A minitype reference radiation(MRR) with dimensions of only 1 m × 1 m × 1 m has been developed for the in situ calibration of photon dosimeters.The present work conducts a feasibility study on determining th...A minitype reference radiation(MRR) with dimensions of only 1 m × 1 m × 1 m has been developed for the in situ calibration of photon dosimeters.The present work conducts a feasibility study on determining the conventional true value of gamma-ray air kerma at the point of test in the MRR.Owing to its smaller dimensions,the scattered gamma-rays in the MRR are expected to induce a non-negligible interference with the radiation field compared with conditions in the standard reference radiation stipulated by ISO4037-1 or GB/T12162.1.A gamma-ray spectrometer was employed to obtain the spectra of scattered gamma-rays within the MRR,and the feature components of the spectra were extracted by principal component analysis to characterize the interference of a dosimeter probe in the radiation field.A prediction model of the CAK at the point of test was built by least squares support vector machine based on the feature component data obtained from nine sample dosimeters under five different dose rates.The mean prediction error of the CAK prediction model was within ±4.5%,and the maximum prediction error was about ±10%.展开更多
The quantification of ionizing energy deposition and non-ionizing energy deposition plays a critical role in precision neutron dosimetry and in the separation of the displacement damage effects and ionizing effects in...The quantification of ionizing energy deposition and non-ionizing energy deposition plays a critical role in precision neutron dosimetry and in the separation of the displacement damage effects and ionizing effects induced by neutron radiation on semiconductor devices. In this report, neutrons generated by the newly built China Spallation Neutron Source (CSNS) are simulated by Geant4 in semiconductor material silicon to calculate the ionizing and non-ionizing kerma factors. Furthermore, the integral method is applied to calculate neutron-induced ionizing at the CSNS and non-ionizing kerma factors according to the standard neutron nuclear database and the incident neutron spectrum. In addition, thermoluminescence dosimeters are utilized to measure the ionizing energy deposition and six series of bipolar junction transistors are used to measure the non-ionizing energy deposition based on their neutron damage constants. The calibrated kerma factors that were experimentally measured agreed well with the simulation and integral calculation results. This report describes a complete set of methods and fundamental data for the analysis of neutron-induced radiation effects at the CSNS on silicon-based semiconductor devices.展开更多
Since the room-temperature detector CdZnTe(CZT) has advantages in terms of detection efficiency,energy resolution, and size, it has been extensively used to detect X-rays and gamma-rays. So far, nuclear radiation dete...Since the room-temperature detector CdZnTe(CZT) has advantages in terms of detection efficiency,energy resolution, and size, it has been extensively used to detect X-rays and gamma-rays. So far, nuclear radiation detectors such as cerium chloride doped with lanthanum bromide(LaBr_3(Ce)), thallium doped with cesium iodide(sI(Tl)), thallium doped with sodium iodide(NaI(Tl)),and high-purity germanium(HPGe) primarily use the spectroscopy-dose rate function(G(E)) to achieve the accurate measurement of air kerma rate(K_a) and ambient dose equivalent rate(H*(10)). However, the spectroscopy-dose rate function has been rarely measured for a CZT detector. In this study, we performed spectrum measurement using a hemispherical CZT detector in a radiation protection standards laboratory. The spectroscopy-dose rate function G(E) of the CZT detector was calculated using the least-squares method combined with the standard dose rate at the measurement position. The results showed that the hemispherical CZT detector could complete the measurement of air kerma rate(K_a) and ambient dose equivalent rate(H*(10)) by using the G(E) function at energies between 48 keV and 1.25 MeV, and the relative intrinsic errors were, respectively, controlled within ± 2. 3 and ± 2. 1%.展开更多
The air-kerma is one of the most important physical quantities in ionizing radiation dosimetry. The measurement of airkerma rate in narrow-spectrum series is the basis to determine the radiation dose at protection lev...The air-kerma is one of the most important physical quantities in ionizing radiation dosimetry. The measurement of airkerma rate in narrow-spectrum series is the basis to determine the radiation dose at protection level. In this article, the absolute measurement method is used to derive the standard air-kerma rate of the ISO 4037 narrow-spectrum series that ranges from 60 kV to 150 kV by a primary standard ionization chamber,it is used in direct comparison for air kerma. The indirect method is used to obtain the air-kerma rate by a secondary standard transfer ionization chamber named A5 chamber with calibration factors of the corresponding reference qualities. The results are very similar comparing between absolute and indirect methods for air-kerma rate, all the differences are within ±3.3%.展开更多
Mammography x-rays standard is required to improve the quality of mammary machine and reduce the dose for w omen and staff. The molybdenum target x-rays machine is used as the radiation source and free-air cylindrical...Mammography x-rays standard is required to improve the quality of mammary machine and reduce the dose for w omen and staff. The molybdenum target x-rays machine is used as the radiation source and free-air cylindrical chamber is designed for detecting photon. Four standard radiation qualities are established w ith international standard documents as references. The Correction factors including air attenuation,scattered radiation,fluorescence,w all transmission,electron loss are studied in the four radiation quality. The uncertainty in absolute measurement of air-kerma includes air volume measurement of ionization chambers,current measurement,measurement of temperature and pressure,measurement of correction factors,physical constants and orientation of the reference distance. The relative combined standard uncertainty is 0.24%.展开更多
On the basis of the light nuclear reaction model, a new kerma coefficient formula has been developed. In terms of the analysis for n＋^16O reactions below 30 MeV, the average energies of all kinds of the emitted parti...On the basis of the light nuclear reaction model, a new kerma coefficient formula has been developed. In terms of the analysis for n＋^16O reactions below 30 MeV, the average energies of all kinds of the emitted particles are presented. The calculated partial kerma coefficients agree well with the existing experimental data. The discrepancies of the total kerma coefficients between the calculation and the measurement are analyzed in detail.展开更多
文摘A minitype reference radiation(MRR) with dimensions of only 1 m × 1 m × 1 m has been developed for the in situ calibration of photon dosimeters.The present work conducts a feasibility study on determining the conventional true value of gamma-ray air kerma at the point of test in the MRR.Owing to its smaller dimensions,the scattered gamma-rays in the MRR are expected to induce a non-negligible interference with the radiation field compared with conditions in the standard reference radiation stipulated by ISO4037-1 or GB/T12162.1.A gamma-ray spectrometer was employed to obtain the spectra of scattered gamma-rays within the MRR,and the feature components of the spectra were extracted by principal component analysis to characterize the interference of a dosimeter probe in the radiation field.A prediction model of the CAK at the point of test was built by least squares support vector machine based on the feature component data obtained from nine sample dosimeters under five different dose rates.The mean prediction error of the CAK prediction model was within ±4.5%,and the maximum prediction error was about ±10%.
