1. ATLAS RPC: Cosmic 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 Introduction R esistive Plate Chambers RPC (Ref.:2) will be used as Muon Trigger Detector in the barrel region  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 m 2. The extreme difficulty in accessing ATLAS detectors, after commissioning, imposes a High Standard Quality Assurance of the chambers. Broad Physics reach triggering with  ’s in ATLAS   Pivot RPC plane High Pt RPC plane > 20GeV Low Pt RPC plane > 6 GeV Barrel SC Toroid 3-9mT Pivot Hit Coincidence window Coincidence window  On-detector electronics  Identify  `s candidate tracks  Assign bunch crossing number  Select Region of Interest (  x  x  )  Programmable Pt thresholds  Provide  second coordinate Fig. 1: General purpose ATLAS (Ref.:1) detector at LHC (7+7TeV p-p collider) Grounded planes Bakelite Plates Foam Graphite electrodes X readout strips HV Y readout strips Gas Polycarbonate spacer Electrodes: graphite layer+ 2 mm thick bakelite (  ~ 1÷4x10 10  cm) + polymerized linseed oil. Gap gas: d = 2 mm, C 2 H 2 F 4 (94.7%)C 4 H 10 (5%)SF 6 (0.3%), HV~10 KV (E gas ~ 5KV/mm) Readout panels: X and Y copper strip (pitch ~3 cm). Ionizing particle Saturated avalanche regime. Bunch crossing ID (TW ~ ns). XY measurement (~ 1 cm). Rate Capability ~1 kHz/cm 2 @Eff.>98% Gap volume size from 1.72×0.75m 2 up to 2.96x1.2m 2. 3 Cosmic Ray teststands Needed to certify RPC’s before shipping to CERN: 1.INFN Naples site (Ref.:3): Scintillator trigger Drift Chamber tracking (400  m single wire res.) More than 500 RPC’s units tested 2.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) 3.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. Upper RPC Trigger Unit’s Lower RPC Trigger Units Up to 8 RPC units under test Iron shielding sheets Good spatial resolution of the track extrapolated on RPC under test using 4 trigger RPC. References 1.ATLAS detector and physics performance. Technical Design Report May 1999 2.R. Santonico and R. Cardarelli: Development of resistive plate counters. NIM 187, 377-380 1981. 3.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 Gas volume inefficiency about 2% due to spacers and frames dead space High efficiency > 98 %  HV 10% 90% Dark current noise rate much less than expected cavern background in typical working conditions. I(A)/N(Hz) ~ 110pC R = Ohmic part I 0 = Av. primary cluster charge/secs V/V 0 =  eff   d where  eff =  Townsend -  attachment 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 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 I leak DAQ: 4608 Front-end channels 72 Custom Receivers (INFN Roma-2) 48 5-bit Latch modules (INFN Lecce) 3 day long automatic test sequence ATLAS RPC Readout panels layout Event Display of a cosmic ray crossing the CRT from left to right  view  left view  right view Residuals distribution of RPC Under test Gas Gap Tomography IV Characteristics Noise-I Characteristics Plateau parameter spread Plateau curve W (‘)  Z (‘)  t  b , H  WW (*) or ZZ (*)  Tri-lepton SUSY signature, B  X (B-physics) Gap down Gap up  Strips left  Strips right