The LHCb Muon System Simone Brusa INFN Ferrara
The LHCb Muon System Simone Brusa / INFN – Ferrara On behalf of LHCb muon group: CAGLIARI, CBPF, CERN, LNF, FERRARA, FIRENZE, PNPI, POTENZA, ROMA II Outline: • • • The LHCb Muon Detector Requirements MWPC & Triple-GEM description Tests & Results Present status Conclusions 10 th International Conference on Advanced Technology and Particle Physics Villa Olmo, Como 8 -12 October 2007
The LHCb experiment Dedicated to the study of CP symmetry violation of b decays Simone Brusa 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 2
2007 © S. Kubrick 2001 3
The LHCb Muon Detector • 5 muon stations, one upstream (M 1), 4 downstream (M 2 -M 5) the calorimeters • Each station is divided in 4 Radial Regions R 1, R 2, R 3, R 4 • 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 Calorimeters Tracker RICH-2 Muon Detectors Iron Filters Magnet 10 m 5 m RICH-1 Vertex Locator 1. 5 m 5 Muon Stations Simone Brusa 0. 5 m Here Station M 5 Region 4 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 4
• 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 m 2 • 12 triple GEM detectors for the highest rate region (M 1 R 1) area ~ 0. 6 m 2 but 20% of triggering muons– challenging for ageing, rate and time resolution Chamber Simone Brusa 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 5
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 mb @14 Te. V, a very specialized trigger is mandatory The L 0 muon system trigger must provide the transverse momentum (pt) for muons with p > 6 Ge. V/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 10 MHz Muon system HCal (visible bunch crossings) Level-0: p. T of μ, e, h, γ 1 MHz ECal HLT: Confirm level-0 Associate Pt/IP Full event reconstr. Inclusive/exclusive selections Simone Brusa 2 k. Hz Calorimeter Muon system Pile-up system L 0: custom hardware Full detector information HLT: CPU farm 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 6
Muon Identification 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 Muon. Chambers to track extrapolation Muon efficiency Muon misidentification probability Simone Brusa 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 7
Requirements • High detection efficiency (> 99%M 2 -M 5 4 -gaps, >96% M 1 2 gaps) per station in a 20 ns time window: good time resolution • Rate capability: up to ~460 k. Hz/cm 2 @ L = 5 • 1032 cm– 2 s-1 in hottest region; low space charge effect • Safe operation in 10 years @ <L> = 2 • 1032 cm– 2 s-1 radiation resistant Simone Brusa 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 8
4 wired panels + 1 cover The MWPC design The main parameter for the chambers design are : 1. Time resolution 4 -5 nsec 2. Gas gain uniformity ± 20% 3. Aging resistant → Material to be used & gas mixture Panel: poliuretanic foam (M 1, honeycomb to reduce X 0) Wires (anode) Detector GND Design specifications: • 4 gaps (2 in M 1) OR-ed (redundancy & high efficiency) • Wires: 30 µm, Au plated W • Gas: Ar/CO 2/CF 4 (40/55/5) • HV ~ 2. 6 KV • Gas Gain: 5 x 104 Simone Brusa Cathode pads 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 Guard trace 9
MWPC readout scheme • The readout scheme is based on a spatial measurements, which granularity goes from (1 x 2. 5)cm 2 to (25 x 30) cm 2. • We have: anode wire readout, cathode pads readout and mixed readout (anode wire + cathode pads) R 4: wire pad readout R 3: cathode pad readout R 1/R 2 -M 2/M 3: mixed readout Wire strip Total amount of ~126000 physical pads! Simone Brusa 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 10
MWPC production Quality Control pre-assembly 1368 MWPC → ~ 3 M wires→ 6 M 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) Gap geometry parameters Uniformity of the electric field HV test in open air (single gap) All data & plots have been recordered in dedicated database Simone Brusa 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 11
EXAMPLES OF W. P. M & W. T. M Ferrara data on 246 chambers WPM distribution: mean 1. 99 mm r. m. s. 0. 01 mm WPM, WTM on a panel WTM distribution: mean 69, 55 g r. m. s. 5. 34 g Simone Brusa 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 12
TEST ON MWPC AFTER ASSEMBLY The quality control test performed after the assembling are: 1. Gas tightness 2. HV test with nominal gas mixture 3. 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: - 0. 7*G 0 and 1. 4*G 0 in 95% of the chamber area (plateau ± 53 V); - 0. 6*G 0 and 1. 7*G 0 in 5% of the chamber area (plateau ± 83 V). M 5 R 4 Simone Brusa 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 13
