Patent Publication Number: US-11043351-B2

Title: X-ray source and method for manufacturing an X-ray source

Description:
FIELD OF THE INVENTION 
     Generally, the invention relates to X-ray imaging. More specifically, the invention relates to an X-ray source for generating X-rays, to an X-ray imaging system comprising such X-ray source and to a method for manufacturing such X-ray source. 
     BACKGROUND OF THE INVENTION 
     X-ray sources and/or X-ray tubes are usually driven by a high electrical voltage supplied via an electrical supply to an X-ray generating element and/or to an emitter arrangement of the X-ray source. To isolate these high voltages of the electrical supply from ground potential, usually high voltage insulators are used, which may form an interface between an ambient pressure and a vacuum in a vacuum compartment of the X-ray source, in which the X-ray generating element and/or the emitter arrangement may be arranged. 
     Components of the X-ray source arranged on the vacuum side of the insulator and/or the X-ray source usually carry and/or comprise heat generating components, such as e.g. the X-ray generating element, components of a cathode and/or components of an anode, which heat generating components may generate heat during operation of the X-ray source. 
     Moreover, on the ambient side of the insulator and/or the X-ray source elements and/or components of the X-ray source may be present which may be degraded due to the heat generated by the heat generating components during operation of the X-ray source. 
     US2010/0111265A1 relates to a high-voltage x-ray tube with an inner vacuum chamber in which lie, oriented opposite one another, a cathode held at a negative high voltage during operating conditions and an anode held at a positive high voltage during operating conditions, wherein the anode is affixed to an anode isolation element such that the anode isolation element has a cylindrical form or a form tapering toward the anode and comprises an opening to receive a high-voltage plug and has a conductor structure via which a coolant can be supplied to the anode. This coolant can be, in particular, an insulating oil or another electrically nonconductive liquid. The conductor structure can, for example, be integrated completely into the interior of the anode isolation element but can also be integrated into the surface of the high-voltage plug. In another possible solution, the conductor structure is integrated into an intermediate element which lies between the anode isolation element and the high-voltage plug. 
     DE674415C relates to insulating high-voltage protective housing for liquid-cooled vacuum, especially X-ray tubes, with a container for the tube and another multiple subdivided container for the liquid coolant. 
     SUMMARY OF THE INVENTION 
     There may therefore be a need for an improved X-ray source allowing to efficiently and reliably dissipate and/or purge heat during operation of the X-ray source. It may, thus, be an object of the present invention to provide and improved and compact X-ray source having improved cooling means as well as having an extended lifetime. 
     The object of the present invention is solved by the subject-matter of the independent claims, wherein further embodiments are incorporated in the dependent claims and the following description. 
     In an aspect, there is provided an X-ray source as defined in appended claim  1 . In another aspect, there is provided an X-ray imaging system as defined in appended claim  13 . In another aspect, there is provided a method of manufacturing an X-ray source as defined in appended claim  14 . 
     According to a first example, an X-ray source and/or an X-ray tube for generating X-rays is provided. The X-ray source comprises an emitter arrangement, at least one emitter element and/or at least one emitter for emitting and/or generating electrons or for emitting and/or generating X-rays. The X-ray source further comprises at least one feedthrough for supplying electrical power to the emitter arrangement, and an insulator configured for isolating an electrical potential of the at least one feedthrough from a ground potential. Therein, the at least one feedthrough extends at least partly through the insulator, and at least a part of the insulator is in thermal contact with at least a part of the emitter arrangement. Further, the insulator comprises at least one cooling channel formed, integrated and/or arranged completely and/or entirely in an interior volume of the insulator and configured to dissipate and/or purge heat from the emitter arrangement, wherein a distance between an outer surface and/or a periphery of the insulator and the cooling channel is at least as large as half of a thickness of the cooling channel. 
     The at least one feedthrough may refer to an electrical supply configured for supplying electrical power to at least a part of the emitter arrangement. Particularly, the at least one feedthrough may refer to at least one conductive pin-like element and/or at least one pin, which may be connected to an external power supply and connected to at least a part of the emitter arrangement. Via and/or by means of the at least one feedthrough high voltage may be supplied to at least a part of the emitter arrangement, wherein high voltage may refer to a voltage above about 1000 Volts. Further, the at least one feedthrough may be configured for controlling a voltage supplied to the emitter arrangement, for controlling a current supplied to the emitter arrangement and/or for conducting other electrical signals, such as e.g. sensor signals. 
