High-frequency absorption device and high-frequency control device

Abstract

A high-frequency absorption device 3 for absorbing high frequency HF comprises: a container 31 extending from one end part to the other end part along an incident axis O of a high frequency HF; a fluid circulation part 32 through which a fluid flows along an inner peripheral surface 311 around the incident axis O in the container 31; an incident part 33 provided at one end part of the container and causing the high frequency HF to enter the container 31; an end member 34 provided at the other end part of the container and having a reflection part for reflecting the high frequency HF; and an intermediate member 35 provided in the container 31 between one end part and the other end part thereof and having a partial passage hole 351 through which the incident axis O passes and a partial reflection part 352 that is provided around the partial passage hole 351 for reflecting part of the high frequency HF.

Description

High frequency absorption device, high frequency control device

[0001] The present disclosure relates to radio frequency absorbing devices and the like.

[0002] Patent Document 1 discloses a gyrotron that is capable of oscillating high-frequency waves such as microwaves and millimeter waves with relatively short wavelengths based on the principle of cyclotron resonance maser. The high-power (e.g., about 1 MW) high-frequency waves (e.g., several tens to several hundreds of GHz) obtained by the gyrotron have recently been used for heating plasma for nuclear fusion, etc.

[0003] The gyrotron in Patent Document 1 is equipped with a dummy load that absorbs unwanted modes of RF power. The dummy load, also known as a water load, converts power into heat by absorbing RF power into water. The RF power absorbed by the water can be calculated by measuring the temperature rise and flow rate of the water in the dummy load. For this reason, the dummy load is used to monitor the RF power during plasma heating and to pre-adjust the RF power before plasma heating.

[0004] A typical dummy load for fusion plasma heating radio frequency waves includes a cylindrical vessel and a tube through which water flows along its inner circumferential surface or inner surface. The radio frequency waves to be absorbed by the dummy load enter through an incident section provided at one end (hereinafter, for convenience, also referred to as the top) of the cylindrical vessel and are reflected by a reflector provided at the other end (hereinafter, for convenience, also referred to as the bottom) of the cylindrical vessel. The conical reflector, whose apex is on the axis of incidence of the radio frequency waves, reflects the radio frequency waves laterally toward the inner circumferential surface of the vessel, where they are absorbed by the water in the tube.

[0005] [Patent Document 1] Japanese Unexamined Patent Publication No. 4-47645 General disclosure

[0006] (Problem to be Solved) As described above, it is expected that the radio frequency waves reflected by the reflector at the bottom of the vessel will be absorbed by the water flowing along the inner circumferential surface of the vessel. However, there is a possibility that the radio frequency waves, which are typically reflected multiple times by the reflector and the inner circumferential surface of the vessel, will exit the dummy load through the entrance port at the top of the vessel and return to the gyrotron before being absorbed by the water. In this way, the radio frequency waves "reflected" from the gyrotron may adversely affect the radio frequency oscillation operation of the gyrotron and may interfere with the heating of the nuclear fusion plasma by the radio frequency waves.

[0007] The present disclosure has been made in view of the above circumstances, and has an object to provide a high-frequency absorbing device or the like that can reduce leakage of high-frequency waves outside a container.

