A Monte Carlo method to study the response of portable detector to terrestrial gamma ray is proposed. This method is based on two-stage Monte Carlo simulation.First, the probability distributions of the phase space co...A Monte Carlo method to study the response of portable detector to terrestrial gamma ray is proposed. This method is based on two-stage Monte Carlo simulation.First, the probability distributions of the phase space coordinates of the events that are most likely to be detected are reconstructed at the phase space shell level. The phase space shell is a closed surface enclosing the detector. The detector response to events originating from the phase space shell is then studied. The full absorption spectra as well as the partial absorption spectra are obtained for natural radionuclides uniformly distributed in the ground. For validation, this method is applied to a Hp Ge portable detector previously studied. The previous study is based on a semiempirical model. Good agreement is achieved when we compare the full-energy peak efficiencies and the total in situ spectra obtained by the two methods. As an application, the effective depth of the activity of the^(137) Cs artificial radionuclide in the soil is determined from the low-energy part of the total in situ spectrum.展开更多
To develop a NaI （T1） detector for in situ radioactivity monitoring in the marine environment and enhance the confidence of the probability of the gamma-spectrum analysis, Monte Carlo simulations using the Monte Car...To develop a NaI （T1） detector for in situ radioactivity monitoring in the marine environment and enhance the confidence of the probability of the gamma-spectrum analysis, Monte Carlo simulations using the Monte Carlo N-Particle （ MNCP ） code were performed to provide the response spectra of some interested radionuclides and the background spectra originating from the natural radionuclides in seawater recorded by a NaI （T1） detector. A newly developed 75 mm × 75 mm NaI （T1） detector was calibrated using four reference radioactive sources 137Cs, 60Co, 40K and 54Mn in the laboratory before the field measurements in seawater. A simulation model was established for the detector immersed in seawater. The simulated spectra were all broadened with Gaussian pulses to reflect the statistical fluctuations and electrical noise in the real measurement. The simulated spectra show that the single-energy photons into the detector are mostly scattering low-energy photons and the high background in the low energy region mainly originates from the Compton effect of the high energy y-rays of natural radionuclides in seawater. The simulated background spectrum was compared with the experimental one recorded in field measurement and they seem to be in good agreement. The simulation method and spectra can be used for the accurate analysis of the filed measurement results of low concentration radioactivity in seawater.展开更多
A newly designed vacuum Compton gamma-ray detector with Ta-Al clad-metal electron converter plate is described. The detecting efficiency for 1.25 MeV gamma-ray is 7.85×10-3 electron/γ,which is 2.5 times higher t...A newly designed vacuum Compton gamma-ray detector with Ta-Al clad-metal electron converter plate is described. The detecting efficiency for 1.25 MeV gamma-ray is 7.85×10-3 electron/γ,which is 2.5 times higher than that with Fe converter plate. The designed detector has the merits of well processed and static vacuum keeping and can be used for intense pulsed gamma ray detecting.展开更多
Average L-shell fluorescence yields of some rare earth elements were determined using HPGe detector employing reflection geometry set up. Target atoms were excited using 59.5 keV gamma rays emerging from Am-241 source...Average L-shell fluorescence yields of some rare earth elements were determined using HPGe detector employing reflection geometry set up. Target atoms were excited using 59.5 keV gamma rays emerging from Am-241 source of strength 300 mCi. Background radiation and multiple scattering effects were minimized by properly shielding the detector. The elemental foils of uniform thickness and 99.9% purity were used in the present investigation. The fluorescent spectra were recorded in a 16 K multichannel - analyzer. The data were carefully analyzed and average L-shell fluorescence yields were calculated. The resulting yield values are compared with the available experimental and theoretical values.展开更多
Abstract： 40K, 238U and 232Th in dust storms samples from AI-Najaf Holy Area - lraq in year 2013 were measured using a high efficiency gamma ray spectroscopy NaI（Tl） detector. From the measured gamma rays spectra, ...Abstract： 40K, 238U and 232Th in dust storms samples from AI-Najaf Holy Area - lraq in year 2013 were measured using a high efficiency gamma ray spectroscopy NaI（Tl） detector. From the measured gamma rays spectra, the specific activity were determined for 40K （range from 237.166 to 368.689 Bq/kg）, 23SU （range from 11.531 to 34.997 Bq/kg） and 232Th （range from 2.805 to 11.162 Bq/kg）. Hazard indices （external hazard index, internal hazard index, radium equivalent activities and absorbed effective dose rates） were calculated for the measured samples to assess the radiation hazards arising from dust storms samples, which is the average of Hazard indices equal （0.214, 0.192, 25.359 nG/y and 50.855 Bq/Kg）, respectively. All results of Hazard indices were compared with safe limit values recommended by UNSCEAR （2008） below the safe limit.展开更多
文摘A Monte Carlo method to study the response of portable detector to terrestrial gamma ray is proposed. This method is based on two-stage Monte Carlo simulation.First, the probability distributions of the phase space coordinates of the events that are most likely to be detected are reconstructed at the phase space shell level. The phase space shell is a closed surface enclosing the detector. The detector response to events originating from the phase space shell is then studied. The full absorption spectra as well as the partial absorption spectra are obtained for natural radionuclides uniformly distributed in the ground. For validation, this method is applied to a Hp Ge portable detector previously studied. The previous study is based on a semiempirical model. Good agreement is achieved when we compare the full-energy peak efficiencies and the total in situ spectra obtained by the two methods. As an application, the effective depth of the activity of the^(137) Cs artificial radionuclide in the soil is determined from the low-energy part of the total in situ spectrum.
