RICH meeting, F.Muheim1 Proposal for MAPMTs as Photodetectors for the LHCb RICH Franz Muheim University of Edinburgh on behalf of the MAPMT group

RICH meeting, F.Muheim2 Outline o Introduction o Multianode Photo Multiplier Tubes o R&D Results o Baseline Design o Conclusion

RICH meeting, F.Muheim3 Photo Detector Requirements o Single photon sensitivity ( nm) with quantum efficiency > 20% o Good granularity: ~ 2.5 x 2.5 mm 2 o Large active area fraction:  73% o LHC speed read-out: 40 MHz Photo detector area: 2.9 m 2 Options: MAPMT or HPD

RICH meeting, F.Muheim4 MAPMT  Combines single photon sensitivity with good spatial resolution o 8x8 dynode chains Gain: at 800 V o Manufacturer: Hamamatsu o 1 mm flange removed, packing fraction increases by 14 % Multianode Photo Multiplier Tube

RICH meeting, F.Muheim5 MAPMT R M64 o Bialkali photo cathode, QE = 22% at = 400 nm o UV glass window replaces borosilicate,  QE dE increased by 50 % Quantum efficiency

RICH meeting, F.Muheim6 Quartz Lenses o MAPMT active area fraction: 38% (includes pixel gap) o Increase with quartz lens with one flat and one curved surface to 85%

RICH meeting, F.Muheim7 Bench Tests o Collection efficiency not very uniform (~20%) o Gap between pixels: 0.2 mm o 40 MHz read-out electronics o Average signal/ pedestal width = 40:1 o Signal loss: 11.5 % (includes 2.5% for no multiplication at 1st dynode) Pixel scan with LEDSingle channel spectrum (LED)

RICH meeting, F.Muheim8 Test Beam Set-up

RICH meeting, F.Muheim9 Single MAPMT Test Beam Good agreement Photo electron yield o CAMAC electronics o RICH 1 prototype

RICH meeting, F.Muheim10 Single MAPMT Test Beam Good agreement Cherenkov angle resolution o CAMAC electronics o RICH 2 prototype –Focal length: 4 m o Angular resolution –0.27 mrad (data) –0.26 mrad (MC)

RICH meeting, F.Muheim11 LHC Speed Electronics

RICH meeting, F.Muheim12 LHC Speed F/E Electronics

RICH meeting, F.Muheim13 Test Beam Set-up o Cluster with quartz lenses o Bleeder board o Cluster: 40 MHz Read-out

RICH meeting, F.Muheim14 o 9 MAPMTs read out with 6 boards o 5  threshold cut, common-mode subtracted o Lots of photons, but cross-talk Cluster Test CF4 Radiator, 700 mbar HV = V

RICH meeting, F.Muheim15 Probability that pixel y causes hit in pixel x Cross-Talk o Asymmetric cross- talk (board 9) o Correlated to neighboring APV Sample channels o Not correlated with neighboring pixels in tube

RICH meeting, F.Muheim16 o Symmetric cross-talk o Correlated with APV input neighbors (ceramic) o Cross-talk source is electronics o MAPMT do not have large cross-talk Probability that pixel y causes hit in pixel x Cross-Talk

RICH meeting, F.Muheim17 o Cross-talk correction applied o Observe 6.4 photo electrons per event o Background: 0.41 p.e. o Few dead pixels o Yield of different tubes With quartz lenses Photon Yields

RICH meeting, F.Muheim18 Photon Yields No lensesQuartz lenses o Ratio with/without lenses = 1.45, expected 1.50

RICH meeting, F.Muheim19 o Analysis includes –Common-mode subtraction –Cross-talk correction –Background subtraction –Signal loss & dead pixel correction o Results: Photon Yields Good agreement Preliminary

RICH meeting, F.Muheim20 Photon Yields Single eventsNumber of photo electrons

RICH meeting, F.Muheim21 Charged Particles o Charged particles traversing the lens & MAPMT produce background hits o Angle scan

RICH meeting, F.Muheim22 Multiplicities o Multiplicity from charged particles –  [5..10] for for most angles –up to 30 for angles around 45 o For MAPMTs, charged particles are a small background

RICH meeting, F.Muheim23 Magnetic Field Tests o LED o Pin hole mask o  -metal shield o MAPMT tested with Helmholtz coil o 0, 10, 20, 30 Gauss

RICH meeting, F.Muheim24 No Shielding o MAPMTs are insensitive to transverse magnetic fields up to 30 G o Expect mainly B y field –B y = G (RICH 1) –B y = 150 G (RICH 2) reduce by ~ 15 with shielding of planes o Sensitive to longitudinal fields  10 G, at 30 G lose 50% top or bottom row (18% average )

