分类: 物理学 >> 核物理学 提交时间: 2023-09-13
摘要: Abstract: In this experimental study, involving deuteriumdeuterium 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- 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 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- 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- 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- discrimination algorithms, and record entire pulse waveforms without any data loss.
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 -ray coding plates with many pixels, few studies have been carried out on -ray computational ghost imaging. Thus, the development of coding plates with fewer pixels is essential to achieve -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 -ray computational ghost imaging.
分类: 天文学 >> 天文学 提交时间: 2023-02-19
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
$2
分类: 天文学 >> 天文学 提交时间: 2023-02-19
摘要: The absorption by neutral hydrogen in the intergalactic medium (IGM) produces
the Ly$\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: 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: 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.