分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-04-12
摘要: A microscopic method for calculating nuclear level density (NLD) based on the covariant density functional theory (CDFT) is developed. The particle-hole state density is calculated by combinatorial method using the single-particle levels schemes obtained from the CDFT, and then the level densities are obtained by taking into account collective effects such as vibration and rotation. Our results are compared with those from other NLD models, including phenomenological, microstatistical and non-relativistic HFB combinatorial models. The comparison suggests that the general trends among these models are basically the same, except for some deviations from different NLD models. In addition, the NLDs of the CDFT combinatorial method with normalization are compared with experimental data, including the observed cumulative number of levels at low excitation energy and the measured NLDs. Compared with the existing experimental data, the CDFT combinatorial method can give reasonable results.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-04-11
摘要: Aluminum is the primary structural material in nuclear engineering, and its cross-section induced by 14 MeV neutrons is of great significance. To address the issue of insufficient accuracy for the 27Al(n,2n)26Al reaction cross-section, the activation method and accelerator mass spectrometry (AMS) technique were used to determine the 27Al(n,2n)26Al cross-section, which could be used as a D-T plasma ion temperature monitor in fusion reactors. At the China Academy of Engineering Physics (CAEP), neutron activation was performed using a K-400 neutron generator produced by the T(d,n)4He reaction. The 26Al/27Al isotope ratios were measured using the newly installed GYIG 1 MV AMS at the Institute of Geochemistry, Chinese Academy of Sciences. The neutron flux was monitored by measuring the activity of 92mNb produced by the 93Nb(n,2n)92mNb reaction. The measured results were compared with available data in the experimental nuclear reaction database, and the measured values showed a reasonable degree of consistency with partially available literature data. Thenewly acquired cross-sectional data at 12 neutron energy points through systematic measurements clarified the divergence, which has two different growth trends from the existing experimental values. The obtained results are also compared with the corresponding evaluated database, and the newly calculated excitation functions with TALYS-1.95 and EMPIRE-3.2 codes, the agreement with CENDL-3.2, TENDL-2021 and EMPIRE-3.2 results are generally acceptable. A substantial improvement in the knowledge of the 27Al(n,2n)26Al reaction excitation function was obtained in the present work, which will lay the foundation for the diagnosis of the fusion ion temperature, testing of the nuclear physics model, and evaluation of nuclear data, etc.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-04-10
摘要: 在核天体物理关心的热核反应中,有一些可以产生短寿命的正电子放射性产物,这些反应产物发射的正电子会在靶中与电子发生湮灭,继而产生一对能量为511 keV的γ射线,可以通过测量这一对γ射线来得到反应产额,从而计算出核反应截面以及天体物理S因子。以往的实验通常将靶辐照后转移到屏蔽体内进行离线活度测量,近期有研究提出了在实验终端上原位测量正电子湮灭的方法,该方法主要是借助511 keV-511 keV γ射线对的方向相反特性,利用探测阵列的对向单元进行空间符合测量,压制本底干扰。本文基于近期自主研发的大型模块化BGO阵列LAMBDA-II,在地面实验室利用强流质子束打靶,对这一方法进行了实验研究和验证,为将来进一步将该方法应用到核天体物理研究中奠定了良好的基础。
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-04-09
摘要: 元素俘获测井可以获取地层中的岩石元素含量,为了查明页岩气储层发育和展布规律,以中扬子地区保靖区块寒武统牛蹄塘组首口页岩气参数井—BY2井为研究对象,通过对元素俘获测井资料的解释和处理,获取精准的页岩储层元素组成及含量,建立牛蹄塘组地球化学指标剖面,利用元素地球化学指标开展古沉积环境的辨识和反演。研究结果表明:牛蹄塘组页岩中元素以Si、Al、Fe为主,少量的K、Ca、Mg、S等,页岩中Si、Fe、S等元素含量较高,页岩可压性较好;牛蹄塘组页岩属活动大陆边缘沉积,沉积物源岩的原始物质应来自西北端康滇古陆,基本为活动大陆构造带、有热液参与的正常沉积,牛蹄塘组上段沉积期气候干燥,为缺氧的滞留盆地边缘缓坡沉积,水体盐度高,陆源供给充分,古生产力低下;牛蹄塘组下段沉积期气候湿润,为深水滞留型盆地沉积,陆源供给不足,水体盐度较高,具有较高的古生产力,有利于有机质的形成,水体环境以贫氧相为主,有利于有机质保存,为页岩气形成和富集的有利沉积环境。
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-04-08
摘要: 中国加速器驱动嬗变研究装置(CiADS)的超导直线段运行在连续波模式下,4K液氦压强波动导致超导腔体产生形变而失谐是影响低β腔稳定运行的重要因素。针对半波长超导谐振腔受氦压波动影响而运行不稳定的问题,以CiADS超导直线段β=0.19的半波长超导谐振腔(HWR019)为例,采用数值模拟的方法对液氦压强波动与该腔的频率变化规律进行仿真研究。通过对腔液氦接触区域、腔体的壁厚、液氦冷却流道的形状与腔体氦压敏感系数(KPrees)之间的关系进行计算分析,实现了将HWR019超导腔KPress值降为接近0的目的;同时通过对腔体进行热力学计算,提供了相应的强化传热方案,有效地降低了超导腔在运行过程中的最高温度,保证了CiADS装置对超导腔稳定运行的需求,其分析优化方法对同类型的低β超导腔也具有借鉴意义。
