The Study of the Highest Energy Cosmic Ray

该项目的主要目的是通过精确测量高能宇宙射线和高能伽马射线来研究宇宙射线的起源。犹他州七望远镜阵列可以用光学方法测量宇宙射线空气阵雨的切伦科夫光和空气荧光。大直径的望远镜记录了气簇的轨迹，其几何结构为我们提供了许多信息，可以高精度地确定气簇的能量和到达方向。自1995年以来，我们一直在研制望远镜。在日本秋野天文台安装了两台望远镜，并对其基本性能进行了检查。经过三年的努力，美国犹他州七架望远镜阵列于1998年建成。犹他州七号望远镜阵列获得的重要结果如下。成功地观测到了蟹状星云、AGN Mrk421、Mrk501和IES1959的高能伽马射线。特别是在对Mrk501的观测中，我们发现其能谱在5-7 TeV附近存在扭结，伽马射线强度具有24天的周期性。通过我们的观测，IES1959被确定为TeV伽玛射线源。为了研究高能宇宙射线，我们在大气中发射了激光束并模拟了空气阵雨。这些图像是由距离22公里的望远镜观测到的，并评估了犹他七望远镜阵列对最高能量宇宙射线的灵敏度。

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.