We present the thorium distribution on the lunar surface derived from observations by the Chang’E-2 gamma-ray spectrometer(CE-2 GRS). This new map shows a similar thorium distribution to previous observations. In com...We present the thorium distribution on the lunar surface derived from observations by the Chang’E-2 gamma-ray spectrometer(CE-2 GRS). This new map shows a similar thorium distribution to previous observations. In combination with this new thorium map and impact cratering model, we investigate the origination of thorium on the Moon’s highlands, which was previously thought to be contributed from Imbrium ejecta. We found that the Imbrium ejecta has a small contribution(~20%–30%) to the thorium on the lunar highlands but most thorium is likely to be indigenous before the deposition of the Imbrium ejecta. This new thorium map also confirms that the eastern highlands have a relatively higher thorium concentration than the western highlands. We propose that the thin crust and large basins on the eastern highlands are responsible for this difference in thorium.展开更多
The main goal of the gamma-ray spectrometer(GRS) onboard Chang'E1(CE-1) is to acquire global maps of elemental abundances and their distributions on the moon,since such maps will significantly improve our underst...The main goal of the gamma-ray spectrometer(GRS) onboard Chang'E1(CE-1) is to acquire global maps of elemental abundances and their distributions on the moon,since such maps will significantly improve our understanding of lunar formation and evolution.To derive the elemental maps and enable research on lunar formation and evolution,raw data that are received directly from the spacecraft must be converted into time series corrected gamma-ray spectra.The data correction procedures for the CE-1 GRS time series data are thoroughly described.The processing procedures to create the time series gamma-ray spectra described here include channel processing,optimal data selection,energy calibration,gain correction,dead time correction,geometric correction,orbit altitude normalization,eliminating unusable data and galactic cosmic ray correction.Finally,descriptions are also given on data measurement uncertainties,which will help the interested scientists to understand and estimate various uncertainties associated with the above data processing.展开更多
Gamma-ray spectrometry is a very powerful tool for radioactivity measurements. The gamma-ray spectrometer laboratory in Centre for Energy Research and Training (CERT), Ahmadu Bello University, Zaria, Nigeria is accred...Gamma-ray spectrometry is a very powerful tool for radioactivity measurements. The gamma-ray spectrometer laboratory in Centre for Energy Research and Training (CERT), Ahmadu Bello University, Zaria, Nigeria is accredited to perform measurements of radioactive content of samples collected from the environment, food chain or industrial products with the aid of a high resolution HPGe detector. For accurate gamma-ray spectrometry, certain measurements were considered;the efficiency of the detector was performed experimentally against energies within the range of 59.50 keV (241Am) to 2204.50 keV (226Ra) for the respective geometries of 1 - 6 cm. The sustained solid angle relations with respect to the inverse square of sample geometries from 1 - 6 cm were evaluated. Another main point of this work was focused on the efficiency at geometry of 5 cm with respect to the three selected energies: 661.60 keV (137Cs), 1173.2 keV (60Co) and 1332 keV (60Co) for the main axis, ten degree off main axis, forty five degree off main axis and ninety degree off the detector main axis. In order to verify optimum geometries in our laboratory for both short lived and long lived radionuclides analyses, the evaluation of efficiencies for the respective energies: 1173.2 keV (60Co), 1332.5 keV (60Co), 1764 keV (226Ra) and 2294 keV (226Ra) were plotted against geometries of 1 to 6 cm from the detector end cap along the main axis.展开更多
Gamma-ray spectrometer(GRS) is used to detect the elemental abundances and distributions on the lunar surface.To derive the elemental abundances,it is vital to acquire background gamma rays except lunar gamma rays.So ...Gamma-ray spectrometer(GRS) is used to detect the elemental abundances and distributions on the lunar surface.To derive the elemental abundances,it is vital to acquire background gamma rays except lunar gamma rays.So GRS would observe background spectra in the course of earth-moon transfer on schedule.But in fact,GRS was not switched on in the course of flying toward the moon.After the CE-1 probe finished one-year mission,GRS car-ried out a test on background data on November 21?22,2008.The authors did conduct research on the methods of background deduction using 2105 hours of usable gamma-ray spectra acquired at the 200-km orbital height by the GRS and more than 5 hours of gamma-ray spectra acquired in the GRS background test.The final research results showed that the method of deducting the background using the minimum counts in the CE-1 GRS pixels is optimal for the elements,U,K and Th.The method applies to such a case that the elemental abundances in the pixel with the minimum counting rate are 0 μg/g and the continuum background counts are constant over the Moon.Based on the method of background deduction,the full energy peak counts of U,K,and Th are calculated.展开更多
Despite the pressing demand for integrated spectrometers,a solution that deliver high-performance while being practically operated is still missing.Furthermore,current integrated spectrometers lack reconfigurability i...Despite the pressing demand for integrated spectrometers,a solution that deliver high-performance while being practically operated is still missing.Furthermore,current integrated spectrometers lack reconfigurability in their performance,which is highly desirable for dynamic working scenarios.This study presents a viable solution by demonstrating a userfriendly,reconfigurable spectrometer on silicon.At the core of this innovative spectrometer is a programmable photonic circuit capable of exhibiting diverse spectral responses,which can be significantly adjusted using on-chip phase shifters.The distinguishing feature of our spectrometer lies in its inverse design approach,facilitating effortless control and efficient manipulation of the programmable circuit.By eliminating the need for intricate configuration,our design reduces power consumption and mitigates control complexity.Additionally,our reconfigurable spectrometer offers two distinct operating conditions.In the Ultra-High-Performance mode,it is activated by multiple phase-shifters and achieves exceptional spectral resolution in the picometer scale while maintaining broad bandwidth.On the other hand,the Ease-of-Use mode further simplifies the control logic and reduces power consumption by actuating a single-phase shifter.Although this mode provides a slightly degraded spectral resolution of approximately 0.3 nm,it prioritizes ease of use and is wellsuited for applications where ultra-fine spectral reconstruction is not a primary requirement.展开更多
