Electron source, electron gun, and device using the same

Abstract

To provide an electron source that can improve the temperature stability of an electron emission part during heating, and an electron gun and an electronic device including the same.SOLUTION: An electron source includes an electron emission part containing an alloy of iridium and rare earth elements, a support part made of metal, and a joint part that joins the electron emission part and the support part. The joint part includes a coating layer containing iridium and metal in the support part.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to an electron source, and an electron gun and device using the same. [Background technology]

[0002] Electron guns equipped with an electron source are used in devices such as X-ray generators, electron beam generators, electron beam type metal 3D printers, and electron microscopes (SEM and TEM). The electron source includes an electron emitter and a filament that heats the electron emitter. As such an electron source, for example, the electron source described in the following Non-Patent Document 1 is known. The document describes that an IrCe emitter is welded to a tungsten heater filament. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Roberto Rao and Oleg Kultashev, “Ir-Ce cathodes as high-density emitters in electron beam ion sources”, 1997, Measurement Science Technology,Volume8, Number 2, 184 Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, in an electron source, it is desirable to stabilize the amount of electron beam emitted from the electron emitting portion, and for this purpose, it is desirable that the temperature of the electron emitting portion be stable when heated. However, the electron source described in Non-Patent Document 1 above has room for improvement in terms of improving the temperature stability of the electron-emitting portion during heating.

[0005] An object of the present disclosure is to provide an electron source capable of improving the temperature stability of an electron emission portion during heating, and an electron gun and an electron device using the same. [Means for solving the problem]

[0006] The present disclosure provides an electron source comprising: an electron emitting portion including an alloy of iridium and a rare earth element; a supporting portion made of a metal; and a joint portion that joins the electron emitting portion and the supporting portion, the joint portion having a coating layer that coats a surface of the supporting portion, the coating layer including iridium and the metal in the supporting portion. According to the electron source, the joint has a coating layer that coats the surface of the support, and the coating layer contains iridium and a metal in the support. That is, the coating layer contains both the iridium in the electron emitter and the metal in the support. Therefore, the thermal expansion coefficient of the coating layer is close to that of the electron emitter and that of the support. Therefore, even if the electron emitter is heated by heat generated by energization of the support, and stress is applied to the joint due to the difference in thermal expansion coefficient between the support and the electron emitter, the stress is alleviated by the coating layer, and the occurrence of cracks in the electron emitter is suppressed. As a result, the electron source of the present disclosure can improve the temperature stability of the electron emitter when heated.

[0007] In the above electron source, it is preferable that the junction bonds the coating layer and the electron emitting portion and further includes an enclosure containing iridium, and that the concentration of the rare earth element in the enclosure is equal to or lower than the concentration of the rare earth element in the electron emitting portion. In this case, since the surrounding portion contains the same iridium as the electron-emitting portion and has a rare earth element concentration equal to or lower than that of the electron-emitting portion, a reaction caused by heat between the electron-emitting portion and the surrounding portion is unlikely to occur, and erosion or contamination of the electron-emitting portion due to the reaction is suppressed. As a result, the electron source can further improve the temperature stability of the electron-emitting portion when heated.

[0008] In the above electron source, it is preferable that the surrounding portion contains an alloy of the iridium and a rare earth element, and the concentration of the rare earth element in the surrounding portion is lower than the concentration of the rare earth element in the electron emission portion. In this case, the melting point of the surrounding portion is lower than the melting point of the electron emission portion, and the surrounding portion is softer than the electron emission portion. Therefore, even if the support portion expands when heated, the stress caused by the expansion is alleviated not only in the coating layer but also in the surrounding portion, so that the occurrence of cracks in the electron emission portion is further suppressed.

[0009] The electron source is particularly useful when the thermal expansion coefficient of the electron-emitting portion is greater than the thermal expansion coefficient of the supporting portion. This is because if the thermal expansion coefficient of the electron-emitting portion is larger than that of the supporting portion, stress is likely to be applied to the joint portion due to the difference in thermal expansion coefficient between the supporting portion and the electron-emitting portion when the electron-emitting portion is heated.

