Vacuum tube, imaging device, and electromagnetic wave detection device

Abstract

The present invention provides a vacuum tube, an imaging device, and an electromagnetic wave detection device. In the vacuum tube (1), the metasurface (S) emits electrons in response to the incidence of electromagnetic waves. The first electrode (81) and the second electrode (82) are spaced apart from each other and apply different electric potentials to the metasurface (S). The bracket (30) is disposed in the housing (10) and holds the electron emitter (20). The first wire (83) of the metasurface (S) is electrically connected to the first electrode (81). The second wire (84) of the metasurface (S) is spaced apart from the first wire (83) and is electrically connected to the second electrode (82). The first wire (83) extends from the first electrode (81) toward the second wire (84). The second wire (84) extends from the second electrode (82) toward the first wire (83).

Description

Technical Field

[0001] The present invention relates to a vacuum tube, an imaging device, and an electromagnetic wave detection device. Background Art

[0002] There are generally four types of electron emission, for example, thermionic emission (achieved by heating an electrode), photoemission (achieved by applying photons), secondary emission (achieved by bombarding light-speed electrons), and field emission (achieved in the presence of an electrostatic field). Known detectors detect electromagnetic waves (see, for example, the specification of U.S. Patent Application Publication No. 2016 / 0216201). The system described in Patent Document 1 is provided with a substrate having a metamaterial structure. The system detects terahertz waves (for example, electromagnetic waves having a frequency of 100 GHz to about 30 THz) in the electromagnetic waves incident on the substrate.

[0003] Patent Document

[0004] Patent Document 1: Specification of U.S. Patent Application Publication No. 2016 / 0216201 Summary of the Invention

[0005] Technical Problem

[0006] In the system described in Patent Document 1, when an electromagnetic wave is incident on a substrate having a metamaterial structure, the substrate emits electrons. The electrons emitted from the substrate excite molecules in the gas (for example, the atmosphere) surrounding the substrate. The excited molecules generate light. A light sensor detects the generated light.

[0007] An object of one aspect of the present invention is to provide a vacuum tube capable of ensuring the detection accuracy of electromagnetic waves. Another object of the present invention is to provide an imaging device capable of ensuring the detection accuracy of electromagnetic waves. Still another object of the present invention is to provide an electromagnetic wave detection device that ensures the detection accuracy of electromagnetic waves.

[0008] Technical Means

[0009] The vacuum tube according to one aspect of the present invention is provided with a housing, an electron emitter, and a support. The housing is sealed and includes a window that transmits electromagnetic waves. The electron emitter is disposed in the housing and includes a meta-surface, a first electrode, and a second electrode. The meta-surface is arranged to emit electrons in response to the incidence of an electromagnetic wave. The first electrode and the second electrode are spaced apart from each other and are respectively arranged to apply different electric potentials to the meta-surface. The support is disposed in the housing and holds the electron emitter. The meta-surface includes a first wire and a second wire. The first wire is electrically connected to the first electrode. The second wire is spaced apart from the first wire and is electrically connected to the second electrode. The first wire extends from the first electrode toward the second wire. The second wire extends from the second electrode toward the first wire.

[0010] On the one hand, an electron emitter having a metasurface is held in a sealed housing by a support. A first wire included in the metasurface is electrically connected to a first electrode, and a second wire included in the metasurface is electrically connected to a second electrode. In the electron tube, by applying different potentials to the first electrode and the second electrode, the electron emission in the metasurface can be increased or suppressed in response to the electromagnetic wave passing through the window. Therefore, by observing the electrons emitted from the electron emitter using the electron tube, the detection accuracy of the electromagnetic wave entering the electron tube can be ensured.

[0011] On the one hand, the support may include a first conductive terminal and a second conductive terminal spaced apart from each other. The first electrode may be electrically connected to the first conductive terminal. The second electrode may be electrically connected to the second conductive terminal. In this case, a voltage can be applied to the electron emitter through the support. Therefore, the number of components in the electron tube can be reduced and the electron tube can be miniaturized.

[0012] On the one hand, the housing may include a first conductive layer and a second conductive layer provided on the inner surface of the housing. The first conductive layer and the second conductive layer may be spaced apart from each other. The first conductive terminal may be in contact with the first conductive layer. The second conductive terminal may be in contact with the second conductive layer. In this case, the first conductive layer and the second conductive layer provided on the inner surface of the housing can apply a potential to the first conductive terminal and the second conductive terminal. Therefore, the electron tube is miniaturized.

[0013] On the one hand, the support may include a plurality of springs. The plurality of springs may be arranged to apply a biasing force to the inner surface of the housing, and the support is positioned relative to the housing by the biasing force. The plurality of springs may include at least one of the first conductive terminal and the second conductive terminal. In this case, although any certain amount of deformation occurs due to manufacturing errors or temperature changes in each component of the electron tube, the support can still be stably held on the housing. A potential can be applied to the electron emitter through the springs.

[0014] On the one hand, the support may include a holding body and a contact electrode. The holding body may have a penetrating opening and be in contact with the electron emitter. The contact electrode may be in contact with one of the first electrode and the second electrode and be spaced apart from the holding body. The metasurface and the electrode in contact with the contact electrode may be exposed from the penetrating opening and be spaced apart from the edge of the penetrating opening. In this case, it is possible to prevent the electrode in contact with the contact electrode from contacting the holding body. Therefore, a desired electrical connection structure can be achieved between the first electrode and the second electrode through a simple structure.

[0015] On the one hand, the electron emitter may include a substrate having a first main surface and a second main surface opposite to each other. The metasurface may be provided on the first main surface.

[0016] On the one hand, at least one of the first electrode and the second electrode can be spaced apart from the entire edge of the first major surface. As long as it is spaced apart from the entire edge of the first major surface, it is possible to easily prevent at least one of the first electrode and the second electrode from coming into contact with the support. Therefore, a desired electrical connection structure can be achieved between the first electrode and the second electrode with a simple structure.

[0017] On the one hand, the support can include a base member and a biasing member. The base member can be in contact with the second major surface. The biasing member can be in contact with the edge of the first major surface and arranged to bias the electron emitter towards the base member. The biasing member can be electrically connected to the second electrode. In this case, even if any certain amount of deformation occurs due to manufacturing errors or temperature changes in each component of the electron tube, the electron emitter can still be stably held on the base member. A voltage can be applied to the electron emitter through the biasing member.

[0018] On the one hand, one of the first electrode and the second electrode can be an electrode arranged to be grounded.

[0019] On the one hand, one of the first wire and the second wire can include an antenna portion and a biasing portion. The antenna portion can be arranged to emit electrons in response to the incidence of electromagnetic waves. The biasing portion can be arranged to generate an electric field with the other of the first wire and the second wire.

[0020] On the one hand, the second wire can be arranged to emit electrons in response to the incidence of electromagnetic waves when a biasing potential is applied to the first electrode. The first wire can be arranged to emit electrons in response to the incidence of electromagnetic waves when a biasing potential is applied to the second electrode.

[0021] On the one hand, the second wire can include an antenna portion arranged to emit electrons in response to the incidence of electromagnetic waves. The first wire can include a portion arranged to generate an electric field with the antenna portion when a biasing potential is applied to the first electrode. In this case, the electric potential can be tilted around the antenna portion. Therefore, it is possible to enhance or suppress electron emission in the metasurface.

[0022] On the one hand, the first wire can include a first end in contact with the first electrode and a second end electrically connected to the first end. The second wire can include a third end in contact with the second electrode and a fourth end electrically connected to the third end. The second end can be arranged to be closer to the fourth end than all other components of the first wire except the second end. In this case, the electric field strength generated between the second end and the fourth end can be increased, and the electric potential around the antenna portion can be further tilted. Therefore, it is possible to enhance or suppress electron emission in the metasurface.

[0023] On the one hand, the second conductor may include a straight portion extending on a virtual straight line extending from the fourth end. The second end may be located on the virtual straight line. In this case, the electrons emitted from the fourth end strike the second end and are amplified. Therefore, the electron emission in the metasurface can be improved.

[0024] On the one hand, the second conductor may include a straight portion extending on a virtual straight line extending from the fourth end. The second end may not be located on the virtual straight line. In this case, the amplification of the electrons emitted from the fourth end caused by the second end can be suppressed. Therefore, electrons are emitted from the metasurface according to the amount of electromagnetic waves passing through the window. Therefore, the amplitude of the electromagnetic waves passing through the window can be detected more accurately.

[0025] On the one hand, the electron tube may further include an electron multiplication unit and an electron collection unit. The electron multiplication unit may be disposed in the housing and arranged to multiply the electrons emitted from the electron emitter. The electron collection unit may be disposed in the housing and arranged to collect the electrons multiplied by the electron multiplication unit. The interior of the housing may be maintained in a vacuum. In this case, the electrons emitted from the electron emitter are amplified in the electron multiplication unit and then collected in the electron collection unit. Therefore, despite the miniaturization of the structure, the detection accuracy can be ensured for the electromagnetic waves incident from the window.

[0026] On the one hand, the electron multiplication unit and the electron collection unit may be diodes and may be integrally configured. In this case, the size of the electron tube can be further reduced.

[0027] On the one hand, the electron multiplication unit may include a plurality of dynodes separated from each other. The electron collection unit may include an anode or a diode arranged to collect the electrons multiplied by the electron multiplication unit. In this case, the electrons emitted from the metasurface are multiplied by the plurality of dynodes. Therefore, the multiplication factor of the electrons collected by the anode or the diode can be increased.

[0028] On the one hand, the electron multiplication unit may include a microchannel plate. The electron collection unit may include an anode or a diode arranged to collect the electrons multiplied by the electron multiplication unit. In this case, compared with the case where the electron multiplication unit includes a plurality of dynodes, the size, weight, and power consumption can be reduced, and the response speed and gain can be increased.

[0029] On the one hand, the electron multiplication unit may include a microchannel plate. The electron collection unit may include a phosphor arranged to receive the electrons multiplied by the electron multiplication unit and emit light. In this case, the two-dimensional position of the electrons emitted from the metasurface can be detected by the light emitted from the phosphor.

[0030] An imaging device according to another aspect of the present invention includes an electron tube and an imaging unit configured to capture an image based on light from a phosphor. On the other hand, the detection accuracy of electromagnetic waves can be ensured.

[0031] An electromagnetic wave detection device according to still another aspect of the present invention includes an electron tube and a light detector. The light detector is arranged to detect light. A housing accommodates a gas that emits light due to electrons emitted from a metasurface. The light detector is arranged to detect the light generated due to the light emission of the gas.

[0032] In still another aspect, the gas may include air, argon, or nitrogen.

[0033] Advantageous Effects

[0034] According to one aspect of the present invention, an electron tube capable of ensuring the detection accuracy of electromagnetic waves is provided. According to another aspect of the present invention, an imaging device capable of ensuring the detection accuracy of electromagnetic waves is provided. According to still another aspect of the present invention, an electromagnetic wave detection device for ensuring the detection accuracy of electromagnetic waves is provided. Description of the Drawings

[0035] Figure 1 is a schematic diagram of an electron tube according to an embodiment;

[0036] Figure 2 is a perspective view of the electron tube;

[0037] Figure 3 is a side view of the electron tube;

[0038] Figure 4 is a side view of the electron tube;

[0039] Figure 5 is a cross-sectional view of the electron tube;

[0040] Figure 6 is a perspective view of the support;

[0041] Figure 7 is a partial cross-sectional view of the support;

[0042] Figure 8 is an exploded view of the components of the support;

[0043] Figure 9 is an exploded view of the components of the holding body;

[0044] Figure 10 is a cross-sectional view showing the state in which the support holds the electron emitter;

[0045] Figure 11 is a view showing the state in which the support is positioned in the housing;

[0046] Figure 12It is a diagram showing the state of the bracket positioned in the housing;

[0047] Figure 13A It is a plan view of the electron emitter in the embodiment;

[0048] Figure 13B and Figure 13C It is a plan view of the electron emitter in the modified example of the embodiment;

[0049] Figure 14 It is a diagram showing the wire structure;

[0050] Figure 15 It is a diagram showing the wire structure in the modified example of the embodiment;

[0051] Figure 16 It is a diagram showing the wire structure in the modified example of the embodiment;

[0052] Figure 17 It is a perspective view of the bracket in the modified example of the embodiment;

[0053] Figures 18A to 18D It is a plan view of the electron emitter in the modified example of the embodiment;

[0054] Figures 19A to 19C It is a plan view of the electron emitter in the modified example of the embodiment;

[0055] Figure 20A and Figure 20B It is a plan view of the electron emitter in the modified example of the embodiment;

[0056] Figure 21 It is a diagram describing the operation of the electron tube in the embodiment;

[0057] Figure 22A and Figure 22B It is a diagram describing the operation of the electron tube in the embodiment;

[0058] Figure 23 It is a diagram describing the operation of the electron tube in the embodiment;

[0059] Figure 24 It is a cross-sectional view of the electron tube in the modified example of the embodiment;

[0060] Figure 25 It is a cross-sectional view of the electron tube in the modified example of the embodiment;

[0061] Figure 26 It is a cross-sectional view of the electron tube in the modified example of the embodiment;

[0062] Figure 27 It is a three-dimensional sectional view of the microchannel plate;

[0063] Figure 28 A partial cross-sectional view of a vacuum tube in a modified example of the embodiment;

[0064] Figure 29 A cross-sectional view of a vacuum tube in a modified example of the embodiment;

[0065] Figure 30 A side view of an imaging device in a modified example of the embodiment;

[0066] Figure 31 A cross-sectional view of a vacuum tube in a modified example of the embodiment; and

[0067] Figure 32 A cross-sectional view of an electromagnetic wave detection device in a modified example of the embodiment. Detailed Embodiment

[0068] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description, the same elements or elements having the same functions will be denoted by the same reference numerals, and redundant explanations will be omitted.

