High Energy Plume Impingement on Spacecraft Systems AFOSR Telecon

1. High Energy Plume Impingement on Spacecraft SystemsAFOSR Telecon Jarred Alexander Young May 13, 2013

2. Current Events • Beam Analysis • Looking into CEX environment for multiple distances and pressures • Hi-definition energy peak scans • Ion Reflection testing • Material Experiments • Completed all tests with Si coupons (150 & 250 eV) • Completed first round of Aluminum sample testing

3. CEX Analysis • Objective: Conduct RPA analysis on ion beam at multiple pressures • Small I-V humps observed during testing of beam for axial profiling • RPA scans centered around these regions to examine beam behavior

4. CEX Analysis

5. CEX Analysis

6. RPA Results Summary

7. CEX Analysis • Third pressure scan reveals interesting beam current structure • Larger CEX energies observed at 14 mtorr than previous pressures • ~25 eV • More likely than “main energy” ions to occur

8. CEX Analysis

9. CEX Analysis

10. RPA Results Summary 2

11. Ion Reflection Testing • RPA pointed at right wall of chamber, about 70 mm away from beam exit • Preliminary Results • Lower pressure: electron current dominated • Higher pressure: 5 nA of ion current reported over small voltage step • Could be mechanical noise • Energy around 10 eV

12. Ion Reflection Testing • RPA pointed at chamber door • Preliminary Results • Lower pressure: ~0.55 nA of electron current • Higher pressure: ~0.86 nA of electron current • Conclusion: Ion reflection not a factor

13. Material Testing • Performed plume exposure tests on Si coupons • Test Parameters • Energy levels: 150 & 250 eV • Exposure times comparable to deposition of 50, 100, or 150 monolayers • Distance from Beam Exit: ~2 cm • Scanned samples for Argon and Tungsten atoms

14. Si Material Testing • Tested all 150 eV and 250 eV samples • Sample 3 had multiple broken tips on top row, but majority of tips were undamaged • Broken tips doped with Aluminum according to EDS • All samples showed elevated levels of Argon • Can’t confirm because no before scans were taken • All samples returned to ISU for APT testing

15. Al Material Testing • Objective: Expose Al samples to ion beam at: • Energy levels: 150 eV, 250 eV • Exposure durations: 1, 2, & 3 hours • Aluminum 1350-O used for samples • Three types of observation • Photographic/Visual • SEM Imaging & EDS • Contact Profilometry

16. Al Material Sample Results • Surface modifications • Pitting and slight polishing effects for low duration exposure • Polishing effect for higher exposure times with minor pitting • EDS scans showed evidence of Chromium • Al 1350-O has low concentration of Cr (.01%) • Could be sputtered material from RPA grids • Average Concentration: 0.4% (Error: 0.1%)

17. Al Sample “After” Photos Sample 3: 150 eV, 3 hour Sample 1: 150 eV, 1 hour Sample 2: 150 eV, 2 hour Sample 4: 250 eV, 1 hour Sample 5: 250 eV, 2 hour Sample 6: 250 eV, 3 hour

18. Future Work • Adapt experimental procedure for second batch of sample experiments • Work on joint abstract for Winter AIAA conference