High Energy Plume Impingement on Spacecraft Systems

AFOSR Telecon

Jarred Alexander YoungDecember 10, 2012

Current Status

Filament power supply has been repaired and returned Beam Testing can continue

Research methods of incorporating data filtering with measurements through Keithley instruments Looked into LabView commands and

programming structure for Keithley instruments

Retarding Potential Analyzer

Used to measure the energy distribution of particle beams

Consists of: Ground grid-allows beam to bias grid to beam bias Retarding grid- sweeps multiple potentials to repel lower energy particles while

higher-energy particles pass freely Supression grid- prevents oppositely-charged particles from affecting data

Fig.1: RPA Conceptual Diagram [1]

Outline of Beam Testing Method

Beam focused through energy analyzing grid aperture current measured by encased collector Retarding sweep provided

by KE2410 Sourcemeter Current measurements

provided by KE6485 picoammeter

Beam sweep conducted remotely through LabView

FC-71-A includes: Floating/ground grid, “G” Retarding Grid, “R” Supression grid for

secondary electrons, “S” Faraday cup for current

collection

Fig. 2: FC-71-A Layout [2]

Beam Analysis Processing

Both Keithley devices contain internal data filtering schemes Moving- allows for readings to be averaged over a

period of time and only takes to account the most recent readings until the procedure is completed

Repeating- allows reading from one source level to be averaged after a certain number of points to produce one reading and does not average data from other levels▪ Useful for source sweeps

Filtering must be activated prior to sweep to smooth data

LabView Issues

Learning LabView commands for Keithley instruments through example files Commands in current program

provide little documentation Example programs do not use

all the commands available

Context help (as pictured on right) indicates each terminal’s function, but not options and their significance More documentation in user’s

manuals for instruments, but not completely relatable to LabView

LabView Issues

Consulted with National Instruments on documentation issues Talked about upgrading to

commands that are NI-supported

Right-clicking on new commands terminals should allow for access to constants

Discovered this works with older commands as well

LabView Issues

Keithley drivers come with “VI Tree” which shows the user the general programming path in LabView for their instruments

Can use this to figure out how to edit current programs with filter commands

Upcoming Tasks

Re-integrate and test filament power supply

Augment LabView programs to allow for both filtering of Picoammeter results and Sourcemeter results

Perform beam testing while measuring current levels of all power supplies

Compile test matrix of energy levels