X-RAY RADIATION GENERATOR

Abstract

The present invention relates to an X-ray tube (30) with an anode (36) that conducts a high voltage, preferably greater than 120 kV, particularly preferably greater than 300 kV, and heats up during operation, wherein the anode is connected in a thermally conductive way to a heat sink (4), which has a base body (10.4) composed of a metal with a heat absorbing surface (12.4) for coupling to the anode (36) as a heat source (36) and a heat dissipating surface (14.4) that is enlarged by means of heat dissipating elements (16.4) that are connected to the base body (10.4), wherein the heat dissipating elements (16.4) are composed of an electrically insulating material having a thermal conductivity on the same order of magnitude as that of the metal of the base body (10.4), and wherein the heat dissipating elements (16.4) have a height (H) starting from the base body (10.4) of the heat sink (4) so that taking into account the high voltage and an insulating medium surrounding the heat dissipating elements (16.4), there is a sufficient insulation breakdown resistance relative to the surroundings of the X-ray tube (30).

Claims

1. An X-ray tube (30) with an anode (36) that conducts a high voltage, preferably greater than 120 kV, particularly preferably greater than 300 kV, and heats up during operation, wherein the anode is connected in a thermally conductive way to a heat sink (4), which has a base body (10.4) composed of a metal with a heat absorbing surface (12.4) for coupling to the anode (36) as a heat source (36) and a heat dissipating surface (14.4) that is enlarged by means of heat dissipating elements (16.4) that are connected to the base body (10.4), wherein the heat dissipating elements (16.4) are composed of an electrically insulating material having a thermal conductivity on the same order of magnitude as that of the metal of the base body (10.4), and wherein the heat dissipating elements (16.4) have a height (H) starting from the base body (10.4) of the heat sink (4) so that taking into account the high voltage and an insulating medium surrounding the heat dissipating elements (16.4), there is a sufficient insulation breakdown resistance relative to the surroundings of the X-ray tube (30).

2. The X-ray tube (30) according to claim 1, wherein the base body (10.4) is composed of a metal, in particular aluminum, copper, silver, or a metal alloy, which preferably has a thermal conductivity coefficient that is greater than 100 W/(m K) and particularly preferably, lies in the range of 100 to 450 W/(m K).

3. The X-ray tube (30) according to claim 1 or 2, wherein the heat dissipating elements (16.4) are composed of a ceramic, in particular of silicon carbide or aluminum nitride, which preferably has a thermal conductivity coefficient that is greater than 100 W/(m K) and particularly preferably, lies in the range of 100 to 350 W/(m K).

4. The X-ray tube (30) according to one of the preceding claims, wherein the heat dissipating elements (16.4) are plate-shaped or pin-shaped or tubular.

5. The X-ray tube (30) according to one of the preceding claims, wherein for each heat dissipating element (16.4), the base body (10.4) has a corresponding socket (18.4), which is dimensioned to accommodate (18.4) a connecting section (20.4) of each of the heat dissipating elements (16.4).

6. The X-ray tube (30) according to claim 5, wherein the heat dissipating elements (16.4) are connected to the base body (10.4) in that the respective connecting section (20.4) is fastened in the associated socket (18.4) by means of a press fit or clamping.

7. The X-ray tube (30) according to claim 5, wherein the heat dissipating elements (16.2; 16.3) are pin-shaped or tubular at least in the region of the connecting section (20.2; 20.3) and have a first thread in the connecting section (20.2; 20.3), the sockets in the base body (10.2; 10.3) are holes with corresponding second threads, and the heat dissipating elements (16.2; 16.3) are connected to the base body (10.2; 10.3) in that the connecting sections (20.2; 20.3) are each fastened in the respective socket (18.2; 18.3) by means of a screw connection.

8. The X-ray tube (30) according to claim 5, wherein the heat dissipating elements (16.4) are attached to the base body (10.4) by being cast in place and an interstice between the respective connecting section (20.4) and the socket (18.4) is filled with a casting compound.

