The energy correlations of prompt fission neutrons have not yet been considered in the related coincidence and multiplication measurement techniques.To measure and verify the energy correlations,an experiment was perf...The energy correlations of prompt fission neutrons have not yet been considered in the related coincidence and multiplication measurement techniques.To measure and verify the energy correlations,an experiment was performed with a total measurement duration of approximately 1200 h.In the experiment,eight CLYC detectors and sixteen EJ309 liquid scintillation detectors were utilized,and the fission moment was tagged with the measured fissionγ-rays.The relative ratios of the energy spectra of the neutrons correlated with different energy neutrons to the^(252)Cf fission neutron energy spectra were obtained.The present results may be helpful for studying fission physics and nuclear technology applications.展开更多
To generate a neutron beam exhibiting a Maxwellian energy distribution with narrow emission angles for measuring the neutron capture reaction rates of the s-process nuclides,a monoenergetic 3.4 MeV proton beam produce...To generate a neutron beam exhibiting a Maxwellian energy distribution with narrow emission angles for measuring the neutron capture reaction rates of the s-process nuclides,a monoenergetic 3.4 MeV proton beam produced by the tandem-accelerator in the China Institute of Atomic Energy was utilized.The proton beam was first transmitted through a 60.5μm aluminum foil and then impinged on a natural LiF target to produce neutron beam via^(7)Li(p,n)7Be reaction.The quasi-Gaussian energy distribution of protons in the LiF target resulted in neutron energy spectra that agreed with a Maxwellian energy distribution at kT=(22±2)keV,which was achieved by integrating neutrons detected within an emission angle of 65.0°±2.6°using a ^(6)Li glass detector positioned at 65°relative to the proton beam direction.The narrow angular spread of the Maxwelliandistributed neutron beam enables direct measurement of neutron capture cross-sections for most s-process nuclides,overcoming previous experimental limitations associated with broad angular distributions.展开更多
The Van Allen radiation belts are doughnut-shaped zones surrounding Earth, filled with highly energetic charged particles whose sources or loss mechanisms have been investigated for decades. As for the inner belt, cos...The Van Allen radiation belts are doughnut-shaped zones surrounding Earth, filled with highly energetic charged particles whose sources or loss mechanisms have been investigated for decades. As for the inner belt, cosmic ray albedo neutron decay(CRAND),radial diffusion, and local acceleration have been considered principal sources of electrons, whereas protons are predominantly from CRAND and solar protons. In this article, lightning-induced neutrons from Earth's upper atmosphere are suggested as a possible source of protons and electrons in the inner radiation belt. These terrestrial neutrons can contribute to the inner belt population by undergoing nuclear decay. Several approaches are proposed and discussed to evaluate the potential contribution of lightning-induced neutrons to the inner belt, including magnitude estimation, Monte Carlo simulations, and in situ observations. This article discusses some avenues of further study to determine the contribution of lightning-induced neutrons to the inner radiation belt.展开更多
Utilizing the laser-driven Z-pinch e ect,we propose an approach for generating an ultrashort,intense Me V neutron source with femtosecond pulse duration.The self-generated magnetic field driven by a petawatt-class las...Utilizing the laser-driven Z-pinch e ect,we propose an approach for generating an ultrashort,intense Me V neutron source with femtosecond pulse duration.The self-generated magnetic field driven by a petawatt-class laser pulse compressed the deuterium in a single nanowire to more than 120 times its initial density,achieving an unprecedented particle number density of 10^(25)cm^(-3).Through full-dimensional kinetic simulations,including nuclear reactions,we found that these Z-pinches can generate high-intensity and short-duration neutron pulses,with the peak flux reaching 10^(27)cm^(-2)s^(-1).Such laser-driven neutron sources are beyond the capabilities of existing approaches and pave the way for groundbreaking applications in r-process nucleosynthesis studies and high-precision time-of-flight neutron data measurements.展开更多
Displacement damage induced by neutron irradiation in China Spallation Neutron Source(CSNS) is studied on bipolar transistors with lateral PNP, substrate PNP, and vertical NPN configurations, respectively. Comparison ...Displacement damage induced by neutron irradiation in China Spallation Neutron Source(CSNS) is studied on bipolar transistors with lateral PNP, substrate PNP, and vertical NPN configurations, respectively. Comparison of the effects on different type transistors is conducted based on displacement damage factor, and the differences are analyzed through minority carrier lifetime calculation and structure analysis. The influence of CSNS neutrons irradiation on the lateral PNP transistors is analyzed by the gate-controlled method, including the oxide charge accumulation, surface recombine velocity,and minority carrier lifetime. The results indicate that the total ionizing dose in CSNS neutron radiation environment is negligible in this study. The displacement damage factors based on 1-MeV equivalent neutron flux of different transistors are consistent between Xi’an pulse reactor(XAPR) and CSNS.展开更多
