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： 2023-09-19
摘要：To accelerate the fractal decoding process, a minimum iterated function system based fast fractal decoding method was proposed in this study. In fractal encoding process, we found that there exists a minimum domain block set (MDBS) which can provide the best-matched domain blocks for all range blocks, and then the domain blocks of MDBS, the range blocks within MDBS, and the associated mapping operations between them constitute the minimum iteration function system (MIFS). In decoding process, MIFS was first recovered in the first iteration. Then, in each of the second to penultimate iterations, only the range blocks within MDBS are reconstructed, and the computations of reconstructing the remaining range blocks can be saved. Finally, all range blocks are reconstructed to obtain the decoded image in the last iteration. Four fractal encoding methods were adopted to assess the performance of the proposed method. Experimental results show that the proposed method can complete the decoding process with fewer computations.
分类： 物理学 >> 核物理学 提交时间： 2023-09-15
摘要：The Trojan horse method was employed to indirectly measure the bare-nucleus reaction cross-section and astrophysical S-factor of the 9Be(p,α) 6Li reaction in the low-energy region , utilizing the three-body reaction 2H(9Be,α 6Li)n. Comparing the two-body reaction data extracted from the Trojan horse method with that obtained through direct measurements, compatibility is observed in the energy region above approximately 100 keV. Additionally, the THM data successfully reproduces the expected low-energy resonance peak around 270 keV. The THM extraction of the astrophysical factor yields S(0) = 21.0 ± 0.8 MeV b, which surpasses the extrapolation obtained from direct measurements. The 9Be(p,α) 6Li reaction channel exhibits a subthreshold resonance with a width of 25 keV, positioned approximately -23 keV below the threshold. However, the strong electron shielding effect near the zero energy position in direct measurements often masks the influence of the subthreshold resonance on the low-energy region. In contrast, the THM method allows us to neglect the electron shielding effect. The THM experimental data were subjected to fitting using the Breit-Wigner function and subsequently compared with directly measured data. Following a comprehensive comparative analysis, it was discerned that the S(0) value obtained through THM exceeded the extrapolated value derived from direct measurements. This disparity was primarily attributed to the influence of the subthreshold resonance.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2023-09-15
摘要：分析指出单极感应磁体磁力线相对于转轴的全对称分布状态没有被引起足够的重视，是导致单极感应问题产生和遗留的根本原因。提出了一种两极球形磁体验证单极感应问题的方案。方案实施容易。只要选择合适的转轴取向，同一磁体既可以实施经典的单极感应，又可以实施找寻单极感应问题答案的两极感应验证实验。两种实验步骤对应实施，实验结果可对比分析。与单极感应全部实验结果两种观点都可以给出合理的解释不同，两极感应验证实验时磁体的磁力线相对于转轴的分布已不再是全对称状态，因此对于验证结果两种观点能给出的合理解释差异凸显出来，对与错已显现。验证结论是：磁体的磁力线随磁体运动。
分类： 物理学 >> 核物理学 提交时间： 2023-09-13
Ma, Pufang
Wang, Jiarong
Zhang, Zixiao
Meng, Tianming
Xia, Zihan
Ren, Baihui
Wei,Long
Yao, Ke
Xiao, Jun
Zou, Yaming
Tu, Bingsheng
Wei, baoren
摘要：The total absolute cross sections of single- and double-electron capture (SEC and DEC) in the collisions of He2+ with He and Ne8+ with O2, N2, and CH4 were studied in the energy ranges 3.5 to 50 keV/u and 2.8 to 40 keV/u, respectively. Through a deep analysis of the experimental systematic uncertainties in the measurement procedure and data evaluation, the error in the experimental results of the SEC cross sections is less than 9%. Within the uncertainties, the present results of the He2+ -He collision show good consistency with previous measurements, validating the experimental system and paving the way for precise measurements of EC cross sections for a variety of ions and neutral gases. The present measurements allow for a test of EC theory and provide crucial EC cross section data for the establishment of plasma models in fusion research and astrophysical X-ray studies.
