The full array of the Large High Altitude Air Shower Observatory(LHAASO)has been in operation since July 2021.For its kilometer-square array(KM2A),we optimized the selection criteria for very high and ultrahigh energy...The full array of the Large High Altitude Air Shower Observatory(LHAASO)has been in operation since July 2021.For its kilometer-square array(KM2A),we optimized the selection criteria for very high and ultrahigh energyγ-rays using data collected from August 2021 to August 2022,resulting in an improvement in significance of the detection in the Crab Nebula of approximately 15%,compared with that of previous cuts.With the implementation of these new selection criteria,the angular resolution was also significantly improved by approximately 10%at tens of TeV.Other aspects of the full KM2A array performance,such as the pointing error,were also calibrated using the Crab Nebula.The resulting energy spectrum of the Crab Nebula in the energy range of 10-1000 TeV are well fitted by a log-parabola model,which is consistent with the previous results from LHAASO and other experiments.展开更多
高海拔宇宙线观测站(Large High Altitude Air Shower Observatory,LHAASO)主要用于探索高能宇宙线起源、高能天体演化以及新物理前沿等。其中的大面积缪子探测器(Muon Detector,MD)阵列,具有对原初伽马射线的高鉴别能力,能够完成超高...高海拔宇宙线观测站(Large High Altitude Air Shower Observatory,LHAASO)主要用于探索高能宇宙线起源、高能天体演化以及新物理前沿等。其中的大面积缪子探测器(Muon Detector,MD)阵列,具有对原初伽马射线的高鉴别能力,能够完成超高能伽马射线的高灵敏度探测。缪子探测器通过阳极和第七打拿极两路信号共同读出的方式,实现1~10000个缪子的大动态范围探测。为了减小在阳极信号饱和后的区域,直接转换为打拿极信号进行测量的误差,提出了将阳极(阳极未饱和部分)和打拿极(阳极饱和部分)两部分信号进行拼接测量的电荷测量优化方案。通过数值模拟得出阳极与打拿极之间的连接方式,可以采用实验室标定的阳极、打拿极关系进行连接。数值模拟结果表明,该方案在1~10000个缪子的大动态范围内有效降低了测量误差,误差小于1%,缪子谱结构得到明显改善。利用全波形信号进行数据分析的结果与模拟结果很好符合,验证了该方案的有效性。展开更多
高海拔宇宙线观测站(Large High Altitude Air Shower Observatory)的核心科学目标是探索高能宇宙线起源以及相关的宇宙演化、高能天体运动和新物理前沿的研究.通过大面积铺设μ子探测器极大地降低宇宙射线背景,从而提升高能伽马射线探...高海拔宇宙线观测站(Large High Altitude Air Shower Observatory)的核心科学目标是探索高能宇宙线起源以及相关的宇宙演化、高能天体运动和新物理前沿的研究.通过大面积铺设μ子探测器极大地降低宇宙射线背景,从而提升高能伽马射线探测的灵敏度.作为μ子探测器的核心部件之一的光电倍增管负责接收水中的切伦科夫光子并将其转换成电信号输出,因此,光电倍增管的性能好坏直接影响μ子探测器的性能.稻城实验室2%抽样测试结果表明,光电倍增管的各性能达到μ子探测器的指标要求,与批量测试结果的相对偏差小于2%.展开更多
The Large High Altitude Air Shower Observatory(LHAASO)has three sub-arrays,KM2A,WCDA,and WFCTA.The flux variations of cosmic ray air showers were studied by analyzing the KM2A data during a thunderstorm on June 10,202...The Large High Altitude Air Shower Observatory(LHAASO)has three sub-arrays,KM2A,WCDA,and WFCTA.The flux variations of cosmic ray air showers were studied by analyzing the KM2A data during a thunderstorm on June 10,2021.The number of shower events that meet the trigger conditions increases significantly in atmospheric electric fields,with a maximum fractional increase of 20%.The variations in trigger rates(increases or decreases)were found to be strongly dependent on the primary zenith angle.The flux of secondary particles increased significantly,following a trend similar to that of shower events.To better understand the observed behavior,Monte Carlo simulations were performed with CORSIKA and G4KM2A(a code based on GEANT4).We found that the experimental data(in saturated negative fields)were in good agreement with the simulations,assuming the presence of a uniform electric field of-700 V/cm with a thickness of 1500 m in the atmosphere above the observation level.Due to the acceleration/deceleration by the atmospheric electric field,the number of secondary particles with energy above the detector threshold was modified,resulting in the changes in shower detection rate.展开更多
The first Water Cherenkov detector of the LHAASO experiment(WCDA-1)has been operating since April 2019.The data for the first year have been analyzed to test its performance by observing the Crab Nebula as a standard ...The first Water Cherenkov detector of the LHAASO experiment(WCDA-1)has been operating since April 2019.The data for the first year have been analyzed to test its performance by observing the Crab Nebula as a standard candle.The WCDA-1 achieves a sensitivity of 65 mCU per year,with a statistical threshold of 5 cr.To accomplish this,a 97.7%cosmic-ray background rejection rate around 1 TeV and 99.8%around 6 TeV with an ap proximate photon acceptance of 50%is achieved after applying an algorithm to separate gamma-induced showers.The angular resolution is measured using the Crab Nebula as a point source to be approximately 0.45°at 1 TeV and better than 0.2°above 6 TeV,with a pointing accuracy better than 0.05°.These values all match the design specifications.The energy resolution is found to be 33%for gamma rays around 6 TeV.The spectral energy distribution of the Crab Nebula in the range from 500 GeV to 15.8 TeV is measured and found to be in agreement with the results from other TeV gamma ray observatories.展开更多
基金Supported by the National Key R&D Program of China(2018YFA0404201,2018YFA0404202,2018YFA0404203,2018YFA0404204)the National Natural Science Foundation of China(12022502,12205314,12105301,12261160362,12105294,U1931201)+2 种基金the Youth Innovation Promotion Association CAS(2022010)in Thailand by the National Science and Technology Development Agency(NSTDA)the National Research Council of Thailand(NRCT):High-Potential Research Team Grant Program(N42A650868)。
文摘The full array of the Large High Altitude Air Shower Observatory(LHAASO)has been in operation since July 2021.For its kilometer-square array(KM2A),we optimized the selection criteria for very high and ultrahigh energyγ-rays using data collected from August 2021 to August 2022,resulting in an improvement in significance of the detection in the Crab Nebula of approximately 15%,compared with that of previous cuts.With the implementation of these new selection criteria,the angular resolution was also significantly improved by approximately 10%at tens of TeV.Other aspects of the full KM2A array performance,such as the pointing error,were also calibrated using the Crab Nebula.The resulting energy spectrum of the Crab Nebula in the energy range of 10-1000 TeV are well fitted by a log-parabola model,which is consistent with the previous results from LHAASO and other experiments.