基金financial support from the International Science & Technology Cooperation Program of China (No. 2013DFR90220)National Natural Science Foundation of China (No. 41206076)Qingdao Applied Basic Research Project (NO. 14-2-4-94-jch)
文摘To develop a NaI （T1） detector for in situ radioactivity monitoring in the marine environment and enhance the confidence of the probability of the gamma-spectrum analysis, Monte Carlo simulations using the Monte Carlo N-Particle （ MNCP ） code were performed to provide the response spectra of some interested radionuclides and the background spectra originating from the natural radionuclides in seawater recorded by a NaI （T1） detector. A newly developed 75 mm × 75 mm NaI （T1） detector was calibrated using four reference radioactive sources 137Cs, 60Co, 40K and 54Mn in the laboratory before the field measurements in seawater. A simulation model was established for the detector immersed in seawater. The simulated spectra were all broadened with Gaussian pulses to reflect the statistical fluctuations and electrical noise in the real measurement. The simulated spectra show that the single-energy photons into the detector are mostly scattering low-energy photons and the high background in the low energy region mainly originates from the Compton effect of the high energy y-rays of natural radionuclides in seawater. The simulated background spectrum was compared with the experimental one recorded in field measurement and they seem to be in good agreement. The simulation method and spectra can be used for the accurate analysis of the filed measurement results of low concentration radioactivity in seawater.
文摘A newly designed vacuum Compton gamma-ray detector with Ta-Al clad-metal electron converter plate is described. The detecting efficiency for 1.25 MeV gamma-ray is 7.85×10-3 electron/γ,which is 2.5 times higher than that with Fe converter plate. The designed detector has the merits of well processed and static vacuum keeping and can be used for intense pulsed gamma ray detecting.
文摘Average L-shell fluorescence yields of some rare earth elements were determined using HPGe detector employing reflection geometry set up. Target atoms were excited using 59.5 keV gamma rays emerging from Am-241 source of strength 300 mCi. Background radiation and multiple scattering effects were minimized by properly shielding the detector. The elemental foils of uniform thickness and 99.9% purity were used in the present investigation. The fluorescent spectra were recorded in a 16 K multichannel - analyzer. The data were carefully analyzed and average L-shell fluorescence yields were calculated. The resulting yield values are compared with the available experimental and theoretical values.
文摘Abstract： 40K, 238U and 232Th in dust storms samples from AI-Najaf Holy Area - lraq in year 2013 were measured using a high efficiency gamma ray spectroscopy NaI（Tl） detector. From the measured gamma rays spectra, the specific activity were determined for 40K （range from 237.166 to 368.689 Bq/kg）, 23SU （range from 11.531 to 34.997 Bq/kg） and 232Th （range from 2.805 to 11.162 Bq/kg）. Hazard indices （external hazard index, internal hazard index, radium equivalent activities and absorbed effective dose rates） were calculated for the measured samples to assess the radiation hazards arising from dust storms samples, which is the average of Hazard indices equal （0.214, 0.192, 25.359 nG/y and 50.855 Bq/Kg）, respectively. All results of Hazard indices were compared with safe limit values recommended by UNSCEAR （2008） below the safe limit.
