With the increasing demand for controllable source logging,research on data-processing algorithms that meet accuracy requirements has become key to the development of controllable-source-logging tools.This study theor...With the increasing demand for controllable source logging,research on data-processing algorithms that meet accuracy requirements has become key to the development of controllable-source-logging tools.This study theoretically derives the relationship between the formation density and inelastic gamma count rate to investigate the data-processing methods for deuterium–tritium(D–T)source neutron-gamma density logging while drilling.Then,algorithms for the net inelastic gamma count-rate extraction and neutron transport correction are studied using Monte Carlo simulations.A new method for fast-neutron effect identification and additional correction is proposed to improve the density-calculation accuracy of gas-filled and heavy-mineral formations.Finally,the effectiveness and accuracy of the proposed data-processing methods are verified based on simulated and measured data.The results show that the density-calculation accuracy of water-bearing conventional formations in simulated data is±0.02 g/cm^(3).The accuracy of gas-filled and heavy-mineral formations after the additional fast-neutron effect correction is±0.025 g/cm^(3).For the measured data from the actual tool,the algorithms perform well in the density calculation.The density results obtained using the processing algorithms are consistent with the density data provided by NeoScope.Therefore,the D–T source neutron-gamma density-logging algorithms proposed in this study can obtain relatively accurate data-processing results for a variety of formations.This study provides technical support for engineering applications and the development of logging tools for controllable-source neutron-density logging.展开更多
Beryllium(^(9)Be)serves as a crucial neutron multiplier and reflection material,being extensively employed in the nuclear industry.The evaluated nuclear data are utilized in the design of the nuclear devices.Following...Beryllium(^(9)Be)serves as a crucial neutron multiplier and reflection material,being extensively employed in the nuclear industry.The evaluated nuclear data are utilized in the design of the nuclear devices.Following the interaction between neutrons and^(9)Be,all neutrons generated stem from the^(9)Be(n,2n)^(8)Be reaction channel,except for the elastic scattering reaction channel.Nevertheless,the data of the outgoing neutron double differential cross section of the reaction channel provided by the latest internationally evaluated libraries still exhibit considerable discrepancies.A shielding integral experiment based on slab^(9)Be samples with measurements of neutron spectra leaked from different angles is an effective approach to verify the double differential cross-section data.Hence,in this study,a shielding integral experiment of^(9)Be samples of different thicknesses was conducted using a nanosecond pulsed deuterium-tritium neutron source established by the China Institute of Atomic Energy.The neutron time-of-flight spectra of three thicknesses(4.4 cm,8.8 cm,and 13.2 cm)and six angles(47°,58°,73°,107°,122°,and 133°)were measured by the neutron time-of-flight method,and 18 sets of experimental data were obtained.Additionally,the MCNP-4C program was used to obtain the simulated results of the leakage neutron spectra using the evaluated nuclear data of^(9)Be from the CENDL-3.2,ENDF/B-Ⅷ.0,JENDL-5,and JEFF-3.3 libraries.The simulated results of the leakage neutron spectra were compared with the experimental results,and the results showed that in the elastic scattering energy region,the simulated results from the CENDL-3.2,ENDF/B-Ⅷ.0,and JENDL-5 libraries were slightly higher at small angles and slightly lower at large angles.In the(n,2n)energy region,the simulated results from the CENDL-3.2 library were significantly different from the experimental results in terms of spectral shape,and the simulated results from the ENDF/B-Ⅷ.0 and the JENDL-5 libraries were in good agreement with the experimental results at small angles but low at large angles.The simulated results from the JEFF-3.3 library showed serious underestimation at all angles.展开更多
Lead(Pb)plays a significant role in the nuclear industry and is extensively used in radiation shielding,radiation protection,neutron moderation,radiation measurements,and various other critical functions.Consequently,...Lead(Pb)plays a significant role in the nuclear industry and is extensively used in radiation shielding,radiation protection,neutron moderation,radiation measurements,and various other critical functions.Consequently,the measurement and evaluation of Pb nuclear data are highly regarded in nuclear scientific research,emphasizing its crucial role in the field.Using the time-of-flight(ToF)method,the neutron leakage spectra from three^(nat)Pb samples were measured at 60°and 120°based on the neutronics integral experimental facility at the China Institute of Atomic Energy(CIAE).The^(nat)Pb sample sizes were30 cm×30 cm×5 cm,30 cm×30 cm×10 cm,and 30 cm×30 cm×15 cm.Neutron sources were generated by the Cockcroft-Walton accelerator,producing approximately 14.5 MeV and 3.5 MeV neutrons through the T(d,n)^(4)He and D(d,n)^(3)He reactions,respectively.Leakage neutron spectra were also calculated by employing the Monte Carlo code of MCNP-4C,and the nuclear data of Pb isotopes from four libraries:CENDL-3.2,JEFF-3.3,JENDL-5,and ENDF/B-Ⅷ.0 were used individually.By comparing the simulation and experimental results,improvements and deficiencies in the evaluated nuclear data of the Pb isotopes were analyzed.Most of the calculated results were consistent with the experimental results;however,a few areas did not fit well.In the(n,el)energy range,the simulated results from CENDL-3.2 were significantly overestimated;in the(n,inl)D and the(n,inl)C energy regions,the results from CENDL-3.2 and ENDF/B-Ⅷ.0 were significantly overestimated at 120°,and the results from JENDL-5 and JEFF-3.3 are underestimated at 60°in the(n,inl)D energy region.The calculated spectra were analyzed by comparing them with the experimental spectra in terms of the neutron spectrum shape and C/E values.The results indicate that the theoretical simulations,using different data libraries,overestimated or underestimated the measured values in certain energy ranges.Secondary neutron energies and angular distributions in the data files have been presented to explain these discrepancies.展开更多
In the past decade,boron neutron capture therapy utilizing an accelerator-based neutron source(ABNS)designed primarily for producing epithermal neutrons has been implemented in the treatment of brain tumors and other ...In the past decade,boron neutron capture therapy utilizing an accelerator-based neutron source(ABNS)designed primarily for producing epithermal neutrons has been implemented in the treatment of brain tumors and other cancers.The specifications for designing an epithermal beam are primarily based on the IAEA-TECODC-1223 report,issued in 2001 for reactor neutron sources.Based on this report,the latest perspectives and clinical requirements,we designed an ABNS capable of adjusting the average neutron beam energy.The design was based on a 2.8 MeV,20 mA proton beam bombarding a lithium target to produce neutrons that were subsequently moderated and tuned through a tunable beam shaping assembly(BSA)which can modify the thicknesses and materials of the coin-shaped moderators,back reflectors,filters,and collimators.The simulation results demonstrated that epithermal neutron beams for deep seated tumor treatment,which were generated by utilizing magnesium fluoride with lengths ranging between 28 and 36 cm as the moderator,possessed a treatment depth of 5.6 cm although the neutron flux peak shifts from 4.5 to 1.0 keV.When utilizing a thinner moderator,a less accelerated beam power can meet the treatment requirements.However,higher powers reduced the treatment time.In contrast,employing a thick moderator can reduce the skin dose.In scenarios that required relatively low energy neutron beams,the removal of the thermal neutron filter can raise the thermal neutron flux at the beam port.And the depth of the dose rate peak could be adjusted between 0.25 and 2.20 cm by combining magnesium fluoride and polyethylene coins of different thicknesses.Hence,this device has a better adaptability for the treatment of superficial tumors.Overall,the tunable BSA provides greater flexibility for clinical treatment than common BSA designs that can only adjust the port size.展开更多