[0008] In order to solve the above-mentioned problems, a radio-frequency absorbing device according to one aspect of the present disclosure is a radio-frequency absorbing device that absorbs radio-frequency waves, and includes: a container extending from one end to the other end along an incident axis of the radio-frequency waves; a fluid flow section through which a fluid flows along an inner circumferential surface of the container around the incident axis; an end member having an incident section provided at the one end for allowing the radio-frequency waves to enter the container; and a reflecting section provided at the other end for reflecting the radio-frequency waves; and an intermediate member provided between the one end and the other end within the container, the intermediate member having a partial passage hole through which the incident axis passes and a partial reflection section around the partial passage hole for reflecting a portion of the radio-frequency waves. In the radio-frequency absorbing device of one aspect, the fluid may absorb the radio-frequency waves. The reflection section may reflect the radio-frequency waves toward the fluid flow section. The partial passage hole may allow a portion of the radio-frequency waves to pass toward the other end. The partial reflection section may reflect another portion of the radio-frequency waves toward the fluid flow section. In the radio-frequency absorbing device of one aspect, the partial reflection section may have a reflection surface facing the one end. The reflecting surface may include an inclined surface that slopes from the partial passage hole toward the one end or the other end of the container in a cross section taken along a plane including the incident axis. In one aspect of the radio-frequency absorbing device, the surface shape of the reflecting portion may be curved or nonlinear, protruding toward the one end or the other end of the container, in a region including at least a portion through which the incident axis passes, in a cross section taken along a plane including the incident axis. In one aspect of the radio-frequency absorbing device, the distance between the bottom surface of the end member and the one end may increase from the portion through which the incident axis passes toward the inner peripheral surface of the container. In one aspect of the radio-frequency absorbing device, the bottom surface of the end member may further include another fluid flow portion through which a fluid flows.

[0009] In this embodiment, an intermediate member is provided between one end or top of the container and the other end or bottom. This intermediate member allows a portion of the high-frequency waves incident through the incident portion at the top to pass toward the end member at the bottom, and reflects the other portion toward the lateral fluid flow portion. Here, even if the high-frequency waves pass through the partial passage hole in the intermediate member toward the bottom side and are repeatedly reflected by the reflecting portion in the end member or the inner peripheral surface of the container, they cannot return to the incident side, i.e., the top side, unless they re-enter the partial passage hole. Even if the high-frequency waves return to the incident side through the partial passage hole, they are unlikely to exit the high-frequency absorption device through the incident portion. Furthermore, at that time, the power of the high-frequency waves is likely to have attenuated to a degree that does not affect the operation of the upstream gyrotron or the like.

[0010] Another aspect of the present disclosure is a high-frequency control device. This device includes a high-frequency oscillation device that oscillates high-frequency waves and a high-frequency absorption device. The high-frequency absorption device includes a container extending from one end to the other end along an incident axis of the high-frequency waves, a fluid flow section through which a fluid that absorbs high-frequency waves flows along an inner circumferential surface of the container around the incident axis, an incident section provided at one end to allow the high-frequency waves to enter the container, and a reflecting section provided at the other end to reflect the high-frequency waves, and an intermediate member provided between the one end and the other end within the container, the intermediate member having a partial passage hole through which the incident axis passes and a partial reflection section around the partial passage hole that reflects a portion of the high-frequency waves. In the high-frequency absorption device of this aspect, the fluid may absorb the high-frequency waves. The reflecting section may reflect the high-frequency waves toward the fluid flow section. The partial passage hole may allow a portion of the high-frequency waves to pass toward the other end. The partial reflection section may reflect another portion of the high-frequency waves toward the fluid flow section.

[0011] Yet another aspect of the present disclosure is a radio-frequency absorbing device. The device is a radio-frequency absorbing device that absorbs radio-frequency waves, and includes a container extending from one end to the other end along an incident axis of the radio-frequency waves; a fluid flow section through which a radio-frequency-absorbing fluid flows along an inner circumferential surface of the container around the incident axis; an incident section provided at the one end for allowing the radio-frequency waves to enter the container; and an end member provided at the other end having a reflecting section for reflecting the radio-frequency waves. The reflecting section increases or decreases in distance from the one end to a point on the incident axis on the inner circumferential side toward the inner circumferential surface of the container on the outer circumferential side, and in a cross section taken along a plane including the incident axis, the inner circumferential portion including at least the point on the reflecting section has a curved or nonlinear shape. The fluid may absorb the radio-frequency waves. The reflecting section may reflect the radio-frequency waves toward the fluid flow section. In one aspect of the radio-frequency absorbing device, the reflecting section may have a distance from the one end to the most prominent point on the incident axis on the inner circumferential side monotonically increasing from the most prominent point on the incident axis on the inner circumferential side toward the inner circumferential surface of the container on the outer circumferential side. In one aspect of the high-frequency absorption device, the distance from the one end of the reflecting portion may monotonically decrease from the point on the incident axis on the inner periphery side toward the inner periphery surface of the container on the outer periphery side.