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-04-08
摘要: 超薄壁钛合金内衬不锈钢真空管道以其结构强度高,横向孔径小,适合于极高真空环境,在快上升磁场中的涡流效应处于可接受范围内,与其他类型的磁场快变化磁铁的真空管道相比成本较低等原因,已经成为HIAF-BRing二极磁铁和四极磁铁真空管道方案的首选。二极铁和四极铁钛合金内衬真空管道是BRing中重要的束流耦合阻抗源。其中,四极铁钛合金内衬的阻抗及其减小措施尚未研究过。在模拟软件CST studio suite中使用传输线法和尾场法分别对各种规格的四极铁钛合金内衬真空管道进行模拟,模拟结果表明1—500 MHz频段内钛合金内衬真空管道主要引入宽带阻抗,且钛合金内衬内表面加薄板的阻抗减小措施同样适用于四极铁真空管道。利用模拟结果计算全环阻抗,发现在106—5x108Hz频段内,钛合金内衬真空管道采取阻抗减小措施能将全环横向宽带阻抗虚部从0.70MΩ/m(水平)和0.82MΩ/m(垂直)减小到0.33MΩ/m(水平)和0.43MΩ/m(垂直),将此结果代入DELPHI中计算78Kr19+单个束团在不同流强下的模式频率移动,发现BRing中Kr束发生横向模耦合不稳定性的流强阈值从2.7x1011 ppp提升到4.4x1011ppp.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-04-08
摘要: In the framework of the Lanzhou Quantum Molecular Dynamics (LQMD) model, a possible probe to the neutron-skin thickness (δnp) of neutron-rich 48Ca is studied in 140A MeV 48Ca + 9Be projectile fragmentation reaction based on parallel momentum distribution (p//) of residual fragments.The Fermi-type density distribution is employed to initiate the neutron density distributions in the LQMD simulation. A combined Gaussian function with different width parameters for the left side (ΓL) and the right side (ΓR) in distribution are used to describe the p// of residual fragments. The value of ΓL, taking neutron-rich sulfur isotopes as examples, shows a sensitive correlation to δnp of 48Ca, which is suggested to be a probe to determine the neutron-skin thickness of the projectile nucleus.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-04-08
摘要: 飞行时间(Time-Of-Flight, TOF)探测器是核与粒子物理实验的重要组成部分,多气隙电阻板室(Multi-gap Resistive Plate Chamber, MRPC)以其高时间精度的特点在TOF测量系统中被广泛应用,放大甄别结合时间数字变换是MRPC电子学读出的一种主流方案。为了满足MRPC读出电子学高时间精度、低功耗、高集成度的需求,设计了一款高速放大甄别原型芯片,该芯片集成了8个通道,通道内包含前置放大器、甄别器和输出驱动电路。前置放大器采用共栅极结构,这种低输入阻抗的结构有利于进行阻抗匹配设计;甄别器采用多级放大器级联的结构产生足够的增益,通过对信号进行饱和放大实现甄别功能;经过甄别后的脉冲波形信号由LVDS输出驱动器送到片外,其前沿和脉宽分别可以表征MRPC信号的到达时间和电荷量信息。基于180 nm的 CMOS 工艺完成了电路的设计、仿真和流片,并在实验室环境下完成了电子学性能测试。测试结果表明,在100 fC ~ 2 pC电荷量下,该芯片的时间精度好于10 ps (rms),单通道功耗约为24 mW。
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-04-07
摘要: Beams usually do not travel through the magnet centers due to errors in storage rings. The beam deviatingfrom the quadrupole centers is affected by additional dipole fields due to magnetic field feed-down. The beambased alignment (BBA) is often performed to find a golden orbit, on which the beam circulates around thequadrupole center axes. For storage rings with a large number of quadrupoles, the conventional BBA procedureis time-consuming, especially in the commissioning phase due to the necessary iterative process. Additionally,the conventional BBA method can be affected by strong coupling and nonlinearity of the storage ring optics.In this work, a novel method based on a neural network is proposed to find the golden orbit in a much shortertime with reasonable accuracy. This golden orbit can be directly used for operation, or can be adopted as thestarting point for the conventional BBA. The method is demonstrated in the HLS-II storage ring for the firsttime, through simulation and online experiments. The results of the experiments show that the golden orbitobtained using this new method is consistent with that from the conventional BBA. The development of thisnew method and corresponding experiments are reported in this paper.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-04-07
摘要: Room-temperature ferromagnetism is observed in the O+-implanted AlN films with O+ doses of 5 × 1016 cm-2 (AlN:O5×1016) and 2 × 1017 cm-2 (AlN:O2×1017). The observed magnetic anisotropy indicate that the ferromagnetism is attributed to the intrinsic properties of O+-implanted AlN films. The out-of-plane saturation magnetization (𝑀S) of the AlN:O5×1016 is about 0.68 emu/g, much higher than that of AlN:O2×1017, 0.09 emu/g, which is due to the excessively high O+ dose made more O+ ions occupy adjacent Al3+ positions in forms of antiferromagnetic coupling. Doppler broadening of positron annihilation radiation measurements demonstrate the existence of Al vacancies in the O+-implanted AlN films. The first-principles calculations suggest that the ferromagnetism originates mainly from the Al vacancies.
