M.Taguchi and T.Nobuhara(Kyoto)

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HPK MPPC(Multi Pixel Photon Counter) status

• M.Taguchi and T.Nobuhara(Kyoto)

Jan.17.2006 _at_KEK T2K280m meeting
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Test Procedure

• Observe the raw signal
• Confirm the fundamental performance
• gain
• noise rate
• crosstalk
• PDE(photo detection efficiency)
• Linearity
• Confirm the performance under the real
  experimental environment
• - scintillatorWLS fiberMPPC
• Laser Test (using BELLE laser system)

Already presented at the previous 280m meeting
Talk at this meeting
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MPPC type used in each measurement
measurement MPPC or Russian SiPM type
Crosstalk HPK 100pixel HPK 400pixel
PDE HPK 100pixel
Linearity HPK 100pixel
Beamtest HPK 100pixel Russian 600pixel
Laser test HPK 100pixel
We studied the property of HPK100pixel type in
detail because we used this type of MPPC in
beamtest
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Crosstalk measurement
Crosstalk? photons emitted from one pixel during
the Geiger discharge causes the Geiger
discharge at neighboring pixels
Assuming 2p.e noise is caused by crosstalk of
1p.e noise(accidental coincidence of 1p.e noise
is negligible)
Crosstalk rate
Maximum crosstalk rate is 0.16(HPK100) and
0.25(HPK400)
Data taken by random trigger
Crosstalk rate
Crosstalk rate
0.25
0.16
HPK100
103
0.10
102
HPK400
0.1
10
(V)
70.3 70.5 70.7 71.0
48.5 49.0 49.3 49.6
0.5p.e
1.5p.e
74 234 478 800
295 448 567 760
(kHz)
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PDE(photon detection efficiency)
PDE(photon detection efficiency) is defined as
the ratio of the number of output p.e to the
number of injected photons

• PDEepixelQEeGeiger

A ratio of active area to total area (3070)
Quantum efficiency of active area (6080)
Probability of Geiger discharge (6080)
Depending on wavelength of injected light
Depending on bias V
Depending on MPPC type
Measured the relative PDE to that of PMT with
the following set up (about four HPK100 MPPCs)
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PDE measurement
only the light going through 1mmfslit is
detected
½ inch PMT
WLS fiber
Scan the MPPC and PMT with moving stage and
search the position with maximum light yield

The view from this side
Blue LED
The ratio of MPPC p.e to PMT p.e is
taken as relative PDE of MPPC to that of PMT
MPPC(total area 1mm2)
1mmfslit
Y
change MPPC bias V
MPPC
slit
light sources are blue LED and wavelength
shifting fiber(Y11)
x
PMT
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PDE measurement(contd)
PDE(MPPC)/PDE(PMT)
HPK10014
Measure PDE at this point
1.4
green
blue
2mm
2mm
MPPC X scan
MPPC Y scan
70.3 70.5 70.8 71.1
Bias V(V)
The width of scan is 2mm
294 388 524 687
Noise rate(kHz)
The max green PDE is about 1.4 times larger than
that of PMT and green PDE is larger than blue PDE
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PDE measurement(contd)
0.8mm
There is a distance(0.8mm) between surface
cover and active area in HPKs MPPC
so PDE should decrease effectively when using a
WLS fiber because light from a WLS fiber spreads
at 40
1mm
40
½ inch PMT
Blue LED
Measured the effective PDE with this set up
about four HPK100e MPPCs(the method of
measurement is the same as before)
WLS fiber(1mmf)
compare the PDE measured in the previous
measurement
MPPC(total area 1mm2)
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PDE measurement(contd)
PDE(MPPC)/PDE(PMT)
HPK10014
54
PDE
3mm
3mm
MPPC X scan
MPPC Y scan
Effective PDE
The width of scan becomes 3mm due to spread of
light from a WLS fiber
Bias V(V)
70.5 70.8 71.1 71.3
388 524 687 864
Noise rate(kHz)
The decrease of PDE due to spread of light from
a WLSF is 4050 about four HPK100 MPPCs
Effective PDE can be increased by improvement of
packaging
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Linearity measurement(HPK100)
inject uniform light from blue LED to PMT
and MPPC monitor the light injected to MPPC by
PMT examine the linearity of MPPC output
against PMT output linearity depends on the
crosstalk rate and the number of pixels, so we
measured the linearity at the point that
crosstalk rate is 0.03 and 0.2
PMT(1/2 inch PMT)
uniform light
Blue LED
MPPC (HPK100)
Set up
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Linearity measurement(contd)
Fired pixel number
Difference from the linear extrapolation
10
Crosstalk rate 0.03
Theoretical curve calculated with the crosstalk
rate and the number of pixels
20
data points agree well with the theoretical
curve HPK100(100pixel) showed 20 nonlinearity
when 3550p.e are injected (depending on
crosstalk rate)
injected p.e
50p.e
Fired pixel number
Difference from the linear extrapolation
10
Crosstalk rate 0.2
20
35p.e
injected p.e
injected p.e
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Beamtest _at_KEK in Nov.2005
setup

