Characteristics of fast timing MCP-PMTs in magnetic fields

The motivation of this paper is to explore the parameters that affect the performance of Microchannel Plate Photomultiplier Tubes (MCP-PMTs) in magnetic fields with the goal to guide their design to achieve a high magnetic field tolerance. MCP-PMTs based on two different designs were tested. The magnetic field tolerance of MCP-PMT based on a design providing independently biased voltages showed a significant improvement (up to 0.7 T) compared to the one utilizing an internal resistor chain design (up to 0.1 T), indicating the importance of individually adjustable voltages. The effects of the rotation angle of the MCP-PMT relative to the magnetic field direction and of the bias voltage between the photocathode and the top MCP were extensively investigated using the MCP-PMT based on the independently biased voltage design. It was found that the signal amplitude of the MCP-PMT exhibits an enhanced performance at a tilt angle of ±8°, due to the 8°bias angle of the MCP pores. The maximum signal amplitude was observed at different bias voltages depending on the magnetic field strength.