分类： 物理学 >> 核物理学 提交时间： 2023-09-13
摘要：Abstract: In this experimental study, involving deuterium–deuterium fusion neutron emission spectroscopy (NES) measurement on the experimental advanced superconducting tokamak (EAST), a liquid scintillator detector (BC501A) was employed. This decision was based on the detector's superior sensitivity, optimal time-response, and its exceptional n-γ discrimination capability. This detector emits fast pulse signals that are as narrow as 100 ns, with high count rates that can peak at several Mcps. However, conventional nuclear circuits faced challenges in performing pulse height analysis, n–γ pulse shape discrimination (PSD), and in recording the entire pulse waveform under such high-count-rate conditions. To address these challenges, a high-speed digital pulse signal acquisition and processing system was designed. The system was developed around a micro-telecommunications computing architecture (MTCA). Within this structure, a signal acquisition and processing (SAQP) module communicated through PCI Express (PCIe) links, achieving a bandwidth of up to 1.6 GB/s. To accurately capture the detailed shape of the pulses, four channels of analog-to-digital converters (ADCs) were used, each with a 500-MSPS sampling rate and a 14-bit resolution, ensuring an accuracy that surpassed 11 bits. An n-γ discrimination algorithm, based on the two-gate integral method, was also developed. Implemented within field programmable gate arrays (FPGA), this algorithm provided a real-time n-γ discrimination spectrum for pulse height analysis. The system underwent rigorous testing in a laboratory setting and during an EAST experiment. The results confirmed that the innovative SAQP system can satisfy the demanding requirements of high-parameter experiments, manage count rates of up to 2 Mcps, execute real-time n-γ discrimination algorithms, and record entire pulse waveforms without any data loss.
分类： 核科学技术 >> 核探测技术与核电子学 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要：Among different heavy liquid metals (HLMs), lead-bismuth eutectic (LBE) is considered at present as a potential candidate for the coolant of new generation fast reactors (critical and subcritical) and for liquid spallation neutron sources and accelerator driven systems (ADS). A high temperature liquid LBE loop, KYLIN-II-M, has been built to study the characteristics of corrosion and fluidity of LBE at the Institute of Nuclear Energy Safety Technology. However, due to the sensors and execution components of the loop work at high temperatures and in severely corrosive environments, the reliability and security of the data acquisition and control system (DACS) of KYLIN-II-M face challenges during the loop operation. In order to meet the urgent needs for KYLIN-II-M’s long-term stable operation, a virtualization and redundancy control system has been developed. The onsite operation result shows that the DACS is stable and reliable. In this paper, the experimental results are described in detail.
分类： 核科学技术 >> 核探测技术与核电子学 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
XI Jian-Bo
LIANG Hao
XIANG Shi-Tao
GUO Di
ZHOU Jin-Jin
LI Yu-Ying
LI Yang
LIU Han-Chao
ZHOU Yong-Zhao
LI Chun-Hua
ZHANG Jia-Wen
CHEN Jin
HE Kang-Lin
ZHU Ke-Jun
摘要：Resistive Plate Chambers (RPCs) built from a new type of Bakelite developed at Institute of High Energy Physics (IHEP), Chinese Academy of Sciences have been used in the BESIII Muon identification system for several years without linseed oil coating, but characteristic aging performances were observed. To adapt to the RPCs in the aging state, the front-end electronics have been upgraded by enhancing the front-end protection, improving the threshold setting circuit, and separating power supplies of the comparator and the field programmable gate array (FPGA). Improvements in system stability, front-end protection and threshold consistency have been achieved. In this paper, the system upgrade and the test results are described in detail.
