X-ray tube

Abstract

X-ray tube, which includes the following: a cathode electrode (11); an anode electrode (14) which is vertically spaced from the cathode electrode (11); a radiator (12) at the cathode electrode; a gate electrode (13) arranged between the cathode electrode (11) and the anode electrode (14), the gate electrode (13) comprising an opening at a location corresponding to the emitter (12); and a spacer (16M) provided between the gate electrode (13) and the anode electrode (14), wherein the spacer (SP2) is a doped region, wherein the doped region is provided with an insulator and comprises conductive dopants doped in the insulator, and wherein the gate electrode (13) is in contact with the doped area.

Description

BACKGROUND

[0001] The present disclosure relates to an X-ray tube.

[0002] An X-ray tube generates X-rays by generating electrons within a vacuum chamber and accelerating the electrons toward an anode electrode, to which a high voltage is applied, so that they collide with a metal target at the anode electrode. A voltage difference between the anode electrode and a cathode electrode is defined here as an accelerating voltage that accelerates the electrons. Depending on the application of the X-ray tube, the electrons are accelerated with an accelerating voltage of several kV to several hundred kV. A gate electrode or the like is provided between the anode electrode and the cathode electrode.

[0003] WO 2005 / 055 270 A1 describes a modular X-ray tube and a method for producing such an X-ray tube, in which an anode and a cathode are arranged opposite each other in a vacuum-sealed interior, whereby electrons are generated at the cathode and X-rays are generated at the anode. The X-ray tube comprises several complementary acceleration modules which comprise at least one potential-carrying acceleration electrode.

[0004] US 2018 / 0 247 787 A1 describes an X-ray source with a sealed vacuum tube. The X-ray source comprises a high-voltage connection module, a tube module, and a magnetic lens system into which the tube module is inserted. The tube module comprises a sealed vacuum tube. The sealed vacuum tube includes a cathode electrode provided at one end thereof, a nanoemitter on the cathode electrode, an anode electrode provided at the other end, and a first insulating spacer provided between the cathode electrode and the anode electrode.

[0005] US 2013 / 0 129 046 A1 describes a radiation generating tube having a cathode connected to an electron gun structure, an anode containing a target and configured to generate radiation, a tubular sidewall disposed between the cathode and the anode to surround the electron gun structure, and an electrical potential definition element disposed at an intermediate portion of the tubular sidewall between the anode and the cathode. SUMMARY

[0006] The present disclosure provides a structure of an X-ray tube that is stably driven even at a high voltage.

[0007] An embodiment of the inventive concept provides an X-ray tube including: a cathode electrode; an anode electrode vertically spaced from the cathode electrode; a radiator on the cathode electrode; a gate electrode disposed between the cathode electrode and the anode electrode, the gate electrode including an opening at a location corresponding to the radiator; and a spacer provided between the gate electrode and the anode electrode, the spacer comprising a doped region, the doped region being provided with an insulator and comprising conductive dopants doped in the insulator, and the gate electrode being in contact with the doped region.

[0008] In one embodiment, the spacer may have a volume resistivity of about 10 9 Ω · cm or more and less than about 10 13 Ω · cm.

[0009] In one embodiment, the insulator may contain aluminum oxide (Al2O3) and the conductive dopants may contain titanium dioxide (TiO2).

[0010] In one embodiment, the spacer may contain more than about 1.64 wt.% and less than about 2.44 wt.% of the conductive dopants.

[0011] In one embodiment, the insulator may comprise a first metal oxide having a resistivity of about 10 13 Ω · cm or more and the conductive dopants may contain a second metal oxide having a resistivity of about 10 8 Ω · cm or less.

[0012] In one embodiment, a voltage applied to the anode electrode may be about 70 kV or more.

[0013] In one embodiment, the gate electrode may further include a protrusion extending toward the anode electrode.

[0014] In one embodiment, the spacer may comprise more than about 1.64 wt.% and less than about 2.44 wt.% titanium oxide (Ti x O y , x = 1 to 3, y = 1 to 3).

[0015] In one embodiment, the spacer may contain about 93 wt% to about 96 wt% alumina.

[0016] In one embodiment of the inventive concept, an X-ray tube includes: a cathode electrode; an anode electrode vertically spaced from the cathode electrode; a target disposed on a surface of the anode electrode, one surface of the anode electrode facing the cathode electrode; a radiator on the cathode electrode; a gate electrode disposed between the cathode electrode and the anode electrode, the gate electrode including an opening at a location corresponding to the radiator;and a spacer provided between the gate electrode and the anode electrode, the spacer including first and second regions between the gate electrode and the anode electrode and a third region between the first and second regions, the first region being in contact with the gate electrode, the second region being adjacent to the anode electrode, each of the first to third regions including an insulator, and each of the first to second regions further including conductive dopants doped in the insulator;

[0017] In one embodiment, both a specific volume resistivity of the first region and a specific volume resistivity of the second region may be smaller than a specific volume resistivity of the third region.