     Generally, the emitter arrangement may refer to a heat generating component and/or a heat source of the X-ray source, wherein at least a part of the emitter arrangement may generate heat during operation of the X-ray source, particularly when electrical power is supplied to the emitter arrangement via the at least one feedthrough. By way of example, the emitter arrangement may comprise e.g. an anode, a cathode, a thermionic cathode, an electron beam gun, a deflection plate, a deflection coil, a rotor drive and/or components of the foregoing. 
     Moreover, the X-ray source may comprise an enclosure at least partly enclosing the emitter arrangement, wherein the insulator may be arranged on a side of the enclosure, and wherein at least a part of the insulator and the enclosure may form a vacuum compartment, in which the emitter arrangement may be arranged. 
     Accordingly, the insulator may form an interface between the vacuum comprised in the vacuum compartment and an ambient pressure, an environment, a surrounding and/or further components of the X-ray source arranged outside the vacuum compartment. In other words, the insulator may comprise a vacuum side facing the vacuum compartment and an opposite side, which may be referred to as ambient side of the insulator in the following. As a consequence, heat generated during operation of the X-ray source by the emitter arrangement may primarily be transferred and/or conducted via the insulator, which is at least partly in thermal contact with at least a part of the emitter arrangement, from the emitter arrangement to ambient, to the environment, to the surrounding and/or to further components of the X-ray source. Accordingly, the heat may be transferred and/or conducted to other components of the X-ray source arranged on the ambient side of the insulator, such as components comprising e.g. plastic, silicon and/or other materials, which may be degraded during lifetime of the X-ray source due to thermal stress and/or thermal load. 
     In conventional X-ray sources, usually cooling means, cooling components and/or cooling structures are arranged on the ambient side of the insulator in order to maintain thermal integrity of components of the X-ray source arranged at the ambient side, such as e.g. plastic, rubber and/or silicone components. Such cooling means in conventional X-ray sources may comprise e.g. a heat pipe, a contact to oil and/or a contact to water, which may be provided and/or arranged at an outer periphery of the insulator. However, these cooling means of conventional X-ray sources may have a rather complex design and may require additional space rendering a construction of conventional X-ray sources bulky. Further, heat may not be dissipated efficiently via such cooling means. 
     By means of the inventive X-ray source with the insulator, in which the at least one cooling channel is formed, arranged and/or integrated, heat may be dissipated and/or purged from the emitter arrangement in an efficient, reliable and comprehensive manner. This in turn may allow to reliably maintain thermal integrity of other components of the X-ray source arranged at the ambient side of the insulator. Accordingly, a lifetime of these components as well as an overall lifetime of the X-ray source may be increased. Also, by integrating the cooling channel in the insulator, no extra space may be required for further cooling means, which may allow to provide a compact X-ray source. 
     Therein, the at least one cooling channel may be integrated completely and/or entirely in the interior volume and/or in an inner volume of the insulator. In other words, the cooling channel may be arranged and/or integrated in the insulator, such that the cooling channel is completely surrounded by material of the insulator. 
     Further, by arranging the cooling channel at a distance between the outer surface of the insulator and the cooling channel, which distance is at least as large as half of a thickness of the cooling channel, it may advantageously be ensured that heat generated by the emitter arrangement and transferred to the insulator may be spread and/or conducted via material of the insulator substantially isotopically around the cooling channel. Therein, the distance between the cooling channel and the outer surface of the insulator may be measured from an outer periphery and/or an outer surface of the cooling channel to the outer surface of the insulator, wherein the outer surface of the cooling channel may face the outer surface of the insulator and/or may be arranged opposite to the outer surface of the insulator. Further, the thickness of the cooling channel may refer to a characteristic dimension and/or a dimension of open space of the cooling channel, particularly a characteristic dimension of a cross-section and/or a cross-sectional area of the cooling channel. Further, the thickness may be measured in direction of the outer surface and/or in direction of an outer periphery of the insulator. By arranging the cooling channel at such distance to the outer surface, it may be ensured that heat is also transferred and/or conducted to a region of the insulator between the outer surface and the cooling channel. This arrangement may further increase a cooling efficiency. It is to be noted that the cooling channel may have an arbitrary shape, such as e.g. a cylindrical, a tube-like, a spiral and/or a helical shape. Further, a cross-section and/or a cross-sectional area of the cooling channel may be arbitrarily shaped, such as e.g. polygon-like, rectangular, round, rounded, triangular, elliptical and/or oval. Also, the cooling channel may be arranged in the insulator such that the distance between the cooling channel and the outer surface is constant or varying along a longitudinal extension direction of the cooling channel. Moreover, the insulator may comprise a plurality of cooling channels, which may be arranged in an arbitrary pattern in the interior volume of the insulator. 
