The GECAM series of satellites utilizes LaBr_(3)(Ce),LaBr_(3)(Ce,Sr),and NaI(Tl)crystals as sensitive materials for gamma-ray detectors(GRDs).To investigate the nonlinearity in the detection of low-energy gamma rays a...The GECAM series of satellites utilizes LaBr_(3)(Ce),LaBr_(3)(Ce,Sr),and NaI(Tl)crystals as sensitive materials for gamma-ray detectors(GRDs).To investigate the nonlinearity in the detection of low-energy gamma rays and address the errors in the calibration of the E-C relationship,comprehensive tests and comparative studies of the three aforementioned crystals were conducted using Compton electrons,radioactive sources,and mono-energetic X-rays.The nonlinearity test results of the Compton electrons and X-rays demonstrated substantial differences,with all three crystals presenting a higher nonlinearity for X/-rays than for Compton electrons.Despite the LaBr_(3)(Ce)and LaBr_(3)(Ce,Sr)crystals having higher absolute light yields,they exhibited a noticeable nonlinear decrease in the light yield,especially at energies below 400 keV.The NaI(Tl)crystal demonstrated an"excess"light output in the 6-200 keV range,reaching a maximum"excess"of 9.2%at 30 keV in the X-ray testing and up to 15.5%at 14 keV during Compton electron testing,indicating a significant advantage in the detection of low-energy gamma rays.Furthermore,we explored the underlying causes of the observed nonlinearity in these crystals.This study not only elucidates the detector responses of GECAM,but also initiates a comprehensive investigation of the nonlinearity of domestically produced lanthanum bromide and sodium iodide crystals.展开更多
Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)is a constellation with four instruments(launch date):GECAM-A/B(10 December 2020),GECAM-C(27 July 2022)and GECAM-D(13 March 2024),which ...Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)is a constellation with four instruments(launch date):GECAM-A/B(10 December 2020),GECAM-C(27 July 2022)and GECAM-D(13 March 2024),which are dedicated to monitoring gamma-ray transients in all-sky.The primary science objectives of GECAM include Gamma-Ray Bursts(GRBs),Soft Gamma-ray Repeaters(SGRs),high energy counterparts of Gravitation Wave(GW)and Fast Radio Burst(FRB),Solar Flares(SFLs),as well as Terrestrial Gamma-ray Flashes(TGFs)and Terrestrial Electron Beams(TEBs).A series of observations and research have been made since the launch of GECAM-A/B.GECAM observations provide new insights into these highenergy transients,demonstrating the unique role of GECAM in the“multi-wavelength,multi-messenger”era.展开更多
The High Altitude Detection of Astronomical Radiation(HADAR)experiment,which was constructed in Tibet,China,combines the wide-angle advantages of traditional EAS array detectors with the high-sensitivity advantages of...The High Altitude Detection of Astronomical Radiation(HADAR)experiment,which was constructed in Tibet,China,combines the wide-angle advantages of traditional EAS array detectors with the high-sensitivity advantages of focused Cherenkov detectors.Its objective is to observe transient sources such as gamma-ray bursts and the counterparts of gravitational waves.This study aims to utilize the latest AI technology to enhance the sensitivity of HADAR experiments.Training datasets and models with distinctive creativity were constructed by incorporating the relevant physical theories for various applications.These models can determine the type,energy,and direction of the incident particles after careful design.We obtained a background identification accuracy of 98.6%,a relative energy reconstruction error of 10.0%,and an angular resolution of 0.22°in a test dataset at 10 TeV.These findings demonstrate the significant potential for enhancing the precision and dependability of detector data analysis in astrophysical research.By using deep learning techniques,the HADAR experiment’s observational sensitivity to the Crab Nebula has surpassed that of MAGIC and H.E.S.S.at energies below 0.5 TeV and remains competitive with conventional narrow-field Cherenkov telescopes at higher energies.In addition,our experiment offers a new approach for dealing with strongly connected,scattered data.展开更多
As a proposed detector,the giant radio array for neutrino detection(GRAND)is primarily designed to discover and study the origin of ultra-high-energy cosmic rays,with ultra-high-energy neutrinos presenting the main me...As a proposed detector,the giant radio array for neutrino detection(GRAND)is primarily designed to discover and study the origin of ultra-high-energy cosmic rays,with ultra-high-energy neutrinos presenting the main method for detecting ultra-high-energy cosmic rays and their sources.The main principle is to detect radio emissions generated by ultra-high-energy neutrinos interacting with the atmosphere as they travel.GRAND is the largest neutrino detection array to be built in China.GRANDProto35,as the first stage of the GRAND experiment,is a coincidence array composed of radio antennas