分类: 核科学技术 >> 核科学与技术 分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-04-05
摘要: Space objects, such as spacecraft or missiles, might be exposed to intense X-rays in outer space, leading to severe damage. How to reinforce these objects to reduce damage from X-ray irradiation is a significant concern. Blow-off impulse (BOI) is a crucial physical quantity for investigating the material damage induced by X-ray irradiation. However, the accurate calculation of the BOI is a challenge, particularly for the large deformation of materials with complex configurations. In this paper, we develop a novel two-dimensional Particle-in-Cell (PIC) code, Xablation2D, to calculate the BOIs under far-field X-ray irradiation. This significantly reduces the dependence on grid shape for numerical simulation. The reliability of this code is verified by the simulation results from the open-source codes, and the calculated BOIs are consistent with experimental and analytical results.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2024-04-04
摘要: The High Energy Fragment Separator (HFRS), which is currently under construction, is a leading international radioactive beam device. Multiple sets of position-sensitive Twin Time Projection Chamber (TPC)detectors are distributed on HFRS for particle identification and beam monitoring. The twin TPCs’ readoutelectronics system operates in a trigger-less mode due to its high counting rate, leading to a challenge of handling large amounts of data. To address this problem, we introduced an event-building algorithm. This algorithmemploys a hierarchical processing strategy to compress data during transmission and aggregation. In addition,it reconstructs twin TPCs’ events online and stores only the reconstructed particle information, which significantly reduces the burden on data transmission and storage resources. Simulation studies demonstrated that thealgorithm accurately matches twin TPCs’ events and reduces more than 98% of the data volume at a countingrate of 500 kHz/channel.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2023-12-22
摘要: The infrared microspectroscopy beamline (BL06B) is a phase II beamline project at the Shanghai Synchrotron Radiation Facility (SSRF). The construction and optical alignment of BL06B were completed by the end of 2020. By 2021, it became accessible to users. The synchrotron radiation infrared (SRIR) source included edge radiation (ER) and bending-magnet radiation (BMR). The extracted angles in the horizontal and vertical directions were 40 and 20 mrad, respectively. The photon flux, spectral resolution, and focused spot size were measured at the BL06B end station, and the experimental results were consistent with theoretical calculations. SRIR light has a small divergence angle, high brightness, and a wide wavelength range. As a source of IR microscopy, it can easily focus on a diffraction-limited spatial resolution with a high signal-to-noise ratio (SNR). The BL06B end station can be applied in a wide range of research fields, including materials, chemistry, biology, geophysics, and pharmacology.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2023-11-24
摘要: Evaluating the comprehensive characteristics of extreme ultraviolet (EUV) photoresists is crucial for their application in EUV lithography, a key process in modern technology. This paper highlights the capabilities of the Shanghai Synchrotron Radiation Facility (SSRF) 08U1B beamline in advancing this field. Specifically, it demonstrates how this beamline can create fringe patterns with a 15-nm half-pitch (HP) on a resist using synchrotron-based EUV lithography (EUV-IL). This achievement is vital for evaluating EUV photoresists at the advanced 5-nm node. We provide a detailed introduction to the methods and experimental setup used at the SSRF 08U1B beamline to assess an EUV photoresist. A significant part of this research involved the fabrication of high-resolution hydrogen silsesquioxane (HSQ) mask gratings. These gratings, with an aspect ratio of approximately 3, were created using electron beam lithography (EBL) on an innovative mask framework. This framework was crucial in eliminating the impact of zeroth-order light on interference patterns. The proposed framework offers a new approach to mask fabrication, particularly beneficial for achromatic Talbot lithography and multicoherent-beam interference applications.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2023-11-22
摘要: Full-field transmission X-ray microscopy (TXM) is a powerful nondestructive three-dimensional (3D) imaging method with a nanoscale spatial resolution that has been used in most synchrotron facilities worldwide. An in-house-designed TXM system was constructed at the BL18B 3D Nanoimaging beamline at the Shanghai Synchrotron Radiation Facility. The beamline operates from 5 to 14 keV and enables 20 nm spatial resolution imaging. The characterization details of the beamline are described in this paper. The performances in terms of spatial resolution, nano-CT, and nano-spectral imaging of the TXM beamline are also presented in this article.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2023-11-06
