Mass Testing and Characterization of 20-inch PMTs for JUNO

TL;DR

This paper details the comprehensive testing and characterization of over 20,000 20-inch photomultiplier tubes (PMTs) for the JUNO neutrino experiment, ensuring their quality for precise energy measurement.

Contribution

It presents the largest dataset of 20-inch PMT performance parameters, including the testing procedures and statistical analysis for JUNO's detector requirements.

Findings

All accepted PMTs meet quality standards.

Detailed statistical characteristics of 20-inch PMTs.

Performance parameters include photocathode uniformity.

Abstract

Main goal of the JUNO experiment is to determine the neutrino mass ordering using a 20kt liquid-scintillator detector. Its key feature is an excellent energy resolution of at least 3 % at 1 MeV, for which its instruments need to meet a certain quality and thus have to be fully characterized. More than 20,000 20-inch PMTs have been received and assessed by JUNO after a detailed testing program which began in 2017 and elapsed for about four years. Based on this mass characterization and a set of specific requirements, a good quality of all accepted PMTs could be ascertained. This paper presents the performed testing procedure with the designed testing systems as well as the statistical characteristics of all 20-inch PMTs intended to be used in the JUNO experiment, covering more than fifteen performance parameters including the photocathode uniformity. This constitutes the largest sample of 20-inch PMTs ever produced and studied in detail to date, i.e. 15,000 of the newly developed 20-inch MCP-PMTs from Northern Night Vision Technology Co. (NNVT) and 5,000 of dynode PMTs from Hamamatsu Photonics K. K.(HPK).