Signal optimization with HV divider of MCP-PMT for JUNO

Abstract

The Jiangmen Underground Neutrino Observatory (JUNO) is proposed to determine the neutrino mass hierarchy using a 20 kiloton underground liquid scintillator detector (CD). One of the keys is the energy resolution of the CD to reach <3% at 1 MeV, where totally 15,000 MCP-PMT will be used. The optimization of the 20″ MCP-PMT is very important for better detection efficiency and stable performance. In this work, we will show the study to optimize the MCP-PMT working configuration for charge measurement. Particularly, the quality of PMT signal is another key for high-precision neutrino experiments while most of these experiments are affected by the overshoot of PMT signal from the positive HV scheme. The overshoot coupled with positive HV which is troubling trigger, dead time and precise charge measurement, we have studied to control it to less than ~1% of signal amplitude for a better physics measurement. In this article, on the one hand, the optimized HV divider ratio will be presented here to improve its collection efficiency; on the other hand, we will introduce the method to reduce the ratio of overshoot from 10% to 1%.