Anode

Abstract

An anode has a base member, on which an X-ray active layer is applied. A first cooling circuit with a first cooling medium extends at least in part in the base member beneath the X-ray active layer. A second cooling circuit with a second cooling medium is arranged beneath the first cooling circuit. The anode exhibits distinctly improved thermo mechanical properties.

Claims

1. An anode, comprising: a base member; an X-ray active layer disposed on said base member, said X-ray active layer including tungsten; at least one first cooling circuit with a first cooling medium extending at least in part in said base member beneath said X-ray active layer; at least one second cooling circuit with a second cooling medium disposed beneath said first cooling circuit; at least one protective layer separating said X-ray active layer from at least one first cooling circuit.

2. The anode according to claim 1, wherein said first cooling circuit, in which the first cooling medium circulates, comprises at least one first cooling duct which is arranged at least in part in said base member.

3. The anode according to claim 1, wherein said second cooling circuit, in which the second cooling medium circulates, comprises at least one second cooling duct which is arranged at least in part in said base member.

4. The anode according to claim 1, wherein said second cooling circuit, in which the second cooling medium circulates, comprises at least one second cooling duct which is arranged outside said base member.

5. The anode according to claim 1, wherein said base member consists of a material having a thermal conductivity 130 W.Math.m-1.Math.K-1.

6. The anode according to claim 1, wherein said at least one first cooling circuit has a plurality of first cooling ducts, and wherein at least one of said first cooling ducts is arranged at least in part at a distance of 0.2 mm to 0.5 mm below said X-ray active layer.

7. The anode according to claim 6, wherein at least one said first cooling duct has a cross-section of 0.5 mm.Math.1.0 mm.

8. The anode according to claim 1, wherein said at least one first cooling circuit has a plurality of first cooling ducts, and wherein said first cooling ducts are arranged at a distance of 0.5 mm from one another.

9. The anode according to claim 1, wherein the first cooling medium consists of at least one liquid metal.

10. The anode according to claim 9, wherein said liquid metal contains gallium.

11. The anode according to claim 1, which comprises at least one separator separating said first cooling circuit and said second cooling circuit from one another.

12. The anode according to claim 1, wherein, in an operating state of the anode, the first cooling medium has a flow velocity vS of 10 mm/s.

13. The anode according to claim 1, wherein a direction of flow of the first cooling medium is oriented substantially perpendicular to a major extent of said X-ray active layer.

14. The anode according to claim 1, which comprises a positive-displacement pump arranged in said first cooling circuit.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

(1) FIG. 1 shows a diagrammatic partial section of a base member of an anode; and

(2) FIG. 2 shows a perspective detail view of a first cooling structure in the base member of the anode according to FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION

(3) Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown an anode 1 which, in the exemplary embodiment shown, takes the form of a stationary anode (fixed anode).

(4) The anode 1 comprises a base member 2 to which an X-ray active layer 3 is applied.

(5) The X-ray active layer 3 consists for example of tungsten and has a thickness of for example approx. 20 m to approx. 500 m. In the operating state, the X-ray active layer 3 is bombarded with electrons which are accelerated towards the anode 1 and focused into an electron beam 5. On impingement of the electron beam 5, X-rays (Bremsstrahlung) are generated in the X-ray active layer 3 in a focal spot 6.

(6) The focal spots typically used in medical technology today have a length c of approx. 5 mm to 10 mm and a width d of approx. 1 mm.

(7) According to the invention, at least one first cooling circuit 11 with a first cooling medium 12 extends at least in part in the base member 2 beneath the X-ray active layer 3. Furthermore, according to the invention, at least one second cooling circuit 21 with a second cooling medium 22 is arranged beneath the first cooling circuit 11.

(8) In the exemplary embodiment shown in FIG. 1, the first cooling circuit 11, in which the first cooling medium 12 circulates at a flow velocity v.sub.S, comprises at least one first cooling duct 13 which is arranged at least in part in the base member 1. As shown in FIG. 2, the first cooling circuit 11 preferably comprises a plurality of first cooling ducts 13. Because of the selected representation, only one first cooling duct 13 of the first cooling ducts 13 is visible in FIG. 1.

(9) The first cooling circuit 11 thus forms a first cooling structure 10 with a predeterminable number of first cooling ducts 13.

(10) The first cooling medium 12, which for example contains gallium, may be heated to elevated temperatures of for example up to approx. 2,000 C.

(11) The second cooling circuit 21, in which the second cooling medium 22 circulates, furthermore comprises at least one second cooling duct 23 which is arranged at least in part in the base member 2.

(12) The second cooling circuit 21 thus forms a second cooling structure 20 with the second cooling duct 23.

(13) The second cooling medium 22 is typically water with appropriate additions, for example anticorrosion agent, antifreeze and biocide.

