Jarred Alexander Young October 2, 2013

 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

TOP VIEWSIDE VIEW z z x y i+i+ i+i+ Probe Mount Probe

Configuration A Configuration B CEX testing from beam scattering

 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)

 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)

 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

 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

 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

 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?

 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?