VCI, 21. 2. 2001 1 1 Werner Riegler RPCs RPCs and Wire Chambers and Wire Chambers for the for the LHCb Muon LHCb Muon System System u u Overview Overview u u Principles Principles u u Performance Comparison: Performance Comparison: Timing, Efficiency, Timing, Efficiency, Crosstalk Crosstalk u u Conclusion Conclusion Werner Riegler, CERN
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RPCs and Wire Chambers for the LHCb Muon System · VCI, 21. 2. 2001 Werner Riegler 1 RPCs and Wire Chambers for the LHCb Muon System Overview Principles Performance Comparison: Timing,
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VCI, 21. 2. 2001
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RPCsRPCs and Wire Chambers and Wire Chambersfor the for the LHCb MuonLHCb Muon System System
�� CMS RPC chip: few CMS RPC chip: few nsnsrise-timerise-time
�� ‘Amplifier should have the‘Amplifier should have thesame rise-time as the RPCsame rise-time as the RPCsignal in order to fully exploitsignal in order to fully exploitthe intrinsic timing of thethe intrinsic timing of thedetector’detector’
RPC MWPC
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ElectronicsElectronics
Time r.m.s. for different preamp peaking times
RPC MWPC
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Direct Induction Direct Induction CrosstalkCrosstalk
�� For a 2.5cm strip the cluster size is For a 2.5cm strip the cluster size is ��1.2 from direct induction1.2 from direct induction(at our working point)(at our working point)
RPC MWPC
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ElectricalElectrical Crosstalk Crosstalk
�� Inhomogeneous Inhomogeneous lossless lossless N-conductor transmission lineN-conductor transmission line�� Completely defined by capacitance and inductance matrix (Completely defined by capacitance and inductance matrix (NxNNxN))
which can be calculated with MAXWELLwhich can be calculated with MAXWELL
RPC MWPC
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ElectricalElectrical Crosstalk Crosstalk
�� N different velocitiesN different velocities(modal dispersion)(modal dispersion)
�� For termination weFor termination wetheoretically need 0.5N(N+1)theoretically need 0.5N(N+1)termination resistorstermination resistors
�� Crosstalk Crosstalk depends ondepends ondistance of the signal fromdistance of the signal frompreamppreamp
�� For long strips For long strips crosstalk crosstalk isissmaller for slow amplifierssmaller for slow amplifiers
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ElectricalElectrical Crosstalk Crosstalk
Far end: Ideal termination
Preamp End: Crosstalk is minimal for Rin = 0You do NOT want to terminate there !
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Rates+Rates+AgeingAgeing
�� �� 1kHz/cm 1kHz/cm22
�� �� 100 Gray in 10 LHC years 100 Gray in 10 LHC years�� Carbon layer ?Carbon layer ?�� Bakelite Bakelite resistivityresistivity ? ?�� Surface effects ?Surface effects ?
�� up to 100kHz/cmup to 100kHz/cm2 2 (space(spacecharge effects expected onlycharge effects expected onlyat 1MHz/cmat 1MHz/cm22))
�� �� 0.7C/cm wire in 10 LHC 0.7C/cm wire in 10 LHCyearsyears
RPC MWPC
�� Tests are ongoingTests are ongoing
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Measured Performance Measured Performance
RPC Efficiency MWPC efficiency
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ConclusionConclusion�� Single Gap Single Gap RPCs RPCs and and MWPCs MWPCs for the for the LHCbLHCb muonmuon system have been system have been
studied in detail.studied in detail.�� The intrinsic time resolution is The intrinsic time resolution is �� 1.2ns for 2mm 1.2ns for 2mm RPCs RPCs and and �� 3ns for 3ns for
5mm 5mm MPWCs MPWCs (1.5mm wire pitch).(1.5mm wire pitch).�� For high threshold, For high threshold, RPCs RPCs lose their efficiency due to small pulseslose their efficiency due to small pulses
while while MWPCs MWPCs lose their efficiency due to decreasing time resolution.lose their efficiency due to decreasing time resolution.
�� Apart from avalanche saturation effects the detectors can be simulatedApart from avalanche saturation effects the detectors can be simulatedvery well in every detail (gas, signals, very well in every detail (gas, signals, crosstalkcrosstalk …) …)
�� Measurements and simulations agree well on the 10-20% level - Measurements and simulations agree well on the 10-20% level -we have a ‘clue’ what we are doing.we have a ‘clue’ what we are doing.
�� Double RPC layers and 4xMWPC layers fulfill the requirements for theDouble RPC layers and 4xMWPC layers fulfill the requirements for theLHCb muon LHCb muon system.system.
�� The crucial issue will be the long term stability of the system ….The crucial issue will be the long term stability of the system ….