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BEST IN PHYSICS (THERAPY): Characterization of a New Type of Colloidal Quantum Dot-Based Liquid Scintillator

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M Delage

M-E Delage1*, M-E Lecavalier2 , D Lariviere2 , C N Allen3 , L Beaulieu1 , (1) Centre Hospitalier Universitaire de Quebec - Universite Laval, Quebec, QC, (2) Universite Laval, Quebec, QC, (3) Centre d'optique, photonique et laser - Universite Laval, Quebec, QC


TU-FG-205-3 (Tuesday, August 1, 2017) 1:45 PM - 3:45 PM Room: 205

Purpose: This study intends to characterize the scintillation and Cherenkov light production of new colloidal quantum dot (cQD)-based liquid scintillators, to be used as a volumetric dosimeter, at various beam energies.

Methods: This systematic investigation was led for three different cQDs-based solutions. The same type of CdSe cQDs was dispersed in alkylbenzene, toluene and hexane at concentrations on the order of micromoles per liter. Irradiation of the samples was done under five beam energies: 120, 180 and 220 kVp (orthovoltage device) and 6 and 23 MV (Linac). The scintillation intensity was collected with a CCD camera. Spectral measurements were also conducted to distinguish Cherenkov light from scintillation, using blank control solutions.

Results: The scintillation intensity measured was found to change based on the nature of the solvents. Alkylbenzene proved to give the better energy transfer to cQDs, resulting in the highest quantum yield, independently of beam energy. As an example, hexane and toluene solutions provided only 17% and 39% of the alkylbenzene solution signal at 180 kVp. In addition to having the best overall scintillation signal, the alkylbenzene solution presents the best ratio of scintillation to Cherenkov light production, ranging from 12.7, 4.3 and 3.1 under 180 kVp, 6 and 23 MV beams respectively; this is almost twice the values for the toluene solution. As expected, the proportion of Cherenkov light contamination is more important with increasing energy. Furthermore, alkylbenzene and toluene solutions showed an almost flat response of the scintillation signal when varying beam energy.

Conclusion: The low contribution of Cherenkov light produced by the solvent to the overall signal underlines the high scintillation efficiency of the cQDs. It is noted that no disturbance of the irradiation beam by the cQDs' high-Z composition was found at the concentration studied, which leads to reliable measurements independently of the beam energy.

Funding Support, Disclosures, and Conflict of Interest: The presenting author is financially supported by an Alexander-Graham Bell doctoral scholarship from the Natural Sciences and Engineering Research Council of Canada (NSERC) and also acknowledges partial support from the CREATE Medical Physics Research Training Network grant of the NSERC (grant number: 432290).

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