New test result of MPPC M Taguchikyoto Contents

New test result of MPPC M. Taguchi(kyoto)

Contents • • New MPPC sample Noise rate, gain, crosstalk rate PDE Long term stability

New MPPC sample recently we got • HPK 32(400 pixel) × 3 Operating voltage : 68~69 V 1 p. e signal width: ~20 ns • HPK 53(100 pixel) × 3 Operating voltage: 68~69 V 1 p. e signal width: ~50 ns • HPK say these have higher PDE than old samples • The test result of HPK 14(100 pixel) that we used at beamtest will be presented for comparison

Noise rate measurement ■ 0. 5 p. e threshold ▲ HPK 53(100 pixel) 1. 5 p. e threshold 　　 HPK 32(400 pixel) 1 MHz 100 k. Hz 15℃ 20℃ 25℃ 68. 4 69. 6 Bias voltage 68. 4 69. 4 Bias voltage

Gain measurement@T=20℃ gain 3× 106 HPK 53(100 pixel) • Gain of new samples >105, so satisfy T 2 K HPK 14(100 pixel) requirement 1× 106 HPK 32(100 pixel) 500 k. Hz 0. 5 p. e 1 MHz threshold noise rate

Crosstalk rate measurement@T=20℃ Cross talk rate HPK 14(100 pixel) HPK 53(100 pixel) 0. 2 • Crosstalk rate of new samples is still high 0. 1 (T 2 K requires crosstalk rate<0. 1) HPK 32(100 pixel) 500 k. Hz 1 MHz 0. 5 p. e threshold noise rate

PDE measurement@T=15℃ MPPC ½inch PMT scan 1 mmφfiber 1 mmφslit MPPC ½inch. PMT scan Blue LED 1 mmφfiber • With this set up all the light going through 1 mmφslit inject to the active area of MPPC • Ratio of MPPC p. e to PMT p. e measured by this set up is defined as PDE • With this set up some light from a fiber don`t reach to the active area of MPPC because there is a distance(~0. 8 mm) between surface cover and active area • Ratio of MPPC p. e to PMT p. e measured by this set up is defined as effective PDE

PDE measurement@T=15° • PDE is showed with relative value to PMT HPK 53(100 pixel) HPK 32(400 pixel) ▲　PDE ■ effective PDE HPK 14(100 pixel) 2 2 1 500 900 Noise rate(k. Hz) ノイズレート(k. Hz) 550 ノイズレート(k. Hz) 900 400 900 Noise rate(k. Hz) • PDE of new sample is 2 times larger than that of old one • Effective PDE is 50~60% of PDE We requested the improveme of MPPC packaging to HPK

Raw signal of new sample HPK 53(100 pixel) Noiserate=1345 k. Hz HPK 32(400 pixel) Noiserate=1246 k. Hz • Noise with large pulse height (～ 10 p. e) is observed when noise rate becomes >1 MHz • There is no problem because T 2 K requires noise rate <1 MHz

Long term stability test@T=20℃ • Test the stability of gain, noise rate, p. e for MIP Cosmic ray Trigger counter 4 layers HPK 32(400 pixel) Blue LED MPPC parameter Bias voltage gain 0. 5 p. e th noiserate Crosstalk rate Effective PDE(including crosstalk) ½ inch　PMT 68. 8 V 5. 6× 105 800 k. Hz 0. 1 • Cosmic trigger 1. 2 • Pedestal trigger(for monitaring noise rate) 3 different triggers • LED trigger(for monitaring MPPC gain)

Cosmic ray event MPPC PMT 14. 8 p. e 20 60 16. 2 p. e 20 60 p. e

Stability of MPPC gain and noiserate gain Noise rate 5% 5% 839 k. Hz 5. 7× 1 05 5% 5% 40 hour RMS/mean=2. 5% 40 hour RMS/mean=4. 3%

Stability of MPPC Light yield for MIP Peak adc count/gain for MIP 5% 5% 14. 7 p. e 5% 5% 40 hour RMS/mean=4. 0% RMS/mean=2. 9% Correction by gain

summary • New MPPC samples have about 2 times larger PDE than that of old ones • MPPC light yield for MIP~15 p. e (at the point where noise rate and gain satisfy T 2 K requirement) • Gain stability ~3% , noise rate stability~4% • Stability of light yield for MIP~3% (about 2 days)

Back up

LED event MPPC PMT

Staibility of PMT gain 1 p. e adc count 5% 5% 40 hour RMS/mean = 4. 7%

Stability of PMT light yield for MIP Peak adc count/gain for MIP 5% 5% 16. 5 p. e 5% 5% 40 hour RMS/mean=4. 6% 40 hour RMS/mean=3. 1% Correction by gain

Operating voltage range which satisfy T 2 K requirement • HPK 32(400 pixel) Upper limit： 1. 5 p. e th noise rate<50 k. Hz 68. 2～ 68. 8 V Lower limit ：PDE >15% • HPK 53(100 pixel) Upper limit： 1. 5 p. eth noise rate<50 k. Hz 68. 3～ 69. 1 V Lower limit：PDE>15%

Recovery time LED 1 HPK 32 (400 pixel) 400 p. e LED 1 LED 2 160 ns • Fire all pixels with LED 1 and study the response of LED 2 with the delay to LED 1 • Saturation signal was observed by LED 2 even with 400 p. e the 120 ns(signal width) delay LED 1 recovery time is about the same as signal width 120 ns LED 2