分类: 核科学技术 >> 核科学与技术 提交时间: 2024-03-15
摘要: 为提高空间堆中子学模拟的可靠性,基于国际临界安全手册中关于空间堆的临界基准实验(HMF005基准实验),采用蒙特卡罗程序对HMF005基准实验中堆芯排布进行建模,结合不同评价核数据库,计算6种堆芯排布下的keff计算值与实验值的偏差,并对计算值与实验值的比值的平均值、标准偏差、χ2和均方根误差等进行深入分析。研究发现,ENDF/B-VII.1、CENDL-3.2、ENDF/B-VIII.0和JEFF-3.3四种评价核数据库计算堆芯keff结果与实验值偏差处于三倍不确定度之内,其中ENDF/B-Ⅶ.1计算结果最接近实验值,CENDL-3.2与实验偏差稍大。CENDL-3.2库计算结果与实验值偏差稍大主要是由于评价库中的钼和铍核素导致,钼的同位素中92Mo的影响最大。同时还进行敏感性分析,92Mo和9Be的总反应敏感性系数主要跟弹性散射敏感性系数相关,CENDL-3.2和ENDF/B-Ⅶ.1中9Be的辐射俘获敏感性差异较大,两者偏差可达34.9%。
分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2024-03-15
摘要: 在软X射线能谱探测中,采用硅漂移探测器(Silicon Drift Detector,SDD)与复位型电荷灵敏前置放大器集成的一体化探测设备,其输出信号为包含射线能谱信息的阶梯型锯齿波。文章针对该设备产生的阶梯型锯齿波信号无法直接精确提取幅度信息的问题,提出了一种用模拟电路对该信号进行整形放大处理的方案,并通过Cadence软件仿真的方法,探究了此方案的可行性以及在该方案下影响能谱能量分辨率的因素。文章还通过对比不同噪声幅度输入时电路的输出信号,最终得到在相应的能量分辨率指标要求下前放输出信号噪声指标的最低要求。
分类: 核科学技术 >> 核材料与工艺技术 提交时间: 2024-03-13
摘要: Cs and I can migrate through the fuel-cladding interface and accelerate the cladding corrosion process induced by the Fuel Cladding Chemical Interaction. Cr coating is an important candidate in mitigating this chemical interaction. First-principles calculations were employed to investigate the diffusion behaviors of Cs and I in Cr bulk and Cr grain boundary, aiming to reveal the microscopic mechanisms for mitigating the interaction at fuel-cladding interface. The interactions between these two fission products and Cr coating were systematically studied, and the temperature-dependent diffusion coeffcients of Cs and I in Cr were obtained using Bocquet’s oversized solute atoms model and Le Claire’s nine-frequency model, respectively. The results show that the migration barriers of Cs and I are significantly lower compared to that of Cr, and the diffusion coeffcients of Cs and I are both more than 3 orders of magnitude larger than Cr self-diffusion coeffcient within the temperature range of Generation IV fast reactors (below 1000 K), which shows the strong penetration ability of Cs and I. Meanwhile, Cs and I are more likely to diffuse along the grain boundary because of the generally low migration barriers, indicating that grain boundary serves as a fast diffusion channel for Cs and I.
分类: 核科学技术 >> 核科学与技术 提交时间: 2024-03-13
摘要: 针对强流下时间投影室TPC(Time Projection Chamber)探测器高计数率,大动态范围、低功耗的读出需求,基于180nm CMOS工艺设计了一种自动调节增益的前放芯片。该芯片由电荷灵敏前放CSA(Charge Sensitive Amplifier)、Class AB输出缓冲级、增益控制模块、触发控制模块构成。通过片内逻辑信号控制多个开关的切换,使芯片的转换增益自适应输入电荷量;并通过开关泄放,使芯片工作于1MHz计数率。经过仿真,在输入信号范围为2.2 fC-16.5 pC时,积分非线性好于0.4%。该芯片已经提交foundry流片。
分类: 核科学技术 >> 核科学与技术 提交时间: 2024-03-12
摘要: This paper presents a new technique for measuring the bunch length of a high-energy electron beam at a bunch-by-bunch rate in storage rings. This technique uses the time–frequency-domain joint analysis of the bunch signal to obtain bunch-by-bunch and turn-by-turn longitudinal parameters, such as bunch length and synchronous phase. The bunch signal is obtained using a button electrode with a bandwidth of several gigahertz. The data acquisition device was a high-speed digital oscilloscope with a sampling rate of more than 10 GS/s, and the single-shot sampling data buffer covered thousands of turns. The bunch length and synchronous phase information were extracted via offline calculations using Python scripts. The calibration coefficient of the system was determined using a commercial streak camera. Moreover, this technique was tested on two different storage rings and successfully captured various longitudinal transient processes during the harmonic cavity debugging process at the Shanghai Synchrotron Radiation Facility (SSRF), and longitudinal instabilities were observed during the single bunch accumulation process at Hefei Light Source (HLS). For Gaussian-distribution bunches, the uncertainty of the bunch phase obtained using this technique was better than 0.2 ps, and the bunch length uncertainty was better than 1 ps. The dynamic range exceeded 10 ms. This technology is a powerful and versatile beam diagnostic tool that can be conveniently deployed in high-energy electron storage rings.
