The XY Scanner ? A Versatile Method of the Absolute End-to-End Calibration of Fluorescence Detectors

PIERRE AUGER COLLABORATION; A. MARIAZZI

Berlin

Conferencia; 37th International Cosmic Ray Conference (ICRC2021); 2021

One of the crucial detector systems of the Pierre Auger Observatory is the fluorescence detectorcomposed of 27 large-aperture wide-angle Schmidt telescopes. In the past, these telescopeswere absolutely calibrated by illuminating the whole aperture with a uniform large-diameter lightsource. This absolute calibration was performed roughly once every three years, while a relativecalibration was performed on a nightly basis. In this contribution, a new technique for an absoluteend-to-end calibration of the fluorescence telescopes is presented. For this technique, a portable,calibrated light source mounted on a rail system is moved across the aperture of each telescopeinstead of illuminating the whole aperture at once. A dedicated setup using a combination ofNIST traceable photodiodes to measure the mean intensity and a PMT for pulse-to-pulse stabilitytracking has been built for the absolute calibration of the light source. As a result of thesecomplementary measurements, the pulse-to-pulse light source intensity can be known to the 3.5%uncertainty level. The analysis of the readout of the PMT camera at each position of the lightsource together with the knowledge of the light source emission provides an absolute end-to-endcalibration of the telescope. We will give a brief overview of this novel calibration method and itscurrent status as well as show preliminary results from the measurement campaigns performed sofar.