[0012] Any combination of the above components, or any conversion of these expressions into methods, devices, systems, recording media, computer programs, etc., are also encompassed within the present disclosure.

[0013] According to the present disclosure, leakage of high frequency waves to the outside of the container of a high frequency absorbing device can be reduced.

[0014] FIG. 1 is a schematic diagram of a high-frequency control device. FIG. 2 is a schematic diagram of a high-frequency oscillator as a gyrotron. FIG. 3 is a schematic diagram of a high-frequency absorbing device or a dummy load. FIG. 4 is an enlarged view of an end member. FIG. 5 shows an example of a simulation of the effect of dispersing high frequency or power by an end member having a curved inner periphery. FIG. 6 is a schematic diagram of a high-frequency absorbing device or a dummy load according to a first modified example. FIG. 7 is a schematic diagram of a high-frequency absorbing device or a dummy load according to a second modified example. FIG. 8 is a schematic diagram of a high-frequency absorbing device or a dummy load according to a third modified example. FIG. 9 is a schematic diagram of a high-frequency absorbing device or a dummy load according to a fourth modified example. FIG. 10 is a schematic diagram of a high-frequency absorbing device or a dummy load according to a fifth modified example. FIG. 11 is a schematic diagram of a high-frequency absorbing device or a dummy load according to a sixth modified example. FIG. 12 is an enlarged view of an end member according to a modified example. FIG. 13 is an enlarged view of an end member according to another modified example. FIG. 14 is an enlarged view of an end member according to another modified example.

[0015] Hereinafter, with reference to the drawings, a detailed description will be given of a mode for carrying out the present disclosure (hereinafter also referred to as an embodiment). In the description and / or drawings, identical or equivalent components, members, processes, etc. are designated by the same reference numerals, and redundant description will be omitted. The scale and shape of each part shown in the drawings are set for convenience to simplify the description and should not be interpreted as limiting unless otherwise specified. The embodiment is an example and does not limit the scope of the present disclosure in any way. Not all features and their combinations presented in the embodiment are necessarily essential to the present disclosure. For convenience, the embodiment is presented broken down into components for each function and / or functional group that realizes the embodiment. However, one component in the embodiment may actually be realized by a combination of multiple separate components, or multiple components in the embodiment may actually be realized by a single integrated component.

[0016] FIG. 1 is a schematic diagram of a radio frequency control device 1 according to this embodiment. The radio frequency control device 1 is a device for controlling radio frequency (HF) waves for heating a nuclear fusion plasma P. In this embodiment, "radio frequency" refers to electromagnetic waves of a relatively high frequency capable of heating the nuclear fusion plasma P. The frequency of such radio frequency (HF) waves for heating a nuclear fusion plasma may be selected, for example, from the range of several GHz to several THz, preferably from the range of several tens of GHz to 1 THz, and more preferably from the range of 100 GHz to several hundreds of GHz. Thus, the "radio frequency" in this embodiment is not limited to a strict frequency range. To avoid unnecessary misunderstanding, the "radio frequency" in this embodiment may be rephrased as "nuclear fusion plasma heating electromagnetic waves" or "plasma heating electromagnetic waves," etc.

[0017] Plasma-state heavy hydrogen (deuterium) and / or tritium (tritium) is typically used as the plasma P for nuclear fusion. The type of fusion reactor (not shown) in which the fusion reaction occurs using the plasma P heated by high frequency HF is arbitrary. For example, although a magnetic confinement fusion reactor, such as a tokamak or helical type, is suitable for this embodiment, this does not preclude application of this embodiment to an inertial confinement fusion reactor, such as a laser fusion reactor.

[0018] The high frequency control device 1 includes a high frequency oscillator 2 that generates high frequency HF to heat the fusion plasma P generated in the fusion reactor, a high frequency absorption device 3 that can absorb at least a portion of the high frequency HF before heating the plasma P, i.e., before being introduced into the fusion reactor, and a transmission system 4 that transmits the high frequency HF generated by the high frequency oscillator 2 to the high frequency absorption device 3 or the fusion reactor.

