Introduction MPPC is new semiconductor photon sensor Technology is very similar to SiPM. Under development by Hamamatsu Photonics (HPK) MPPC have not

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Multi Pixel Photon Counter

T. Nakadaira

KEK

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Introduction

z

MPPC is new semiconductor photon sensor

Technology is very similar to SiPM.

Under development by Hamamatsu Photonics (HPK)

• MPPC have not been listed in their products yet.

• HPK delivered many kinds of test samples to T2K and ILC-CAL.

z

R&D groups in JP-HEP.

ILC Calorimeter (Kobe U,

Niigata U, Sinsyu U, Tsukuba U)

T2K Near detector (Kyoto U)

KEK Detector Technology

Development group

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Principal of MPPC

z Micro APD pixel array

# of pixels … 100, 400, 1600

Each pixel is operated in Geiger-mode.

• Bias voltage = 40 ~ 70V

… Only one operation parameter

Outputs from all pixels are directory connected (“Wired-OR”)

• # of read out = 1 channel / device

• Pulse height of output signal ÅÆ # of hit pixels

# of hit pixels ÅÆ # of photons

zGain = ~106

No amplifier is needed

zCompact size

Suitable for optical fiber readout.

zWorks in the Magnetic field.

zHigh QE is expected.

zExpected cost is ~ $10 / device.

1p.e 2p.e 3p.e Raw signal HPK 100pixel MPPC 1mV/div 100ns/div T.Nobuhara (Kyoto U)

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R&D Items

z

Measurement of basic performance w/ LED

Gain, Noise rate, Cross talk, Photon Detection Efficiency (PDE), linearity

Å These parameters strongly depends on the bias voltage.

z

Pixel by Pixel uniformity

Inject photon to pixel by pixel using well focused laser beam

• 532nm Laser system @ Niigata University

• 825nm Laser system @ KEK

z

Beam test @ KEK 12GeV PS test beam line

Detect the particle using Plastic-scintillator + WLS optical fiber + MPPC

Beam data is taken in Nov, 2005

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0 500 1000 1500 2000 2500 80 100 120 140 160 180 200 220 240

Photon counting by MPPC

z

Charge distribution

LED light (HPK 100 pixel)

We can distinguish up to 45 p.e. peak.

Variation of Intervals between peaks is in 2%. Æ Gains for each pixels are uniform.

0 100 200 300 400 500 250 300 350 400 450 500 550 600 30p.e Charge # event 1p.e 0p.e 2p.e 3p.e # event

Increasing LED light

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1300 1400 1500 1600 1700 1800 1900 2000 x 104 46.8 47 47.2 47.4 47.6 47.8 48 48.2 48.4 4600 4800 5000 5200 5400 5600 5800 6000 6200 6400 x 10 3 47.5 47.75 48 48.25 48.5 48.75 49 49.25 49.5

Bias Voltage (V) Bias voltage (V)

HPK 100 pixel HPK 400 Pixel 47 48.4 _47.5 49.5 2×107 1.5×107 Gain 6×106 5×106 Gain

MPPC Gain

z

Gain = 8×10

5

~ 2×10

7

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1 10 102 103 0 100 200 300 400 500 600 700 800

Noise Rate

z

Measure the signal rate w/o LED light.

Charge

1p.e. pulse … noise

w/o LED

0p.e

1p.e

w/o LED

2p.e

Charge distribution for Noise

0.5p.e

400 pixel

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10 2 10 3 10 4 10 5 10 6 47 47.5 48 48.5 49 49.5 0.5p.e threshold 1.5p.e threshold noise rate (Hz) Bias voltage (V)

Noise > 1p.e.

is less than

10 %

1MHz 100 pixel 400 pixel

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0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0 1 2 3 4 5 6 7

Cross talk among the pixels

z

Cross talk is measures in 2 methods.

