PMT overshoot study for JUNO prototype detector

TL;DR

This study investigates PMT signal overshoot in the JUNO prototype detector, identifying its cause and significantly reducing its amplitude to improve signal quality for neutrino experiments.

Contribution

It provides a detailed analysis of PMT overshoot, identifies its cause as capacitor discharging, and achieves a tenfold reduction in overshoot amplitude without affecting other PMT parameters.

Findings

Overshoot ratio reduced to ~1% from ~10%.

Overshoot caused by capacitor discharging in HV-splitter and voltage divider.

Improved signal quality benefits neutrino detection experiments.

Abstract

The quality of PMT signal is one of the key items for a large and high precision neutrino experiment, like Daya Bay, JUNO, while most of the experiments are affected by the PMT signal overshoot from its positive HV-single cable scheme. For JUNO prototype detector, we have a detailed study on the PMT overshoot and successfully reduced the ratio of overshoot amplitude to signal to ~1% from previous typical ~10%, with no affection to PMT other parameters. Furthermore, we calculated that the overshoot is a result of discharging of capacitors in the HV-signal splitter and the PMT voltage divider. The study result is extremely important for JUNO and other similar experiments.