Here, we report on a particular type of RPC that presents up to 99% efficie
ncy for minimum ionizing particles and a very sharp time resolution, below
50 ps sigma in the most optimized conditions. Our 9 cm(2) cells, made with
glass and metal electrodes that form accurately spaced gaps of a few hundre
d micrometers, are operated at atmospheric pressure in non-flammable gases
and can be economically produced in large quantities, opening perspectives
for the construction of large area time-of-flight systems. (C) 2000 Elsevie
r Science B.V. All rights reserved.