1. Development of Multi-Pixel Photon Counters and readout electronics Makoto Taguchi High Energy Group

2. Contents  T2K experiment  Multi-Pixel Photon Counters (MPPC)  Basic performance  Laser test  Readout electronics of MPPC  Conclusion

3. T2K experiment

4. search for appearance precise measurement of disappearance T2K experiment J-PARC SK main goals

5. Photosensor for T2K # of channels ~ 60,000 and space is limited  compact & low cost under 0.2T environment  tolerance to magnetic field efficiency for the detection of particles  large light yield target 0.2T magnet Magnet use scintillator+wave length shifting fiber for the near detectors MPPC is chosen as the photosensor for T2K that satisfies these requirements requirements to photosensor T2K near detectors

6. Multi-Pixel Photon Counters(MPPC)

7. Multi-Pixel Photon Counter(MPPC)  New(~2years ago) photosensor produced by Hamamatsu Photonics ~5mm Geiger-APD pixels 100um 100 or 400 avalanche photodiode(APD) pixels in 1mm 2 Each pixel works in Geiger mode above breakdown voltage  output from each pixel is independent of # of created p.e. within the pixel The output from MPPC is a sum of output charge from all APD pixels  output from MPPC is proportional to the # of fired pixels photon high (~10 6 ) gain  Geiger mode insensitive to magnetic field  semiconductor compact, low cost (~2000Yen?) excellent photon counting attractive feature

8. Measurement of basic performance of MPPC  Test samples ・・・ latest (Oct. 2006) 100 and 400 pixel samples  Test items ・・・ raw signal gain noise rate Photon detection efficiency crosstalk-rate Linearity recovery time presented here Basic performance of MPPC satisfies the T2K requirement? MPPC is a new photodetector Motivation

9. Raw signal blue LED 1p.e. 2p.e. 3p.e. output charge oscilloscope or ADC 1p.e. 2p.e. 3p.e. gate photon MPPC Excellent photon counting capability! pedestal

10. Gain pedestal 1p.e. Gain = Q/e Q bias voltage 15deg. 20deg. 25deg. Gain = 1.0x10 6 ~ 3.0x10 6 and increases with lower temperature linear dependence on bias voltage, G = C (V-V bd ) ADC distribution C : capacitance V: bias voltage V bd : breakdown voltage

11. Noise rate MPPC emits thermal noise without external light count the rate above thresholds of 0.5p.e. and 1.5p.e. bias voltage (kHz) 15deg. 20deg. 25deg. 1.5p.e. th. 0.5p.e. th. noise rate at 0.5p.e. th. <500kHz and becomes higher with higher temperature noise rate at 1.5p.e. th. <100kHz and becomes higher with lower temperature  cross-talk effect

12. Cross-talk “photons generated during an avalanche trigger another avalanche in neighboring pixel” crosstalk rate = f estimated : estimated fraction of 1p.e. events from that of pedestal events assuming Poisson f observed : observed fraction of 1p.e. events 1- f estimated f observed bias voltage 15deg. 20deg. 25deg. ADC dist.  Crosstalk rate 0.2 ~ 0.4 and increases with lower temperature

13. Photon Detection Efficiency(PDE) PDE =x QE x geometrical efficiency ~70% quantum efficiency of APD ~70% Geiger probability (V,T) ~90% MPPC PMT 1mmφslit WLS fiber blue LED PDE(MPPC)/QE(PMT) setup 15deg. 20deg. 25deg. p.e.(MPPC) p.e.(PMT) V  PDE of MPPC is 2~3 higher than that of PMT and increases with lower temperature

14. Summary of basic performance 100pixel400pixelRequirement for T2K Gain1.0~3.0x10 6 ~1.0x10 6 ~10 6 Noise rate at 0.5p.e. th. 100~500kHz <1000kHz Noise rate at 1.5p.e th. 10~100kHz <50kHz Cross-talk rate0.2~0.4 PDE20~45%20~30%>15% Linearity~40p.e.~120p.e.~100p.e. @20deg. Performance of MPPC satisfies the requirements for T2K!

