A GEM Detector System for an Upgrade of the CMS Muon Endcaps

Notice that pivot and feet must both be mounted with a rotation of 180 ◦ with respect to the chimney, depending
on the type of SC. If better mounting precision would be needed, the central screws of the feet can be replaced by
pins. Similar solution for pivots
Due to the weight of each SC, a jig could be necessary for the insertion. The one which was used for the Muon
chambers could probably be adapted for that purpose (Fig. 78). The rails with T-grooves, for sliding and then
stopping (eventually rotating) the SC, are already mounted in the back-flanges of CMS.
B.5 Preliminary considerations GE2/1
Based on the work accomplished for GE1/1, we have begun studies with the purpose of also installing GEM
chambers in the zone ME2/1, more exactly on the backside of YE1 (compression side).
This zone was in principle foreseen for containing RE2/1 chambers but they have never being mounted there. In
fact, only RE2/2 and RE2/3 were installed. In the following photo, the red painted circle on the yoke would be the
place to be used for GE2/1 chambers:
In each side of the detector the set consists of 18 GE2/1 chambers, each spanning 20 ◦ in φ angle. As seen in
GE1/1, the GE2/1 chambers overlap to provide continuous coverage in φ. There are 2 possible geometries to be
envisaged. They depend on the possibility of cantilever a part of each chamber on top of the neutron shielding of
YE/1 disk (short version in blue, long version in grey). As you can see above, the distance from the beamline to
the bottom side of the chamber is 1960 (short version). Hereafter its shown the distance from the IP to the backside
of the yoke (7869mm), but the gap between the yoke and the chambers is not definitely determined yet.
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