     According to an embodiment, the distance between the outer surface and the cooling channel is a smallest distance between the outer surface and the cooling channel, wherein the distance is measured parallel to a surface normal vector of the outer surface and/or a surface normal vector of a periphery of the insulator. Therein, the surface normal vector may be directed to an outside of the insulator. Further, the distance may be measured from an outer periphery and/or an outer surface of the cooling channel to the outer surface of the insulator, wherein the outer surface of the cooling channel may face the outer surface of the insulator and/or may be arranged opposite to the outer surface of the insulator. Alternatively, or additionally, the thickness of the cooling channel is measured parallel to the surface normal vector of the outer surface. In other words, the distance of the cooling channel to the outer surface and the thickness of the cooling channel may both be measured in a direction parallel to and/or along the surface normal vector of the outer surface of the insulator. By arranging the cooling channel at this specified distance, a heat transfer to the cooling channel and/or a heat dissipation via the cooling channel may advantageously be increased. 
     According to an embodiment, a cross-section of the cooling channel is rounded and/or round. Alternatively, or additionally the thickness of the cooling channel is a diameter of the cooling channel. Accordingly, the distance between the cooling channel and the outer surface of the insulator may be at least as large as a radius of the cooling channel. 
     According to an embodiment, the cooling channel at least partly surrounds the feedthrough along a circumferential direction of the insulator. By way of example, the insulator may be a flat insulator, commonly referred to as pancake insulator, wherein the feedthrough may extend through and/or may be arranged in a center region of the insulator. The feedthrough may at least partly be embedded in the center region of the insulator. Alternatively, or additionally the distance between the outer surface of the insulator and the cooling channel is equidistant along a periphery of the insulator. By arranging the cooling channel such that it at least partly surrounds the feedthrough at a constant distance to the surface of the insulator along the circumferential direction, it may be ensured that the insulator is homogenously and efficiently cooled by the cooling channel. 
     According to an embodiment, the insulator is cylindrical or conical. The insulator may e.g. be an axisymmetric insulator being symmetric around an axis of symmetry, of the insulator. Alternatively, or additionally the feedthrough extends through the insulator parallel to an axis of symmetry of the insulator. 
     According to an embodiment, the cooling channel is configured to guide a coolant such that heat from the emitter arrangement is dissipated by means of convection cooling via the coolant. The coolant may be a fluid coolant, such as a liquid and/or gaseous coolant. By way of example, the coolant may comprise oil, water, ester and/or any other suitable fluid coolant, including liquid and/or gaseous coolants. Also, the coolant may be oil based, water based, water-alcohol based, ester based and/or a gas. By means of the coolant, which may be contained in the cooling channel, a transfer and/or heat dissipation may be further increased. 
     According to an embodiment, the X-ray source further comprises an inlet fluidly coupled to and/or in fluid communication with the cooling channel and configured to supply a coolant to the cooling channel. Alternatively, or additionally, the X-ray source comprises an outlet fluidly coupled to and/or in fluid communication with the cooling channel and configured for purging a coolant from the cooling channel. The coolant may e.g. have pumped by means of a pump device into the inlet and/or purged from the outlet to generate a flow of coolant through the cooling channel. Thereby, a cooling effect may be further enhanced. 
     According to an embodiment, at least a part of the insulator is manufactured by sintering, gluing and/or three-dimensional (3D) printing. Accordingly, the insulator may be comprised of sub-components, such as e.g. particles and/or granules of insulator material, in the raw stage, which may be joined together during manufacturing, production and/or assembly of the insulator. By employing sintering, gluing and/or 3D printing techniques, the insulator with the integrated cooling channel may be processed and/or manufactured precisely in a single processing step. This in turn may allow to manufacture the insulator and/or the X-ray source in a cost efficient manner. 
     According to an embodiment the insulator is a single homogenous block of isotropic material, such as ceramics material and/or alumina. By way of example, the insulator may comprise Silicon Carbid (SiC), glass, and/or doped alumina, which may be partly conducting. However, the insulator may comprise any other suitable material, such as e.g. reinforced ceramics materials. By forming the insulator as a single homogenous block of isotropic material, in which the cooling channel may be embedded, a heat transfer rate and/or a thermal conductivity of the insulator may be homogenous, such that heat may be conducted efficiently to the cooling channel and dissipated via the cooling channel. 
