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： In the process of neutron spectrum measurement using the multi-sphere neutron spectrometer, energy response functions and detector readings should be applied to neutron spectrum unfolding. Mathematically, there can be multiple solutions to this problem, but only one actual neutron spectrum exists. Compared with common numerical spectrum unfolding methods, genetic algorithms have the characteristics of global optimization and probabilistic search. Therefore, they are chosen to be the spectrum unfolding algorithms for the multi-sphere neutron spectrometer (MNS IL100) developed by Tsinghua University. Firstly, the detector and different size polyethylene spheres of MNS IL100 were modeled to calculate the energy response functions by applying Monte Carlo simulation. Then based on the physical and mathematical properties of the spectrum unfolding problem by using genetic algorithms, effective search space and proper fitness function were determined to improve the efficiency of search and iteration. The elitism replacement scheme was used to ensure convergence and the pseudo-parallel strategy was used to inhibit premature convergence. According to the algorithms mentioned above, a spectrum unfolding code was developed and tested with several typical neutron spectra. At last, MNS IL100 and the spectrum unfolding code were used in actual experiment of 252Cf neutron source spectrum measurement. The experimental result is in good agreement with the 252Cf standard neutron spectrum, verifying the effectiveness and practicality of using genetic algorithms to unfold the neutron spectrum with combination of several processing strategies.
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 Monte Carlo method can be widely applied to particle transport through numerous simulated data processing operations. However, this process consumes much time. Traditional parallel computing based on multi-CPU or multi-core CPU can effectively address this issue, but it is limited by inadequate computer hardware. Nonetheless, the current programmability and parallel processing capability of digital graphics processing units (GPUs) can sustain general computing applications such as Monte Carlo program simulation. This paper presents a method that facilitates the parallel computation of the Monte Carlo procedure through GPUs. Its feasibility is verified through a sample of simplified photon transport program, the results indicate that execution time can be shortened by approximately 90 times. Based on the general Monte Carlo program Geant4, the photon and electronic coupled transport module was examined, analyzed, and rewritten using the GPU programming language OpenCL to generate a Geant4 parallel tool [base on GPU parallel computing tool (BOGPT)]. The simulation results of the standard examples demonstrated that the outcomes of the BOGPT program are similar to those of Geant4 and the simulation time can be reduced by approximately three times. Finally, the GPU programming-based parallel computing method for Monte Carlo applications is accelerated and implementation prospects are broadened following further optimization.
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： Induced radioactivity is one of the essential problems in the radiation protection field of proton accelerators. Research on the induced radioactivity of low-energy proton accelerators is highly limited. Given such context, this study investigates the cross section of 63Cu (p, n) 63Zn and 65Cu (p, n) 65Zn in Cu targets at 11 MeV proton accelerators through an activation experiment. The uncertainties of the results are analyzed in detail. Results show that the cross section of the reaction of 65Cu (p, n) 65Zn in the experiment is only 1.36% lower than that of the FLUKA simulation, whereas the reaction of 63Cu (p, n) 63Zn in the experiment is 25.4% higher than that of the FLUKA simulation. Given that the benchmark for the FLUKA code of low-energy proton accelerators is very limited, this study provides a reference in this field.
分类： 地球科学 >> 地质学 提交时间： 2017-08-10 合作期刊: 《古脊椎动物学报》
摘要： Here we briefly review the history of research on the Laiyang dinosaur and dinosaur egg faunas, summarize the contributions of C. C. Young and other elder paleontologists to the discoveries of the Late Cretaceous dinosaurs and dinosaur eggs from Laiyang, and introduce the new discoveries and the advances in the research on the Laiyang faunas. The new investigations in Laiyang from 2008 have found a series of valley developed in plain and more than ten new dinosaur or dinosaur egg fossil beds. In 2010, we began the massive excavations at two localities in Jingangkou and collected abundant dinosaurs and other vertebrate fossils, such as a new saurolophine, some theropod material and a new taxon of turtle egg. The bone beds in Locality 2 with the typical sedimentary and burial patterns of mudflow, and these fossil deposits are interpreted as having been carried and deposited by mudflow. The re-observation and the CT scanning data of the crest of Tsintaosaurus spinorhinus (IVPP V 725) show that the crest is fractured and solid. However, based on the re-observations of its cranial and postcranial specimens, we consider that Tsintaosaurus spinorhinus is a valid taxon of lambeosaurines, which have the hollow crest. Therefore, the crest of Tsintaosaurus might not belong to the skull of this individual, and the true form of the crest needs to be confirmed in the future work. We reassess the three species of Tanius, and obtain several results. 1) Tanius sinensis and Tanius chingkankouensis are the valid species of Tanius; 2) Tanius laiyangensis is invalid.; 3) the sacrum and ilium of Tanius chingkankouensis with typical hadrosaurid features should not be referred to Tanius. 简要回顾了莱阳恐龙和恐龙蛋化石群的研究历史和以杨钟健为代表的老一代地质古生物学者对莱阳恐龙和恐龙蛋研究和发现的杰出贡献，并介绍了莱阳恐龙和恐龙蛋的最新发现和若干研究进展。在近年来对莱阳周边地层进行的大规模考察中，发现了一系列发育在平原上的恐龙峡谷群；以及其中蕴含的十几个恐龙和恐龙蛋新地点和新层位。2010年开始，在对莱阳金岗口村附近的2个化石地点的发掘中，发现了以鸭嘴龙科为主的大量脊椎动物化石和蛋化石，包括一类新的栉龙亚科成员，一些大型兽脚类恐龙化石，以及一新的龟鳖类蛋化石等。2号地点化石富集层具有典型的泥石流沉积特征和骨骼埋藏特征。对棘鼻青岛龙的特殊头饰进行了CT扫描和三维重建，发现其头饰是实心结构，但其他骨骼特征证明棘鼻青岛龙属于具有头饰的赖氏龙亚科是确定无疑的，所以目前发现的头饰应不是其真实状态或根本不属于其头部骨骼。此外，对谭氏龙1属3种的重新观察研究得出以下结论：中国谭氏龙和金刚口谭氏龙应是有效属种，但部分骨骼还有疑问，还需要进一步研究，而莱阳谭氏龙为无效属种。
分类： 物理学 >> 核物理学 提交时间： 2016-08-31
摘要： The ability of background discrimination using pulse shape discrimination (PSD) in broad-energy germanium (BEGe) detectors makes them as competitive candidates for neutrinoless double beta decay (0{\nu}\b{eta}\b{eta}) experiments. The measurements of key parameters for detector modeling in a commercial p-type BEGe detector are presented in this paper. Point-like sources were used to investigate the energy resolution and linearity of the detector. A cylindrical volume source was used for the efficiency calibration. With an assembled device for source positioning, a collimated 133Ba point-like source was used to scan the detector and investigate the active volume. A point-like source of 241Am was used to measure the dead layer thicknesses, which are approximately 0.17 mm on the front and 1.18 mm on the side. The described characterization method will play an important role in the 0{\nu}\b{eta}\b{eta} experiments with BEGe detectors at China JinPing underground Laboratory (CJPL) in the future.
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