R&D of MPPC for T2K experiment PD07 : Photosensor Workshop 2007 2007/6/28 (Thu) S.Gomi　T.Nakaya M.Yokoyama　H.Kawamuko ( Kyoto University ) T.Nakadaira T.Murakami　(ＫＥＫ)

T2K experiment MAIN GOAL Kamioka Tokai search for νμ→νe appearance precise measurement of νμ→ντ disappearance Kamioka Tokai

MPPC satisfy those requirement! T2K experiment SK Far detector Near detector MPPC satisfy those requirement! Target Proton beam Requirement to photosensor… 1. Almost of near detector composed of segmented scintillator and WLS fiber. The number of total readout channels is ~60000. 1. Compact size, low cost 2. Off-axis detector placed under 0.2T magnetic field. 2. Insensitive to the magnetic field Iron + scintillator

Basic performances of MPPC 　gain 　photon detection efficiency (PDE) 　noise rate 　cross-talk rate

MPPC output signal We report the basic performances of MPPC samples, S10362-11-100MOD, 400pixel sample. MPPC raw signal MPPC Histogram Pedestal Pedestal 1PE 1PE 2PE 3PE 2PE 3PE MPPC has good photon counting capability. We can observe 1p.e signal peak, 2p.e signal peak, …

ADC distribution of MPPC Gain measurement Definition of gain of MPPC set up Measuring the little light from the blue LED by MPPC. Gain is measured by ADC distribution. blue LED MPPC ADC distribution of MPPC Pedestal 1PE 2PE We can define gain of MPPC by this difference. 3PE

Result of gain measurement Blue : 15℃　 Green : 20℃　 Red : 25℃　 Gain : 400pixel S10362-11-100MOD ×10^3 C/e 1×10^6 VBD V 5×10^5 69.5 70 70.5 Bias voltage Bias voltage (V) From the result of gain, Breakdown voltage (VBD) and capacitance of MPPC can be measured.

Result of gain measurement From bias voltage and breakdown voltage, ΔV of each MPPCs can be measured. Gain DV : 400pixel S10362-11-100MOD ×10^3 1×10^6 VBD V 5×10^5 ΔV 0.5 1 1.5 2 2.5 Bias voltage ΔV (V) Blue : 15℃　 Green : 20℃　 Red : 25℃　 MPPC is a high gain device.

PDE measurement The ratio of p.e of MPPC to that of PMT is taken as relative PDE of MPPC. ( p.e. = # of photo electron ) set up MPPC MPPC ( total area 1mm2) 1.55PE 1mmφslit 1.55 0.789 =1.96 PMT PMT PDE = 1.96 Blue LED 0.789PE Moving stage

Result of PDE measurement Relative PDE 400pixel Relative PDE 400pixel : ΔV 2×PMT 1×PMT 69 .5 70 70.5 0.5 1 1.5 2 2.5 Bias voltage [V] Over voltage [V] PDE of MPPC is about 2 times higher than that of PMT. Blue : 15℃　 Green : 20℃　 Red : 25℃　

Noise rate measurement pedestal MPPC Gate=800nsec without Light source (random gate) free to cross-talk & after pulse Number of pedestal event 1p.e Poisson distribution 2p.e ・・・ estimated 1p.e value = P(1) ≠ because of cross-talk & after pulse estimated 2p.e value = P(2) ・・・

Result of noise rate measurement Noise rate [kHz] 400pixel Noise rate [kHz] 400pixel : ΔV 500kHz 1p.e noise 2p.e noise 250kHz 69 .5 70 70.5 0.5 1 1.5 2 2.5 Bias voltage [V] Over voltage [V] Blue : 15℃　 Green : 20℃　 Red : 25℃　 1p.e noise rate is small enough to the requirement of T2K(<1MHz)

Cross-talk & After pulse rate measurement In this measurement, we use ADC distribution for measurement of total influences that make 1p.e signal to 2p.e signal. We cannot distinguish this 2 component. Measurement without light source The number of pedestal is free to cross-talk & A.P. Poisson distribution The number of >2p.e : N>2p.e ( estimated by pedestal ) || Without Cross-talk & A.P. The number of >2p.e : N>2p.e ( measurement ) || With Cross-talk & A.P. This difference corresponds to the decrease by cross-talk & after pulse. Cross-talk & A.P. rate is defined.

Result of cross-talk & after pulse rate measurement Cross-talk & after pulse rate 400pixel Cross-talk & after pulse rate 400pixel : ΔV 50% 25% Vop(HPK) 69 .5 70 70.5 0.5 1 1.5 2 2.5 Bias voltage [V] Over voltage [V] Cross-talk & after pulse rate is a function of ΔV. Blue : 15℃　 Green : 20℃　 Red : 25℃　

Cross-talk rate & After pulse rate we cannot distinguish those in ADC distribution. we can distinguish those by differences of threshold in Scalar. 0.5p.e After pulse 1.5p.e 1p.e noise 1 gate 0.5p.e Cross-talk 1.5p.e 1 gate

Noise rate The noise rate measured by scalar is not equal to the noise rate measured by ADC distribution. Why not? 　the influence of after pulse We reject all influences that make 1p.e to 2p.e, when we measure noise rate with ADC distribution. The other hands, noise rate measured by Scalar may contain the influence of after pulse, and therefore this value is higher. 0.5p.e In Scalar, it seem to be 2 noises. After pulse In ADC distribution, it seem to be 1 noise.