分类: 核科学技术 >> 核科学与技术 提交时间: 2024-03-08
摘要: Various electromagnetic signals are excited by the beam in the acceleration and beam-diagnostic elements of a particle accelerator. It is important to obtain time-domain waveforms of these signals with high temporal resolution for research, such as the study of beam-cavity interactions and bunch-by-bunch parameter measure#2;ments. Therefore, a signal reconstruction algorithm with ultrahigh spatiotemporal resolution and bunch phase compensation based on equivalent sampling is proposed in this paper. Compared with traditional equivalent sampling, the use of phase compensation and setting the bunch signal zero-crossing point as the time reference can construct a more accurate reconstructed signal. The basic principles of the method, simulation, and experi#2;mental comparison are also introduced. Based on the beam test platform of the Shanghai Synchrotron Radiation Facility (SSRF) and the method of experimental verification, the factors that affect the reconstructed signal qual#2;ity are analyzed and discussed, including the depth of the sampled data, quantization noise of analog-to-digital converter (ADC), beam transverse oscillation, and longitudinal oscillation. The results of the beam experiments show that under the user operation conditions of the Shanghai Synchrotron Radiation Facility (SSRF), a beam excitation signal with an amplitude uncertainty of 2% can be reconstructed.
分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2024-03-07
摘要: The High Energy Cosmic-Radiation Detection (HERD) facility is planned to launch in 2027 and scheduled to be installed on the China Space Station. It serves as a dark matter particle detector, a cosmic ray instrument, and an observatory for high-energy gamma rays. A transition radiation detector placed on one of its lateral sides serves dual purpose, (i) calibrating HERD’s electromagnetic calorimeter in the TeV energy range, and (ii) serving as an independent detector for high-energy gamma rays. In this paper, the prototype readout electronics design of the transition radiation detector is demonstrated, which aims to accurately measure the charge of the anodes using the SAMPA application specific integrated circuit chip. The electronic performance of the prototype system is evaluated in terms of noise, linearity, and resolution. Through the presented design, each electronic channel can achieve a dynamic range of 0-100 fC, the RMS noise level not exceeding 0.15 fC, and the integral nonlinearity was less than 0.2%. To further verify the readout electronic performance, a joint test with the detector was carried out, and the results show that the prototype system can satisfy the requirements of the detector’s scientific goals.
分类: 核科学技术 >> 核科学与技术 提交时间: 2024-03-03
摘要: 针对天环一号(CAT-1: China Astro-Torus 1)偶极场等离子体物理实验要求,装置要求中心漂浮超导线圈在无冷却和无电源条件下稳定悬浮至少5hr,设计了超导托举线圈与中心漂浮线圈耦合系统的悬浮控制系统。为确保1200 kg、5 MA悬浮磁体稳定悬浮,完成了控制系统的Simulink模型建立和仿真,基于 Routh-Hurwitz稳定判据,研究了PID控制策略对稳定控制影响,确定了稳定控制参数选取的范围:当驱动托举线圈的电源响应频率应大于9 Hz,输出电流的误差小于0.1%时,理想条件下PD控制系统最有控制效果为延迟时间为0.0463 s、上升时间为0.1545 s、峰值时间为0.6283 s、调节时间0.0848 s、超调量δ=1.6,稳态误差err小于0.05 mm,为电源相应频率大于9 Hz,输出误差小于0.05%。结果表明:基于PID能够在较短的时间内将悬浮超导环在预设位置,且采用合适的启动方式情况下,可极大的降低电路的负载,并为悬浮超导悬浮偶极场装置的技术可行性提供有力支撑。
分类: 核科学技术 >> 核科学技术其他学科 分类: 物理学 >> 核物理学 提交时间: 2024-02-28
摘要: Ferritic/martensitic (F/M) steels have been widely used as structural material for thermal and nuclear power plants. However, it is susceptible to intergranular damage in service conditions, which is expected to be critical issues. In order to improve the intergranular damage resistance of F/M steel, thermomechanical process (TMP) was employed to achieve a grain boundary engineering (GBE) microstructure in a kind of F/M steel P92 in this study. TMP, including cold rolling to 6%, 9%, and 12% thickness reduction, respectively, followed by austenization at 1323 K for 40 min plus tempering at 1053 K for 45 min, were applied on as-received (AR) P92 steel. Both prior austenite grain (PAG) size, prior austenite grain boundary character distribution (GBCD), and the connectivity of prior austenite grain boundaries (PAGBs) were investigated. Compared with AR specimen, the PAG size does not change significantly. The fraction of coincident site lattice boundaries (CSLBs, 3 ≤ Σ ≤ 29) and Σ3n boundaries along PAGBs decreases with increasing reduction ratio due to the recrystallization fraction increases with increasing reduction ratio. The PAGBs connectivity of the 6%-deformed specimen deteriorates compared with that of AR specimen slightly. Moreover, the potentiodynamic polarization studies revealed that the intergranular damage resistance of studied steel could be improved by enhancing the fraction of CSLBs along PAGBs, indicating that TMP, involving low deformation, could enhance the intergranular damage resistance.
