vacuum tubes

Abstract

An electron tube capable of improving resistance to vibration or impact is provided. [Solution] The electron tube 1 comprises a housing 2 having a window 21a that transmits electromagnetic waves W, an electron emitter 3 that is disposed within the housing 2 facing the window 21a and includes a metasurface 32 that emits electrons on the side opposite the window 21a in response to the incidence of the electromagnetic waves W, and an electron multiplier 4 that is disposed within the housing 2 on the side opposite the window 21a with respect to the electron emitter 3 and multiplies the electrons emitted from the electron emitter 3. The electron multiplier 4 is fixed to the housing 2. The electron emitter 3 is fixed to the electron multiplier 4.

Description

[Technical Field]

[0001] The present invention relates to an electron tube. [Background technology]

[0002] An electron tube (a so-called head-on type electron tube) is known that includes a housing having a window that transmits electromagnetic waves, an electron emitter that is arranged within the housing facing the window and includes a metasurface that emits electrons on the opposite side of the window in response to incident electromagnetic waves, and an electron multiplier that is arranged within the housing on the opposite side of the window from the electron emitter and multiplies the electrons emitted from the electron emitter (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2023-512566 Summary of the Invention [Problem to be solved by the invention]

[0004] In the electron tube described above, if the position of the electron emitting section relative to the window section and the electron multiplier section is shifted due to vibration or impact, there is a risk that electromagnetic waves will not be properly incident on the electron emitting section, or that electrons emitted from the electron emitting section will not properly reach the electron multiplier section.

[0005] An object of the present invention is to provide an electron tube that can improve resistance to vibrations or shocks. [Means for solving the problem]

[0006] The electron tube of the present invention is [1] "an electron tube comprising: a housing having a window portion that transmits electromagnetic waves; an electron emitter portion that is arranged within the housing facing the window portion and includes a metasurface that emits electrons on the opposite side of the window portion in response to the incidence of the electromagnetic waves; and an electron multiplier portion that is arranged within the housing on the opposite side of the window portion from the electron emitter portion and multiplies the electrons emitted from the electron emitter portion, wherein the electron multiplier portion is fixed to the housing and the electron emitter portion is fixed to the electron multiplier portion."

[0007] In the electron tube, the electron multiplier section is fixed to the housing, and the electron emitter section is fixed to the electron multiplier section. This makes it possible to reliably prevent the electron emitter section from being misaligned with respect to the window section and the electron multiplier section due to vibration or impact, compared to when the electron emitter section and the electron multiplier section are separately fixed to the housing. Therefore, the electron tube can improve its resistance to vibration or impact.

[0008] The electron tube of the present invention may be [2] "the electron tube according to the above [1], further comprising a support portion that supports the electron emitter, the electron emitter being attached to the electron multiplier portion via the support portion." With this electron tube, it is possible to easily and reliably realize a configuration in which the electron emitter is fixed to the electron multiplier portion.

[0009] The electron tube of the present invention may be [3] "the electron tube according to the above [2], in which the support portion has a plurality of contact portions in contact with the inner surface of the housing." With this electron tube, the electron emitter is fixed not only to the electron multiplier portion but also to the housing, thereby further improving resistance to vibration or impact.

[0010] The electron tube of the present invention may be [4] "the electron tube according to any one of the above [1] to [3], wherein the electron multiplier section includes a plurality of dynodes." With this electron tube, electrons emitted from the electron emitter in response to incidence of electromagnetic waves can be reliably multiplied.

[0011] The electron tube of the present invention may be [5] "the electron tube according to [4], wherein the electron multiplier section further includes a support supporting the plurality of dynodes, and the electron emitter section is attached to the support." With this electron tube, it is possible to easily and reliably realize a configuration in which the electron emitter section is fixed to the electron multiplier section.

[0012] The electron tube of the present invention may be [6] "the electron tube according to [4] or [5], wherein the electron multiplier section is fixed to the housing by being supported by a plurality of lead pins electrically connected to the plurality of dynodes." With this electron tube, a configuration in which the electron multiplier section is fixed to the housing can be easily and reliably achieved. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide an electron tube that can improve resistance to vibrations and shocks. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional view of an example electron tube. [Figure 2] 2 is a bottom view of the electron-emitting portion shown in FIG. 1. FIG. [Figure 3] 2 is a cross-sectional view of a portion of the electron tube shown in FIG. 1. [Figure 4] FIG. 4 is an exploded perspective view of a portion of the electron tube shown in FIG. 3. [Figure 5] FIG. 10 is a cross-sectional view of a portion of a modified electron tube. [Figure 6] FIG. 6 is an exploded perspective view of a portion of the electron tube shown in FIG. 5. DETAILED DESCRIPTION OF THE INVENTION

[0015] An example of the present invention will now be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and redundant explanations will be omitted. [Example of electron tube configuration]

[0016] As shown in FIG. 1 , the electron tube 1 includes a housing 2, an electron emitter 3, an electron multiplier 4, a first mesh electrode 5, a second mesh electrode 6, and a plurality of lead pins 7. The electron emitter 3, the electron multiplier 4, the first mesh electrode 5, and the second mesh electrode 6 are disposed within the housing 2. The electron emitter 3 emits electrons in response to incidence of electromagnetic waves W. The electron multiplier 4 multiplies the electrons emitted from the electron emitter 3. Each lead pin 7 penetrates the housing 2. Each lead pin 7 is used to apply a potential to each of the electron emitter 3, the electron multiplier 4, the first mesh electrode 5, and the second mesh electrode 6, and to output a signal current from the electron multiplier 4. In the electron tube 1, the end of each lead pin 7 within the housing 2 is electrically connected to each of the electron emitter 3, the electron multiplier 4, the first mesh electrode 5, and the second mesh electrode 6 via wiring 70. Each wire 70 is a linear member made of metal, and has a strength that enables "support of the electron multiplier section 4 by the plurality of lead pins 7 and the plurality of wires 70" to be described later.

