sTGC pad, wire and strip segmentation Daniel Lellouch Weizmann Institute. Parameter book: https://twiki.cern.ch/twiki/bin/viewauth/Atlas/NSWParameterBook Physicist’s ( ROOT) drawings : https:// twiki.cern.ch/twiki/bin/viewauth/Atlas/NSWlayout.
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sTGC pad, wire and strip segmentationDaniel LellouchWeizmann Institute
Physicist’s (ROOT) drawings:
Large Pivot Confirm
Small Confirm Pivot
Trigger: 3-out-of 4 & 3-out-of-4
Strips measure θ
Strip pitch: 3.2 mm
Typical number of strips in a gas-volume : D1/D2/D3: 400/360/360
Therefore main contribution to overall channel number: 280K out of 360K
Size of active volumes all designed to hold exactly (n+½) strips.
To avoid problems of track hitting inter-strip gaps in more than one layer, strips are staggered across layers:
Layers 1 and 3: ½,1,1,1,1,1,1,…
Layers 2 and 4: …..,1,1,1,1,1,½
Note: this is not really needed because lack of projectivity does the job since θ●Δz > pitch. (“Maximum shuffling” argument)
Avalanche is late if originates half the distance between two wires, causing inefficiency.
Since we want a 3 out 4 trigger, wires have to be staggered in 4 planes of modules to avoid situations with two late avalanches.
Reminder: wires measure “φ”.
Bending angles and distances involved make this possible in the following arrangement:
0, ¼, ¾, ½
which are themselves staggered
in the 4 layers by 0, ¼, ½, ¾.