1. Simone Brusa / INFN – Ferrara On behalf of LHCb muon group:
The LHCb Muon System
Simone Brusa / INFN – Ferrara
On behalf of LHCb muon group:
CAGLIARI, CBPF, CERN, LNF, FERRARA, FIRENZE, PNPI, POTENZA, ROMA I, ROMA II
Outline:
The LHCb Muon Detector
Detector Requirements
MWPC & Triple-GEM description
Tests & Results
Present status
Conclusions
10th International Conference on Advanced Technology and Particle Physics
Villa Olmo, Como 8-12 October 2007

2. The LHCb experiment
Dedicated to the study of CP symmetry violation of b decays
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

3. 2007
© S.Kubrick
2001

4. The LHCb Muon Detector 10m 5m 0.5m  Here Station M5 Region 4
5 muon stations, one upstream (M1), 4 downstream (M2-M5) the calorimeters
Each station is divided in 4 Radial Regions R1,R2,R3,R4
The muon detector must provide Pt information to the Level-0 muon trigger through a coincidence of hits in all five stations within the bunch crossing time of 25 ns
It also provides, the muon identification for the high-level trigger (HLT) and off-line analisys
5 Muon Stations
Calorimeters
Tracker
RICH-2
Vertex Locator
Magnet
RICH-1
Muon Detectors
Iron Filters
10m 5m
0.5m
1.5m
 Here Station M5 Region 4
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

5. • Granularity shaped according to particle density & Dimensions scales according to a pointing geometry
• 20 different chamber dimensions for a total of 1368 MWPC chambers, ~ 435 m2
• 12 triple GEM detectors for the highest rate region (M1R1) area ~ 0.6 m2 but 20% of triggering muons– challenging for ageing, rate and time resolution
 Chamber
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

6. (visible bunch crossings)
Muon System Trigger
As the experiment is dedicated to b physics whose cross section is only 0.5 mb over a total pp cross section of 100 TeV, a very specialized trigger is mandatory
The L0 muon system trigger must provide the transverse momentum (pt) for muons with p > 6 GeV/C,searches for hits defining a straight line through the five muon stations and pointing towards the interaction point. The position of a track in the first two stations allows the determination of pt.
The muon stand-alone momentum measurements gives an accuracy δpt /pt ~ 20%.
SEED STATION
HCal
ECal
Muon system
10 MHz
(visible bunch crossings)
Level-0:
pT of
μ, e, h, γ
Calorimeter
Muon system
Pile-up system
1 MHz
HLT:
Confirm level-0
Associate Pt/IP
Full event reconstr.
Inclusive/exclusive
selections
Full detector
information
2 kHz
L0: custom hardware
HLT: CPU farm
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

7. Muon Identification Main discriminant variable for μ/π/K separation:
Muon ID is crucial because many of the key channels for CP violation measurements are muonic and semileptonic and because very efficient single muon identification is one of the trigger system requirements
Main discriminant variable for μ/π/K separation:
distance of the closest hit in the MuonChambers to track extrapolation
Muon efficiency
Muon misidentification probability
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

8. Requirements
High detection efficiency (> 99%M2-M5 4-gaps, >96% M1
2 gaps) per station in a 20 ns time window:
good time resolution
Rate capability:
up to ~460 L = 5•1032 cm–2 s-1 in hottest region;
low space charge effect
Safe operation in 10 <L> = 2•1032 cm–2 s-1
radiation resistant
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

9. The MWPC design 4 wired panels + 1 cover Design specifications:
The main parameter for the chambers design are :
Time resolution 4-5 nsec
Gas gain uniformity ±20%
Aging resistant → Material to be used & gas mixture
4 wired panels + 1 cover
Panel:
poliuretanic foam
(M1,honeycomb to reduce X0)
Wires (anode)
Detector GND
Design specifications:
4 gaps (2 in M1) OR-ed (redundancy & high efficiency)
Wires: 30 µm,Au plated W
Gas:Ar/CO2/CF4 (40/55/5)
HV ~ 2.6 KV
Gas Gain: 5x104
Cathode pads
Guard trace
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

10. MWPC readout scheme
The readout scheme is based on a spatial measurements, which granularity goes from (1x2.5)cm2 to (25x30) cm2.
We have: anode wire readout, cathode pads readout and mixed readout (anode wire + cathode pads)
R4: wire pad readout
R3: cathode pad readout
R1/R2-M2/M3: mixed readout
To keep noise & dead time of FE acceptable,we need of smallest pads than spatial resolution needs.
The Logical Pads are then reconstructed by the coincidence of two crossing strips.
Wire strip
Total amount of ~ physical pads!
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

11. MWPC production Quality Control pre-assembly
1368 MWPC → ~ 3M wires→ 6M of soldered pads
6 production centers: INFN Frascati Ferrara Firenze, CERN,
PNPI I-II
Need of automatic processing as: wiring, gluing, soldering,
assembling (developed in each production centers)
Quality control during the production on all components:
Panels thickness and planarity
Wire Pitch Measurements (WPM)
Wire Tension Measurements (WTM)
HV test in open air (single gap)
All data & plots have been recordered in dedicated database
Gap geometry parameters
Uniformity of the electric field
Simone Brusa
10th International Conference on Advance Technology and Particle Physics,
Villa Olmo, Como 8-12 October 2007

12. Ferrara data on 246 chambers
EXAMPLES OF W.P.M & W.T.M
WPM distribution: mean 1.99 mm
r.m.s. 0.01mm
WPM,WTM on a panel
Ferrara data on 246 chambers
WTM distribution: mean 69,55 g
r.m.s g
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

