PDE of 1600-pixel MPPC
Sudo Yuji
Tsukuba Univ.
2007.1.23
Photon Detection Efficiency ( PDE )
~ a probability that detect a photoelectron for one photon
e MPPC  Q.E.  e Geiger  e geom
• Q.E. : quantum efficiency that is a probability of
creation of a pair of e- h+ for one photon
 eGeiger : a probability that arise avalanche for electron
 egeom : a proportion of effective region in a sensor
Measurement method
• Relative # of p.e. for reference PMT MPPC
e MPPC 
N
MPPC
p .e .
PMT
p .e .
N
WLSF
e PMT
PMT
Φ0.5
LED
Set up
Gate
Clock
Generator
Generator
PC
Gate
Signal
Delay
input
AMP *63
Green
MPPC
WLSF
LED
Voltage
Voltage
source
Stage
PMT
HV
Thermo-static chamber
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 )
0.5 p.e.
pedestal threshold
Events
0.5 p.e.
threshold
pedestal
Events
Calculation of Np.e.
• 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.
off / NLED off = e-μnoise
f(0,μnoise) = NLED
all
pedestal
on / NLED on =e-μLED on
f(0,μLED on) = NLED
pedestal
all
• 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) )
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 %
Photon Detection Efficiency ( PDE )
e MPPC 
N pMPPC
.e .
N
PMT
p .e .
e PMT
±~ 6.3 %
Max
Min
• PDE of PMT is ~ 16.7 %
• 6.3 % uncertainty cames from estimation of PMT P.D.E
Summary
• We measured PDE of a 1600-pixel MPPC.
• P.D.E increases with over voltage ( Vbias – V0), and
saturated around 23 %.
• But we don’t know correct QE data and light yeild
distribution of a WLS fiber ( Y-11 ) .
• It gives uncertainty of 6.3% on the P.D.E
measurement.
• We will have three PMTs on 2/14 that have QE data
which are measured by HPK .
• For further improvement, We should use light
source which emits well-known wave length ,
otherwise we have to measure spectrum of wave
length emitted by WLS fiber.
Buck up