首页|Study on decreasing the systematic deviation of perturbation for the absorbed dose in <sup>60</sup>Co γ radiation measured with water calorimeter
Study on decreasing the systematic deviation of perturbation for the absorbed dose in <sup>60</sup>Co γ radiation measured with water calorimeter
Jin, Dr. Sunjun Wang, Dr. Zhipeng da Silva, Dr. Tiago Fiorini Wang, Mr. Ji Wang, Dr. Pingquan Li, Dr. Mengfei He, Dr. Mingzhao Qi, Dr. Yaping Huang, Dr. Ji Zhang, Prof. Hui Wang, Dr. Kun
Study on decreasing the systematic deviation of perturbation for the absorbed dose in <sup>60</sup>Co γ radiation measured with water calorimeter
Study on decreasing the systematic deviation of perturbation for the absorbed dose in <sup>60</sup>Co γ radiation measured with water calorimeter
摘要
The medium involved in the particle transport is decisive to the properties of energy spectrum, which is then the foundation for all the measurements arisen by energy transfer. The properties of 60Co γ energy spectrum in water are crucial to clarify the accurate absorbed dose in this medium of biological significance. The energy spectrum from the relevant 60Co source features high-emitting rate(e.g. 108 cm−2·s−1·sr−1), which is several orders of magnitude larger than the capability of available systems for detection. To this end, Monte Carlo simulations were performed through comprehensively constructing the components interact with the photons starting from the 60Co source region. It is found that the 60Co γ energy spectrum demonstrates sophisticated behavior even in homogeneous water, the lowenergy photons below 0.2MeV are increased obviously due to the multiple scattering as the photons going deeper in water. The perturbation from the non-water materials, such as the thin quartz wall, that being assembled into the vessel for water calorimetry measurement, is likely to be overestimated up to 0.35%, if it is evaluated by a traditional ionization chamber, which neglects the influences from the low-energy photon events being stopped in the chamber wall. Meanwhile, the convergence of the results from different vessels will be deteriorated from 0.18% to 0.24%. When it comes to the water calorimetric measurement, the interactions between photons and mediums are crucial to determine the perturbation from non-water materials. Consequently, Monte Carlo simulations incorporating the particle transport can be an optimal solution, which allows the detailed analyses to be performed by exploring the spectral properties due to interactions and converges the results from 0.18% to 0.15%, decreasing the deviation of measured absorbed dose from the real value by 0.35%, which is almost the uncertainty level of conventional water calorimetric measurement.