X-ray tube

• US 5,511,104 A
• Filed: 02/21/1995
• Issued: 04/23/1996
• Est. Priority Date: 03/11/1994
• Status: Expired due to Term

• Current Assignee: Siemens AG
• Original Assignee: Siemens AG
• Inventors: Friedel, Rudolf, Schmidt, Roland, Mueller, Werner, Bittl, Herbert, Krogmann, Henrik
• Primary Examiner(s): Porta, David P.
• Assistant Examiner(s): WONG, DON KITSUN
• Application Number:
  US08/393,932
• Time in Patent Office: 427 Days
• Field of Search: 378/119, 378/121, 378/125, 378/127, 378/137, 378/138, 378/139, 378/140, 378/141, 378/142
• US Class Current: 378/125
• CPC Class Codes: H01J 2235/168 against charged particles
• CPC Class Codes: H01J 35/16 Vessels; Containers; Shields associated therewith

Abstract

An x-ray tube, in addition to an anode and a cathode arrangement, has first and second electrodes that are located in an evacuated housing provided with a beam exit window. The anode and the first electrode are at potentials that are positive in comparison to the potentials of the cathode arrangement and the second electrode. Further, the first and the second electrode are arranged lying opposite one another such that secondary electrons emanating from the anode must pass through the space located between the first and the second electrode in order to proceed to the beam exit window. These secondary electrons are thus substantially all prevented from reaching the beam exit window, thereby avoiding excessive heating of the beam exit window.

Claims

1. An x-ray tube comprising:

an evacuated housing having a beam exit window;

a cathode assembly and an anode disposed in said housing;

means for placing said anode and said cathode assembly at respective electrical potentials with the electrical potential of said anode being positive in comparison to the electrical potential of said cathode assembly for causing said anode to emit x-rays, and said anode also emitting secondary electrons, said anode being oriented so that said x-rays exit said housing through said beam exit window; and

first and second electrodes disposed opposite each other in said housing and means for placing said first and second electrodes at respective electrical potentials with the electrical potential of said first electrode being positive in comparison to the electrical potential of said cathode assembly and the electrical potential of said second electrode, said first and second electrodes being oriented in said housing so that secondary electrons emanating from said anode must pass between said first and second electrodes before reaching said beam exit window, and said first and second electrodes and said means for placing said first and second electrodes at respective electrical potentials comprising, in combination, means for preventing substantially any of said secondary electrons from reaching said beam exit window.

6. An x-ray tube as claimed in claim 1 wherein at least one of said first and second electrodes comprises a plate-shaped electrode.

7. An x-ray tube as claimed in claim 6 wherein said anode has a substantially planar target surface and wherein said first electrode has a substantially planar surface facing said second electrode, said surface of said first electrode facing said second electrode being parallel to said target surface of said anode.

8. An x-ray tube as claimed in claim 6 wherein said anode has a substantially planar target surface, and wherein said second electrode has a substantially planar surface facing said first electrode, said substantially planar surface of said second electrode being parallel to said target surface of said anode.

9. An x-ray tube as claimed in claim 6 wherein said anode comprises a rotating anode having a target surface, and wherein said first electrode has a surface facing said second electrode disposed substantially parallel to said target surface of said rotating anode.

10. An x-ray tube as claimed in claim 6 wherein said anode comprises a rotating anode having a target surface, and wherein said second electrode has a surface facing said first electrode disposed substantially parallel to said target surface of said rotating anode.

11. An x-ray tube as claimed in claim 6 wherein said first and second electrodes have respective surfaces facing each other and said surfaces being spaced from each other so that said x-ray beam emanating from said anode and passing through said beam exit window proceeds completely between said surfaces of said electrodes.

12. An x-ray tube as claimed in claim 6 wherein said x-ray beam emanating from said anode has a central ray, and wherein said first and second electrodes have respective surfaces facing each other with at least one of said surfaces being disposed substantially parallel to said central ray.

13. An x-ray tube as claimed in claim 1 wherein said anode and said cathode assembly have a spacing therebetween including a smallest spacing, and wherein said first and second electrodes are spaced from each other by a distance which is not substantially less than said smallest spacing.

14. An x-ray tube as claimed in claim 1 wherein said anode and said cathode assembly have a spacing from each other which includes a smallest spacing, and wherein said second electrode is spaced from said housing by a distance which is not substantially less than said smallest spacing.

2. An x-ray tube as claimed in claim I wherein said means for placing said anode at an electrical potential and said means for placing said first electrode at an electrical potential comprise, in combination, means for placing said anode and said first electrode at a common, first potential, and wherein said means for placing said cathode assembly at an electrical potential and said means for placing said second electrode at an electrical potential comprise, in combination, means for placing said cathode assembly and said second electrode at a common, second potential which is negative in comparison to said first potential.

3. An x-ray tube as claimed in claim 2 further comprising means for placing said housing at said first potential in common with said anode and said first electrode.

4. An x-ray tube as claimed in claim 3 wherein said means for placing said housing at said first potential comprises a direct an electrical connection between said housing and said first electrode.

5. An x-ray tube as claimed in claim 2 wherein said means for placing said cathode assembly and said second electrode at said common, second potential comprises a direct electrically conductive connection between said second electrode and said cathode assembly.

15. An x-ray tube comprising:

an evacuated housing having a beam exit window;

a cathode assembly and an anode disposed in said housing;

means for placing said anode and said cathode assembly at respective electrical potentials with the electrical potential of said anode being positive in comparison to the electrical potential of said cathode assembly for allowing said anode to emit x-rays during operation of said x-ray tube, said anode being oriented so that said x-rays exit said housing trough said beam exit window, and secondary electrons emanating from said anode during operation of said x-ray tube; and

first and second electrodes disposed opposite each other in said housing and means for placing said first and second electrodes at respective electrical potentials with the electrical potential of said first electrode being positive in comparison to the electrical potential of said cathode assembly and the electrical potential of said second electrode and with the electrical potential of said second electrode being negative in comparison to the electrical potential of said anode, said first and second electrodes being oriented opposite each other in said housing so that secondary electrons emanating from said anode must pass between said first and second electrodes before reaching said beam exit window, and said first and second electrodes and said means for placing said first and second electrodes at respective electrical potentials, in combination, preventing substantially any of said secondary electrons from reaching said beam exit window.