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 γ-ray coding plates with many pixels, few studies have been carried out on γ-ray computational ghost imaging. Thus, the development of coding plates with fewer pixels is essential to achieve γ-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 γ-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
Li, Haoqing
Sheng, Liang
Zhang, Changqing
Du, Yingchao
Zhou, Zheng
Weng, Xiufeng
Xiao, Jiahao
Yin, Hongqiao
Sun, Bin
Wei, Kun
Li, Yang
Duan, Baojun
Liu, Yongtang
Zhang, Yanhong
Zhang, Mei
Song, Yan
Zhang, Xiaodong
Liu, Jun
Fu, Zhuming
Xu, Qing
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： 天文学 >> 天文学 提交时间： 2023-02-19
摘要：The absorption by neutral hydrogen in the intergalactic medium (IGM) produces
the Ly$\alpha$ forest in the spectra of quasars. The Ly$\alpha$ forest
absorbers have a broad distribution of neutral hydrogen column density $N_{\rm
HI}$ and Doppler $b$ parameter. The narrowest Ly$\alpha$ absorption lines (of
lowest $b$) with neutral hydrogen column density above $\sim 10^{13}{\rm
cm^{-2}}$ are dominated by thermal broadening, which can be used to constrain
the thermal state of the IGM. Here we constrain the temperature-density
relation $T=T_0(\rho/\bar{\rho})^{\gamma-1}$ of the IGM at $1.6
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要：The absorption by neutral hydrogen in the intergalactic medium (IGM) produces
the Ly$\alpha$ forest in the spectra of quasars. The Ly$\alpha$ forest
absorbers have a broad distribution of neutral hydrogen column density $N_{\rm
HI}$ and Doppler $b$ parameter. The narrowest Ly$\alpha$ absorption lines (of
lowest $b$) with neutral hydrogen column density above $\sim 10^{13}{\rm
cm^{-2}}$ are dominated by thermal broadening, which can be used to constrain
the thermal state of the IGM. Here we constrain the temperature-density
relation $T=T_0(\rho/\bar{\rho})^{\gamma-1}$ of the IGM at $1.6
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要：The neutral hydrogen (HI) intensity mapping (IM) survey is regarded as a promising approach for cosmic large-scale structure (LSS) studies. A major issue for the HI IM survey is to remove the bright foreground contamination. A key to successfully remove the bright foreground is to well control or eliminate the instrumental effects. In this work, we consider the instrumental effect of polarization leakage and use the U-Net approach, a deep learning-based foreground removal technique, to eliminate the polarization leakage effect.In this method, the principal component analysis (PCA) foreground subtraction is used as a preprocessing step for the U-Net foreground subtraction. Our results show that the additional U-Net processing could either remove the foreground residual after the conservative PCA subtraction or compensate for the signal loss caused by the aggressive PCA preprocessing. Finally, we test the robustness of the U-Net foreground subtraction technique and show that it is still reliable in the case of existing constraint error on HI fluctuation amplitude.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要：The neutral hydrogen (HI) intensity mapping (IM) survey is regarded as a promising approach for cosmic large-scale structure (LSS) studies. A major issue for the HI IM survey is to remove the bright foreground contamination. A key to successfully remove the bright foreground is to well control or eliminate the instrumental effects. In this work, we consider the instrumental effect of polarization leakage and use the U-Net approach, a deep learning-based foreground removal technique, to eliminate the polarization leakage effect.In this method, the principal component analysis (PCA) foreground subtraction is used as a preprocessing step for the U-Net foreground subtraction. Our results show that the additional U-Net processing could either remove the foreground residual after the conservative PCA subtraction or compensate for the signal loss caused by the aggressive PCA preprocessing. Finally, we test the robustness of the U-Net foreground subtraction technique and show that it is still reliable in the case of existing constraint error on HI fluctuation amplitude.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要：In this work, we consider a new cosmological model (named $\tilde\Lambda$CDM) in which the vacuum energy interacts with matter and radiation, and test this model using the current cosmological observations. We find that this model can significantly relieve the $H_0$ tension, and at the same time it can also slightly reduce the $S_8$ tension, which cannot be easily observed in other cosmological models. Using the CMB+BAO+SN (CBS) data to constrain the model, we obtain the results of $H_0=70.6^{+1.4}_{-1.7}~\rm{km~s^{-1} Mpc^{-1}}$ and $S_8=0.820\pm 0.011$, and thus the $H_0$ and $S_8$ tensions are relieved to $1.28\sigma$ and $2.67\sigma$, respectively. However, in this case the $\tilde\Lambda$CDM