Electron beam emission structure and electric field radiation device

Abstract

The electron beam emitting structure (1) includes an electron source (2) and a protective electrode (3). The electron source (2) emits an electron beam (B) toward the target (4) of the electric field emitting device. The protective electrode (3) is disposed around the electron source (2). In the electron source (2), the end face opposite to the target (4) constitutes an electron emitting surface (20). In the electron emitting surface (20), a curved concave surface (21) is formed in the central part and a curved convex surface (22) is formed in the peripheral part.

Description

Technical Field

[0001] This invention relates to the construction of an electron source related to the miniaturization of a cold cathode type electric field radiation device. Background Technology

[0002] In addition to low power consumption, cold cathode X-ray tubes can be miniaturized, and they also have a fast response speed and high electron density, giving them an advantage over hot cathode X-ray tubes. Furthermore, in order to reduce the focal spot size, this X-ray tube employs methods such as miniaturizing the electron source, incorporating a convergence tube, and setting an angle for the target (Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2010-56062 Summary of the Invention

[0006] In conventional electric field emission devices such as those described in Patent Document 1, the electron beam is narrowed by the shape of the electron emitting surface of the electron source and the electric field generated by the protective electrode. However, according to the structure of this prior art, the narrowing of the electron beam is limited.

[0007] exist Figure 6 In the electron source 2 shown in (a) with an electron emitting surface 20 forming a curved concave surface, when it has Figure 6 When the protective electrode 3 of (b) is used, as shown below, the shape of the electron beam B in the central part and the peripheral part of the electron emission surface 20 of the electron source 2 becomes different.

[0008] The central portion of the electron emitting surface 20 is perpendicular to the direction of travel of the electron beam B, and the electron beam B is output in a manner parallel to the direction of travel, thus not being easily affected by the electric field of the protective electrode 3 and traveling in a straight line. Since the peripheral portion of the electron emitting surface 20 forms a slight angle with respect to the direction of travel of the electron beam B, the electron beam B is output towards the central axis a. Influenced by the electric field of the protective electrode 3, it is concentrated towards the central axis a of the electron source 2 under the combined force of these two forces.

[0009] When attempting to narrow the electron beam B from the central portion of the electron emitting surface 20 onto the surface of the target 4, such as Figure 6 As shown in (c), the electron beam B from the peripheral portion of the electron emitting surface 20 crosses before reaching the target 4. Furthermore, when an attempt is made to narrow the electron beam B from the peripheral portion, the narrowing of the electron beam B from the central portion is insufficient, and it remains relatively thick.

[0010] It is known that discharge in a vacuum occurs not only at the peak of the electric field, but also at approximately 80% of the peak value. To protect electron source 2, a strong electric field peak needs to be formed on the protective electrode 3 to enable its operation. However, when a strong electric field peak is formed on the protective electrode 3, the focusing ability of the electron beam B increases, the intersection point shifts towards the electron source 2, and the electron beam B diffuses near the target 4.

[0011] In view of the above, the present invention addresses the technical challenge of achieving the emission of high-intensity electron beams over a wide area from an electron emitting surface and minimizing the focal point of the electron beam.

[0012] Therefore, one aspect of the present invention is an electron beam emission structure comprising: an electron source for emitting an electron beam toward a target; and a protective electrode disposed around the electron source, wherein a curved concave surface is formed in the central portion and a curved convex surface is formed in the peripheral portion of the electron emission surface of the electron source emitting the electron beam.

[0013] In one embodiment of the invention, in the electron beam emission configuration, the protective electrode has a covering portion that covers the periphery.

[0014] In one aspect of the invention, in the electron beam emitting configuration, the boundary between the curved concave surface and the curved convex surface on the electron emitting surface has a smooth surface.

[0015] One aspect of the present invention is an electric field emission device having the above-described electron beam emission structure.

