COATED X-RAY WINDOW

• US 20150146866A1
• Filed: 05/29/2012
• Published: 05/28/2015
• Est. Priority Date: 05/29/2012
• Status: Active Grant

• Current Assignee: Excillum Ab
• Original Assignee: Excillum Ab
• Inventors: Tuohimaa, Tomi, Hemberg, Oscar
• Granted Patent: US 9,245,707 B2
• Time in Patent Office: Days
• US Class Current: 378/140
• CPC Class Codes: H01J 35/025 X-ray tubes with structurally associated circuit elements
• CPC Class Codes: H01J 35/18 Windows
• CPC Class Codes: H05G 1/02 Constructional details

Abstract

An X-ray window includes a primary and a secondary window element. In order to evaporate debris by ohmic heating, current flows through the secondary (upstream) window element. Meanwhile, electric charge originating from electron irradiation and/or depositing charged particles is to be drained off the secondary window element via a charge-drain layer. To prevent large debris particles from short-circuiting the secondary window element, the current for heating the window element flows through heating circuitry which is electrically insulated from the charge-drain layer.

Claims

1. An X-ray window for separating an ambient pressure region from a reduced pressure region, the window comprising:

a primary X-ray-transparent window element separating the ambient pressure region from an intermediate region;

a secondary window element separating the intermediate region from the reduced pressure region, which secondary window element comprises a side facing the reduced pressure region for receiving a contaminant depositing thereon; and

heating means for applying an electric voltage between terminals of said secondary window element for thereby evaporating contaminant having deposited thereon,

wherein said secondary window element comprises;

a charge-drain layer, which faces the reduced pressure region and is connected to a charge sink; and

heating circuitry, which is electrically insulated from the charge-drain layer, wherein said terminals, between which the voltage is applied, are located at a plurality of distinct points on the heating circuitry.

2. The X-ray window of claim 1, wherein the heating circuitry comprises an insulated wire.

3. The X-ray window of claim 2, wherein the heating circuitry is arranged in abutment with the charge-drain layer.

4. The X-ray window of claim 1, further comprising an electrically insulating layer arranged to electrically insulate the charge-drain layer from the heating circuitry.

5. The X-ray window of claim 1, wherein the secondary window element further comprises a first region and a second region, wherein the first region has a higher transparency to X-ray radiation than the second region.

6. The X-ray window of claim 4, wherein the electrically insulating layer comprises an indentation located in said first region.

7. The X-ray window of claim 4, wherein the electrically insulating layer defines an aperture located in said first region.

8. The X-ray window any of claim 1, wherein the heating circuitry is arranged in an undulating pattern.

9. The X-ray window of claim 4, wherein the undulating pattern has a lower density in said first region than in said second region.

10. The X-ray window of claim 1, wherein the charge-drain layer defines an indentation located in said first region.

11. The X-ray window of claim 1, wherein the heating circuitry is a bifurcated circuit.

12. The X-ray window of claim 1, wherein the window is secured by being inserted into a slit after coating with colloidal graphite.

13. The X-ray window of any of claim 1, wherein the heating circuitry contains one of the following materials:

graphite,

pyrolytic carbon,

high-resistance metal,

high-resistance alloy.

14. The X-ray window of claim 4, wherein:

the heating wire is encapsulated in the electrically insulating layer.

15. The X-ray window of claim 4, wherein:

the heating circuitry extends at most over the electrically insulating layer; and

the charge-drain layer extends at least a distance outside the heating circuitry, at least over a portion of the boundary.

16. The X-ray window of claim 14, wherein a portion of the boundary of the window is inserted into a slit in a reservoir containing electrically conducting fluid.

17. The X-ray window of any one of claim 1, wherein the electrically insulating layer extends at least a first distance outside the heating wire and at least a second distance outside the charge-drain layer, at least over a portion of the boundary.

18. An X-ray-source housing comprising:

a gas-tight housing; and

the X-ray window of claim 1, provided in an outer wall of said housing.

19. An X-ray source comprising:

the X-ray-source housing of claim 18;

an electron source provided inside the housing; and

a liquid-jet electron target provided inside the housing.