分类： 核科学技术 >> 核科学与技术 提交时间： 2024-04-27
摘要： 研究针对核反应堆板状燃料组件出现的鼓泡现象，利用Fluent软件进行了数值模拟研究，并对比了裂变气体鼓泡和以往研究中固体鼓泡的区别。研究发现：气体鼓泡会导致局部温度升高，鼓泡周围热通量密度提高3倍，但燃料板整体热通量变化较小；鼓泡的形成会使鼓泡局部换热能力提高约10%，鼓泡侧热通量提高4%左右；在高流速条件下，鼓泡的存在会导致燃料板两侧流体产生较大的压力差，使得燃料板发生变形，甚至堵塞流道。研究结果为板状燃料元件设计和安全评估提供了重要参考。
分类： 核科学技术 >> 核科学技术其他学科 提交时间： 2024-05-01
摘要： 本文针对核燃料棒焊缝质量检测的高效率和高精度需求，设计并实现了一套在线自动化评价系统。该系统采用B/S架构，结合先进的AI技术，实现了燃料棒焊缝的实时图像采集、管理和智能分析。系统前端使用Electron.js、React和Ant Design框架，后端基于Spring Cloud和Docker技术，确保了操作的便捷性和系统的稳定性。通过集成的AI模型，系统能够有效识别焊缝缺陷，提高了检测的准确性和生产效率。系统的成功实施，为核电站的安全运行和核能行业的质量控制提供了有力支持，并为未来自动化检测技术的发展奠定了基础。
分类： 核科学技术 >> 核科学与技术 提交时间： 2024-05-01
摘要： 天环一号（CAT-1: China Astro-Torus 1）是国内首个采用磁悬浮偶极场磁体设计的磁约束等离子体装置。本文根据CAT-1装置总体目标和参数设计要求，采用线电流简化模型，基于矢量磁场、力学平衡及动力学等方法，对悬浮磁体稳定性进行了分析计算，给出了装置悬浮磁体、托举线圈和TSR线圈的总体尺寸、空间位置与布局、电流、重量、特征稳定性能及作用关系等设计参数。结果表明：对于CAT-1装置的悬浮磁体1200kg、电流5MA、悬浮距离2.0 m设计目标，托举线圈半径最优值为1.7 m，相应的电流为 3.49 kA，为实现对悬浮磁体偏移运动的有效阻减及控制，平衡点附近工作区域应限制在Δz < 100 mm、er < 50 mm、α< π/24。
分类： 核科学技术 >> 核科学技术其他学科 提交时间： 2024-05-02
摘要： 摘要：[目的] 为解决核聚变发电热功率输出不稳定性和汽轮发电机组平稳运行之间的矛盾，CFETR核聚变发电厂可运用储热技术可对核聚变堆的功率输出进行削峰平谷。储热技术有多种类型，各类储热技术对于核聚变发电厂的适用性亟需进行对比。[方法] 文章选取核聚变反应堆氦冷陶瓷增殖包层的参数作为储热技术边界条件，通过对储热技术适用温度范围进行评估，初步分析出有潜力运用于CFETR核聚变发电厂的三种储热技术，并对其进行成本进行初步预测。[结果]三大类储热技术均可选出适用CFETR核聚变发电厂氦冷增殖包层温度参数的储热介质。但化学储热由于其吸热和放热存在温差，造成能量的损耗的同时不利于系统的稳定性，显热储热技术和相变储热技术吸热温度和放热温度温差较小，具有应用于CFETR核聚变发电厂的潜力。初步经济性分析结果显示，相变储热成本最低，其次为熔融盐储热，再次为固相显热储热技术中利用硅砖作为储热介质，固相显热储热技术中利用铸钢作为储热介质成本最高。 [结论]储热技术中，熔融盐储热技术、相变储热技术、固相显热储热具有应用于CFETR核聚变发电厂氦冷增殖包层的先决条件。熔融盐储热技术成熟度较高，有大量工程应用，造价在相变储热和固相显热储热之间，运用潜力较大。相变储热的成本最低，参数同样适用于核聚变发电，但其技术成熟度较低，有望成为未来研究的重点。
分类： 化学 >> 核化学 提交时间： 2024-05-02
摘要： 背景：人表皮生长因子受体2(HER2)广泛存在于多种恶性肿瘤，且与预后不良有关。尤其在乳腺癌中，但HER2表达存在异质性，目前常用免疫组织化学和荧光原位杂交在评估HER2状态存在明显局限性。HER2受体显像有明显优势。放射性标记的模拟肽是检测HER2阳性病变的潜在选择。目的：制备一种18F标记的人表皮生长因子受体２（HER2）模拟肽显像剂18F-NFP-B2-S22-AFA（以下简称为18F-NFP-TP1296），探讨其microPET显像及生物分布。方法 采用一步法标记18F-NFP-TP1296被应用于HER2乳腺癌异种移植小鼠的PET-CT成像。在SKBR-3乳腺癌模型中进行了体外研究和MicroPET成像。结果18F-NFP-TP1296制备过程大约30分钟内完成，总标记率为1.5%，放化纯＞95%。MicroPET成像显示，SKBR-3异种肿瘤清晰可见，注射30、60和120min后，SKBR-3移植瘤摄取值分别为5.63±0.14%ID/g、6.26±0.27%ID/g和5.83±0.44%ID/g。30、60和120min肿瘤与血液和肿瘤与肌肉的比率分别为3.21±0.32、4.08±0.73和1.69±0.18；1.55±0.11、1.84±0.12和3.10±0.30。另外肺转移瘤注射后30、60和120min肿瘤的摄取值2.2%ID/g、2.5%ID/g及2.1%ID/g。结论：18F-NFP-B2-S22-AFA具有合成简便、药代动力学良好等优点，有望成为体内检测HER2状态的示踪剂，对肿瘤的鉴别诊断、分子靶向治疗及预后判断有一定的参考价值。
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Diffraction gratings with high upward diffraction efficiency and large effective length are required for chip-scale light detection and ranging. In this paper, we propose a diffraction grating based on a multilayer silicon nitride waveguide, which theoretically achieves an upward diffraction efficiency of 92$\%$, a near-field effective length of 376 $\mu m$ and a far-field divergence angle of 0.105$^{\circ}$ at a wavelength of 850 nm. The diffraction grating has a high tolerance to process variations based on Monte Carlo Analysis. When the conditions are $\pm$5$\%$ layer thickness variation, $\pm$50 nm lithographic variation and $\pm$20 nm wavelength drift, more than 71$\%$ of the grating samples have a diffraction efficiency higher than 80$\%$, and 100$\%$ of the samples have an effective length larger than 200 $\mu m$ (corresponding to a far-field divergence <0.2$ ^{\circ}$). Furthermore, the near-field effective length of the grating with an upward diffraction efficiency above 90$\%$ can be adjusted from hundreds of microns to centimeters by changing the etching layer thickness and the grating duty cycle. This diffraction grating has potential application in optical sensing and imaging from visible to near-infrared wavelengths.