分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-08-06
Yang Junkai
Wang Ping Quan
Zhang hui
Chungming Paul Chu
Hu Zhimeng
Li Fan
Zeng Junmei
Xiao Lin
Guo Hongyu
Zhang Jian
Giuseppe Gorini
摘要： The neutron radiation field has vital applications in areas such as biomedicine, geology, radiation safety, andmany others for neutron detection and neutron metrology. Correcting neutron fluence rate perturbation accuratelyis an important yet challenging problem. This study proposes a correction method that analyzes threephysical processes. This method, which transforms the detection process from point detection to area detection,is based on a novel physical model and has been validated through theoretical analyses, experiments, and simulations.According to the average differences between the calculated and experimental results, the new method(1.67%)demonstrated better accuracy than the traditional simulation (2.17%). In a closed thermal neutron radiationfield, the detector or strong neutron absorption material significantly perturbs the neutron fluence rate,whereas its impact on the energy spectrum shape and neutron directionality is relatively minor. Furthermore,based on the calculation results of the perturbation rate formula for medium materials with different compositionsand sizes, the larger the volume and capture cross-section of the medium, the higher the perturbation rategenerated in the closed radiation field
分类： 核科学技术 >> 辐射物理与技术 分类： 物理学 >> 核物理学 提交时间： 2024-08-06
摘要： The back-streaming white-neutron beam line (Back-n) of the China Spallation Neutron Source is an essential neutron-research platform built for the study of nuclear data, neutron physics, and neutron applications. Many types of cross-sectional neutron-reaction measurements have been performed at Back-n since early 2018. These measurements have shown that a significant number of gamma rays can be transmitted to the experimental stations of Back-n along with the neutron beam. These gamma rays, commonly referred to as in-beam gamma rays, can induce a non-negligible experimental background in neutron-reaction measurements. Studying the characteristics of in-beam gamma rays is important for understanding the experimental background. However, measuring in-beam gamma rays is challenging because most gamma-ray detectors are sensitive to neutrons; thus, discriminating between neutron-induced signals and those from in-beam gamma rays is difficult. In this study, we propose the use of the black resonance filter method and a CeBr3 scintillation detector to measure the characteristics of the in-beam gamma rays of Back-n. Four types of black resonance filters, 181Ta, 59Co, natAg, and natCd, were used in this measurement. The time-of-flight (TOF) technique was used to select the detector signals remaining in the absorption region of the TOF spectra, which were mainly induced by in-beam gamma rays. The energy distribution and flux of the in-beam gamma rays of Back-n were determined by analyzing the deposited energy spectra of the CeBr3 scintillation detector and using Monte Carlo simulations. Based on the results of this study, the background contributions from in-beam gamma rays in neutron-reaction measurements at Back-n can be reasonably evaluated, which is beneficial for enhancing both the experimental methodology and data analysis.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-07-31
摘要： Short-lived medical isotopes and their generators are typically produced in nuclear reactors and cyclotrons that require extensive facilities. However, considering the environmental concerns and economic costs of these traditional approaches, modern laser technology, which provides extremely strong electric fields within tabletopsized areas, can serve as a potential supplementary method. Focusing specifically on the (γ, p) generation of the vital medical isotopes 47Sc and 67Cu, we used both experimental results and PIC-GEANT4 simulations to demonstrate that laser-induced photonuclear reaction is a promising method for isotope production. We developed a model capable of calculating isotope yields under various laser conditions and acceleration mechanisms. The findings revealed that a 200 TW laser can sufficiently produce diagnostic amounts of 47Sc and 67Cu, while simultaneously providing high specific activity, which is significant in medical applications for improving treatment efficacy, enhancing image resolution, and reducing side effects.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-07-30
摘要： The covariant density functional theory (CDFT) and five-dimensionalcollective Hamiltonian (5DCH) are used to analyze the experimentaldeformation parameters and moments of inertia (MoIs) of 12 triaxialnuclei extracted by Allmond and Wood [J. M. Allmond and J. L. Wood,\href{https://doi.org/10.1016/j.physletb.2017.01.072}{Phys. Lett. B \textbf{767},226 (2017)}]. It is found that the CDFT MoIs are generally smaller thanexperimental values but show qualitative consistency with irrotationalflow and experimental data for the relative MoIs, supporting that theintermediate axis has the largest MoI. It is furtherfound that the collapse of pairing interaction can lead to the nucleibehave like a rigid-body flow as exhibited in the casesof \ce{^{186-192}Os}}. In addition, by incorporating enhancedCDFT MoIs (a factor of $f\approx 1.55$) into 5DCH,the experimental low-lying energy spectra and deformation parametersare reproduced successfully. When contrasted with both the CDFT andthe triaxial rotor model (TRM), the 5DCH demonstrates superioragreement with experimental deformation parameters and low-lyingenergy spectra, respectively. This emphasizes theimportance of accounting for the shape fluctuations.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-07-29
