Thermionic electron emitters
AssigneeE M I-Varian Limited
InventorMichael C. Green
Life of this patent
Estimating the term…
Abstract
A thermionic cathode (FIG. 1) comprises an emitter (3) comprising a matrix (4) of tungsten impregnated with an alkaline earth activator. The matrix is coated with a coating (5) of about 20-30% osmium fully alloyed with tungsten formed by cosputtering osmium and tungsten onto the matrix. A diffusion barrier (6) of osmium may be interposed between the matrix 4 and coating (5) (FIG. 2) and, optionally, osmium may be diffused into the matrix (4). Alternatively the whole matrix may comprise a mixture of about 20-30% osmium fully alloyed with tungsten (FIG. 3). Alternative to osmium and tungsten may be used, and various modifications may be made, and other methods of making the emitter may be used. In particular the proportion of osmium may be about 40%.
Claims27
A thermionic emitter comprising:
- a porous body of metal selected from the group consisting of tungsten, molybdenum and alloys thereof;
- an emissive surface layer of a fully alloyed material being a coating on said porous body;
- said fully alloyed material consisting solely of 15 to 45% of a first metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium and alloys thereof, fully alloyed with 85 to 55% of a second metal selected from the group consisting of tungsten, molybdenum and alloys thereof, such that said fully alloyed material has said first metal and said second metal substantially fully interdiffused therein;
- and,
- an alkaline earth activator dispersed within said porous body.
A thermionic emitter comprising:
- a porous body formed of a fully alloyed material;
- said fully alloyed material consisting solely of 15 to 45% of a first metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium and alloys thereof, fully alloyed with 85 to 55% of a second metal selected from the group consisting of tungsten, molybdenum and alloys thereof, such that said fully alloyed material has said first metal and said second metal substantially fully interdiffused therein;
- and,
- an alkaline earth activator dispersed within said porous body.
A method of making a thermionic electron emitter comprising the steps of:
- providing a first metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium and alloys thereof and a second metal selected from the group consisting of tungsten, molybdenum and alloys thereof,
- providing a porous body;
- fully alloying said first and second metals to form at least an emissive surface layer on said porous body as a fully alloyed material consisting solely of 15 to 45% of said first metal and about 85 to 55% of said second metal, such that said fully alloyed material has said first and said second metal substantially interdiffused therein;
- and
- incorporating an alkaline earth activator in said porous body.
A method of making a thermionic electron emitter comprising the steps of:
- (i) providing a porous matrix of a metal selected from the group consisting of tungsten, molybdenum and alloys thereof;
- (ii) impregnating the matrix with an alkaline earth activator;
- and
- (iii) providing a first metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium, and alloys thereof and a second metal selected from the group consisting of tungsten, molybdenum and alloys thereof;
- (iv) fully alloying said first and second metals and forming a fully alloyed coating as an emissive surface layer on the impregnated matrix, said fully alloyed coating consisting solely of 15 to 45% of said first metal and about 85 to 55% of said first metal, and said fully alloyed coating having said first and said second metal substantially interdiffused therein.
A method of making a thermionic electron emitter comprising the steps of:
- (i) providing a first metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium, and alloys thereof and a second metal selected from the group consisting of tungsten, molybdenum and alloys thereof;
- (ii) pressing a mixture of 15 to 45% of said first metal with about 85 to 55% of said second metal;
- (iii) sintering said mixture to form a porous matrix;
- (iv) producing a fully alloyed material consisting solely of said first metal fully alloyed with said second metal by heating said porous matrix, said fully alloyed material having said first and said second metal substantially interdiffused therein;
- and
- (v) impregnating said porous matrix with an alkaline earth activator.
A method of making a thermionic emitter comprising the steps of:
- (i) providing a powder of fully alloyed material comprising 15 to 45% of a first metal selected from the group consisting of osmium, iridium, ruthenium, rhodium, rhenium and alloys thereof and 85 to 55% of a second metal selected from the group consisting of tungsten, molybdenum, and alloys thereof, the particles of the fully alloyed powder having said first and said second metal substantially interdiffused therein;
- (ii) placing said powder in a mold;
- (iii) pressing said powder;
- (iv) sintering the pressed powder to form a porous matrix;
- and,
- (v) impregnating said porous matrix with an alkaline earth activator.
Dependencies are inferred from the claim text.