model is not favored by the data, compared with $\Lambda$CDM. We find that when the $H_0$ and $S_8$ data are added into the data combination, the situation is significantly improved. In the CBS+$H_0$ case, we obtain the result of $H_0=72.2\pm 1.2$ ${\rm km~s^{-1}~Mpc^{-1}}$, which relieves the $H_0$ tension to $0.53\sigma$, and in this case the model is favored over $\Lambda$CDM. In the CBS+$H_0$+$S_8$ case, we get a synthetically best situation, $H_0=71.9\pm 1.1$ ${\rm km~s^{-1}~Mpc^{-1}}$ and $S_8=0.8071\pm 0.0099$, in which the $H_0$ and $S_8$ tensions are relived to $0.75\sigma$ and $2.09\sigma$, respectively. In this case, the model is most favored by the data. Therefore, such a cosmological model can greatly relieve the $H_0$ tension, and at the same time it can also effectively alleviate the $S_8$ tension.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要：In this work, we consider a new cosmological model (named $\tilde\Lambda$CDM) in which the vacuum energy interacts with matter and radiation, and test this model using the current cosmological observations. We find that this model can significantly relieve the $H_0$ tension, and at the same time it can also slightly reduce the $S_8$ tension, which cannot be easily observed in other cosmological models. Using the CMB+BAO+SN (CBS) data to constrain the model, we obtain the results of $H_0=70.6^{+1.4}_{-1.7}~\rm{km~s^{-1} Mpc^{-1}}$ and $S_8=0.820\pm 0.011$, and thus the $H_0$ and $S_8$ tensions are relieved to $1.28\sigma$ and $2.67\sigma$, respectively. However, in this case the $\tilde\Lambda$CDM model is not favored by the data, compared with $\Lambda$CDM. We find that when the $H_0$ and $S_8$ data are added into the data combination, the situation is significantly improved. In the CBS+$H_0$ case, we obtain the result of $H_0=72.2\pm 1.2$ ${\rm km~s^{-1}~Mpc^{-1}}$, which relieves the $H_0$ tension to $0.53\sigma$, and in this case the model is favored over $\Lambda$CDM. In the CBS+$H_0$+$S_8$ case, we get a synthetically best situation, $H_0=71.9\pm 1.1$ ${\rm km~s^{-1}~Mpc^{-1}}$ and $S_8=0.8071\pm 0.0099$, in which the $H_0$ and $S_8$ tensions are relived to $0.75\sigma$ and $2.09\sigma$, respectively. In this case, the model is most favored by the data. Therefore, such a cosmological model can greatly relieve the $H_0$ tension, and at the same time it can also effectively alleviate the $S_8$ tension.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要：In the neutral hydrogen (HI) intensity mapping (IM) survey, the foreground contamination on the cosmological signals is extremely severe, and the systematic effects caused by radio telescopes themselves further aggravate the difficulties in subtracting foreground. In this work, we investigate whether the deep learning method, concretely the 3D U-Net algorithm here, can play a crucial role in foreground subtraction when considering the systematic effect caused by the telescope's primary beam. We consider two beam models, i.e., the Gaussian beam model as a simple case and the Cosine beam model as a sophisticated case. The traditional principal component analysis (PCA) method is employed as a comparison and, more importantly, as the preprocessing step for the U-Net method to reduce the sky map dynamic range. We find that in the case of the Gaussian beam, the PCA method can effectively clean the foreground. However, the PCA method cannot handle the systematic effect induced by the Cosine beam, and the additional U-Net method can improve the result significantly. In order to show how well the PCA and U-Net methods can recover the HI signals, we also derive the HI angular power spectra, as well as the HI 2D power spectra, after performing the foreground subtractions. It is found that, in the case of Gaussian beam, the concordance with the original HI map using U-Net is better than that using PCA by $27.4\%$, and in the case of Cosine beam, the concordance using U-Net is better than that using PCA by $144.8\%$. Therefore, the U-Net based foreground subtraction can efficiently eliminate the telescope primary beam effect and shed new light on recovering the HI power spectrum for future HI IM experiments.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要：We investigate an extended cosmological model motivated by the asymptotic safety of gravitational field theory, in which the matter and radiation densities and the cosmological constant receive a correction parametrized by the parameters $\delta_G$ and $\delta_\Lambda$, leading to that both the evolutions of the matter and radiation densities and the cosmological constant slightly deviate from the standard forms. Here we explain this model as a scenario of vacuum energy interacting with matter and radiation. We consider two cases of the model: {(i) ${\tilde\Lambda}$CDM with one additional free parameter $\delta_G$, with $\delta_{\rm G}$ and $\delta_\Lambda$ related by a low-redshift limit relation and (ii) e${\tilde\Lambda}$CDM with two additional free parameters $\delta_G$ and $\delta_\Lambda$ that are independent of each other.