Study on 3-inch Hamamatsu photomultipliers

Valentina Giordano,Emanuele Leonora,Sebastiano Aiello

doi:10.1051/epjconf/201612105017

Abstract

Several kinds of photomultipliers are widely used in astroparticle physics detectors to measure Cherenkov light in media like water or ice. In neutrino telescopes the key element of the detector is the optical module, which consists of one or more photodetectors inside a transparent pressure-resistant glass sphere. It serves as mechanical protection while ensuring good light transmission. The KM3NeT collaboration has developed an innovative design of an optical module composed by 31 photomultipliers (PMTs) of 3-inch diameter housed in a 17-inch glass shpere. The performance of the telescope is largely dependent on the presence on noise pulses present on the anode of the photomultipliers. A study was conducted of noise pulses of Hamamatsu 3-inch diameter photomultipliers measuring time and charge distributions of dark pulses, pre-pulses, delayed pulses and after-pulses, focusing in particular on analysis on multiple afterpulses. Effects of the Earth's magnetic field on 3-inch PMTs were also studied.

Highlights

C The Authors, published by EDP Sciences
The KM3NeT collaboration has developed an innovative design of an optical module composed by 31 photomultipliers (PMTs) of 3-inch diameter housed in a 17-inch glass shpere
A study was conducted of noise pulses of Hamamatsu 3-inch diameter photomultipliers measuring time and charge distributions of dark pulses, pre-pulses, delayed pulses and after-pulses, focusing in particular on analysis on multiple afterpulses

Summary

Introduction

C The Authors, published by EDP Sciences. Their performance due to Earth’s magnetic field must be investigated. The performance of a PMT could be subject to significant variation due to magnetic fields. Transit time spread (TTS) and gain were measured simultaneously while varying the PMT’s orientations with respect to the Earth’s magnetic field, both with and without a mu-metal cage as magnetic shielding

Noise and spurious pulses measurements

Influence of the Earth’s magnetic field

Findings

Conclusion