[0010] In the above electron source, the coating layer is preferably a sintered body containing voids. When the coating layer is a sintered body containing voids, even if stress is applied to the coating layer during heating, the stress is easily absorbed and alleviated by the voids in the sintered body, and the occurrence of cracks in the electron emission section is further suppressed. As a result, the electron source can further improve the temperature stability of the electron emission section during heating.

[0011] The surrounding portion is preferably a sintered body containing voids. When the surrounding portion is a sintered body including voids, even if stress is applied to the surrounding portion during heating, the stress is easily absorbed and alleviated by the voids in the sintered body, and the occurrence of cracks in the electron emission portion is further suppressed. As a result, the electron source can further improve the temperature stability of the electron emission portion during heating.

[0012] In the above electron source, it is preferable that a part of the supporting portion penetrates the joint portion. In this case, the contact area between the support and the joint is larger than when a part of the support does not penetrate the joint, and heat generated by energizing the support is transferred to the electron emitter via the joint, so that the electron emitter can be heated efficiently. Also, since a part of the support penetrates the joint, the support is firmly fixed by the joint, so that the electron emitter is less likely to fall off the support.

[0013] In the above electron source, the metal in the supporting portion is preferably at least one selected from the group consisting of tungsten, iridium, molybdenum, tantalum, and rhenium. In this case, even if the supporting portion is electrically heated to a temperature at which electrons are emitted from the electron emitting portion, deformation of the supporting portion can be suppressed.

[0014] In the above electron source, the rare earth element of the electron emitting portion may be at least one selected from the group consisting of cerium, lanthanum, and praseodymium.

[0015] In the above electron source, it is preferable that the rare earth element is cerium, and the alloy of the electron emitting portion is made of at least one selected from the group consisting of Ir2Ce, Ir3Ce, Ir5Ce, and Ir7Ce2. In this case, the life of the electron emitting portion can be extended, and therefore the life of the electron source can be extended.

[0016] Another aspect of the present disclosure provides an electron gun including the electron source described above. According to this electron gun, when the electron source is heated, electrons are emitted from the electron emitting portion and are emitted as an electron beam. At this time, since the electron source can improve the temperature stability of the electron emitting portion during heating, the electron gun can improve the stability of the emission amount of the electron beam.

[0017] Yet another aspect of the present disclosure provides a device including the electron gun described above. According to this device, the stability of the emission amount of the electron beam can be improved, and therefore the performance of the device can be improved. Effect of the Invention

[0018] According to the present disclosure, there are provided an electron source capable of improving the temperature stability of an electron emission portion during heating, and an electron gun and device using the same. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 is a schematic diagram showing an embodiment of a device according to the present disclosure. [Diagram 2] 2 is a partial cross-sectional front view showing one embodiment of the electron gun of FIG. 1. [Diagram 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. [Figure 4] FIG. 4 is a diagram showing a modified example of the electron source in FIG. [Diagram 5] 2 is a cross-sectional view showing another embodiment of the electron gun of FIG. 1. [Figure 6] 4 is a graph showing the change over time in temperature of the electron emitting portion according to Example 1. [Figure 7] 10 is a graph showing the change over time in temperature of the electron emitting portion according to Example 2. [Figure 8] 13 is a graph showing changes over time in temperature of the electron emitting portion according to Comparative Example 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, preferred embodiments of the electron source, the electron gun, and the device of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, the same elements or elements having equivalent functions are denoted by the same reference numerals, and duplicated descriptions will be omitted.

[0021] The device 100 shown in FIG. 1 is an X-ray generating apparatus that generates X-rays XR, and includes an X-ray emission unit 10 that emits X-rays XR, a power supply unit 20 connected to the X-ray emission unit 10, and a vacuum pump 50 connected to the X-ray emission unit 10.

[0022] The power supply unit 20 includes a power source 21 and a metal case 22 that houses the power source 21. The power source 21 is molded in the case 22 with an electrically insulating resin (for example, epoxy resin).

