p. lecoq, e. auffray , s. gundacker cern, geneva, switzerland
DESCRIPTION
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. Why fast timing in HEP?. TOF for Particle ID - PowerPoint PPT PresentationTRANSCRIPT
P. Lecoq CERN 1March 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
P. Lecoq CERNMarch 2014 2Fast 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?
P. Lecoq CERNMarch 2014 3Fast 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
P. Lecoq CERNMarch 2014 4Fast timing workshop, Clermont Fd, March 12-14, 2014
State of th Art: CTR with NINO chip (Time over Threshold)
P. Lecoq CERNMarch 2014 5Fast 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
P. Lecoq CERNMarch 2014 6Fast 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 cells3.5x3.5x15mm3
crystals80mm 3M ESR gap
Discrete Silicon-through-via
(TPV) MPPC arrayHamamatsu (S12643-
050CN)3x3mm2, 0.6mm gap
To be compared to ≈ 550(350) ps
on commercial systems
P. Lecoq CERNMarch 2014 7Fast timing workshop, Clermont Fd, March 12-14, 2014
The detection chain
q2
SiPMCrystal electronics
g
Dt
tkth pe = Dt
Conversion depth
+ tk’ ph
Scintillation process
+ ttransit
Transit timejitter
+ tSPTR
Single photon time spread
+ tTDC
TDC conversion time
Random deletion 1Absorption
Self-absorption
Random deletion 2SiPM PDE
Unwanted pulses 2DCR
Unwanted pulses 1DCR, cross talk
Afterpulses
P. Lecoq CERNMarch 2014 8Fast timing workshop, Clermont Fd, March 12-14, 2014
Modeling the whole chain
SiPM
S. GundackerThesis, CERN,
Feb2014
P. Lecoq CERNMarch 2014 9Fast timing workshop, Clermont Fd, March 12-14, 2014
Analog vs Digital approachCramer-Rao lower bound
Under investigation – in the frame of the FP7 EndoTOFPET-US project– with the Philips digital evaluation kit recently ordered
S. GundackerThesis, CERN,
Feb2014
P. Lecoq CERNMarch 2014 10Fast 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
P. Lecoq CERNMarch 2014 11Fast 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 (LYLO) Impact on photostatistics Weights the distribution of light propagation modes
P. Lecoq CERNMarch 2014 12Fast timing workshop, Clermont Fd, March 12-14, 2014
Influence of prompt photons
2x2x3mm3 LSO:Ce, Ca with 70ps rise timeand an arbitrary number of prompt photons generated
P. Lecoq CERNMarch 2014 13Fast timing workshop, Clermont Fd, March 12-14, 2014
Light generation in scintillators
Rare Earth4f
5d
P. Lecoq CERNMarch 2014 14Fast 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 Whn/Wphonon = 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-00194-2013M. Korzhik, P. Lecoq, A. Vasil’ev
P. Lecoq CERNMarch 2014 15Fast timing workshop, Clermont Fd, March 12-14, 2014
Photon propagation time spread
xL
€
Dt prop max = nxc cos(θ1)
− (2L − x) nc cos(θ 2)
with q1 0 q2 qc
For L = 20mm LSO (n = 1.82)ngrease= 1.41 qc = 50.8°
q2
Dtmax= 71 ps for x = LDtmax= 384 ps for x = 0
Photodetector
g
P. Lecoq CERNMarch 2014 16Fast timing workshop, Clermont Fd, March 12-14, 2014
Photonic crystals
Crystal
Crystal- air interface with PhC grating:
θ>θc
Total Reflection at the interface Extracted Modeθ>θc
Nanostructured interface allowing to couple light propagation modes inside and outside the crystal
air
θ>θc
P. Lecoq CERNMarch 2014 17Fast timing workshop, Clermont Fd, March 12-14, 2014
Use large LYSO crystal: 10x10mm2 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
P. Lecoq CERNMarch 2014 18Fast 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
P. Lecoq CERNMarch 2014 19Fast timing workshop, Clermont Fd, March 12-14, 2014
Conclusions
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