The First Full-Scale Prototypes of the Fluorescence detector Array of Single-pixel Telescopes

TL;DR

This paper presents the development, deployment, and preliminary results of full-scale prototypes of the FAST fluorescence detector array, a low-cost, large-area observatory for ultra-high energy cosmic rays, demonstrating promising initial measurements and potential for systematic studies.

Contribution

The paper introduces the first full-scale prototypes of FAST telescopes, detailing their design, installation, and initial data collection for ultra-high energy cosmic ray detection.

Findings

Successful deployment of three prototypes at Telescope Array site

Preliminary measurements of artificial light sources and UHECRs

Potential for systematic atmospheric and cross-calibration studies

Abstract

The Fluorescence detector Array of Single-pixel Telescopes (FAST) is a design concept for a next-generation UHECR observatory, addressing the requirements for a large-area, low-cost detector suitable for measuring the properties of ultra-high energy cosmic rays (UHECRs), having energies exceeding $10^{19.5}$\,eV, with an unprecedented aperture. We have developed a full-scale prototype consisting of four 200\,mm diameter photo-multiplier tubes at the focus of a segmented mirror of 1.6\,m in diameter. In October 2016, September 2017, and September 2018 we installed three such prototypes at the Black Rock Mesa site of the Telescope Array experiment in central Utah, USA. All three telescopes have been steadily taking data since installation. We report on the design and installation of these prototypes, and present some preliminary results, including measurements of artificial light sources, distant ultraviolet lasers, and UHECRs. Furthermore, we discuss some additional uses for these simplified low-cost fluorescence telescopes, including the facilitation of a systematic comparison of the transparency of the atmosphere above the Telescope Array experiment and the Pierre Auger Observatory, a study of the systematic uncertainty associated with the existing fluorescence detectors of these two experiments, and a cross-calibration of their energy and $X_{\text{max}}$ scales.