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
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: 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 >> 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: 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.
分类: 物理学 >> 核物理学 提交时间: 2023-12-29
摘要: The energetic bremsstrahlung photons up to 100 MeV produced in heavy ion collisions can be used as asensitive probe to the short range correlation in atomic nuclei. The energy of the -rays can be measuredby collecting theˇCerenkov light in medium induced by the fast electrons generated in Compton scattering orelectromagnetic shower of the incident ray. Two types of detectors, based on pure water and lead glass asthe sensitive material respectively, are designed for the above purpose. The response and optical photonpropagation in detectors have been simulated based on the electromagnetic and optical processes in Geant4.The inherent energy resolution of 0.022(4) + 0.51(2)/E 1/2 for water and 0.0026(3) + 0.446(3)/E 1/2 forlead glass are obtained. The geometry size of lead glass and water are optimized at 30 30 30 cm3 and60 60 120 cm3 , respectively, for detecting high energy -rays at 160 MeV. Hough transform method hasbeen applied to reconstruct the direction of the incident -rays, giving the ability to distinguish experimentallythe high-energy rays produced in the reactions on the target from the random background cosmic ray muons.
分类: 物理学 >> 核物理学 提交时间: 2023-06-07
摘要: 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 high 1 energy 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.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-05-31
摘要: To further research on high-parameter plasma, we plan to develop a two-dimensional hard X-ray (HXR) imag#2;ing system at the HL-3 tokamak to measure HXRs with energies ranging from 20 to 300 keV. The application of an array-structured detector ensures that this system can measure HXR-radiation spectra from the entire plasma cross section. Therefore, it is suitable for the study of fast-electron physics, such as radio-frequency wave current drives, fast electrons driving instabilities, and plasma disruptions in fusion research. In this study, we develop a simulation for calculating fast-electron bremsstrahlung in the HL-3 tokamak based on the Monte Carlo simulation code Geant4, in which the plasma geometry and forward scattering of fast-electron bremsstrahlung are considered. The preliminary calculation results indicate that the HXR energy deposition on the detector is symmetrically distributed, even though the plasma distribution is asymmetric owing to the toroidal effect. These simulation results are helpful in constructing the relationship between the energy deposition on the de#2;tector and parameter distribution on the plasma cross section during HL-3 experiments. This is beneficial for the reconstruction of the fast-electron distribution function and for optimizing the design of the HXR-imaging system.
分类: 物理学 >> 核物理学 提交时间: 2023-06-09 合作期刊: 《Nuclear Science and Techniques》
摘要: Real-time monitoring of the 14-MeV D-T fusion neutron yield is urgently required for the triton burnup study on the Experimental Advanced Superconducting Tokamak (EAST). In this study, we developed an optimal design of a fast-neutron detector based on the scintillating fiber (Sci-Fi) to provide D-T neutron yield through Geant4 simulation. The effect on the detection performance is concerned when changing the number of the Sci-Fis embedded in the probe head, minimum distance between the fibers, length of the fibers, or substrate material of the probe head. The maximum number of scintillation photons generated by the n/γ source particles and output by the light guide within an event (event: the entire simulation process for one source particle) was used to quantify the n/γ resolution of the detector as the main basis. And the intrinsic detection efficiency was used as another evaluation criterion. The results demonstrate that the optimal design scheme is to use a 5-cm probe head whose substrate material is pure aluminum, in which 463 Sci-Fis with the same length of 5 cm are embedded, and the minimum distance between the centers of the two fibers is 2 mm. The optimized detector exhibits clear directionality in the simulation, which is in line with the expectation and experimental data provided in the literature. This study presents the variation trends of the performance of the Sci-Fi detector when its main parameters change, which is beneficial for the targeted design and optimization of the Sci-Fi detector used in a specific radiation environment.
分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2024-05-11
摘要: 针对钍基熔盐堆白光中子源(TMSR-PNS)在运行过程中出现中子束流掉束或打火导致的束流不稳定的问题,有必要设计研发一种具有高计数率、低中子束流影响、高中子/伽马甄别性能的中子束流监测器。基于蒙特卡洛模拟软件Geant4系统研究了薄膜塑料闪烁中子束流监测器的中子转换层厚度、闪烁体厚度、以及外壳材料等关键参数对薄膜闪烁体的影响规律,分析结果表明:闪烁体中子转换层厚度约为2 um时具有相对合适的本征探测效率,闪烁体厚度为2 mm、甄别阈值为0.1 MeV时监测器具备伽马射线不灵敏性能。同时,通过对比不同外壳材料对于γ射线产生电子的影响,选取电子产生较少的铁作为外壳材料。研究结果可为后续的中子束流监测器实物制备提供理论依据。
分类: 物理学 >> 核物理学 提交时间: 2024-03-28
摘要: 中能区电荷交换反应可以从自旋-同位旋激发的角度研究原子核复杂结构。利用中国科学院近代物理研究所的放射性束流线,利用逆运动学方法进行电荷交换反应实验,可以将研究的对象核素拓展至丰中子核乃至不稳定核。基于此,设计了用于电荷交换反应实验的探测器系统,该系统主要包括了3He气体靶、TPC和CsI(Tl) 阵列,其中TPC和CsI(Tl) 阵列构成ΔE-E系统。利用Geant4、Garfield++等模拟软件,优化了TPC的工作条件,确定了实验研究的运动学区间和探测器的基本设计,考察了探测系统的粒子鉴别能力。基于模拟优化,搭建了探测系统。
分类: 物理学 >> 核物理学 提交时间: 2023-08-11
摘要: 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 DT 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 (
分类: 物理学 >> 核物理学 提交时间: 2023-06-26
摘要: Neutral Particle Analyzer (NPA) is one of the crucial diagnostic devices on Tokamak facilities. Stripping unit is one of the main parts of the NPA. A windowless gas stripping room with two differential pipes is adopted in a parallel direction of electric and magnetic fields (E//B) NPA. The pressure distributions in the stripping chamber are simulated by Ansys Fluent together with MolFlow+. Based on the pressure distributions extracted from the simulation, the stripping efficiency of the E//B NPA is studied with GEANT4. The hadron reaction physics is modified to track the charge state of each particle in a cross section base method in GEANT4. The transmission rates ($R$) and the stripping efficiencies $f_{+1}$ are examined for the particle energy ranging from 20 to 200 keV at the input pressure ($P_0$) ranging from 20 to 400 Pa. According to the combined global efficiency, $R \times f_{+1}$, $P_0$ = 240 Pa is obtained as the optimum pressure for the maximum global efficiency in the incident energy range investigated.
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: A Neutron Time-Of-Flight (NTOF) spectrometer, based at the Heavy Ion Research Facility in Lanzhou (HIRFL) was developed for studies of neutron production of proton induced spallation reactions related to the ADS project. After the presentation of comparisons between calculated spallation neutron production double-differential cross sections and the available experimental data, a detailed description of the NTOF spectrometer is given. Test beam results show that the spectrometer works well and data analysis procedures are established. The comparisons of the test beam neutron spectra with those of GEANT4 simulations are presented.