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Alexander Akindinov ITEP(Moscow) on behalf of ALICE-ITEP group

Development of scintillation detectors with MRS APD light readout for CBM Muon system and ECAL preshower. Alexander Akindinov ITEP(Moscow) on behalf of ALICE-ITEP group. Outlook. MRS APD – fast Geiger mode high gain photodetector START – technology

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Alexander Akindinov ITEP(Moscow) on behalf of ALICE-ITEP group

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  1. Development of scintillation detectors with MRS APD light readout for CBM Muon system and ECAL preshower Alexander Akindinov ITEP(Moscow) on behalf of ALICE-ITEP group

  2. Outlook • MRS APD – fast Geiger mode high gain photodetector • START – technology • ALICE CRTF – first implementation for START technology • Counters for CBM muon systems • Counters for EMCAL preshower • Conclusion

  3. Readout -Voper MRS APD – fast Geiger mode high gain photodetector M = C*(U - Ubr) MRS APD structure Many other name: SiPM, MPPC, GAPD… Slope corresponds to elementary micro-cell capacity Q/U. Q = Ncell*C*(U - Ubr) Single electron resolution is a result of dispersion of Ubr and Ccell across diode area.

  4. Optical trench(CPTA) – low optical coupling between cells.Acceptable noise rate for reasonable thresholds Probability to have more than one pixel fired from a single primary e-h pair  = (N n+1)/ (N n ) Noise spectrum slope is a result of “red” cross-talks between cells, when avalanche in one cell initiate avalanche in neighboring one via photon. PDE is optimize for WLS fibers P.D.E. = Q.E. * g* R εg – geometrical fill-factor R – probability to initiate Geiger avalanche Q.E. – quantum efficiency CPTA MRS APD α= 0.1 For 4th cell threshold noise count about a few kHz High geometrical factor

  5. START- (Scintillation Tile with MRS APD Light ReadouT) MRS APD optimize geometry (d=1.15 mm) for the fiber readout σ-shape groove for uniform response Two MRS APD in coincidence “On board” FEE Mosaic array Signal/noise Threshold Cosmic μ Polisterol 165 150X150X10 mm 1 groove, 2 rings Y11 and glued

  6. First implementation - ALICE CRTF Upper plane 10 strips 8 STARTs in each (80 STARTS) Bottom plane 10 strips 8 STARTs in each (80 STARTS) Up to 5 ALICE TOF modules under the test.

  7. Trigger and monitoring Simple logic block for trigger configuration and monitoring were connected via USB to LabView • !!Monitoring the only by counting rate of individual detector, no any LED system was used.!!! • Efficiency was measured as difference in counting rate for 80 pairs.

  8. Long term operation results First real experiment with 320 new photosensors (CPTA firm MRS APD). About 3 years of continues operation, all 87 ALICE TOF modules was tested. Summary of “dead” and replaced diodes

  9. Counters for CBM muon system “Develop and produce START prototypes adapted for dE/dx measurements. Five detectors of each of two types of START will be produced: tiles sized 100x100x 10 mm3 and strips sized 5x200x10 mm3 INTAS Ref. Nr 06-1000012-8781 Strips 5x200x10 mm3 Tiles with different groove diameters to find optimal uniformity (d = 90, 80, 70, 60, 50 mm) ROLAND milling machine !!!Many thanks to our friends from ITEP-CALICE group!!!!

  10. New package to minimize “dead zone” and new connector TO-18 New package Very uniform response (about 8%). Main sources - regions near optical connectors and groove. New transparent optical connector produced by the same digital milling machine as tiles

  11. Diodes calibration and fiber cut Each diode after placement into connector was checked (how well diode active area is with connector hole) Setup to cut fiber with microscope Setup for diodes test Mixer 12 channel board

  12. Diodes calibration and fiber cut Number of photoelectrons for given light was checked I-U curve to find out breakdown point Single cell noise and photoionization (α) coefficient were measured

  13. Detector assembly and electronics FEE card for tiles Simple amplifier for strips (10mm width) Tiles were wrapped in Tyveсk and light shield

  14. FEE for tiles Ubias сontrol Test input (50 Ω) Jumper 2 for test Jumper 1 for test Ubias Amplitude 2 (50 Ω) Amplitude 1 (50 Ω) Threshold Jumper 2 for coincidence (on) Jumper 1 for coincidence (on) LED LVDS GND +4-+10 V

  15. First task: find optimal geometry for uniform response D=50 mm D=80 mm D=90 mm D=60 mm D=70 mm Scans were done using Ru β – source with 2.5 mm collimator. 19x19 points (5 mm step).

  16. New improved MRS APD (2007) Data was taken from http://www.photonique.ch/ Photonique SA C.P. 15621211 Geneva-1Switzerland Reduced thickness of n+ - PDE increased + blue enhanced 2005 – diodes for ALICE CRTF New diodes 2007

  17. Light yield with old and new diodes Beam test CERN PS (2x2 cm2 trigger center of tile) N ≈ 29 ph.e. N ≈16 ph.e. N ≈ 22 ph.e. “43V” old “23V”new “23V”new Tile 100x100x10 mm3 Tile 150x150x10 mm3 With this significant improvement can we work with one diode?

  18. Tiles with single diodes Three reasons to produce tiles with one diode: To check if we can improve light yield using another glue Check if we can work with one diode Make prototype for ECAL preshower 3 tiles were used for test 2 were assembled for cosmic test 100x100x10 mm3 with one output for fiber ( d=80 mm ) So called “half-board” designed for long strips

  19. Other task: to improve gluing How it’s important 4 grams each time Accuracy up to 0.01g Measurements were done before and after gluing with the same diode Does not depend on plastic type Since refractive indexes almost the same we can suppose that difference is due to acid type (groove walls “melting” – more uniform and transparent volume). For our milling process – Epo-Tek 301 is the best.

  20. Cosmic ray test one diode “Soft” Muons Ped Muons Diode noise “Soft” and “hard” part of cosmic ray It works!!! We can use only one diode.

  21. Last task: Strips 3M tape R.M.S ≈ 12% 4 stripes shows some “oscillating” signals. Reason bad 3M mirror contact. All tiles were reassembled. New test will be done about 20 of October.

  22. Conclusion • START detector was adopted for dE/dx measurements • Optimal diameter d=80 mm for tile 100x100x10 mm3 response was found (r.m.s < 5.0 %). • EPO-TEK 301 glue was found as optimal to increase light yield. • 3 types of FEE board were produced (all commercially evaluable) • Progress in MRS APD development allows to use only one diode for readout keeping signal/noise ratio almost the same like for two old diodes • 4 strips 200x10x5 mm3 were reassembled and will be tested again. Good one has 12% r.m.s.(?) • Tools for mass production were produced.

  23. Thank you!

  24. BACKUP

  25. MRS APD calibration Ubias for given amplification about 106 Thank to Yuri Musienko from CMS APD lab.

  26. Response and leakage tests All current is due to intrinsic noise, no significant leakage Difference – small difference in αand coupling with fiber (epoxy layer share)

  27. Noisemeasurements Photoionization α Difference – different field noise contribution to the thermal noise

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