[0069] First, with reference to Figures 1 to 5 The configuration of a vacuum tube according to an embodiment of the present invention will be described. Figure 1 A perspective view of a vacuum tube according to an embodiment of the present invention. Figure 2 A perspective view of the vacuum tube. In Figure 2 The internal structure of the vacuum tube is also shown by solid lines. Figure 3 A side view of the vacuum tube. Figure 4 A side view of the vacuum tube. Figure 5 A cross-sectional view of the vacuum tube.

[0070] The vacuum tube 1 is a photomultiplier tube that outputs an electrical signal in response to the incidence of electromagnetic waves. In this specification, the "electromagnetic waves" incident on the vacuum tube are electromagnetic waves included in the frequency band from so-called millimeter waves to infrared light. When electromagnetic waves are incident, electrons are emitted inside the vacuum tube 1 and the emitted electrons are multiplied. In the embodiment, the vacuum tube 1 causes electromagnetic waves to be incident on the photocathode and multiplies the electrons emitted from the photocathode by the external photoelectric effect. The vacuum tube 1 includes a housing 10, an electron emitter 20, a support 30, an electron multiplier unit 40, and an electron collection unit 50.

[0071] The housing 10 includes a valve body 11 and a stem 12. The inside of the housing 10 is hermetically sealed by the valve body 11 and the stem 12. In the embodiment, the inside of the housing 10 is maintained in a vacuum. The vacuum includes not only an absolute vacuum but also a state in which the housing is filled with a gas having a pressure lower than the atmospheric pressure. For example, the inside of the housing 10 is maintained at 1×10 -4 to 1×10 -7Pa. The tube body 11 includes a window 11a having electromagnetic wave transmissivity. In this specification, "electromagnetic wave transmissivity" refers to the property of transmitting at least a part of the frequency band of the incident electromagnetic wave. In the present embodiment, the housing 10 has a cylindrical shape. The base 12 configures the bottom surface of the housing 10. The tube body 11 configures the side surface of the housing 10 and the bottom surface facing the base 12.

[0072] The window 11a configures the bottom surface facing the base 12. For example, the window 11a has a circular shape in the plan view. The frequency characteristics of the transmittance of the electromagnetic wave vary depending on the material. Therefore, the window 11a is made of an appropriate material according to the frequency band of the electromagnetic wave entering the electron tube 1. For example, the window 11a includes at least one selected from quartz, silicon, germanium, sapphire, zinc selenide, zinc sulfide, magnesium fluoride, lithium fluoride, barium fluoride, calcium fluoride, magnesium oxide, calcium carbonate, and chalcogenide glass. The window 11a made of the material selected from them enables the electromagnetic wave having any frequency band between millimeter waves and infrared light to be guided to the inside of the housing 10. For example, quartz can be selected as the material of the member that transmits the electromagnetic wave having a frequency band of 0.1 to 5 THz, silicon can be selected as the material of the member that transmits the electromagnetic wave having a frequency band of 0.04 to 11 THz and above 46 THz, magnesium fluoride can be selected as the material of the member that transmits the electromagnetic wave having a frequency band of above 40 THz, germanium can be selected as the material of the member that transmits the electromagnetic wave having a frequency band of above 13 THz, and zinc selenide can be selected as the material of the member that transmits the electromagnetic wave having a frequency band of above 14 THz.

[0073] The electron tube 1 includes a plurality of electric wires 13 that can electrically connect between the outside and the inside of the housing 10. The plurality of electric wires 13 are, for example, leads or pins. In the embodiment, the plurality of electric wires 13 are pins penetrating the base 12 and extending from the inside of the housing 10 to the outside thereof. At least one of the plurality of electric wires 13 is connected to various members provided inside the housing 10.

[0074] The housing 10 has conductive layers 15 and 16 provided on the inner surface 10a of the housing 10. The conductive layers 15 and 16 are spaced apart from each other. Different electric potentials are applied to the conductive layers 15 and 16 from the outside of the housing 10. The conductive layer 15 has an elliptical shape in the plan view. The conductive layer 15 extends along the tube axis TA of the housing 10. The conductive layer 15 extends in the direction from the window 11a toward the base 12.

[0075] The conductive layer 16 is disposed around the window 11a. The conductive layer 16 surrounds the support 30 around the tube axis TA along the inner surface 10a of the housing 10. In the extending direction of the conductive layer 15, the conductive layer 16 is disposed in a region closer to the window 11a than the conductive layer 15. The conductive layer 16 extends along the tube axis TA of the housing 10 at a position opposite to the conductive layer 15. Therefore, the conductive layer 16 also includes a portion extending in the direction from the window 11a toward the base 12. In the embodiment, the shortest distance between the conductive layer 15 and the conductive layer 16 is about 1 mm. The conductive layers 15 and 16 are formed by vapor-depositing a metal on the inner surface 10a of the housing 10. The materials of the conductive layers 15 and 16 include, for example, aluminum. When the conductive layer 15 is the first conductive layer, the conductive layer 16 is the second conductive layer.

[0076] The electron emitter 20 is disposed inside the housing 10 and emits electrons in response to the incidence of electromagnetic waves inside the housing 10. The electron emitter 20 includes a substrate 21 and a metasurface S. The substrate 21 has a main surface 21a and a main surface 21b facing each other. In the embodiment, the substrate 21 is plate-shaped. For example, when the main surface 21a constitutes the second main surface, the main surface 21b constitutes the first main surface.

[0077] The main surfaces 21a and 21b are disposed parallel to the window 11a. The main surface 21a faces the window 11a. The main surface 21a includes an incident surface 22, and the electromagnetic waves passing through the window 11a are incident on the incident surface 22. The substrate 21 has electromagnetic wave transmissivity for the electromagnetic waves passing through the window 11a. Therefore, the substrate 21 transmits at least a part of the frequency band of the electromagnetic waves passing through the window 11a. The material of the substrate 21 includes, for example, quartz. The material of the substrate 21 may include, for example, silicon. The substrate 21 has a rectangular shape in a plan view. The substrate 21 is spaced apart from the window 11a and the electron multiplier unit 40.

[0078] The metasurface S emits electrons in response to the incidence of electromagnetic waves. The metasurface S is included in an oxide layer or a metal layer patterned on the substrate 21. The material of the oxide layer is, for example, silicon dioxide and titanium dioxide. The material of the metal layer is, for example, gold. In the embodiment, an oxide layer is formed on the main surface 21b of the substrate 21 made of quartz, and a metal layer is formed on the oxide layer. The metasurface S has a rectangular shape in a plan view. In the embodiment, the metasurface S is disposed on the main surface 21b. The metasurface S may be disposed on the main surface 21a.

[0079] The bracket 30 holds the electron emitter 20 inside the housing 10. The bracket 30 is positioned on the inner surface 10a of the housing 10. The bracket 30 positions the electron emitter 20 on the housing 10. The bracket 30 has a frame shape along the inner surface 10a of the housing 10, and a through-opening 31 is formed in the bracket 30. When viewed from a direction orthogonal to the main surfaces 21a, 21b of the electron emitter 20, the incident surface 22 of the electron emitter 20 and the metasurface S are provided inside the edges defining the through-opening 31. In a state where the bracket 30 is positioned on the housing 10, the tube axis TA of the housing 10 passes through the through-opening 31. The bracket 30 is positioned on the housing 10 such that the optical axis of the electromagnetic wave passing through the through-opening 31 (hereinafter referred to as "the axis of the bracket 30") is parallel to the tube axis TA of the housing 10. The axis HA of the bracket 30 is orthogonal to the main surfaces 21a and 21b of the electron emitter 20. The bracket 30 is connected to at least one of the plurality of electric wires 13. In the embodiment, the bracket 30 applies a voltage to the electron emitter 20.

[0080] The bracket 30 has conductive terminals 33 and 34. The conductive terminals 33 and the conductive terminal 34 are spaced apart from each other. Different potentials are applied to the conductive terminals 33 and the conductive terminal 34 through the conductive layers 15 and 16. The conductive terminal 33 extends toward the conductive layer 15 and elastically contacts the conductive layer 15. Accordingly, the conductive terminal 33 is electrically connected to the conductive layer 15. The conductive terminal 34 extends toward the conductive layer 16 and elastically contacts the conductive layer 16. Accordingly, the conductive terminal 34 is electrically connected to the conductive layer 16. When the conductive terminal 33 is the first conductive terminal, the conductive terminal 34 is the second conductive terminal.

[0081] The electron multiplier unit 40 is provided inside the housing 10 and includes an incident surface 40a on which electrons emitted from the electron emitter 20 are incident. The electron multiplier unit 40 multiplies the electrons entering the incident surface 40a. In the embodiment, the main surface 21b of the electron emitter 20 faces the incident surface 40a of the electron multiplier unit 40. The metasurface S faces the incident surface 40a of the electron multiplier unit 40, and the electrons emitted from the metasurface S enter the incident surface 40a. The main surface 21a of the electron emitter 20 faces the window 11a of the housing 10.

[0082] In this specification, "A faces B" means that B is located in the normal direction of A rather than the plane in contact with A. In other words, "A faces B" means that when the space is bisected by the surface in contact with A, B is located on the A side rather than the back side of A. For example, in the electron tube 1, as described above, the metasurface S faces the incident surface 40a of the electron multiplier unit 40. This means that the incident surface 40a of the electron multiplier unit 40 is located in the normal direction of the metasurface S rather than the plane in contact with the metasurface S.

[0083] In an embodiment, as Figure 1 shown, the electron multiplication unit 40 includes so-called linear-focused multistage dynodes. In an embodiment, the electron multiplication unit 40 includes a focusing electrode 41 arranged to converge electrons, and multistage dynodes 42a and 42b spaced apart from each other. The dynode 42a includes the above-described incident surface 40a. In an embodiment, the electron multiplication unit 40 includes ten-stage dynodes 42a and 42b. The nine-stage dynode 42b is provided at a subsequent stage of the dynode 42a. At the central portion of the focusing electrode 41, a circular incident opening 41a is provided. The dynodes 42a and 42b are provided at a subsequent stage of the incident opening 41a. One of the plurality of wires 13 is connected to each of the dynodes 42a and 42b. A predetermined electric potential is applied to each of the dynodes 42a and 42b through the wire 13. The dynodes 42a and 42b multiply the electrons passing through the incident opening 41a according to the applied electric potential.

[0084] The focusing electrode 41 has conductive terminals 43 and 44 spaced apart from each other. Different electric potentials from each other are applied to the conductive terminal 43 and the conductive terminal 44 through the conductive layers 15 and 16. One of the conductive layer 15 and the conductive layer 16 may be ground. The conductive terminal 43 extends toward the conductive layer 15 and elastically contacts the conductive layer 15. Accordingly, the conductive terminal 43 is electrically connected to the conductive layer 15. The conductive terminal 44 extends toward the conductive layer 16 and elastically contacts the conductive layer 16. Accordingly, the conductive terminal 44 is electrically connected to the conductive layer 16.

[0085] The electron collection unit 50 is provided inside the housing 10 and collects the electrons multiplied by the electron multiplication unit 40. In an embodiment, the electron collection unit 50 includes a mesh anode 51. The anode 51 is located at a position closer to the base 12 than the main surface 21b of the electron emitter 20. One of the plurality of wires 13 is connected to the anode 51. A predetermined electric potential is applied to the anode 51 through the wire 13. The anode 51 captures the electrons multiplied by the dynodes 42a and 42b. The electron collection unit 50 may include a diode instead of the anode 51.

[0086] In an embodiment, the electron tube 1 includes a pair of insulating substrates 52 that fix the dynodes 42a, 42b, and the anode 51 inside the housing 10. The pair of insulating substrates 52 is made of alumina. The pair of insulating substrates 52 faces each other. The dynodes 42a and 42b include a pair of end portions extending in the direction in which the pair of insulating substrates 52 face each other. The anode 51 includes a pair of end portions extending in the direction in which the pair of insulating substrates 52 face each other. The end portions of the dynodes 42a, 42b, and the anode 51 are inserted into slit-shaped through holes provided in the pair of insulating substrates 52 in advance.

[0087] The electron tube 1 includes a shielding plate 55 that surrounds a part of the dynodes 42a, 42b, and the anode 51. The shielding plate 55 prevents light and ions generated by the collision of electrons multiplied by the dynodes 42a and 42b from scattering inside the housing 10. The shielding plate 55 is connected to one of the plurality of electric wires 13. A predetermined electric potential is applied to the shielding plate 55 through the electric wire 13.

[0088] Next, the structure of the bracket 30 will be described in detail with reference to Figures 5 to 10 FIGs. Figure 6 FIG. 10 is a perspective view of the bracket 30. Figure 7 FIG. 11 is a partial cross-sectional view of the bracket 30. Figure 8 FIG. 12 is an exploded view of the components of the bracket 30. Figure 9 FIG. 13 is an exploded view of a part of the bracket 30 further disassembled. Figure 10 FIG. 14 is an enlarged end view showing the state in which the bracket 30 holds the electron emitter.

[0089] The bracket 30 has a contact member 60 and a holding body 70. The contact member 60 is engaged with the holding body 70. The holding body 70 has the above-described through-opening 31. The main surfaces 21a and 21b of the electron emitter 20 are exposed from the through-opening 31. The metasurface S is exposed from the through-opening 31.

[0090] As Figure 8 shown, the contact member 60 includes the above-described conductive terminal 33, a washer 61, an insulator 62, an insulator 63, an attaching board 64, a contact electrode 65, and a post electrode 66. The conductive terminal 33 has a long plate shape. One end of the conductive terminal 33 is connected to the attaching board 64, and the other end of the conductive terminal 33 is elastically in contact with the above-described conductive layer 15.

[0091] In a state where the bracket 30 is located inside the housing 10, the washer 61, the insulator 62, the holding body 70, the insulator 63, and the attaching board 64 are arranged in sequence from the window 11a side. The holding body 70 is located between the insulator 62 and the insulator 63. Each of the washer 61, the insulator 62, the insulator 63, the attaching board 64, and the holding body 70 has a through-hole 60a. The post electrode 66 is inserted into the through-hole 60a of each of the conductive terminal 33, the washer 61, the insulator 62, the insulator 63, the attaching board 64, and the holding body 70. The contact member 60 is fixed to the holding body 70 by the post electrode 66.

