Patent Application
20170092456
Embodiments of the present specification relate generally to X-ray tubes, and more particularly to a flexible flat emitter in the X-ray tubes.
Typically, an X-ray tube is provided with tube current that heats an emitter in the X-ray tube to emit electrons towards a focal spot in the X-ray tube. In conventional systems, emitters are made of tungsten filament consisting of coiled wires. However, these filament emitters have very less emission area, which results in slow computed tomography (CT) scans or interventional scans. Also, as these emitters have small area, the emitters may heat up to a very high temperature during operation. As a consequence, the emitters may have very high evaporation rate that may physically damage the emitters and/or the X-ray tube.
In other conventional systems, thermionic flat emitters are employed in the X-ray tube for emitting the electrons. The thermionic flat emitters are more convenient to provide a larger emission area than traditional filament emitters. The thermionic flat emitters include emission segments that are separated by slots. Also, the area of flat emitters may be easily increased compared to the filament emitters. As a result, the temperature of the flat emitters is lower than the temperature of the filament emitters for similar amount of emission, and as a consequence the evaporation rate of the material of the flat emitters is less in comparison to that of the material of the filament emitters. Therefore, the flat emitters have an excellent life advantage. However, thermal cyclic deformation of the flat emitters is a challenge due to higher stiffness in the flat emitters. Particularly, when the emitters are subjected to cyclic thermal loading, it is often observed that the flat emitters exhibit lower flexibility as compared to the filament emitters. Due to lower flexibility, the flat emitters tend to distort/deform permanently over a period of time. Also, this deformation in the flat emitters may cause the flat emitters to lose their original shape and flatness. As a consequence, the focal spot quality of the flat emitters in the X-ray tube may degrade over a period of time.
In accordance with aspects of the present specification, a flat emitter configured for use in an X-ray tube is presented. The X-ray tube includes a first conductive section including a first terminal. Further, the X-ray tube includes a second conductive section including a second terminal. Also, the X-ray tube includes a third conductive section disposed between the first conductive section and the second conductive section, wherein the third conductive section is configured to emit electrons toward a determined focal spot, and wherein the third conductive section includes a plurality of slits subdividing the third conductive section into a winding track coupled to the first conductive section and the second conductive section, wherein at least two of the plurality of slits are interwound spirally to compose the winding track, and wherein the winding track is configured to expand and contract based on heat provided to the third conductive section.
In accordance with a further aspect of the present specification, an X-ray tube is presented. The X-ray tube includes a cathode unit configured to emit electrons toward an anode unit. Further, the cathode unit includes a cathode cup including a first voltage terminal and a second voltage terminal. Also, the cathode unit includes a flat emitter coupled to the cathode cup. The flat emitter includes a first conductive section including a first terminal coupled to the first voltage terminal. Further, the flat emitter includes a second conductive section including a second terminal coupled to the second voltage terminal. Also, the flat emitter includes a third conductive section disposed between the first conductive section and the second conductive section, wherein the third conductive section is configured to emit the electrons toward a determined focal spot on the anode unit, and wherein the third conductive section includes a plurality of slits subdividing the third conductive section into a winding track coupled to the first conductive section and the second conductive section, wherein at least two of the plurality of slits are interwound spirally to compose the winding track and wherein the winding track is configured to expand and contract based on heat provided to the third conductive section.
In accordance with another aspect of the present specification, a method includes subdividing a conductive section in a flat emitter by a plurality of slits so as to compose a winding track between a first terminal and a second terminal of the flat emitter, wherein at least two of the plurality of slits are interwound spirally to compose the winding track, wherein the winding track is configured to provide one or more winding current paths in the conductive section, and wherein the winding track is configured to expand and contract based on heat provided to the conductive section.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
As will be described in detail hereinafter, various embodiments of exemplary systems and methods for controlling plastic deformation of a flat emitter are presented. In particular, the flat emitter presented herein at least partly controls mechanical stress imposed on the flat emitter during cyclic thermal loading, which, in turn, at least partly prevents the plastic deformation of the flat emitter. Also, by employing the exemplary flat emitter, evaporation rate of the flat emitter may be significantly reduced, thereby enhancing the life of the flat emitter.
