21 September 2015 Investigation of contamination of thin-film aluminum filters by MMH-NTO plumes exposed to UV radiation
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Abstract
Thin-film aluminum filters degrade in space with significant reduction of their Extreme Ultraviolet (EUV) transmission. This degradation was observed on the EUV Spectrophotometer (ESP) onboard the Solar Dynamics Observatory’s EUV Variability Experiment and the Solar EUV Monitor (SEM) onboard the Solar and Heliospheric Observatory. One of the possible causes for deterioration of such filters over time is contamination of their surfaces from plumes coming from periodic firing of their satellite’s Monomethylhydrazine (MMH) – Nitrogen Tetroxide (NTO) thrusters. When adsorbed by the filters, the contaminant molecules are exposed to solar irradiance and could lead to two possible compositions. First, they could get polymerized leading to a permanent hydrocarbon layer buildup on the filter’s surface. Second, they could accelerate and increase the depth of oxidation into filter’s bulk aluminum material. To study the phenomena we experimentally replicate contamination of such filters in a simulated environment by MMH-NTO plumes. We apply, Scanning Electron Microscopy and X-Ray photoelectron spectroscopy to characterize the physical and the chemical changes on these contaminated sample filter surfaces. In addition, we present our first analysis of the effects of additional protective layer coatings based on self-assembled carbon monolayers for aluminum filters. This coverage is expected to significantly decrease their susceptibility to contamination and reduce the overall degradation of filter-based EUV instruments over their mission life.
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Vaibhav Gupta, Vaibhav Gupta, Seth Wieman, Seth Wieman, Leonid Didkovsky, Leonid Didkovsky, Ralf Haiges, Ralf Haiges, Yuhan Yao, Yuhan Yao, Wei Wu, Wei Wu, Mike Gruntman, Mike Gruntman, Dan Erwin, Dan Erwin, } "Investigation of contamination of thin-film aluminum filters by MMH-NTO plumes exposed to UV radiation", Proc. SPIE 9604, Solar Physics and Space Weather Instrumentation VI, 960408 (21 September 2015); doi: 10.1117/12.2186812; https://doi.org/10.1117/12.2186812
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