Study of Ultra-High Energy Cosmic Rays at Tibetan highlands

西藏羊八井（海拔4,300米，东经90.5度，北纬30.1度）的西藏空气簇射阵自1990年1月以来一直在中国科学家的参与下连续运行。本阵列由65个闪烁探测器组成，它们被放置在15米间距的网格中。模式能量的观测阵雨估计约为7 TeV的伽马射线。通过观察月球对宇宙射线的遮蔽，可以很好地检验角分辨率。观测到的月影具有7.1sigma的显著性，对模式能量为7TeV的簇射的角分辨率估计为0.88 μ m，对模式能量为35TeV的簇射的角分辨率估计为0.52 μ m。日影的观测方向分别是向西0.70度和向南0.40度。这种偏转被认为是由两个磁场的联合作用引起的。 ...更多信息 甚至太阳和地球。请注意，这些数据是在1990年至1993年太阳仍处于活跃期时拍摄的。这是首次观测到的宇宙线阴影效应，有望为太阳和行星际磁场的大尺度结构及其时变提供新的信息。我们已经对蟹状星云、天鹅座X-3和海尔座X-1等多个点源进行了10 TeV γ射线稳定发射的探索。对于Cyg X-3，在10 TeV和30 TeV的Cyg X-3获得的通量极限远低于通过外推基尔通量获得的水平。对于蟹状星云，没有过量的结果与THEMISTOCLE实验的正结果不一致，但仍与维普莱的新数据一致。我们还在康普顿GRO上用EGRET探测了活动星系核（AGN）的γ射线辐射，特别是最近的活动星系核Markarian 421在10TeV的γ射线辐射，这一结果是令人感兴趣的，对该源的进一步观测将为宇宙中红外光子场的强度提供新的信息。目前的空气簇射阵列将在1994年扩大到3.7 * 10^4平方米的有效面积。该阵列将由221个电离层探测器组成，这些探测器以15米的间距排列。触发速率取为约250 Hz，死区时间小于30%。质子簇射的模式能量估计为5TeV。这一新的阵列将在不久的将来提供行星际磁场以及宇宙线加速的重要信息。少

The Tibet Air shower array at Yangbajing (4,300m, 90.5ﾟ E and 30.1ﾟ N) in Tibet has been operated continuously since January 1990, with Chinese scientists. The present array consists of 65 scintillation detectors which are placed in a lattice of 15m spacing. The mode energy of observed showers is estimated to be about 7 TeV for gamma rays. The angular resolution was well examined by observing the shadowing of cosmic rays by the moon. The moon shadow was observed with the significance of 7.1sigma and the angular resolution of the array is estimated to be 0.88ﾟ for showers with its mode energy 7 TeV and 0.52ﾟ for those with its mode energy 35 TeV.A small deflection of the shadow to the west by about 0.16ﾟ is comparable with that expected from the geomagnetic field effect.On the other hand, the sun shadow was observed in the direction away from the sun by 0.70ﾟ to the west and 0.40ﾟ to the south. This deflection is considered to be caused by the combined effect of the magnetic fields betw … More een the sun and the earth. Note that these data were taken when the sun was still in an active phase between 1990 and 1993. Such effect on the cosmic ray shadow is the first observation and is expected to bring us new information on the large scale structure of the solar and interplanetary magnetic field and its time variation.A search for steady emission of 10 TeV gamma rays has been made for various point sources including the Crab nebula, Cyg X-3 and Her X-1. For Cyg X-3, flux limits obtained at 10 TeV and 30 TeV for Cyg X-3 are far below the levels obtained by extrapolation of the Kiel flux. For the Crab nebula, the result obtained with no excess is inconsistent with the possitive results from the THEMISTOCLE experiment, while still being consistent with the Whipple new data. We also searched for gamma-ray emission from active galactic nuclei (AGNs) which have been reported to be poweful gamma-ray sources by EGRET on board the Compton GRO.In particular, the result for the nearest AGN,Markarian 421 at 10 TeV is interesting, and the further observation on this source will provide new information on the strength of infrared photon field in the universe. The present air shower array will be extended up to an effective area of 3.7 *10^4 m^2 in 1994. This array will consist of 221 scintilation detectors which are placed in a lattice of 15 m spacing. The trigger rate is taken to be about 250 Hz with a dead time less than 30 %. The mode energy for proton showers is estmated to be about 5 TeV.This new array will provide important information on the interplanetary magnetic field as well as acceleration of cosmic rays in the very near future. Less