NDLI: A study of the inter-diffusion of tungsten and osmium-ruthenium in M-cathodes and the effects on performance and life

Content Provider	IEEE Xplore Digital Library
Author	Falce, L.R.
Copyright Year	2004
Description	Author affiliation: Commun. & Power Industries, Palo Alto, CA, USA (Falce, L.R.)
Abstract	M type cathodes have become the most widely used electron sources for microwave vacuum electron devices such as klystrons and travelling wave tubes. These cathodes are barium calcium aluminate impregnated porous tungsten over coated with 5000 /spl Aring/ of osmium ruthenium. The advantages of this type of cathode are the ability to achieve over two times higher current densities at the same temperature as an uncoated, impregnated porous tungsten cathode or achieving the same current at between 75 and 100/spl deg/C lower temperatures. The latter can result in eight times longer life expectancy. A concern among users is the permanency of the osmium ruthenium coating. This study reveals that from the very beginning of life that tungsten does diffuse to the emitting surface. However instead of a deterioration of performance with time as a result of this activity an improvement is actually achieved. Data is presented showing the effects of the diffusion on the tungsten surface concentration. Auger depth profiling is used to demonstrate the phenomenon. Data is presented for the initial status after cathode activation, after 33,517 hours of aging at 1000/spl deg/C and after 53,142 aging at 1000/spl deg/C. Data will also be presented showing surface tungsten concentration versus aging time at different temperatures.
Sponsorship	IEEE Elec. Devices Soc
Starting Page	356
Ending Page	357
File Size	90975
Page Count	2
File Format	PDF
ISBN	0780382617
DOI	10.1109/IVELEC.2004.1316359
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2004-04-27
Publisher Place	USA
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Tungsten Cathodes Temperature Aging Electron sources Microwave devices Electron devices Klystrons Electron tubes Barium
Content Type	Text
Resource Type	Article

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