This study investigates the effects of displacement damage on the dark signal of a pinned photodiode CMOS image sensor(CIS)following irradiation with back-streaming white neutrons from white neutron sources at the Chi...This study investigates the effects of displacement damage on the dark signal of a pinned photodiode CMOS image sensor(CIS)following irradiation with back-streaming white neutrons from white neutron sources at the China spallation neutron source(CSNS)and Xi'an pulsed reactor(XAPR).The mean dark signal,dark signal non-uniformity(DSNU),dark signal distribution,and hot pixels of the CIS were compared between the CSNS back-n and XAPR neutron irradiations.The nonionizing energy loss and energy distribution of primary knock-on atoms in silicon,induced by neutrons,were calculated using the open-source package Geant4.An analysis combining experimental and simulation results showed a noticeable proportionality between the increase in the mean dark signal and the displacement damage dose(DDD).Additionally,neutron energies influence DSNU,dark signal distribution,and hot pixels.High neutron energies at the same DDD level may lead to pronounced dark signal non-uniformity and elevated hot pixel values.展开更多
Neutron-sensitive microchannel plates(nMCPs)have applications in neutron detection,including energy spectrum measurements,neutron-induced cross sections,and neutron imaging.10B-doped MCPs(B-MCPs)have attracted signifi...Neutron-sensitive microchannel plates(nMCPs)have applications in neutron detection,including energy spectrum measurements,neutron-induced cross sections,and neutron imaging.10B-doped MCPs(B-MCPs)have attracted significant attention owing to their potential for exhibiting a high neutron detection efficiency over a large neutron energy range.Good spatial and temporal resolutions are useful for neutron energy-resolved imaging.However,their practical applications still face many technical challenges.In this study,a B-MCP with 10 mol%10B was tested for its response to wide-energy neutrons from eV to MeV at the Back-n white neutron source at the China Spallation Neutron Source.The neutron detection efficiency was calibrated at 1 eV,which is approximately 300 times that of an ordinary MCP and indicates the success of 10 B doping.The factors that caused the reduction in the detection efficiency were simulated and discussed.The neutron energy spectrum obtained using B-MCP was compared with that obtained by other measurement methods,and showed very good consistency for neutron energies below tens of keV.The response is more complicated at higher neutron energy,at which point the elastic and nonelastic reactions of all nuclides of B-MCP gradually become dominant.This is beneficial for the detection of neutrons,as it compensates for the detection efficiency of B-MCP for high-energy neutrons.展开更多
This paper deal with a nonlinear transport equation with delayed neutron andgeneral boundary conditions. We establish, via the nonlinear semigroups approach, the exis-tence and uniqueness of the mild solution, weak so...This paper deal with a nonlinear transport equation with delayed neutron andgeneral boundary conditions. We establish, via the nonlinear semigroups approach, the exis-tence and uniqueness of the mild solution, weak solution, strong solution and local solutionon LP-spaces （1 ≤ p 〈 ＋∞）. Local and non local evolution problems are discussed.展开更多
Stable neutron generation with a yield of ~1.2×10^(4) neutrons per pulse was obtained during d(d,n)^(3)He reaction initiated by the high-voltage nanosecond discharge in a gap with a potential tungsten cylinder(an...Stable neutron generation with a yield of ~1.2×10^(4) neutrons per pulse was obtained during d(d,n)^(3)He reaction initiated by the high-voltage nanosecond discharge in a gap with a potential tungsten cylinder(anode)and a grounded deuterated zirconium plate(cathode)filled with deuterium at a pressure of ~10^(2) Pa.Estimated duration of the neutron pulse was ~1.5 ns.Less intensive neutron emission was registered without deuterated plate.Splashing of material of the tungsten electrode was observed during the high-voltage nanosecond discharge in the deuterium,hydrogen,helium and argon at pressures of 10^(2)-10^(4) Pa.展开更多
Purpose: To understand the late effects on bonemarrow after widefield or total body irrdiation withvarious types of radiation.Materials and Methods: Total body irradiationwith single dose of P(35) Be fast Neutrons and...Purpose: To understand the late effects on bonemarrow after widefield or total body irrdiation withvarious types of radiation.Materials and Methods: Total body irradiationwith single dose of P(35) Be fast Neutrons and γ raysrespectively have been used in this study. Kunming strainmice were irradiated by fast neutrons produced bybombardment of beryllium target with 35MeV protonsand the dose rate was 0.12 to 0.14 Gy/min. Nine doselevels were used in fast neutrons irradiation from 0.20 to3.50Gy. The dose rate of 60Co γ rays was 0.60Gy/min andirradiation was in the range of 0.25 to 9.00Gy. Sixteendose points were studied. All animals without anesthesiawere irradiated whole body with single doses by fastneutrons and γ rays respectively, One group withoutirradiation was regarded as control group. 90 days afterirradiation all animals were sacrificed. The nucleatedcells of bone marrow and the peripheral blood cellsincluding WBC and lymphocytes were counted.Results: our study shows that the number ofnucleated cells of bone marrow in both fast neutrons andγ ray groups decreased with increase of the doses. Thereare significant differences between irradiated groups andzero line (control group) and the slopes are -1.41 ±0.55(p=0.038) and -0.98 ± 0. 