分类: 物理学 >> 核物理学 分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2024-02-27
摘要: 正在建设中的强流重离子加速器装置 HIAF 配备了一条先进的放射性束流线 HFRS,建成后将为中国 高能放射性核束物理研究提供新的机遇。HFRS 的特点是流强极高 (初级束流强度 1 × 1011 ppp),这对用于粒 子鉴别的能损探测器提出了非常高的计数率要求。传统的能损探测器对信号处理一般依次采用电荷灵敏前放、 主放、ADC 的技术路线。该方案存在电子学响应速度较慢、灵活性较差、难以处理高计数率下信号堆积严重 等问题。我们对此提出一种新的适用于高计数率的能损探测器方案:以耐辐照的多次取样电离室为能损探测 器,优化结构和读出方式提高探测器响应速度,使用快电荷灵敏前放对能损探测器信号初步放大后、直接用 波形数字化仪采集波形再进行后续数字算法处理。并利用放射源和束流对该方案进行了验证测试。利用 3 组 分 𝛼 源测试时,对采集的波形使用数字成形算法处理,能量分辨率(FWHM)可达 1.31%。在 RIBLL2 提供 300 MeV/u 的 56Fe 束流测试中,采用时间常数 𝜏f = 2 𝜇𝑠 的快电荷灵敏前放在计数率接近 1 MHz 时仍未发生明显堆积。
分类: 物理学 >> 核物理学 分类: 核科学技术 >> 核聚变工程技术 提交时间: 2024-02-27
摘要: The helium bubbles induced by 14 MeV neutron irradiation can cause intergranular fractures in reduced activation ferritic martensitic (RAFM) steel, which is a candidate structural material for fusion reactors. In order to elucidate the susceptibility of different grain boundaries (GBs) to helium-induced embrittlement, the tensile fracture processes of 10 types of GBs with and without helium bubbles in body-centered cubic (bcc) iron at the relevant service temperature of 600 K were investigated via molecular dynamics methods. The results indicate that in the absence of helium bubbles, the GBs studied here can be classified into two distinct categories: brittle GBs and ductile GBs. The atomic scale analysis shows that the plastic deformation of ductile GB at high temperatures originates from complex plastic deformation mechanisms, including the Bain/Burgers path phase transition and deformation twinning, in which the Bain path phase transition is the most dominant plastic deformation mechanism. However, the presence of helium bubbles severely inhibits the plastic deformation channels of the GBs, resulting in a significant decrease in elongation at fractures. For bubble-decorated GBs, the ultimate tensile strength increases with the increase of the misorientation angle. Interestingly, the coherent twin boundary Ʃ3{112} was found to maintain relatively high fracture strength and maximum failure strain under the influence of helium bubbles.