[0018] In one embodiment, each of the first region and the second region may have a volume resistivity of about 10 6 Ω · cm or more and less than about 10 9 Ω · cm and the third region can have a specific volume resistivity of about 10 13 Ω · cm or more.

[0019] In one embodiment, each of the first region and the second region may contain about 3 wt% or more of conductive dopants.

[0020] In one embodiment, the third region may further include conductive dopants in the insulator; the first region may have a conductive dopant concentration that decreases in a first direction from the cathode electrode toward the anode electrode, the second region may have a conductive dopant concentration that increases in the first direction, and the third region may have a conductive dopant concentration that decreases and then increases in the first direction.

[0021] In one embodiment, both a first length of the first region in a first direction from the cathode electrode toward the anode electrode and a second length of the second region in the first direction may be smaller than a third length of the third region in the first direction.

[0022] In one embodiment, a sum of a volume of the first region and a volume of the second region may be smaller than a volume of the third region.

[0023] In one embodiment, a height of the uppermost portion of the first region may be greater than a height of the uppermost portion of the gate electrode, and a height of the lowermost portion of the second region may be less than a height of the lowermost portion of the anode electrode.

[0024] In one embodiment, the x-ray tube may further include at least one focusing electrode between the gate electrode and the anode electrode, wherein the height of the uppermost portion of the first region may be greater than a height of the uppermost portion of the focusing electrode, and wherein the first region may be in contact with the focusing electrode. BRIEF DESCRIPTION OF THE CHARACTERS

[0025] The accompanying drawings are included to provide a further understanding of the inventive concept and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments of the inventive concept and, together with the description, serve to explain the principles of the inventive concept; in the following: Fig. 1A is a cross-sectional view illustrating a structure of an X-ray tube according to the inventive concept; Fig. 1B is a cross-sectional view illustrating a structure of an X-ray tube according to the embodiment; Fig. 2 is a cross-sectional view of an X-ray tube according to Comparative Example; Fig. 3 is a cross-sectional view of an X-ray tube according to the embodiment; Fig. 4A is a cross-sectional view illustrating an X-ray tube according to the embodiment; Fig.4B is a cross-sectional view illustrating an X-ray tube according to the embodiment; Fig. 5 is a cross-sectional view of an x-ray tube according to embodiments; Fig. 6 is a graph showing an emission current versus a voltage applied to an X-ray tube according to Comparative Example 1; Fig. 7 is a graph showing a current flowing through a second spacer versus the current applied to an X-ray tube according to Comparative Examples 2 and 3; Fig. 8A and Fig. 8B Graphs showing the emission current applied to an X-ray tube according to Comparative Example 1; and Fig. 9 is a graph showing the current flowing through a second spacer as a function of the current applied to the X-ray tube according to Experimental Examples 1 and 2. DETAILED DESCRIPTION

[0026] Exemplary embodiments of the present invention will be described with reference to the accompanying drawings in order that the structures and effects of the present invention will be sufficiently understood. However, the present disclosure may be embodied in other forms and should not be construed 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. Furthermore, the present invention is only defined by the scope of the claims. In the accompanying drawings, components are shown enlarged for convenience of illustration, and the proportions of components may be exaggerated or reduced for clarity of illustration.

[0027] Unless otherwise defined, terms used in embodiments of the present invention should be understood to have meanings commonly understood by those skilled in the art. The present disclosure will be described in detail below by explaining preferred embodiments of the invention with reference to the accompanying drawings. Embodiment 1

[0028] Fig. 1A is a cross-sectional view illustrating a structure of an X-ray tube according to an embodiment of the inventive concept.

[0029] Based on Fig. 1A, an X-ray tube 1100 according to an embodiment of the inventive concept may include a cathode electrode 11, a radiator 12, an anode electrode 14, a target 15, a gate electrode 13, a first spacer SP1, and a second spacer SP2.

[0030] The cathode electrode 11 and the anode electrode 14 are arranged opposite each other and may be spaced apart in a first direction D1. In this patent specification, the first direction D1 represents a direction perpendicular to an upper surface of the cathode electrode 11. Alternatively, the first direction D1 refers to a direction from the cathode electrode 11 toward the anode electrode 14. A second direction D2 represents a direction parallel to the upper surface of the cathode electrode 11.

[0031] The cathode electrode 11, the anode electrode 14, and the gate electrode 13 can be electrically connected to an external power source (not shown). For example, a positive voltage or a negative voltage can be applied to the cathode electrode 11, or it can be connected to a ground power source. A voltage with a higher potential than that of the anode electrode 11 can be applied to the anode electrode 14 and the gate electrode 13.

