分类： 物理学 >> 核物理学 提交时间： 2023-08-29
摘要： The sensitivity of an experiment to detect the Majorana neutrino mass via neutrinoless double beta decay (0) strongly depends on the rate of background events that can mimic this decay. One major source of this background is the radioactive emissions from the laboratory environment. In our study, we focused on assessing the background contributions from environmental gamma rays, neutrons, and underground muons to the Jinping bolometric demonstration experiment. This experiment uses an array of lithium molybdate crystal bolometers to probe the potential 0 decay of the 100Mo isotope at the China Jinping Underground Laboratory. We also evaluated the shielding effectiveness of the experimental setup through an attenuation study. Our simulations indicate that the combined background from environmental gamma rays, neutrons, and muons in the relevant 100Mo 0 Q-value region can be reduced to approximately 0.003 cts/kg/keV/yr.
分类： 物理学 >> 凝聚态:结构、力学和热性能 提交时间： 2017-03-26
Xin Lai
Xiaopan Jiang
Xingzhong Cao
Xi Zhang
Zhiming Zhang
Xuexiang Cao
Gang Xiang
Baoyi Wang
Long Wei
摘要： In this paper, backscattering of 3-50 keV positrons on Al, Cu, Ag and Au metallic targets has been systematically investigated using GEANT4 code. The dependence of positron backscattering coefficients on atomic number Z, target thickness, incident energy and angles has been discussed comprehensively. Besides, positron backscattering spectra for those metallic targets at different discrete scattering angles were also studied to provide theoretical basis of the most appropriate scattering angle selected for simulation parameters and specified applied measurement techniques. The impact of atomic number Z of targets on positron backscattering spectra was investigated as well. Simulation results are in reasonable agreement with previous experiment data and theoretical work.
分类： 物理学 >> 核物理学 提交时间： 2016-09-13
摘要： The Jiangmen Underground Neutrino Observatory (JUNO) is an experiment proposed to determine the neutrino mass hierarchy and probe the fundamental properties of neutrino oscillation. The JUNO central detector is a spherical liquid scintillator detector with 20 kton fiducial mass. It is required to achieve a 3%/E(MeV)−−−−−−−√ energy resolution with very low radioactive background, which is a big challenge to the detector design. In order to ensure the detector performance can meet the physics requirements, reliable detector simulation is necessary to provide useful information for detector design. A simulation study of natural radioactivity backgrounds in the JUNO central detector has been performed to guide the detector design and set requirements to the radiopurity of detector materials.
分类： 物理学 >> 核物理学 提交时间： 2025-06-06
摘要： Leakage neutron spectra from a pure 238U slab sample (dimensions: 100 mm × 100 mm × 20 mm) bombarded by broad-spectrum neutrons were measured at 0° using the time-of-flight method. The experiment was carried out at the Radioactive Ion Beam Line of the Heavy Ion Research Facility in Lanzhou at the Institute of Modern Physics, Chinese Academy of Sciences. Broad-spectrum neutrons were generated by bombarding a tungsten target with 80.5 MeV/u 12C ions. Additionally, calculations were performed in GEANT4 with the INCL, BIC and BERT physics models, in combination with the evaluated nuclear data libraries ENDF/BVIII, JEFF-3.3, and JENDL-4.0, and the theoretical results for the leakage neutron spectrum of the 238U were obtained under the same experimental conditions. The results indicate that the GEANT4 calculations can reasonably reproduce the experimental data.
分类： 物理学 >> 核物理学 提交时间： 2025-04-11
摘要： The ultra-low background gamma detector designed in this study consists of a compact stacked anti-Compton gamma detector composed of a LaBr₃(Ce) primary crystal and a CsI(Tl) secondary crystal. Based on Geant4 simulations, the anti-coincidence system combining LaBr₃(Ce) and CsI(Tl) crystals was optimized to shield more than 99% of cosmic ray muons while reducing Compton continuum counts and improving the peak-to-Compton ratio, achieving a Compton suppression factor of 5.73 for 137Cs. Geant4 simulations and neural network algorithms were employed to optimize the physical shielding system surrounding the detector. The optimized shielding configuration effectively reduces background counts caused by low- and medium-energy neutrons (below 20 MeV) from cosmic rays by approximately 90% and blocks nearly all gamma rays emitted from laboratory walls. Furthermore, Geant4 simulations estimate that the shielding efficiency of an eight-story building and basement structure for high-energy neutrons (above 20 MeV) from cosmic rays is close to 99%.