[0019] The high-frequency oscillator 2 is configured, for example, by a gyrotron. A gyrotron is a vacuum tube capable of oscillating high-frequency HF, such as microwaves or millimeter waves, with a relatively short wavelength based on the cyclotron resonance maser principle. Recent gyrotrons are capable of generating high-power HF of the 1 MW class or exceeding 1 MW. Details of the high-frequency oscillator 2 as a gyrotron will be described later. Note that the high-frequency oscillator 2 is not limited to a gyrotron and may be configured as any type of device as long as it can generate high-frequency HF or electromagnetic waves of any frequency or wavelength that can heat the plasma P for nuclear fusion.

[0020] Typically, the high-frequency absorbing device 3, which absorbs high-frequency waves using water, is also called a water load or a dummy load. However, the high-frequency absorbing device 3 in this embodiment may be configured to absorb all or part of the high-frequency waves generated by the high-frequency oscillator 2 using any fluid other than water, i.e., any liquid and / or gas. The power of the high-frequency waves absorbed by a fluid such as water is converted into heat and appears as a temperature rise in the fluid. By measuring or monitoring this temperature rise and the flow rate of the fluid in the high-frequency absorbing device 3, the power of the high-frequency waves absorbed by the fluid can be calculated.

[0021] Therefore, the radio frequency absorbing device 3 or the dummy load can be used to monitor the power of the radio frequency HF while heating the plasma P in the fusion reactor, or to pre-adjust the power of the radio frequency HF before heating the plasma P in the fusion reactor. In the former case, a small portion of the radio frequency HF oscillated by the radio frequency oscillator 2 is branched to the radio frequency absorbing device 3 through the transmission system 4, and most of the remaining radio frequency HF is introduced into the fusion reactor through the transmission system 4. In the latter case, substantially all of the radio frequency HF oscillated by the radio frequency oscillator 2 is introduced into the radio frequency absorbing device 3 through the transmission system 4. The radio frequency absorbing device 3 and the dummy load will be described in detail later.

[0022] The transmission system 4 includes a waveguide 41 such as a corrugated waveguide that connects between the high-frequency oscillator 2 and the fusion reactor, and between the high-frequency oscillator 2 and the high-frequency absorption device 3 in a manner that allows transmission of high-power high-frequency waves such as microwaves and millimeter waves. The waveguide 41 may be configured, for example, by a main waveguide 411 that connects between the high-frequency oscillator 2 and the fusion reactor, and a sub-waveguide 412 that branches off from the main waveguide 411 toward the high-frequency absorption device 3. In this case, a waveguide switch 42 is provided at the connection point between the main waveguide 411 and the sub-waveguide 412.

[0023] This waveguide switch 42 can arbitrarily switch or adjust the destination or transmission ratio of the high frequency HF from the high frequency oscillator 2 between the fusion reactor and the high frequency absorption device 3. For example, depending on the situation, the waveguide switch 42 may transmit substantially all of the high frequency HF from the high frequency oscillator 2 to the fusion reactor, or may transmit substantially all of the high frequency HF from the high frequency oscillator 2 to the high frequency absorption device 3, or may transmit a desired ratio (e.g., 90% or more) of the high frequency HF from the high frequency oscillator 2 to the fusion reactor and the remainder (e.g., 10% or less) to the high frequency absorption device 3.

[0024] The transmission system 4 includes a matching optics unit (MOU) 43 as an interface with the high-frequency oscillator 2 serving as a gyrotron. The MOU 43 introduces the high-frequency wave HF oscillated by the high-frequency oscillator 2 to the input end (the right end in FIG. 1 ) of the main waveguide 411 via a plurality of (for example, two) quasi-optical mirrors. The MOU 43 may be considered to be part of the high-frequency oscillator 2.