24(P= 0.0015) for fast neutronsand γ rays respectively. There is no significant differencebetween the two kinds of radiation (p>0.05). The lateeffects on peripheral blood cells (WBC and lymphocytes)in mice after irradiation with single doses of neutrons andγ rays were signincantly lower than unirradiated group(P< 0.05). However, the dependence of the values ofperipheral blood cells on doses is not found and there areno significant differences between neutrons and γ raysgroups.Conclusions: Total body irradiation with neutronsor γ rays can suppress marrow in mice in the long-term,and is more obvious with increase of doses. There is nosignificant difference between neutrons and γ rays for thelate effects studied.展开更多
The early RBE of the bone marrow in mice after studied irradiation with fast neutrons(35 MeVp→Be) was studied.60Co-γ ray was used for referent beams.Using the dos.making 50% loss of the nucleated cells of bone marro...The early RBE of the bone marrow in mice after studied irradiation with fast neutrons(35 MeVp→Be) was studied.60Co-γ ray was used for referent beams.Using the dos.making 50% loss of the nucleated cells of bone marrow in mice relative to control group mice to calculated the RBE value which was 2.13±0.18.Meanwhile,the relationship of the RBE values and the dose of neutrons was noted.On log-log plot the RBE values decrease with increasing dose of fast neutrons and it is consistent with a slope of -0.39± 0.10.The α/β ratios were estimated from linear-quadratic model of cell survival,they are 14.4±1.30 Gy for fast neutrons and 0.83±0.10 Gy for γ-ray,respectively.展开更多
The radiation effect of neutrons in a reactor on polyurethane was studied.The gases produced by irradiated samples were analyzed by gas chromatography,and the dynamic mechanical and compression properties of the sampl...The radiation effect of neutrons in a reactor on polyurethane was studied.The gases produced by irradiated samples were analyzed by gas chromatography,and the dynamic mechanical and compression properties of the samples were also studied.The positron annihilation lifetime of irradiated samples was measured at room temperature in vacuum.The experimental results indicate that gas chromatography is a powerful tool to quantitatively analyze the gas products from neutron-irradiated polyurethane and characterizes the chemical changes in the sample.And the changes in microstructure determined from the PAL correlate well with the measurements of the mechanical properties by dynamic mechanical analysis（DMA）.展开更多
The change of light output power of LEDs based on A1GalnP heterostructures with multiple quantum wells （590 nm and 630 nm） under irradiation by fast neutrons depends on the operating current density. It can be disti...The change of light output power of LEDs based on A1GalnP heterostructures with multiple quantum wells （590 nm and 630 nm） under irradiation by fast neutrons depends on the operating current density. It can be distinguished the regions of high, average and low electron injection. Operating current, this corresponds to the position of the boundary between the selected levels of the electron injection, increases with increasing neutron fluence. The final stage of the reducing process of the light output power under irradiation is the regime of low electron injection. The relative change in light output power depends on the operating current （operating current density） and can be described by a fairly simple equation. Established relations predict radiation resistance of LEDs, and it makes the most rational justification of operating modes of light-emitting diodes in terms of radiation resistance.展开更多
In recent years а significant number of both theoretical and experimental works devoted to the influence of external electromagnetic fields and ionization on the probability of beta decays have been published. The pr...In recent years а significant number of both theoretical and experimental works devoted to the influence of external electromagnetic fields and ionization on the probability of beta decays have been published. The present work investigates the feasibility of using this physical effect as the main mechanism for controlling the reactor. In this paper a system of equations is written and studied that allows one to describe the work of a nuclear reactor in the case where the probability of beta decay and, therefore, the fraction of delayed neu-trons is a function of time. It is shown that in the case of a constant fraction of delayed neutrons, the pro-posed system of equations is identical to the known system. As can be seen from analysis of a solution of the new system of equations for the proposed method of reactor control, acceleration by instantaneous neutrons is impossible even theoretically.展开更多
Measurement of the neutron yield is performed at a primary energy of 400 MeV/u carbons for the Pb target.Water-bath activation-foil method is used in a moderation measurement with Au foils to detect the moderated neut...Measurement of the neutron yield is performed at a primary energy of 400 MeV/u carbons for the Pb target.Water-bath activation-foil method is used in a moderation measurement with Au foils to detect the moderated neutrons. The neutron yield is determined to be 18.4±2.1 per carbon by integrating the neutron flux over the entire water volume. The corresponding simulation values are performed by Geant4 code with three models to compare with the experimental results. The comparison shows that the calculated result with the INCL model is in good agreement with the experimental data.展开更多