and a scintillation detector,the latter of which,as a traditional detector,is used to perform cross-validation with radio detection,thus verifying the radio detection efficiency and enabling study of the background exclusion method.This study focused on the implementation of the optimization simulation and experimental testing of the performance of the prototype scintillation detector used in GRANDProto35.A package based on GEANT4 was used to simulate the details of the scintillation detector,including the optical properties of its materials,the height of the light guide box,and position inhomogeneity.The surface of the scintillator and the reflective materials used in the detector was optimized,and the influence of light guide heights and position inhomogeneity on the energy and time resolutions of the detector was studied.According to the simulation study,the number of scintillator photoelectrons increased when changing from the polished surface to the ground surface,with the appropriate design height for the light guide box being 50 cm and the appropriate design area for the scintillator being 0.5 m^(2).The performance of the detector was tested in detail through a coincidence experiment,and the test results showed that the number of photoelectrons collected in the detector was$84 with a time resolution of~1 ns,indicating good performance.The simulation results were consistent with those obtained from the tests,which also verified the reliability of the simulation software.These studies provided a full understanding of the performance of the scintillation detector and guidance for the subsequent operation and analysis of the GRANDProto35 experimental array.展开更多
The soft X-ray polarimeter(SXP)is a detector with a wide energy range,large area,and large field of view.A SXP will be mounted on the Chinese Space Station and will mainly focus on detecting the polarization of transi...The soft X-ray polarimeter(SXP)is a detector with a wide energy range,large area,and large field of view.A SXP will be mounted on the Chinese Space Station and will mainly focus on detecting the polarization of transient soft X-ray(2–10 keV)sources,especially gamma-ray bursts(GRBs).In this work,a polarimeter detector unit is taken as an example,and Geant4 and Garfield++software are used to simulate the detection efficiency and track production.An improved track reconstruction algorithm is proposed and used to reconstruct two-dimensional images of the tracks.In this method,the initial emission angle of photoelectrons is reconstructed from the initial part of the track by shortening or extending the initial part of the track until the remaining track is straight,and the number of pixels is within an adjustable threshold.The modulation factor of the photoelectronic tracks after reconstruction reaches approximately 57%in the photon energy range of 7–10 keV.展开更多
The cosmic-ray particles of TeV-regime, outside the solar system are blocked in their way to the Earth, a deficit of particles is observed corresponding to the location of the Sun known as the Sun shadow. The center o...The cosmic-ray particles of TeV-regime, outside the solar system are blocked in their way to the Earth, a deficit of particles is observed corresponding to the location of the Sun known as the Sun shadow. The center of the Sun shadow is shifted from its nominal position due to the presence of magnetic fields in interplanetary space,and this shift is used indirectly as a probe to study the solar magnetic field that is difficult to measure otherwise.A detailed Monte Carlo simulation of galactic cosmic-ray propagation in the Earth-Sun system is carried out to disentangle the cumulative effects of solar, interplanetary and geomagnetic fields. The shadowing effects and the displacements results of the Sun shadow in different solar activities are reproduced and discussed.展开更多
The high-altitude detection of astronomical radiation(HADAR)experiment is a new Cherenkov observation technique with a wide field of view(FoV),aimed at observing the prompt emissions ofγ-ray bursts(GRBs).The bottlene...The high-altitude detection of astronomical radiation(HADAR)experiment is a new Cherenkov observation technique with a wide field of view(FoV),aimed at observing the prompt emissions ofγ-ray bursts(GRBs).The bottleneck for this type of experiment can be found in determining how to reject the high rate of nightsky background(NSB)noise from random stars.In this work,we propose a novel method for rejecting noise,which considers the spatial properties of GRBs and the temporal characteristics of Cherenkov radiation.In space coordinates,the map between the celestial sphere and the fired photomultiplier tubes(PMTs)on the telescope's camera can be expressed as f(δ(i,j))=δ'(i',j'),which means that a limited number of PMTs is selected from one direction.On the temporal scale,a 20-ns time window was selected based on the knowledge of Cherenkov radiation.This allowed integration of the NSB for a short time interval.Consequently,the angular resolution and effective area at 100 GeV in the HADAR experiment were obtained as 0.2°and 10^(4)m^(2),respectively.This method can be applied to all wide-FoV experiments.展开更多