分类： 物理学 >> 核物理学 提交时间： 2025-03-26
Wang, Prof. Xiaoli
Shi, Mr. Shucheng
Han, Mr. Chenyao
Ma, Mr. Yiming
Shi, Prof. Quanqi
Wang, Dr. Shuai
Feng, Ms. Jiao
Wang, Mr. Shuai
摘要： In recent years, there have been fewer missions to detect neutrons in the low Earth orbit (LEO), and the data obtained have been extremely limited. Studying the distribution of the neutron energy spectrum in LEO through detection can help to solve three major scientific problems: the source of particles in the inner radiation belt, information on solar accelerated particles and the proportion of neutrons from different sources in near-Earth space. The detection efficiency and accuracy of neutrons are affected by the charged particles and primary particles in the environment and the secondary neutrons produced by the spacecraft itself, which has been a hot research topic. The neutron spectrometer developed in this paper adopts two combinations of 15 silicon detectors in terms of detector type and arrangement, which are used for neutron detection by nuclear reaction method and recoil proton method, respectively, in which 27 $\upmu$m-thick $^6$LiF conversion layer is used for thermal neutron detection up to 0.4 eV and 300 $\upmu$m-thick high density polyethylene (HDPE) conversion layer is used for fast neutron detection up to 14 MeV and below. The design of the detector set can also remove the influence of primary charged particles and secondary neutrons in the environment to be detected to a certain extent, improving the accuracy of neutron detection. This paper has completed the neutron spectrometer hardware, firmware, software design, and the basic performance of the front-end readout chip SKIROC2A was tested, the readout circuit of each channel baseline ADC code is less than 17, so the channel consistency is good. The RMS noise of the channel baseline is only 7.1 mV and has good stability. The maximum number of events that can be processed per second is 75. The overall power consumption is 3 W, weight is 792 g, and volume is less than 1 dm$^{3}$. In addition, the neutron spectrometer was tested for principle and detection efficiency using various neutron sources such as $^{241}$Am-Be neutron source, 2.5 MeV neutron beam current, 14 MeV neutron beam current, etc., and the experiments were analyzed with corresponding simulations. The experimental data and the simulation results are in good agreement and meet the design expectations. The intrinsic detection efficiency of the probes used in neutron spectrometer is 1.05\% for 14 MeV fast neutrons.
分类： 物理学 >> 核物理学 提交时间： 2025-01-22
Wang, Prof. Xiaoli
Shi, Mr. Shucheng
Han, Mr. Chenyao
Ma, Mr. Yiming
Shi, Prof. Quanqi
Wang, Dr. Shuai
Feng, Ms. Jiao
Wang, Mr. Shuai
摘要： In recent years, there have been fewer missions to detect neutrons in the low Earth orbit (LEO), and the data obtained have been extremely limited. Studying the distribution of the neutron energy spectrum in LEO through detection can help to solve three major scientific problems: the source of particles in the inner radiation belt, information on solar accelerated particles and the proportion of neutrons from different sources in near-Earth space. The detection efficiency and accuracy of neutrons are affected by the charged particles and primary particles in the environment and the secondary neutrons produced by the spacecraft itself, which has been a hot research topic. The neutron spectrometer developed in this paper adopts two combinations of 15 silicon detectors in terms of detector type and arrangement, which are used for neutron detection by nuclear reaction method and recoil proton method, respectively, in which 27 $\upmu$m-thick $^6$LiF conversion layer is used for thermal neutron detection up to 0.4 eV and 300 $\upmu$m-thick high density polyethylene (HDPE) conversion layer is used for fast neutron detection up to 14 MeV and below. The design of the detector set can also remove the influence of primary charged particles and secondary neutrons in the environment to be detected to a certain extent, improving the accuracy of neutron detection. This paper has completed the neutron spectrometer hardware, firmware, software design, and the basic performance of the front-end readout chip SKIROC2A was tested, the readout circuit of each channel baseline ADC code is less than 17, so the channel consistency is good. The RMS noise of the channel baseline is only 7.1 mV and has good stability. The maximum number of events that can be processed per second is 75. The overall power consumption is 3 W, weight is 792 g, and volume is less than 1 dm$^{3}$. In addition, the neutron spectrometer was tested for principle and detection efficiency using various neutron sources such as $^{241}$Am-Be neutron source, 2.5 MeV neutron beam current, 14 MeV neutron beam current, etc., and the experiments were analyzed with corresponding simulations. The experimental data and the simulation results are in good agreement and meet the design expectations. The intrinsic detection efficiency of the probes used in neutron spectrometer is 1.05\% for 14 MeV fast neutrons.
