分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: A theoretical framework in the spherical polar coordinate system is developed to systematically treat the correlation between intensity fluctuations (CIF) of electromagnetic light waves on scattering from a collection of particles of $\mathcal{L}$ types. Two $\mathcal{L}\times \mathcal{L}$ matrices called pair-potential matrix (PPM) and pair-structure matrix (PSM) are introduced to jointly formulate the normalized CIF of the scattered field for the first time. We build a closed-form relation that associates the normalized CIF with the PPM and the PSM as well as the spectral degree of polarization $\mathcal{P}$ of the incident field, showing that the normalized CIF is closely related to the trace of the product of the PSM and the transpose of the PPM, and its dependence on $\mathcal{P}$ is completely determined by the scattering polar angle and azimuth angle. For a special case where the spatial distributions of scattering potentials of particles of different types are similar and the same is true of their density distributions, the PPM and the PSM will reduce to two new matrices whose elements separately quantify the degree of angular correlation of the scattering potentials of particles and their density distributions, and the number of species of particles in this special case appears as a scaled factor to ensure the normalization of the CIF. The effects of the off-diagonal elements of the PPM and the PSM on the normalized CIF and its dependence on $\mathcal{P}$ are illustrated by two numerical examples.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: A new approach is developed within the first-order Born approximation to light scattering from a collection of particles with $\mathcal{L}$ types. Two $\mathcal{L}\times\mathcal{L}$ matrices called pair-potential matrix (PPM) and pair-structure matrix (PSM) are introduced to jointly formulate the coherence properties of the scattered field. We derive a closed-form relation that associates the cross-spectral density function of the scattered field with the PPM and the PSM, showing that the the cross-spectral density function equals the trace of the product of the PSM and the transpose of the PPM. Based on this, the spectral degree of coherence (SDOC) of the scattered field is further analysed. We show that for a special case where the spatial distributions of scattering potentials of different types of particles are similar and the same is true of their density distributions, the PPM and the PSM will reduce to two new matrices whose elements separately quantify degree of angular correlation of the scattering potentials of particles and their density distributions, and the number of species of particles in this special case as a scaled factor ensures the normalization of the SDOC. Two special hybrid particulate systems as examples are given to illustrate the importance of our new approach.
分类: 物理学 >> 交叉学科物理及相关领域的科学与技术 分类: 材料科学 >> 陶瓷学 提交时间: 2024-03-20
摘要: 高放废物固化体的长期辐照稳定性是评价其深地质处置安全性的关键指标之一。本文利用 500 keV He2+离子束辐照 2M、 3O 和 4M 型钙钛锆石陶瓷固化体, 研究高放核素长期α 衰变辐照对陶瓷结构的损伤行为。三种钙钛锆石样品通过传统高温固相法(1400 ℃, 48h两次烧结)合成。掠入射 X 射线衍射(GIXRD) 、 Raman 光谱和 XPS 研究结果发现在 α 粒子辐照下, zirconolite-2M 固化体在辐照非晶化的过程中经历了 zirconolite-2M 到 zirconolite-4M 到 pyrochlore 的结构演变; zirconolite-3O 在 5×1015 ions/cm2 剂量下部分晶体结构转变为钙钛矿,在 1×1016 ions/cm2 以上剂量快速转变为无序烧绿石; zirconolite-4M 样品在 1×1017 ions/cm2 剂量时依旧保留 zirconolite-4M 主相,次生无序烧绿石/缺陷萤石晶相。综上, 从维持晶体结构稳定性来看 zirconolite-2M 和 zirconolite-3O 的抗 α 粒子辐照能力相似,略弱于zirconolite-4M 固化体。
分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Differing from radiography without lens system, the high-energy proton radiography (PRAD) uses Zumbro lens system to focus the penetrating protons. Since the Zumbro lens system is able to limit the range of multiple Coulomb scattering angles of the protons, the low-energy PRAD with Zumbro lens system is also feasible, although the attenuation of probing protons in the object is negligible. Low-energy PRAD is superior to the high-energy PRAD for diagnosing the objects of small thicknesses. To verify the imaging principle of Zumbro lens system, 11 MeV PRAD experiments were performed at the China Academy of Engineering Physics (CAEP) recently. The experiment results demonstrated that this 11 MeV PRAD was able to radiograph objects of area density less than 2.7�10-2 g/cm2 and the area density discrepancy less than 2.3% could be distinguished.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: Standard stellar evolution model predicts a severe depletion of lithium (Li) abundance during the first dredge-up process (FDU). Yet a small fraction of giant stars are still found to preserve a considerable amount of Li in their atmospheres after FDU. Those giants are usually identified as Li-rich by a widely used criterion, A(Li) $ > 1.5$\,{\it dex}. A large number of works dedicated to search for and investigate this minority of the giant family, and the amount of Li-rich giants has been largely expanded, especially in the era of big data. In this paper, we present a catalog of Li-rich giants found from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey with Li abundances derived from a template matching method developed for LAMOST low-resolution spectra. The catalog contains $10,535$ Li-rich giants with Li abundances from $\sim 1.5$\,{\it dex} to $\sim 4.9$\,{\it dex}. We also confirm that the ratio of Li-rich phenomenon among giant stars is about one percent, or for a more expression, $1.29\%$ from our statistically important sample. This is the largest Li-rich giant sample ever reported to date, which significantly exceeds amount of all the reported Li-rich giants combined. The catalog will help the community to better understand the Li-rich phenomenon in giant stars.
分类: 核科学技术 >> 粒子加速器 提交时间: 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要: Proton radiography experiment with a Zumbro lens system was carried out on an 11 MeV proton cyclotron. The experimental results show that the image blurring is improved markedly. Clear images and good spatial resolution of the density step edges are obtained, which is important for hydrotest experiments, and the spatial resolution can achieve 100 m.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) Low Resolution Spectroscopic Survey (LRS) provides massive spectroscopic data of M-type stars, and the derived stellar parameters could bring vital help to various studies. We adopt the ULySS package to perform $\chi^2$ minimization with model spectra generated from the MILES interpolator, and determine the stellar atmospheric parameters for the M-type stars from LAMOST LRS Data Release (DR) 8. Comparison with the stellar parameters from APOGEE Stellar Parameter and Chemical Abundance Pipeline (ASPCAP) suggests that most of our results have good consistency. For M dwarfs, we achieve dispersions better than 74 K, 0.19 dex and 0.16 dex for $T_{\rm eff}$, $\log{g}$ and [Fe/H], while for M giants, the internal uncertainties are 58 K, 0.32 dex and 0.26 dex, respectively. Compared to ASPCAP we also find a systematic underestimation of $\Delta {T_{\rm eff}} =$ $-$176 K for M dwarfs, and a systematic overestimation of $\Delta {\log{g}} =$ 0.30 dex for M giants. However, such differences are less significant when we make comparison with common stars from other literature, which indicates that systematic biases exist in the difference of ASPCAP and other measurements. A catalog of 763,136 spectra corresponding to 616,314 M-type stars with derived stellar parameters is presented. We determine the stellar parameters for stars with $T_{\rm eff}$ higher than 2,900 K, with $\log{g}$ from -0.24 dex to 5.9 dex. The typical precisions are 45 K, 0.25 dex and 0.22 dex, for $T_{\rm eff}$, $\log{g}$ and [Fe/H], respectively, which are estimated from the duplicate observations of the same stars.