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Development of Multi-Pixel Photon Counters (1)

Development of Multi-Pixel Photon Counters (1). S.Gomi, T.Nakaya, M. Yokoyama, M.Taguchi, (Kyoto University) T.Nakadaira, K.Yoshimura, (KEK). for KEK-DTP photon sensor group. Oct.31.2006 Hawaii. Contents. Introduction Measure the fundamental performance Check the MPPC raw signal GAIN

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Development of Multi-Pixel Photon Counters (1)

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  1. Development ofMulti-Pixel Photon Counters (1) S.Gomi, T.Nakaya, M.Yokoyama, M.Taguchi, (Kyoto University) T.Nakadaira, K.Yoshimura, (KEK) for KEK-DTP photon sensor group Oct.31.2006 Hawaii

  2. Contents • Introduction • Measure the fundamental performance • Check the MPPC raw signal • GAIN • noise rate • Cross-talk rate • Photon Detection Efficiency ( PDE ) • Linearity • LASER test ( KEK-DTP LASER system)

  3. Introduction

  4. Multi-Pixel Photon Counter ( MPPC ) • Multi-Pixel Photon Counter ( = MPPC ) is a new type of photo detector developed by Hamamatsu Photonics (HPK). • MPPC consists of 100~1600 small avalanche photo diodes( APD ) in 1mm×1mm sensitive region. 1pixel 6mm MPPC Sensitive region of MPPC 400pixel type

  5. Operation principle of MPPC • Each APD pixel operate in Geiger mode. Gain is proportional to the applied voltage above the breakdown voltage( Vbd ). • In Geiger mode, the output charge Q from a single pixel is independent of the number of injected photons within the pixel. Extrapolated to GAIN=0 Vbd V

  6. Combining the output from all the pixels, the total charge from one MPPC is quantized to multiples of Q . MPPC advantages Compact Insensitive to magnetic field High gain( ~106 ), low bias voltage( ~70V ) Low-cost 5mm 6mm MPPC character the MPPC is an excellent photon counting device • We measured the basic performance of two kinds of MPPC, 100 pixel type, and 400 pixel type.

  7. Measure the fundamental performance check the MPPC raw signal gain noise rate cross-talk rate Photon Detection Efficiency ( PDE ) Linearity

  8. The raw signal of MPPC • MPPC has good photon counting capability. We can observe 1p.e signal peak, 2p.e signal peak, … * ADC distribution * 1p.e signal 2p.e 1p.e 2p.e … 3p.e pedestal 4p.e …

  9. set up blue LED • Measuring the little light from the blue LED by MPPC. • Gain is measured by ADC distribution. MPPC ADC distribution * STATUS DATA * 400 pixel MPPC BIAS : 70.0V / VBD =68.8V Gain • Gain of MPPC is defined as this equation. • Gain is measured by analyzing ADC distributions of MPPC signals. 1p.e signal 2p.e 3p.e pedestal 4p.e … The gain can be estimated at intervals between 1p.e and the pedestal.

  10. Gain Gain 100pixel Gain 400pixel • From gain-voltage relation, the break down voltage can be measured. 69.6 70 70.6 69 69.5 69.8 Bias voltage [V] Bias voltage [V] MPPC is a high gain device. Blue : 15degree Green : 20degree Red : 25degree The break down voltage depends on the temperature.

  11. Gain Gain 100pixel Gain 400pixel 0.2 1 1.6 0.8 1 2 2.4 DV DV • Gain is a function of DV. Blue : 15degree Green : 20degree Red : 25degree

  12. Noise rate • MPPC is a noisy photo detector. The origin of these noises is the thermo electron. So, the signals of noise are 1p.e signal typically. • The noise rate is measured by counting the rate of signal with their height over the threshold, imposed on 0.5p.e and 1.5p.e . “ 1p.e noise ” 0.5 p.e = threshold “ 2p.e noise ” 1 p.e Noise signal of 100pixel MPPC at 25 degree. ( integrated ) 1.5 p.e = threshold

  13. Blue : 15degree Green : 20degree Red : 25degree Noise rate Noise rate [ MHz ] 100pixel Noise rate [ kHz ] 400pixel • 1p.e noise rate is about 100~400 kHz. • 2p.e noise rate is about 0~200 kHz. 400kHz 500kHz 1p.e 2p.e 1p.e noise 2p.e noise 100kHz 100kHz 69.5 69.1 70 69.2 70 70.4 Bias voltage [V] Bias voltage [V]

  14. Noise rate Noise rate [ MHz ] 100pixel Noise rate [ kHz ] 400pixel • 1p.e noise rate is a function of both temperature and DV. 400kHz 500kHz 1p.e 2p.e 1p.e 2p.e 100kHz 100kHz 1 0.4 1.6 0.5 1 1.5 2 2.3 DV DV Blue : 15degree Green : 20degree Red : 25degree 2p.e noise rate seem to be a function of DV. This is due to “Cross-talk”.

