Considering the significance of low-energy electrons(LEEs;0–20 eV) in radiobiology, the sensitization potential of gold nanoparticles(AuNPs) as high-flux LEE emitters when irradiated with sub-keV electrons has been s...Considering the significance of low-energy electrons(LEEs;0–20 eV) in radiobiology, the sensitization potential of gold nanoparticles(AuNPs) as high-flux LEE emitters when irradiated with sub-keV electrons has been suggested. In this study, a track-structure Monte Carlo simulation code using the dielectric theory was developed to simulate the transport of electrons below 50 keV in gold. In this code, modifications, particularly for elastic scattering, are implemented for a more precise description of the LEE emission in secondary electron emission. This code was validated using the secondary electron yield and backscattering coefficient. To ensure dosimetry accuracy, we further verified the code for energy deposition calculations using the Monte Carlo toolkit, Geant4. The development of this code provides a basis for future studies regarding the role of AuNPs in targeted radionuclide radiotherapy.展开更多
In this research, different parameters of plastic scintillator detector were investigated by Geant4 simulation toolkit. These parameters consisted of radius, length and position of PMT as well as surface reflective ty...In this research, different parameters of plastic scintillator detector were investigated by Geant4 simulation toolkit. These parameters consisted of radius, length and position of PMT as well as surface reflective type and finish options. Furthermore, response time distributions of two organic plastic materials were studied. The results indicated that collecting optical photons has a linear relationship with PMT radius head. Also, the vertical location of PMT has a non-linear relationship with the optical photons collection. However, the collection decreased by increasing PMT length or moving PMT head horizontal position. The response functions of two plastic scintillator materials were in good agreement with experimental published results. Also, Geant4 radiation transport code can simulate incident radiation photon and predict subsequent events to the PMT head very well. The results indicated that BC-404 has faster scintillation properties versus BC-400 organic scintillator materials. Comparison between Geant4 outputs illustrates that the best reflector material and surface finish type for optical photons is ground TiO2.展开更多
This paper shows the calculations of radioactivity and afterheat in the components of the China Spallation Neutron Source （CSNS） target station, with the Monte Carlo codes LAHET, MCNP4C and the multigroup code CINDE...This paper shows the calculations of radioactivity and afterheat in the components of the China Spallation Neutron Source （CSNS） target station, with the Monte Carlo codes LAHET, MCNP4C and the multigroup code CINDER＇90. These calculations provide essential data for the detailed design and maintenance of the CSNS target station.展开更多
In order to calculate the electron energy distribution in the fuel rod gap of a VVER- 1000 nuclear reactor, the Fokker-Planck equation （FPE） governing the non-equilibrium behavior of electrons passing through the fu...In order to calculate the electron energy distribution in the fuel rod gap of a VVER- 1000 nuclear reactor, the Fokker-Planck equation （FPE） governing the non-equilibrium behavior of electrons passing through the fuel-rod gap as an absorber has been solved in this paper. Besides, the Monte Carlo Geant4 code was employed to simulate the electron migration in the fuel-rod gap and the energy distribution of electrons was found. As for the results, the accuracy of the FPE was compared to the Geant4 code outcomes and a satisfactory agreement was found. Also, different percentage of the volatile and noble gas fission fragments produced in fission reactions in fuel rod, i.e. Krypton, Xenon, Iodine, Bromine, Rubidium and Cesium were employed so as to investigate their effects on the electrons＇ energy distribution. The present results show that most of the electrons in the fuel rod＇s gap were within the thermal energy limitation and the tail of the electron energy distribution was far from a Maxwellian distribution. The interesting outcome was that the electron energy distribution is slightly increased due to the accumulation of fission fragments in the gap. It should be noted that solving the FPE for the energy straggling electrons that are penetrating into the fuel-rod gap in the VVER-1000 nuclear reactor has been carried out for the first time using an analytical approach.展开更多
Purpose The Astro Bio Cube Sat(ABCS)was successfully deployed in its circular orbit at an altitude of 5850 km in the Van Allen Belt.Besides the primary mission of validating the analytical platform hosted in the paylo...Purpose The Astro Bio Cube Sat(ABCS)was successfully deployed in its circular orbit at an altitude of 5850 km in the Van Allen Belt.Besides the primary mission of validating the analytical platform hosted in the payload in such a harsh radiation environment,we used the telemetry data related to the dosimetry readings transmitted during the active mission period to back-validate the satellite’s radiation transport model,which was already used for the payload shielding design.Methods The radiation transport model was implemented with the high-energy Monte Carlo transport code FLUKA,and the definition of the orbital radiation sources were calculated using the SPENVIS code.In the actual work,the orbital radiation sources were defined at the mission epoch using SPENVIS and IRENE codes.In the FLUKA model,we implemented the dosimeters and further payload components,such as a battery pack and pump,which could furnish further shielding.The simulations executed with this upgraded model estimate the average dose rate measured during the mission period.To quantify the model validity,we compare the simulated dose rate with the one derived by fitting the telemetric integral dose data transmitted during the mission,finding a good agreement.An analysis of uncertainties and some consideration of space weather conditions are also considered to explain the agreement.Conclusion Based on the measured dose rate,the payload shielding was satisfactory.The agreement between the calculated and measured dose rates confirms the adequateness of the Monte Carlo model.Further work will be devoted to applying biasing techniques to speed up the simulation time.展开更多
