1. Study of the MPPC performance - R&D status for the GLD calorimeter readout – http://ppwww.phys.sci.kobe-u.ac.jp/~kawagoe/gldcal/index.php?MPPC Nov 6-10 2006 International Linear Collider Workshop Valencia Satoru Uozumi Shinshu University, Japan for the GLD Calorimeter group and KEK Detector Technology Project / Photon Sensor Group

2. High Gain (10 5 ~10 6 ) Good Photon Detection Efficiency (25~65%) Compact (package size ~ a few mm) Low Cost Magnetic-field tolerant High dark noise (order of 100-1000 kHz) Response against input light yield is non-linear ~ 1 mm Depletion region ~ 2  m Substrate substrate p + p-p- Guard ring n - Al conductor p+p+ n+n+ Si Resistor V bias The Multi Pixel Photon Counter (MPPC) - A novel semiconductor photon sensor - The MPPC is a still developing, but promising device !

3. The MPPC is drastically evolving … Mar. 2005 ● 100/400 pixels ● First sample from Hamamatsu Jan. 2006 ● 100/400/1600 pixels ● Smaller pixel size results in more number of pixels Oct. 2006 ● 100/400/1600 pixels commercialized ● Improved Gain and dark noise Sometime in future ● Larger sensor area ● More number of pixels ● And perhaps more… ?

4. 4 mm 1 x 1 mm 1.3 mm Side 3 mm The New MPPC Sample Latest 1600 pixel MPPC 20 samples arrived in October. Very compact plastic package suitable for attaching to scintillator strips. (this package is customized for our ECAL module, and not going to be commercialized) 500 more for ECAL beam test will be arrived in this month. Front MPPC Scintillator strip WLS fiber Side view

5. Old 1600pixel sample New 1600 pixel sample Excellent photon counting ability 0,1,2,3,4,5,6,7,... Photoelectrons ! ~ 25  m

6. Performance of the latest 1600 pixel MPPC Gain, Noise Rate, Cross-Talk –Device-by-device variation –Temperature dependence All results are yet preliminary

7. Gain = C (V bias -V 0 ) / e C : Pixel capacity V 0 : Breakdown voltage Variation of the Gain over 20 samples Good Uniformity ! Mean : 23.82 fF Variation ~ 3.1 % 20 samples @ 25 o C Mean : 75.55 V Variation : 0.22 V

8. 30 o C 25 o C 20 o C 15 o C 10 o C 0 o C -20 o C  V 0 /  T = (57.3 0.1) (mV/ o C) Temperature dependence of the Gain Breakdown voltage is linear to temperature. Thus the temperature change affects to the over-voltage ( = V bias -V 0 (T)).  eventually affects to all the MPPC properties.

9. Variation of the Noise Rate Cross-talk 20 samples @ 25 o C > 0.5 p.e. > 1.5 p.e. ● Dark counting rate with threshold of 0.5 and 1.5 photoelectron. ● Test 20 samples @ 25 o C

10. Temperature dependence of the Noise Rate / Cross-talk 30 o C 25 o C 20 o C 15 o C 10 o C 0 o C -20 o C Lower temperature  lower dark noise Cross-talk is not affected by temperature change. 30 o C 25 o C 20 o C 15 o C 10 o C 0 o C -20 o C > 0.5 p.e.

11. KEK Detector Technology Project Photon Sensor Group (http://rd.kek.jp/) (KEK, Kobe, Kyoto, Nagoya, Nara-WU, NDA, Shinshu, Tokyo/ICEPP, Tsukuba) Develop and study the MPPC with Hamamatsu Aiming to have satisfactory performance to use at : –GLD calorimeter –T2K near detector –Belle Aerogel Cerenkov Counter Provide important feedbacks to Hamamatsu for improvement of fundamental properties

12. News : The MPPCs are finally on catalog ! Number of pixels1004001600 Sensor size1 x 1 mm 2 Nominal Bias Volt.70 10 V77 10 V Gain (x 10 5 )24.07.52.75 Noise Rate (kHz)400270100 Photon Detection Efficiency 65 %50 %25 % Temperature dependence (  V 0 /  T) 50 mV / o C Hamamastu will start to deliver the MPPC in early 2007. See following page for more information: http://jp.hamamatsu.com/en/hamamatsu/press/ 2006/2006_10_26.html (Numbers from HPK catalog)

13. Summary We now have the new 1600 pixel MPPCs for the GLD EMCAL test module. Performance of the new MPPC is sufficient for EMCAL beam test. –Gain (2-8)x10 5, Noise Rate 50-300kHz, Cross-talk prob. < 2-20% –However properties are sensitive to temperature change.  Need temperature control / monitoring at practical use. The MPPC is being commercialized soon ! Measure properties of 500 samples used for the scintillator-W EMCAL module (will arrive in this month). Practical use for the calorimeter readout at the coming beam test (  next talk ) The MPPC R&D will be continued until we achieve the necessary performance for the GLD calorimeter readout. –Improvement of the dynamic range (num. of pixels) is especially important! Also need to measure non-linearity, stability, robustness to have deeper understanding of the device. Plans

14. Backups

15. Photon Detection Efficiency by Hamamatsu

16. Measurement with Microscopic Laser System １６００ pixel MPPC Introduced by KEK-Detector Technology Project YAG Laser, = 532 nm (green) Pulse width ~ 2 nsec, rate ~ 8 kHz Spot size ~ 1  m Light yield ~ 0.5 p.e. (not calibrated) Can perform precise pinpoint scan with the well-focused laser ~25  m Laser spot

17. PMTMPPC Gain~10 6 10 5 ~10 6 Photon Detection Eff.0.1 ~ 0.20.2~ 0.7 Responsefast Photon countingYesGreat Bias voltage~ 1000 V~ 70 V SizeSmallCompact B fieldSensitiveInsensitive CostExpensiveNot expensive Dynamic rangeGoodDetermined by # of pixels Long-term StabilityGoodUnknown RobustnessdecentUnknown, maybe good Noise (fake signal by thermions) QuietNoisy (order of 100 kHz) The MPPC performance The MPPC looks feasible for the GLD Calorimeter readout!

18. Required performance for the GLD Calorimeter Gain: ~ Best to have 10 6, at least 10 5 Dynamic range: can measure ~1000 p.e. – satisfactory to measure EM shower maximum – need > 2500 pixels Photon Detection Efficiency ~ 30 % – to distinguish MIP signal Noise rate : ~ 1 MHz (threshold = 0.5 p.e., threshold =1.5 p.e is also acceptable) good uniformity, small cross-talk Timing Resolution ~ 1 nsec – Necessary for bunch ID, slow neutron separation Sensor area: 1.5 x 1.5 mm – suitable for 1.5 mm  fiber Should be stable against bias voltage / temperature / time

19. The MPPC performance looks feasible for the GLD calorimeter readout, but still not sufficient. Need study and improvement of the fundamental property to achieve our goal. Now we are measuring performance of latest 400 / 1600 pixel MPPC prototypes provided by Hamamatsu. Based on its results, we provide feedback to Hamamatsu to have improved sample. R&D Status @ GLD Calorimeter Evaluate performance of the MPPC prototypes Provide feedback to HPK Improved samples from HPK

20. Setup

21. Response / Correction curves ( with small cross-talk ) Response curve Correction curve R -1 (p;N fired ) p=0.1 R (p;N pe ) p=0.1 (no cross-talk) p=0