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  • Maximizing output power in P-N junction betavoltaic batteries via Monte Carlo and Physics-Based Compact Model Co-Simulation

    分类: 核科学技术 >> 核科学技术其他学科 提交时间: 2024-02-28

    摘要: Betavoltaic nuclear batteries show promise as compact and enduring power sources for microelectromechanical systems (MEMS). Current theoretical calculations often overlook practical diode characteristics like surface recombination (S), bulk recombination within the space-charge region (R-SCR), series resistance (Rs) and shunt resistance (Rsh), resulting in significant gaps between theoretical predictions and experimental results, with differences in JSC, VOC, or converter efficiency up to tenfold. To address this, a Practical Diode Model, integrating these practical characteristics, is developed via Monte Carlo and Physics-Based Compact Model Co-Simulation.We quantitatively analyze the differential impacts and synergistic effects of these practical characteristics on JSC, VOC, FF, and Pout, highlighting the detrimental effects of S, R-SCR, and Rs, while emphasizing the beneficial role of Rsh. Further analysis of the degree of influence of S, Rs, and Rsh on output power reveals a priority ranking order of Rs, S, and Rsh for Si-based batteries, and S, Rsh, and Rs for SiC-based batteries. This approach effectively bridges the theoretical-experimental gap, evidenced by J-V curves closely matching tested batteries and negligible relative errors of -0.8% to 0.6% between Pout values and their tested counterparts, emphasizing its accuracy in predictions. We predict output performance across material qualities, obtaining achievable powers of 16.82 and 73.90 nW/cm2 for planar Si- and SiC-based batteries, and evaluate the quality levels of existing batteries. Furthermore, our model can forecast the performance of 3D batteries by incorporating an extended electron-hole pair generation rate model into 3D structures, achieving 28 μW/cm3 for the 63Ni-Si-based multi-layer battery, surpassing planar silicon and suitable for MEMS applications.

  • Grain boundary engineering for enhancing intergranular damage resistance of ferritic/martensitic steel P92

    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.

  • 一种高计数率的能损探测器方案研究

    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。

  • Atomistic study on the microscopic mechanism of grain boundary embrittlement induced by small dense helium bubbles in iron

    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.

  • HIRFL-CSR 外靶实验终端 Veto 探测器的刻度

    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。

  • Design and test for the CEPC muon subdetector based on extruded scintillator and SiPM

    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.

  • Design and performance evaluation of a large field-of-view dual-particle time-encoded imager based on a depth-of-interaction detector

    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°.

  • Review on synergistic damage effect of irradiation and corrosion on reactor structural alloys

    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.

  • Corrosion behavior of pure metals (Ni and Ti) and alloys (316H SS and GH3535) in liquid GaInSn

    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

  • An efficient parallel algorithm of variational nodal method\\for heterogenous neutron transport problems

    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.

  • Atmospheric Transmission Algorithm for Pulsed X-rays from High-Altitude Nuclear Detonations Based on Scattering Correction

    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.

  • FPGA-based position reconstruction method for neutron beam flux spatial distribution measurement in BNCT

    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.

  • CAFE-2同步定时触发系统设计

    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。
     

  • 基于载流子演化的3D P+PNN+多沟槽结构提升Betavoltaic核电池性能

    分类: 核科学技术 >> 核动力工程技术 提交时间: 2024-02-01

    摘要: 贝塔辐射伏特核电池,利用放射性同位素所释放的贝塔粒子来实现电能转化,被广泛视为一项备受期待的替代能源技术。为满足微机电系统(MEMS)的功率需求,研究人员已提出采用三维(3D)结构作为一种潜在的解决方案。在此背景下,本研究引入了一种全新的3D电池设计,基于63Ni-SiC材料构建了一种P+PNN+多沟槽结构。这一结构的独特之处在于,无需在半导体器件的沟槽内表面外延PN结,以降低漏电流和功率损失。
    通过蒙特卡洛模拟方法,充分考虑了完全耦合的物理模型,我们成功将电子-空穴对产生率(G(x))扩展到了3D结构中,使得高效设计和开发具有复杂3D结构的贝塔辐射伏特电池成为可能。研究结果表明,相较于传统的平面电池,我们提出的3D电池在最大输出功率密度方面表现卓越,达到了19.74 µW/cm2,相应的短路电流、开路电压和转换效率分别为8.57 µA/cm2、2.45 V和4.58%。
    此外,我们还利用COMSOL Multiphysics软件对载流子的传输和收集特性进行了深入分析,为电池输出功率提升机制提供了深刻见解,并对贝塔辐射伏特电池的理想性能与仿真性能之间的差异进行了阐释。本研究为高输出性能的贝塔辐射伏特核电池的设计与优化提供了前瞻性方法,同时也为未来电池器件制造提供了有价值的参考。

  • 大功率晶闸管在聚变环境中受中子辐照影响研究

    分类: 核科学技术 >> 核科学与技术 提交时间: 2024-01-26

    摘要: 大功率晶闸管器件以其良好的经济性和适用性,被广泛应用于大型聚变装置的供电系统中。氘-氚(D-T)聚变反应产生的高剂量中子长时间照射晶闸管,将导致晶闸管的电学特性发生变化,最终造成不可逆的损伤。本文以聚变装置超导磁体失超保护系统(QPS)中换流回路的晶闸管开关为研究对象。建立了辐照晶闸管内部物理结构与外部电气参数之间的关系。然后,进行了一系列有针对性的晶闸管物理模拟和中子辐照实验,验证了理论分析的正确性。此外,通过精确仿真研究了辐照晶闸管电气特性变化对QPS的影响,为QPS的维护和改造提供了有价值的指导。

