1. Pixilated Photon Detectors and possible uses at ILC and SLHC WSU, 23 Oct 09 Rubinov “at” fnal.gov 23 Nov 091Rubinov, WSU HEP seminar

2. Intro to SiPM  Q: What is an SiPM?  A: SiPM (Silicon Photo Multiplier)‏ 23 Nov 09Rubinov, WSU HEP seminar MRS-APD (Metal Resistive Semiconductor APD)‏ SPM (Silicon Photo Multiplier)‏ MPGM APD (Multi Pixel Geiger-mode APD) AMPD (Avalanche Micro-pixel Photo Diode) SSPM (Solid State Photo Multiplier) GM-APD (Geiger Mode APD) SPAD (Singe Photon Avalanche Diode) MPPC (Multi Pixel Photon Counter)‏ From Yamamoto Pixelated Photon Detector 2 -- T. Nakaya (Kyoto) @ Pixel08 -- 2

3. 3 Photodiodes: p-n junction, reverse bias Electron-hole pair generated by an incoming photon drifts to the edges of the depleted region I(t) = QE * q * dN/dt(t)‏ Absolute calibration No gain Suitable for large signals From A Para (Fermilab)‏ 23 Nov 09Rubinov, WSU HEP seminar Photodiodes, Avalanche, Geiger Mode 3

4. 4 Avalanche Photodiodes: Photodiodes operating at higher bias voltage Higher voltage  stronger electric field  higher energy of drifting carriers  impact ionization  Gain (Im)Balance between the number of carriers leaving the depletion region and the number generated carriers per unit time: dN leave /dt > dN generated /dt Stochastic process: signal quenches when the ‘last’ electron/hole fails to ionize. Large fluctuations of the multiplication process  Gain fluctuations Excess noise factor (beyond-Poisson fluctuations)‏ From A Para (Fermilab)‏ 23 Nov 09Rubinov, WSU HEP seminar4

5. 5 Geiger Mode Avalanche Photodiodes: Avalanche Photodiodes operated at the elevated bias voltage. Larger field  carriers gain kinetic energy faster  shorter mean free path Breakdown voltage: nothing really breaks down, but dN leave /dt = dN generated /dt (on average) at this voltage Some electrons can generate self- sustaining avalanche (current limited eventually by the series resistance) Probability of the avalanche generation increases with bias voltage (electric field)‏ Operation mode: one photon  (sometimes) ~1e6 electron avalanche From A Para (Fermilab)‏ 23 Nov 09Rubinov, WSU HEP seminar Photodiodes, Avalanche, Geiger Mode 5

6. First prototype of MAPD (MRS APD 1989) First metall-resistor-semiconductor APD (MRS APD) structure was designed by A.Gasanov, V.Golovin, Z.Sadygov (russian patent #1702881, from 10/11/1989) Low-light intensity spectrum of MRS APD (A. Akindinov et. al, NIM387 (1997) 231 PDE of MRS APD is just few % Anfimov Nikolay, Dubna, JINR 23 Nov 096Rubinov, WSU HEP seminar

7. 7 23 Nov 09Rubinov, WSU HEP seminar7

8. 23 Nov 09Rubinov, WSU HEP seminar8

9. 9 Q=C D *(V bias- V bd )‏ 23 Nov 09Rubinov, WSU HEP seminar9

10. Intro to SiPMs  Analogy  When comparing PMTs to SiPMs, SiPMs enthusiast usually list advantages of SiPMs BORING and PREDICTABLE  I list advantages of conventional PMTs on next slide from a tube company 23 Nov 09Rubinov, WSU HEP seminar10

11. PMT vs SiPM Adapted from IEEE & Eric Barbour Tubes: Advantages 1. Characteristics highly independent of temperature. 1. Characteristics highly independent of temperature. 2. Wider dynamic range, due to higher operating voltages. 2. Wider dynamic range, due to higher operating voltages. 3. Very low dark current. 3. Very low dark current. SiPM: Disadvantages SiPM: Disadvantages 1. Device parameters vary considerably with temperature, complicating biasing. 1. Device parameters vary considerably with temperature, complicating biasing. 2. May need cooling, because lower operating temperature may be required. 2. May need cooling, because lower operating temperature may be required. 23 Nov 09Rubinov, WSU HEP seminar11