[0025] The transmission system 4 includes a vacuum window 44 and a quasi-optical antenna 45 as interfaces with the fusion reactor. The vacuum window 44 forms the interface between the output end (left end in FIG. 1 ) of the main waveguide 411 and the plasma vessel of the fusion reactor that contains the plasma P. The quasi-optical antenna 45, which is composed of a quasi-optical focusing mirror and a movable mirror, focuses the high frequency HF introduced into the plasma vessel through the vacuum window 44 at a desired heating position within the plasma P. The plasma P, thus heated in a concentrated manner by the high-power high frequency HF, reaches a temperature of, for example, 100 million degrees or more at least locally, causing a nuclear fusion reaction. The vacuum window 44 and the quasi-optical antenna 45 may be considered to be part of the fusion reactor.

[0026] Fig. 2 is a schematic diagram of a high-frequency oscillator 2 serving as a gyrotron. This high-frequency oscillator 2 includes a gyrotron main body 21, an electron gun 22, a superconducting magnet 23, and a DC power supply unit 24. The gyrotron main body 21, which is a cylindrical vacuum tube that is long in the vertical direction in Fig. 2, includes a cavity 211, a mode converter 212, a group of mirrors 213, an output window 214, a collector 215, and a DC breaker 216.

[0027] In the following, the vertical direction in Figure 2, which is the direction of the central axis of the approximately cylindrical gyrotron body 21, will be conveniently referred to as the axial direction, the direction perpendicular to the central axis (for example, the left-right direction in Figure 2) will be conveniently referred to as the radial direction, and the direction around the central axis will be conveniently referred to as the circumferential direction.

[0028] The cavity 211 provided at the input side or axially lower end of the gyrotron main body 21 is a cylindrical cavity resonator. Further axially lower than this cavity 211, i.e., below the entire gyrotron main body 21, is provided an electron gun 22, also known as a magnetron injection gun (MIG). The electron gun 22 has an annular electron emission surface with the axial direction as its normal direction, and emits an electron beam EB (schematically represented by a dotted line in FIG. 2 ) toward the output side or axially upward by thermionic emission from the electron gun.

[0029] The electron beam EB emitted from the electron gun 22 swirls in the circumferential direction due to an axial magnetic field (not shown) generated by the superconducting magnet 23, which circumferentially surrounds at least a portion of the electron gun 22, the cavity 211, and the mode converter 212. Specifically, the electron beam EB emitted from the annular electron emission surface of the electron gun 22 has a radially inward motion component in addition to an axially upward motion component (i.e., as schematically shown in FIG. 2 , the electron beam EB is emitted obliquely upward). This radially inward motion component or current component is affected by the axial magnetic field generated by the superconducting magnet 23, resulting in a circumferential swirling motion of the electron beam EB. In this way, the electron beam EB emitted from the electron gun 22 travels toward the axially upper cavity 211 while swirling in the circumferential direction. In other words, the electron beam EB emitted from the electron gun 22 becomes a hollow electron beam EB that moves spirally along the axial magnetic field generated by the superconducting magnet 23 and enters the cavity 211 .

[0030] In the cavity 211, which serves as a resonator, the rotational or gyrating motion of the electron beam EB is converted into high-power radio frequency (HF). The rotational motion of the electron beam EB is cyclotron motion, and the cavity 211 has a resonant frequency close to the cyclotron frequency. Such a cavity 211 generates radio frequency (HF) waves having a frequency substantially equal to the resonant frequency. The cyclotron frequency of the electron beam EB, which must be close to the resonant frequency of the cavity 211, can be adjusted by the magnetic field of the superconducting magnet 23. Although not shown in detail, the diameter of the cavity 211 increases continuously or stepwise from the axially lower inlet to the axially upper outlet. Therefore, the radio frequency (HF) waves generated in the cavity 211 are efficiently extracted from the outlet.

[0031] The mode converter 212 provided on the exit side or axially above the cavity 211, together with the downstream MOU 43 (FIG. 1), converts a complex transmission mode such as a TE mode or a circular polarization mode of the high frequency HF generated in the cavity 211 into a desired transmission mode suitable for transmission through the waveguide 41 (FIG. 1). For example, in the corrugated waveguide 41, a hybrid mode of the TE mode and the TM mode, such as a HE mode, is generated.11 Mode is typically preferred. 11 The mode is also called a linearly polarized (LP) mode or a fundamental propagation mode, and its intensity distribution shows a substantially Gaussian distribution centered on the central axis of the waveguide 41. Specifically, the HE 11 The mode is described by the lowest order Bessel function, and the radial position where it becomes zero coincides with the inner peripheral surface of the corrugated waveguide 41. The transmission mode of the high frequency HF when it leaves the mode converter 212 is a vacuum propagation mode exhibiting a Gaussian distribution, and passes through the subsequent mirror group 213 and MOU 43 to become a waveguide transmission mode, HE 11 is adjusted to the mode.