Back-streaming neutrons from the spallation target of the China Spallation Neutron Source(CSNS)that emit through the incoming proton channel were exploited to build a white neutron beam facility(the so-called Back-n w...Back-streaming neutrons from the spallation target of the China Spallation Neutron Source(CSNS)that emit through the incoming proton channel were exploited to build a white neutron beam facility(the so-called Back-n white neutron source),which was completed in March 2018.The Back-n neutron beam is very intense,at approximately 29107 n/cm2/s at 55 m from the target,and has a nominal proton beam with a power of 100 kW in the CSNS-I phase and a kinetic energy of 1.6 GeV and a thick tungsten target in multiple slices with modest moderation from the cooling water through the slices.In addition,the excellent energy spectrum spanning from 0.5 eV to 200 MeV,and a good time resolution related tothe time-of-flight measurements make it a typical white neutron source for nuclear data measurements;its overall performance is among that of the best white neutron sources in the world.Equipped with advanced spectrometers,detectors,and application utilities,the Back-n facility can serve wide applications,with a focus on neutron-induced cross-sectional measurements.This article presents an overview of the neutron beam characteristics,the experimental setups,and the ongoing applications at Backn.展开更多
Effect of various spatial and energy distributions of fusion neutron sourceon the calculation of neutron wall loading of Tokamak D-D fusion device has been investigated bymeans of the 3-D Monte Carlo code MCNP. A real...Effect of various spatial and energy distributions of fusion neutron sourceon the calculation of neutron wall loading of Tokamak D-D fusion device has been investigated bymeans of the 3-D Monte Carlo code MCNP. A realistic Monte Carlo source model was developed based onthe accurate representation of the spatial distribution and energy spectrum of fusion neutrons tosolve the complicated problem of tokamak fusion neutron source modelling. The results show thatthose simplified source models will introduce significant uncertainties. For accurate estimation ofthe key nuclear responses of the tokamak design and analyses, the use of the realistic source isrecommended. In addition, the accumulation of tritium produced during D-D plasma operation should becarefully considered.展开更多
Owing to the immobility of traditional reactors and spallation neutron sources,the demand for compact thermal neutron radiography(CTNR)based on accelerator neutron sources has rapidly increased in industrial applicati...Owing to the immobility of traditional reactors and spallation neutron sources,the demand for compact thermal neutron radiography(CTNR)based on accelerator neutron sources has rapidly increased in industrial applications.Recently,thermal neutron radiography experiments based on a D-T neutron generator performed by Hefei Institutes of Physical Science indicated a significant resolution deviation between the experimental results and the values calculated using the traditional resolution model.The experimental result was up to 23%lower than the calculated result,which hinders the achievement of the design goal of a compact neutron radiography system.A GEANT4 Monte Carlo code was developed to simulate the CTNR process,aiming to identify the key factors leading to resolution deviation.The effects of a low collimation ratio and high-energy neutrons were analyzed based on the neutron beam environment of the CTNR system.The results showed that the deviation was primarily caused by geometric distortion at low collimation ratios and radiation noise induced by highenergy neutrons.Additionally,the theoretical model was modified by considering the imaging position and radiation noise factors.The modified theoretical model was in good agreement with the experimental results,and the maximum deviation was reduced to 4.22%.This can be useful for the high-precision design of CTNR systems.展开更多
The utilization of neutrons markedly affects the medical isotope yield of a subcritical system driven by an external D-T neutron source.The general methods to improve the utilization of neutrons include moderating mul...The utilization of neutrons markedly affects the medical isotope yield of a subcritical system driven by an external D-T neutron source.The general methods to improve the utilization of neutrons include moderating multiplying,and reflecting neutrons,which ignores the use of neutrons that backscatter to the source direction.In this study,a stacked structure was formed by assembling the multiplier and the low-enriched uranium solution to enable the full use of neutrons that backscatter to the source direction and further improve the utilization of neutrons.A model based on SuperMC was used to evaluate the neutronics and safety behavior of the subcritical system,such as the neutron effective multiplication factor,neutron energy spectrum,medical isotope yield,and heat deposition.Based on the calculation results,when the intensity of the neutron source was 59×10^(13)n/s,the optimized design with a stacked structure could increase the yield of ^(99)Mo to182 Ci/day,which is approximately 16% higher than that obtained with a single-layer structure.The inlet H_(2)O coolant velocity of 1.0 m/s and initial temperature of 20℃ were also found to be sufficient to prevent boiling of the fuel solution.展开更多
A neutron source driven by electron accelerator is proposed in Shanghai Institute of Applied Physics (SINAP). The facility is planned for the study of nuclear data in Thorium-Uranium cycling system, and for material r...A neutron source driven by electron accelerator is proposed in Shanghai Institute of Applied Physics (SINAP). The facility is planned for the study of nuclear data in Thorium-Uranium cycling system, and for material research. A detailed simulation of the neutron source is performed for the program to get the neutron generation maximum economically. Several parameters of the facility, which affect the neutron yield and the neutron escape from outer surface of the target, are analyzed respectively. Besides, the yielding neutron spectrum and the escaping neutron angular distribution are calculated and discussed.展开更多
Controllable D-D neutron sources have a long service life,low cost,and non-radioactivity.There are favorable prospects for its application in geophysical well logging,since traditional chemical radioactive sources use...Controllable D-D neutron sources have a long service life,low cost,and non-radioactivity.There are favorable prospects for its application in geophysical well logging,since traditional chemical radioactive sources used for well logging pose potential threats to the safety of the human body and environment.This paper presents an improved method to measure formation density that employs a D-D neutron source.In addition,the lithological effect on the measured density was removed to better estimate the formation porosity.First,we investigated the spatial distribution of capture gamma rays through Monte Carlo simulations as well as the relationship between the ratio of capture gamma ray counts and formation density to establish theoretical support for the design of density logging tools and their corresponding data processing methods.Second,we obtained the far to near detector counts of captured gamma rays for an optimized tool structure and then established its correlation with the density and porosity of three typical formations with pure quartz,calcite,and dolomite minerals.Third,we determined the values for correcting the densities of sandstone and dolomite with the same porosity using limestone data as the reference and established the equations for calculating the correction values,which lays a solid foundation for accurately calculating formation porosity.We observed that the capture gamma ray counts first increased then decreased and varied in different formations;this was especially observed in high-porosity formations.Under the same lithologic conditions(rock matrix),as the porosity increases,the peak value of gamma ray counts moves toward the neutron source.At different detector-source distances,the ratio of the capture gamma ray counts was well correlated with the formation density.An equation of the formation density conversion was established based on the ratio of capture gamma ray counts at the detector-source distances of 30 cm and 65 cm,and the calculated values were consistent with the true values.After correction,the formation density was highly consistent with the true value of the limestone density,and the mean absolute error was 0.013 g/cm3.The calculated porosity values were very close to the true values,and the mean relative error was 2.33%,highlighting the accuracy of the proposed method.These findings provide a new method for developing D-D neutron source logging tools and their well-log data processing methods.展开更多