摘要： Machine learning algorithms are considered to be effective methods to improve the effectiveness of neutron-gamma (n-γ) discrimination. In this paper, we propose an intelligent discrimination method, GMM-KNN, which combines Gaussian Mixture Model with K Nearest Neighbor. Firstly, the unlabeled training and test data is categorized into 3 energy ranges: 0-25 keV, 25-100 keV, and 100-2100 keV. Secondly, GMM-KNN achieves small batch clustering in three energy intervals with only the tail integral Qtail and the total integral Qtotal as the pulse features. Then we select pulses with probability greater than 99% from the GMM clustering results to construct training set. Finally, we improve the KNN algorithm, so that GMM-KNN achieves the classification and regression algorithms through LabVIEW language, the outputs of GMM-KNN are the category or regression predictions. The GMM-KNN not only constructs the training set using unlabeled real pulse data, but also achieves n-γ discrimination of 241Am-Be pulses with the LabVIEW program. The experimental results show that GMM-KNN is highly robust and flexible. Even when using only 1/4 of the training set, the execution time of GMM-KNN is only 2021ms, with a difference of just 0.13% compared to the results obtained with the full training set. Furthermore, the accuracy of GMM-KNN is superior to that of the Charge Comparison Method (CCM), correctly classifying 5.52% of the ambiguous pulses. In addition, the GMM-KNN regressor achieves a higher Figure of Merit (FOM), with FOM values of 0.877, 1.262 and 1.020 corresponding to the three energy ranges, in particular showing a 32.08% improvement in the 0-25 keV. In conclusion, the GMM-KNN algorithm demonstrates accurate and readily deployable real-time n-γ discrimination performance, rendering it suitable for on-site analysis.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-07-29
Can Cheng
Yong-Ji Xie
Xun-Rong Xia
Jia-Yu Gu
Dong Zhao
Yi-Ze Chen
Ai-Yun Sun
Xu-Wen Liang
Wen-Bao Jia
Da-Qian Hei
摘要： Neutron-induced gamma-ray imaging is a spectroscopic technique that uses characteristic gamma rays to infer the elemental distribution of an object. Currently, this technique requires the use of large facilities to supply a high neutron flux and a time-consuming detection procedure involving direct collimating measurements. In this study, a new method based on low neutron flux was proposed. A single-pixel gamma ray detector combined with random pattern gamma ray masks was used to measure the characteristic gamma rays emitted from the sample. Images of the elemental distribution in the sample, comprising 30 × 30 pixels, were reconstructed using the maximum-likelihood expectation-maximization algorithm. The results demonstrate that the elemental imaging of the sample can be accurately determined using this method. The proposed approach, which eliminates the need for high neutron flux and scanning measurements, can be used for in-field imaging applications.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-07-29
摘要： The off-situaccurate reconstruction of the core neutron field is an important step in realizing real-time reactor monitoring. The existing off-situreconstruction method of the neutron field is only applicable to cases wherein a single region changes at a specified location of the core. However, when the neutron field changes are complex, the accurate identification of the individual changed regions becomes challenging, which seriously affects the accuracy and stability of the neutron field reconstruction. Therefore, this study proposed a dual-task hybrid network architecture (DTHNet) for off-situreconstruction of the core neutron field, which trained the outermost assembly reconstruction task and the core reconstruction task jointly such that the former could assist the latter in the reconstruction of the core neutron field under core complex changes. Furthermore, to exploit the characteristics of the ex-core detection signals, this study designed a global-local feature upsamplingmodule that efficiently distributed the ex-core detection signals to each reconstruction unit to improve the accuracy and stability of reconstruction. Reconstruction experiments were performed on the simulation datasets of the CLEAR-I reactor to verify the accuracy and stability of the proposed method. The results showed that when the location uncertainty of a single region did not exceed nine and the number of multiple changed regions did not exceed five. Further, the reconstructed ARD was within 2%, RDmaxwas maintained within 17.5%, and the number of RD≥10% was maintained within 10. Furthermore, when the noise interference of the ex-core detection signals were within ±2%, although the average number of RD≥10%increased to 16, the average ARD was still within in 2%, and the average RDmaxwas within 22%. Collectively, these results show that, theoretically, the DTHNetcan accurately and stably reconstruct most of the neutron field under certain complex core changes.