12. Analogy? I think we have seen transition from vacuum tubes to solid state before. Transistors are not tiny vacuum tubes and SiPMs are not tiny PMTs 23 Nov 09Rubinov, WSU HEP seminar I think that the reason we have transistors instead of tubes boils down to this: $ 12

13. Is the SiPM the perfect LLL sensor? Die eierlegende Woll-Milch-Sau (german)Die eierlegende Woll-Milch-Sau (german) (approximate english translation: all-in-one device suitable for every purpose) ‏ 23 Nov 09Rubinov, WSU HEP seminar R. Mirzoyan There will be different devices optimized for different applications 13

14. SiPM Animal  Research in SiPMs is very active, in many different directions – I’m not going to do a survey  Extended blue sensitivity (Cherenkov light, dual readout calorimetry)‏  Increased PDE ( muon detectors)‏  Reduced crosstalk (improved noise factor)‏  Improved timing (PET)‏  Large area (Cherenkov)‏  Increased dynamic range (Calorimeters)‏  LOWER COST (everyone)‏ 23 Nov 09Rubinov, WSU HEP seminar14

15. Areas of interest for LHC  Issues of special interest to SLHC (more detail on CMS specifics later)  Radiation hardness  Dynamic range/Linearity  Stability (radiation, temperature and time)  CERN has a strong, active community working on all these issues 23 Nov 09Rubinov, WSU HEP seminar15

16. Areas of interest for LC  Issues of special interest to LC (more detail on SiD specifics later)  Blue sensitivity  Cost/unit area  Optical coupling to detector  Calice is a strong collaboration doing fantastic work on these areas 23 Nov 09Rubinov, WSU HEP seminar16

17. Understanding SiPM operation  Here I'm going to focus on 2 issues  DC measurements  Vb determination  Rquench determination  Cross talk measurement  Pulse measurements  Afterpulsing measurements 23 Nov 09Rubinov, WSU HEP seminar17

18. DC Measurements  Static characteristics - IV curves at fixed temperatures:  Keithley 2400 sourcemeter  Temperature controlled chamber  Labview data acquisition program  Forward bias  series (quenching) resistance  Reverse bias  breakdown voltage, integral behaviour of the detector s a function of the operating temperature 18 23 Nov 09Rubinov, WSU HEP seminar18

19. Forward Bias Scan 19 Exponential growth with V Limited by quenching resistor dI/dV = 1/R Resistance decreases with temperature (polysilicone) ‏ 23 Nov 09Rubinov, WSU HEP seminar19

20. Quenching Resistance Summary for MPPCs Detector type Quenching Resistor @ 25 o C, k  dR/dT k  / o C 1/R dR/dT 25  2002.230.011 50  1051.080.010 100  850.910.011 20 From A Para (Fermilab)‏ 23 Nov 09Rubinov, WSU HEP seminar20

21. Reverse Bias Scan 21 100 pA 1 V above breakdown I~5x10 -7 A Gain ~ 4x10 6 ‘ Photodiode’ current level ~ 10 -13 A How relevant is the current below the breakdown voltage? 1 V above breakdown I~5x10 -7 A Gain ~ 4x10 6 ‘ Photodiode’ current level ~ 10 -13 A How relevant is the current below the breakdown voltage? Quenching resistance Temperature Breakdown From A Para (Fermilab)‏ 23 Nov 09Rubinov, WSU HEP seminar21

22. Vbd(T). Preliminary analysis 23 Nov 09Rubinov, WSU HEP seminar IRST #30 Fermilab August 29 th 2008 Diego Cauz University & INFN of Udine 22

23. Cross Talk Measurement Single avalanche rate Single + 1 cross talk Single +2 cross talk Single +3 cross talk Ratios of rates give relative probabilities of 1,2,3 extra pixels firing due to cross-talk 23 Nov 09Rubinov, WSU HEP seminar23

24. Cross Talk Rates as a Function of Bias Voltage Cross talk probability increases with the bias voltage Cross talk probability is bigger for larger size pixels But… The cross talk is mediated by infrared photons produced in the avalanche, hence is ought to be proportional to the gain. And different size pixel detectors have different gain ! 23 Nov 09Rubinov, WSU HEP seminar24

25. Cross Talk Probability as a Function of Gain At the same gain the cross-talk probability is much larger for smaller size pixels At the operating point the Hamamatsu detectors have very small cross talk (~few %) ‏ 23 Nov 09Rubinov, WSU HEP seminar25