分类： 物理学 >> 核物理学 提交时间： 2023-09-13
摘要：Abstract: In this experimental study, involving deuterium–deuterium fusion neutron emission spectroscopy (NES) measurement on the experimental advanced superconducting tokamak (EAST), a liquid scintillator detector (BC501A) was employed. This decision was based on the detector's superior sensitivity, optimal time-response, and its exceptional n-γ discrimination capability. This detector emits fast pulse signals that are as narrow as 100 ns, with high count rates that can peak at several Mcps. However, conventional nuclear circuits faced challenges in performing pulse height analysis, n–γ pulse shape discrimination (PSD), and in recording the entire pulse waveform under such high-count-rate conditions. To address these challenges, a high-speed digital pulse signal acquisition and processing system was designed. The system was developed around a micro-telecommunications computing architecture (MTCA). Within this structure, a signal acquisition and processing (SAQP) module communicated through PCI Express (PCIe) links, achieving a bandwidth of up to 1.6 GB/s. To accurately capture the detailed shape of the pulses, four channels of analog-to-digital converters (ADCs) were used, each with a 500-MSPS sampling rate and a 14-bit resolution, ensuring an accuracy that surpassed 11 bits. An n-γ discrimination algorithm, based on the two-gate integral method, was also developed. Implemented within field programmable gate arrays (FPGA), this algorithm provided a real-time n-γ discrimination spectrum for pulse height analysis. The system underwent rigorous testing in a laboratory setting and during an EAST experiment. The results confirmed that the innovative SAQP system can satisfy the demanding requirements of high-parameter experiments, manage count rates of up to 2 Mcps, execute real-time n-γ discrimination algorithms, and record entire pulse waveforms without any data loss.
分类： 物理学 >> 核物理学 分类： 物理学 >> 地球物理学、天文学和天体物理学 提交时间： 2023-09-12
Yang, Gaole
An, Zhendong
Jiang, Wei
Li,Xiankai
Qiu, Weiwei
Liao, Zhengfa
Zhuang, Ziyue
Zhang, Xiaoping
Chen,Shengli
Xiao, Erxi
Fang,Xiao
Li,XinXiang
Hu, Xinrong
Jiang, Bing
Wang, Jincheng
Ren, Jie
Luo, Wen
Zhu, ZhiChao
Lan, Haoyang
Cao, Zongwei
摘要：The neutron capture cross sections (${n, upgamma}$) of Bromine was performed with the time-of-flight (TOF) technique at the Back-n facility of the China Spallation Neutron Source (CSNS). Prompt $ upgamma$-rays originating from neutron-induced capture events were detected by four C${}_6$D${}_6$ detectors. The pulse height weighting technique (PHWT) and the double-bunch unfolding method based on the Bayesian theory were used in the data analysis. To obtain reliable measurement results, background deductions, normalization, and corrections were carefully considered. The multilevel R-matrix Bayesian code SAMMY was used to extract the resonance parameters in the resolved resonance region (RRR). The average cross sections in unresolved resonance region the was obtained from 10 to 400 keV. The experimental results were compared with the data of several evaluated libraries and previous experiments in the resolved and unresolved resonance region. The TALYS code was used to describe the average cross sections in the unresolved resonance region. Astrophysical Maxwell average cross sections (MACSs) of ${}^{79,81}$Br from $ kT $ = 5 to 100 keV was calculated over a sufficiently wide range of neutron energies. At a thermal energy of $kT=30$ keV, the MACS value for ${}^{79}$Br 638$ pm$64 mb is in good agreement with the KADoNiS recommended value. By contrast, the value of 293$ pm$29 mb for ${}^{81}$Br is substantially higher than those of the evaluated database and the KADoNiS recommended value.
分类： 物理学 >> 地球物理学、天文学和天体物理学 提交时间： 2023-09-12
摘要：General relativity (GR) is characterized by natural singularity. In this approach, it is demonstrated that there are two different kinds of Einsteinian singularities. If the divergent term in the Kreshmann scalar has a cutoff, the singularity will be finite and discrete will occur automatically near the singularity based on the general shape of the singularity.