15. Laser test for the old samples, gain in the edge of pixel is higher than that in the center of pixel breakdown voltage is different in each pixel  check the response within one pixel /of each pixel for the new samples test items ・・・ gain, efficiency, cross-talk green laser movable stage MPPC uniformity within one pixel pixel-to-pixel uniformity setup efficiency = # of total events # of events > 0.5p.e. Motivation presented here 10um

16. gain efficiency uniformity within one pixel pixel-to-pixel uniformity efficiency RMS/mean =2.0% RMS/mean =3.3% RMS/mean =2.5% Response within one pixel/of each pixel is well uniform!

17. Readout electronics of MPPC

18. Readout electronics of MPPC with “Trip-t” chip  use ~60,000 MPPCs in T2K and compact&multi-channel electronics is necessary  establishment of test system for mass production of MPPC is also needed  we have developed the readout electronics with Trip-t ASIC produced at Fermilab 32 channel inputs for negative charge 1) serialized analog output corresponding to the amplitude of input charge 2) serialized analog output corresponding to the timing of input charge 3) discriminated output for each channel Motivation Trip-t 14mm # of readout channels 32  1 14mm

19. Trip-t front end Pipeline Digital multiplexer analog multiplexer A_OUT (charge ) T_OUT (timing) D_OUT(digital) amplifier (gain is adjustable) generate digital signals store signals before readout (depth 1~48) serialize 32ch signals input charge charge timing digital ch1 ch2 ch3 ch1 ch2 ch3

20. Readout of MPPC with Trip-t 1p.e. 2p.e. output from Trip-t 4MPPC 3p.e. LED test board(4ch) AD conversion by flash ADC 100pixel 400pixel readout 4 MPPCs simultaneously  succeed in developing the multi-channel readout electronics of MPPC!

21. Dynamic range of Trip-t charge (-pC) ADC count saturation >> Trip-t gain Dynamic range ~40p.e. with the lowest gain of Trip-t, assuming MPPC gain of 7.5x10 5  OK for test of large number of MPPCs  not OK for T2K (requires ~100p.e.) MPPC 100pF 10pF high gain channel low gain channel high/low gain method for real type elec. high gain channel ・・ determine gain w/ photopeaks low gain channel ・・ accommodate large signal Trip-t can be used for the readout electronics of MPPC in T2K

22. Conclusion MPPC is a new photodetector produced by Hamamatsu Photonics and chosen as the photosensor for T2K Basic performance of MPPC satisfies the requirements for T2K Response within one pixel/of each pixel is well uniform Trip-t which was produced at Fermilab can be used for the readout electronics of MPPC in T2K future development ・・ test of large number of MPPCs with 32ch Trip-t board Our study is an important step not only for T2K but also for wide use of MPPC

23. backup

24. Principle of APD high reverse bias voltage applied to a pn junction  multiplication region, where created e - - e + pairs cause an avalanche multiplication Normal mode - operate below the breakdown voltage(V bd ) - gain < ~ 100 - have linear output to # of injected photons Geiger mode - operate above the breakdown voltage(V bd ) - gain ~10 6 - does not have linear output to # of injected photons E reverse bias

25. Gain 100pixel400pixel bias 15deg. 20deg. 25deg.

26. gain(2) 100pixel 400pixel 15deg. 20deg. 25deg. ΔV ΔV =V-V bd Gain is a function of only ΔV

27. Device-by-device gain variation bias V Device-by-device gain variation comes from the device-by-device variation of V bd ΔV =V-V bd 400pixel #2 #1 #3 #2 #1 #3

28. Noise rate 100pixel bias (kHz) 15deg. 20deg. 25deg. 1.5p.e. th. 0.5p.e. th. 1.5p.e. th. 400pixel

29. Device-by-device variation of noise rate at 0.5p.e. th. bias V Device-by-device variation of noise rate comes from the device-by-device variation of V bd (kHz) 400pixel #2 #1 #3 #2 #1 #3 ΔV =V-V bd

30. Cross-talk rate bias 100pixel 400pixel 15deg. 20deg. 25deg.

31. Cross-talk rate(2) 100pixel 400pixel ΔV 15deg. 20deg. 25deg. cross-talk rate is a function of only ΔV ΔV =V-V bd

32. Device-by-device variation of cross-talk rate bias V ΔV = V-V bd Device-by-device variation of cross-talk rate comes from the device-by-device variation of V bd 400pixel #2 #1 #3 #2 #1 #3