[0092] Each of the insulators 62 and 63 has insulating properties. Each of the conductive terminals 33, the washer 61, the attachment plate 64, the contact electrode 65, and the columnar electrode 66 has conductive properties. The materials of the insulators 62 and 63 include, for example, ceramics. The materials of the washer 61 and the attachment plate 64 include, for example, stainless steel. The materials of the conductive terminals 33 and the contact electrode 65 include, for example, stainless steel. The material of the columnar electrode 66 includes, for example, nickel.

[0093] At least when the electron tube 1 is not operating, the conductive terminal 33 is insulated from the holder 70. The conductive terminal 33 is electrically connected to the contact electrode 65. The contact electrode 65 is electrically connected to the electron emitter 20. The conductive terminal 33 is electrically connected to the electron emitter 20 through the contact electrode 65. The contact electrode 65 is spaced apart from the holder 70.

[0094] The holder 70 includes a base member 71, a frame member 72, an intermediate member 73, a first positioning member 74, a second positioning member 75, and a pin electrode 76. In a state where the support 30 is located in the housing 10, the base member 71, the frame member 72, the intermediate member 73, the first positioning member 74, and the second positioning member 75 are sequentially provided from the window 11a side. The holder 70 contacts the electron emitter 20. The contact member 60 engages with the first positioning member 74 and the base member 71. The base member 71, the frame member 72, the intermediate member 73, the first positioning member 74, and the second positioning member 75 are welded to each other in a state where they hold the electron emitter 20.

[0095] The base member 71 has a flat plate portion 71c, on which an opening 71a and a through hole 71b are formed. The base member 71 contacts the main surface 21a of the electron emitter 20 on the flat plate portion 71c. The opening 71a forms a through opening 31 of the holder 70. The base member 71 contacts the main surface 21a of the electron emitter 20 at an edge portion that divides the opening 71a. The incident surface 22 of the electron emitter 20 is exposed from the opening 71a. The opening 71a has a rectangular shape or a circular shape. In the embodiment, the opening 71a has a rectangular shape. The pin electrode 76 is inserted into the through hole 71b.

[0096] In the embodiment, as Figure 5 shown, the base member 71 has a U-shaped cross-section in a cross-section passing through the axis HA of the support 30. The base member 71 further has a frame portion 71d that extends from the outer peripheral edge of the flat plate portion 71c in the direction of the axis HA of the support 30 to the opposite side of the frame member 72.

[0097] The frame member 72 is located between the base member 71 and the intermediate member 73. The frame member 72 has a flat plate portion 72c, on which an opening 72a and a through hole 72b are formed. The opening 72a forms a through opening 31 of the support 30. The opening 72a of the frame member 72 has a shape along the edge of the electron emitter 20. The frame member 72 surrounds the edge of the electron emitter 20. The opening 72a is in contact with the edge of the electron emitter 20. The frame member 72 restricts the movement of the electron emitter 20 in a direction orthogonal to the main surfaces 21a and 21b through the edge of the opening 72a. The opening 72a has a rectangular shape or a circular shape. In the embodiment, the opening 72a has a rectangular shape.

[0098] The frame member 72 positions the electron emitter 20 on the support 30 in a direction orthogonal to the axis HA of the support 30. The thickness T1 of the frame member 72 is equal to or less than the thickness T2 of the electron emitter 20. In the embodiment, the thickness T1 of the frame member 72 is less than the thickness T2 of the electron emitter 20.

[0099] The frame member 72 includes a first conductive portion 72d, an insulating portion 72e, and a second conductive portion 72f. The insulating portion 72e is located between the first conductive portion 72d and the second conductive portion 72f. The opening 72a of the frame member 72 is demarcated by the insulating portion 72e and the second conductive portion 72f. The second conductive portion 72f and the insulating portion 72e are in contact with the electron emitter 20. However, the first conductive portion 72d is not in contact with the electron emitter 20. The through hole 72b is formed in the insulating portion 72e. A pin-shaped electrode 76 is inserted into the through hole 72b. The insulating portion 72e is fixed to the base member 71 through the pin-shaped electrode 76.

[0100] The intermediate member 73 includes a spacer 73a and a fixing portion 73b. The spacer 73a and the fixing portion 73b are spaced apart from each other. The spacer 73a has a flat plate shape and has the same thickness as the fixing portion 73b. The spacer 73a is in contact with the first conductive portion 72d. The first conductive portion 72d is sandwiched between the spacer 73a and the base member 71. The fixing portion 73b has a flat plate portion 73c and a plurality of energizing portions 73d. In the embodiment, the flat plate portion 73c and the plurality of energizing portions 73d are integrally formed. The flat plate portion 73c is in contact with the second conductive portion 72f, and each energizing portion 73d is in contact with the electron emitter 20. The second conductive portion 72f is sandwiched between the flat plate portion 73c and the base member 71. The edge of the spacer 73a and the edge of the fixing portion 73b form the through opening 31 of the support 30.

[0101] Each biasing portion 73d has a plate shape and functions as a leaf spring that biases the electron emitter 20 toward the base member 71. Accordingly, the intermediate member 73 functions as a biasing member that biases the electron emitter 20 toward the base member 71. In a state before each biasing portion 73d contacts the electron emitter 20, it is integrally formed flush with the flat portion 73c. Each biasing portion 73d projects from the flat portion 73c in a direction orthogonal to the axis HA of the support 30 toward the axis HA. In other words, each biasing portion 73d extends from the flat portion 73c toward the center closer to the penetration opening 31.

[0102] Each biasing portion 73d contacts an edge of the main surface 21b and elastically biases the electron emitter 20 toward the flat portion 71c of the base member 71 by applying a biasing force F1 to the edge. Each biasing portion 73d is electrically connected to the main surface 21b. That is, the support 30 is electrically connected to the main surface 21b through the plurality of biasing portions 73d. The electron emitter 20 is electrically connected to the electric wire 13 connected to the support 30 through the plurality of biasing portions 73d.

[0103] As Figure 10 shown, each biasing portion 73d contacts an edge of the main surface 21b of the electron emitter 20 to elastically deform and applies a biasing force F1 to the main surface 21b of the electron emitter 20. The thickness T3 of each biasing portion 73d is less than the thickness T2 of the electron emitter 20. The thickness T3 of each biasing portion 73d is less than the thickness T1 of the frame member 72. The thickness of the flat portion 73c is equal to the thickness T3 of each biasing portion 73d. The term "equal" includes the manufacturing tolerance range.

[0104] In the embodiment, the plurality of biasing portions 73d have a shape in which a plurality of notch-like gaps 73e are provided at an edge of the fixed portion 73b in a direction orthogonal to the axis HA of the support 30. Each biasing portion 73d is divided into a plurality of sheet portions 73f by the gaps 73e. Each of the plurality of sheet portions 73f is a metal sheet that elastically biases the electron emitter 20 toward the base member 71. In the embodiment, each biasing portion 73d is divided into three sheet portions 73f having a rectangular shape in a plan view. Each biasing portion 73d may be divided into two portions or may be divided into four or more portions.

[0105] The first positioning member 74 and the second positioning member 75 position the support 30 within the housing 10. The first positioning member 74 includes a first positioning member 74a and a first positioning member 74b that are spaced apart from each other. Each of the first positioning members 74a and 74b has a flat portion 74c and a plurality of springs 74d. The flat portion 74c and the plurality of springs 74d are integrally formed. The plurality of springs 74d includes at least one of the conductive terminals 33 and 34. In the embodiment, the plurality of springs 74d includes the conductive terminal 34.

[0106] The flat portions 74c of each of the first positioning members 74a and 74b form a through-opening 31 in the bracket 30. The flat portion 74c of the first positioning member 74a contacts the spacer 73a. The flat portion 74c of the first positioning member 74b contacts the flat portion 73c of the fixing portion 73b.

[0107] The plurality of springs 74d extend in directions different from each other. In an embodiment, when viewed from the direction of the axis HA of the bracket 30, the plurality of springs 74d are arranged in a rotationally symmetric manner in the circumferential direction of the bracket 30. In an embodiment, the plurality of springs 74d are arranged at equal intervals in the circumferential direction of the tube axis TA along the inner surface 10a of the housing 10. In an embodiment, each of the first positioning members 74a and 74b has two springs 74d.

[0108] The second positioning member 75 includes a second positioning member 75a and a second positioning member 75b spaced apart from each other. Each of the second positioning members 75a and 75b has a flat portion 75c and a plurality of springs 75d. The flat portion 75c and the plurality of springs 75d are integrally formed. The plurality of springs 75d includes at least one of the conductive terminals 33 and 34. In an embodiment, the plurality of springs 75d includes the conductive terminal 34.

[0109] The edges of the flat portions 75c of each of the second positioning members 75a and 75b form a through-opening 31 in the bracket 30. The flat portion 75c of the second positioning member 75a contacts the flat portion 74c of the first positioning member 74a. The flat portion 75c of the second positioning member 75b contacts the flat portion 74c of the first positioning member 74b.

[0110] The plurality of springs 75d extend in directions different from each other. In an embodiment, when viewed from the direction of the axis HA of the bracket 30, the plurality of springs 75d are arranged in the circumferential direction of the bracket 30 to be rotationally symmetric. The plurality of springs 75d are arranged at equal intervals in the circumferential direction of the tube axis TA along the inner surface 10a of the housing 10. Each spring 75d extends in a direction away from the window 11a. In an embodiment, each of the second positioning members 75a and 75b has two springs 75d.

[0111] The base member 71, the first conductive portion 72d and the second conductive portion 72f of the frame member 72, the intermediate member 73, the first positioning member 74, and the second positioning member 75 have conductivity. The insulating portion 72e of the frame member 72 has insulation. The materials of the base member 71, the first positioning member 74, and the second positioning member 75 include, for example, stainless steel. The materials of the first conductive portion 72d and the second conductive portion 72f of the frame member 72 and the intermediate member 73 include, for example, stainless steel. The material of the pin-shaped electrode 76 includes, for example, nickel.

[0112] Next, the configurations of the first positioning member 74 and the second positioning member 75 will be described in more detail with reference to Figure 11 and Figure 12 More specifically, the configurations of the first positioning member 74 and the second positioning member 75 will be described. Figure 11 and Figure 12 are diagrams showing the state of the bracket 30 located within the housing 10.

[0113] The first positioning member 74 and the second positioning member 75 position the bracket 30 within the housing 10 by means of a plurality of springs 74d and a plurality of springs 75d. When viewed from a direction orthogonal to the axis HA of the bracket 30, each spring 74d is arranged closer to the window 11a than the plurality of springs 75d. Each spring 74d of the first positioning member 74 extends in the direction of the axis HA of the bracket 30 and in a direction orthogonal to the axis HA. The front ends of the plurality of springs 74d are in elastic contact with the conductive layer 16. Each spring 74d serves as a conductive terminal 34, electrically connecting the conductive layer 16 and the bracket 30.

[0114] Each spring 74d has a T-shaped configuration, and its front end is divided into two parts. When viewed from the direction of the axis HA of the bracket 30, the front end of each spring 74d is divided in the circumferential direction of the bracket 30 into directions opposite to each other. Each spring 74d applies a biasing force F2 to the inner surface 10a of the housing 10 by means of the two front ends of the spring 74d. Each spring 74d elastically holds the position of the bracket 30 within the housing 10 in a direction orthogonal to the tube axis TA of the housing 10. In other words, the plurality of springs 74d position the bracket 30 within the housing 10 by applying a biasing force to the inner surface 10a of the housing 10.

[0115] Each spring 75d of the second positioning member 75 extends in the direction of the axis HA of the bracket 30 and in a direction orthogonal to the axis HA. Each spring 75d applies a biasing force F3 to the inner surface 10a of the housing 10 by means of the front end of the spring 75d. The second positioning member 75 prevents the bracket 30 from moving in the direction of the tube axis TA of the housing 10 by the frictional force between the plurality of springs 75d and the inner surface 10a of the housing 10. In other words, the plurality of springs 75d position the bracket 30 within the housing 10 by applying a biasing force to the inner surface 10a of the housing 10. The front end of each spring 75d is in elastic contact with the conductive layer 16. Each spring 75d serves as a conductive terminal 34, electrically connecting the conductive layer 16 and the bracket 30.

[0116] Next, the configuration of the electron emitter 20 will be described in detail with reference to Figures 12 to 14 The configuration of the electron emitter 20 will be described in detail. Figure 13A is a plan view of the electron emitter. Figure 13B and Figure 13C are plan views of the electron emitter in a modified example of the embodiment. Figure 14 is a diagram showing the configuration of the wire.

[0117] The main surfaces 21a and 21b of the substrate 21 have a rectangular shape. The main surface 21b is delimited by four edges 21c, 21d, 21e, and 21f. The edge 21c and the edge 21e are opposite to each other, and the edge 21d and the edge 21f are opposite to each other.

[0118] In addition to the metasurface S, the electron emitter 20 has a first electrode 81 and a second electrode 82 that are electrically connected to the metasurface S. The first electrode 81 and the second electrode 82 are spaced apart from each other. When the electron tube 1 operates, different electric potentials are applied to the first electrode 81 and the second electrode 82. One of the first electrode 81 and the second electrode 82 can be arranged to be grounded. The first electrode 81 and the second electrode 82 are insulated at least when the electron tube 1 is not operating.

[0119] As Figure 6 shown, in the embodiment, at least a part of the metasurface S and the first and second electrodes 81, 82 protrude from the through-hole 31 of the holding body 70. The first electrode 81 is electrically connected to the conductive terminal 33. The second electrode 82 is electrically connected to the conductive terminal 34. One of the first electrode 81 and the second electrode 82 is in contact with the contact electrode 65. In the embodiment, the contact electrode 65 is in elastic contact with the first electrode 81. Therefore, the contact electrode 65 is electrically connected to the first electrode 81. The biasing portion 73d is in elastic contact with the second electrode 82. Therefore, the biasing portion 73d is electrically connected to the second electrode 82.