It has recently been shown that incident particles, neutrons, can initiate the freezing in a supercooled water volume. This new finding may have ramifications for the interpretation of both experimental data on the nu...It has recently been shown that incident particles, neutrons, can initiate the freezing in a supercooled water volume. This new finding may have ramifications for the interpretation of both experimental data on the nucleation of laboratory samples of supercooled water and perhaps more importantly on the interpretation of ice nucleation involved in cloud physics. For example, if some fraction of the cloud nucleation previously attributed to dust, soot, or aerosols has been caused by cosmogenic neutrons, fresh consideration is required in the context of climate models. Moreover, as cosmogenic neutrons, most being muon-induced, have much greater flux at high latitudes, estimates of ice nucleates in these regions may be larger than required to accurately model cloud and condensation properties. This discrepancy has been pointed out in IPCC reports. Our paper discusses the connection between the new concept of neutrons nucleating supercooled water and the need for a new source of nucleation in high latitude clouds, ideally causing others to review current data, or to analyse future data with this idea in mind. .展开更多
Integral experiments on tungsten slab samples were carried out on the D-T neutron source facility at China Institute of Atomic Energy. Leakage neutron spectra from the irradiated tungsten target were measured by the t...Integral experiments on tungsten slab samples were carried out on the D-T neutron source facility at China Institute of Atomic Energy. Leakage neutron spectra from the irradiated tungsten target were measured by the time-of-flight technique. Accuracy of the nuclear data for tungsten was examined by comparing the measured neutron spectra with the leakage neutron spectra simulated using the MCNP-4C code with evaluated nuclear data of the JEFF-3.2, FENDL-3.0 and TENDL-2014 libraries. The results show that the calculations with JEFF-3.2 agree well with the measurements in the whole energy range and all angles, whereas the spectra calculated with FENDL-3.0 and TENDL-2014 have some discrepancies with the experimental data.展开更多
This paper presents the effects of the low-dose irradiation on Tilapia Nilotica. In laboratory experiments the Tilapia Nilotica irradiated by integrated flux of fast neutrons 1×10 9 neutrons/m2 and 1 ×10 10...This paper presents the effects of the low-dose irradiation on Tilapia Nilotica. In laboratory experiments the Tilapia Nilotica irradiated by integrated flux of fast neutrons 1×10 9 neutrons/m2 and 1 ×10 10 neutrons/m2 gave a growth rate more than 40% and 32 % compared with those of controls respectively. The yield of the irradiated Tilapia Nilotica growing with non-irradiated carps and silver carps in a mixed feed condition increased by 8. 6%, 157% and 11. 0% more than those of the controls in the pilot test. The survival rate increases by 21. 8%, 149% and 16. 2% for the aboye-mentioned three species. An increased yield of 52 098 kg fish under irradiation with low dose was obtained in 18. 7 hectare water surface. The results of biological experiments show that the main organic coefficients of the Tilapia Nilotica are greater than those of the controls, and this may be related to the increase of the capabilities of metabolism and resistance to diseases.展开更多
A new scintillating fiber detector inside magnetic shielding tube was designed and assembled for use in the next round of fusion experiments in the experimental advanced superconducting tokamak to provide D–T neutron...A new scintillating fiber detector inside magnetic shielding tube was designed and assembled for use in the next round of fusion experiments in the experimental advanced superconducting tokamak to provide D–T neutron yield with time resolution.In this study,Geant4 simulations were used to obtain the pulse height spectra for ideal signals produced when detecting neutrons and gamma rays of multiple energies.One of the main sources of interference was found to be low-energy neutrons below 10–5 MeV,which can generate numerous secondary particles in the detector components,such as the magnetic shielding tube,leading to high-amplitude output signals.To address this issue,a compact thermal neutron shield containing a 1-mm Cd layer outside the magnetic shielding tube and a 5-mm inner Pb layer was specifically designed.Adverse effects on the measurement of fast neutrons and the shielding effect on gamma rays were considered.This can suppress the height of the signals caused by thermal neutrons to a level below the height corresponding to neutrons above 4 MeV because the yield of the latter is used for detector calibration.In addition,the detector has relatively flat sensitivity curves in the fast neutron region,with the intrinsic detection efficiencies(IDEs)of approximately 40%.For gamma rays with energies that are not too high(<8 MeV),the IDEs of the detector are only approximately 20%,whereas for gamma rays below 1 MeV,the response curve cuts off earlier in the low-energy region,which is beneficial for avoiding counting saturation and signal accumulation.展开更多
