Study on the linearity of 20" dynode and MCP PMTs

TL;DR

This study evaluates the linear charge response of 20-inch dynode and MCP photomultiplier tubes using waveform analysis, revealing good linearity up to 1,000 photoelectrons and notable differences in signal features between the two types.

Contribution

It introduces a relative measurement method using a 3-inch PMT to assess the linearity of large 20-inch PMTs in pulse mode, providing new insights into their signal characteristics.

Findings

20" PMTs show linear response up to 1,000 photoelectrons

Distinct waveform features observed between MCP-PMT and dynode-PMT

Correlation analysis of signal parameters with output charge

Abstract

The linearity of charge response is an important feature of photomultiplier tubes (PMT) for physics measurements, especially the newly developed 20" MCP-PMT. In this paper, in addition to the traditional method of double light sources, we applied another relative method of 20" PMT to 3" PMT to measure the linearity of the 20" dynode and MCP PMTs in pulse mode with a waveform digitizer. The measurements show a good linear response of 20" PMTs to 1,000 photoelectrons (p.e.). The correlations of the amplitude, rise-time, fall-time, FWHM, baseline recovery, overshoot, and late-pulse to the output charge of the 20" PMTs derived from the waveform analysis, where the MCP-PMT shows very different features compared to the dynode-PMT in particular.