High dynamic range base design and characterization of an 8-inch photomultiplier tube CR365-02-2 for the LHAASO-MD experiment

TL;DR

This paper presents the design and characterization of an 8-inch photomultiplier tube base with high dynamic range for the LHAASO-MD experiment, enabling effective gamma-ray detection and background suppression.

Contribution

It introduces a novel high dynamic range base design for CR365-02-2 PMTs, with detailed testing results demonstrating its performance for the LHAASO-MD project.

Findings

Achieved a dynamic range from single photoelectrons to 7×10^5 photoelectrons.

Ensured anode-to-dynode amplitude ratio below 160 for overlap.

Tested parameters include SPE response, linearity, dark count, and afterpulse rate.

Abstract

Ultra-high-energy ($>$ 100 TeV) gamma-ray detection benefits from the use of muon detectors (MDs) thanks to their capability of suppressing the cosmic-ray background. More than 1100 8-inch photomultiplier tubes (PMTs), CR365-02-2 from Beijing Hamamatsu Photon Techniques INC. (BHP), will be deployed for the LHAASO-MD experiment. In this paper, the design of the photomultiplier base for CR365-02-2 is presented. Signals are extracted from two outputs: the anode and the 7th dynode. This design ensures a high dynamic range, from single photoelectron (SPE, peak-to-valley ratio $>$ 2), up to bunches of $7\times10^5$ photoelectrons, with an equivalent anode peak current of up to 1600 mA. The anode-to-dynode amplitude ratio (A/D) is below 160 in order to ensure enough overlap between the two outputs. Test results of 4 PMTs, including the SPE response, A/D, linearity, dark count rate, and afterpulse rate, are reported.