The kinetics of molecular transport of contaminant species is highly dependent on the distribution of desorption activation energies. Accurate measurements of these kinetics are essential to improving confidence in molecular transport modeling and setting appropriate beginning of life (BOL) cleanliness requirements. We present results that combine laboratory experiments with computer simulations to determine the distribution of effective activation energies for outgassing species from a urethane paint system and non-volatile residue (NVR) collected from an ISO Class 5 cleanroom contamination monitoring plate. Outgassing from samples of primer overcoated with urethane paint were analyzed with the temperature controlled quartz crystal microbalance thermogravimetric analysis (QTGA) technique during the final stages of vacuum baking; cleanroom NVR was also analyzed via QTGA. A computer model was developed to simulate the QTGA results. Data from the experimental QTGA were compared to the simulated QTGA to obtain a distribution of desorption activation energies for contaminant species. The interior of the Ozone Mapping and Profiler Suite (OMPS) science instrument is primed and painted with polyurethane/epoxy material. The distribution of activation energies derived in this study was incorporated in the molecular transport model of the OMPS science instrument, on the Suomi National Polar-Orbiting Partnership Satellite, yielding results that are consistent with the on-orbit optical performance data.
We have developed surface chemical modification processes which when applied to a variety of surfaces renders the
surfaces resistant to particulate contamination. Chemically modified surfaces are shown to shed particles at a
dramatically higher level as compared to native surfaces. This is demonstrated on a variety of surfaces that include
optics, polymers, metals and silicon. The adhesive force between lunar stimulant particles (JSC-1AF) and black
Kapton is measured to decrease by 95% when the black Kapton surface is chemically modified. The chemical
modification process is demonstrated to not change the surface roughness of a smooth silicon wafer while decreasing
particle affinity. The optical properties of chemically modified surfaces are reported. The surface modification
process is robust and stable to aggressive cleaning. The particle shedding properties of chemically modified surfaces
are retained after simulated extraterrestrial vacuum ultra-violet light exposure and temperature excursions to 140°C.
This technology has the potential to provide a robust passive particle mitigation solution for optics, mechanical
systems and particle sensitive applications.
Amorphous fluorocarbon (a-C:F) thin films have been developed that protect surfaces from molecular and particulate contamination. The surface energies of the thin films are low and primarily dispersive in origin with values of energies measured to be as low as 18 mJ/m2 (17.5 dispersive, 0.5 polar). The films are transparent to visible light and have a refractive index of ~1.4. The a-C:F surface energy was found to be thermally stable when exposed to temperatures that range from 77°K to 400°C. Molecular absorption rates are significantly reduced on gold surfaces when over-coated with an a-C:F thin film. The adhesion force of particles to the a-C:F surface is low and can dramatically decrease the susceptibility of particles to adhere to surfaces over-coated with the thin film. The robust nature of the diamond-like thin films make them candidates for protecting aerospace surfaces, such as optical surfaces, from contamination.
Conference Committee Involvement (1)
Optical System Contamination: Effects, Measurements, and Control 2012
13 August 2012 | San Diego, California, United States