The result of noise rate by 2 method The result by ADC distribution is smaller than the result by scalar. By assuming this difference come from only after pulse, we can obtain after pulse rate. 1p.e Noise (kHz) ■・・・Scalar ●・・・ADC distribution

After pulse rate & Cross-talk rate After pulse rate : 400pixel Cross-talk rate [Scalar] : 400pixel 10.55% 6.64% All 1p.e  2p.e The influence of after pulse is larger. 6.64% 14.11% Cross-talk 10.55% 3.08% After pulse

MPPC 300 sample test 300 MPPC samples are in our hands. Those are all 400pixel samples. (S10362-11-050CK) We measured the basic performances of those 300 samples and check the device-by-device variation of their performances. Gain PDE Noise rate Cross-talk & after pulse rate

Set up of measurement Light source LED We measured 32 MPPCs at once by using the custom electronics with Trip-T MPPC WLS fiber + Connector each fiber ･･･ ・・・ ×32 VME Trip-t PC

Set up of measurement with light source WLS fiber Light source to Trip-t chip MPPC × 32 with Plastic connector Those are set up of measurement. MPPC is connected with fiber by plastic connector

Shade the light from LED Light source Light source for measurement Using the light from LED(Blue)×1 defused by 2 plastic plate. Light from LED conduct to MPPC sensitive region by WLS fiber . Plastic connector Cookie and WLS fiber LED MPPC with connector on Trip-t board Shade the light from LED

Plastic connector for MPPC fiber coupling Prototype of Connector Fiber housing Fiber housing connect MPPC housing MPPC housing We make the prototype of plastic connector for MPPC WLS fiber coupling. We use this connector for measurement of PDE.

Trip-t chip test board developed by KEK MPPC Hole 5.3φ （32 Mount） Bias control Bias control ±5VIN 155mm 190mm 190mm 65mm In this measurement, we use Trip-t chip test board. This board can measure 32 MPPCs at the same time.

Gain measurement ( 300 samples ) Gain : 400pixel 20℃ 300samples Gain DV : 400pixel 20℃ 300samples ×10^3 ×10^3 1×10^6 5×10^5 69 70 71 1 1.5 2 2.5 Bias voltage (V) ΔV (V) Gain・・・7.3~8.5×10^5 300 MPPC samples have same gain-ΔV relation.

Break-down voltage (20℃) (V) Distributions of Capacitance and Breakdown voltage Capacitance/e : 400pixel 300samples VBD 20℃ : 400pixel 300samples The slope of gain-(VBias-VBD) relation ~ 2V ±10% ~ 1V Capacitance (×e 10^5) Break-down voltage　(20℃) (V) 300 MPPC samples have same capacitance.

With plastic connector Measurement of PDE The ratio of p.e of MPPC to that of PMT is taken as relative PDE of MPPC. ( p.e. = # of photo electron ) MPPC With plastic connector MPPC 1.55PE 1.55 0.789 =1.96 Same light value PDE = 1.96 PMT 0.789PE ( reference )

PDE measurement ( 300 samples ) PDE : 400pixel 20℃ 300samples PDE DV : 400pixel 20℃ 300samples 3×PMT 2×PMT 69 69.5 70 70.5 1 1.5 2 2.5 Bias voltage (V) ΔV (V) PDE・・・1.7~2.2×PMT 300 MPPC samples have same PDE-ΔV relation.

Noise rate measurement ( 300 samples ) Noise rate [kHz] : 20℃ 300samples Noise rate [kHz] DV : 20℃ 300samples 500kHz 250kHz 69.5 70 70.5 71 71.5 1.5 2 2.5 ΔV (V) Bias voltage (V) Noise rate・・・200~400kHz

Cross-talk & after pulse rate・・・18~23% Cross-talk & after pulse rate measurement ( 300 samples ) cross-talk & after pulse rate : 20℃ 300samples cross-talk & after pulse rate DV : 20℃ 300samples 50% 30% 69.5 70 70.5 71 71.5 1.5 2 2.5 ΔV (V) Bias voltage (V) Cross-talk & after pulse rate・・・18~23% 300 MPPC samples have same cross-talk & after pulse rate-ΔV relation.