MWPC Chamber & Front-End Electronics (FEE) 8000 FEE, IBM 0. 25 μm radiation tolerant technology, LHCb design The acquisition basic unit Chamber: 2 bigaps Single pad OR OR Faraday cage Spark protection board Ch A Ch B CONTROL logic SPB CONTROL 2 CARIOCAs + LVDS READOUT Ch(AB) DIALOG = FEE (CARDIAC) CARIOCA: 8 chs current-mode (Amplifier –shaper-discriminator) • signal amplification and shaping • tail cancellation • discrimination • Zin =50 ohm • ENC=2000 + 40 e- /p. F • Peaking time ~ 10 ns for Cdet = (40 ÷ 220) p. F Simone Brusa 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 I 2 C protocol 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 14
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 noise @ 3 thresholds Electronic noise acceptable up to 1 KHz @ nominal thresholds Test C: cosmics test Cosmic Acquisition Chamber: M 3 R 3 (at CERN) Threshold: 7 f. C HV: 2. 55 KV Non-uniformity: ~ 3% M 5 R 4 Simone Brusa 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 15
The Triple GEM Main specificatons: Active area 20 x 24 cm 2 192 channels per detector Gas Mixture: Ar/CO 2/CF 4 (45/15/40) Gas gain: ~ 6000 A chamber consist of Two triple-GEM OR-ed GEM detector dressing GEM foil detail GEM foil stretching Specific CARDIAC-GEM FEE board developed For more details, see M. Alfonsi‘s talk (parallel session VIII on Advance Detectors & Particle Identification) Simone Brusa 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 16
Triple GEM test & Results Before the construction several checks are performed on: Ø Panels (cathode and pad PCB): planarity ≤ 50 µm Ø GEM foil HV test: current <1 n. A @ 500 V Tests on assembled detector: Ø Gas chamber leakage: typically < 2 mbar/day Ø Gain uniformity with X-ray: < 10 % Ø Cosmics rays test Performance measured on 25 ns SPS beam : ε>96% at gain of 4000 GEM foil HV test SP Sb ea m tes t Gain uniformity Simone Brusa 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 17
MWPC PERFORMANCES : COSMIC RAYS STUDIES (I) • Studies with cosmic rays on chambers sample Roma 2, cosmics station • Trigger uses the coincidence signal from two scintillators placed above and under the chambers to be tested. 4 ns μ Simone Brusa 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 18
MWPC PERFORMANCES : STUDIES WITH COSMIC RAYS (II) Anodic pads Cathod pads q 4 gap efficiency is 99% at the operational voltage of 2. 65 KV(M 1, two gaps everywhere, >95%) q The cross talk make worse spatial resolution and give more fired channels q Cross talk estimation using the mean cluster size dimension selecting just vertical tracks q. Cluster size < 1. 1 For more details, see D. Pinci‘s talk (parallel session VIII on Advance Detectors & Particle Identification) Simone Brusa 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 19
INSTALLATION IN THE PIT M 2 -M 5 INSTALLATION COMPLETED Chamber Alignment Done on every chamber Gas Piping Simone Brusa Accuracy ~ 1 mm 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 20
Iron filter M 2 -M 5 status: a snapshot from the pit M 4 wall Simone Brusa 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 M 5 wall 21
CONCLUSIONS • All M 2 -M 5 chambers are installed (around 1100 chambers) • All M 2 -M 5 chambers succesfully tested (gas, cables, noise, HV) • Alignment of the detectors ongoing • M 1 station under istallation at the moment - MWPC M 1 & GEM test ongoing • End of the commissioning of the muon detector : april 2008 Simone Brusa 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 22
SPARES Simone Brusa 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 23
MWPC & GEM HIGH RADIATION TESTS Aging test have been performed @ ENEA Casaccia: Calliope Facility, on MWPC & GEM prototype: • Source: 60 Co (~ 1015 Bq) <Eγ> ~ 1. 25 Me. V A charge of ~ 0, 5 C/cm corresponding to 5 -8 years (MWPC: M 1 R 2, M 2 R 1), 2. 2 C/cm 2 (GEM) corresponding to 12 years of data taking @ 2 x 1032 cm-2 s-1 have been integrated. No significant effects have been detected High rate behaviour studies have been performed @ GIF on a M 3 R 3 chamber in final configuration : • Source 137 Cs & X 5 muon beam Eμ ~ 100 Ge. V The four gaps chamber reached ε 99% in 20 ns at 2. 55 k. V No visible space charge effect on efficiency & time performances up to a particle rate of 10 k. Hz cm-2 Simone Brusa 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 24
M 1 STATUS Simone Brusa 10 th International Conference on Advance Technology and Particle Physics, Villa Olmo, Como 8 -12 October 2007 25
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