Thermionic cathode, thruster, rocket, artificial satellite, and space probe

Abstract

To provide a new technology.SOLUTION: A thermionic cathode according to an embodiment of the present invention includes an electron source and a plurality of grids. The electron source is configured to emit electrons when heated. The plurality of grids have through holes that allow electrons emitted from the electron source to pass in a predetermined direction. At least one of the grids is configured to slow down the traveling speed of the electrons.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thermionic cathode, a thruster, a rocket, an artificial satellite, and a space probe. [Background technology]

[0002] Patent Document 1 discloses a technique for extending the life of a field emission cathode type electron source by preventing deterioration and thinning of the cathode due to atomic oxygen and plasma ions in outer space.

[0003] The technology for extending the life of this field emission cathode type electron source comprises a field emission cathode type electron source for use in space, which comprises a cathode for emitting electrons, an extraction electrode having an opening window through which the electrons pass in order to extract the electrons from the cathode, and an extraction power supply for applying an extraction voltage between the cathode and the extraction electrode in order to extract the electrons from the cathode, and a transparent thin film that allows electrons to pass through but does not allow substances larger than electrons to pass through is disposed over the opening window of the extraction electrode so as to cover it. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2021-182537 Summary of the Invention [Problem to be solved by the invention]

[0005] However, there is still room for improvement in the above-mentioned known techniques.

[0006] In view of the above circumstances, the present invention provides a novel technique. [Means for solving the problem]

[0007] According to one aspect of the present invention, there is provided a thermionic cathode. The thermionic cathode includes an electron source and a plurality of grids. The electron source is configured to emit electrons when heated. The plurality of grids have through holes that allow electrons emitted from the electron source to pass in a predetermined direction. At least one of the grids is configured to slow down the traveling speed of the electrons.

[0008] According to this aspect, it is possible to provide a technology relating to a thermionic cathode that can emit many electrons with low energy by adjusting the electron movement speed or suppressing thermal radiation using a grid having a surface treatment layer. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an example of the overall configuration of a moving body 100. FIG. [Figure 2] FIG. 2 is a cross-sectional view of the thermionic cathode 1 in the state shown in FIG. 1B along the line AA, as viewed from above. [Figure 3] FIG. 2 is a front view of a plurality of grids 3 and a shield 4. [Figure 4] 3 is an enlarged view of an area B shown in FIG. 2, showing the configuration of an electron source 2 and a plurality of grids 3. FIG. [Figure 5] 3 is an enlarged view of region B shown in FIG. 2, illustrating an example of how to use the thermionic cathode 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. Various features shown in the following embodiments can be combined with each other.

[0011] Incidentally, the program for realizing the software appearing in one embodiment may be provided as a non-transitory computer-readable medium, or may be provided so that it can be downloaded from an external server, or may be provided so that the program is started on an external computer and its functions are realized on a client terminal (so-called cloud computing).

[0012] Furthermore, various information processing according to an embodiment may realize input and output corresponding to the input. Here, the form of information referenced in such information processing (hereinafter referred to as reference information) is not limited as long as an output is obtained as a result of the input. The reference information may be, for example, rule-based information such as a database, a lookup table, or a predetermined function (including a decision formula such as a regression formula constructed by a statistical method), a trained model that has previously trained the correlation between input and output, or a large-scale language model that can output a desired result by inputting a prompt.

[0013] In one embodiment, a "unit" may include, for example, a combination of hardware resources implemented by a circuit in the broad sense and software information processing that can be specifically realized by these hardware resources. In one embodiment, various information is handled, and this information is represented, for example, by physical values ​​of signal values ​​representing voltage and current, high and low signal values ​​as a binary bit set consisting of 0 or 1, or quantum superposition (so-called quantum bits), and communication and calculations can be performed on a circuit in the broad sense.

[0014] Furthermore, a circuit in the broad sense is a circuit realized by at least an appropriate combination of a circuit, circuitry, processor, memory, etc. The processor may be a general-purpose processor or a dedicated circuit. That is, it includes an application specific integrated circuit (ASIC), a programmable logic device (e.g., a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA)), etc.

[0015] 1. Hardware configuration of the mobile unit 100 First, the hardware configuration of a moving body 100 according to one embodiment will be described. FIG. 1 is a diagram showing an example of the overall configuration of the moving body 100. In the following description, the directions of the moving body 100 and each component constituting the moving body 100 will be defined based on "up," "down," "left," "right," "front," and "rear" shown in FIG. 1 (as well as FIGS. 2 to 5). Furthermore, in the following description, "up" will also be referred to as "upper side" or "upward," and "down" will also be referred to as "lower side" or "downward." The direction formed by "up" and "down" will be referred to as "upper" or "upper / lower direction." The same applies to "down," "left," "right," "front," and "rear."

[0016] The moving body 100 is, for example, a rocket, an artificial satellite, a space probe, etc., and is equipped with various devices depending on its purpose, one of which is a structurally and electrically connected propulsion unit 110. That is, in this case, the rocket, artificial satellite, space probe, etc. is equipped with the structurally and electrically connected propulsion unit 110.

[0017] (Propulsion machine 110) Furthermore, the propulsion device 110 according to one embodiment is a device that generates thrust using electrical energy, i.e., an electric propulsion device, such as a Hall thruster, an ion engine, etc. As shown in FIG.

[0018] The anode 111 accelerates and releases ions obtained from the propellant in a predetermined direction D. A reaction force caused by the acceleration and release of the ions generates a propulsive force that moves the moving body 100 forward.

