Study of the MPPC performance RD status for

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 Satoru Uozumi Shinshu University, Japan for the GLD Calorimeter group and KEK Detector Technology Project / Photon Sensor Group Nov 6 -10 2006 International Linear Collider Workshop Valencia

The Multi Pixel Photon Counter (MPPC) - A novel semiconductor photon sensor ~ 1 mm Depletion region ~ 2 m Substrate Si Resistor Guard ring np+ n+ Vbias Al conductor p- substrate p+ • High Gain (105~106) • Good Photon Detection Efficiency (25~65%) • Compact (package size ~ a few mm) • Low Cost • Magnetic-field tolerant • High dark noise (order of 100 -1000 k. Hz) • Response against input light yield is non-linear The MPPC is a still developing, but promising

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… ● ?

The New MPPC Sample 4 mm 3 mm 1. 3 mm Side Front • 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. Scintillator strip 1 x 1 mm WLS fiber Side view MPPC

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

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

Variation of the Gain over 20 samples Mean : 23. 82 f. F Variation ~ 3. 1 % 20 samples @ 25 o. C Mean : 75. 55 V Variation : 0. 22 V Gain = C (Vbias-V 0) / e C : Pixel capacity V 0 : Breakdown voltage Good Uniformity !

Temperature dependence of the Gain • • 30 o. C 25 o. C 20 o. C 15 o. C 10 o. C -20 o. C • Breakdown voltage is linear to temperature. • Thus the temperature change affects to the over -voltage ( = Vbias-V 0(T)). g eventually affects to all the MPPC properties. DV 0/DT = (57. 3 0. 1) (m. V/o. C)

Variation of the Noise Rate Cross-talk Dark counting rate with threshold of 0. 5 and 1. 5 photoelectron. o ● Test 20 samples @ 25 C ● > 0. 5 p. e. > 1. 5 p. e. 20 samples @ 25 o. C

Temperature dependence of the Noise Rate / Cross-talk • • 30 o. C 25 o. C 20 o. C 15 o. C 10 o. C -20 o. C > 0. 5 p. e. • • 30 o. C 25 o. C 20 o. C 15 o. C 10 o. C -20 o. C • Lower temperature g lower dark noise • Cross-talk is not affected by temperature change.

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 – T 2 K near detector – Belle Aerogel Cerenkov Counter • Provide important feedbacks to Hamamatsu for improvement of fundamental properties

News : The MPPCs are finally on catalog ! Number of pixels 100 400 Sensor size Nominal Bias Volt. Gain (x 105) 1 x 1 mm 2 70 10 V 24. 0 7. 5 Noise Rate (k. Hz) 400 65 % Photon Detection Efficiency Temperature dependence (DV 0/DT) 270 50 % 1600 77 10 V 2. 75 100 25 % 50 m. V / o. C (Numbers from HPK catalog) • 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

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)x 105, Noise Rate 50 -300 k. Hz, Cross-talk prob. < 2 -20% –However properties are sensitive to temperature change. g Need temperature control / monitoring at practical use. • The MPPC is being commercialized soon ! Plans • 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 ( g 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.

Backups

Photon Detection Efficiency by Hamamatsu

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 k. Hz • 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

The MPPC performance PMT MPPC Gain ~106 105~106 Photon Detection Eff. 0. 1 ~ 0. 2~ 0. 7 Response fast Photon counting Yes Great Bias voltage ~ 1000 V ~ 70 V Size Small Compact B field Sensitive Insensitive Cost Expensive Not expensive Dynamic range Good Determined by # of pixels Long-term Stability Good Unknown Robustness decent Unknown, maybe good Noise (fake signal by thermions) Quiet Noisy (order of 100 k. Hz) The MPPC looks feasible for the GLD Calorimeter readout!

Required performance for the GLD Calorimeter • Gain: ~ Best to have 106 , at least 105 • 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 mmf fiber • Should be stable against bias voltage / temperature / time

R&D Status @ GLD Calorimeter • 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. Evaluate performance of the MPPC prototypes Provide feedback to HPK Improved samples from HPK

Setup

Response / Correction curves ( with small cross-talk ) R (p; Npe) p=0. 1 p=0 (no cross-talk) Response curve Correction curve R-1(p; Nfired) p=0. 1