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 137 Cs Source spectrum for MPPC (time permitting)

2 R. Wagner, MPPC/SiPM Timing Resolution PD07 Kobe University 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 1 st 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 Prototype Support Structure Design for a Two Mirror Aplanatic Telescope Victor Guarino, Argonne Natl. Lab.

3 R. Wagner, MPPC/SiPM Timing Resolution PD07 Kobe University Experimental Setups Timing Resolution MEPhI and CPTA SiPM Test Board 408nm Diode Laser 75ps pulse width Bias voltage & output to CFD/ADC Neutral Density Filters Single pe, Linearity, Source Spectra Blue (468nm peak) LED and exponentially-graded filter wheel R580 reference PMT 50μm Pixel MPPC 1x1x10mm 2 LYSO Single pe and Linearity measurements made with correlated double sample-and-hold (Fermilab CDF RABBIT System). 1.2μs effective gate. Timing measurements use output from Ortec 9307 CFD → 25ps/count Phillips 9186 TDC

4 R. Wagner, MPPC/SiPM Timing Resolution PD07 Kobe University 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 Fit has no background! Just sum of 6 Gaussians (pedestal pe). 1x1mm 2 effective area 50μm pixel size 400 total pixels

5 R. Wagner, MPPC/SiPM Timing Resolution PD07 Kobe University 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

6 R. Wagner, MPPC/SiPM Timing Resolution PD07 Kobe University 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.

7 R. Wagner, MPPC/SiPM Timing Resolution PD07 Kobe University Initial Timing Resolution Results (2) – MEPhI E404  Gain ~ 4 x 10 5

8 R. Wagner, MPPC/SiPM Timing Resolution PD07 Kobe University Energy Spectra from LYSO Background ( 176 Lu) & 137 Cs Hamamatsu 25μm pixel MPPC at V = 78.94V MEPhI Sample operated at V = 43.0V Background decays of 176 Lu in 1x1x10mm 3 crystal 200ns

9 R. Wagner, MPPC/SiPM Timing Resolution PD07 Kobe University Energy Spectra from LYSO Background ( 176 Lu) & 137 Cs σ/E ~ 9.2% (22% FWHM) Expanded scale from those on left. Rough absolute zero approximated. Background spectrum from 176 Lu decays? Uncalibrated horizontal scales

10 R. Wagner, MPPC/SiPM Timing Resolution PD07 Kobe University 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 137 Cs and 22 Na –Place 4x4 array against LYSO & BGO crystals to study position resolution and depth of 1 st interaction

11 R. Wagner, MPPC/SiPM Timing Resolution PD07 Kobe University 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.

12 R. Wagner, MPPC/SiPM Timing Resolution PD07 Kobe University Backup Slides Follow

13 R. Wagner, MPPC/SiPM Timing Resolution PD07 Kobe University Laser Timing Synch output from laser MPPC output from laser pulse

14 R. Wagner, MPPC/SiPM Timing Resolution PD07 Kobe University Saturation Measurement of Hamamatsu MPPC MPPC μm pixel size with 400 total pixels ADC counts corresponds to 34.3pC. For Gain = 5.65x10 5, implies about 380 pe. (or fired pixels at full gain)

15 R. Wagner, MPPC/SiPM Timing Resolution PD07 Kobe University 25μm Pixel Size I-V Curve

16 R. Wagner, MPPC/SiPM Timing Resolution PD07 Kobe University 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