An innovative monochromator shielding is designed and implemented for the cold neutron spectrometers XINGZHI and BOYA operated by Renmin University of China at China Advanced Research Reactor.Via Monte Carlo simulatio...An innovative monochromator shielding is designed and implemented for the cold neutron spectrometers XINGZHI and BOYA operated by Renmin University of China at China Advanced Research Reactor.Via Monte Carlo simulations and careful mechanical designs,a shielding configuration has been successfully developed to satisfy safety requirements of below 3μSv/h dose rate at its exterior,meanwhile fulfilling space,floor load and nonmagnetic requirements.Composite materials are utilized to form the sandwich-type shielding walls:the inner layer of boron carbide rubber,the middle layer of steel-encased lead and the outer layer of borated polyethylene.Special-shaped liftable shielding blocks are incorporated to facilitate a continuous adjustment of the neutron energy while preventing radiation leakage.Our work has demonstrated that by utilizing composite shielding materials,along with the sandwich structure and liftable shielding blocks,a compact and lightweight shielding solution can be achieved.This enables the realization of advanced neutron scattering instruments that provide expanded space of measurement,larger energy and momentum coverage,and higher flux on the sample.This shielding represents the first of its kind in neutron scattering instruments in China.Following its successful operation,it has been subsequently employed by other neutron instruments across the country.展开更多
Currently,with the advent of high-repetition-rate laser-plasma experiments,the demand for online diagnosis for the X-ray spectrum is increasing because the laser-plasma-generated X-ray spectrum is very important for c...Currently,with the advent of high-repetition-rate laser-plasma experiments,the demand for online diagnosis for the X-ray spectrum is increasing because the laser-plasma-generated X-ray spectrum is very important for characterizing electron dynamics and applications.In this study,scintillators and silicon PIN(P-type–intrinsic-N-type semiconductor)diodes were used to construct a wideband online filter stack spectrometer.The X-ray sensor and filter arrangement was optimized using a genetic algorithm to minimize the condition number of the response matrix.Consequently,the unfolding error was significantly reduced based on numerical experiments.The detector responses were quantitatively calibrated by irradiating the scintillator and PIN diode with various nuclides and comparing the measuredγ-ray peaks.A prototype 15-channel spectrometer was developed by integrating an X-ray detector with front-and back-end electronics.The prototype spectrometer could record X-ray pulse signals at a repetition rate of 1 kHz.Furthermore,an optimized spectrometer was employed to record the real-time spectra of laser-driven bremsstrahlung sources.This optimized spectrometer offers a compact solution for spectrum diagnostics of ultrashort X-ray pulses,exhibiting improved accuracy in terms of spectrum measurements and repetition rates,and could be widely used in next-generation high-repetition-rate high-power laser facilities.展开更多
A Johann-type X-ray spectrometer was successfully developed at the hard X-ray branch(in-vacuum undulator with a 24-mm periodic length)of the energy material beamline(E-line)at the Shanghai Synchrotron Radiation Facili...A Johann-type X-ray spectrometer was successfully developed at the hard X-ray branch(in-vacuum undulator with a 24-mm periodic length)of the energy material beamline(E-line)at the Shanghai Synchrotron Radiation Facility(SSRF).This spectrometer was utilized to implement X-ray emission spectroscopy(XES),high-energy resolution fluorescence-detected X-ray absorption spectroscopy(HERFD-XAS),and resonant inelastic X-ray scattering.Seven spherically bent crystals were positioned on the respective vertical 500-mm-diameter Rowland circles,adopting an area detector to increase the solid angle to 1.75%of 4πsr,facilitating the study of low-concentrate systems under complex reaction conditions.Operated under the atmosphere pressure,the spectrometer covers the energy region from 3.5 to 18 keV,with the Bragg angle ranging from 73°to 86°during vertical scanning.It offers a promised energy resolution of sub-eV(XES)and super-eV(HERFD-XAS).Generally,these comprehensive core-level spectroscopy methods based on hard X-rays at the E-line with an extremely high photon flux can meet the crucial requirements of a green energy strategy.Moreover,they provide substantial support for scientific advances in fundamental research.展开更多
Optical frequency combbased Fourier transform spectroscopy has the features of broad spectral bandwidth,high sensitivity,andmultiplexed trace gas detection,which has valuable application potential in the fields of pre...Optical frequency combbased Fourier transform spectroscopy has the features of broad spectral bandwidth,high sensitivity,andmultiplexed trace gas detection,which has valuable application potential in the fields of precision spectroscopy and trace gas detection.Here,we report the development of a mid-infrared Fourier transform spectrometer based on an optical frequency comb combined with a Herriott-type multipass cell.Using this instrument,the broadband absorption spectra of several important molecules,including methane,acetylene,water molecules and nitrous oxide,are measured by near real-time data acquisition in the 2800-3500 cm^(-1)spectral region.The achieved minimum detectable absorption of the instrument is 4.4×10^(-8)cm^(-1)·Hz^(-1/2)per spectral element.Broadband spectra of H_(2)0 are fited using the Voigt profile multispectral fitting technique and the consistency of the concentration inversion is 1%.Our system also enables precise spectroscopic measurements,and it allows the determination of the spectral line positions and upper state constants of N_(2)O in the(0002)-(1000)band,with results in good agreement with those reported by Toth[Appl.Opt.30,5289(1991)].展开更多
To detect radioactive substances with low activity levels,an anticoincidence detector and a high-purity germanium(HPGe)detector are typically used simultaneously to suppress Compton scattering background,thereby resul...To detect radioactive substances with low activity levels,an anticoincidence detector and a high-purity germanium(HPGe)detector are typically used simultaneously to suppress Compton scattering background,thereby resulting in an extremely low detection limit and improving the measurement accuracy.However,the complex and expensive hardware required does not facilitate the application or promotion of this method.Thus,a method is proposed in this study to discriminate the digital waveform of pulse signals output using an HPGe detector,whereby Compton scattering background is suppressed and a low minimum detectable activity(MDA)is achieved without using an expensive and complex anticoincidence detector and device.The electric-field-strength and energy-deposition distributions of the detector are simulated to determine the relationship between pulse shape and energy-deposition location,as well as the characteristics of energy-deposition distributions for fulland partial-energy deposition events.This relationship is used to develop a pulse-shape-discrimination algorithm based on an artificial neural network for pulse-feature identification.To accurately determine the relationship between the deposited energy of gamma(γ)rays in the detector and the deposition location,we extract four shape parameters from the pulse signals output by the detector.Machine learning is used to input the four shape parameters into the detector.Subsequently,the pulse signals are identified and classified to discriminate between partial-and full-energy deposition events.Some partial-energy deposition events are removed to suppress Compton scattering.The proposed method effectively decreases the MDA of an HPGeγ-energy dispersive spectrometer.Test results show that the Compton suppression factors for energy spectra obtained from measurements on ^(152)Eu,^(137)Cs,and ^(60)Co radioactive sources are 1.13(344 keV),1.11(662 keV),and 1.08(1332 keV),respectively,and that the corresponding MDAs are 1.4%,5.3%,and 21.6%lower,respectively.展开更多
