  This paper reports on the time resolution of two photodetectors operated as
single photon counters at high rate: a Hamamatsu R13742-103-M64 "conventional"
(based on metal dynodes) multi-anode photomultiplier tube (MaPMT) and a
Hamamatsu R10754-07-M16 microchannel plate photomultiplier tube (MCP-PMT). The
MCP-PMT shows a time resolution (transit time spread, or jitter) of ~70 ps FWHM
(~30 ps RMS) at low photon rates, but saturates above ~100 kHz/mm^2. The MaPMT
can handle photon counting rates up to the highest tested, 10 MHz/mm^2. Its
time resolution is ~250 ps FWHM (~110 ps RMS) when only the pixel center is
illuminated, but pixel edge effects degrade the resolution to ~400 ps FWHM
(~170 ps RMS) when the entire pixel area is illuminated.