分类: 核科学技术 >> 核探测技术与核电子学 分类: 物理学 >> 核物理学 提交时间: 2024-02-26
摘要: 使用宇宙射线对兰州重离子加速器冷却储存环 (HIRFL-CSR) 外靶实验终端 (ETF) 的 Veto 探测器开展了
刻度工作,工作主要分为位置刻度与时间刻度两部分。位置刻度可给出粒子在探测器上的击中位置,时间刻
度则能为粒子在探测器上击中时刻的探测建立统一标准。这些信息是剔除入射到中子墙探测器的带电粒子事
件的依据,可为中子墙探测器物理目标的实现提供重要支持。在刻度过程中,得到了 Veto 探测器的位置分辨
半高全宽 (FWHM) 为 2.53 cm,所有单元条时间归一后的时间分辨 FWHM 为 1.09 ns。
分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2024-02-25
摘要:
A combination of scintillator, wavelength shifting (WLS) fiber, and silicon photomultiplier (SiPM) shows excellent performance in the `KL and μ detector (KLM)' of the Belle II experiment. We describe the R&D for a similar detection technology with a new scintillator and SiPM, which can be implemented for a muon detector for the proposed CEPC experiment and the upgrade of KLM in Belle II. The R&D contains the study of the performance of a new scintillator with a length of 150 cm, the NDL SiPM with a sensitive surface of 3 mm × 3 mm or the Hamamatsu MPPC with a sensitive surface of 1.3 mm × 1.3 mm, the construction of a detector strip, and the methods to achieve excellent light collection. The cosmic ray tests show good photon collections by NDL SiPM or MPPC, efficiencies well above 90% with a threshold of 8 p.e., and time resolutions of better than 1.7 ns for the hits at the far end of a scintillator strip. The performance shows a good option for an excellent muon detector for CEPC and the possible upgrade of Belle II KLM.
分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2024-02-23
摘要: Time-encoded imaging is useful for identifying potential special nuclear materials and other radioactive sources at a distance. In this study, a large field-of-view time-encoded imager was developed for gamma-ray and neutron source hotspot imaging based on a depth-of-interaction (DOI) detector. The imager primarily consists of a DOI detector system and a rotary dual-layer cylindrical coded mask. An EJ276 plastic scintillator coupled with two SiPMs was designed as the DOI detector to increase the field of view and improve the imager performance. The difference in signal time at both ends and the log of the signal amplitude ratio were used to calculate the interaction position resolution. The position resolution of the DOI detector was calibrated using a collimated Cs-137 source, and the full width at half maximum of the reconstruction position of the Gaussian fitting curve was approximately 4.4 cm. The DOI detector can be arbitrarily divided into several units to independently reconstruct the source distribution images. The unit length was optimized via Am-Be source-location experiments. A multidetector filtering method is proposed for image denoising. This method can effectively reduce image noise caused by poor DOI detector position resolution. The vertical field of view of the imager was (-55°, 55°) when the detector was placed in the center of the coded mask. A DT neutron source at 20 m standoff could be located within 2400 s with an angular resolution of 3.5°.
分类: 核科学技术 >> 核材料与工艺技术 提交时间: 2024-02-20
摘要: The synergistic damage effect of irradiation and corrosion of reactor structural materials has been a prominent research focus. This paper provides a comprehensive review of the synergistic effects on the third- and fourth-generation fission nuclear energy structural materials used in pressurized water reactors and molten salt reactors. The competitive mechanisms of multiple influencing factors, such as the irradiation dose, corrosion type, and environmental temperature, are summarized in this paper. Conceptual approaches are proposed to alleviate the synergistic damage caused by irradiation and corrosion, thereby promoting in-depth research in the future and solving this key challenge for the structural materials used in reactors.
分类: 核科学技术 >> 核科学与技术 提交时间: 2024-02-19
摘要: In this study, the interactions between a Ga-based liquid metal,GaInSn, and several metal materials, including pure metals (Ni and Ti) and alloys (316H stainless steel (SS) and GH3535), at 650 °C were investigated. The aim was to evaluate the corrosion performance and select a suitable candidate material for use as a molten salt manometer diaphragm in thermal energy storage systems. The results indicated that the alloys (316H SS and GH3535) exhibited less corrosion than pure metals (Ni and Ti) in liquid GaInSn. Ga-rich binary intermetallic compounds were found to form on the surfaces of all the tested metal materials exposed to liquid GaInSn, as a result of the decomposition of liquid GaInSn and its reaction with the constituent elements of the metal materials. The corrosion mechanism for all the tested materials exposed to liquid GaInSn was also investigated and proposed, which may aid in selecting the optimal candidate material when liquid GaInSn is used as the pressure-sensing medium
分类: 核科学技术 >> 核科学与技术 提交时间: 2024-02-13
摘要: The heterogeneous variational nodal method (HVNM) has emerged as a potential approach for solving high-fidelity neutron transport problems. However, achieving accurate results with HVNM in large-scale problems using high-fidelity models has been challenging due to the prohibitive computational costs. This paper presents an efficient parallel algorithm tailored for HVNM based on the Message Passing Interface standard. The algorithm evenly distributes the response matrix sets among processors during the matrix formation process, thus enabling independent construction without communication. Once the formation tasks are completed, a collective operation merges and shares the matrix sets among the processors. For the solution process, the problem domain is decomposed into subdomains assigned to specific processors, and the red-black Gauss-Seidel iteration is employed within each subdomain to solve the response matrix equation. Point-to-point communication is conducted between adjacent subdomains to exchange data along the boundaries. The accuracy and efficiency of the parallel algorithm are verified using the KAIST and JRR-3 test cases. Numerical results obtained with multiple processors agree well with those obtained from Monte Carlo calculations. The parallelization of HVNM results in eigenvalue errors of 31 pcm/-90 pcm and fission rate RMS errors of 1.22%/0.66%, respectively, for the 3D KAIST problem and the 3D JRR-3 problem. In addition, the parallel algorithm significantly reduces computation time, with an efficiency of 68.51% using 36 processors in the KAIST problem and 77.14% using 144 processors in the JRR-3 problem.