Noise rate … (Noise > 1.5 p.e ) / (Noise > 0.5 p.e)

Discrepancy of charge distribution from Poisson distribution.

adc count 160 180 200 220 240 260 280 300 h1 Entries 50000 Mean 198.3 RMS 4.671 adc count 160 180 200 220 240 260 280 300 1 10 2 10 3 10 4 10 _h1 Entries 50000 Mean 198.3 RMS 4.671 HPK14 0.5p.e 1.5p.e 104 103 102 10 Poisson dist. Data HPK 400pixel V=48.6 p.e ratio

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X-talk v.s. bias V (２０℃)

X- talk Rate 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 47 47.5 48 48.5 49 49.5 bias voltage (V) HPK400b by poisson law HPK100a by noise rate

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Linearity measurement

z

If the light intensity became large, several photons

injected in a pixel.

Æ Counted as single photon because of the

Geiger-mode operation.

z

Linearity measurement is important to determine the

number of pixels.

z

Linearity is also affected by cross talk.

Linearity is measured by changing the bias voltage to check the x-talk effect.

z

We use the PMT as a reference of light intensity.

Blue LED

PMT MPPC

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Linearity (HPK 100 pixel)

ADC(PMT) 0 10 20 30 40 50 ADC(PMT) 0 10 20 30 40 50 ADC(MPPC) 0 100 200 300 400 500 600 700 HPK14 linearity ADC(PMT) 0 5 10 15 20 25 30 35 ADC(PMT) 0 5 10 15 20 25 30 35 ADC(MPPC) 0 50 100 150 200 250 300 HPK14 linearity MPPC ADC count

Fit with line

injeceted photo electron number 10 20 30 40 50 60 70 80

injeceted photo electron number 10 20 30 40 50 60 70 80 ratio 0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 10% 20% HPK14 linearity

injected photo electron number 10 20 30 40 50 60 70

injected photo electron number 10 20 30 40 50 60 70 ratio 0.7 0.75 0.8 0.85 0.9 0.95 1 1.05 10% 20% HPK14 linearity 20%@50p.e 20% 40 # of photon 50 PMT ADC count 20% Discrepancy(%) 0% 0% X-talk rate =0.03 X-talk rate =0.2 # of photon 20%@40p.e M.Taguchi (Kyoto U)

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PDE (photon detection efficiency)

PDE relative to PMT is measured.

Quantum Eff. (60~80%)

Probability for p.e. to invoke Geiger

discharge (60~80%)

z # of photo electron in signal/ # of injected photon

PDE=

ε

pixel

× Q.E. ×

ε

Geiger

Depends on bias voltage

Geometrical Eff. (30~50%)

Depends on

MPPC type _{Depends on wave length}

MPPC(1mm2₎ PMT(13mmφ) 1mmφslit 青色LED / 赤LED MPPC(1mm2₎ PMT Blue LED 1mmφ WLS fiber Dispersion is not taken into account in calc.

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noise rate(kHz) 300 350 400 450 500 550 600 650 700 noise rate(kHz) 300 350 400 450 500 550 600 650 700 MPPC(p.e)/PMT(p.e) 0.4 0.5 0.6 0.7 0.8 0.9 1 green blue HPK14 PDE

Measured PDE

noise rate(kHz) 300 400 500 600 700 800 noise rate(kHz) 300 400 500 600 700 800 PDE(%) 5 6 7 8 9 10 11 12 Max: 12% (PMT Q.E ~ 2%) 300 400 500 600 700 1 noise rate (kHz) PDE(MPPC)/PDE(PMT) Blue/ green 0.5 PDE(MPPC) Red assuming PDE(PMT=2%)

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Performance test w/ Laser

z

Test MPPC pixel by pixel (HPK 100 pixel)

Micro Scope Laser Light source 825nm 50ps XY moving stage (1µm pitch control) Spot size ~ 10µm MPPC

• Check the uniformity of efficiency in single pixel •Pixel by Pixel deviation of gain and efficiency

の測定を行った

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Uniformity: Single pixel

0 100 200 300 400 500 600 700 80 100 120 140 160 180 100 µm Laser spot 10µm pitch HPK 100pixel Charge dist. in a point Efficiency= signal>0.5 p.e / Total event 0p.e. 1p.e. 0.5p.e. Efficiency x y Flat area: 60x60 µm2 100μm 100μm Sensitive region 70x70μm

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Uniformity: Pixel by Pixel

0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0.92 0.94 0.96 0.98 1 1.02 1.04 1.06 0 1 2 3 4 5 6 7 8 9 10 0 1 2 3 4 5 6 7 8 9 10 0.96 0.98 1 1.02 1.04

Set laser spot @ center of each pixel

HPK 100 pixel y y x x Relative Gain Relative Efficiency r.m.s./mean = 3.6% r.m.s./mean = 2.5%

Very good uniformity

1mm 1mm

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Summary& Prospect

z

MPPC is promising device for photon counting.