The molten salt reactor(MSR) has received much recent attention. The presence of beryllium and the mixing of actinides with light nuclei in the fuel salt result in a relatively strong neutron source that can affect th...The molten salt reactor(MSR) has received much recent attention. The presence of beryllium and the mixing of actinides with light nuclei in the fuel salt result in a relatively strong neutron source that can affect the surveillance at subcritical and transient characteristics during operation. In this study, we predict the inherent neutron sources based on a MSR model. The calculation shows that in the fresh core, the inherent neutron sources are mainly from alpha-induced neutrons. After power operation, the inherent neutron sources become remarkably stronger due to photoneutrons. Although being an insignificant part in the total neutron population during operation, the inherent neutron sources can be used as the installed neutron source after shutdown. If the MSR has continuously operated at full power(2 MWt) for 10 days,then there would be no need for the installed source within80 days after shutdown. After operating constantly for500 days, the installed neutron source can be eliminated within 2 years after shutdown.展开更多
This paper proposes a sub-critical nuclear energy system driven by fusion neutron source, FDS, which can be used to transmute long-lived radioactive wastes and to produce fissile nuclear fuel as a way for early applic...This paper proposes a sub-critical nuclear energy system driven by fusion neutron source, FDS, which can be used to transmute long-lived radioactive wastes and to produce fissile nuclear fuel as a way for early application of fusion technology. The necessity and feasibility to develop that system in China are illustrated on the basis of prediction of the demand of energy source in the first half of the 21th century, the status of current fission energy supply and the progress in fusion technology in the world. The characteristics of fusion neutron driver and the potential for transmutation of long-lived nuclear wastes and breeding of fissile nuclear fuel in a blanket are analyzed. A scenario of development steps is proposed.展开更多
Relativistic electron beams driven by laser wakefield acceleration were utilized to produce ultrashort neutron sources.The experiment was carried out on the 38 fs,~0.5 J,800 nm Ti:Sapphire laser in the 10 TW UT 3 lase...Relativistic electron beams driven by laser wakefield acceleration were utilized to produce ultrashort neutron sources.The experiment was carried out on the 38 fs,~0.5 J,800 nm Ti:Sapphire laser in the 10 TW UT 3 laser lab at University of Texas at Austin.The target gas was a high density pulsed gas jet composed of 90%He and 10%N 2.The laser pulse with a peak intensity of 1.5×10^(18) W/cm^(2) interacted with the target to create a cylindrical plasma channel of 60 mm radius(FWHM)and 1.5 mm length(FWHM).Electron beams of~80 pC with the Gaussian energy distribution centered at 37 MeV and a width of 30 MeV(FWHM)were produced via laser wakefield acceleration.Neutron fluences of~2.4×10^(6) per shot with hundreds of ps temporal length were generated through bremsstrahlung and subsequent photoneutron reactions in a 26.6 mm thick tungsten converter.Results were compared with those of simulations using EPOCH and GEANT4,showing agreement in electron spectrum,neutron fluence,neutron angular distribution and conversion rate.展开更多
Gamma-emitting radionuclide ^(99m)Tc is globally used for the diagnosis of various pathological conditions owing to its ideal single-photon emission computed tomography (SPECT) characteristics.However,the short half-l...Gamma-emitting radionuclide ^(99m)Tc is globally used for the diagnosis of various pathological conditions owing to its ideal single-photon emission computed tomography (SPECT) characteristics.However,the short half-life of ^(99m)Tc (T_(1/2)=6 h)makes it difficult to store or transport.Thus,the production of ^(99m)Tc is tied to its parent radionuclide ^(99)Mo (T_(1/2)=66 h).The major production paths are based on accelerators and research reactors.The reactor process presents the potential for nuclear proliferation owing to its use of highly enriched uranium (HEU).Accelerator-based methods tend to use deuterium–tritium(D–T) neutron sources but are hindered by the high cost of tritium and its challenging operation.In this study,a new ^(99)Mo production design was developed based on a deuterium–deuterium (D–D) gas dynamic trap fusion neutron source (GDT-FNS) and a subcritical blanket system (SBS) assembly with a low-enriched uranium (LEU) solution.GDT-FNS can provide a relatively high-neutron intensity,which is one of the advantages of ^(99)Mo production.We provide a Monte Carlo-based neutronics analysis covering the calculation of the subcritical multiplication factor (k_(s)) of the SBS,optimization design for the reflector,shielding layer,and ^(99)Mo production capacity.Other calculations,including the neutron flux and nuclear heating distributions,are also provided for an overall evaluation of the production system.The results demonstrated that the SBS meets the nuclear critical safety design requirement (k_(s)<0.97) and maintained a high ^(99)Mo production capacity.The proposed system can generate approximately 157 Ci ^(99)Mo for a stable 24 h operation with a neutron intensity of 1×10^(14) n/s,which can meet 50%of China’s demand in 2025.展开更多
To further investigate the fusion neutron source based on a gas dynamic trap （GDT）, characteristics of the GDT were analyzed and physics analyses were made for a fusion neutron source based on the GDT concept. The p...To further investigate the fusion neutron source based on a gas dynamic trap （GDT）, characteristics of the GDT were analyzed and physics analyses were made for a fusion neutron source based on the GDT concept. The prior design of a GDT-based fusion neutron source was optimized based on a refreshed understanding of GDT operation. A two-step progressive development route of a GDT-based fusion neutron source was suggested. Potential applications of GDT are discussed. Preliminary analyses show that a fusion neutron source based on the GDT concept is suitable for plasma-material interaction research, fusion material and subcomponent testing, and capable of driving a proof-of-principle fusion fission hybrid experimental facility.展开更多
Boron neutron capture therapy(BNCT)is recognized as a precise binary targeted radiotherapy technique that effectively eliminates tumors through the^(10)B(n,α)^(7)Li nuclear reaction.Among various neutron sources,acce...Boron neutron capture therapy(BNCT)is recognized as a precise binary targeted radiotherapy technique that effectively eliminates tumors through the^(10)B(n,α)^(7)Li nuclear reaction.Among various neutron sources,accelerator-based sources have emerged as particularly promising for BNCT applications.The^(7)Li(p,n)^(7)Be reaction is highly regarded as a potential neutron source for BNCT,owing to its low threshold energy for the reaction,significant neutron yield,appropriate average neutron energy,and additional benefits.This study utilized Monte Carlo simulations to model the physical interactions within a lithium target subjected to proton bombardment,including neutron moderation by an MgF_(2)moderator and subsequent BNCT dose analysis using a Snyder head phantom.The study focused on calculating the yields of epithermal neutrons for various incident proton energies,finding an optimal energy at 2.7 MeV.Furthermore,the Snyder head phantom was employed in dose simulations to validate the effectiveness of this specific incident energy when utilizing a^(7)Li(p,n)^(7)Be neutron source for BNCT purposes.展开更多
