development of multi-pixel photon counters(2) m.taguchi, t.nakaya, m.yokoyama, s.gomi(kyoto)...
TRANSCRIPT
Development of Multi-pixel photon counters(2)
M.Taguchi, T.Nakaya, M.Yokoyama, S.Gomi(kyoto)
T.Nakadaira, K.Yoshimura(KEK)
for KEKDTP photon sensor group
Contents
• Application of MPPC for T2K experiment
• device-by-device variation of gain, noise rate
• Calibration of MPPC signal• summary
•precise measurement of disappearance
•search for appearance
T2K experiment
J-PARCSuper KamioKande
main goal
μν νeνμν
ν
Application of MPPC for T2K
• use scintillator+wave length shifting fiber for almost all near detectors
need compact & low cost photo sensors
• OffAxis detector is put under 0.2T environment
need tolerance of magnetic field
OffAxis detector
OnAxis detector
MPPC is the only candidate to satisfy these requirements
target
SK
ν
0.2T magnet
280m
295km
Item Requirement Status
Area 1.2×1.2mm2 HPK now working
No. of pixel 100/400 OK
gain ~106 OK
Noise rate with 0.5p.e. threshold
<1MHz OK
crosstalk <10% HPK now working
PDE >30% OK
Timing resolultion ~2,3ns OK
requirement from T2K
The requirement from T2K is satisfactory except for area and crosstalk
Device-by-device variation
• Basic performance of MPPC is almost satisfactory• We plan to use ~50000 MPPCs next, device-by-device variation of basic performance
when mass production?• if variation is large, - one MPPC is in geiger mode but other is not… - readout electronics needs to cover more dynamic ran
ge trim bias voltage for each MPPC? We measured the device-by-device variation of gain, n
oise rate for seven 100 and 400 pixel samples which are the same types
Motivation
tested samples
Number of pixels
Pixel pitch(μm) Area Operating voltage
Geometrical efficiency
100 100 1.0x1.0mm2
69-70V 64%
400 50 1.0x1.0mm2
69-70V 55%
•samples which was delivered at this month
device-by-device variation ~gain~
69.4V70.4V69.4V 70.4V
variation 3.0×106~3.6×[email protected]
variation 9.0×105~1.3×[email protected]
1.0×106
4.0×105
1.2×106
100pixel
400pixel
•20℃•different colors correspond to data at different samples
3.0×106
device-by-device variation ~ 0.5p.e.threshold noise
rate ~
69.4V 70.4V 69.4V 70.4Vvariation [email protected]
variation [email protected]
100pixel
400pixel
100kHz
500kHz
100kHz
400kHz
•20℃
device-by-device variation ~ noise rate as a function of ΔV ~
0.5 2 0.5 2
100pixel
400pixel
100kHz
500kHz
400kHz
100kHz
Vbd : breakdown voltage(derived by linearly extrapolating the gain-voltage curve to the point where gain becomes zero)
Vbd V
Gain
•noise rate as a function of ΔV takes the same value for different samples
variation of noise rate comes from variation of breakdown voltage
•20℃
Δ V = V - Vbd
Δ VΔ V
device-by-device variation ~breakdown voltage~
•20℃
400pixel Vbd100pixel Vbd
68.4 69.0 68.1
69.1
0.6V
1.0V
•variation of Vbd is about 1V we requested HPK to reduce the variation
Electronics is designed to be able to trim bias voltage for each MPPC
•we are going to check the variation for ~500 samples next March
Calibration of MPPC signal
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 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 will present two methods for calibrating MPPC signal (explain each method later)
Set up for calibration test
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 viewed by
four MPPCs(two are 400 pixel and two are 100pixel)
• change temperature intentionally like 20℃25℃
• The same bias voltage is applied to four MPPCs
• two triggers(cosmic,LED)
temperature chamber
※ we used old samples for this test
Calibration Method 1
gain crosstalkPDE(MPPC)/QE(PMT)
Vbd: breakdown voltage
V: bias voltage
•gain, PDE, crosstalk are all functions of (independent of temperature)
•can calibrate all parameters by monitoring only one parameter(for example, gain)
different colors correspond to data at different temperatures
Δ VΔ VΔ V
Δ V
Δ V = V - Vbd
calibration constant=
gain x PDE x
MIP ADC counts
1- crosstalk1
Calibration Method 1
0p.e.
1p.e.
gain
VΔ
1. measure the variation of gain(from 1p.e.and pedestal peak)
①2. can estimate the variation of
②
Δ VΔ
crosstalk
PDE(MPPC)/QE(PMT)
②
②
Δ V
Δ V3. can estimate the variation of PDE( ), crosstalk( ) Δ V Δ V
③
③
Calibration Method2
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 same light intensity as MIP light yield
Stability of device response after calibration(100pixel)
+3%
-3%
20℃ 25℃
method1
+3%
-3%
-3%
+3%
20℃
25℃
method2
calibration constant
calibration constant
•precision of calibration is ~3% by both methods
•response of other three samples is also well calibrated
• only the errors of MIP ADC count and gain are included
hour hour
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%
Summary and discussion about calibration test
RMS/mean of calibration constant
•required precision is a few % (this depends on the type of detector)
both calibration methods satisfy the requirement!
Summary• use of MPPC at T2K is determined • performance of MPPC is satisfactory for T2K except for crosstalk and area now HPK is working• device-by-device variation among seven samples is 1V we requested HPK to reduce the variation we are going to check the variation for ~500 samples
next March
• our calibration methods satisfy the requirement
future plan
• 2007 Spring - production of 500~1000 samples - beamtest of Scinti+WLSF+MPPC Summer - decide the final spec for T2K - install MPPCs for SciBooNE
experiment ? Autumn - mass production• 2008~ detector construction• 2009 Spring~ : T2K starts
supplement
measurement of gain
0p.e.
1p.e. MPPC gain = 1p.e. charge
e(1.6×10-19)
ADC distribution
blue LED
measurement of noise rate•count the rate above 0.5 and 1.5p.e. threshold without external light
0.5p.e.
1.5p.e.
measurement of crosstalk
103
102
10
・ Assuming 2p.e. noise is caused by crosstalk of 1p.e noise(accidental coincidence of 1p.e.noise is subtracted)
0.5p.ethanmoreevents1.5p.ethanmoreevents
Cross-talk rate =
Data taken by random trigger
0.5p.e. 1.5p.e
.
measurement of PDE
MPPC(total area 1mm2)
½ inch PMT
1mmφslit
MPPC x
Y
slitPMT
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
blue LED
Crosstalk
• assume the crosstalk takes place sequentially at the same probability
• 1p.e. looks like:1+(crosstalk)+(crosstalk)2+‥=
correction factor of crosstalk=
1
1-crosstalk
1-crosstalk
1
setup for calibration test
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:
Raw signal and ADC distribution
Where does the requirement to MPPC come from?
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 set disc. threshold with reasonable precision
Noise rate <1MHz To reduce accidental hits to TDC
crosstalk <5% To reduce the noise rate with 1.5p.e. threshold
PDE >30% To keep as large PDE as that of PMT at least
Timing resol. 2-3ns Not so meaningful requirement
T2K near detectorname type requiremen
tnote
INGrid tracker ~10% See muon track
TPC tracker No MPPC
FGD Tracker +target
~5% P/π separation
P0D Calorimeter a few % Energy resol.
ECAL Calorimeter a few % Energy resol.
SMRD Calorimeter a few % Energy resol.