Requirement from T2K experiment for 300 MPPC samples (S10362-11-050CK 400pixel type 1mm^2) index Requirement Result Sensitive region 1.2×1.2mm2 now testing… Number of pixels 100/400 (/mm^2) OK Gain ~1×106 7.3~8.5×105 1PE noise rate <1MHz 200~400kHz Cross talk + After pulse <5% 13~22% Photon detection efficiency (PDE) >1×PMT 1.7~2.2×PMT MPPC satisfy those requirements from T2K experiment.

Summary MPPC 1×1mm2 sample satisfy the requirement from T2K experiment. The device-by-device variation of basic performances come from the device-by-device variation of breakdown voltage, except for the noise rate.  ΔV control gain, PDE, and cross-talk rate. Future plan Test the new sample of MPPC that has 1.3×1.3mm2 sensitive region.

Back up

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

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. Vbd Extrapolated to GAIN=0 V

the MPPC is an excellent photon counting device MPPC character Combining the output from all the pixels, the total charge from one MPPC is quantized to multiples of Q . the MPPC is an excellent photon counting device MPPC advantages Compact Insensitive to magnetic field High gain( ~106 ), low bias voltage( ~70V ) High photon detection efficiency Low-cost 5mm 6mm

MPPC 100 sample test 100 MPPC samples have come. Those are all 400pixel samples. (S10362-11-100MOD) We measured the basic performances of those 100 samples and check the device-by-device variation of their performances.

Light Source Light source for measurement Using the light from LED(Blue)×1 defused by 2 papers. Distance from the MPPC is maximum. Paper Blue LED Box Check the light distribution by scanning using PMT (with window Φ1mm). PDE is defined by this distribution. LED voltage

MPPC Base Board I made new MPPC base board to fixed MPPC. 4 MPPCs can be measured by using this new board. This board has 2 layer, readout electronics is on the downer board and upper board fix MPPC. Readout ×4 50mm Bias MPPC ×4

MPPC Base Board Stand This stand should have complete reproducibility. This stop the board. By rotating, we can detaching.

Measurement System Those is measurement system. Those system is stable and has good reproducibility !

Result of measurement of gain ( 100 samples ) Gain : 400pixel 20℃ 100samples Gain DV : 400pixel 20℃ 100samples Vop(HPK) ×10^3 ×10^3 1×10^6 5×10^5 69 70 71 0.5 1 1.5 2 2.5 Bias voltage (V) ΔV (V) Gain・・・~8.0×10^5 100 MPPC samples have same gain-ΔV relation.

Break-down voltage (20℃) (V) Distributions of Capacitance and Breakdown voltage The slope of gain-(VBias-VBD) relation Capacitance/e : 400pixel 300samples VBD 20℃ : 400pixel 300samples ~ 0.4V ±2% Capacitance (×e 10^5) Break-down voltage　(20℃) (V) About 100 samples, MPPC have same capacitance.

Result of measurement of PDE ( 100 samples ) PDE : 400pixel 20℃ 100samples PDE DV : 400pixel 20℃ 100samples Vop(HPK) 2×PMT 1×PMT 69 70 71 0.5 1 1.5 2 2.5 Bias voltage (V) ΔV (V) PDE・・・~1.5×PMT 100 MPPC samples have same PDE-ΔV relation.

Result of measurement of noise rate ( 100 samples ) Noise rate [kHz] : 20℃ 100samples Noise rate [kHz] DV : 20℃ 100samples Vop(HPK) 500kHz 250kHz 69 70 71 0.5 1 1.5 2 2.5 Bias voltage (V) ΔV (V) Noise rate・・・130~310kHz Noise rate looks like contain another factor.

Result of measurement of cross-talk rate ( 100 samples ) cross-talk rate DV : 20℃ 100samples 50% Vop(HPK) 25% 69 70 71 0.5 1 1.5 2 2.5 Bias voltage (V) ΔV (V) Cross-talk rate・・・~23% 100 MPPC samples have same cross-talk rate-ΔV relation.

Measurement of noise rate time 1 1 1 1 2 ・・・5/Time or 6/Time 1 2 1 2 ・・・4/Time or 6/Time 3 1 2 ・・・3/Time or 6/Time Time Cross-talk(1p.e2p.e) If 1p.e noise is defined as the integral value of signals over the threshold on 0.5p.e, noise rate is changed by the gate length that used in measurement. On the other hands, P(n) is defined as the integral value of n p.e signals and if noise is defined as Σn・P(n), we cannot distinguish 2 noise from the influences of cross-talk. MPPC has cross-talk, so it is impossible to distinguish when we use ADC distribution.

Shade the light from LED Light source WLS fiber MPPC LED + Connector each fiber ･･･ Light source (image) ･･･×32 Shade the light from LED Light Distribution measured by PMT

Trip-t chip Trip-t ･･･TRIgger and Pipeline with Timing Developed by FNAL Used in D0 experiment Plan to use in T2K experiment Input 32ch Analog signal (negative) Output : Total 128pins Discri signal of each 32ch Analog signal proportional to input signal Analog signal proportional to the time between input signal and gate signal