Cooling device for x-ray generators

Abstract

A cooling device for x-ray tubes in x-ray generators, comprising a housing with a central receiving device for receiving an x-ray tube with an inlet opening for supplying a gaseous coolant, an outlet opening for discharging the gaseous coolant, and a gas-conducting channel which extends between the inlet opening and the outlet opening. The gas-conducting channel is designed to conduct the gaseous coolant directly by the high-voltage x-ray tube housing during operation. The gas-conducting channel additionally extends in a helical manner about the x-ray tubes such that the electric potential applied to the x-ray tubes drops to zero potential along the gas-conducting channel.

Claims

1. A cooling device for x-ray tubes in x-ray generators comprising a housing with a central receiving device for receiving an x-ray tube, an inlet opening for supplying a gaseous cooling medium, an outlet opening for discharging the gaseous cooling medium and a gas-conducting channel, which extends between the inlet opening and the outlet opening, wherein the gas-conducting channel is designed such that it guides the gaseous cooling medium directly past the high-voltage housing of the x-ray tube during operation, and wherein the gas-conducting channel extends spirally around the x-ray tube, with the result that the electric potential applied to the x-ray tube drops to zero potential along the gas-conducting channel, and the gas-conducting channel is formed of at least two spirally arranged inner walls of the housing of the cooling device.

2. The cooling device for x-ray generators according to claim 1, wherein the housing of the cooling device consists of electrically insulating material, including one or more thermoplastic materials including polycarbonate, PVC or polyolefins, of Plexiglas or of polyoxymethylene.

3. The cooling device for x-ray generators according to claim 1, wherein the thickness of the inner walls is chosen such that the sum of the wall thicknesses in the radial direction is sufficiently large, with the result that, in the case of the high voltage used in each case, a radial sparking is prevented through the inner walls.

4. The cooling device for x-ray generators according to claim 1, wherein the housing of the cooling device comprises two housing parts connected in a re-sealable manner, and each housing part comprises spiral inner walls which, in the assembled state, engage in one another and thereby define the gas-conducting channel.

5. The cooling device for x-ray generators according to claim 1, wherein one housing part of the cooling device is or can be connected to a high-voltage generator, and wherein the other housing part of the cooling device is or can be connected to an x-ray tube.

6. An x-ray generator comprising: the cooling device according to claim 1, a high-voltage generator and an x-ray tube, wherein the high-voltage generator generates the high voltage necessary for the operation of the x-ray tube, wherein the x-ray tube is mechanically and electrically connected to the high-voltage generator via a high-voltage contact, and wherein the cooling device extends spirally around the x-ray tube in order to cool the x-ray tube and at the same time to shield it electrically.

7. A method for cooling an x-ray generator comprising the steps of: providing a high-voltage generator for generating a high voltage, providing an x-ray tube which can be mechanically and electrically connected to the high-voltage generator via a high-voltage contact, providing a cooling device comprising a housing including a central receiving device for receiving an x-ray tube, an inlet opening for supplying a gaseous cooling medium, an outlet opening for discharging the gaseous cooling medium and a gas-conducting channel, which extends between the inlet opening and the outlet opening, wherein the gas-conducting channel is designed such that it guides the gaseous cooling medium directly past the high-voltage housing of the x-ray tube during operation, wherein the gas-conducting channel extends spirally around the x-ray tube, with the result that the electric potential applied to the x-ray tube drops to zero potential along the gas-conducting channel, and the gas-conducting channel is formed of at least two spirally arranged inner walls of the housing of the cooling device, wherein the gas-conducting channel of the cooling device extends spirally around the x-ray tube in order to cool the x-ray tube and at the same time to shield it electrically, wherein a gaseous cooling fluid is conducted through the cooling system for cooling the x-ray generator.

8. The method according to claim 7, wherein the cooling power of the cooling device provided by the gaseous cooling fluid is up to 40 W.

9. The method according to claim 7, wherein the x-ray tube is operated in pulsed mode, with the result that the generation of waste heat is reduced.

10. The method according to claim 8, wherein the x-ray tube is operated in pulsed mode, with the result that the generation of waste heat is reduced.

11. A cooling device for x-ray tubes in x-ray generators comprising a housing with a central receiving device for receiving an x-ray tube, an inlet opening for supplying a gaseous cooling medium, an outlet opening for discharging the gaseous cooling medium and a gas-conducting channel, which extends between the inlet opening and the outlet opening, wherein the gas-conducting channel is designed such that it guides the gaseous cooling medium directly past the high-voltage housing of the x-ray tube during operation, and wherein the gas-conducting channel extends spirally in a radial direction around the x-ray tube, with the result that the electric potential applied to the x-ray tube drops to zero potential along the gas-conducting channel.

12. The cooling device for x-ray generators according to claim 11, wherein the housing of the cooling device consists of electrically insulating material, including one or more thermoplastic materials including polycarbonate, PVC or polyolefins, of Plexiglas or of polyoxymethylene.