26. Pulse measurements 23 Nov 09Rubinov, WSU HEP seminar  MPPC-11-050C#37 at 71.1deg F operating at 69.81 (recommended V is 70.02 at 25C)  Current reading is 0.044uA  1pe is about 13.25mV 26

27. A little bit about after pulses Observed signal grows with the bias voltage. This growth has several components: increase of the gain increase of afterpulsing. The latter is a much bigger effect. So what?? Afterpulses provide a kind of additional gain. True, but this contribution fluctuates  degrades the charge measurement resolution (excess noise factor). Relative width of the observed pulse height spectrum slightly decreases with bias voltage for 10 nsec gate (presumably a reflection of the increased number of detected photons), but it increases for longer gates. Bottom plot shows a contribution to resolution from fluctuations of the afterpulses contribution in different gates. 23 Nov 09Rubinov, WSU HEP seminar27

28. Detector Recovery / Afterpulsing  Pulse arrival distribution: clear afterpulsing for about~ 1  sec  At least two components:  1 =39 nsec  2 =202 nsec  These components probably correspond to traps with different lifetimes 28 23 Nov 09Rubinov, WSU HEP seminar28

29. 29 F. Retiere @ NDIP08 Photo-Electrons Time after the first pulse (ns)‏ S10262-11-050C Time after the first pulse (ns)‏  short ~15ns  long ~85ns Dark-noise rate 23 Nov 0929Rubinov, WSU HEP seminar

30.  After subtracting the effects of cross-talk + after pulse, the dark noise is found to be linear to  V. 30 F. Retiere @ NDIP08 23 Nov 0930Rubinov, WSU HEP seminar

31. SiPM pulse shape  Actually, there is some subtle issues in measuring pulse shape 23 Nov 09Rubinov, WSU HEP seminar31

32.  The idea is to model the avalanche as a fast, brief (almost) short across a capacitor (Cdet) which is then recharged through a resistor (Rq)  this is one micro pixel, so 1 pe by definition  Also include parasitic capacitance across this resistor (Crq)  Also model the rest of the device by a collection of Cdetp, Rqp, Crqp  the parallel stuff is important, it gives that characteristic “kink”

33. This kink There are 4 values of Crq from 1 to 10 fF. So Crq is important for “spike” but not “tail” is this plus this

34.  and this is what we are left with...  So the size of the “spike” makes a huge difference to the shape of what is observed- including the integral Crq= 10fF, 5fF, 2.5fF, 1fF

35.  But, the slow component is not so affected  This fig has 8 plots: before and after the filter for each value of Crq

36.  But its even worse than that...  The details of the assumed filter make a big difference as well  I picked this very gentle, 6db stop band filter to prevent this...

37. ... how about we lower the HiFreq cutoff and concentrate on the shape of the falling edge. Lets say cut at 100MegHz  So that corresponds to digitizing at 200MSPS For this run, I dropped the Crq=10fF curve These are 5fF, 2.5fF and 1fF curves recall that Cdet is 3fF for this MPPC 025u

38. 38 Simulation vs reality

39. Using SiPMs 23 Nov 09Rubinov, WSU HEP seminar Until you have spread your wings, you will have no idea how far you can walk despair.com 39

40. CMS  Two approaches  Straight replacement of the HPD  Coupling individual fibers to individual SiPMs: Electrical Decoder Unit 23 Nov 09Rubinov, WSU HEP seminar40

41. 23 Nov 09Rubinov, WSU HEP seminar41

42. CMS 23 Nov 09Rubinov, WSU HEP seminar42

43. Linearity  number of cells is the issue 23 Nov 09Rubinov, WSU HEP seminar43

44. Radiation is an issue 23 Nov 0944

45. EDU 23 Nov 09Rubinov, WSU HEP seminar45  The EDU  100% compatible with existing mechanics/optics

46. CMS Either of these could use fantastic new devices from Zecotek 23 Nov 09Rubinov, WSU HEP seminar46

47. MAPD-1 with surface pixels (p-type substrate) 556 pixels*mm -2 MAPD-3N with deep microwells (n-type substrate) 15 000 pixels*mm -2 47 MAPDs main characteristics Anfimov Nikolay, Dubna, JINR

