ATLAS%20RPC:%20Cosmic%20Ray%20Teststand%20at%20INFN%20Lecce

1
ATLAS RPCCosmic Ray Teststand at INFN Lecce
G. Chiodini, M. Bianco, E. Brambilla, G. Cataldi,
R. Coluccia, P. Creti, G. Fiore, R. Gerardi, E.
Gorini, F. Grancagnolo, A. Miccoli, R. Perrino,
S. Podkladkin, M. Primavera, S. Spagnolo, G.
Tassielli and A. Ventura. INFN Lecce
via Arnesano 73100 - Italy
Broad Physics reach triggering with ms in ATLAS

• Introduction
• Resistive Plate Chambers RPC (Ref.2) will be
  used as Muon Trigger Detector in the barrel
  region (-1lt hlt1) of the ATLAS experiment at LHC
  (Fig. 1).
• A total number of 1116 RPC units will be
  installed, covering a total surface of about 3800
  m2.
• The extreme difficulty in accessing ATLAS
  detectors, after commissioning, imposes a High
  Standard Quality Assurance of the chambers.

W()mn, Z()mm, t bmn, H WW()or ZZ(),
Tri-lepton SUSY signature, BmmX (B-physics)
m-
m
Barrel SC Toroid 3-9mT
Coincidence window
High Pt RPC plane gt 20GeV
Pivot Hit
Pivot RPC plane
Coincidence window
Low Pt RPC plane gt 6 GeV

• 3 Cosmic Ray teststands
• Needed to certify RPCs before shipping to CERN
• INFN Naples site (Ref.3)
• Scintillator trigger
• Drift Chamber tracking (400 mm single wire res.)
• More than 500 RPCs units tested
• INFN Lecce site
• Trigger and tracking by tested ATLAS RPC units
• Tracking resolution of projected track about 7
  mm.
• 48 ATLAS-RPC units tested and re-tested by INFN
  Naples (cross-check)
• INFN Roma site
• Trigger and tracking by tested ATLAS RPC units
• Capable of testing the largest size RPC units
  (BOL)
• Tens of BOL units tested.

• On-detector electronics
• Identify ms candidate tracks
• Assign bunch crossing number
• Select Region of Interest (DhxDf0.1x0.1)
• Programmable Pt thresholds
• Provide f second coordinate

Fig. 1 General purpose ATLAS (Ref.1) detector
at LHC (77TeV p-p collider)
ATLAS RPC
Readout panels layout
Grounded planes
Gas
HV

• Saturated avalanche regime.
• Bunch crossing ID (TW ns).
• XY measurement ( 1 cm).
• Rate Capability 1 kHz/cm2_at_Eff.gt98
• Gap volume size from 1.720.75m2 up to
  2.96x1.2m2.

Polycarbonate spacer
Ionizing particle

• Electrodes graphite layer 2 mm thick bakelite
  (? 14x1010 ?cm) polymerized linseed oil.
• Gap gas d 2 mm, C2H2F4(94.7)C4H10(5)SF6(0.3
  ), HV10 KV (Egas 5KV/mm)
• Readout panels X and Y copper strip (pitch 3
  cm).

• CRT at INFN Lecce
• Labview based software
• Detector Control System
• T, P, and RH environmental t
• 16 Dp monitored gas line
• 48 independent HV, Vth, and Ileak
• DAQ
• 4608 Front-end channels
• 72 Custom Receivers (INFN Roma-2)
• 48 5-bit Latch modules (INFN Lecce)
• 3 day long automatic test sequence

IV Characteristics

• QUALITY CONTROL TESTS
• Gas volume leak test
• Dead and noisy channel maps
• V-I characteristics
• Efficiency curve
• Front-end voltage threshold scans
• Efficiency and noise rate maps

Upper RPC Trigger Units
Up to 8 RPC units under test
Noise-I Characteristics
I(A)/N(Hz) 110pC
Dark current noise rate much less than expected
cavern background in typical working conditions.

• R Ohmic part
• I0 Av. primary cluster charge/secs
• V/V0aeff d where aeff aTownsend-hattachment

Lower RPC Trigger Units
Iron shielding sheets
Plateau parameter spread
High efficiency gt 98
DHV1090
f view
h left view
h right view
Plateau curve
Event Display of a cosmic ray crossing the CRT
from left to right
Gas Gap Tomography
Gas volume inefficiency about 2 due to spacers
and frames dead space

• References
• ATLAS detector and physics performance.
  Technical Design Report May 1999
• R. Santonico and R. Cardarelli Development of
  resistive plate counters. NIM 187, 377-380 1981.
• M. Alviggi et al., First results of the cosmic
  ray test of the RPC of the ATLAS muon
  spectrometer at LHC. NIM A518,79-81 2004

Residuals distributionof RPC Under test
f-h Strips right
f-h Strips left
Gap down
Good spatial resolution of the track extrapolated
on RPC under test using 4 trigger RPC.
Gap up