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Ultimate Time Resolution in Ultimate Time Resolution in

Ultimate Time Resolution in - PowerPoint Presentation

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Ultimate Time Resolution in - PPT Presentation

Scintillator based detectors for Calorimetry and TimeofFlight PET P Lecoq E Auffray S Gundacker CERN Geneva Switzerland This work is supported under the ERC Grant Agreement N338953TICAL ID: 396321

light time tof resolution time light resolution tof crystal propagation crystals modes photonic scintillation timing ctr yield scintillator art

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Slide1

Ultimate Time Resolution in Scintillator-based detectors for Calorimetry and Time-of-Flight PET

P. Lecoq, E. Auffray, S. GundackerCERN, Geneva, Switzerland

This

work

is

supported

under

the ERC Grant Agreement N°338953–TICALSlide2

TOF forParticle IDPileup mitigation at

high luminosity collidersImprove pattern recognition in Cerenkov detectorsCerenkov/Scintillation differentiation (Dual Readout Cal)Bring additional information on the shower

development in a segmented calorimeterCurrent state of the art for TOF in Alice expt: 75psMajor advances in detector/enabling technologiesFast and high light yield scintillatorsSiPMs, MCPsFast low noise FE electronics (NINO)A 4D imaging HHCAL is within reach

Why

fast

timing in HEP?Slide3

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/NRequires 100ps

TOF

resolution for x5 S/N improvement, which brings a potential sensitivity gain (dose reduction) TOF for direct 3D informationRequires 20ps TOF resolution for 3mm resolution along LOR TOF for restoring image quality for limited angle tomographySlide4

State of th Art: CTR

with NINO chip (Time over Threshold)Slide5

Influence of

crystal

length on CTRS. Gundacker et.al., NIMA, dx.doi.org/10.1016/j.nima.2013.11.025Slide6

CTR distribution of 168 Modules (4x4 cells each)

, 2688 LORsThe bias voltage applied to each module is fixed to 2.5 Volt over breakdown Voltage.Same

threshold

and temp for all channelsState of the art: EndoTOFPET system performance

239 ps

NINO

ASIC

4x4

cells

3.5x3.5x15mm

3

crystals

80

m

m 3M ESR gap

Discrete

Silicon-through-via

(TPV) MPPC

array

Hamamatsu (S12643-050CN)

3x3mm

2

, 0.6mm gap

To be compared to ≈

550(350) ps

on commercial systemsSlide7

The detection chain

q2

SiPM

Crystal

electronics

g

D

t

t

kth

pe

=

D

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

AfterpulsesSlide8

Modeling the whole chain

SiPMS. GundackerThesis, CERN, Feb2014Slide9

Analog vs Digital approachCramer-Rao lower bound

Under investigation in the frame of the FP7 EndoTOFPET-US projectwith the Philips digital evaluation kit recently ordered

S.

GundackerThesis, CERN, Feb2014Slide10

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 Slide11

Factors influencing scintillator time resolution

Besides all factors related to photodetection and readout electronics the

scintillator

contributes to the time resolution through:The scintillation mechanismLight yield, Rise time, Decay time P. Lecoq et al, IEEE Trans. Nucl. Sci. 57 (2010) 2411-2416

The light transport in the

crystal

Time

spread

related

to

different

light propagation modes

The light extraction

efficiency

(LY

LO)

Impact on

photostatistics

Weights

the distribution of light propagation modesSlide12

Influence of prompt photons2x2x3mm3 LSO:Ce

, Ca with 70ps rise timeand an arbitrary number of prompt photons generated Slide13

Light

generation in scintillators

Rare Earth

4f5dSlide14

Wide emission spectrum from UV to IR

Ultrafast emission in the ps rangeIndependant of temperatureIndependant of defectsAbsolute Quantum Yield

Whn/Wphonon = 10-8/(10-11-10-12) ≈ 10-3 to 10-4 ph/eh pairHigher yield if structures or dips in CB? Interesting to look at CeF3Hot

intraband

luminescence

More details in SCINT2013 paper

TNS-00194-2013

M.

Korzhik

, P. Lecoq, A.

Vasil’evSlide15

Photon propagation time spread

x

L

with

q

1

0

q

2

q

c

For L = 20mm LSO (

n

= 1.82)

n

grease

= 1.41

q

c = 50.8°

q2

D

t

max

=

71

ps

for

x

= L

D

t

max

= 384

ps

for

x

= 0

Photodetector

gSlide16

Photonic crystals

Crystal

Crystal- air interface with

PhC grating:θ>θcTotal Reflection at the interface

Extracted Mode

θ

>

θ

c

Nanostructured

interface

allowing

to couple light propagation modes

inside

and

outside

the

crystal

air

θ

>

θ

cSlide17

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

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, 2011Slide18

Regular LYSO

a)

Extract more photons at first incidence with

PhC

= better timing

b)

Photonic

crystals

compress

the light propagation modesSlide19

ConclusionsStandard scintillation mechanisms are

unlikely to give access to the 10ps rangeA 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 jitterBy redistributing the light in the fastest propagation modes in the crystal