Saturation mitigation strategies in microchannel plate photomultiplier tubes

With signal levels increasing in inertial confinement fusion (ICF) facilities, attention is being applied to the prevention of saturation in the microchannel plate (MCP) photomultiplier tubes (PMTs), which are a key component in gamma and neutron detection diagnostics. We present two alternative strategies for the mitigation of saturation. The first is the dynamic modulation of the electron gain of the PMT, allowing the gain to be adjusted during the ICF event and therefore to time the linear response of the detector to coincide with the chosen region of interest while having some level of detection during the whole event. This contrasts with fast photocathode gating which only allows a binary on/off option. The other strategy is to use a segmented photocathode with three independently gated sections of the active area. These areas vary significantly in size to limit the saturation during the three different time gating windows. Results of preliminary tests will be presented with recommended next steps for fieldable devices.