Gyrotron

Abstract

This gyrotron (10) comprises: a cavity resonator (16) that interacts with an electron beam (28) to generate an electromagnetic wave (30); a collector (26) on which the electron beam (28) that has passed through the cavity resonator (16) is incident; a main body container (40) that has an output window (24) positioned between the cavity resonator (16) and the collector (26); an output mirror (22) that is disposed inside the body container (40), and that reflects electromagnetic wave (30) toward the output window (24); a transmission mirror (20) that is disposed inside the body container (40), and that reflects the electromagnetic wave toward the output mirror (22); and a shield (42) that is disposed inside the body container (40), extends cylindrically in the traveling direction of the electron beam (28) on the outer periphery of a range including the transmission mirror (20) and a region through which the electron beam (28) passes, and has the same potential as the transmission mirror (20).

Description

Gyrotron

[0001] The present disclosure relates to gyrotrons.

[0002] The use of gyrotrons, which emit electromagnetic waves such as millimeter waves and microwaves, is being considered as a means of heating the plasma inside a nuclear fusion reactor. A gyrotron uses a magnetic field to cause an electron beam emitted from an electron gun to spiral, and the energy of the electron's spiral motion is converted into electromagnetic waves by a cavity resonator and extracted. The electromagnetic waves generated in the cavity resonator are extracted to the outside via a mode converter and mirrors. The electron beam that has passed through the cavity resonator is captured by a collector. To reduce the thermal load on the collector and recover the power of the electron beam to improve efficiency, a reduction voltage may be applied between the main body housing the cavity resonator and the collector.

[0003] Japanese Patent Publication No. 2017-76575

[0004] When there is a potential difference between the gyrotron's body and collector, an electric field is generated between the components housed in the body and the collector. If this electric field has a component perpendicular to the magnetic field, the pivot point of the spirally moving electrons drifts, resulting in what is known as E×B drift. When the electron beam drift causes the electron beam to enter components other than the collector, it results in losses and reduces the gyrotron's output efficiency.

[0005] The present disclosure has been made in light of these circumstances, and aims to provide a technique for suppressing a decrease in the output efficiency of a gyrotron.

[0006] A gyrotron in one aspect of the present disclosure includes: a cavity resonator that interacts with an electron beam to generate electromagnetic waves; a collector into which the electron beam that has passed through the cavity resonator is incident; a main body container having an output window located between the cavity resonator and the collector; an output mirror disposed inside the main body container and reflecting electromagnetic waves toward the output window; a transmission mirror disposed inside the main body container and transmitting electromagnetic waves toward the output mirror; and a shield disposed inside the main body container, extending cylindrically in the direction of electron beam propagation on the outer periphery of a region including the area through which the electron beam passes and the transmission mirror, and having the same potential as the transmission mirror.

[0007] This is a schematic cross-sectional view showing the configuration of a gyrotron according to an embodiment. This is a schematic cross-sectional view showing the configuration of a gyrotron according to an embodiment. This is a schematic diagram showing the E×B drift of electrons occurring in a gyrotron according to a comparative example. This is a schematic cross-sectional view showing the configuration of a gyrotron according to another embodiment.

[0008] The embodiments for carrying out the present invention will be described in detail below. The configurations described below are illustrative and do not limit the scope of the present invention in any way. Furthermore, the same elements are denoted by the same reference numerals in the drawings, and redundant explanations are omitted as appropriate. Also, the sizes and thicknesses of the components in the drawings referenced in the following description are for illustrative purposes only and do not necessarily represent actual dimensions or proportions.

[0009] 1 is a cross-sectional view showing a schematic configuration of a gyrotron 10 according to an embodiment. The gyrotron 10 includes an electron gun 12, a beam tunnel 14, a cavity resonator 16, a mode converter 18, a transmission mirror 20, an output mirror 22, an output window 24, and a collector 26.

[0010] In this specification, the side closer to the electron gun 12 and the side closer to the collector 26 may be referred to as the upstream side and the downstream side, respectively, with reference to the direction of propagation of the electron beam 28 from the electron gun 12 toward the collector 26. The direction toward the collector 26 from the electron gun 12 may be referred to as the axial direction. The direction of propagation of the electron beam 28 is approximately along the axial direction.