33. PDE(MPPC)/QE(PMT) bias 100pixel 400pixel 15deg. 20deg. 25deg.

34. PDE(MPPC)/QE(PMT)(2) ΔV 100pixel400pixel 15deg. 20deg. 25deg. PDE is a function of only ΔV ΔV =V-V bd

35. Device-by-device variation of PDE bias V ΔV = V-V bd Device-by-device variation of PDE comes from the device-by-device variation of V bd 400pixel #2 #1 #3 #2 #1 #3

36. V bd vs T V bd degree V bd is proportional to the temperature 100pixel 400pixel

37. Comparison of latest and old samples (gain) latest old latest old 100pixel400pixel ΔV

38. Comparison of latest and old samples (noise rate) latest old 100pixel latest old 400pixel (kHz) ΔV noise rate of latest sample is lower

39. Comparison of latest and old samples (cross-talk rate) latest old 100pixel ΔV latest old 400pixel cross-talk rate of latest sample is higher  increase of geometrical efficiency

40. Comparison of latest and old samples (PDE) latest old 100pixel ΔV latest old 400pixel PDE of latest sample is higher  increase of geometrical efficiency

41. Linearity paper setup # of injected p.e. to MPPC is estimated by the p.e. detected by a monitor PMT expected response: MPPC PMT N fired : # of fired pixels N 0 : # of pixels c : Cross-talk rate x : # of injected p.e. LED

42. 100pixel 400pixel +10% +20% -10% injected p.e. # of fired pixel (Data-exp.)/Data(%) Data expectation

43. Linearity(3) 100pixel 400pixel # of injected p.e. (Data-Fit)/Data(%) -20%

44. Recovery time “time to quench an avalanche and then reset the applied voltage to its initial value” fire all pixels by the light from LED1 and check the response to the light from another LED(LED2) with changing the time difference between the LED1 and LED2

45. Recovery time(2) 100 pixel 400 pixel All pixels are recovered 100ns after all pixels are fired Recovery time < 100ns

46. uniformity of cross-talk rate within one pixel cross-talk rate = # of events > 0.5p.e. # of events > 1.5p.e. 100pixel 400pixel

47. Pixel-to-pixel uniformity of cross-talk rate 100pixel 400pixel

48. Measurement of active area inside one pixel 100pixel 400pixel 100um 85um 50um 38um um laser spot scan efficiency =72% =58%

49. Correction of MPPC signal Motivation Gain, PDE, crosstalk of MPPC are all sensitive to the temperature and bias voltage It is necessary to correct the variation of gain, PDE,crosstalk when temperature or bias voltage changes MPPC Signal ∝ Gain(T,V) x PDE(T,V) x 1-crosstalk(T,V) 1 T : temperature V : bias voltage I have studied two correction methods

50. Set up 1/2inch PMT cosmic-ray 1mm φfiber MPPC2(100) MPPC1(100) MPPC3(400) MPPC4(400) scintillator blue LED put scintillators in four layers inserted fibers are connected by four MPPCs(two are 400 pixel and two are 100pixel) change temperature intentionally between 20 and 25 degree The same bias voltage is applied to four MPPCs two triggers(cosmic,LED) temperature chamber With this setup we have traced the variation of light yield for cosmic-ray

51. Correction method A gain cross-talk ratePDE ΔV 1) monitor the variation of gain 1) 2) 2) estimate the variation of Δ V 3) estimate the variation of crosstalk,PDE 3) 15deg. 20deg. 25deg.

