X-ray tube with a multi-piece yoke for the magnetic deflection of electrons

Abstract

X-ray tube (10), comprising - an evacuated housing (11), - an electron emitter (13) for generating electrons within the evacuated housing (11), - an anode (14) for generating X-rays depending on the generated electrons, - a magnetic deflection unit (15) for deflecting the generated electrons with a magnetic field, - wherein the magnetic deflection unit (15) comprises a yoke (16, 19, 20, 21) and a coil (17) wound around the yoke (16, 19, 20, 21) for generating the magnetic field, - wherein the coil (17) is arranged outside the evacuated housing (11) and - wherein the yoke (16, 19, 20, 21) extends from outside the evacuated housing (11) into the interior (18) of the evacuated housing (11), characterized in that the yoke (16, 19, 20, 21) is formed in several pieces, wherein an outer part (19) of the yoke (16) is arranged outside the housing (11) and vacuum-compatible parts (20, 21) of the yoke (16) are arranged inside the housing (11).

Description

The invention relates to an X-ray tube.The invention is based on an X-ray tube which has an evacuated housing, an electron emitter for generating electrons within the evacuated housing, an anode for generating X-rays in dependence on the generated electrons and a magnetic deflection unit for deflecting the generated electrons with a magnetic field, wherein the magnetic deflection unit has a yoke and a coil wound around the yoke for generating the magnetic field, wherein the coil is arranged outside the evacuated housing and wherein the yoke extends from outside the evacuated housing into the interior space of the evacuated housing.An X-ray tube of this kind having a magnetic deflection unit is known, for example, from US 2013 / 182 825 A1. It is in particular specific to this X-ray tube that the yoke is at the same electrical potential as the focus head of the X-ray tube. Alternative deflection units are known, for example, in the form of an electrical deflection from DE 10 2012 211 281 A1 or in the form of a magnetic deflection unit arranged entirely in vacuum from DE 10 2014 211 694 A1.US 2013 / 182 825 A1 describes an X-ray tube cathode with magnetic electron beam control. In an exemplary embodiment, an x-ray tube cathode includes a cathode head and an electron emitter. The cathode head is made of electrically conductive, non-magnetic material integrated with magnetic material. The cathode head defines an emitter slot in a portion of the electrically conductive and non-magnetic material positioned between two portions of the magnetic material. The electron emitter is positioned within the emitter slot. The electron emitter is configured to emit an electron beam. The electron beam is configured to be both focused by the electrically conductive and non-magnetic material and controlled by the magnetic material during beam formation.In general, x-ray tubes are regularly moved with respect to the examination object, in particular the patient, of an imaging examination. Typical applications of imaging examinations are computed tomography, digital breast tomosynthesis, C-arm angiography, etc. If x-rays are generated during the movement for the imaging, the spatial distribution of the x-ray source point on the anode may become blurred, as a result of which a spatial resolution and / or an image quality is deteriorated. It is therefore fundamentally known to counteract this movement of the electrons counter to the direction of movement of the X-ray tube, for example by a deflection unit.An additional or alternative application of such a deflection unit is to be able to jump back and forth between different X-ray source points on the anode. In this case, the X-ray tube itself can be configured to be stationary in particular relative to an X-ray detector. Jumping the x-ray source spots may improve location resolution and / or image quality.The object of the invention is to specify an improved X-ray tube.The object is achieved by the features of the independent claims. Advantageous embodiments are described in the dependent claims.The X-ray tube according to the invention hasan evacuated housing,an electron emitter for generating electrons within the evacuated housing,an anode for generating X-rays in response to the generated electrons; anda magnetic deflection unit for deflecting the generated electrons with a magnetic field,wherein the magnetic deflection unit comprises a yoke and a coil wound around the yoke for generating the magnetic field,wherein the coil is disposed outside the evacuated housing, andwherein the yoke extends from the outside of the evacuated housing into the interior of the evacuated housing,characterized in that the yoke is formed in multiple pieces, wherein an outer part of the yoke is arranged outside the housing and vacuum-fit parts of the yoke are arranged inside the housing.According to one embodiment, the outer part of the yoke is connected to the vacuum-fit parts of the yoke via at least one electrical, high-voltage-resistant insulator through the evacuated housing.According to