[0019] The cathode 112 emits electrons E in a predetermined direction D. The cathode 112 emits the same amount of electrons E as the ions emitted from the anode 111 so that the moving body 100 is not negatively charged by the ions emitted from the anode 111. A thermionic cathode 1 using thermal electrons is employed as the cathode 112 according to one embodiment. In other words, the propulsion device 110 includes the thermionic cathode 1 that is structurally and electrically connected.

[0020] 2. Hardware configuration of thermionic cathode 1 Next, the hardware configuration of the thermionic cathode 1 according to one embodiment will be described with reference to other figures. Fig. 2 is a cross-sectional view of the thermionic cathode 1 as viewed from above in the state represented by the AA cross section shown in Fig. 1B. Fig. 2 shows the thermionic cathode 1 in cross section, thereby illustrating an example of the internal and external configuration of the thermionic cathode 1. As shown in Fig. 2, the thermionic cathode 1 includes an electron source 2, multiple grids 3, a shield 4, a potential supply source 5, a heat insulating section 6, and a resistor 7.

[0021] (electron source 2) The electron source 2 has a substantially cylindrical shape. The electron source 2 shown in FIG. 2 is shown in a cross section defined by front-rear and left-right along the central axis of the substantially cylindrical shape. The electron source 2 employs a material that stably and efficiently emits electrons E in a vacuum. Specifically, for example, the electron source 2 may employ materials such as LaB6, BaO, and electride, which have a low work function (the minimum energy required for electrons E to escape from a solid surface or a substance) and a high electron emissivity.

[0022] The electron source 2 is disposed adjacent to or in contact with the resistor 7. The electron source 2 is heated by the resistor 7 generating heat when current is applied. Specifically, as shown in FIG. 2, the electron source 2 is configured to heat the front side of the surface defined by the top, bottom, and left, and right. The electron source 2 is further configured to emit electrons E when heated. Specifically, as shown in FIG. 2, the electron source 2 has a surface 2cs on the rear side of the surface defined by the top, bottom, and left, and emits electrons E from the surface 2cs. As shown in FIG. 2, the surface 2cs is disposed in contact with at least a portion of the grid 3. The electrons E emitted from the surface 2cs pass through the through-holes 3a in the grid 3 and the through-holes 4a in the shield 4. The electrons E are then emitted to the outside of the thermionic cathode 1 along a predetermined direction D. The grid 3, the shield 4, and the resistor 7 will be described in detail later.

[0023] (Grid 3) FIG. 3 is a view of the plurality of grids 3 and the shield 4 as viewed from the front side. FIG. 4 is an enlarged view of region B shown in FIG. 2, showing the configuration of the electron source 2 and the plurality of grids 3. The plurality of grids 3 are made up of two or more grids 3, and specifically, for example, the plurality of grids 3 are made up of a focusing grid 31, an accelerating grid 32, and a decelerating grid 33. As shown in FIG. 3, the plurality of grids 3 have substantially the same outer shape, that is, a substantially disk-shaped outer shape. Note that the plurality of grids 3 shown in FIG. 2 are shown in a cross section defined by front-rear and left-right along the central axis of the substantially disk-shaped outer shape.

[0024] 2, the multiple grids 3 are arranged in the following order from the front: focusing grid 31, accelerating grid 32, and decelerating grid 33. In other words, the focusing grid 31 is located closer to the electron source 2 than the accelerating grid 32. The decelerating grid 33 is located farther from the electron source 2 than the accelerating grid 32. The multiple grids 3 are arranged in layers with a predetermined interval between them. In this case, the predetermined interval may be determined depending on the thickness of the grid 3, the size of the through-holes 3a in the multiple grids 3, and the like, and is, for example, 0.1 to 10 mm, preferably 0.5 to 7 mm, and more preferably 1 to 5 mm. Specifically, for example, the predetermined intervals are 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8, 5, 5.2, 5.4, 5.6, 5.8, 6, 6.2, 6.4, 6.6, 6.8, 7, 7.2, 7.4, 7.6, 7.8, 8, 8.2, 8.4, 8.6, 8.8, 9, 9.2, 9.4, 9.6, 9.8, 10 mm, and may be within a range between any two of the numerical values ​​exemplified here. The predetermined distance between the convergence grid 31 and the acceleration grid 32 and the predetermined distance between the acceleration grid 32 and the deceleration grid 33 may be the same or different.

[0025] 2 to 4, the convergent grid 31 has a surface 31cs which is the front surface among the surfaces defined by the top, bottom, left, and right. The convergent grid 31 is arranged so as to abut the surface 31cs against a surface 2cs which is at least a part of the electron source 2. In other words, the plurality of grids 3 have convergent grids 31 which are arranged so as to abut against at least a part of the electron source 2 (for example, the surface 2cs).

[0026] 2 to 4, the grid 3 has a predetermined number of through-holes 3a penetrating in the front-rear direction. Specifically, for example, the focusing grid 31, the accelerating grid 32, and the decelerating grid 33 have a predetermined number of through-holes 31a, a predetermined number of through-holes 32a, and a predetermined number of through-holes 33a, respectively. The through-holes 31a of the focusing grid 31 are arranged on a surface 31cs, so that the electrons E emitted from the electron source 2 can pass through them.