Synthetic aperture radar(SAR)and wave spectrometers,crucial in microwave remote sensing,play an essential role in monitoring sea surface wind and wave conditions.However,they face inherent limitations in observing sea...Synthetic aperture radar(SAR)and wave spectrometers,crucial in microwave remote sensing,play an essential role in monitoring sea surface wind and wave conditions.However,they face inherent limitations in observing sea surface phenomena.SAR systems,for instance,are hindered by an azimuth cut-off phenomenon in sea surface wind field observation.Wave spectrometers,while unaffected by the azimuth cutoff phenomenon,struggle with low azimuth resolution,impacting the capture of detailed wave and wind field data.This study utilizes SAR and surface wave investigation and monitoring(SWIM)data to initially extract key feature parameters,which are then prioritized using the extreme gradient boosting(XGBoost)algorithm.The research further addresses feature collinearity through a combined analysis of feature importance and correlation,leading to the development of an inversion model for wave and wind parameters based on XGBoost.A comparative analysis of this model with ERA5 reanalysis and buoy data for of significant wave height,mean wave period,wind direction,and wind speed reveals root mean square errors of 0.212 m,0.525 s,27.446°,and 1.092 m/s,compared to 0.314 m,0.888 s,27.698°,and 1.315 m/s from buoy data,respectively.These results demonstrate the model’s effective retrieval of wave and wind parameters.Finally,the model,incorporating altimeter and scatterometer data,is evaluated against SAR/SWIM single and dual payload inversion methods across different wind speeds.This comparison highlights the model’s superior inversion accuracy over other methods.展开更多
Microsatellites have recently opened windows of frequent and low cost missions for planetary exploration. The performance of gamma-ray and neutron spectrometers on future microsatellite missions is simulated to assess...Microsatellites have recently opened windows of frequent and low cost missions for planetary exploration. The performance of gamma-ray and neutron spectrometers on future microsatellite missions is simulated to assess the possibility of observation of hydrogen and major elements, given their concentration on the observation target. The measured elemental abundance will provide important geological constraints, and some of them may serve as space resources. Four different types of target bodies with various hydrogen concentrations in the range of 0 - 20,000 ppm are assumed as target compositions;Earth’s core, C-type, S-type and Martian meteorites. Gamma-ray and neutron emission rates show unique footprints that are related to the different elemental compositions. The starting point is the solid angle subtended between observation target and spectrometers that allow estimating the gamma-ray and neutron count rates emitted by the celestial bodies. In this work, three types of gamma-ray detectors;high-purity germanium (HPGe), CeBr3 and LaBr3(Ce), a neutron spectrometer combining a lithium glass scintillator with a boron loaded plastic scintillator and a dual mode spectrometer Cs2LiYCl6(Ce) (CLYC) are simulated, focusing on their observation backgrounds as a model case for microsatellite based measurements. The background count level of both gamma-ray (except for the LaBr3 detector) and neutron count rates was negligible under these particular conditions. The gamma-ray detectors were compared by the figure of merit, which was determined by their efficiency and energy resolution. It was found that each detector has unique advantages. The HPGe detector has the highest figure of merit due to its excellent energy resolution, whereas the CLYC detector is low in weight and power consumption due to its dual sensitivity to gamma-ray and neutron. The CeBr3 detector is an intermediate choice. The neutron count rates are calculated separately in three energy ranges, i.e. , thermal (<0.5 eV), epithermal (0.5 eV - 500 keV), and fast (>500 keV), as a function of the hydrogen concentration in the 0 - 20,000 ppm range. The thermal and epithermal neutron count rates are found to decrease with hydrogen concentration, while the fast neutron count rate increases with the target average atomic mass. The optimal detector should be decided by the mission restraints on mass, power consumption, and heat thermal design.展开更多
The Very Large Area gamma-ray Space Telescope(VLAST)is a mission concept proposed to detect gamma-ray photons through both Compton scattering and electron–positron pair production mechanisms,thus enabling the detecti...The Very Large Area gamma-ray Space Telescope(VLAST)is a mission concept proposed to detect gamma-ray photons through both Compton scattering and electron–positron pair production mechanisms,thus enabling the detection of photons with energies ranging from MeV to TeV.This project aims to conduct a comprehensive survey of the gamma-ray sky from a low-Earth orbit using an anti-coincidence detector,a tracker detector that also serves as a low-energy calorimeter,and a high-energy imaging calorimeter.We developed a Monte Carlo simulation application of the detector using the GEANT4 toolkit to evaluate the instrument performance,including the effective area,angular resolution,and energy resolution,and explored specific optimizations of the detector configuration.Our simulation-based analysis indicates that the current design of the VLAST is physically feasible,with an acceptance above 10 m^(2)sr which is four times larger than that of the Fermi-LAT,an energy resolution better than 2%at 10 GeV,and an angular resolution better than 0.2◦at 10 GeV.The VLAST project promises to make significant contributions to the field of gamma-ray astronomy and enhance our understanding of the cosmos.展开更多
Laser-driven proton-induced x-ray emission(laser-PIXE) is a nuclear analysis method based on the compact laser ion accelerator. Due to the transient process of ion acceleration, the laser-PIXE signals are usually spur...Laser-driven proton-induced x-ray emission(laser-PIXE) is a nuclear analysis method based on the compact laser ion accelerator. Due to the transient process of ion acceleration, the laser-PIXE signals are usually spurted within nanoseconds and accompanied by strong electromagnetic pulses(EMP), so traditional multi-channel detectors are no longer applicable.In this work, we designed a reflective elliptical crystal spectrometer for the diagnosis of laser-PIXE. The device can detect the energy range of 1 keV–11 ke V with a high resolution. A calibration experiment was completed on the electrostatic accelerator of Peking University using samples of Al, Ti, Cu, and ceramic artifacts. The detection efficiency of the elliptical crystal spectrometer was obtained in the order of 10-9.展开更多
[Objectives]This study was conducted to establish an uncertainty evaluation method for the determination of ethyl maltol by ultra-high performance liquid chromatograph-mass spectrometer(UPLC-MS).[Methods]A mathematica...[Objectives]This study was conducted to establish an uncertainty evaluation method for the determination of ethyl maltol by ultra-high performance liquid chromatograph-mass spectrometer(UPLC-MS).[Methods]A mathematical model of uncertainty was established by analyzing the method for determining ethyl maltol using UPLC-MS.The sources of uncertainty were analyzed,and the components of uncertainty were calculated to evaluate the expanded uncertainty of the method.[Results]When the content of ethyl maltol in edible vegetable oil was 1657μg/kg,the expanded uncertainty was 22.4μg/kg(K=2,P=95%).[Conclusions]The uncertainty in this evaluation model mainly came from standard solution preparation,sample weighing,dilution of sample to constant volume,standard curve fitting,and repeated measurement.展开更多
