Re-generable field emission cathodes part II: Quenched emitter performance analyses

Document Type

Conference Proceeding

Publication Date

1-1-2010

Abstract

Field emission cathodes have been considered for use as neutralizers on electric propulsion systems. In order to be compatible with EP, the field emission electron sources must be capable of long-life operation and must be robust enough to survive in a wide range of vacuum environments. This paper reports on field-emitters that can achieve long life due to their ability to be re-generated - repairing wear-induced damage. The re-generable emitters were tested against tungsten emitters to compare the re-generable technology with historically proven field emitters. The first type of tungsten emitter used was a DC electrochemically etched tungsten wire with a relatively smooth surface and a single sharp endpoint. The second was a DC and AC electrochemically etched tungsten wire with a roughened surface and a sharp endpoint. The electrochemically etched tungsten field emitters were used to establish electron field emission at pressures of < 10-8 Torr. They were then exposed to elevated pressure while observing emission. The smooth pure tungsten emitters survived 1 - 2 exposures to increased pressure but required increased extraction voltage to obtain emission with each subsequent test and the roughened pure tungsten emitters lasted 4 - 7 exposures to increased pressure before being permanently damaged. The re-generable emitters were also used to obtain electron emission at a vacuum pressure of < 10-8 Torr and then the emitters were exposed to elevated vacuum pressure, up to 10 -5 Torr. In all cases emission from the re-generable emitters lasted 10's of hours longer at increased pressure even before they needed to be re-generated. After re-generation the tips demonstrated the same performance as when new. Copyright © 2010 by Jason M. Makela.

Publication Title

46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit

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