Displacement damage effects on the charge-coupled device(CCD)induced by neutrons at the back-streaming white neutron source(Back-n)in the China Spallation Neutron Source(CSNS)are analyzed according to an online irradi...Displacement damage effects on the charge-coupled device(CCD)induced by neutrons at the back-streaming white neutron source(Back-n)in the China Spallation Neutron Source(CSNS)are analyzed according to an online irradiation experiment.The hot pixels,random telegraph signal(RTS),mean dark signal,dark current and dark signal non-uniformity(DSNU)induced by Back-n are presented.The dark current is calculated according to the mean dark signal at various integration times.The single-particle displacement damage and transient response are also observed based on the online measurement data.The trends of hot pixels,mean dark signal,DSNU and RTS degradation are related to the integration time and irradiation fluence.The mean dark signal,dark current and DSNU2 are nearly linear with neutron irradiation fluence when nearly all the pixels do not reach saturation.In addition,the mechanisms of the displacement damage effects on the CCD are demonstrated by combining the experimental results and technology computer-aided design(TCAD)simulation.Radiation-induced traps in the space charge region of the CCD will act as generation/recombination centers of electron-hole pairs,leading to an increase in the dark signal.展开更多
The energy-resolved neutron imaging spectrometer(ERNI)will be installed in 2022 according to the spectrometer construction plan of the China Spallation Neutron Source(CSNS).The instrument requires neutron detectors wi...The energy-resolved neutron imaging spectrometer(ERNI)will be installed in 2022 according to the spectrometer construction plan of the China Spallation Neutron Source(CSNS).The instrument requires neutron detectors with the coverage area of approximately 4 m^(2)in 5°-170°neutron diffraction angle.The neutron detection efficiency needs to be better than 40%at 1 A neutron wavelength.The spatial resolution should be better than 3 mm×50 mm in the horizontal and vertical directions respectively.We develop a one-dimensional scintillator neutron detector which is composed of the^(6)Li F/Zn S(Ag)scintillation screens,the wavelength-shifting fiber(WLSF)array,the silicon photomultipliers(Si PMs),and the self-designed application-specific integrated circuit(ASIC)readout electronics.The pixel size of the detector is designed as 3 mm×50 mm,and the neutron-sensitive area is 50 mm×200 mm.The performance of the detector prototype is measured using neutron beam 20#of the CSNS.The maximum counting rate of 247 k Hz,and the detection efficiency of63%at 1.59 A are obtained.The test results show that the performance of the detector fulfills the physical requirements of the ERNI under construction at the CSNS.展开更多
Experiments were performed on a high-speed online random neutron analyzing system (HORNA system) with a 252Cf neutron source (up to 1 GHz sampling rate and 3 input data channel),to obtain timeand frequency dependent s...Experiments were performed on a high-speed online random neutron analyzing system (HORNA system) with a 252Cf neutron source (up to 1 GHz sampling rate and 3 input data channel),to obtain timeand frequency dependent signatures which are sensitive to changes in the composition,fissile mass and configuration of the fissile assembly.The data were acquired by three high-speed synchronized acquisition cards at different detector angles,source-detector distances and block sizes.According to the relationship between 252Cf source and the ratio of power spectral density,Rpsd,all the signatures were calculated and analyzed using correlation and periodogram methods.Based on the results,the simulated autocorrelation functions were utilized for identifying different fissile mass with Elman neural network.The experimental results show that the Rpsd almost remains at constant amplitude in frequency range of 0-100 MHz,and is only related to the angle and source-detector distance.The trained Elman neural network is able to distinguish the characteristics of autocorrelation function and identify different fissile mass.The average identification rate reached 90% with high robustness.展开更多
<正>A mathematical method was developed to calculate the yield,energy spectrum and angular distribution of neutrons from D(d,n)~3He(D-D)reaction in a thick deuterium-titanium target for incident deuterons in ene...<正>A mathematical method was developed to calculate the yield,energy spectrum and angular distribution of neutrons from D(d,n)~3He(D-D)reaction in a thick deuterium-titanium target for incident deuterons in energies lower than 1.0MeV.The data of energy spectrum and angular distribution were applied to set up the neutron source model for the beam-shaping-assembly(BSA)design of Boron-Neutron-Capture-Therapy(BNCT)using MCNP-4C code. Three cases of D-D neutron source corresponding to incident deuteron energy of 1000,400 and 150 key were inves- tigated.The neutron beam characteristics were compared with the model of a 2.45 MeV mono-energetic and isotropic neutron source using an example BSA designed for BNCT irradiation.The results show significant differences in the neutron beam characteristics,particularly the fast neutron component and fast neutron dose in air,between the non-isotropic neutron source model and the 2.5 MeV mono-euergetic and isotropic neutron source model.展开更多
基金supported by the Natural Science Foundation of Shandong(ZR2022MD019)Technology Development Project of China Oilfield Services Limited(G2317A-0414T077)+3 种基金Science and Technology Project of China National O shore Oil Corporation(CNOOC-KJ GJHXJSGG YF 2022-01)Open Fund Project of CNPC Logging(CNLC2022-9C06)Fundamental Research Foundation for Central Universities(22CX01001A-2)China National Petroleum Corporation Scientific Research and Technology Development Project(2021DJ3801)。
文摘With the increasing demand for controllable source logging,research on data-processing algorithms that meet accuracy requirements has become key to the development of controllable-source-logging tools.This study theoretically derives the relationship between the formation density and inelastic gamma count rate to investigate the data-processing methods for deuterium–tritium(D–T)source neutron-gamma density logging while drilling.Then,algorithms for the net inelastic gamma count-rate extraction and neutron transport correction are studied using Monte Carlo simulations.A new method for fast-neutron effect identification and additional correction is proposed to improve the density-calculation accuracy of gas-filled and heavy-mineral formations.Finally,the effectiveness and accuracy of the proposed data-processing methods are verified based on simulated and measured data.The results show that the density-calculation accuracy of water-bearing conventional formations in simulated data is±0.02 g/cm^(3).The accuracy of gas-filled and heavy-mineral formations after the additional fast-neutron effect correction is±0.025 g/cm^(3).For the measured data from the actual tool,the algorithms perform well in the density calculation.The density results obtained using the processing algorithms are consistent with the density data provided by NeoScope.Therefore,the D–T source neutron-gamma density-logging algorithms proposed in this study can obtain relatively accurate data-processing results for a variety of formations.This study provides technical support for engineering applications and the development of logging tools for controllable-source neutron-density logging.