This work aims at online calibration of signal attenuation of the long cable used in Tibet water Cherenkov muon detector array-A (Tibet MD-A) under the Tibet air shower array.Based on a waterproof connection of the si...This work aims at online calibration of signal attenuation of the long cable used in Tibet water Cherenkov muon detector array-A (Tibet MD-A) under the Tibet air shower array.Based on a waterproof connection of the signal cable to PMT (R3600_06) and characters of the high voltage divider,terminal reflection method is used for measuring the signal attenuation with a practical way to eliminate contribution of the pulse baseline.Comparison measurement data-taking method (with charge-to-digital conversion) was carried out by using open-ended cables,confirming that terminal reflection method is a fast and convenient,and suitable to online calibration of the signal attenuation for Tibet MD-A.At 26℃,the measured attenuation coefficient with the 250-m cable connected permanently to the PMT,was ～13.9%.The cable frequency response was measured by using the sinusoidal signals.The method could be used to study time dispersion of signals produced with Tibet MD-A detector via Fourier analysis.展开更多
We investigate the cosmological evolution of a two-field model of dark energy, where one is a dilaton field with canonical kinetic energy and the other is a phantom field with a negative kinetic energy term. Phase-pla...We investigate the cosmological evolution of a two-field model of dark energy, where one is a dilaton field with canonical kinetic energy and the other is a phantom field with a negative kinetic energy term. Phase-plane analysis shows that the ＂phantom＂-dominated scaling solution is the stable late-time attractor of this type of model. We find that during the evolution of the universe, the equation of state w changes from w 〉 -1 to w 〈 -1, which is consistent with recent observations.展开更多
The superconducting quantum interference device（SQUID） amplifier is widely used in the field of weak signal detection for its low input impedance, low noise, and low power consumption. In this paper, the SQUIDs with...The superconducting quantum interference device（SQUID） amplifier is widely used in the field of weak signal detection for its low input impedance, low noise, and low power consumption. In this paper, the SQUIDs with identical junctions and the series SQUIDs with different junctions were successfully fabricated. The Nb/Al-AlOx/Nb trilayer and input Nb coils were prepared by asputtering equipment. The SQUID devices were prepared by a sputtering and the lift-off method.Investigations by AFM, OM and SEM revealed the morphology and roughness of the Nb films and Nb/Al-AlOx/Nb trilayer.In addition, the current–voltage characteristics of the SQUID devices with identical junction and different junction areas were measured at 2.5 K in the He^3 refrigerator. The results show that the SQUID modulation depth is obviously affected by the junction area. The modulation depth obviously increases with the increase of the junction area in a certain range. It is found that the series SQUID with identical junction area has a transimpedance gain of 58 Ω approximately.展开更多
Fast radio bursts(FRBs) are highly dispersed millisecond-duration radio bursts,[1,2]of which the physical origin is still not fully understood. FRB 20201124A is one of the most actively repeating FRBs. In this paper, ...Fast radio bursts(FRBs) are highly dispersed millisecond-duration radio bursts,[1,2]of which the physical origin is still not fully understood. FRB 20201124A is one of the most actively repeating FRBs. In this paper, we present the collection of 1863 burst dynamic spectra of FRB 20201124A measured with the Five-hundred-meter Aperture Spherical radio Telescope(FAST). The current collection, taken from the observation during the FRB active phase from April to June 2021, is the largest burst sample detected for any FRB so far. The standard PSRFITs format is adopted, including dynamic spectra of the burst, and the time information of the dynamic spectra, in addition, mask files help readers to identify the pulse positions are also provided. The dataset is available in Science Data Bank, with the link https://www.doi.org/10.57760/sciencedb.j00113.00076.展开更多