文摘高海拔宇宙线观测站(Large High Altitude Air Shower Observatory,LHAASO)主要用于探索高能宇宙线起源、高能天体演化以及新物理前沿等。其中的大面积缪子探测器(Muon Detector,MD)阵列,具有对原初伽马射线的高鉴别能力,能够完成超高能伽马射线的高灵敏度探测。缪子探测器通过阳极和第七打拿极两路信号共同读出的方式,实现1~10000个缪子的大动态范围探测。为了减小在阳极信号饱和后的区域,直接转换为打拿极信号进行测量的误差,提出了将阳极(阳极未饱和部分)和打拿极(阳极饱和部分)两部分信号进行拼接测量的电荷测量优化方案。通过数值模拟得出阳极与打拿极之间的连接方式,可以采用实验室标定的阳极、打拿极关系进行连接。数值模拟结果表明,该方案在1~10000个缪子的大动态范围内有效降低了测量误差,误差小于1%,缪子谱结构得到明显改善。利用全波形信号进行数据分析的结果与模拟结果很好符合,验证了该方案的有效性。
文摘高海拔宇宙线观测站(Large High Altitude Air Shower Observatory)的核心科学目标是探索高能宇宙线起源以及相关的宇宙演化、高能天体运动和新物理前沿的研究.通过大面积铺设μ子探测器极大地降低宇宙射线背景,从而提升高能伽马射线探测的灵敏度.作为μ子探测器的核心部件之一的光电倍增管负责接收水中的切伦科夫光子并将其转换成电信号输出,因此,光电倍增管的性能好坏直接影响μ子探测器的性能.稻城实验室2%抽样测试结果表明,光电倍增管的各性能达到μ子探测器的指标要求,与批量测试结果的相对偏差小于2%.
基金Supported in China by National Key R&D program of China(2018YFA0404201,2018YFA0404202,2018YFA0404203,2018YFA0404204)NSFC(U2031101,11475141,12147208)in Thailand by RTA6280002 from Thailand Science Research and Innovation。
文摘The Large High Altitude Air Shower Observatory(LHAASO)has three sub-arrays,KM2A,WCDA,and WFCTA.The flux variations of cosmic ray air showers were studied by analyzing the KM2A data during a thunderstorm on June 10,2021.The number of shower events that meet the trigger conditions increases significantly in atmospheric electric fields,with a maximum fractional increase of 20%.The variations in trigger rates(increases or decreases)were found to be strongly dependent on the primary zenith angle.The flux of secondary particles increased significantly,following a trend similar to that of shower events.To better understand the observed behavior,Monte Carlo simulations were performed with CORSIKA and G4KM2A(a code based on GEANT4).We found that the experimental data(in saturated negative fields)were in good agreement with the simulations,assuming the presence of a uniform electric field of-700 V/cm with a thickness of 1500 m in the atmosphere above the observation level.Due to the acceleration/deceleration by the atmospheric electric field,the number of secondary particles with energy above the detector threshold was modified,resulting in the changes in shower detection rate.
基金Supported by the following grants:the National Key R&D program of China(2018YFA0404201,2018YFA0404202,2018YFA0404203)the National Natural Science Foundation of China(12022502,11905227,U1931112,11635011,11761141001,Y811A35,11675187,U1831208,U1931111)in Thailand by RTA6280002 from Thailand Science Research and Innovation。
文摘The first Water Cherenkov detector of the LHAASO experiment(WCDA-1)has been operating since April 2019.The data for the first year have been analyzed to test its performance by observing the Crab Nebula as a standard candle.The WCDA-1 achieves a sensitivity of 65 mCU per year,with a statistical threshold of 5 cr.To accomplish this,a 97.7%cosmic-ray background rejection rate around 1 TeV and 99.8%around 6 TeV with an ap proximate photon acceptance of 50%is achieved after applying an algorithm to separate gamma-induced showers.The angular resolution is measured using the Crab Nebula as a point source to be approximately 0.45°at 1 TeV and better than 0.2°above 6 TeV,with a pointing accuracy better than 0.05°.These values all match the design specifications.The energy resolution is found to be 33%for gamma rays around 6 TeV.The spectral energy distribution of the Crab Nebula in the range from 500 GeV to 15.8 TeV is measured and found to be in agreement with the results from other TeV gamma ray observatories.