A benchmark experiment on^(238)U slab samples was conducted using a deuterium-tritium neutron source at the China Institute of Atomic Energy.The leakage neutron spectra within energy levels of 0.8-16 MeV at 60°an...A benchmark experiment on^(238)U slab samples was conducted using a deuterium-tritium neutron source at the China Institute of Atomic Energy.The leakage neutron spectra within energy levels of 0.8-16 MeV at 60°and 120°were measured using the time-of-flight method.The samples were prepared as rectangular slabs with a 30 cm square base and thicknesses of 3,6,and 9 cm.The leakage neutron spectra were also calculated using the MCNP-4C program based on the latest evaluated files of^(238)U evaluated neutron data from CENDL-3.2,ENDF/B-Ⅷ.0,JENDL-5.0,and JEFF-3.3.Based on the comparison,the deficiencies and improvements in^(238)U evaluated nuclear data were analyzed.The results showed the following.(1)The calculated results for CENDL-3.2 significantly overestimated the measurements in the energy interval of elastic scattering at 60°and 120°.(2)The calculated results of CENDL-3.2 overestimated the measurements in the energy interval of inelastic scattering at 120°.(3)The calculated results for CENDL-3.2 significantly overestimated the measurements in the 3-8.5 MeV energy interval at 60°and 120°.(4)The calculated results with JENDL-5.0 were generally consistent with the measurement results.展开更多
基金supported by the National Natural Science Foundation of China(No.12105257)the Research and Development Fund(No.JMJJ202401)。
文摘The energy correlations of prompt fission neutrons have not yet been considered in the related coincidence and multiplication measurement techniques.To measure and verify the energy correlations,an experiment was performed with a total measurement duration of approximately 1200 h.In the experiment,eight CLYC detectors and sixteen EJ309 liquid scintillation detectors were utilized,and the fission moment was tagged with the measured fissionγ-rays.The relative ratios of the energy spectra of the neutrons correlated with different energy neutrons to the^(252)Cf fission neutron energy spectra were obtained.The present results may be helpful for studying fission physics and nuclear technology applications.
基金National Natural Science Foundation of China(12125509,11961141003,12275361,U2267205,12175152,12175121)National Key Research and Development Project(2022YFA1602301)Continuous-support Basic Scientific Research Project。
文摘To generate a neutron beam exhibiting a Maxwellian energy distribution with narrow emission angles for measuring the neutron capture reaction rates of the s-process nuclides,a monoenergetic 3.4 MeV proton beam produced by the tandem-accelerator in the China Institute of Atomic Energy was utilized.The proton beam was first transmitted through a 60.5μm aluminum foil and then impinged on a natural LiF target to produce neutron beam via^(7)Li(p,n)7Be reaction.The quasi-Gaussian energy distribution of protons in the LiF target resulted in neutron energy spectra that agreed with a Maxwellian energy distribution at kT=(22±2)keV,which was achieved by integrating neutrons detected within an emission angle of 65.0°±2.6°using a ^(6)Li glass detector positioned at 65°relative to the proton beam direction.The narrow angular spread of the Maxwelliandistributed neutron beam enables direct measurement of neutron capture cross-sections for most s-process nuclides,overcoming previous experimental limitations associated with broad angular distributions.
基金supported by the National Natural Science Foundation of China (No. 42225405 and No. 42350710200)。
文摘The Van Allen radiation belts are doughnut-shaped zones surrounding Earth, filled with highly energetic charged particles whose sources or loss mechanisms have been investigated for decades. As for the inner belt, cosmic ray albedo neutron decay(CRAND),radial diffusion, and local acceleration have been considered principal sources of electrons, whereas protons are predominantly from CRAND and solar protons. In this article, lightning-induced neutrons from Earth's upper atmosphere are suggested as a possible source of protons and electrons in the inner radiation belt. These terrestrial neutrons can contribute to the inner belt population by undergoing nuclear decay. Several approaches are proposed and discussed to evaluate the potential contribution of lightning-induced neutrons to the inner belt, including magnitude estimation, Monte Carlo simulations, and in situ observations. This article discusses some avenues of further study to determine the contribution of lightning-induced neutrons to the inner radiation belt.
基金supported by the National Key R&D Program of China(Nos.2022YFA1602402,2022YFA1602404)the National Natural Science Foundation of China(Nos.12235003,12388102)。
文摘Utilizing the laser-driven Z-pinch e ect,we propose an approach for generating an ultrashort,intense Me V neutron source with femtosecond pulse duration.The self-generated magnetic field driven by a petawatt-class laser pulse compressed the deuterium in a single nanowire to more than 120 times its initial density,achieving an unprecedented particle number density of 10^(25)cm^(-3).Through full-dimensional kinetic simulations,including nuclear reactions,we found that these Z-pinches can generate high-intensity and short-duration neutron pulses,with the peak flux reaching 10^(27)cm^(-2)s^(-1).Such laser-driven neutron sources are beyond the capabilities of existing approaches and pave the way for groundbreaking applications in r-process nucleosynthesis studies and high-precision time-of-flight neutron data measurements.
