Status of the LHCb RPC detector Changes with respect to Note cm strips instead of 3 cm (cost optimization) All gaps same size (standardization) Sensitive area defined by graphite paint GaAs discarded in favor of CMS chip for F/E Muon Meeting - March 2001 G.C. Roma 2 Ongoing/planned tests Ageing at GIF (January } June) 6 cm strips non-oiled gaps

1500 Schematic layout for region IV (M4-M5) Strip width: 58 mm (M4) 62 mm (M5) strips/chamber 1 chamber: 2 gas gaps192 chambers/station 9216 physical channels/station Total region IV: 768 gas gaps, physical channels 310 Logical pad

1500 Schematic layout for region III (M4-M5) Strip width: 58 – 62 mm strips/chamber 1 chamber: 2 gas gaps 48 chambers/station 4608 physical channels/station Total region III : 192 gas gaps, 9216 physical channels Split Strips 310 Logical pad

RPC cross-section Muon Meeting - March Al-poly sandwich 2.HV connection 3.Gas-gap 4.Signal connectors 5.Spacing button 6.Strip planes 7.Al box

RPC construction Muon Meeting - March 2001 Chambers: 480 } 960 gas-gaps Bakelite: 960x1 m 2 Z1 week production time Resistivity measurement in factory (CMS facility) Gas-gap production: industry (GT) also first HV check Detector assembly and test: in FI and RM2 I-V characteristic of gas-gaps chamber assembly (strip planes, external panels) installation of electronics boards cosmic ray test  = (8 G 2) 10 9  cm Database

FE electronics Muon Meeting - March 2001 G.C. Roma 2 Baseline choice: CMS BiCMOS chip Technology0.8 um BiCMOS Dimensions2.9x2.6 mm Input impedance15 ohm Dynamic range20 fC - 20 pC Charge sensitivity1 mV/fC Bandwidth90 MHz Dead time50 ns Prototype board used in beam tests (8 ch) Final board will be 16 ch Region III: 6 boards/chamber } 576 boards Region IV: 3 boards/chamber } 1152 boards LVDS output

FE electronics: test setup Muon Meeting - March 2001 G.C. Roma 2

Muon Meeting - March 2001 Rms noise fC Time Jitter < 0.2 ns Channel-to-channel delay spread 0.35 ns

HV system Muon Meeting - March 2001 G.C. Roma HV and LV supplies are needed CAEN system with Distributor Boxes Each DB has 2 HV and 4 LV outputs HV: up to 12 kV/1 mA LV: 7V/1A Use 1 HV channel to power 2 gas-gaps ecah chamber will have independent supplies for the 2 gaps Plateau of gaps must match closely! x axis HV beam axis

GIF Ageing test GIF test: started Jan. 15, to be continued up to June Z 0.12 C cm -2 /month } 4 LHCb years possible in 6 months ( bad GIF duty cycle: up to now only 0.15 C cm -2 ) Muon Meeting - March 2001 G.C. Roma 2 Ageing in LHCb (with safety factors) J = 18 nA cm year fluence   = cm pC/avalanche } 1.8 C cm -2 in 10 years CMS test0.2 C cm -2 ATLAS test0.3 C cm -2

Muon Meeting - March 2001 RPC under test 1 meter A second equal RPC is monitored as a reference Both RPC were previoulsy measured on test beam. They will be measured again in April and in June to check any change in performance.  =  cm (oiled) Gas mixture: 95% C 2 H 2 F 4 4% I-C 4 H 10 1% SF 6 0.5x0.5 m 2

Muon Meeting - March 2001 G.C. Roma 2 GIF Ageing test Duty cycle about 50%

GIF Ageing test Muon Meeting - March 2001 G.C. Roma 2 Irradiated RPCReference RPC

Muon Meeting - March 2001

About oil DRPC 50x50 cm2, tested in 1999 The gaps were powered in parallel The current I is the average per gap Muon Meeting - March 2001 G.C. Roma 2 Current density: 10 nA/cm2 From physics in LHCb: expect < 18 nA/cm2 Linseed oil on bakelite improves Noise (less load on trigger) Dark current (less ageing) makes construction more critical

Muon Meeting - March 2001 Plateau from 1 kHz/cm2

Muon Meeting - March 2001 GIF Abs=1 data (oiled RPC) Dark current data (non-oiled DRPC) Note: RPC area=0.25 m 2

Effect of noise on trigger Muon Meeting - March Hz/cm 2

Oil vs. non-oil: current and noise ok without oil. However we favor a solution without oil. Milestones: by October prove that: 1.the current density can be kept below 2 nA/cm 2 (20  A /m 2 ) (extra ageing effect < 10%) 2.the noise rate can be kept below 200 Hz/cm 2 (can be handled safely by the trigger) Muon Meeting - March 2001 New melaminic bakelite plates without oil to be tested soon Conclusions Ageing: Test to be continued up to the end of the year Milestones: June and December