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Invited Article: Physical and chemical analyses of impregnated cathodes operated in a plasma environment
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10.1063/1.3005784
/content/aip/journal/rsi/79/11/10.1063/1.3005784
http://aip.metastore.ingenta.com/content/aip/journal/rsi/79/11/10.1063/1.3005784

Figures

Image of FIG. 1.
FIG. 1.

Schematic of the discharge-cathode assembly.

Image of FIG. 2.
FIG. 2.

Pre- and post-test comparison of the DCA following of operation inside of an operating ion thruster discharge chamber.

Image of FIG. 3.
FIG. 3.

NCA engineering schematic.

Image of FIG. 4.
FIG. 4.

Comparison of the pretest and in-test neutralizer-cathode orifices.

Image of FIG. 5.
FIG. 5.

The exterior of the discharge-cathode insert after of operation.

Image of FIG. 6.
FIG. 6.

Post-test insert emission surface (left to right) from downstream to upstream end.

Image of FIG. 7.
FIG. 7.

Tungsten crystallite formation at the downstream end of the discharge insert.

Image of FIG. 8.
FIG. 8.

Discharge insert surface with axial distance from the orifice plate. Lower right image is the unused insert for comparison.

Image of FIG. 9.
FIG. 9.

Ba:W ratio comparison for the discharge-cathode insert and control insert to indicate extent of impregnate depletion.

Image of FIG. 10.
FIG. 10.

Ba:W signal strength at from the surface as a function of axial distance from the orifice plate for the discharge-cathode insert.

Image of FIG. 11.
FIG. 11.

Impregnate depletion depth as a function of axial distance from the orifice plate for the discharge-cathode insert.

Image of FIG. 12.
FIG. 12.

Fracture surface of the (top row) downstream end of the discharge cathode and (bottom row) unused insert at 100, 300, and from the surface.

Image of FIG. 13.
FIG. 13.

Post-test discharge-cathode tube condition.

Image of FIG. 14.
FIG. 14.

(a) Post-test condition of the downstream side of the cathode-orifice plate. (b) Cross-sectional view of the post-test cathode-orifice plate to tube weld with a box indicating the extent of erosion from the pretest condition.

Image of FIG. 15.
FIG. 15.

Comparison of (a) post-test and (b) pretest discharge-cathode orifice plate upstream surface. The post-test surface has extensive tungsten deposition in the orifice and on the plate surface.

Image of FIG. 16.
FIG. 16.

Post-test condition of the discharge-cathode keeper tube.

Image of FIG. 17.
FIG. 17.

Discharge-cathode keeper tube deposition structure.

Image of FIG. 18.
FIG. 18.

Cross section of (a) the eroded downstream coil and (b) uneroded coil of the discharge-cathode heater.

Image of FIG. 19.
FIG. 19.

Post-test condition of the discharge-cathode low-voltage propellant isolator assembly. Insert in image is the post-test condition of the propellant line screen located downstream of the isolator.

Image of FIG. 20.
FIG. 20.

Neutralizer insert surface and subsurface at 100, 350, and from the surface.

Image of FIG. 21.
FIG. 21.

Comparison of the Ba:W ratio for the neutralizer insert and an unoperated 4:1:1 insert.

Image of FIG. 22.
FIG. 22.

Erosion of the neutralizer-keeper tube on the beam-exposed side.

Image of FIG. 23.
FIG. 23.

(a) Post-test neutralizer-keeper orifice indicating. (b) Magnification of keeper orifice deposit structure.

Image of FIG. 24.
FIG. 24.

Comparison of the post-test condition of the neutralizer-cathode orifice and chamfer.

Image of FIG. 25.
FIG. 25.

Predicted discharge-cathode insert depletion depth.

Tables

Generic image for table
Table I.

ELT test segment summary.

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/content/aip/journal/rsi/79/11/10.1063/1.3005784
2008-11-20
2014-04-24
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Invited Article: Physical and chemical analyses of impregnated cathodes operated in a plasma environment
http://aip.metastore.ingenta.com/content/aip/journal/rsi/79/11/10.1063/1.3005784
10.1063/1.3005784
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