摘要: HVE-400 ion implanter is special ion implantation equipment for semiconductor materials boron and phosphorus doping. The ion source and extraction deflection system are at high voltage platform, while the corresponding control system is at ground voltage position. The control signals and measurement signals of various parameters at the high-voltage end need to be transmitted between ground voltage and high voltage through optical fibers to isolate high voltage. Upgrading is carried out due to the aging of the optical fiber transmission control and monitoring system, which cannot work stably. The transformation replaces the original distributed single-point control method with an advanced distributed centralized control method, and integrates all control and monitoring functions into an industrial control computer for digital operation and display. In the computer software, two kinds of automatic calculation of ion mass number are designed.After upgrading, the implanter high-voltage platform control and monitoring system features digitalization, centralized control, high reliability, strong anti-interference, fast communication speed, and easy operation.
分类: 核科学技术 >> 辐射物理与技术 分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 分类: 光学 >> 计算中的光学 分类: 核科学技术 >> 核科学技术其他学科 提交时间: 2023-06-08
摘要: Owing to the constraints on the fabrication of -ray coding plates with many pixels, few studies have been carried out on -ray computational ghost imaging. Thus, the development of coding plates with fewer pixels is essential to achieve -ray computational ghost imaging. Based on the regional similarity between Hadamard subcoding plates, this study presents an optimization method to reduce the number of pixels of Hadamard coding plates. First, a moving distance matrix was obtained to describe the regional similarity quantitatively. Second, based on the matrix, we used two ant colony optimization arrangement algorithms to maximize the reuse of pixels in the regional similarity area and obtain new compressed coding plates. With full sampling, these two algorithms improved the pixel utilization of the coding plate, and the compression ratio values were 54.2% and 58.9%, respectively. In addition, three undersampled sequences (the Harr, Russian dolls, and cake-cutting sequences) with different sampling rates were tested and discussed. With different sampling rates, our method reduced the number of pixels of all three sequences, especially for the Russian dolls and cake-cutting sequences. Therefore, our method can reduce the number of pixels, manufacturing cost, and difficulty of the coding plate, which is beneficial for the implementation and application of -ray computational ghost imaging.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2023-06-01
摘要: Image distortion caused by angular misalignment of quadrupole magnets in high energy electron radiography is studied systematically. We propose that the distortion originates from the coupling of the motions of electron in transverse directions based on theoretical analysis via transfer matrix method. The relative angular rotation between the second and third magnetic quadrupoles is identified to be the main contributor to image distortion, which is verified by both beam dynamics simulation and experimental outcomes. In addition, different strategies to mitigate this image distortion are explored, including magnets online tuning, using higher beam energy and larger magnification factor. This study provides some criteria for designing experiments, and paves the way to achieve higher image precision.
分类: 核科学技术 >> 辐射物理与技术 提交时间: 2023-06-01
摘要: In recent years, graphics processing units (GPUs) have been applied to accelerate Monte Carlo (MC) simulations for proton dose calculation in radiotherapy. Nonetheless, current GPU platforms, such as CUDA and OpenCL, suffer from cross-platform limitation or relatively high programming barrier. However, the Taichi toolkit, which was developed to overcome these difficulties, has been successfully applied to high-performance numerical computations. Based on the class II condensed history simulation scheme with various proton-nucleus interactions, we developed a proton MC transport GPU-accelerated engine using the Taichi toolkit. Dose distributions in homogeneous and heterogeneous materials were calculated for 110, 160, and 200 MeV protons and were compared with those obtained by full MC simulations using Topas. The gamma passing rates were greater than 0.99 and 0.95 with criteria of 2 mm, 2% and 1 mm, 1%, respectively, in all the tested conditions. Moreover, the calculation speed was at least 5800 times faster than that of Topas, and the number of lines of code was approximately 10 times lesser than those of CUDA or OpenCL. Our study provides a highly accurate, efficient, and easy-to-use proton dose calculation engine for algorithm developers, students, and medical physicists.