[0017] The electromagnetic wave W is an electromagnetic wave having a predetermined electric field oscillation direction V perpendicular to the propagation direction T of the electromagnetic wave W (i.e., an electromagnetic wave having a predetermined polarization (polarization) component). The electromagnetic wave W is, for example, an electromagnetic wave in a predetermined band included in the frequency band from millimeter waves to infrared light, and in this example, is a terahertz wave. Hereinafter, a direction parallel to the electric field oscillation direction V of the electromagnetic wave W is referred to as a first direction D1, and a direction perpendicular to the propagation direction T of the electromagnetic wave W and the electric field oscillation direction V is referred to as a second direction D2. In this example, the second direction D2 is a direction perpendicular to the first direction D1.

[0018] The housing 2 has a bulb 21 and a stem 22. The bulb 21 is formed into a cylindrical shape with a bottom and made of a material (e.g., quartz) that is transparent to the electromagnetic wave W. As an example, the bulb 21 is formed into a cylindrical shape with a bottom and a center line that is an axis A parallel to the traveling direction T. In this case, the height of the bulb 21 is several tens of millimeters, and the outer diameter of the bulb 21 is several millimeters to a dozen or so millimeters. The bottom of the bulb 21 functions as a window 21a that allows the electromagnetic wave W to enter the bulb 21. The stem 22 is airtightly fixed to the opening 21b of the bulb 21 and faces the window 21a on the axis A. The stem 22 is made of, for example, glass. The space inside the housing 2 is a vacuum space. It is sufficient that at least the window 21a of the housing 2 is transparent to the electromagnetic wave W.

[0019] The electron emitter 3, the second mesh electrode 6, the first mesh electrode 5, and the electron multiplier 4 are arranged in this order from the window 21a side along the axis A. That is, the first mesh electrode 5 is disposed between the electron emitter 3 and the electron multiplier 4, and the second mesh electrode 6 is disposed between the electron emitter 3 and the first mesh electrode 5. The first mesh electrode 5, the second mesh electrode 6, and the electron emitter 3 are supported by the electron multiplier 4. The electron multiplier 4 is supported by a plurality of lead pins 7. In the electron tube 1, the electron multiplier 4 is supported by a plurality of lead pins 7 and a plurality of wirings 70. Each lead pin 7 extends in a direction parallel to the axis A and airtightly penetrates the stem 22.

[0020] As shown in FIG. 2, the electron emitter 3 includes a substrate 31, a metasurface 32, a pair of electrodes 33, and a metal layer 34. The substrate 31 is formed in a plate shape (e.g., a rectangular plate shape) from a material that is transparent to electromagnetic waves W. The substrate 31 is made of an electrically insulating material (e.g., silicon, quartz, sapphire, zinc selenide, etc.). The metasurface 32 and the pair of electrodes 33 are formed on a surface 31a of the substrate 31. The metal layer 34 is formed on the surface 31a of the substrate 31, covering the metasurface 32 and the pair of electrodes 33. The surface 31a is the surface of the substrate 31 on the electron multiplier section 4 side. Note that in FIG. 2, the metal layer 34 is indicated by a two-dot chain line.

[0021] The metasurface 32 includes a plurality of antenna structures 35 arranged two-dimensionally along the surface 31a. Each antenna structure 35 emits electrons in response to incidence of an electromagnetic wave W whose electric field oscillation direction V is the first direction D1. That is, the metasurface 32 emits electrons in response to incidence of the electromagnetic wave W having the electric field oscillation direction V. As an example, each antenna structure 35 is configured as a bowtie antenna, a dipole antenna, a split ring antenna, or a double split ring antenna, and includes a pair of ends facing each other in the first direction D1. In this case, the metasurface 32 emits electrons when the direction in which the straight line connecting the pair of ends of each antenna structure 35 extends coincides with the electric field oscillation direction V of the electromagnetic wave W.

[0022] The metasurface 32 is disposed on the axis A. A pair of electrodes 33 are disposed on both sides of the metasurface 32. Each electrode 33 is electrically connected to a corresponding antenna structure 35 via wiring (not shown). A predetermined potential difference is applied between a pair of ends of each antenna structure 35 via the pair of electrodes 33. The metasurface 32 is formed of a conductive material (e.g., a metal material such as gold, platinum, aluminum, silver, or copper, or an inorganic carbon material having electrical conductivity such as graphene or graphite). The metasurface 32 is formed by patterning a conductive material. Each electrode 33 is formed, for example, of the same material as the metasurface 32. The metal layer 34 entirely covers the metasurface 32 and the pair of electrodes 33 and is in contact with the metasurface 32 and the pair of electrodes 33. The metal layer 34 is deposited to a thickness of approximately one to several atomic layers using a metal (e.g., an alkali metal such as cesium) having a lower work function than the material of the metasurface 32. The metal layer 34, when attached to the surface of each antenna structure 35, has the effect of lowering the work function of the surface of the material constituting each antenna structure 35, thereby promoting field electron emission from each end of each antenna structure 35. In other words, the metal layer 34 functions to improve the sensitivity (electron emission ability) of the metasurface 32. In this example, different potentials are applied to each of the pair of electrodes 33 so that a predetermined potential difference is applied between the pair of ends of each antenna structure 35. However, instead of the pair of electrodes 33, a frame-shaped electrode 33 may be formed on the surface 31a. In this case, a uniform potential is applied to the entire metasurface 32.

