1. Study of Silicon Photomultipliers Joëlle Barral, MPI, 25th June 2004

2. Joëlle Barral MPI 25th June 2004 Study of Silicon Photomultipliers A. Why SiPM : how to detect good detectors…? B. From Avalanche PhotoDiodes to Silicon PhotoMultipliers C. Some Features

3. Joëlle Barral MPI 25th June 2004 Why SiPM ? Or how to detect good detectors… Caran d’Ache Une planche qui regarde passer le train High time resolution Short rise time Short recovery time = FAST DETECTORS

4. Joëlle Barral MPI 25th June 2004 High precision  Low noise rate  Single photon resolution  Efficiency Additional features  Low sensitivity to high magnetic / electric field  « low sensitivity to magnetic fields of the order of the gauss »…  Hadron calorimeter : 4T  Behaviour with temperature Why SiPM ? Or how to detect good detectors…

5. Joëlle Barral MPI 25th June 2004 From APD to SiPM… Basic structure of an APD Geiger mode→binary device

6. Joëlle Barral MPI 25th June 2004 From APD to SiPM… Pixels of the SiPM SiPM Silicon PhotoMultiplier (SiPM) MEPhI&PULSAR Each pixel = binary deviceSiPM=analogue detector 42 µm 20 µm 1 mm 24*24=576 pixels

7. Joëlle Barral MPI 25th June 2004 Electric field distribution in epitaxy layer Topology of SiPM From APD to SiPM… Electrical decoupling to readout the signal Uniformity of the electric field

8. Joëlle Barral MPI 25th June 2004 Features Energy  Gain  Single photon resolution  Dynamic range Noise  Dark noise  Afterpulse  Crosstalk Time  Time resolution  Rise time  Recovery time Parameters  Overvoltage  Temperature  Light wavelength (393 nm) → enough?

9. Joëlle Barral MPI 25th June 2004 Gain vs overvoltage Calibration on the dark noise (cross-talk) Area on the scope (nVs) Geiger mode : C = 36 pF Gain~1.5 10 6 → low electronic noise ( APD Proportional mode : Gain~200 )

10. Joëlle Barral MPI 25th June 2004 Single Photoelectron Counting Poisson statistics? 54 V A preamplifier is used 52 V 56 V B. Dolgoshein Int. Conf. On New Developments in Photodetection, Beaune, France, 2002

11. Joëlle Barral MPI 25th June 2004 Limited Dynamic Range Saturation of the SiPM signal with increased light intensity (Average number of photoelectrons per pixel) Number of photons arriving on the SiPM Number of pixels fired Statistics=10 for each number of photons arriving m=total number of pixels=576 Joëlle Barral MPI 25th June 2004 0 200 400 600 800 1000 1200 1400 1600 1800 2000 700 600 500 400 300 200 100 0

12. Joëlle Barral MPI 25th June 2004 B. Dolgoshein The Silicon Photomultipliers in Particle Physics: Possibilities and Limitations ε=photon detection efficiency Limited Dynamic Range Joëlle Barral MPI 25th June 2004

13. m=576 or ? … Number of pixels fired Joëlle Barral MPI 25th June 2004 B. Dolgoshein An advanced study of Silicon Photomultiplier Limited Dynamic Range 1 1.4 1.8 2.2 2.6 3 3.4 3.8 Average number of photoelectrons per pixel 600 500 400 300 200 100 0

14. Joëlle Barral MPI 25th June 2004 Limited Dynamic Range Total number of pixels Average number of photoelectrons per pixel 20 photons firing The increase of total pixel number seems technologically possible up to ~4000/mm ² Hadron Calorimeter - minimal signal 20 photons/mm² - maximal signal 5000 photons/mm² 5000 photons firing Average number of photoelectrons per pixel Total number of pixels Irradiance of EUSO (clear sky conditions, primary proton E~10 20 eV, 45° zenith angle…) = 550 photons/m² Joëlle Barral MPI 25th June 2004 1 1.4 1.8 2.2 2.6 3 3 3.8 0 400 800 1200 1600 2000 2400 2800 3200 3600 40001.7 2.1 2.5 2.9 3;3 3.7 4.1 1200 1600 2000 2400 2800 3200 3600 4000

15. Joëlle Barral MPI 25th June 2004 Limited Dynamic Range Taking into account only the saturation of the pixels… N photons >4056 576 pixels fired 10 % 1 % Signal dispersion Pessimistic… B. Dolgoshein An advanced study of Silicon Photomultiplier Relevant ? for Si, 400 nm ~70% 1 2 3 4 5 6 Average number of photoelectrons per pixel

16. Joëlle Barral MPI 25th June 2004 Limited Dynamic Range Less pessimistic… Simulation -Poisson statistics -Saturation : incertitude in the number of photons detected -Fluctuations around the saturation Statistics = 50 0 400 800 1200 1600 2000 2400 2800 3200 600 500 400 300 200 100 0 Number of pixels fired 12 10 8 6 4 2 0 0 400 800 1200 1600 2000 2400 2800 3200