文摘Displacement damage induced by neutron irradiation in China Spallation Neutron Source(CSNS) is studied on bipolar transistors with lateral PNP, substrate PNP, and vertical NPN configurations, respectively. Comparison of the effects on different type transistors is conducted based on displacement damage factor, and the differences are analyzed through minority carrier lifetime calculation and structure analysis. The influence of CSNS neutrons irradiation on the lateral PNP transistors is analyzed by the gate-controlled method, including the oxide charge accumulation, surface recombine velocity,and minority carrier lifetime. The results indicate that the total ionizing dose in CSNS neutron radiation environment is negligible in this study. The displacement damage factors based on 1-MeV equivalent neutron flux of different transistors are consistent between Xi’an pulse reactor(XAPR) and CSNS.
基金supported by the Young Elite Scientists Sponsorship Program by CAST(No.YESS20210441)the National Natural Science Foundation of China(Nos.U2167208,11875223)。
文摘This study investigates the effects of displacement damage on the dark signal of a pinned photodiode CMOS image sensor(CIS)following irradiation with back-streaming white neutrons from white neutron sources at the China spallation neutron source(CSNS)and Xi'an pulsed reactor(XAPR).The mean dark signal,dark signal non-uniformity(DSNU),dark signal distribution,and hot pixels of the CIS were compared between the CSNS back-n and XAPR neutron irradiations.The nonionizing energy loss and energy distribution of primary knock-on atoms in silicon,induced by neutrons,were calculated using the open-source package Geant4.An analysis combining experimental and simulation results showed a noticeable proportionality between the increase in the mean dark signal and the displacement damage dose(DDD).Additionally,neutron energies influence DSNU,dark signal distribution,and hot pixels.High neutron energies at the same DDD level may lead to pronounced dark signal non-uniformity and elevated hot pixel values.
基金supported by the Guangdong Basic and Applied Basic Research Foundation(No.2023A1515030074)the National Natural Science Foundation of China(No.12035017)。
文摘Neutron-sensitive microchannel plates(nMCPs)have applications in neutron detection,including energy spectrum measurements,neutron-induced cross sections,and neutron imaging.10B-doped MCPs(B-MCPs)have attracted significant attention owing to their potential for exhibiting a high neutron detection efficiency over a large neutron energy range.Good spatial and temporal resolutions are useful for neutron energy-resolved imaging.However,their practical applications still face many technical challenges.In this study,a B-MCP with 10 mol%10B was tested for its response to wide-energy neutrons from eV to MeV at the Back-n white neutron source at the China Spallation Neutron Source.The neutron detection efficiency was calibrated at 1 eV,which is approximately 300 times that of an ordinary MCP and indicates the success of 10 B doping.The factors that caused the reduction in the detection efficiency were simulated and discussed.The neutron energy spectrum obtained using B-MCP was compared with that obtained by other measurement methods,and showed very good consistency for neutron energies below tens of keV.The response is more complicated at higher neutron energy,at which point the elastic and nonelastic reactions of all nuclides of B-MCP gradually become dominant.This is beneficial for the detection of neutrons,as it compensates for the detection efficiency of B-MCP for high-energy neutrons.
文摘This paper deal with a nonlinear transport equation with delayed neutron andgeneral boundary conditions. We establish, via the nonlinear semigroups approach, the exis-tence and uniqueness of the mild solution, weak solution, strong solution and local solutionon LP-spaces （1 ≤ p 〈 ＋∞）. Local and non local evolution problems are discussed.
文摘Stable neutron generation with a yield of ~1.2×10^(4) neutrons per pulse was obtained during d(d,n)^(3)He reaction initiated by the high-voltage nanosecond discharge in a gap with a potential tungsten cylinder(anode)and a grounded deuterated zirconium plate(cathode)filled with deuterium at a pressure of ~10^(2) Pa.Estimated duration of the neutron pulse was ~1.5 ns.Less intensive neutron emission was registered without deuterated plate.Splashing of material of the tungsten electrode was observed during the high-voltage nanosecond discharge in the deuterium,hydrogen,helium and argon at pressures of 10^(2)-10^(4) Pa.
