ATLAS RPC: Cosmic Ray Teststand at INFN Lecce

1. Bakelite Plates X readout strips Foam Y readout strips Graphite electrodes 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 Broad Physics reach triggering with m’s in ATLAS • Introduction • Resistive Plate Chambers RPC (Ref.:2) will be used as Muon Trigger Detector in the barrel region (-1< h<1) 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 Assuranceof the chambers. W(‘)®mn, Z(‘)®mm, t® bmn, H® WW(*)or ZZ(*), Tri-lepton SUSY signature, B®mmX (B-physics) m- m+ Barrel SC Toroid 3-9mT Coincidence window High Pt RPC plane > 20GeV Pivot Hit Pivot RPC plane Coincidence window Low Pt RPC plane > 6 GeV • 3 Cosmic Ray teststands • Needed to certify RPC’s before shipping to CERN: • INFN Naples site (Ref.:3): • Scintillator trigger • Drift Chamber tracking (400 mm single wire res.) • More than 500 RPC’s 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 m`s candidate tracks • Assign bunch crossing number • Select Region of Interest (DhxDf=0.1x0.1) • Programmable Pt thresholds • Provide f second coordinate Fig. 1: General purpose ATLAS (Ref.:1) detector at LHC (7+7TeV 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@Eff.>98% • Gap volume size from 1.72×0.75m2 up to 2.96x1.2m2. Polycarbonate spacer Ionizing particle • Electrodes: graphite layer+ 2 mm thick bakelite (~ 1÷4x1010 cm) + polymerized linseed oil. • Gap gas: d = 2 mm, C2H2F4(94.7%)C4H10(5%)SF6(0.3%), HV~10 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 Unit’s 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/V0=aeff·d where aeff= aTownsend-hattachment Lower RPC Trigger Units Iron shielding sheets Plateau parameter spread High efficiency > 98 % DHV10%90% h left view f 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