13. TEST ON MWPC AFTER ASSEMBLY
The quality control test performed after the assembling are:
Gas tightness
HV test with nominal gas mixture
Gas gain uniformity :
automatic system to scan all chambers with source
The specifications for a single gap were defined such as the gas gain is within:
*G0 and 1.4*G0 in 95% of the chamber area (plateau ±53V);
*G0 and 1.7*G0 in 5% of the chamber area (plateau ±83V).
From test beams: plateau width ~150V for 4-gap
Lower limit ε>99% (2.55 KV), upper limit cluster size <1.2 (2.7 KV)
G0 average value KV.
working point at ~2620 KV
M5R4
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

14. 8000 FEE, IBM 0.25 μm radiation tolerant technology, LHCb design
MWPC Chamber & Front-End Electronics (FEE)
8000 FEE, IBM 0.25 μm radiation tolerant technology, LHCb design
The acquisition basic unit
Faraday cage
Chamber: 2 bigaps
Spark protection board
Single pad
Ch A OR
LVDS
READOUT
Ch(AB)
CONTROL
LVDS READOUT
SPB
logic
Ch B OR
CONTROL
2 CARIOCAs DIALOG
= FEE (CARDIAC)
CARIOCA: 8 chs current-mode
(Amplifier –shaper-discriminator)
signal amplification and shaping
tail cancellation
discrimination
Zin =50 ohm
ENC= e- /pF
Peaking time ~ 10 ns for Cdet = (40 ÷ 220) pF
DIALOG: 16 chs control chip
8-bits DACs for threshold setting
width and delay adjustment
masking
24-bits scaler
pulse injection feature
access via LVDS-based I2C protocol
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

15. Several tests performed at LNF, CERN and in the PIT
MWPC Chamber Electronics tests
Several tests performed at LNF, CERN and in the PIT
Two tests are performed before the installation:
Test A: check cabling, dead-open channels, short circuit, check 3 thresholds
Electronic noise acceptable up to nominal thresholds
Test C: cosmics test
Cosmic Acquisition
Chamber: M3R3 (at CERN)
Threshold: 7 fC
HV: 2.55KV
Non-uniformity: ~ 3%
M5R4
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

16. The Triple GEM GEM detector Main specificatons: Active area 20x24 cm2
192 channels per detector
Gas Mixture: Ar/CO2/CF4 (45/15/40)
Gas gain: ~ 6000
A chamber consist of Two triple-GEM OR-ed
GEM detector
GEM detector dressing
GEM foil stretching
GEM foil detail
Specific CARDIAC-GEM FEE board developed
For more details, see M. Alfonsi‘s talk (parallel session VIII on Advance Detectors & Particle Identification)
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

17. Triple GEM test & Results
Before the construction several checks are performed on:
Panels (cathode and pad PCB): planarity ≤ 50 µm
GEM foil HV test: current <1 500V
Tests on assembled detector:
Gas chamber leakage: typically < 2 mbar/day
Gain uniformity with X-ray: < 10 %
Cosmics rays test
Performance measured on 25 ns SPS beam : ε>96% at gain of 4000
GEM foil HV test
SPS beam test
Gain uniformity
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

18. MWPC PERFORMANCES : COSMIC RAYS STUDIES (I)
Studies with cosmic rays on chambers sample
Trigger uses the coincidence signal from two scintillators placed above and under the chambers to be tested.
Roma2, cosmics station
4 ns μ
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

19. MWPC PERFORMANCES : STUDIES WITH COSMIC RAYS (II)
Anodic pads
Cathod pads
4 gap efficiency is 99% at the operational voltage of 2.65 KV(M1, two gaps everywhere,>95%)
The cross talk make worse spatial resolution and give more fired channels
Cross talk estimation using the mean cluster size dimension selecting just vertical tracks
Cluster size < 1.1
For more details, see D. Pinci‘s talk (parallel session VIII on Advance Detectors & Particle Identification)
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

20. INSTALLATION IN THE PIT M2-M5 INSTALLATION COMPLETED
Chamber Alignment
Done on every chamber
Accuracy ~ 1 mm
Gas Piping
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

21. M2-M5 status: a snapshot from the pit
Iron filter
M5 wall
M4 wall
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

22. CONCLUSIONS All M2-M5 chambers are installed (around 1100 chambers)
All M2-M5 chambers succesfully tested (gas, cables, noise, HV)
Alignment of the detectors ongoing
M1 station under istallation at the moment
- MWPC M1 & GEM test ongoing
End of the commissioning of the muon detector : april 2008
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

23. SPARES
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

24. MWPC & GEM HIGH RADIATION TESTS
Aging test have been ENEA Casaccia: Calliope Facility, on MWPC & GEM prototype:
Source: 60Co (~ 1015 Bq) <Eγ> ~ 1.25 MeV
A charge of ~ 0,5 C/cm corresponding to 5-8 years (MWPC: M1R2,M2R1), 2.2 C/cm2 (GEM) corresponding to 12 years of data 2 x 1032 cm-2 s-1 have been integrated.
No significant effects have been detected
High rate behaviour studies have been GIF
on a M3R3 chamber in final configuration :
Source 137Cs & X5 muon beam Eμ ~ 100 GeV
Casaccia at double nominal gain
The four gaps chamber reached ε 99% in 20 ns at 2.55 kV
No visible space charge effect on efficiency & time performances up to a particle rate of 10 kHz cm-2
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007

25. M1 STATUS
Simone Brusa
10th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8-12 October 2007