Introduction to scintillator physics W Wolszczak Scintillation Screens

Introduction to scintillator physics W. Wolszczak Scintillation Screens and Optical Technology for transverse Profile Measurements 31 Mar 2019 → 3 Apr 2019 Challenge the future 1

The outline • Short recap on solid state physics • Point defects, polarons, self-trapped charges • Scintillation mechanisms • The state of the art Cs. I: Tl model • Non-proportionality of response • How it is measured? • At what conditions is observed? • What is the reason? Challenge the future 2

Point defects in crystals Challenge the future 3

F-centers An anion vacancy can trap an electron • Radiation damage • Non-stechiometric growth Challenge the future 4

F-center absorbance Na. Cl, KCl, and KBr Challenge the future 5

Exciton – a hydrogen-like neutral quasiparticle Challenge the future 6

Free excitons absorption and emission • Kitamura et al. , Quantum number dependence of the photoluminescence broadening of excitonic Rydberg states in cuprous oxide, 2017 Challenge the future 7

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Polaron model • Electron/hole interacts with phonon modes • Lattice polarization Challenge the future 9

Self-Trapped Hole Self-trapped hole (Vk center) in an alkali halide with the Na. Cl structure Challenge the future 10

Optical absorption o STH Optical absorption of STH in KBr Challenge the future 11

Self-trapped exciton: Vk centre + e- (on-centre configuration) Challenge the future 12

STE luminescence in alkali halides Responsible for the host luminescence in alkali halides K. Song, R. T. Williams, Self-Trapped Excitons, 1993 Challenge the future 13

Cs. I light yield vs temperature STE emission is strongly quenched at room temperature Challenge the future 14

Scintillation mechanism Challenge the future 15

Scintillator Nvis visible light/UV photons Single photon E Scintillator Evis • Nvis ~ E • Nvis Challenge the future 16

Basic scintillation mechanism Challenge the future 17

Emission wavelength From Mc. Gregor 2018 Challenge the future 18

Intensity vs temperature From Mc. Gregor 2018 Challenge the future 19

High density track Challenge the future 20

STH formation Challenge the future 21

Electrons at thermal equlibrium Challenge the future 22

Trapping and recombination Challenge the future 23

Non-proportionality of response Challenge the future 24

Non-proportional response Gamma photons Electrons Alekhin 2013 Challenge the future 25

Surface effects Khodyuk 2013 Challenge the future 26

Characterization of non-proportionality } • With radioactive sources • Compton Scattering Coincidence Technique • K-dip spectroscopy • Alpha/beta ratio • Z-scan optical Nuclear techniques Challenge the future 27

K-dip spectroscopy Challenge the future 28

From Mc. Gregor 2018 Challenge the future 29

From Mc. Gregor 2018 Challenge the future 30

Z-scan Challenge the future 31

Schematic of a z-scan setup • the non-linear index (Kerr nonlinearity) • non-linear absorption coefficient • interband Z-scan luminescence yield measurements of nonlinear quenching rates and kinetic order Challenge the future 32

Ca. Mo. O 4 Spassky 2019 Challenge the future 33

Zn. Mo. O 4 Ca. Mo. O 4 Spassky 2019 Challenge the future 34

The alpha/beta ratio Challenge the future 35

Stopping power Challenge the future 36

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e Thermalization Energy losses e e h Deep traps 1 th order h h Exciton-exciton Anihilation 2 nd order ee h h h Auger quenching 3 rd order Challenge the future 39

Local densities across ionization track Challenge the future 40

Local densities across ionization track 2 Challenge the future 41

Stopping power: H+ in Na. I SRIM Challenge the future 42

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Thank you! Challenge the future 44