(14) In the exemplary embodiment shown, the first cooling circuit 11 and the second cooling circuit 21 are separated from one another by a separator 30. Arranging at least one separator 30 between the first cooling circuit 11 and the second cooling circuit 21 makes it straightforwardly possible to increase surface area on at least one side, for example by forming grooves or by sand-blasting.

(15) The X-ray active layer 3 is furthermore separated from the first cooling circuits 11 of the first cooling structure 10 by a protective layer 40. Arranging at least one protective layer 40 between the X-ray active layer 3 and the first cooling circuit 11 makes it possible to select the material of the X-ray active layer 3 very largely independently of the first cooling medium 12.

(16) In the solution according to the invention, the direction and flow rate combined with the admissible high temperature level of the first cooling medium 12 accelerate heat propagation and thus heat dissipation in the focal spot 6 (region occupied by the electron beam 5).

(17) In order to achieve the necessary flow velocity for the first cooling medium 12 in the embodiment of the anode 1 shown in FIG. 1, a positive-displacement pump 14 is arranged in the first cooling circuit 11.

(18) A large area at a high temperature level is furthermore achieved. As a result, more heat can be transported from the high temperature level in the first cooling circuit 11 (first temperature level) to the second cooling circuit 21 which, relative to the first cooling circuit 11, has a lower temperature level (second temperature level). At the same time, the high temperature of the first cooling medium 12 reduces thermo mechanical stresses in the X-ray active layer 3, so likewise here extending load limits towards a higher electron intensity. Moreover, the boiling temperature of the second cooling medium 22 (for example water) no longer limits the temperature of the first cooling medium 12 (for example liquid metal).

(19) In the development shown in FIG. 1 of the anode 1 which comprises a plurality of first cooling ducts 13, the first cooling ducts 13 are, as shown in FIG. 2, arranged at a distance t of 0.2 mm to 0.5 mm below the X-ray active layer 3. The maximal possible layer thickness of the separator 40 corresponds to the distance t between the cooling duct 13 and the X-ray active layer 3.

(20) In the embodiment shown, the first cooling ducts 13 have a cross-section Q of 0.5 mm.Math.1.0 mm, wherein the cross-sections Q, as shown in FIG. 2, need not necessarily be rectangular. Depending on circumstances or requirements, other cross-sections may also be convenient for the first cooling ducts 13. Cross-sections which may be provided as required include for example circular, triangular or oval cross-sections. In the case of a plurality of first cooling ducts 13, different cross-sections may also be provided for each individual first cooling duct 13. It may also be advantageous in individual cases not to retain a constant cross-section of the first cooling duct 13 in question but instead, as a function of thermodynamic conditions, to vary this cross-section Q over the length of the first cooling duct 13. In the exemplary embodiment shown in FIG. 1, the first cooling duct 13 has a smaller cross-section Q beneath the X-ray active layer 3 than in the adjoining regions.

(21) In the case of a plurality of first cooling ducts 13, it is advantageous, as shown in FIG. 2, to arrange the first cooling ducts 13 at a distance a of 0.5 mm from one another.

(22) When selecting a (width of the first cooling duct) and a (distance of the cooling ducts from one another), a is <c (approx. by a factor of >10), c being the length of the focal spot, and a is <c (approx. by a factor of 10). In addition, a may be no greater than the distance t between the X-ray active layer and the first cooling structure.

(23) The direction of flow of the first cooling medium 12 need not necessarily be constant within the first cooling structure 10. Instead, the flow of the first cooling medium 12 within the first cooling structure 10 may vary by an appropriate course of the first cooling ducts 13. Advantageously, the direction of flow of the first cooling medium 12 is oriented substantially perpendicular to the greater extent of the X-ray active layer 3 and thus perpendicular to the longitudinal direction of the X-ray active layer 3 (see FIG. 2).

(24) FIG. 1 and FIG. 2 show a combination of a (miniaturized version of a) liquid metal cooling system (in a first cooling circuit 11) with a water cooling system (in a second cooling circuit 21) in a stationary anode. Due to the rapid passage of the first cooling medium 12 (liquid metal) in the first cooling circuit 11, the cooling area is locally flared.

(25) The invention is, however, not restricted to this exemplary embodiment. Instead, it is straightforwardly possible, on the basis of the described embodiment, for a person skilled in the art also to create other advantageous developments of the inventive concept defined in the following claims.

(26) The solution shown is accordingly suitable not only for stationary anodes but also for rotating anodes (rotary anode X-ray tubes or rotary piston X-ray tubes). At least one rotary transmission lead through, not shown in FIG. 1, for the cooling media involved is necessary in the case of a rotating anode (rotary anode) for transferring the first cooling medium 12 and optionally the second cooling medium 22 to the rotating system.

(27) Combinations of different first cooling media with different second cooling media are furthermore possible for the purposes of the invention.