分类： 物理学 >> 核物理学 提交时间： 2023-09-11
摘要：The NaI:Tl scintillator is an innovative material for dual-gamma-ray and neutron detection with a low 6Li concentration. To achieve real-time n/γ discrimination, a zero-crossing time comparison algorithm based on trapezoidal pulse shaping was developed. The algorithm can operate efficiently at low sampling rates and was implemented on a single-probe portable digital n/γ discriminator based on a feld-programmable gate array (FPGA). The discriminator and NaI:Tl,6Li detector were tested in a neutron-gamma mixed field produced by an 241Am-Be neutron source to evaluate the performance of the algorithm. The Figure of Merits (FoM) was measured as 2.88 at a sampling rate of 50 MHz, indicating that the discriminator with its embedded algorithm has a promising n/γ discrimination capability. Efficient discrimination at sampling rates of 40 and 25 MHz demonstrates that the capability of this method is not limited by low sampling rates.
分类： 物理学 >> 核物理学 提交时间： 2023-09-11
摘要：本工作制作了一套由快发光塑料闪烁体耦合快光电倍增管组成的塑料闪烁体飞行时间探测器的样机，通过皮秒脉冲激光测试了探测器的时间性能，旨在为将来的 HIAF-HFRS 飞行时间探测器作预研。对于两种不同尺寸的塑闪探测器，通过改变激光的光斑大小、频率、光强和位置等各项参数来模拟真实束流的情况，并使用 CAEN-DT5742 数字化仪以及 Mesytec-MCFD16+MTDC32 电子学系统进行了系统的测试。使用聚焦激光照射在塑闪中心位置时，小尺寸 (7 cm×7 cm) 塑闪探测器的 ToF 分辨最好可达 8 ps；小-大 (26 cm×10 cm) 塑闪探测器的 TOF 分辨最好可达到 12 ps。在改变激光各项参数后，得到的响应时间分辨为 10–16 ps 和 19–46 ps。测试结果表明，所得到的 ToF 分辨满足 HFRS 束线的时间分辨性能要求，为飞行时间探测器的优化奠定了基础。
分类： 物理学 >> 核物理学 提交时间： 2023-09-11
Liu, Xiangman
Tang, Shuwen
Wang, Wei
Yu, Yuhong
Sun, Zhiyu
Zhang, Yongjie
Fang, Fang
Yan, Duo
Wang, ShiTao
Zhang, Xueheng
Jin, Shuya
Hu, Bitao
摘要：Gamma-ray polarimetry is a new and prospective tool for studying various extreme high-energy celestial objects and is of great significance for the development of astrophysics. With the rapid development of microsatellite technology, the advantages in space exploration are becoming increasingly apparent. Therefore, in this paper, we conducted a simulation study on a soft gamma-ray polarimeter for a microsatellite in space. Here, we proposed a unique design structure for the polarimeter based on the microsatellite design concept and the Compton scattering principle. And then, the detailed Monte Carlo simulations using mono-energetic gamma-ray linear polarization sources and the Crab-like sources in the energy range of 0.1-10 MeV with full consideration of the orbital background were performed. The simulation results show that the polarimeter can exhibit excellent polarization detection performance. The modulation factor is 0.80±0.01, and the polarization angles are accurate within an error of 0.2° at 200 keV for on-axis incidence. For the Crab-like sources for on-axis incidence, the polarization degrees are consistent with the set values within the error tolerance, the modulation factor is 0.76±0.01, and the minimum detectable polarization reaches 2.4% at 3σ for an observation time of 106 seconds. In addition, the polarimeter has recoil electron tracking, imaging, and powerful background suppression at a large field of view (∼2π sr). The polarimeter designed can meet the requirements of a space-soft gamma-ray polarization detector very well and has a bright research prospect.