[0023] The X-ray emission unit 10 includes an electron gun 11 that emits an electron beam EB, and a cylindrical portion 12 that is connected to a case 22 and that houses the electron gun 11 and is made of metal (for example, stainless steel). The electron gun 11 is fixed to a neck portion 13 made of resin or the like within the cylindrical portion 12, and is electrically connected to a power source 21. The electron gun 11 is capable of emitting an electron beam EB by power supplied from the power source 21. A target 14 is fixed to the tip of the cylindrical portion 12, which converts the electron beam EB emitted from the electron gun 11 into X-rays XR and emits the X-rays. A partition plate 18 is installed inside the cylindrical portion 12, and an electron path 15 extends along a direction connecting the partition plate 18 and the target 14. A pair of cylindrical coil portions 16 and 17 that function as electromagnetic lenses are arranged around and along the electron path 15. The vacuum pump 50 is connected to the cylindrical portion 12 and is capable of evacuating the internal space of the cylindrical portion 12 to create a vacuum state.

[0024] In the device 100, when the inside of the cylindrical portion 12 is evacuated by the vacuum pump 50 and power is supplied from the power supply 21 to the electron gun 11, an electron beam EB is emitted from the electron gun 11. The electron beam EB passes through the electron path 15 while being focused and deflected by the coil portions 16 and 17, and is irradiated onto the target 14, which then emits X-rays XR.

[0025] The electron gun 11 will be described in detail with reference to Figures 2 and 3. Figure 2 is a partially sectional front view showing one embodiment of the electron gun of Figure 1, and Figure 3 is a sectional view taken along line III-III of Figure 2. 2, the electron gun 11 includes an electron source 30 and an electrode 40. A voltage can be applied to the electron source 30 and the electrode 40 by a power source 21.

[0026] The electrode 40 has a beam passage opening 41 through which the electron beam EB emitted from the electron source 30 passes.

[0027] The electron source 30 includes a plate-shaped electron emitting portion 31 disposed opposite the electrode 40, a linear filament (support portion) 32 having a circular cross section, and a joint portion 33 that joins the electron emitting portion 31 and the filament 32. The electron emitting portion 31 contains an alloy of iridium and a rare earth element, and the filament 32 is made of a metal. In this embodiment, the filament 32 is fixed to the back surface of the electron emitting portion 31 opposite to the electron emitting surface from which electrons are emitted.

[0028] A power supply pin 34 is connected to each end of the filament 32, and the power supply pin 34 may pass through a plate-shaped insulating support member 35 and be fixed to the insulating support member 35. The insulating support member 35 is made of, for example, ceramic. The power supply pin 34 is capable of supplying electric power.

[0029] 3, the joint 33 includes a coating layer 33a that contains iridium and a metal in the filament 32. The joint 33 may further include an enclosure 33b that surrounds a part of the coating layer 33a. Here, the enclosure 33b can also be said to be a joining portion that joins the coating layer 33a and the electron emission portion 31.

[0030] According to the electron source 30, the joint 33 has a coating layer 33a that coats the surface of the filament 32, and the coating layer 33a contains iridium and a metal in the filament 32. That is, the coating layer 33a contains both the iridium in the electron emitter 31 and the metal in the filament 32. Therefore, the thermal expansion coefficient of the coating layer 33a is close to that of the electron emitter 31 and that of the filament 32. Therefore, even if the electron emitter 31 is heated by heat generated by energization of the filament 32 and stress is applied to the joint 33 due to the difference in thermal expansion coefficient between the filament 32 and the electron emitter 31, the stress is alleviated by the coating layer 33a, and the occurrence of cracks in the electron emitter 31 is suppressed. As a result, the electron emitter 31 and the filament 32 can maintain a stable bonding state, and the electron source 30 can improve the temperature stability of the electron emitter 31 during heating. Therefore, the electron gun 11 can improve the stability of the emission amount of the electron beam EB. This makes it possible to improve the performance of the device 100. Specifically, it is possible to improve the stability of the amount of X-rays XR emitted.

[0031] The electron source 30 will now be described in more detail.

[0032] <Electron emission section> The electron emitting portion 31 is a portion that is heated by a filament 32 and emits electrons. The electron emitting portion 31 contains an alloy of iridium and a rare earth element.

