arXiv subjects

H. Z. Wang

Publications and source records attributed to H. Z. Wang.

13 recordsLinked to original sources

arXiv2024

Sudden polarization angle jumps of the repeating fast radio burst FRB 20201124A

We report the first detection of polarization angle (PA) orthogonal jumps, a phenomenon previously only observed from radio pulsars, from a fast radio burst (FRB) source FRB 20201124A. We find three cases of orthogonal jumps in over two thousand bursts, all resembling those observed in pulsar single pulses. We propose that the jumps are due to the superposition of two orthogonal emission modes that could only be produced in a highly magnetized plasma, and they are caused by the line of sight sweeping across a rotating magnetosphere. The shortest jump timescale is of the order of one-millisecond, which hints that the emission modes come from regions smaller than the light cylinder of most pulsars or magnetars. This discovery provides convincing evidence that FRB emission originates from the complex magnetosphere of a magnetar, suggesting an FRB emission mechanism that is analogous to radio pulsars despite a huge luminosity difference between two types of objects.

astro-ph.HE↗

arXiv2021

The Design and Performance of Charged Particle Detector onboard the GECAM Mission

The Gravitational Wave highly energetic Electromagnetic Counterpart All-sky Monitor (GECAM) is dedicated to detecting gravitational wave gamma-ray bursts. It is capable of all-sky monitoring over and discovering gamma-ray bursts and new radiation phenomena. GECAM consists of two microsatellites, each equipped with 8 charged particle detectors (CPDs) and 25 gamma-ray detectors (GRDs). The CPD is used to measure charged particles in the space environment, monitor energy and flow intensity changes, and identify between gamma-ray bursts and space charged particle events in conjunction with GRD. CPD uses plastic scintillator as the sensitive material for detection, silicon photomultiplier (SiPM) array as the optically readable device, and the inlaid Am-241 radioactive source as the onboard calibration means. In this paper, we will present the working principle, physical design, functional implementation and preliminary performance test results of the CPD.

astro-ph.IM↗

arXiv2021

Quality assurance test and Failure Analysis of SiPM Arrays of GECAM Satellites

The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) satellite consists of two small satellites. Each GECAM payload contains 25 gamma ray detectors (GRD) and 8 charged particle detectors (CPD). GRD is the main detector which can detect gamma-rays and particles and localize the Gamma-Ray Bursts (GRB),while CPD is used to help GRD to discriminate gamma-ray bursts and charged particle bursts. The GRD makes use of lanthanum bromide (LaBr3) crystal readout by SiPM. As the all available SiPM devices belong to commercial grade, quality assurance tests need to be performed in accordance with the aerospace specifications. In this paper, we present the results of quality assurance tests, especially a detailed mechanism analysis of failed devices during the development of GECAM. This paper also summarizes the application experience of commercial-grade SiPM devices in aerospace payloads, and provides suggestions for forthcoming SiPM space applications.

physics.ins-det↗

arXiv2021

Dedicated SiPM array for GRD of GECAM

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.

hep-ex↗

arXiv2021

Inflight performance of the GECAM Gamma-ray and Charge particle Detectors

The GECAM mission consists of two identical microsatellites (GECAM-A and GECAM-B). Each satellite is equipped with 25 gamma-ray detectors (GRD) and 8 charged particle detectors (CPD). The main scientific objective of the GECAM mission is to detect gamma-ray bursts (GRBs) associated with the gravitational wave events produced by the merging of binary compact stars. After the launch on Dec. 10, 2020 , we carried out a series of on orbit tests. This paper introduces the test results of the GECAM-B satellite. According to the in-flight performance, the energy band for gamma-ray detection of GECAM-B is from about 7 keV to 3.5 MeV. GECAM-B can achieve prompt localization of GRBs. For the first time, GECAM-B realized a quasi-real-time transmission of trigger information using Beidou-3 RDSS. Keywords GECAM, gamma-ray burst, gravitational wave, GRD, CPD

physics.ins-det↗

arXiv2021

The SiPM Array Data Acquisition Algorithm Applied to the GECAM Satellite Payload

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.

astro-ph.IM↗

arXiv2021

Ground-based calibration and characterization of GRD of GECAM: 8-160 keV

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.

astro-ph.IM↗

arXiv2021

The design and performance of GRD onboard the GECAM satellite

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.