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： 核科学技术 >> 辐射物理与技术 提交时间： 2024-07-22
摘要： A novel particle encoding mechanism has been proposed that seamlessly incorporates the quantum properties of particles, with a specific emphasis on constituent quarks. The primary objective of thismechanism is to facilitate the digital recording and identification of a wide range of particle information. Its design ensures easy integration with different event generators and digital simulations commonly utilized in high-energy experiments. Moreover, this innovative framework can be effortlessly expanded to encode complex multi-quark states comprising up to 9 valence quarks and accommodating angular momentum up to 99/2. This versatility and scalability make it a valuable tool.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-07-14
摘要： 上海硬X射线自由电子激光装置（SHINE）的一台磁体长度为4 m、周期长度16 mm、磁气隙为5 mm的超导波荡器样机目前已完成集成和测试。本文针对这种超小间隙的超导波荡器，提出了一种基于双霍尔探头的磁场点测量方法，描述了其测量原理，并对样机做了磁场测量和优化实验。通过分段调节其2 m段超导磁体的激磁电流对磁场进行优化，使该段在100 A激磁电流下的相位误差小于5°满足设计要求。实验结果表明了本文提出的磁场测量和优化方法是有效的。
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-07-12
摘要： 研究了在 700 ◦C 高温下暴露的 UNS N10003 合金激光焊缝的微观组织和拉伸断裂机制的演变。暴露 100 小时后，熔合区中初生共晶 M6C-γ 碳化物周围析出了细小的 M6C 碳化物。在长期热暴露过程中，细小的 M6C 碳化物的尺寸增大。当暴露时间延长至 10 000 小时时，焊态熔合区中的共晶 M6C-γ 碳化物转变为球形 M6C 碳化物。此外，随着暴露时间的增加，球形 M6C 颗粒的尺寸出现粗化。共晶 M6C-γ 碳化物的演变和 M6C 碳化物的粗化不会对焊接接头的拉伸性能产生不利影响。
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-07-08
摘要： 废物桶中基体材料的存在限制了主动质询系统对核材料质量测量的准确性，确保核保障测量结果不受基体材料的影响至关重要。因此，基于通量监测器响应，本文在传统校正方法的基础上开发了一种新的基体校正方法。为了验证新方法的有效性，利用Geant4工具包构建了WM3210 PAN Shuffler系统模型以及常见的基体材料，并开展了模拟研究。结果表明，对于不同富集度以及分布状态的U3O8材料，传统校正方法与新校正方法均可以有效的降低基体材料对核材料质量测量的影响，但相较于传统方法，新方法表现出更好的校正能力。对于U3O8材料位于基体中心的情况，新校正方法得到的235U质量平均相对偏差为13.6%，而对于U3O8材料均匀弥散在基体中的情况，新校正方法得到的235U质量平均相对偏差为7.78%。
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-07-04
摘要： The octupole deformation and collectivity in octupole double-magic nucleus144Ba are investigated using theCranking covariant density functional theory in a three-dimensional lattice space. The reducedB(E3)transi#2;tion probability is implemented for the first time in semiclassical approximation based on the microscopicallycalculated electric octupole moments. The available data, including theI–ωrelation and electric transitionalprobabilitiesB(E2)andB(E3)are well reproduced. Furthermore, it is shown that the ground state of144Baexhibits axial octupole and quadrupole deformations that persist up to high spins (I≈24ℏ).
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-07-03
摘要： Ultrahigh-dose rate radiotherapy (FLASH-RT) is a revolutionary radiotherapy technology that can spare normal tissues without compromising tumor control. Although qualitative experimental results have been reported, quantitative and systematic analysis of data is necessary. Particularly, the FLASH effect response model to the dose or dose rate is still unclear. This study investigated the relationships between the FLASH effect and experimental parameters, such as dose, dose rate, and other factors by analyzing published in vivo experimental data from animal models. The data were modeled based on logistic regression analysis using the sigmoid function. The model was evaluated using prediction accuracy, receiver operating characteristic (ROC) curve, and area under the ROC curve. Results showed that the FLASH effect was closely related to the dose, mean dose rate, tissue type, and corresponding biological endpoints. The dose rate corresponding to a 50% probability of triggering cognitive protection in the brain was 45Gy s−1. The dose rate corresponding to a 50% probability of triggering intestinal crypt survival and regeneration was 140Gy s−1. For the skin toxicity effect, the dose corresponding to a 50% probability of triggering the FLASH effect was 24Gy. This study helps to characterize the conditions underlying the FLASH effect and provides important information for optimizing experiments.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-06-27
