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Timing Studies of Hamamatsu MPPCs
and MEPhI SiPM Samples
Bob Wagner, Gary Drake, Patrick DeLurgio
Argonne National Laboratory
Qingguo Xie
Department of Radiology
University of Chicago
Topics:
 Applications and Goals
 Experimental Setup
 MPPC Single pe observation at room temperature
with 1.2 μs effective gate
 Initial Time Resolution Studies
 137Cs Source spectrum for MPPC (time permitting)
Applications and Goals
 Improved small animal PET scanner
– Finer spatial resolution using
MPPC array on crystal(s)
• LYSO, LSO, BGO
• Combination with differing
decay characteristics to
determine depth of 1st
interaction
– Good time resolution (< 50ps) of
511 keV γs to provide real time
imaging (10 ps resolution ≡ 3mm)
 Fine-grained camera for Imaging
Atmospheric Cherenkov Gamma-Ray
Telescope (AGIS collab in U.S.)
– Optical design reduces aberrations
by adding curvature to the camera
“plane”. (UCLA collaborators)
– Small feature size photodetectors
required
Victor Guarino, Argonne Natl. Lab.
Prototype Support Structure Design for a
Two Mirror Aplanatic Telescope
R. Wagner, MPPC/SiPM Timing Resolution
PD07 Kobe University
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Experimental Setups
Single pe, Linearity, Source Spectra
Timing Resolution
408nm Diode Laser
75ps pulse width
R580
reference
PMT
0.1-3.0 Neutral
Density Filters
Bias voltage
& output to
CFD/ADC
Blue (468nm peak) LED
and exponentially-graded
filter wheel
MEPhI and CPTA
SiPM Test Board
Timing measurements use
output from Ortec 9307 CFD →
25ps/count Phillips 9186 TDC
50μm Pixel
MPPC
1x1x10mm2
LYSO
Single pe and Linearity
measurements made with correlated
double sample-and-hold (Fermilab
CDF RABBIT System).
1.2μs effective gate.
R. Wagner, MPPC/SiPM Timing Resolution
PD07 Kobe University
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MPPC Individual Photoelectron Observation
MPPC Sample 53
operating V = 70.23V
• Noise at operating voltage at
room temperature is quite low!!
• Gate of 1.2μs substantially
longer than most other studies
1x1mm2 effective area
50μm pixel size
400 total pixels
• Fit has no background! Just
sum of 6 Gaussians (pedestal +
1-5 pe).
R. Wagner, MPPC/SiPM Timing Resolution
PD07 Kobe University
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Comparison to Single pe Detection in MEPhI SiPM
Cooled to ~ -15°C using dry ice
Same at room temperature
Both measurements using correlated double sampled
readout with Before/After effective gate width 1.2μs
R. Wagner, MPPC/SiPM Timing Resolution
PD07 Kobe University
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Initial Timing Resolution Results (1) – MPPCs
Time
Time resolution at
highest light levels.
Substantial
saturation of MPPC
Pulse
Height
Attenuation of laser
pulse to few pe level.
Individual pe evident
No deconvolution of contribution from
laser, CFD, and TDC has been done.
R. Wagner, MPPC/SiPM Timing Resolution
PD07 Kobe University
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Initial Timing Resolution Results (2) – MEPhI E404
 Gain ~ 4 x 105
R. Wagner, MPPC/SiPM Timing Resolution
PD07 Kobe University
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Energy Spectra from LYSO Background (176Lu) & 137Cs
Background decays of 176Lu in
1x1x10mm3 crystal
200ns
200ns
Hamamatsu 25μm pixel
MPPC at V = 78.94V
MEPhI Sample operated at V = 43.0V
R. Wagner, MPPC/SiPM Timing Resolution
PD07 Kobe University
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Energy Spectra from LYSO Background (176Lu) & 137Cs
Uncalibrated horizontal scales
σ/E ~ 9.2% (22% FWHM) Expanded
scale from those on left.
Rough absolute zero approximated.
Background spectrum from 176Lu decays?
R. Wagner, MPPC/SiPM Timing Resolution
PD07 Kobe University
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Future Plans
 Building several 4x4 MPPC arrays close-packed.
 We are upgrading the timing DAQ in laser test stand with TAC/ADC
capable of 10ps resolution.
 Three studies with arrays:
– Install one test 4x4 array in Argonne/UC TrICE Cherenkov Telescope
• Use existing TrICE Front End Electronics for readout
• Determine MPPC sensitivity to Cherenkov light from
imaged showers
– Study position resolution with
charge division with 3 MPPC linear
array viewing LYSO crystal
irradiated with 137Cs and 22Na
– Place 4x4 array against LYSO &
BGO crystals to study position
resolution and depth of 1st interaction
R. Wagner, MPPC/SiPM Timing Resolution
PD07 Kobe University
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Conclusions
 Initial studies indicate good timing resolution with both
Hamamatsu MPPC and MEPhI SiPM detectors
 Hamamatsu MPPC has very good performance for low noise
 We are still very early in our studies but making good
progress. We expect to learn much more in our work over
next months with arrays plus work on individual devices both
in timing and energy resolution.
R. Wagner, MPPC/SiPM Timing Resolution
PD07 Kobe University
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Backup Slides Follow
R. Wagner, MPPC/SiPM Timing Resolution
PD07 Kobe University
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Laser Timing
Synch output from laser
MPPC output from
laser pulse
R. Wagner, MPPC/SiPM Timing Resolution
PD07 Kobe University
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Saturation Measurement of Hamamatsu MPPC
 MPPC 53 -- 50μm pixel size with 400
total pixels
 30000 ADC counts corresponds to
34.3pC. For Gain = 5.65x105, implies
about 380 pe. (or fired pixels at full
gain)
R. Wagner, MPPC/SiPM Timing Resolution
PD07 Kobe University
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25μm Pixel Size I-V Curve
R. Wagner, MPPC/SiPM Timing Resolution
PD07 Kobe University
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RABBIT Before/After Timing
RABBIT Before/After timing with
respect to signal from MEPhI SiPM
Blue - Before
Purple – After
Yellow – SiPm signal using LED pulser
R. Wagner, MPPC/SiPM Timing Resolution
PD07 Kobe University
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