Vacuum encapsulated hermetically sealed diamond amplified cathode capsule and method for making same

1. A diamond amplified cathode capsule for generating an electron beam of secondary electrons, the capsule comprising:

a cathode element having a primary emission surface adapted to emit primary electrons;

an annular insulating spacer;

a diamond window element comprising a diamond material and having a secondary emission surface adapted to emit secondary electrons in response to primary electrons impinging on the diamond window element;

a first cold-weld ring disposed between said cathode element and said annular insulating spacer; and

a second cold-weld ring disposed between said annular insulating spacer and said diamond window element,

wherein said cathode capsule is formed by a vacuum cold-weld process such that said first cold-weld ring forms a hermetical seal between said cathode element and said annular insulating spacer and said second cold-weld ring forms a hermetical seal between said annular spacer and said diamond window element whereby a vacuum encapsulated chamber is formed within said capsule.

2. A diamond amplified cathode capsule as defined in claim 1 , wherein said cathode element comprises a photo-sensitive material such that said cathode element forms a photocathode element.

3. A diamond amplified cathode capsule as defined in claim 1 , wherein said first and second cold-weld rings comprise a material selected from the group consisting of indium, lead and tin.

4. A diamond amplified cathode capsule as defined in claim 1 , wherein said cathode element, said diamond window element and said annular insulating spacer comprise interface surfaces coated with a metallic wetting material, said metallic wetting material being in contact with one of said first and second cold-weld rings to promote atomic adhesion therebetween.

5. A diamond amplified cathode capsule as defined in claim 4 , wherein said first and second cold-weld rings comprise an indium material and said metallic wetting material comprises nickel.

6. A diamond amplified cathode capsule as defined in claim 4 , wherein said cathode element comprises a copper base and said metallic wetting material comprises a nickel material vacuum sputtered on an outer peripheral rim of said copper base.

7. A diamond amplified cathode capsule as defined in claim 4 , wherein said cathode element comprises a nickel base having a major surface with a center, and a photo-sensitive oxygen-free copper material layer disposed in said center, said photo-sensitive oxygen-free copper material layer forming said primary emission surface.

8. A method for fabricating a diamond amplified cathode capsule for generating an electron beam of secondary electrons, the method comprising:

providing a cathode element having a primary emission surface adapted to emit primary electrons;

providing an annular insulating spacer;

providing a diamond window element comprising a diamond material and having a secondary emission surface adapted to emit secondary electrons in response to primary electrons impinging on the diamond window element;

stacking a first cold-weld ring between the cathode element and the annular insulating spacer;

stacking a second cold-weld ring between the annular insulating spacer and the diamond window element; and

cold-welding the cathode element, the annular insulating spacer, the diamond window element and the first and second cold-weld rings under vacuum such that the first cold-weld ring forms a hermetical seal between the cathode element and the annular insulating spacer and the second cold-weld ring forms a hermetical seal between the annular spacer and the diamond window element, whereby a vacuum encapsulated chamber is formed within the capsule.

9. A method as defined in claim 8 , further comprising coating interface surfaces of the cathode element, the annular insulating spacer and the diamond window element with a metallic wetting material, the metallic wetting material being in contact with the first and second cold-weld rings to promote atomic adhesion therebetween.

10. A method as defined in claim 9 , wherein the metallic wetting material is coated on the interface surfaces by a vacuum sputtering process.

11. A method as defined in claim 8 , wherein providing the cathode element comprises:

forming a copper base;

vacuum sputtering a nickel wetting material on an outer peripheral rim of the copper base to form a nickel coated copper base;

cleaning the nickel coated copper base by abrasion; and

etching the cleaned nickel coated copper base.

12. A method as defined in claim 8 , wherein providing the diamond window element comprises:

forming a diamond base having a face;

metalizing the face of the diamond base;

vacuum sputtering a nickel wetting material on an outer peripheral rim of the diamond base to form a nickel coated diamond base;

cleaning the nickel coated diamond base by abrasion; and

etching the nickel coated diamond base.

13. A method as defined in claim 8 , further comprising:

coiling a first length of indium wire having opposite ends around a pin;

joining the opposite ends of the first length of indium wire to form a contiguous ring;

etching and drying the contiguous ring to form the first cold-weld ring; and

repeating the coiling, joining, etching and drying with a second length of indium wire to form the second cold-weld ring.

14. A method as defined in claim 8 , wherein the cathode element, the insulating spacer, the diamond window element and the first and second cold-weld rings are stacked in an alignment fixture prior to cold-welding.

15. A method as defined in claim 14 , further comprising securing the alignment fixture to an anvil of a vacuum press, wherein the cold-welding is performed in the vacuum press.

16. A method as defined in claim 8 , wherein the cold-welding is performed in a vacuum press.

17. A method as defined in claim 8 , wherein the cathode element comprises a photo-sensitive material such that the cathode element forms a photocathode element.

18. A method for reducing contamination of a diamond amplified cathode capsule caused by out-gassing during use of the capsule, the method comprising:

installing a hermetically sealed, vacuum encapsulated, diamond amplified cathode capsule within an electron gun chamber;

heating the capsule to a temperature sufficient to clean a diamond element of the capsule;

deforming the capsule during the heating to break the hermetical seal of the capsule, whereby an interior of the capsule is brought into fluid communication with the electron gun chamber; and

pumping the electron gun chamber to evacuate out-gases from both the chamber and the interior of the capsule.

19. A method as defined in claim 18 , wherein the capsule is formed by a cold-weld process and comprises at least one cold-weld ring forming the hermetical seal of the capsule, and wherein the at least one cold-weld ring softens during heating and deforming, thereby breaking the hermetical seal.

20. A method as defined in claim 19 , wherein deforming comprises forming a fissure in the at least one cold-weld ring, the fissure providing a fluid passage way between the interior of the capsule and the electron gun chamber.

21. A method as defined in claim 19 , wherein the cold-weld ring comprises indium, and wherein the capsule is heated to a temperature of about 300-400° C., the indium cold-weld ring softening at about 150° C.

22. A method as defined in claim 18 , wherein the capsule is pulled in opposite directions during deforming by a moveable arm arrangement disposed within the electron gun chamber.