A Positive Ion Beamline for Space Qualification of Birefringent Materials
Date
2019-07-26
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Degree Level
Doctoral
Abstract
The constant advancements in spaceborne technology have provided an immense increase to the boundaries of human knowledge in a variety of research fields. As these continue, and new technologies arise, their suitability for deployment in the space environment must be assessed due to the harsh operating environment of space. One component of the space environment is intense radiation, specifically charged particle radiation, which can cause damage to a variety of system components. Effects include changes to electrical, structural, and optical properties, the latter of which is the focus of this work.
A recently introduced technology to spaceborne imaging instrumentation is Acousto-Optic Tunable Filters. These devices use the Acousto-Optic effect and birefringent materials, such as tellurium dioxide and lithium niobate, to create narrow band image quality tunable filters. As common radiation damage effects include changes to transmittance, reflectance and absorbance of optical materials, as well as changes to the atomic structure causing changes to refractive indices and birefringence, radiation testing of these devices to assess long term performance is critical to further development of the technology for space applications.
Radiation testing involves accelerated lifetime testing of materials under multiple years' worth of equivalent radiation in much shorter time frames (hours), using charged particle radiation provided by an ion accelerator. This work details the development of a positive ion accelerator and its use for radiation testing. The accelerator can provide beam energies from 5 - 20 keV, beam diameters of 0.8 - 2.5 cm and beam currents from 0.5 - 15 $\mu$A, all adjustable by user input settings. The system can also accommodate other ion species such as helium ions. The system was primarily used with proton radiation, due to its dominance in the solar wind and general space environment, to examine induced damage effects in silicon, quartz, lithium niobate and tellurium dioxide as a function of fluence (protons/$\text{cm}^2$). Measurements of transmittance, reflectance and absorbance, as well as an investigation with Raman spectroscopy, were completed for all materials at varying fluences. Comparison of results to those in the literature shows good agreement, however, not all results have comparable data available in the current literature. Results are used to assess space mission suitability and show that tellurium dioxide has the highest radiation resistance of the investigated materials.
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Keywords
Radiation Damage, Ion Beam, Charged Particle, Plasma, Birefringent Materials
Citation
Degree
Doctor of Philosophy (Ph.D.)
Department
Physics and Engineering Physics
Program
Physics