13. The cooling device for x-ray generators according to claim 11, wherein the gas-conducting channel is formed of at least two spirally arranged inner walls of the housing of the cooling device.

14. The cooling device for x-ray generators according to claim 11, wherein the device comprises the inner walls having a thickness chosen such that the sum of the wall thicknesses in the radial direction is sufficiently large, with the result that, in the case of the high voltage used in each case, a radial sparking is prevented through the inner walls.

15. The cooling device for x-ray generators according to claim 11, wherein the housing of the cooling device comprises two housing parts connected in a re-sealable manner, and each housing part comprises spiral inner walls which, in the assembled state, engage in one another and thereby define the gas-conducting channel.

16. The cooling device for x-ray generators according to claim 11, wherein one housing part of the cooling device is or can be connected to a high-voltage generator, and wherein the other housing part of the cooling device is or can be connected to an x-ray tube.

17. An x-ray generator comprising: the cooling device according to claim 11, a high-voltage generator and an x-ray tube, wherein the high-voltage generator generates the high voltage necessary for the operation of the x-ray tube, wherein the x-ray tube is mechanically and electrically connected to the high-voltage generator via a high-voltage contact, and wherein the cooling device extends spirally around the x-ray tube in order to cool the x-ray tube and at the same time to shield it electrically.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiment examples of the disclosure are explained in the following with reference to the drawings, in which:

(2) FIG. 1 is a structure of a cooling device according to the disclosure in an x-ray generator;

(3) FIG. 2 is a radial cross section of the cooling device according to the disclosure along the broken line 2-2 from FIG. 1;

(4) FIG. 3 is a schematic curve of the electrical potential through the inside of the cooling device according to the disclosure;

(5) FIG. 4 is a two-part embodiment of the cooling device according to the disclosure;

(6) FIG. 5 is the two housing parts of the embodiment according to FIG. 4; and

(7) FIG. 6 is an axial cross section through the cooling device according to FIG. 4.

DETAILED DESCRIPTION

(8) FIG. 1 shows an arrangement 10 according to the disclosure for generating x-ray radiation, comprising an x-ray tube 12, a cooling device 14 and a high-voltage source 16. The cooling device 14 extends around part of the x-ray tube 12 and serves both for cooling and for electrical insulation of the x-ray tube 12 from the surroundings.

(9) The cooling device 14 has a housing 18 with a gas inlet opening 20 and a gas outlet opening 22 for supplying or for discharging the gaseous coolant. In the interior of the cooling device 14, the coolant is guided past the x-ray tube 12 on a spiral path in a gas-conducting channel 24. The coolant absorbs the heat generated by the x-ray tube 12 and dissipates it to the surroundings.

(10) The x-ray tube 12 is usually operated at a high voltage of between 20 and 150 kV. The required high voltage is provided by the high-voltage source 16 and applied to the x-ray tube 12 via a correspondingly provided contacting. In order to guarantee the operational safety of the arrangement, the accessible housing parts, in particular the housing 18 of the cooling device 14, are connected to ground.

(11) The cooling device 14 therefore not only needs to be designed such that the heat generated by the x-ray tube 12 can be dissipated but must at the same time also insulate the x-ray tube 12 electrically with respect to the surroundings.

(12) The housing 18 of the cooling device 14 is therefore expediently manufactured from thermoplastic, e.g. from polysulfone. In the embodiment shown in FIG. 1, the gas inlet opening 20 and the gas outlet opening 22 are each located on an end wall of the housing 18 of the cooling device 14.

(13) The course of the gas-conducting channel 24 in the interior of the cooling device 14 is depicted in the cross section of FIG. 2. The cross section is taken along the line 2-2 from FIG. 1. The cooling gas is conducted from the gas inlet opening 20 along the spiral gas-conducting channel 24 through the housing 18 of the cooling device 14. In the centre of the cooling device 14, the cooling gas enters into a heat exchange relationship with the x-ray tube 12 and absorbs heat generated by the x-ray tube 12. The heated cooling gas is then guided further through the gas-conducting channel 24 until it finally exits the housing 18 of the cooling device 14 at the gas outlet opening 22. The inner walls of the cooling device, which are arranged helically and define the gas-conducting channel 24, predefine the route of the gas stream by means of their spiral arrangement.

(14) The length of the gas-conducting channel 24 must be dimensioned such that sparking between the centrally arranged x-ray tube 12 at high-voltage potential and the outside of the housing 18 of the cooling device 14 at ground potential is prevented.

(15) The minimum length of the gas-conducting channel to be used in each case depends on the level of the operating voltage of the x-ray tube. In general it can be said that the length of the gas-conducting channel should be approximately 3 mm/kV. In the case of a 100-kV x-ray tube this means that the length of the gas-conducting channel between the centrally arranged x-ray tube and the gas inlet opening or the gas outlet opening should be approximately 30 cm.

(16) In order to guarantee the operational safety of the arrangement 10, not only must the spiral gas-conducting channel 24 of the cooling device 14 be designed sufficiently long but it must also be ensured that no sparking can occur in the radial direction through the inner and outer walls of the housing 18 of the cooling device 14.

