HPK MPPC(Multi Pixel Photon
Counter) status
M.Taguchi and T.Nobuhara(Kyoto)
Jan.17.2006 @KEK T2K280m meeting
Test Procedure
・ Observe the raw signal
・ Confirm the fundamental performance
Already presented at the
・ gain
previous 280m meeting
・ noise rate
・ crosstalk
Talk at this meeting
・ PDE(photo detection efficiency)
・ Linearity
・ Confirm the performance under the real experimental
environment
- scintillator+WLS fiber+MPPC
・ Laser Test (using BELLE laser system)
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
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)
events　more　than 1.5p.e
Crosstalk rate =
events　more　than 0.5p.e
Maximum crosstalk
rate is 0.16(HPK100)
and
Crosstalk
Crosstalk
rate
rate
0.25(HPK400) 0.16
0.25
Data taken by
random trigger
HPK100
103
0.10
102
0.1
10
0.5p.e
1.5p.e
70.3
295
70.5 70.7 71.0
448 567 760
HPK400
48.5 49.0 49.3
74
234 478
49.6 (V)
800 (kHz)
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
PDE=εpixel×QE×εGeiger
A ratio of active
area to total area
(30%~70%)
Depending on
MPPC type
Quantum efficiency of
active area (60~80%)
Depending on wavelength
of injected light
Probability of Geiger
discharge (60~80%)
Depending on bias V
Measured the relative PDE to that of PMT with the
following set up (about four HPK100 MPPCs)
PDE measurement
・only the light going through
½ inch PMT
1mmφslit is detected
WLS fiber
The
view
from
this side
Blue LED
MPPC(total area
1mm2)
1mmφslit
Y
・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
・ change MPPC bias V
MPPC
PMT
slit
x
・ light sources are blue LED
and wavelength shifting
fiber(Y11)
PDE measurement(cont’d)
Measure PDE at this point
PDE(MPPC)/
PDE(PMT)
HPK100#14
green
2mm
MPPC X scan
×1.4
blue
2mm
MPPC Y scan
・The width of scan is 2mm
70.3 70.5
294 388
・The max green PDE is about 1.4 times larger than
that of PMT and green PDE is larger than blue PDE
70.8
524
71.1 Bias V(V)
687 Noise
rate(kHz)
PDE measurement(cont’d)
・There is a distance(~0.8mm)
between surface cover and active
area in HPK’s MPPC
・so PDE should decrease
effectively when using a WLS
fiber because light from a WLS
1mm
fiber spreads at 40°
½ inch PMT
Blue LED
WLS
fiber(1mmφ)
MPPC(total area
1mm2)
~0.8mm
40°
・Measured the effective PDE with this set up
about four HPK100e MPPCs(the method of
measurement is the same as before)
・compare the PDE measured in the previous
measurement
PDE measurement(cont’d)
PDE(MPPC)
HPK100#14
/PDE(PMT)
54%
PDE
3mm
MPPC X scan
3mm
MPPC Y scan
・The width of scan becomes 3mm due
to spread of light from a WLS fiber
・The decrease of PDE due to spread of light from
a WLSF is 40~50% about four HPK100 MPPCs
Effective PDE can be increased
by improvement of packaging
Effective PDE
70.5 70.8
388
524
71.1
687
71.3 Bias V(V)
864 Noise
rate(kHz)
Linearity measurement(HPK100
PMT(1/2 inch
PMT)
・ inject uniform light from blue LED
uniform light
Blue LED
MPPC
(HPK100)
Set up
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
Linearity
measurement(cont’d)
Fired
pixel
number
Crosstalk
rate 0.03
Difference from
the linear
extrapolation
10%
Theoretical curve
calculated with the
crosstalk rate and the
number of pixels
20%
・data points agree well with the theoretical curve
50p.e
Fired
pixel
・HPK100(100pixel)
number
showed
20% from
nonlinearity when
Difference
the linear
35~50p.e are injected (depending
on crosstalk rate)
Crosstalk
rate 0.2
extrapolation
injected
p.e
10%
20%
injected
p.e
35p.e
injected
p.e
Beamtest @KEK in Nov.2005
Motivation
・Can the light yield for
T2K near detector be
obtained?