[0120] As Figure 13A shown, in the embodiment, the first electrode 81 and the second electrode 82 are arranged to face each other in the main surface 21b of the substrate 21. In the embodiment, when viewed from a direction orthogonal to the main surface 21b, each of the first electrode 81 and the second electrode 82 has a rectangular shape. When viewed from a direction orthogonal to the main surface 21b, the edge of the first electrode 81 completely overlaps with the entire edge 21c, a part of the edge 21d, and a part of the edge 21f. When viewed from a direction orthogonal to the main surface 21b, the edge of the second electrode 82 completely overlaps with the entire edge 21e, a part of the edge 21d, and a part of the edge 21f.

[0121] The metasurface S is of an active type, and when electromagnetic waves are incident on the metasurface S, electron emission is controlled by applying different electric potentials to the first electrode 81 and the second electrode 82. The metasurface S is provided at the center of the main surface 21b. In the embodiment, the metasurface S is provided between the first electrode 81 and the second electrode 82 in the main surface 21b. In the embodiment, the first electrode 81, the metasurface S, and the second electrode 82 are arranged in sequence along the first direction α.

[0122] The metasurface S includes a plurality of first conductors 83 and a plurality of second conductors 84. The first conductors 83 and the second conductors 84 are spaced apart from each other. Each first conductor 83 is electrically connected to the first electrode 81 and extends from the first electrode 81 toward the second electrode 82. In an embodiment, each first conductor 83 extends in a first direction α in which edges 21c and 21e face each other. Each second conductor 84 is electrically connected to the second electrode 82 and extends from the second electrode 82 toward the first electrode 81. In an embodiment, each second conductor 84 extends in the first direction α in which edges 21e and 21c face each other.

[0123] The shapes of the first electrode 81 and the second electrode 82 are not limited to Figure 13A the rectangular configuration shown, as long as they are spaced apart from each other. For example, the first electrode 81 and the second electrode 82 may be as Figure 13B and Figure 13C shown in the configuration. In the configuration as Figure 13B shown, the second electrode 82 extends along edge 21d toward edge 21c and along edge 21f toward edge 21c. The second electrode 82 is spaced apart from edge 21c. In the configuration as Figure 13B shown, when viewed from a direction orthogonal to the main surface 21b, the edge of the second electrode 82 completely overlaps a part of edge 21d, the entire edge 21e, and a part of edge 21f.

[0124] In the configuration as Figure 13C shown, when viewed from a direction orthogonal to the main surface 21b, the edge of the first electrode 81 completely overlaps only a part of edge 21c and a part of edge 21d. In the configuration as Figure 13C shown, when viewed from a direction orthogonal to the main surface 21b, the edge of the second electrode 82 completely overlaps only a part of edge 21e and a part of edge 21f. In the configuration as Figure 13C shown, when viewed from a direction orthogonal to the main surface 21b, each of the first electrode 81 and the second electrode 82 has a square shape. In the configuration as Figure 13C shown, the plurality of first conductors 83 and the second conductors 84 corresponding to the first conductors 83 extend in the first direction α, the second direction β, and a direction intersecting both the first direction α and the second direction β. When the Figure 13C shown electron emitter 20 is employed, the configuration of the bracket 30 may be deformed from the Figure 6 shown configuration so that the contact electrode 65 contacts the first electrode 81.

[0125] Figure 14Partial enlarged view of the first wire 83 and the second wire 84 in the metasurface S of the embodiment. Each first wire 83 extends from the first electrode 81 towards the corresponding second wire 84. Each second wire 84 extends from the second electrode 82 towards the corresponding first wire 83. Each first wire 83 includes a first end 83a and a plurality of second ends 83b. As Figure 13A shown, the first end 83a is in contact with the first electrode 81. In other words, the first end 83a is directly coupled to the first electrode 81. Each second end 83b is electrically connected to the first end 83a. Each second wire 84 includes a third end 84a and a plurality of fourth ends 84b. The third end 84a is in contact with the second electrode 82. In other words, the third end 84a is directly coupled to the second electrode 82. The fourth end 84b is electrically connected to the third end 84a. The first wire 83 extends from the first end 83a in the first direction α and branches at the metasurface S, thereby forming a plurality of second ends 83b. The second wire 84 extends from the third end 84a in the first direction α and branches at the metasurface S, thereby forming a plurality of fourth ends 84b. The first end 83a may be indirectly connected to the first electrode 81. The third end 84a may be indirectly connected to the second electrode 82.

[0126] As Figure 14 shown, the second end 83b and the fourth end 84b corresponding to the second end 83b are opposite to each other and adjacent to each other. One fourth end 84b is arranged adjacent to one second end 83b. The second end 83b is arranged closer to the corresponding fourth end 84b than all other parts of the first wire 83 except the second end 83b. The shortest distance between the corresponding second end 83b and the fourth end 84b is, for example, 1.8 μm. The shortest distance may be less than 1.8 μm. For example, the shortest distance may be 10 nm. As the shortest distance decreases, the sensitivity of the metasurface increases.

[0127] In the embodiment, as Figure 14 shown, the first wire 83 in the metasurface S includes a straight portion 83c extending linearly in the first direction α and a straight portion 83d branching from the straight portion 83c and extending linearly towards the opposite second wire 84. The straight portion 83d includes the second end 83b. The second wire 84 includes a straight portion 84c extending linearly in the first direction α, and a straight portion 84d branching from the straight portion 84c and extending linearly towards the opposite first wire 83. The straight portion 84d includes the fourth end 84b. The straight portion 83c and the straight portion 84c extend parallel to each other. In the embodiment, the straight portion 83d and the straight portion 84d extend in a second direction β orthogonal to the first direction α.

[0128] The corresponding straight portions 83d and 84d extend on the same virtual straight line R1. The corresponding straight portions 83d and 84d refer to the straight portion 83d and the straight portion 84d, and the straight portion 83d and the straight portion 84d include the second end portion 83b and the fourth end portion 84b that face each other and are adjacent to each other. The straight portion 83d of the first wire 83 is located on the virtual straight line R1 extending along the second direction β from the second end portion 83b, and the fourth end portion 84b of the straight portion 84d corresponding to the straight portion 83d is located on the virtual straight line R1. In other words, the straight portion 84d of the second wire 84 is located on the virtual straight line R1 extending along the second direction β from the fourth end portion 84b, and the second end portion 83b of the straight portion 83d corresponding to the straight portion 84d is located on the virtual straight line R1. Only one straight portion 83d extends toward the fourth end portion 84b of one straight portion 84d. The corresponding straight portions 83d and 84d have the same length. The term "same" includes the manufacturing tolerance range. In the structure as shown in Figure 14 , the first wire 83 and the second wire 84 are formed to be mirror-symmetrical to each other.

[0129] The plurality of first wires 83 and the plurality of second wires 84 are formed by, for example, evaporation processing and etching processing. The materials of the plurality of first wires 83 and the plurality of second wires 84 include, for example, gold. In the embodiment, the first wire 83 and the second wire 84 are included in the above metal layer and are formed on the above oxide layer. In the electron emitter 20, the first electrode 81 and the first wire 83, and the second electrode 82 and the second wire 84 are connected through the oxide layer and are insulated from each other at least when the electron tube 1 is not operating.

[0130] At least one of the first wire 83 and the second wire 84 is included in the antenna portion 85 and the bias portion 87. In the structure as shown in Figure 14 , the straight portion 83d of the first wire 83 and the straight portion 84d of the second wire 84 are configured as the antenna portion 85 and the bias portion 87.

[0131] The antenna portion 85 emits electrons in response to the incidence of electromagnetic waves. In the embodiment, when electromagnetic waves are incident on the antenna portion 85, an electric field is induced around the antenna portion 85. Therefore, the potential barrier at the antenna-vacuum interface becomes thinner, and the electrons existing in the antenna portion 85 slide out of the potential barrier due to the tunneling effect. The electrons that slide out of the potential barrier are accelerated by the electric field around the antenna portion 85. Therefore, field electron emission is generated by the incidence of electromagnetic waves on the antenna portion 85. When a bias potential is applied, the bias portion 87 generates an electric field between the bias portion 87 of the corresponding wire and the antenna portion 85.

[0132] In the structure as shown in Figure 14In the configuration shown, the straight portion 83d of the first conductor 83 includes: an antenna portion 85 that emits electrons in response to the incidence of electromagnetic waves; and a bias portion 87 that generates an electric field between the bias portion 87 of the second conductor 84 and the straight portion 84d when a bias potential is applied to the first electrode 81. The second conductor 84 includes: an antenna portion 85 that emits electrons in response to the incidence of electromagnetic waves; and a bias portion 87 that generates an electric field between the bias portion 87 of the first conductor 83 and the straight portion 83d when a bias potential is applied to the second electrode 82. That is, one of the first conductor 83 and the second conductor 84 includes: an antenna portion 85 that emits electrons in response to the incidence of electromagnetic waves; and a bias portion 87 that generates an electric field between the bias portion 87 and the other of the first conductor 83 and the second conductor 84. In the configuration as shown in Figure 14 When a bias potential is applied to the first electrode 81, the second conductor 84 emits electrons in response to the incidence of electromagnetic waves. When a bias potential is applied to the second electrode 82, the first conductor 83 emits electrons in response to the incidence of electromagnetic waves.

[0133] The antenna portion 85 having a smaller size tends to generate the emission of electric field electrons for electromagnetic waves having a shorter wavelength, that is, electromagnetic waves having a larger frequency. According to the change in the structure of the antenna portion 85, the metasurface S can correspond to a frequency band of about 0.01 to 150 THz, that is, a frequency band from so-called millimeter waves to infrared light. For example, the metasurface S can be configured to correspond to a frequency band of 0.01 to 10 THz equivalent to the frequency band from so-called millimeter waves to terahertz waves. For example, the metasurface S can be configured to correspond to a frequency band of 10 to 150 THz equivalent to the frequency band from terahertz waves to infrared light, which is equivalent to the frequency band from terahertz waves to infrared light. In an embodiment, the size of the main surface 21b of the electron emitter 20 is 10×10 mm. The size of the metasurface S in the plan view is 3.2×3.2 mm. The pitch of each antenna portion 85 is about 70 μm to 100 μm. The metasurface S corresponds to electromagnetic waves having a frequency of 0.5 THz.

[0134] In an embodiment, the metasurface S is a transmissive metasurface. In a transmissive metasurface, when electromagnetic waves are incident, electrons are emitted from the side opposite to the surface on which the incident electromagnetic waves are located. In the electron tube 1, the electromagnetic waves passing through the window 11a are incident on the main surface 21a of the substrate 21. The electromagnetic waves passing through the substrate 21 enter the metasurface S provided on the main surface 21b. The metasurface S emits electrons in response to the electromagnetic waves incident thereon after passing through the window 11a and the substrate 21.

[0135] Next, reference will be made to Figure 15 and Figure 16Describe the structures of the first wire 83 and the second wire 84 in the modification examples of this embodiment. These modification examples are substantially similar to or the same as the above-described embodiment. These modification examples are different from the above-described embodiment in the structures of the first wire 83 and the second wire 84. In these modification examples, the first wire 83 and the second wire 84 are formed to be mirror-asymmetric with respect to each other. Hereinafter, the differences between the embodiment and the modification examples will be mainly described. Figure 15 It is a partial enlarged view of the first wire 83 and the second wire 84 in the metasurface S according to the modification example of the embodiment. Figure 16 It is a partial enlarged view of the first wire 83 and the second wire 84 in the metasurface S according to another modification example of the embodiment.

[0136] In the structure as Figure 15 shown, the straight portion 83d of the first wire 83 extends along the second direction β toward each of a pair of second wires 84 sandwiching the straight portion 83c connected to the straight portion 83d. The straight portion 84d of the second wire 84 extends along the second direction β toward each of a pair of first wires 83 sandwiching the straight portion 84c connected to the straight portion 84d. In the structure as Figure 15 shown, the straight portion 83c and the straight portion 83d branched from the straight portion 83c cross in a cross shape. The straight portion 84c and the straight portion 84d branched from the straight portion 84c cross in a cross shape.

[0137] The corresponding straight portions 83d and 84d extend on the same virtual straight line R2. The straight portion 83d of the first wire 83 is located on the virtual straight line R2 extending from the second end portion 83b along the second direction β, and the fourth end portion 84b of the straight portion 84d corresponding to the straight portion 83d is located on the virtual straight line R2. In other words, the straight portion 84d of the second wire 84 is located on the virtual straight line R2 extending from the fourth end portion 84b along the second direction β, and the second end portion 83b of the straight portion 83d corresponding to the straight portion 84d is located on the virtual straight line R2. Only one straight portion 83d extends toward the fourth end portion 84b of one straight portion 84d. Only one straight portion 84d extends toward the second end portion 83b of one straight portion 83d.

[0138] In the structure as Figure 15 shown, the straight portion 84d of the second wire 84 is configured as the antenna portion 85. The straight portion 83d of the first wire 83 is configured as the bias portion 87, and when a bias potential is applied to the first electrode 81, an electric field is generated between the bias portion 87 and the antenna portion 85 of the second wire 84. In the structure as Figure 15In the shown configuration, the length of the straight portion 84d along the second direction β is greater than the length of the straight portion 83d along the second direction β. The term "length of the straight portion 83d" refers to the distance from the portion coupled to the straight portion 83c to the second end portion 83b. The term "length of the straight portion 84d" refers to the distance from the portion coupled to the straight portion 84c to the fourth end portion 84b. For example, the length of the straight portion 83d along the second direction β is 5.6 μm, and the length of the straight portion 84d along the second direction β is 116 μm. The thickness of the straight portion 83c is greater than the thicknesses of the straight portion 83d, the straight portion 84c, and the straight portion 84d. The term "thickness of the straight portion" refers to the width of each straight portion in the direction orthogonal to the extension direction of the straight portion. For example, the thickness of the straight portion 83c is 7.8 μm, and the thicknesses of the straight portion 83d, the straight portion 84c, and the straight portion 84d are 4.9 μm.