[0033] The rare earth elements include cerium, lanthanum and praseodymium, which may be used alone or in combination of two or more. Here, it is preferable that the rare earth element is cerium, and the alloy of the electron emitting portion 31 is composed of at least one selected from the group consisting of Ir2Ce, Ir3Ce, Ir5Ce, and Ir7Ce2. In this case, the life of the electron emitting portion 31 can be extended, and therefore the life of the electron source 30 can be extended. In particular, the alloy of the electron emitting portion 31 is preferably composed of at least one selected from the group consisting of Ir2Ce, Ir3Ce, and Ir7Ce2. In this case, the electron emitting portion 31 is less likely to change over time, and a longer life is possible.

[0034] The thermal expansion coefficient of the electron emitter 31 may be greater than or less than that of the filament 32, but the electron source 30 is particularly useful when it is greater than that of the filament 32. This is because if the thermal expansion coefficient of the electron emitter 31 is greater than that of the filament 32, stress is likely to be applied to the joint 33 due to the difference in thermal expansion coefficient between the filament 32 and the electron emitter 31 when the electron emitter 31 is heated.

[0035] The electron emitting portion 31 may be a sintered body containing voids or a solid body containing no voids, but is preferably a solid body containing no voids. If the electron emitting section 31 is a solid body containing no voids, the electron emitting section 31 is less likely to change over time, and a longer life can be achieved.

[0036] <Filament> The filament 32 is made of a metal. The metal is not particularly limited as long as it is a metal that does not deform or melt when heated by current flow up to a temperature at which electrons are emitted from the electron emitting portion 31, and may be iridium or a metal other than iridium. As the above metal, a high melting point metal is preferable. A refractory metal is a metal that has a melting point of about 1800°C or higher. As the high melting point metal, for example, tungsten, iridium, molybdenum, tantalum and rhenium are preferable. These may be used alone or in combination of two or more. In this case, even if the filament 32 is heated by current application to a temperature at which electrons are emitted from the electron emitting portion 31, deformation of the filament 32 can be suppressed. As the high melting point metal, tungsten is preferable because it has a low thermal expansion coefficient and is particularly resistant to deformation when an electric current is passed through it.

[0037] The filament 32 has a fixing portion 32a that is fixed to the joint portion 33. The fixing portion 32a may be embedded in the joint portion 33 and may pass through the joint portion 33, or may be exposed on the surface of the joint portion 33 and may not pass through the joint portion 33. However, it is preferable that the fixing portion 32a is embedded in the joint portion 33 and passes through the joint portion 33. In this case, the contact area between the filament 32 and the joint 33 is larger than when the fixing portion 32a of the filament 32 does not penetrate the joint 33, and heat generated at the fixing portion 32a by energizing the filament 32 is transferred to the electron emitting portion via the joint 33, so that the electron emitting portion can be heated efficiently. In addition, since the filament 32 has the fixing portion 32a and the fixing portion 32a penetrates the joint 33, the filament 32 is firmly fixed by the joint 33, so that the electron emitting portion 31 is less likely to fall off the filament 32.

[0038] In FIG. 3, the fixing portion 32a of the filament 32 is a cylinder having a circular cross section, and the filament 32 as a whole is made of, for example, a linear member, but as shown in FIG. 4, it may be a ribbon (flat member) having a rectangular cross section. In this case, when the long side of the rectangular cross section of the fixing portion 32a of the filament 32 faces the electron emitter 31, it is possible to increase the contact area between the electron emitter 31 and the fixing portion 32a of the filament 32 via the coating layer 33a of the joint portion 33, so that the electron emitter 31 can be stably fixed on the filament 32. Note that the coating layer 33a may cover the entire circumference of the fixing portion 32a of the filament 32 as shown in FIG. 4, or may cover only a part of the fixing portion 32a.

[0039] Furthermore, the fixing portion 32a of the filament 32 may be an annular body. In this case, it is possible to increase the contact area between the electron emitter 31 and the fixing portion 32a of the filament 32 via the coating layer 33a of the joint portion 33, so that the electron emitter 31 can be stably fixed onto the filament 32. Furthermore, when the fixing portion 32a is an annular body, it is possible to reduce the temperature difference between the inner and outer portions of the annular body on the back surface of the electron emitter 31, and it is possible to reduce temperature unevenness overall in the electron emitter 31.