     According to an embodiment the insulator comprises a first side facing the emitter arrangement and a second side opposite to the first side. Therein, the first side may refer to the vacuum side of the insulator and the second side may refer to the ambient side of the insulator. Therein, the insulator comprises a first ceramics material at the first side and a second ceramics material at the second side, wherein the first material and the second material differ from each other in at least one of a chemical composition, a density and an electrical conductivity. Generally, the first and second materials, which may be isotropic materials, may have different electrical characteristics. For instance, an electrical conductivity of the first material may be less than an electrical conductivity of the second material, as an electrical field strength may be higher on and/or near the first side, which may face the vacuum compartment of the X-ray source. Generally, manufacturing the first side and the second side of the insulator from different ceramics materials may allow to produce a cost-efficient insulator, as e.g. expensive ceramics material may only be used for the first side whereas cheaper ceramics material may be used for the second side. 
     According to an embodiment, at least a part of a surface of the cooling channel is metallized and/or a metal layer may be arranged on at least a part of the surface of the cooling channel. The surface of the cooling channel may refer to an outer surface of the cooling channel or to an inner surface of the cooling channel. By metallizing the surface of the cooling channel a heat transfer and/or a thermal conductivity may be further increased. The surface of the cooling channel may be metallized with a metal material comprising e.g. copper and/or any other material having a comparatively high thermal conductivity. Alternatively, or additionally, the cooling channel is comprised of at least one tube formed in the interior volume of the insulator and/or the cooling channel may be comprised of at least one integrated pipe. Also this configuration may further increase a heat transfer from the insulator to the cooling channel. The pipe may comprise metal, such as copper and/or any other material having a comparatively high thermal conductivity. 
     According to an embodiment, the emitter arrangement comprises at least a part of at least one of an anode, a cathode, a deflection plate, a deflection coil, and an electron beam gun. 
     According to an embodiment, the X-ray source further comprises an enclosure at least partly enclosing the emitter arrangement, wherein the insulator is arranged on a side of the enclosure, and wherein at least a part of the insulator and the enclosure form a vacuum compartment, in which the emitter arrangement is arranged. 
     A second example relates to an X-ray imaging system. The X-ray imaging system comprises an X-ray source for generating X-rays, as described above and in the following, and an X-ray detector for detecting X-rays. X-rays generated by the X-ray source may be emitted e.g. in direction of an object of interest, and X-rays passing through the object of interest may be detected with the X-ray detector to generate an X-ray image of the object of interest. The X-ray imaging system may refer to a projection X-ray imaging system, a cone beam imaging system, a computed tomography (CT) imaging system and/or any other X-ray imaging system. Further, it is to be noted that the inventive X-ray source may also be used in an X-ray radiotherapy system. 
     It is to be noted that features functions, elements and/or characteristics of the X-ray source, as described above and in the following, may be features, functions, elements and/or characteristics of the X-ray imaging system, as described above and in the following, and vice versa. 
     A third example relates to a method for manufacturing and/or producing an X-ray source for emitting X-rays. Particularly the method may be a method for manufacturing an X-ray source, as described above and in the following. The X-ray source comprises an emitter arrangement for emitting electrons or X-rays, at least one feedthrough for supplying electrical power to the emitter arrangement, and an insulator configured for isolating an electrical potential of the at least one feedthrough from a ground potential. The method comprises the steps of: 
     forming at least one cooling channel in an interior volume of the insulator, such that the cooling channel is completely arranged in the interior volume of the insulator; and arranging the insulator on a side of the emitter arrangement, such that at least a part of the insulator is in thermal contact with at least a part of the emitter arrangement; 
     Therein, the cooling channel is formed at a distance between an outer surface of the insulator and the cooling channel, which distance is at least as large as half of a thickness of the cooling channel. 
     It is to be noted that features functions, characteristics, elements and/or steps of the method, as described above and in the following, may be features, functions, elements and/or characteristics of the X-ray source and/or of the X-ray imaging system, as described above and in the following, and vice versa. In other words, features, elements, functions, characteristics and/or steps described above and in the following with reference to one aspect of the invention may be features, functions, elements, characteristics and/or steps of any other aspect of the invention. 
     According to an embodiment, at least a part of the insulator and the cooling channel are formed by three-dimensional printing, sintering and/or gluing. 
     These and other aspects of the invention will be apparent from and elucidated with reference to the exemplary embodiments described hereinafter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The subject-matter of the invention will be explained in more detail in the following with reference to exemplary embodiments which are illustrated in the attached drawings. 
         FIG. 1  shows schematically an X-ray imaging system according to exemplary embodiment. 
         FIG. 2A  shows schematically a cross-sectional view of an X-ray source according to an exemplary embodiment. 
         FIG. 2B  shows schematically a top view of a part of the X-ray source of  FIG. 2A . 
