硅光电倍增管在大气契伦科夫望远镜和荧光探测器上的应用研究

The air Cherenkov telescope and fluorescence detector based on photomultiplier tube (PMT) have obtained a great achievement in the gamma ray source search and the measurement of high energy cosmic ray energy spectrum. However, only 10% duty cycle is a weakness of this kind of optical detector and greatly limits their development and application, especially in the TeV gamma ray astronomy and extremely high energy cosmic ray. Silicon photomultiplier (SiPM) has been developed during recent years and promised to be an alternative to photomultiplier tube. SiPM has many advantages like single photon response, high detection efficiency, high gain at low bias voltage，no aging and no sensitive to magnetic fields. Because SiPM not aging due to light exposure, SiPM-based camera can be operated in half moon conditions, thus achieve a longer exposure time than PMT-based camera. The exposure time of SiPM-based camera is about 30%. In addition, the price of SiPM is much cheaper than the PMT, is usually more than half of the PMT. Thus, SiPM-based camera can effectively reduce the cost of the detector. The project will study the application of SiPM which is international leading optical detection technology in the air Cherenkov telescope and fluorescence detector. It can ensure that our air Cherenkov light and fluorescence light detection technology are on the international leading position.

基于光电倍增管（PMT）的大气契伦科夫望远镜技术和荧光探测器技术已在伽马射线源寻找和甚高能宇宙线能谱测量方面取得的举世曙目的成绩。然而，不超过10%的有效观测时间一直是此类光学探测器的弱点，极大地限制了其发展和应用，特别是在TeV伽马天文和极高能宇宙线领域的应用。近几年快速发展起来的硅光电倍增管（SiPM）相对于PMT具有很多显著的优点，如单光子响应、高光探测效率、对磁场不敏感、遇强光不老化、高增益和低偏置电压等。其中最突出的优点是在强曝光下不老化，可以在半月晚上观测。因此，采用此SiPM技术，可以使契伦科夫望远镜或荧光探测器的有效观测时间从10%增加到30%。而且SiPM的价格比PMT的价格便宜一半以上，有效地降低了探测器的制作成本。本项目将研究国际领先的SiPM光电探测技术在大气契伦科夫望远镜和荧光探测器上的应用,保证我国在大气契伦科夫光/荧光探测技术上处于国际领先地位。

本项目的主要研究目标是实现硅光电倍增管（SiPM）技术在大气契伦科夫望远镜上的应用。本项目研究的SiPM技术已成功应用在LHAASO广角切伦科夫望远镜上，成功实现基于SiPM技术的广角切伦科夫望远镜在有月晚上观测，有效观测时间是PMT技术的2倍，突破了传统切伦科夫望远镜有效观测时间瓶颈，使我国在大气契伦科夫探测技术上处于国际领先地位。本项目的主要研究成果有：1）完成SiPM选型和性能研究：关于SiPM性能和大动态范围读出电路设计的文章已发表在Nuclear Instruments and Methods in Physics Research A上。2）完成光收集器研制：引入光收集器后，望远镜SiPM成像探头的光接收有效面积从34%增加到86%。光收集器性能和设计值在±3%之内吻合，达到预期要求。3）SiPM技术已成功应用在LHAASO广角切伦科夫望远镜上：LHAASO实验已有15台基于SiPM技术的广角切伦科夫望远镜在四川稻城海子山LHAASO站点稳定运行。15台望远镜共使用约3.4平米的SiPM，成功实现SiPM技术在宇宙线领域的大规模应用。4）完成SiPM相机性能分析：SiPM相机研制和性能分析的文章已完成投稿，正在评审中。