48. ILC- SiD  For SiD there are two possible uses of SiPM  HCAL : 3x3 cm cells directly coupled to SiPMs  Tail catcher/Muon system with scintilator strips and WLS fibers coupled to SiPMs 23 Nov 09Rubinov, WSU HEP seminar48

49. Scint HCAL for SiD 23 Nov 09Rubinov, WSU HEP seminar49 The key issue here is coupling of the scintillator to SiPM Northern Illinois University has some very clever and pioneering work on this (basic idea is to put a dimple in the center of the cell) We have made an Integrated Readout Layer board for tests of these cells

50. SiD muon system  For SiD muon system there are 3 main issues 1.Cost 2.Cost 3.Cost 23 Nov 09Rubinov, WSU HEP seminar50

51. Our setup Detail of optical coupling and adopter board using Keithley 2400 for bias (not shown)‏ 23 Nov 09Rubinov, WSU HEP seminar51

52. MTest 2008 Beam from Nov10 to 16 Minerva test of TOF counters Added one bar with SiPM for testing (Ham, IRST)‏ Using NIM based 6ch amp built at Fermilab for this work Using optical coupling designed at Notre Dame Using 120 GeV proton beam (1in x 1in spot)‏ Very preliminary results below 23 Nov 09Rubinov, WSU HEP seminar52

53. Single PE signals  Scope traces 5mv/div using LED 23 Nov 09Rubinov, WSU HEP seminar53

54. Ham-100 during beam spill Notice the Y scale is 100mv/div! Ham-100 during beam spill Notice the Y scale is 100mv/div! 23 Nov 09Rubinov, WSU HEP seminar54

55. 23 Nov 09Rubinov, WSU HEP seminar55 IRST SiPM with 1.8m sint in 120Gev Beam at 34V, I=1.1uA Notice the Y scale is 100mv/div! IRST SiPM with 1.8m sint in 120Gev Beam at 34V, I=1.1uA Notice the Y scale is 100mv/div!

56. Summary of test beam  If you have enough photons, SiPMs will make PERFECT muon detectors.  So the questions are:  Size of scintillation strip and WLS fiber diameter (cost)  Length of strip and WLS fiber (cost)  Area of the SiPM (coupling the fiber to the SiPM) (cost)  Electronics to readout the SiPM – does not drive the cost 23 Nov 09Rubinov, WSU HEP seminar56

57. Conclusion We are on a cusp of a revolution in Low Light Level photo detectors. The only questions is are we going to be manning the barricades 23 Nov 09Rubinov, WSU HEP seminar57

58. 58 The Future  I have seen the future of SiPM readout  Readout electronics will be integrated into the SiPM! because  SiPM is an inherently digital device  We ALWAYS convert the signal from the SiPM to digital  So why do we have an analog step in between?!? 0pe 1pe 2pe ADC 0pe 1pe 2pe

59. 59 The Future  Ingredients required for integrated readout 1.SiPM is CMOS compatible RMD makes SiPMs through Mosis 2.Will work for in HEP applications Pixel architectures have demonstrated readout of arrays like this 3.Cost effective (in volume)

60. 60 So why DIGITAL-ANALOG-DIGITAL?  Because this requires an ASIC  The people who make SiPMs do not know what we want  The people who know what we want do not make SiPMs (yet) Application Specific IC has to have a specific application Because it gives us the most flexibility

61. 61 Back from the future  Our current strategy is to maximize flexibility  which is the opposite of what we eventually want

62. 62 Next step(s): 4ch board  Still very generic, but now think infrastructure  Best available commercial components without heroic efforts (~1ns resolution, ~400 pe range)  Integrated with SiPM specific features (bias generator, current readback, temp sensor)  Optimized for medium ch count (dozen(s) SiPMs)  Flexible: using 50ohm input, generic daughter board connection to support faster readout/more memory  Large FPGA to allow DSP and TDC features

63. 63 Next step(s)  Still very generic, but now think infrastructure

64. 64  Still very generic, but now think infrastructure CW bias generator bias offset/ch hi res current readback/ch 2 stages of diff amps 12bit, 250MSP S ADCs largish FPGA simple USB interface daughter brd for faster interface

65. 65  Still very generic, but now think infrastructure CW bias generator bias offset/ch hi res current readback/ch

66. 66 Near future  Move from more generic to more specific  Develop a simple ASIC  Optimize for 100s of SiPMs