[0032] Each of the anode electrode 14 and the cathode electrode 11 and the gate electrode 13 may contain a conductive material. The conductive material may, for example, contain a metal material such as copper (Cu), aluminum (Al), molybdenum (Mo), and the like. The anode electrode 14 may be a rotatable anode electrode that rotates in one direction or a stationary anode electrode.

[0033] The gate electrode 13 may be arranged between the radiator 12 and the anode electrode 14. The gate electrode 13 may be arranged adjacent to the radiator 12 instead of the anode electrode 14. The gate electrode 13 may be arranged above the cathode electrode 11 and may include an opening OP at a location corresponding to the radiator 12. If multiple radiators are arranged on the cathode electrode 11, the gate electrode 13 may include multiple openings OP. The gate electrode 13 may, for example, have a mesh shape.

[0034] The emitter 12 may, for example, contain a carbon nanotube. The emitter 12 may be arranged in the form of a dot array or may have the shape of a yarn formed by twisting carbon nanotubes.

[0035] The target 15 may be provided below the anode electrode 14. A lower surface of the target 15, i.e., a surface 15S opposite the cathode electrode 11, may be inclined. The target 16 may contain, for example, molybdenum (Mo) and / or tantalum (Ta) and / or tungsten (W) and / or copper (Cu) and / or gold (Au).

[0036] The electron beam (E-beam) emitted by the emitter 12 can be generated and accelerated in a vacuum state. The E-beam emitted by the emitter 12 can pass through the opening OP of the gate electrode 13 to be focused onto the target 15. The electron beam collides with the target 15 to generate X-rays.

[0037] To create the negative pressure state, the X-ray tube 1000 may be manufactured in a completely sealed state. Alternatively, the interior of the X-ray tube 1000 may be in a negative pressure state according to the manufacturing method by a vacuum pump (not shown) connected to the exterior.

[0038] Both the first spacer SP1 and the second spacer SP2 may have a tubular shape. The first spacer SP1 may be arranged between the cathode electrode 11 and the gate electrode 13. The second spacer SP2 may be arranged between the gate electrode 13 and the anode electrode 14.

[0039] Both the first spacer SP1 and the second spacer SP2 may contain a solid material, even in a negative pressure state. The first spacer SP1 may contain a high-resistance insulator, a medium-resistance insulator, or a low-resistance insulator, which will be described later. For example, the first spacer SP1 may contain a medium-resistance insulator 16M.

[0040] The second spacer SP2 may include the medium-resistance insulator 16M. In this specification, the low-resistance insulator, the medium-resistance insulator, and the high-resistance insulator may be defined according to a volume resistivity (or resistivity) strength.

[0041] The low resistance insulator can be defined as a material with a resistivity of about 10 6 Ω · cm to about 10 9Ω · cm, the medium resistance insulator can be defined as materials with a specific resistance of about 10 9 Ω · cm to about 10 13 Ω · cm and the high resistance insulator can be defined as a material with a resistivity of 10 13 Ω · cm or more.

[0042] The second spacer SP2 may include an insulator and conductive dopants dispersed in the insulator. The conductive dopant may be uniformly distributed in the insulator. Medium-resistivity insulator properties 16M of the second spacer SP2 may be provided by doping conductive dopants into the insulator at a predetermined ratio. For example, the insulator may be included in the second spacer SP2 at a ratio of about 93 wt.% to about 96 wt.%. An amount of conductive dopants in the second spacer SP2 may range from about 1.64 wt.% to about 2.44 wt.%. Further, the second spacer SP2 may include an additive or other impurities. A total amount of the additive in the second spacer SP2 may range from about 1 wt.% to about 4 wt.%.A total amount of impurities in the second spacer SP2 may be less than about 2 wt%.

[0043] The insulator may contain a first metal oxide, and the conductive dopants may contain a second metal oxide. The second metal oxide may have a lower resistivity than the first metal oxide. For example, the first metal oxide may contain aluminum oxide (Al2O3), and the second metal oxide may contain titanium oxide (Ti x O y , x = 1 to 3, y = 1 to 3). The second metal oxide may, for example, contain TiO2 and / or Ti2O3 and / or TiO. For another example, the second metal oxide may contain chromium oxide (Cr2O3).

[0044] The additive may contain a material such as silicon oxide (SiO2) and manganese dioxide (MnO2), which can improve the rigidity of the second spacer SP2 and its adhesion to electrodes during a brazing process described later. The impurities may include carbon and other oxides.

[0045] The aluminum oxide can have a specific resistance of about 10 14 Ω · cm and the titanium dioxide (TiO2) may have a resistivity equal to or less than about 10 9 Ω · cm. Ti2O3 may have a resistivity equal to or less than about 10 -1 Ω · cm and TiO may have a resistivity equal to or less than about 10 -4 Ω · cm.

[0046] Some electrons of the e-beam emitted by the emitter 12 may collide with the gate electrode 13 and thus be scattered. The scattered electrons may collide with the second spacer SP2. Some electrons of the e-beam may be deflected from a normal trajectory to collide with the second spacer SP2.