[0139] As Figure 16 shown in the configuration is different from that as Figure 15 shown in that the corresponding straight portion 83c does not lie on the virtual straight line R3 along which the straight portion 84c extends. Hereinafter, the differences between the above-described embodiment and the modification will be mainly described. In as Figure 16 shown in the configuration, the straight portion 84d of the second wire 84 is also configured as the antenna portion 85. In as Figure 16 shown in the configuration, the straight portion 83d of the first wire 83 is also configured as the bias portion 87, and when a bias potential is applied to the first electrode 81, an electric field is generated near the antenna portion 85 of the second wire 84.

[0140] In as Figure 16 shown in the configuration, a plurality of straight portions 83d extend toward the fourth end portion 84b of one straight portion 84d. A plurality of second end portions 83b are provided adjacent to one fourth end portion 84b. The number of the plurality of straight portions 83d extending toward one fourth end portion 84b can be two or three or more. In as Figure 16 shown in the configuration, two straight portions 83d extend toward the fourth end portion 84b of one straight portion 84d. Each of the two second end portions 83b faces one fourth end portion 84b. The distances between each of the two second end portions 83b and one fourth end portion 84b are equidistant. The term "equidistant" includes the range of manufacturing tolerances.

[0141] In as Figure 16 shown in the configuration, the straight portion 83d extends from the straight portion 83c toward the fourth end portion 84b in a direction intersecting both the extension direction of the straight portion 83c and the extension direction of the straight portion 84d. The straight portion 84d of the second wire 84 extends on the virtual straight line R3 extending from the fourth end portion 84b along the second direction β. The second end portion 83b of the straight portion 83d corresponding to the straight portion 84d does not lie on the virtual straight line R3.

[0142] Next, the structures of the support 30 and the electron emitter 20 in a modified example of the present invention will be described in detail with reference to Figures 17 to 18D FIGs. Figure 17 is a perspective view of the support 30 in a modified example of the embodiment. Figures 18A to 18D is a plan view of the electron emitter 20. The modified example is substantially similar to or the same as the above-described embodiment. The modified example is different from the above-described embodiment and modified example in the structures of the first electrode 81 and the second electrode 82 and the structure of the frame member 72. Hereinafter, the differences between the above-described embodiment and the modified example will be mainly described.

[0143] As Figure 17 shown, in the modified example, the frame member 72 only includes a conductive portion 72g, and only a single electric potential is applied to the frame member 72. The frame member 72 in the modified example does not include a portion corresponding to the insulating portion 72e. In the modified example, the entire first electrode 81, a part of the second electrode 82, and the metasurface S are exposed from the through-hole 31 of the holder 70. At least one of the first electrode 81 and the second electrode 82 is spaced apart from the holder 70 of the support 30. In the modified example, the first electrode 81 in contact with the contact electrode 65 is spaced apart from the edge of the through-hole 31 of the holder 70. The contact electrode 65 is elastically in contact with the first electrode 81.

[0144] At least one of the first electrode 81 and the second electrode 82 is spaced apart from all the edges 21c, 21d, 21e, and 21f of the substrate 21. In the modified example, similar to the above-described embodiment, the first electrode 81 and the second electrode 82 have a rectangular shape. In the structure as Figure 18A shown, the long sides of the first electrode 81 and the second electrode 82 extend in the second direction β. When viewed from a direction orthogonal to the main surface 21b, the edge of the second electrode 82 completely overlaps with the entire edge 21e, a part of the edge 21d, and a part of the edge 21f. The edge of the first electrode 81 does not completely overlap with any of the edges 21c, 21d, 21e, and 21f of the substrate 21. As Figure 18A shown, the first electrode 81 is spaced apart from all the edges 21c, 21d, 21e, and 21f of the substrate 21 in the main surface 21b.

[0145] Figures 18B to 18D shows a modified example of the structure as Figure 18A shown. For example, the first electrode 81 and the second electrode 82 can be configured as Figures 18A to 18D shown. In the structure as Figure 18B shown, the second electrode 82 extends along the edge 21d toward the edge 21c and along the edge 21f toward the edge 21c. In the structure as Figure 18B shown, the second electrode 82 is spaced apart from the edge 21c. In the structure asFigure 18B In the structure shown, when viewed from a direction orthogonal to the main surface 21b, the edge of the second electrode 82 completely overlaps with a part of the edge 21d, the entire edge 21e, and a part of the edge 21f.

[0146] In the structure as Figure 18C shown, the second electrode 82 is spaced apart from the edges 21d and 21f of the substrate 21. In the structure as Figure 18C shown, the first electrode 81 and the second electrode 82 have the same shape. In the structure as Figure 18C shown, when viewed from a direction orthogonal to the main surface 21b, the edge of the second electrode 82 completely overlaps with the edge 21e of the substrate 21.

[0147] In the structure as Figure 18D shown, the second electrode 82 extends along the edge 21d to the edge 21c and along the edge 21f to the edge 21c. In the structure as Figure 18D shown, when viewed from a direction orthogonal to the main surface 21b, the edge of the second electrode 82 completely overlaps with a part of the edge 21c, the entire edge 21d, the entire edge 21e, and the entire edge 21f.

[0148] Next, a structure of the electron emitter 20 according to still another modification of the structure shown in Figures 19A to 19C will be described in detail. The modification is substantially similar or the same as the modification shown in Figure 17 and Figures 18A to 18D . Hereinafter, the differences of the modification shown in Figure 17 and Figures 18A to 18D will be mainly described. Figure 17 and Figures 18A to 18D is a plan view of the electron emitter. Figures 19A to 19C is a plan view of the electron emitter.

[0149] In the structure as Figure 19A shown, when viewed from a direction orthogonal to the main surface 21b, the edge of the first electrode 81 completely overlaps only with a part of the edge 21c and a part of the edge 21d. In the structure as Figure 19A shown, when viewed from a direction orthogonal to the main surface 21b, the edge of the second electrode 82 completely overlaps with a part of the edge 21d, the entire edge 21e, the entire edge 21f, and a part of the edge 21c. In the structure as Figure 19A shown, when viewed from a direction orthogonal to the main surface 21b, the first electrode 81 has a rectangular shape and the second electrode 82 has an L-shaped shape. In the structure as Figure 19A shown, the first electrode 81, the metasurface S, and the second electrode 82 are sequentially arranged in a direction intersecting both the first direction α and the second direction β. In the structure as Figure 19AIn the structure shown, a plurality of first wires 83 and second wires 84 corresponding to the first wires 83 extend in a first direction α, a second direction β, and a direction intersecting both the first direction α and the second direction β. When using Figure 19A the electronic emitter 20 shown, the structure can be deformed from the Figure 17 structure of the bracket 30 shown, so that the contact electrode 65 contacts the first electrode 81.

[0150] In the structure such as Figure 19B shown, when viewed from a direction orthogonal to the main surface 21b, the edge of the second electrode 82 completely overlaps the entire edge 21c, the entire edge 21d, the entire edge 21e, and the entire edge 21f. In the structure such as Figure 19B shown, when viewed from a direction orthogonal to the main surface 21b, the first electrode 81 has a rectangular shape and is disposed at the center of the main surface 21a, and the second electrode 82 has an O shape and surrounds the first electrode 81. In the structure such as Figure 19B shown, the metasurface S is surrounded by the second electrode 82 and surrounds the first electrode 81. In the structure such as Figure 19B shown, a plurality of first wires 83 and second wires 84 corresponding to the first wires 83 extend radially from the center of the main surface 21b. When using the electronic emitter 20 such as Figure 19B shown, the structure can be deformed from the structure of the bracket 30 such as Figure 17 shown, so that the contact electrode 65 contacts the first electrode 81.

[0151] In the structure such as Figure 19C shown, the edge of the first electrode 81 does not completely overlap any of the edges 21c, 21d, 21e, and 21f of the substrate 21. In the structure such as Figure 19C shown, when viewed from a direction orthogonal to the main surface 21b, the edge of the first electrode 81 is spaced apart from all the edges 21c, 21d, 21e, and 21f of the substrate 21. In the structure such as Figure 19C shown, when viewed from a direction orthogonal to the main surface 21b, the edge of the second electrode 82 completely overlaps a part of the edge 21d, the entire edge 21e, the entire edge 21f, and a part of the edge 21c. In the structure such as Figure 19C shown, when viewed from a direction orthogonal to the main surface 21b, the first electrode 81 has a rectangular shape and the second electrode 82 has an L shape. In the structure such as Figure 19C shown, the long side of the first electrode 81 extends in the first direction α.

[0152] In the structure such as Figure 19C shown, the first electrode 81, the metasurface S, and the second electrode 82 are sequentially arranged in the second direction β. In the structure such as Figure 19CIn the configuration shown, a plurality of first wires 83 and second wires 84 corresponding to the first wires 83 extend in the second direction β. When an electron emitter 20 as shown in Figure 19C is used, the configuration of the bracket 30 can be deformed from the configuration as shown in Figure 17 so that a contact member having the same configuration as the contact member 60 connected to the first electrode 81 is connected to the second electrode 82.

[0153] The electron emitter 20 is not limited to Figures 13A to 13C 、 Figures 18A to 18D and Figures 19A to 19C the configurations shown. For example, the electron emitter can be configured as shown in Figure 20A and Figure 20B .

[0154] In the configuration as shown in Figure 20A , when viewed from a direction orthogonal to the main surface 21b, the first electrode 81 and the second electrode 82 have a rectangular shape. In the configuration as shown in Figure 20A , the long sides of the first electrode 81 and the second electrode 82 extend in the second direction β. In the configuration as shown in Figure 20A , the edge of the first electrode 81 does not completely overlap with any of the edges 21c, 21d, 21e, and 21f of the substrate 21. In the configuration as shown in Figure 20A , when viewed from a direction orthogonal to the main surface 21b, the edge of the first electrode 81 is spaced apart from all the edges 21c, 21d, 21e, and 21f of the substrate 21. In the configuration as shown in Figure 20A , the first electrode 81 and the second electrode 82 have the same shape and are arranged to be rotationally symmetric and linearly symmetric on the main surface 21b.

[0155] In the configuration as shown in Figure 20A , the first electrode 81, the metasurface S, and the second electrode 82 are sequentially arranged in the first direction α. In the configuration as shown in Figure 20A , a plurality of first wires 83 and second wires 84 corresponding to the first wires 83 extend in the first direction α. When an electron emitter 20 as shown in Figure 20A is used, the first electrode 81, the second electrode 82, and the metasurface S are exposed from the opening 72a and are spaced apart from the edge of the opening 72a. When an electron emitter 20 as shown in Figure 20A is used, two contact members each having the same configuration as the contact member 60 connected to the first electrode 81 can be used. In this case, the two contact electrodes 65 spaced apart from each other are in contact with the first electrode 81 and the second electrode 82 respectively.

[0156] In the configuration as shown in Figure 20BIn the configuration shown, when viewed from a direction orthogonal to the main surface 21b, the edge of the first electrode 81 completely overlaps a part of the edge 21c, the entire edge 21d, and a part of the edge 21e. In the configuration as shown in Figure 20B In the configuration shown, when viewed from a direction orthogonal to the main surface 21b, the edge of the second electrode 82 completely overlaps a part of the edge 21e, the entire edge 21f, and a part of the edge 21c. In the configuration as shown in Figure 20B In the configuration shown, the first electrode 81 and the second electrode 82 have edges with a concavo-convex shape in directions opposite to each other. In the configuration as shown in Figure 20B In the configuration shown, the first electrode 81, the metasurface S, and the second electrode 82 are sequentially arranged in the second direction β. In the configuration as shown in Figure 20B In the configuration shown, the first wire 83 and the second wire 84 corresponding to the first wire 83 extend along the second direction β.

[0157] Next, the operation of the electron tube 1 according to the embodiment will be described. Electric potentials are applied to the support 30, the dynodes 42a and 42b, and the anode 51 through the wire 13, respectively. The electric potentials applied to the support 30, the dynodes 42a and 42b, and the anode 51 are set to increase sequentially from the support 30 toward the anode 51.

[0158] An electric potential is applied to the first electrode 81 of the electron emitter 20 through the conductive layer 15 and the conductive terminal 33. An electric potential is applied to the second electrode 82 of the electron emitter 20 through the conductive layer 16 and the conductive terminal 34. Electric potentials different from each other are applied to the first electrode 81 and the second electrode 82. One of the first electrode 81 and the second electrode 82 may be grounded.

[0159] Electromagnetic waves enter the opening 71a of the base member 71 in the support 30 after passing through the window 11a of the housing 10. The electromagnetic waves passing through the opening 71a enter the incident surface 22 of the electron emitter 20. The electromagnetic waves pass through the substrate 21 and enter the metasurface S. When the electromagnetic waves are incident on the metasurface S, an electric field is induced around the antenna portion 85. Therefore, the potential barrier at the antenna-vacuum interface becomes thinner, and the electrons present in the antenna portion 85 slide out of the potential barrier due to the tunneling effect. The electric field around the antenna portion 85 accelerates the electrons that slide out of the potential barrier. Therefore, the electron emitter 20 emits electrons from the metasurface S in response to the incidence of the electromagnetic waves. The electrons emitted from the electron emitter 20 are guided to the incident surface 40a of the electron multiplier unit 40.

[0160] Electrons emitted from the electron emitter 20 are converged by the focusing electrode 41 and sent to the first-stage dynode 42a. When the electrons enter the first-stage dynode 42a, secondary electrons are emitted to the second-stage dynode 42b. When the electrons enter the second-stage dynode 42b, secondary electrons are emitted to the third-stage dynode 42b. In this way, the electrons are continuously emitted while being multiplied from the first-stage dynode 42a to the tenth-stage dynode 42b. For the electrons emitted from the electron emitter 20, cascade multiplication is performed by the electron multiplier unit 40. The electrons multiplied by the electron multiplier unit 40 are collected by the anode 51 serving as the electron collection unit 50, and are output as an output signal through the wire 13 from the anode 51.