17. Joëlle Barral MPI 25th June 2004 Limited Dynamic Range Statistics = 1000 2500 firing photons 10% 3700 firing photons

18. Joëlle Barral MPI 25th June 2004 Rise time U bias =56V One-pixel amplitude~6 V Rise time~1 ns FWHM~2 ns

19. Joëlle Barral MPI 25th June 2004 Rise time FHWM~2 ns U bias =56V Rise time~1 ns ~500 pixels fired APD : rise time=1ns

20. Joëlle Barral MPI 25th June 2004 Time resolution Dependence with the number of pixels fired Poisson statistics One-pixel time resolution σ=17ps FWHM = 402 ps σ=171ps Best time resolution ( 27 ps ) Oscilloscope time resolution Picosecond Pulsed Diode Laser PDL 800-B : Synchronisation Output < 20 ps Electronics noise σ/√2=7 ps Traps in deep levels

21. Joëlle Barral MPI 25th June 2004 Time resolution Randomness in physical mechanisms : ultimate limits  Photon absorption in the depletion layer Distance point of absorption / High field region Depth of the depletion layer Position over the active area : transverse propagation of the avalanche activation (lateral drift and diffusion of free carriers)  Avalanche multiplication = stochastic process Fluctuation (number, position) of ionizing events

22. Joëlle Barral MPI 25th June 2004 Recovery time Quenching  Passive  Active Joëlle Barral MPI 25th June 2004 S. Cova et al. Evolution and Prospect of Single-Photon Avalanche Diodes and Quenching Circuits Difficult for each pixel

23. Joëlle Barral MPI 25th June 2004 Recovery time Diode model Dependence of the overvoltage 1.2 µs but… Joëlle Barral MPI 25th June 2004 R pixel C pixel =400 kΩ *36 fF ~ 15 ns all pixels fired

24. Joëlle Barral MPI 25th June 2004 Recovery time 40 ns ? ( It’s bad…) U bias =56V

25. Joëlle Barral MPI 25th June 2004 Recovery time All pixels fired  Limits of the dynamical range  Recovery time τ of one pixel → τ one pixel =1.2 µs Some pixels fired ? Recovery time for one pixel

26. Joëlle Barral MPI 25th June 2004 Recovery time Signal detected (normalized / number of pixels fired) Delay t between the two firing signals (ns) 63% of maximal value Recovery time = 119 ns formula simulation 0 1000 2000 3000 4000 5000 250 230 210 190 170 150 130 Example with two firing signals of 300 photons

27. Joëlle Barral MPI 25th June 2004 Recovery time Number of photons firing ( >264) Recovery time (ns) if >0… N photons firing = 815 N pixels fired = 436 63% 200 600 1000 1400 1800 2200 2600 3000 1200 1000 800 600 400 200 0

28. Joëlle Barral MPI 25th June 2004 Dark noise Electron-hole recombinations / Carrier generations Optical electron-hole pair generation Thermal electron-hole pair generation Impact ionization Theoretically impossible in indirect semiconductor Dark counting rate @ room temperature ~1 MHz

29. Joëlle Barral MPI 25th June 2004 Afterpulsing Time Correlated Carrier Counting θ=dark-noise rateTrapping levels

30. Joëlle Barral MPI 25th June 2004 Afterpulsing Hold-off time = 3.4µs τ 1 =141 ns τ 2 =289 ns τ 3 =155 ns τ 4 =393 µs Probability<10% Dark counting rate 56 V : 1 MHz →1/θ=1 µs

31. Joëlle Barral MPI 25th June 2004 Crosstalk Trenches 1 pixel : 76% 2 pixels : 18% 3 pixels : 5% 4 pixels 1% 1 2 3 Hot carrier luminescence : 10 5 avalanche carriers→1 photon emitted 1.Direct cross-talk 2.Inside the depletion layer 3.Through reflection Dolgoshein Status of upgrade SiPM developments 1 pixel 3 pixels 2 pixels

32. Joëlle Barral MPI 25th June 2004 Application : Positron-Emission Tomography 22 Na decay : β + emission Annihilation radiation Coincidence measurement 22 Na γ 511keV γ 511keV LSO scintillator 2mm*2mm*10mm SiPM 1mm*1mm enough?

33. Joëlle Barral MPI 25th June 2004 Application : Positron-Emission Tomography PET for brain MPI für neurologische Forschung, Köln Philips, PET, Allegro

34. Joëlle Barral MPI 25th June 2004 Application : Positron-Emission Tomography Compton scattering interaction Photopeak Energy windows around the 511 keV photopeaks to : reduce the chance of fortuit coincidence cut the spatial dispersion (Compton)

35. Joëlle Barral MPI 25th June 2004 Application : Positron-Emission Tomography σ =1.3 ns S.R. Cherry Planar APD Arrays for High Resolution PET σ =2.04 ns 4*4 APD coupled to 2*2*10 mm LSO arrays Pichler Entwicklung eines Detektors für die hochauflösende PET(…) σ =1.4 ns 2*8 LSO-APD matrix

36. Joëlle Barral MPI 25th June 2004 QUESTIONS ?