Controlled porosity sheet for thermionic dispenser cathode and method of manufacture
AssigneeThe United States of America as represented by the Secretary of the Navy
InventorsRichard E. Thomas, Richard F. Greene
Life of this patent
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Abstract
A controlled porosity sheet defining a surface for a thermionic dispenser thode and a method of manufacture. Starting with a generally flat silicon template substrate structure having an array of upstanding microposts 1-25 microns across on 5-100 micron spacings from each other, a layer of metal is deposited on the substrate to surround the microposts and cover the substrate structure to a desired depth. The metal layer is then abraded to a smooth, flat surface which exposes the microposts. Thereafter, the silicon substrate and microposts are completely etched away, leaving a metal sheet having micron-size holes therethrough.
Claims18
A method of making a controlled porosity surface sheet useful in cathode structures comprising:
- manufacturing a substrate of single crystal silicon which has a predetermined array of microposts upstanding from the substrate, said manufacturing including the step of etching the substrate surface in a crystallographically orientation-dependent etch;
- applying a metal layer upon the silicon substrate to a desired thickness including covering the microposts;
- abrading the resultant structure in order to remove the surface metal and expose tips of the microposts;
- and
- etching away the silicon substrate including the microposts with an anisotropic etching agent to leave a porous sheet.
In a thermionic dispenser type cathode having an emissive member comprising a backing plug, active cathode material adjacent the backing plug and a thin foil facing the backing plug, the foil being formed from at least one refractory metal with a set of uniformly sized and spaced holes therein to permit the active cathode material to migrate through the holes and to spread over the exposed surface of the foil when the active cathode material is heated to the proper temperature, the improvement which comprises the holes having a pore width of 1-25 microns on the side of the foil facing away from the cathode material and a larger pore width of 25-100 microns on the other side, pore spacings of from 5-100 microns, and foil thickness from 25-100 microns, said active cathode material substantially filling the portion of the pores having the larger pore width.
A thermionic dispenser type cathode comprising an emissive member comprising a backing plug, a nonporous reservoir of active cathode material adjacent the backing plug and a thin foil on the outer surface of the reservoir, the foil being formed from a least one refractory metal with a set of uniformly sized and regularly spaced slots therein to permit the active electron-emitting material to migrate through the slots and to spread over the exposed surface of the foil when the reservoir material is heated to the proper temperature, said slots having a width of 1-25 microns in one transverse direction on spacings of 5-100 microns and a length in a second transverse direction substantially larger than the width.
Dependencies are inferred from the claim text.