分类： 天文学 >> 天文学 提交时间： 2023-02-19
Z. H. An
X. L. Sun
D. L. Zhang
S. Yang
X. Q. Li
X. Y. Wen
K. Gong
X. H. Liang
X. J. Liu
Y. Q. Liu
Y. G. Li
S. L. Xiong
Y. B. Xu
Fan Zhang
X. Y. Zhao
C. Cai
Z. Chang
G. Chen
C. Chen
Y. Y. Du
摘要： Background: Each GECAM satellite payload contains 25 gamma-ray detectors (GRDs), which can detect gamma-rays and particles and can roughly localize the Gamma-Ray Bursts (GRBs). GRD was designed using lanthanum bromide (LaBr3) crystal as the sensitive material with the rear end coupled with silicon photomultiplier (SiPM) array for readout. Purpose: In aerospace engineering design of GRD, there are many key points to be studied. In this paper, we present the specific design scheme of GRD, the assembly and the performance test results of detectors. Methods: Based on Monte Carlo simulation and experimental test results, the specific schematic design and assembling process ofGRDwere optimized. After being fully assembled, theGRDswere conducted performance tests by using radioactive source and also conducted random vibration tests. Result and conclusion: The test results show that all satellite-borne GRDs have energy resolution <16% at 59.5 keV, meeting requirements of satellite in scientific performance. The random vibration test shows that GRD can maintain in a stable performance, which meets the requirement of spatial application.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
D. L. Zhang
X. L. Sun
Z. H. An
X. Q. Li
X. Y. Wen
K. Gong
C. Cai
Z. Chang
G. Chen
C. Chen
Y. Y. Du
M. Gao
R. Gao
D. Y. Guo
J. J. He
D. J. Hou
Y. G. Li
C. Y. Li
G. Li
L. Li
摘要： The discovery of gravitational waves and gamma-ray bursts heralds the era of multi-messenger astronomy. With the adoption of two small satellites to achieve the all-sky monitoring of gamma-ray bursts, the gravitational wave high-energy electromagnetic counterpart all-sky monitor (GECAM) possesses a quasi-real-time early warning ability and plays an important role in positioning the sources of gravitational waves and in subsequent observations.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Y. Q. Liu
K. Gong
X. Q. Li
X. Y. Wen
Z. H. An
C. Cai
Z. Chang
G. Chen
C. Chen
Y. Y. Du
M. Gao
R. Gao
D. Y. Guo
J. J. He
D. J. Hou
Y. G. Li
C. Y. Li
G. Li
L. Li
X. F. Li
摘要： The Gravitational Wave Burst High-energy Electromagnetic Counterpart All-sky Monitor (GECAM), consists of 2 small satellites that each contain 25 LaBr3 (lanthanum bromide doped with cerium chloride) detectors and 8 plastic scintillator detectors. The detector signals are read out using a silicon photomultiplier (SiPM) array. In this study, an acquisition algorithm for in-orbit real-time SiPM array data is designed and implemented, and the output event packet is defined. Finally, the algorithm's efficacy for event acquisition is verified.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： The close correlation observed between emission state and spin-down rate change of pulsars has many implications both for the magnetospheric physics and the neutron star interior. The middle-aged pulsar PSR J0738$-$4042, which had been observed to display variations in the pulse profile associated with its spin-down rate change due to external effects, is a remarkable example. In this study, based on the 12.5-yr combined public timing data from UTMOST and Parkes, we have detected a new emission-rotation correlation in PSR J0738$-$4042 concurrent with a glitch. A glitch that occurred at MJD 57359(5) (December 3, 2015) with $\Delta\nu/\nu \sim 0.36(4)\times 10^{-9}$ is the first glitch event observed in this pulsar and is probably the underlying cause of the emission-rotation correlation. Unlike the usual post-glitch behaviours, the braking torque on the pulsar has continued to increase over 1380 d, corresponding to a significant decrease in $\ddot{\nu}$. As for changes in the pulse profile after the glitch, the relative amplitude of the leading component weakens drastically, while the middle component becomes stronger. A combined model of crustquake induced platelet movement and vortex creep response is invoked to account for this rare correlation. In this scenario, magnetospheric state-change is naturally linked to the pulsar-intrinsic processes that give rise to a glitch.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
J. J. He
Z. H. An
W. X. Peng
