1. R Lambert, LHCb RICHPD07, 28th June 20071 The LHCb Pixel Hybrid Photon Detectors Robert W. Lambert, University of Edinburgh On behalf of the LHCb RICH collaboration

2. R Lambert, LHCb RICHPD07, 28th June 20072 Outline  Introduction: LHCb and Particle ID  Hybrid Photon Detectors (HPDs)  HPD Manufacture  Testing and Results  RICH Installation Progress  Summary

3. R Lambert, LHCb RICHPD07, 28th June 20073 LHCb  LHCb will examine CP-violation in B-mesons [1]  Why is there a matter-antimatter asymmetry in the universe?  What are the reasons for the parameters in the Standard Model?  Is there physics beyond the Standard Model?

4. R Lambert, LHCb RICHPD07, 28th June 20074 LHCb @-100m RICH 1MagnetRICH 2

5. R Lambert, LHCb RICHPD07, 28th June 20075 RICH 1 and RICH 2  Ring Imaging CHerenkov (RICH) detectors [2]  Relativistic charged particles in a medium radiate light  Characteristic cone angle, cos  = 1/  n RICH 1 (Vertical) RICH 2 (Horizontal) MAGNET TT T1-T3

6. R Lambert, LHCb RICHPD07, 28th June 20076 Cherenkov Imaging  Rings reconstructed  Velocity  Cone angle ≡ Ring radius  Combine with momentum to get Particle ID RICH 1 for 1 < p < 60 GeV/c RICH 2 for p < 100 GeV/c ~20 hits/ring ~4 hits/ring ~25 hits/ring

7. R Lambert, LHCb RICHPD07, 28th June 20077 Requirements  Stringent requirements for RICH photodetectors –2.6 m 2 detector plane –Single-photon sensitive –65% active area overall –80% for cylindrical devices –Cherenkov Spectrum –2.5 mm x 2.5 mm granularity –25 ns Clock  <25ns response –40 MHz Clock  40 MHz read out –Trigger decision  4  s data buffer –Photon yield  High Signal:Noise –5-10 year lifetime –Radiation tolerant  30 krad –Fringe magnetic field C 4 F 10 200-600nm

8. R Lambert, LHCb RICHPD07, 28th June 20078 Hybrid Photon Detectors  484 Hybrid Photon Detectors HPDs required [3] + Photocathode (S20) + Silicon sensor + Binary read-out chip 120 mm 87 mm 8192 Vacuum Electrode Photoelectrons Solder bump bonds Ceramic Carrier Binary electronics chip Photon Photocathode (S20) at -20kV Si Sensor 8192 pixels Quartz Window

9. R Lambert, LHCb RICHPD07, 28th June 20079 HPD Manufacture (1)  Production at IBM, Canberra, Kyocera, VTT, HCM, DEP-Photonis  Full testing and gold plating by LHCb at CERN Packaging Ceramic carrier Brazing and gold-plating Readout chip Silicon sensor Bump- bonding

10. R Lambert, LHCb RICHPD07, 28th June 200710 HPD Manufacture (2)  Encapsulated by DEP-Photonis  Testing by LHCb Tube body assembly Photo-cathode deposition and vacuum sealing Packaging

11. R Lambert, LHCb RICHPD07, 28th June 200711 HPD Production 536 / 550 HPDs Produced 18 th June 2007 519 / 536 HPDs Tested

12. R Lambert, LHCb RICHPD07, 28th June 200712 PDTF  Photo-Detector Test Facilities  2 centres (2 stations each)  Test 1 HPD/site/day  506 of 519 HPDs pass Failures Replaced.

13. R Lambert, LHCb RICHPD07, 28th June 200713 PDTF Tests  Check out every function of the HPD, from the ground up Readout Chip Connections Communications DAQ Readout Dead Channels Noisy Channels Masking Responses Threshold Noise Photocathode Dark Count Response to light Quantum Efficiency HPD Body Dimensions HV Stability Vacuum Quality Electron Optics Image Size Image Centre HV Stability Field Distortions Silicon Sensor IV Curve Efficiency (Backpulse)

14. R Lambert, LHCb RICHPD07, 28th June 200714 Silicon Sensor  PDTF perform a bias scan of each sensor  Measures sensor quality Contract Typical 1  A H527009, 0.46  A leakage at 80V Operating Point, 80V Ramp-up Ramp-down

15. R Lambert, LHCb RICHPD07, 28th June 200715 Readout Chip  Low number of faulty channels  Average 0.15% dead channels << 5% specification  Average 0.02% noisy channels << 5% specification Specification < 400 Specification < 400

