High Energy Plume Impingement on Spacecraft Systems

AFOSR Telecon

Jarred Alexander YoungSeptember 18, 2013

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

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 10 12 14 16 18 20 22 24

-5.00E-10

0.00E+00

5.00E-10

1.00E-09

1.50E-09

2.00E-09

2.50E-09

Energy Distribution Comparisons

Particle Energy (eV)

Curr

ent

Spec

tral

Den

sity

(A/

V)

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

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

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

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

Sample Comparison

SAMPLE 1, PRE-BEAM SAMPLE 1, POST-BEAM

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

PRE BEAM POST BEAM

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

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

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

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