma ray detector should be calibrated prior to the measurement of activity in samples. The aim of this research is to develop a simple experimental technique to calibrate the efficiency of detectors for geometrical sources by replicating their responses from virtually equivalent sources (VES) constructed from a collection of Standard Point Source (SPS) measurements. Experiments were performed to replicate the response of a disk source of 5.2 cm radius by equivalent disk sources (EDS) reconstructed from a collection of 19, 91 and 169 SPS measurements to optimize the number of measurements, response of detector for radially symmetric SPS locations was verified through Absolute Peak Efficiency (APE) calculations. APE was calculated experimentally for the actual disk source and EDS as well as using EGS5 simulations. The difference between experimentally measured and simulated APE for 5.2 cm EDS was observed to be about 7.8 %, 5.2 % and 5.4 % for 137Cs and about -1.3 %, 1.3 % and 2.7 % for 22Na for the EDS constructed from 19, 91- and 169 SPS measurements respectively
Polymer matrix composite (PMCs) materials developed by room temperature vulcanization having various compositions i.e. 0, 30.1, 47.8, 59.8, 68.1 and 88.1 wt. % of tungsten incorporated in silicon rubber matrix were investigated using EGS5 Monte Carlo Code. Narrow beam geometry similar to experimental setup was modeled and validated for Monte Carlo simulation by making a comparison with standard XCOM (NIST) results. Gamma-ray shielding features of all composite materials were studied for several photon energies (122, 511, 662, 837, 1173, 1332 and 1811 keV) and compared with the XCOM and previously reported experimental results. Monte Carlo simulation results were in high accordance with the previous experimental study at gamma ray energy of 662 keV and maximum deviation was observed to be around 10 %. Thus, it can be concluded that this method is suitable for predicting the shielding characteristics of different materials. Additionally, mass attenuation coefficients (μ/ρ), mean free path (MFP), half-value layer (HVL), tenth value layer (TVL) were determined and effective atomic numbers (Zeff) is calculated using Power law for all PMCs. PMCs with tungsten loading above 68% showed mass attenuation coefficients greater than lead with additional feature of flexibility which makes them promising candidate in radiation shielding. In addition, these silicon/tungsten composites having 68 and 88 % of tungsten are 3.6 and 1.7 times lighter than lead respectively.
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