[0032] Although not shown in detail, the mode converter 212 has a long cylindrical or tapered waveguide in the axial direction, through which the high frequency wave HF passes. The surface shape of the wall or inner peripheral surface of this waveguide is periodically changed in the circumferential direction and / or the axial direction, so that the high frequency wave HF is shaped into a desired transmission mode and intensity distribution. In particular, by cutting the exit side or the upper axial side of this waveguide in an appropriate shape, a linear polarization mode or HE with an intensity distribution of approximately Gaussian distribution can be formed. 11 High frequency HF modes are obtained.

[0033] The high frequency HF, whose transmission mode and / or intensity distribution has been adjusted by the mode converter 212, is guided through a mirror group 213 made up of multiple mirrors to an output window 214 provided on the side (left side in FIG. 2) of the gyrotron main body 21. The output window 214 is a vacuum window that separates the gyrotron main body 21, which is a vacuum tube, from the MOU 43 (FIG. 1), which may be in a non-vacuum state. The output window 214, made of a dielectric such as CVD diamond, extracts the high frequency HF from the inside of the gyrotron main body 21, which is in a vacuum state, to the inside of the MOU 43.

[0034] The inside of MOU43 is vacuumed by a turbo molecular pump or other vacuum pump to prevent arc discharge caused by high frequency HF on metal edges, etc. -3It is preferable that the inside of the MOU 43 be kept in a vacuum state of about 100 Pa. If an arc discharge occurs, the high frequency HF may return to the inside of the gyrotron body 21 and cause damage. However, since the risk of arc discharge is low, particularly with high frequency HF of relatively low power and / or relatively short pulse length, the inside of the MOU 43 may be in a non-vacuum state (e.g., atmosphere). In either case, the degree of vacuum inside the gyrotron body 21, which is a vacuum tube, is much higher, so an output window 214 is required to isolate it from the inside of the MOU 43.

[0035] The collector 215 is an electrode that collects the electron beam EB after it has been used to generate high frequency HF in the cavity 211. As will be described later, the collector 215, to which a DC voltage of opposite polarity to that of the cavity 211 is applied, decelerates and collects the electron beam EB. The axially long, cylindrical collector 215 constitutes the axially upper end of the gyrotron body 21. As schematically shown in FIG. 2 , the electron beam EB is mainly collected on the inner circumferential surface of the collector 215. However, the electron beam EB may also be collected at the axially upper, closed end of the collector 215.

[0036] 2, a high frequency wave HF and an electron beam EB emerge generally axially upward from the cavity 211 or the mode converter 212. The electron beam EB continues to travel generally straight upward in the axial direction and is collected by a collector 215. As described above, the high frequency wave HF is redirected by the mirror group 213 to travel in a direction different from that of the electron beam EB, and is extracted from an output window 214.

[0037] The DC power supply unit 24 supplies or applies a DC voltage or DC potential to each part of the radio frequency oscillator 2 serving as a gyrotron in order to realize the desired operation of the radio frequency oscillator 2. The DC power supply unit 24 includes three DC power sources 241 to 243.

[0038] The first DC power supply 241 applies a positive voltage with an absolute value of approximately 30 kV with respect to the ground potential GND to the axially lower part of the gyrotron body 21, including the cavity 211 and the conduit extending downward. The second DC power supply 242 applies a negative voltage with an absolute value of approximately 10 kV with respect to the ground potential GND to the anode of the electron gun 22. The third DC power supply 243 applies a negative voltage with an absolute value of approximately 50 kV with respect to the ground potential GND to the cathode of the electron gun 22. The axially upper part of the gyrotron body 21, including the collector 215, is connected to the ground potential GND. A DC disconnecting part 216 provided in the axially intermediate part of the gyrotron body 21 is provided to insulate the ground potential GND applied to the axially upper part of the gyrotron body 21 from the voltage of the first DC power supply 241 applied to the axially lower part of the gyrotron body 21.