[0047] At a triple point P1, electrons other than the e-beam can be emitted under high-voltage conditions. The triple point P1 can be a point where the vacuum, the metal of the gate electrode 13, and the insulator of the second spacer SP2 meet, with strong electric fields also being applied and electrons being emitted from the metal. The emitted electrons can collide with the second spacer SP2.

[0048] According to the inventive concept, the medium-resistance insulator 16M can exhibit a certain level of low conductivity under the high-voltage condition, and thus cannot generate separated secondary electrons after collision, even if the electrons collide with the second spacer SP2. The electrons can move toward the anode electrode 14 through the second spacer SP2.

[0049] The second spacer SP2 according to the inventive concept is formed by the following method. For example, more than about 2 wt.% and less than about 2.5 wt.% of titanium dioxide (TiO2) can be added and sintered based on the total amount of the alumina (Al2O3) insulator containing the additive. A high-temperature heat treatment can be performed in a hydrogen gas atmosphere to reduce the resistivity of the second spacer SP2. At least a portion of the titanium dioxide (TiO2) can be reduced in the hydrogen gas atmosphere to produce Ti2O3 and / or TiO.

[0050] The following Table 1 shows electrical properties of an alumina (Al2O3) insulator when about 4 wt% of a titanium dioxide (TiO2) dopant is added, and the electrical properties after heat treatment for about 30 minutes at a temperature of about 1300 °C in the hydrogen gas atmosphere. [Table 1] Electrical properties of the insulator without added conductive dopant Electrical properties of the insulator with added conductive dopant Electrical properties after heat treatment of the insulator with added conductive dopant in hydrogen atmosphere Surface resistance (Q / square) 2,2 · 10 15 3,0 · 10 8 Volume resistivity (Q cm) ~10 14 9,25 · 10 13 6,0 · 10 7 Electrical conductivity (S / cm) 1,12 · 10 -14 1,9 · 10 -8

[0051] From Table 1, it can be seen that the volume resistivity decreases when the dopant is added to the insulator, and that the volume resistivity further decreases when the heat treatment is performed in a hydrogen atmosphere. Additionally, a metallization process may be performed on a portion of the second spacer SP2 that is in contact with the anode electrode 14 and on a portion of the second spacer SP2 that is in contact with the gate electrode 13. The adhesion between the second spacer SP2, both the anode electrode 14 and the gate electrode 13 in the vacuum state may be increased by the metallization process (braze bonding). Embodiment 2

[0052] Fig.Fig. 1B is a cross-sectional view illustrating a structure of an X-ray tube according to the embodiment. Since the above-described content except for the following content to be described below is Fig. 1A, the duplicated content is omitted.

[0053] Based on Fig. 1B, a gate electrode 13 may further include a protrusion 13U protruding from a periphery of an opening OP toward an anode electrode 14. The protrusion 13U may be spaced apart from a second spacer SP2 in the second direction D2. The protrusion 13U may serve to focus the E-beam such that the E-beam passing through the opening OP is directed toward a target.

[0054] Since strong electric fields are applied to an edge P2 of the protrusion 13U according to a high-voltage condition, electrons other than the e-beam can be emitted. The emitted electrons can collide with the second spacer SP2. After the collision, the electrons can move toward the anode 14 without generating the separated secondary electrons. Comparison example

[0055] Fig. 2 is a cross-sectional view of an X-ray tube according to Comparative Example.

[0056] An X-ray tube 2000 according to Comparative Example may include a second spacer SP2 provided as a high-resistance insulator 16H. The high-resistance insulator 16H does not contain a conductive dopant. In the case of the present inventions, in order to achieve stable driving even at a high acceleration voltage of approximately 70 kV or more (a voltage difference between an anode electrode and a cathode electrode), the present second spacer SP2 may generally use the high-resistance insulator 16H.

[0057] Scattered electrons, electrons deviated from a normal trajectory, and electrons emitted from a triple point P1 can collide with the second spacer SP2. Due to the collision, secondary electrons are generated, and the second spacer SP2 becomes charged with a positive charge (e.g., a charging phenomenon), creating a risk of arcing.

[0058] Since the second spacer SP2 is again based on Fig. 1A and Fig.1B in the X-ray tubes 1100 and 1200 according to the inventive concept, the medium-resistance insulator 16M allows electrons to move in a direction of the anode electrode 14 despite collisions with the electrons without generating secondary electrons. Furthermore, the medium-resistance insulator 16M can reduce the strength of electric fields near the triple point P1 and reduce electron emission at the triple point P1. Accordingly, the X-ray tube according to the inventive concept can be stably driven even in a high-voltage state, improving reliability. Embodiment 3

[0059] Fig. 3 is a cross-sectional view of an X-ray tube according to the embodiment. Since the above-described content except the following content to be described below is Fig. 1, the duplicated content is omitted.