This study presents an electronics system for cosmic X-ray polarization detection(CXPD).The CXPD was designed as a high-sensitivity soft X-ray polarimeter with a measurement energy range of 2-10 keV carried by a CubeS...This study presents an electronics system for cosmic X-ray polarization detection(CXPD).The CXPD was designed as a high-sensitivity soft X-ray polarimeter with a measurement energy range of 2-10 keV carried by a CubeSat.A stable and functionally complete electronics system under power and space constraints is a key challenge.The complete CXPD electronics system(CXPDES)comprises hardware and firmware.CXPDES adopts a three-layer electronic board structure based on functionality and available space.Two gas pixel detectors(GPDs)were placed on the top layer board,and CXPDES provided the GPDs with voltages up to-4000 V.Each GPD signal was digitized,compressed,encoded,and stored before being transmitted to the ground.The CXPDES provided stable and high-speed communication based on a scheme that separated command and data transmission,and it supports the CXPDES in-orbit upgrade.In addition,environmental monitors,silicon photomultiplier(SiPM)triggers,power management,GPDs configuration,and mode switches were included in the overall operating logic of the CXPDES.The results obtained by testing the CXPDES showed that it satisfied all the requirements of CXPD.The CXPDES provides design experience and technological readiness for future large-area X-ray polarimetry missions.展开更多
The science analysis of the data from the High Energy X-ray Telescope(HE) on the Hard X-ray Modulation Telescope(HXMT) satellite is organized in three stages:calibration,screening and extraction of high-level scientif...The science analysis of the data from the High Energy X-ray Telescope(HE) on the Hard X-ray Modulation Telescope(HXMT) satellite is organized in three stages:calibration,screening and extraction of high-level scientific products.At the first stage,the raw PHA value of each event is converted to PI value accounting for temporal changes in gain and energy offset.At the second stage,the calibrated events are screened by applying cleaning criteria.At the third stage,scientific products,i.e.spectra,light curves and redistribution matrix files,are extracted.This work will introduce the three stages as well as the screening criteria and the data combining method.展开更多
In the first part of this paper,we describe briefly the mid and long-term plan of Chinese space astronomy,its preliminary study program,the current status of satellite missions undertaken, and the current status of as...In the first part of this paper,we describe briefly the mid and long-term plan of Chinese space astronomy,its preliminary study program,the current status of satellite missions undertaken, and the current status of astronomy experiments in China's manned space flight program.In the second part,the recent research progress made in the fields of solar physics is summarized briefly, including solar vector magnetic field,solar flares,CME and filaments,solar radio and nonthermal processes,EUV waves,MHD waves and coronal waves,solar model and helioseismology,solar wind and behavior of solar cycle.展开更多
Radiative energy losses are very important in regulating the cosmic ray electron and/or positron(CRE) spectrum during their propagation in the Milky Way. Particularly, the Klein–Nishina(KN) effect of the inverse Comp...Radiative energy losses are very important in regulating the cosmic ray electron and/or positron(CRE) spectrum during their propagation in the Milky Way. Particularly, the Klein–Nishina(KN) effect of the inverse Compton scattering(ICS) results in less efficient energy losses of high-energy electrons, which is expected to leave imprints on the propagated electron spectrum. It has been proposed that the hardening of CRE spectra around 50 GeV observed by Fermi-LAT, AMS-02, and DAMPE could be due to the KN effect. We show in this work that the transition from the Thomson regime to the KN regime of the ICS is actually quite smooth compared with the approximate treatment adopted in some previous works. As a result, the observed spectral hardening of CREs cannot be explained by the KN effect. It means that an additional hardening of the primary electrons spectrum is needed. We also provide a parameterized form for the accurate calculation of the ICS energy-loss rate in a wide energy range.展开更多
Purely kinetic k-essence models in which the Lagrangian contains only a kinetic factor and does not depend explicitly on the field itself are considered, and a theoretical constraint is obtained： Fx -= F0a^-3. Under ...Purely kinetic k-essence models in which the Lagrangian contains only a kinetic factor and does not depend explicitly on the field itself are considered, and a theoretical constraint is obtained： Fx -= F0a^-3. Under this theoretical constraint, we discuss a kind of purely κ-essence with form F（X） = -（1 ＋ 2X^n）^1/2n, which can be considered as the generalized tachyon field, and find that this kind of κ-essence is not likely a candidate of dark energy to describe the present accelerated expansion of the Universe. This is contrary to a previous suggestion that κ-essence with such a form may be used to describe phantom cosmologies.展开更多
基金This work was supported by the National Key Research and Development Program(Nos.2022YFB3503600 and 2021YFA0718500)Strategic Priority Research Program of the Chinese Academy of Sciences(Nos.XDA15360102)National Natural Science Foundation of China(Nos.12273042 and 12075258).
