The Pierre Auger Observatory surface detector array

Abstract

ABSTRACT The Auger Observatory southern site’s surface detector will consist of 1600 water Cerenkov detectors spaced 1.5 km apart on a 3000 km 2 site in Mendoza, Argentina. A discussion of the design and results from deployment of an engineering array are presented. Keywords : cosmic rays, air shower arrays, Cerenkov detectors 1. THE AUGER OBSERVATORY SURFACE DETECTOR An overview of the Auger Project may be found elsewhere in these proceedings. 1 In this paper, we focus on the design and performance of the surface detector array. The surface detector array is designed to detect cosmic ray showers by detecting coincident events in widely separated detectors on the Earth’s surface. We employ water Cerenkov detectors spaced 1.5 km apart. The size and spacing of these surface detector stations is chosen to achieve greater than 95% efficiency at 10 19 electron-volts (eV) with the requirement of five triggered stations per event. The direction of the shower is reconstructed from the times of shower front passage through the detectors, and the shower energy and core position are determined by fitting the integrated signal in the tanks to a lateral distribution function. Signals are recorded using fast analog-to-digital converters to take advantage of the wide time spread of signals from extremely energetic showers at large core distances. The time structure of the signals provides information about the composition of the cosmic ray primary, and aids in forming a trigger on extremely high energy shower candidates. The detector site must be remote and sparsely populated so that it is sufficiently dark to facilitate the use of fluorescence detectors together with the surface array. Such sites lack electrical, communications, and transportation infrastructure. The surface detector stations have been designed with the requirements of this type of site in mind. The stations operate using 10 watts provided by a