one embodiment, an electrical potential of the outer part of the yoke differs from an electrical potential of the vacuum-fit parts of the yoke.According to one embodiment, the vacuum-capable parts of the yoke differ in their electrical potential in order to electrically deflect the electrons in a direction perpendicular to the direction of deflection with the magnetic field.According to one embodiment, the electron emitter is a field effect emitter.According to one embodiment, the field effect emitter is arranged on a ceramic.According to one embodiment, the ceramic forms the at least one electrical, high-voltage-resistant insulator.According to one embodiment, the ceramic is a multilayer ceramic having at least one electrically conductive section.According to one embodiment, the at least one electrically conductive section is designed to supply the electrical potential of a vacuum-compatible part of the yoke or of the field effect emitter.According to one embodiment, the ceramic forms a portion of the housing, such that one side of the ceramic is the vacuum side of this portion of the housing and the side of the ceramic opposite the vacuum side is the outer side of this portion of the housing.According to one embodiment, the vacuum-fit parts of the yoke each have an L-shape.According to one embodiment, the legs of the vacuum-fit parts are aligned with one another.According to an embodiment, the outer part of the yoke has substantially a V-shape.According to one embodiment, the outer part of the yoke consists of a transformer sheet.According to one embodiment, the vacuum-fit parts of the yoke consist of an iron.An advantage of the x-ray tube according to the invention is that, due to the multi-piece construction of the yoke, the electrical potentials of the parts of the yoke can be different. As a result, the X-ray tube according to the invention enables an improved deflection, wherein in the present description deflection can comprise a focusing, a defocusing, a blocking and / or a deflection of at least a part of the electrons.The X-ray tube according to the invention is particularly advantageous if it is a so-called bipolar X-ray tube in which the anode and the electron emitter are each at a high-voltage potential with different signs. This specific embodiment is made possible in particular by the at least one electrical, high-voltage-resistant insulator.A further advantage concerns the fact that a production of the X-ray tube according to the invention is simplified by the multi-piece yoke. This is because the outer part of the yoke can be attached to the housing from the outside after the production of the housing, in particular after the generation of the high vacuum inside the housing.Regardless of the grammatical sex of a certain term, individuals with male, female or other sex identity are included.The invention is described and explained in more detail below with reference to the exemplary embodiments shown in the figures. In principle, structures and units that remain substantially the same are denoted by the same reference sign as when the respective structure or unit occurs for the first time in the following description of the figures.The following are shown: FIG. 1 shows an X-ray tube according to the invention, and FIG. 2 shows a first exemplary embodiment of the X-ray tube.FIG. 1 shows a schematic section through the X-ray tube 10 according to the invention.The X-ray tube 10 according to the invention has an evacuated housing 11. The evacuated housing 11 forms a casing which limits a high vacuum in the interior 18 of the housing 11 in a vacuum-tight manner. The evacuated housing 11 has an X-ray exit window 12 through which X-rays can exit from the high vacuum. The X-ray window 12 may be made of a glass and / or a metal.The X-ray tube 10 further comprises an electron emitter 13. The electron emitter 13 is arranged within the evacuated housing 11 and is designed for generating electrons. In FIG. 1, the electron emitter 13 is a helical emitter. In an alternative embodiment, the electron emitter 13 can be a sheet metal emitter or field effect emitter. The electron emitter 13 is surrounded by a cathode of the X-ray tube 10, wherein the cathode can be designed as a focus head.The X-ray tube 10 further includes an anode 14. The anode 14 is disposed within the evacuated housing 11 and is adapted to generate X-rays in dependence on the generated electrons. The anode 14 is a rotating anode in FIG. 1. In an alternative embodiment, the anode 14 may be a stand anode.The X-ray tube 10 further includes a magnetic deflection unit 15. The magnetic deflection unit 15 is configured to deflect the generated electrons with a magnetic field. The magnetic deflection unit 15 includes a yoke 16 and a coil 17 wound around the yoke 16 for generating the magnetic field. The coil 17 is arranged outside the evacuated housing 11, i.e. not under high vacuum. The coil 17 is wound around a central portion of the yoke 16.The yoke 16 extends from the outside of the evacuated housing 11 into the interior 18 of the evacuated housing 11. In FIG. 1, the