[0040] Furthermore, the fixing portion 32a of the filament 32 may be a spiral body. In this case, it is possible to increase the contact area between the electron emitter 31 and the fixing portion 32a of the filament 32 via the coating layer 33a of the joint portion 33, so that the electron emitter 31 can be stably fixed onto the filament 32. Furthermore, when the fixing portion 32a is a spiral body, the fixing portion 32a can be brought into contact with most of the back surface of the electron emitter 31, so that the temperature unevenness in the electron emitter 31 as a whole can be sufficiently reduced.

[0041] <Joint part> (covering layer) The coating layer 33a contains iridium and the metal in the filament 32. When the metal contained in the filament 32 is tungsten, the coating layer 33a becomes an alloy layer containing an alloy of iridium and tungsten (Ir-W). The coating layer 33a may be a sintered body containing voids or a solid body containing no voids, but is preferably a sintered body containing voids. Since the covering layer 33a is a sintered body including voids, even if stress is applied to the covering layer 33a during heating, the stress is easily absorbed and alleviated by the voids in the sintered body, and the occurrence of cracks in the electron emitting section 31 is further suppressed. As a result, the electron source 30 can further improve the temperature stability of the electron emitting section 31 during heating. When the coating layer 33a is a sintered body containing voids, the coating layer 33a can be formed by fixing iridium powder onto the filament 32 by sintering.

[0042] The thickness of the coating layer 33a is not particularly limited, but is preferably 1 μm or more, and more preferably 10 μm or more. The thickness of the coating layer 33a may be 100 μm or less, or may be 50 μm or less. Although the covering layer 33a is in contact with the rear surface of the electron emitting portion 31 in FIG.

[0043] (Enclosure) The surrounding portion 33b contains iridium, and the concentration of the rare earth element in the surrounding portion 33b is preferably equal to or lower than the concentration of the rare earth element in the electron emitting portion 31. For example, when the electron emitting portion 31 contains Ir2Ce, the surrounding portion 33b may contain at least one selected from the group consisting of Ir2Ce, Ir3Ce, Ir7Ce2, Ir5Ce, and Ir. When the electron emitting portion 31 contains Ir3Ce, the surrounding portion 33b may contain at least one selected from the group consisting of Ir3Ce, Ir7Ce2, Ir5Ce, and Ir. When the electron emitting portion 31 contains Ir7Ce2, the surrounding portion 33b may contain at least one selected from the group consisting of Ir7Ce2, Ir5Ce, and Ir. When the electron emitting portion 31 contains, for example, Ir5Ce, the surrounding portion 33b may contain Ir5Ce and Ir. The surrounding portion 33b may contain the metal in the filament 32. When the concentration of the rare earth element in the surrounding portion 33b is equal to or lower than the concentration of the rare earth element in the electron emitting portion 31, the surrounding portion 33b contains the same iridium as the electron emitting portion 31 and has a rare earth element concentration equal to or lower than the concentration of the rare earth element in the electron emitting portion 31. This makes it difficult for a reaction caused by heat to occur between the electron emitting portion 31 and the joint portion 33, and suppresses erosion and contamination of the electron emitting portion 31 due to the reaction. As a result, the electron source 30 can further improve the temperature stability of the electron emitting portion 31 during heating. The concentration of the rare earth element in the surrounding portion 33b may be zero. In other words, the surrounding portion 33b may not contain a rare earth element. Furthermore, it is preferable that the surrounding portion 33b contains an alloy of iridium and a rare earth element, and the concentration of the rare earth element in the surrounding portion 33b is lower than the concentration of the rare earth element in the electron emitting portion 31. For example, when the electron emitting portion 31 contains Ir2Ce, the surrounding portion 33b may contain at least one selected from the group consisting of Ir3Ce, Ir7Ce2, and Ir5Ce. When the electron emitting portion 31 contains Ir3Ce, the surrounding portion 33b may contain at least one selected from the group consisting of Ir7Ce2 and Ir5Ce. When the electron emitting portion 31 contains Ir7Ce2, the surrounding portion 33b may contain at least one selected from the group consisting of Ir5Ce. When the concentration of the rare earth element in the surrounding portion 33b is lower than the concentration of the rare earth element in the electron emitting portion 31, the melting point of the surrounding portion 33b becomes lower than the melting point of the electron emitting portion 31, and the surrounding portion 33b becomes softer than the electron emitting portion 31. Therefore, even if the filament 32 expands when heated, the stress caused by the expansion is mitigated not only by the coating layer 33a but also by the surrounding portion 33b, so that the occurrence of cracks in the electron emitting portion 31 is further suppressed.