分类： 物理学 >> 核物理学 提交时间： 2023-09-11
Guo, Dong
Haoqian Xyu
DongDong Qi
HeXiang Wang
Lei Zhang
Zhengyang Sun
Zhi Qin
Botan Wang
Yingjie Zhou
Zekun Wang
Yuansheng Yang
Yuhao Qin
Xianglun Wei
Herun Yang
Yuhong Yu
Lei Zhao
Zhigang Xiao
摘要：A trigger system has been designed and implemented for the HIRFL-CSR external target experiment (CEE), the spectrometer for studying nuclear matter properties with heavy ion collisions in the GeV energy region. The system adopts master-slave structure and serial data transmission mode using optical fiber to deal with different types of detectors and long-distance signal transmission. The trigger logic can be accessed based on command register and controlled by a remote computer. The overall field programmable gate array (FPGA) logic can be flexibly reconfigured online to match the physical requirements of the experiment. The trigger system has been tested in beam experiment. It is demonstrated that the trigger system functions correctly and meets the physical requirements of CEE.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2023-09-10
摘要：本文首先还原了基于大量力学实验的真正经验规律，从中获得质点动力学的因果关系。其次，通过因果对称和一致的基本要求，在牛顿动力学的框架下引入了对称形式的新质点动力学方程。新方程可以直接适用于任意平动的参考系，之所以对称是因为待考察的运动物体和参考物体完全被置于了同等的地位。当参考物的真实受力恒为零时，对称新方程即退化到牛顿第二定律，而此时的参考系也即对应为惯性系。因为参考系的加速直接取决于参考物的加速，而参考物的加速直接取决于参考物的受力，因此，惯性力的本质揭示为质量平权后的参考物的真实受力，且这一定性解释是普适的。而对于平动参考系，惯性力的定性解释可以通过具体的理论计算表达式得到进一步明确。理论分析表明，对称新方程可以自然地融合经典力学的理论框架，且比牛顿第二定律更加符合实验和经验规律。最后，在此基础上，我们通过具体的例子全方位地比较分析了对称新方程在应用上的优势。
分类： 物理学 >> 核物理学 提交时间： 2023-09-07
摘要：In this study, we developed a neural network that incorporates a fully connected layer with a convolutional layer to predict the nuclear charge radii based on the relationships between four local nuclear charge radii.
The convolutional neural network (CNN) combines the isospin and pairing effects to describe the charge radii of nuclei with $A geq $ 39 and $Z geq $ 20. The developed neural network achieved a root--mean--square (RMS) deviation of 0.0195 fm for a dataset with 928 nuclei. Specifically, the CNN reproduced the trend of the inverted parabolic behavior and odd--even staggering observed in the calcium isotopic chain, demonstrating reliable predictive capability.
分类： 物理学 >> 核物理学 提交时间： 2023-09-07
摘要：Helium–xenon cooled microreactors are a vital technological solution for portable nuclear reactor power sources. To examine the convective heat transfer behavior of helium–xenon gas mixtures in a core environment, numerical simulations are conducted on a cylindrical coolant channel and its surrounding solid regions. Validated numerical methods are used to determine the effect and mechanisms of power and its distribution, inlet temperature and velocity, and outlet pressure on the distribution and change trend of the axial Nusselt number. Furthermore, a theoretical framework that can describe the effect of power variation on the evolution of the thermal boundary layer is employed to formulate an axial distribution correlation for the Nusselt number of the coolant channel, under the assumption of a cosine distribution for the axial power. Based on the simulation results, the correlation coefficients are determined, and a semi-empirical relationship is identified under the corresponding operating conditions. The correlation derived in this study is consistent with the simulations, with an average relative error of 5.3% under the operating conditions. Finally, to improve the accuracy of the predictions near the entrance, a segmented correlation is developed by combining the Kays correlation with the aforementioned correlation. The new correlation reduces the average relative error to 2.9% and maintains satisfactory accuracy throughout the entire axial range of the channel, thereby demonstrating its applicability to turbulent heat transfer calculations for helium–xenon gas mixtures within the core environment. These findings provide valuable insights into the convective heat transfer behavior of a helium–xenon gas mixture in a core environment.