setup
• 0.5～1.4GeV/c
• proton & pion
• ～100 event/spill
• beam size 1x1cm2
beam
64ch MAPMT
(as reference)
(more than 5p.e for MIP) HPK100e or Russian SiPM
4 layers
1mmΦ fiber
Scintillator 1.3x2.5x50 cm3
(used in K2K scibar detector)
Alignment of fiber
・The X Y position of active area of HPK’s MPPC
is different by each sample,so alignment of
fiber is necessary by each sample
X
Y
MPPC
・Scan the fiber with
moving stage and fix the
fiber with screws at the
point where MPPC signal
becomes maximum
screw for
fixing fiber
fiber
About 20% loss of light yield is possible due
to misalignment of fiber
Beamtest@KEK(cont’d)
MPPC type
MPPC p.e for MIP
PMT p.e for MIP
Ratio of MPPC p.e
with PMT(%)
HPK100#13
9.9
18.3
54
HPK100#14
10.2
18.2
56
HPK100#16
We
73
could13.3
obtain the light18.2
yield for T2K near
detector22.9
Russian600#13
18.2
126
Russian600#14
17.1
18.2
94
・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
Laser test(HPK100)
Picture of microscope
100μm
・study the response of
each pixel of MPPC
Laser
source
λ=825nm
width 50ps
microscope
Motivation
Feed back this information
to HPK
MPPC
We studied
・Efficiency distribution
within 1pixel
・Uniformity of gain and
efficiency in each pixel
Moving stage
1μm pitch (x , y)
Laser spot size
≒10μm
Efficiency distribution within 1pixel
efficiency
1pixel
100μm
Efficiency flat region
of 60μm×60μm
・Scan the laser in
the 10mm pitch
within 1 pixel(total
100scan)
laser
1p.e.
0p.e.
100μm
100μm
Efficiency =Ratio of
events more than
0.5p.e to total events
0.5p.e.
Response of each pixel
y
・Inject laser to the center of each
pixel and study the response of
each pixel
Relative
gain
1.06
x
Total 100pixel
Relative
efficiency
1.04
Response of each pixel is uniform!
RMS/mean=3.6%
RMS/mean=2.5%
0.96
0.92
y
x
y
x
Summary
About HPK100pixel MPPC
 The green PDE is larger than that of PMT
 Light yield for MIP is 10~13p.e (at the point that
noise rate and gain satisfy T2K requirement)
 Response of each pixel is uniform
Show 20% nonlinearity when 35~50p.e are injected
→ need more than 200pixel
The loss of light yield due to spread of light from a
WLS fiber is 40~50%
→ can be improved by packaging
supplement
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 @KEK

MPPC(Multi pixel photon
coutner)
MPPC characters:
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 :30~75V
High gain:105~107
Signal and p.e peak
HPK100a V=48V
2p.e
1p.e
30p.e
0p.e
Increasing the
injected light
・We can count the peak up to 4p.e
・the interval between each peak completes by 4%
Summary of gain measuremnt
・T=20°
・Gain=3×105~2×107
・The (dG/dV)depends on
the capacitance of pixel
HPK100a
RUS#14
RUS#20
RUS#22
35
43 Bias V
HPK100f
HPK100d
HPK100e
HPK400b
Bias V
47
RUS#23
49
HPK1600a
70
Bias V
74.5
Summary of gain measurement
・dG/dV depends on capacitance of pixel
・Typical gain 7×105～6×106 @T=20°
gain
gain
HPK100e
2×106
gain
HPK400b
6×106
70
71
Bias V
Russian
5×105
47.5
49.5
Bias V
35
36
Bias V
Summary of noise rate
measurement
noise rate(Hz)
HPK100f
HPK100e
70
HPK100d
noise rate (Hz)
106
106
RUS#14
HPK1600a
bias voltage (V)
74
RUS#20
35
RUS#23
RUS#22
bias voltage (V)
0.5p.e threshold by pulse height
0.5p.e threshold by charge (in progress)
1.5p.e threshold by pulse height
43
@T=20
°
Summary of noise rate
measurement
・Maximum noise rate~ a few MHz
・Noise rate increases by an order of magnitude with 0.5p.e threshold
increasing bias V by 1V
1.5p.e threshold
Noise rate
(Hz)
HPK100e
Noise rate
(Hz)
HPK400b
106
106
Noise rate
(Hz)
Russian
106
104
104
104
70
71
Bias V
48
Bias V
50
35
Bias V
37
P/π separation
1.2GeV
π
p
0.8GeV
1.0GeV
0.9GeV
1.2GeV
1.0GeV
0.8GeV
P/π separation is possible0.7GeV
0.7GeV
0.5GeV
0.6GeV
0.5GeV
MPPC
MAPMT
0.9GeV
0.6GeV