52. Correction method A(2) calibration constant= gain x PDE x MIP ADC counts 1- crosstalk 1 this value must be constant if we can correct the variation of gain, crosstalk,PDE

53. Correction method B MIP ADC count ∝ gain(T,V)×PDE(T,V)× LED ADC count ∝ gain(T,V)×PDE(T,V)× 1 1- crosstalk(T,V) 1 MIP ADC count LED ADC count calibration constant = MIP ADC count LED ADC count dist.taken by cosmic trig. dist.taken by LED trig. Inject the light from LED with the similar light intensity as MIP light yield

54. Variation of calibration constant +3% -3% method A +3% -3% +3% method B calibration constant only the errors of MIP ADC count and gain are included hour detector response can be corrected within 3% level by both methods

55. MPPC1(100)MPPC2(100)MPPC3(400)MPPC4(400) Method A2.5%2.3%3.8%3.1% Method B2.5%1.3%2.4%1.4% Summary of correction methods RMS/mean of calibration constant Required precision is a few % (This depends on the type of detector)  Both correction methods satisfy the requirement!

56. Requirement to MPPC ItemRequirementFrom where Area1.2x1.2mm 2 To match 1.0mm fiber No. of pixel100/400To keep dynamic range up to ~100p.e. Gain~10 6 To match readout electronics Noise rate<1MHzTo reduce accidental hits Crosstalk<5%To reduce the noise rate with 1.5p.e. threshold PDE>15%Light yield Timing resol.2-3nsNot so meaningful requirement

57. Specification of Trip-t Size : 14mm x 14mm Power supplies : +2.5V Power consumption < 10mW per channel

58. Trip-t gain pipeline 1pF 3pF preamp gain x1 or x4 opamp gain x2,x4,x8… preamp input opamp Trip-t gain can be changed by programming the registers

59. Setup for readout of MPPC FADC A_OUT - + opamp Trip-t +5V -5V Digital wave generator Control signals Trigger MPPC LED 4m flat cable AD conversion Trigger

60. Readout sequence of Trip-t A_OUT(charge) MPPC signal (ch1) preamp integrate signal after preamp A_OUT Multiplexer clock 01233 ch1

61. A_OUT charge = -1.5pCcharge = -0.5pC

62. A_OUT linearity ADC count charge(-pC) Trip-t gain >> >> nonlinearity in the low pulse amplitude  will be fixed for the new version of chip (Data-linear)/Data(%)

63. Crosstalk of A_OUT signal observed in the channel where the charge is not injected ch 0.4% 15 crosstalk(i) = ADC charge (i)-ADC nocharge (i) ADC charge (15)-ADC nocharge (15) ADC (no)charge (i) = ADC count in the channel i when the charge is (not) injected crosstalk<0.4%

64. Variation of Trip-t gain variation is ~4% chgain (ADC count/-pC) 15730 16710 31735 32732

65. Readout sequence of Trip-t T_OUT(timing) MPPC signal (ch1) preamp integrate signal after preamp T_OUT Multiplexer clock 01233 pipeline clock ch1

66. T_OUT time difference = 200ns time difference = 100ns

67. T_OUT linearity ns ADC count (Data-linear)/Data(%) saturation

68. T_OUT conversion factor variation is ~25% chConversion factor (ADC count/ns) 158.52 168.60 318.00 329.97

69. D_OUT(Digital) Trip-t 1pF charge injection 10ns Delay inside Trip-t is ~10ns

70. 100pixel 400pixel MPPC gain measured by CAMAC and Trip-t bias Trip-t gain is well calibrated Trip-t CAMAC Trip-t CAMAC

71. Current design of real type electronics for T2K 16 MPPCs Trip-t ADC FPGA Trip-t 16MPPCs Trip-t 64MPPCs per board with 16 high/low gain channels per chip control of Trip-t and ADC by FPGA temperature monitoring HV trimming DAC

72. spill(8bunch) integrate (~300ns) reset (~50ns) Chip time structure (preliminary) 5.6us readoutcatch late signal ~3us~50us beam

73. high/low gain method high low ~300p.e.~30p.e.

74. ADC distribution with lowest gain of Trip-t MPPC gain = 7.7x10 5 S/N=3

75. VA chip ASIC used for the K2K SciBar detector - 64ch inputs - VA does not have pipeline - VA itself cannot issue discriminated output - VA gain cannot be changed

76. Readout sequence of VA MPPC signal (ch1) signal after shaper amp outm 0 ch1 12 hold_b Multiplexer clock

77. Readout of MPPC with VA MPPC gain = 2.7x10 6, noise rate at 0.5p.e. th. = 240kHz pileup of MPPC noise S/N=1.7