Development of Multi-Pixel Photon

Counters(MPPC)

Makoto Taguchi Kyoto University

Contents

Photosensor for T2KMulti-Pixel Photon Counters(MPPC)Basic performance Laser test in KEKSummary

Photosensor for T2K

# of channels ~60,000 and space constraint

Compact, low-cost0.2T magnetic field Tolerance to

magnetic field

Magnet

Readout with scintillators and wavelength shifting fibers

developed a new photodetector, “MPPC” for T2K

ν

T2K near detectors

Multi-Pixel Photon Counter(MPPC)Semiconductor photon counting device which

consists of many Geiger-mode APD pixelsWe have developed with Hamamatsu Photonics

since 2 years ago

PMT MPPC

Size ~10cm 6mm

Voltage 1000~2000V

~70V

Magnetic field × ○

Gain ~106 ~106

Photon detection efficiency

~15% 30~45%

Excellent performance!

APD pixels

1mm

Operation principle of one pixelquenching

resistor

Geiger-mode APD

Vbd ：　　　　　　　Breakdown voltage

Vbias ： applied voltage

Geiger discharge

Linear mode

Geiger mode

quenching

　 = C ×(Vbias-Vbd) = ~106 x e

Vbias

I

capacitance ~200fF ~1V

charge from one pixel : Q

Photon

charge

Operation principle of MPPCEach pixel only shows whether photon is injected or not to the pixel

Output from MPPC is a sum of output from APD pixels

Signal proportional to the # of injected photons

1p.e.2p.e.

3p.e.

Measurement of basic performance

Test samples ・・・ Latest (Oct.2006) 100, 400pixel Test items ・・・ Raw signal Gain Photon detection efficiency Noise rate Cross-talk rate Linearity

only shown here

Basic performance of MPPC satisfies the T2K requirements?

MPPC is a new photodetector

Motivation

@20℃

Raw signalLED

1p.e.

2p.e.

outputoscilloscope, ADC

photon

MPPC

Excellent photon counting capability!

1p.e.2p.e.

60ns60ns

3p.e.

3p.e.

Gain

0p.e.

１p.e. Q

1.0×106 ~ 3.0×106

Linear dependence on the applied voltage Q = C (Vbias-Vbd)

applied voltage(V)

1.0x106

3.0x106

Gain = Q/e

MPPC

PMT

1mmφslit

fiber

LED

PDE (relative to PMT)

applied voltage(V)

Larger PDE with larger applied voltage

PDE is 2~3 times larger than that of PMT!

=p.e.(MPPC)

p.e.(PMT)

Photon Detection Efficiency(PDE)

Setup 3

2

Noise rate

applied voltage(V)

Larger noise rate with larger applied voltage

1p.e. noise rate < 500kHz

2p.e. noise rate < 100kHz

MPPC emits thermal noise without external light input

Count # of pulses above the 0.5 or 1.5p.e. threshold without external light1p.e.

noise

2p.e. noise

0.5p.e.

1.5p.e.

(kHz)

100

1p.e. noise

2p.e.noise

500

Inter-pixel crosstalk

• Photons generated during an avalanche in one pixel trigger another avalanche in neighboring pixels

Crosstalk rate = 1- festimated

fobserved

festimated : Fraction of 1p.e. events calculated from that of pedestal events assuming Poisson distribution

fobserved : Observed fraction of 1p.e. events

Inter-pixel crosstalk(2)

Larger cross-talk rate with larger applied voltage

Cross-talk rate < 0.4

applied voltage(V)

0.4

Linearity• MPPC cannot count

# of injected photons correctly if several photons come to the same one pixel

• Linearity of MPPC is intrinsically limited by a finite number of pixels

paper

setup

MPPC

PMT

LED

Linearity(2)

expected curve calculated from # of pixels and cross-talk rate

# of injected p.e.

# of fired pixels

+10%

-10%

Deviation from expected curve

# of injected p.e.Response to a large amount of

light is well understood within 10%

Laser test in KEK Check intra & inter-pixel uniformityImportant information for product development

movable stage

MPPC

Motivation

Test items : Intra & inter pixel uniformity of gain and efficiency

green laser

100um

Intra-pixel uniformity

Inter-pixel uniformity

・・10u

m

=# of total events

# of events > 0.5p.e.

Uniformity of gain Intra-pixel Inter-pixel

RMS/mean = 2.0%

RMS/mean = 3.3%

•100pixel

Uniformity of efficiency

Intra-pixel Inter-pixel

RMS/mean = 2.0%

RMS/mean = 2.5%

•100pixel

SummaryWe have developed MPPC for T2K

100pixel

20℃

Intra & inter-pixel uniformity is <3.0%

Items Performance

Requirements

Gain (1.0~3.0)x106

~106

Photon detection efficiency

2~3 times > PMT

>PMT

1p.e. noise rate 100~500kHz

<1000kHz

2p.e. noise rate 10~100kHz <50kHz

Cross-talk rate <0.4

MPPC satisfies the T2K requirements!

backup

Gain

100pixel 400pixel

15℃20℃25℃

VbiasVbias

Noise rate

(kHz) (kHz)

15℃20℃25℃

2p.e. noise

1p.e. noise

1p.e. noise

2p.e. noise

Vbias Vbias

100pixel 400pixel

Cross-talk rate

100pixel 400pixel

15℃20℃25℃

Vbias Vbias

PDE

100pixel 400pixel

15℃20℃25℃

Vbias Vbias

Photon detection efficiency(PDE)

• PDE = εgeom x QE x εGeiger

-εgeom : Fraction of active area to total area~70%

- QE : Quantum efficiency of APD ~ 70% - εGeiger : Geiger probability(V) ~90%

Recovery time• Time to quench an avalanche• Fire all pixels by one LED and check

the response to the light from another LED

100p.e.

100ns

all pixels are recovered after 100ns

recovery time <100ns

100pixel

400pixel

+10%

+20%

-10%

-10%

Deviation from expectation

Data

Data

Expectation

Expectation

Readout electronics

Total # of readout channels ~60,000 in T2KNeed compact and multi-channel readout electronics

Motivation

14mm

ch1

ch2

ch32

ch1

ch2ch32Trip-t

parallel serial

# of channels 321

Trip-t chip produced at FNAL 　　　　　　

time

Developed readout electronics with Trip-t chip

Readout of MPPC with Trip-t

LED

Test board(4ch)

Readout 4 MPPCs simultaneously

X4

develop 32ch Trip-t board and test a large number of MPPCs

Future plan

MPPC

photopeaks

Fiber housing

MPPC housing

Optical connection