[0060] Based on Fig. 3, an x-ray tube 1300 may further include at least one focusing electrode 17 according to some embodiments.

[0061] The focusing electrode 17 may be arranged between a gate electrode 13 and an anode electrode 14. The focusing electrode 17 may be arranged adjacent to the gate electrode 13 instead of the anode electrode 14. The focusing electrode 17 may have a similar shape to the gate electrode 13.

[0062] The X-ray tube 1300 may include a first spacer SP1, a second spacer SP2, and a third spacer SP3. The first spacer SP1 may be disposed between the anode electrode 14 and the gate electrode 13. The second spacer SP2 may be disposed between the gate electrode 13 and the focusing electrode 17. The third spacer SP3 may be disposed between the focusing electrode 17 and the anode electrode 14. Each of the first and second spacers SP1 and SP2 may include a low-resistance insulator, a medium-resistance insulator, or a high-resistance insulator. For example, each of the first and second spacers SP1 and SP2 may include a medium-resistance insulator 16M.

[0063] The third spacer SP3 may include the medium-resistance insulator 16M. A triple point P1 may be provided at a point where the third spacer SP3, the focusing electrode 17, and the vacuum meet. At the triple point P1, electrons other than the e-beam may be emitted under high-voltage conditions. The emitted electrons may collide with the third spacer SP3. After the collision, the electrons may move toward the anode electrode 14 through the third spacer SP3. Embodiments 4 and 5

[0064] Fig. 4A is a cross-sectional view illustrating an X-ray tube according to the embodiment. Fig. Fig. 4B is a cross-sectional view illustrating an X-ray tube according to the embodiment. Since the above-described content except for the following content to be described below is Fig.1, the duplicated content is omitted.

[0065] Based on Fig. 4A, an x-ray tube 1300 may include a second spacer SP2 including a first region R1, a second region R2, and a third region R3 arranged in the first direction D1, according to some embodiments.

[0066] The first region R1 may be a portion adjacent to a gate electrode 13, and the second region R2 may be a portion adjacent to an anode electrode 14. The third region R3 may be arranged between the first region R1 and the second region R2.

[0067] The first region R1 and the second region R2 may be sections of the second spacer SP2 at which the scattered electrons, the electrons deviated from the normal trajectory and the electrons emitted from the triple point P1, which are in Fig.1A, collide with each other relatively frequently.

[0068] A height of the uppermost portion R1U of the first region R1 may be greater than a height of the uppermost portion of the gate electrode 13. A height of the lowermost portion R2B of the second region R2 may be less than a height of a lower surface 15S of a target 15.

[0069] Each of the first region R1, the second region R2, and the third region R3 can have a first length, a second length, and a third length in the first direction D1. The third length can be greater than either the first length or the second length.

[0070] Each of the first region R1 and the second region R2 may include a low-resistance insulator 16L. The third region R3 may include a high-resistance insulator 16H. Both the first volume resistivity of the first region R1 and the second volume resistivity of the second region R2 may be less than a third volume resistivity of the third region R3.

[0071] Each of the first region R1 and the second region R2 may contain an insulator and conductive dopants dispersed in the insulator. Each of the first region R1 and the second region R2 may contain conductive dopants present in a ratio exceeding 3 wt.%. The third region R3 may contain an insulator and may contain substantially no conductive dopants. That is, each of the first region R1 and the second region R2 may optionally contain the conductive dopants. According to one embodiment, the third region R3 may contain less than about 1 wt.% conductive dopants.

[0072] The insulator may contain a first metal oxide, and the conductive dopants may contain a second metal oxide. The first metal oxide may, for example, contain aluminum oxide (Al2O3), and the second metal oxide may be titanium oxide (Ti x O y, x = 1 to 3, y = 1 to 3). The second metal oxide may contain TiO2 and / or Ti2O3 and / or TiO.

[0073] If the first to third areas R3 are all titanium oxide (Ti x O y , x = 1 to 3, y = 1 to 3), a concentration of Ti2O3 and / or TiO in both the first region R1 and the second region R2 is greater than that of Ti2O3 and / or TiO in the third region R3.

[0074] According to the inventive concept, generation of secondary electrons in the scattered electrons, in the electrons that have deviated from the normal trajectory, and in the electrons that have been emitted from the triple point P1, which are in Fig. 1A, although the electrons with the first region R1 and with the second region R2 are Fig.4A collide. In addition, the emission of electrons at the triple point P1 can be reduced because the first region R1 contains a low-resistance insulator 16L.

[0075] As in Fig. 4B, according to some embodiments, a gate electrode 13 may further include a protrusion 13U. A height of the uppermost portion R1U of the first region R1 may be greater than a height of the uppermost portion of the protrusion 13U. The electrons emitted from an edge P2 of the protrusion 13U may collide relatively much in the first region R1 and / or the second region R2, and even if the electrons collide, the generation of the secondary electrons may be reduced.

