Performance of new MPPC

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Performance of new MPPC

• Nov. 21 (Tue.)/2006 _at_ Korea-Japan joint meeting
• Takashi Maeda
• Hideki Yamazaki Yuji Sudo(University of Tsukuba)

• --- Contents ---
• Measurements of basic characteristics
• Measurements with laser system
• Summary / Plans

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Characteristics of the new MPPC

• Evaluate performance
• Gain, Noise Rate, Cross-Talk
• Check temperature dependence
• Breakdown Voltage, Pixel Capacitance
• Evaluate the Uniformity with in a sensor using
  microscopic laser system _at_KEK
• Efficiency, Gain

3
ADC distribution

• Vbias 77.7 V
• Temperature 15 oC

Pedestal peak 1 p.e. peak
2 p.e. peak
4
Gain results

• S ADC sensitivity
• 0.25 pC/ADC count
• A Amp gain
• 63
• e electron charge
• 1.6 x10-19 C

30oC 25oC 20oC 15oC 10oC 0oC -20oC
New MPPC samples have higher gain and are
operated at higher voltage than old sample
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Variation of Breakdown Voltage V0

• V0 Breakdown voltage
• C Pixel Capacitance 0.02 pF

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Noise Rate
rate of avalanche signals induced by thermal
electrons

• 30oC
• 25oC
• 20oC
• 15oC
• 10oC
• 0oC
• -20oC

New MPPC samples have lower noise rate than old
one
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Cross-talkprobability
cross-talk to adjacent pixels is caused by
photons created in an avalanche
30oC 25oC 20oC 15oC 10oC 0oC -20oC

• Measured from dark noise rate
• Stable with temperature
• Increase aboveVover gt 4 V

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Measurement by microscopic laser system
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the Microscopic laser system _at_ KEK

• YAG laser, l 532 nm
• Pulse width 2 nSec, rate 8 kHz

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Microscopic picture of a pixel

• No difference between an old sample and new one
  at a rough estimate
• Difficult to match a focus
• with laser light(without filters)
• Diffused reflection!?
• Can we performprecise scan?

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ADC distribution

• Injected laser light
• Bias Voltage 78.0 V _at_ Room temperature

Pedestal peak 1 pix. fired peak
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Laser scan - Efficiency

• 2-dimensional scan
• can see sensitive region
• Variation within a sensitive region 6.3 (RMS)

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Laser scan - Gain
x105

• Gain results with same data
• Center parts have higher gain
• Variation within a sensitive region 0.9 (RMS)

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• Summary
• Check performance of new MPPC samples
• Have greater performance than old one
• Variation check is still ongoing
• We perform laser scan within a sensor
• Plans
• Measure other MPPC samples
• Need to measure P.D.E., Linearity
• Evaluate uniformity within a sensor
• We need more measurements and analyses

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Back up
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New sample
MPPC
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Set up for gain measurements
Green LED
MPPC
Thermostatic Chamber
Thermostatic Chamber
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Pulse shape

• Bias voltage 78.0 V

1 p.e. 2 p.e.
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Low powered microscopic picture
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Results of the old MPPC sample
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Results of the old MPPC sample
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Results of the old MPPC sample