[0027] A predetermined number of through holes 3a are regularly arranged in a plane defined by the top and bottom and the left and right of the grid 3. In other words, the through holes 31a, the through holes 32a, and the through holes 33a are arranged according to a common rule in a plane defined by the top and bottom and the left and right of the convergence grid 31, the acceleration grid 32, and the deceleration grid 33. Specifically, for example, when the predetermined number is 19, 19 through holes 3a are regularly arranged in one grid 3 so as to penetrate in the front-rear direction. In more detail, for example, as shown in FIG. 3A, 19 through holes 31a are regularly arranged in the convergence grid 31 so as to penetrate in the front-rear direction, as shown in FIG. 3B, 19 through holes 32a are regularly arranged in the acceleration grid 32 so as to penetrate in the front-rear direction, and as shown in FIG. 3C, 19 through holes 33a are regularly arranged in the deceleration grid 33 so as to penetrate in the front-rear direction.

[0028] In this case, the predetermined number may be determined depending on the size of the surface 2cs of the electron source 2 that emits electrons E, the size of the through-holes 3a, the outer size of the grid 3, and the like, and is, for example, 3 to 50, preferably 10 to 30, and more preferably 15 to 20. Specifically, the predetermined number may be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, or 50, or may be within a range between any two of the numerical values ​​exemplified here.

[0029] 2 and 4, when the focusing grid 31, the accelerating grid 32, and the decelerating grid 33 are arranged in layers, a predetermined number of regularly arranged through-holes 31a, 32a, and 33a form paths Ro through which electrons E can pass. That is, the same number of paths Ro as the predetermined number are formed. Specifically, as shown in FIGS. 2 and 4, the paths Ro are formed by linearly arranging the through-holes 31a, 32a, and 33a. In more detail, the paths Ro are formed by aligning the approximate centers of the through-holes 31a, 32a, and 33a along the axis CA. By forming the paths Ro in this way, electrons E emitted from the electron source 2 can travel in a predetermined direction D via the paths Ro. In other words, the multiple grids 3 have through-holes 3a that allow the electrons E emitted from the electron source 2 to pass in the predetermined direction D.

[0030] 4, the through holes 3a in a plane defined by the top, bottom, left, and right axes have widths L1, L2, and L3, respectively, for the through holes 31a, 32a, and 33a. The widths L1, L2, and L3 preferably have a relationship such that, in descending order, they are L1, L3, and L2. In other words, the through holes 32a of the acceleration grid 32 are preferably smaller than the through holes 31a of the focusing grid 31.

[0031] Here, the size of width L1 may be, for example, 0.5 to 4, preferably 1 to 3, and more preferably 1.5 to 2.5, when the size of width L2 is 1. Specifically, for example, the size of width L1 may be 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, or 4, when the size of width L2 is 1, and may be within a range between any two of the numerical values ​​exemplified here.

[0032] Furthermore, the size of width L3 may be, for example, 1 to 4, preferably 1.2 to 3, and more preferably 1.5 to 2.5, when the size of width L2 is 1. Specifically, for example, the size of width L3 may be 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, or 4, when the size of width L2 is 1, and may be within a range between any two of the numerical values ​​exemplified here.

[0033] According to this embodiment, it is possible to effectively block the radiant heat radiated from the heat-generating portion toward the acceleration grid 32, and to emit a large number of electrons E from the thermionic cathode 1 with lower energy. The heat-generating portion in this case is the electron source 2 heated by the resistance 7, the focusing grid 31 heated by heat transfer from the electron source 2, etc.

[0034] 2 to 4, the through-holes 3a may have a shape that prevents passing electrons E from contacting the inner walls of the through-holes 3a. For example, the through-holes 3a may have a circular, elliptical, or polygonal shape, or a slit shape, in a plane defined by the top, bottom, and left, right. The size of the through-holes 3a in the plane defined by the top, bottom, and left, right may be configured to vary from front to rear, or may be configured to become larger or smaller from front to rear. According to this embodiment, by adopting an optimal shape for the through-holes 3a of the grid 3, the electrons E can pass through the through-holes 3a without contacting the inner walls of the through-holes 3a, allowing the thermionic cathode 1 to emit a large number of electrons E with lower energy.

[0035] The material of the plurality of grids 3 may be any of carbon, tantalum, molybdenum, titanium, tungsten, zirconium, niobium, and substances containing these. According to this embodiment, it is possible to adopt an optimum material as the material of the grids 3, and it is possible to emit a large number of electrons E from the thermionic cathode 1 with lower energy.

[0036] At least one of the grids 3 may be configured to have a surface treatment layer STL. The surface treatment layer STL may be a layer with low emissivity. Specifically, for example, the surface treatment layer STL may be included in at least one of the focusing grid 31, the accelerating grid 32, and the decelerating grid 33. More specifically, for example, the surface treatment layer STL may be included in at least one of the surfaces defined by the top, bottom, left, and right of the focusing grid 31, the accelerating grid 32, and the decelerating grid 33 and the inner wall of the through-hole 3 a. The surface treatment layer STL may be made of platinum, titanium, nickel, zirconium, or a substance containing at least one of these metals. According to this embodiment, the grid 3 has a low emissivity surface treatment layer STL, so that the grid 3 has a low emissivity surface regardless of the material of the grid 3. Furthermore, according to this embodiment, it is possible to suppress thermal radiation by using a grid 3 having a surface treatment layer STL composed of a layer with low emissivity, and it is possible to emit a large number of electrons E from the thermoelectron cathode 1 with lower energy.

