Study of High Energy Cosmic Particles in Tibet

自1995年以来，在西藏羊八井（海拔4,300米）的空气簇射阵列（西藏-II）一直在工作，以寻找10 TeV的伽马射线点源，并研究高能初级宇宙线。1996年，在西藏二号卫星内部还安装了一个高密度的空气簇射阵列，其探测器放置在7.5米的网格上，以探测能量超过3 TeV的簇射事件。随着这种高密度空气簇射阵列的出现，来自蟹状星云的信号首次被传统的空气簇射阵列探测到。此外，我们还成功地探测到了附近活动星系核Mrk 501的信号，该活动星系核在1997年处于非常高的状态。核心探测器的总面积为80 m2。对包含在空气簇射中的高能粒子束的观测提供了关于初级粒子中质子成分的直接信息。应用人工神经网络方法从爆发探测器获得的数据集，我们得到了200 TeV和1000 TeV之间的质子的能谱。在1999年秋天，我们构建了一个新的空气簇射阵列，由545个探测器被放置在一个7.5平方米的网格。覆盖探测器阵列的有效面积约为22，000平方米。簇射的阈值能量约为3 TeV，触发频率约为700 Hz。该阵列自1999年11月中旬以来一直在运作。

Since 1995, an air shower array (Tibet-II) has been operating at Yangbajing (4,300m above sea level) in Tibet to search for 10 TeV gamma-ray point sources, as well as to study the primary cosmic rays at high energies. In 1996, a high density air shower array whose detectors are placed on a 7.5 m grid was also set up inside the Tibet-II to detect shower events with energy above 3 TeV. With the advent of this high density air shower array, a signal from the Crab Nebula has been detected for the first time with a conventional air shower array. Furthermore, we also succeeded to detect signals from the nearby AGN Mrk501 which was in a very high state in 1997.A hybrid experiment of air shower array and core detector (consisting of emulsion chambers and burst detector) was done during the period from 1996 summer through 199g summer. The total area of the core detector is 80 m2. Observation of a bundle of high energy particles contained in the air shower provides a direct information about the proton component in the primary particles. Applying an artificial neural network method to the data set obtained from the burst detectors, we obtained the energy spectrum of protons between 200 TeV and 1000 TeV.In the fall of 1999, we constructed a new air shower array consisting of 545 detectors which are placed on a 7.5 m square grid. The effective area covering the detector array is about 22,000 m2. The threshold energy of showers is about 3 TeV and the trigger rate is about 700 Hz. The array has been operated since the middle of November 1999.