astro-ph.IM↗

arXiv2019

Earth wind as a possible source of lunar surface hydration

Understanding the sources of lunar water is crucial for studying the history of lunar evolution, and also the solar wind interaction with the Moon and other airless bodies. Recent observations revealed lunar hydration is very likely a surficial dynamic process driven by solar wind. Solar wind is shielded over a period of 3-5 days as the Moon passes through the Earth's magnetosphere, during which a significant loss of hydration is expected from previous works.Here we study lunar hydration inside the magnetosphere using orbital spectral data, which unexpectedly found that the polar surficial OH/H2O abundance remains at the same level when in the solar wind and in the magnetosphere. We suggest that particles from the magnetosphere (Earth wind, naturally different from solar wind) contribute to lunar hydration. From lunar orbital plasma observations, we find the existence of optimal energy ranges, other than 1 keV as previously thought, for surface hydration formation. These optimal energy ranges deduced from space observations may provide strong implications for laboratory experiments simulating lunar hydration processes.

astro-ph.EP↗

arXiv2010

Splitting broad beams into arrays of dissipative spatial solitons by material and virtual gratings

We elaborate two generic methods for producing two-dimensional (2D) spatial soliton arrays (SSAs) in the framework of the cubic-quintic (CQ) complex Ginzburg-Landau (CGL) model. The first approach deals with a broad beam launched into the dissipative nonlinear medium, which is equipped with an imprinted grating of a sufficiently sharp form. The beam splits into a cluster of jets, each subsequently self-trapping into a stable soliton, if the power is sufficient for that. We consider two kinds of sharp gratings -- "raised-cosine" (RC) and Kronig-Penney (KP) lattices -- and two types of the input beams, fundamental and vortical. By selecting appropriate parameters, this method makes it possible to create various types of solitons arrays, such as solid, annular (with single and double rings), and cross-shaped ones. The second method uses a "virtual lattice", in the form of a periodic transverse phase modulation imprinted into the broad beam, which is passed through an appropriate phase mask and then shone into a uniform nonlinear medium. Two different types of the masks are considered, in the form of a "checkerboard" or "tilings". In that case, broad fundamental and vortical beams may also evolve into stable SSAs, if the beam's power and spacing of the virtual phase lattice are large enough. By means of the latter technique, square-shaped, hexagonal, and quasi-crystalline SSAs can be created.

nlin.PS↗

arXiv2008

Universal condition for the existence of interface modes in the whole momentum space with arbitrary materials

It is shown that, by theoretical and experimental results, a universal zero-impedance condition exists for two kinds of localized interface modes in the whole momentum space (both above and below the light line). It can be applied at the interface between any two materials including photonic crystals, single-negative (negative-permittivity or negative-permeability) materials, or double-negative metamaterials. In addition, it presents an intuitive physical concept, and also provides a feasible way to determine interface modes, which will have predominance in various applications.

physics.optics↗

arXiv2007

Fusion of necklace-ring patterns into vortex and fundamental solitons in dissipative media

We demonstrate that necklace-shaped arrays of localized spatial beams can merge into stable fundamental or vortex solitons in a generic model of laser cavities, based on the two-dimensional complex Ginzburg-Landau equation with the cubic-quintic nonlinearity. The outcome of the fusion is controlled by the number of beads in the initial necklace, 2N, and its topological charge, M. We predict and confirm by systematic simulations that the vorticity of the emerging soliton is the absolute value of difference of N and M. Threshold characteristics of the fusion are found and explained too. If the initial radius of the array (R0) is too large, it simply keeps the necklace shape (if R0 is somewhat smaller, the necklace features a partial fusion), while, if R0 is too small, the array disappears.

nlin.PS↗

arXiv2007

Holographic formation of large area split-ring arrays for magnetic metamaterials

We theoretically demonstrate the formation of different kinds of two-dimensional split-ring arrays in both triangular and square lattices by one-step holographic interference. The slit width of the split-ring can be adjusted by proper polarization configurations. The dimension of the rings can be adjusted easily by using different wavelengths for interference, so the resonant frequency of the split-rings can be obtained in a wide range. Our theory is also proved in experiment. Our work would extend the application of holographic lithography to the fabrication of magnetic metamaterials.

physics.optics↗