         FIG. 2C  shows schematically a top view of a part of the X-ray source of  FIG. 2A . 
         FIG. 3  shows schematically a cross-sectional view of an X-ray source according to an exemplary embodiment. 
         FIG. 4  shows a flow chart illustrating steps of a method for manufacturing an X-ray source according to an exemplary embodiment. 
     
    
    
     In principle, identical and/or similar parts are provided with the same reference symbols in the figures. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
       FIG. 1  shows an X-ray imaging system  100  according to exemplary embodiment. 
     The X-ray imaging system  100  comprises an X-ray source  10  for generating and/or emitting X-rays  11 . Further, the X-ray imaging system  100  comprises an X-ray detector  102  for detecting X-rays  11 . The X-ray source  10  may emit X-rays  11  in direction of an object of interest  104 , which may be e.g. a patient and/or any other object to be examined, and the X-ray detector  102  may detect X-rays  11  passing through and/or traversing the object of interest  104  to generate an X-ray image of at least a part of the object of interest  104 . 
     Further, the X-ray imaging system  100  comprises a controller  106  coupled to the X-ray source  10  and/or to the X-ray detector  102 . The controller  106  may be configured for controlling the X-ray source  10  and/or the X-ray detector  102 . Also, the controller  106  may be configured to process detector signals of the X-ray detector  102  to generate the X-ray image. 
     Further, the X-ray imaging system  100  comprises a power supply  108  for supplying electrical power to the X-ray source  10  and/or to the X-ray detector  102 . The power supply  108  may be coupled to the controller  106 , wherein the controller  106  may be configured to control and/or adjust a power level, such as e.g. a voltage value and/or a current value, supplied to the X-ray source  10 . 
     The X-ray source  10  of  FIG. 1  will be explained in more detail with reference to the following figures. 
       FIG. 2A  shows schematically a cross-sectional view of an X-ray source  10  according to an exemplary embodiment.  FIGS. 2B and 2C  each show schematically a top view of a part of the X-ray source  10  of  FIG. 2A . 
     The X-ray source  10  comprises an emitter arrangement  12  for emitting electrons and/or X-rays  11 . For this purpose, the emitter arrangement  12  comprises a first emitter element  14  and a second emitter element  16  arranged opposite to the first emitter element  14 . The emitter arrangement  12 , the first emitter element  14  and/or the second emitter element  16  comprises at least a part of at least one of an anode, a cathode, a deflection plate, a deflection coil, a rotor drive, and an electron beam gun. By way of example the first emitter element  14  may be and/or may comprise a cathode  14  and/or an electron beam gun  14 , wherein in this case emitter element  16  may be an anode  16 . Electrons emitted by the first emitter element  14  may be accelerated by an acceleration potential between the first emitter element  14  and the second emitter element  16  in direction of the second emitter element  16 , wherein X-rays  11  may be generated by electrons impinging onto the second emitter element  16 . Alternatively, the first emitter element  14  may be an anode  14  and the second emitter element  16  may be an electron beam gun  16  and/or a cathode  16 . Likewise, electrons emitted by the second emitter element  16  may be accelerated by an acceleration potential between the first emitter element  14  and the second emitter element  16  in direction of the first emitter element  14 , wherein X-rays  11  may be generated by electrons impinging onto the first emitter element  14 . 
     The X-ray source  10  further comprises an enclosure  18  and an insulator  20  arranged on a side of the enclosure  18 . At least a part of the insulator  20  and the enclosure  18  form a vacuum compartment  19 , in which the emitter arrangement  12  is arranged. 
     The insulator  20  comprises a first side  22  facing the vacuum compartment  19 , wherein the first side  22  may also be referred to as vacuum side  22 .  FIG. 2B  shows a top view onto the first side  22  of the insulator  20 . The insulator  20  further comprises a second side  24  opposite to the first side  14 , wherein the second side  24  faces an ambient, a surrounding, an outside and/or an environment of the X-ray source  10 .  FIG. 2C  shows a top view onto the second side  24  of the insulator  20 . The second side  24  of the insulator  20  may also be referred to as ambient side  24  of the insulator  20 . Accordingly, the insulator  20  may form an interface between the vacuum in the vacuum compartment  19  and an ambient pressure in the surrounding of and/or around the X-ray source  10 . 
     In the example shown in  FIGS. 2A-2C , the insulator  20  is cylindrically shaped and/or the insulator  20  is an axisymmetric insulator  20 . Such insulators  20  may be referred to as pancake insulators  20  and/or as flat insulators  20 . However, the insulator  20  may have any other shape, such as e.g. a conical shape. An axis of symmetry of the insulator  20  illustrated in  FIGS. 2A-2C  may be arranged substantially perpendicular to the plane of projection of  FIGS. 2B and 2C . 
