  The E864 experiment at BNL requires a beam counter and multiplicity detector
system that can perform at an incident beam rate of 10^7 Au ions per second. We
have developed and tested a 150 micrometer thick quartz Cherenkov beam counter
and a scintillator based multiplicity-trigger counter during the first run of
this experiment in 1994. We obtained a time resolution of 78 ps for the beam
counter at an incident beam rate 5 x 10^5 Hz and 100 ps at a rate of 1 x 10^7
Hz. Pulse height discrimination is used to obtain a minimum bias and a 10%
centrality trigger from the multiplicity detectors. The multiplicity counter
has a time resolution of 250 ps.