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Electromagnetic spins, including longitudinal and transverse ones, have been playing important roles in light-matter interactions. Here, we formulate a unified equation to uncover the physical origins and topological properties of longitudinal and transverse spins in a generic electromagnetic field. The equation reveals universally that the transverse spin is locked with the kinetic momentum and originated from the transverse inhomogeneities of field, whereas the helix-dependent longitudinal spin orients parallel to the local wavevector. Remarkably, a hidden extraordinary helix-dependent transverse spin possessing helix-dependent spin-momentum locking is discovered and the number of locking states consistent with the nontrivial topological spin Chern number. Furthermore, this spin which determines the inverted helical components is related to the Berry curvature closely. The findings, which are demonstrated experimentally by measuring the three-dimensional spin components in the focusing configuration, will deepen the understanding the underlying physics of spins and open an avenue for chiral quantum optical applications.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Polarization vectors of light traveling in a coiled optical fiber rotate around its propagating axis even in the absence of birefringence. This rotation was usually explained due to the Pancharatnam-Berry phase of spin-1 photons. Here, we use a purely geometric method to understand this rotation. We show that similar geometric rotations also exist for twisted light carrying orbital angular momentum (OAM). The corresponding geometric phase can be applied in photonic OAM-state-based quantum computation and quantum sensing.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Optical forces in the near fields have important applications in on-chip optical manipulations of small particles and molecules. Here, we report a study of optical force and torque on small particles induced by the optical polarization singularities of a gold cylinder. We show that the scattering of the cylinder generates both electric and magnetic C lines (i.e., lines of polarization singularities) in the near fields, and the C lines can induce complex force and torque on a dielectric/magnetic particle. The force and torque manifest dramatic spatial variations with interesting symmetry properties, providing rich degrees of freedom for near-field optical manipulations. The study, for the first time to our knowledge, uncovers the effect of optical polarization singularities on light-induced force and torque on small particles. The results contribute to the understanding of chiral light-matter interactions and can find applications in on-chip optical manipulations and optical sensing.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： How migratory birds can find the right way in navigating over thousand miles is an intriguing question, which much interested researchers in both fields of biology and physics for centuries. There several putative proposals that sound intuitively plausible all remain contested so far because those hypothesis-models of magnetoreceptor to sense geomagnetic field need either extremely high sensitivity or humankind-like intelligence to guide. Here we explore theoretically that the birds can navigate to their destination through an entirely new scenario to sense the geomagnetic field. Our proposal is based on separate peaks of the resonance-fluorescence spectrum of a four-level system derived from the ferric sulfide cluster which exists in a protein complex (Drosophila CG8198) of migratory birds. As the separation of spectral peaks contains information about geomagnetic field at both current location and birthland, the change of such separation cues the bird to choose a right direction to move and double-resonance emerges once arrived the destination. Our theoretical mechanism can explain previous experiments on the disorientation of migratory birds caused by oscillating magnetic field naturally and more precisely. This work provides insight to explain migratory navigation and motivates possible manmade practical devices.