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Development of Multi-pixel photon counters(2)

Development of Multi-pixel photon counters(2). M.Taguchi, T.Nakaya, M.Yokoyama, S.Gomi(kyoto) T.Nakadaira, K.Yoshimura(KEK). Contents. Application of MPPC for T2K experiment device-by-device variation of gain, noise rate Calibration method summary. T2K experiment. main goal.

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Development of Multi-pixel photon counters(2)

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  1. Development of Multi-pixel photon counters(2) M.Taguchi, T.Nakaya, M.Yokoyama, S.Gomi(kyoto) T.Nakadaira, K.Yoshimura(KEK)

  2. Contents • Application of MPPC for T2K experiment • device-by-device variation of gain, noise rate • Calibration method • summary

  3. T2K experiment main goal • precise measurement of disappearance • search for  appearance Super KamioKande J-PARC

  4. use scintillator+wave length shifting fiber for almost all near detectors  need compact & low cost photo sensor OffAxis detector is put under 0.2T environment  need tolerance of magnetic field Application of MPPC for T2K OffAxis detector target OnAxis detector MPPC satisfy these requirements! SK

  5. requirement from T2K ※ PDE…. without/with including the loss of light due to current package of MPPC fiber ~0.5mm MPPC 1mm

  6. Device-by-device variation Motivation • Basic performance of MPPC is almost satisfactory  next, device-by-device variation of basic performance when mass production? • if variation is large, - cannot apply the same bias voltage for all MPPCs - readout electronics needs to cover more dynamic range We measured the device-by-device variation of gain, noise rate for seven 100 and 400 pixel samples which are the same types

  7. tested samples • latest samples which was delivered at this month

  8. device-by-device variation ~gain~ • 20℃ • different colors correspond to data at different samples 400pixel 100pixel 1.2×106 3.0×106 1.0×106 4.0×105 69.4V 70.4V 69.4V 70.4V variation 3.0×106~3.6×106@70.4V variation 9.0×105～1.3×106@70.4V

  9. device-by-device variation ~ 0.5p.e.threshold noise rate ~ • 20℃ 100pixel 400pixel 400kHz 500kHz 100kHz 100kHz 69.4V 70.4V 69.4V 70.4V variation 250~650kHz@70.4V variation 150~370KHz@70.4V

  10. device-by-device variation ~ noise rate as a function of V-Vbd ~ • 20℃ Gain Vbd : breakdown voltage(derived by linearly extrapolating the gain-voltage curve to the point where gain becomes zero) Vbd V 100pixel 400pixel • noise rate as a function of V-Vbd takes the same value for different samples • variation of noise rate comes from variation of breakdown voltage 400kHz 500kHz 100kHz 100kHz 0.5 2 V-Vbd 0.5 2 V-Vbd

  11. device-by-device variation ~breakdown voltage~ • 20℃ 400pixel 100pixel • variation of Vbd is about 1V •  a bit large! we request HPK to make this variation small • we are going to check the variation for ~500 samples next March

  12. Calibration test Motivation Gain, PDE, crosstalk of MPPC are all sensitive to the temperature and bias voltage 1 MPPC Signal ∝ Gain(T,V) x PDE(T,V) x 1-crosstalk(T,V) T : temperature V : bias voltage It is necessary to calibrate the variation of gain, PDE,crosstalk when temperature or bias voltage changes I will present two calibration methods(explain each method later)

  13. put scintillators in four layers inserted fibers are viewed by four MPPCs(two are 400 pixel and two are 100pixel) change temperature intentionally like 20℃25℃ The same bias voltage (69.0V) is applied to four MPPCs two triggers(cosmic,LED) Set up for calibration test ※ we used old samples for this test cosmic-ray blue LED MPPC1(100) MPPC2(100) 1/2inch PMT MPPC3(400) MPPC4(400) scintillator 1mm φfiber temperature chamber

  14. Calibration Method 1 gain PDE(MPPC)/QE(PMT) crosstalk • gain, PDE, crosstalk are all functions of V-Vbd (independent of temperature) • can calibrate all parameters by monitoring only one parameter(for example, gain) V-Vbd V-Vbd V-Vbd V: bias voltage different colors correspond to data at different temperatures Vbd: breakdown voltage

  15. PDE(MPPC)/QE(PMT) measure the variation of gain gain LED trigger data 1p.e. 0p.e. V-Vbd crosstalk calibration constant= V-Vbd MIP ADC counts 1 gain x PDE x V-Vbd 1- crosstalk Calibration Method 1 LED trigger data 1p.e. estimate the variation of V-Vbd 0p.e. estimate the variation of PDE(V-Vbd),crosstalk(V-Vbd)

  16. calibration constant = MIP ADC count LED ADC count Calibration Method2 MIP ADC count　∝ gain(T,V)×PDE(T,V)× LED ADC count ∝ gain(T,V)×PDE(T,V)× 1 1- crosstalk(T,V) 1 1- crosstalk(T,V) cosmic ray LED Inject the light from LED with the same light intensity as MIP light yield LED ADC count MIP ADC count

  17. Stability of device response after calibration(100pixel) calibration constant method1 calibration constant method2 • precision of calibration is ~3% by both methods • response of other three samples is also well calibrated +3% +3% +3% -3% -3% -3% 20℃ 25℃ 20℃ 25℃ hour hour • only the errors of MIP ADC count and gain are included

  18. Summary and discussion about calibration test Stability of each MPPC response after calibration in RMS/mean calibration is possible by two methods (the precision of calibration is better for method 2) • measure the PDE, cross-talk rate as a function of V-Vbd before installation for method 1 We need to • guarantee the stability of light from LED for method 2

  19. Summary • use of MPPC at T2K is determined • device-by-device variation among seven samples is a bit large  we request HPK to make this variation small • we are going to check the variation for ~500 samples next March • calibration is possible by two methods  it is necessary to test much larger number of samples

  20. supplement

  21. measurement of gain ADC distribution MPPC gain = 1p.e. 1p.e. charge 0p.e. e(1.6×10-19) blue LED

  22. measurement of noise rate • count the rate above 0.5 and 1.5p.e. threshold without external light 0.5p.e. 1.5p.e.

  23. Basic performance ~crosstalk~ Data taken by random trigger Cross-talk rate = 0.5p.e. 1.5p.e. 103 102 ・Assuming 2p.e. noise is caused by crosstalk of 1p.e noise(accidental coincidence of 1p.e noise is subtracted) 10

  24. measurement of PDE ½ inch PMT blue LED ・only the light going through 1mmφslit is detected WLS fiber The view from this side ・Scan the MPPC and PMT with moving stage and search the position with maximum light yield MPPC(total area 1mm2) 1mmφslit Y ・The ratio of MPPC p.e. to PMT p.e. is taken as relative PDE of MPPC to that of PMT PMT MPPC slit x

  25. Crosstalk • assume the crosstalk takes place sequentially at the same probability • 1p.e. looks like: 1+(crosstalk)+(crosstalk)2+‥= correction factor of crosstalk= 1 1-crosstalk 1 1-crosstalk

  26. setup for calibration test

  27. MPPC(Multi pixel photon coutner) MPPC characters: • 100~1000 APD pixel in 1mm2 • Each pixel operates as Geiger mode (independent of input light) • The output is a sum of all the APD signals • Compact • Low-cost • Insensitive to the magnetic field • Low bias voltage :40~75V • High gain:105~107

  28. Raw signal and ADC distribution

  29. Where does the requirement to MPPC come from?

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