文摘Purpose: To understand the late effects on bonemarrow after widefield or total body irrdiation withvarious types of radiation.Materials and Methods: Total body irradiationwith single dose of P(35) Be fast Neutrons and γ raysrespectively have been used in this study. Kunming strainmice were irradiated by fast neutrons produced bybombardment of beryllium target with 35MeV protonsand the dose rate was 0.12 to 0.14 Gy/min. Nine doselevels were used in fast neutrons irradiation from 0.20 to3.50Gy. The dose rate of 60Co γ rays was 0.60Gy/min andirradiation was in the range of 0.25 to 9.00Gy. Sixteendose points were studied. All animals without anesthesiawere irradiated whole body with single doses by fastneutrons and γ rays respectively, One group withoutirradiation was regarded as control group. 90 days afterirradiation all animals were sacrificed. The nucleatedcells of bone marrow and the peripheral blood cellsincluding WBC and lymphocytes were counted.Results: our study shows that the number ofnucleated cells of bone marrow in both fast neutrons andγ ray groups decreased with increase of the doses. Thereare significant differences between irradiated groups andzero line (control group) and the slopes are -1.41 ±0.55(p=0.038) and -0.98 ± 0. 24(P= 0.0015) for fast neutronsand γ rays respectively. There is no significant differencebetween the two kinds of radiation (p>0.05). The lateeffects on peripheral blood cells (WBC and lymphocytes)in mice after irradiation with single doses of neutrons andγ rays were signincantly lower than unirradiated group(P< 0.05). However, the dependence of the values ofperipheral blood cells on doses is not found and there areno significant differences between neutrons and γ raysgroups.Conclusions: Total body irradiation with neutronsor γ rays can suppress marrow in mice in the long-term,and is more obvious with increase of doses. There is nosignificant difference between neutrons and γ rays for thelate effects studied.
文摘The early RBE of the bone marrow in mice after studied irradiation with fast neutrons(35 MeVp→Be) was studied.60Co-γ ray was used for referent beams.Using the dos.making 50% loss of the nucleated cells of bone marrow in mice relative to control group mice to calculated the RBE value which was 2.13±0.18.Meanwhile,the relationship of the RBE values and the dose of neutrons was noted.On log-log plot the RBE values decrease with increasing dose of fast neutrons and it is consistent with a slope of -0.39± 0.10.The α/β ratios were estimated from linear-quadratic model of cell survival,they are 14.4±1.30 Gy for fast neutrons and 0.83±0.10 Gy for γ-ray,respectively.
基金Funded by the Joint Foundation of the National Natural Science Foundation Committee and China Academy of Engineering Physics (No.10576029)
文摘The radiation effect of neutrons in a reactor on polyurethane was studied.The gases produced by irradiated samples were analyzed by gas chromatography,and the dynamic mechanical and compression properties of the samples were also studied.The positron annihilation lifetime of irradiated samples was measured at room temperature in vacuum.The experimental results indicate that gas chromatography is a powerful tool to quantitatively analyze the gas products from neutron-irradiated polyurethane and characterizes the chemical changes in the sample.And the changes in microstructure determined from the PAL correlate well with the measurements of the mechanical properties by dynamic mechanical analysis（DMA）.
文摘The change of light output power of LEDs based on A1GalnP heterostructures with multiple quantum wells （590 nm and 630 nm） under irradiation by fast neutrons depends on the operating current density. It can be distinguished the regions of high, average and low electron injection. Operating current, this corresponds to the position of the boundary between the selected levels of the electron injection, increases with increasing neutron fluence. The final stage of the reducing process of the light output power under irradiation is the regime of low electron injection. The relative change in light output power depends on the operating current （operating current density） and can be described by a fairly simple equation. Established relations predict radiation resistance of LEDs, and it makes the most rational justification of operating modes of light-emitting diodes in terms of radiation resistance.
文摘In recent years а significant number of both theoretical and experimental works devoted to the influence of external electromagnetic fields and ionization on the probability of beta decays have been published. The present work investigates the feasibility of using this physical effect as the main mechanism for controlling the reactor. In this paper a system of equations is written and studied that allows one to describe the work of a nuclear reactor in the case where the probability of beta decay and, therefore, the fraction of delayed neu-trons is a function of time. It is shown that in the case of a constant fraction of delayed neutrons, the pro-posed system of equations is identical to the known system. As can be seen from analysis of a solution of the new system of equations for the proposed method of reactor control, acceleration by instantaneous neutrons is impossible even theoretically.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11575267,11775284,11575289 and 11605258
文摘Measurement of the neutron yield is performed at a primary energy of 400 MeV/u carbons for the Pb target.Water-bath activation-foil method is used in a moderation measurement with Au foils to detect the moderated neutrons. The neutron yield is determined to be 18.4±2.1 per carbon by integrating the neutron flux over the entire water volume. The corresponding simulation values are performed by Geant4 code with three models to compare with the experimental results. The comparison shows that the calculated result with the INCL model is in good agreement with the experimental data.
文摘It has recently been shown that incident particles, neutrons, can initiate the freezing in a supercooled water volume. This new finding may have ramifications for the interpretation of both experimental data on the nucleation of laboratory samples of supercooled water and perhaps more importantly on the interpretation of ice nucleation involved in cloud physics. For example, if some fraction of the cloud nucleation previously attributed to dust, soot, or aerosols has been caused by cosmogenic neutrons, fresh consideration is required in the context of climate models. Moreover, as cosmogenic neutrons, most being muon-induced, have much greater flux at high latitudes, estimates of ice nucleates in these regions may be larger than required to accurately model cloud and condensation properties. This discrepancy has been pointed out in IPCC reports. Our paper discusses the connection between the new concept of neutrons nucleating supercooled water and the need for a new source of nucleation in high latitude clouds, ideally causing others to review current data, or to analyse future data with this idea in mind. .
