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Characterization of cathode keeper wear by surface layer activation

Show simple item record Polk, James E. 2006-04-12T18:29:52Z 2006-04-12T18:29:52Z 2003-07-21
dc.identifier.citation Joint Propulsion Conference, Huntsville, Alabama, July 21-23, 2003 en
dc.identifier.clearanceno 03-1913
dc.description.abstract In this study, the erosion rates of the discharge cathode keeper in a 30 cm NSTAR configuration ion thruster were measured using a technique known as Surface Layer Activation (SLA). This diagnostic technique involves producing a radioactive tracer in a given surface by bombardment with high energy ions. The decrease in activity of the tracer material may be monitored as the surface is subjected to wear processes and correlated to a depth calibration curve, yielding the eroded depth. Analysis of the activities was achieved through a gamma spectroscopy system. The primary objectives of this investigation were to reproduce erosion data observed in previous wear studies in order to validate the technique, and to determine the effect of different engine operating parameters on erosion rate. The erosion profile at the TH 15 (23 kw) setting observed during the 8200 hour Life Demonstration Test (LDT) was reproduced. The maximum keeper erosion rate at this setting was determined to be 0.085 pm/hr. Testing at the TH 8 (1.4 kw) setting demonstrated lower erosion rates than TH 15, along with a different wear profile. Varying the keeper voltage was shown to have a significant effect on the erosion, with a positive bias with respect to cathode potential decreasing the erosion rate significantly. Accurate measurements were achieved after operating times of only 40 to 70 hours, a significant improvement over other erosion diagnostic methods. en
dc.description.sponsorship NASA/JPL en
dc.format.extent 3926874 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US en
dc.publisher Pasadena, CA : Jet Propulsion Laboratory, National Aeronautics and Space Administration, 2003 en
dc.subject materials erosion en
dc.subject surface layer activation en
dc.title Characterization of cathode keeper wear by surface layer activation en
dc.type Preprint en

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