Atomic Scale Modeling of the Effect of Irradiation on Silica Optical Fibers
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Series/Report no.:2011 Edward F. Hayes Graduate Research Forum. 25th
Optical fibers and optically-based sensors find extensive use in instrumentation and control systems in nuclear power plants due to their desirable characteristics and advantages over traditional electrical transmission systems, such as immunity to electromagnetic interference (EMI). Vitreous silica which has a high melting point (~1650°C), is a suitable material for optical fiber and sensor applications within high-temperature reactor pressure vessels. However, although pure vitreous silica-core fibers are transparent over a broad spectrum (ultraviolet to near infrared), irradiation causes the optical fibers to “darken” and form “color centers”. This leads to preferential absorption of light at frequencies specific to the defect type, resulting in the attenuation of signals, and is a major concern for these applications. While abundant experimental information exists on the various defects in silica and their corresponding optical properties, there still needs to be an accurate and predictive modeling approach that can provide useful information about defect evolution in the structure and crystallization effects upon heating and irradiation, and establish the correlation between the local structural defects caused by irradiation to optical transmission losses over typical lengths of the fiber. This paper presents a computational approach using molecular dynamics calculations to simulate irradiation damage, a set of techniques to extract and correlate the structural defects thus created, and ab-initio electronic structure calculations with Hybrid Density Functional Theory (DFT) methods to model the effect of the structural defects on the electronic and optical properties.
Poster Division: Engineering, Math, and Physical Sciences: 1st Place (The Ohio State University Edward F. Hayes Graduate Research Forum)
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