High Energy Plume Impingement on Spacecraft Systems AFOSR Telecon

1. High Energy Plume Impingement on Spacecraft SystemsAFOSR Telecon Jarred Alexander Young September 18, 2013

2. Current Events • Beam Analysis • Performed scans with RPA perpendicular to beam to look at possible CEX behavior • Material Experiments • Completed second round of experiments with Aluminum samples

3. CEX Beam Data • Beam Data from recent experiments shows that CEX energy distribution peak increases in energy and probability with axial distance • Tests performed with a background pressure ~3-5E-4 torr

4. CEX Beam Data • Most papers indicate that CEX energy levels are heavily influenced by facility environment • High background pressures lead to higher densities of CEX ions • Papers indicate that CEX environment found in lab testing is usually not indicative of space conditions • Electron temperature plays a great part in CEX ion energy distribution • Higher Te leads to higher CEX energy peaks • Paper: Far Field Modeling of the Plasma Plume of a Hall Thruster, Boyd and Dressler, 2002

5. CEX Beam Data • Possible plan of attack: analyze electron temperature of ion beam • Set up and use an array of langmuir probes to gather plasma characteristics of the beam and facility environment for clues to CEX energy trends • Previous data sent to Burak for implementation to simulation

6. Samples, Pre-Beam Sample 1, 150 eV Sample 2, 150 eV Sample 3, 150 eV Sample 4, 150 eV Sample 5, 150 eV Sample 6, 150 eV

7. Samples, Post-Beam Sample 1, 150 eV Sample 2, 150 eV Sample 3, 150 eV Sample 4, 150 eV Sample 5, 150 eV Sample 6, 150 eV

8. Sample Comparison Sample 1, Pre-Beam Sample 1, Post-Beam

9. Comparison of EDS Results Pre & Post-Sample 1 (whole surface) Pre Beam Post Beam

10. Spots on SEM Images • Heavier elements in SEM show up as bright-colored • Spots are made up of lighter elements • Concentrated amounts of Mg, Si, C, and O appear in majority of “dark” areas

12. Summary of Sample Results • All samples show signs of all major elements represented in Al 6061-T4 • Copper retroactively found in samples scanned last week • Two samples showed traces of Rhodium in small amounts (which may also be in Al 6061-T4) • Samples appear polished and no sign of material removal

13. Implications of Sample Results • Different types of ion impingement • Backstreaming ions  low energy • Interested in sheath potentials of spacecraft in LEO-GEO • High energy ion plume (> 300 eV) • Find suitable power supply solution • Expanding tests to other materials • Looking into solar cell cover glass • Mylar

14. 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