The accuracy(repeatability and reproducibility) of the iron content analysis of galvanized coating using an X-ray fluorescence spectrometer with an L-spectrum is not better than that of flame atomic absorption spectro...The accuracy(repeatability and reproducibility) of the iron content analysis of galvanized coating using an X-ray fluorescence spectrometer with an L-spectrum is not better than that of flame atomic absorption spectrometry, sometimes it exceeds the quality control limit.Influences, such as current, voltage, equipment(internal circulating water, 10%CH4+90%Ar, and vacuum) checking, instrument monitoring, sample cleaning, and oper-ators, were investigated by means of 6-sigma and lean operations to improve accuracy.展开更多
GRB 200612A could be classified as an ultralong gamma-ray burst due to its prompt emission lasting up to~1020 s and the true timescale of the central engine activity t_(burst)≥4×10^(4) s.The late X-ray light cur...GRB 200612A could be classified as an ultralong gamma-ray burst due to its prompt emission lasting up to~1020 s and the true timescale of the central engine activity t_(burst)≥4×10^(4) s.The late X-ray light curve with a decay index ofα=7.53 is steeper than the steepest possible decay from an external shock model.We propose that this X-ray afterglow can be driven by dipolar radiation from the magnetar spindown during its early stage,while the magnetar collapsed into the black hole before its spindown,resulting in a very steep decay of the late X-ray light curve.The optical data show that the light curve is still rising after 1.1 ks,suggesting a late onset.We show that GRB 200612A’s optical afterglow light curve is fitted with the forward shock model by Gaussian structured off-axis jet.This is a special case among GRBs,as it may be an ultralong gamma-ray burst powered by a magnetar in an off-axis observation scenario.展开更多
The occurrence of the first significant digits from real world sources is usually not equally distributed,but is consistent with a logarithmic distribution instead,known as Benford’s law.In this work,we perform a com...The occurrence of the first significant digits from real world sources is usually not equally distributed,but is consistent with a logarithmic distribution instead,known as Benford’s law.In this work,we perform a comprehensive investigation on the first digit distributions of the duration,fluence,and energy flux of gamma-ray bursts (GRBs) for the first time.For a complete GRB sample detected by the Fermi satellite,we find that the first digits of the duration and fluence adhere to Benford’s law.However,the energy flux shows a significant departure from this law,which may be due to the fact that a considerable part of the energy flux measurements is restricted by lack of spectral information.Based on the conventional duration classification scheme,we also check if the durations and fluences of long and short GRBs (with duration T_(90)>2 s and T_(90)≤2 s,respectively) obey Benford’s law.We find that the fluences of both long and short GRBs still agree with the Benford distribution,but their durations do not follow Benford’s law.Our results hint that the long–short GRB classification scheme does not directly represent the intrinsic physical classification scheme.展开更多
The prompt emission mechanism of gamma-ray bursts(GRBs)is still unclear,and the time-resolved spectral analysis of GRBs is a powerful tool for studying their underlying physical processes.We performed a detailed time-...The prompt emission mechanism of gamma-ray bursts(GRBs)is still unclear,and the time-resolved spectral analysis of GRBs is a powerful tool for studying their underlying physical processes.We performed a detailed time-resolved spectral analysis of 78 bright long GRB samples detected by Fermi/Gamma-ray Burst Monitor.A total of 1490 spectra were obtained and their properties were studied using a typical Band-shape model.First,the parameter distributions of the time-resolved spectrum are given as follows:the low-energy spectral indexα~-0.72,high-energy spectral indexβ~2.42,the peak energy E_(p)~221.69 keV,and the energy flux F~7.49×10^(-6)erg cm^(-2)s^(-1).More than 80%of the bursts exhibit the hardest low-energy spectral indexα_(max),exceeding the synchrotron limit(-2/3).Second,the evolution patterns of a and E_(p)were statistically analyzed.The results show that for multi-pulse GRBs the intensity-tracking pattern is more common than the hard-to-soft pattern in the evolution of both E_(p)andα.The hard-to-soft pattern is generally shown in single-pulse GRBs or in the initial pulse of multi-pulse GRBs.Finally,we found a significant positive correlation between F and E_(p),with half of the samples exhibiting a positive correlation between F andα.We discussed the spectral evolution of different radiation models.The diversity of spectral evolution patterns indicates that there may be more than one radiation mechanism occurring in the GRB radiation process,including photo spheric radiation and synchrotron radiation.However,it may also involve only one radiation mechanism,but more complicated physical details need to be considered.展开更多
In spite of the importance of studying the cosmic generation of heavy elements through the r-process,the detection of a kilonova resulting from the merger of a neutron star binary is still a challenging task.In this p...In spite of the importance of studying the cosmic generation of heavy elements through the r-process,the detection of a kilonova resulting from the merger of a neutron star binary is still a challenging task.In this paper,we show that the Visible Telescope(VT)onboard the ongoing SVOM space mission is powerful for identifying kilonova candidates associated with short gamma-ray bursts up to a distance of 600 Mpc.A significant color variation,turning blue and then turning red,is revealed by calculating the light curves in both red and blue channels of VT by a linear combination of an afterglow and an associated kilonova.The maximum color variation is as high as~0.5-1 mag,which is far larger than the small photometry error of~0.2 mag of VT for a point source with a brightness of 23 mag.Up to a distance of 600 Mpc,~1-2 kilonova candidates per year are predicted to be identified by VT.展开更多
基金supported by the National Natural Science Foundation of China(11773087)the Science and Technology Development Fund of Macao(079/2018/A2)
文摘We present the thorium distribution on the lunar surface derived from observations by the Chang’E-2 gamma-ray spectrometer(CE-2 GRS). This new map shows a similar thorium distribution to previous observations. In combination with this new thorium map and impact cratering model, we investigate the origination of thorium on the Moon’s highlands, which was previously thought to be contributed from Imbrium ejecta. We found that the Imbrium ejecta has a small contribution(~20%–30%) to the thorium on the lunar highlands but most thorium is likely to be indigenous before the deposition of the Imbrium ejecta. This new thorium map also confirms that the eastern highlands have a relatively higher thorium concentration than the western highlands. We propose that the thin crust and large basins on the eastern highlands are responsible for this difference in thorium.