[0037] (Shield 4) As shown in FIGS. 2 and 3D , the shield 4 has a hollow cylindrical shape extending in the front-rear direction and has a through-hole 4a on its rear surface, which is defined by the top-bottom and left-right axes. The through-hole 4a is formed to be smaller than the hollow portion of the shield 4. The shield 4 is configured to cover the electron source 2, the plurality of grids 3, the heat insulating portion 6, and the resistor 7. In other words, the shield 4 is located distal to the plurality of grids 3 as viewed from the electron source 2. The shield 4 is configured so that the electrons E pass through the through-hole 4a after passing through a path Ro formed by the through-holes 3a of the plurality of grids 3. This embodiment makes it possible to prevent electrons E from flowing back from outside the thermionic cathode 1 and to prevent ions emitted from the anode 111 from entering the thermionic cathode 1, thereby enabling a large number of electrons E to be emitted from the thermionic cathode 1 with lower energy.

[0038] (Potential supply source 5) As shown in FIG. 2 , the potential supply source 5 includes an electron acceleration power supply 52, an electron deceleration power supply 53, and a heating power supply 57, and is electrically connected to predetermined components. The potential supply source 5 generates a predetermined potential difference between the predetermined components and the ground G, or supplies a predetermined power to the predetermined components. Specifically, for example, the electron acceleration power supply 52 is electrically connected to the acceleration grid 32 and the ground G, and generates a predetermined potential difference between the acceleration grid 32 and the ground G. The electron deceleration power supply 53 is electrically connected to the deceleration grid 33 and the ground G, and generates a predetermined potential difference between the deceleration grid 33 and the ground G. That is, a potential difference is generated between a predetermined component having a predetermined potential difference between the ground G and a component having the same or similar potential as the ground G. In this case, the component having the same or similar potential as the ground G is, for example, the electron source 2, the focusing grid 31, the shield 4, etc. Furthermore, the electron acceleration power supply 52 is configured to generate a higher potential difference than the electron deceleration power supply 53. In other words, the potential supply source 5 generates a potential difference between the electron source 2 and the plurality of grids 3. The focusing grid 31 is configured to have the same or similar potential as the electron source 2. The accelerating grid 32 is configured to have a higher potential than the electron source 2. The decelerating grid 33 is configured to have a lower potential than the accelerating grid 32.

[0039] In this way, since the focusing grid 31 has the same or similar potential as the electron source 2 and the focusing grid 31 has the through-holes 31a, an equipotential surface according to the shape of the through-holes 31a is formed inside the through-holes 31a. Specifically, inside the through-holes 31a, an equipotential surface is formed such that as the electrons E emitted from the electron source 2 pass through the through-holes 31a, the electrons E move away from the inner wall of the through-holes 31a, that is, the electrons E move toward approximately the center of the through-holes 31a. In other words, the through-holes 31a of the focusing grid 31 are configured to converge the electrons E and cause them to travel toward approximately the center of the through-holes 31a.

[0040] Furthermore, since the acceleration grid 32 and the deceleration grid 33 have a predetermined potential difference with respect to the electron source 2 and the convergence grid 31, and the acceleration grid 32 has a high potential difference with respect to the deceleration grid 33, equipotential surfaces are formed along the path Ro so that the electrons E are accelerated and then decelerated. Specifically, along the path Ro, from the position of the through-hole 31a in the convergence grid 31 to the position of the through-hole 32a in the acceleration grid 32, an equipotential surface is formed so that the potential becomes higher as the electrons approach the through-hole 32a. Furthermore, along the path Ro, from the position of the through-hole 32a in the acceleration grid 32 to the position of the through-hole 33a in the deceleration grid 33, an equipotential surface is formed so that the potential becomes lower as the electrons approach the through-hole 33a.

[0041] The configurations of the potential supply source 5, the acceleration grid 32, and the deceleration grid 33 can be summarized as follows. The through-holes 32a of the acceleration grid 32 are configured to accelerate the electrons E by the potential supply source 5. That is, at least one of the multiple grids 3 is configured to accelerate the movement speed of the electrons E. Furthermore, the through-holes 32a of the acceleration grid 32 and the through-holes 33a of the deceleration grid 33 are configured to accelerate the electrons E and then decelerate them by the potential supply source 5. That is, at least one of the multiple grids 3 is configured to decelerate the movement speed of the electrons E. According to this embodiment, it is possible to adjust the movement speed of the electrons E, and more electrons E can be emitted from the thermionic cathode 1 with lower energy. Furthermore, the multiple grids 3 include at least an acceleration grid 32 that accelerates the electrons E that have passed through it and a deceleration grid 33 that decelerates the electrons that have passed through it. According to this embodiment, it is possible to decelerate the electrons E accelerated by the acceleration grid 32 by the deceleration grid 33, and it is possible to emit a large number of electrons E from the thermionic cathode 1 with lower energy.

[0042] Furthermore, as described above, the width L2 of the through-hole 32a of the acceleration grid 32 is configured to be smaller than the width L1 of the through-hole 31a of the focusing grid 31. According to this embodiment, the electrons E that have traveled while converging toward approximately the center of the through-hole 31a proceed to the through-hole 32a while substantially maintaining their travel direction, and therefore the electrons E can pass a position close to the inner wall of the through-hole 32a without coming into contact with the acceleration grid 32, and a large number of electrons E can be accelerated efficiently with lower energy.

[0043] As described above, the width L3 of the through-holes 33a of the decelerator grid 33 is set to a width L larger than the width L2 of the through-holes 32a of the accelerator grid 32. That is, the through-holes 32a of the accelerator grid 32 are smaller than the through-holes 33a of the accelerator grid 33. According to this embodiment, the decelerator grid 33 can decelerate the electrons E and increase the distance between the electrons E, thereby preventing repulsion between the electrons E that may occur as the electrons E decelerate. Furthermore, this embodiment can prevent a large number of electrons E from being emitted from the thermionic cathode 1 with lower energy. Furthermore, according to this embodiment, it is possible to prevent the electrons E before, during, or after passing through the through-holes 33a of the decelerator grid 33 from flowing back toward the accelerator grid 32.

