PROPOSED PHYSICAL MODEL FOR THE IMPREGNATED TUNGSTEN CATHODE BASED ON AUGER SURFACE STUDIES OF THE BA-O-W SYSTEM

被引:55
作者
FORMAN, R
机构
[1] NASA Lewis Research Center, Cleveland
关键词
D O I
10.1016/0378-5963(79)90037-0
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
Auger and work function measurements have been made on a tungsten surface containing absorbed layers of (a) barium, and (b) barium and oxygen. The experimental techniques employed enabled one to distinguish the quantitative effects of oxygen on the barium-oxygen- tungsten surface reaction. It was found that the barium on an impregnated tungsten cathode is not oxidized barium (BaO), nor is it present as metallic barium chemisorbed on tungsten; rather it seems to be in an intermediate state probably as a coadsorbed (barium and oxygen) layer on tungsten. As a result of these studies a physical model for the impregnated tungsten cathode is proposed. The model assumes that the surface of the cathode, during life, has an adsorbed surface layer of a monolayer or less of both barium and oxygen on the surface. With life the barium is depleted leading to a higher work function surface. End of life occurs when the barium partial monolayer is so low that the resultant high cathode work function cannot sustain the required emission level. Recent NASA life test results on TWT type tubes are reported and explained by the proposed model. © 1979.
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页码:258 / 274
页数:17
相关论文
共 15 条
[1]  
Beck A. H. W., 1963, J ELECTRON CONTR, V14, P623
[2]   THE NATURE OF THE EMITTING SURFACE OF BARIUM DISPENSER CATHODES [J].
BRODIE, I ;
JENKINS, RO .
BRITISH JOURNAL OF APPLIED PHYSICS, 1957, 8 (01) :27-29
[3]  
DUPRE FK, 1951, PHYS REV, V82, P574
[4]   SURFACE STUDIES OF BARIUM AND BARIUM OXIDE ON TUNGSTEN AND ITS APPLICATION TO UNDERSTANDING MECHANISM OF OPERATION OF AN IMPREGNATED TUNGSTEN CATHODE [J].
FORMAN, R .
JOURNAL OF APPLIED PHYSICS, 1976, 47 (12) :5272-5279
[5]   USE OF AUGER-SPECTROSCOPY IN EVALUATION OF THERMIONIC CATHODES [J].
FORMAN, R .
IEEE TRANSACTIONS ON ELECTRON DEVICES, 1977, 24 (01) :56-61
[6]   EFFECTS OF S, BA, AND C ON IMPREGNATED CATHODE SURFACES [J].
HAAS, GA ;
GRAY, HF ;
THOMAS, RE .
JOURNAL OF APPLIED PHYSICS, 1975, 46 (08) :3293-3301
[7]   VERIFICATION OF METAL-RICH SURFACE MODEL FOR OXIDATION OF SR, BY AUGER-ELECTRON SPECTROSCOPY [J].
HELMS, CR ;
SPICER, WE .
PHYSICAL REVIEW LETTERS, 1974, 32 (05) :228-232
[8]  
KOHL WH, 1960, MATERIALS TECHNIQUES, P274
[9]   NEW DISPENSER TYPE THERMIONIC CATHODE [J].
LEVI, R .
JOURNAL OF APPLIED PHYSICS, 1953, 24 (02) :233-233
[10]   IMPROVED IMPREGNATED CATHODE [J].
LEVI, R .
JOURNAL OF APPLIED PHYSICS, 1955, 26 (05) :639-639