9. The X-ray tube (30) according to one of the preceding claims, wherein the heat dissipating elements (16.4) are attached to the base body (10.4) by being glued with an organic or inorganic adhesive.

10. The X-ray tube (30) according to claim 5, wherein the heat dissipating elements (16.4) are attached to the base body (10.4) by means of soldering and preferably, at least the connecting section (20.4) of the heat dissipating element (16.4) is metallized.

11. The X-ray tube (30) according to one of the preceding claims, wherein the base body (10.4) is a turned element with an inner surface (12.4) of an axially extending recess (22) that is adapted for coupling to the anode (36) as the heat source, an outer surface (14.4) as part of the heat dissipating surface has the sockets (18.4) for the heat dissipating elements (16.4), and a heat dissipating element (16.4) is inserted into each of the sockets (18.4).

12. The X-ray tube (30) according to claim 11, wherein the sockets (18.4) are axially extending slots or grooves into which are inserted plate-shaped ceramic elements serving as the heat dissipating elements (16.4).

Description

[0032] FIGS. 1a and 1 b show a first exemplary embodiment of a heat sink.

[0033] FIGS. 2a and 2b show a second exemplary embodiment of a heat sink.

[0034] FIGS. 3a and 3b show a third exemplary embodiment of a heat sink.

[0035] FIG. 4a shows a fourth exemplary embodiment of a heat sink with a cylindrical base body made of metal and cooling fins made of ceramic.

[0036] FIG. 4b shows the cross-section AA of FIG. 4a.

[0037] FIG. 5a shows a cross-section of an X-ray tube with the heat sink from FIGS. 4a and 4b functioning as an anode heat sink.

[0038] FIG. 5b is a perspective view of the X-ray tube of FIG. 5a.

[0039] The FIGS. 1a to 3b show three exemplary embodiments for heat sinks 1, 2, and 3, each having a base body 10.1, 10.2, 10.3 made of metal.

[0040] The base body has a respective heat absorbing surface 12.1, 12.2, 12.3 for coupling to a heat source. The heat source can be a component, which heats up or is heated during operation. During operation, heat is conveyed into the base body of the heat sink in a known way by means of thermal conduction. In other words, the heat absorbing surface essentially corresponds to the contact area with the heat source.

[0041] By means of thermal conduction, thermal radiation, and convection via its outer surfaces that are not in contact with the heat source, the base body 10.1, 10.2, 10.3 can, as a heat dissipating surface, dissipate the heat to an insulating medium (usually a fluid such as the ambient air in the simplest case) surrounding the heat dissipating surfaces. Essentially, the part of the outer surface of the base body 10.1, 10.2, 10.3, which is situated opposite from the heat absorbing surface 12.1, 12.2, 12.3, constitutes the heat dissipating surface 14.1, 14.2, 14.3 of the base body 10.1, 10.2, 10.3.

[0042] To enlarge the effective heat dissipating surface, with heat dissipating elements 16.1, 16.2, 16.3, which are connected to the base body 10.1, 10.2, 10.3 in a thermally conductive way, are situated on the base body 10.1, 10.2, 10.3 in the region of the heat dissipating surface 14.1, 14.2, 14.3. The heat dissipating surface area 14.1, 14.2, 14.3 of the base body 10.1, 10.2, 10.3 is thus increased by the surface areas of the heat dissipating elements 16.1, 16.2, 16.3. The heat dissipating elements 16.1, 16.2, 16.3 are made of an electrically insulating material, which preferably has a thermal conductivity on the same order of magnitude as that of the metal of the base body 10.1, 10.2, 10.3. The respective connecting sections 20.1, 20.2, 20.3 of the heat dissipating elements 16.1, 16.2, 16.3 are inserted into correspondingly shaped sockets 18.1, 18.2, 18.3, which are molded into the base body 10.1, 10.2, 10.3 in a way that conducts heat into the base body 10.1, 10.2, 10.3.

[0043] FIG. 1a shows the first exemplary embodiment of the heat sink 1 with plate-shaped heat dissipating elements 16.1. FIG. 1b shows one of the heat dissipating elements 16.1 from FIG. 1a by itself. The heat dissipating element 16.1 is embodied in the shape of a plate, i.e. it is plate-shaped.