基金supported by the National High Technology Research and Development Program of China (Grant Nos. 2008AA12A212 and 2010AA122202)the National Natural Science Foundation of China (Grant Nos. 41040031 and 40904024)
文摘The main goal of the gamma-ray spectrometer(GRS) onboard Chang'E1(CE-1) is to acquire global maps of elemental abundances and their distributions on the moon,since such maps will significantly improve our understanding of lunar formation and evolution.To derive the elemental maps and enable research on lunar formation and evolution,raw data that are received directly from the spacecraft must be converted into time series corrected gamma-ray spectra.The data correction procedures for the CE-1 GRS time series data are thoroughly described.The processing procedures to create the time series gamma-ray spectra described here include channel processing,optimal data selection,energy calibration,gain correction,dead time correction,geometric correction,orbit altitude normalization,eliminating unusable data and galactic cosmic ray correction.Finally,descriptions are also given on data measurement uncertainties,which will help the interested scientists to understand and estimate various uncertainties associated with the above data processing.
文摘Gamma-ray spectrometry is a very powerful tool for radioactivity measurements. The gamma-ray spectrometer laboratory in Centre for Energy Research and Training (CERT), Ahmadu Bello University, Zaria, Nigeria is accredited to perform measurements of radioactive content of samples collected from the environment, food chain or industrial products with the aid of a high resolution HPGe detector. For accurate gamma-ray spectrometry, certain measurements were considered;the efficiency of the detector was performed experimentally against energies within the range of 59.50 keV (241Am) to 2204.50 keV (226Ra) for the respective geometries of 1 - 6 cm. The sustained solid angle relations with respect to the inverse square of sample geometries from 1 - 6 cm were evaluated. Another main point of this work was focused on the efficiency at geometry of 5 cm with respect to the three selected energies: 661.60 keV (137Cs), 1173.2 keV (60Co) and 1332 keV (60Co) for the main axis, ten degree off main axis, forty five degree off main axis and ninety degree off the detector main axis. In order to verify optimum geometries in our laboratory for both short lived and long lived radionuclides analyses, the evaluation of efficiencies for the respective energies: 1173.2 keV (60Co), 1332.5 keV (60Co), 1764 keV (226Ra) and 2294 keV (226Ra) were plotted against geometries of 1 to 6 cm from the detector end cap along the main axis.
基金supported by the Na-tional High Technology Research and Development Program of China (Nos. 2008AA12A212,2010AA122201 and 2010AA122202)the National Natural Science Foundation of China (Nos.41040031 and 40904024)
文摘Gamma-ray spectrometer(GRS) is used to detect the elemental abundances and distributions on the lunar surface.To derive the elemental abundances,it is vital to acquire background gamma rays except lunar gamma rays.So GRS would observe background spectra in the course of earth-moon transfer on schedule.But in fact,GRS was not switched on in the course of flying toward the moon.After the CE-1 probe finished one-year mission,GRS car-ried out a test on background data on November 21?22,2008.The authors did conduct research on the methods of background deduction using 2105 hours of usable gamma-ray spectra acquired at the 200-km orbital height by the GRS and more than 5 hours of gamma-ray spectra acquired in the GRS background test.The final research results showed that the method of deducting the background using the minimum counts in the CE-1 GRS pixels is optimal for the elements,U,K and Th.The method applies to such a case that the elemental abundances in the pixel with the minimum counting rate are 0 μg/g and the continuum background counts are constant over the Moon.Based on the method of background deduction,the full energy peak counts of U,K,and Th are calculated.
基金supports from following sources:National Key R&D Program of China(grant No.2021YFB2801500)National Natural Science Foundation of China(grant No.62375126,No.62105149 and No.62334001)+1 种基金Natural Science Foundation of Jiangsu Province(grant No.BK20210288)Opening Foundation of Key Laboratory of Laser&Infrared System(Shandong University),Minister of Education Key Lab of Modern Optical Technologies of Education Ministry of China,Soochow University State Key Laboratory of Advanced Optical Communication Systems and Networks,China Specially-appointed Professor Fund of Jiangsu.
文摘Despite the pressing demand for integrated spectrometers,a solution that deliver high-performance while being practically operated is still missing.Furthermore,current integrated spectrometers lack reconfigurability in their performance,which is highly desirable for dynamic working scenarios.This study presents a viable solution by demonstrating a userfriendly,reconfigurable spectrometer on silicon.At the core of this innovative spectrometer is a programmable photonic circuit capable of exhibiting diverse spectral responses,which can be significantly adjusted using on-chip phase shifters.The distinguishing feature of our spectrometer lies in its inverse design approach,facilitating effortless control and efficient manipulation of the programmable circuit.By eliminating the need for intricate configuration,our design reduces power consumption and mitigates control complexity.Additionally,our reconfigurable spectrometer offers two distinct operating conditions.In the Ultra-High-Performance mode,it is activated by multiple phase-shifters and achieves exceptional spectral resolution in the picometer scale while maintaining broad bandwidth.On the other hand,the Ease-of-Use mode further simplifies the control logic and reduces power consumption by actuating a single-phase shifter.Although this mode provides a slightly degraded spectral resolution of approximately 0.3 nm,it prioritizes ease of use and is wellsuited for applications where ultra-fine spectral reconstruction is not a primary requirement.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.12004426,U2030106,and 12304185)the National Key Scientific Instrument and Equipment Development Project of NSFC(Grant No.11227906)the National Key R&D Program of China(Grant No.2023YFA1406500)。
文摘An innovative monochromator shielding is designed and implemented for the cold neutron spectrometers XINGZHI and BOYA operated by Renmin University of China at China Advanced Research Reactor.Via Monte Carlo simulations and careful mechanical designs,a shielding configuration has been successfully developed to satisfy safety requirements of below 3μSv/h dose rate at its exterior,meanwhile fulfilling space,floor load and nonmagnetic requirements.Composite materials are utilized to form the sandwich-type shielding walls:the inner layer of boron carbide rubber,the middle layer of steel-encased lead and the outer layer of borated polyethylene.Special-shaped liftable shielding blocks are incorporated to facilitate a continuous adjustment of the neutron energy while preventing radiation leakage.Our work has demonstrated that by utilizing composite shielding materials,along with the sandwich structure and liftable shielding blocks,a compact and lightweight shielding solution can be achieved.This enables the realization of advanced neutron scattering instruments that provide expanded space of measurement,larger energy and momentum coverage,and higher flux on the sample.This shielding represents the first of its kind in neutron scattering instruments in China.Following its successful operation,it has been subsequently employed by other neutron instruments across the country.
