1. P. Lecoq CERN 1 March 2014 Fast timing workshop, Clermont Fd, March 12-14, 2014 Ultimate Time Resolution in Scintillator-based detectors for Calorimetry and Time-of-Flight PET P. Lecoq, E. Auffray, S. Gundacker CERN, Geneva, Switzerland This work is supported under the ERC Grant Agreement N°338953–TICAL

2. P. Lecoq CERN March 2014 2 Fast timing workshop, Clermont Fd, March 12-14, 2014 TOF for –Particle ID –Pileup mitigation at high luminosity colliders Improve pattern recognition in Cerenkov detectors Cerenkov/Scintillation differentiation (Dual Readout Cal) Bring additional information on the shower development in a segmented calorimeter Current state of the art for TOF in Alice expt: 75ps Major advances in detector/enabling technologies –Fast and high light yield scintillators –SiPMs, MCPs –Fast low noise FE electronics (NINO) A 4D imaging HHCAL is within reach Why fast timing in HEP?

3. P. Lecoq CERN March 2014 3 Fast timing workshop, Clermont Fd, March 12-14, 2014 Why fast timing in PET? TOF for rejecting background events (event collimation) –Requires 200ps TOF resolution for a few cm ROI (EndoTOFPET-US FP7 project) TOF for improving image S/N –Requires 100ps TOF resolution for x5 S/N improvement, which brings a potential sensitivity gain (  dose reduction) TOF for direct 3D information –Requires 20ps TOF resolution for 3mm resolution along LOR TOF for restoring image quality for limited angle tomography

4. P. Lecoq CERN March 2014 4 Fast timing workshop, Clermont Fd, March 12-14, 2014 State of th Art: CTR with NINO chip (Time over Threshold)

5. P. Lecoq CERN March 2014 5 Fast timing workshop, Clermont Fd, March 12-14, 2014 Influence of crystal length on CTR S. Gundacker et.al., NIMA, dx.doi.org/10.1016/j.nima.2013.11.025

6. P. Lecoq CERN March 2014 6 Fast timing workshop, Clermont Fd, March 12-14, 2014 CTR distribution of 168 Modules (4x4 cells each), 2688 LORs The bias voltage applied to each module is fixed to 2.5 Volt over breakdown Voltage. Same threshold and temp for all channels State of the art: EndoTOFPET system performance 239 ps NINO ASIC 4x4 cells 3.5x3.5x15mm 3 crystals 80  m 3M ESR gap Discrete Silicon- through-via (TPV) MPPC array Hamamatsu (S12643- 050CN) 3x3mm 2, 0.6mm gap

7. P. Lecoq CERN March 2014 7 Fast timing workshop, Clermont Fd, March 12-14, 2014 The detection chain  SiPMCrystalelectronics  tt t kth pe = t t Conversion depth + t k’ ph Scintillation process + t transit Transit time jitter + t SPTR Single photon time spread + t TDC TDC conversion time Random deletion 1 Absorption Self-absorption Random deletion 2 SiPM PDE Unwanted pulses 2 DCR Unwanted pulses 1 DCR, cross talk Afterpulses

8. P. Lecoq CERN March 2014 8 Fast timing workshop, Clermont Fd, March 12-14, 2014 Modeling the whole chain SiPM S. Gundacker Thesis, CERN, Feb2014

9. P. Lecoq CERN March 2014 9 Fast timing workshop, Clermont Fd, March 12-14, 2014 Analog vs Digital approach Cramer-Rao lower bound Under investigation –in the frame of the FP7 EndoTOFPET-US project –with the Philips digital evaluation kit recently ordered S. Gundacker Thesis, CERN, Feb2014

10. P. Lecoq CERN March 2014 10 Fast timing workshop, Clermont Fd, March 12-14, 2014 Parameters of interest to improve timing resolution CTR improves like SQRT (photon time density) Rise time influence limited by SPTR (66ps) Parameters for LSO: Ce, Ca and Hamamatsu S10931-050P MPPC

11. P. Lecoq CERN March 2014 11 Fast timing workshop, Clermont Fd, March 12-14, 2014 Factors influencing scintillator time resolution Besides all factors related to photodetection and readout electronics the scintillator contributes to the time resolution through: 1.The scintillation mechanism Light yield, Rise time, Decay time P. Lecoq et al, IEEE Trans. Nucl. Sci. 57 (2010) 2411-2416 2.The light transport in the crystal Time spread related to different light propagation modes 3.The light extraction efficiency (LY  LO) Impact on photostatistics Weights the distribution of light propagation modes

12. P. Lecoq CERN March 2014 12 Fast timing workshop, Clermont Fd, March 12-14, 2014 Influence of prompt photons 2x2x3mm 3 LSO:Ce, Ca with 70ps rise time and an arbitrary number of prompt photons generated

13. P. Lecoq CERN March 2014 13 Fast timing workshop, Clermont Fd, March 12-14, 2014 Light generation in scintillators Rare Earth 4f 5d

14. P. Lecoq CERN March 2014 14 Fast timing workshop, Clermont Fd, March 12-14, 2014 Wide emission spectrum from UV to IR Ultrafast emission in the ps range Independant of temperature Independant of defects Absolute Quantum Yield W h /W phonon = 10 -8 /(10 -11 -10 -12 ) ≈ 10 -3 to 10 -4 ph/eh pair Higher yield if structures or dips in CB? Interesting to look at CeF3 Hot intraband luminescence More details in SCINT2013 paper TNS-00194-2013 M. Korzhik, P. Lecoq, A. Vasil’ev

15. P. Lecoq CERN March 2014 15 Fast timing workshop, Clermont Fd, March 12-14, 2014 Photon propagation time spread x L with  1 0  2  c For L = 20mm LSO (n = 1.82) n grease = 1.41   c = 50.8°   t max = 71 ps for x = L  t max = 384 ps for x = 0 Photodetector 

16. P. Lecoq CERN March 2014 16 Fast timing workshop, Clermont Fd, March 12-14, 2014 Photonic crystals Crystal Crystal- air interface with PhC grating: θ>θcθ>θc Total Reflection at the interface Extracted Mode θ>θcθ>θc Nanostructured interface allowing to couple light propagation modes inside and outside the crystal air θ>θcθ>θc

17. P. Lecoq CERN March 2014 17 Fast timing workshop, Clermont Fd, March 12-14, 2014 Use large LYSO crystal: 10x10mm 2 to avoid edge effects 6 different patches (2.6mm x 1.2mm) and 1 (1.2mm x 0.3mm) of different PhC patterns 0°45° Photonic crystals increase the light extraction efficiency A. Knapitsch et al, “Photonic crystals: A novel approach to enhance the light output of scintillation based detectors, NIM A268, pp.385-388, 2011

18. P. Lecoq CERN March 2014 18 Fast timing workshop, Clermont Fd, March 12-14, 2014 Regular LYSO a) Extract more photons at first incidence with PhC = better timing b) Photonic crystals compress the light propagation modes

19. P. Lecoq CERN March 2014 19 Fast timing workshop, Clermont Fd, March 12-14, 2014Conclusions Standard scintillation mechanisms are unlikely to give access to the 10ps range A number of transient phenomena could generate ps measurable signals Photonic crystals improve scintillator timing resolution by two means: –By increasing the light output and therefore decreasing the photostatistics jitter –By redistributing the light in the fastest propagation modes in the crystal