| Name |
Domed, 40-cm-Diameter Ion Optics for an Ion Thruster |
| Description |
The results of performance tests with two 40 cm ion optics sets are presented and compared to those of 30 cm
ion optics with similar aperture geometries. The 40 cm ion optics utilized both NSTAR and TAG (Thick-
Accelerator-Grid) aperture geometries. All 40 cm ion optics tests were conducted on a NEXT (NASA’s
Evolutionary Xenon Thruster) laboratory model ion engine. Ion optics performance tests were conducted
over a beam current range of 1.20–3.52 A and an engine input power range of 1.1–6.9 kW. Measured ion
optics’ performance parameters included near-field radial beam current density profiles, impingement-
limited total voltages, electron backstreaming limits, screen grid ion transparencies, beam divergence angles,
and start-up transients. Impingement-limited total voltages for 40 cm ion optics with the NSTAR aperture
geometry were 60–90 V lower than those with the TAG aperture geometry. This difference was speculated to
be due to an incomplete burn-in of the TAG ion optics. Electron backstreaming limits for the 40 cm ion optics
with the TAG aperture geometry were 8–19 V higher than those with the NSTAR aperture geometry due to
the thicker accelerator grid of the TAG geometry. Because the NEXT ion engine provided beam flatness
parameters that were 40–63% higher than those of the NSTAR ion engine, the 40 cm ion optics outperformed
the 30 cm ion optics.
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