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ToF -LR HV upgrade

ToF -LR HV upgrade. Current status: 1) 2 Caen crates (right 1 and 2) replaced with BG crates 2) Both crates connected via RS485 link to computer in counting room 3) Connection established, beta version of monitoring program working well . ToF -LR HV upgrade. All hardware finished!.

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ToF -LR HV upgrade

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  1. ToF-LR HV upgrade • Current status:1) 2 Caen crates (right 1 and 2) replacedwith BG crates2) Both crates connected via RS485 link to computer in counting room3) Connection established, beta version of monitoring program working well

  2. ToF-LR HV upgrade All hardware finished!

  3. ToF-LR HV upgrade • Crate R3 already in CERN, wait to be installed, Crate R4 still in Belgrade • All distributors (HV readout) have to be calibrated! • Finishing of the work foreseen for August this year

  4. Pixels repair - ToF (especially ToF-L) performance decreases with time,too many pixels on ToF-L out of order, repair needed - Currently, 98 pixels on ToF-L don't work, and 24 on ToF-R (our analysis, based on ToF online monitoring program) - Szymon analysis (pp80, more sophisticated) and our new analysis (pp158, 2009) show even worst situation!

  5. ToF-LR pixel efficiency

  6. Pixels statistic February 2013, Be @ 30 GeV

  7. Pixels statistic Left side: 81 dead pixels (9.1%) (~70 PMT!) 17 almost dead (1.9%) ------------------------------- 98 not working (11.0%) Right side: 20 dead pixels (2.2%) (~16 PMT!) 4 almost dead (0.5%) ------------------------------- 24 not working (2.7%)

  8. Cassette inspection

  9. Broken PMT

  10. Spare parts • We found some spare PMTs with scintilators 6 cm – 1 pcs (needed ~30) 7 cm – 17 pcs (needed ~30) 8 cm – 25 pcs (needed ~30) -------------- 43 pcs (needed ~90) • Replacing foreseen for middle of August (13.8 - 23.8)

  11. New parts • FEU-87 doesn’t produce any more • No leftovers in Dubna! • Replacement: Hammamatsu R3478 from Buda wall (~400 pieces with HV voltage dividers, optical coupled with grease, can be use again) • Smaller then FEU, mechanically can be adapted to fit in existing cassette (photocatode 15mm instead of 22!)

  12. New parts

  13. Hammamatsu PMT • Wavelength (Peak): 420nm • Dynode Stages: 8(FEU-87 11!) • Anode to Cathode Supply Voltage: 1700V • Max Anode to Cathode Voltage: 1800V • Gain Typ.: 1.7 x 106 • Rise Time Typ.: 1.3 ns • Assembled with our ToF-LR scintilators an tested (cosmic) • Nominal HV (1700V) too high (gain too high)! Use ~1000V • More current consumption (~30%) compared to FEU-87!

  14. Hammamatsu PMT

  15. Hammamatsu PMT

  16. PMT from the right wall

  17. PMT from the right wall

  18. Pulse shape

  19. Amplitude spectra

  20. Conclusion • Hammamatsu PMTs performed very well during testing (in spite of their smaller photocatode) • Seems that its possible to produce replacement for broken pixels on the ToF left wall based on Hammamatsu PMTs • However, lots of problems are foreseen!

  21. Conclusion • A lot of mechanical work needed!- new cassettes have to be produced (12 of them)- new scintilators wanted- electrical cables have to be extended- mechanical support for (smaller) PMTs for tight fit to existing space in cassette- light guides for laser calibration system needed- replacing the old cassette with the new one, then use good FEU-87 pixels as spare part for the rest of the wall- HV calibration needed! - Current consumption?

  22. Conclusion • Price (in CHF and man power) cannot be estimate at the moment – mostly for traveling expenses and men work! • Further study needed – how to mechanically adapt smaller PMTs to tight fit in existing cassette space? • Cost-benefit analysis needed: what we will get and how much does itcost!

  23. Thank you!

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