Study of ultra-high energy cosmic rays at Tibetan highlands.

中国物理学家在西藏羊八井(海拔4300米)建造了一个新的空气簇射阵列，以寻找来自Cyg等天体点源的超高能伽马射线。X-3-3。主要目的是研究高能宇宙线的起源和加速机制，该阵列由65个闪烁探测器组成，其中49个探测器以间隔15m的栅格方式排列，每个探测器的面积为0.5m×2，以测量每个空气簇射的到达时间和粒子密度，并具有可行的精度。该系统由微型机控制的TKO和CAMAC组成。数据记录在2.3G字节8 mm的录像带中。通过使用GPS和RB时钟，实现了每天约10秒的时间分辨率。目前，空气簇射的触发频率约为20赫兹。与详细的蒙特卡罗模拟结果对比表明，观测到的簇射平均能量约为20TeV，能量在10TeV左右或小于10TeV的簇射可被d…在没有严重偏见的情况下进行了更多的检查。角分辨率约为1度。只有我们的阵列才能以可行的精度探测到这样的低能量簇射，这主要是因为它的观测水平很高。由于严重的探测偏差，工作在密封层附近的空气切伦科夫探测器和空气簇射阵列都无法观测到这些伽马射线。我们的阵列很好地观测到了高能宇宙射线的月影，偏差约为4.2西格玛。根据TITIS的结果，直接估计其角分辨率约为1度。X-3，她。X-1和蟹状星云/脉冲星，其中包括一颗神经元恒星，并发出强大的X射线，已经被仔细地研究过了，结果是负面的。估算它们的通量上限(95%CL)分别为2.03×10~(-2)/cm^2·秒、0.59×10~(-12)/cm^2·秒和1.48×10~(-2)/cm^2·秒。利用惠普尔-切伦科夫望远镜在TeV区观测到了蟹状星云的伽马射线。在进一步运行一年后，我们的实验可以在10TeV能区对这一结果进行检验。而且我们需要提前将有效区域的平面扩大到3x10^4m^2

A new air shower array has been constructed at Yangbajing (4300m above sea level) in Tibet with Chinese physicists to search for ultra-high energy gamma-rays from celestial point sources such as Cyg. X-3-3. The main aim is to study the origin and acceleration mechanism of high energy cosmic rays.The array consists of 65ch scintllation detectors, among which 49 detectors of 0.5mX^2 area eacti are arranged in a grid pattern of a spacing 15m to measure the arrival time and particle density of each air shower with a feasible accuracy. The system is composed of TKO and CAMAC which are controlled by a micro-computer. Data is recorded in a 2.3 Gbyte 8mm video tape. The time resolution of about 10 sec/day was achieved by use of a GPS and a Rb clock.At present air showerr are triggered at a rate of about 20 Hz. In comparison with a detailed Monte Carlo simulation, it is shown that the mean energy of observed showers is about 20 TeV and showers with energies around or less than 10 TeV could be d … More etected with no serious bias. The angular resolution is shown to be about 1 degree. Only our array can detect such low energy showers with a feasible accuracy, mainly because of high observation level. Both of air Cerenkov detectors and air shower arrays working near the seal level can never observe those gamma-rays because of serious detection biases.A moon shadow by high energy cosmic rays was well observed by our array, with a deficit of about 4.2 sigma. From titis result, the angular resolution is directly estimated to be about 1 degrees.Searches for high energy gamma-rays from Cyg. X-3, Her. X-1 and Crab nebula/pulsar, which include a neurton star and emit powerful X-rays, have been carefully done with negative results. The flux upper limits (95%CL) for them are then estimated to be 2.03x10^<-12>/cm^2. sec, 0.59x10^<-12>/cm^2. sec and 1.48x10^<-12>/cm^2/cm^2. sec, respectively. Gamma-rays from Crab nebula have been observed in TeV region with the Whipple Cerenkov mirrors. This result may be checked in 10 TeV energy region by our experiment after further one year operation. And We need early enlarge the plane of the effective area 3x10^4m^2 Less