28th International Cosmic Ray Conference 635 Systematic Calculation of the Efficiency of the Fluorescence Detector using Appropriate EAS Simulations Athanasios Geranios 1 , Emmanuel Fokitis 2 , Stavros Maltezos 2 , Konstantinos Patrinos 2 , and Alexandros Dimopoulos 1 (1) Physics Department, Nuclear and Particle Physics Section, University of Athens, Ilissia GR 15771, Greece (2) Physics Department, National Technical University of Athens, Zografos GR 15780, Greece Abstract The detection efficiency of a pixel detector of an EAS telescope using optical UV filters is determined in this work. Based on the Auger Fluorescence Detector geometry, we have calculated the overall efficiency of the pixel detector using an appropriate method which takes into account the particular spectral functions and the dependence on the angle of incidence of the optical filter used. Assuming EAS events developed with various inclinations generated by AIRES code, we calculate the number of electrons and positrons produced during the development of the EAS. The detection efficiency of the pixel detector is taken into account in estimating the signal to be recorded(number of photoelectrons). 1. Introduction The study of the longitudinal evolution of Extensive Air Showers (EAS) in the atmosphere was proposed by Greisen [1]. The electrons and positrons of the electrophotonic part, causes among other effects, the emission of fluorescence light. The fluorescence light propagating through the atmosphere triggers an array of sensitive photomultiplier tubes (PMT) on the ground. This array can record the intensity of the fluorescence light as a function of the atmospheric depth along the shower axis. Therefore, it could trace the track of a CR in the atmosphere as a moving spot and by triggering the PMTs it could depict the sky projection of the EAS trajectory. The total photon intensity gives an estimate of the energy of the primary CR and the PMT whose signal is the largest, corresponds to the atmospheric depth of the maximum intensity of the shower. The estimate of this depth of shower “maximum” is a valuable parameter for the isotopic identification of the primary CR. A full fluorescence detector (FD) array with appropriate filters, mirror and camera for the Pierre Auger Observatory is described elsewhere [2,3]. pp. 635–638 c 2003 by Universal Academy Press, Inc.