A Novel Tool for the Absolute End-to-End Calibration of Fluorescence Telescopes – The XY-Scanner
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et al.; Institute for Cosmic Ray Research (ICRR) Univeristy of Tokyo; International Union of Pure and Applied Physics (IUPAP); JPS; Nagoya Convention and Visitors Bureau; Nagoya University
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The Pierre Auger Observatory uses 27 large-aperture wide-angle Schmidt telescopes to measure the longitudinal profile of air showers using the air-fluorescence technique. Up to the year 2013, the absolute calibration of the telescopes was performed by mounting a uniform large-diameter light source on each of the telescopes and illuminating the entire aperture with a known photon flux. Due to the high amount of work and person-power required, this procedure was only carried out roughly once every three years, and a relative calibration was performed every night to track short-term changes. Since 2013, only the relative calibration has been performed. In this paper, we present a novel tool for the absolute end-to-end calibration of the fluorescence detectors, the XY-Scanner. The XY-Scanner uses a portable integrating sphere as a light source, which has been absolutely calibrated. This light source is installed onto a motorized rail system and moved across the aperture of each telescope. We mimic the illumination of the entire aperture by flashing the light source at ∼1700 positions evenly distributed across the telescope aperture. For the absolute calibration of the light source, we built a dedicated setup that uses a NIST-calibrated photodiode to measure the average photon flux and a PMT to track the pulse-to-pulse stability. We present the laboratory setups used to study the characteristics of the employed light sources and discuss the inter-calibration between selected telescopes. © Copyright owned by the author(s) under the terms of the Creative Commons.
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Airborne telescopes, Linear accelerators, Optical telescopes, Photons, X ray detectors, Absolute calibration, End to end, Fluorescence telescopes, Large aperture, Photon flux, Pierre Auger observatory, Relative calibrations, Schmidt telescope, Wide angle, XY-scanners, Fluorescence