[0023] As shown in FIG. 1 , the electron multiplier unit 4 has a pair of support walls (supports) 41, a plurality of dynodes 42, and an anode 43. The pair of support walls 41 face each other in the first direction D1. Each support wall 41 is formed into a plate shape from an electrically insulating material. The plurality of dynodes 42 and the anode 43 are disposed between the pair of support walls 41 and are sandwiched between the pair of support walls 41. Each dynode 42 is electrically connected to a wiring 70 connected to a corresponding lead pin 7 on the outer side of the pair of support walls 41. Similarly, the anode 43 is electrically connected to a wiring 70 connected to a corresponding lead pin 7 on the outer side of the pair of support walls 41. In this way, in the electron tube 1, the pair of support walls 41, the plurality of dynodes 42, and the anode 43 are unitized as the electron multiplier unit 4, and the unitized electron multiplier unit 4 is supported by a plurality of lead pins 7 within the housing 2.

[0024] The multiple dynodes 42 include a first dynode 421 and a second dynode 422. The first dynode 421 is the first-stage dynode 42, and the second dynode 422 is the second-stage dynode 42. The electron emission surface 42a of the first dynode 421 faces the electron emitter 3 and the electron emission surface 42a of the second dynode 422, respectively. The electron emission surface 42a of each dynode 42 from the second stage onwards, except for the final-stage dynode 42, faces the electron emission surface 42a of the preceding-stage dynode 42 and the electron emission surface 42a of the succeeding-stage dynode 42, respectively. The electron emission surface 42a of the final-stage dynode 42 faces the electron emission surface 42a of the preceding-stage dynode 42 and the anode 43, respectively.

[0025] With a predetermined potential applied to each dynode 42 via the corresponding lead pin 7 and wiring 70, electrons emitted from the electron emitter 3 pass through the second mesh electrode 6 and the first mesh electrode 5 and are incident on the electron emission surface 42a of the first dynode 421, causing secondary electrons to be emitted from the electron emission surface 42a of the first dynode 421, and these secondary electrons are then incident on the electron emission surface 42a of the second dynode 422. Electrons sequentially multiplied at each dynode 42 by such incidence and emission of secondary electrons finally enter the anode 43, and a signal current is output from the anode 43 via the corresponding wiring 70 and lead pin 7.

[0026] 3 and 4, the electron tube 1 includes a base 8, a first support portion (support portion) 11, a second support portion 12, a third support portion 13, and a spacer 14. The first support portion 11 supports the electron emitter 3. The second support portion 12 supports the first mesh electrode 5. The third support portion 13 supports the second mesh electrode 6. The base 8, the second support portion 12, the spacer 14, the third support portion 13, and the first support portion 11 are arranged in this order from the electron multiplier portion 4 side along the axis A. In other words, the spacer 14 is disposed between the first mesh electrode 5 and the second mesh electrode 6.

[0027] The base 8 is formed into a frame shape using, for example, a metal plate. The base 8 includes a frame portion 81 having an opening 81a and a plurality of spring portions 82. The frame portion 81 is disposed on a pair of support walls 41 of the electron multiplier section 4. When viewed from a direction parallel to the axis A, the opening 81a overlaps the electron emission surface 42a of the first dynode 421. Each spring portion 82 extends outward from the frame portion 81 (i.e., on the opposite side from the opening 81a). Each spring portion 82 contacts the inner surface of the bulb 21. A pair of notches 81b are formed in the frame portion 81. Each notch 81b engages with a protrusion 41a that protrudes from the corresponding support wall 41 toward the window portion 21a.

[0028] The second support portion 12 is formed in a frame shape using, for example, a metal plate. The second support portion 12 includes a frame portion 121 having an opening 121a and a plurality of second claw portions 122. The frame portion 121 is disposed on the frame portion 81 of the base 8. When viewed from a direction parallel to the axis A, the opening 121a overlaps the opening 81a of the frame portion 81. Each second claw portion 122 extends from the frame portion 121 toward the window portion 21a. More specifically, each second claw portion 122 extends from the frame portion 121 toward the spacer 14. A pair of through holes 121b is formed in the frame portion 121. A protrusion 41a of each support wall 41 engages with each through hole 121b.

[0029] The first mesh electrode 5 includes a frame 51 and a plurality of wires 52. The first mesh electrode 5 is formed by etching a plate-like member, and the frame 51 and the plurality of wires 52 are integrally formed. The first mesh electrode 5 is made of a conductive metal material such as copper, nickel, titanium, or stainless steel. The plurality of wires 52 are hung across the frame 51, defining a plurality of openings in the inner region of the frame 51. The frame 51 is fixed to the surface of the frame portion 121 facing the electron emitter 3. When viewed from a direction parallel to the axis A, the inner region of the frame 51 overlaps with the openings 121a of the frame portion 121. Wiring 70 connected to the corresponding lead pins 7 is connected to the second support portion 12, and a predetermined potential is applied to the first mesh electrode 5 via the second support portion 12. The first mesh electrode 5 may be formed by forming the frame 51 and the plurality of wires 52 separately, and then suspending the plurality of wires 52 around the frame 51.

[0030] The spacer 14 is formed in a frame shape from an electrically insulating material. As an example, the spacer 14 is formed in a circular frame shape from ceramic. The spacer 14 is disposed on the frame portion 121 of the second support portion 12. When viewed in a direction parallel to the axis A, the spacer 14 surrounds the first mesh electrode 5. The spacer 14 has a first surface 14a on the electron emitter 3 side and a second surface 14b on the electron multiplier 4 side. The spacer 14 is formed with a plurality of first through-holes 141, a plurality of second through-holes 142, and a plurality of third through-holes 143. Each of the through-holes 141, 142, and 143 defines a space penetrating the spacer 14 between the first surface 14a and the second surface 14b. In the electron tube 1, each of the through-holes 141, 142, and 143 is a through-hole that opens toward the electron emitter 3 side and the electron multiplier 4 side.

