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Development of Multi-Pixel
Photon Counters and
readout electronicsMakoto Taguchi High Energy Group
Contents
T2K experimentMulti-Pixel Photon Counters (MPPC)Basic performanceLaser testReadout electronics of MPPC Conclusion
T2K experiment
• search for appearance
•precise measurement of disappearance
T2K experiment
J-PARCSK
μνeν
ν
main goals
Photosensor for T2K
• # of channels ~ 60,000 and space is limited
compact & low cost • under 0.2T environment tolerance to magnetic
field• efficiency for the
detection of particles large light yield
target0.2T magnetMagnet use scintillator+wave lengt
h shifting fiber for the near detectors
MPPC is chosen as the photosensor for T2K that satisfies these requirements
requirements to photosensor
T2K near detectors
Multi-Pixel Photon Counters(MPPC)
Multi-Pixel Photon Counter(MPPC)New(~2years ago) photosensor produced by
Hamamatsu Photonics
~5mm
Geiger-APD pixels 100u
m
100 or 400 avalanche photodiode(APD) pixels in 1mm2
Each pixel works in Geiger mode above breakdown voltage
output from each pixel is independent of # of created p.e. within the pixel
The output from MPPC is a sum of output charge from all APD pixels
output from MPPC is proportional to the # of fired pixels
photon
high (~106) gain Geiger mode
insensitive to magnetic field semiconductor
compact, low cost (~2000Yen?)
excellent photon counting
attractive feature
Measurement of basic performance of MPPC
Test samples ・・・ latest (Oct. 2006) 100 and 400 pixel samples Test items ・・・ raw signal gain noise rate Photon detection efficiency crosstalk-rate Linearity recovery time
presented here
Basic performance of MPPC satisfies the T2K requirement?
MPPC is a new photodetector
Motivation
Raw signalblue LED
1p.e.2p.e.3p.e.
output charge oscilloscope or
ADC
1p.e.
2p.e. 3p.
e.
gate
photon
MPPC
Excellent photon counting capability!
pedestal
pedestal
Gain
pedestal
1p.e.
Gain = Q/e
Q
bias voltage
15deg.20deg.25deg.
•Gain = 1.0x106 ~ 3.0x106 and increases with lower temperature
•linear dependence on bias voltage, G = C (V-Vbd)
ADC distribution
C : capacitance
V: bias voltage
Vbd : breakdown voltage
Noise rate• MPPC emits thermal noise without external light• count the rate above thresholds of 0.5p.e. and
1.5p.e.
bias voltage
(kHz)
15deg.20deg.25deg.
1.5p.e. th.
0.5p.e. th.
•noise rate at 0.5p.e. th. <500kHz and becomes higher with higher temperature
•noise rate at 1.5p.e. th. <100kHz and becomes higher with lower temperature
cross-talk effect
Cross-talk• “photons generated during an avalanche trigger
another avalanche in neighboring pixel”crosstalk rate =
festimated : estimated fraction of 1p.e. events from that of pedestal events assuming Poisson
fobserved : observed fraction of 1p.e. events
1-festimated
fobserved
bias voltage
15deg.20deg.25deg.
ADC dist.
Crosstalk rate 0.2 ~ 0.4 and increases with lower temperature
Photon Detection Efficiency(PDE)• PDE = Geigerεgeomε x QE x
geometrical efficiency ~70%
quantum efficiency of APD ~70%
Geiger probability (V,T) ~90%
MPPC
PMT
1mmφslit
WLS fiber
blue LED
PDE(MPPC)/QE(PMT)
setup
15deg.20deg.25deg.p.e.(MPPC)
p.e.(PMT)V
PDE of MPPC is 2~3 higher than that of PMT and increases with lower temperature
Summary of basic performance
100pixel 400pixel Requirement for T2K
Gain 1.0~3.0x106 ~1.0x106 ~106
Noise rate at 0.5p.e. th.
100~500kHz
100~500kHz
<1000kHz
Noise rate at 1.5p.e th.
10~100kHz 10~100kHz <50kHz
Cross-talk rate
0.2~0.4 0.2~0.4
PDE 20~45% 20~30% >15%
Linearity ~40p.e. ~120p.e. ~100p.e.
@20deg.
Performance of MPPC satisfies the requirements for T2K!