Turning now to the drawings and referring to
Furthermore, the anode assembly 104 includes a rotary anode disc 112 and a stator (not shown). The stator is provided with necessary magnetic field to rotate the rotary anode disc 112. Also, the rotary anode disc 112 is positioned in the direction of emitted electrons to receive the electrons from the cathode cup 108. In one example, a copper base with a target surface having materials with high atomic numbers (“Z” numbers), such as rhodium, palladium, and/or tungsten, is employed in the rotary anode disc 112. It may be noted that a stationary anode may also be used instead of the rotary anode disc 112 in the X-ray tube 100.
During operation, the flat emitter 110 in the cathode cup 108 emits a beam of electrons that is accelerated towards the rotary anode disc 112 of the anode assembly 104 by applying a high voltage potential between the cathode assembly 102 and the anode assembly 104. These electrons impinge upon the rotary anode disc at a focal spot and release kinetic energy as electromagnetic radiation of very high frequency, i.e., X-rays. Particularly, the electrons are rapidly decelerated upon striking the rotary anode disc 112, and in the process, the X-rays are generated therefrom. These X-rays emanate in all directions from the rotary anode disc 112. A portion of these X-rays may pass through a window or X-ray port 114 of the evacuated enclosure 106 to exit the X-ray tube 100 and be utilized to interact in or on a material sample, patient, or other object (not shown).
Referring to
In a presently contemplated configuration, the cathode cup 200 includes one or more support tabs 204 on a bottom surface 205 of the cavity structure 202 and a focus tab 206 on sides of the cavity structure 202. In the example of
The support tab 204 is configured to hold a flat emitter 210 that is positioned upon the support tab 204. Further, the support tab 204 includes conductive protrusions 208, 209 at two ends of the support tab 204. These conductive protrusions 208, 209 are electrically conductive structures that are configured to act as voltage terminals, such as a first voltage terminal and a second voltage terminal for the flat emitter 210. Consequently, the conductive protrusion 208 at one end may be referred to as a first voltage terminal, while the conductive protrusion 209 at the other end may be referred to as a second voltage terminal.
Further, the flat emitter 210 includes a first terminal 212 and a second terminal 214 at two opposite ends of the flat emitter 210. Also, the first terminal 212 includes a first aperture or hole 216, while the second terminal 214 includes a second aperture or hole 218. Further, when the flat emitter 210 is mounted on the support tab 204, the conductive protrusions 208, 209 of the support tab 204 may overlap or extend out through the corresponding aperture of the flat emitter 210. Particularly, when the flat emitter 210 is mounted on the support tab 204, the first voltage terminal 208 of the support tab 204 may extend out through the first aperture 216 and may electrically couple with the first terminal 212 of the flat emitter 210. In a similar manner, the second voltage terminal 209 of the support tab 204 may extend out through the second aperture 218 and may electrically couple with the second terminal 214 of the flat emitter 210.
Furthermore, the flat emitter 210 is provided with electric current by employing the voltage terminals of the support tab 204. This electric current is used to heat the flat emitter 210 to a very high temperature, e.g., 2500° C., to provide or emit electrons from the flat emitter 210. In one example, the electrons may be emitted from the flat emitter 210 by thermionic emission. Further, the focus tab 206 of the cathode cup 108 aids in focusing the emitted electrons towards the focal spot on the rotary anode disc 112. Moreover, during operation, the flat emitter 210 may be subjected to a sequence of cooling and heating cycles to provide a desired beam of electrons towards the focal spot. These cooling and heating cycles may be referred to as cyclic thermal loading, which is explained in greater detail with reference to
Advantageously, the flat emitter 210 is configured to withstand cyclic thermal loading, while maintaining reasonable flexibility. Accordingly, the flat emitter 210 experiences lower mechanical stress and lower or negligible amounts of plastic deformation over a period of time. Consequently, the flat emitter 210 may be able to substantially retain its original shape as well as flatness. As a result, the focal spot quality of the X-ray tube may be retained.