To estimate the physical dose of skin and key organs in a case of overexposure during a cardiac interventional procedure.Methods The female patient aged 50 suffered from owerexposure during ardiac interventional thera...To estimate the physical dose of skin and key organs in a case of overexposure during a cardiac interventional procedure.Methods The female patient aged 50 suffered from owerexposure during ardiac interventional therapy in a hospital,Xinxiang city,Henan province,China in January 2020.The mesh-type phantom for the patient was constructed based on the adult mesh-type reference computational phantoms(MRCPs)released by the International Comission on Radiological Protection Publication 145 (ICRP145)and phantom deformation technology.Models of exposure scenario were constructed and simulated with particle and heavy ion transport code system(PHTTS)according to exposure conditions.Resuts:The maximum absorbed dose of key organs/tissues under iradiation in posteroanterior(PA)and 30°left anterior oblique directions(LOA)was 632.4 and 305.6 mGy,respectively.The let lung,heart,and left mammary gland received a larger dose under both iradiation conditions.The ratio of the absorbed dose with and without shielding was a lculated,and the relative difference in most organs was<1%between two directions.The iso-dose curve of the back skin revealed the ditribution of the absorbed dose(0.1-5.2 Gy).The dose estimate of key tssues/organs was higher than the conventional level,especially the local skin,up to 5.2 Gy.Concusions The interventional procedure in this ase resulted in a higher dose.Monte Carlo codes combined with the MRCPs can be employed to estimate physical dose to individuals in concrete irradia tion scenarios.展开更多
One of the significant characteristics of the sky is the polarization of light,which is formed through the multi-scattering process of atmospheric molecules,aerosols and earth's surface,and thus contains informati...One of the significant characteristics of the sky is the polarization of light,which is formed through the multi-scattering process of atmospheric molecules,aerosols and earth's surface,and thus contains information on these three factors.It has recently been paid more attentions to retrieve the characteristic parameters of the aerosol and surface of the earth from the skylight polarization information.Observation of the skylight polarization over Beijing has been conducted with a multi-wavelength polarimeter developed by LAGEO(Laboratory for Middle Atmosphere and Global Environment Observation),IAP(Institute of Atmospheric Physics)since November 1995.With these observation data,both the seasonal variations of the maximum degree of polarization of the skylight and the effect of the surface situation are studied in this paper.A Monte Carlo code for the vector radiative transfer calculation is used to simulate and compare with observation.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 12004180, 21906083, 11975122, and 22006067)the Natural Science Foundation of Jiangsu Province (No. BK20190384)the Fundamental Research Funds for the Central Universities (Nos. NE2020006, NS2022095)。
文摘Considering the significance of low-energy electrons(LEEs;0–20 eV) in radiobiology, the sensitization potential of gold nanoparticles(AuNPs) as high-flux LEE emitters when irradiated with sub-keV electrons has been suggested. In this study, a track-structure Monte Carlo simulation code using the dielectric theory was developed to simulate the transport of electrons below 50 keV in gold. In this code, modifications, particularly for elastic scattering, are implemented for a more precise description of the LEE emission in secondary electron emission. This code was validated using the secondary electron yield and backscattering coefficient. To ensure dosimetry accuracy, we further verified the code for energy deposition calculations using the Monte Carlo toolkit, Geant4. The development of this code provides a basis for future studies regarding the role of AuNPs in targeted radionuclide radiotherapy.
文摘In this research, different parameters of plastic scintillator detector were investigated by Geant4 simulation toolkit. These parameters consisted of radius, length and position of PMT as well as surface reflective type and finish options. Furthermore, response time distributions of two organic plastic materials were studied. The results indicated that collecting optical photons has a linear relationship with PMT radius head. Also, the vertical location of PMT has a non-linear relationship with the optical photons collection. However, the collection decreased by increasing PMT length or moving PMT head horizontal position. The response functions of two plastic scintillator materials were in good agreement with experimental published results. Also, Geant4 radiation transport code can simulate incident radiation photon and predict subsequent events to the PMT head very well. The results indicated that BC-404 has faster scintillation properties versus BC-400 organic scintillator materials. Comparison between Geant4 outputs illustrates that the best reflector material and surface finish type for optical photons is ground TiO2.
文摘This paper shows the calculations of radioactivity and afterheat in the components of the China Spallation Neutron Source （CSNS） target station, with the Monte Carlo codes LAHET, MCNP4C and the multigroup code CINDER＇90. These calculations provide essential data for the detailed design and maintenance of the CSNS target station.