分类： 物理学 >> 核物理学 提交时间： 2023-10-31
摘要： The Coulomb barrier and electron screening cause difficulties in directly measuring nuclear reaction cross sections of charged particles in astrophysical energies. The Trojan-horse method has been introduced to solve the difficulties as a powerful indirect tool. In order to understand experimental spectra better, Geant4 is employed to simulate the method for the first time. Validity and reliability of the simulation are examined by comparing the experimental data with simulated results. The Geant4 simulation can give useful information to understand the experimental spectra better in data analysis and is beneficial to the design for future related experiments.
分类： 核科学技术 >> 核材料与工艺技术 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： The average absorbed dose in glandular tissue is the most appropriate parameter for the assessment of the radiation-induced risk during breast imaging. The aims of this work concern: (1) the investigation of the variation effect of any related update to photon cross-section data-bases on the computation of the normalized glandular dose (DgN) for mammography quality control tests and (2) the proposition of a parameterization method leading to provide DgN values function of the breast thickness (T) and the particle energy (E) instead of E alone, as normally known. We analyzed the change effect of the photon cross-section data-bases on the computation of DgN. Those coefficients, generated using the Geant4 Monte Carlo toolkit, were studied over a range of compressed breast thickness of 28 cm for monoenergetic (1120 keV by 1 keV intervals) and polyenergetic (2335 kVp by 2 kVp intervals) X-ray beams. Moreover, breast tissue composition ranging from about 0% glandular (about 100% adipose) to 100% glandular (0% adipose) was also covered. The successful parameterization of DgN look-up table function of the breast thickness and energy, will compact its analytical form without loss of accuracy. All parameterization fits resulted in r2 values of 0.999 or better.
分类： 物理学 >> 基本粒子与场物理学 分类： 物理学 >> 核物理学 分类： 物理学 >> 交叉学科物理及相关领域的科学与技术 提交时间： 2024-12-24
摘要： Cerenkov detector has its advantage to construct the reaction vertex and incident direction of the energetic particles, and thus to locate the emission source. We propose to measure the neutrino source by modular photomultiplier tube (PMT) array using clean and transparent deep sea water as sensitive medium. The feasibility of the detection of solar neutrino is demonstrated by full simulation based on Geant4 packages. The production and transport of Cerenkov photons generated by the neutrino electron scattering are simulated. Houth transform method is applied to reconstruct the vertex and the direction of the high-speed electron, as well as the incident direction of the neutrinos. The dominant background of gamma radiation from 40K in sea water can be suppressed by a factor of 10^7 if a threshold on the number of firing PMTs is introduced. The total reconstruction efficiency increases with the incident energy, reaching 25% for 6 MeV neutrino and 52% for 10 MeV neutrino, respectively. To locate an existing neutrino source, a certain number of neutrino events are required, depending on the background intensity above the threshold. The simulation results reveal how feasible to measure solar neutrino using deep sea water.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-07-28
Ma, Long
Xie, Dehao
Wang, Yanxi
Wang, Shuo
Han, Jifeng
Lin, Weiping
Liu, Jianli
Liu, Xingquan
Liu, Yuguo
Luo, Xiaobing
Luo, Yuan
Qu, Guofeng
Qu, Yufan
Ren, Peipei
Wada, Roy
Zang, Linge
Zhu, Jingjun
摘要： Stripping unit plays an important role in the neutral particle analyzer (NPA). An updated gas stripping unit was constructed for the newly designed E//B NPA. The pressures at the gas inlet ($P_0$) and the vacuum chamber ($P_3$) were measured with the working gas of H$_2$, and the pressure distribution inside the gas stripping room was calculated using Ansys Fluent with the measured $P_0$ and $P_3$ as the boundary conditions. The stripping efficiency of the stripping unit is then simulated using Geant4 Monte Carlo code for H and D particles. The pressure $P_0$ = 40 Pa, which is four times less than that in previous design and corresponds to a thickness of 1.27$\times 10^{17}$ atoms/cm$^2$, is obtained as the optimum working pressure for the updated stripping unit.A 50 kV electron cyclotron resonance (ECR) ion source platform has been designed and constructed for the E//B NPA calibration, and its performance was measured. Utilizing the ECR ion source platform, the efficiency of the stripping unit was measured in an inverse experiment with proton beams. The current ratio of the measurements with and without H$_2$ gas are compared with those of Geant4 simulation. Good agreements of the overall trend between the experiment and the simulation are found. The large deviation at the incident energy below 20 keV could be the scattering effect of low energy protons, where the accuracy breaks down in the single scattering physics involved in the Geant4 simulations. {After the scattering corrections observed in the reverse experiments, more accurate stripping efficiencies for H and D atoms in the energy range of 20-200 keV are obtained and the global efficiency reaches the maximum values of 95.0\% for H atoms and 78.9\% for D atoms at 200 keV.