[0031] The third support portion 13 is formed into a frame shape using, for example, a metal plate. The third support portion 13 includes a frame portion 131 having an opening 131a, a plurality of connecting portions 132, and a plurality of third claw portions 133. The frame portion 131 is surrounded by the spacer 14 when viewed in a direction parallel to the axis A. The opening 131a overlaps the opening 121a of the frame portion 121 when viewed in a direction parallel to the axis A. Each connecting portion 132 extends outward from the frame portion 131 (i.e., opposite the opening 131a). The plurality of connecting portions 132 are disposed on the spacer 14. Each third claw portion 133 extends from each connecting portion 132 to the opposite side of the window portion 21a. More specifically, each third claw portion 133 extends from each connecting portion 132 toward the spacer 14.

[0032] The second mesh electrode 6 includes a frame 61 and multiple wires 62. The second mesh electrode 6 is formed by etching a plate-like member, and the frame 61 and the multiple wires 62 are integrally formed. The second mesh electrode 6 is made of a conductive metal material such as copper, nickel, titanium, or stainless steel. The multiple wires 62 are hung across the frame 61, defining multiple openings in the inner region of the frame 61. The frame 61 is fixed to the surface of the frame portion 131 facing the electron emitter 3. When viewed from a direction parallel to the axis A, the inner region of the frame 61 overlaps with the openings 131a of the frame portion 131. Wiring 70 connected to the corresponding lead pins 7 is connected to the third support portion 13, and a predetermined potential is applied to the second mesh electrode 6 via the third support portion 13. The second mesh electrode 6 may be formed by forming the frame 61 and the plurality of wires 62 separately, and then suspending the plurality of wires 62 over the frame 61.

[0033] The first support section 11 has a first support plate 111, a second support plate 112, and a plurality of support pieces 113. The first support plate 111 is formed in a frame shape from an electrically insulating material such as ceramic. The first support plate 111 is disposed on a plurality of connection portions 132 of the third support section 13. The electron emitter 3 is disposed in an opening 111a of the first support plate 111. This restricts movement of the electron emitter 3 in a direction perpendicular to the axis A.

[0034] The second support plate 112 is formed into a frame shape using, for example, a metal plate. The second support plate 112 includes a frame portion 114 having an opening 114a and a plurality of claw portions 115. The frame portion 114 is disposed on the first support plate 111. The opening 114a overlaps with the metasurface 32 of the electron emitter 3 when viewed from a direction parallel to the axis A. Each of the claw portions 115 extends from the frame portion 114 to the side opposite the window portion 21a. More specifically, each of the claw portions 115 extends from the frame portion 114 toward the spacer 14.

[0035] Each support piece 113 includes a spring portion 116 and a first claw portion 117. Each support piece 113 is formed, for example, into an L-shape using a metal plate. The spring portion 116 of each support piece 113 presses the electron emitter 3 against the second support plate 112 between the spacer 14 and the first support plate 111 so that the electron emitter 3 is spaced from the second mesh electrode 6 and the substrate 31 of the electron emitter 3 contacts the second support plate 112. In each support piece 113, the first claw portion 117 extends from the spring portion 116 to the side opposite the window portion 21a. More specifically, the first claw portion 117 extends from the spring portion 116 toward the spacer 14. A wiring 70 connected to a corresponding lead pin 7 is electrically connected to each pair of support pieces 113 among the plurality of support pieces 113. Each electrode 33 of the electron emitter 3 is in physical and electrical contact with the respective spring portions 116 of the pair of support pieces 113, and a predetermined potential is applied to the metasurface 32 of the electron emitter 3 via the pair of support pieces 113.

[0036] The first claw portions 117 of each support piece 113 of the first support portion 11 are inserted into the respective first through-portions 141 of the spacer 14, and then the tips of the first claw portions 117 are crimped, thereby engaging with the spacer 14. The second claw portions 122 of each second support portion 12 are inserted into the respective second through-portions 142 of the spacer 14, and then the tips of the second claw portions 122 are crimped, thereby engaging with the spacer 14. The third claw portions 133 of the third support portion 13 are inserted into the respective third through-portions 143 of the spacer 14, and then the tips of the third claw portions 133 are crimped, thereby engaging with the spacer 14. Each of the first support portion 11 and the third support portion 13 exposes a plurality of second through-portions 142 on the first surface 14a of the spacer 14. This prevents the second claw portions 122 engaged with the second through portions 142 from physically interfering with the first support portion 11 and the third support portion 13. The second support portion 12 exposes the multiple first through portions 141 and the multiple third through portions 143 on the second surface 14b of the spacer 14. This prevents the first claw portions 117 engaged with the first through portions 141 and the third claw portions 133 engaged with the third through portions 143 from physically interfering with the second support portion 12.