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Narrow linewidth laser(NLL) of high frequency stability and small form factor is essential to enable applications in long range sensing, quantum information and atomic clocks. Various high performance NLL have been demonstrated by Pound-Drever Hall(PDH) lock or self injection lock(SIL) of a seed laser to a vaccum-stabilized FP cavity of ultrahigh quality factor(Q). However they are often complicated lab setups due to the sophisticated stabilizing system and locking electronics. Here we report a compact NLL of 68mL volume, realized by SIL of a diode laser to a miniature FP cavity of 7.7x108 Q and 0.5mL volume, bypassing table-size vaccum, thermal and vibration isolation. We characterized the NLL with a self-delayed heterodyne system, the Lorentzian linewidth reaches 60mHz, and the integrated linewidth is ~80Hz. The frequency noise performance exceeds that of commercial NLLs and the best reported hybrid-integrated NLL realized by SIL to high Q on-chip ring resonators. Our work marks a major step toward a field-deployable NLL of superior performance utilizing ultra-high Q FP cavity.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Conventional coherent absorption occurs only when two incident beams exhibit mirror symmetry with respect to the absorbing surface, i.e., the two beams have the same incident angles, phases, and amplitudes. In this work, we propose a more general metasurface paradigm for coherent perfect absorption, with impinging waves from arbitrary asymmetric directions. By exploiting excitation of unidirectional evanescent waves, the output can be fixed at one reflection direction for any amplitude and phase of the control wave. We show theoretically and confirm experimentally that the relative amplitude of the reflected wave can be tuned continuously from zero to unity by changing the phase difference between the two beams, i.e. switching from coherent perfect absorption to full reflection. We hope that this work will open up promising possibilities for wave manipulation via evanescent waves engineering with applications in optical switches, one-side sensing, and radar cross section control.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
Lingya Yu
Zengbo Wang
Lizhou Xu
Liyang Yue
Bing Yan
Igor V. Minin
Oleg V. Minin
Baidong Wu
Yiduo Chen
摘要： Photonic hook (PH) is a new type of artificial self-bending beam focused by a dielectric particle-lens with a curved waist smaller than the wavelength, which has the potential to revolutionize mesoscale photonics in many applications, e.g., optical trapping, signal switching, imaging, etc. In this paper, we discover a new mechanism that the highly curved PHs can be realised by the light interaction with the fully or partially metal-coated microchannels. The generated W-shaped and J-shaped PHs have bending angles exceeding 80-degree. Compared to other PH setups, the proposed design has a larger range to flexibly control the bending angle through the coating process and can be easily integrated with the established microfluidic systems.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： We show that the time-averaged Poynting vector in parity-time (PT ) symmetric coupled waveguides is always positive and cannot explain the stopped light at exceptional points (EPs). In order to solve this paradox, we must accept the fact that the fields E and H and the Poynting vector in non-Hermitian systems are in general complex. Based on the original definition of the instantaneous Poynting vector, a formula on the group velocity is proposed, which agrees perfectly well with that calculated directly from the dispersion curves. It explains not only the stopped light at EPs, but also the fast-light effect near it. This investigation bridges a gap between the classic electrodynamics and the non-Hermitian physics, and highlights the novelty of non-Hermitian optics.