VCI, 21. 2. 2 001 1 1 Werner Riegler RPCs and Wire Chambers RPCs and Wire Chambers for the LHCb Muon for the LHCb Muon System System Overview Overview Principles Principles Performance Comparison: Performance Comparison: Timing, Efficiency, Crosstalk Timing, Efficiency, Crosstalk Conclusion Conclusion Werner Riegler, CERN
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1 VCI, 21. 2. 2001 1Werner Riegler RPCs and Wire Chambers for the LHCb Muon System Overview Principles Performance Comparison: Timing, Efficiency,
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VCI, 21. 2. 2001
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RPCs and Wire Chambers RPCs and Wire Chambers for the LHCb Muon Systemfor the LHCb Muon System
A muon trigger is given by a A muon trigger is given by a coincidence of all 5 muon coincidence of all 5 muon stations within 25ns stations within 25ns
>99% efficiency/station >99% efficiency/station in 20ns time windowin 20ns time window
Time resolution <3nsTime resolution <3ns Up to 100kHz/cmUp to 100kHz/cm22
CMS RPC chip: few ns CMS RPC chip: few ns rise-time rise-time
‘‘Amplifier should have the Amplifier should have the same rise-time as the RPC same rise-time as the RPC signal in order to fully exploit signal in order to fully exploit the intrinsic timing of the the intrinsic timing of the detector’ 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 CrosstalkDirect Induction Crosstalk
For a 2.5cm strip the cluster size is For a 2.5cm strip the cluster size is 1.2 from direct induction (at 1.2 from direct induction (at our working point) our working point)
RPC MWPC
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Electrical CrosstalkElectrical Crosstalk
Inhomogeneous lossless N-conductor transmission lineInhomogeneous lossless N-conductor transmission line Completely defined by capacitance and inductance matrix (NxN) Completely defined by capacitance and inductance matrix (NxN)
which can be calculated with MAXWELLwhich can be calculated with MAXWELL
RPC MWPC
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Electrical CrosstalkElectrical Crosstalk
N different velocities N different velocities (modal dispersion)(modal dispersion)
For termination we For termination we theoretically need 0.5N(N+1) theoretically need 0.5N(N+1) termination resistors termination resistors
Crosstalk depends on Crosstalk depends on distance of the signal from distance of the signal from preamp preamp
For long strips crosstalk is For long strips crosstalk is smaller for slow amplifierssmaller for slow amplifiers
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Electrical CrosstalkElectrical Crosstalk
Far end: Ideal termination
Preamp End: Crosstalk is minimal for Rin = 0 You do NOT want to terminate there !
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Rates+Ageing Rates+Ageing
1kHz/cm1kHz/cm22
100 Gray in 10 LHC years100 Gray in 10 LHC years Carbon layer ?Carbon layer ? Bakelite resistivity ?Bakelite resistivity ? Surface effects ?Surface effects ?
up to 100kHz/cmup to 100kHz/cm2 2 (space (space charge effects expected only charge effects expected only at 1MHz/cmat 1MHz/cm22) )
0.7C/cm wire in 10 LHC years0.7C/cm wire in 10 LHC years
RPC MWPC
Tests are ongoingTests are ongoing
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Measured Performance Measured Performance
RPC Efficiency MWPC efficiency
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Conclusion Conclusion Single Gap RPCs and MWPCs for the LHCb muon system have been Single Gap RPCs and MWPCs for the LHCb muon system have been
studied in detail. studied in detail. The intrinsic time resolution is The intrinsic time resolution is 1.2ns for 2mm RPCs and 1.2ns for 2mm RPCs and 3ns for 3ns for
5mm MPWCs (1.5mm wire pitch).5mm MPWCs (1.5mm wire pitch). For high threshold, RPCs lose their efficiency due to small pulses For high threshold, RPCs lose their efficiency due to small pulses
while MWPCs lose their efficiency due to decreasing time resolution.while MWPCs lose their efficiency due to decreasing time resolution.
Apart from avalanche saturation effects the detectors can be simulated Apart from avalanche saturation effects the detectors can be simulated very well in every detail (gas, signals, crosstalk …)very well in every detail (gas, signals, crosstalk …)
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 the Double RPC layers and 4xMWPC layers fulfill the requirements for the LHCb muon system.LHCb muon 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 ….