Date of Award

2013

Degree Type

Thesis

Degree Name

Bachelor of Science (Physics) Honours

School

School of Engineering

Faculty

Computing, Health and Science

First Advisor

Associate Professor Steven Hinckley

Abstract

The effects of Gamma Radiation on Fibre Bragg Gratings (FBGs), when used as a radiation dosimeter, was proposed. The focus of this study centred on the FBG performance, and in particular the Bragg Wavelength Shift (BWS) whilst being exposed to ionizing radiation. Current research suggests that certain types of fibres manufactured by varying methods produce different results. The different responses to exposure from gamma irradiation between Germanium (Ge) doped optical fibres, with and without Hydrogen loading, along with the standard SMF-28 fibre with Hydrogen, were used and results noted and compared to previous work. The FBG’s in each fibre were written by Ultraviolet (UV) low energy irradiation. The results indicated that radiation sensitivity is dependent on Ge doping and Hydrogen loading. The increased sensitivity resulted in an overall average BWS of 151.6 pm. Results from the second re-irradiation gave an indication of the effects of pre-irradiation. The BWS average reduced to 88.3pm, showing that possible radiation hardening from pre irradiation produce insensitive and possibly more stable FBGs.

As FBG sensors are already in use to detect variations in temperature, pressure, stress strain, vibration, electromagnetic fields and virtually any other physical parameter with great success, the progression through to gamma radiation detection is conceivable. One of the main attributes of FBG sensors is their immunity to electromagnetic interference. Gamma rays are a form of electromagnetic radiation. In nuclear environments when FBG’s are exposed to gamma irradiation results have shown changes in the Bragg wavelength, although the exact cause or trigger is still unclear.

The main outcome was to achieve results that are compatible with the established data that will help in establishing FBG’s as a replacement to current physical and chemical sensors currently being used as radiation dosimeters. Our study has given results that are in keeping with the established data

Throughout my literature review I did not come across any published papers with a similar methodology with regards to the irradiation stages we used i.e. an initial dose of 206kGy over two days followed by one day of relaxation and then repeated. This I feel, reinforces our overall result and paves the way for future irradiation studies with a new generation of FBGs and optical fibre.

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