El telescopio de fluorescencia del Observatorio Pierre Auger: Su calibracion

A.C. ROVERO, C. BONIFAZI, A. ETCHEGOYEN, A. FILEVICH, M.C. MEDINA, D.G. MELO, D. SUPANITSKY Y A. TAMASHIRO

La Plata, Pcia. de Buenos Aires, Argentina

Congreso; 46a Reunion anuan de la Asociacion Argentina de Astronomia; 2003

The southern Pierre Auger Observatory is under construction in Malargüe, Mendoza (Argentina). Yet under construction, it has become the largest cosmic ray detector ever made. The observatory will measure the ultrahigh energy spectrum of cosmic rays, with energies above 10^18 eV, for the next twenty years, aiming to understand the origin, nature and acceleration mechanisms of these energetic rays.Two different detectors are been constructed to simultaneously register the atmospheric showers produced by primary cosmic rays: the Surface Detector detects secondary particles reaching the earth surface and the Fluorescence Detector (FD) detects the fluorescence light emitted by the air's Nitrogen atoms excited by shower's charged particles. The FD has 24 telescopes (6 already working) pointing to a fixed position, covering the air volume where showers develop. Using traces and signals recorded by each telescope from the shower in the atmosphere it is possible to determine the arrival direction and energy of the primary cosmic ray.The correct determination of primary energy for the FD relays on the absolute calibration of the telescopes, each of which use 440 photomultipliers and digital electronics to register the signals. In the Auger Observatory two ways to calibrate are used so far: laser shots and by means of an broad light source placed on the telescope'saperture that simulates a punctual source at infinity. So far only averaged absolute calibrations have been obtained for each telescope using both methods, for only two wavelengths.In this presentation we describe the general features of the FD and the absolute calibration obtained so far for the Auger Collaboration. A discussion follows regarding future work to get the calibration for each photomultiplier and for several wavelengths.