[0037] Each claw portion 115 of the second support plate 112 in the first support portion 11 is inserted into a through-hole 121c formed in the frame portion 121 of the second support portion 12 via a notch 144 formed in the spacer 14, and then the tip of the claw portion 115 is crimped to engage with the frame portion 121. This unitizes the electron emitter 3, the first mesh electrode 5, the second mesh electrode 6, the first support portion 11, the second support portion 12, and the third support portion 13 via the spacer 14, and in this unitized state, electrical insulation is ensured between the metasurface 32 of the electron emitter 3, the first mesh electrode 5, and the second mesh electrode 6. In the electron tube 1, the metasurface 32 of the electron emitter 3 and the multiple support pieces 113 of the first support unit 11 are at the same potential, the first mesh electrode 5, the second support unit 12, and the second support plate 112 of the first support unit 11 are at another same potential, and the second mesh electrode 6 and the third support unit 13 are at yet another same potential. Note that the second support plate 112 of the first support unit 11 is in contact with the substrate 31 of the electron emitter 3, which is made of an electrically insulating material, so electrical insulation between the second support plate 112 and the metasurface 32 is ensured.

[0038] In the electron tube 1 configured as described above, a predetermined potential is applied to the metasurface 32 of the electron emitter 3, the second mesh electrode 6, the first mesh electrode 5, the dynodes 42 of the electron multiplier unit 4, and the anode 43 of the electron multiplier unit 4. The potential applied to the first dynode 421 is a potential that is positive relative to the potential of the metasurface 32. The potential applied to the second dynode 422 is a potential that is positive relative to the potential of the first dynode 421. The potential applied to the first mesh electrode 5 is a potential that is positive relative to the potential of the metasurface 32. In this example, the first mesh electrode 5 is electrically connected to the first dynode 421, and the same potential as that of the first dynode 421 is applied to the first mesh electrode 5. The potential applied to the second mesh electrode 6 is a potential that is negative relative to the potential of the metasurface 32. That is, a potential that suppresses the movement of electrons from the metasurface 32 side to the first mesh electrode 5 side is applied to the second mesh electrode 6. That is, a reverse bias voltage is applied between the metasurface 32 and the second mesh electrode 6. As an example, the potential applied to the metasurface 32 is approximately −1500 V, the potential applied to the second mesh electrode 6 is approximately −several volts with respect to the potential of the metasurface 32, the potential applied to the first mesh electrode 5 and the first dynode 421 is approximately +100 to 200 V with respect to the potential of the metasurface 32, and the potential applied to the second dynode 422 is approximately +several hundred volts with respect to the potential of the first dynode 421.

[0039] With a predetermined potential applied to each component of the electron tube 1, when electromagnetic waves W having a predetermined electric field oscillation direction V pass through the window 21a of the bulb 21 and the substrate 31 of the electron emitter 3 and strike the metasurface 32, electrons are emitted from each antenna structure 35 of the metasurface 32 in response to the electromagnetic waves W. The electrons emitted from each antenna structure 35 are accelerated by the electric field of the incident electromagnetic waves W, giving them high energy and causing them to fly in random directions. The electrons emitted from the metasurface 32 in response to the electromagnetic waves W pass through the second mesh electrode 6 and the first mesh electrode 5 and strike the electron emission surface 42a of the first dynode 421. Even if electrons other than those emitted from the antenna structures 35 (noise electrons) are emitted from the electron emitter 3, the noise electrons are prevented from passing through the second mesh electrode 6 because a potential (reverse bias voltage) that is negative relative to the potential of the metasurface 32 is applied to the second mesh electrode 6. This is because the energy of noise electrons (for example, 10 eV or less) is significantly smaller than the energy (for example, several keV or more) of electrons emitted from the metasurface 32 in response to the incidence of electromagnetic waves W. Examples of noise electrons include photoelectrons emitted due to the photoelectric effect and thermoelectrons emitted depending on the temperature.

[0040] When electrons passing through the second mesh electrode 6 and the first mesh electrode 5 are incident on the electron emission surface 42a of the first dynode 421, secondary electrons are emitted from the electron emission surface 42a of the first dynode 421, and these secondary electrons are incident on the electron emission surface 42a of the second dynode 422. At this time, because the first mesh electrode 5 is disposed between the metasurface 32 and the first dynode 421, the potential of the metasurface 32 is prevented from penetrating into the first dynode 421. This prevents the electric field formed between the first dynode 421 and the second dynode 422, which guides the secondary electrons, from being distorted by the potential of the metasurface 32. This prevents the path of the secondary electrons from being affected by the electron emitter 3. The electrons sequentially multiplied at each dynode 42 by the incidence and emission of secondary electrons ultimately enter the anode 43. The total number of electrons incident on the anode 43 is output as a signal as a current value via the wiring 70 and the lead pin 7 electrically connected to the anode 43 .

[0041] In the above example, the first mesh electrode 5 and the first dynode 421 are at the same potential, but this is not limited to this. A potential different from that of the first dynode 421 may be applied to the first mesh electrode 5. More specifically, a potential that is positive with respect to the potential of the metasurface 32 and negative with respect to the potential of the first dynode 421 may be applied to the first mesh electrode 5. This configuration enables favorable secondary electron multiplication while suppressing the propagation of noise electrons. [Support structure for electron emission section and electron multiplication section]

[0042] The support structure for the electron emitter 3 and electron multiplier 4 in the electron tube 1 will be described in more detail. As a premise, the electron tube 1 is configured as a so-called head-on type electron tube. That is, in the electron tube 1, the electron emitter 3 is disposed within the housing 2 so as to face the window 21a, and includes a metasurface 32 that emits electrons on the opposite side of the window 21a in response to incidence of electromagnetic waves W, and the electron multiplier 4 is disposed within the housing 2 so as to be located on the opposite side of the window 21a with respect to the electron emitter 3. In other words, the window 21a, the electron emitter 3, and the electron multiplier 4 are disposed in this order along the axis A.

