The LHCb Muon SystemBurkhard Schmidt / CERNon behalf of the LHCb collaboration
LHCb Muon Group:Cagliari, CERN, Ferrara, Frascati, Marseille, PNPI,
Potenza, Roma ‘La Sapienza’, Roma ‘Tor Vergata’, UFRJ
2nd International Symposium “LHC Physics and Detectors”JINR Dubna, 28-30 June 2000
28-30 June 2000 2B. Schmidt / CERN
LHCb Muon SystemOutline:
• Introduction– Physics Goals and Requirements– Background Conditions
• Overview of the Muon System– Detector Layout– Detector Technologies
• Performance Studies• FE-electronics
– FE-chip– Electronics Architecure
• Planning and Conclusions
28-30 June 2000 3B. Schmidt / CERN
IntroductionPhysics Goals:
• The Muon system of LHCb is primarily used as an identifier- and trigger system for muons produced in the decay of B-mesons: B X ;In particular: Bd J/(+-) Ks ; Bs J/(+-) ; Bs +-
• The muon momentum is measured precisely in the tracking system; the muon chambers are used to validate the muon candidate and match it with the track of the tracking system.
Requirements:• Modest momentum resolution (~25%) for a robust PT -selective trigger• Good time resolution (few ns) for reliable bunch-crossing identification• Good muon identification
28-30 June 2000 4B. Schmidt / CERN
IntroductionBackground sources in the LHC environment:
• Primary background:- hadron punch-through including muons generated in the hadron shower- ,K X decays
• Radiation background:Photon “gas” generated via n- processes by hadrons interacting in the absorber
• Machine background:Energetic muons produced in beam-gas interactions and in machine elements upstream of the experimental area
Requirements:• High rate capability of chambers and good ageing properties of
detector components• System layout of sufficient granularity to provide a redundant muon
trigger.
28-30 June 2000 5B. Schmidt / CERN
Overview
• 5 Muon stations with 2 layers/station
• 870m2 of detector area arranged in ~1500 chambers
• Hadron Absorber of 21 thickness
• Stations M1 and M2 are used for the PT-measurement• Stations M2, M3 (trigger seed), M4 and M5 for muon track finding
M1 M2 M3 M4 M5
28-30 June 2000 6B. Schmidt / CERN
Muon Detector LayoutTP-Layout Optimized Layout
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Station 1
28-30 June 2000 7B. Schmidt / CERN
Muon Detector LayoutOptimized Layout:• Stations are subdivided in 4 regions with different pad size
-> Region- and Pad-sizes scale by factor 2• Pad dimensions scale with station number
-> Projectivity to interaction point• Physical pads in stations M2-M5 are grouped to logical strips• Due to the high occupancy in M1 strips are not possible.
-> Significant reduction of channel number:Total number of physical channels: ~150 k
(TP: ~240k) Total number of logical channels: ~ 26k(TP: ~45k)
• Required resolution in the bending plane leads to an x/y aspect ratio of 1/4 in stations M2 and M3 and 1/2 in M1
28-30 June 2000 8B. Schmidt / CERN
Particle Rates in the Muon System
M1 M2 M3 M4 M5
R 17.010-3
560 kHz2.510-4
100 kHz2.010-4
80 kHz1.210-4
48 kHz1.210-4
48 kHz
R 24.0 10-3
320 kHz1.210-4
48 kHz2.010-5
8 kHz1.010-5
4 kHz8.010-6
3.2 kHz
R 31.010-3
80 kHz4.010-5
16 kHz4.010-6
1.6 kHz3.010-6
1.2 kHz3.010-6
1.2 kHz
R43.010-4
24 kHz5.010-6
2 kHz1.010-6
400 Hz7.510-7
300 Hz3.010-6
1.2 kHz
Applied Procedure:• LHCb peak Luminosity of 51032 cm2/s has been assumed• Estimation based on MARS as simulation package • Safety factor of 2.5 has been applied for M2-M5 and 2 for M1
dN/dA /cm2/int Required Rate Capability
Three areas can be distinguished:I) Rate 100 KHz II) 100 kHz Rate 1Khz III) Rate 1kHz
28-30 June 2000 9B. Schmidt / CERN
Muon System TechnologiesTechnology Choice:• In the outer part of M4 and M5 a technology with moderate rate capability can be used -> RPC
– covers 48% of muon system • For most of the regions MWPC with anode wire and/or cathode pad readout are the optimal
solution – covers 52% of the total area
• No technology has been chosen yet for the inner part of station 1– integrated charge in 108s in a MWPC would be ~ 2-5 C/cm– area size corresponds to < 1% of total muon system
M1 M2 M3 M4 M5R 1 ? MWPC MWPC MWPC MWPCR 2 ? MWPC MWPC MWPC MWPCR 3 MWPC MWPC MWPC RPC RPCR 4 MWPC MWPC MWPC RPC RPC
28-30 June 2000 10B. Schmidt / CERN
RPC Detector: OverviewCharacteristics:• Provides excellent timing (time resolution < 2ns) • Robust and flexible: electrodes and detector are independent
several configurations possible (single-, double-gap) • Cheap and simple to construct -> Produced in Industry Requirements:• Rate capability: 1.2 kHz/cm2
-> Avalanche mode operation with C2H2F4/C4H10/SF6 95/4/1 gas mixture-> Use low-resistive Bakelite ( < 1010 Ohm cm )
• Redundant spatial efficiency: > 99% / station -> Use two gaps (DRPC or OR-ed SRPC)
• Average cluster size < 1.2 strips (M3) and < 2 strips in M4/M5 • Max. radiation dose (10 y) 100 Gy
Activities: Carried out by Firenze and Roma ‘Tor Vergata’ groups
28-30 June 2000 11B. Schmidt / CERN
RPC Detector: LayoutSchematic Layout for Regions 3+4:• 1 chamber: 2 gas gaps (2 SRPC with independent FE-chips or DRPC)• Each electrode measures space points (no x-y coincidence required!)