[0044] The expression “plate-shaped” essentially means that the heat dissipating element 16.1 has significantly greater dimensions in length and height than it does in comparison to the width.

[0045] The plate-shaped heat dissipating element 16.1 has a width B and a height, which is composed of a height h of the connecting section 20.1 and the remaining length H with which the latter protrudes from the base body 10.1 after being inserted into it. The longitudinal span of the heat dissipating element 16.1 is labeled L. Since B<<L and B<<(h+H), the heat dissipating element is plate-shaped.

[0046] With the connecting section 20.1, the heat dissipating element 16.1 is inserted into the recesses 18.1 provided or embodied in the base body 10.1 and is then fastened in it in a thermally conductive way by means of one of the measures discussed below.

[0047] FIG. 2a shows the second exemplary embodiment of the heat sink 2. In this case, the heat dissipating elements 16.2 are pins or rods, which are composed of an electrically insulating material and once again have a thermal conductivity on the same order of magnitude as that of the metal of the base body 10.2. Similar to what is shown in FIG. 1a, the pin-shaped or rod-shaped heat dissipating elements 16.2 are inserted with a respective connecting section 20.2 into recesses 18.2 correspondingly machined or molded into the base body 10.2 and are fastened therein with high thermal conductivity.

[0048] One of the pin-shaped heat dissipating elements 16.2 is shown by itself in FIG. 2b. The heat dissipating element 16.2 is essentially cylindrical and has a length L and a diameter D. The length L is of the connecting section 20.2, which similar to the one in FIGS. 1a and 1b, has the length h that corresponds to the depth of one of the respective sockets 18.2 in the base body 10. The remaining part of the pin-shaped heat dissipating element 16.2 has the length H that protrudes from the base body 10.2 when the heat dissipating element 16.2 has been inserted into the base body 10.2; in other words, L equals (h+H) in this case.

[0049] FIG. 3a shows the third exemplary embodiment of the heat sink 3. In this case (as in the first and second exemplary embodiment), the heat dissipating surface 14.3 of the base body 10.3 has sockets 18.3 formed in it, into which the tubular heat dissipating elements 16.3 are inserted and fastened. The tubular heat dissipating elements 16.3 are once again composed of an electrically insulating material having a thermal conductivity on the same order of magnitude as that of the metal of the base body 10.3. The tubular heat dissipating elements 16.3 in the exemplary embodiment are in the form of a hollow cylinder with an outer diameter D, an inner diameter d, and a length L. The length of the heat dissipating element 16.3 is divided into the connecting section 20.3 with a length h, which sections are inserted to a depth h into the correspondingly formed sockets 18.3 of the base body 10.3. The remaining section of the heat dissipating element 16.3 that protrudes from the base body 10.3 when the heat dissipating element 16.3 has been inserted into the base body 10.3, has the length H; in other words, here—as in FIGS. 2a and 2b—L equals (h+H).

[0050] As mentioned above, in the heat sinks 1, 2, and 3 described in conjunction with FIGS. 1a to 3b, the base body 10.1, 10.2, 10.3 is made out of a metal with a high thermal conductivity, preferably with a thermal conductivity coefficient of 100 W/(m K) or more. For the exemplary embodiments, aluminum with a thermal conductivity coefficient of approx. 240 W/(m K) or copper with a thermal conductivity coefficient of approx. 400 W/(m K) is used. Naturally, the base body 10.1, 10.2, 10.3 can also be composed of another metal or metal alloy.

[0051] The heat dissipating elements 16.1, 16.2, and 16.3 are composed of a ceramic that has a thermal conductivity coefficient on the same order of magnitude as that of the metal of the base body 10.1, 10.2, 10.3. Preferably, the ceramic thus likewise has a thermal conductivity coefficient of greater than 100 W/(m K). For the exemplary embodiments, aluminum nitride with a thermal conductivity coefficient of approx. 180 to 220 W/(m K) or silicon carbide with a thermal conductivity coefficient of approx. 350 W/(m K) was used.