Laser test for the old samples,• gain in the edge of pixel is higher than that in the center of pixel • breakdown voltage is different in each pixelcheck the response within one pixel /of each pixel for the new samples
• test items ・・・ gain, efficiency, cross-talk
green laser
movable stage
MPPC
•uniformity within one pixel
•pixel-to-pixel uniformity
setupefficiency =
# of total events
# of events > 0.5p.e.
Motivation
presented here
10um
gaingain
efficiency
uniformity within one pixel
pixel-to-pixel uniformity
efficiency
RMS/mean=2.0%
RMS/mean=2.0%
RMS/mean=3.3%
RMS/mean=2.5%
Response within one pixel/of each pixel is well uniform!
Readout electronics of MPPC
Readout electronics of MPPC with “Trip-t” chip
use ~60,000 MPPCs in T2K and compact&multi-channel electronics is necessary
establishment of test system for mass production of MPPC is also needed
we have developed the readout electronics with Trip-t• ASIC produced at Fermilab• 32 channel inputs • for negative charge1) serialized analog output corresponding
to the amplitude of input charge2) serialized analog output corresponding
to the timing of input charge3) discriminated output for each channel
Motivation
Trip-t
14mm# of readout channels 321
14mm
Trip-t
front end
Pipeline
Pipeline
Digital multiplexer
analog multiplexer
analog multiplexer
A_OUT (charge)
T_OUT (timing)
D_OUT(digital)
•amplifier (gain is adjustable)
•generate digital signals
store signals before readout (depth 1~48)
serialize 32ch signals
input charge
charge
timing
digital
ch1
ch2
ch3
ch1ch2
ch3
Readout of MPPC with Trip-t
1p.e.2p.e.
output from Trip-t
4MPPC
3p.e.
LED
test board(4ch)
AD conversion by flash ADC
100pixel 400pixel 400pixel 400pixel
readout 4 MPPCs simultaneously
succeed in developing the multi-channel readout electronics of MPPC!
Dynamic range of Trip-t
charge(-pC)
ADC count
saturation
> >Trip-t gain
•Dynamic range ~40p.e. with the lowest gain of Trip-t, assuming MPPC gain of 7.5x105
OK for test of large number of MPPCs
not OK for T2K (requires ~100p.e.)
MPPC
100pF
10pF
high gain channel
low gain channel
high/low gain method for real type elec.
•high gain channel ・・determine gain w/ photopeaks
•low gain channel ・・accommodate large signal
Trip-t can be used for the readout electronics of MPPC in T2K
Conclusion• MPPC is a new photodetector produced by
Hamamatsu Photonics and chosen as the photosensor for T2K
• Basic performance of MPPC satisfies the requirements for T2K
• Response within one pixel/of each pixel is well uniform
• Trip-t which was produced at Fermilab can be used for the readout electronics of MPPC in T2K
• future development ・・ test of large number of MPPCs with 32ch Trip-t board
• Our study is an important step not only for T2K but also for wide use of MPPC
backup
Principle of APD•high reverse bias voltage applied to a pn junction
multiplication region, where created e- -e+ pairs cause an avalanche multiplication
•Normal mode - operate below the breakdown voltage(Vbd) - gain < ~ 100 - have linear output to # of injected photons
•Geiger mode - operate above the breakdown voltage(Vbd)
- gain ~106 - does not have linear output to # of injected photons
E
reverse bias
Gain
100pixel
400pixel
bias bias
15deg.20deg.25deg.
gain(2)
100pixel
400pixel
15deg.20deg.25deg.
ΔV ΔV
ΔV =V-Vbd
Gain is a function of only ΔV
Device-by-device gain variation
bias V
Device-by-device gain variation comes from the device-by-device variation of Vbd
ΔV =V-Vbd
•400pixel
#2#1
#3#2#1
#3
Noise rate
100pixel
bias bias
(kHz) (kHz)
15deg.20deg.25deg.
1.5p.e. th.
0.5p.e. th.
0.5p.e. th.
1.5p.e. th.
400pixel
Device-by-device variation of noise rate at 0.5p.e. th.
bias V
Device-by-device variation of noise rate comes from the device-by-device variation of Vbd
(kHz) (kHz)
•400pixel
#2#1
#3
#2#1
#3
ΔV =V-Vbd
Cross-talk rate
bias bias
100pixel
400pixel
15deg.20deg.25deg.
Cross-talk rate(2)
100pixel
400pixel
ΔV ΔV
15deg.20deg.25deg.
cross-talk rate is a function of only ΔV
ΔV =V-Vbd
Device-by-device variation of cross-talk rate
bias V ΔV = V-Vbd
Device-by-device variation of cross-talk rate comes from the device-by-device variation of Vbd
•400pixel
#2#1
#3#2#1
#3
PDE(MPPC)/QE(PMT)
bias bias
100pixel
400pixel
15deg.20deg.25deg.
PDE(MPPC)/QE(PMT)(2)
ΔV ΔV
100pixel
400pixel
15deg.20deg.25deg.