基金supported by the National Natural Science Foundation of China(No.11605097,91426301,and 11605257)Doctoral Scientific Research Foundation of Inner Mongolia University for the Nationalities(No.BS365)the‘‘ADS project 302’’of the Chinese Academy of Sciences(No.XDA03030200)
文摘Integral experiments on tungsten slab samples were carried out on the D-T neutron source facility at China Institute of Atomic Energy. Leakage neutron spectra from the irradiated tungsten target were measured by the time-of-flight technique. Accuracy of the nuclear data for tungsten was examined by comparing the measured neutron spectra with the leakage neutron spectra simulated using the MCNP-4C code with evaluated nuclear data of the JEFF-3.2, FENDL-3.0 and TENDL-2014 libraries. The results show that the calculations with JEFF-3.2 agree well with the measurements in the whole energy range and all angles, whereas the spectra calculated with FENDL-3.0 and TENDL-2014 have some discrepancies with the experimental data.
文摘This paper presents the effects of the low-dose irradiation on Tilapia Nilotica. In laboratory experiments the Tilapia Nilotica irradiated by integrated flux of fast neutrons 1×10 9 neutrons/m2 and 1 ×10 10 neutrons/m2 gave a growth rate more than 40% and 32 % compared with those of controls respectively. The yield of the irradiated Tilapia Nilotica growing with non-irradiated carps and silver carps in a mixed feed condition increased by 8. 6%, 157% and 11. 0% more than those of the controls in the pilot test. The survival rate increases by 21. 8%, 149% and 16. 2% for the aboye-mentioned three species. An increased yield of 52 098 kg fish under irradiation with low dose was obtained in 18. 7 hectare water surface. The results of biological experiments show that the main organic coefficients of the Tilapia Nilotica are greater than those of the controls, and this may be related to the increase of the capabilities of metabolism and resistance to diseases.
基金supported by the University Synergy Innovation Program of Anhui Province(No.GXXT-2022-001)the Institute of Energy,Hefei Comprehensive National Science Center(Anhui Energy Laboratory)under Grant No.21KZS205 and 21KZL401the Comprehensive Research Facility for Fusion Technology Program of China(No.2018-000052-73-01-001228).
文摘A new scintillating fiber detector inside magnetic shielding tube was designed and assembled for use in the next round of fusion experiments in the experimental advanced superconducting tokamak to provide D–T neutron yield with time resolution.In this study,Geant4 simulations were used to obtain the pulse height spectra for ideal signals produced when detecting neutrons and gamma rays of multiple energies.One of the main sources of interference was found to be low-energy neutrons below 10–5 MeV,which can generate numerous secondary particles in the detector components,such as the magnetic shielding tube,leading to high-amplitude output signals.To address this issue,a compact thermal neutron shield containing a 1-mm Cd layer outside the magnetic shielding tube and a 5-mm inner Pb layer was specifically designed.Adverse effects on the measurement of fast neutrons and the shielding effect on gamma rays were considered.This can suppress the height of the signals caused by thermal neutrons to a level below the height corresponding to neutrons above 4 MeV because the yield of the latter is used for detector calibration.In addition,the detector has relatively flat sensitivity curves in the fast neutron region,with the intrinsic detection efficiencies(IDEs)of approximately 40%.For gamma rays with energies that are not too high(<8 MeV),the IDEs of the detector are only approximately 20%,whereas for gamma rays below 1 MeV,the response curve cuts off earlier in the low-energy region,which is beneficial for avoiding counting saturation and signal accumulation.
基金This work was supported by the general program(No.1177531)joint funding(No.U2067205)from the National Natural Science Foundation of China.
文摘A benchmark experiment on^(238)U slab samples was conducted using a deuterium-tritium neutron source at the China Institute of Atomic Energy.The leakage neutron spectra within energy levels of 0.8-16 MeV at 60°and 120°were measured using the time-of-flight method.The samples were prepared as rectangular slabs with a 30 cm square base and thicknesses of 3,6,and 9 cm.The leakage neutron spectra were also calculated using the MCNP-4C program based on the latest evaluated files of^(238)U evaluated neutron data from CENDL-3.2,ENDF/B-Ⅷ.0,JENDL-5.0,and JEFF-3.3.Based on the comparison,the deficiencies and improvements in^(238)U evaluated nuclear data were analyzed.The results showed the following.(1)The calculated results for CENDL-3.2 significantly overestimated the measurements in the energy interval of elastic scattering at 60°and 120°.(2)The calculated results of CENDL-3.2 overestimated the measurements in the energy interval of inelastic scattering at 120°.(3)The calculated results for CENDL-3.2 significantly overestimated the measurements in the 3-8.5 MeV energy interval at 60°and 120°.(4)The calculated results with JENDL-5.0 were generally consistent with the measurement results.