[0011] The electron gun 12 generates an electron beam 28. The electron gun 12 is, for example, a magnetron injection electron gun (MIG) and generates, for example, a cylindrical electron beam or a hollow swirling electron beam. The electron gun 12 is connected to a main power supply 32, to which a negative voltage is applied. The applied voltage of the main power supply 32 is not particularly limited, but is, for example, -10kV to -100kV.

[0012] The beam tunnel 14 is located downstream of the electron gun 12. The beam tunnel 14 guides the electron beam 28 emitted from the electron gun 12 to the cavity resonator 16. The beam tunnel 14 has a tapered shape with an opening diameter that gradually decreases toward the cavity resonator 16. The beam tunnel 14 is connected to a body power supply 34, and a body potential, which is a positive voltage, is applied to the beam tunnel 14 by the body power supply 34. The voltage applied to the body power supply 34 is not particularly limited, but is, for example, +10 kV to +50 kV. The electron beam 28 emitted from the electron gun 12 is accelerated by the potential difference between the electron gun 12 and the beam tunnel 14.

[0013] The cavity resonator 16 is located downstream of the beam tunnel 14. The cavity resonator 16 interacts with an electron beam 28 passing through the cavity resonator 16 to generate an electromagnetic wave 30. An axial magnetic field indicated by arrow Z is applied to the cavity resonator 16 by a magnet device 36 such as a superconducting magnet. The electron beam 28 passing through the cavity resonator 16 moves in a spiral motion, wrapping around the axial magnetic field. The spiraling kinetic energy of the electron beam 28 is converted into an electromagnetic wave 30 such as a millimeter wave or microwave in the cavity resonator 16 by the cyclotron resonance maser effect. The cavity resonator 16 has a body potential.

[0014] The mode converter 18 is located downstream of the cavity resonator 16. The mode converter 18 separates the electron beam 28 passing through the cavity resonator 16 from the electromagnetic wave 30 generated in the cavity resonator 16. The mode converter 18 is, for example, a Vlasov-type radiator, and has an output end that is spirally or obliquely cut so as to have a shape corresponding to the propagation mode of the electromagnetic wave 30. The electromagnetic wave 30 output from the mode converter 18 is, for example, output obliquely to the axial direction and directed toward the transmission mirror 20. The electron beam 28 passing through the mode converter 18 travels in the axial direction. The mode converter 18 has a body potential.

[0015] The transmission mirror 20 is located downstream of the mode converter 18. The transmission mirror 20 transmits the electromagnetic wave 30 from the cavity 16 toward the output mirror 22. The transmission mirror 20 shapes the electromagnetic wave 30 output from the mode converter 18 into a quasi-optical mode and transmits it. The transmission mirror 20 has a body potential.

[0016] The transmission mirror 20 may include multiple mirrors, for example, a first transmission mirror 20a facing the mode converter 18 and a second transmission mirror 20b facing the output mirror 22. The first transmission mirror 20a is, for example, a parabolic mirror. The second transmission mirror 20b is, for example, a plane mirror. The transmission mirror 20 may include three or more mirrors, and may include an additional mirror positioned between the first transmission mirror 20a and the second transmission mirror 20b.

[0017] The output mirror 22 is located downstream of the transmission mirror 20. The output mirror 22 reflects the electromagnetic waves 30 from the transmission mirror 20 toward the output window 24. The output mirror 22 is, for example, a parabolic mirror. The output mirror 22 may be equipped with a drive mechanism (not shown) for varying the orientation of the output mirror 22 in order to adjust the misalignment of the optical axis of the electromagnetic waves 30 toward the output window 24. The output mirror 22 is positioned, for example, so that the electromagnetic waves 30 emitted from the output mirror 22 travel in a direction perpendicular to the axial direction. The output mirror 22 has a ground potential.

[0018] The output window 24 allows electromagnetic waves 30 from the output mirror 22 to pass through to the outside. The output window 24 is made of a material that transmits electromagnetic waves 30, such as alumina, sapphire, or diamond. Figure 1 shows a case where only one output window 24 is provided in the output direction of the electromagnetic waves 30, but the output window 24 may be made up of a combination of two or more window members of different thicknesses.

[0019] The collector 26 is located downstream of the output mirror 22 and the output window 24. The collector 26 captures the electron beam 28 that has passed through the cavity resonator 16. The collector 26 has a cylindrical shape that extends axially. The collector 26 has, for example, ground potential and a negative potential relative to the cavity resonator 16. Therefore, the electron beam 28 traveling from the cavity resonator 16 to the collector 26 is slowed down by the potential difference between the cavity resonator 16 and the collector 26. Outside the collector 26, a cooling tank 38 is provided to cool the collector 26, which is heated by the incident electron beam 28.