分类: 核科学技术 >> 核爆炸工程 提交时间: 2024-02-08
摘要: In high-altitude nuclear detonations, the proportion of pulsed X-ray energy can exceed 70%, making it a specific monitoring signal for such events. These pulsed X-rays can be captured using a satellite-borne X-ray detector following atmospheric transmission. To quantitatively analyze the effects of different satellite detection altitudes, burst heights, and transmission angles on the physical processes of X-ray transport and energy fluence, we developed an atmospheric transmission algorithm for pulsed X-rays from high-altitude nuclear detonations based on scattering correction. The proposed method is an improvement over the traditional analytical method that only computes direct-transmission X-rays. The traditional analytical method exhibits a maximum relative error of 67.79% compared with the Monte Carlo method. Our improved method reduces this error to within 10% under the same conditions, even reaching 1% in certain scenarios. Moreover, its computation time is 48000 times faster than that of the Monte Carlo method. These results have important theoretical significance and engineering application value for designing satellite-borne nuclear detonation pulsed X-ray detectors, inverting nuclear detonation source terms, and assessing ionospheric effects.
分类: 核科学技术 >> 核探测技术与核电子学 分类: 核科学技术 >> 核仪器、仪表 提交时间: 2024-02-07
摘要: A new measurement method for the spatial distribution of neutron beam flux in boron neutron capture therapy (BNCT) is being developed based on the two-dimensional Micromegas detector. To address the issue of long processing time in traditional offline position reconstruction methods, this paper proposes an FPGA-based online position reconstruction method, grounded in the micro time projection chamber principle. This method encapsulates key technical aspects: self-adaptive serial link technique built upon the dynamical adjustment of delay chain length, fast sorting and coordinate matching technique based on the mapping between signal timestamps and random access memory (RAM) addresses, and precise start point merging technique utilizing a circular combined RAM. The performance test of the self-adaptive serial link shows the bit error rate of the link is better than 10^-12 at a confidence level of 99%, ensuring reliable data transmission. The combined experiment of the readout electronics and the Micromegas detector shows a spatial resolution of approximately 1.4 mm, surpassing the current method's resolution level of 5 mm. The beam experiment confirms that the readout electronics system can obtain the flux spatial distribution of neutron beam online, thus validating the feasibility of the position reconstruction method. The online position reconstruction method avoids traditional methods such as bubble sorting and traversal searching, simplifying the design of logic firmware and reducing the time complexity from O(n^2) to O(n). This study contributes to the advancement in measuring neutron beam flux for BNCT.
分类: 核科学技术 >> 核科学与技术 提交时间: 2024-02-04
摘要: CAFE-2是中国科学院近代物理研究所于2021年建造、用于开展超重新核素合成、超重元素化学性质、超重核结构和性质等方面的研究的超导直线加速器。同步定时触发系统是CAFE-2的重要子系统,在CAFE-2的运行中起着关键性的作用。为了满足CAFE-2在加速器调试及终端运行两种运行模式下不同运行时序及同步触发的需求,CAFE-2主同步定时系统采用了经典的基于事件的定时方案,同时通过耦合电路及联锁逻辑设计,在终端运行模式下将旋转靶调制的同步脉冲信号与主定时CW(Continuous-wave)模式下的触发信号进行耦合,解决了CAFE-2在终端运行模式下触发信号必须与旋转靶脉冲信号同步的难题。本文介绍了CAFE-2同步定时触发系统的结构,并阐述了CAFE-2在不同运行模式下同步定时触发系统的工作原理与方案。