基金partially supported by the Natural Science Foundation of China(Nos.12004353,11975214,11991071,11905202,12175212,and 12120101005)the Key Laboratory Foundation of the Science and Technology on Plasma Physics Laboratory(Nos.6142A04200103 and 6142A0421010).
文摘Currently,with the advent of high-repetition-rate laser-plasma experiments,the demand for online diagnosis for the X-ray spectrum is increasing because the laser-plasma-generated X-ray spectrum is very important for characterizing electron dynamics and applications.In this study,scintillators and silicon PIN(P-type–intrinsic-N-type semiconductor)diodes were used to construct a wideband online filter stack spectrometer.The X-ray sensor and filter arrangement was optimized using a genetic algorithm to minimize the condition number of the response matrix.Consequently,the unfolding error was significantly reduced based on numerical experiments.The detector responses were quantitatively calibrated by irradiating the scintillator and PIN diode with various nuclides and comparing the measuredγ-ray peaks.A prototype 15-channel spectrometer was developed by integrating an X-ray detector with front-and back-end electronics.The prototype spectrometer could record X-ray pulse signals at a repetition rate of 1 kHz.Furthermore,an optimized spectrometer was employed to record the real-time spectra of laser-driven bremsstrahlung sources.This optimized spectrometer offers a compact solution for spectrum diagnostics of ultrashort X-ray pulses,exhibiting improved accuracy in terms of spectrum measurements and repetition rates,and could be widely used in next-generation high-repetition-rate high-power laser facilities.
基金supported by the National Key Research and Development Program of China(Nos.2022YFA1503801,2021YFA1600800)the Photon Science Center for Carbon Neutrality of Chinese Academy of Sciences+2 种基金Shanghai Science and Technology Development Funds(Nos.22YF1454500,23ZR1471400)the CAS Project for Young Scientists in Basic Research(No.YSBR-022)the National Natural Science Foundation of China(No.12305375)。
文摘A Johann-type X-ray spectrometer was successfully developed at the hard X-ray branch(in-vacuum undulator with a 24-mm periodic length)of the energy material beamline(E-line)at the Shanghai Synchrotron Radiation Facility(SSRF).This spectrometer was utilized to implement X-ray emission spectroscopy(XES),high-energy resolution fluorescence-detected X-ray absorption spectroscopy(HERFD-XAS),and resonant inelastic X-ray scattering.Seven spherically bent crystals were positioned on the respective vertical 500-mm-diameter Rowland circles,adopting an area detector to increase the solid angle to 1.75%of 4πsr,facilitating the study of low-concentrate systems under complex reaction conditions.Operated under the atmosphere pressure,the spectrometer covers the energy region from 3.5 to 18 keV,with the Bragg angle ranging from 73°to 86°during vertical scanning.It offers a promised energy resolution of sub-eV(XES)and super-eV(HERFD-XAS).Generally,these comprehensive core-level spectroscopy methods based on hard X-rays at the E-line with an extremely high photon flux can meet the crucial requirements of a green energy strategy.Moreover,they provide substantial support for scientific advances in fundamental research.
基金supported by the National Natural Science Foundation China(No.42022051,No.U21A2028)Youth Innovation Promotion Association of the Chinese Academy of Sciences(No.Y202089)the HFIPS Director's Fund(No.YZJJ202101,No.BJPY2023A02).
文摘Optical frequency combbased Fourier transform spectroscopy has the features of broad spectral bandwidth,high sensitivity,andmultiplexed trace gas detection,which has valuable application potential in the fields of precision spectroscopy and trace gas detection.Here,we report the development of a mid-infrared Fourier transform spectrometer based on an optical frequency comb combined with a Herriott-type multipass cell.Using this instrument,the broadband absorption spectra of several important molecules,including methane,acetylene,water molecules and nitrous oxide,are measured by near real-time data acquisition in the 2800-3500 cm^(-1)spectral region.The achieved minimum detectable absorption of the instrument is 4.4×10^(-8)cm^(-1)·Hz^(-1/2)per spectral element.Broadband spectra of H_(2)0 are fited using the Voigt profile multispectral fitting technique and the consistency of the concentration inversion is 1%.Our system also enables precise spectroscopic measurements,and it allows the determination of the spectral line positions and upper state constants of N_(2)O in the(0002)-(1000)band,with results in good agreement with those reported by Toth[Appl.Opt.30,5289(1991)].
基金This work was supported by the National Key R&D Program of China(Nos.2022YFF0709503,2022YFB1902700,2017YFC0602101)the Key Research and Development Program of Sichuan province(No.2023YFG0347)the Key Research and Development Program of Sichuan province(No.2020ZDZX0007).
文摘To detect radioactive substances with low activity levels,an anticoincidence detector and a high-purity germanium(HPGe)detector are typically used simultaneously to suppress Compton scattering background,thereby resulting in an extremely low detection limit and improving the measurement accuracy.However,the complex and expensive hardware required does not facilitate the application or promotion of this method.Thus,a method is proposed in this study to discriminate the digital waveform of pulse signals output using an HPGe detector,whereby Compton scattering background is suppressed and a low minimum detectable activity(MDA)is achieved without using an expensive and complex anticoincidence detector and device.The electric-field-strength and energy-deposition distributions of the detector are simulated to determine the relationship between pulse shape and energy-deposition location,as well as the characteristics of energy-deposition distributions for fulland partial-energy deposition events.This relationship is used to develop a pulse-shape-discrimination algorithm based on an artificial neural network for pulse-feature identification.To accurately determine the relationship between the deposited energy of gamma(γ)rays in the detector and the deposition location,we extract four shape parameters from the pulse signals output by the detector.Machine learning is used to input the four shape parameters into the detector.Subsequently,the pulse signals are identified and classified to discriminate between partial-and full-energy deposition events.Some partial-energy deposition events are removed to suppress Compton scattering.The proposed method effectively decreases the MDA of an HPGeγ-energy dispersive spectrometer.Test results show that the Compton suppression factors for energy spectra obtained from measurements on ^(152)Eu,^(137)Cs,and ^(60)Co radioactive sources are 1.13(344 keV),1.11(662 keV),and 1.08(1332 keV),respectively,and that the corresponding MDAs are 1.4%,5.3%,and 21.6%lower,respectively.