[0020] The gyrotron 10 further includes a main body vessel 40. The main body vessel 40 functions as part of a vacuum vessel for maintaining a vacuum in the region through which the electron beam 28 passes. The main body vessel 40 is located between the electron gun 12 and the collector 26, and has an output window 24. The main body vessel 40 can include an upstream vessel 40a and a downstream vessel 40b.

[0021] The upstream container 40a is a portion that extends cylindrically in the axial direction outside the cavity resonator 16. The beam tunnel 14, the cavity resonator 16, and the mode converter 18 are disposed inside the upstream container 40a. The upstream container 40a may house at least a portion of the transmission mirror 20. The upstream container 40a may house at least a portion of the first transmission mirror 20a, for example.

[0022] The downstream container 40b has an inner diameter larger than that of the upstream container 40a. The downstream container 40b has an output window 24. The transmission mirror 20 and the output mirror 22 are disposed inside the downstream container 40b. A collector 26 is attached downstream of the downstream container 40b. The downstream container 40b may house only a portion of the transmission mirror 20. The downstream container 40b may house the second transmission mirror 20b. The downstream container 40b may house a portion of the first transmission mirror 20a.

[0023] The main container 40 has a ground potential. Because the main container 40 has a ground potential, it is not necessary to consider the potential difference between the main container 40 and the support structure for supporting the main container 40 from the outside. The collector 26 can have the same potential as the main container 40 and can also have a ground potential.

[0024] The gyrotron 10 further includes a shield 42. The shield 42 is disposed inside the main body container 40 and extends cylindrically in the axial direction. The shield 42 is connected to the body power supply 34 and has a positive body potential with respect to the main body container 40. Therefore, the shield 42 has a different potential from that of the main body container 40.

[0025] The shield 42 is disposed around the outer periphery of the component having a body potential. In other words, the shield 42 is disposed between the main body container 40 and the component having a body potential different from that of the main body container 40. The shield 42 is made of a conductive material, for example, a metal material such as copper. The shield 42 has the function of blocking the electric field caused by the potential difference with the main body container 40 so that the electric field does not act on the electron beam 28. The component having a body potential is at least one of the beam tunnel 14, the cavity resonator 16, the mode converter 18, and the transmission mirror 20.

[0026] The shield 42 may have an upstream shield portion 42a, a downstream shield portion 42b, a connecting portion 42c, and a flange 42d.

[0027] The upstream shield part 42a is a part that is disposed inside the upstream container 40a and has a first inner diameter d1. The beam tunnel 14, the cavity resonator 16, the mode converter 18, and the first transmission mirror 20a are disposed inside the upstream shield part 42a. The second transmission mirror 20b is disposed outside the upstream shield part 42a.

[0028] The downstream shield part 42b is a part that is disposed inside the downstream container 40b and has a second inner diameter d2 that is larger than the first inner diameter d1. The second transmission mirror 20b is disposed inside the downstream shield part 42b.

[0029] The connecting part 42c is a part that connects the upstream shield part 42a and the downstream shield part 42b. The connecting part 42c is, for example, a ring-shaped member that extends in a radial direction perpendicular to the axial direction from the downstream end of the upstream shield part 42a to the upstream end of the downstream shield part 42b.

[0030] The flange 42d is a portion that extends radially outward from the upstream shield portion 42a and is located between the electron gun 12 and the beam tunnel 14. The flange 42d is located downstream of the electron gun 12 and upstream of the beam tunnel 14.

[0031] The downstream end 42e of the shield 42 is located downstream of a component to which a body potential is applied. For example, the downstream end 42e of the shield 42 is located downstream of the transmission mirror 20 (e.g., the second transmission mirror 20b). The downstream end 42e of the shield 42 is located upstream of a component having a ground potential. For example, the downstream end 42e of the shield 42 is located upstream of the output mirror 22.

[0032] A notch (not shown) may be provided in a portion of the downstream end 42e of the shield 42. The notch provided in the downstream end 42e of the shield 42 can be provided, for example, at a position where the shield 42 intersects with the electromagnetic wave 30 traveling from the transmission mirror 20 (e.g., the second transmission mirror 20b) toward the output mirror 22.