yoke 16 consists of a total of three parts 19, 20, 21, which are each formed in one piece. The yoke 16 is axis-symmetrical.An outer part 19 of the yoke is arranged outside the housing 11. The outer part 19 of the yoke essentially has a V-shape, as shown in FIG. 1. The outer part 19 of the yoke consists of a transformer sheet. The coil 17 is wound around the outer member 19.The two vacuum-fit parts 20, 21 of the yoke are arranged inside the housing 11. The vacuum-fit parts 20, 21 of the yoke each have an L-shape, wherein the legs of the vacuum-fit parts 20, 21 are aligned with one another. The vacuum-fit parts 20, 21 of the yoke consist of an iron.The outer part 19 of the yoke 16 is connected to the vacuum-fit parts 20, 21 of the yoke 16 via at least one electrical, high-voltage-resistant insulator 22, 23 through the casing of the evacuated housing 11. In FIG. 1, two insulators 22, 23 are shown, which connect one end of the outer yoke 19 to one end of one of the vacuum-fittable parts 20 and the other end of the outer yoke 19 to one end of the other of the vacuum-fittable parts 21. The two insulators 22, 23 comprise two parts and are formed in a discontinuous manner.Structurally, the two insulators 22, 23 belong more to the housing 11 so that the casing of the housing 11 can still be vacuum-tight. Functionally, the two insulators 22, 23 are configured in such a way that the two vacuum-fit parts 20, 21 of the yoke together with the outer part 19 of the yoke form a magnetic circuit for guiding the magnetic flux, with the result that, above all, the electrons emitted by the electron emitter 13 can be deflected with the magnetic field in the space between the two mutually opposite ends of the vacuum-fit parts 20, 21.FIG. 1 shows further electrical insulators 24, 25 which are resistant to high voltages and which enable the feedthroughs for the electron emitter 13 and the anode 14 to pass through the envelope of the evacuated housing 11.According to the invention, an electrical potential of the outer part 19 of the yoke can differ from an electrical potential of the vacuum-fit parts 20, 21 of the yoke. Alternatively or additionally, the vacuum-fit parts 20, 21 of the yoke can differ in their electrical potential in order to electrically deflect the electrons in a direction perpendicular to the direction of deflection with the magnetic field.FIG. 2 shows a schematic section through the first exemplary embodiment of the X-ray tube 10 according to the invention.The electron emitter 13 is a field effect emitter. The field effect emitter has in particular a multiplicity of field effect emitter needles, which preferably consist of silicon. The field effect emitter may be a pixelated field effect emitter with a plurality of groups of field effect emitter needles.The field effect emitter is arranged on a ceramic 26 or embedded in it. The ceramic 26 forms a portion of the housing 11 so that one side of the ceramic 26 is the vacuum side of this portion of the housing 11 and the side of the ceramic 26 opposite to the vacuum side is the outside of this portion of the housing 11.The ceramic 26 forms the at least one electrical, high-voltage-resistant insulator 22. Different portions of the insulator 22 connect the one end of the outer yoke 19 to one end of one of the vacuumable members 20 and the other end of the outer yoke 19 to one end of the other of the vacuumable members 21.The ceramic 26 is a multilayer ceramic having at least one electrically conductive section. The multilayer ceramic can be, in particular, an LTCC, "low temperature co-fired ceramic". The multi-ply ceramic has a layered structure in which ceramic and thus electrically insulating and non-ceramic, preferably electrically conductive plies alternate. The outer layers are preferably ceramic layers. The at least one electrically conductive section can be part of an electrically conductive layer or an electrically conductive layer can form the at least one electrically conductive section. It is conceivable that the at least one electrically conductive section is designed in the form of a conductor track. The at least one electrically conductive section is designed to supply the electrical potential of a vacuum-compatible part 20, 21 of the yoke or of the field effect emitter 13. If the multilayer ceramic has a plurality of electrically conductive sections which are electrically separated from one another, one of these sections can supply, for example, the electrical potential of one vacuum-compatible part 20 or of the other vacuum-compatible part 21 or of a base of the field effect emitter 13 or of a gate of the field effect emitter 13.Although the invention has been illustrated and described in more detail by the preferred exemplary embodiments, the invention is nevertheless not restricted by the disclosed examples and other variations can be derived therefrom by the person skilled in the art without departing from the scope of protection of the invention.References included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedUS 2013 / 182 825 A1 [0003, 0004]DE 10 2012 211 281 A1