[0016] According to the present invention described above, it is possible to emit high-intensity electron beams over a wide area from the electron emitting surface and to focus the electron beam into a smaller focal point. Attached Figure Description

[0017] Figure 1 This is a cross-sectional view of the electron beam emission structure according to Embodiment 1 of the present invention.

[0018] Figure 2 A cross-sectional view of the electron beam emission structure of Embodiment 1, which shows the shape of the electron beam.

[0019] Figure 3 This is a cross-sectional view of the electron beam emission structure according to Embodiment 2 of the present invention.

[0020] Figure 4 This is an electric field distribution diagram of the electron beam emission structure in Embodiment 2.

[0021] Figure 5 This is a cross-sectional view of the electron beam emission structure according to Embodiment 3 of the present invention.

[0022] Figure 6 (a) is a cross-sectional view showing the convergence of an electron beam from a conventional electron source having a curved concave surface in the central portion. Figure 6 (b) is a cross-sectional view showing the convergence of an electron beam from a conventional electron source equipped with a protective electrode. Figure 6 (c) is a cross-sectional view showing the convergence of an electron beam from a conventional electron source having a protective electrode and a curved concave surface in the center. Detailed Implementation

[0023] The embodiments of the present invention will be described below with reference to the accompanying drawings.

[0024] [Implementation Method 1]

[0025] Figure 1 The electron beam emission structure 1 shown as an embodiment 1 of the present invention includes an electron source 2 and a protection electrode 3.

[0026] The electron source 2 functions as the emitter of the electron beam B to the target 4 (anode) of an electric field radiation device, such as a cold cathode X-ray tube. The electron source 2 is made of a known material suitable for the emitter of a cold cathode X-ray tube, etc., and is cylindrical in shape. The end face opposite to the target 4 forms the electron emission surface 20. Moreover, in this electron emission surface 20, a curved concave surface 21 is formed in the central part and a curved convex surface 22 is formed in the peripheral part.

[0027] The protective electrode 3 is made of a known material suitable for protective electrodes of cold cathode X-ray tubes, etc., and is disposed around the electron source 2.

[0028] Reference Figure 1 and Figure 2 A working example of Implementation Method 1 will be described.

[0029] An electron beam B emitted from the central portion of the electron emitting surface 20 irradiates the center of the target 4 through the curved concave surface 21 of that central portion. At the periphery of the electron emitting surface 20, the electron beam B irradiates outwards, but due to the electric field formed by the guard electrode 3, it deflects towards the central axis a of the electron source 2 and converges towards the center of the target 4. At the central portion of the electron emitting surface 20, the curved concave surface 21 focuses the electron beam B, while at the periphery, the electric field formed by the guard electrode 3 focuses it further; therefore, the electron beam B is no longer doubly focused.

[0030] In addition, by utilizing the curved convex surface 22 of the peripheral portion, the overall electric field of the peripheral portion of the electron emitting surface 20 can be reduced, the electric field concentration in the peripheral portion can be suppressed, and the risk of discharge due to insulation breakdown can be reduced.

[0031] According to existing technology, it is difficult to focus the electron beam B onto the central axis a of the electron source 2.

[0032] In contrast, according to Embodiment 1, the electron beam B emitted from the central portion of the electron emission surface 20 of the electron source 2 and the electron beam B emitted from the peripheral portion of the electron emission surface 20 can be converged to the central axis a of the electron source 2.

[0033] [Implementation Method 2]

[0034] exist Figure 3 In the electron beam emission structure 1 shown as an embodiment 2 of the present invention, except that a covering portion 31 covering the periphery of the electron emission surface 20 of the electron source 2 is provided at the end of the protective electrode 3, it is the same as in embodiment 1. The surface of the covering portion 31 has a curved convex surface 32 that matches the electric field of the curved concave surface 21 of the electron emission surface 20.

[0035] Reference Figure 3 and Figure 4 A working example of Implementation Method 2 will be described.

