The Study of the Highest Energy Cosmic Ray

该项目的主要目的是通过精确测量最高能量宇宙射线和高能伽马射线来研究宇宙射线的起源。利用犹他州七望远镜阵列可以用光学方法测量宇宙线空气簇射产生的切伦科夫光和空气荧光。大口径望远镜记录了大气簇射的轨迹，它的几何结构给我们提供了许多信息，可以高精度地确定能量和到达方向。在日本的Akeno天文台安装了两台望远镜，并对基本性能进行了检查。经过三年的努力，美国犹他州七台望远镜阵列于1998年建成，其主要成果如下：对蟹状星云、活动星系核Mrk 421、Mrk 501和IES 1959的高能γ射线进行了成功的观测。特别是在对Mrk 501的观测中，我们发现在5-7 TeV附近的能谱中存在扭结，γ射线强度存在24天的周期性。我们的观测结果证实了IES 1959是TeV的γ射线源。为了研究高能宇宙线，我们将激光束射入大气，模拟了大气簇射。这些图像由22公里外的望远镜观测，并评估了犹他州七望远镜阵列对最高能量宇宙线的灵敏度。

The main purpose of this project is to investigate the origin of cosmic rays by measuring the highest energy cosmic rays and high energy gamma rays precisely. The Cerenkov light and Air fluorescence light from cosmic ray air showers can be measured by the Utah Seven Telescopes Array in optical method. The tracks of air showers is recorded by the telescopes of large diameter and their geometrical structures give us many informations, and the energy and arrival direction can be determined with high accuracy.Since 1995, we have developped the telescope. Two telescopes were installed at Akeno Observatory in Japan and the fundamental performance was examined. The construction of seven telescopes array at Utah, USA was completed in 1998 after three years effort.The significant results obtained from this Utah Seven Telescope Array are as follows. The high energy gamma rays from Crab Nebula, AGN Mrk421, Mrk501 and IES1959 were successfully observed. Especially, the in the observation of Mrk501, we have discovered the existence of the kink in the energy spectrum around 5-7 TeV andI the periodicity of 24days in the gamma ray intensities. The object IES1959 were identified as a TeV gamma ray sources by our observations. For the study of the highest energy cosmic rays, we have shoot the laser beam in the atmosphere and simulated the air showers. These images were observed by telescopes at a distance of 22km and the sensitivity for the highest energy cosmic rays by the Utah Seven Telescope Array were evaluated.