摘要： 为提升辐射伏特电池的总转换效率和输出功率，综合考虑耗尽区宽度、扩散长度及电极结构等因素对电荷收集效率、总转换效率及输出功率的影响，通过优化换能器件及电极结构，成功制备出总转换效率及输出功率较高的63Ni-SiC基PIN结换能器件。所制备的辐伏电池的短路电流、开路电压、输出功率及总转换效率分别达到了10.29 – 13.43 nA/cm2、1.32 – 1.44 V、11.66 – 14.69 nW/cm2及2.24% –2.82%。与团队之前的工作相比，开路电压、FF因子及总转换效率分别平均提高了127.50%、114.47%及512.10%，且总转换效率高于文献报道的结果（0.5% – 1.99%）。结果表明，通过采用具有“浓度梯度层I层”的PIN结构、优化结区宽度和掺杂浓度，以及优化电极材料和结构，可显著提升辐伏电池的总转换效率和输出功率，为辐伏电池的设计与制备提供了重要的理论参考和实验依据。
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-06-27
摘要： 为提升辐射伏特电池性能，研究了耗尽区宽度、扩散长度及电极结构等因素对输出功率的影响，并通过放射源厚度、换能器件结构、电极等方面的设计优化和工艺改进，制备获得了放射源与换能器件集成化的氚化钛-SiC基辐射伏特电池。与未集成化的氚化钛-SiC基电池的测试结果相比，氚化钛与换能器件集成化的方式显著提升了辐射伏特电池的输出性能，其中最大输出功率达到了21.4 nW，在已公开报道的同类型辐射伏特电池中处于较高水平。本工作为制备高性能辐射伏特电池提供了有价值的参考。
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-06-27
摘要： 废物桶中基体材料的存在限制了主动质询系统对核材料质量测量的准确性，确保核保障测量结果不受基体材料的影响至关重要。因此，基于通量监测器响应，本文在传统校正方法的基础上开发了一种新的基体校正方法。为了验证新方法的有效性，利用Geant4工具包构建了WM3210 PAN Shuffler系统模型以及常见的基体材料，并开展了模拟研究。结果表明，对于不同富集度以及分布状态的U3O8材料，传统校正方法与新校正方法均可以有效的降低基体材料对核材料质量测量的影响，但相较于传统方法，新方法表现出更好的校正能力。对于U3O8材料位于基体中心的情况，新校正方法得到的235U质量平均相对偏差为13.6%，而对于U3O8材料均匀弥散在基体中的情况，新校正方法得到的235U质量平均相对偏差为7.78%。
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-06-27
摘要： 电子束辐照作为一种高级氧化法，利用其产生的具有强氧化性和强还原性的活性自由基对水中有机物进行处理已经受到广泛研究。目前缺乏利用高级氧化法降解链霉素的研究。因此，采用电子束辐照作为一种新的途径，来探究链霉素降解的可行性。实验结果表明，在1MeV电子束能量和10kGy辐照剂量的条件下，5mg/L的链霉素得到了完全降解。通过DFT预测反应位点，并结合质谱数据分析链霉素降解产物的结构，得到了4种电子束辐照下链霉素的降解产物。同时根据不同辐照剂量下降解产物的成分和含量对降解路径进行合理推测。
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-06-19
摘要： In energy-dispersive X-ray fluorescence spectroscopy, the estimation of the pulse amplitude determines the accuracy of the spectrum measurement. The error generated by the amplitude estimation of the pulse output distorted by the measurement system leads to false peaks in the measured spectrum. To eliminate these false peaks and achieve an accurate estimation of the distorted pulse amplitude, a composite neural network model is proposed, which embeds long and short-term memory (LSTM) into the UNet structure. The UNet network realizes the fusion of pulse sequence features and the LSTM model realizes pulse amplitude estimation. The model is trained using simulated pulse datasets with different amplitudes and distortion times. For the pulse height estimation, the average relative error of the trained model on the test set was approximately 0.64%, which is 27.37% lower than that of the traditional trapezoidal shaping algorithm. Offline processing of a standard iron source further validated the pulse height estimation performance of the UNet-LSTM model. After estimating the amplitude of the distorted pulses using the model, the false-peak area was reduced by approximately 91% over the full spectrum and was corrected to the characteristic peak region of interest (ROI). The corrected peak area accounted for approximately 1.32% of the characteristic peak ROI area. The results indicate that the model can accurately estimate the height of distorted pulses and has substantial corrective effects on false peaks.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2024-06-14
摘要： The evolution of dislocation loops in austenitic steels irradiated with Fe+ is investigated using cluster dynam ics (CD) simulations by developing a CD model. The CD predictions are compared with experimental results in the literature. The number density and average diameter of the dislocation loops obtained from the CD simula tions are in good agreement with the experimental data obtained from transmission electron microscopy (TEM) observations of Fe+-irradiated Solution Annealed 304, Cold Worked 316, and HR3 austenitic steels in the liter ature. The CD simulation results demonstrate that the diffusion of in-cascade interstitial clusters plays a major role in the dislocation loop density and dislocation loop growth; in particular, for the HR3 austenitic steel, the CDmodel has verified the effect of temperature on the density and size of the dislocation loops.
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