[0044] The electron acceleration power supply 52 generates a predetermined potential difference with respect to the acceleration grid 32 relative to the ground G, for example, a potential difference of 0.5 to 5 kV, preferably a potential difference of 0.8 to 4 kV, and more preferably a potential difference of 1 to 3 kV. Specifically, for example, the electron acceleration power supply 52 generates a predetermined potential difference with respect to the acceleration grid 32 relative to the ground G as follows: 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9, 5 kV, and may generate a potential difference within a range between any two of the numerical values ​​exemplified here.

[0045] The electronic deceleration power supply 53 generates a predetermined potential difference with respect to the deceleration grid 33 relative to the ground G, for example, a potential difference of 0 to 100 V, preferably a potential difference of 5 to 80 V, and more preferably a potential difference of 10 to 60 V. Specifically, for example, the electronic deceleration power supply 53 generates a predetermined potential difference relative to the ground G with respect to the deceleration grid 33 of 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76, 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, or 100 V, or may generate a potential difference within a range between any two of the numerical values ​​exemplified here.

[0046] The heating power supply 57 is electrically connected to the resistor 7 and supplies a predetermined power to the resistor 7. In this case, the predetermined power may be, for example, 1 to 100 W, preferably 5 to 75 W, and more preferably 10 to 50 W. Specifically, the power of the heating power supply 57 may be 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 W, or may be within a range between any two of the values ​​exemplified here. Details of the resistor 7 will be described later.

[0047] (Insulation section 6) As shown in Fig. 2, the heat insulating section 6 has a generally box-shaped outer shape, with an opening 61 on the rear surface defined by the top, bottom, left, and right. The heat insulating section 6 also has a multi-layer heat insulating structure in the wall of the generally box-shaped section. In this case, the number of layers in the multi-layer heat insulating structure is, for example, 2 to 15 layers, preferably 4 to 10 layers, and more preferably 5 to 7 layers. Specifically, the number of layers in the multi-layer heat insulating structure may be 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 layers, or may be within a range between any two of the numerical values ​​exemplified here.

[0048] 2, the heat insulating part 6 is disposed so as to cover the electron source 2. Furthermore, a plurality of grids 3 are disposed in the vicinity of the opening 61 of the heat insulating part 6. This forms a space between the heat insulating part 6 and the plurality of grids 3. According to this embodiment, by insulating the electron source 2, a large number of electrons E can be emitted from the thermionic cathode 1 with lower energy.

[0049] (Resistance 7) 2, the resistor 7 is electrically connected to the heating power supply 57 of the potential supply source 5 and configured to generate heat when a predetermined power is supplied from the heating power supply 57. Furthermore, the resistor 7 is disposed in proximity to or in contact with the electron source 2 and configured to generate heat to heat the electron source 2 to a predetermined temperature. In this case, the predetermined temperature may be, for example, 800 to 2200°C, preferably 1000 to 1800°C, and more preferably 1200 to 1600°C. Specifically, for example, the predetermined temperature may be 800, 850, 900, 950, 1000, 1050, 1100, 1150, 1200, 1250, 1300, 1350, 1400, 1450, 1500, 1550, 1600, 1650, 1700, 1750, 1800, 1850, 1900, 1950, 2000, 2050, 2100, 2150, or 2200°C, or may be within a range between any two of the values ​​exemplified here.

[0050] 3. How to use thermionic cathode 1 Next, the use of the thermionic cathode 1 will be described with reference to other drawings. Fig. 5 is an enlarged view of region B shown in Fig. 2, illustrating an example of how to use the thermionic cathode 1.

[0051] [1] First, the thermionic cathode 1 is prepared to emit electrons E. In this preparation, the electron acceleration power supply 52 and the electron deceleration power supply 53 of the potential supply source 5 generate a predetermined potential difference with respect to the ground G for the acceleration grid 32 and the deceleration grid 33, respectively. The deceleration grid 33 is configured to be at a lower potential than the acceleration grid 32. Furthermore, in this preparation, power is supplied to the resistor 7 by the heating power supply 57 of the potential supply source 5 so that the resistor 7 heats the electron source 2 to a predetermined temperature. As a result, the resistor 7 begins to generate heat. The electron source 2, the focusing grid 31, and the shield 4 are configured to be at the same or approximately the same potential as the ground G.

[0052] [2] Next, in the thermionic cathode 1, the electron source 2 is heated to a predetermined temperature (for example, 1000°C), which causes the electron source 2 to start emitting electrons E. As shown in FIG. 5A, the electrons E are emitted from the surface 2cs of the electron source 2 and travel in a predetermined direction D, i.e., backward.

[0053] [3] Then, as shown in FIGS. 5A to 5C, the emitted electrons E travel sequentially along the path Ro.

[0054] First, as shown in Fig. 5A, electrons E traveling along path Ro travel from the front to the rear through the through-hole 31a of the focusing grid 31. Specifically, for example, the electrons E travel along the dashed arrows shown in Fig. 5A. More specifically, the electrons E traveling inside the through-hole 31a travel so as to converge approximately at the center of the through-hole 31a as they travel from the front to the rear through the through-hole 31a. In other words, the electrons E travel without coming into contact with the through-hole 31a.

