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The BaBar Muon System Upgrade

Wolfgang MengesQueen Mary, University of London

On behalf of the BaBar LST Group

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The BaBar LST Group

M. Andreotti, D. Bettoni, R. Calabrese, V. Carassiti, G. Cibinetto, A. Cotta Ramusino, N. Gagliardi, M. Negrini, L. Piemontese, V. SantoroUniversita di Ferrara and INFN

P. PatteriLaboratori Nazionali di Frascati dell’INFN

R. Capra, M. Lo Vetere, S. Minutoli, P. Musico, E. Robutti, S. TosiUniversita di Genova and INFN C. Simani, D. Lange, C-S Cheng

Lawrence Livermore National LaboratoryY. Zheng

Massachusetts Institute of TechnologyT. Allmendinger, G. Benelli, M. Gee, L. Corwin, K.Honscheid, R. Kass, R. King, J. Regensburger, C. Rush, S. Smith, Q. Wong

Ohio State UniversityC. Fanin, M. Morandin, M. Posocco, M. Rotondo, R. Stroili

Universita di Padova and INFNR. Covarelli

Universita di Perugia and INFNW. Menges

Queen Mary, University of LondonJ. Biesiada, G-L. Cavoto, N. Danielson, R. Fernholz, Y. Lau, C. Lu, J. Olsen, W. Sands, A.J.S. Smith, A. Telnov

Princeton UniversityB. Fulsom

University of British ColumbiaT. M. Hong

University of California at Santa BabaraS. Chen, J. Zhang

University of ColoradoD. Warner

Colorado State UniversityP.Trapani

TorinoM. Lu, N. Sinev, J. Strube

University of OregonS. Morganti , G Piredda, C. Voena

Universita di Roma La Sapienza and INFNH.P. Paar

University of California at San DiegoR. Boyce , M. R. Convery, P. Kim, J. Krebs , R. Messner, M. Olson , R. Schindler, S. Swain, T. Weber , W. Wisniewski, C. Young

Stanford Linear Accelerator Center

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The BaBar Detector

Problems with RPCs:-> upgrade forward system-> replace barrel system with

Limited Streamer Tubes

Single Layer Efficiency:

Initial technology for muon system was Resistive Plate Chambers.

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The BaBar Muon System

Problems with RPCs:-> upgrade forward system-> replace barrel system with 2002 project start

Limited Streamer Tubes 2004 1st installation phase

2006 2ndinstallation phase

Forward System

Backward System

Barrel System

• 12 layers of detector

• 6 layers of brass• 1 layer not used

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LSTs were choosen as replacement:-> robust and simple technology-> time / resource constraints-> successful history (SLD, ZEUS, LEP experiments)

Limited Streamer Tubes

Main components: coordinate -> tube z coordinate -> z-plane

Other components:

• gas system

• HV system

• signal readout

Physical principle is simple:-> single wire in a cell

(gas filled, on HV)

-> charged particle ionises gas

-> streamer build up

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Limited Streamer Tubes

•tubes consist of 7 or 8 cells•cell dimensions: 15 mm x 17mm x ~4m•consists of gold-plated anode wire and

graphite-painted PVC walls (cathode)

•enclosed in PVC sleeve•endcaps include HV / gas connections•4 signal channels per tube

15 mm

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Z-planes

Solder joints need monitoring before

and after installation.

(a few broken joints)

Vacuum laminated Mylar planes:-> 35 mm wide copper strips-> 2 mm wide gaps-> 96 channels bundled to 6

cables

Solder joints

~3.8m

~4m

Flat cables for signal readout

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Quality Control

Rigorous QC is mandatory at all production stages

for an excellent performance of the detector!

QC station at SLAC

1275 tubes under long term testing for 2nd installation

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Quality Control: Scan Test

Quality Tests:•resistance•capacitance•gas leaks•source scan •HV conditioning•singles rates

•scan tube with radioactive source

•tube current should be ~1 A

•repair or reject failed tubes (open tube in clean room)

Continuous

discharge

Source removed

6 wire holder

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Quality Tests:•resistance•capacitance•gas leaks•Source scan•HV conditioning•singles rates

Burn-in Process

Quality Control: HV

Operation at 5500V

Plateau

60004600 HV (V)

Counts

/10

0s

3000

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Installation Summer 2004

18 empty layers

z-planes

tubes

12 layers of

LSTs

6 layers of brass

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Gas System

0 1 2 3 4 5 6

7

7.5

8

8.5

9

9.5

10

Flammable Boundary (9.7% isobutane at 0% argon)Runnable Boundary (9.41 % isobutane at 0% argon)Target Mix (8.0% isobutane, 3.0% argon)Try 1Try 2

Per Cent Argon

%CO2=100-%Ar-%Isobutane

Gas Mixture:CO2/Ar/

Isobutane89% / 3% / 8%

Digital Bubbler

Design goals:• non flammable• good quenching

properties -> no secondary

streamers

Gas Mixer

Mass Flow Controllers

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HV System

Custom-built power supplies:• operation range: 0V - 6000V• over-current protections starts at ~3 A,

protection circuit per channel • four independent groups a 20 channels,

each HV channel split into 4 pins -> 4000 HV cables

• 7 PS installed

Custom-built HV cables:• 24 km of multi-conductor Kerpen cable• two parts: (custom-inline connector)

– short-haul at tube– long-haul at power supply

Design goal: high granularity

easy access

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Front End Electronics

New front end electronics have been developed:

• common mother board for wires and strips

• different daughter boards for signal

-> simple components

Front end cards are located in near vicinity of the BaBar detector.

Signals are amplified, discriminated and put into the BaBar DAQ system.

4 daughter boards

Mother board

Analog in

Digital out

Strips

Wire

Raw Signals

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Data Taking

Run 5

Run 5 started March 2005

-> 60 fb-1 collected until Oct 05

-> 250 fb-1 expected by summer 05

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lower sextant

Monitoring: Wires and Strips

Installed LST tubes:-> 388 tubes - 1552 phi channels

-> excellent performance-> monthly testing with Single Rates-> problems with 5 channels < 0.4 %

Installed Z-planes: -> 24 Z-planes - 2284 strip channels -> 5 dead strips < 0.3% -> bad solder joints

Running since October 2004!Layer

Layer

Strips for upper sextant

ChannelChannel

.Dead strip

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Efficiency

Average wire efficiency

Average strip efficiency

Time

•average efficiency per layer ~90%

•geometrical efficiency 92.5%

•wire and strip performance excellent

•efficiency stable over time

Time

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RPCs

LSTs

Impact on Physics

Use muon selection for performance check:

• neural network based selector

-> first year with LSTs is better performing than first year with RPCs

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Summary

The installation in summer 2004 was a success!

• the installed components are working well– > 99.6% of the wire channels are working– > 99.7% of the z-strips are working– muon selection efficiency is better than ever

• quality control is essential for this– Tubes: source scan, HV conditioning, singles rate– Z-planes: capacitance measurement

• tubes and z-planes ready for 2nd Phase of installation in 2006