[0003] DE 10 2014 211 694 A1

[0003]

Claims

X-ray tube (10), comprising - an evacuated housing (11), - an electron emitter (13) for generating electrons within the evacuated housing (11), - an anode (14) for generating x-rays in dependence on the generated electrons, - a magnetic deflection unit (15) for deflecting the generated electrons with a magnetic field, - wherein the magnetic deflection unit (15) comprises a yoke (16, 19, 20, 21) and a coil (17) wound around the yoke (16, 19, 20, 21) for generating the magnetic field, - wherein the coil (17) is arranged outside the evacuated housing (11) and - wherein the yoke (16, 19, 20, 21) extends from outside the evacuated housing (11) into the interior space (18) of the evacuated housing (11), characterized in that the yoke (16, 19, 20, 21) is formed in multiple pieces, wherein an outer part (19) of the yoke (16) is arranged outside the housing (11) and vacuum-fit parts (20, 21) of the yoke (16) are arranged inside the housing (11).The X-ray tube (10) of claim 1, wherein the outer part (19) of the yoke (16) is connected to the vacuumable parts (20, 21) of the yoke (16) via at least one electrical high voltage resistant insulator (22, 23) through the evacuated housing (11).The X-ray tube (10) of claim 2, wherein an electric potential of the outer part (19) of the yoke (16) is different from an electric potential of the vacuumable parts (20, 21) of the yoke (16).The X-ray tube (10) according to any one of claims 2 or 3, wherein the vacuum-capable parts (20, 21) of the yoke (16) differ in electric potential to electrically deflect the electrons in a direction perpendicular to the direction of deflection with the magnetic field.X-ray tube (10) according to one of the preceding claims, wherein the electron emitter (13) is a field effect emitter.X-ray tube (10) according to claim 5, wherein the field effect emitter (13) is arranged on a ceramic (26).X-ray tube (10) according to one of claims 2 to 4 and according to one of claims 5 or 6, wherein the ceramic (26) forms the at least one electrical, high-voltage-resistant insulator (22).The x-ray tube (10) of any of claims 6 or 7, wherein the ceramic (26) is a multi-layer ceramic having at least one electrically conductive portion.The X-ray tube (10) according to claim 8, wherein the at least one electrically conductive section is configured to supply the electrical potential of a vacuum-compatible part (20, 21) of the yoke (16) or of the field effect emitter (13).The X-ray tube (10) according to any one of claims 6 to 9, wherein the ceramic (26) forms a portion of the housing (11) such that one side of the ceramic (26) is the vacuum side of that portion of the housing (11) and the side of the ceramic (26) opposite the vacuum side is the outside of that portion of the housing (11).The X-ray tube (10) according to any one of the preceding claims, wherein the vacuum-fit parts (20, 21) of the yoke (16) each have an L-shape.The x-ray tube (10) of claim 11, wherein the legs of the vacuumable portions (20, 21) are aligned with each other.The X-ray tube (10) according to any of the preceding claims, wherein the outer part (19) of the yoke (16) has a substantially V-shape.An X-ray tube (10) according to any preceding claim, wherein the outer part (19) of the yoke (16) is made of a transformer sheet.The X-ray tube (10) according to any one of the preceding claims, wherein the vacuum-fit parts (20, 21) of the yoke (16) are made of an iron.

Images