PDE is a function of only ΔV
ΔV =V-Vbd
Device-by-device variation of PDE
bias V ΔV = V-Vbd
Device-by-device variation of PDE comes from the device-by-device variation of Vbd
•400pixel
#2#1
#3#2#1
#3
Vbd vs TVbd
Vbd
degree degree
Vbd is proportional to the temperature
100pixel 400pixel
Comparison of latest and old samples (gain)
latest
old
latest
old
100pixel 400pixel
ΔV ΔV
Comparison of latest and old samples (noise rate)
latest
old
100pixel
latest
old
400pixel(kHz) (kHz)
ΔV ΔVnoise rate of latest sample is lower
Comparison of latest and old samples (cross-talk rate)
latestold
100pixel
ΔV ΔV
latest
old
400pixel
cross-talk rate of latest sample is higher increase of geometrical efficiency
Comparison of latest and old samples (PDE)
latest
old
100pixel
ΔV ΔV
latest
old
400pixel
PDE of latest sample is higher increase of geometrical efficiency
Linearity
paper
setup •# of injected p.e. to MPPC is estimated by the p.e. detected by a monitor PMT
•expected response:MPPC
PMT
))N
c)x(1exp((1NN
00fired
Nfired : # of fired pixels
N0 : # of pixels
c : Cross-talk rate
x : # of injected p.e.
LED
100pixel
400pixel
+10%
+20%
-10%
-10%
injected p.e.
injected p.e.
injected p.e.
injected p.e.
# of fired pixel
# of fired pixel
(Data-exp.)/Data(%)
(Data-exp.)/Data(%)
Data
Data
expectation
expectation
Linearity(3)
100pixel 400pixel
# of injected p.e.
# of injected p.e.
(Data-Fit)/Data(%) (Data-Fit)/Data(%)
-20% -20%
Recovery time
• “time to quench an avalanche and then reset the applied voltage to its initial value”
• fire all pixels by the light from LED1 and check the response to the light from another LED(LED2) with changing the time difference between the LED1 and LED2
Recovery time(2)
•100 pixel
•400 pixel
All pixels are recovered 100ns after all pixels are fired
Recovery time < 100ns
uniformity of cross-talk rate within one pixel
cross-talk rate = # of events > 0.5p.e.
# of events > 1.5p.e.
100pixel 400pixel
Pixel-to-pixel uniformity of cross-talk rate
100pixel 400pixel
Measurement of active area inside one pixel
100pixel
400pixel
100um
85um
50um
38um
um um
laser spot
scan
efficiencyefficiency
geomε =72%
geomε =58%
Correction of MPPC signal
MotivationGain, PDE, crosstalk of MPPC are all sensitive to the temperature and bias voltage
It is necessary to correct the variation of gain, PDE,crosstalk when temperature or bias voltage changes
MPPC Signal ∝ Gain(T,V) x PDE(T,V) x 1-crosstalk(T,V)
1
T : temperature V : bias voltage
I have studied two correction methods
Set up
1/2inch PMT
cosmic-ray
1mm φfiber
MPPC2(100)
MPPC1(100)
MPPC3(400)
MPPC4(400)
scintillator
blue LED
• put scintillators in four layers• inserted fibers are connected
by four MPPCs(two are 400 pixel and two are 100pixel)
• change temperature intentionally between 20 and 25 degree
• The same bias voltage is applied to four MPPCs
• two triggers(cosmic,LED)
temperature chamber
With this setup we have traced the variation of light yield for cosmic-ray
Correction method Again
cross-talk rate PDE
ΔVΔVΔV
1) monitor the variation of gain
1)
2) 2) 2)
2) estimate the variation of ΔV
3) estimate the variation of crosstalk,PDE
3)
3)
15deg.20deg.25deg.
Correction method A(2)
calibration constant=
gain x PDE x
MIP ADC counts
1- crosstalk1
•this value must be constant if we can correct the variation of gain, crosstalk ,PDE
Correction method B
MIP ADC count ∝ gain(T,V)×PDE(T,V)×
LED ADC count ∝ gain(T,V)×PDE(T,V)×1
1- crosstalk(T,V)
1- crosstalk(T,V)
1
MIP ADC count
LED ADC count
calibration constant =
MIP ADC count
LED ADC count
dist.taken by cosmic trig.
dist.taken by LED trig.