} We use two data combinations, CMB+BAO+SN (CBS) and CMB+BAO+SN+$H_0$ (CBSH), to constrain the models. We find that, in the case of using the CBS data, neither ${\tilde\Lambda}$CDM nor e${\tilde\Lambda}$CDM can effectively alleviate the $H_0$ tension. However, it is found that using the CBSH data the $H_0$ tension can be greatly relieved by the models. In particular, in the case of e${\tilde\Lambda}$CDM, the $H_0$ tension can be resolved to 0.71$\sigma$. We conclude that as an interacting dark energy model, ${\tilde\Lambda}$CDM is much better than $\Lambda(t)$CDM in the sense of both relieving the $H_0$ tension and fitting to the current observational data.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Li Yang
Zheng Zheng
Hélion du Mas des Bourboux
Kyle Dawson
Matthew M. Pieri
Graziano Rossi
Donald P. Schneider
Axel de la Macorra
摘要：We investigate the metal species associated with the Ly$\alpha$ forest in the
eBOSS quasar spectra. Metal absorption lines are revealed in the stacked
spectra from cross-correlating the selected Ly$\alpha$ absorbers in the forest
and the flux fluctuation field. Up to 13 metal species are identified
associated with relatively strong Ly$\alpha$ absorbers (those with flux
fluctuation $-1.0<\delta_{\rm Ly\alpha}<-0.6$ and with neutral hydrogen column
density of ~ $10^{15-16}$ $\rm cm^{-2}$) over absorber redshift range of
$2
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要：Even and odd vector modes in optical fibers are represented with linear combinations of orbital angular momentum modes, and considered as single-photon spin-orbit entangled states. It renders generating such states with fiber structures possible.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要：In nanoscale imaging technique and ultrafast laser, the reconstruction procedure is normally formulated as a blind phase retrieval (BPR) problem, where one has to recover both the sample and the probe (pupil) jointly from phaseless data. This survey first presents the mathematical formula of BPR, related nonlinear optimization problems and then gives a brief review of the recent iterative algorithms. It mainly consists of three types of algorithms, including the operator-splitting based first-order optimization methods, second order algorithm with Hessian,and subspace methods. The future research directions for experimental issues and theoretical analysis are further discussed.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要：We show that, in the pure-quartic systems, modulation instability (MI) undergoes heteroclinic-structure transitions (HSTs) at two critical frequencies of {\omega} c1 and {\omega} c2 ( {\omega} c2 > {\omega} c1 ), which indicates that there are significantchanges of the spatiotemporal behavior in the system. The complicated heteroclinic structure of instability obtained by the mode truncation method reveals all possible dynamic trajectories of nonlinear waves, which allows us to discover the various types of Fermi-Pasta-Ulam (FPU) recurrences and Akhmediev breathers (ABs). When the modulational frequency satisfies {\omega} < {\omega} c2 , the heteroclinic structure encompasses two separatrixes corresponding to the ABs and the nonlinear wave with a modulated final state, which individually separate FPU recurrences into three different regions. Remarkably, crossing critical frequency {\omega} c1 , both the staggered FPU recurrences and ABs essentially switch their patterns. These HST behaviors will give vitality to the study of MI.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要：Irreversible entropy production (IEP) plays an important role in quantum thermodynamic processes. Here we investigate the geometrical bounds of IEP in nonequilibrium thermodynamics by exemplifying a system coupled to a squeezed thermal bath subject to dissipation and dephasing, respectively. We find that the geometrical bounds of the IEP always shift in contrary way under dissipation and dephasing, where the lower and upper bounds turning to be tighter occurs in the situation of dephasing and dissipation, respectively. However, either under dissipation or under dephasing, we may reduce both the critical time of the IEP itself and the critical time of the bounds for reaching an equilibrium by harvesting the benefits of squeezing effects, in which the values of the IEP, quantifying the degree of thermodynamic irreversibility, also becomes smaller. Therefore, due to the nonequilibrium nature of the squeezed thermal bath, the system-bath interaction energy brings prominent impact on the IEP, leading to tightness of its bounds. Our results are not contradictory with the second law of thermodynamics by involving squeezing of the bath as an available resource, which can improve the performance of quantum thermodynamic devices.