分类： 物理学 >> 核物理学 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： The characteristic gamma-ray spectrum of TNT in the soil induced by DT neutrons is measured by the PFTNA demining system. The GEANT4 toolkit is used to simulate the whole experimental procedure. The simulated spectra are compared with the experimental spectra, and they are mainly consistent. The share of the background sources such as neutrons and gamma is obtained and the contribution that the experimental apparatus to the background, such as shielding, detector sleeve and moderator, is analyzed. The effective gamma signal (from soil and TNT) is 29% of the full spectrum signal, and the background signal, more than 68%, this is mainly produced by shielding and the detector sleeve. By gradually optimizing the shielding and the cadmium sheet of the detector sleeve, the share of the effective gamma signal increases to 47%, and the background signal reduces to 18%.
分类： 核科学技术 >> 核探测技术与核电子学 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： A concept of space radiation-voltaic batteries (SRVBs) based on various space radiation environments, including the earth radiation belt ( ERB), solar proton event ( SPE), and galactic cosmic rays ( GCRs) is presented in this paper. The energy deposition, structural parameter optimization, and output performance of SRVBs are studied through the Monte Carlo toolkit Geant4 and theoretical formulas. Energy deposition in the three radiation environments monotonically decreases as the depth in both silicon film models and energy conversion units of the SRVBs increase. The recommended junction depths of SRVBs based on ERB, SPE, and GCR are 0.5, 3.0, and 0.5 m, respectively. In the proposed design scheme, the maximum output power density of SRVBs in ERB, SPE, and GCR are 2.02210-7, 1.11310-3, and 3.84410-17 Wcm-2, respectively. Calculation results suggest that SRVBs based on ERB and SPE are high-potential candidates for space power sources. The results could help raise awareness on the use of space radiation particle energy and facilitate research on SRVBs.
分类： 核科学技术 >> 核探测技术与核电子学 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： With a Geant4 software package based on the Monte Carlo method, a multi-cell 4 detection system is designed, which consists of 40 Gadolinium-loaded liquid scintillation detectors. These detectors, associated with a fission chamber in its geometrical center, constitute a platform. This platform is mainly used for the measurement of a fissionable nucleus (n, 2n) reaction cross section. In order to properly determine the experimental set-up, we carry out a systematic numerical simulation using our model which is established by the Geant4 software package. This work provides rich and valuable reference data for experiments on the fissionable nucleus (n, 2n) cross section measurement in the future.
分类： 核科学技术 >> 粒子加速器 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： Direct demodulation method (DDM) was applied to reconstruct -ray spectra. Boosted Richardson-Lucy iteration was introduced into DDM. Monte Carlo method (here GEANT 4) was proposed to calibrate response function and establish response matrix. First, gauss function was regarded as total energy peak. Spectra line was simulated with nine gauss functions. And afterwards DDM was applied to reconstruct the simulated spectra line and determine peak positions and areas. Compared with original spectra, for case that peak position interval was about 1/3 full width half maximum (FWHM), the error of rebuilding peak position was 2 channels. The rest of peaks could be searched accurately. The relative errors of all peaks area were less than 4%. Then, three key factors, including noise, background, response matrix, were discussed. Finally, DDM was applied to calibrate the field NaI gamma spectrometer. The errors of U, Th, K were less than 5%. Comprehensive studies have shown that it is feasible to reconstruct gamma-ray spectra with DDM. DDM can significantly pseudo-improve energy resolution of gamma spectrometer, effectively decompose doublets whose peak potential interval is 1/3 FHWM, and accurately search peak and calculate areas. DDM can restrain noise strongly but is greatly influenced by background. And DDM can improve the accuracy of qualitative and quantitative analysis in combination with the conventional spectrum analysis method.
分类： 物理学 >> 核物理学 提交时间： 2025-05-22
摘要： The Cerenkov detector has a distinct advantage in constructing the reaction vertex and incident direction of energetic particles, enabling the identification of emission sources. We propose a novel approach to measure neutrino sources by employing a modular photomultiplier tube (PMT) array, utilizing clean and transparent deep sea water as the sensitive medium. The feasibility of detecting solar neutrinos is demonstrated through extensive simulations using the Geant4 package. These simulations incorporate the production and transport of Cerenkov photons generated by electron scattering, with the Hough transform method applied to enhance the accuracy of vertex and direction reconstruction, particularly in the presence of noisy or incomplete data. The dominant background from γ-radiation due to 40K in seawater can be suppressed by a factor of 10^7 by introducing a threshold on the number of triggered PMTs. The total reconstruction efficiency increases with incident energy, achieving 25% for 6 MeV neutrinos and 52% for 10 MeV neutrinos, respectively. For source localization, a sufficient number of neutrino events must be detected, depending on background intensity above the threshold. The Hough transform is also applied to manage high noise levels during this process. The simulation results confirm the feasibility of detecting solar neutrinos using deep sea water, paving the way for future underwater neutrino detection systems.