[0039] 3 is a schematic diagram of a radio frequency absorbing device 3 or a dummy load. The radio frequency absorbing device 3 may include a container 31, a fluid flow portion 32, an incident portion 33, an end member 34, and an intermediate member 35.

[0040] The container 31, made of stainless steel or the like, is a long cylinder extending in the vertical direction in Fig. 3. For example, the container 31 is substantially cylindrical with its central axis at O. Here, the central axis O of the container 31 substantially coincides with the incident axis O of the high frequency HF introduced from the high frequency oscillator 2 and the waveguide 41. In this way, the container 31 according to this embodiment extends from one end or top to the other end or bottom along the incident axis O of the high frequency HF. The inside of the container 31 is evacuated by a vacuum pump such as a turbo molecular pump. -3 Preferably, the pressure is kept in a vacuum of the order of Pa, but non-vacuum conditions (e.g., atmospheric air) are acceptable, particularly for relatively low power and / or relatively short pulse length high frequency HF where the risk of arcing is low.

[0041] In the following, the vertical direction in Figure 3, which is the central axis O of the approximately cylindrical container 31 or the direction of the incident axis O of the high frequency HF, will be conveniently referred to as the axial direction or incident direction, the direction perpendicular to the axis O (for example, the left-right direction in Figure 3) will be conveniently referred to as the radial direction, and the direction around the axis O will be conveniently referred to as the circumferential direction.

[0042] In the fluid circulation portion 32, a fluid that absorbs high frequency waves HF flows along an inner peripheral surface 311 of the container 31 around the incident axis O. In the illustrated schematic example, the fluid circulation portion 32 is configured by one or more tubes made of, for example, polytetrafluoroethylene (in this embodiment, four tubes (not shown) are provided in each of the spaces S1 to S3 described below) that are arranged in a spiral or ring shape in the circumferential and / or axial directions along the inner peripheral surface 311 of the substantially cylindrical container 31. Note that, in FIG. 3 , the tubes of the fluid circulation portion 32 are arranged along the inner peripheral surface 311 within the container 31; however, if the inner peripheral surface 311 of the container 31 is formed of a material such as ceramic that absorbs high frequency waves HF, the tubes of the fluid circulation portion 32 for cooling it may be arranged on the outer periphery of the inner peripheral surface 311.

[0043] Water or other fluid flows through each tube. As will be described later, the high frequency HF introduced into the container 31 is absorbed by the fluid in each tube. From another perspective, the high frequency HF introduced into the container 31 is cooled by the fluid flowing through the fluid flow portion 32. In this way, any fluid, not limited to water, that can function as a refrigerant for the high frequency HF may be flowed through the tubes serving as the fluid flow portion 32.

[0044] The power of the high frequency HF absorbed by a fluid such as water flowing through the fluid flow section 32 is converted into heat and appears as a temperature rise of the fluid. The power of the high frequency HF absorbed by the fluid can be calculated by measuring or monitoring this temperature rise and the flow rate of the fluid in the fluid flow section 32. Therefore, the high frequency HF absorbing device 3 or the dummy load can be used to monitor the power of the high frequency HF while heating the plasma P in the fusion reactor, or to pre-adjust the power of the high frequency HF before heating the plasma P in the fusion reactor.

