Thermionic cathode having an embedded grid, process for its fabrication, and high frequency electron tubes using such a cathode
AssigneeThomson-CSF
InventorsJean Montgaillard, Arvind Shroff
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Abstract
The invention relates to metal oxide activated porous tungsten cathodes and methods of their manufacture. A cathode 1 of porous tungsten activated by metal oxides is mounted on a housing 2 which has a heating filament 3. On the outer face of the cathode there is a pattern or grid of pure tungsten (preferably formed by a chemical vapor deposition of WCl.sub.6 or WF.sub.6) of crystalline material the outer face of which has an orientation in the (100) or (110) plane and is parallel to the surface of the cathode. The invention will find particular use in the cathode guns of high frequency tubes such as traveling wave tubes and klystrons.
Claims9
A thermionic cathode with an embedded grid comprising a cathode body of porous tungsten with an emissive activator and having at an emissive surface of the cathode non-emissive zones;
- said zones being of a center cubic crystalline material and having at least one face having a crystal plane of 100 to 110 whose work function is higher than that of the cathode body;
- said face being parallel to the emissive surface of the cathode.
A thermionic cathode with an embedded grid consisting of a cathode body of porous tungsten with an emissive activator and an emissive surface of low work function, zones of a center cubic crystalline material at said emissive surface, said zones having a face which is parallel to and faces away from the emissive surface of the cathode, and whose work function is higher than that of the cathode body, said material being essentially tungsten, and said face having a crystal plane of (100) or (110).
A Process for making a thermionic cathode with an embedded grid, comprising a cathode body of porous tungsten with an emissive activator and having at one surface non-emissive zones of a center cubic crystalline material having at least one face with a crystal plane 100 or 110 whose work function is higher than that of the cathode body and is parallel to the emissive surface of the cathode, said process comprising the following steps:
- depositing on the emissive surface of the cathode body a layer of said material by decomposition in vapor phase of a halogen compound of the material and with the face away from the cathode body being that face having the higher work function, and
- removing portions of said deposited layer without substantially modifying its crystalline orientation to expose regions of the cathode body that should be emissive.
A process for making a thermionic cathode with an embedded grid, comprising a cathode body of porous tungsten with an emissive activator and having at one surface non-emissive zones of a center cubic crystalline material having at least one face with a crystal plane of 100 or 110 whose work function is higher than that of the cathode body and is parallel to the emissive surface of the cathode, said process comprising the following steps:
- forming hollows in the surface of the cathode body in those zones which are to be non-emissive,
- depositing on this surface a layer of said material by decomposition in vapor phase of a halogen compound of the material and with the face away from the cathode body being the face having the higher work function,
- removing a portion of said layer down to said cathode face, without substantially modifying its crystalline orientation until the surface of the material in the hollows and the emissive surface regions of the cathode body are both exposed.
A process for making a thermionic cathode with an embedded grid, comprising a cathode body of porous tungsten with an emissive activator and having at one surface non-emissive zones of a center cubic crystalline material having at least one face with a crystal plane of 100 to 110 whose work function is higher than that of the cathode body and is parallel to the emissive surface of the cathode, said process comprising the following steps:
- forming a support grid of a material not suceptible to chemical reaction with the cathode body,
- depositing on at least one face of said support grid a layer of said material and
- attaching said grid to the cathode body.
Dependencies are inferred from the claim text.