A Test System for the JUNO 20-inch PMTs Prior to Installation

Abstract: The JUNO experiment requires an excellent energy resolution of 3\% at 1 MeV. To achieve this objective, a total of 20,012 20-inch photomultiplier tubes (PMTs) will be deployed for JUNO, comprising 15,012 multi-channel plate (MCP) PMTs and 5,000 dynode PMTs. Currently, JUNO is in the process of detector installation, with PMTs being installed from the top to the bottom of the stainless-steel structure located in the underground experimental hall. In order to validate the functionality of the PMTs and ensure there are no malfunctions prior to installation, a test system has been established at the JUNO site, and testing is being conducted. This paper presents an overview of the test system and reports on the initial test results.