1. Performance of new MPPC Nov. 21 (Tue.)/2006 @ Korea-Japan joint meeting Takashi Maeda Hideki Yamazaki Yuji Sudo (University of Tsukuba) --- Contents --- Measurements of basic characteristics Measurements with laser system Summary / Plans

2. 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 @KEK  Efficiency, Gain

3. ADC distribution ► V bias ~ 77.7 V ► Temperature = 15 o C Pedestal peak 1 p.e. peak 2 p.e. peak …

4. Gain results S : ADC sensitivity = 0.25 pC/ADC count = 0.25 pC/ADC count A : Amp gain = 63 = 63 e : electron charge = 1.6 x10 -19 C = 1.6 x10 -19 C Bias voltage (V) New MPPC samples have higher gain and are operated at higher voltage than old sample 30 o C 25 o C 20 o C 15 o C 10 o C 0 o C -20 o C

5. Variation of Breakdown Voltage V 0 ► V0 : Breakdown voltage ► C : Pixel Capacitance ~ 0.02 pF

6. Noise Rate rate of avalanche signals induced by thermal electrons New MPPC samples have lower noise rate than old one 30 o C 25 o C 20 o C 15 o C 10 o C 0 o C -20 o C

7. Cross-talk probability ► Measured from dark noise rate ► Stable with temperature ► Increase above V over > 4 V cross-talk to adjacent pixels is caused by photons created in an avalanche 30 o C 25 o C 20 o C 15 o C 10 o C 0 o C -20 o C

8. Measurement by microscopic laser system

9. the Microscopic laser system @ KEK ► YAG laser,  = 532 nm ► Pulse width ~ 2 nSec, rate ~ 8 kHz The MPPC

10. 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 perform precise scan?

11. ADC distribution ► Injected laser light ► Bias Voltage 78.0 V @ Room temperature Pedestal peak 1 pix. fired peak

12. Laser scan - Efficiency ► 2-dimensional scan ► can see sensitive region ► Variation within a sensitive region ~ 6.3% (RMS)

13. Laser scan - Gain ► Gain results with same data ► Center parts have higher gain ► Variation within a sensitive region ~ 0.9 % (RMS) x10 5

14. 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

15. Back up …

16. MPPC New sample

17. Set up for gain measurements Thermostatic Chamber Green LED MPPC Thermostatic Chamber

18. Pulse shape ► Bias voltage 78.0 V 1 p.e. 2 p.e.

19. Low powered microscopic picture

20. Results of the old MPPC sample