PDE of 1600-pixel MPPC

Sudo Yuji 　Tsukuba Univ.

2007.1.23

Photon Detection Efficiency ( PDE )

• Q.E. : quantum efficiency that is a probability of

creation of a pair of e- h+ for one photon Geiger : a probability that arise avalanche for electron

geom : a proportion of effective region in a sensor

Measurement method• Relative # of p.e. for reference PMT

~ a probability that detect a photoelectron for one photon

geomGeigerMPPC EQ ..

MPPC

PMTΦ0.5

LEDWLSF

PMTPMTep

MPPCep

MPPC N

N

..

..

Set up

Gate

Generator

Delay

Voltage

source

HV

PMT

MPPC

Stage

WLSF

Green

LED

AMP *63

Signal

input

Gate

PC

Thermo-static chamber

Clock

Generator

Voltage

source

Light yeild measurement( with noise and cross-talk subtraction)• Measure light yeild of

LED light pulse

• Fit ADC distributon

• Supposed signals are dominated by Poisson statistics

• Count number of events below 0.5 p.e. threshold ( both LED on and off )

pedestal Events 　　　　　

0.5 p.e. threshold

0.5 p.e. threshold

pedestal Events 　　　　　

Calculation of Np.e.

• f(0,μLED on) = f(0, μ+μnoise)

= f(0,μ) × f(0,μnoise)

f(0,μ) = f(0,μLED on) / f(0,μnoise) = e-μ

μ = -ln( f(0,μ) )

• f(n,μ) is Poisson distribution function

• μ is Expectated number of Np.e.

• f(0,μLED on), f(0,μLED off ) are probability of 0 p.e.

f(0,μnoise) = NLED off / NLED off = e-μnoise

f(0,μLED on) = NLED on / NLED on =e-μLED on

pedestal all

pedestal all

NpeMPPC / NpePMT (Npe ratio)

WLS Fiber Y-11

Reference : JLC ストリップ・ファイバー電磁カロリメータの性能研究

　　　　　　　　 関口克巳　平成 15 年 3 月　　

QE of H1161GS

Mean of QE for 1 p.e.QE × relative light yeild on each wave length

∑ （ QE × relative light yeild on each wave length ）

= Mean of QE for 1 p.e. ~16.7 %

Max

Min

Photon Detection Efficiency ( PDE )

•　 PDE of PMT is ~ 16.7 %

• 6.3 % uncertainty cames from estimation of PMT P.D.E

±~ 6.3 %

PMTPMTep

MPPCep

MPPC N

N

..

..

Summary• We measured PDE of a 1600-pixel MPPC.• P.D.E increases with over voltage ( Vbias – V0), and s

aturated around 23 %.• But we don’t know correct QE data and light yeild di

stribution of a WLS fiber ( Y-11 ) .• It gives uncertainty of 6.3% on the P.D.E measurem

ent.• We will have three PMTs on 2/14 that have QE data

which are measured by HPK .• For further improvement, We should use light sourc

e which emits well-known wave length , otherwise we have to measure spectrum of wave length emitted by WLS fiber.

Buck up