Date of Completion

Spring 5-6-2012

Thesis Advisor(s)

Cynthia Peterson

Honors Major

Physics

Disciplines

Other Physics | Physics

Abstract

Unlike regular TLD, an accurate and consistent annealing of the high-sensitivity TLD at 240 ˚C for 15 minutes is challenging using conventional annealing ovens because the temperature in the oven chamber varies drastically over the 15-minute period after the opening (to put the TLD tray in) and closing of oven door. The temperature in the oven drops dramatically after the door is opened and ramps up gradually after the door is closed, often accompanied with significant temperature overshoot. Because an overshoot by more than 5 ˚C can significantly reduce the sensitivity of the TLD and the ramp-up profile varies with the duration of door opening, the goal of this project was to build a heat reservoir in the oven chamber to provide more stable annealing temperature to the TLDs. A heat reservoir was designed and manufactured. A LabView interface was written for accurate and efficient monitoring of the temperature in the oven chamber, the heat reservoir, and the TLD annealing tray. The temperature profile in the oven chamber was fully characterized for various conditions. Complete temperature profiles of the TLD annealing tray over the entire annealing process were measured and used to optimize the oven temperature settings. A successful and consistent annealing of high-sensitivity TLDs was carried out, which enabled the experimental tests of high-sensitivity TLDs for dosimetric characterization of low-energy brachytherapy sources. This thesis will review the theory of TLD dosimetry and summarize the experimental characterizations of thermal annealing of the high-sensitivity TLDs using a novel custom-built thermal reservoir.

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