分类： 物理学 >> 核物理学 提交时间： 2025-04-06
摘要： The Cerenkov detector has a distinct advantage in constructing the reaction vertex and incident direction of energetic particles, enabling the identification of emission sources. We propose a novel approach to measure neutrino sources by employing a modular photomultiplier tube (PMT) array, utilizing clean and transparent deep sea water as the sensitive medium. The feasibility of detecting solar neutrinos is demonstrated through extensive simulations using the Geant4 package. These simulations incorporate the production and transport of Cerenkov photons generated by electron scattering, with the Hough transform method applied to enhance the accuracy of vertex and direction reconstruction, particularly in the presence of noisy or incomplete data. The dominant background from γ-radiation due to 40K in seawater can be suppressed by a factor of 10^7 by introducing a threshold on the number of triggered PMTs. The total reconstruction efficiency increases with incident energy, achieving 25% for 6 MeV neutrinos and 52% for 10 MeV neutrinos, respectively. For source localization, a sufficient number of neutrino events must be detected, depending on background intensity above the threshold. The Hough transform is also applied to manage high noise levels during this process. The simulation results confirm the feasibility of detecting solar neutrinos using deep sea water, paving the way for future underwater neutrino detection systems.
分类： 物理学 >> 核物理学 提交时间： 2025-01-06
摘要： Cerenkov detector has its advantage to construct the reaction vertex and incident direction of the energetic particles, and thus to locate the emission source. We propose to measure the neutrino source by modular photomultiplier tube (PMT) array using clean and transparent deep sea water as sensitive medium. The feasibility of the detection of solar neutrino is demonstrated by full simulation based on Geant4 packages. The production and transport of Cerenkov photons generated by the νe-e scattering are simulated. Houth transform method is applied to reconstruct the vertex and the direction of the high-speed electron, as well as the incident direction of the neutrinos. The dominant background of gamma radiation from 40K in sea water can be suppressed by a factor of 10^7 if a threshold on the number of firing PMTs is introduced. The total reconstruction efficiency increases with the incident energy, reaching 25% for 6 MeV neutrino and 52% for 10 MeV neutrino, respectively. To locate an existing neutrino source, a certain number of neutrino events are required, depending on the background intensity above the threshold. The simulation results reveal how feasible to measure solar neutrino νe using deep sea water.
分类： 核科学技术 >> 核探测技术与核电子学 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： The Dragon-I linear induction accelerator (LIA) at China Academy of Engineering Physics generates 20 MeV flash X-rays mainly for radiography applications in fluid dynamics. Its spectral information is quite important for diagnostic X-ray imaging applications, but because of its short pulse and great radiation intensity, direct measurement is impossible. In this work, we propose a new method based on transmission measurements to obtain the flash X-ray spectrum. Pure iron cylinders were used as attenuation material, and alanine dosimeters were attached on their rear bottom to record the dose after different degrees of attenuation. Iterative least square method was used to unfold the spectrum, while Geant4 Monte Carlo code was used to simulate the X-ray spectrum. The unfolded spectrum and the simulated spectrum have a high degree of consistency, with the reduced chi-square value of 0.044. This shows that the method is reliable in estimating megavoltage high-intensity X-ray spectrum.
分类： 核科学技术 >> 核探测技术与核电子学 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： In order to realize the on-line real-time measurement of neutron spectrum of ITER fusion, this paper presents a multi-sphere spectrometer system which consists of eight thermal neutron detectors, namely SP9 3He proportional counter, embedded in eight different diameter polyethylene spheres. The response function of eight polyethylene spheres of multi-sphere neutron spectrometer was calculated after the simulation of the neutron transport processes in multi-sphere spectrometer by adopting software Geant4. The peak of the response function is in the low energy region for smaller diameter polyethylene sphere. As the polyethylene sphere diameter increased, the peak of the response function moves to the high energy region. The experimental calibration adopts 241Am-Be neutron source. The relative error between normalized data of experiment 4 solid angle counts and normalized data of simulated detection efficiency of 4in to 8in polyethylene sphere is from 1.152% to 12.222%.The experimental results verify the response function of the simulation. All these results provide a theoretical and experimental basis for solving the on-line real-time neutron spectrum of ITER fusion.
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