Ion sensor

1. An ion sensor comprising:

an annular electron repelling electrode to be placed at a negative electric potential, wherein the electron repelling electrode is formed by a diaphragm element having a single central circular diaphragm opening for the passage of an ion beam,

an ion repelling electrode to be placed at a variable positive electric potential, and

a collector face for detecting impinging ions,

wherein the ion repelling electrode forms a blind hole which faces the diaphragm opening with an open hole end and a hole surface of which forms the collector face.

2. The ion sensor according to claim 1 , wherein the hole bottom of the blind hole is formed with a depression.

3. The ion sensor according to claim 2 , wherein the depression is in the form of a conical funnel.

4. The ion sensor according to claim 3 , wherein the funnel angle is between 100 and 135 degrees.

5. The ion sensor according to claim 3 , wherein the funnel angle is between 105 and 130 degrees.

6. The ion sensor according to claim 3 , wherein the funnel angle is between 110 and 125 degrees.

7. The ion sensor according to claim 3 , wherein the funnel angle is between 115 and 120 degrees.

8. The ion sensor according to claim 3 , wherein the funnel angle is approximately 118 degrees.

9. The ion sensor according to claim 1 , wherein the blind hole has a cylindrical hole perimeter.

10. The ion sensor according to claim 9 , wherein the cylindrical hole perimeter is circular-cylindrical.

11. The ion sensor according to claim 1 , wherein the blind hole has a constant cross-section, starting from the open hole end, at least over a large part of its hole depth reaching to the hole bottom.

12. The ion sensor according to claim 1 , wherein the blind hole has a minimum hole depth of not less than 15 mm.

13. The ion sensor according to claim 1 , wherein the blind hole has a maximum hole depth of not less than 18 mm.

14. The ion sensor according to claim 1 , wherein the blind hole has a maximum hole depth of not less than 21 mm.

15. The ion sensor according to claim 1 , wherein the blind hole has a maximum hole depth of not more than 34 mm.

16. The ion sensor according to claim 1 , wherein the blind hole has a maximum hole depth of not more than 31 mm.

17. The ion sensor according to claim 1 , wherein the blind hole has a maximum hole depth of not more than 28 mm.

18. The ion sensor according to claim 1 , wherein the ion repelling electrode is formed by a cup body, the cup height of which is greater than the cup inside diameter.

19. The ion sensor according to claim 18 wherein the cup height is at least 1.3 times greater than the cup inside diameter.

20. A method of using an ion sensor for testing a plasma, the ion sensor comprising:

an annular electron repelling electrode which is to be placed at a negative electric potential, wherein the electron repelling electrode is formed by a diaphragm element having a single central circular diaphragm opening for the passage of an ion beam,

an ion repelling electrode which is to be placed at a variable positive electric potential, and

a collector face for detecting impinging ions,

wherein the ion repelling electrode forms a blind hole which faces the diaphragm opening with an open hole end and a hole surface of which forms the collector face;

the method comprising the steps:

connecting the electron repelling electrode to a source of a negative electric potential,

connecting the ion repelling electrode to a source of a variable positive electric potential,

introducing the ion sensor into an ion beam, and

measuring an electric current tapped at the ion repelling electrode.