[0043] As shown in FIG. 1 , the electron multiplier unit 4 is fixed to the housing 2. Here, "the electron multiplier unit 4 is fixed to the housing 2" may mean that the electron multiplier unit 4 is attached to the housing 2 via at least one member other than the electron emitter 3, or may mean that the electron multiplier unit 4 is attached to the housing 2 without any member. In the electron tube 1, the electron multiplier unit 4 is fixed to the housing 2 by being supported by a plurality of wires 70 and a plurality of lead pins 7. That is, in the electron tube 1, the electron multiplier unit 4 is attached to the housing 2 via a plurality of wires 70 and a plurality of lead pins 7. More specifically, in the electron tube 1, each lead pin 7 is fixed to the stem 22 of the housing 2, and each dynode 42 is electrically and physically connected to an end of the corresponding lead pin 7 via the corresponding wire 70 outside the pair of support walls 41, and the anode 43 is electrically and physically connected to an end of the corresponding lead pin 7 via the corresponding wire 70 outside the pair of support walls 41.

[0044] As shown in FIGS. 3 and 4 , the electron emitter 3 is fixed to the electron multiplier section 4. In other words, the electron emitter 3 and the electron multiplier section 4 are unitized and configured as an integral part. Here, "the electron emitter 3 is fixed to the electron multiplier section 4" does not include a configuration in which the electron emitter 3 is fixed to the electron multiplier section 4 only via the housing 2. As an example, "the electron emitter 3 is fixed to the electron multiplier section 4" may mean that the electron emitter 3 is attached to the electron multiplier section 4 via at least one member other than the housing 2, or that the electron emitter 3 is attached to the electron multiplier section 4 without any member. In the electron tube 1, the electron emitter 3 is attached to the electron multiplier section 4 via a first support section 11. More specifically, in the electron tube 1, the electron emitter 3 is attached to a pair of support walls 41 of the electron multiplier section 4 via a base 8, a first support section 11, a second support section 12, a third support section 13, and a spacer 14.

[0045] In the electron tube 1, the second support plate 112 contacts the inner surface 21c of the bottom wall portion (the wall portion including the window portion 21a) of the bulb 21, and the multiple spring portions 82 of the base 8 contact the inner surface 21d of the side wall portion of the bulb 21. The multiple spring portions 82 are arranged to surround the axis A when viewed from a direction parallel to the axis A, and each spring portion 82 presses against the inner surface 21d. As an example, the multiple spring portions 82 are arranged so that the pressing forces of each spring portion 82 cancel each other out in the first direction D1 and the second direction D2, respectively. The contact of the spring portions 82 of the base 8 with the inner surface 21d of the bulb 21 restricts movement of the electron emitter 3 and the electron multiplier portion 4 in a direction intersecting the axis A. This helps to fix the electron emitter 3 and the electron multiplier portion 4 to the housing 2, so that the electron emitter 3 and the electron multiplier portion 4 are more stably fixed to the housing 2. [Action and effect]

[0046] In the electron tube 1, the electron multiplier section 4 is fixed to the housing 2, and the electron emitter section 3 is fixed to the electron multiplier section 4. This makes it possible to reliably prevent the electron emitter section 3 from being misaligned with respect to the window section 21a and the electron multiplier section 4 due to vibration or impact, compared to when the electron emitter section 3 and the electron multiplier section 4 are separately fixed to the housing 2, for example. Therefore, the electron tube 1 can improve resistance to vibration or impact (vibration resistance or impact resistance).

[0047] In the electron tube 1, the electron emitter 3 is attached to the electron multiplier 4 via the first support 11. This makes it possible to easily and reliably achieve a configuration in which the electron emitter 3 is fixed to the electron multiplier 4.

[0048] In the electron tube 1, the electron multiplier section 4 includes a plurality of dynodes 42. This makes it possible to reliably multiply the electrons emitted from the electron emitter 3 in response to the incidence of the electromagnetic wave W.

[0049] In the electron tube 1, the electron emitter 3 is attached to a pair of support walls 41. This makes it possible to easily and reliably realize a configuration in which the electron emitter 3 is fixed to the electron multiplier section 4.

[0050] In the electron tube 1, the electron multiplier section 4 is supported by a plurality of lead pins 7 electrically connected to a plurality of dynodes 42, and is thereby fixed to the housing 2. This makes it possible to easily and reliably realize a configuration in which the electron multiplier section 4 is fixed to the housing 2.

[0051] In the electron tube 1, the first support portion 11 is in contact with the inner surface 21c of the window portion 21a. This means that the electron emitter 3 is fixed not only to the electron multiplier portion 4 but also to the housing 2, thereby further improving resistance to vibrations and impacts.

[0052] In the electron tube 1, the electron emitter 3 is attached to the electron multiplier 4 via the base 8, and a plurality of spring portions 82 of the base 8 are in contact with the inner surface 21d of the housing 2. This means that the electron emitter 3 is fixed not only to the electron multiplier 4 but also to the housing 2, thereby further improving resistance to vibrations and impacts. [Configuration of the electron tube of the modified example]

[0053] The electron tube 1 may not have either the first mesh electrode 5 or the second mesh electrode 6. The configuration around the electron emitter 3 in an electron tube 1A that does not have the second mesh electrode 6 will be described with reference to Figures 5 and 6. Note that, among the configuration around the electron emitter 3 in the electron tube 1A, the description of the same configuration as that of the electron tube 1 described above will be omitted.

[0054] As shown in FIGS. 5 and 6, the electron tube 1A includes an electron emitter 3, a first mesh electrode 5, a base 8, a first support 11, a second support 12, and a spacer 14. The electron emitter 3 has a configuration similar to that of the electron emitter 3 of the electron tube 1 described above. The first mesh electrode 5 has a configuration similar to that of the first mesh electrode 5 of the electron tube 1 described above. The base 8 differs from the base 8 of the electron tube 1 described above in that it does not include multiple spring portions 82 (see FIG. 4). Except for this, the base 8 has a configuration similar to that of the base 8 of the electron tube 1 described above. The second support 12 has a configuration similar to that of the second support 12 of the electron tube 1 described above. The spacer 14 has a configuration similar to that of the spacer 14 of the electron tube 1 described above. In the electron tube 1A, the spacer 14 is disposed between the electron emitter 3 and the first mesh electrode 5.

