Electron gun providing improved thermal isolation

1. An electron gun comprising:

a shell having distal and proximal ends;

a cathode structure disposed within the shell and having an electron emitting surface;

an anode physically coupled to the shell at the distal end and spaced a fixed distance from the emitting surface, the anode having an aperture for passage therethrough of a beam of electrons emitted by the emitting surface;

a plurality of leads adapted to apply a voltage to the cathode structure with respect to the anode sufficient to cause emission of the beam from the emitting surface;

a first insulator disposed within the shell proximal to the cathode structure, the first insulator having plural apertures having respective sizes in relation to corresponding ones of the plurality of leads such that the plurality of leads pass therethrough without contacting the first insulator, the first insulator providing stand-off for the voltage;

a second insulator disposed with the shell proximal from the first insulator, the second insulator having plural apertures permitting the plurality of leads to pass therethrough, the plurality of leads being tightly engaged within corresponding ones of the plural apertures of the second insulator to provide a vacuum barrier of the shell; and

a thermal choke coupled between the first insulator and second insulator to provide an indirect thermal path therebetween.

2. The electron gun of claim 1 , wherein the thermal choke comprises a cylindrical structure having plural regions removed from each respective end, the plural regions of each such end being substantially offset from one another.

3. The electron gun of claim 1 , wherein the first insulator comprises a disk shape.

4. The electron gun of claim 3 , wherein the second insulator comprises a disk shape.

5. The electron gun of claim 1 , wherein one of the plurality of leads is electrically coupled to the cathode structure through a plurality of conductive spacers.

6. The electron gun of claim 1 , wherein the cathode structure further comprises a heater, and one of the plurality of leads is electrically coupled to the heater.

7. The electron gun of claim 1 , wherein one of the plurality of leads is electrically coupled to the anode through a corresponding sleeve having a discontinuous portion comprising a plurality of bands.

8. The electron gun of claim 1 , wherein the shell has a cylindrical shape.

9. The electron gun of claim 1 , wherein the first and second insulators are comprised of ceramic material.

10. The electron gun of claim 1 , wherein the cathode structure comprises at least one focusing electrode.

11. The electron gun of claim 1 , wherein the thermal choke comprises a metal material.

12. The electron gun of claim 1 , further comprising potting material disposed within a proximal region of the shell bounded by the second insulator.

13. An electron gun comprising:

a shell having distal and proximal ends;

a cathode structure disposed within the shell and having an electron emitting surface;

an anode physically coupled to the shell at the distal end and spaced a fixed distance from said emitting surface, the anode having an aperture for passage therethrough of a beam of electrons emitted by the emitting surface;

a plurality of leads adapted to apply a voltage to the cathode structure with respect to the anode sufficient to cause emission of the beam from the emitting surface;

first means for insulating the cathode structure, the first insulating means providing passage of the plurality of leads therethrough without physical contact, the first insulating means further providing stand-off for the voltage;

second means for insulating the cathode structure spaced from the first insulating means, the second insulating means providing passage of the plurality of leads therethrough while providing a vacuum barrier of the shell; and

means for coupling the first and second insulating means together to provide an indirect thermal path therebetween.

14. The electron gun of claim 13 , wherein the coupling means comprises a cylindrical structure having plural regions removed from each respective end, the plural regions of each such end being substantially offset from one another.

15. The electron gun of claim 13 , wherein the first insulating means comprises a first ceramic disk.

16. The electron gun of claim 15 , wherein the second insulating means comprises a second ceramic disk.

17. The electron gun of claim 13 , wherein one of the plurality of leads is electrically coupled to the cathode structure through a plurality of spaced conductors.

18. The electron gun of claim 13 , wherein the cathode structure further comprises a heater, and one of the plurality of leads is electrically coupled to the heater.

19. The electron gun of claim 13 , wherein one of the plurality of leads is electrically coupled to the anode through a corresponding sleeve having a discontinuous portion comprising a plurality of bands.

20. The electron gun of claim 13 , wherein the shell has a cylindrical shape.

21. The electron gun of claim 13 , wherein the cathode structure comprises at least one focusing electrode.

22. The electron gun of claim 13 , further comprising potting material disposed within a proximal region of the shell bounded by the second insulating means.