Method for preventing deterioration of mixed oxide cathodes in low density gas tubes caused by ion bombardment is discussed. Construction of cathode is described and illustration is furnished. Electron emission through space charge to neutralize ion-filled regions is basic process

Bennett, W. H.

English

NASA Technical Reports Server

August 1972	 B72-10530 
•	 NASA TECH BRIEF 
NASA Headquarters 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
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be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Cathode. for Use With Low Density Gases 
The problem: 
Back bombardment of mixed oxide cathodes by 
positive ions in low density gas tubes causes rapid 
deterioration of the cathode. 
The solution: 
A cathode of metal mesh coated with electron emis-
sion enhancers is placed in a metal cup which has the 
heater wire wound around the exterior of the cup.
How it's done: 
A cathode is filled with a knitted nickel or tungsten 
mesh which is coated with an electron emission enhanc-
ing material. The cup is filled with the mesh in any 
desired configuration, flush, concave, or convex. Back 
bombardment by ions can destroy only that portion of 
the coating which faces the oncoming ions. The activated 
surfaces on the other side of each individual wire are 
protected and can produce electron emission through 
the space charge neutralizing ion-filled regions in the 
interstices. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
NASA Headquarters 
Code KT 
Washington, D.C. 20546 
Reference: B72-10530 
Patent status: 
No patent action is contemplated by NASA. 
Source: Willard H. Bennett of
North Carolina State University 
under contract to
NASA Headquarters
(HQN- 10687) 
Heater 
Wire
Category 01 
This document was prepared under the sponsorship of the National
	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States
	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States
	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19720000529 2020-03-17T03:35:15+00:00Z


Cathode for use with low density gases

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