Test and Performances of the RPC Trigger Chambers of the ATLAS Experiment at LHC

1
Test and Performances of the RPC Trigger
Chambers of the ATLAS Experiment at LHC

• Paolo Iengo University
  of Naples INFN Naples On behalf
  of Atlas RPC Groups

VIIth Workshop on Resistive Plate Chambers and
Related Detectors 20-22 October 2003
Clermont-Ferrand, France
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Outline

• Introduction to ATLAS
• The ATLAS RPCs
• The Test Stand in Naples
• The Test Procedure
• Examples of Test Results
• Statistical Distributions
• Few words on H8 test-beam
• Conclusions

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The ATLAS Experiment and the Muon
Spectrometer
The first station (RPC-MDT sandwich) assembled
this year at CERN
RPCs used as trigger chambers in the barrel region
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The RPCs in ATLAS

• 3 planes of RPCs 2 in the middle station, 1 in
  the outher
• 16 sectors following the 8-fold structure of the
  toroid magnet
• More than 1000 modules (Standard Special Units)
  about 3500 G.V.
• 16 different type with dimensions ranging from
  720x3200 mm2 to 1080x5090 and 1200x3680 mm2
• More than 8000 strip panels and about 370000
  strips with the corresponding read-out channels
• Huge efforts for producing and testing the ATLAS
  RPC chambers

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The RPCs of ATLAS
Grounded plane
Each unit contains 2 layers 4 gas volume (2 for
one type). 2mm gas gap, bakelite resistivity
1-4x1010 ?cm Eta and Phi read-out copper strips
panels, pitch ranging from 26.4 to 33.9 mm
Gas mixture C2H2F4
94.7 - C4H10 5 - SF6 0.3 Avalanche regime
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The RPC Production chain
Bakelite resistive plates
Panpla
Gas volumes
General Tecnica
Lecce
Support panels
Support structures
Protvino
CERN/ Protvino
Lecce
Assembled units
QA
Alcan Protvino
Lateral profiles
Napoli
Napoli
Roma 2
Roma 2
General Tecnica
Strip panels
Punching
FE equipped strips
GIGA / TriQuint
GaAs die
Assembled boards
MicroTel
FE BE Printed boards
Zener
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The Naples Test Stand (I)
A cosmic ray stand was designed and built in the
Naples laboratory in order to test the ATLAS RPCs
The stand can hosts up to 8 units simultaneusly
corresponding to more than 3000 read-out channels
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The Naples Test Stand (II)
Trigger TOP BOTTOM layers 2 x 1 m2
scintillators common stop trigger on the bottom
layer
R a c k HV BT
R a c k Gas
H V Sy 127
C A MA C
V M E
Tracking system 2 Drift Chambers 2x and 2y
planes per layer. Single wire resolution 400mm
Scintillators
Drift Chambers
PC Slow Control
PC DAQ
The 2 modules housing scintillators tracking
chambers are moved by step motors automatically
during data taking. Gas flow 4l/h per chamber
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The Test Procedure
Testing a set of chambers (8 RPCs) takes about
6-10 days

• Preliminary Operations (installing and cabling,
  flushing, leak test)
• Threshold scan (0.1 1.5 V nominal value) _at_ HV
  1 kV (Single Rate)
• HV Scan (1.0 - 10.5 kV) _at_ th 1 V n.v. (Current
  Scan)
• Threshold scan (0.1 - 1.5 V n.v.) _at_ HV 10.5 kV
  (Single Rate)
• Random Trigger _at_ HV 10.5 kV th 1 V n.v.
  (Noise measurement)
• Efficiency plateau at three different thresholds
  (0.9, 1.0, 1.1 V n.v.)
• Radiography _at_ HV 10.5 kV, th 1 V n.v.
• HV Scan (1.0 - 10.5 kV) _at_ th 1 V n.v. (Current
  Scan)
• During the test the working and environmental
  parameters (HV, gap and CAEN currents, gas flow,
  temperature, humidity, atmospheric pressure etc.)
  are continuously monitored and stored in a
  dedicated database
• HV normalized to Naples standard 1013 mbar,
  20.5 C

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Chamber Tested since Aug. 2002
Up to now more than 260 chambers (1040 GV)
tested
Upgrade to 8 chambers on the stand
Upgrade to 4 chambers on the stand
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Examples of Plateau
BMLD 12.5 K (2.5K x 5) events per fixed HV and
th
Fitted with Fermis function
V0 is the HV at 50 of maximum efficiency A ?V
4 ln81/B is the difference between HV at 90 and
10 of maximum efficiency
Cluster Multiplicity Cluster Size
HV(V)
HV(V)
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Plateau Statistics
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Single and Random Rates
Mean uncorrelated activity of the chamber lt 10
Hz/cm2
Single Rate vs (-Th) Physical Th.
(1.5 - Th)/A lt 10 Hz/cm2 for
tipical working conditions
Single rate vs HV
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Radiography
BML-D 1.25 M (250K x 5) events per fixed HV and
threshold.
Inefficiency of gas volume (not ? neither ?)
Measured inefficiencies (2) correspond to
spacers and frames.
DEAD FE CARD
BAD GAP
Electronic Inefficiency (? yes ? no and
viceversa). Useful to find out readout channels
with problems
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Radiography Statistics (I)
Gas Volume Efficiency Distribution for 504 GV
Gas volume efficiencies obtained with radiography
for BML-D chambers More than 90 of G.V. have
efficiency above 97
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Radiography Statistics (II)
Read-out elx efficiency
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Currents Scan
Fitted with function I abV
I0exp(V/k)
Current _at_ HV10.5 kV for more than 300 G.V.
BAD CURRENT
Gas Volume rejected having too high current
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Test Production DB
Statistical distributions are consultable on the
production DB http//pcatlas2.na.infn.it
All the results are available on the ATLAS Naples
web page http//lxatlas.na.infn.it
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Test in H8
8 BML-D chambers ( 4 BOL-B) tested in Naples
were installed in the H8 test-beam area at CERN
where the first integrated test of MDTRPCLVL1
Trigger Logic and read-out was performed using a
muon beam from the SPS machine
Chamber BML-D 008 in H8 (Eta strips)
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Conclusions

• A complete C. R. test stand was built up in the
  Naples laboratory to test the ATLAS RPCs
• The test is going on at a rate of about 8
  chambers per week
• Up to now 260 standard chambers have been tested
  (over more than 1000, but soon two more test site
  will be available)
• The test procedure allows to certificate each
  chamber analyzing all its working parameters (gas
  volume efficiency, electronics, currents, plateau
  etc). A chamber is accepted only if it does
  satisfy all the Quality Assurance criteria. All
  test results are available on the web
  http//lxatlas.na.infn.it with overall
  statistics on the production DB
  http//pcatlas2.na.infn.it together with the
  detailed infos on ATLAS RPC
• Statistical distributions show good efficiency
  for both the gas volume and the read-out chain
• After the test the chambers are sent to CERN
  ready to be assembled and installed
• During the summer the first integrated test-beam
  was performed in H8, confirming the good
  efficiency and detector performances measured in
  a completely different environment on the Naples
  test stand and after traveling to CERN