分类： 物理学 >> 核物理学 提交时间： 2023-09-07
摘要：The thermodynamic properties of charged particles, such as the energy density, pressure, entropy density, particle density, and squared speed of sound at the kinetic freeze-out in the $ mathrm{Au+Au}$ collisions from the relativistic heavy ion collider (RHIC) beam energy scan program ($ sqrt{s_ text{NN}}$=7.7--200 GeV) and in the $ mathrm{Cu+Cu}$ collisions at $ sqrt{s_ text{NN}}$=62.4, 200 GeV are studied using the thermodynamically consistent Tsallis distribution. The energy density, pressure, and particle density decrease monotonically with the collision energy for the same collision centrality; These properties also decrease monotonically from the central to peripheral collisions at the same collision energy. While the scaled energy density $ varepsilon/T^4$ and scaled entropy density $s/T^3$ demonstrate the opposite trend with the collision energy for the same collision centrality. There is a correlation between $ varepsilon/T^4$ and $s/T^3$ at the same centrality. In addition, the squared speed of sound was calculated to determine that all the collision energies share nearly the same value at different collision centralities.
分类： 物理学 >> 核物理学 提交时间： 2023-09-07
Zehua Yang
Jingtao Zhu
Zhongliang Li
Hongxin Luo
Shangyu Si
Yunping Zhu
Li Zhao
Kuan Ren
Feng Wang
Rongqing Yi
摘要：Multilayer interference mirrors play a pivotal role in spectroscopic diagnostic systems, which probe electron temperature and density during inertial confinement fusion processes. In this study, aperiodic Mo/B4C multilayer mirrors of varied thicknesses were investigated for X-ray plasma diagnostics at the 9.67-keV W-Lbeta line. The thickness distribution of the aperiodic multilayers was designed using the 1st Bragg diffraction condition and then optimized through a simplex algorithm to realize a narrow bandwidth and consistent spectral response. To enhance spectral accuracy, further refinements were undertaken by matching the grazing incidence X-ray reflectivity data with actual structural parameters. X-ray reflectivity measurements from the SSRF synchrotron radiation facility on the optimized sample showed a reflectivity of 29.7% ±2.6%, flat-band range of 1.3 keV, and bandwidth of 1.7 keV, making it suitable for high-temperature plasma diagnostics. The study explored the potential of predicting the 9.67 keV reflectivity spectrum using the fitting data from the Grazing incidence X-ray reflectivity (GIXRR) curves at 8.05 keV. Additionally, the short-term thermal stability of an aperiodic multilayer was assessed using temperature-dependent in situ X-ray measurements. Shifts in the reflectivity spectrum during annealing were attributed to interdiffusion and interfacial relaxation. The research team recommends the aperiodic Mo/B4C multilayer mirror for operations below 300 ℃.
