High Energy Plume Impingement on Spacecraft Systems AFOSR Telecon

1. High Energy Plume Impingement on Spacecraft SystemsAFOSR Telecon Jarred Alexander Young October 2, 2013

2. Current Events • 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

3. Langmuir Probe Test Arrangment Probe Mount y x Probe i+ i+ z z TOP VIEW SIDE VIEW

4. RPA Configurations for Beam Testing Configuration A Configuration B CEX testing from beam scattering

5. Near-Earth Plasma Environment • 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)

6. Near Earth Plasma Environment Source: The Near-Earth Plasma EnvironmentPlaff (2012) • 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

7. Near-Earth Plasma Environment • 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

8. Electron Temperature Data

9. Old Wall Potential Data

10. Investigation into Al Sample Results • 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

11. Investigation into Al Sample Results • 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

12. Investigation into Al Sample Results • 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?

13. Future Work • 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?