Patent Application
20130336459
This U.S. non-provisional patent application claims priority under 35 U.S.C. §119 of Korean Patent Application No. 10-2012-0064759, filed on Jun. 18, 2012, the entire contents of which are hereby incorporated by reference.
The present invention disclosed herein relates to an X-ray and a method of focusing electronic beams, and more particularly, to a field emission X-ray tube and a method of focusing electronic beams using the same.
X-rays generally used for medical purposes, industrial purposes, and research purposes are obtained by colliding electrons on an anode electrode of a metal target, in which, as an electron source used for this, there are a thermionic source including electron discharge by heating a metallic material and a field emission source using nano materials.
Thermionic sources have a relatively short lifespan, are difficult to reduce a size thereof. Also, since electron discharge is performed as a dipole, it is difficult to control the strength of an X-ray and difficult to perform integration, and miniaturization thereof. On the contrary, in case of field emission sources using nano-materials, it is possible to discharge electrons as triode structures, to have various electric, physical shapes, to generate X-rays with relatively higher outputs than thermionic sources, and to easily perform controlling the strength of X-rays, integration, and miniaturization thereof. There have been many researches to apply field emission sources to industrial defect and quality inspection systems, medical brachytherapy systems, and three-dimensional digital diagnosis system using such merits of field emission sources.
However, there are some limitations on nano-material-based field emission sources in aspect of technologies up to now. When field emission occurs, there is a limitation of present electron beam focusing, which should be priorly solved. As the limitation occurring due to omission of electron beam focusing, there is electric charge accumulation occurring on a sidewall of ceramic used for insulation in such a way that electron beams are not transmitted to an anode electrode, thereby preventing generation of X-rays, an electronic source is damaged and demolished due to arcing, and it is impossible to form focal spots in sizes of micro meter μm or nano-meter nm to obtain an X-ray image with high output and high resolution.
To overcome such limitation, it is needed to provide a gate electrode structure including electron beam focusing of a new concept and to provide a vacuum seaming technology for manufacturing an X-ray generator such as an X-ray tube.
The present invention provides a field emission X-ray tube preventing electron accumulation simultaneously with forming an electron beam spot with a size of micro meters or less.
The present invention also provides a method of focusing electron beams emitted from a field emission emitter to form an electron beam spot with a size of micro meters or less on an anode electrode.
The provided is not limited to the described above and clearly understood by those skilled in the art from following description.
Embodiments of the present invention provide field emission X-ray tubes including: a cathode electrode provided on one end of a vacuum container, including a field emission emitter; a gate electrode provided inside the vacuum container to be adjacent to the cathode electrode, including a first opening; a focusing electrode electrically connected to the gate electrode and provided on one surface of the gate electrode to be farther from the cathode electrode than the gate electrode while including a second opening with a greater width than that of the first opening; and an anode electrode provided inside the vacuum container on another end thereof in a direction where the vacuum container is extended. A height of the focusing electrode may be identical to the width of the second opening, and the width of the first opening may be ⅓ or less of the second opening.
In some embodiments, the focusing electrode may be in physical contact with the one surface of the gate electrode.
In other embodiments, an outer circumference of the focusing electrode may be smaller than that of the gate electrode.
In still other embodiments, a cross-section of the first opening may be one of a circle and a polygon.
In still other embodiments, the width of the first opening may be greater than a maximum width of a cross-section of the field emission emitter.
In still other embodiments, the first opening may include a shape penetrating the gate electrode.
In still other embodiments, a cross-section of the field emission emitter may be one of a circle and a polygon.
In still other embodiments, a cross-section of the second opening may be one of a circle and a polygon.
In still other embodiments, the second opening may include a shape penetrating the focusing electrode.
In still other embodiments, the field emission emitter may include nano-materials.
In still other embodiments, the anode electrode is inclined with respect to the cathode electrode.
In other embodiments of the present invention, methods of focusing electron beams. The method may include one of controlling the height of the focusing electrode and changing the width of the first opening in the field emission X-ray tube including the configuration described above.
In some embodiments, the method may further include changing a distance between the field emission emitter and the gate electrode.
In other embodiments, the focusing electrode may be in physical contact with the one surface of the gate electrode.
In still other embodiments, the anode electrode may be inclined with respect to the cathode electrode.
The accompanying drawings are included to provide a further understanding of the present invention, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the present invention and, together with the description, serve to explain principles of the present invention. In the drawings:
Preferred embodiments of the present invention will be described below in more detail with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be constructed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Like reference numerals refer to like elements throughout.
Terms used in the description are just for describing embodiments but not limit the present inventive concept. In the specification, a singular form includes a plural form if there is no particular mention about it in phrases. Comprises and/or comprising used in the specification do not exclude presence or addition of one or more elements in addition to a mentioned element. Also, since it is according to preferable embodiments thereof, reference numerals mentioned according to a sequence of description are not limited to the sequence. In addition, in the present specification, it will also be understood that when a layer (or film) is referred to as being ‘on’ another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present.
