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

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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)

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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 (lt 50ps) of 511 keV ?s 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.
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Experimental Setups
Single pe, Linearity, Source Spectra
R580 reference PMT
50µm Pixel MPPC
1x1x10mm2 LYSO
Blue (468nm peak) LED and exponentially-graded
filter wheel
Timing measurements use output from Ortec 9307
CFD ? 25ps/count Phillips 9186 TDC
Single pe and Linearity measurements made with
correlated double sample-and-hold (Fermilab CDF
RABBIT System). 1.2µs effective
gate.
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MPPC Individual Photoelectron Observation

• Noise at operating voltage at room temperature
  is quite low!!
• Gate of 1.2µs substantially longer than most
  other studies
• Fit has no background! Just sum of 6 Gaussians
  (pedestal 1-5 pe).

1x1mm2 effective area 50µm
pixel size 400
total pixels
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Comparison to Single pe Detection in MEPhI SiPM
Cooled to -15C using dry ice
Same at room temperature
Both measurements using correlated double sampled
readout with Before/After effective gate width
1.2µs
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Initial Timing Resolution Results (1) MPPCs
Time resolution at highest light levels.
Substantial saturation of MPPC
Time
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.
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Initial Timing Resolution Results (2) MEPhI E404
? Gain 4 x 105
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Energy Spectra from LYSO Background (176Lu)
137Cs
Background decays of 176Lu in 1x1x10mm3 crystal
MEPhI Sample operated at V 43.0V
Hamamatsu 25µm pixel MPPC at V 78.94V
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Energy Spectra from LYSO Background (176Lu)
137Cs
Uncalibrated horizontal scales
s/E 9.2 (22 FWHM) Expanded scale from those
on left. Rough absolute zero approximated.
Background spectrum from 176Lu decays?
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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

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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.

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Backup Slides Follow
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Laser Timing
Synch output from laser
MPPC output from laser pulse
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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)

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25µm Pixel Size I-V Curve
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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