Timing Characteristics of Large Area Picosecond Photodetectors

The LAPPD Collaboration was formed to develop ultrafast large-area imaging photodetectors based on new methods for fabricating microchannel plates (MCPs). In this paper we characterize the time response using a pulsed, subpicosecond laser. We observe single-photoelectron time resolutions of a 20 cm x 20 cm MCP consistently below 70 picoseconds, spatial resolutions of roughly 500 microns, and median gains higher than 10 7 . The RMS measured at one particular point on an LAPPD detector is 58 psec, with 1 of 47 psec. The dierential time resolution between the signal reaching the two ends of the delay line anode is measured to be 5.1 psec for large signals, with an asymptotic limit falling below 2 picoseconds as noise-over-signal approaches zero.