分类： 天文学 >> 天文学 提交时间： 2024-03-29 合作期刊: 《Research in Astronomy and Astrophysics》
摘要： The development of spectroscopic survey telescopes like Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), Apache Point Observatory Galactic Evolution Experiment and Sloan Digital Sky Survey has opened up unprecedented opportunities for stellar classification. Specific types of stars, such as early-type emission-line stars and those with stellar winds, can be distinguished by the profiles of their spectral lines. In this paper, we introduce a method based on derivative spectroscopy (DS) designed to detect signals within complex backgrounds and provide a preliminary estimation of curve profiles. This method exhibits a unique advantage in identifying weak signals and unusual spectral line profiles when compared to other popular line detection methods. We validated our approach using synthesis spectra, demonstrating that DS can detect emission signals three times fainter than Gaussian fitting. Furthermore, we applied our method to 579,680 co-added spectra from LAMOST Medium-Resolution Spectroscopic Survey, identifying 16,629 spectra with emission peaks around the Hα line from 10,963 stars. These spectra were classified into three distinct morphological groups, resulting in nine subclasses as follows. (1) Emission peak above the pseudo-continuum line (single peak, double peaks, emission peak situated within an absorption line, P Cygni profile, Inverse P Cygni profile); (2) Emission peak below the pseudo-continuum line (sharp emission peak, double absorption peaks, emission peak shifted to one side of the absorption line); (3) Emission peak between the pseudo-continuum line.
分类： 物理学 >> 核物理学 提交时间： 2024-12-16
wang, Dr. haitao
Zhang, Prof. Yan
Liu, Mr. Chi
Xu, Mr. Jian-Qiang
Zhang, Dr. Li-Jiao
LIU, Prof. Zhi-feng
Zhang, Dr. Xiongjie
Chen, Dr. Rui
Liu, Dr. Qi
Wang, Dr. Ren-Bo
Zhou, Mr. Shumin
Tang, Prof. Bin
摘要： The domestically developed prompt fission neutron uranium logging(PFNUL) instrument for uranium exploration represents a significant advancement in China deep uranium mining efforts, though it comes with considerable challenges and complexity. This paper presents the development of a new prompt fission neutron uranium logging instrument(named UNL4) , integrates a domestic D-T neutron generator, two 3He proportional detectors, a lanthanum bromide (LaBr3) gamma-ray detector, and digital multi-channel pulse amplitude analyzer. The near 3He detector is shielded with 1mm of Cadmium (Cd) and 5mm of high-density polyethylene(HDPE), enabling efficient epithermal neutron detection, while the far 3He detector measures thermal neutron. The LaBr3 detector is employed for gamma-ray detection, primarily originating from uranium decay. High-speed ADC and FPGA technologies were used to achieve rapid acquisition and transmission of both dual neutron time spectra and gamma spectra.Moreover, this paper proposes a fast signal shaping method, which reduces the dead time effect in $^3$He detectors on neutron time spectra. Experiments conducted in standard model boreholes with varying uranium content demonstrated a strong linear relationship between the epithermal-to-thermal neutron ratio (E/T) and uranium content, with a fitting coefficient of R2>0.999, confirming the instruments accuracy. The E/T value repeatability, both in short-term (3.16% RSD) and long-term (1.2% RSD) measurements, showed excellent stability. In addition, the instrument demonstrated good performance at neutron logging speeds of 0.3∽3 m/min (E/T values) and gamma logging speeds of 1∽10 m/min. By conducting measurements in two ore sections of the PU model with lithium contents of 87.1 ppm and 45.6 ppm, the RD is less than about 10% in both logging cases, meeting the requirements for engineering applications. This marks the first successful development of a neutron logging instrument for uranium exploration based on a domestic neutron generator, signifying an important contribution to uranium resource exploration.
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