Cathode support structure designed around a titanium diaphragm prevents radial misalignment between the cathode and anode in amplitrons. The titanium exhibits low thermal conductivity, tolerates lateral thermal expansion of the cathode, and is a poor primary and secondary emission medium

Teich, W. W.

English

NASA Technical Reports Server

Ceramic
Platinum 
Washer 
October 1965
	 Brief 65-10298 
NASA TECH BRIEF 
NASA Tech Briefs are issued by the Technology Utilization Division to summarize specific 
technical innovations derived from the space program. Copies are available to the public from 
the Clearinghouse for Federal Scientific and Technical information, Springfield, Virginia, 22151. 
Titanium Diaphragm Makes Excellent Amplitron Cathode Support 
Molybdenum Hub 
The problem: To prevent radial misalignment be-
tween the cathode and anode in amplitrons. 
The solution: A cathode support structure designed 
around a titanium diaphragm that exhibits low ther-
mal conductivity, tolerates lateral thermal expansion 
of the cathode, and is a poor primary and secondary 
emission medium. 
How it's done: The titanium diaphragm is brazed 
to the ceramic support structure after first metalliz-
ing the surface of the ceramic by conventional tech-
niques. A gold-nickel eutectic is used as a brazing ma-
terial since it melts in a desirable temperature range. 
A molybdenum hub isolates the nickel cathode from 
the titanium diaphragm since their eutectic point is 
at approximately the same temperature as that re-
quired during cathode processing. The molybdenum
hub is welded to the titanium diaphragm with a thin 
platinum washer. The cathode is welded to the molyb-
denum hub after the parts have been assembled in the 
amplitron tube. 
Notes: 
I. The strength of titanium, even at elevated tempera- 
tures, allows lateral thermal expansion of the cath- 
ode without loss of the necessary radial alignment 
with respect to the anode. 
2. Because of its poor primary and secondary emis-
sion characteristics, the titanium acts as an end 
shield to prevent spreading of the electron cloud 
in the interaction space. It also contributes to per-
formance stability by its effective absorption of 
residual gases in a high-vacuum environment. 
(continued overleaf) 
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.
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3. Inquiries concerning this innovation may be di-
	 Patent status: NASA encourages commercial use 
rected to:	 of this innovation. No patent action is contemplated 
Technology Utilization Officer
	 by NASA. 
Goddard Space Flight Center
	 Source: W. W. Teich of Raytheon Company 
Greenbelt, Maryland, 20771
	 under contract to 
Reference: B65-10298
	
	 Goddard Space Flight Center

(G S FC-394)
. Brief 65-10298	 Category 01


Titanium diaphragm makes excellent amplitron cathode support

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