29-31cm
Total region 3 : • 48 chambers/station• 4.6k-9.2k FE-ch./station Total region 4 : • 96-192 chambers/station• 9.2k FE-ch./station
split strips in region 3with 96-192 strips/chamber
140-150cm
28-30 June 2000 12B. Schmidt / CERN
RPC Detector: PerformanceResults from tests at the CERN PS:
• Time resolution ~1.3 ns• Full efficiency within 10 ns time window
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28-30 June 2000 13B. Schmidt / CERN
RPC Detector: Cluster SizeContributions to the Cluster Size:• direct induction -> geometrical effect, largest between strips•cross-talk SRPC -> depends on electrical characteristics of strip planes Scan over adjacent strips
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DRPC(strips less shielded)
28-30 June 2000 14B. Schmidt / CERN
RPC Detector: Performance Cluster Size Studies:
• Cluster size decreases with increasing threshold• At a given efficiency OR of two SRPC allows lower cluster size
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SRPC
Two SRPCin OR
28-30 June 2000 15B. Schmidt / CERN
RPC Detector: Rate CapabilityResults from GIF-Tests: • GIF Photon rate:
R = 740 GBq 0.85(BR) 0.5/Att. 1/4r2
• Procedure:Determine R from measured plateau curve with photons
R = 3.1 (1/Att)0.76 kHz/cm2
Calculate photon sensitivity factor
~1/800
28-30 June 2000 16B. Schmidt / CERN
RPC Detector: Rate CapabilityResults from tests at GIF:
• Gamma Irradiation Facility allows to test muon chambers under conditions comparable to those expected at the LHC.
• Test of 3 SRPC with x and y planes
->Efficiencies of >95% have been obtained at 1.8 KHz/cm2
->RPC of low resistive material show good rate capability behavior
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x-planes y-planes
28-30 June 2000 17B. Schmidt / CERN
MWPC Detector: OverviewCharacteristics:
• MWPC with anode and/or cathode readout are very well known• Integrated charge in 10 LHC years (108s) is <1 C/cm in all regions considered• MWPC operated with Ar/CO2/CF4 40/50/10 mixture has good aging properties
Requirements:• Efficiency within 20 ns time window: > 95%
-> Two gaps, staggered, 1.5mm wire spacing • Redundant spatial efficiency: > 99% /station
-> Two independent double gap chambers Activities: Carried out by PNPI (proponent), CERN, Firenze, Ferrara, Roma I (Potenza) and UFRJ groups
28-30 June 2000 18B. Schmidt / CERN
Muon Detector LayoutChamber arrangement:Frontview Sideview
28-30 June 2000 19B. Schmidt / CERN
MWPC : PerformanceTiming Properties: time distribution
Time resolution <3ns at operating point
Time resolution at 3.15kV (ASDQ) y = 0.0075x + 1.1609
0
1
2
3
4
5
6
0 100 200 300 400 500 600
Threshold (x10) (mV)
RM
S (n
s)
Time resolution
01234567
2.8 3 3.2 3.4 3.6
HV (kV)
RM
S (n
s)PNPI (4x8, Cdet=60pF)
ASDQ (2x8, Cdet=40pF)
28-30 June 2000 20B. Schmidt / CERN
MWPC: PerformanceMWPC test at CERN PS:
Gas Mixture:Ar/CO2/CF4 40/50/10FE-electronics:Custom made (SMD) peaking time ~10ns
-> Efficiency >99% within 20ns time window-> Dark count rate below < 50Hz/pad
-> plateau length:~ 400V for WPC ~ 300V for CPC
MWPC, anode wire readout (Pad size 4x16cm)
0.8
0.85
0.9
0.95
1
1.05
2.85 2.95 3.05 3.15 3.25 3.35 3.45
HV (kV)
Effi
cien
cy
0
50
100
150
Noi
se c
ount
(Hz) 50ns
25ns
20ns
15ns
noise
MWPC, cathode pad readout (Pad size 4x8cm)
0.8
0.85
0.9
0.95
1
1.05
2.85 2.95 3.05 3.15 3.25 3.35 3.45
HV (kV)
Effi
cien
cy
010203040506070
Noi
