YAG :Ce3+/4+ aerogels : efficiency, timing, diffusion and self-absorption
Résumé
Detection of radionuclides that decay directly to the ground state in the atmosphere requires to detect the beta or alpha radiation directly, which is very challenging due to their short mean free path in air at normal pressure. This suggests that the highest detection efficiency is obtained when the radionuclide is incorporated in the sensing part of the detector, which is applied with different gas radionuclides in ionisation chambers (gas-gas mixing) and for liquid solution in the liquid scintillation counting (LSC) technique (gas-liquid mixing). We hereby introduce the concept of gas-solid mixing to design an efficient detector, wherein the radioactive gas is introduced into a highly porous transparent inorganic scintillator. In this frame we have prepared YAG:Ce aerogels from sol-gel nanoparticle dispersion. Post-synthesis thermal treatment (sintering/calcination) at several temperatures was applied to the aerogels demonstrating a significant impact on the cerium oxidation state and transparency. The focus of this work is also the investigation of the aerogel optical properties after being altered by sub-calcination/sintering temperature treatments in H2 or air ambient gases. This low-temperature (400°C) treatment has managed to significantly change the ratio of Ce3+/4+ population in the sample, thus introducing a novel, easy and reversible approach to change scintillating properties of YAG:Ce aerogel. In this presentation, the effect of the thermal treatment on the transparency, diffusion, self-absorption, photoluminescence and scintillation efficiency and timing will be discussed in the frame of their use as sensor in the Triple to Double Ratio method, the standard technique used for liquid scintillation and the metrology of radionuclides.
Mots clés
radioactivity
metrology
YAG
material characterisation
scintillation efficiency
self-absorption
photoluminescence
YAG:Ce aerogel
nanoparticle
thermal treatment
sintering
calcination
cerium
oxidation
transparency
diffusion
detector
instrumentation
nuclear instrumentation
ionization chamber
liquid scintillation counting
gas-solid mixing
porous inorganic scintillator
ionizing radiation
beta-rays
alpha particules
detection efficiency
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