High-frequency electron source

1. A high-frequency electron source, comprising:

a discharge chamber having at least one gas inlet for a gas to be ionized and at least one extraction opening for electrons;

a first electrode at least partially surrounding the discharge chamber;

a keeper electrode at least partially surround the discharge chamber, wherein the first electrode and the keeper electrode are configured to provide a high-frequency electric field therebetween; and

first and second auxiliary electrodes mounted on the discharge chamber and configured to provide d.c. voltage between the first and second auxiliary electrodes.

2. The high-frequency electron source as recited in claim 1 , further comprising a plasma chamber surrounding the discharge chamber.

3. The high-frequency electron source as recited in claim 1 , wherein the high-frequency electric field is provided parallel to a direction of electron extraction.

4. The high-frequency electron source as recited in claim 1 , wherein the high-frequency electric field is provided perpendicular to a direction of electron extraction.

5. The high-frequency electron source as recited in claim 1 , wherein the high-frequency electric field has a frequency between 100 KHz and 50 MHz.

6. The high-frequency electron source as recited in claim 1 , wherein the first electrode and the second electrode are further configured to provide a d.c. voltage therebetween.

7. The high-frequency electron source as recited in claim 1 , wherein at least one of the first, keeper, and auxiliary electrodes include a metallic material selected from the group consisting of titanium, molybdenum, tungsten, aluminum, tantalum, and steel.

8. The high-frequency electron source as recited in claim 1 , wherein at least one of the first, keeper, and auxiliary electrodes include a non-metallic material selected from the group consisting of a graphite, a carbon compound, and a ceramic.

9. The high-frequency electron source as recited in claim 1 , wherein the high-frequency electron source is included in an ion source neutralizer.

10. The high-frequency electron source as recited in claim 1 , wherein the high-frequency electron source is included in an ion thruster.

11. The high-frequency electron source as recited in claim 1 , wherein the first electrode forms a plasma chamber.

12. The high-frequency electron source as recited in claim 11 , wherein the first electrode includes a hollow cathode.

13. The high-frequency electron source as recited in claim 1 , further comprising a high-frequency generator for generating the high-frequency electric field provided between the first electrode and the keeper electrode.

14. The high-frequency electron source as recited in claim 13 , wherein the first electrode is connected to an active output of the high-frequency generator and the keeper electrode has frame potential.

15. The high-frequency electron source as recited in claim 13 , wherein the high-frequency generator includes a radio frequency generator having an adaptation network.

16. The high-frequency electron source as recited in claim 15 , wherein the adaptation network includes a toroidal core transformer.

17. The high-frequency electron source as recited in claim 13 , wherein the keeper electrode is connected to an active output of the high-frequency generator and the first electrode has frame potential.

18. The high-frequency electron source as recited in claim 17 , further comprising a shield electrode surrounding the keeper electrode.

19. A high-frequency electron source, comprising:

a discharge chamber having at least one gas inlet for a gas to be ionized and at least one extraction opening for electrons;

a first electrode at least partially surrounding the discharge chamber and including a hollow cathode; and

a keeper electrode at least partially surround the discharge chamber, wherein the first electrode and the keeper electrode are configured to provide a high-frequency electric field therebetween.

20. The high-frequency electron source as recited in claim 19 , further comprising a plasma chamber surrounding the discharge chamber.

21. The high-frequency electron source as recited in claim 19 , wherein the high-frequency electric field is provided parallel to a direction of electron extraction.

22. The high-frequency electron source as recited in claim 19 , wherein the high-frequency electric field is provided perpendicular to a direction of electron extraction.

23. The high-frequency electron source as recited in claim 19 , wherein the high-frequency electric field has a frequency between 100 KHz and 50 MHz.

24. A high-frequency electron source, comprising:

a discharge chamber having at least one gas inlet for a gas to be ionized and at least one extraction opening for electrons;

a first electrode at least partially surrounding the discharge chamber;

a keeper electrode at least partially surround the discharge chamber; and

a shield electrode surrounding the keeper electrode, wherein the first electrode and the keeper electrode are configured to provide a high-frequency electric field therebetween.

25. The high-frequency electron source as recited in claim 24 , further comprising a high-frequency generator for generating the high-frequency electric field provided between the first electrode and the keeper electrode.

26. The high-frequency electron source as recited in claim 24 , wherein the high-frequency generator includes a radio frequency generator having an adaptation network.

27. The high-frequency electron source as recited in claim 24 , wherein the adaptation network includes a toroidal core transformer.

28. The high-frequency electron source as recited in claim 24 , wherein the keeper electrode is connected to an active output of the high-frequency generator and the first electrode has frame potential.

29. The high-frequency electron source as recited in claim 24 , wherein the first electrode is connected to an active output of the high-frequency generator and the keeper electrode has frame potential.

30. The high-frequency electron source as recited in claim 24 , wherein the first electrode and the second electrode are further configured to provide a d.c. voltage therebetween.