Photo-sensors for a Multi-PMT optical module in KM3NeT

A deep-sea Neutrino Telescope of at least 1 km(3) size (KM3NeT) is being designed to search for high-energy (1-1000 TeV) neutrinos originating from galactic and extragalactic sources. The detection principle exploits the measurement of Cherenkov light emitted by charged particles resulting from neutrino interactions in the matter surrounding the telescope. An optical module containing an array of 31 3-in, diameter photomultiplier tubes is a promising alternative to an optical module containing one 10-in, diameter phototube. The single photo-electron response of 3-in. diameter phototubes (Photonis XP53B20 and ETEL 9822B) has been investigated. Phototube characteristics such as the collection efficiency, transit-time spread and peak-to-valley ratio were determined at various positions across the photocathode surface in a remote-controlled 2D scanning system. Results of these investigations are reported and the perspectives to employ the investigated phototube types in the Multi-PMT optical module of the future KM3NeT detector are discussed. (C) 2010 Elsevier B.V. All rights reserved.