Electron tube with dispenser cathode

In a microwave electron tube, an improved cathode for use therein for producing a high current density stream of electrons when heated, comprising a matrix of compacted metal particles formed with interstices therebetween which are substantially uniformly dispersed throughout the matrix and define therein an initial predetermined porosity, said matrix consisting of a mixture of metal particles of a first metal selected from the group of tungsten and molybdenum together with particles of a second metal selected from the group consisting of iridium, osmium, ruthenium and rhenium, said second metal particles comprising at least 10% to 90% by weight of said matrix, said matrix being compressed and treated to bring said particulate mixture into intimate particle-to-particle contact in which said particles are bonded together at regions of contact therein in which each metal component retains its discrete character and in which the interstices provide a substantial void volume throughout said matrix, and an electron emissive material comprising an alkaline earth aluminate including at least barium aluminate filling the interstices of said matrix to form therewith a solid cathode body of negligible porosity, said cathode body being formed with an electron emitting surface having a conformation which exposes the filled interstices and particulate matrix thereof to define, in operation, a plurality of exposed alkaline earth portions throughout the exposed surface of the mixture of matrix metal particles, said cathode being adapted for being heated to electron emitting temperature whereat the second metal and the alkaline earth aluminate interact during operation to reduce the work function for electron emission at said surface while the second metal is prevented from being sputtered away from said surface by its structural embodiment throughout the body of the cathode, means for heating said cathode to cause electron emission therefrom, an anode spaced from said cathode for accelerating the emitted electrons into an electron beam directed toward said anode, an interaction structure disposed in said tube to cause modulation of the electron beam at microwave frequencies, means for extracting microwave power from said tube.

In an electron tube, an improved cathode for use therein for producing a high current density stream of electrons when heated, comprising a matrix of compacted metal particles formed with interstices therebetween which are substantially uniformly dispersed throughout the matrix and define therein an initial predetermined porosity, said matrix consisting of a mixture of metal particles of a first metal selected from the group of tungsten and molybdenum together with particles of a second metal selected from the group consisting of iridium, osmium, ruthenium and rhenium, said second metal particles comprising at least 10% to 90% by weight of said matrix, said matrix being compressed and treated to bring said particulate mixture into intimate particle-to-particle contact in which said particles are bonded together at regions of contact therein in which each metal component retains its discrete character and in which the interstices provide a substantial void volume throughout said matrix, and an electron emissive material comprising an alkaline earth aluminate including at least barium aluminate filling the interstices of said matrix to form therewith a solid cathode body of negligible porosity, said cathode body being formed with an electron emitting surface having a conformation which exposes the filled interstices and particulate matrix thereof to define, in operation, a plurality of exposed alkaline earth portions throughout the exposed surface of the mixture of matrix metal particles, said cathode being adapted for being heated to electron emitting temperature whereat the second metal and the alkaline earth aluminate interact during operation to reduce the work function for electron emission at said surface while the second metal is prevented from being sputtered away from said surface by its structural embodiment throughout the body of the cathode, means for heating said cathode to cause electron emission therefrom, an anode spaced from said cathode for accelerating said electrons into an electron beam directed toward said anode, means for controlling the movement of said electron beam.