[0055] Next, as shown in FIGS. 5A and 5B , electrons E traveling along path Ro pass through the through-hole 31a, enter the through-hole 32a of the acceleration grid 32 from the front, and then travel backward. Specifically, for example, the electrons E travel along the dashed arrows shown in FIGS. 5A and 5B . In this case, the acceleration grid 32 has a high potential difference with respect to the electron source 2 and the focusing grid 31, so that the electrons E travel while accelerating. Furthermore, the electrons E traveling while converging toward approximately the center of the through-hole 31a travel toward the through-hole 32a while substantially maintaining their traveling direction. This allows the electrons E to travel without contacting the surfaces defined by the top, bottom, left, and right of the acceleration grid 32 or the inner wall of the through-hole 32a. Furthermore, because the through-hole 32a is configured to be smaller than the through-hole 31a and optimally sized, the electrons E do not contact the acceleration grid 32, i.e., without loss of electrons E due to contact with the acceleration grid 32, and are efficiently accelerated.

[0056] 5B and 5C, electrons E traveling along the path Ro pass through the through-holes 32a, enter the through-holes 33a of the decelerator grid 33 from the front, and then travel backward. Specifically, for example, the electrons E travel along the dashed arrows shown in FIGS. 5B and 5C. In this case, the decelerator grid 33 has a lower potential difference with respect to the acceleration grid 32, so the electrons E travel while decelerating. In addition, the through-holes 33a are larger than the through-holes 32a and configured to an optimal size, so the electrons E travel while increasing the spacing between the electrons E. By decelerating and increasing the spacing between the electrons E, the electrons E travel while avoiding repulsion between the electrons E that may occur as the electrons E decelerate. Furthermore, the electrons E travel along the path Ro without flowing backward through the through-holes 33a of the decelerator grid 33.

[0057] [4] Furthermore, the electrons E that have passed through the path Ro pass through the through-hole 4a of the shield 4. As a result, the electrons E are emitted from the thermionic cathode 1 in a predetermined direction D.

[0058] The thermionic cathode 1 can be used in the above manner. Furthermore, in a propulsion device 110 employing the thermionic cathode 1 as the cathode 112, the thermionic cathode 1 is used so as to emit the same amount of electrons E as the ions emitted from the anode 111. This prevents the moving body 100 equipped with the propulsion device 110 from being negatively charged. The moving body 100 (e.g., a rocket, an artificial satellite, a space probe, etc.) equipped with the propulsion device 110 can be propelled by the obtained thrust. According to this embodiment, the propulsion device 110 can be provided with the thermionic cathode 1 capable of emitting many electrons E with low energy. Furthermore, according to this embodiment, the moving body 100 (e.g., a rocket, an artificial satellite, a space probe, etc.) equipped with the propulsion device 110 employing the thermionic cathode 1 capable of emitting many electrons E with low energy can be provided.

[0059] [others] The thermionic cathode 1 according to one embodiment can also be implemented in the following manner.

[0060] In the above embodiment, the electron source 2 has been described as having an approximately cylindrical shape, but this is not limited thereto. For example, it is sufficient that electrons E can be emitted from the surface 2cs of the electron source 2, and the surface including the surface 2cs may have a shape such as an ellipse or a polygon.

[0061] In the above embodiment, the multiple grids 3 have approximately the same outer shape and are approximately disk-shaped, but this is not limited to this. For example, the grids 3 may have different outer shapes as long as they have a shape that can form the path Ro, and the surfaces defined by the top, bottom, left, and right may have shapes such as an ellipse, a polygon, etc.

[0062] In the above embodiment, the case has been described in which the plurality of grids 3 include the focusing grid 31, the accelerating grid 32, and the decelerating grid 33, and further include the shield 4. However, the present invention is not limited to this, and the plurality of grids 3 may be configured with, for example, two grids 3, or four or more grids 3. Specifically, for example, the electron source 2 and the focusing grid 31 may be configured as an integral unit, and the plurality of grids 3 may be configured with the accelerating grid 32 and the decelerating grid 33. Furthermore, the plurality of grids 3 may be configured with four or more grids 3 by including a plurality of at least one of the focusing grid 31, the accelerating grid 32, and the decelerating grid 33. Furthermore, for example, the shield 4 may be omitted.

[0063] In the above embodiment, the surface 2cs of the electron source 2 and the surface 31cs of the focusing grid 31 are in contact with each other, but the present invention is not limited to this and may have a predetermined distance therebetween. In this case, the predetermined distance is, for example, 0.1 to 10 mm, preferably 0.5 to 7 mm, and more preferably 1 to 5 mm. Specifically, for example, the predetermined intervals are 0.1, 0.2, 0.4, 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8, 5, 5.2, 5.4, 5.6, 5.8, 6, 6.2, 6.4, 6.6, 6.8, 7, 7.2, 7.4, 7.6, 7.8, 8, 8.2, 8.4, 8.6, 8.8, 9, 9.2, 9.4, 9.6, 9.8, 10 mm, and may be within a range between any two of the numerical values ​​exemplified here.

[0064] In the above embodiment, the case where the electron source 2 and the resistor 7 are arranged close to or in contact with each other has been described. However, this is not limited to this, and for example, all or part of the resistor 7 may be configured integrally with the electron source 2.

[0065] Furthermore, it may be provided in the following aspects.

[0066] (1) A thermionic cathode comprising an electron source and a plurality of grids, the electron source being configured to emit electrons when heated, the plurality of grids having through holes that allow the electrons emitted from the electron source to pass in a predetermined direction, at least one of the grids being configured to slow down the movement speed of the electrons.

[0067] According to this embodiment, it is possible to provide a technology relating to a thermionic cathode that can emit a large number of electrons with low energy by adjusting the electron movement speed.

