Stgc pad wire and strip segmentation daniel lellouch weizmann institute
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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 segmentation Daniel Lellouch Weizmann Institute

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Stgc pad wire and strip segmentation daniel lellouch weizmann institute

sTGC pad, wire and strip segmentationDaniel LellouchWeizmann 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


Stgc pad wire and strip segmentation daniel lellouch weizmann institute

Large Pivot Confirm

Small Confirm Pivot

MM

Trigger: 3-out-of 4 & 3-out-of-4

Pad

Strips

11 mm

290 mm

Wire groups


Strip segmentation

Strip segmentation

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)


Wire staggering

Wire staggering

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


Wire group segmentation

Wire group segmentation

  • Wires are bundled in “groups”,

    which are themselves staggered

    in the 4 layers by 0, ¼, ½, ¾.

  • Group size:

    • D0 : 20 (not read out)

    • D1 : 10 , Δφ = 13/8 mrad at high/low η

    • D2 : 20 , Δφ = 16/10 mrad at high/low η

    • D3 : 20 ,Δφ = 10/8 mradat high/low η

  • VMM channel filling

    • from 45 to 64 (out of 64 max.)

  • Rates: see slides prepared for tomorrow’s discussion


Improving granularity by pad staggering

Improving granularity by Pad staggering

Pivot

Layers 1&2

Pivot

Layers 3&4


Pivot confirm wedges are also staggered wrt each other 1 4th pad granularity

Pivot/Confirm wedges are also staggered wrt each other: 1/4th pad granularity

Pivot

Layers 1&2

Confirm

Layers 1&2

Pivot

Layers 3&4

Confirm

Layers 3&4


Reducing bandwidth inside wedges by pad fuzzyness

Reducing bandwidth inside wedges by pad “fuzzyness”

Pivot

Layer 1

Pivot

Layer 2

Pivot

Layer 3

Pivot

Layer 4


T he complete picture

The complete picture

Pivot

Layers 1&3

Pivot

Layers 2&4

Confirm

Layers 1&3

Confirm

Layers 2&4


In real l ife

In real life

  • Pad size is a compromise between :

    • Number of channels

    • Individual rate

  • Each quadruplet is built from two face-to-face doublets

    • η fuzziness achieved for free by Z

    • φ fuzziness achieved by construction

  • Typical pad height ~80 mm (~25 strips)


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