[0044] The surrounding portion 33b may be a sintered body containing voids or a solid body containing no voids, but is preferably a sintered body containing voids. Since the surrounding portion 33b is a sintered body including voids, even if stress is applied to the surrounding portion 33b during heating, the stress is easily absorbed and alleviated by the voids in the sintered body, and the occurrence of cracks in the electron emitter 31 is further suppressed. As a result, the electron source 30 can further improve the temperature stability of the electron emitter 31 during heating. In addition, when the surrounding portion 33b is a sintered body containing voids, the surrounding portion 33b can be formed by bonding the electron emission portion 31 and a composite formed by forming a coating layer 33a on the filament 32, for example, by sintering an alloy powder of iridium and a rare earth element.

[0045] The present disclosure is not limited to the above embodiment. For example, in the electron source 30 of the above embodiment, the filament 32 is fixed to the back surface of the electron emitter 31 opposite to the electron emission surface from which electrons are emitted, but as in the electron source shown in FIG. 5, the electron emitter 31 may be fixed inside the cylindrical filament 32 via a joint 33. Here, the coating layer 33a (not shown in FIG. 5) of the joint 33 is provided on the inner surface side of the filament 32. Also, the cylindrical filament 32 may be in the form of a wire material having a circular cross section wound in a coil shape (see FIG. 5), or in the form of a ribbon material having a rectangular cross section wound in a coil shape. As shown in FIG. 5, a pedestal 37 supporting the electron emitter 31 may be further provided inside the cylindrical filament 32, or the pedestal 37 may be omitted and the electron emitter 31 may be extended downward. The pedestal 37 may be made of the same material as the filament 32, for example, and in this case, it is preferable that a joint 33 is also provided between the pedestal 37 and the electron emitter 31. Here, the coating layer 33a of the joint 33 is provided on the side of the base 37. The power supply pin 34 may be connected to the filament 32 via a tantalum foil 36 or the like. The electron source shown in FIG. 5 can be obtained by fixing a base 37 to the inside of a cylindrical filament 32, fixing the electron emitter 31 inside the filament 32 using a powder or molded body made of an alloy of iridium and the metal in the filament 32 as a brazing material, and then welding the power supply pin 34 via a tantalum foil 36. Furthermore, in the above embodiment, the electron gun 11 includes the electron source 30 and the electrode 40 , but the electron gun of the present disclosure does not necessarily need to include the electrode 40 .

[0046] Moreover, the electron source of the present disclosure may have the electron emitting portion 31 fixed onto the filament 32 containing a metal foil via a joint portion 33. This electron source can be obtained by fixing the electron emitting portion 31 to the metal foil of the filament 32 by using a powder or molded body made of an alloy of iridium and a metal in the filament 32 as a brazing material on the metal foil of the filament 32.

[0047] The device of the present disclosure is not limited to the device of the above embodiment. For example, the device 100 of the above embodiment is an X-ray generator, but the device of the present disclosure is not particularly limited as long as it is a device equipped with an electron source, and may be an electron beam generator, an electron beam type metal 3D printer, an electron microscope (SEM and TEM), etc.

