Cosmic ray test of RPC for the ATLAS experiment

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Cosmic ray test of RPC for the ATLAS experiment
Givi Sekhniaidze
VI Workshop on Resistive Plate Chambers and
Related Detector Coimbra 26-27 November 2001
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The Test Station
Atlas RPC
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The Test Station II

• Tracking system
• Drift chambers
• TOP BOTTOM layer 1 m2
• 2 x and 2 y plane per layer
• Resolution in track reconstruction s lt 400 mm

• Trigger
• TOP BOTTOM layer
• 1 m2 plastic scintillators per layer

The 2 module housing scintillators tracking
chamber are moved by 2 step motors automatically
during data taking
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The Trigger system
The trigger signal is delayed and then used by
DAQ to generate the COMMON STOP for the TDC
A time resolution of 1 ns is achieved
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The Drift chambers
Each chambers has 2 X layers and 2 Y layers
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The Drift velocity
Drift velocity has to be determined to have the
time to space relation. At good level of
approximation it can be considered costant over
the cell.
A very rough estimate can be given by geometrical
consideration
All events
N hit 8
N hit gt 8
d cell width
N hit lt 8
Anyway we need a better estimate
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Drift Velocity
The distribution of residuals change according to
the drift velocity used.
Two peaks appear unless the correct drift
velocity is found
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Drift Velocity
The plot of the distance between peaks versus
the drift velocity approaches a minimum for the
correct drift velocity
This autocalibration is included in the
reconstruction program
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The Tracker
One of the four layers showed a resolution lower
than the other
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The tracker
Using the other 3 layer we check the worst one
and we disantangled a misalignement of the wires
and ...
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The Tracker
... we correct it!
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What we are going to do
The station aims at testing up to eight ATLAS RPC
modules simultaneously in completly automatic
way. We can scan the all RPC surface in order to
check its uniform behaviour.
Impact points distribution of reconstructed
tracks on RPC plane.
RPC border
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What we have already done
The L3 RPC were tested in the station
Spacers clearly visible