RICH meeting, F.Muheim25 With  -Metal Shielding o  -metal: t = 0.9 mm o Extension: d = 10, 13, 32 mm o Reduced loss at 30 G – % worst row (d=10,13 mm) –no structure (d = 32 mm) o Expect low B z field –B z = G (RICH 1) –B z = G (RICH 2) reduce by ~ 15 with shielding of planes

RICH meeting, F.Muheim26 MAPMT R & D Summary o Successfully tested close-packed 3x3 array of MAPMTs –Quartz lenses work as expected o Measured photon yield in agreement with simulation o Demonstrated 40 MHz read-out Commercial MAPMT fulfils LHCb RICH specifications

RICH meeting, F.Muheim27 Baseline Design o Pointing geometry o 4x4 array, 1024 channels o Bleeder board with 8 F/E chips o  -metal shield o Pixel size at lens: 3.0 x 3.0 mm 2 o Filling factor: 0.79 Tilted Modules

RICH meeting, F.Muheim28 Half Planes RICH 1 RICH 2 o  = 440 mrad o 5 columns o 10 rows o Total 232 modules, 3504 tubes o Outermost modules only partially equipped o  = 240 mrad o 6 columns o 11 rows

RICH meeting, F.Muheim29 o Little distance between Vertex tank and RICH 1 Tracker 1 must also fit o Cooling for 8.8 W /module Integration o MAPMT pitch: 26.7 mm o Module pitch: mm o  -metal shield: 0.4 mm o Mounting frame: carbon fibre, G10 MAPMT geometryRICH 1 integration MAPMT  Vertex tank RICH 1

RICH meeting, F.Muheim30 F/E Electronics o Characteristics –Spread:3 –Signal/pedestal width:60:1 –Dynamic range:3 photons 5000 … 1’560’000 e o Attenuation:6 o F/E chip input: –Noise/ dynamic range: ’000 e –ADC bits:9 o Occupancy:3 % Single photon signal: 300’000 e

RICH meeting, F.Muheim31 F/E Electronics Baseline o APVm chip not suitable (shaping time) o SCTA128 is baseline (analogue) o Changes necessary to existing chip –Back-end (32 multiplexing), same as for the vertex detector –Gain adaptation for MAPMT signals, attenuation, additional work o Alternative: BEETLE chip –when it becomes available

RICH meeting, F.Muheim32 L0 & L1 Electronics o Level 0: –# of modules / # of chips:232 / 1856 –# of channels per module:1024 –# of channels total: –# of data links:7424 o Level 1: –Bandwidth (3% occ.)85/7.7 Gbits/s with/ without Zero suppression –# of VME modules:78 –# of multiplexers:5

RICH meeting, F.Muheim33 Performance o Performance study  Guy Wilkinson o Preliminary results: – –Identification efficiencies  :86 %,K :87 % –Fake rates  :1.4 %,K :3.0 %

RICH meeting, F.Muheim34  Schedule o Photo detectors must be ready by 1/7/2004 o Testing takes  2 years o Must place order by 1/3/2001 o Photo detectors are on critical path o F/E electronics design by 1/10/2000  1/7/2004today

RICH meeting, F.Muheim35 MAPMT Test Station o Automated test bench –LED or Laser light source –Optical stages –Measure gain of each tube, pixel scan –HV scan o QE measurements (~10% of tubes) –Monochromator –Calibrated standard o Measure Cherenkov light (~10% of tubes) –  source in quartz bar & MWPC

RICH meeting, F.Muheim36 MAPMT Costs Unit costCost Subtotal o Tube [kSFr][kSFr] [kSFr] –MAPMT –Lenses o Level 0 –F/E chip, hybrid –Motherboard –TTC, DCS, Data Links o Level 1 –9U VME boards –Links, crates, MUX, RU, etc o Total cost:5066

RICH meeting, F.Muheim37 Risk Assessment 4 Baseline design is very close to what we have already tested 4MAPMT photon yield and  resolution 4LHC speed read-out electronics 4Close packing (quartz lenses) 4 Commercial photo detector 4Possible delays, Note: LHCb is tomorrow 4Manpower 7Cost

RICH meeting, F.Muheim38 Risk Assessment 4 Performance 4Photon yield, angular resolution 4Charged particles 4Magnetic stray fields 4 Electronics 7Adapt F/E chip 4Not on critical path 4 Stability 4Radiation damage 4HV

RICH meeting, F.Muheim39 Risk / Improvements o Further improvements possible –2-3% higher QE is possible (manufacturer)  % 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, F.Muheim40 is a viable choice as photo detector for Conclusions o Results of the MAPMT R&D program –Device performs according to specifications –LHC speed read-out demonstrated o Baseline design presented –Mechanics, Electronics, Integration –Schedule, Cost