[0161] will be described with reference to Figures 21 to 23 the operation of the electron emitter 20 in more detail. In Figures 21 to 23 , the vertical axis represents the potential energy U, and the horizontal axis represents the distance X from the edge of the antenna portion 85. Figure 21 , Figure 22A and Figure 22B as well as Figure 23 are diagrams for describing different operation modes.

[0162] First, the threshold mode will be described with reference to Figure 21 . When the electron tube 1 operates, a bias voltage is applied to the electron emitter 20 between the first electrode 81 and the second electrode 82. In other words, a bias voltage is applied to the antenna portion 85 through the first wire 83 and the second wire 84. Therefore, the electric potential around the antenna portion 85 is inclined as shown by the solid straight line 91 in Figure 21 compared to the state before the electromagnetic wave is incident on the metasurface S. Therefore, when an electromagnetic wave is incident on the metasurface S in a state where a bias voltage is applied to the antenna portion 85, the electric potential around the antenna portion 85 is further inclined as shown by the dotted line 92. Therefore, when the amplitude of the electromagnetic wave is small, the number of electrons EL that slide out of the potential barrier due to the tunneling effect increases compared to the case where no bias is applied. According to the above operation mode, for example, it is possible to detect whether the output is set in an electromagnetic wave with a low output.

[0163] Next, the modulation mode will be described with reference to Figure 22A and Figure 22B . In this operation mode, a bias voltage higher than that in the threshold mode is applied to the antenna portion 85. Therefore, as shown by the solid straight line 94 in Figure 22A , before the electromagnetic wave enters the metasurface S, the electric potential around the antenna portion 85 is further inclined. That is, Figure 22A the solid straight line 94 in Figure 21The straight solid line 91 in [the figure] is more inclined. Specifically, the bias voltage is set such that electrons in the antenna section 85 slip out of the potential barrier before the electromagnetic wave enters the metasurface S. When the electromagnetic wave is incident on the metasurface S in this state, the electric potential around the antenna section 85 is further inclined as shown by the dashed line 95. According to the above working mode, very small changes in the electromagnetic wave incident on the metasurface S can be detected. Therefore, for example, the stability of the electromagnetic wave incident on the metasurface S can be measured.

[0164] Next, reference will be made to Figure 23 to describe the reverse bias mode. In this working mode, a reverse bias voltage is applied to the antenna section 85. Therefore, as Figure 23 shown by the straight solid line 96 in [the figure], before the electromagnetic wave enters the metasurface S, the electric potential around the antenna section 85 is inclined in the direction opposite to that of the above threshold mode and modulation mode. When an electromagnetic wave with high output is incident on the metasurface S in this state, the electric potential around the antenna section 85 is inclined as shown by the dashed line 97. As a result, due to the tunnel effect, electrons are emitted from the metasurface S. According to this operation mode, even when an electromagnetic wave with high output is incident on the metasurface S, stable measurement can be achieved and damage to the device can be suppressed.

[0165] Next, reference will be made to Figure 24 to describe the electron tube according to a modification of the embodiment. Figure 24 is a cross-sectional view showing an example of the electron tube. Figure 24 The modification shown is substantially similar or the same as the above embodiment. However, the difference between the modification and the embodiment is that a window 11a is provided on the side surface of the housing 10, the incident direction of the electromagnetic wave to the metasurface S is different, and the electron multiplication unit 40 includes a so-called circular-cage multi-stage dynode. Hereinafter, the differences between the embodiment and the modification will be mainly described.

[0166] In Figure 24 the electron tube 1A shown, the window 11a is provided on the side surface of the cylindrical housing 10. In the electron tube 1A, the electron emitter 20 is also held by the bracket 30. In the electron tube 1A, the main surface 21b of the substrate 21 faces the window 11a and the incident surface 40a of the electron multiplication unit 40. That is, the metasurface S provided in the main surface 21b faces the window 11a and the incident surface 40a of the electron multiplication unit 40.

[0167] In the electron tube 1A, the metasurface S of the electron emitter 20 is a reflective metasurface. In a reflective metasurface, when an electromagnetic wave is incident, electrons are emitted in a direction opposite to the surface on which the electromagnetic wave has been incident. In the electron tube 1A, the electromagnetic wave passing through the window 11a enters the metasurface S provided on the main surface 21b of the substrate 21 without passing through the substrate 21. The metasurface S emits electrons in response to the electromagnetic wave incident thereon after passing through the window 11a.

[0168] The electron tube 1A includes a grid 37 between the metasurface S and the window 11a. The electromagnetic wave passing through the window 11a passes through the grid 37 and is incident on the metasurface S. A voltage is applied to the grid 37 through the wire 13. Due to the influence of the electric field caused by the grid 37, the electrons emitted from the metasurface S are guided to the incident surface 40a of the electron multiplier unit 40.

[0169] The electron multiplier unit 40 of the electron tube 1A includes so-called circular cage multi-stage dynodes 42a and 42b. The dynode 42a includes the incident surface 40a. In this modification, the electron multiplier unit 40 includes nine-stage dynodes 42a and 42b. The eight-stage dynode 42b is provided at the subsequent stage of the dynode 42a. The dynodes 42a and 42b are provided around the electron emitter 20 along the side surface of the housing 10. A predetermined electric potential is applied to each of the dynodes 42a and 42b through the wire 13. The dynodes 42a and 42b multiply the incident electrons according to the applied electric potential.

[0170] The electron collection unit 50 of the electron tube 1A is surrounded by the curved dynode 42b. In this modification, the electron collection unit 50 is the anode 51. One of the plurality of wires 13 is connected to the anode 51. A predetermined electric potential is applied to the anode 51 through the wire 13. The anode 51 captures the electrons multiplied by the dynodes 42a and 42b.

[0171] In Figure 24 In the shown electron tube 1A, if an electromagnetic wave passes through the window 11a of the housing 10, the electromagnetic wave passes through the grid 37 and is incident on the metasurface S provided on the main surface 21b of the substrate 21. The metasurface S emits electrons in response to the incidence of the electromagnetic wave. The electrons emitted from the metasurface S are emitted to the incident surface 40a of the electron multiplier unit 40 under the influence of the electric field caused by the grid 37.

[0172] Electrons emitted from the metasurface S are sent to the first-stage dynode 42a. When the electrons enter the first-stage dynode 42a (the incident surface 40a), secondary electrons are emitted from the dynode 42a to the second-stage dynode 42b. When the electrons enter the second-stage dynode 42b, secondary electrons are emitted from the dynode 42b to the third-stage dynode 42b. Thus, while the electrons are multiplied from the first-stage dynode 42a to the ninth-stage dynode 42b, they are continuously sent around the substrate 21. The electrons multiplied by the electron multiplier unit 40 are collected by the anode 51 serving as an electron collection unit 50 and output from the anode 51 as an output signal through the wire 13.

[0173] Next, a vacuum tube according to a modified example of the embodiment will be described with reference to Figure 25 a cross-sectional view showing an example of the vacuum tube. Figure 25 is a cross-sectional view showing an example of the vacuum tube. Figure 25 The modified example shown is substantially similar or identical to the above-described embodiment. However, the modified example differs from the above-described embodiment in that the electron multiplier unit 40 and the electron collection unit 50 are integrally configured as a diode 100. Hereinafter, the differences between the above-described embodiment and the modified example will be mainly described.

[0174] In Figure 25 the vacuum tube 1B shown, the electron multiplier unit 40 and the electron collection unit 50 are the diode 100. In the vacuum tube 1B, the electron multiplier unit 40 and the electron collection unit 50 are integrally configured. In the vacuum tube 1B, the metasurface S faces the window 11a.

[0175] In this modified example, the diode 100 is an avalanche diode. The diode 100 has a rectangular shape in a top view and includes a pair of main surfaces 101 and 102 facing each other. The main surface 101 includes an electron incident surface 101a. The main surface 101 faces the window 11a of the housing 10. The main surface 102 faces the base 12 of the housing 10. The main surfaces 101 and 102 are arranged parallel to the window 11a, the substrate 21, and the metasurface S.

[0176] An insulating layer 105 is provided on the main surface 102 of the diode 100. The diode 100 is connected to the base 12 in such a manner that the insulating layer 105 is located between the diode 100 and the base 12. One of the plurality of wires 13 is connected to each of the main surfaces 101 and 102.

[0177] A reverse bias voltage is applied to the diode 100 through the wire 13. In this modification, a reverse bias voltage higher than the breakdown voltage is applied between the main surface 101 (electron incident surface 101a) side of the diode 100 and the main surface 102 side of the diode 100. In the electron tube 1B, when electrons emitted from the metasurface S of the substrate 21 are incident on the electron incident surface 101a of the diode 100, the incident electrons are multiplied by avalanche multiplication inside the diode 100. The multiplied electrons are output as an output signal through the wire 13.

[0178] Next, reference will be made to Figure 26 and Figure 27 to describe an electron tube according to a modification of the embodiment. Figure 26 is a cross-sectional view showing an example of an electron tube. Figure 27 The modification shown is substantially similar or identical to the above-described embodiment. However, the modification differs from the above-described embodiment in that the electron multiplier unit 40 includes a microchannel plate 110 instead of the focusing electrode 41 and the plurality of dynodes 42a and 42b. Hereinafter, the differences between the above-described embodiment and the modification will be mainly described.

[0179] In Figure 26 the electron tube 1C shown, the microchannel plate 110 is supported by the inner edges of attachment members 111 and 112 fixed to the inner wall of the tube body 11. The microchannel plate 110 is disposed between the electron emitter 20 and the electron collection unit 50. Specifically, the microchannel plate 110 is disposed between the substrate 21 provided with the metasurface S and the anode 51. The microchannel plate 110 is spaced apart from the substrate 21 and the anode 51. Even in the electron tube 1C, the electron collection unit 50 may include a diode instead of the anode 51.

[0180] Figure 27 is a perspective cross-sectional view of an example of a microchannel plate. In this modification, as Figure 27 shown, the microchannel plate 110 includes a substrate 113, a plurality of channels 114, a partition wall portion 115, and a frame member 116. The substrate 113 includes an input surface 113a and an output surface 113b opposite to the input surface 113a. The substrate 113 is formed in a disc shape. The input surface 113a faces the substrate 21. The output surface 113b faces the anode 51 which is the electron collection unit 50. The input surface 113a and the output surface 113b are arranged parallel to the window 11a, the substrate 21, and the metasurface S. The anode 51 has a flat plate shape and is arranged parallel to the output surface 113b of the microchannel plate 110.

[0181] A plurality of channels 114 are formed in the substrate 113 from the input surface 113a to the output surface 113b. Specifically, each channel 114 extends from the input surface 113a to the output surface 113b in a direction orthogonal to the input surface 113a and the output surface 113b. The plurality of channels 114 are arranged in a matrix shape in a top view. Each channel 114 has a circular cross-sectional shape. A partition wall portion 115 is provided between the plurality of channels 114. The microchannel plate 110 functions as an electron multiplier and includes a resistance layer and an electron emission layer (not shown in the figure) on the surface of the partition wall portion 115 in the channel 114. The frame member 116 is provided on the peripheral edge portions of the input surface 113a and the output surface 113b of the substrate 113.

[0182] In the electron tube 1C, one of the plurality of wires 13 is connected to each of the attachment members 111 and 112. In the microchannel plate 110, a voltage is applied to the input surface 113a and the output surface 113b through the wires 13 and the attachment members 111 and 112. Specifically, an electric potential is applied to the input surface 113a and the output surface 113b such that the output surface 113b has a higher electric potential than the input surface 113a. When electrons emitted from the metasurface S are incident on the input surface 113a, the electrons are multiplied by the channels 114 and emitted from the output surface 113b. The electrons multiplied by the microchannel plate 110 are collected by the anode 51 serving as an electron collection unit 50, and are output from the anode 51 as an output signal through the wire 13.

[0183] Next, reference will be made to Figure 28 and Figure 29 to describe an electron tube according to a modification of the embodiment. Figure 28 is a partial cross-sectional view showing an example of an electron tube. Figure 29 is showing Figure 28 a cross-sectional view of a part of the electron tube shown in Figure 28 and 29 The modifications shown in

[0184] In Figure 28 the electron tube 1D shown in Figure 26The electron tube 1C shown, in the electron tube 1D, the electron multiplication unit 40 includes a microchannel plate 110 instead of the focusing electrode 41 and the dynodes 42a and 42b. In the electron tube 1D, the electron collection unit 50 includes a phosphor 121 instead of the anode 51. In the electron tube 1D, the metasurface S, the microchannel plate 110, and the phosphor 121 are close to each other in the housing 120.

[0185] The housing 120 includes a side wall 122, an incident window 123 (window 11a), and an exit window 124. The side wall 122 has a hollow cylindrical shape. Each of the incident window 123 and the exit window 124 has a disk shape. By hermetically sealing both ends of the side wall 122 with the incident window 123 and the exit window 124, the inside of the housing 120 is maintained in a vacuum. For example, the inside of the housing 120 is maintained at 1×10 -5 to 1×10 -7 Pa.

[0186] For example, the side wall 122 includes a side tube 125, a molding member 126 that covers the side of the side tube 125, and a case member 127 that covers the side and bottom of the molding member 126. Each of the side tube 125, the molding member 126, and the case member 127 has a hollow cylindrical shape. The side tube 125 is made of, for example, ceramic. The molding member 126 is made of, for example, silicone rubber. The case member 127 is made of, for example, ceramic.

[0187] Through holes are formed in each of the two ends of the molding member 126. One end of the case member 127 is open. The other end of the case member 127 is provided with a through hole. The through hole of the case member 127 includes an edge that completely overlaps the edge position of a through hole of the molding member 126. At one end of the molding member 126, the incident window 123 is joined to the surface surrounding the through hole of the molding member 126. Similar to the window 11a of the electron tube 1, the incident window 123 transmits electromagnetic waves. Similar to the window 11a of the electron tube 1, the incident window 123 includes at least one selected from quartz, silicon, germanium, sapphire, zinc selenide, zinc sulfide, magnesium fluoride, lithium fluoride, barium fluoride, calcium fluoride, magnesium oxide, and calcium carbonate.