[0055] The first support section 11 has a first support plate 91 and a second support plate 92. The first support plate 91 is formed into a frame shape using, for example, a metal plate. The first support plate 91 includes a frame portion 93 having an opening 93a and a plurality of spring portions 94. The frame portion 93 is disposed on the electron emitter 3. When viewed from a direction parallel to the axis A, the opening 93a overlaps with the metasurface 32 of the electron emitter 3. Each spring portion 94 extends outward from the frame portion 93 (i.e., on the opposite side from the opening 93a). Each spring portion 94 contacts the inner surface of the bulb 21.

[0056] The second support plate 92 is formed into a frame shape using, for example, a metal plate. The second support plate 92 includes a frame portion 95 having an opening 95a, multiple spring portions 96, and multiple first claw portions 97. The frame portion 95 is joined to the frame portion 93 of the first support plate 91. The frame portion 95 is disposed on the spacer 14. When viewed from a direction parallel to the axis A, the frame portion 95 surrounds the electron emitter 3. That is, when viewed from a direction parallel to the axis A, the electron emitter 3 is located within the opening 95a. Each spring portion 96 extends inward (i.e., toward the axis A) from the frame portion 95. Each spring portion 96 presses the electron emitter 3 against the first support plate 91 so that the substrate 31 of the electron emitter 3 contacts the first support plate 91. Each first claw portion 97 extends from the frame portion 95 on the side opposite to the window portion 21a.

[0057] In the second support plate 92, each spring portion 96 is in contact with each electrode 33 of the electron emitter 3. The second support plate 92 is connected to a wiring 70 that is connected to a corresponding lead pin 7, and a predetermined potential is applied to the metasurface 32 of the electron emitter 3 via the second support plate 92.

[0058] Each first claw portion 97 of the second support plate 92 of the first support portion 11 engages with each first through portion 141 of the spacer 14. Each second claw portion 122 of the second support portion 12 engages with each second through portion 142 of the spacer 14. The first support portion 11 exposes the multiple second through portions 142 on the first surface 14a of the spacer 14. This prevents the second claw portions 122 engaged with the respective second through portions 142 from physically interfering with the first support portion 11. The second support portion 12 exposes the multiple first through portions 141 on the second surface 14b of the spacer 14. This prevents the first claw portions 97 engaged with the respective first through portions 141 from physically interfering with the second support portion 12.

[0059] In the electron tube 1A, the electron emitter 3, first mesh electrode 5, first support 11, and second support 12 are unitized via a spacer 14, ensuring electrical insulation between the metasurface 32 of the electron emitter 3 and the first mesh electrode 5. In the electron tube 1A, the metasurface 32 of the electron emitter 3 and the first support 11 are at the same potential. In addition, the first mesh electrode 5, the first dynode 421, the base 8, and the second support 12 are at another same potential.

[0060] In the electron tube 1A configured as described above, a predetermined potential is applied to the metasurface 32 of the electron emitter 3, the first mesh electrode 5, each dynode 42 of the electron multiplier unit 4, and the anode 43 of the electron multiplier unit 4. The potential applied to the first dynode 421 is a potential that is positive relative to the potential of the metasurface 32. The potential applied to the second dynode 422 is a potential that is positive relative to the potential of the first dynode 421. The potential applied to the first mesh electrode 5 is a potential that is positive relative to the potential of the metasurface 32 and negative relative to the potential of the first dynode 421. As an example, the potential applied to the metasurface 32 is approximately −1500 V, the potential applied to the first mesh electrode 5 and the first dynode 421 is approximately +100 to +200 V relative to the potential of the metasurface 32, and the potential applied to the second dynode 422 is approximately +several hundred volts relative to the potential of the first dynode 421.

[0061] With a predetermined potential applied to each part of the electron tube 1A in this manner, when electromagnetic waves W having a predetermined electric field oscillation direction V pass through the window portion 21a of the bulb 21 and the substrate 31 of the electron emitter 3 and are incident on the metasurface 32, electrons are emitted from each antenna structure 35 of the metasurface 32 in response to the incidence of the electromagnetic waves W. The electrons emitted from the metasurface 32 in response to the incidence of the electromagnetic waves W pass through the first mesh electrode 5 and are incident on the electron emission surface 42a of the first dynode 421.

[0062] When electrons that have passed through the first mesh electrode 5 are incident on the electron emission surface 42a of the first dynode 421, secondary electrons are emitted from the electron emission surface 42a of the first dynode 421, and these secondary electrons are incident on the electron emission surface 42a of the second dynode 422. At this time, because a potential that is positive with respect to the potential of the metasurface 32 and negative with respect to the potential of the first dynode 421 is applied to the first mesh electrode 5, the movement of secondary electrons from the first dynode 421 to the second dynode 422 is prevented from being affected by the electric field on the electron emitter 3 side. Then, the electrons that have been sequentially multiplied in each dynode 42 by the incidence and emission of secondary electrons finally enter the anode 43.

[0063] The support structure of the electron emitter 3 and electron multiplier 4 in the electron tube 1A will be described in more detail. As a premise, the electron tube 1A is configured as a so-called head-on type electron tube, similar to the above-mentioned electron tube 1.

