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RICH meeting, 3.11.99 F.Muheim 1
Proposal for MAPMTs as Proposal for MAPMTs as Photodetectors for the Photodetectors for the
LHCb RICHLHCb RICH
Proposal for MAPMTs as Proposal for MAPMTs as Photodetectors for the Photodetectors for the
LHCb RICHLHCb RICH
Franz Muheim
University of Edinburgh
on behalf of the MAPMT group
RICH meeting, 3.11.99 F.Muheim 2
OutlineOutline
Introduction Multianode Photo Multiplier Tubes R&D Results Baseline Design Conclusion
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Photo Detector RequirementsPhoto Detector Requirements
Single photon sensitivity (200 - 600 nm) with quantum efficiency > 20%
Good granularity: ~ 2.5 x 2.5 mm2
Large active area fraction: 73% LHC speed read-out: 40 MHz
Photo detector area: 2.9 m2
Options: MAPMT or HPD
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MAPMT MAPMT
Combines single photon sensitivity with good spatial resolution
8x8 dynode chains Gain: 3.105 at 800 V
Manufacturer: Hamamatsu 1 mm flange removed,
packing fraction increases by 14 %
Multianode Photo Multiplier Tube
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MAPMT R7600-03-M64MAPMT R7600-03-M64
Bialkali photo cathode, QE = 22% at = 400 nm
UV glass window replaces borosilicate, QE dE increased by 50 %
Quantum efficiency
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Quartz LensesQuartz Lenses MAPMT active area fraction:
38% (includes pixel gap) Increase with quartz lens
with one flat and one curved surface to 85%
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Bench Tests Bench Tests
Collection efficiency not very uniform (~20%)
Gap between pixels: 0.2 mm
40 MHz read-out electronics Average signal/ pedestal width = 40:1 Signal loss: 11.5 % (includes 2.5% for
no multiplication at 1st dynode)
Pixel scan with LED Single channel spectrum (LED)
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Test Beam Set-up Test Beam Set-up
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Single MAPMT Test BeamSingle MAPMT Test Beam
Air radiatorLensPressure
Run 2059Yes
49 mbar
Run 2057No
49 mbar
Run 2042Yes
960 mbar
Run 2039No
960 mbarNumber ofdetectedphotoelectrons
DataSimulation
0.300.29
0.320.32
1.141.16
0.930.89
Good agreement
Photo electron yield CAMAC electronics RICH 1 prototype
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Single MAPMT Test BeamSingle MAPMT Test Beam
Good agreement
Cherenkov angle resolution
CAMAC electronics RICH 2 prototype
– Focal length: 4 m Angular resolution
– 0.27 mrad (data)– 0.26 mrad (MC)
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LHC Speed ElectronicsLHC Speed Electronics
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LHC Speed F/E ElectronicsLHC Speed F/E Electronics
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Test Beam Set-upTest Beam Set-up Cluster with quartz lenses Bleeder board Cluster: 40 MHz Read-out
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9 MAPMTs read out with 6 boards
5 threshold cut, common-mode subtracted
Lots of photons, but cross-talk
Cluster TestCluster Test
CF4 Radiator, 700 mbarHV = -1000 V
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Probability that pixel y causes hit in pixel x
Cross-TalkCross-Talk
Asymmetric cross-talk (board 9)
Correlated to neighboring APV Sample channels
Not correlated with neighboring pixels in tube
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Symmetric cross-talk
Correlated with APV input neighbors (ceramic)
Cross-talk source is electronics
MAPMT do not have large cross-talk
Probability that pixel y causes hit in pixel x
Cross-TalkCross-Talk
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Cross-talk correction applied
Observe 6.4 photo electrons per event
Background: 0.41 p.e. Few dead pixels Yield of different tubes
With quartz lenses
Photon YieldsPhoton Yields
0.57 1.07 0.64
1.03 0.00 1.08
0.61 0.88 0.69
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Photon YieldsPhoton YieldsNo lenses Quartz lenses
Ratio with/without lenses = 1.45, expected 1.50
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Analysis includes– Common-mode subtraction– Cross-talk correction– Background subtraction – Signal loss & dead pixel correction
Results:
Photon YieldsPhoton Yields
Quartz Lenses Yes No
DataSimulation
7.36.9
5.24.6
Good agreement
Preliminary
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Photon YieldsPhoton Yields
Single events Number of photo electrons
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Charged ParticlesCharged Particles
Charged particles traversing the lens & MAPMT produce background hits
Angle scan
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MultiplicitiesMultiplicities
Multiplicity from charged particles – [5..10] for for
most angles– up to 30 for angles
around 45o
For MAPMTs, charged particles are a small background
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Magnetic Field TestsMagnetic Field Tests
LED Pin hole mask -metal shield
MAPMT tested with Helmholtz coil 0, 10, 20, 30 Gauss
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No ShieldingNo Shielding
