Development of an instrument for spatially resolved, optically stimulated luminescence dosimetry of cobble and dosimeter surfaces

Abstract

Optically stimulated luminescence (OSL) dosimetry is a method used to determine the amount of energy stored within a crystalline insulator due to ionizing radiation. At its most fundamental, OSL dosimetry requires optical stimulation to induce a sample to emit luminescence, a light detection apparatus to collect the luminescence signal, and a calibrating radiation source to convert the acquired signal into an equivalent dose. Conventional instruments have successfully integrated these components to perform OSL dosimetry on sediment and dosimeters. In this dissertation, an instrument was developed that improves upon commercially available instruments by providing spatial information that allows dose-mapping. The novel instrument LuCIDD (Luminescence instrument with Confocal and Imaging unit for Dating and Dosimetry) is based on the principles of a confocal microscope. This dissertation outlines the requirements for spatially resolved dosimetry mapping and describes the design and construction of LuCIDD. Tests of LuCIDD's lasers' ability to perform spatially resolved stimulating measurements were made by measuring their focal spot size, power density, and penetration depth. Used for calibration, the built-in X-ray source's energy spectrum, uniformity, and dose rate were characterized. The minimum resolution and stimulation time of measurements were determined, quantifying the amount of time to complete a dose map of a sample's surface. Lastly, LuCIDD's ability to recover a known applied dose from single points was verified to provide a proof-of-concept for future dose-mapping measurements.