[0064] The electron multiplier unit 4 is fixed to the housing 2. In the electron tube 1A, the electron multiplier unit 4 is fixed to the housing 2 by being supported by a plurality of lead pins 7. That is, in the electron tube 1A, the electron multiplier unit 4 is attached to the housing 2 via a plurality of lead pins 7. More specifically, in the electron tube 1A, each lead pin 7 is fixed to the stem 22 of the housing 2, and each dynode 42 is electrically and physically connected to an end of the corresponding lead pin 7 outside the pair of support walls 41, and the anode 43 is electrically and physically connected to an end of the corresponding lead pin 7 outside the pair of support walls 41.

[0065] The electron emitter 3 is fixed to the electron multiplier section 4. In the electron tube 1A, the electron emitter 3 is attached to the electron multiplier section 4 via a first support section 11. More specifically, in the electron tube 1A, the electron emitter 3 is attached to a pair of support walls 41 of the electron multiplier section 4 via the first support section 11, a second support section 12, and a spacer 14.

[0066] In the electron tube 1A, a first support plate 91 contacts the inner surface 21c of the bulb 21, and multiple spring portions 94 of the first support plate 91 contact the inner surface 21d of the bulb 21. In the electron tube 1A, each spring portion 94 includes a pair of arms 94a extending along the outer edge of the frame portion 93 and a pair of contact portions 94b provided at both ends of the pair of arms 94a. The multiple contact portions 94b are arranged to surround the axis A when viewed from a direction parallel to the axis A, and each spring portion 94 presses against the inner surface 21d at each contact portion 94b. As an example, the multiple contact portions 94b are arranged so that the pressing forces of the spring portions 94 cancel each other out in the first direction D1 and the second direction D2.

[0067] As described above, in the electron tube 1A, the electron multiplier section 4 is fixed to the housing 2, and the electron emitter section 3 is fixed to the electron multiplier section 4. This makes it possible to reliably prevent the electron emitter section 3 from being misaligned with respect to the window section 21a and the electron multiplier section 4 due to vibration or impact, compared to, for example, a case in which the electron emitter section 3 and the electron multiplier section 4 are separately fixed to the housing 2. Therefore, the electron tube 1A can improve its resistance to vibration or impact.

[0068] In the electron tube 1A, the electron emitter 3 is attached to the electron multiplier 4 via the first support 11, and the multiple contact portions 94b of the first support 11 are in contact with the inner surface 21d of the housing 2. This means that the electron emitter 3 is fixed not only to the electron multiplier 4 but also to the housing 2, thereby further improving resistance to vibrations and impacts. [Variations]

[0069] The present invention is not limited to the above-described examples. For example, in the above-described electron tubes 1 and 1A, the electron emitter 3 is attached to the electron multiplier 4 via the first support 11, but the electron emitter 3 may be attached to the electron multiplier 4 via at least one member other than the first support 11. Alternatively, the electron emitter 3 may be attached to the electron multiplier 4 without any member.

[0070] In the above-described electron tubes 1 and 1A, the electron multiplier section 4 is attached to the housing 2 via a plurality of lead pins 7, but the electron multiplier section 4 may be attached to the housing 2 via at least one member other than the plurality of lead pins 7. Alternatively, the electron multiplier section 4 may be attached to the housing 2 without any member.

[0071] In the above-described electron tubes 1 and 1A, the electron emitter 3 is supported by the first support 11 made up of a plurality of members, but the electron emitter 3 may be supported by a support made up of a single member. In this case, the electron emitter 3 may be attached to the electron multiplier 4 via the support made up of a single member.

[0072] In the above-described electron tubes 1 and 1A, the plurality of dynodes 42 are supported by a pair of support walls 41, but the plurality of dynodes 42 may be supported by a support member made of a single member. In this case, the electron emitter 3 may be attached to the support member made of a single member.

[0073] In the above-described electron tubes 1 and 1A, the electron multiplier section 4 does not have to include multiple dynodes 42. As an example, the electron multiplier section 4 may include a microchannel plate. In this case, too, it is possible to reliably multiply electrons emitted from the electron emitter 3 in response to the incidence of the electromagnetic wave W having the predetermined electric field oscillation direction V. [Explanation of symbols]

[0074] 1, 1A...electron tube, 2...housing, 3...electron emission section, 4...electron multiplier section, 7...lead pin, 11...first support section (support section), 21a...window section, 21d...inner surface, 32...metasurface, 41...support wall (support), 42...dynode, 94b...contact section, W...electromagnetic wave.

Claims

1. a housing having a window that transmits electromagnetic waves; an electron emitter disposed in the housing to face the window and including a metasurface that emits electrons to the opposite side of the window in response to the electromagnetic wave; an electron multiplier section that is disposed in the housing so as to be located on the opposite side of the window section with respect to the electron emitting section, and that multiplies the electrons emitted from the electron emitting section, the electron multiplier unit is fixed to the housing, The electron tube, wherein the electron emitting section is fixed relative to the electron multiplier section.

2. a support portion supporting the electron emission portion, 2. The electron tube according to claim 1, wherein the electron emitting section is attached to the electron multiplier section via the support section.

3. 3. The electron tube according to claim 2, wherein the support portion has a plurality of contact portions in contact with the inner surface of the housing.

4. 4. The electron tube according to claim 1, wherein the electron multiplier section includes a plurality of dynodes.

5. the electron multiplier section further includes a support supporting the plurality of dynodes, 5. The electron tube according to claim 4, wherein the electron-emitting portion is attached to the support.

6. 5. The electron tube according to claim 4, wherein the electron multiplier section is fixed to the housing by being supported by a plurality of lead pins electrically connected to the plurality of dynodes.

Images