[0033] The shield 42 also functions as a support structure that supports components having a body potential inside the main body container 40. At least one of the beam tunnel 14, the cavity 16, the mode converter 18, and the transmission mirror 20, which have a body potential, can be fixed to and supported by the shield 42.

[0034] The gyrotron 10 further includes at least one insulating member disposed between the main body container 40 and the shield 42. The shield 42 can be fixed to the main body container 40 via at least one insulating member. The gyrotron 10 can include, for example, at least one of a first insulating member 44a, a second insulating member 44b, and a third insulating member 44c.

[0035] The first insulating member 44a is disposed between the upstream end 40c of the main container 40 and the flange 42d of the shield 42. The first insulating member 44a is sandwiched axially between the main container 40 and the shield 42. The first insulating member 44a functions as a so-called DC breaker. The second insulating member 44b is disposed between the inner circumferential surface of the upstream container 40a and the outer circumferential surface of the upstream shield part 42a. The second insulating member 44b is sandwiched radially between the main container 40 and the shield 42. The third insulating member 44c is disposed between the inner surface of the downstream container 40b and the connecting part 42c. The third insulating member 44c is sandwiched axially between the main container 40 and the shield 42.

[0036] The electron gun 12 can be fixed to the shield 42 via an insulating member 46. The insulating member 46 that supports the electron gun 12 can be attached to an upstream end 42f of the shield 42. The upstream end 42f of the shield 42 is located upstream of the upstream end 40c of the main body container 40 and is exposed to the outside of the main body container 40.

[0037] The gyrotron 10 can further include an electromagnetic wave absorber 48 disposed between the main body container 40 and the shield 42. The electromagnetic wave absorber 48 is disposed between the downstream container 40b and the downstream shield portion 42b. The electromagnetic wave absorber 48 is configured in a cylindrical shape on the outer periphery of the downstream shield portion 42b. The electromagnetic wave absorber 48 can be attached to the inner surface of the main body container 40. The electromagnetic wave absorber 48 may also be attached to the outer periphery of the shield 42.

[0038] FIG. 2 is a cross-sectional view of the gyrotron 10 according to the embodiment, viewed in the axial direction, taken along the line A-A in FIG. 1 . The region 50 indicated by the dashed line in the center of FIG. 2 is the region through which the electron beam 28 passes toward the collector 26. The electron beam 28 mainly passes near the boundary of the region 50, i.e., along the circumference indicated by the dashed line. The shield 42 is disposed to surround the outer periphery of the region 50 through which the electron beam 28 passes and the transmission mirror 20. Because the shield 42 has the same potential as the transmission mirror 20, the potential inside the shield 42 can be kept constant. As a result, an electric field having a component perpendicular to the axial direction is prevented from occurring inside the shield 42. As a result, electrons traveling inside the shield 42 undergo a circular motion, as indicated by the reference numeral 52, wrapping around the magnetic field B applied axially by the magnet device 36, and there is almost no drift perpendicular to the axial direction. As a result, most of the electron beam 28 travels inside the region 50 through which the electron beam 28 is designed to pass.

[0039] Figure 3 schematically shows the E x B drift of electrons occurring in a gyrotron 10A according to a comparative example. The comparative example differs from the above embodiment in that a shield 42 is not placed inside the main body container 40. In the comparative example, because there is no shield 42, there is an electric field E that flows from the transmission mirror 20, which has a positive body potential, to the main body container 40, which has a ground potential. Since the electric field E is perpendicular to the axial magnetic field B, an E x B drift occurs in electrons traveling inside the shield 42. As a result, electrons traveling inside the shield 42 drift in the direction along the reflective surface 56 of the transmission mirror 20, as indicated by reference numeral 54. If the amount of drift is large, electrons deviate outside the region 50 through which the electron beam 28 is designed to pass.

[0040] Inside the gyrotron 10A, there are not only electrons traveling downstream from the electron gun 12 towards the collector 26, but also electrons reflected by the collector 26 and traveling upstream. When electrons traveling upstream drift and deviate outside the region 50, they enter components with a body potential (e.g., the beam tunnel 14, the cavity resonator 16, the mode converter 18, or the transmission mirror 20), leading to an increase in body current. An increase in body current means an increase in electrons that are not captured by the collector 26 and are lost, reducing the efficiency of the gyrotron 10A.