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： During the last few decades, solid-core photonic crystal fibers (PCFs) have been extensively explored to generate broadband, high-coherence supercontinua (SC). Limited by the material absorption and relatively low nonlinearity of fused silica, spectral broadening in silica PCF-based SCs is usually restricted to the blue to near-infrared spectral regions, even in developed commercial sources. The output spectra of these sources are missing short wavelengths of the full range. Many efforts have been spent to break the limitation. Among them, dispersive-wave (DW) generation has been investigated for triggering new frequencies in short wavelengths. With satisfied phase-matching conditions, excessive energy can be directly transferred from solitons of the anomalous dispersion region to DWs of the short wavelengths. However, a systematical study of factors, including phase-matched DWs, strongly related to the dispersion tailoring of higher-order modes (HOMs), has rarely been shown. This study reports the experimental observations of HOM-enhanced phase-matchings for the DW generation in the deep-blue and ultraviolet regions. A solid-core PCF-based, UV-extended SC source spanning a 2.8-octave-wide (350 nm to 2500 nm) is demonstrated. Meanwhile, we carefully verify our findings via numerical calculations.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Mode-locked lasers, which produce ultrashort pulses in the picosecond and femtosecond range, have enabled some of the most precise measurements. However, despite significant recent progress, resolving the temporal behavior of their short pulses is still a challenge. State-of-the-art oscilloscopes with tens of picosecond resolution prevent time-resolved observations in mode-locked lasers and limit the real-time pulse evolution tracking of ultrafast lasers. Here, using the time-lens technique with a Raman amplifier, we implement an ultrafast single-shot time-microscope (TM) with a high temporal magnification factor of 355 and a time measurement window of 1 millisecond that contains ~1.8*10^4 consecutive pulses. We use this TM to characterize the temporal evolution of mode-locked lasers and reveal a temporal sideway oscillation (winding) behavior, a previously unobserved feature of lasers in both theory and experiment. Our experimental observations confirm that the winding behavior is an essential feature in the operation of mode-locked lasers. We theoretically and experimentally found that the winding characteristic evolution originates from gain-induced fluctuations for relatively high gain energies, while Q-switched modulations being the main cause for lower energies. Our findings based on advanced real-time measurements open up new insights into ultrafast and transient optics and may impact future laser designs, modern ultrafast diagnostics, and influence progress in nonlinear optics in general.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Halide perovskite materials raised tremendous interest in recent years since their cheap fabrication, superior performance in both solar cell and light emitting diode (LED). Due to the existence of layered quantum well structure, quasi two-dimensional(2D) halide perovskite has more intriguing spin related physics than its 3D counterpart. For instance, the detection and brightening of dark exciton (DX) in 2D halide perovskite attracts much attention since these species can be used in opto-spintronic and quantum computing devices. Here, we report the gradually brightened emission of the DX at 2.33 eV with the thickness decreases in (PEA)2PbI4 single crystalline nanoflake, which hitherto has not been reported. By coupling with in-plane (IP) magnetic field in Voigt configuration, the DX emission can be sharply enhanced, while for the out-of-plane (OP) magnetic field in Faraday configuration, the DX emission has no noticeable change, which can be reconciled with the theory interpretation of magnetic field dependent wave function mixing between the four exciton states fi1, fi2, fi3- , fi3+. The emission of DX fi2 at 2.335 eV and the fine splitting of all the four states are observed in static PL spectroscopy for the first time. Our work thus clarifies the debating questions regarding to previous research on DX behavior in 2D halide perovskite material and sheds light on the road of realizing opto-spintronic or quantum computing devices with these materials.