文摘The GECAM series of satellites utilizes LaBr_(3)(Ce),LaBr_(3)(Ce,Sr),and NaI(Tl)crystals as sensitive materials for gamma-ray detectors(GRDs).To investigate the nonlinearity in the detection of low-energy gamma rays and address the errors in the calibration of the E-C relationship,comprehensive tests and comparative studies of the three aforementioned crystals were conducted using Compton electrons,radioactive sources,and mono-energetic X-rays.The nonlinearity test results of the Compton electrons and X-rays demonstrated substantial differences,with all three crystals presenting a higher nonlinearity for X/-rays than for Compton electrons.Despite the LaBr_(3)(Ce)and LaBr_(3)(Ce,Sr)crystals having higher absolute light yields,they exhibited a noticeable nonlinear decrease in the light yield,especially at energies below 400 keV.The NaI(Tl)crystal demonstrated an"excess"light output in the 6-200 keV range,reaching a maximum"excess"of 9.2%at 30 keV in the X-ray testing and up to 15.5%at 14 keV during Compton electron testing,indicating a significant advantage in the detection of low-energy gamma rays.Furthermore,we explored the underlying causes of the observed nonlinearity in these crystals.This study not only elucidates the detector responses of GECAM,but also initiates a comprehensive investigation of the nonlinearity of domestically produced lanthanum bromide and sodium iodide crystals.
文摘Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor(GECAM)is a constellation with four instruments(launch date):GECAM-A/B(10 December 2020),GECAM-C(27 July 2022)and GECAM-D(13 March 2024),which are dedicated to monitoring gamma-ray transients in all-sky.The primary science objectives of GECAM include Gamma-Ray Bursts(GRBs),Soft Gamma-ray Repeaters(SGRs),high energy counterparts of Gravitation Wave(GW)and Fast Radio Burst(FRB),Solar Flares(SFLs),as well as Terrestrial Gamma-ray Flashes(TGFs)and Terrestrial Electron Beams(TEBs).A series of observations and research have been made since the launch of GECAM-A/B.GECAM observations provide new insights into these highenergy transients,demonstrating the unique role of GECAM in the“multi-wavelength,multi-messenger”era.
文摘The High Altitude Detection of Astronomical Radiation(HADAR)experiment,which was constructed in Tibet,China,combines the wide-angle advantages of traditional EAS array detectors with the high-sensitivity advantages of focused Cherenkov detectors.Its objective is to observe transient sources such as gamma-ray bursts and the counterparts of gravitational waves.This study aims to utilize the latest AI technology to enhance the sensitivity of HADAR experiments.Training datasets and models with distinctive creativity were constructed by incorporating the relevant physical theories for various applications.These models can determine the type,energy,and direction of the incident particles after careful design.We obtained a background identification accuracy of 98.6%,a relative energy reconstruction error of 10.0%,and an angular resolution of 0.22°in a test dataset at 10 TeV.These findings demonstrate the significant potential for enhancing the precision and dependability of detector data analysis in astrophysical research.By using deep learning techniques,the HADAR experiment’s observational sensitivity to the Crab Nebula has surpassed that of MAGIC and H.E.S.S.at energies below 0.5 TeV and remains competitive with conventional narrow-field Cherenkov telescopes at higher energies.In addition,our experiment offers a new approach for dealing with strongly connected,scattered data.
基金supported by the National Natural Science Foundation of China(Nos.11705103,12005120).
文摘As a proposed detector,the giant radio array for neutrino detection(GRAND)is primarily designed to discover and study the origin of ultra-high-energy cosmic rays,with ultra-high-energy neutrinos presenting the main method for detecting ultra-high-energy cosmic rays and their sources.The main principle is to detect radio emissions generated by ultra-high-energy neutrinos interacting with the atmosphere as they travel.GRAND is the largest neutrino detection array to be built in China.GRANDProto35,as the first stage of the GRAND experiment,is a coincidence array composed of radio antennas and a scintillation detector,the latter of which,as a traditional detector,is used to perform cross-validation with radio detection,thus verifying the radio detection efficiency and enabling study of the background exclusion method.This study focused on the implementation of the optimization simulation and experimental testing of the performance of the prototype scintillation detector used in GRANDProto35.A package based on GEANT4 was used to simulate the details of the scintillation detector,including the optical properties of its materials,the height of the light guide box,and position inhomogeneity.The surface of the scintillator and the reflective materials used in the detector was optimized,and the influence of light guide heights and position inhomogeneity on the energy and time resolutions of the detector was studied.According to the simulation study,the number of scintillator photoelectrons increased when changing from the polished surface to the ground surface,with the appropriate design height for the light guide box being 50 cm and the appropriate design area for the scintillator being 0.5 m^(2).The performance of the detector was tested in detail through a coincidence experiment,and the test results showed that the number of photoelectrons collected in the detector was$84 with a time resolution of~1 ns,indicating good performance.The simulation results were consistent with those obtained from the tests,which also verified the reliability of the simulation software.These studies provided a full understanding of the performance of the scintillation detector and guidance for the subsequent operation and analysis of the GRANDProto35 experimental array.