文摘In order to calculate the electron energy distribution in the fuel rod gap of a VVER- 1000 nuclear reactor, the Fokker-Planck equation （FPE） governing the non-equilibrium behavior of electrons passing through the fuel-rod gap as an absorber has been solved in this paper. Besides, the Monte Carlo Geant4 code was employed to simulate the electron migration in the fuel-rod gap and the energy distribution of electrons was found. As for the results, the accuracy of the FPE was compared to the Geant4 code outcomes and a satisfactory agreement was found. Also, different percentage of the volatile and noble gas fission fragments produced in fission reactions in fuel rod, i.e. Krypton, Xenon, Iodine, Bromine, Rubidium and Cesium were employed so as to investigate their effects on the electrons＇ energy distribution. The present results show that most of the electrons in the fuel rod＇s gap were within the thermal energy limitation and the tail of the electron energy distribution was far from a Maxwellian distribution. The interesting outcome was that the electron energy distribution is slightly increased due to the accumulation of fission fragments in the gap. It should be noted that solving the FPE for the energy straggling electrons that are penetrating into the fuel-rod gap in the VVER-1000 nuclear reactor has been carried out for the first time using an analytical approach.
基金supported by ASI/INAF agreement no.2019-30-HH.0。
文摘Purpose The Astro Bio Cube Sat(ABCS)was successfully deployed in its circular orbit at an altitude of 5850 km in the Van Allen Belt.Besides the primary mission of validating the analytical platform hosted in the payload in such a harsh radiation environment,we used the telemetry data related to the dosimetry readings transmitted during the active mission period to back-validate the satellite’s radiation transport model,which was already used for the payload shielding design.Methods The radiation transport model was implemented with the high-energy Monte Carlo transport code FLUKA,and the definition of the orbital radiation sources were calculated using the SPENVIS code.In the actual work,the orbital radiation sources were defined at the mission epoch using SPENVIS and IRENE codes.In the FLUKA model,we implemented the dosimeters and further payload components,such as a battery pack and pump,which could furnish further shielding.The simulations executed with this upgraded model estimate the average dose rate measured during the mission period.To quantify the model validity,we compare the simulated dose rate with the one derived by fitting the telemetric integral dose data transmitted during the mission,finding a good agreement.An analysis of uncertainties and some consideration of space weather conditions are also considered to explain the agreement.Conclusion Based on the measured dose rate,the payload shielding was satisfactory.The agreement between the calculated and measured dose rates confirms the adequateness of the Monte Carlo model.Further work will be devoted to applying biasing techniques to speed up the simulation time.
基金National Natural Science Foundation of China(No.12105200,12175161,U186720)Collaborative Innovation Center of Radiological Medicine of Jiangsu Higher Education Institutions+1 种基金Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD),ChinaNuclear Energy Development Project,China(No.2016-1295).
文摘To estimate the physical dose of skin and key organs in a case of overexposure during a cardiac interventional procedure.Methods The female patient aged 50 suffered from owerexposure during ardiac interventional therapy in a hospital,Xinxiang city,Henan province,China in January 2020.The mesh-type phantom for the patient was constructed based on the adult mesh-type reference computational phantoms(MRCPs)released by the International Comission on Radiological Protection Publication 145 (ICRP145)and phantom deformation technology.Models of exposure scenario were constructed and simulated with particle and heavy ion transport code system(PHTTS)according to exposure conditions.Resuts:The maximum absorbed dose of key organs/tissues under iradiation in posteroanterior(PA)and 30°left anterior oblique directions(LOA)was 632.4 and 305.6 mGy,respectively.The let lung,heart,and left mammary gland received a larger dose under both iradiation conditions.The ratio of the absorbed dose with and without shielding was a lculated,and the relative difference in most organs was<1%between two directions.The iso-dose curve of the back skin revealed the ditribution of the absorbed dose(0.1-5.2 Gy).The dose estimate of key tssues/organs was higher than the conventional level,especially the local skin,up to 5.2 Gy.Concusions The interventional procedure in this ase resulted in a higher dose.Monte Carlo codes combined with the MRCPs can be employed to estimate physical dose to individuals in concrete irradia tion scenarios.
文摘One of the significant characteristics of the sky is the polarization of light,which is formed through the multi-scattering process of atmospheric molecules,aerosols and earth's surface,and thus contains information on these three factors.It has recently been paid more attentions to retrieve the characteristic parameters of the aerosol and surface of the earth from the skylight polarization information.Observation of the skylight polarization over Beijing has been conducted with a multi-wavelength polarimeter developed by LAGEO(Laboratory for Middle Atmosphere and Global Environment Observation),IAP(Institute of Atmospheric Physics)since November 1995.With these observation data,both the seasonal variations of the maximum degree of polarization of the skylight and the effect of the surface situation are studied in this paper.A Monte Carlo code for the vector radiative transfer calculation is used to simulate and compare with observation.
