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MPPC update

S.Gomi, T.Nakaya,M.Yokoyama, M.Taguchi, (Kyoto University)

T.Nakadaira (KEK)

Nov.8.2006 KEK

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Contents

Ceramic package of MPPC

• We obtain the latest sample of MPPC this October. – Ceramic package, prepared for T2K experiment.– 100pixel×10, 400pixel×10

• We measured the fundamental performance of this sample.– Gain– Noise rate– Cross-talk rate– Photon detection efficiency ( PDE )

5mm6

mm

3

Gain

BlueBlue : : 15degree15degreeGreenGreen : : 20degree20degreeRedRed : : 25degree25degree

Gain 400pixel

610

5105

Bias voltage [V]69.6 70 70.6

Gain 100pixel

6103

610

Bias voltage [V]69 69.5 69.8

• Gain of old sample was…– 1.0×106~3.0×106 (100pixel)– 0.4×106~1.0×106 (400pixel)

Gain of new sample is not so Gain of new sample is not so changed compared to old sample.changed compared to old sample.

Estimated by 1p.e signal peak .

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The measurement of noise rate• 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 .

( The old sample have ~1.2MHz 1p.e noise rate. )

Noise signal of 100pixel MPPC at 25 degree.

( integrated )

1 p.e

0.5 p.e = threshold

1.5 p.e = threshold

“ 1p.e noise ”

“ 2p.e noise ”

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Noise rate

• 1p.e noise rate is about ~0.4 MHz. (old ~1.2 MHz)• 2p.e noise rate is about ~0.2 MHz. (old ~0.2 MHz)

100kHz

400kHz

Bias voltage [V]69.2 70 70.4

Noise rate [ kHz ] 400pixelNoise rate [ MHz ] 100pixel

100kHz

500kHz

Bias voltage [V]

69.1 69.5 70

BlueBlue : : 15degree15degreeGreenGreen : : 20degree20degreeRedRed : : 25degree25degree

1p.e noise

2p.e noise

1p.e

2p.e

Improved!Improved!

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The measurement of cross-talk rate

• Sensitive area of 100pixel type is enlarged by 40%. Geometrical efficiency is increased.

• The separation between pixels is smaller than the old sample. Cross-talk rate may be increasedCross-talk rate may be increased

Old sample( 100pixel )

New sample( 100pixel )

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• The probability of cross-talk is estimated by the number of 1p.e .

Measurement of cross-talk rate

ondistributi-Poisson

-measuredondistributi-Poisson

)1(P

P(1)- )1(P rate talk cross

The cross talk rate is determined.

The number of pedestal are free to cross-talk

• 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.

measurement

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Cross-talk rate

( Cross-talk rate of the old sample is ~30%. ) Cross-talk rate of new sample is ~1.6 times Cross-talk rate of new sample is ~1.6 times larger than old sample.larger than old sample.

10%

50%

Cross-talk rate 400pixelCross-talk rate 100pixel

10%

50%

Bias voltage [V]69.6 70 70.6

Bias voltage [V]69 69.5 69.8

BlueBlue : : 15degree15degreeGreenGreen : : 20degree20degreeRedRed : : 25degree25degree

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relative PDE measurement

MPPC

1mmφslit

Blue LED

( total area 1mm2)

PMT

p.e.(PMT)

p.e.(MPPC)PDE relative

PMT made by HPK, type H8643

set up Moving stage

• Geometrical efficiency is larger than that of the old sample. So, PDE of new sample should be higher.

• PDE relative to PMT is measured.

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relative PDE

• PDE is about 2~3 times higher than that of PMT.

(Old sample was ~2×PMT) ~1.4 times larger PDE than old ~1.4 times larger PDE than old sample. sample.

1

2

Relative PDE 400pixelRelative PDE 100pixel

1

2

3

Bias voltage [V]69.6 70 70.6

Bias voltage [V]69 69.5 69.8

BlueBlue : : 15degree15degreeGreenGreen : : 20degree20degreeRedRed : : 25degree25degree

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Summary of measurement

Old sample New sample

Gain

Noise rate(1p.e) [ kHz ] ~1200 ~400Cross-talk rate ~30% ~50%PDE

66 103~101

PMT 2~

66 103~101

• The new sample have good performance! But, Cross-talk become worse. feed back to Hamamatsu

PMT 3or 2~

Improved!Improved!

Improved!Improved!

Become worse…Become worse…

About the region the gains of 2sample are same…

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Future plan…• We will check the device-to-device variation for 500

MPPCs in this ceramic package next March. • So, we have to make system to test many samples. • We want to measure as many sample as possible at

once.– Plastic connector– Read out electronics

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Supplements

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Gain bdBIAS V V V

BlueBlue : : 15degree15degreeGreenGreen : : 20degree20degreeRedRed : : 25degree25degree

610

6105

Gain 400pixelGain 100pixel

6103

610

0.2 1 1.6 0.8 1 2 2.4

V V

15

BlueBlue : : 15degree15degreeGreenGreen : : 20degree20degreeRedRed : : 25degree25degree

Noise rate

• This new sample have noise rate less than the half of old sample.

100kHz

400kHz

Noise rate [ kHz ] 400pixelNoise rate [ MHz ] 100pixel

100kHz

500kHz

0.4 1 1.6 0.5 1 1.5 2 2.3

1p.e

2p.e

V V

bdBIAS V V V

1p.e

2p.e

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Cross-talk rate

• Cross-talk rate is a function of V.

10%

50%

1 2Delta V

Cross-talk rate 400pixelCross-talk rate 100pixel

10%

50%

0.2 1 1.6 0.8 1 2 2.4

BlueBlue : : 15degree15degreeGreenGreen : : 20degree20degreeRedRed : : 25degree25degree

V V

bdBIAS V V V

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relative PDE

• PDE is a function of Delta V.

1

2

Relative PDE 400pixelRelative PDE 100pixel

1

2

3

0.2 1 1.6 0.8 1 2 2.4

BlueBlue : : 15degree15degreeGreenGreen : : 20degree20degreeRedRed : : 25degree25degree

V V

bdBIAS V V V

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Set up for measuring linearity

set up

MPPCThe number of photons emitted to MPPC are monitored by PMT.

PM

T

Paper ( to shade off LED light )

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00fired N

exp1NNx

Linearity

• The green line shows the expectation value calculated from number of pixels.

ronphotoelect injected :

pixels ofnumber the:N0

x

BlueBlue : DATA plot: DATA plotGreenGreen : expectation: expectation

Linearity 400pixel

Injected photoelectron per pixel F

ired

pix

el [

% ]

MPPC can operate as linear device.MPPC can operate as linear device.~25p.e about 100pixel type~100p.e about 400pixel type.

linear

Linearity 100pixel

Fir

ed p

ixel

[ %

]

Injected photoelectron per pixel

linear

25%25%

BlueBlue : DATA plot: DATA plotGreenGreen : expectation: expectation