[0076] The second spacer SP2 according to the inventive concept is formed by the following method. For example, an alumina (Al2O3) insulator can be sintered by selectively adding 3% or more of titanium dioxide (TiO2) to the first region R1 and the second region R2. Thereafter, a heat treatment can be performed on the first region R1 and the second region R2 under a hydrogen reduction atmosphere.

[0077] According to some embodiments, a hydrogen concentration may increase only in portions corresponding to the first region R1 and the second region R2, a heat treatment temperature may increase, or a heat treatment time may increase to promote the reduction reaction of titanium dioxide (TiO2) in the second region R2. If the reduction reaction is promoted, the concentration of Ti2O3 and / or TiO may increase. Embodiment 6

[0078] Fig.5 is a cross-sectional view of an X-ray tube according to embodiments. Components associated with the Fig. 4A are duplicated are omitted.

[0079] Based on Fig. 5, an x-ray tube 1600 may include a second spacer SP2 in which an amount of conductive dopant is gradually changed in the first direction D1, according to some embodiments.

[0080] Each of the first to third regions R1 to R3 may contain an insulator and conductive dopants.

[0081] The first region R1 may have a resistivity that gradually increases in the first direction D1. The first region R1 may include a low-resistance insulator 16L in a portion adjacent to a gate electrode 13 and a medium-resistance insulator 16M in a portion adjacent to the third region R3.

[0082] In the first region R1, a concentration of the conductive dopants may gradually increase in the first direction D1. That is, the concentration of the conductive dopants in the first region R1 may be highest in the portion adjacent to the gate electrode 13 and may be lowest in the portion adjacent to the third region R3.

[0083] According to some embodiments, a concentration of Ti2O3 and / or TiO in the first region R1 may be highest in the portion adjacent to the gate electrode 13 and lowest in the portion adjacent to the third region R3.

[0084] The second region R2 may have a resistivity that gradually decreases in the first direction D1. The second region R2 may include a medium-resistance insulator 16M in the portion adjacent to the third region R3 and a low-resistance insulator 16L in a portion adjacent to the anode electrode 14.

[0085] In the second region R2, a concentration of the conductive dopants may gradually increase in the first direction D1. That is, the concentration of the conductive dopants in the second region R2 may be lowest in the portion adjacent to the third region R3 and highest in the portion adjacent to the anode electrode 14.

[0086] According to some embodiments, a concentration of Ti2O3 and / or TiO in the second region R2 may be highest in the portion adjacent to the anode electrode 14 and lowest in the portion adjacent to the third region R3.

[0087] The third region R3 may have a resistivity that gradually decreases in the first direction D1 and then gradually decreases. The third region R3 may include a medium-resistance insulator in a portion adjacent to both the first region R1 and the second region R2, and may include a high-resistance insulator 16H in an intermediate portion.

[0088] In the third region R3, a concentration of the conductive dopants may gradually decrease in the first direction D1 and then gradually increase. The concentration of conductive dopants in the third region R3 may be highest in both the portion adjacent to the first region R1 and the portion adjacent to the second region R2, and may be lowest in the intermediate portion. According to some embodiments, a concentration of Ti2O3 and / or TiO in the third region R3 may be highest in both the portion adjacent to the first region R1 and the portion adjacent to the second region R2, and may be lowest in a portion between the two portions described above.

[0089] Table 2 below shows experimental values ​​of the volume resistivity of the second spacer according to the amount of conductive dopant added. Samples were prepared by adding varying amounts of titanium dioxide (TiO2) to approximately 95 wt% to approximately 96 wt% alumina (Al2O3) and then performing molding and sintering. The volume resistivity of each sample was then measured. [Table 2] Amount of TiO2 added specific volume resistivity R v (Ω cm) Test procedures 1 wt.% 4,6 · 10 13 ASTM D257 2 wt.% 6,8 · 10 12 ASTM D257 3 wt.% 7,1 · 10 9 ASTM D257 4 wt.% 6,0 · 10 7 ASTM D991

[0090] Fig. Figure 6 is a graph illustrating the emission current versus a voltage applied to an X-ray tube according to Comparative Example 1. An X-ray tube according to Comparative Example 1 includes a second spacer made of Al2O3 that does not contain a conductive dopant.

[0091] Based on Fig.6, a current of approximately 0.5 mA was applied to the X-ray tube, and the voltage was gradually increased from approximately 10 kV to approximately 60 kV. The applied voltage was maintained for approximately 3 minutes, and the X-ray tube was driven under conditions of approximately 0.1 msW and approximately 1 sP. As indicated by the arrow, the current increased rapidly at a voltage of approximately 60 kV, generating an arc. In this case, there is a risk of tube damage.

[0092] Fig. 7 is a graph showing the current flowing through a second spacer versus the current applied to an X-ray tube according to Comparative Examples 2 and 3.