MAPMTs are insensitive to transverse magnetic fields up to 30 G
Expect mainly By field
– By = 21 ..27 G (RICH 1)
– By = 150 G (RICH 2) reduce by ~ 15 with shielding of planes
Sensitive to longitudinal fields 10 G, at 30 G lose 50% top or bottom row (18% average)
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With With -Metal Shielding-Metal Shielding
-metal: t = 0.9 mm Extension:
d = 10, 13, 32 mm Reduced loss at 30 G
– 7 .. 25 % worst row (d=10,13 mm)
– no structure (d = 32 mm)
Expect low Bz field
– Bz = 0 .. 5 G (RICH 1)
– Bz = 0 .. 38 G (RICH 2) reduce by ~ 15 with shielding of planes
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MAPMT R & D SummaryMAPMT R & D Summary
Successfully tested close-packed 3x3 array of MAPMTs– Quartz lenses work as expected
Measured photon yield in agreement with simulation
Demonstrated 40 MHz read-out
Commercial MAPMT fulfilsLHCb RICH specifications
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Baseline DesignBaseline Design
Pointing geometry 4x4 array,
1024 channels Bleeder board with
8 F/E chips -metal shield Pixel size at lens:
3.0 x 3.0 mm2
Filling factor: 0.79
Tilted Modules
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Half PlanesHalf Planes
RICH 1 RICH 2
= 440 mrad
5 columns
10 rows
Total 232 modules, 3504 tubes
Outermost modules only partially equipped
= 240 mrad
6 columns
11 rows
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Little distance between Vertex tank and RICH 1 Tracker 1 must also fit
Cooling for 8.8 W /module
IntegrationIntegration
MAPMT pitch: 26.7 mm Module pitch: 108.8 mm -metal shield: 0.4 mm Mounting frame: carbon
fibre, G10
MAPMT geometry RICH 1 integration
MAPMT
Vertex tank
RICH 1
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F/E Electronics F/E Electronics
Characteristics– Spread: 3 – Signal/pedestal width: 60:1– Dynamic range: 3 photons
5000 … 1’560’000 e Attenuation: 6 F/E chip input:
– Noise/ dynamic range: 833 ... 260’000 e– ADC bits: 9
Occupancy: 3 %
Single photon signal: 300’000 e
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F/E Electronics BaselineF/E Electronics Baseline
APVm chip not suitable (shaping time) SCTA128 is baseline (analogue) Changes necessary to existing chip
– Back-end (32 multiplexing), same as for the vertex detector
– Gain adaptation for MAPMT signals, attenuation, additional work
Alternative: BEETLE chip – when it becomes available
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L0 & L1 ElectronicsL0 & L1 Electronics Level 0:
– # of modules / # of chips: 232 / 1856– # of channels per module: 1024– # of channels total: 224256– # of data links: 7424
Level 1:– Bandwidth (3% occ.) 85/7.7 Gbits/s
with/ without Zero suppression – # of VME modules: 78– # of multiplexers: 5
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PerformancePerformance
Performance study Guy Wilkinson Preliminary results:
–
– Identification efficiencies: 86 %, K : 87 %
– Fake rates: 1.4 %, K : 3.0 %
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ScheduleSchedule
Photo detectors must be ready by 1/7/2004
Testing takes 2 years
Must place order by 1/3/2001
Photo detectors are on critical path
F/E electronics design by 1/10/2000
1/7/2004today
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MAPMT Test StationMAPMT Test Station
Automated test bench– LED or Laser light source– Optical stages – Measure gain of each tube, pixel scan– HV scan
QE measurements (~10% of tubes)– Monochromator– Calibrated standard
Measure Cherenkov light (~10% of tubes) source in quartz bar & MWPC
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MAPMT Costs MAPMT Costs
Unit cost Cost Subtotal Tube [kSFr] [kSFr] [kSFr]
– MAPMT 0.931 3262
– Lenses 0.070 245 3507
Level 0– F/E chip, hybrid 0.200 371
– Motherboard 2.000 464
– TTC, DCS, Data Links 135 970
Level 1– 9U VME boards5.000 390
– Links, crates, MUX, RU, etc 199 589
Total cost: 5066
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Risk AssessmentRisk Assessment
Baseline design is very close to what we have already tested MAPMT photon yield and resolutionLHC speed read-out electronicsClose packing (quartz lenses)
Commercial photo detectorPossible delays, Note: LHCb is tomorrowManpower Cost
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Risk AssessmentRisk Assessment
PerformancePhoton yield, angular resolutionCharged particlesMagnetic stray fields
Electronics Adapt F/E chipNot on critical path
StabilityRadiation damage HV
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Risk / ImprovementsRisk / Improvements
Further improvements possible– 2-3% higher QE is possible (manufacturer)
9 -14 % more photons– Incorporate lens into vessel window
8% more photons– Optical coupling between lens & MAPMT
8% more photons– Use 4 threshold cut
Smaller signal loss– Binary electronics Cost savings
RICH meeting, 3.11.99 F.Muheim 40
is a viable choice
as photo detector
for
ConclusionsConclusions Results of the MAPMT R&D program
– Device performs according to specifications
– LHC speed read-out demonstrated Baseline design presented
– Mechanics, Electronics, Integration – Schedule, Cost