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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