分类： 核科学技术 >> 辐射物理与技术 提交时间： 2021-12-31 合作期刊: 《Nuclear Science and Techniques》
摘要：Controllable D-D neutron sources have a long service life, low cost, and non-radioactivity. There are favorable prospects for its application in geophysical well logging, since traditional chemical radioactive sources used for well logging pose potential threats to the safety of the human body and environment. This paper presents an improved method to measure formation density that employs a D-D neutron source. In addition, the lithological effect on the measured density was removed to better estimate the formation porosity. First, we investigated the spatial distribution of capture gamma rays through Monte Carlo simulations as well as the relationship between the ratio of capture gamma ray counts and formation density to establish theoretical support for the design of density logging tools and their corresponding data processing methods. Second, we obtained the far to near detector counts of captured gamma rays for an optimized tool structure, and then established its correlation with the density and porosity of three typical formations with pure quartz, calcite, and dolomite minerals. Third, we determined the values for correcting the densities of sandstone and dolomite with the same porosity using limestone data as the reference and established the equations for calculating the correction values, which lays a solid foundation for accurately calculating formation porosity. We observed that the capture gamma ray counts first increased then decreased and varied in different formations; this was especially observed in high-porosity formations. Under the same lithologic conditions (rock matrix), as the porosity increases, the peak value of gamma ray counts moves toward the neutron source. At different detector-source distances, the ratio of the capture gamma ray counts was well correlated with the formation density. An equation of the formation density conversion was established based on the ratio of capture gamma ray counts at the detector-source distances of 30 cm and 65 cm, and the calculated values were consistent with the true values. After correction, the formation density was highly consistent with the true value of the limestone density, and the mean absolute error was -0.013 g/cm3. The calculated porosity values were very close to the true values, and the mean relative error was 2.33%, highlighting the accuracy of the proposed method. These findings provide a new method for developing D-D neutron source logging tools and their well-log data processing methods.
分类： 医学、药学 >> 基础医学 提交时间： 2017-12-27 合作期刊: 《南方医科大学学报》
摘要：Objective To investigate the protective effects of tea polyphenols (TP) against myocardial ischemia/reperfusion (IR) injuries and explore the possible mechanisms. Methods Langendorff-perfused rat hearts were subjected to ischemia for 30 min followed by reperfusion for another 30 min. Myocardial function indices were measured by a left ventricular cannula via a pressure transducer connected to the polygraph in isolated Langendorff hearts and energy metabolism was measured using 31P nuclear magnetic resonance (NMR) spectroscopy. Whole-cell patch-clamp technique was used to record calcium inward current (ICa-L) in cultured rat cardiac myocytes. Results Compared with the control hearts, the ex vivo rat hearts with 2.5 mg/L TP treatment showed significantly increased left ventricular developed pressure (LVDP), maximal rise rate of LVDP (+ dp/dtmax), maximal fall rate of LVDP (-dp/dtmax), and coronary flow (CF) (P<0.05). During both cardiac ischemia and reperfusion phase, ATP and PCr levels were elevated significantly in TP-treated hearts compared with those in the control hearts (P<0.05). In cultured rat cardiac myocytes, ICa-L was remarkably decreased by TP at the doses of 2.5 and 5.0 mg/L (P<0.01). Conclusion Our results support a possible protective role of TP against myocardial IR injury by improving myocardial energy metabolism and inhibiting ICa-L in the cardiac myocytes.
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