Development of high-energy particle astrophysics in Tibet

西藏羊八井目前的空气簇射阵列于2003年秋末建成，至今已陆续投入使用。该阵列(西藏-III)由大约800个闪烁计数器组成，分布在一个7.5m的网格上，覆盖37000m^2的面积。空气簇射事件的触发频率被设置为大约1.7 kHz，在3TeV以上的能区内可以估计每个事件的到达方向，误差小于0.9度。主要目标是从活跃的天体中寻找高能伽马射线，并研究超高能银河系宇宙射线。这些观测对于阐明宇宙线的起源及其加速机制是非常重要的。目前所获得的主要结果如下：1)观测到了全粒子宇宙线的能谱，能量范围从10^&lt；14；ev到10^&lt；17&gt；eV，在能量约为4×1015 eV处有一个陡峭的拐点。2)初级质子和氦…的能谱3)从蟹状星云和活动星系核如MRK421和MRK501成功地观测到了约3TeV以上的高能伽马射线。观测到了RV伽马射线S与来自XMM牛顿卫星的X射线耀斑之间的长期相关性，以提供源上电子加速的信息。4)首次观测到银河系宇宙线大尺度各向异性的能量依赖性，并观察到多TeV宇宙线在天鹅座方向上的显著各向异性。5)利用空气簇射阵列连续监测了太阳活动周期中太阳阴影的变化，并成功地获得了关于太阳磁场的新信息。去年，我们在西藏空气簇射阵列地下建造了一个100m^2水切伦科夫型介子探测器。在不久的将来，Muon探测器的总面积将扩大到约10000平方米。这台大视场的仪器就变得最灵敏了吗？世界上能量超过10TeV数倍的伽马射线探测器。预计这项实验将使我们能够提供关于高能宇宙射线加速的非常重要的结果，这仍然是一个悬而未决的问题。较少

The present air-shower array at Yangbajing in Tibet was completed in the late fall of 2003 and has then been successively operating to date. The array(Tibet-III) consists of about 800 scintillation counters, which are deployed at a grid of 7.5m spacing covering the area of 37000m^2. The trigger rate of air-shower events is set to about 1.7kHz and the arrival direction of each event can be estimated with an inaccuracy of less than 0.9 degrees in the energy region over 3 TeV. The main objectives are to search for high-energy gamma rays from active celestial objects and to study very high energy Galactic cosmic rays. These observations are very important to clarify the origin of cosmic rays and their acceleration mechanism.The main results obtained until now are as follows.1) The energy spectrum of all-particle cosmic rays has been observed in the wide energy range from 10^<14> to 10^<17> eV with a sharp knee at the energy around 4x1015 eV.2) The energy spectra of primary protons and heli … More ums are for the first time observed in the knee energy region.3) High energy gamma rays above about 3 TeV have been successfully observed from the Crab Nebula and active galactic nuclei such as Mrk421 and Mrk501. A long-term correlation between RV gamma-ray s and X-ray flares from XMM Newton satellite was observed to provide information about electron acceleration at the source.4) An energy dependence of the large-scale anisotropy of the Galactic cosmic rays has been for the first time observed and also significant anisotropy of multi-TeV cosmic rays is observed in the direction of Cygnus region.5) A variation of the sun shadow during the solar activity cycles was successively monitored with the air shower array, and we succeeded to get new information about the solar magnetic field.Last year we constructed a 100m^2 water-Cherenkov-type muon detector in the underground of the Tibet air shower array. The total area of muon detectors will be expanded up to about 10000m^2 in the very near future. This instrument with a wide field of view then becomes the most sensitive? gamma-ray detector at energies above several times 10 TeV in the world. It is expected that this experiment enables us to provide very important results on the acceleration of high energy cosmic rays, which is still unresolved. Less