基金This work was supported by the National Natural Science Foundation of China(Nos.U1731239,12027803,11851304,U1938201,11575193,and U1732266)the Guangxi Science Foundation(Nos.2018GXNSFGA281007,2017AD22006,2018JJA110048)Key Research Program of Frontier Sciences,CAS(No.QYZDB-SSW368 SLH039)。
文摘The soft X-ray polarimeter(SXP)is a detector with a wide energy range,large area,and large field of view.A SXP will be mounted on the Chinese Space Station and will mainly focus on detecting the polarization of transient soft X-ray(2–10 keV)sources,especially gamma-ray bursts(GRBs).In this work,a polarimeter detector unit is taken as an example,and Geant4 and Garfield++software are used to simulate the detection efficiency and track production.An improved track reconstruction algorithm is proposed and used to reconstruct two-dimensional images of the tracks.In this method,the initial emission angle of photoelectrons is reconstructed from the initial part of the track by shortening or extending the initial part of the track until the remaining track is straight,and the number of pixels is within an adjustable threshold.The modulation factor of the photoelectronic tracks after reconstruction reaches approximately 57%in the photon energy range of 7–10 keV.
基金Supported by the National Natural Science Foundation of China under Grant No 11675187the Specialized Research Fund for State Key Laboratoriesthe CAS-TWAS President Fellowship Programme
文摘The cosmic-ray particles of TeV-regime, outside the solar system are blocked in their way to the Earth, a deficit of particles is observed corresponding to the location of the Sun known as the Sun shadow. The center of the Sun shadow is shifted from its nominal position due to the presence of magnetic fields in interplanetary space,and this shift is used indirectly as a probe to study the solar magnetic field that is difficult to measure otherwise.A detailed Monte Carlo simulation of galactic cosmic-ray propagation in the Earth-Sun system is carried out to disentangle the cumulative effects of solar, interplanetary and geomagnetic fields. The shadowing effects and the displacements results of the Sun shadow in different solar activities are reproduced and discussed.
基金supported by the Key R&D Program of Sichuan Province (Nos. 2019ZYZF0001 and 2020YFSY0016)the National Natural Science Foundation of China (Nos. 11873005,12047575, 11705103, 11635011, U1831208, U1632104, 11875264U2031110)
文摘The high-altitude detection of astronomical radiation(HADAR)experiment is a new Cherenkov observation technique with a wide field of view(FoV),aimed at observing the prompt emissions ofγ-ray bursts(GRBs).The bottleneck for this type of experiment can be found in determining how to reject the high rate of nightsky background(NSB)noise from random stars.In this work,we propose a novel method for rejecting noise,which considers the spatial properties of GRBs and the temporal characteristics of Cherenkov radiation.In space coordinates,the map between the celestial sphere and the fired photomultiplier tubes(PMTs)on the telescope's camera can be expressed as f(δ(i,j))=δ'(i',j'),which means that a limited number of PMTs is selected from one direction.On the temporal scale,a 20-ns time window was selected based on the knowledge of Cherenkov radiation.This allowed integration of the NSB for a short time interval.Consequently,the angular resolution and effective area at 100 GeV in the HADAR experiment were obtained as 0.2°and 10^(4)m^(2),respectively.This method can be applied to all wide-FoV experiments.
基金supported by the National Natural Science Foundation of China (No.111 072552430)the Key Laboratory of Particle Astrophysics,Institute of High Energy Physics,Chinese Academy of Sciences
文摘This work aims at online calibration of signal attenuation of the long cable used in Tibet water Cherenkov muon detector array-A (Tibet MD-A) under the Tibet air shower array.Based on a waterproof connection of the signal cable to PMT (R3600_06) and characters of the high voltage divider,terminal reflection method is used for measuring the signal attenuation with a practical way to eliminate contribution of the pulse baseline.Comparison measurement data-taking method (with charge-to-digital conversion) was carried out by using open-ended cables,confirming that terminal reflection method is a fast and convenient,and suitable to online calibration of the signal attenuation for Tibet MD-A.At 26℃,the measured attenuation coefficient with the 250-m cable connected permanently to the PMT,was ～13.9%.The cable frequency response was measured by using the sinusoidal signals.The method could be used to study time dispersion of signals produced with Tibet MD-A detector via Fourier analysis.