[0041] Furthermore, while the body power supply 34 can output high voltage, it is often a power supply with a low rated current. If drifting electrons enter unintended locations and increase the body current, it will exceed the rating of the body power supply 34, making operation impossible, and thus the output of the gyrotron 10A must be reduced. Moreover, adopting a power supply with a high rated current would lead to a significant increase in the size and cost of the device, as well as a decrease in efficiency.

[0042] According to this embodiment, since the shield 42 is placed between the main body container 40 and the transmission mirror 20, drift of the electron beam 28 passing near the transmission mirror 20 can be prevented or suppressed. As a result, the proportion of the electron beam 28 that is lost without entering the collector 26 can be suppressed, and the output efficiency of the gyrotron 10 can be improved.

[0043] According to this embodiment, the entire main vessel 40 is at ground potential, so there is no need to consider insulation between the main vessel 40 and the support structure for supporting the main vessel 40. For example, the main vessel 40 can be directly fixed to the upper surface of the magnet device 36 by a flange 40d provided on the main vessel 40.

[0044] According to this embodiment, since the main body container 40 and the collector 26 have the same potential, there is no need to provide an insulating member called a DC break between the main body container 40 and the collector 26. Therefore, the axial size of the downstream container 40b that houses the transmission mirror 20 and the output mirror 22 can be reduced, and the overall axial size of the gyrotron 10 device can be suppressed. For example, it becomes possible to increase the axial length of the collector 26 in order to increase output power while maintaining the overall axial size of the gyrotron 10 device.

[0045] Fig. 4 is a cross-sectional view showing the schematic configuration of a gyrotron 60 according to another embodiment. The following description of the gyrotron 60 according to this embodiment will focus on the differences from the embodiment shown in Fig. 1, and will omit a description of the commonalities as appropriate.

[0046] The gyrotron 60 comprises an electron gun 12, a beam tunnel 14, a cavity resonator 16, a mode converter 18, a transmission mirror 20, an output mirror 22, an output window 24, and a collector 26. The gyrotron 60 may further include a main power supply 32, a body power supply 34, a magnet device 36, and a cooling tank 38. These are the same as those in the embodiment shown in Figure 1 above.

[0047] The transmission mirror 20 may include a third transmission mirror 20c in addition to the first transmission mirror 20a and the second transmission mirror 20b. The third transmission mirror 20c is located between the first transmission mirror 20a and the second transmission mirror 20b and reflects the electromagnetic waves reflected by the first transmission mirror 20a toward the second transmission mirror 20b. The third transmission mirror 20c is, for example, a plane mirror.

[0048] The gyrotron 60 further comprises a main body container 62, a body container 64, and an insulating member 66. The main body container 62, the body container 64, and the insulating member 66 function as vacuum vessels for maintaining a vacuum in the region through which the electron beam 28 passes.

[0049] The main body container 62 is located between the transmission mirror 20 and the collector 26 and has an output window 24. The main body container 62 houses the output mirror 22. The main body container 62 has a ground potential. The body container 64 is located between the electron gun 12 and the transmission mirror 20 and houses the beam tunnel 14, the cavity resonator 16, and the mode converter 18. The body container 64 has a body potential due to the body power supply 34. The insulating member 66 is located between the main body container 62 and the body container 64 and extends cylindrically to connect them. The insulating member 66 is a DC breaker that electrically insulates the main body container 62 and the body container 64. The insulating member 66 is arranged, for example, on the outer periphery of the transmission mirror 20.

[0050] The gyrotron 60 further includes a shield 68. The shield 68 is disposed at least inside the main body container 62 and extends cylindrically in the axial direction. The shield 68 is attached to the body container 64 and has the same body potential as the body container 64. The shield 68 can be disposed between the transmitting mirror 20 and the insulating member 66.

[0051] The shield 68 has an upstream end 68a and a downstream end 68b. The upstream end 68a of the shield 68 is attached to a component to which a body potential is applied, for example, attached to the body container 64. The downstream end 68e of the shield 68 is located downstream of the component to which the body potential is applied. For example, the downstream end 68e of the shield 68 is located downstream of the transmission mirror 20 (e.g., the second transmission mirror 20b). The downstream end 68e of the shield 68 is located upstream of the component having a ground potential. For example, the downstream end 68e of the shield 68 is located upstream of the output mirror 22.