In certain embodiments, the exemplary flat emitter 210 is employed in the cathode cup 200 to lower or substantially avoid plastic deformation and to improve the focal spot quality in the X-ray tube 100. Particularly, the flat emitter 210 is provided with spring structure that is configured to expand and contract under cyclic thermal loading. Advantageously, this spring structure in the flat emitter 210 may aid in substantially reducing mechanical stress on the flat emitter 210, which in turn reduces plastic deformation and improves the life of the flat emitter 210. The aspect of reducing the plastic deformation in the flat emitter 210 is explained in greater detail with reference to
Referring to
Further, the first conductive section 302 includes a first terminal 308, while the second conductive section 304 includes a second terminal 310. The first terminal 308 may include a first aperture 312 that is configured to electrically couple with a first voltage terminal 208 of the cathode cup 200 (see
In certain embodiments, the third conductive section 306 includes a plurality of slits or cuts 316 that define a winding track 318 in the third conductive section 306. Particularly, the plurality of slits or cuts 316 are formed in a predefined pattern to obtain a plurality of emission segments 320 that are serially coupled/connected to each other. In one example, the width 307 of each of the plurality of slits 316 is in a range from about 20 μm to about 60 μm. Further, these individual connected emission segments 320 in the third conductive section 306 are collectively referred to as the winding track 318. It may be noted that the winding track 318 is a physically continuous structure with no joints or cuts in between. However, in the present technique, the winding track 318 is shown as the segments serially connected to each other for understanding of the present technique. In one example, the plurality of slits or cuts 316 may be formed by using electrical discharge machining (EDM) or laser machining. Further, the winding track 318 includes a first end 322 coupled to the first conductive section 302 and a second end 324 coupled to the second conductive section 310. Furthermore, the width (Wt), represented by reference numeral 309, of the winding track 318 is in a range from about 0.2 mm to about 0.4 mm.
Moreover, in the exemplary embodiment of
Further, the first pair of bent slits 326 is interwound spirally at the first end 322 of the third conductive section 306 to compose a pair of emission segments 334 into a spiral shape at the first end 322, as depicted in
During operation, these spiral emission segments 338 may act like spring structure and may substantially reduce stiffness at the ends 322, 324 of the third conductive section 306. Also, as these spiral emission segments 338 are longer in length compared to the length of the vertical emission segments 333, the spiral emission segments 338 may provide larger deflection compared to the vertical emission segments 333. Particularly, as depicted in
Further, as depicted in
Furthermore, as depicted in
Advantageously, the spiral emission elements 338 of the exemplary flat emitter 300 are configured to substantially reduce the mechanical stress otherwise imposed by cyclic thermal loading on the flat emitter 300. Also, the spiral elements 338 of the exemplary flat emitter 300 are configured to prevent or substantially reduce plastic deformation of the flat emitter 300, which in turn facilitates in maintaining the focal spot quality in the X-ray tube. It may be noted that the illustrated designs/structures of the flat emitter should not be construed as restrictive, and that other such structures having spring like design are envisioned within the purview of the present application.
Referring to
During operation, the spiral emission segments 504 in the flat emitter 500 may provide winding current paths along the third conductive section 502 of the flat emitter 500. Further, when electric current flows through these meandering current paths, the flat emitter 500 is heated to a very high temperature, e.g., 2500° C. At this high temperature, the flat emitter 500 may expand and may induce mechanical stress, particularly at the ends of the flat emitter 500. However, the exemplary flat emitter 500 includes spiral emission segments 504 that are longer in length and may act like spring structure when the flat emitter 500 is heated to this high temperature. This in turn, reduces mechanical stress on the flat emitter 500 and may prevent plastic deformation of the flat emitter 500.
Turning to
Further, the sinusoidal emission segment 616 has longer length compared to the spiral emission segment 338 in
Referring to
Further, the double spiral emission segment 712 may have longer length compared to the spiral emission segments 338 of
In one another embodiment, the plurality of slits may include a first number of slits that are arranged vertically and/or horizontally to compose at least a portion of the winding track into a sinusoidal shape. In yet another embodiment, the plurality of slits may include a second number of slits that are arranged spirally to compose at least a portion of the winding track into a spiral shape.
During operation, these emission segments in the winding track may provide elasticity to the flat emitter. Particularly, when the flat emitter is subjected to cyclic thermal loading, the emission segments in the flat emitter may provide larger deflection compared to the conventional flat emitter. As a result of this larger deflection in the flat emitter, mechanical stress on the flat emitter may be substantially reduced. This in turn prevents plastic deformation of the flat emitter. Also, by employing the exemplary flat emitter, evaporation rate of the flat emitter may be significantly reduced. This in turn improves the life of the emitter and reduces maintenance cost of the X-ray cathode and the X-ray tube.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
