mppc status m.taguchi(kyoto) t2k nd280 meeting@kek 2006/7/7
TRANSCRIPT
MPPC status
M.Taguchi(kyoto)
T2K ND280 meeting@KEK 2006/7/7
Contents
Test sample Device-by-device
variation
Calibration test Conclusion
Test sample
•latest samples which was delivered in Jan.2006
•We have three samples for each typedevice-by-device variation is tested at the point bias V=69.0V
(at this point gain~106, noise [email protected]. threshold <1MHz)
Number of pixels
Pixel pitch(μm)
Area Operating voltage
Geometrical efficiency
100 100 1.0x1.0mm2
69-70V 46%
400 50 1.0x1.0mm2
69-70V 55%
HPK now develops 100pixel sample with larger geometrical efficiency
Gain ~device-by-device variation~
100pixel gain
400pixel gain
variation ~7%
variation ~10%
69.0V69.0V
3×106
1×106
15℃ 15℃
Noise rate ~device-by-device variation~
69.0V
100pixel Noise rate @0.5p.e. threshold
69.0V
vairation~30% vairation~13%
400pixel Noise rate @0.5p.e. threshold
700kHz
800kHz
15℃ 15℃
PDE ~device-by-device variation~
2
100pixel
69.0V
69.0 V
100pixel PDE(MPPC)/QE(PMT)
400pixel PDE(MPPC)/QE(PMT)
variation ~10% variation ~20%
•measure the PDE of MPPC relative to that of a PMT
15℃ 15℃
2
Summary of device-by-device variation
100pixel 400pixel
gain 2.6x106~ 3.0x106
9.2x105~ 9.8x105
Noise rate @0.5p.e. th
480~620 KHz
750~850kHz
PDE(MPPC)/ QE(PMT)
1.8~1.95 1.8~2.0
•T=15℃, bias V=69.0V
Device-by-device variation is small, but it is necessary to test much larger number of samples
Calibration test
MotivationGain, PDE, crosstalk of MPPC are all sensitive to the temperature and bias voltage
It is necessary to calibrate the variation of Gain, PDE, crosstalk
if temperature of bias voltage change
MPPC Signal ∝ Gain(T,V) x PDE(T,V) x 1-crosstalk(T,V)
1
T: temperature V: bias voltage
evaluate the stability of device response by two calibration methods(explain each method later)
Set up for calibration test
1inch PMT
cosmic-ray
1mm φfiber
MPPC2(100)
MPPC1(100)
MPPC3(400)
MPPC4(400)
scintillator
blue LED
put scintillators in four layers inserted fibers are viewed by
four MPPCs(two are 400 pixel and two are 100pixel)
change temperature intentionally like 20℃25℃
The same bias voltage (69.0V) is applied to four MPPCS
temperature chamber
Method 1
100pixel gain
100pixel crosstalk
100pixel PDE(MPPC)/QE(PMT)
•gain, PDE, crosstalk are all functions of V-Vbd
V-Vbd V-Vbd V-Vbd
Vbd:breakdown voltage (derived by linearly extrapolating the gain-voltage curve to the point where gain becomes zero) V
Gain
Vbd
Method 1
corrected light yield =
gainxPDEx
MIP ADC counts
1-crosstalk1
20℃ 25℃
measure the variation of gain(V-Vbd)
estimate variation of V-Vbd
estimate the variation of PDE(V-Vbd),crosstalk(V-Vbd)
variation of gain (100pixel)
Stability of device response(method1)
+3%
-3%
20℃ 25℃
corrected light yield(100pixel)
• device response is stable within ~3% after calibration of method 1
• response of other three samples is also well calibrated
Method2 MIP ADC count ∝ gain(T,V)×PDE(T,V)×
LED ADC count ∝gain(T,V)×PDE(T,V)× 11- crosstalk(T,V)
1- crosstalk(T,V)
1
MIP ADC count
LED ADC count
we can calibrate the variation of gain, PDE, crosstalk by taking the ratio of MIP ADC count to LED ADC count
corrected light yield =
MIP ADC countLED ADC count
Stability of device response(method2)
+3%
-3%-3%
+3%
20℃ 25℃
corrected light yield(100pixel)
• device response is stable within ~3% after calibration of method 2
• response of other three samples are also well calibrated
MPPC1(100)
MPPC2(100)
MPPC3(400)
MPPC4(400)
Method1 2.5% 2.3% 3.8% 3.1%
Method2 2.5% 1.3% 2.4% 1.4%
We need to
guarantee the stability of light from LED for method 2
measure the PDE, cross-talk rate as a function of V-Vbd before installation for method 1
Summary and discussion about calibration test
Stability of each MPPC response after calibration in RMS/mean
calibration is possible by two methods
(the precision of calibration is better for method 2)
Conclusion
device-by-device variation among three samples is small, but it is necessary to test much larger number of samples
calibration is possible by two methods further test of much larger number of
samples
back up
MPPC(Multi pixel photon coutner)
100~1000 APD pixel in 1mm2
Each pixel operates as Geiger mode
(independent of input light)
The output is a sum of all the APD signals
Compact Low-cost Insensitive to the magnetic
field Low bias voltage :40~75V High gain:105~107
MPPC characters:
Basic performance ~Gain~
MPPC gain = output charge from a single pixel
0p.e.
