Study of Silicon Photomultipliers

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

2. Study of Silicon Photomultipliers • Why SiPM : how to detect good detectors…? • From Avalanche PhotoDiodes to Silicon PhotoMultipliers • Some Features

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

4. Why SiPM ?Or how to detect good detectors… • 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

5. E + h – e + n p š Avalanche region S.O.Kasap, Optoelectronics Impact ionization releasing EHPs and resulting avalanche multiplication From APD to SiPM… Basic structure of an APD Geiger mode→binary device

6. From APD to SiPM… Silicon PhotoMultiplier (SiPM) MEPhI&PULSAR 42 µm SiPM 1 mm 20 µm 1 mm 24*24=576 pixels Pixels of the SiPM Each pixel = binary device SiPM=analogue detector

7. Electrical decoupling to readout the signal Uniformity of the electric field From APD to SiPM… Topology of SiPM Electric field distribution in epitaxy layer

8. Features • Time • Time resolution • Rise time • Recovery time • Parameters • Overvoltage • Temperature • Light wavelength (393 nm) • Energy • Gain • Single photon resolution • Dynamic range • Noise • Dark noise • Afterpulse • Crosstalk → enough?

9. Gain vs overvoltage Calibration on the dark noise (cross-talk) Gain~1.5 106→ low electronic noise ( APD Proportional mode : Gain~200 ) Geiger mode : C = 36 pF Area on the scope (nVs)

10. Single Photoelectron Counting • Poisson statistics? 52 V 54 V 56 V A preamplifier is used B. Dolgoshein Int. Conf. On New Developments in Photodetection, Beaune, France, 2002

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

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

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

14. Limited Dynamic Range The increase of total pixel number seems technologically possible up to ~4000/mm² Hadron Calorimeter - minimal signal 20 photons/mm² - maximal signal 5000 photons/mm² 20 photons firing 5000 photons firing Average number of photoelectrons per pixel 1.7 2.1 2.5 2.9 3;3 3.7 4.1 Average number of photoelectrons per pixel 1 1.4 1.8 2.2 2.6 3 3 3.8 1200 1600 2000 2400 2800 3200 3600 4000 0 400 800 1200 1600 2000 2400 2800 3200 3600 4000 Total number of pixels Total number of pixels Irradiance of EUSO (clear sky conditions, primary proton E~1020eV, 45° zenith angle…) = 550 photons/m² Joëlle Barral MPI 25th June 2004

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

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

17. 10% 3700 firing photons 2500 firing photons Limited Dynamic Range Statistics = 1000

18. Rise time FWHM~2 ns One-pixel amplitude~6 V Rise time~1 ns Ubias=56V

19. Rise time FHWM~2 ns ~500 pixels fired APD : rise time=1ns Rise time~1 ns Ubias=56V

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

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

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

24. Recovery time Ubias=56V ( It’s bad…) 40 ns ?

25. Recovery time • All pixels fired • Limits of the dynamical range • Recovery time τ of one pixel →τone pixel=1.2 µs • Some pixels fired ? Recovery time for one pixel

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

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

28. Dark noise • Electron-hole recombinations / Carrier generations Impact ionization Optical electron-hole pair generation Thermal electron-hole pair generation Dark counting rate @ room temperature ~1 MHz Theoretically impossible in indirect semiconductor

29. Afterpulsing • Time Correlated Carrier Counting θ=dark-noise rate Trapping levels

30. Afterpulsing Hold-off time = 3.4µs τ3=155 ns τ4=393 µs τ1=141 ns τ2=289 ns Probability<10% Dark counting rate 56 V : 1 MHz →1/θ=1 µs

31. 3 2 1 Crosstalk Hot carrier luminescence : 105 avalanche carriers→1 photon emitted 1 pixel 2 pixels 3 pixels Dolgoshein Status of upgrade SiPM developments • Direct cross-talk • Inside the depletion layer • Through reflection 1 pixel : 76% Trenches 2 pixels : 18% 3 pixels : 5% 4 pixels 1%

32. enough? 22Na γ 511keV γ 511keV LSO scintillator 2mm*2mm*10mm SiPM 1mm*1mm Application : Positron-Emission Tomography • 22Na decay : β+ emission • Annihilation radiation • Coincidence measurement

33. Application : Positron-Emission Tomography PET for brain MPI für neurologische Forschung, Köln Philips, PET, Allegro

34. Application : Positron-Emission Tomography Compton scattering interaction • Energy windows around the 511 keV photopeaks to : • reduce the chance of fortuit coincidence • cut the spatial dispersion (Compton) Photopeak

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

36. QUESTIONS ?