• 0.51.4GeV/c
• proton pion
• 100 event/spill
• beam size 1x1cm2

Motivation Can the light yield for T2K near
detector be obtained?
beam
64ch MAPMT (as reference)
(more than 5p.e for MIP)
HPK100e or Russian SiPM
4 layers
Scintillator 1.3x2.5x50 cm3 (used in K2K scibar
detector)
1mmF fiber
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Alignment of fiber
X
The X Y position of active area of HPKs MPPC is
different by each sample,so alignment of fiber is
necessary by each sample
Y
Scan the fiber with moving stage and fix the
fiber with screws at the point where MPPC signal
becomes maximum
MPPC
screw for fixing fiber
fiber
About 20 loss of light yield is possible due to
misalignment of fiber
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Beamtest_at_KEK(contd)
MPPC type MPPC p.e for MIP PMT p.e for MIP Ratio of MPPC p.e with PMT()
HPK10013 9.9 18.3 54
HPK10014 10.2 18.2 56
HPK10016 13.3 18.2 73
Russian60013 22.9 18.2 126
Russian60014 17.1 18.2 94
We could obtain the light yield for T2K near
detector
The measured PDE including optical contact for
HPK100 and Russian SiPM are about 0.7 and 1.0 of
PMT, so obtained light yield is consistent with
the expectation considering the misalignment of a
fiber
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Laser test(HPK100)
Picture of microscope
100µm
microscope
Motivation study the response of each pixel of
MPPC
Laser source
?825nm width 50ps
Feed back this information to HPK
Laser spot size ?10µm
MPPC
We studied
Moving stage 1µm pitch (x , y)
Efficiency distribution within 1pixel
Uniformity of gain and efficiency in each pixel
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Efficiency distribution within 1pixel
1pixel
Scan the laser in the 10mm pitch within 1
pixel(total 100scan)
100µm
efficiency
laser
1p.e.
Efficiency Ratio of events more than 0.5p.e to
total events
0p.e.
100µm
100µm
0.5p.e.
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Response of each pixel
y
Inject laser to the center of each pixel and
study the response of each pixel
x
Total 100pixel
Relative gain
Relative efficiency
1.06
1.04
Response of each pixel is uniform!
RMS/mean3.6
RMS/mean2.5
0.96
0.92
y
y
x
x
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Summary
About HPK100pixel MPPC

• The green PDE is larger than that of PMT
• Light yield for MIP is 1013p.e (at the point
  that noise rate and gain satisfy T2K requirement)
• Response of each pixel is uniform

Show 20 nonlinearity when 3550p.e are
injected ? need more than 200pixel The
loss of light yield due to spread of light from a
WLS fiber is 4050
? can be improved by
packaging
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supplement
20
Future plan

• Test the new samples which recently we got
• (HPK say these have higher PDE than others)
• Study the response of each pixel more in detail
  with the laser system for MPPC _at_KEK

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MPPC(Multi pixel photon coutner)
MPPC characters

• 1001000 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 3075V
• High gain105107

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Signal and p.e peak
HPK100a V48V
2p.e
1p.e
30p.e
Increasing the injected light
0p.e
We can count the peak up to 4p.e the interval
between each peak completes by 4
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Summary of gain measuremnt
RUS14
T20
RUS23
RUS20
Gain31052107
The (dG/dV)depends on the capacitance of pixel
RUS22
Bias V
43
35
HPK100f
HPK100d
HPK100a
HPK100e
HPK400b
Bias V
HPK1600a
Bias V
47
49
70
74.5
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Summary of gain measurement
dG/dV depends on capacitance of pixel
Typical gain 71056106 _at_T20
gain
gain
gain
Russian
HPK100e
HPK400b
6106
2106
5105
70
35
36
47.5
49.5
71
Bias V
Bias V
Bias V
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Summary of noise rate measurement
106
106
noise rate (Hz)
noise rate(Hz)
HPK100d
HPK100f
RUS14
RUS23
HPK100e
HPK1600a
RUS20
RUS22
35
43
70
74
bias voltage (V)
bias voltage (V)
0.5p.e threshold by pulse height
_at_T20
0.5p.e threshold by charge (in progress)
1.5p.e threshold by pulse height
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Summary of noise rate measurement
Maximum noise rate a few MHz
Noise rate increases by an order of magnitude
with increasing bias V by 1V
0.5p.e threshold
1.5p.e threshold
Noise rate (Hz)
Noise rate (Hz)
Noise rate (Hz)
HPK100e
Russian
HPK400b
106
106
106
104
104
104
35
37
70
71
48
50
Bias V
Bias V
Bias V
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P/p separation is possible
P/p separation
1.2GeV
1.0GeV
0.9GeV
1.2GeV
1.0GeV
0.9GeV
p
p
0.8GeV
0.8GeV
0.7GeV
0.6GeV
0.7GeV
0.6GeV
0.5GeV
0.5GeV
MPPC
MAPMT