  • Optimized online filter stack spectrometer for ultrashort X-ray pulses

    分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2024-01-26

    摘要: 激光等离子体X射线能谱的诊断对于表征电子动力学和辐射源应用非常重要,高重复率超强飞秒激光器和高重复频率激光等离子体实验对脉冲X射线能谱的在线诊断技术提出了需求。 在本文中,使用闪烁体和硅PIN(P型本征N型半导体)二极管构建了宽带在线滤片堆栈谱仪。 使用遗传算法优化 了X 射线传感器和滤片的布置,使响应矩阵的条件数最小化,以优化谱仪的解谱误差。通过核素照射闪烁体和PIN二极管并比较测量的γ射线峰值,对探测器的响应进行了标定。 通过将 X 射线探测器与前端和后端电子学的集成化设计,研制了紧凑的 15 通道在线滤片堆栈谱仪原型系统。 原型系统可以以 1 kHz 的重复率测量脉冲X 射线能谱,并在激光驱动轫致辐射源的实时能谱监测中得到成功应用。 本文提出的优化在线滤片堆栈谱仪为超短X射线脉冲的能谱诊断提供了紧凑的解决方案,在能谱测量和重复率方面具有显著优势,可广泛用于未来的高重复率高功率激光装置实验。

  • 用于粒子物理实验数据传输系统中的高速电荷泵锁相环设计

    分类: 核科学技术 >> 核探测技术与核电子学 提交时间: 2024-01-22

    摘要: 本文在UMC 55nm CMOS工艺下,实现了一款10GHz高速输出、低功耗的高性能电荷泵锁相环设计,可以为粒子物理实验中数据传输系统提供高频差分时钟脉冲。设计了一种双支路通路电荷泵,通过引入运算放大器、虚拟管等措施抑制非理想因素对电路造成的影响。设计了高速、低功耗的64分频电路将锁相环输出的10 GHz差分时钟转化成156.25MHz的单端时钟。设计了采用了互补交叉耦合结构的LC压控振荡器,使其在快速起振的同时又具有较小的相位噪声。仿真结果表明,在经典工艺角下VCO在1MHz频偏处的相位噪声为-104.14dBc/Hz。PLL在500ns完成锁定,功耗22.34mW,峰峰值抖动为6.59ps。
     

  • 基于速度-动能法的中子诱发裂变谱仪物理设计

    分类: 核科学技术 >> 核科学与技术 提交时间: 2024-01-22

    摘要: 随着第四代核反应堆和新型核能利用系统的快速发展,以及超重核熔合机制和天体核物理中的快中子俘获反应等领域的研究进展,使得中子诱发重核裂变研究及裂变数据测量成为国际上核物理研究的新热点。本工作完成了基于速度-动能法的中子诱发裂变谱仪的物理设计。设计了MCP二次电子时间探测器,二次电子飞行时间展宽控制在50ps,TOF长度设计为70cm。选择屏栅电离室为能量探测器,工作气体选择为异丁烷,最佳约化场强为6V/(cm·torr),气压为37.5Torr,采用COMSOL、Geant4、Garfield++等程序耦合计算了裂变碎片在屏栅电离室中的能量响应,谱仪系统的能量分辨率为0.36~0.55%。综合分析,本工作设计的基于速度-动能法的中子诱发裂变谱仪,轻裂变碎片能量分辨率小于0.8%,重裂变碎片小于0.6%,中子诱发重核裂变的质量分辨小于1amu。此外,基于设计的裂变谱仪物理结构,本工作模拟计算了14MeV中子诱发238U裂变产额质量分布与电荷分布数据,与ENDF-VII基本一致,为中子诱发典型锕系重核裂变物理实验测量准备了条件。

  • 基于LaBr3 全国产化𝛾 能谱仪性能研究

    分类: 核科学技术 >> 核仪器、仪表 提交时间: 2024-01-15

    摘要: 随着国内半导体企业技术的发展,部分国产元器件性能指标已经与进口元器件相当,能够满足核辐射监测仪器仪表的性能需求。论文基于1.5 英寸LaBr3 闪烁体设计了一套全国产化的𝛾 能谱仪,包括闪烁体、光电倍增管和电子元器件均选用国产厂家产品。经测试,能谱仪在常温下的分辨率可以达到2.8%@662keV。工作温度范围可达-40℃ 至50℃,且全温度范围内的能量分辨率均优于3.0%,137Cs 全能峰道址随温度变化率约为-0.67/℃,且线性度良好。高压调整率为0.02V,满足0.2V /℃ 的稳谱高压调整率要求。谱仪的能量非线性好于99.99%。实验数据显示,现阶段国产LaBr3 闪烁体、光电倍增管及电子元器件能够满足𝛾 能谱仪的设计需求。

  • Design of Weak Current Measurement System and Research on Temperature Impact

    分类: 核科学技术 >> 核科学与技术 提交时间: 2024-01-10

    摘要: To measure the weak currents generated by the neutron ionization chamber, a dedicated weak current measurement system was designed. This system incorporates a second-order low-pass filter circuit and the Kalman filtering algorithm to effectively filter out noise and minimize interference on the measurement results. Testing conducted under normal temperature conditions has demonstrated the system's high precision performance. However, it was observed that temperature variations can affect the measurement performance. To address this issue, data was collected across temperatures ranging from -20 to 70°C, and a temperature correction model was established through linear regression fitting. The feasibility of the temperature correction model was confirmed at temperatures of -5 and 40°C, where relative errors remained below 0.1% after applying the temperature correction. The research indicate that the designed measurement system exhibits excellent temperature adaptability and high precision, making it particularly suitable for measuring weak currents.