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ATLAS RPC: ATLAS RPC: Cosmic Ray Teststand at INFN Cosmic Ray Teststand at INFN Lecce 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 Resistive 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 (xx) 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 electrod es 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 % % 90 % 10 % 50 @ 1 ) ( HV HV HV Plateau a Eff HV Eff HV 10% 90% Dark current noise rate much less than expected cavern background in typical working conditions. I(A)/ N(Hz) ~ 110pC 0 0 V V e I R V I • 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 P l a t e a u c u r v e W (‘) Z (‘) t b, H WW (*) or ZZ (*) Tri-lepton SUSY signature, BX (B-physics) Gap down Gap up Strips left Strips right