基金supported by the National Natural Science Foundation of China(Nos.11775311,U2167203,U2067205 and 12075105)Research and development project of China National Nuclear Corporation(FD010241222552)+2 种基金Continuous-Support Basic Scientific Research Project(BJ010261223282)Major Science and Technology Projects of Gansu Province(22ZD6GB020)Fundamental Research Funds for the Central Universities(lzujbky-2024-jdzx10)。
文摘Beryllium(^(9)Be)serves as a crucial neutron multiplier and reflection material,being extensively employed in the nuclear industry.The evaluated nuclear data are utilized in the design of the nuclear devices.Following the interaction between neutrons and^(9)Be,all neutrons generated stem from the^(9)Be(n,2n)^(8)Be reaction channel,except for the elastic scattering reaction channel.Nevertheless,the data of the outgoing neutron double differential cross section of the reaction channel provided by the latest internationally evaluated libraries still exhibit considerable discrepancies.A shielding integral experiment based on slab^(9)Be samples with measurements of neutron spectra leaked from different angles is an effective approach to verify the double differential cross-section data.Hence,in this study,a shielding integral experiment of^(9)Be samples of different thicknesses was conducted using a nanosecond pulsed deuterium-tritium neutron source established by the China Institute of Atomic Energy.The neutron time-of-flight spectra of three thicknesses(4.4 cm,8.8 cm,and 13.2 cm)and six angles(47°,58°,73°,107°,122°,and 133°)were measured by the neutron time-of-flight method,and 18 sets of experimental data were obtained.Additionally,the MCNP-4C program was used to obtain the simulated results of the leakage neutron spectra using the evaluated nuclear data of^(9)Be from the CENDL-3.2,ENDF/B-Ⅷ.0,JENDL-5,and JEFF-3.3 libraries.The simulated results of the leakage neutron spectra were compared with the experimental results,and the results showed that in the elastic scattering energy region,the simulated results from the CENDL-3.2,ENDF/B-Ⅷ.0,and JENDL-5 libraries were slightly higher at small angles and slightly lower at large angles.In the(n,2n)energy region,the simulated results from the CENDL-3.2 library were significantly different from the experimental results in terms of spectral shape,and the simulated results from the ENDF/B-Ⅷ.0 and the JENDL-5 libraries were in good agreement with the experimental results at small angles but low at large angles.The simulated results from the JEFF-3.3 library showed serious underestimation at all angles.
基金supported by the National Natural Science Foundation of China(Nos.11775311 and U2067205)the Stable Support Basic Research Program Grant(BJ010261223282)the Research and Development Project of China National Nuclear Corporation。
文摘Lead(Pb)plays a significant role in the nuclear industry and is extensively used in radiation shielding,radiation protection,neutron moderation,radiation measurements,and various other critical functions.Consequently,the measurement and evaluation of Pb nuclear data are highly regarded in nuclear scientific research,emphasizing its crucial role in the field.Using the time-of-flight(ToF)method,the neutron leakage spectra from three^(nat)Pb samples were measured at 60°and 120°based on the neutronics integral experimental facility at the China Institute of Atomic Energy(CIAE).The^(nat)Pb sample sizes were30 cm×30 cm×5 cm,30 cm×30 cm×10 cm,and 30 cm×30 cm×15 cm.Neutron sources were generated by the Cockcroft-Walton accelerator,producing approximately 14.5 MeV and 3.5 MeV neutrons through the T(d,n)^(4)He and D(d,n)^(3)He reactions,respectively.Leakage neutron spectra were also calculated by employing the Monte Carlo code of MCNP-4C,and the nuclear data of Pb isotopes from four libraries:CENDL-3.2,JEFF-3.3,JENDL-5,and ENDF/B-Ⅷ.0 were used individually.By comparing the simulation and experimental results,improvements and deficiencies in the evaluated nuclear data of the Pb isotopes were analyzed.Most of the calculated results were consistent with the experimental results;however,a few areas did not fit well.In the(n,el)energy range,the simulated results from CENDL-3.2 were significantly overestimated;in the(n,inl)D and the(n,inl)C energy regions,the results from CENDL-3.2 and ENDF/B-Ⅷ.0 were significantly overestimated at 120°,and the results from JENDL-5 and JEFF-3.3 are underestimated at 60°in the(n,inl)D energy region.The calculated spectra were analyzed by comparing them with the experimental spectra in terms of the neutron spectrum shape and C/E values.The results indicate that the theoretical simulations,using different data libraries,overestimated or underestimated the measured values in certain energy ranges.Secondary neutron energies and angular distributions in the data files have been presented to explain these discrepancies.
