The triple GEM detector is a micropattern gas detector which consists of a
primary ionisation gap and three consecutive gas electron multiplier (GEM)
foils. A printed circuit board with readout strips detects the current induced
by the drifting electron cloud originating from the last GEM stage. Thus the
gas amplification and the signal readout are completely separated. Triple GEM
detectors are being developed as a possible technology for the inner tracking
in the LHCb experiment.
In an earlier note we have reported first experience with such a detector in
a test beam at PSI. Here we describe the construction of an improved version
(thinner transfer gaps, segmented GEM foils, two dimensional readout). Results
from performance measurements are presented using intense hadronic beams as
well as cosmic ray data.Comment: 20 pages, 24 figure