     The X-ray source  10  further comprises a first insulating element  30  and a second insulating element  32  arranged on the second side of the insulator  20 . The first insulating element  30  may e.g. be a silicone slab  30 , e.g. a silicone rubber slab  30 , and/or the second insulating element  32  may e.g. be a plastic insulator  32 . The first insulating element  30  may provide an electrically stable interface. It is to be noted that the X-ray source  10  may comprise further components arranged on the ambient side  24  of the insulator  20 . 
     The insulator  20  is at least partly surrounded, encased and/or encompassed by a metal element  34  and/or a metal ring  34 , wherein the metal element  34  may be kept at an electrical ground potential. 
     The X-ray source  10  further comprises at least one feedthrough  38  extending at least partly through the insulator  20 , e.g. through an opening  39  and/or a through hole  39 . The at least one feedthrough  38  may be arranged in a center region  23  of the insulator  20  and/or it may be at least partly embedded in the insulator  20 . The feedthrough  38  may be a pin-like conductive element  38  and/or a pin  38  coupled to a power supply  108  and coupled to at least a part of the emitter arrangement  12  such that at least a part of the emitter arrangement  12  is supplied with electrical power via the feedthrough  38 . The X-ray source  10  may comprise a plurality of feedthroughs  38 . As illustrated in  FIG. 2C , the X-ray source  10  may comprise four feedthroughs  38  which may be arranged parallel to each other, wherein each feedthrough  38  may be arranged in an opening  39  and/or a through hole  39 . The feedthroughs  38  may generally be configured for supplying voltage and/or current to at least a part of the emitter arrangement  12  and/or for conducting sensor signals. 
     Generally, the insulator  20  is configured for isolating an electrical potential of the at least one feedthrough  38  from ground potential, on which the metal element  34  is kept. Therein, the electrical potential of the feedthrough  38  may be above about 1000 V, particularly above about 100 kV. Accordingly, the insulator  20  may be a high voltage insulator  20 , e.g. a high voltage ceramics insulator  20 . To sufficiently isolate the feedthrough  38  from the ground potential and/or from the metal element  34 , at least one ridge  21   a ,  21   b  and/or rib  21   a ,  21   b  is arranged and/or formed on the first side  22  of the insulator  20 . As illustrated in  FIGS. 2A and 2B , the insulator  20  comprises a first ridge  21   a  surrounding the feedthrough  38  and/or the center region  23  of the insulator  20  along a circumferential direction  40  of the insulator  20 . Further, the insulator  20  comprises a second ridge  21   b  also surrounding the center region  23  and/or the feedthrough  38  along the circumferential direction  40 . Accordingly, the first ridge  21   a  and the second ridge  21   b  are arranged concentrically with respect to each other and are spaced apart from each other in a radial direction  41  of the insulator  20 . The ridges  21   a ,  21   b  may serve to increase a creep distance between the metal element  34  and the emitter arrangement  12  and/or the first emitter element  14  in order to avoid an electrical flashover and/or spark over. It is to be noted that in case the first emitter element  14  is a cathode  14 , the electrical potential of the feedthrough  38  is negative and in case the first emitter element  14  is an anode  14 , the electrical potential of the feedthrough  38  may be positive. 
     The X-ray source  10  and/or the insulator  20  further comprises a cooling channel  28 , which is completely and/or entirely integrated, formed and/or arranged in an interior volume  25  and/or an inner volume  25  of the insulator  20 , such that the cooling channel  28  is substantially completely surrounded by insulator material of the insulator  20 . The cooling channel  28  surrounds the feedthrough  38  and/or the center region  23  of the insulator  20  along the circumferential direction  40 . Further, the cooling channel  28  is arranged at a distance  29  to an outer surface  26  and/or an outer periphery  26  of the insulator  20 , on which outer surface  26  the metal element  34  is arranged. The distance  29  between the cooling channel  28  and the outer surface  26  of the insulator may be measured from an outer surface of the cooling channel  28  to the outer surface  26  of insulator, which outer surface of the cooling channel  28  may face and/or may be arranged opposite to the outer surface  26  of the insulator  20 . Accordingly, the distance  29  may be measured along and/or parallel to the radial direction  41  of the insulator  20 . Accordingly, the distance  29  may be a radial distance  29 . Alternatively, or additionally, the distance  29  may be measured parallel and/or along a surface normal vector  42  of the insulator  20 , wherein the surface normal vector  42  may be parallel to the radial direction  41  of the insulator  20  in the example illustrated in  FIGS. 2A-2C . The distance  29  may be a smallest distance  29  between the outer surface  26  and the cooling channel  28  along a periphery of the insulator  20  in circumferential direction  41 . 