[0068] (2) A thermionic cathode comprising an electron source and a plurality of grids, the electron source being configured to emit electrons when heated, the plurality of grids having through holes that allow the electrons emitted from the electron source to pass in a predetermined direction, and at least one of the grids having a surface treatment layer.

[0069] According to this aspect, it is possible to provide a technology relating to a thermionic cathode that can emit many electrons with low energy by suppressing thermal radiation using a grid having a surface treatment layer.

[0070] (3) A thermionic cathode according to (1) or (2) above, wherein the plurality of grids include at least an acceleration grid that accelerates the electrons that have passed through it and a deceleration grid that decelerates the electrons that have passed through it, and the deceleration grid is located farther from the electron source than the acceleration grid.

[0071] According to this aspect, it is possible to provide a technology relating to a thermionic cathode that can emit a large number of electrons with low energy by decelerating the electrons accelerated by the acceleration grid using the deceleration grid.

[0072] (4) The thermionic cathode according to (3) above, wherein the through holes of the acceleration grid are smaller than the through holes of the deceleration grid.

[0073] According to this aspect, it is possible to provide a technology relating to a thermionic cathode that can emit a large number of electrons with low energy by decelerating the electrons accelerated by the acceleration grid using the deceleration grid.

[0074] (5) The thermionic cathode according to (3) or (4) above, further comprising a potential supply source, the potential supply source generating a potential difference between the electron source and the plurality of grids, the accelerating grid being configured to have a higher potential than the electron source, and the decelerating grid being configured to have a lower potential than the accelerating grid.

[0075] According to this aspect, it is possible to provide a technology relating to a thermionic cathode that can emit a large number of electrons with low energy by decelerating the electrons accelerated by the acceleration grid using the deceleration grid.

[0076] (6) A thermionic cathode according to any one of (3) to (5) above, wherein the plurality of grids further includes a focusing grid arranged to abut against at least a portion of the electron source, and the focusing grid is located closer to the electron source than the accelerating grid.

[0077] According to this aspect, a technology can be provided for a thermionic cathode that can emit many electrons at low energy by using a focusing grid to move electrons so that they do not come into contact with the acceleration grid, and then using a deceleration grid to decelerate the electrons accelerated by the acceleration grid.

[0078] (7) The thermionic cathode according to (6) above, wherein the through holes of the acceleration grid are smaller than the through holes of the focusing grid.

[0079] According to this aspect, a technology can be provided for a thermionic cathode that can emit many electrons at low energy by using a focusing grid to move electrons so that they do not come into contact with the acceleration grid, and then using a deceleration grid to decelerate the electrons accelerated by the acceleration grid.

[0080] (8) The thermionic cathode according to (6) or (7) above, further comprising a potential supply source, the potential supply source generating a potential difference between the electron source and the plurality of grids, the focusing grid being configured to have the same or similar potential as the electron source, the accelerating grid being configured to have a higher potential than the electron source, and the decelerating grid being configured to have a lower potential than the accelerating grid.

[0081] According to this aspect, a technology can be provided for a thermionic cathode that can emit many electrons at low energy by using a focusing grid to move electrons so that they do not come into contact with the acceleration grid, and then using a deceleration grid to decelerate the electrons accelerated by the acceleration grid.

[0082] (9) The thermionic cathode according to any one of (1) to (8) above, wherein the through-holes have a circular, elliptical or polygonal shape, or a slit shape.

[0083] According to this embodiment, it is possible to adopt an optimum shape for the through holes of the grid, and it is possible to provide a technology relating to a thermionic cathode that can emit many electrons with low energy.

[0084] (10) The thermionic cathode according to any one of (1) to (9) above, further comprising a shield, the shield being located farther from the electron source than the plurality of grids.

[0085] According to this embodiment, it is possible to provide a technology relating to a thermionic cathode that can emit many electrons with low energy by preventing electrons from flowing back from the outside of the thermionic cathode.

[0086] (11) The thermionic cathode according to any one of (1) to (10) above, further comprising a heat insulating part, the heat insulating part having a multi-layer heat insulating structure and arranged to cover the electron source.

[0087] According to this embodiment, by insulating the electron source, it is possible to provide a technology relating to a thermionic cathode that can emit many electrons with low energy.

[0088] (12) A thermionic cathode according to any one of (1) to (11) above, wherein the material of the plurality of grids is any one of carbon, tantalum, molybdenum, titanium, tungsten, zirconium, niobium, and substances containing these.

[0089] According to this embodiment, it is possible to use an optimum material as the grid material, and it is possible to provide a technology relating to a thermionic cathode that can emit many electrons with low energy.

[0090] (13) The thermionic cathode according to (2) above, wherein the surface treatment layer is composed of a layer with low emissivity.

[0091] According to this embodiment, the grid can have a surface treatment layer with low emissivity, and a technology relating to a thermionic cathode that can emit many electrons with low energy can be provided.

[0092] (14) The thermionic cathode according to (13) above, wherein the material of the surface treatment layer is platinum, titanium, nickel, zirconium, or a substance containing at least one of these.

[0093] According to this embodiment, the grid can have a surface treatment layer with low emissivity, and a technology relating to a thermionic cathode that can emit many electrons with low energy can be provided.

[0094] (15) A thruster comprising a structurally and electrically connected thermoelectron cathode, the thermoelectron cathode being the thermoelectron cathode described in any one of (1) to (14) above.

[0095] According to this aspect, it is possible to provide a technique relating to a thruster equipped with a thermionic cathode capable of emitting a large number of electrons with low energy.