se c
ount
(Hz) 50ns
25ns
20ns
15ns
noise
28-30 June 2000 21B. Schmidt / CERN
MWPC: PerformanceHigh rate performance:• FE-chip: ASDQ (has baseline restoration)
Time resolution at 3.15kV
00.5
11.5
22.5
33.5
0 20 40 60 80 100
Intensity (kHz/cm^2)
RM
S (n
s)
Efficiency at 3.15kV
0.95
0.96
0.97
0.98
0.99
1
0 20 40 60 80 100
Intensity (kHz/cm^2)
Effi
cien
cy 25ns
20ns
15ns
-> Efficiency > 98% within 20ns time window-> No deterioration of timing properties
28-30 June 2000 22B. Schmidt / CERN
FE - Electronics FE-chip specifications:• Peaking time ~10ns• Rin: < 50 • Cdet: 10-250pF• Polarities: +/-• Rate: up to 1MHz• Dead time: < 50ns• Dose: up to 1Mrad• Sensitivity: ~10mV/fC (@Cdet =0)• Low noise . . .
( Less stringent requirements for RPC FE-chip)
->Try to find existing chip satisfying our requirements
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Inefficiency due to ASD pulse-width
28-30 June 2000 23B. Schmidt / CERN
FE - Electronics FE-chip candidates:MWPC:• PNPI SMD (only for prototype studies)• SONY ASD (Tested, radiation limit ~ 50krad, dead time ~90ns) • ASDQ (Rin = 280, requires slight modification.)
-> Performs in general very well• MINSK ASD (matches well specifications, to be tested)• CMP 16 (for anode readout of CMS-EMU-chambers, to be tested)• GaAs (to be tested) • CARIOCA (0.25 CMOS) (under development)
RPC:• GaAs (0.6 MFET) (ATLAS RPC chip, very fast, radiation hard)
-> Baseline option• Bari (0.8 BiCMOS) (CMS RPC chip)
28-30 June 2000 24B. Schmidt / CERN
FE-ArchitectureStatus: – Basic concept of the FE-Architecture has been developed– Data reduction from physical channels (~150k ) to logical channels (~26k) done in intermediate boards– Synchronization of data from the various stations (timing alignment of signals) with muons using a 3-bit TDC
-> (ASD-chip) -> digital signals (~6m)-> channel reduction, FE-control (~4m)-> Synchronization, Pipelines, Trigger interface
FE-boards
Intermediate boards
Off Detector boards
28-30 June 2000 25B. Schmidt / CERN
FE-Electronics LocationsBaseline Locations for FE-Electronics:• FE-boards with kind of ASD chip on the chambers• Intermediate boards on the sides of each station• Off detector Boards performing synchronization, Data Format+BC Id,
LO-Pipeline and L1-Buffer on the sides of each station• L0-Muon-Trigger-Electronics on the sides of station 3
28-30 June 2000 26B. Schmidt / CERN
Project Plan
Schedule: • Decision on optimized muon detector layout Jan. 2000• Choice of detector technologies Feb/May 2000• Finalization of chamber design End 2000 • Baseline choice of FE-chip End 2000 • Technical Design Report (TDR) Early 2001 • Preparation of Production lines 2001• Construction and test of muon chambers 2002-2003• Installation and commissioning of the muon system 2004
28-30 June 2000 27B. Schmidt / CERN
Conclusions Layout and Architecture:
• Optimized layout has been found, requiring less physical and logical channels
• Realistic data flow between chambers and the Trigger/DAQ System
Detector Technologies:• RPC: - Rate capability of ~ 3 kHz/cm2 has been obtained
- Time resolution of 1.3 ns with efficiency >99% in 10 ns time window• MWPC: - Chambers perform very well up to rates > 100 kHz/cm2
- Time resolution < 3 ns with efficiency > 99% in 20 ns time window - Good ageing properties for Ar/CO2/CF4 (local tests > 13C/cm)
Muon System is proceeding well towards the Technical Design Report