基金supported by the National Natural Science Foundation of China(Nos.11690040 and 11690043)the Foundation of State Key Laboratory of China(Nos.SKLIPR1801Z and 6142802180304)
文摘The quantification of ionizing energy deposition and non-ionizing energy deposition plays a critical role in precision neutron dosimetry and in the separation of the displacement damage effects and ionizing effects induced by neutron radiation on semiconductor devices. In this report, neutrons generated by the newly built China Spallation Neutron Source (CSNS) are simulated by Geant4 in semiconductor material silicon to calculate the ionizing and non-ionizing kerma factors. Furthermore, the integral method is applied to calculate neutron-induced ionizing at the CSNS and non-ionizing kerma factors according to the standard neutron nuclear database and the incident neutron spectrum. In addition, thermoluminescence dosimeters are utilized to measure the ionizing energy deposition and six series of bipolar junction transistors are used to measure the non-ionizing energy deposition based on their neutron damage constants. The calibrated kerma factors that were experimentally measured agreed well with the simulation and integral calculation results. This report describes a complete set of methods and fundamental data for the analysis of neutron-induced radiation effects at the CSNS on silicon-based semiconductor devices.
基金supported by the National Key Scientific Instruments to Develop Dedicated(Nos.2013YQ090811 and 2016YFF0103800)
文摘Since the room-temperature detector CdZnTe(CZT) has advantages in terms of detection efficiency,energy resolution, and size, it has been extensively used to detect X-rays and gamma-rays. So far, nuclear radiation detectors such as cerium chloride doped with lanthanum bromide(LaBr_3(Ce)), thallium doped with cesium iodide(sI(Tl)), thallium doped with sodium iodide(NaI(Tl)),and high-purity germanium(HPGe) primarily use the spectroscopy-dose rate function(G(E)) to achieve the accurate measurement of air kerma rate(K_a) and ambient dose equivalent rate(H*(10)). However, the spectroscopy-dose rate function has been rarely measured for a CZT detector. In this study, we performed spectrum measurement using a hemispherical CZT detector in a radiation protection standards laboratory. The spectroscopy-dose rate function G(E) of the CZT detector was calculated using the least-squares method combined with the standard dose rate at the measurement position. The results showed that the hemispherical CZT detector could complete the measurement of air kerma rate(K_a) and ambient dose equivalent rate(H*(10)) by using the G(E) function at energies between 48 keV and 1.25 MeV, and the relative intrinsic errors were, respectively, controlled within ± 2. 3 and ± 2. 1%.
文摘The air-kerma is one of the most important physical quantities in ionizing radiation dosimetry. The measurement of airkerma rate in narrow-spectrum series is the basis to determine the radiation dose at protection level. In this article, the absolute measurement method is used to derive the standard air-kerma rate of the ISO 4037 narrow-spectrum series that ranges from 60 kV to 150 kV by a primary standard ionization chamber,it is used in direct comparison for air kerma. The indirect method is used to obtain the air-kerma rate by a secondary standard transfer ionization chamber named A5 chamber with calibration factors of the corresponding reference qualities. The results are very similar comparing between absolute and indirect methods for air-kerma rate, all the differences are within ±3.3%.
文摘Mammography x-rays standard is required to improve the quality of mammary machine and reduce the dose for w omen and staff. The molybdenum target x-rays machine is used as the radiation source and free-air cylindrical chamber is designed for detecting photon. Four standard radiation qualities are established w ith international standard documents as references. The Correction factors including air attenuation,scattered radiation,fluorescence,w all transmission,electron loss are studied in the four radiation quality. The uncertainty in absolute measurement of air-kerma includes air volume measurement of ionization chambers,current measurement,measurement of temperature and pressure,measurement of correction factors,physical constants and orientation of the reference distance. The relative combined standard uncertainty is 0.24%.
基金Supported by National Natural Science Foundation of China (10547005)
文摘On the basis of the light nuclear reaction model, a new kerma coefficient formula has been developed. In terms of the analysis for n＋^16O reactions below 30 MeV, the average energies of all kinds of the emitted particles are presented. The calculated partial kerma coefficients agree well with the existing experimental data. The discrepancies of the total kerma coefficients between the calculation and the measurement are analyzed in detail.