基金The project supported by Key Laboratory of Space Ocean Remote Sensing and Application,Ministry of Natural Resources under contract No.2023CFO016the National Natural Science Foundation of China under contract No.61931025+1 种基金the Innovation Fund Project for Graduate Student of China University of Petroleum(East China)the Fundamental Research Funds for the Central Universities under contract No.23CX04042A.
文摘Synthetic aperture radar(SAR)and wave spectrometers,crucial in microwave remote sensing,play an essential role in monitoring sea surface wind and wave conditions.However,they face inherent limitations in observing sea surface phenomena.SAR systems,for instance,are hindered by an azimuth cut-off phenomenon in sea surface wind field observation.Wave spectrometers,while unaffected by the azimuth cutoff phenomenon,struggle with low azimuth resolution,impacting the capture of detailed wave and wind field data.This study utilizes SAR and surface wave investigation and monitoring(SWIM)data to initially extract key feature parameters,which are then prioritized using the extreme gradient boosting(XGBoost)algorithm.The research further addresses feature collinearity through a combined analysis of feature importance and correlation,leading to the development of an inversion model for wave and wind parameters based on XGBoost.A comparative analysis of this model with ERA5 reanalysis and buoy data for of significant wave height,mean wave period,wind direction,and wind speed reveals root mean square errors of 0.212 m,0.525 s,27.446°,and 1.092 m/s,compared to 0.314 m,0.888 s,27.698°,and 1.315 m/s from buoy data,respectively.These results demonstrate the model’s effective retrieval of wave and wind parameters.Finally,the model,incorporating altimeter and scatterometer data,is evaluated against SAR/SWIM single and dual payload inversion methods across different wind speeds.This comparison highlights the model’s superior inversion accuracy over other methods.
基金This paper is a part of the outcome research performed under a Waseda University Grant for Special Research Project(Project number:2017B-208).
文摘Microsatellites have recently opened windows of frequent and low cost missions for planetary exploration. The performance of gamma-ray and neutron spectrometers on future microsatellite missions is simulated to assess the possibility of observation of hydrogen and major elements, given their concentration on the observation target. The measured elemental abundance will provide important geological constraints, and some of them may serve as space resources. Four different types of target bodies with various hydrogen concentrations in the range of 0 - 20,000 ppm are assumed as target compositions;Earth’s core, C-type, S-type and Martian meteorites. Gamma-ray and neutron emission rates show unique footprints that are related to the different elemental compositions. The starting point is the solid angle subtended between observation target and spectrometers that allow estimating the gamma-ray and neutron count rates emitted by the celestial bodies. In this work, three types of gamma-ray detectors;high-purity germanium (HPGe), CeBr3 and LaBr3(Ce), a neutron spectrometer combining a lithium glass scintillator with a boron loaded plastic scintillator and a dual mode spectrometer Cs2LiYCl6(Ce) (CLYC) are simulated, focusing on their observation backgrounds as a model case for microsatellite based measurements. The background count level of both gamma-ray (except for the LaBr3 detector) and neutron count rates was negligible under these particular conditions. The gamma-ray detectors were compared by the figure of merit, which was determined by their efficiency and energy resolution. It was found that each detector has unique advantages. The HPGe detector has the highest figure of merit due to its excellent energy resolution, whereas the CLYC detector is low in weight and power consumption due to its dual sensitivity to gamma-ray and neutron. The CeBr3 detector is an intermediate choice. The neutron count rates are calculated separately in three energy ranges, i.e. , thermal (<0.5 eV), epithermal (0.5 eV - 500 keV), and fast (>500 keV), as a function of the hydrogen concentration in the 0 - 20,000 ppm range. The thermal and epithermal neutron count rates are found to decrease with hydrogen concentration, while the fast neutron count rate increases with the target average atomic mass. The optimal detector should be decided by the mission restraints on mass, power consumption, and heat thermal design.
基金supported by the National Key Research and Development Program of China(No.2021YFA0718404)the National Natural Science Foundation of China(Nos.12220101003,12173098,U2031149)+2 种基金the Project for Young Scientists in Basic Research of Chinese Academy of Sciences(CAS)(No.YSBR-061)the Scientific Instrument Developing Project of CAS(No.GJJSTD20210009)the Youth Innovation Promotion Association of CAS,and the Young Elite Scientists Sponsorship Program by the China Association for Science and Technology(No.YESS20220197).
文摘The Very Large Area gamma-ray Space Telescope(VLAST)is a mission concept proposed to detect gamma-ray photons through both Compton scattering and electron–positron pair production mechanisms,thus enabling the detection of photons with energies ranging from MeV to TeV.This project aims to conduct a comprehensive survey of the gamma-ray sky from a low-Earth orbit using an anti-coincidence detector,a tracker detector that also serves as a low-energy calorimeter,and a high-energy imaging calorimeter.We developed a Monte Carlo simulation application of the detector using the GEANT4 toolkit to evaluate the instrument performance,including the effective area,angular resolution,and energy resolution,and explored specific optimizations of the detector configuration.Our simulation-based analysis indicates that the current design of the VLAST is physically feasible,with an acceptance above 10 m^(2)sr which is four times larger than that of the Fermi-LAT,an energy resolution better than 2%at 10 GeV,and an angular resolution better than 0.2◦at 10 GeV.The VLAST project promises to make significant contributions to the field of gamma-ray astronomy and enhance our understanding of the cosmos.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11975037 and 11921006)the National Grand Instrument Project of China (Grant Nos. 2019YFF01014400 and 2019YFF01014404)。
文摘Laser-driven proton-induced x-ray emission(laser-PIXE) is a nuclear analysis method based on the compact laser ion accelerator. Due to the transient process of ion acceleration, the laser-PIXE signals are usually spurted within nanoseconds and accompanied by strong electromagnetic pulses(EMP), so traditional multi-channel detectors are no longer applicable.In this work, we designed a reflective elliptical crystal spectrometer for the diagnosis of laser-PIXE. The device can detect the energy range of 1 keV–11 ke V with a high resolution. A calibration experiment was completed on the electrostatic accelerator of Peking University using samples of Al, Ti, Cu, and ceramic artifacts. The detection efficiency of the elliptical crystal spectrometer was obtained in the order of 10-9.
