This invention relates to a cooling device for a rotatable anode for producing X-radiation in a X-ray tube, whereby the rotatable anode has a focal path onto which an electron flow hits and bearing parts.
Cooling devices for X-ray rotatable anodes are known from the prior art. X-ray rotatable anodes are used for example for research, medical radiology, structure and material research or even in medical diagnostic applications. In case of X-ray rotatable anodes, thermal output is delivered at high vacuum on the focal surface of the anode by the electron bombardment. In order to avoid a fusing of the anode material, the anode has to be cooled. Since the cooling due only to rotation or increase of the rotational speed of the anode is insufficient, in nowadays technology the anode is water-cooled. However, a cooling by water has the disadvantage that a turbulent flow is necessary for the efficient heat transfer. This flow produces a loss due to friction (friction) which also has to be cooled off.
Presentation of the Invention, aim, Solution, Advantages
Thus, the aim of this invention is to make available a cooling device for a rotatable anode which makes possible a more efficient cooling.
This aim is achieved by a cooling device with the characteristics indicated in claim 1.
The basic idea of the invention is to base the cooling of the anode on the so-called heat pipe principle. The fact that there is a liquid between the focal path and the bearing parts which evaporates on the evaporation surface serves for this purpose. The evaporation surface is heated up by the electron bombardment onto the focal surface. This vapour arrives then to the bearing parts on which there is a depression because of the temperature gradient and a condensation takes place. The condensation surface results from the temperature gradient which adjusts between the evaporation surface and the bearing parts which also fulfil the function of a condensation surface. The transport of the condensate back to the focal path is carried out by the centrifugal forces of the rotating anode. In this manner the heat circuit of a heat pipe is closed.
The advantage of the invention is to be seen in that the evaporation heat of the liquid in the concerned temperature range achieves an additional cooling effect compared to the normal cooling by flowing. The heat transfer is much higher than that in case of a flowing liquid. Additionally, the construction of the cooling device which is based on the heat pipe principle is simple and cost saving since only the space between the bearing parts and the focal path is used.
A practicable alternative of the invention provides that the condensate arrives to the evaporation surface which is formed on the focal surface.
It is advantageous that the parts of the bearing are connected gas-tightly with the focal path. This takes into consideration that the rotatable anode is at high-vacuum.
Sliding bearings are considered to be effective condensation surfaces. Thus, the bearing is preferably a sliding bearing.
The fact that there are ribs on the bearing parts also serves this purpose. The ribs additionally serve to the bearing stiffness.
An advantageous configuration of the invention provides that the liquid is water. This takes into consideration that it is known that water has a high heat capacity.
But it is also conceivable that the liquid is alcohol.
In order to guarantee the discharge of the heat flow, claim 8 provides that a cooling flow flows in the bearing parts. For the cooling flow, the matter can also be, for example, of nitrogen or cooling gas. A cooling of a rotatable anode by means of a cooling flow is disclosed, for example, in the patent document DE 36 44 719 C1 and can be used within the scope of this invention.
An advantageous configuration of the invention provides that the ribs are placed on the bearing parts in axial direction.
In order to generate a quicker evaporation, a practicable alternative of the invention provides that the evaporation surface is enlarged by knurls and/or ribs. Due to the fact that the evaporation surface is enlarged by knurling and/or ribs, a rough surface is created which causes a quicker evaporation.
Finally, the invention provides a method for cooling a rotatable anode for which liquid is evaporated on a focal path of the rotatable anode and the evaporated liquid simultaneously arrives to bearing parts which act as condensation surface on which the evaporated liquid will condense, whereby the condensate of the focal path is fed again by the centrifugal force of the rotatable anode. This being, the condensate can arrive to an evaporation surface which is configured on the focal path.
Preferably, the bearing parts are then gas-tightly connected with the focal path, whereby the bearing parts are used as sliding bearing.
According to the method, ribs can be used on the bearing parts.
Embodiments of the invention are explained below by reference to the drawings.
A cooling device according to the invention 100 of a rotatable anode 10 is represented in
In
Number | Date | Country | Kind |
---|---|---|---|
20 2005 013 232.2 | Aug 2005 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/EP2006/008161 | 8/18/2006 | WO | 00 | 3/1/2010 |