基金supported by the National Nature Science Foundation of China(No.1210050454)the program of Chinese Scholarship Council(No.202106280126)。
文摘In the past decade,boron neutron capture therapy utilizing an accelerator-based neutron source(ABNS)designed primarily for producing epithermal neutrons has been implemented in the treatment of brain tumors and other cancers.The specifications for designing an epithermal beam are primarily based on the IAEA-TECODC-1223 report,issued in 2001 for reactor neutron sources.Based on this report,the latest perspectives and clinical requirements,we designed an ABNS capable of adjusting the average neutron beam energy.The design was based on a 2.8 MeV,20 mA proton beam bombarding a lithium target to produce neutrons that were subsequently moderated and tuned through a tunable beam shaping assembly(BSA)which can modify the thicknesses and materials of the coin-shaped moderators,back reflectors,filters,and collimators.The simulation results demonstrated that epithermal neutron beams for deep seated tumor treatment,which were generated by utilizing magnesium fluoride with lengths ranging between 28 and 36 cm as the moderator,possessed a treatment depth of 5.6 cm although the neutron flux peak shifts from 4.5 to 1.0 keV.When utilizing a thinner moderator,a less accelerated beam power can meet the treatment requirements.However,higher powers reduced the treatment time.In contrast,employing a thick moderator can reduce the skin dose.In scenarios that required relatively low energy neutron beams,the removal of the thermal neutron filter can raise the thermal neutron flux at the beam port.And the depth of the dose rate peak could be adjusted between 0.25 and 2.20 cm by combining magnesium fluoride and polyethylene coins of different thicknesses.Hence,this device has a better adaptability for the treatment of superficial tumors.Overall,the tunable BSA provides greater flexibility for clinical treatment than common BSA designs that can only adjust the port size.
基金This work was jointly supported by the National Key Research and Development Program of China(No.2016YFA0401600)National Natural Science Foundation of China(Nos.11235012 and 12035017)+1 种基金the CSNS Engineering Projectthe Back-n Collaboration Consortium fund。
文摘Back-streaming neutrons from the spallation target of the China Spallation Neutron Source(CSNS)that emit through the incoming proton channel were exploited to build a white neutron beam facility(the so-called Back-n white neutron source),which was completed in March 2018.The Back-n neutron beam is very intense,at approximately 29107 n/cm2/s at 55 m from the target,and has a nominal proton beam with a power of 100 kW in the CSNS-I phase and a kinetic energy of 1.6 GeV and a thick tungsten target in multiple slices with modest moderation from the cooling water through the slices.In addition,the excellent energy spectrum spanning from 0.5 eV to 200 MeV,and a good time resolution related tothe time-of-flight measurements make it a typical white neutron source for nuclear data measurements;its overall performance is among that of the best white neutron sources in the world.Equipped with advanced spectrometers,detectors,and application utilities,the Back-n facility can serve wide applications,with a focus on neutron-induced cross-sectional measurements.This article presents an overview of the neutron beam characteristics,the experimental setups,and the ongoing applications at Backn.
基金The project supported partly by the National Science Foundation of Anhui Province (No. 0104360)
文摘Effect of various spatial and energy distributions of fusion neutron sourceon the calculation of neutron wall loading of Tokamak D-D fusion device has been investigated bymeans of the 3-D Monte Carlo code MCNP. A realistic Monte Carlo source model was developed based onthe accurate representation of the spatial distribution and energy spectrum of fusion neutrons tosolve the complicated problem of tokamak fusion neutron source modelling. The results show thatthose simplified source models will introduce significant uncertainties. For accurate estimation ofthe key nuclear responses of the tokamak design and analyses, the use of the realistic source isrecommended. In addition, the accumulation of tritium produced during D-D plasma operation should becarefully considered.
基金supported by the Nuclear Energy Development Project of China (No.[2019]1342)the Presidential Foundation of HFIPS (No.YZJJ2022QN40)。
文摘Owing to the immobility of traditional reactors and spallation neutron sources,the demand for compact thermal neutron radiography(CTNR)based on accelerator neutron sources has rapidly increased in industrial applications.Recently,thermal neutron radiography experiments based on a D-T neutron generator performed by Hefei Institutes of Physical Science indicated a significant resolution deviation between the experimental results and the values calculated using the traditional resolution model.The experimental result was up to 23%lower than the calculated result,which hinders the achievement of the design goal of a compact neutron radiography system.A GEANT4 Monte Carlo code was developed to simulate the CTNR process,aiming to identify the key factors leading to resolution deviation.The effects of a low collimation ratio and high-energy neutrons were analyzed based on the neutron beam environment of the CTNR system.The results showed that the deviation was primarily caused by geometric distortion at low collimation ratios and radiation noise induced by highenergy neutrons.Additionally,the theoretical model was modified by considering the imaging position and radiation noise factors.The modified theoretical model was in good agreement with the experimental results,and the maximum deviation was reduced to 4.22%.This can be useful for the high-precision design of CTNR systems.
基金supported by the Natural Science Foundation of Anhui Province(No.1808085MA10)Anhui Provincial Key R&D Program(No.202104g0102007)the National Natural Science Foundation of China(No.21805283)。
文摘The utilization of neutrons markedly affects the medical isotope yield of a subcritical system driven by an external D-T neutron source.The general methods to improve the utilization of neutrons include moderating multiplying,and reflecting neutrons,which ignores the use of neutrons that backscatter to the source direction.In this study,a stacked structure was formed by assembling the multiplier and the low-enriched uranium solution to enable the full use of neutrons that backscatter to the source direction and further improve the utilization of neutrons.A model based on SuperMC was used to evaluate the neutronics and safety behavior of the subcritical system,such as the neutron effective multiplication factor,neutron energy spectrum,medical isotope yield,and heat deposition.Based on the calculation results,when the intensity of the neutron source was 59×10^(13)n/s,the optimized design with a stacked structure could increase the yield of ^(99)Mo to182 Ci/day,which is approximately 16% higher than that obtained with a single-layer structure.The inlet H_(2)O coolant velocity of 1.0 m/s and initial temperature of 20℃ were also found to be sufficient to prevent boiling of the fuel solution.
文摘A neutron source driven by electron accelerator is proposed in Shanghai Institute of Applied Physics (SINAP). The facility is planned for the study of nuclear data in Thorium-Uranium cycling system, and for material research. A detailed simulation of the neutron source is performed for the program to get the neutron generation maximum economically. Several parameters of the facility, which affect the neutron yield and the neutron escape from outer surface of the target, are analyzed respectively. Besides, the yielding neutron spectrum and the escaping neutron angular distribution are calculated and discussed.