     Moreover, the cooling channel  28  has a thickness  27 , which may be measured parallel to and/or along the radial direction  41  and/or the surface normal vector  42 . Therein, the distance  29  between the outer surface  26  of the insulator  20  and the cooling channel  28  is at least as large as half of the thickness  27  of the cooling channel  28 . As at least a part of the insulator  20 , particularly the center region  25 , is in thermal contact with at least a part of the emitter arrangement  12 , particularly the first emitter element  14 , heat generated during operation of the X-ray source  10  may be conducted from the emitter arrangement  12  to the center region  23  of the insulator  20  and then spread over substantially the entire inner volume  25  of the insulator  20 . As the distance  29  is at least as large as half of the thickness  27  of the cooling channel  28 , heat may also be conducted to an outer region  31  of the insulator  20 , which outer region  31  is arranged between the outer surface  26  of the insulator  20  and the cooling channel  28 . Accordingly, heat may be spread in the interior volume  25  of the insulator  20  such that the heat may be spread and/or distributed around the cooling channel  28 . Due to the arrangement of the cooling channel  28  at the distance  29 , a cooling efficiency and/or a cooling rate may be significantly increased. Particularly, by arranging the cooling channel  28  in the insulator  20  heat may be dissipated such that a thermal integrity of the further components of the X-ray source  10  arranged at the ambient side  24  of the insulator  20 , such as e.g. the first insulator elements  30  and/or the second insulator element  32 , is maintained. Also, this may increase a lifetime of the X-ray source  10 . 
     The cooling channel  28  may generally have an arbitrarily shaped cross section and/or an arbitrarily shaped cross-sectional area, such as e.g. a polygon-like, a rectangular, a round, a rounded, an oval, a triangular, or an elliptical shape. In the example illustrated in  FIGS. 2A-2C  the cooling channel  28  has a round shape. Accordingly, the thickness  27  of the cooling channel  28  refers to a diameter  28  of the cooling channel  28  and the distance  29  may be at least as large as half of a radius of the cooling channel  28 . However, generally the thickness  27  of the cooling channel  28  may refer to a characteristic dimension of the cooling channel  28  measured along and/or parallel to the radial direction  41  and/or the surface normal vector  42 . Accordingly, in case the cross-section of the cooling channel  28  is rectangular, the thickness  27  may refer to an edge length  27  of the cooling channel  28 . 
     In the example shown in  FIGS. 2A-2C , the cooling channel  28  surrounds the center region  23  along the circumferential direction  40 , wherein the distance  29  between the cooling channel  28  and the outer surface  26  is constant. Accordingly, the first ridge  21   a , the second ridge  21   b  and the cooling channel  28  may be arranged concentrically with respect to each other. However, the distance  29  may also vary along the circumferential direction  41 . By way of example, the cooling channel  28  may be arranged in the outer region  31  of the insulator  20 , wherein the cooling channel  28  may at least partly overlap with a region of the insulator  20 , in which the first ridge  21   a  is arranged. Alternatively or additionally, the cooling channel  28  may be arranged in a region of the insulator  28  between the first ridge  21   a  and the second ridge  21   b , wherein the cooling channel  28  may at least partly overlap with the first ridge  21   a  and/or the second ridge  21   b . Alternatively or additionally, the cooling channel  28  may be arranged between the center region  23  and a region of the insulator  20 , in which the second ridge  21   b  is arranged, wherein the cooling channel  28  may also at least partly overlap with the second ridge  21   b . Further, the cooling channel may also at least partly be arranged in the first ridge  21   a  and/or the second ridge  21   b . However, it is to be noted that the cooling channel  28  may be arranged at a certain minimum distance to the feedthrough  38  to avoid a flashover and/or spark over via the cooling channel  28 . 
     Optionally, the cooling channel  28  is configured to guide a coolant  44 , which may comprise, water, alcohol, ester and/or any other suitable coolant material. To supply coolant  44  to the cooling channel  28 , the X-ray source  10  and/or the insulator  20  may comprise an inlet  46  in fluid communication with the cooling channel  28 , as illustrated in  FIGS. 2B and 2C . To purge coolant  44  from the cooling channel  28  the X-ray source  10  and/or the insulator  20  may also comprise an outlet  48  in fluid communication with the cooling channel  28 . The inlet  46  and/or the outlet  48  may be arranged in the outer region  31  of the insulator  20  and may extend parallel or transverse to the radial direction  41  and/or the surface normal vector  42 . Further, a pump device (not shown) may be arranged between inlet  46  and outlet  48  to provide a flow of coolant  44  through the cooling channel  28 , thereby increasing a cooling rate. 