分类： 物理学 >> 电磁学、光学、声学、传热、经典力学和流体动力学 提交时间： 2023-09-06
摘要：The aim of this research is to reconstruct the 3D X-ray refractive index gradient maps by the proposed vector Radon transform and its inverse, assuming that the small-angle deviation condition is met. Theoretical analyses show that the X-ray beam can be modeled as a streamline with continuous change of direction in a row when measured in one grating period, which allows the extraction of the refraction angle signals. Experimental results show that all the 2D refraction signals of different directions can be acquired by a standard circular scanning procedure, which is typically used in the X-ray differential phase-contrast computed tomography. Furthermore, the 3D refractive index gradient maps that contain the directional density changes, can also be accurately reconstructed.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2023-09-05
摘要：This study introduces a novel algorithm to detect and identify radioactive materials in urban settings using time-series detector response data. To address the challenges posed by varying backgrounds and to enhance the quality and reliability of the energy spectrum data, we devised a temporal energy window. This partitioned the time-series detector response data, resulting in energy spectra that emphasize the vital information pertaining to radioactive materials. We then extracted characteristic features of these energy spectra, relying on the formation mechanism and measurement principles of the gamma-ray instrument spectrum. These features encompassed aggregated counts, peak-to-flat ratios, and peak-to-peak ratios. This methodology not only simplified the interpretation of the energy spectra’s physical significance but also eliminated the necessity for peak searching and individual peak analyses. Given the requirements of imbalanced multi-classification, we created a detection and identification model using a weighted k-nearest neighbors (KNN) framework. This model recognized that energy spectra of identical radioactive materials exhibit minimal inter-class similarity. Consequently, it considerably boosted the classification accuracy of minority classes, enhancing the classifier’s overall efficacy. We also executed a series of comparative experiments. Established methods for radionuclide identification classification, such as standard k-nearest neighbors (KNN), support vector machine (SVM), Bayesian network, and
random tree, were used for comparison purposes. Our proposed algorithm realized an F1 measure of 0.9868 on the time-series detector response data, reflecting a minimum enhancement of 0.3% in comparison to other techniques. The results conclusively show that our algorithm outperforms others when applied to time-series detector response data in urban contexts.
分类： 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间： 2023-09-05
摘要：To enhance the accuracy of 2πα and 2πβ particle surface emission rate measurements and address the identification issues of nuclides in conventional methods, this study introduces two artificial neural network (ANN) algorithms: back propagation (BP) and genetic algorithm-based back propagation (GA-BP). These algorithms classify pulse signals from distinct α and β particles. Their discrimination efficacy is assessed by simulating standard pulse signals and those produced by contaminated sources, mixing α and β particles within the detector. This study initially showcases energy spectrum measurement outcomes, subsequently tests the ANNs on the measurement and validation datasets, and contrasts the pulse shape discrimination efficacy of both algorithms. Experimental findings reveal that the proportional counter's energy resolution is not ideal, thus rendering energy analysis insufficient for distinguishing between 2πα and 2πβ particles. The BP neural network realizes approximately 99% accuracy for 2πα particles and approximately 95% for 2πβ particles, thus surpassing the GA-BP's performance. Additionally, the results suggest enhancing β particle discrimination accuracy by increasing the digital acquisition card's threshold lower limit. This study offers an advanced solution for the 2πα and 2πβ surface emission rate measurement method, presenting superior adaptability and scalability over conventional techniques.
分类： 物理学 >> 核物理学 提交时间： 2023-09-04
Li, Yunxiang
Meng, Lu
Huang, Zinan
Li, Song
Wang, Disi
Liu, Bo
Zhang, Youpeng
Peng, Tianji
Zhang, Lu
Su, Xingkang
Jiang, Wei
摘要：Steam generator tube rupture (SGTR) accident is an important scenario needed to be considered in the safety analysis of lead-based fast reactors. When the steam generator tube breaks close to the main pump, water vapor will enter the reactor core, resulting in a two-phase flow of heavy liquid metal and water vapor in fuel assemblies. The thermal-hydraulic problems caused by the SGTR accident may seriously threaten reactor core’s safety performance. In this paper, the open source CFD calculation software OpenFOAM was used to encapsulate the improved Euler method into the self-developed solver LBEsteamEulerFoam. By changing different heating boundary conditions and inlet coolant types, the two-phase flow in the fuel assembly with different inlet gas content was simulated under various accident conditions. The calculation results show that the water vapor may accumulate in edge and corner channels. With the increase of inlet water vapor content, outlet coolant velocity increases gradually. When the inlet water vapor content is more than 15%, the outlet coolant temperature rises sharply with strong temperature fluctuation. When the inlet water vapor content is in the range of 5% to 20%, the upper part of the fuel assembly will gradually accumulate to form large bubbles. Compared with the VOF method, Euler method has higher computational efficiency. However, Euler method may cause an underestimation of the void fraction, so it still needs to be calibrated with future experimental data of the two-phase flow in fuel assembly.
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