[0052] A notch (not shown) may be provided in a portion of the downstream end 68e of the shield 68. The notch provided in the downstream end 68e of the shield 68 can be provided, for example, at a position where the shield 68 intersects with the electromagnetic wave 30 traveling from the transmission mirror 20 (e.g., the second transmission mirror 20b) toward the output mirror 22.

[0053] The shield 68 can achieve the same effect as the shield 42 according to the embodiment shown in Fig. 1 described above. Like the shield 42 shown in Fig. 2, the shield 68 is arranged to surround the outer periphery of an area including the region 50 through which the electron beam 28 passes and the transmission mirror 20. By arranging such a shield 68, it is possible to prevent or suppress drift of the electron beam 28 passing near the transmission mirror 20. As a result, it is possible to suppress the proportion of the electron beam 28 that is lost without entering the collector 26, and it is possible to improve the output efficiency of the gyrotron 60.

[0054] The present disclosure has been described above based on the embodiments. Various modifications are possible to the combinations of the components and processes in the exemplary embodiments, and it will be obvious to those skilled in the art that such modifications are included within the scope of the present disclosure.

[0055] According to certain aspects of the present disclosure, the output efficiency of a gyrotron can be improved.

[0056] 10... gyrotron, 12... electron gun, 16... cavity resonator, 20... transmission mirror, 20a... first transmission mirror, 20b... second transmission mirror, 22... output mirror, 24... output window, 26... collector, 28... electron beam, 30... electromagnetic wave, 40... main body container, 42... shield, 42a... upstream shield portion, 42b... downstream shield portion, 42c... connection portion, 44a... first insulating member, 44b... second insulating member, 44c... third insulating member, 46... insulating member, 48... electromagnetic wave absorber.

Claims

1. A gyrotron comprising: a cavity resonator that interacts with an electron beam to generate electromagnetic waves; a collector that captures the electron beam that has passed through the cavity resonator; a main body container having a window located between the cavity resonator and the collector; a first mirror that is located inside the main body container and reflects the electromagnetic waves toward the window; a second mirror that is located inside the main body container and reflects the electromagnetic waves toward the first mirror; and a shield that is located inside the main body container and extends cylindrically in the direction of propagation of the electron beam around the outer periphery of a range that includes a region through which the electron beam passes and the second mirror, and has the same potential as the second mirror.

2. A gyrotron according to claim 1, wherein the end of the shield is located downstream of the second mirror in the direction of travel of the electron beam.

3. A gyrotron according to claim 2, wherein the end of the shield is located upstream of the first mirror in the direction of travel of the electron beam.

4. A gyrotron according to any one of claims 1 to 3, wherein the shield has a different potential from the main body vessel.

5. The gyrotron according to claim 4, further comprising an insulating member disposed between the main body container and the shield.

6. The gyrotron according to claim 5, further comprising an electromagnetic wave absorber disposed between the main body container and the shield.

7. A gyrotron as claimed in any one of claims 1 to 3, wherein the shield comprises an upstream shield section, a downstream shield section having an inner diameter larger than that of the upstream shield section, and a connecting section connecting the upstream shield section and the downstream shield section.

8. The gyrotron according to claim 7, wherein the second mirror is arranged outside the upstream shield section and inside the downstream shield section.

9. The gyrotron according to claim 8, further comprising a third mirror disposed inside the upstream shield portion and reflecting electromagnetic waves toward the second mirror.

10. The gyrotron according to claim 7, further comprising an insulating member disposed between the main body container and the connecting portion of the shield.

11. A gyrotron as claimed in any one of claims 1 to 10, wherein the main body container has a portion that extends cylindrically in the direction of propagation of the electron beam around the outer periphery of the cavity resonator, and the shield has a portion that extends cylindrically in the direction of propagation of the electron beam between the inner surface of the main body container and the cavity resonator.

12. The gyrotron according to claim 11, further comprising an insulating member disposed between the main body container and the shield, and positioned upstream of the cavity resonator in the direction of travel of the electron beam.

13. A gyrotron as claimed in any one of claims 1 to 12, further comprising: a body container that houses the cavity resonator; and an insulating member that connects the body container and the body container, wherein the shield is attached to the body container and is positioned between the second mirror and the insulating member.

14. A gyrotron according to any one of claims 1 to 13, further comprising an electron gun that emits the electron beam toward the cavity resonator, the electron gun being fixed to the shield via an insulating member.

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