Inject the light from LED with the similar light intensity as MIP light yield
Variation of calibration constant
+3%
-3%
method A
+3%
-3%
-3%
+3%
method Bcalibration constant
calibration constant
• only the errors of MIP ADC count and gain are included
hour hour
C20○
C20○C25○ C25○
•detector response can be corrected within 3% level by both methods
MPPC1(100)
MPPC2(100)
MPPC3(400)
MPPC4(400)
Method A 2.5% 2.3% 3.8% 3.1%
Method B 2.5% 1.3% 2.4% 1.4%
Summary of correction methods
RMS/mean of calibration constant
•Required precision is a few % (This depends on the type of detector)
Both correction methods satisfy the requirement!
Requirement to MPPC
Item Requirement From where
Area 1.2x1.2mm2 To match 1.0mm fiber
No. of pixel 100/400 To keep dynamic range up to ~100p.e.
Gain ~106 To match readout electronics
Noise rate <1MHz To reduce accidental hits
Crosstalk <5% To reduce the noise rate with 1.5p.e. threshold
PDE >15% Light yield
Timing resol. 2-3ns Not so meaningful requirement
Specification of Trip-t
• Size : 14mm x 14mm• Power supplies : +2.5V• Power consumption < 10mW per
channel
Trip-t gain
pipeline
1pF
3pF
preamp gain x1 or x4
opamp gain x2,x4,x8…
preamp
input
opamp
•Trip-t gain can be changed by programming the registers
Setup for readout of MPPC
FADCA_OUT
-+
opampTrip-t
+5V
-5V
Digital wave generator
Control signals
Trigger
MPPC
LED
4m flat cable
AD conversionTrigger
Readout sequence of Trip-t A_OUT(charge)
MPPC signal (ch1)
preamp integrate
signal after preamp
A_OUT
Multiplexer clock0 1 2 33
ch1
A_OUT
charge = -1.5pC
charge = -0.5pC
A_OUT linearityADC count
charge(-pC) charge(-pC)
Trip-t gain
> >
Trip-t gain
> >
nonlinearity in the low pulse amplitude will be fixed for the new version of chip
(Data-linear)/Data(%)
Crosstalk of A_OUT• signal observed in the channel where
the charge is not injected
ch
0.4%
15
•crosstalk(i) =
ADCcharge(i)-ADCnocharge(i)
ADCcharge(15)-ADCnocharge(15)
•ADC(no)charge(i) = ADC count in the channel i when the charge is (not) injected
crosstalk<0.4%
Variation of Trip-t gain
• variation is ~4%ch gain (AD
C count/-pC)15 730
16 710
31 735
32 732
Readout sequence of Trip-t T_OUT(timing)
MPPC signal (ch1)
preamp integrate
signal after preamp
T_OUT
Multiplexer clock0 1 2 33
pipeline clock
ch1
T_OUT
time difference = 200ns
time difference = 100ns
T_OUT linearity
ns ns
ADC count
(Data-linear)/Data(%)
saturation
T_OUT conversion factor
• variation is ~25%ch Conversion factor (ADC count/ns)
15 8.52
16 8.60
31 8.00
32 9.97
D_OUT(Digital)
Trip-t1pF
charge injection
10ns •Delay inside Trip-t is
~10ns
100pixel 400pixel
MPPC gain measured by CAMAC and Trip-t
bias bias
Trip-t gain is well calibrated
Trip-t
CAMAC
Trip-t
CAMAC
Current design of real type electronics for T2K
16 MPPCs
16MPPCs
Trip-t
ADC ADCFPGA
Trip-t
16MPPCs
16 MPPCs
Trip-t
Trip-t
•64MPPCs per board with 16 high/low gain channels per chip
•control of Trip-t and ADC by FPGA
•temperature monitoring
•HV trimming DAC
spill(8bunch)
integrate(~300ns)
reset (~50ns)
Chip time structure (preliminary)
5.6us
readout catch late signal
~3us ~50us
beam
10
2
3
4
5
678
100
2
3
4
5
678
1000
2
3
4
AD
C u
nits
5 6 7 80.1
2 3 4 5 6 7 81
2 3 4 5 6 7 810
2 3 4
total external charge injected [pC]
high/low gain method
high
low
~300p.e.
~30p.e.
ADC distribution with lowest gain of Trip-t
•MPPC gain = 7.7x105
•S/N=3
VA chip• ASIC used for the K2K SciBar detector - 64ch inputs - VA does not have pipeline - VA itself cannot issue discriminated output - VA gain cannot be changed
Readout sequence of VAMPPC signal (ch1)
signal after shaper amp
outm
0
ch1
1 2
hold_b
Multiplexer clock
Readout of MPPC with VA•MPPC gain = 2.7x106, noise rate at 0.5p.e. th. = 240kHz
pileup of MPPC noise
S/N=1.7