  15. Cross-talk rate. • The origin of the cross-talk is presumed to be optical photons emitted during avalanche which enter neighboring pixels and trigger another Geiger discharge. APD that should not detect any photons from outside also operate signals. Neighborhood pixel Avalanche g “ Cross-talk “ g

  16. Cross-talk rate measurement • The probability of cross-talk is estimated by the number of 1p.e . The number of pedestal are free to cross-talk measurement • the number of each p.e is assumed to be follow the Poisson distribution The number of 1p.e : P(1) ( estimated by pedestal ) || without cross-talk The number of 1p.e : P(1) ( measured ) || with cross-talk This difference corresponds to the decrease by cross-talk. The cross talk rate is determined.

  17. Blue : 15degree Green : 20degree Red : 25degree Cross-talk rate Cross-talk rate 100pixel Cross-talk rate 400pixel • Cross-talk rate at operation voltage defined by HPK is about 20% at 20degree. ( We measured within the wider range about bias voltage. ) 50% 50% 10% 10% 69.6 70 70.6 69 69.5 69.8 Bias voltage [V] Bias voltage [V]

  18. Cross-talk rate Cross-talk rate 100pixel Cross-talk rate 400pixel • Cross-talk rate is a function of DV. 50% 50% 10% 10% 1 2 0.2 1 1.6 0.8 1 2 2.4 Delta V DV DV Blue : 15degree Green : 20degree Red : 25degree

  19. Photon Detection Efficiency • Photon Detection Efficiency ( = PDE ) is defined as this equation. PDE consists of three elements. Geometrical Efficiency. A ratio of active area to total area (50%~70%) Quantum Efficiency of active area (60~80%) Probability of Geiger discharge (60~90%) Depending on MPPC type Depending on wavelength of injected light Depending on bias V MPPC have the highest QE in Green light.

  20. relative PDE measurement ・only the light going through 1mmφslit is detected. set up Moving stage 1mmφslit ・The ratio of p.e of MPPC to that of PMT is taken as relative PDE of MPPC. PMT Blue LED MPPC ( total area 1mm2) PMT made by HPK, type H8643

  21. relative PDE Relative PDE 100pixel Relative PDE 400pixel • PDE is about 2~3 times higher than that of PMT. 3 2 2 1 1 69.6 70 70.6 69 69.5 69.8 Bias voltage [V] Bias voltage [V] Blue : 15degree Green : 20degree Red : 25degree

  22. relative PDE Relative PDE 100pixel Relative PDE 400pixel • PDE is a function of Delta V. 3 2 2 1 1 0.2 1 1.6 0.8 1 2 2.4 DV DV Blue : 15degree Green : 20degree Red : 25degree

  23. Linearity MPPC have the fixed number of pixel ( 100pixel, 400pixel,… ) • The linearity become those equation. MPPC is non-linear device when the number of injected photons is not small compared to pixel number.

  24. Linearity Linearity 100pixel Linearity 400pixel linear linear • The green line shows the expectation value calculated from number of pixels. Fired pixel [ % ] Fired pixel [ % ] 25% 25% Blue : DATA plot Green : expectation Blue : DATA plot Green : expectation Injected photoelectron per pixel Injected photoelectron per pixel MPPC can operate as linear device. ~25p.e about 100pixel type ~100p.e about 400pixel type.

  25. LASER test(using KEK-DTP LASER system)

  26. Laser test at KEK, Japan Picture of microscope 100μm microscope • Motivation • ・study the response of each pixel of MPPC • Uniformity within 1pixel • Uniformity in each pixel Laser source λ=825nm width 50ps Laser spot size 　≒10μm MPPC Uniformity… • gain Moving stage 1μm pitch (x , y) • cross-talk rate • efficiency Feed back this information to HPK

  27. efficiency Uniformity within 1pixel Sensitive region Efficiency, Gain (in sensitive region) Cross-talk rate (in sensitive region) RMS/mean=2% 100pixel Response within 1 pixels is uniform High at edge of sensitive region When the avalanche occur at edge of pixel, it is easy to emit to the next pixel(this is cross-talk). Cross talk rate GAIN 0.25 RMS/mean=2%

  28. Uniformity of each pixel Response of each pixel is uniform 100pixel efficiency GAIN RMS/mean=3% RMS/mean=3%

  29. Summary • MPPC has good performance !

  30. Supplements

  31. MPPC ceramic package for T2K • This ceramic package make their alignment by the out side frame.

  32. The principle of operation of 1APD pixel • APD (Avalanche Photo Diode) is a photo-diode that amplify the signal by operating the electron avalanche, that occur on the regions of pn-connection with high electric field. This high electric field is formed by applying bias voltage oppositely. Amplifying by electron avalanche γ V+ p+ absorption region p n When the bias voltage exceed the threshold voltage ( that is named “Break Down Voltage” ), very little light can make APD to occur the electrical discharge. This amplify is become about 106, and the height of signal doesn’t relate to the number of injected photon. hole e- GND E We can know only “the photon has come” or “not”.

  33. Temperature dependent of VBD • The results become linear.

  34. Set up for measuring linearity Paper set up ( to shade off LED light ) MPPC The number of photons emitted to MPPC are monitored by PMT. PMT

  35. efficiency Uniformity within 1pixel 400pixel RMS/mean=1.7% Cross talk rate GAIN 0.25 RMS/mean=1.6%

  36. efficiency Uniformity of each pixel RMS/mean=3.4% 400pixel Cross talk rate GAIN 0.18 RMS/mean=2.9%

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