WO2009068891A4

WO2009068891A4 - Precession anode x-ray tube

Info

Publication number: WO2009068891A4
Application number: PCT/GB2008/003979
Authority: WO
Inventors: Damian Kucharczyk; Paul William Loeffen
Original assignee: Oxford Diffraction Ltd; Damian Kucharczyk; Paul William Loeffen
Priority date: 2007-11-30
Filing date: 2008-11-28
Publication date: 2009-07-16
Also published as: GB2455140A; EP2225769A1; JP2011505657A; GB0723513D0; WO2009068891A1

Abstract

An X-ray tube is described having a filament for generating electrons (5), a cathode, and an anode (8) which comprises an elongate member (17) having a fixed point relative to the sealed housing of the tube and an end that is moveable relative to the sealed housing. The longitudinal axis of the elongate member in a rest position is laterally displaced relative to the path of the accelerating electrons, whereby a spherical target surface on the moveable end of the member may be moved relative to the impinging electrons such that the spatial location of X-ray generation in the tube is invariant relative to the sealed housing, thereby spreading localised heating caused by the X-ray generation over a greater portion of the target surface. The member is typically driven such that the anode precesses about the X-ray beam.

Claims

30AMENDED CLAIMS received by the International Bureau on 01 June 2009 (01.06.09); original claims 1-29 replaced by amended claims 1-16.

1. An X-ray tube comprising a sealed housing defining an interior vacuum envelope when evacuated, the housing including a window through which generated X-rays exit, the X-ray tube further comprising within the housing: a filament for generating electrons; a cathode; and, an anode spatially separated from the cathode, the anode and the cathode adapted to define a potential difference therebetween for accelerating electrons from the filament so as to impinge on a target surface of the anode and thereby generate X-rays, wherein the anode comprises an elongate member having a first end and a second end, the anode being configured such that: a longitudinal axis of the elongate member in a rest position is laterally displaced relative to the path of the accelerating electrons; a point on the length of the elongate member from the first end to the second end is substantially fixed relative to the sealed housing; the target surface of the anode is spherical and is disposed on the second end of the elongate member, whereby in the rest position the electrons impinge on a part of the spherical target surface inclined towards the window in the housing; and, the second end of the elongate member is moveable relative to the sealed housing, whereby the spherical target surface may be moved relative to the impinging electrons such that the spatial location of X-ray generation in the tube is invariant relative to the sealed housing, thereby spreading localised heating caused by the X-ray generation over a greater portion of the target surface.

2. An X-ray tube according to claim 1 , in which the longitudinal axis of the elongate member lies along a radius of the spherical target surface and the radius is equal to the distance from the anode surface to the substantially fixed point on the length of the elongate member. 31

3. An X-ray tube according to claim 1 or claim 2, in which the anode is adapted to be driven such that the target surface of the second end moves along an oscillatory path relative to the impinging electrons.

4. An X-ray tube according to claim 3, in which the anode is adapted to be driven such that the target surface of the second end moves along an elliptical oscillatory path relative to the impinging electrons.

5. An X-ray tube according to claim 1 or claim 2, in which the anode is adapted to be driven such that the target surface is exposed to the impinging electrons for an exposure time which is varied in a predetermined manner.

6. An X-ray tube according to any preceding claim, further comprising means for anti-resonant damping of the motion of the elongate member.

7. An X-ray tube according to any one of claims 1 to 6, in which the elongate member of the anode comprises a flexible monolithic rod which is fixed at the first end relative to the housing and is moveable relative to the housing at the-«second end by a flexing action.

8. An X-ray tube according to claim 7, in which the rod passes through an airtight aperture in the housing and is formed of a thermally conductive material for conducting heat away from the target surface and to the exterior of the housing.

9. An X-ray tube according to any one of claims 1 to 6, in which the elongate anode member is rigid and comprises an internal pathway for the flow of a liquid coolant to and from the proximity of the target surface for conducting heat away from the target surface, wherein the internal pathway comprises a diffusing structure proximate the target surface for diffusing the coolant to ensure uniform cooling.

10. An X-ray tube according to claim 9, further comprising flexible tubing coupled to the internal pathway of the rigid member and to the exterior of the housing for carrying the coolant to and from the rigid member, wherein the tubing is configured as a double helix around the rigid member at the first end.

11. An X-ray tube according to any one of claims 1 to 6, in which the elongate anode member is rigid and comprises an internal pathway for the flow of a liquid coolant to and from the proximity of the target surface for conducting heat away from the target surface, the X-ray tube further comprising flexible tubing coupled to the internal pathway of the rigid member and to the exterior of the housing for carrying the coolant to and from the rigid member, wherein the tubing is configured as a double helix around the rigid member at the first end.

12. An X-ray tube according to any one of claims 9 to 11 when dependent on claim 6, wherein the anti-resonant damping means comprises liquid coolant flowing in or around the rigid member.

13. An X-ray tube according to claim 6, in which the elongate anode member is rigid and comprises an internal pathway for the flow of a liquid coolant to and from the proximity of the target surface for conducting heat away from the target surface, wherein the anti-resonant damping means comprises liquid coolant flowing in or around the rigid member.

14. An X-ray tube according to any one of claims 1 to 6 or claims 9 to 11 , in which the elongate anode member is rigid and comprises an internal pathway for the flow of a liquid coolant to and from the proximity of the target surface for conducting heat away from the target surface, wherein the anode is adapted to be driven by the passage of the liquid coolant so as to move the target surface relative to the impinging electrons.

15. An X-ray tube according to any one of claims 1 to 13, further comprising means within the housing for conveying an electromagnetic driving force to the second end of the elongate member for moving the second end, wherein the force conveying means comprises a disc of magnetic material having a central aperture through which the elongate member passes proximate the second end and having a peripheral region retained in an annular slot in the housing.

16. An X-ray tube assembly comprising an X-ray tube according to any one of claims 1 to 13 and a mechanical actuator disposed external to the housing for 33

driving the anode so as to move the target surface relative to the impinging electrons.