文摘[Objectives]This study was conducted to establish an uncertainty evaluation method for the determination of ethyl maltol by ultra-high performance liquid chromatograph-mass spectrometer(UPLC-MS).[Methods]A mathematical model of uncertainty was established by analyzing the method for determining ethyl maltol using UPLC-MS.The sources of uncertainty were analyzed,and the components of uncertainty were calculated to evaluate the expanded uncertainty of the method.[Results]When the content of ethyl maltol in edible vegetable oil was 1657μg/kg,the expanded uncertainty was 22.4μg/kg(K=2,P=95%).[Conclusions]The uncertainty in this evaluation model mainly came from standard solution preparation,sample weighing,dilution of sample to constant volume,standard curve fitting,and repeated measurement.
文摘The accuracy(repeatability and reproducibility) of the iron content analysis of galvanized coating using an X-ray fluorescence spectrometer with an L-spectrum is not better than that of flame atomic absorption spectrometry, sometimes it exceeds the quality control limit.Influences, such as current, voltage, equipment(internal circulating water, 10%CH4+90%Ar, and vacuum) checking, instrument monitoring, sample cleaning, and oper-ators, were investigated by means of 6-sigma and lean operations to improve accuracy.
基金supported by the National Natural Science Foundation of China(Nos.U1938201 and 12373042)。
文摘GRB 200612A could be classified as an ultralong gamma-ray burst due to its prompt emission lasting up to~1020 s and the true timescale of the central engine activity t_(burst)≥4×10^(4) s.The late X-ray light curve with a decay index ofα=7.53 is steeper than the steepest possible decay from an external shock model.We propose that this X-ray afterglow can be driven by dipolar radiation from the magnetar spindown during its early stage,while the magnetar collapsed into the black hole before its spindown,resulting in a very steep decay of the late X-ray light curve.The optical data show that the light curve is still rising after 1.1 ks,suggesting a late onset.We show that GRB 200612A’s optical afterglow light curve is fitted with the forward shock model by Gaussian structured off-axis jet.This is a special case among GRBs,as it may be an ultralong gamma-ray burst powered by a magnetar in an off-axis observation scenario.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(grant No.XDB0550400)the Key Research Program of Frontier Sciences(grant No.ZDBS-LY-7014)of Chinese Academy of Sciences+1 种基金the National Natural Science Foundation of China(NSFC,Grant Nos.12373053 and 12321003)the Natural Science Foundation of Jiangsu Province(grant No.BK20221562)。
文摘The occurrence of the first significant digits from real world sources is usually not equally distributed,but is consistent with a logarithmic distribution instead,known as Benford’s law.In this work,we perform a comprehensive investigation on the first digit distributions of the duration,fluence,and energy flux of gamma-ray bursts (GRBs) for the first time.For a complete GRB sample detected by the Fermi satellite,we find that the first digits of the duration and fluence adhere to Benford’s law.However,the energy flux shows a significant departure from this law,which may be due to the fact that a considerable part of the energy flux measurements is restricted by lack of spectral information.Based on the conventional duration classification scheme,we also check if the durations and fluences of long and short GRBs (with duration T_(90)>2 s and T_(90)≤2 s,respectively) obey Benford’s law.We find that the fluences of both long and short GRBs still agree with the Benford distribution,but their durations do not follow Benford’s law.Our results hint that the long–short GRB classification scheme does not directly represent the intrinsic physical classification scheme.
基金performed under the auspices of the Science and Technology Foundation of Guizhou Province(grant No.Qian Ke He Ji Chu ZK[2021]027)Major Science and Technology Program of Xinjiang Uygur Autonomous Region through No.2022A03013-1+1 种基金the National Key Research and Development Program of China(No.2022YFC2205202)the National Natural Science Foundation of China grants 12288102,12041304 and 11847102。
文摘The prompt emission mechanism of gamma-ray bursts(GRBs)is still unclear,and the time-resolved spectral analysis of GRBs is a powerful tool for studying their underlying physical processes.We performed a detailed time-resolved spectral analysis of 78 bright long GRB samples detected by Fermi/Gamma-ray Burst Monitor.A total of 1490 spectra were obtained and their properties were studied using a typical Band-shape model.First,the parameter distributions of the time-resolved spectrum are given as follows:the low-energy spectral indexα~-0.72,high-energy spectral indexβ~2.42,the peak energy E_(p)~221.69 keV,and the energy flux F~7.49×10^(-6)erg cm^(-2)s^(-1).More than 80%of the bursts exhibit the hardest low-energy spectral indexα_(max),exceeding the synchrotron limit(-2/3).Second,the evolution patterns of a and E_(p)were statistically analyzed.The results show that for multi-pulse GRBs the intensity-tracking pattern is more common than the hard-to-soft pattern in the evolution of both E_(p)andα.The hard-to-soft pattern is generally shown in single-pulse GRBs or in the initial pulse of multi-pulse GRBs.Finally,we found a significant positive correlation between F and E_(p),with half of the samples exhibiting a positive correlation between F andα.We discussed the spectral evolution of different radiation models.The diversity of spectral evolution patterns indicates that there may be more than one radiation mechanism occurring in the GRB radiation process,including photo spheric radiation and synchrotron radiation.However,it may also involve only one radiation mechanism,but more complicated physical details need to be considered.
基金supported by the Strategic Pioneer Program on Space Science,Chinese Academy of Sciences,grant XDB0550401supported by the National Natural Science Foundation of China(NSFC,grant No.12173009)+2 种基金by the Natural Science Foundation of Guangxi(2020GXNSFDA238018)by the Bagui Young Scholars Programsupported by the National Postdoctoral Program for Innovative Talents(grant No.GZB20230765)。
文摘In spite of the importance of studying the cosmic generation of heavy elements through the r-process,the detection of a kilonova resulting from the merger of a neutron star binary is still a challenging task.In this paper,we show that the Visible Telescope(VT)onboard the ongoing SVOM space mission is powerful for identifying kilonova candidates associated with short gamma-ray bursts up to a distance of 600 Mpc.A significant color variation,turning blue and then turning red,is revealed by calculating the light curves in both red and blue channels of VT by a linear combination of an afterglow and an associated kilonova.The maximum color variation is as high as~0.5-1 mag,which is far larger than the small photometry error of~0.2 mag of VT for a point source with a brightness of 23 mag.Up to a distance of 600 Mpc,~1-2 kilonova candidates per year are predicted to be identified by VT.