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： Traditional lasers function using resonant cavities, in which the round-trip optical path is exactly equal to an integer multiple of the intracavity wavelengths to constructively enhance the spontaneous emission rate. By taking advantage of the enhancement from the resonant cavity, the narrowest sub-10-mHz-linewidth laser and a $10^{-16}$-fractional-frequency-stability superradiant active optical clock (AOC) have been achieved. However, a laser with atomic spontaneous radiation being destructively inhibited in an anti-resonant cavity, where the atomic resonance is exactly between two adjacent cavity resonances, has not been reported. Herein, we experimentally demonstrate inhibited stimulated emission and termed it an inhibited laser. Compared with traditional superradiant AOCs, which exhibit superiority in terms of the high suppression of cavity noise, the suppression of the cavity-pulling effect of an inhibited laser can be further improved by a factor of $(2F/pi)^2$, i.e., 2.07 in this work, which was improved from 26 to 53 times. This study will guide further development of AOCs with better stability, and thus, it is significant for quantum metrology and may lead to new research in the laser physics and cavity quantum electrodynamics fields.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： In many-cycle plane waves at intermediate intensities, the nonlinear trident process can be well-approximated by the two sequential steps of nonlinear Compton scattering of a polarised real photon followed by its transformation into an electron-positron pair via nonlinear Breit-Wheeler pair creation. We investigate this two-step process in the intermediate intensity regime by employing the locally monochromatic approximation for each step and numerically evaluating resulting expressions. When photon polarisation is included, it is found to produce an order 10% decrease in the trident rate: the importance of polarisation increases at lower intensities, and decreases at higher intensities. Its importance persists at higher intensities in a linearly-polarised background, but disappears at high intensities in a circularly-polarised background. If the two steps are made to take place in two linearly-polarised plane wave pulses with perpendicular polarisations, the pair yield can be increased by approximately 30% compared to two plane waves with the same polarisation. It is also shown that harmonic structures in the Compton step can be passed to the pair step if the Compton edge is at an energy of the order of the threshold for linear Breit-Wheeler.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： The effect of the pulse envelope on electron-positron pair creation in a circularly-polarised laser pulse is investigated. Interference on the length scale of the pulse envelope, and smoothness of the pulse edges are found to influence the pair spectrum. A toy model of a flat-top pulse is used to identify pulse envelope effects inaccessible to local approaches. Broadening of channel openings and a widening of the energy and transverse momentum distribution of the pair are found to receive contributions that are below the local harmonic threshold. By comparing pair yields in a flat-top, sine-squared and Gaussian pulse, a link between pulse shape and photon-polarised Breit-Wheeler is found. In the transverse momentum distribution, a signal of pulse envelope interference is found in an azimuthal asymmetry, which appears in intense fields and persists in long pulses.
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