Air shower observation by a simple structured Fresnel lens telescope with a single pixel for the next generation of ultra-high-energy cosmic ray observatories

Abstract

Improved statistics and observations sensitive to mass composition are required to clarify the origin of ultra-high-energy cosmic rays (UHECRs). Inevitably, in the future UHECR observatories will have to be expanded due to the small flux; however, such upgrades will be expensive with the detectors currently in use. Hence, we are developing a new fluorescence detector for UHECR observation. The proposed fluorescence detector, called a cosmic ray air fluorescence Fresnel lens telescope (CRAFFT), has an extremely simple structure and can observe the longitudinal development of an air shower. Furthermore, CRAFFT has the potential to significantly reduce costs for the realization of a huge observatory for UHECR research. We deployed four CRAFFT detectors at the Telescope Array site and conducted a test observation. We have successfully observed ten air shower events using CRAFFT. Thus, CRAFFT can be a solution to help realize the next generation of UHECR observatories.