基金supported by the National Natural Science Foundation of China(Nos.41704113,41674129)Key R&D Projects in Shandong Province(No.2019GSF109047)+1 种基金China Postdoctoral Science Foundation Grant(No.2019M661912)Science and Technology Plan Project of Shandong Education of China(Nos.J18KA190 and J18KA128)。
文摘Controllable D-D neutron sources have a long service life,low cost,and non-radioactivity.There are favorable prospects for its application in geophysical well logging,since traditional chemical radioactive sources used for well logging pose potential threats to the safety of the human body and environment.This paper presents an improved method to measure formation density that employs a D-D neutron source.In addition,the lithological effect on the measured density was removed to better estimate the formation porosity.First,we investigated the spatial distribution of capture gamma rays through Monte Carlo simulations as well as the relationship between the ratio of capture gamma ray counts and formation density to establish theoretical support for the design of density logging tools and their corresponding data processing methods.Second,we obtained the far to near detector counts of captured gamma rays for an optimized tool structure and then established its correlation with the density and porosity of three typical formations with pure quartz,calcite,and dolomite minerals.Third,we determined the values for correcting the densities of sandstone and dolomite with the same porosity using limestone data as the reference and established the equations for calculating the correction values,which lays a solid foundation for accurately calculating formation porosity.We observed that the capture gamma ray counts first increased then decreased and varied in different formations;this was especially observed in high-porosity formations.Under the same lithologic conditions(rock matrix),as the porosity increases,the peak value of gamma ray counts moves toward the neutron source.At different detector-source distances,the ratio of the capture gamma ray counts was well correlated with the formation density.An equation of the formation density conversion was established based on the ratio of capture gamma ray counts at the detector-source distances of 30 cm and 65 cm,and the calculated values were consistent with the true values.After correction,the formation density was highly consistent with the true value of the limestone density,and the mean absolute error was 0.013 g/cm3.The calculated porosity values were very close to the true values,and the mean relative error was 2.33%,highlighting the accuracy of the proposed method.These findings provide a new method for developing D-D neutron source logging tools and their well-log data processing methods.
基金supported by the Chinese TMSR Strategic Pioneer Science and Technology Project under Grant No.XDA02010000
文摘The molten salt reactor(MSR) has received much recent attention. The presence of beryllium and the mixing of actinides with light nuclei in the fuel salt result in a relatively strong neutron source that can affect the surveillance at subcritical and transient characteristics during operation. In this study, we predict the inherent neutron sources based on a MSR model. The calculation shows that in the fresh core, the inherent neutron sources are mainly from alpha-induced neutrons. After power operation, the inherent neutron sources become remarkably stronger due to photoneutrons. Although being an insignificant part in the total neutron population during operation, the inherent neutron sources can be used as the installed neutron source after shutdown. If the MSR has continuously operated at full power(2 MWt) for 10 days,then there would be no need for the installed source within80 days after shutdown. After operating constantly for500 days, the installed neutron source can be eliminated within 2 years after shutdown.
文摘This paper proposes a sub-critical nuclear energy system driven by fusion neutron source, FDS, which can be used to transmute long-lived radioactive wastes and to produce fissile nuclear fuel as a way for early application of fusion technology. The necessity and feasibility to develop that system in China are illustrated on the basis of prediction of the demand of energy source in the first half of the 21th century, the status of current fission energy supply and the progress in fusion technology in the world. The characteristics of fusion neutron driver and the potential for transmutation of long-lived nuclear wastes and breeding of fissile nuclear fuel in a blanket are analyzed. A scenario of development steps is proposed.
基金This paper is based upon work supported by the Air Force Office of Scientific Research under award number FA9550-14-1-0045The project was also supported by the NNSA coop-erative agreement DE-NA0002008the Defense Advanced Research Projects Agency's PULSE program(12-63-PULSE-FP014).
文摘Relativistic electron beams driven by laser wakefield acceleration were utilized to produce ultrashort neutron sources.The experiment was carried out on the 38 fs,~0.5 J,800 nm Ti:Sapphire laser in the 10 TW UT 3 laser lab at University of Texas at Austin.The target gas was a high density pulsed gas jet composed of 90%He and 10%N 2.The laser pulse with a peak intensity of 1.5×10^(18) W/cm^(2) interacted with the target to create a cylindrical plasma channel of 60 mm radius(FWHM)and 1.5 mm length(FWHM).Electron beams of~80 pC with the Gaussian energy distribution centered at 37 MeV and a width of 30 MeV(FWHM)were produced via laser wakefield acceleration.Neutron fluences of~2.4×10^(6) per shot with hundreds of ps temporal length were generated through bremsstrahlung and subsequent photoneutron reactions in a 26.6 mm thick tungsten converter.Results were compared with those of simulations using EPOCH and GEANT4,showing agreement in electron spectrum,neutron fluence,neutron angular distribution and conversion rate.
基金supported by Anhui Provincial Key R&D Program (202104g0102007)Hefei Municipal Natural Science Foundation (2022011)+2 种基金Collaborative Innovation Program of Hefei Science CenterChinese Academy of Sciences(2022HSC CIP024)International Partnership Program of Chinese Academy of Sciences (116134KYSB20200001)。
文摘Gamma-emitting radionuclide ^(99m)Tc is globally used for the diagnosis of various pathological conditions owing to its ideal single-photon emission computed tomography (SPECT) characteristics.However,the short half-life of ^(99m)Tc (T_(1/2)=6 h)makes it difficult to store or transport.Thus,the production of ^(99m)Tc is tied to its parent radionuclide ^(99)Mo (T_(1/2)=66 h).The major production paths are based on accelerators and research reactors.The reactor process presents the potential for nuclear proliferation owing to its use of highly enriched uranium (HEU).Accelerator-based methods tend to use deuterium–tritium(D–T) neutron sources but are hindered by the high cost of tritium and its challenging operation.In this study,a new ^(99)Mo production design was developed based on a deuterium–deuterium (D–D) gas dynamic trap fusion neutron source (GDT-FNS) and a subcritical blanket system (SBS) assembly with a low-enriched uranium (LEU) solution.GDT-FNS can provide a relatively high-neutron intensity,which is one of the advantages of ^(99)Mo production.We provide a Monte Carlo-based neutronics analysis covering the calculation of the subcritical multiplication factor (k_(s)) of the SBS,optimization design for the reflector,shielding layer,and ^(99)Mo production capacity.Other calculations,including the neutron flux and nuclear heating distributions,are also provided for an overall evaluation of the production system.The results demonstrated that the SBS meets the nuclear critical safety design requirement (k_(s)<0.97) and maintained a high ^(99)Mo production capacity.The proposed system can generate approximately 157 Ci ^(99)Mo for a stable 24 h operation with a neutron intensity of 1×10^(14) n/s,which can meet 50%of China’s demand in 2025.
