  The CMS GEM collaboration is considering Gas Electron Multipliers (GEMs) for
upgrading the CMS forward muon system in the 1.5<|eta|<2.4 endcap region. GEM
detectors can provide precision tracking and fast trigger information. They
would improve the CMS muon trigger and muon momentum resolution and provide
missing redundancy in the high-eta region. Employing a new faster construction
and assembly technique, we built four full-scale Triple-GEM muon detectors for
the inner ring of the first muon endcap station. We plan to install these or
further improved versions in CMS during the first long LHC shutdown in 2013/14
for continued testing. These detectors are designed for the stringent rate and
resolution requirements in the increasingly hostile environments expected at
CMS after the second long LHC shutdown in 2018/19. The new prototypes were
studied in muon/pion beams at the CERN SPS. We discuss our experience with
constructing the new full-scale production prototypes and present preliminary
performance results from the beam test. We also tested smaller Triple-GEM
prototypes with zigzag readout strips with 2 mm pitch in these beams and
measured a spatial resolution of 73 microns. This readout offers a potential
reduction of channel count and consequently electronics cost for this system
while maintaining high spatial resolution.