16. R Lambert, LHCb RICHPD07, 28th June 200716 Sensor + Readout  Thresholds and noise  Threshold scan performed on all 8192 pixels  ~85% sensor efficiency, Typical signal is 5000 e- = 145 e- = 1063 e-

17. R Lambert, LHCb RICHPD07, 28th June 200717 HV Stability  PDTF perform a HV scan of each HPD  Measures HV stability  Pulsed LED used at each voltage step H527009, a typical HPDH527009, 200k events, LED run Operating Point, 20kV Backscatter Reflections

18. R Lambert, LHCb RICHPD07, 28th June 200718 Vacuum Quality  Ion-feedback (IFB), afterpulse  Ionisation of residual gas atoms, particularly He, produces afterpulse  At 20 kV, IFB measures the vacuum quality Residual Gas Ionised Ion liberates many secondary electrons Secondaries measured after characteristic delay 1 2 3 Specification < 1% = 0.03%

19. R Lambert, LHCb RICHPD07, 28th June 200719 Dark Count  Thermionic emission, noise, and IR-sensitivity produce Dark Count  Specification 5 kHz cm -2  Average 2.6 kHz cm -2 ≡ 0.003 hit / event / HPD in LHCb Specification < 5kHz cm -2 H520009, 5M events, 2.0 kHz cm -2

20. R Lambert, LHCb RICHPD07, 28th June 200720 Quantum Efficiency  QE is a function of wavelength, large improvement seen  Independent measurements: photocurrent from known light level  DEP improved the QE with each batch (i.e. with time) Increased over time Decreased over time Expectation from preseries Agreement across measurements

21. R Lambert, LHCb RICHPD07, 28th June 200721  QE  E   QE  E, integrate improvement in QE across energy  Cherenkov light has flat energy spectrum  24% relative increase in  QE  E over expectations from preseries Expectation from preseries

22. R Lambert, LHCb RICHPD07, 28th June 200722 HPDs in use  HPDs fulfil or exceed all requirements for the LHCb RICH  Excellent performance demonstrated in testbeam scenarios Ring from Pions, over 3 HPDs 124k events, with C 4 F 10 Frequency, thousands of events Hit spectrum, 124k events Hit Count in expected region of ring for 1 HPD signal pedestal and noise PRELIMINARY In agreement with expected yields

23. R Lambert, LHCb RICHPD07, 28th June 200723 HPD Integration  HPDs -> Columns + Magnetic Sheilds + Level-0 Data Processing + LV power distribution + HV power distribution HPD L0 LV HV

24. R Lambert, LHCb RICHPD07, 28th June 200724 RICH 2 Installation

25. R Lambert, LHCb RICHPD07, 28th June 200725 Summary  484 HPDs are required for the LHCb RICH  536 HPDs have now been produced  519 tested at PDTF with 506 passes  Excellent results overall  24% relative improvement in QE will directly improve photon yields  RICH is now under installation and commissioning  RICH 2 fully populated with HPDs  LHCb is getting ready for data….

26. R Lambert, LHCb RICHPD07, 28th June 200726 References 1.LHCb collaboration, LHCb Technical Proposal, CERN-LHCC-98- 004 LHCb, 20 th February 1998 2.LHCb collaboration, LHCb RICH, Technical Design Report 3, CERN-LHCC-2000-037 LHCb, 7 th September 2000 3.T. Gys, LHCb RICH, “Production of 500 pixel hybrid photon detectors for the RICH counters of the LHCb,” NIM A 567 (2006), pp. 176-179

27. R Lambert, LHCb RICHPD07, 28th June 200727 Backup  Additional slides hereafter

28. R Lambert, LHCb RICHPD07, 28th June 200728 Physics and Photons  RICH crucial to separate Kaons and Pions [1]  Similar hadrons, different in mass  Contribute to different physics  Important to separate Signal B d   +  -

29. R Lambert, LHCb RICHPD07, 28th June 200729 HPDs Realised  Hybrid Photon Detectors Quartz window thin metal Photocathode (S20) 20kV accelerating potential Photoelectric effect produces electrons Pixelated anode 8192 pixels 500  m x 62.5  m Amplifier, Thresholder, Buffer, Read out 87 mm 120 mm