基金supported by the IAEA Coordinate Research Project F1.30.15 Conceptual Development of Steady-State Compact Fusion Neutron Sources,the Knowledge Innovation Projects of Chinese Academy of Sciences(No.KJCX2-YW-N37)National Magnetic Confinement Fusion Science Program of China(No.2011GB114004)
文摘To further investigate the fusion neutron source based on a gas dynamic trap （GDT）, characteristics of the GDT were analyzed and physics analyses were made for a fusion neutron source based on the GDT concept. The prior design of a GDT-based fusion neutron source was optimized based on a refreshed understanding of GDT operation. A two-step progressive development route of a GDT-based fusion neutron source was suggested. Potential applications of GDT are discussed. Preliminary analyses show that a fusion neutron source based on the GDT concept is suitable for plasma-material interaction research, fusion material and subcomponent testing, and capable of driving a proof-of-principle fusion fission hybrid experimental facility.
文摘Boron neutron capture therapy(BNCT)is recognized as a precise binary targeted radiotherapy technique that effectively eliminates tumors through the^(10)B(n,α)^(7)Li nuclear reaction.Among various neutron sources,accelerator-based sources have emerged as particularly promising for BNCT applications.The^(7)Li(p,n)^(7)Be reaction is highly regarded as a potential neutron source for BNCT,owing to its low threshold energy for the reaction,significant neutron yield,appropriate average neutron energy,and additional benefits.This study utilized Monte Carlo simulations to model the physical interactions within a lithium target subjected to proton bombardment,including neutron moderation by an MgF_(2)moderator and subsequent BNCT dose analysis using a Snyder head phantom.The study focused on calculating the yields of epithermal neutrons for various incident proton energies,finding an optimal energy at 2.7 MeV.Furthermore,the Snyder head phantom was employed in dose simulations to validate the effectiveness of this specific incident energy when utilizing a^(7)Li(p,n)^(7)Be neutron source for BNCT purposes.
基金Project supported by the Foundation of State Key Laboratory of China(Grant Nos.SKLIPR1903Z,1803)the National Natural Science Foundation of China(Grant Nos.U2167208 and 11875223).
文摘Displacement damage effects on the charge-coupled device(CCD)induced by neutrons at the back-streaming white neutron source(Back-n)in the China Spallation Neutron Source(CSNS)are analyzed according to an online irradiation experiment.The hot pixels,random telegraph signal(RTS),mean dark signal,dark current and dark signal non-uniformity(DSNU)induced by Back-n are presented.The dark current is calculated according to the mean dark signal at various integration times.The single-particle displacement damage and transient response are also observed based on the online measurement data.The trends of hot pixels,mean dark signal,DSNU and RTS degradation are related to the integration time and irradiation fluence.The mean dark signal,dark current and DSNU2 are nearly linear with neutron irradiation fluence when nearly all the pixels do not reach saturation.In addition,the mechanisms of the displacement damage effects on the CCD are demonstrated by combining the experimental results and technology computer-aided design(TCAD)simulation.Radiation-induced traps in the space charge region of the CCD will act as generation/recombination centers of electron-hole pairs,leading to an increase in the dark signal.
基金the National Natural Science Foundation of China(Grant Nos.11875273,U1832111,61964001,and 12275049)the Science Foundation of Guangdong Province of China(Grant No.2020B1515120025)+3 种基金the Neutron Physics Laboratory Funding of China Academy of Engineering Physics(Grant No.2018BC03)the General Project of Jiangxi Province Key Research and Development Program(Grant No.20212BBG73012)the Key Scientific Research Projects of Henan Higher Education Institutions(Grant Nos.23A490002 and 24A490001)the Engineering Research Center of Nuclear Technology Application(Grant No.HJSJYB2021-4)。
文摘The energy-resolved neutron imaging spectrometer(ERNI)will be installed in 2022 according to the spectrometer construction plan of the China Spallation Neutron Source(CSNS).The instrument requires neutron detectors with the coverage area of approximately 4 m^(2)in 5°-170°neutron diffraction angle.The neutron detection efficiency needs to be better than 40%at 1 A neutron wavelength.The spatial resolution should be better than 3 mm×50 mm in the horizontal and vertical directions respectively.We develop a one-dimensional scintillator neutron detector which is composed of the^(6)Li F/Zn S(Ag)scintillation screens,the wavelength-shifting fiber(WLSF)array,the silicon photomultipliers(Si PMs),and the self-designed application-specific integrated circuit(ASIC)readout electronics.The pixel size of the detector is designed as 3 mm×50 mm,and the neutron-sensitive area is 50 mm×200 mm.The performance of the detector prototype is measured using neutron beam 20#of the CSNS.The maximum counting rate of 247 k Hz,and the detection efficiency of63%at 1.59 A are obtained.The test results show that the performance of the detector fulfills the physical requirements of the ERNI under construction at the CSNS.
基金Supported by Natural Science Foundation Project of CQ (CSTC2009BB2188)Fundamental Research Funds for Central Universities (No. CDJXS10120013)
文摘Experiments were performed on a high-speed online random neutron analyzing system (HORNA system) with a 252Cf neutron source (up to 1 GHz sampling rate and 3 input data channel),to obtain timeand frequency dependent signatures which are sensitive to changes in the composition,fissile mass and configuration of the fissile assembly.The data were acquired by three high-speed synchronized acquisition cards at different detector angles,source-detector distances and block sizes.According to the relationship between 252Cf source and the ratio of power spectral density,Rpsd,all the signatures were calculated and analyzed using correlation and periodogram methods.Based on the results,the simulated autocorrelation functions were utilized for identifying different fissile mass with Elman neural network.The experimental results show that the Rpsd almost remains at constant amplitude in frequency range of 0-100 MHz,and is only related to the angle and source-detector distance.The trained Elman neural network is able to distinguish the characteristics of autocorrelation function and identify different fissile mass.The average identification rate reached 90% with high robustness.
文摘<正>A mathematical method was developed to calculate the yield,energy spectrum and angular distribution of neutrons from D(d,n)~3He(D-D)reaction in a thick deuterium-titanium target for incident deuterons in energies lower than 1.0MeV.The data of energy spectrum and angular distribution were applied to set up the neutron source model for the beam-shaping-assembly(BSA)design of Boron-Neutron-Capture-Therapy(BNCT)using MCNP-4C code. Three cases of D-D neutron source corresponding to incident deuteron energy of 1000,400 and 150 key were inves- tigated.The neutron beam characteristics were compared with the model of a 2.45 MeV mono-energetic and isotropic neutron source using an example BSA designed for BNCT irradiation.The results show significant differences in the neutron beam characteristics,particularly the fast neutron component and fast neutron dose in air,between the non-isotropic neutron source model and the 2.5 MeV mono-euergetic and isotropic neutron source model.