1p.e.
2p.e.
3p.e.
ADC counts
calculate gain from the number of ADC counts between 1p.e. and pedestal peak
Basic performance ~gain~
3×106
100pixel gain
bias V68.4V
69.6V
1×106
1×106
68.4V 69.4Vbias V
400pixel gain
3×105
Basic performance ~Noise rate~
count the rate above 0.5 and 1.5p.e. threshold without external light
Noire rate measured at the 1.5p.e. threshold increases as the temperature becomes lower
68.2V
69.8V
1MHz
■ ■ ■ : 0.5p.e threshold
▲ ▲ ▲ : 1.5p.e threshold
100kHz
because the cross-talk rate increases as the temperature becomes lower
100pixel Noise rate @0.5p.e. threshold
bias V
Basic performance ~crosstalk~
103
102
10
・ Assuming 2p.e. noise is caused by crosstalk of 1p.e noise(accidental coincidence of 1p.e noise is subtracted)
e.p5.0thanmoreevents
e.p5.1thanmoreevents
Cross-talk rate =
Data taken by random trigger
0.5p.e.
1.5p.e.
Basic performance ~PDE~
MPPC(total area 1mm2)
½ inch PMT
1mmφslit
MPPC
x
Y
slit
PMT
The view from this side
・ only the light going through 1mmφslit is detected ・ Scan the MPPC and PMT with moving stage and search the position with maximum light yield ・ The ratio of MPPC p.e to
PMT p.e is taken as relative PDE of MPPC to that of PMT
WLS fiber
Basic performance ~linearity(100pixel)~
30
80injected p.e.
30
80injected p.e.
fired pixel number
(Data-Exp)/Exp(%)
6expected curve calculated from number of pixels and measured cross-talk rate
Basic performance ~linearity(400pixel)~
injected p.e.100 30
0100
300injected p.e.
fired pixel number
(Data-Exp)/Exp(%)
6
expected curve calculated from number of pixels and measured cross-talk rate
Photoelectrons for MIP
photoelectrons at 20℃ are about 20% smaller than that at 25℃
need to correct for the variation of PDE, cross-talk rate
photoelectrons for MPPC3 are much smaller than that for other MPPCs
due to misalignment of a fiber to the MPPC
MPPC1(100) MPPC2(100)
MPPC3(400)
MPPC4(400)
16
13
15
12
7
5.5
16
13
20℃ 25℃
Uniformity within 1pixel
RMS/mean=2%
efficiency
Gain
RMS/mean=2%
Cross-talk rate
0.25
100pixel
efficiency
100pixel
Gain
RMS/mean=3%
RMS/mean=3%Cross-talk
rate0.22
Uniformity of each pixel
efficiency
RMS/mean=1.7%
Gain
RMS/mean=1.6%
Cross-talk rate
Uniformity within 1pixel
400pixel
0.25
RMS/mean=2.9%
RMS/mean=3.4%
Gain
efficiency
Cross-talk rate
Uniformity of each pixel
400pixel
0.18
Laser test
laser
1pixel•spot size~ a few μm
•wavelength ~532nm
•light intensity ~a few photons
100pixel efficiency measured the geometrical effic
iency(εgeom) by scanning the laser with 0.1μm pitch
efficiency is calculated from the fraction of events with more than 0.5p.e. to the total events
68μm
100μmεgeom=46% for 100 pixelεgeom=55% for 400 pixel
HPK now develops new 100pixel sample with larger geometrical efficiency
100μm
Variation of 1p.e. ADC count
1p.e. ADC count changes about 20% when temperature changes from 20℃ to 25℃
14
12
16
13
5.4
4.4
5.6
4.6
MPPC1(100)
MPPC2(100)
MPPC3(400)
MPPC4(400)
20℃
25℃
40hours
MPPC1(100)
MPPC2(100)
MPPC3(100)
MPPC4(100)
-3%
+3%
corrected light yield
corrected light yield
=MIP ADC count
1p.e. ADC count
x PDE x
1
(1-cross-talk rate)
Stability of light yield ~method 1~
20℃ 25℃
Stability of light yield ~method2~
MPPC1(100)
MPPC2(100)
MPPC3(400)
MPPC4(400)
+3%
-3%
20℃
25℃
LED ADC count
=
corrected light yield
corrected light yield
MIP ADC count
light yield distribution for MIP is fitted with Landau distribution
temperature coefficient of scintillator and fiber is very small
240
160
220
160
38
24
90
60
MPPC1(100) MPPC2(100)
MPPC3(400) MPPC4(400)
MIP ADC count
20℃ 25℃
400pixel gain
400pixel PDE(MPPC)/QE(PMT)
400pixel crosstalk
V-Vbd V-Vbd V-Vbd
Gain,PDE,crosstalk are functions of V-Vbd