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Published byTodd Spencer Roberts Modified over 9 years ago
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Jarred Alexander Young October 2, 2013
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Langmuir Probe testing Probes completed and setting up for electron temperature scanning Power Supply High voltage supply for ion source currently being designed ▪ Based on COTS parts Plasma Environment Looking into surface potentials of spacecraft in near-LEO and GEO orbits Researching surface charging effects
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TOP VIEWSIDE VIEW z z x y i+i+ i+i+ Probe Mount Probe
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Configuration A Configuration B CEX testing from beam scattering
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Plasma environment on orbit mostly consists of atomic hydrogen and oxygen Densities of plasma lower as altitude increases Temperature increases with altitude Source: Spacecraft Charging and Hazards to Electronics in Space (Mikaelian, 2001)
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The Plasmasphere, which extends to 4 earth radii from the equator, is made up of a dense plasma with an electron temperature of roughly 1 eV GEO usually lies outside of the Plasmapause, where the density of the plasma environment drops, but subsequently has a higher electron temperature Plasmapause location varies based on time of day Plasmapause environment has non-collisional plasma, but causes electrically coupled charging on spacecraft Source: The Near-Earth Plasma Environment Plaff (2012)
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Extrapolated data points from Denton, et al. (1999) Electron temperature varies from daytime to night time and magnetic latitude Data was only taken up to ~8500 km Data used to calculate sheath potentials on spacecraft
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Recent Al sample experiments showed no material removed, yet evidence of smaller, lighter elements reaching surface of samples Gregov and Lawson (1971) showed that significant damage was not caused to W samples until around 400 eV with Ar + Large number of vacancy clusters were created where atoms were missing or misplaced due to ionic impact. Results also showed misplaced atomic material being diffused to the surface during the annealing process
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Shin (2002) showed that Ar + could cause sputtering in Si samples at energy ranges of 500 eV and more through MEIS testing At 500 eV, a sputter depth of 5.1 nm was achieved Takeaway Ion beam needs to be more energetic to actually cause material damage
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NASA Handbook on Surface Charging References penetration depth of Aluminum according to Mass Stopping Power (concept used in radiation therapy) Based on graph and projected calculations, our ion beams have only penetrated the samples by 5 Å ▪ Can we confirm this using a ReaxFF simulation?
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Work on electron temperature gathering for PSU group Data will be included into plasma simulation Work on next phase of material testing Develop power supply solution for high energy beam testing Determine energies for low energy testing ▪ Go through SCATHA and ATS-6 mission data for plasma parameters in GEO Work on SciTech paper More Si samples to be tested? More data from ISU group from APT?
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