[0188] In the electron tube 1D, the electron emitter 20 having the metasurface S is held by the bracket 30 and is disposed in the housing 120. In the housing 120, conductive layers spaced apart from each other are provided on the inner surface of the housing 120 and are in contact with the bracket 30. Therefore, in the electron tube 1D, different potentials can be applied to the first electrode 81 and the second electrode 82 of the electron emitter 20.

[0189] In the electron tube 1D, the metasurface S faces the microchannel plate 110 which serves as an electron multiplication unit 40. The microchannel plate 110 is disposed between the metasurface S and the phosphor 121. The microchannel plate 110 is spaced apart from the metasurface S and the phosphor 121.

[0190] On the other end side of the molding member 126, the exit window 124 is fitted in another through hole of the molding member 126. The exit window 124 is, for example, a fiber plate constructed by aggregating a large number of optical fibers in a plate shape. The optical fibers of each fiber plate are configured such that the end face 124a inside the housing 120 is flush with each optical fiber. The end face 124a is disposed parallel to the metasurface S.

[0191] The phosphor 121 is disposed on the end face 124a. For example, the phosphor 121 is formed by coating a fluorescent material on the end face 124a. The fluorescent material is, for example, (ZnCd)S:Ag (zinc cadmium sulfide doped with silver). On the surface of the phosphor 121, a metal back layer and a low electron reflectivity layer are stacked in sequence. For example, the metal back layer is formed by vapor deposition of Al, has a relatively high reflectivity for light passing through the microchannel plate 110, and has a relatively high transmittance for electrons emitted from the microchannel plate 110. In addition, the low electron reflectivity layer is formed by vapor deposition of, for example, C (carbon), Be (beryllium), etc., and has a relatively low reflectivity for electrons emitted from the microchannel plate 110.

[0192] Similar to the electron tube 1C, in the electron tube 1D, one of the plurality of wires 13 extending to the outside of the housing 120 is connected to the attachment members 111 and 112 that hold the microchannel plate 110. In the microchannel plate 110, a voltage is applied to the input surface 113a side and the output surface 113b side through the attachment members 111 and 112.

[0193] When electrons emitted from the metasurface S are incident on the input surface 113a, the electrons are multiplied by the channels 114 and emitted from the output surface 113b. In the electron tube 1D, the electrons multiplied by the microchannel plate 110 are collected in the phosphor 121. The phosphor 121 receives the electrons multiplied by the microchannel plate 110 and emits light. The light emitted from the phosphor 121 passes through the fiber plate and is emitted to the outside of the housing 120 from the exit window 124.

[0194] Next, with reference to Figure 30 An imaging device including an electron tube according to a modification of the embodiment will be described. Figure 30 It is a side view of the imaging device. Figure 30The imaging device 130 shown acquires an image based on electromagnetic waves emitted from an observation object or electromagnetic waves reflected or scattered by the observation object. The imaging device 130 includes, as components, an electron tube 1D as an image intensifier, an objective lens 131, a relay lens 132, and an imaging unit 133. In the imaging device 130, the components are joined in the order of the objective lens 131, the electron tube 1D, the relay lens 132, and the imaging unit 133.

[0195] The objective lens 131 includes a lens having a refractive index among the electromagnetic waves incident on the electron tube 1D. The objective lens 131 guides the electromagnetic wave T from the observation object to the incident window 123 of the electron tube 1D. The relay lens 132 guides the light emitted from the exit window 124 of the electron tube 1D to the imaging unit 133. The imaging unit 133 captures an image based on the light guided from the relay lens 132, that is, the light emitted from the phosphor 121. The imaging unit 133 is, for example, a CCD camera.

[0196] Next, an electron tube according to a modification of the embodiment will be described with reference to Figure 31 FIG. Figure 31 is a partial cross-sectional view showing an example of the electron tube. Figure 31 The modification shown is substantially similar to or the same as the above-described embodiment. However, the modification differs from the above-described embodiment in that the electron multiplication unit 40 includes an electron multiplier 145 instead of the focusing electrode 41 and the dynodes 42a and 42b. Hereinafter, the differences between the above-described embodiment and the modification will be mainly described. The electron multiplier 145 is a so-called channel electron multiplier (CEM).

[0197] In Figure 31 the electron tube 1E shown, the electron multiplier 145 is supported by a support member 146 fixed to the inner wall of the tube body 11. The electron multiplier 145 is disposed between the electron emitter 20 and the electron collection unit 50. Specifically, the microchannel plate 110 is disposed between the window 11a provided with the metasurface S and the anode 51. The electron multiplier 145 is spaced apart from the window 11a and the anode 51. Even in the electron tube 1E, the electron collection unit 50 may include a diode instead of the anode 51.

[0198] In this modification, the electron multiplier 145 includes an input surface 145a and an output surface 145b opposite to the input surface 145a. The input surface 145a faces the window 11a. The output surface 145b faces the anode 51 that is the electron collection unit 50. The input surface 145a and the output surface 145b are disposed parallel to the window 11a and the metasurface S. The anode 51 has a flat plate shape and is disposed parallel to the output surface 145b of the electron multiplier 145. In the embodiment, in the direction orthogonal to the input surface 145a, the distance D between the input surface 145a and the metasurface S is, for example, 0.615 mm.

[0199] The electron multiplier 145 includes a main body portion 147 and a plurality of channels 148. The main body portion 147 has a rectangular parallelepiped shape. The plurality of channels 148 are defined by the main body portion 147. Each channel 148 is formed to extend from an input surface 145a to an output surface 145b. Specifically, each channel 148 extends from the input surface 145a to the output surface 145b in a direction orthogonal to both the input surface 145a and the output surface 145b. In Figure 31 the configuration shown, three channels 148 are distributed in one direction parallel to the input surface 145a.

[0200] Each channel 148 includes an electron incident portion 148a and a multiplication portion 148b. The electron incident portion 148a of each channel 148 has an opening provided on the input surface 145a. When viewed from a direction orthogonal to the input surface 145a, the opening of the electron incident portion 148a is rectangular. The electron incident portion 148a gradually narrows in the arrangement direction of the plurality of channels 148 from the input surface 145a to the output surface 145b. That is, the electron incident portion 148a has a conical shape whose diameter decreases in a direction perpendicular to the input surface 145a.

[0201] When viewed from a direction parallel to the input surface 145a and orthogonal to the arrangement direction of the plurality of channels 148, the multiplication portion 148b of each channel 148 is formed in a serrated or wavy shape. In other words, the multiplication portion 148b has a shape that repeatedly bends in the arrangement direction of the plurality of channels 148.

[0202] In the electron tube 1E, two of the plurality of wires 13 are connected to the support member 146. A voltage is applied to the electron multiplier 145 through the wires 13 and the support member 146. Specifically, an electric potential is applied to the input surface 145a and the output surface 145b such that the output surface 145b has a higher electric potential than the input surface 145a. Wires 13 different from the wires 13 connected to the support member 146 are connected to the anode 51. The support member 146 and the anode 51 are electrically insulated from each other by an insulating member 149.

[0203] Electrons emitted from the metasurface S enter the opening of the input surface 145a of any one of the channels 148, and then enter the multiplication portion 148b through the electron incident portion 148a. Therefore, the electrons emitted from the metasurface S are multiplied by the channels 148 and emitted from the output surface 145b. The electrons multiplied by the electron multiplier 145 are collected by the anode 51 serving as an electron collection unit 50, and are output from the anode 51 as an output signal through the wires 13.

[0204] Next, a description will be made with reference to Figure 32 a electromagnetic wave detection device according to a modification of the embodiment. Figure 32 is a schematic diagram showing an example of the electromagnetic wave detection device.Figure 32 The electron tubes of the illustrated modified examples are substantially similar to or the same as the above-described embodiments. However, the electron tubes of the modified examples differ from the above-described embodiments in that the electron tubes are configured to contain a gas and detect light generated by the emission of electrons from the electron emitter. Hereinafter, the differences between the above-described embodiments and the modified examples will be mainly described.

[0205] Figure 32 The illustrated electromagnetic wave detection device 150 includes an electron tube 1F and a photodetector 151. The electron tube 1F contains a gas inside the housing 10. The housing 10 is sealed in a state where the gas is contained. The gas contained in the housing 10 is excited by electrons emitted from the electron emitter 20 and emits light. The gas contained in the housing 10 includes, for example, air, argon, or nitrogen. In the modified example, the gas contained in the housing 10 is nitrogen and emits ultraviolet light due to electrons emitted from the electron emitter 20.

[0206] In the electron tube 1F, the housing 10 has a window 11b in addition to the window 11a. The window 11b transmits the light L1 generated by the emission of light from the gas. In the embodiment, the window 11b is provided to face the main surface 21b of the electron emitter 20. In the modified example, the light L1 is ultraviolet light, and the window 11b transmits ultraviolet light. The material of the window 11b includes, for example, quartz.

[0207] The photodetector 151 detects the light L1 passing through the window 11b. In other words, the photodetector 151 detects the light L1 generated by the emission of light from the gas. The electromagnetic wave incident on the metasurface S is detected by referring to the detection result in the photodetector 151.

[0208] As described above, in the electron tubes 1, 1A, 1B, 1C, 1D, 1E, and 1F, the electron emitter 20 having the metasurface S is held in the housing 10 sealed by the bracket 30. The first wire 83 included in the metasurface S is electrically connected to the first electrode 81, and the second wire 84 included in the metasurface S is electrically connected to the second electrode 82. In the electron tubes 1, 1A, 1B, 1C, 1D, 1E, and 1F, by applying different potentials to the first electrode 81 and the second electrode 82, it is possible to promote or suppress the electron emission in the metasurface S in response to the electromagnetic wave incident from the window 11a. Therefore, by using the electron tubes 1, 1A, 1B, 1C, 1D, 1E, and 1F and observing the electrons emitted from the electron emitter 20, the detection accuracy of the electromagnetic wave incident on the electron tubes 1, 1A, 1B, 1C, 1D, 1E, and 1F can be ensured.

[0209] The support 30 has conductive terminals 33 and 34 spaced apart from each other. The first electrode 81 is electrically connected to the conductive terminal 33. The second electrode 82 is electrically connected to the conductive terminal 34. In this case, a voltage can be applied to the electron emitter 20 through the support 30. Therefore, reduction in the number of components of the electron tubes 1, 1A, 1B, 1C, 1D, 1E, and 1F and miniaturization of the electron tubes 1, 1A, 1B, 1C, 1D, 1E, and 1F can be achieved.

[0210] The housing 10 has conductive layers 15 and 16 provided on the inner surface 10a of the housing 10. The conductive layers 15 and 16 are spaced apart from each other. The conductive terminal 33 is in contact with the conductive layer 15. The conductive terminal 34 is in contact with the conductive layer 16. In this case, an electric potential can be applied to the conductive terminal 33 and the conductive terminal 34 through the conductive layers 15 and 16 provided on the inner surface 10a of the housing 10. Therefore, miniaturization of the electron tubes 1, 1A, 1B, 1C, 1D, 1E, and 1F can be achieved.

[0211] The support 30 has a plurality of springs 74d and 75d. The plurality of springs 74d and 75d position the support 30 relative to the housing 10 by applying a biasing force to the inner surface 10a of the housing 10. The plurality of springs 74d and 75d include at least one of the conductive terminal 33 and the conductive terminal 34. In this case, although any deformation occurs in each component of the electron tubes 1, 1A, 1B, 1C, 1D, 1E, and 1F due to a certain amount of manufacturing error or temperature change, the support 30 is stably held on the housing 10. An electric potential can be applied to the electron emitter through the springs 74d and 75d.

[0212] The support 30 includes a holding body 70 and a contact electrode 65. The holding body 70 is in contact with the electron emitter 20 and has a penetrating opening 31. The contact electrode 65 is spaced apart from the frame member 72 and contacts one of the first electrode 81 and the second electrode 82. The metasurface S and the electrode in contact with the contact electrode 65 are exposed from the penetrating opening 31 and are spaced apart from the edge of the penetrating opening 31. In this case, contact between the electrode in contact with the contact electrode 65 and the holding body 70 is prevented. Therefore, a desired electrical connection structure can be achieved between the first electrode 81 and the second electrode 82 and the support 30. For example, a configuration in which the electrode in contact with the contact electrode 65 is insulated from the holding body 70 can be easily achieved. In the above embodiment, the contact electrode 65 is in contact with the first electrode 81. The first electrode 81 in contact with the contact electrode 65 and the metasurface S are exposed from the penetrating opening 31 and are spaced apart from the edge of the penetrating opening 31.

[0213] In Figure 20A the configuration shown, Figure 6The two contact electrodes 65 shown are spaced apart from each other and are in contact with the first electrode 81 and the second electrode 82 respectively. The first electrode 81, the second electrode 82, and the metasurface S are exposed from the through-opening 31 and are spaced apart from the edge of the through-opening 31. Thus, a configuration in which the first electrode 81 and the second electrode 82 in contact with each contact electrode 65 are insulated from the holding body 70 can be easily achieved.

[0214] At least one of the first electrode 81 and the second electrode 82 is spaced apart from the entire edges 21c, 21d, 21e, and 21f of the main surface 21b. As long as it is spaced apart from the entire edge of the main surface 21b, contact between the bracket 30 and at least one of the first electrode 81 and the second electrode 82 can be easily prevented. Thus, a desired electrical connection structure can be achieved between the bracket 30 and the first electrode 81 and the second electrode 82 with a simple configuration. For example, for at least one of the first electrode 81 and the second electrode 82, insulating characteristics with respect to the bracket 30 can be ensured.