30. R Lambert, LHCb RICHPD07, 28th June 200730 HPD Production 536 / 550 HPDs Produced 18 th June 2007

31. R Lambert, LHCb RICHPD07, 28th June 200731 PDTF Progress 15 th May 2007 519 / 550 HPDs tested

32. R Lambert, LHCb RICHPD07, 28th June 200732 QE at PDTF  Uses existing Darkbox  PC at -100V, focussing cathodes at -100V, Anode at ground Quartz-tungsten halogen lamp (6V, 50 W) LOT Oriel Fused silica lens f = 50 mm, diam. = 25.4 mm IR-blocking filter (Schott KG-5) bandpass filter (+- 10 nm FWHM) lamp housing Calibrated photodiode (Newport 818-UV unbiased) HPD  q (HPD) =  q (pd) * I (HPD) / I (pd) I pd (pA) I HPD (pA) ND filter (where required) Shutter/iris combination Shutter/iris combination 100V RLRL

33. R Lambert, LHCb RICHPD07, 28th June 200733 Results Summary  HPD Quality Assurance  506 of 519 tubes pass A+: Exceeds key specifications. A specifically recommended HPD A: Pass all aspects of tests B: Falls beneath contracted specifications, but still recommended for use in the RICH E: HPD qualified for use in the RICH, but is flagged with an issue F: Clear failure of HPD, such that it is unusable in the RICH. HPD returned to DEP if possible for replacement HPDs with higher darkcount HPDs with high leakage current and with >1% dead pixels

34. R Lambert, LHCb RICHPD07, 28th June 200734 HPD electron optics  Reliable manufacture  73% of centres within 1 pixel of chip centre  standard deviation of image size ~ ¼ pixel 1 Pixel

35. R Lambert, LHCb RICHPD07, 28th June 200735 Peak QE  QE peaks at ~270 nm  Consistent improvement of QE with batch,  All production HPDs are over specifications Contract Minimum 20.0% = 30.9%

36. R Lambert, LHCb RICHPD07, 28th June 200736 Backpulse  Efficiency of hit detection,  Si  Pixel chip efficiency important for reconstruction  Probability that the chip registers a hit, given a photoelectron has struck  Comparing the number of photoelectrons seen by the chip (via normal chip readout) to the number arriving at the backplane of the Si sensor.  We measure:  si = (87±2)%. Fit to charge spectrum at backplane 1 electron 2 electrons 3 electrons 4 electrons 5 electrons

37. R Lambert, LHCb RICHPD07, 28th June 200737 Afterpulse  Ion Feedback from Strobe Scan  Consistently low, indicating excellent vacuum in all tubes  Single HPD, H546002, displayed IFB and dark-count anomalies Very low IFB <<1% Specification < 1% = 0.03%

38. R Lambert, LHCb RICHPD07, 28th June 200738 Source Sites  HPD sourced from around the world ! ItemSourceLocationTestLocation Readout WaferIBMFranceCERNSwitzerland SensorCanberraBelgiumCERNSwitzerland CarrierKyoceraJapanCERNSwitzerland Gold PlatingCERNSwitzerlandCERNSwitzerland Bump-BondingVTTFinlandCERNSwitzerland PackagingHCMFranceCERNSwitzerland Quartz WindowChina, Lithuania AssemblyDEPHollandPDTFScotland

39. R Lambert, LHCb RICHPD07, 28th June 200739 QW Reflections  As predicted by naïve CAD approximations  75% of light reflected off Chromium coating  TIR at QW-Air interface  ~20% reflection at QW-PC interface

40. R Lambert, LHCb RICHPD07, 28th June 200740 Reflective Effects  Activating QW reflections and Chromium reflections  8.0% more hits (naïve estimate would predict ~11%) Improved Geometrical Description 1.5 M events, 4,992,419 Hits Reflections Activated 1.5 M events, 5,393,100 Hits

41. R Lambert, LHCb RICHPD07, 28th June 200741 Backscatter  Only ~85% of all real photoelectrons produce digital hits  Thermal effects  Thresholding effects  Backscatter effects + + + - - - + - - + Normal Case ~5000 e-h pairs Thermal absorption v. few e-h pairs, Damage to lattice Charge Sharing. <5000 e-h pairs per pixel Backscatter. Smaller amount of energy deposited Electron “may” Fall back onto Si sensor Si Sensor

42. R Lambert, LHCb RICHPD07, 28th June 200742 RICH in UV  Below 200 nm photon yield is limited by absorption of air

43. R Lambert, LHCb RICHPD07, 28th June 200743 Expected Spectra  Folding in the expected QE Cherenkov spectrum for RICH radiators RICH 1, C 4 F 10 RICH 2, CF 4 RICH 1, Aerogel Wavelength [nm] Cherenkov Photons