Low work function electron beam filament assembly

Patent metadata

Field	Value
Publication number	US-10796876-B2
Application number	US-201815983967-A
Country	US
Kind code	B2
Filing date	May 18, 2018
Priority date	Mar 22, 2016
Publication date	Oct 6, 2020
Grant date	Oct 6, 2020

Abstract

A filament assembly can include: a button having a planar emitter region with one or more apertures extending from an emission surface of the planar emitter region to an internal surface opposite of the emission surface; an inlet electrical lead coupled to the button at a first side; an outlet electrical lead coupled to the button at a second side opposite of the first side; and a low work function object positioned adjacent to the internal surface of the planar emitter region and retained to the button. The planar emitter region can include a plurality of apertures. The low work function object can include a porous ceramic material having the barium, and may have a polished external surface. An electron gun can include the filament assembly. An additive manufacturing system can include the electron gun having the filament assembly.

First claim

What is claimed is:

1. A filament assembly comprising:
a button having a planar emitter region with one or more apertures extending from an emission surface of the planar emitter region to an internal surface opposite of the emission surface;
an inlet electrical lead coupled to the button at a first side;
an outlet electrical lead coupled to the button at a second side opposite of the first side; and
a low work function object positioned adjacent to the internal surface of the planar emitter region and retained to the button, wherein:
the low work function object includes barium and is configured to evolve barium therefrom when heated;
the low work function material of the low work function object includes a porous ceramic material having the barium;
the porous ceramic material includes a refractory metal distributed with a ceramic that includes barium oxide, calcium oxide, and an other oxide;
the other oxide includes at least one of aluminum oxide, samarium oxide, or magnesium oxide; and
the refractory metal makes up at least 50% of the low work function object by weight.

2. The filament assembly of claim 1 , wherein the planar emitter region comprises a plurality of apertures.

3. The filament assembly of claim 1 , further comprising a retainer member coupled with the button to form a housing having an internal chamber, wherein the low work function object is retained within the internal chamber.

4. The filament assembly of claim 3 , wherein at least one of the button or retainer member includes tantalum.

5. The filament assembly of claim 1 , further comprising a basket having the low work function object located in the basket.

6. The filament assembly of claim 5 , wherein the basket includes tantalum foil.

7. The filament assembly of claim 1 , wherein the low work function object further comprises an additive metal that includes at least one of nickel, iridium, osmium, titanium, molybdenum, or tantalum.

8. An electron gun comprising:
a cathode;
the filament assembly of claim 1 adjacent to the cathode with a gap therebetween; and an anode spaced apart from the cathode.

9. An additive manufacturing system comprising:
the electron gun of claim 8 ; and
a wire feeder configured to feed wire into a path of an electron beam emitted from the filament assembly.

10. A plasma bridge neutralizer comprising:
a chamber having a gas inlet; and
the filament assembly of claim 1 located in the chamber with the planar emitter region facing gas in the chamber.

11. A method of emitting electrons from a filament assembly, the method comprising:
providing the filament assembly of claim 1 ;
passing current from the inlet electrical lead through the filament assembly to the outlet electrical lead; and
heating the filament assembly until electrons are emitted from the planar emitter region of the button.

12. A method of manufacturing the filament assembly of claim 1 , the method comprising:
forming the button to have a body with a planar emitter region;
forming the one or more apertures through the body at the planar emitter region;
positioning the low work function object adjacent to the internal surface of the planar emitter region; and
attaching the inlet electrical lead and outlet electrical lead to opposite sides of the button.

13. The method of claim 12 , further comprising polishing the low work function object by one of:
abrasive polishing with a dry abrasive;
ion beam polishing; or
abrasive polishing with a dry abrasive followed by ion beam polishing.

14. The filament assembly of claim 1 , wherein the one or more apertures are transmissive to electrons.

15. The filament assembly of claim 1 , wherein the one or more apertures allow migration of atoms and/or molecules from the low work function object to the emissive surface.

16. The filament assembly of claim 1 , wherein the refractory metal includes tungsten.

17. The filament assembly of claim 1 , wherein the low work function object has a polished external surface.

18. A filament assembly comprising:
a button having a planar emitter region with one or more apertures extending from an emission surface of the planar emitter region to an internal surface opposite of the emission surface;
an inlet electrical lead coupled to the button at a first side;
an outlet electrical lead coupled to the button at a second side opposite of the first side;
a low work function object positioned adjacent to the internal surface of the planar emitter region and retained to the button; and
a cylindrical tantalum foil associated with the button.

19. The filament assembly of claim 18 , wherein the cylindrical tantalum foil extends from the button away from the low work function object.

20. A method of emitting electrons from a filament assembly, the method comprising:
providing a filament assembly comprising:
a button having a planar emitter region with one or more apertures extending from an emission surface of the planar emitter region to an internal surface opposite of the emission surface;
an inlet electrical lead coupled to the button at a first side;
an outlet electrical lead coupled to the button at a second side opposite of the first side; and
a low work function object positioned adjacent to the internal surface of the planar emitter region and retained to the button;

passing current from the inlet electrical lead through the filament assembly to the outlet electrical lead;
heating the filament assembly until electrons are emitted from the planar emitter region of the button;
decontaminating the button by flash heating the button to a first temperature that vaporizes one or more contaminants such that the low work function object is at a second temperature that is lower than the first temperature so that barium is not evolved therefrom;
cooling the button to an operational temperature; and
heating the low work function object to the operational temperature.

Assignees

• Univ Colorado State Res Found

Inventors

• Nguyen Bao Gia
• Williams John D
• Williams Desiree D
• Farnell Casey C
• Ham Ryan Kenneth
• Greiner Kathryn Elizabeth

Classifications

• B22F10/66

  by mechanical means · CPC title

• B22F10/25

  Direct deposition of metal particles, e.g. direct metal deposition [DMD] or laser engineered net shaping [LENS] · CPC title

• B22F10/18

  by mixing binder with metal in filament form, e.g. fused filament fabrication [FFF] · CPC title

• B22F12/53

  Nozzles · CPC title

• H01J37/32596

  Hollow cathodes · CPC title