羊八井太阳中子望远镜和中子监测器对2005年1月20日GLE事件的探测

西藏羊八井位于东经90.53°, 北纬30.11°, 海拔4310m, 垂直地磁截止刚度14.1GV. 2005年1月20日羊八井太阳中子望远镜和中子监测器探测到与X7.1/2b太阳耀斑相关的GLE事件, 其中太阳中子望远镜能量>40MeV的能道在5min(07:00—07:05UT)和20min(07:00—07:20UT)的时间间隔内计数率增长的统计显著性分别是3.7σ和6.0σ, 同时羊八井中子监测器也探测到计数率的增长,初始时间为06:51—06:52UT. 观测表明在这次GLE事件中太阳质子可被加速到能量大于10GeV.     

基于DAMPE的暗物质间接探测研究进展

20世纪30年代天文学观测对标准宇宙模型提出了严峻挑战,为了调和观测数据与理论模型的矛盾,理论物理学家提出了暗物质理论;此后,实验物理学家据此摸索出了各种暗物质探测方案.本文将从暗物质概念的由来、暗物质基本性质、暗物质探测原理及方法和DAMPE在探测暗物质方面的最新进展几个方面展开介绍.重点以DAMPE的数据为基础,以电子谱分析为核心,在前人的研究基础上,对DAMPE数据和结果进行多层次、多方位的综合,进一步阐述了DAMPE电子谱中出现的TeV拐折和尖锐信号包含的深刻意义;最后依托研究过程中得到的一些信息,对未来暗物质探测实验提出一点看法和见解.     

西藏羊八井ARGO实验大厅内氡浓度的变化规律研究

利用Lomb-Scargle傅里叶变换法和统计折叠周期分析法,对2009年8月到2011年10月期间西藏羊八井国际宇宙线站的ARGO实验大厅内的氡浓度监测数据进行研究。结果表明,实验大厅内的氡浓度具有1日和半日周期变化规律,其中以1日周期变化为主。在1 d中氡浓度的平均值为(567.2±1.1)Bq/m3,变化幅度为(79.0±1.4)Bq/m3,北京时间约11:20时达到最大,北京时间约23:20达到最小。分析还表明,在一年中月平均浓度的最小值出现在6月份,而较大值出现在下半年的某些月份,每月的日变化幅度和浓度最大时的时间多变。这些结果对环境氡的浓度变化规律及其相关理论模型研究具有重要的意义,同时对西藏地区居住环境监测评价提供了重要的参考。     

Extinction coefficients of surface atmospheric aerosol above LHAASO

We investigate the extinction coefficients of the surface atmospheric aerosol over the Large High Altitude Air Shower Observatory(LHAASO),located at the Haizi Mountain,Daocheng County,China.To this end,we utilize the Longtin model,Mie scattering theory,and experimental data obtained by the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation(CALIPSO).Our theoretical calculations show that the total extinction coefficients of the atmospheric aerosol at the wavelength of 200-500 nm are inversely proportional to the laser wavelength,and influenced by the wind speed.From July 2015 to October 2016,the extinction coefficient of the surface atmospheric aerosols at 532 nm wavelength reached 0.04 km~(-1) with no wind,while it increased to 0.1 km~(-1) with gusts.In this period,the extinction coefficients of the surface atmospheric aerosol at 532 nm wavelength,obtained by the CALIPSO,change from 0.01 to 0.07 km~(-1),which is less than the values obtained the theoretical calculation and larger than the average of Tibetan Plateau in 2006-2016.These calculations and experimental evidence provide important arguments to the model of atmospheric aerosol to be applied in the calibration of LHAASO.Our results suggest that the extinction coefficients over LHAASO require further study,including research on the size distribution,shape,concentration of aerosols particles,wind dependence,relative humidity dependence,etc.     

利用羊八井中子监测器研究宇宙线的太阳日周期变化

通过对宇宙线周期变化研究可以得到宇宙线产生和传播区域的重要信息,是宇宙线长期研究的重要热点问题。利用位于西藏羊八井(地磁截止刚度:14.1 GeV) 的中子监测器2006 至2011年的观测数据,研究宇宙线的太阳日周期变化。在对中子监测器观测数据进行气压修正后,通过Lomb-Scargle 傅立叶变换法对修正后的数据进行周期分析,发现宇宙线计数率存在超过地球公转运动Compton-Getting 效应的太阳日周期变化,该周期变化可能是地球公转效应和宇宙线传播物理过程调制效应以及剩余气象效应的叠加。计算分析了1 日周期信号的振幅和初相位随时间的变化,发现1 日周期变化的初相位存在较为明显的年周期变化规律,这可能是地球公转和自转合成运动的结果;1 日周期变化幅度在2010 年后出现增大趋势。这些结果对宇宙线周期变化和各向异性的研究具有重要参考意义。With the study of the cosmic rays' solar diurnal variation we can get the important information about Cosmic Ray's production and propagation. It's important issues of cosmic rays' studies. We analyze the temporal variation of cosmic rays rate observed with the Yangbajing neutron monitor during 2006 to 2011, and nd semidiurnal and diurnal period signals included in the rates of cosmic rays with vertical rigidity equal to 14.1 GV. We have checked the time dependence of the phase and the amplitude of semidiurnal and diurnal anisotropy, and nd that the phase of diurnal signal varies yearly, it could be a synthetic movement of the earth's rotation and revolution. The amplitude before 2010 is obvious smaller than that after 2010. These results are of great reference value for studying the anisotropy and time variation of cosmic rays.     

Study on the optimization of the water Cherenkov detector array of the LHAASO project for surveying VHE gamma ray sources

It is prpopsed that a water Cherenkov detector array, LHAASO-WCDA, is to be built at Shangri-la, Yunnan Province, China. As one of the major components of the LHAASO project, the main purpose of it is to survey the northern sky for gamma ray sources in the energy range of 100 GeV—30 TeV. In order to design the water Cherenkov array efficiently to economize the budget, a Monte Carlo simulation is carried out. With the help of the simulation, the cost performance of different configurations of the array are obtained and compared with each other, serving as a guide for the more detailed design of the experiment in the next step.