Area and extraction field analysis of the analogue saturation of 40 mm microchannel plate photomultiplier tubes.

Microchannel plate (MCP) photomultiplier tubes (PMTs) are a well-established instrument for the inertial confinement fusion (ICF) community, with several detectors installed at NIF, Omega (LLE Rochester), and Orion (AWE). The analog signals produced at these major ICF facilities cover many orders of magnitude and often need multiple detectors operating at different levels of electron gain. As such, understanding the upper saturation limit of MCP-PMTs to large, low rate signals takes on a high importance. A previous study looked at the saturation limit of double and single MCP-PMTs over their full working area with pulse widths between 4 ns and 100 ns. This follow-on analysis will look at the effect of how the illuminated area affects the saturation limit and at the impact of the MCP to anode extraction field on the impulse response and the level of saturation.