基金Supported by the Ministry of Education of China, the Knowledge Innovation Project of Chinese Academy of Sciences under Grant No KJCX2-YW-T03, and the National Natural Science Foundation of China under Grant Nos 10521001, 10733010 and 10725313, and the National Basic Research Program of China under Grant No 2009CB824800.
文摘We investigate the cosmological evolution of a two-field model of dark energy, where one is a dilaton field with canonical kinetic energy and the other is a phantom field with a negative kinetic energy term. Phase-plane analysis shows that the ＂phantom＂-dominated scaling solution is the stable late-time attractor of this type of model. We find that during the evolution of the universe, the equation of state w changes from w 〉 -1 to w 〈 -1, which is consistent with recent observations.
基金Project supported by the National Natural Science Foundation of China(Grant No.11653001)the National Basic Research Program of China(Grant No.2011CBA00304)Tsinghua University Initiative Scientific Research Program,China(Grant No.20131089314)
文摘The superconducting quantum interference device（SQUID） amplifier is widely used in the field of weak signal detection for its low input impedance, low noise, and low power consumption. In this paper, the SQUIDs with identical junctions and the series SQUIDs with different junctions were successfully fabricated. The Nb/Al-AlOx/Nb trilayer and input Nb coils were prepared by asputtering equipment. The SQUID devices were prepared by a sputtering and the lift-off method.Investigations by AFM, OM and SEM revealed the morphology and roughness of the Nb films and Nb/Al-AlOx/Nb trilayer.In addition, the current–voltage characteristics of the SQUID devices with identical junction and different junction areas were measured at 2.5 K in the He^3 refrigerator. The results show that the SQUID modulation depth is obviously affected by the junction area. The modulation depth obviously increases with the increase of the junction area in a certain range. It is found that the series SQUID with identical junction area has a transimpedance gain of 58 Ω approximately.
基金supported by the National SKA Program of China (Grant Nos. 2020SKA0120100 and 2020SKA0120200)the National Natural Science Foundation of China (Grant Nos. 12041304, 11873067, 11988101, 12041303, 11725313, 11725314, 11833003, 12003028, 12041306, 12103089, U2031209, U2038105, and U1831207)+8 种基金the National Key Research and Development Program of China (Grant Nos. 2019YFA0405100, 2017YFA0402602, 2018YFA0404204, and 2016YFA0400801)Key Research Program of the Chinese Academy of Sciences (Grant No. QYZDJ-SSW-SLH021)Natural Science Foundation of Jiangsu Province (Grant No. BK20211000)Cultivation Project for FAST Scientific Payoff and Research Achievement of CAMS-CAS, the Strategic Priority Research Program on Space Science, the Western Light Youth Project of Chinese Academy of Sciences (Grant Nos. XDA15360000, XDA15052700, and XDB23040400)funding from the MaxPlanck Partner Group, the science research grants from the China Manned Space Project (Grant Nos. CMS-CSST2021-B11 and CMS-CSST-2021-A11)PKU development (Grant No. 7101502590)support from the XPLORER PRIZEsupported by Fundamental Research Funds for the Central Universities (Grant No. 14380046)the Program for Innovative Talents, Entrepreneur in Jiangsu。
文摘Fast radio bursts(FRBs) are highly dispersed millisecond-duration radio bursts,[1,2]of which the physical origin is still not fully understood. FRB 20201124A is one of the most actively repeating FRBs. In this paper, we present the collection of 1863 burst dynamic spectra of FRB 20201124A measured with the Five-hundred-meter Aperture Spherical radio Telescope(FAST). The current collection, taken from the observation during the FRB active phase from April to June 2021, is the largest burst sample detected for any FRB so far. The standard PSRFITs format is adopted, including dynamic spectra of the burst, and the time information of the dynamic spectra, in addition, mask files help readers to identify the pulse positions are also provided. The dataset is available in Science Data Bank, with the link https://www.doi.org/10.57760/sciencedb.j00113.00076.
