1. Multipixel Geiger mode photo-sensors (MRS APD’s) Yury Kudenko ISS meeting, KEK, 25 January 2006 INR, Moscow

2. 2 Near Detectors at 280m Off-axis (~2 o ) On-axis (0 o )  19m Super-K Beam center 37m ND280m hall - ~ 10 5 WLS fiber channels - individual readout

3. 3 Principles of MRS APD operation Principles of MRS APD operation Number of pixels  450 - 4000 Q pixel = C pixel x  V = C pixel x (V bias - V breakdown ) C pixel  50fmF  V  few volts  Q pixel  2x10 6 electrons Depletion region  2  m Drift velosity  10 7 cm/s Field  (2-3)x10 5 V/cm CPTA, Moscow (MRS APD) MePhi/PULSAR, Moscow (SiPM) Dubna limited Geiger mode PMT: diameter 20 mm MRS: active area 1x1mm 2 diam 1 mm Multipixel Geiger mode APD’s invented in Russia in 1980’s

4. 4 MRS APD One pixel ~ 40 x 40  m 2

5. 5 MRS APD New devices - Dark noise rate - PDE - Dynamic range, linearity of signal - Temperature effects - Long time stability - Lifetime - Recovery time - Diameter of active area 1.1 mm - Number of pixels 556 - Geometrical efficiency 70-80 % - Photon detection efficiency at th=0.5 p.e. and dark rate ~1MHz 10-15% - Bias voltage range 25-75 V - Gain 10 6 - 10 7 - Sensitivity to magnetic field (  9T) no - Cross talk 4-6% - Auto calibration and control separated p.e. peaks - Dark noise rate (th =0.5 p.e)  1 MHz LED signal

6. 6 1pe 2pe 3pe Dark noise rate Threshold, p.e. Dark rate, MHz 0.5 1.0 1.5 ~0.1 2.5  0.01 Dark noise rate Temperature dependence ~70 – 100 kHz/deg

7. 7 Photon detection efficiency (PDE) PDE=ε pixel × QE × ε Geiger 30-70% 60-80% 50-80% PDE=12% 1 MHz Typical PDE ~12% (at 1 MHz (th=0,5 p.e.) New CPTA devices PDE ~15%

8. 8 Linearity and cross talk MRS APD, 556 pixels The same LED signal to MRS APD and PMT through Y11 fiber Crosstalk Bias voltage = 40.0 V Dark rate (0.5p.e) ~ 1MHz Crosstalk = 5-6%

9. 9 Temperature effects PDE gradient ~ -1.8%/deg Dark noise rate gradient ~70-90 kHz/deg

10. 10 Stability and lifetime study l.y. measurement After temp correction For 2 years ~150 CPTA devices are studied 3 dead High temperature test On-going test: 10 devices are at 80 deg and HV for 15 days All OK

11. 11 Recovery time t Large pulse >600 p.e. Dec’05 MRS #1710-002 Second pulse ~100 p.e. First pulse: Black – 50 p.e Red - 100 p.e. Green - 300 p.e. Second: - 100 p.e.

12. 12 Beam test of SMRD detector Beam test at KEK, Nov 2005. Sci/WLS/(both end MRS readout) detector 1.4 GeV/c pions and protons l.y. from one end of slab Ped Extruded scintillator (Vladimir, Russia) Chemical reflector Fiber KURARAY Y11, double clad, 1 mm SMRD: about 5000 extruded scintillator slabs ~ 90 cm x 20 cm x 1.0 cm 8p.e.

13. 13 Beam test results S-type SMRD detector: l.y. (sum of 2 ends) 15  2 p.e. MIP efficiency >99% Timing at 15 p.e. ~ 1.7 ns (  ) Space resolution ~12 cm (  ) Beam scan along the slab Time resolution

14. 14 Summary and outlook Status Perspectives Diameter 1.1mm 1.1, 1.2-1.5 mm PDE 12-15% OK, R&D  20% Dark noise rate ~1 MHz (0.5 p.e.) manufacturers aim to decrease 100 kHz (1.5 p.e) OK Time resolution 1- 3 ns (  ) with Y11 OK, both end readout to suppress noise Cross talk  4-6% OK Gain 10 6 – 10 7 OK Linearity range 200 p.e. 600 pixels OK, 1000-2000 pixels 20-30 p.e. 100 pixels OK for SMRD, on-axis Long term stability ~1000 hrs, 1-2% OK, more tests Lifetime 3 of 450 are dead looks not bad, study is ongoing Temperature Dark noise rate +(70-90) kHz/deg PDE -1.8%/deg 22-25 deg OK, low temp is better Recovery time  1-5  s OK - Great progress in development of Multi-pixel Silicon devices for last 2-3 years - Such devices are now considered as base-line photo-sensors for the T2K near detector at 280 m