     In order to further increase a cooling effect and/or a cooling efficiency, at least a part of a surface  50  of the cooling channel  28  may be metallized, e.g. with copper. The surface  50  of the cooling channel  28  may be an inner surface  50  or an outer surface  50  of the cooling channel  28 . Accordingly, the cooling channel  28  may comprise a layer  52  of metal arranged on the surface  50  of the cooling channel  28 . Alternatively, or additionally, the cooling channel  28  may be comprised of at least one tube  52  formed in the interior volume  25  of the insulator  20 . 
     Further, at least a part of the insulator  20  may be manufactured by sintering, gluing and/or three-dimensional printing, which may allow to cost-efficiently produce a homogenous insulator  20  conducting heat homogenously in the interior volume  25 . The insulator  20  may be a single homogenous block of isotropic material, such as e.g. alumina, SiC, doped alumina, glass, ceramics material and/or any other suitable material. Alternatively, the insulator  20  may comprise a first material, particularly a first ceramics material, on the first side  22  facing the emitter arrangement  12  and a second material, particularly a second ceramics material, on the second side  24  opposite to the first side  22 , wherein the first material and the second material may differ from each other in at least one of a chemical composition, a density and an electrical conductivity. 
       FIG. 3  shows schematically a cross-sectional view of an X-ray source  10  according to an exemplary embodiment. If not stated otherwise, the X-ray source  10  of  FIG. 3  comprises the same features, functions, characteristics and/or elements as the X-ray source  10  described with reference to previous figs, particularly  FIGS. 2A-2C . 
     The Insulator  20  of the X-ray source  10  depicted in  FIG. 3  comprises a first cooling channel  28   a  and a second cooling channel  28   b , which may be arranged concentrically to each other. To allow a coolant  44  to be guided by both cooling channels  28   a ,  28   b , the cooling channels  28   a ,  28   b  may be interconnected with each other by one or more connecting channels  54 , which may extend parallel and/or transverse to the radial direction  41  and/or the surface normal vector  42 . Therein, a radial distance between the first cooling channel  28   a  and the second cooling channel  28  may be smaller than a radial distance between the feedthrough  38  and the second cooling channel  28   b  to prevent any flashover. Further, the cooling channels  28   a ,  28   b  may have the same thickness  27  or they may have different thicknesses  27 . Particularly, a thickness  27  of the second cooling channel  28   b , which is arranged closer to the feedthrough  38  than the first cooling channel  28   a , may be smaller than a thickness  27  of the first cooling channel  28   a  to avoid any flashover. However, the distance  29  between the outer surface  26  and the first cooling channel  28   a , which is arranged closer to the outer surface  26  than the second cooling channel  28   b , may in either arrangement be at least as large as the thickness  27  of the first cooling channel  28   a . Further, it is to be noted that the X-ray source  10  and/or the insulator  20  may also comprise more than two cooling channels  28   a ,  28   b.    
       FIG. 4  shows a flow chart illustrating steps of a method for manufacturing an X-ray source  10  according to an exemplary embodiment, wherein the X-ray source  10  may be an X-ray source  10  as described with reference to  FIGS. 1-3 . 
     Particularly the X-ray source  10  comprises an emitter arrangement  12  for emitting electrons or X-rays, at least one feedthrough  38  for supplying electrical power to the emitter arrangement  12 , and an insulator  20  configured for isolating an electrical potential of the at least one feedthrough  38  from a ground potential. 
     In a first step S 1  at least one cooling channel  28  is formed in an interior volume  25  of the insulator  20 , such that the cooling channel  28  is completely arranged in the interior volume  25  of the insulator  20 . In step S 1 , the entire insulator  20  with the cooling channel  28  may be formed in a single process step, e.g. by three-dimensional printing, sintering and/or gluing of insulator sub-components, such as e.g. particles and/or granules of insulator material. Therein, the cooling channel  20  is formed at a distance  29  between an outer surface  26  of the insulator  20  and the cooling channel  28 , which distance  29  is at least as large as half of a thickness  27  of the cooling channel  28 . 
     In a second step S 2  the insulator  20  is arranged on a side of the emitter arrangement  12 , such that at least a part of the insulator  20  is in thermal contact with at least a part of the emitter arrangement  12 . 
     While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art and practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. 
     In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.