[0093] Based on Fig.7, the X-ray tube according to Comparative Example 2 contains a second spacer to which about 2 wt.% titanium dioxide (TiO2) is added. The X-ray tube according to Comparative Example 3 contains a second spacer to which about 2.5 wt.% titanium dioxide (TiO2) is added. The amount of added titanium dioxide was expressed based on a total weight of the second spacer before the titanium dioxide is added. The second spacer before the addition of the titanium dioxide (TiO2) contains about 94 wt.% to about 96 wt.% Al2O3 and about 1 wt.% to about 4 wt.% of an additive. Fig.7, it was observed that in Comparative Example 2, almost no current flows at the high voltage (about 70 kV), and in Comparative Example 3, an excessive amount of current, for example, about 200 µA, flows at the high voltage (about 70 kV). It can be seen that the amount of titanium dioxide (TiO2) added is preferably greater than about 2 wt% and less than about 2.5 wt%.

[0094] Based on Fig. 7 and Table 1 it can be seen that the second spacer has a volume resistivity of about 6.8 10 12 Ω · cm to about 7.1 · 10 9 Ω · cm when TiO2 is contained in a ratio ranging from about 2 wt% to about 3 wt%. It can be seen that the second spacer has a volume resistivity of about 10 9 Ω · cm and less than about 10 13Ω · cm when titanium dioxide (TiO2) is present in a ratio of about 1.64 wt% to about 2.44 wt%.

[0095] Fig. 8A and Fig. 8B are graphs illustrating the current applied to an X-ray tube according to Experimental Examples 1 and 2, respectively.

[0096] Fig. 8A and Fig. 8B are graphs illustrating the emission current applied to an X-ray tube according to Experimental Example 1. In Experimental Example 1, the X-ray tube contains a second spacer to which about 2.15 wt% titanium dioxide (TiO2) is added. The second spacer contained about 94 wt% to about 96 wt% Al2O3 and about 1 wt% to about 4 wt% of an additive prior to the addition of the titanium dioxide (TiO2). Fig.8A represents the emission current when the voltage conditions of about 20 mA, about 1 msW, about 100 msP, and about 120 kV are maintained for about 3 minutes in Experimental Example 1. Fig. Figure 8A represents the emission current when the voltage conditions of about 10 mA, about 100 msW, about 6 sP, and about 120 kV are maintained for about 10 minutes in Experimental Example 1. Fig. 8A and Fig. 8B shows that the emission current in Experimental Example 1 is maintained stable even under the high voltage condition of 120 kV.

[0097] Fig.Figure 9 is a graph illustrating the current flowing through a second spacer versus the current applied to the X-ray tube according to Experimental Examples 1 and 2. An X-ray tube according to Experimental Example 1(A) contains a second spacer to which about 2.15 wt% titanium dioxide (TiO2) is added. An X-ray tube according to Experimental Example 2(B) contains a second spacer to which about 2.25 wt% titanium dioxide (TiO2) is added.

[0098] In both experimental examples 1(A) and 2(B), the second spacer contained about 94 wt% to about 96 wt% Al2O3 and about 1 wt% to about 4 wt% of an additive prior to the addition of titanium dioxide (TiO2).

[0099] In Experimental Example 1(A), the current was maintained at approximately 0.8 µA as a result of maintaining a voltage of 150 kV for approximately 5 minutes. In Experimental Example 2(B), the current increased from 23 µA to approximately 37 µA as a result of maintaining a voltage of 150 kV for approximately 5 minutes. It can be seen that the second spacer in both Experimental Examples 1(A) and 2(B) has a certain level of low conductivity, which is desirable in the inventive concept under high voltage conditions. [Table 3] composition component Mass ratio (wt%) insulator Al2O3 94,0 Additive MgO 0,76 SiO2 2,37 Conductive dopant TiO2 (other Ti oxides) 1,77 Contamination Fe2O3, Na2O, K2O, ZrO2, ZnO, C and the like 1,11

[0100] Table 3 shows a composition ratio of the second spacer after sintering the second spacer under the hydrogen atmosphere by adding about 2.15 wt% TiO2, based on a total amount of the second spacer containing about 95 wt% to about 96 wt% Al2O3 and about 4 wt% of the additive. From Table 3, it was observed that a final second spacer contains about 1.77 wt% titanium oxide when about 2.15 wt% TiO2 is added. Furthermore, it was observed that the final second spacer contains about 94 wt% Al2O3.

[0101] When about 2 wt% TiO2 is added in the above manner, the final second spacer contains about 1.64 wt% titanium oxide, and when about 2.5 wt% TiO2 is added, the final second spacer contains about 2.44 wt% titanium oxide.

[0102] The X-ray tube according to the inventive concept may include the insulator and the conductive dopants doped in the insulator at the predetermined ratio to be driven even at the high voltage.

