A high-speed imaging system developed for two-dimensional counting of charged particles is presented. Microchannel plates coupled with a phosphor screen of a short emission lifetime (<1 μs) are used to visualize the two-dimensional positions of charged-particle impacts, and the image on the phosphor screen is captured with a 1 kHz complementary metal oxide semiconductor (CMOS) image sensor (512×512 pixels). A multistage image intensifier consisting of the first and second generation devices was used to compensate for the low sensitivity of CMOS. The centers of gravity (COG) of individual light spots in each image frame are calculated in real time by a field programmable gate array circuit. The performance of this system is tested by time-resolved photoelectron imaging (TR-PEI) of NO using (1+ 1′) resonance enhanced multiphoton ionization via the A 2 + state with a femtosecond laser operated at 1 kHz. The new system enabled COG detection for more than ten particles in each frame at 1 kHz and achieved an extremely high degree of accuracy in the measurement of photoelectron angular distributions in TR-PEI.
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