[0215] The bracket 30 has a base member 71 and an intermediate member 73 as biasing members. The base member 71 is in contact with the main surface 21a. The intermediate member 73 is in contact with the edge of the main surface 21b and elastically biases the electron emitter 20 toward the base member 71. The intermediate member 73 is electrically connected to the second electrode 82. In this case, although any deformation occurs in each member of the electron tubes 1, 1A, 1B, 1C, 1D, 1E, and 1F due to a certain amount of manufacturing error or temperature change, the electron emitter 20 is stably held on the base member 71. A voltage can be applied to the electron emitter 20 through the intermediate member 73.

[0216] The second wire 84 includes an antenna portion 85 that emits electrons in response to the incidence of electromagnetic waves. The first wire 83 includes a bias portion 87 that generates an electric field between the bias portion 87 and the antenna portion 85 when a bias potential is applied to the first electrode 81. In this case, the electric potential can be inclined around the antenna portion 85. Thus, electron emission in the metasurface S can be promoted or inhibited.

[0217] The first wire 83 includes a first end portion 83a in contact with the first electrode 81 and a second end portion 83b electrically connected to the first end portion 83a. The second wire 84 includes a third end portion 84a in contact with the second electrode 82 and a fourth end portion 84b electrically connected to the third end portion 84a. The second end portion 83b is disposed closer to the fourth end portion 84b than all other portions of the first wire 83 except the second end portion 83b. In this case, the intensity of the electric field generated between the second end portion 83b and the fourth end portion 84b can be increased, and the electric potential around the antenna portion 85 is further inclined. Thus, electron emission in the metasurface S can be promoted or inhibited.

[0218] The second conductor 84 includes a straight portion 84d extending on a virtual straight line extending from the fourth end portion 84b. The second end portion 83b is located on the virtual straight line. In this case, electrons emitted from the fourth end portion 84b strike the second end portion 83b and are amplified. Accordingly, electron emission in the metasurface S is enhanced.

[0219] The second end portion 83b may not be located on the virtual straight line as Figure 16 shown. In this case, amplification of electrons emitted from the fourth end portion 84b by the second end portion 83b is suppressed. Accordingly, electrons are emitted from the metasurface S in accordance with the amount of electromagnetic waves passing through the window 11a. Accordingly, the amplitude of the electromagnetic waves passing through the window 11a can be detected more accurately.

[0220] The electron tubes 1, 1A, 1B, 1C, 1D, and 1E include an electron multiplication unit 40 and an electron collection unit 50. The electron multiplication unit 40 is provided in the housing 10 and multiplies electrons emitted from the electron emitter 20. The electron collection unit 50 is provided in the housing 10 and collects the electrons multiplied by the electron multiplication unit 40. The inside of the housing 10 is maintained in a vacuum. In this case, electrons emitted from the electron emitter 20 are amplified in the electron multiplication unit 40 and then collected in the electron collection unit 50. Accordingly, detection accuracy can be ensured for electromagnetic waves incident from the window 11a despite the miniaturization of the structure.

[0221] In the electron tube 1B, the electron multiplication unit 40 and the electron collection unit 50 are a diode 100 and are integrally formed. In this case, the size of the electron tube can be further reduced.

[0222] In the electron tubes 1 and 1A, the electron multiplication unit 40 has a plurality of dynodes 42a and 42b spaced apart from each other. The electron collection unit 50 has an anode 51 or a diode arranged to collect the electrons multiplied by the electron multiplication unit 40. In this case, electrons emitted from the metasurface S are multiplied by the plurality of dynodes 42a and 42b. Accordingly, the multiplication factor of the electrons collected by the anode 51 or the diode is increased.

[0223] In the electron tube 1C, the electron multiplication unit 40 has a microchannel plate 110. The electron collection unit 50 has an anode 51 or a diode 100 arranged to collect the electrons multiplied by the electron multiplication unit 40. In this case, compared with the case where a plurality of dynodes are used for the electron multiplication unit 40, the size, weight, and power consumption are reduced, and the response speed and gain are increased.

[0224] In the electron tube 1D, the electron collection unit 50 has a phosphor 121 that receives the electrons multiplied by the electron multiplication unit 40 and emits light. In this case, the two-dimensional position of the electrons emitted from the metasurface S can be detected by the light emitted from the phosphor 121.

[0225] The imaging device 130 includes an electron tube 1D and an imaging unit 133 that captures an image based on light from the phosphor 121. Thus, the detection accuracy of the above-described electromagnetic wave is ensured.

[0226] Although embodiments and modifications of the present invention have been described, the present invention is not necessarily limited to the embodiments and modifications, and various changes can be made without departing from its gist.

[0227] For example, in the embodiment, the bracket 30 has been described as having a configuration with an intermediate member 73. However, the bracket 30 can be configured such that a plurality of biasing portions 73d extend from the edge of the flat portion 71c of the base member 71. In this case, the plurality of biasing portions 73d can be formed to extend from the edge of the flat portion 71c of the base member 71 toward the main surface 21b of the electron emitter 20 and then bend in a direction parallel to the main surface 21b. Even in this case, the plurality of biasing portions 73d elastically contact the edge of the main surface 21b and bias the electron emitter 20 toward the flat portion 71c of the base member 71.

[0228] In the electron tube 1, the electron collection unit 50 can have a diode instead of the anode 51. In this case, the electrons multiplied by the electron multiplier unit 40 are collected by the diode.

[0229] The shapes of the housings 10 and 120 are not limited to a cylindrical shape. For example, the housings 10 and 120 can have a tubular shape with a polygonal cross-section.

[0230] In the electron tube 1C, a sweep electrode can be provided between the metasurface S and the microchannel plate 110. Thus, a so-called streak tube can be constructed. In this case, a slit on which the measurement light is incident and a lens system arranged to capture an image of the slit can be provided outside the window 11a of the electron tube 1C used as a streak tube. Thus, a so-called streak camera can be constructed.

[0231] In the imaging device 130, the electrons multiplied by the microchannel plate 110 in the electron tube 1D are collected in the phosphor 121, and the light emitted from the phosphor 121 is arranged to be captured by the imaging unit 133 provided outside the electron tube 1E. In this regard, by providing an electron-bombarded solid-state image sensor instead of the phosphor 121 as the electron collection unit 50 inside the electron tube, the electron tube can be configured to be used as an imaging device. In this case, the electrons multiplied by the microchannel plate 110 can be arranged to be captured by the electron-bombarded solid-state image sensor without providing the imaging unit 133 outside the electron tube. The electron-bombarded solid-state image sensor is, for example, an electron-bombarded charge-coupled device (EBCCD).

[0232] Reference Signs:

[0233] 1, 1A, 1B, 1C, 1D, 1E, 1F Electron Tubes

[0234] 10, 120 Housing

[0235] 10a Inner Surface

[0236] 11a, 11b Windows

[0237] 20 Electron Emitter

[0238] 21 Substrate

[0239] 21c, 21d, 21e, 21f Edges

[0240] 30 Bracket

[0241] 31 Penetration Opening

[0242] 40 Electron Multiplication Unit

[0243] 42a, 42b Dynodes

[0244] 50 Electron Collection Unit

[0245] 51 Anode

[0246] 70 Holding Body

[0247] 71 Base Member

[0248] 74d, 75d Springs

[0249] 81 First Electrode

[0250] 82 Second Electrode

[0251] 83 First Wire

[0252] 83a First End

[0253] 83b Second End

[0254] 83c, 83d, 84c, 84d Straight Portions

[0255] 84 Second Wire

[0256] 84a Third End

[0257] 84b Fourth End

[0258] 85 Antenna Portion

[0259] 87 Bias Portion

[0260] 100 Diode

[0261] 110 Microchannel Plate

[0262] 121 Phosphor

[0263] 130 Imaging Device

[0264] 133 Imaging Unit

[0265] 150 Electromagnetic Wave Detection Device

[0266] 151 Photodetector

[0267] F2, F3 Auxiliary Forces

[0268] S Metasurface

[0269] R1, R2, R3 Virtual Lines

Claims

1. An electron tube, comprising: A housing, which is sealed and includes a window that transmits electromagnetic waves; An electron emitter, disposed in the housing and including a metasurface, a first electrode, and a second electrode, the metasurface being arranged to emit electrons in response to the incidence of the electromagnetic waves, the first electrode and the second electrode being spaced apart from each other and respectively arranged to apply different electric potentials to the metasurface; And A bracket, disposed in the housing and holding the electron emitter, wherein, The metasurface includes: a first wire electrically connected to the first electrode; and a second wire spaced apart from the first wire and electrically connected to the second electrode, The first wire extends from the first electrode towards the second wire, and The second wire extends from the second electrode towards the first wire, The first wire includes: a first end in contact with the first electrode; and a second end electrically connected to the first end, The second wire includes: a third end in contact with the second electrode; and a fourth end electrically connected to the third end, and The second end is arranged to be closer to the fourth end than all other components of the first wire except the second end.

2. The electron tube according to claim 1, wherein The bracket includes a first conductive terminal and a second conductive terminal spaced apart from each other, The first electrode is electrically connected to the first conductive terminal, and The second electrode is electrically connected to the second conductive terminal.

3. The electron tube according to claim 2, wherein The housing includes a first conductive layer and a second conductive layer provided on the inner surface of the housing, The first conductive layer and the second conductive layer are spaced apart from each other, The first conductive terminal is in contact with the first conductive layer, and The second conductive terminal is in contact with the second conductive layer.

4. The electron tube according to claim 2, wherein The bracket includes a plurality of springs arranged to apply a force to the inner surface of the housing, and the springs position the bracket relative to the housing through the force, and At least one of the plurality of springs includes the first conductive terminal and the second conductive terminal.

5. The electron tube according to claim 3, wherein The bracket includes a plurality of springs arranged to apply a force to the inner surface of the housing, and the springs position the bracket relative to the housing through the force, and At least one of the plurality of springs includes the first conductive terminal and the second conductive terminal.

6. The electron tube according to any one of claims 1 to 5, wherein the bracket comprises: A holding body, having a penetrating opening and in contact with the electron emitter; And a contact electrode in contact with one of the first electrode and the second electrode and spaced apart from the holding body, and The metasurface and the electrode in contact with the contact electrode are exposed from the penetrating opening and spaced apart from the edge of the penetrating opening.

7. The electron tube according to any one of claims 1 to 5, wherein The electron emitter includes a substrate having a first main surface and a second main surface opposite to each other, and The metasurface is provided on the first main surface.

8. The electron tube according to claim 6, wherein The electron emitter includes a substrate having a first main surface and a second main surface opposite to each other, and The metasurface is provided on the first main surface.

9. The electron tube according to claim 7, wherein At least one of the first electrode and the second electrode is spaced apart from the entire edge of the first main surface.

10. The electron tube according to claim 8, wherein, At least one of the first electrode and the second electrode is spaced apart from the entire edge of the first main surface.

11. The electron tube according to claim 7, wherein, The bracket includes: a base member that contacts the second main surface; and a biasing member that contacts an edge of the first main surface and is arranged to bias the electron emitter toward the base member, and the biasing member is electrically connected to the second electrode.

12. The electron tube according to any one of claims 8 to 10, wherein, The bracket includes: a base member that contacts the second main surface; and a biasing member that contacts an edge of the first main surface and is arranged to bias the electron emitter toward the base member, and the biasing member is electrically connected to the second electrode.

13. The electron tube according to any one of claims 1 to 5, wherein, One of the first electrode and the second electrode is an electrode arranged to be grounded.

14. The electron tube according to any one of claims 1 to 5, wherein, One of the first wire and the second wire includes: an antenna portion arranged to emit electrons in response to the incidence of the electromagnetic wave; and a biasing portion arranged to generate an electric field with the other of the first wire and the second wire.

15. The electron tube according to any one of claims 1 to 5, wherein, The second wire is arranged to emit electrons in response to the incidence of the electromagnetic wave when a bias potential is applied to the first electrode, and / or The first wire is arranged to emit electrons in response to the incidence of the electromagnetic wave when a bias potential is applied to the second electrode.

16. The electron tube according to any one of claims 1 to 5, wherein, The second wire includes an antenna portion arranged to emit electrons in response to the incidence of the electromagnetic wave, and The first wire includes a biasing portion arranged to generate an electric field with the antenna portion when a bias potential is applied to the first electrode.

17. The electron tube according to claim 1, wherein, The second wire includes a straight portion extending on a virtual straight line extending from the fourth end, and the second end is located on the virtual straight line.

18. The electron tube according to claim 1, wherein, The second wire includes a straight portion extending on a virtual straight line extending from the fourth end, and the second end is not located on the virtual straight line.

19. The electron tube according to any one of claims 1 to 5, wherein, Further included is: an electron multiplication unit provided in the housing and arranged to multiply electrons emitted from the electron emitter; and an electron collection unit provided in the housing and arranged to collect electrons multiplied by the electron multiplication unit, wherein The interior of the housing is maintained at a pressure below atmospheric pressure. In particular, the interior of the housing is maintained at 1×10 -4 to 1×10 -7 Pa.

20. The electron tube according to claim 19, wherein, the electron multiplication unit and the electron collection unit are diodes and integrally configured.

21. The electron tube according to claim 19, wherein, The electron multiplication unit includes a plurality of dynodes spaced apart from each other, and the electron collection unit includes an anode or a diode arranged to collect electrons multiplied by the electron multiplication unit.

22. The electron tube according to claim 19, wherein, The electron multiplication unit includes a microchannel plate, and, the electron collection unit includes an anode or a diode arranged to collect electrons multiplied by the electron multiplication unit.

23. The electron tube according to claim 19, wherein, The electron multiplication unit includes a microchannel plate, and, the electron collection unit includes a phosphor arranged to receive electrons multiplied by the electron multiplication unit and emit light.

24. An imaging device, comprising: The electron tube according to claim 23; and an imaging unit arranged to capture an image based on light from the phosphor.

25. An electromagnetic wave detection device, comprising: The electron tube according to any one of claims 1 to 19; and a light detector arranged to detect light, wherein the housing accommodates a gas that emits light by electrons emitted from the metasurface, and the light detector is arranged to detect light generated by light emission of the gas.

26. The electromagnetic wave detection device according to claim 25, wherein, The gas includes air, argon, or nitrogen.

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