[0052] As is clear from FIGS. 1a, 2a, and 3a, the heat dissipating elements 16.1, 16.2, and 16.3 are each inserted into corresponding sockets 18.1, 18.2, and 18.3 that have been produced in the base body 10.1, 10.2, 10.3. Various joining techniques can be used to ensure a sufficient fastening of the heat dissipating elements 16.1, 16.2, and 16.3 that has a particularly good thermal conductivity.

[0053] For example, in the exemplary embodiments shown in FIGS. 1a and 2a, the respective heat dissipating element 16.1 or 16.2 can be joined to the base body 10.1, 10.2 with form-fitting engagement and/or with frictional, nonpositive engagement in that the respective use section 20.1, 20.2 is fastened in the associated socket 18.1, 18.2 by means of a press fit or by means of clamping. In order to insert the heat dissipating elements into the corresponding sockets in the base body 10.1, 10.2, it is possible, for example, to correspondingly heat the base body 10.1, 10.2 so that the base body 10.1, 10.2 expands. In this state, the ceramic heat dissipating elements 16.1, 16.2 can be inserted into the respective sockets 18.1, 18.2. Once the base body 10.1, 10.2 has cooled again, the heat dissipating elements 16.1, 16.2 are firmly attached to the base body 10.1, 10.2. In this case, it is only necessary to make sure that the dimensions of the recesses 18.1, 18.2 are sized so that the heat dissipating elements 16.1, 16.2 cannot come loose due to the expansion of the metal of the base body 10.1, 10.2 at the temperatures that are achieved during proper operation.

[0054] An alternative fastening variant is possible in the exemplary embodiments of FIGS. 2a and 3a. To this end, a first thread can be machined or molded into the heat dissipating elements 16.2, 16.3, at least in the region of the respective connecting section 20.2, 20.3 (not shown). Then corresponding second threads can be machined into the corresponding sockets 18.2, 18.3 in the base body 10.2, 10.3, which in this case are then embodied in the form of holes. Correspondingly, the heat dissipating elements 16.2, 16.3 can be connected to the base body 10.2, 10.3 in that the connecting sections 20.2, 20.3 are each fastened in the respective socket 18.2, 18.3 by means of being screwed into it. If the base body 10.2, 10.3 heats up and thus expands during operation of the heat sink, the ceramic heat dissipating elements 16.2, 16.3 are only subjected to compressive strain, which additionally reduces the heat transfer resistance between the base body and the heat dissipating elements.

[0055] Alternatively, the heat dissipating elements 16.1, 16.2, or 16.3 of the exemplary embodiments in FIGS. 1a to 3a are fastened in the respective base body 10.1, 10.2, 10.3 by being cast in place. In this case, the sockets 18.1, 18.2, 18.3 that are machined into the base body 10.1, 10.2, 10.3 and/or the dimensions of the respective connecting section 20.1, 20.2, 20.3 are sized so that between the base body 10.1, 10.2, 10.3 and the heat dissipating element 16.1, 16.2, 16.3, an interstice is formed after the insertion. This interstice between each connecting section 20.1, 20.2, 20.3 and the respective socket 18.1, 18.2, 18.3 can be filled in or filled up with a very thermally conductive casting compound that solidifies and preferably hardens. After the casting compound solidifies or hardens, the respective heat dissipating element is firmly connected to the base body 10.1, 10.2, 10.3.

[0056] Another alternative for fastening the heat dissipating elements 16.1, 16.2, 16.3 in the respective sockets 18.1, 18.2, 18.3 provided in the base bodies 10.1, 10.2, 10.3 can be achieved by means of gluing or sticking them in place with a suitable adhesive.

[0057] Another option for producing a connection between the heat dissipating elements 16.1, 16.2, 16.3 in the sockets 18.1, 18.2, 18.3 machined into the respective base body 10.1, 10.2, 10.3 is soldering. To that end, after being inserted into the corresponding socket 18.1, 18.2, 18.3 in the base body 10.1, 10.2, 10.3, the respective heat dissipating element 16.1, 16.2, 16.3 is soldered to the base body 10.1, 10.2, 10.3 in an intrinsically known way with a suitable solder.