Embodiments will be described with reference to preferable cross-sectional views and/or top views. In the drawings, the dimensions of layers and regions are exaggerated for clarity of illustration. Accordingly, a formation of an exemplary view may vary with manufacturing technologies and/or an allowable error. Accordingly, the embodiments of the present inventive concept are not limited certain illustrated forms but include variances in shapes generated by a manufacturing process. For example, an etching region illustrated as a right angle may be a shape with a round part or with a curvature. Accordingly, a region illustrated in the drawings has schematic characteristics and shapes of regions illustrated in the drawings are provided just for showing certain forms of the regions of a device, which do not restrict the scope of the present inventive concept.
Referring to
Since the anode electrode 160 is inclined toward the cathode electrode 110 with a certain angle, the field emission X-ray tube according to the present embodiment may be a reflective field emission X-ray source. The reflective field emission X-ray source may further include, to emit X-rays generated from the anode electrode 160 outwardly, a window including metallic materials such as beryllium Be and molybdenum Mo. On the contrary, when the anode electrode 160 includes a metallic material and a conductive material such as ceramic, the field emission X-ray tube may be a transmissive field emission X-ray tube. Emitting electrons from the field emission emitter 120 of the cathode electrode 110 and focusing electron beams those are arrows shown in the drawing are performed by an electric field, and the gate electrode 130 and the focusing electrode 140 perform the emission of electrons and focusing electron beams. The cathode electrode 110 may include a metal. The field emission emitter may include nano-materials such as carbon nano-tubes. The gate electrode 130 and the focusing electrode 140 may include metallic materials such as Aluminum Al, stainless steel, and a Kobar alloy.
Structure and size of the vacuum container 150 of the field emission X-ray tube and locations and sizes of the gate electrode 130 and the focusing electrode 140 may vary with purposes of the electron beams. The vacuum container 150 may include an insulating material such as ceramic. A vacuum seaming method for manufacturing the field emission X-ray tube may use a brazing method and frit that is a chemical adhesion material.
A gate electrode formed in a mesh shape provided inside the vacuum container 150 is used for a general field emission X-ray tube. On the contrary, the gate electrode 130 may have a shape with one opening. Since emission of electrons e from the field emission emitter 120 of the cathode electrode 110 is performed by an electric field, the gate electrode 130 may emit electrons e using only one opening.
General reflective field emission X-ray tubes generate X-rays when the electron beams emitted from the field emission emitter 120 that is an electron source are focused on and collide with the anode electrode 160 inclined with a certain angle. The anode electrode 160 may include polycrystalline and/or single-crystal metals such as tungsten W, molybdenum Mo, and copper Cu. To allow the field emission X-ray tube to generate X-rays with high output characteristics, the anode electrode 160 may include a single-crystal metal.
Referring to
A cross-section of the first opening of the gate electrode 130 may be a circle or a polygon. Preferably, the cross-section of the first opening according to the present embodiment may be a concentric circle. The first opening may have a shape penetrating the gate electrode 130. A cross-section of the second opening may be a circle or polygon. Preferably, the cross-section of the second opening according to the present embodiment may be a concentric circle, an oval, or a quadrangle. The second opening may have a shape penetrating the focusing electrode 140.
The first opening of the gate electrode 130 may have a greater width than a maximum width of the field emission emitter 120. The width of the first opening may not allow field-emitted electron beams to be induced to an edge of the first opening. This is for preventing a great increase of a leakage current caused by inducing electron beams to the edge of the first opening. The thinner thickness of the gate electrode 130 the better. However, the gate electrode 130 may have a thickness capable of preventing a vibration occurring due to an applied voltage.
The second opening of the focusing electrode 140 may be manufactured to have a greater width than that of the first opening considering that the electron beams passing through the first opening radially spread out. This may be for naturally focusing the electron beams in a triangular shape as shown in
Referring to
Referring to
Referring to
Referring to
Referring to
As a result thereof, the bonding structure electrode 200 should be inserted inside the vacuum container 150 under a condition of
The field emission X-ray tube includes a focusing electrode with a height as the same as a width of an opening of the focusing electrode and a gate electrode having an opening with a width of ⅓ or less of the width of the opening of the focusing electrode, thereby focusing electron beams to form a micro-sized or nano-sized spot without charge accumulation. Accordingly, it is possible to provide the field emission X-ray tube capable of preventing charge accumulation simultaneously with forming an electron beam spot with a size of microns or less.
Also, electron beams may be focused to form a micro-sized or nano-sized spot without charge accumulation by controlling the height of the focusing electrode or the width of the gate electrode of the field emission X-ray tube according to the present embodiment. Accordingly, it is possible to an electron beam spot with a size of microns or less on an anode electrode thereby focusing electron beams emitted from a field emission emitter.
As a result thereof, since the filed emission X-ray tube according to the present embodiment is able to prevent a damage and demolition of a filed emission electron source, to reduce power, to minimize a size thereof, to be highly integrated, and to control the strength of X-rays, thereby being applied to industrial systems for inspecting defects and quality of products, medical brachytherapy systems, and three-dimensional digital diagnosis systems.
The above-disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments, which fall within the true spirit and scope of the present invention. Thus, to the maximum extent allowed by law, the scope of the present invention is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2012-0064759 | Jun 2012 | KR | national |