[0048] The outline of this disclosure is as follows. [1] An electron emitting portion including an alloy of iridium and a rare earth element; A support part made of metal; a joining portion that joins the electron emission portion and the support portion, the joint portion has a coating layer that coats a surface of the support portion, The electron source, wherein the coating layer comprises iridium and the metal in the support. [2] The joint further includes an enclosure portion that surrounds at least a portion of the coating layer and contains iridium; The electron source according to [1], wherein the concentration of the rare earth element in the surrounding portion is equal to or lower than the concentration of the rare earth element in the electron emission portion. [3] The electron source according to [2], wherein the concentration of the rare earth element in the surrounding portion is lower than the concentration of the rare earth element in the electron emission portion. [4] The electron source according to any one of [1] to [3], wherein the electron emission section has a larger thermal expansion coefficient than the support section. [5] The electron source according to any one of [1] to [4], wherein the coating layer is a sintered body containing voids. [6] The electron source according to [2] or [3], wherein the surrounding portion is a sintered body containing voids. [7] The electron source according to any one of [1] to [6], wherein a part of the supporting portion penetrates the joint. [8] The electron source according to any one of [1] to [7], wherein the metal in the supporting portion is at least one selected from the group consisting of tungsten, iridium, molybdenum, tantalum, and rhenium. [9] The electron source according to any one of [1] to [8], wherein the rare earth element of the electron emitting portion is at least one selected from the group consisting of cerium, lanthanum, and praseodymium.

[10] The rare earth element is cerium; The electron source according to [9], wherein the alloy of the electron emitting portion is composed of at least one selected from the group consisting of Ir2Ce, Ir3Ce, Ir5Ce, and Ir7Ce2.

[11] An electron gun comprising the electron source according to any one of [1] to

[10] .

[12] A device comprising an electron gun according to

[11] . EXAMPLES

[0049] The present disclosure will be described more specifically below based on examples, but the present disclosure is not limited to the following examples.

[0050] Example 1 The electron source 30 shown in FIG. 2 was fabricated without the power supply pin 34 and the insulating support member 35. Specifically, a disk-shaped electron-emitting portion made of Ir2Ce with a thickness of 0.3 mm and a diameter of 2.0 mm was prepared. Meanwhile, a tungsten filament having a length of 10 mm and a diameter of 0.15 mm was prepared and bent into a U shape. Then, Ir powder was prepared, and the center of the U-shaped tungsten filament was embedded in the Ir powder, and the Ir powder was sintered at 1600°C for 15 hours to form a coating layer made of the first sintered body around the center of the tungsten filament. Thus, a tungsten filament with a coating layer was obtained. Next, a tungsten filament with a coating layer was placed so that the coating layer was located on the back surface of the electron emission section opposite the electron emission surface, and with the coating layer embedded in the Ir5Ce powder, the Ir5Ce powder was sintered at 1600°C for 15 hours to form an enclosing section consisting of a second sintered body. In this manner, an electron source was obtained. The compositions of the formed coating layer and the surrounding portion were analyzed by energy dispersive X-ray spectroscopy, and it was confirmed that the coating layer contained Ir and W, and the surrounding portion contained Ir3Ce, Ir7Ce2, Ir5Ce, and Ir-W. The thickness of the coating layer was 40 μm.

[0051] Example 2 The electron source 30 shown in FIG. 2 was fabricated without the power supply pin 34 and the insulating support member 35. Specifically, a disk-shaped electron-emitting portion made of Ir2Ce having a thickness of 0.5 mm and a diameter of 0.8 mm was prepared in the same manner as in Example 1. Meanwhile, a tungsten filament having a length of 10 mm and a diameter of 0.15 mm was prepared and bent into a U shape. A tungsten filament was then placed so that its central portion was located on the back surface of the electron-emitting portion opposite the electron-emitting surface, and with the central portion embedded in Ir5Ce powder, the Ir5Ce powder was sintered at 1600°C for 15 hours to form a sintered body. An electron source was obtained in this manner. The composition of the sintered body thus formed was analyzed by energy dispersive X-ray spectroscopy, and it was confirmed that the sintered body was composed of a coating layer that covered the center of the tungsten filament and an enclosure that connected the coating layer to the electron emission part, that the coating layer contained Ir-W, and that the enclosure contained Ir3Ce, Ir7Ce2, Ir5Ce, and Ir-W.