[0036] An electron beam B emitted from the central portion of the electron emitting surface 20 of the electron source 2 converges toward the target 4. At the periphery of the electron emitting surface 20, the electron beam B irradiates outwards, but as shown in the figure, due to the electric field generated by the protective electrode 3, the electron beam B is deflected toward the central axis a of the electron source 2 and converges toward the target 4. Furthermore, the periphery of the electron emitting surface 20 is covered by the covering portion 31 of the protective electrode 3, thereby mechanically smoothing the boundary between the protective electrode 3 and the electron emitting surface 20, and aligning the electric fields of the protective electrode 3 and the electron emitting surface 20. Accordingly, the concentration of the electric field at the periphery of the electron emitting surface 20 is suppressed, thus preventing malfunctions caused by accidental abnormal discharges.

[0037] According to the above implementation method 2, such as Figure 4 As shown in the electric field distribution diagram, no electric field concentration physically occurs at the periphery of the electron emitting surface 20, thus suppressing electric field concentration at this periphery. Therefore, the risk of discharge can be reduced, a stronger electric field can be obtained in the electron source 2, and thus a large current can be achieved.

[0038] [Implementation Method 3]

[0039] exist Figure 5 In the electron beam emission structure 1 shown as an embodiment 3 of the present invention, the boundary between the curved concave surface 21 and the curved convex surface 22 of the electron emission surface 20 has a smooth surface 23. The smooth surface 23 is formed in such a way that the electric fields of the curved concave surface 21 and the curved convex surface 22 are matched. Furthermore, the smooth surface 23 may also be curved.

[0040] The working example of Implementation Method 3 will be described with reference to the figure.

[0041] Similar to Embodiment 1, the electron beam B from the central portion of the electron emitting surface 20 converges toward the target 4. At the periphery of the electron emitting surface 20, the electron beam B irradiates outwards, but due to the electric field formed by the protective electrode 3, the electron beam B is deflected toward the central axis a of the electron source 2 and converges toward the target 4.

[0042] As in implementation method 3 Figure 4 As shown, accidental discharges caused by the concentration of the electric field at the protection electrode 3 in the electron source 2 can be avoided and reduced. However, when the electric field is concentrated at the protection electrode 3, the electron beam B focusing ability of the protection electrode 3 becomes higher. At the center of the electron emitting surface 20, the large R-shape of the curved concave surface 21 is used to focus the electron beam B. At the periphery of the electron emitting surface 20, the electric field of the protection electrode 3 focuses the electron beam B. The boundary between the curved concave surface 21 and the curved convex surface 22 of the electron emitting surface 20 is the point where the focusing state of the electron beam B changes. By ensuring a smooth surface 23 at the boundary and the point of change that matches the electric fields of the curved concave surface 21 and the curved convex surface 22, the electron beams B that converge from the curved concave surface 21 and the curved convex surface 22 in different forms can be mixed together.

[0043] According to the above-described embodiment 3, the electron beam B can be focused while the protection electrode 3 is at risk of abnormal discharge. Furthermore, by providing a smooth surface 23 connecting the curved concave surface 21 and the curved convex surface 22 of the electron emitting surface 20, the electron beam B emitted from the central portion of the electron emitting surface 20 and the beam emitted from the peripheral portion of the electron emitting surface 20 can be mixed together.

Claims

1. An electron beam emitting structure, characterized in that, have: An electron source emits an electron beam toward a target; and A protective electrode is disposed separately from the electron source and around the electron source. In the electron emitting surface of the electron source that emits the electron beam, a curved concave surface is formed in the central part, while a curved convex surface is formed in the peripheral part. The end of the protective electrode is positioned opposite the target on the side closer to the target than the electron emitting surface, and has a curved convex surface. In the electron emitting surface, the boundary between the curved concave surface and the curved convex surface has a smooth surface.

2. An electric field radiating device, wherein, It has the electron beam emission structure as described in claim 1.

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