[0096] (16) A rocket comprising a structurally and electrically connected propulsion device, the propulsion device being the propulsion device described in (15) above.

[0097] According to this aspect, it is possible to provide a technology relating to a rocket equipped with a thruster that employs a thermionic cathode that can emit many electrons with low energy.

[0098] (17) An artificial satellite comprising a structurally and electrically connected propulsion device, the propulsion device being the propulsion device described in (15) above.

[0099] According to this aspect, it is possible to provide a technology relating to an artificial satellite equipped with a thruster that employs a thermionic cathode that can emit many electrons with low energy.

[0100] (18) A space probe comprising a structurally and electrically connected propulsion device, the propulsion device being the propulsion device described in (15) above.

[0101] According to this aspect, it is possible to provide a technology relating to a space probe equipped with a thruster that employs a thermionic cathode that can emit many electrons with low energy. Of course, this is not the case.

[0102] Finally, while various embodiments of the present invention have been described, these are presented by way of example only and are not intended to limit the scope of the invention. The novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. Such embodiments and modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the inventions and their equivalents as defined in the accompanying claims. [Explanation of symbols]

[0103] 100: Mobile 110: Propulsion machine 111: Anode 112: Cathode 1: Thermionic cathode 2: Electron source 2cs: surface 3: Grid 3a: Through hole 31: Convergence grid 31a: Through hole 31cs: Surface 32: Acceleration grid 32a: Through hole 33: Deceleration grid 33a: Through hole 4: Shield 4a: Through hole 5: Potential supply source 52:Electronic acceleration power supply 53:Electronic reduction power supply 57:Heating power supply 6: Insulation section 61: Opening 7: Resistance B :Area CA: Axis D :Predetermined direction E:Electronic G: Ground L: Width L1:Width L2:Width L3:Width Ro: Route STL: Surface treatment layer

Claims

1. a thermionic cathode, an electron source and a plurality of grids; the electron source is configured to emit electrons when heated; The plurality of grids include: a through hole through which the electrons emitted from the electron source pass in a predetermined direction; at least one of the thermionic cathodes configured to slow down the rate of travel of said electrons;

2. a thermionic cathode, an electron source and a plurality of grids; the electron source is configured to emit electrons when heated; The plurality of grids include: a through hole through which the electrons emitted from the electron source pass in a predetermined direction; Thermionic cathodes, at least one of which is configured with a surface treatment layer.

3. 2. The thermionic cathode of claim 1, The plurality of grids include: an acceleration grid that accelerates the electrons that have passed through it; a deceleration grid that decelerates the electrons that have passed through it; The deceleration grid is located distally of the acceleration grid from the electron source.

4. 4. The thermionic cathode according to claim 3, The thermionic cathode, wherein the through holes in the acceleration grid are smaller than the through holes in the deceleration grid.

5. 4. The thermionic cathode according to claim 3, Further, a potential supply source is provided, the potential supply source generates a potential difference between the electron source and the plurality of grids; the accelerating grid is configured to be at a high potential relative to the electron source; The thermionic cathode is configured such that the decelerating grid is at a lower potential relative to the accelerating grid.

6. 4. The thermionic cathode according to claim 3, the plurality of grids further includes a focusing grid arranged to abut on at least a portion of the electron source; The focusing grid is positioned closer to the electron source than the accelerating grid.

7. 7. The thermionic cathode according to claim 6, a thermionic cathode, wherein the through holes in the acceleration grid are smaller than the through holes in the focusing grid.

8. 7. The thermionic cathode according to claim 6, Further, a potential supply source is provided, the potential supply source generates a potential difference between the electron source and the plurality of grids; the focusing grid is configured to be at the same or similar potential as the electron source; the accelerating grid is configured to be at a high potential relative to the electron source; The thermionic cathode is configured such that the decelerating grid is at a lower potential relative to the accelerating grid.

9. 2. The thermionic cathode of claim 1, A thermionic cathode, wherein the through-hole has a circular, elliptical or polygonal shape, or a slit shape.

10. 2. The thermionic cathode of claim 1, Furthermore, it is equipped with a shield, The shield is located distal to the plurality of grids from the electron source.

11. 2. The thermionic cathode of claim 1, Furthermore, it has a heat insulating section, The heat insulating portion is It has a multi-layer insulation structure, a thermionic cathode positioned over the electron source;

12. 2. The thermionic cathode of claim 1, A thermionic cathode, wherein the material of the plurality of grids is any one of carbon, tantalum, molybdenum, titanium, tungsten, zirconium, niobium, and materials containing these.

13. 3. The thermionic cathode according to claim 2, A thermionic cathode, wherein the surface treatment layer is a low emissivity layer.

14. 14. The thermionic cathode of claim 13, A thermionic cathode, wherein the material of the surface treatment layer is platinum, titanium, nickel, zirconium, or a substance containing at least one of these.

15. A propulsion machine, a thermionic cathode structurally and electrically connected thereto; A thruster, wherein the thermionic cathode is a thermionic cathode according to any one of claims 1 to 14.

16. It is a rocket, a propulsion unit structurally and electrically connected thereto; 16. A rocket, wherein the propulsion device is a propulsion device according to claim 15.

17. An artificial satellite, a propulsion unit structurally and electrically connected thereto; 16. An artificial satellite, wherein the propulsion device is a propulsion device according to claim 15.

18. A space probe, a propulsion unit structurally and electrically connected thereto; 16. A space probe, wherein the propulsion device is a propulsion device according to claim 15.

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