Development of Air Shower UV Cherenkov Detector to Servay gamma-ray Point Soura

利用空气簇射产生的大气切伦科夫光观测TeV宇宙线是一种流行的方法。由于来自太阳的紫外光被大气吸收，预计检测切伦科夫光的紫外光成分将提高S/N，并使该技术适用于新的地区。Mt.Mt.Norikura被用作观测切伦科夫光的观测点，切伦科夫光比海平面被大气吸收得更少。我们模拟了1991-93年的观测。我们用直径60-80 cm的反射镜、紫外光电倍增管、可见光管、赤道板等对切伦科夫光以及星光和月光等背景进行了测量，发现在450 nm以下的波长范围内，背景随波长的增加而增加。我们用带通滤光片测量了切伦科夫光的光谱。光谱的峰值出现在300 nm附近。切伦科夫光到达地球表面的波长下限为240 nm。这些结果表明，在山区的切伦科夫探测中，波长较短时，可获得较高的S/氮比。我们研制了一种对可见光几乎不透明的NiSO4和CoSO4溶液的液体滤光片。它将满月的光线抑制了1/25。此外，还利用直径1.8m的反射镜和口径为100 mm的CSTE光电阴极的UV-IIT获得了簇射图像，即切伦科夫光子的角分布。这种IIT是第一次专门为本研究开发的。结合大阪市立大学闪烁体阵列采集的数据和我们的数据，我们估算了簇射图像中切伦科夫光的光子数与初级宇宙线能量的关系，以及我们系统的触发效率。

It is prevailing to utilize atmospheric Cherenkov light from air shower to observe TeV cosmic ray. Since UV light coming from the iniverse is absorbed by the atmosphere, it is expected that detecting UV component of Cherenkov light improves S/N and makes the technique applicable to new regions. Mt. Norikura was adopted as the observation site where Cherenkov light is observed which is less absorbed by the atmosphere than at sea level. We mode observation in 1991-93. We measured Cherenkov light, and also background such as starlight and moonlight using mirrors of diameter 60-80cm, with UV PMTs, visible tubes, an equatorial plate etc. It turned out that background increases with wavelength in the region of wavelength below 450nm. We measured the spectra of Cherenkov light with bandpass filters. The peak of the spectrum appears around 300nm. The lower limit of wavelength Cherenkov light of which arrives at the surface of the earth is 240nm. These results make it clear that higher S/N is achieved at shorter wavelength in Cherenkov detection at the mountain altitude. We developed a liquid filter of solution of NiSO_4 and CoSO_4 which is almost opaque for visible light. It suppressed the light of the full moon by a factor of 1/25. In addition, shower images, that is to say, angular distributions of Cherenkov photons are obtained using a mirror of diameter 1.8m and a UV-IIT of aperture 100mm with CsTe photocathode. Such kind of IIT was developed especially for this research for the first time. We estimated the relationship between the photon number of Cherenkov light of shower image and the primary cosmic ray energy, and the trigger efficiency of our system by combining data acquired by a scintillation array of Osaka City University at the same site and our ones.