Claims

[1] X-ray tube comprising: a cathode electrode (11); an anode electrode (14) vertically spaced from the cathode electrode (11); a radiator (12) on the cathode electrode; a gate electrode (13) arranged between the cathode electrode (11) and the anode electrode (14), the gate electrode (13) comprising an opening at a position corresponding to the radiator (12); and a spacer (16M) provided between the gate electrode (13) and the anode electrode (14), wherein the spacer (SP2) comprises a doped region, the doped region being provided with an insulator and comprising conductive dopants doped in the insulator, and wherein the gate electrode (13) is in contact with the doped region. [2] X-ray tube according to claim 1, wherein the spacer (SP2) has a volume resistivity of about 10 9 Ω · cm or more and less than about 10 13 Ω · cm. [3] An X-ray tube according to claim 1 or 2, wherein the insulator comprises aluminum oxide (Al2O3) and the conductive dopants comprise titanium dioxide (TiO2). [4] The x-ray tube of claim 1, 2 or 3, wherein the spacer (SP2) comprises more than about 1.64 wt% and less than about 2.44 wt% of the conductive dopants. [5] X-ray tube according to one of claims 1-4, wherein the insulator comprises a first metal oxide having a resistivity of about 10 13 Ω · cm or more, and the conductive dopants are a second metal oxide with a resistivity of about 10 8 Ω · cm or less. [6] An X-ray tube according to any one of claims 1-5, wherein a voltage applied to the anode electrode is about 70 kV or more. [7] An X-ray tube according to any one of claims 1-6, wherein the gate electrode (13) further comprises a projection (13U) extending toward the anode electrode (14). [8] X-ray tube according to one of claims 1-7, wherein the spacer (SP2) comprises more than about 1.64 wt.% and less than about 2.44 wt.% titanium oxide (Ti x O y , x = 1 to 3, y = 1 to 3). [9] An X-ray tube according to any one of claims 1-8, wherein the spacer (SP2) comprises about 93 wt% to about 96 wt% alumina. [10] X-ray tube comprising: a cathode electrode (11); an anode electrode (14) vertically spaced from the cathode electrode (11); a target arranged on a surface of the anode electrode (14), one surface of the anode electrode (14) facing the cathode electrode (11); a radiator (12) on the cathode electrode; a gate electrode (13) arranged between the cathode electrode (11) and the anode electrode (14), the gate electrode (13) comprising an opening at a position corresponding to the radiator (12); and a spacer (SP2) provided between the gate electrode (13) and the anode electrode (14), wherein the spacer (SP2) comprises a first and a second region (R1, R2) between the gate electrode (13) and the anode electrode (14) and a third region (R3) between the first and the second region (R1, R2), wherein the first region (R1) is in contact with the gate electrode (13), wherein the second region (R2) is adjacent to the anode electrode (14), wherein each of the first to third regions (R1, R2, R3) comprises an insulator, and each of the first to second regions (R1, R2) further comprises conductive dopants doped in the insulator. [11] The X-ray tube according to claim 10, wherein both a volume resistivity of the first region and a volume resistivity of the second region are smaller than a volume resistivity of the third region. [12] X-ray tube according to claim 10 or 11, wherein both the first region (R1) and the second region (R2) have a volume resistivity of about 10 6 Ω · cm or more and less than about 10 9 Ω · cm, and wherein the third region (R3) has a specific volume resistivity of about 10 13 Ω · cm or more. [13] An x-ray tube according to any one of claims 10-12, wherein each of the first region (R1) and the second region (R2) comprises about 3 wt% or more of conductive dopants. [14] An X-ray tube according to any one of claims 10-13, wherein the third region (R3) further comprises conductive dopants in the insulator; the first region (R1) has a concentration of the conductive dopants which decreases in a first direction from the cathode electrode (11) towards the anode electrode (14), the second region (R2) has a concentration of the conductive dopants that increases in the first direction, and the third region (R3) has a concentration of the conductive dopants that decreases in the first direction and then increases. [15] X-ray tube according to one of claims 10-14, wherein both a first length of the first region (R1) in a first direction from the cathode electrode (11) towards the anode electrode (14) and a second length of the second region in the first direction are smaller than a third length of the third region in the first direction. [16] X-ray tube according to one of claims 10-15, wherein a sum of a volume of the first region (R2) and a volume of the second region (R2) is smaller than a volume of the third region (R3). [17] An X-ray tube according to any one of claims 10-16, wherein a height of the uppermost portion of the first region (R1) is greater than a height of the uppermost portion of the gate electrode (13), and a height of the lowermost portion of the second region (R2) is less than a height of the lowermost portion of the anode electrode (14). [18] X-ray tube according to claim 17, further comprising at least one focusing electrode (17) between the gate electrode (13) and the anode electrode (14), wherein the height of the uppermost portion of the first region (R1) is greater than a height of the uppermost portion of the focusing electrode (17), and wherein the first region is in contact with the focusing electrode (17).

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