Gain ~ 106_-107

Noise rate: O(1MHz) for >0.5 p.e., O(10~100kHz) for >1.5 p.e.

X-talk rate: < ~0.2

Photon Detection Efficiency: comparable to PMT

linearity: Discrepancy within 20% up to 40% of # of pixels

Efficiency in single pixel is uniform

Pixel by Pixel deviation of gain and efficiency is very small

z

HPK delivered new samples to T2K and ILC-CAL

group.

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64ch MAPMT (as reference) ビームシンチレータ1.3x2.5x50 cm3 (K2K実験のScibar検出器で使用していたもの）ファイバー1mmΦ MPPC (HPK or Russia) 4 layers

ビームによるシンチ＋ファイバー読み出しのテスト

• 0.5∼1.4GeV/c • proton & pion • ∼100 event/spill • beam size 1x1cm2 T2K 前置検出器と同じ読み出し条件で、 MPPCによってT2Kの要請を満たす光量が得られるか。さらに、pとπの識別が可能か動機 4ch全てのビームによるMPPC シグナルを見ることができた MIPに対して5p.e.以上 _setup

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HPK製MPPCにおけるファイバーのalignment

HPK製MPPCの受光面とパッケージの位置関係 • Z方向 : 透明カバーと受光面に隙間が存在受光面‐ファイバー間距離は0.8mmとなる • X,Y方向 : サンプルごとにばらつきがあるサンプルごとにファイバーの位置合わせを行った Y X Z 0.8mm ファイバー(1mmφ) 固定具ファイバー固定ネジ移動ステージでファイバーをスキャンし、 MPPCシグナルが最大の点でファイバーの位置を固定した X、Y方向位置合わせ MPPC X,Y方向の位置のずれにより最大20%,Z方向の隙間により約60％の光量のロスが存在現段階のパッケージ構造によるもので、デバイスの性能からくるものではないファイバーから40°で一様に光が広がっているとした場合の値

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MIPによる光量 (p.e.) Ⅰ

0 20 40 60 80 100 120 140 160 0 5 10 15 20 25 30 35 40 45 50 0 20 40 60 80 100 120 140 160 180 0 10 20 30 40 50 60 70

17.1p.e.

13.3p.e.

Photon Detection Efficiency (PDE）=MPPCの受光面(1mm2 _{)にフォト} ンが入射したときに、それを検出する確率（バイアス電圧に依存する） PMTと比較したPDEを、HPK製は70%, ロシア製は100% となるようにバイアス電圧を設定した p.e. _p.e. #event #event

HPK

_ロシア

MIPによるパルスの電荷量分布においてピークをみることができた

この分布の平均p.e.数から、MPPCによって

得られた光量を求めた

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MIPによる光量 (p.e.) Ⅱ

39 7.2 #17 73 13.3 #16 56 10.2 #14 54 9.9 #13 PMTとの比 (%) 光量(p.e.) Serial# HPK PDEがPMTの70%のときの光量(p.e.) ロシア PDEがPMTの100%のときの光量(p.e.) 94 17.1 #14 126 22.9 #13 PMTとの比(%) 光量(p.e.) Serial# PDEはZ方向のロスを含めた値ロシアの方はファイバーと受光面間での光のロスは十分小さい（パッケージ構造上） MIPにより、MAPMTで得られた光量は18.2p.e.だった期待される光量からのずれの原因としては、ともにPDEの測定誤差があり、さらにHPK製において、ファイバーのX,Y方向の位置のずれによる光のロスが挙げられる

MPPCにおいて、T2Kからの要請をみたす

光量が得られた

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p/π Separation

1.2GeV 1.0GeV 0.9GeV

0.8GeV _0.7GeV _0.6GeV

0.5GeV