Thèses
Tuesday 23 May 2023 à 14h00.
Novel ultra-dense thin film and alternative micro-structured scintillators for synchrotron X-ray imaging
Laura Wollensen
Salle Fontannes, Bâtiment C.Darwin
présentera en 1 heure :
''Directeur de thèse / thesis director : Christophe Dujardin, Paul Antoine Douissard
Membres du jury / jury members :
Patrice Camy
Paul Antoine Douissard
Christophe Dujardin
Alexandra Pena Revellez
Anne Pillonnet
Audrey Potdevin
Invitée: Thu Nhi Tran Caliste
Résumé / Abstract :
The development of scintillators with high stopping power for high spatial resolution
X-ray imaging at synchrotrons has been performed by employing two approaches.
The first approach was to grow thin Single Crystalline Films (SCFs) of high density
and high effective Z number by Liquid Phase Epitaxy (LPE). This aimed to reach
a high spatial resolution while maximizing the absorption efficiency of the films.
Before attempting to develop the LPE procedures, the compounds were investigated
with a Geant4, Monte Carlo simulation tool, combined with subsequent analytical
calculations to evaluate their scintillating spatial response. Ultra high density com-
pound, Lu2Hf2O7, and other hafnates have, in this framework, been successfully
grown on ZrO2:Y substrates. The atomic structure of the films was confirmed to be
iso-structural with the substrate and have a low lattice mismatch. It was observed
that various elements could enter the structure, and the flexibility of the hafnate
system for LPE growth is thereby realized. The grown films of Lu2Hf2O7 doped
with europium were detected to scintillate, however, the substrate itself displays
low-intensity emission. The films have a low light output but deliver a good spatial
response, validated by MTFs as well as radiography and tomography experiments.
The second approach was to grow state-of-the-art SCF scintillators in a micro-
structured manner by LPE. The aim was to increase the stopping power by having
tall pillars containing light while maintaining a good spatial response. LSO:Tb
and GGG:Eu, were grown micro-structured onto laser-treated LYSO:Ce and GGG
substrates, respectively. The morphology of the pillars varies depending on the
compound and the substrate orientation. The atomic structures and luminescent
properties are comparable to their normal SCF counterparts, therefore a proof of
concept has been demonstrated.
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