[0052] Comparative Example 1 First, a cylindrical electron-emitting portion made of Ir7Ce2 having a thickness of 1.0 mm and a diameter of 1.2 mm was prepared in the same manner as in Example 1. On the other hand, a tantalum foil having a thickness of 0.03 mm, a width of 0.6 mm, and a length of 4.5 mm was prepared, and two rhenium filaments having a length of 4.5 mm and a diameter of 0.2 mm were prepared. Two rhenium filaments were then welded to the electron emitter via the tantalum foil and tungsten powder. In this manner, an electron source was obtained.

[0053] <Evaluation of temperature stability of electron emission part in electron source> For the electron sources of the examples and comparative examples obtained as described above, the electron emitting section was electrically heated while a current of 4 to 5 A was applied, and the temperature of the electron emitting section was measured every 5 or 10 seconds to examine the change in temperature of the electron emitting section over time. The results are shown in Figs. 6 to 8. In Figs. 6 to 8, the vertical axis indicates the difference between the measured temperature and the average temperature, and the horizontal axis indicates the elapsed time (minutes) from the start of measurement. At this time, the temperature of the electron emitting section was measured using a two-color thermometer, which is a non-contact thermometer. In addition, the average temperature and standard deviation of the measured temperatures were calculated based on the measurement results of the temperature of the electron emitting section. The results are shown in Table 1. Since the standard deviation indicates the variation of the measured temperature from the average temperature, the value of this standard deviation was used as an evaluation index of the temperature stability.

[0054] [Table 1]

[0055] From the results shown in Table 1, it was found that the electron sources of Examples 1 and 2 had smaller standard deviations of the temperatures of the electron emitting portions than the electron source of Comparative Example 1. Therefore, it was confirmed that the electron source according to the present disclosure can improve the temperature stability of the electron emission portion during heating. [Industrial Applicability]

[0056] The electron source of the present disclosure can be used in electron guns, X-ray generators, electron beam generators, electron beam type metal 3D printers, electron microscopes (SEM and TEM), and the like. [Explanation of symbols]

[0057] 100...device, 11...electron gun, 16, 17...coil portion, 30...electron source, 31...electron emission portion, 32...filament (support portion), 33...joint portion, 33a...coating layer, 33b...enclosure portion, 40...electrode, EB...electron beam, XR...X-ray.

Claims

1. an electron emission portion including an alloy of iridium and a rare earth element; A support part made of metal; a joining portion that joins the electron emission portion and the support portion, the joint portion has a coating layer that coats a surface of the support portion, The electron source, wherein the coating layer comprises iridium and the metal in the support.

2. the joint further includes an enclosure portion that surrounds at least a portion of the coating layer and contains iridium; 2. The electron source according to claim 1, wherein the concentration of the rare earth element in said surrounding portion is equal to or lower than the concentration of said rare earth element in said electron emitting portion.

3. 3. The electron source according to claim 2, wherein the surrounding portion contains an alloy of the iridium and a rare earth element, and the concentration of the rare earth element in the surrounding portion is lower than the concentration of the rare earth element in the electron-emitting portion.

4. 4. The electron source according to claim 1, wherein the thermal expansion coefficient of the electron emission portion is greater than the thermal expansion coefficient of the support portion.

5. 4. The electron source according to claim 1, wherein the covering layer is a sintered body containing voids.

6. The electron source according to claim 2 , wherein the surrounding portion is a sintered body containing voids.

7. 4. The electron source according to claim 1, wherein a part of the support portion penetrates the joint portion.

8. 4. The electron source according to claim 1, wherein the metal in the support portion is at least one selected from the group consisting of tungsten, iridium, molybdenum, tantalum, and rhenium.

9. 4. The electron source according to claim 1, wherein the rare earth element of the electron emission portion is at least one selected from the group consisting of cerium, lanthanum, and praseodymium.

10. the rare earth element is cerium; The alloy of the electron emitting portion is Ir ２ Ce, Ir ３ Ce, Ir ５ Ce and Ir ７ C ２ The electron source according to claim 9 , which is composed of at least one selected from the group consisting of:

11. An electron gun comprising the electron source according to claim 1 .

12. A device comprising the electron gun of claim 11.

Images