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Status of the MaPMT

Status of the MaPMT. Status quo Ongoing work Issues mechanics electronics schedule Conclusions. LHCb meeting Milano 26. 9. 2000. Franz Muheim University of Edinburgh. Status Quo. Successful test of 3x3 array of MaPMTs Quartz lenses and close packing work

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Status of the MaPMT

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  1. Status of the MaPMT Status quo Ongoing work Issues mechanics electronics schedule Conclusions LHCb meeting Milano 26. 9. 2000 Franz Muheim University of Edinburgh

  2. Status Quo • Successful test of 3x3 array of MaPMTs • Quartz lenses and close packing work • Measured photon yield as expected • Demonstrated 40 MHz read-out with APVm chip • MaPMT works in LHCb environment • charged particles traversing lens and photocathode • magnetic field • MaPMT fulfills LHCb RICH requirements • Front-end electronics needs to be optimised LHCb RICH meeting

  3. Pixel HPD is baseline must fulfill milestones assessed at the end of 2000 MaPMT is backup Keep the MaPMT viable until end 2000 recommended work programme F/E readout: SCT128A gain matching Attenuators or reduced gain of MaPMT final decision: end 2000 Photo Detector Decision LHCb RICH meeting

  4. Improvements • Further improvements possible • 3-5 % higher QE is possible (manufacturer)  14-23 % more photons • Incorporate lens into vessel window 8% more photons • Optical coupling between lens & MAPMT  8% more photons • Binary electronics  Cost savings • Use 4  threshold cut  Smaller signal loss LHCb RICH meeting

  5. Laboratory Results Single channel spectrum (LED) Pixel scan with LED -900 V • Signal / pedestal s = 40:1 • Signal loss below 5 s cut: 11.5 % • Better focusing improves collection efficiency LHCb RICH meeting

  6. Low Gain • Additional studies with better sensitivity needed • Looks promising LHCb RICH meeting

  7. Mechanics • In good shape • for the photo detector decision 12/99 • MAPMT pitch: 26.7 mm • Module pitch: 108.8 mm • -metal shield: 0.4 mm • Mounting frame: carbon fibre, G10 • Have enough time to finalise design LHCb RICH meeting

  8. Front-end Electronics • Options: 4 x 2 (SCTA128 or BEETLE) all would probably work • preamplifier with lower gain • attenuator network, separate chip or passive • low gain • Preamplifier modification • preferred solution • needs design effort: J. Buytaert & N. Smale • Attenuator network • passive Xtalk? • active decouples preamp, needs design effort • Low gain • increases signal loss, less flexibility LHCb RICH meeting

  9. Status of ASICs • SCTA128A_VELO • modified backend - 32 MUX • submission delayed Nov 2000 - with CMS • tested march 2001 • SCTA “2” used by vertex group and Pad HPD • SCTA “3” production problem, available end Nov • Beetle • arrived at Heidelberg 3 weeks ago • shortcut in buffers prevents programming with I2C try to fix with ion beam • test structures with low gain “The results look good and close to simulation” - N. Smale • next submission planned Jan 2001 LHCb RICH meeting

  10. Binary Readout • Only with Beetle, SCTA128 is analogue • Advantages • ODE design for Pixel HPD can be taken “asis” • Optical links and 80 m between F/E and ODE • Cost • Does it work? HERA-B RICH has MaPMTs with binary readout • Must be studied - before end 2000 Estimate signal loss, parameters: • measured signal shape • mean gain of tube • spread of gain from pixel to pixel • collection efficiency within pixel LHCb RICH meeting

  11. New Schedule LHCb RICH meeting

  12. Discussion • Mechanicsok • Front-end chip and mother board on critical path • Mother board • can profit from design studies for the photo detector choice but lots of effort needed • need motherboard to test MaPMTs 1/2002 • Front-end chip • gain matching needs effort and time • binary read-out has many advantages • Prefer same choice as vertex detector • analogue read-out restricts ODE to 12 m, copper links, radiation - single event upsets, same for vertex detector • need a functional front-end electronics for 1/2002 LHCb RICH meeting

  13. Conclusion • Multianode Photomultiplier Tubes are an excellent backup solution • No primary worries left • Big effort needed for proper Front-end and Off-detector electronics • Front-end chip and mother board on critical path • Need a fully committed team and a final decision should be taken at 12/2000 • Backup solutions are only taken serious once the baseline has failed • We cannot afford to delay a decision after 12/2000 without delaying the LHCb RICH project LHCb RICH meeting

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