X. Q. Li
S. L. Xiong
D. L. Zhang
R. Qiao
D. Y. Guo
C. Cai
Z. Chang
C. Chen
G. Chen
Y. Y. Du
M. Gao
R. Gao
K. Gong
D. J. Hou
C. Y. Li
G. Li
L. Li
摘要： As the main detector of the GECAM satellite, the calibration of the energy response and detection efficiency of the GRD detector is the main content of the ground-based calibration. The calibration goal requires the calibrated energy points to sample the full energy range (8 keV-2 MeV) as much as possible. The low energy band (8-160 keV) is calibrated with the X-ray beam, while the high energy band (>160 keV) with radioactive sources. This article mainly focuses on the calibration of the energy response and detection efficiency in the 8-160 keV with a refined measurement around the absorption edges of the lanthanum bromide crystal. The GRD performances for different crystal types, data acquisition modes, working modes, and incident positions are also analyzed in detail. We show that the calibration campaign is comprehensive, and the calibration results are generally consistent with simulations as expected.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： We propose a novel ultrasonic sensor structure composed of Cantilever arm structure slot dual-micro-ring resonators(DMRR).We present a theoretical analysis of transmission by using the coupled mode theory.The mode field distributions and sound pressure distributions of transmission spectrum are obtained from 3D simulations based on Comsol Multi-physics(COMSOL)method.Our ultrasonic sensor exhibit theoretical sensitivity as high as 1462.5mV/kPa,which is 22 times higher than that of single slot-based micro-ring ultrasonic sensor.Our ultrasonic sensor offers higher sensitivity and a larger detection frequency range than conventional piezoelectric based ultrasound transducer.The results show that the sensing characteristics of our system can be optimized through changing the position and the angle of sound field.Our ultrasonic sensor with an area of 25um*60um, the-factor can be approximately 1540 with radius of 5um We detect an angular range of -90o to 90o and a minimum distance of 0.01um. Finally,we calculate the Cantilever arm structure slot DMRR array ultrasonic sensor's optical performance. Our proposed design provides a promising candidate for a hydrophone.
分类： 光学 >> 量子光学 提交时间： 2023-02-19
摘要： We propose a novel bio-sensor structure composed of slot dual-micro-ring resonators and mono-layer graphene.Based on the electromagnetically induced transparency (EIT)-like phenomenon and the light-absorption characteristics of graphene,we present a theoretical analysis of transmission by using the coupled mode theory and Kubo formula.The results demonstrate the EIT-like spectrum with asymmetric line profile.The mode-field distributions of transmission spectrum obtained from 3D simulations based on finite-difference time-domain (FDTD) method.Our bio-sensor exhibit theoretical sensitivity of 330nm/RIU, a minimum detection limit of 3600RIU,the maximum extinction ratio of 4.4dB,the quality factor of 1288 and a compact structure of 15um*10um.Finally, the bio-sensor's performance is simulated for glucose solution.Our proposed design provide a promising candidate for on-chip integration with other silicon photonic element.
分类： 物理学 >> 核物理学 提交时间： 2016-09-14
摘要： We infer the emission positions of twin kilohertz quasi-periodic oscillations (kHz QPOs) in neutron star low mass X-ray binaries (NS-LMXBs) based on the Alfven wave oscillation model (AWOM). For most sources, the emission radii of kHz QPOs cluster around a region of 16-19 km with the assumed NS radii of 15 km. Cir X-1 has the larger emission radii of 23-38 km than those of the other sources, which may be ascribed to its large magnetosphere-disk radius or strong NS surface magnetic field. SAX J1808.4-3658 is also a particular source with the relative large emission radii of kHz QPOs of 20 - 23 km, which may be due to its large inferred NS radius of 18 - 19 km. The emission radii of kHz QPOs for all the sources are larger than the NS radii, and the possible explanations of which are presented. The similarity of the emission radii of kHz QPOs (16-19 km) for both the low/high luminosity Atoll/Z sources is found, which indicates that both sources share the similar magnetosphere- disk radii.
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