(17) In order to prevent such radial sparking, the sum of the wall thicknesses of the gas-conducting channel 24 in the radial direction of the cooling device 14 must be chosen such that the resulting total wall thickness prevents such sparking. The required total thickness of the walls depends on the dielectric properties of the material which is used for the housing 18 of the cooling device 14. Typically used thermoplastics have a dielectric strength of from 10 to 20 kV/mm. For a 100-kV x-ray tube this in turn means that a total wall thickness of approximately 10 mm should be provided in order to also prevent radial sparking.

(18) The curve of the electrostatic potential in the radial direction along the line 3-3 of FIG. 2 is represented by way of example in FIG. 3. The line 3-3 runs in the radial direction from the outside of the housing 18 through three wall areas A, B, C to the x-ray tube 12. On this route, the entire high-voltage potential of the x-ray tube drops to ground. Because of the much higher dielectric constant of the plastic material of the cooling device 14 compared with the dielectric constant of air, there is a much steeper drop in potential within the wall areas A, B, C than inside the gas-conducting channel 24. As can be seen from the potential curve in FIG. 3, the total thickness of the wall areas is dimensioned sufficiently, with the result that the entire electric potential of the x-ray tube can drop in the radial direction over the wall areas without arcing occurring.

(19) FIGS. 4 to 6 show a preferred embodiment of the present disclosure in which the housing 18 of the cooling device 14 is designed in two parts. One part 18a of the housing of the cooling device 14 is connected to the high-voltage generator 16. The other part 18b of the housing 18 is connected to the x-ray tube 12. As illustrated in FIG. 5, the two housing parts 18a, 18b each comprise spirally arranged inner walls 26a, 26b which define the spiral gas-conducting channel 24. The outer walls of the two housing components 18a, 18b are designed such that they form a stable plug-in connection. In the assembled state, the spiral inner walls 26a, 26b engage in each other in the axial direction such that the free ends of the inner walls of one housing part 18a, 18b reach in each case to the end wall 28b, 28a of the respectively other housing part 18b, 18a. The thus-defined gas-conducting channel 24 substantially corresponds to the gas-conducting channel 24 as it was described with reference to FIGS. 1 to 3.

(20) In order to prevent sparking also in this embodiment of the cooling device 14, the same criteria as in the previously described embodiment apply to the length of the gas-conducting channel 24 and to the sum of the wall thicknesses in the radial direction.

(21) FIG. 6 shows a cross section in the axial direction through a cooling device designed in two parts. As already discussed above, although the spiral inner walls 26a, 26b of the individual housing parts 18a, 18b extend in each case to the end walls 28b, 28a of the respectively other housing part 18b, 18a, an airtight connection is not absolutely necessary to achieve the cooling effect of the present disclosure. However, a non-airtight connection between the two housing parts opens up a further potential route for sparking through the cooling device.

(22) This potential route for sparking is represented in FIG. 6. The two housing parts 18a and 18b each have a circular end wall 28a and 28b. The spiral inner walls 26a and 26b which form the gas-conducting channel 24 extend in each case from this end wall. The size of the axial extent of the inner walls 26a and 26b in each case is such that the free ends thereof touch the respectively opposite end wall 28b and 28a, with the result that in this embodiment too the gaseous cooling medium is substantially conducted along the thus-formed gas-conducting channel 24.

(23) Remaining interspaces between the free ends of the inner walls 26a and 26b and the respectively opposite end walls 28a and 28b are represented exaggerated in FIG. 6 for reasons of clarity. In actual cooling devices, at the most narrow slits would occur, which would allow only a very small quantity of cooling fluid to pass through.

(24) However, even narrow slits would be sufficient to make sparking possible. A potential spark path is drawn in as a broken line in FIG. 6. Since narrow slits between the housing parts cannot be avoided or are to be accepted because of the negligible impact on the cooling effect, in this embodiment it must be ensured that the depth of the inner walls 26a, 26b of the two housing parts 28a, 28b engaging in each other is chosen such that the resulting spark gap is likewise again long enough to prevent sparking along the potential spark path drawn in FIG. 6 at the high voltages used.

(25) Moreover, when non-hazardous cooling gases such as air or nitrogen are used it is also not absolutely necessary to ensure a completely gas-tight connection between the two housing parts 18a and 18b. Nevertheless, escaping cooling gas does mix with the ambient air, but does not lead to contamination of the components or of the products to be examined, in contrast to the dielectric oils otherwise usually used.

(26) The above embodiments serve only to illustrate the present disclosure and are not to be interpreted as limiting. Of course, a person skilled in the art will also combine individual or all features which are described in connection with individual embodiments with other embodiments of the present disclosure.

LIST OF REFERENCE NUMERALS

(27) 10 x-ray generator arrangement 12 x-ray tube 14 cooling device 16 HV generator 18 housing of the cooling device 20 gas inlet opening 22 gas outlet opening 24 gas-conducting channel 26 inner walls of the housing 28 end walls of the housing 30 potential spark gap