[0058] In a modification, in order to achieve a better wetting of the heat dissipating element 16.1, 16.2, 16.3 composed of ceramic with solder, this element is previously metallized in the region of the connecting section 20.1, 20.2, 20.3.

[0059] FIG. 4a shows a fourth exemplary embodiment of a heat sink 4. Basically, that which has been stated about the exemplary embodiments in FIGS. 1a to 3b also applies correspondingly to the fourth exemplary embodiment.

[0060] The base body 10.4 of the fourth exemplary embodiment is rotationally symmetrical in comparison to the base bodies 10.1, 10.2, 10.3. The base body 10.4 can be produced as a turned element or produced by means of a CNC machine.

[0061] The base body 10.4 has an inner surface 12.4 of a recess 22 extending axially in the base body 10.4. The inner surface 12.4 is once again used for coupling to a heat source from which heat is to be dissipated by means of the heat sink.

[0062] The outer surface 14.4 of the base body 10.4 is part of the heat dissipating surface into which the sockets 18.4 for the heat dissipating elements 16.4 are machined. The sockets 18.4 are machined into the base body 10.4, for example by means of milling, in the form of axially extending slots.

[0063] Plate-shaped ceramic elements functioning as the heat dissipating elements 16.4 are inserted into the axially extending slots in order to enlarge the effective heat dissipating surface area. The heat dissipating elements 16.4 are spaced apart from one another uniformly and in a star-pattern around the circumference of the base body 10.4. A uniform enlargement of the effective heat dissipating surface area is thus achieved across the entire circumference region of the base body 10.4.

[0064] The heat sink 4 shown in FIGS. 4a and 4b is particularly well-suited for use, for example, as a heat sink for an anode of an X-ray tube used as an X-ray radiation generator of the kind that is known, for example, from DE 10 2008 006 620 A1. FIG. 5a shows a cross-section through an example of an X-ray tube 30, which has an anode 36 as a component that conducts a high voltage and heats up during operation. In order to cool the anode 36 during the operation of the X-ray tube 30, the heat sink 4 that is shown in FIGS. 4a and 4b, is fastened in a thermally conductive way to the part of the anode 36 leading out of the X-ray tube 30. In order to dissipate the heat from the heat sink, the X-ray tube is positioned in a tank (not shown) that is filled with oil acting as the insulating medium. The high heat capacity of oil makes it possible to transport heat away from the heat sink by means of the oil through the use of a heat exchanger. Basically, air could also be used as an insulating medium. Air does not have as good cooling properties, though.

[0065] The design of the X-ray tube 30 is essentially known; details thereof are also not relevant to the comprehension of the heat sink 4. The X-ray tube 30 essentially has an evacuated cylindrical housing 32, which is likewise composed of a ceramic. Firstly, the housing 32 contains a heated cathode 34, which can be contacted from the outside by means of corresponding lines 37 via corresponding through openings in the housing 32. Situated opposite from the cathode 34 is the anode 36, which during the operation of the X-ray tube 30, is acted on with a corresponding high voltage in order to accelerate the electrons emitted by the cathode 34. On the anode 36, there is a target 38, for example composed of tungsten, which is customarily provided in order to produce X-ray radiation. X-rays, which are generated by the electrons that penetrate into the target 38 and are decelerated by it, exit the X-ray tube 30 by means of a radiation window 40 in the housing 32. A titanium foil 42 can be positioned in the optical path for beam hardening of the X-ray radiation.

[0066] The connecting end of the cathode 34 leads out from the end 43 of the housing 32. At this location, the heat sink 4 is connected to the anode 36 in a way that provides good thermal conduction in order to dissipate the heat that is generated during operation.

[0067] FIG. 5b provides a supplementary perspective view of the X-ray tube 30 from FIG. 5a for the sake of better illustration.