Date of Award

3-11-2011

Document Type

Thesis

Degree Name

Master of Science

Department

Department of Engineering Physics

First Advisor

Benjamin R. Kowash, PhD.

Abstract

The properties of thin, cerium activated, yttrium aluminum garnet (YAG:Ce), scintillating fiber-shaped crystals were investigated for particle tracking and calorimetric applications such as Compton imaging of Special Nuclear Material from remote platforms at standoff ranges. Silicon photomultipliers (SiPMs) are relatively new, efficient, single photon sensitive, solid-state photodiode arrays which are well suited for the readout of scintillating fibers. Using SiPMs, the scintillation decay time profiles of six 400 micrometers YAG:Ce fiber crystals were measured under alpha and gamma irradiation. Interestingly, the observed decay times in the thin fibers were substantially slower than values for bulk single crystal YAG:Ce reported in open scientific literature; possible explanations are explored. Both laser induced photoluminescence and alpha scintillation measurements were conducted to estimate the effective attenuation length of the YAG:Ce fibers. Using the measured attenuation lengths, position-of-interaction measurements were conducted to determine the achievable position resolution in YAG:Ce fibers using dual fiber end SiPM readouts. The measured results are compared to theoretical calculations and Monte Carlo simulations. Finally, improvements to the detector concept, including a formula to determine the best SiPM model based on device parameters and the Birks' figure of merit of the scintillating material, are presented.

AFIT Designator

AFIT-GNE-ENP-11-M11

DTIC Accession Number

ADA538424

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