基金supported by the National Natural Science Foundation of China (Nos.11875146,U1932143)National Key Research and Development Program of China (No.2020YFE0202002)。
文摘This study presents an electronics system for cosmic X-ray polarization detection(CXPD).The CXPD was designed as a high-sensitivity soft X-ray polarimeter with a measurement energy range of 2-10 keV carried by a CubeSat.A stable and functionally complete electronics system under power and space constraints is a key challenge.The complete CXPD electronics system(CXPDES)comprises hardware and firmware.CXPDES adopts a three-layer electronic board structure based on functionality and available space.Two gas pixel detectors(GPDs)were placed on the top layer board,and CXPDES provided the GPDs with voltages up to-4000 V.Each GPD signal was digitized,compressed,encoded,and stored before being transmitted to the ground.The CXPDES provided stable and high-speed communication based on a scheme that separated command and data transmission,and it supports the CXPDES in-orbit upgrade.In addition,environmental monitors,silicon photomultiplier(SiPM)triggers,power management,GPDs configuration,and mode switches were included in the overall operating logic of the CXPDES.The results obtained by testing the CXPDES showed that it satisfied all the requirements of CXPD.The CXPDES provides design experience and technological readiness for future large-area X-ray polarimetry missions.
基金Supported by the National Natural Science Foundation of China(11303027,11503029)the Strategic Priority Research Program on Space Science of the Chinese Academy of Sciences(XDA04010300)
文摘The science analysis of the data from the High Energy X-ray Telescope(HE) on the Hard X-ray Modulation Telescope(HXMT) satellite is organized in three stages:calibration,screening and extraction of high-level scientific products.At the first stage,the raw PHA value of each event is converted to PI value accounting for temporal changes in gain and energy offset.At the second stage,the calibrated events are screened by applying cleaning criteria.At the third stage,scientific products,i.e.spectra,light curves and redistribution matrix files,are extracted.This work will introduce the three stages as well as the screening criteria and the data combining method.
文摘In the first part of this paper,we describe briefly the mid and long-term plan of Chinese space astronomy,its preliminary study program,the current status of satellite missions undertaken, and the current status of astronomy experiments in China's manned space flight program.In the second part,the recent research progress made in the fields of solar physics is summarized briefly, including solar vector magnetic field,solar flares,CME and filaments,solar radio and nonthermal processes,EUV waves,MHD waves and coronal waves,solar model and helioseismology,solar wind and behavior of solar cycle.
基金Supported by the National Key Research and Development Program of China(Grant No.2016YFA0400203 and 2016YFA0400204)the National Natural Science Foundation of China(Grant Nos.11722328,U1738205,U1738203,11851303 and 11851305)the Program for Innovative Talents and Entrepreneur in Jiangsu。
文摘Radiative energy losses are very important in regulating the cosmic ray electron and/or positron(CRE) spectrum during their propagation in the Milky Way. Particularly, the Klein–Nishina(KN) effect of the inverse Compton scattering(ICS) results in less efficient energy losses of high-energy electrons, which is expected to leave imprints on the propagated electron spectrum. It has been proposed that the hardening of CRE spectra around 50 GeV observed by Fermi-LAT, AMS-02, and DAMPE could be due to the KN effect. We show in this work that the transition from the Thomson regime to the KN regime of the ICS is actually quite smooth compared with the approximate treatment adopted in some previous works. As a result, the observed spectral hardening of CREs cannot be explained by the KN effect. It means that an additional hardening of the primary electrons spectrum is needed. We also provide a parameterized form for the accurate calculation of the ICS energy-loss rate in a wide energy range.
基金Supported in part by the Ministry of Education of China, the Directional Research Project of the Chinese Academy of Sciences under Grant No KJCX2-YW-T03, and the National Natural Science Foundation of China under Grant Nos 10521001, 10733010 and 10725313. We thank Chang-Jun Gao, Pu-Xun Wu, Hao Wei, Yan Wu, Wei-Ke Xiao, Jian-Feng Zhou, Zhi-Xing Ling, and Bi-Zhu Jiang for discussions.
文摘Purely kinetic k-essence models in which the Lagrangian contains only a kinetic factor and does not depend explicitly on the field itself are considered, and a theoretical constraint is obtained： Fx -= F0a^-3. Under this theoretical constraint, we discuss a kind of purely κ-essence with form F（X） = -（1 ＋ 2X^n）^1/2n, which can be considered as the generalized tachyon field, and find that this kind of κ-essence is not likely a candidate of dark energy to describe the present accelerated expansion of the Universe. This is contrary to a previous suggestion that κ-essence with such a form may be used to describe phantom cosmologies.