[0045] The incident portion 33, which allows the high frequency HF to enter the vessel 31, is provided at one end or the top of the vessel 31. Specifically, the incident portion 33 is a circular or rectangular hole provided in the center of the top of the vessel 31. The center of the incident portion 33 is preferably located on the incident axis O of the high frequency HF. Furthermore, the center of the incident portion 33 is preferably located on the central axis (coincident with the incident axis O) of the auxiliary waveguide 412 that introduces the high frequency HF into the vessel 31. The incident portion 33 may be provided with a gate valve (not shown) to separate the inside of the vessel 31, which is in a vacuum state, from the inside of the auxiliary waveguide 412, which is in a non-vacuum state. In this embodiment, the cross-sectional shape of the auxiliary waveguide 412 and the shape of the incident portion 33 as a hole are assumed to be identical circles. As described above, such an auxiliary waveguide 412 and incident portion 33 are configured to transmit the HE in a linear polarization mode. 11 The high frequency HF of the mode is introduced into the container 31 along the incident axis O. 11 The intensity distribution of the high frequency HF in the mode exhibits a Gaussian distribution centered on the incidence axis O, i.e., the central axis O of the container 31. Furthermore, the high frequency HF introduced into the container 31 in this embodiment has a high power of 1 MW class, a relatively long pulse length on the order of several seconds (e.g., 1 s to 2 s), and a frequency of 100 GHz to several hundred GHz (e.g., 104 GHz or 137 GHz).

[0046] An end member 34, which may be referred to as a reflector, is provided at the other end or bottom of the container 31. As will be described in detail later, the end member 34 is generally conical, with its apex or most prominent point located on the incident axis O. The axially upper surface of the end member 34 (i.e., the side surface or conical surface of the generally conical end member 34) forms a reflecting portion that reflects the high frequency HF incident along the incident axis O toward the fluid flow portion 32 laterally or radially outward. The end member 34 is made of any material capable of reflecting the high frequency HF, for example, aluminum or another metal material or alloy material.

[0047] One or more intermediate members 35 may be provided between the top of the container 31 where the incident portion 33 is provided and the bottom of the container 31 where the end member 34 is provided. In the example shown in the figure, the intermediate member 35 includes a first intermediate member 35A on the top side and a second intermediate member 35B on the bottom side adjacent to the first intermediate member 35A. Note that no intermediate member 35 needs to be provided. Furthermore, when three or more intermediate members 35 are provided at different axial positions, the following description will largely apply if, of any two axially adjacent intermediate members 35, the one on the top side is interpreted as the first intermediate member 35A and the one on the bottom side is interpreted as the second intermediate member 35B.

[0048] 3, the first intermediate member 35A and the second intermediate member 35B are substantially the same except for their axial positions, and therefore will be collectively referred to as the intermediate member 35. The intermediate member 35, which is provided between the top and bottom of the container 31, has a partial passing hole 351 on the incident axis O that passes a portion of the high frequency HF incident along the incident axis O toward the bottom (downward in FIG. 3), and has a partial reflecting portion 352 around the partial passing hole 351 that reflects another portion of the high frequency HF toward the fluid circulation portion 32 on the side or radially outward.

[0049] The partial reflection portion 352 may have a protrusion that protrudes toward the top between the partial passage hole 351 on the inner circumferential side or radially inside and the inner circumferential surface 311 of the container 31 on the outer circumferential side or radially outside. In this case, as shown in Fig. 3 , in a cross section taken along a plane including the incident axis O, the partial reflection portion 352 has one protrusion on each side of the incident axis O (the left and right sides in Fig. 3 ).

[0050] At the inner circumferential portion 353 on the inner circumferential side or radially inward of each protrusion, the distance from the top of the container 31 (the vertical distance in FIG. 3 ) monotonically decreases from the partial passing hole 351 toward the most protruding point 355. For this reason, the thickness of the intermediate member 35 at the inner circumferential portion 353 (the vertical dimension in FIG. 3 ) is smallest at the center where the partial passing hole 351 is provided.

[0051] When the high frequency HF passes through the partial passing hole 351, it also flows as a current on its inner circumferential surface, generating heat according to the resistance of the material constituting the intermediate member 35. Therefore, minimizing the thickness or distance of the partial passing hole 351 as described above leads to a reduction in the amount of heat generated in the intermediate member 35. Furthermore, by forming the intermediate member 35 from a material containing copper or the like that has low resistance or high electrical conductivity, the amount of heat generated in the intermediate member 35 can be further reduced. Thus, in this embodiment, the intermediate member 35 is formed from a material such as copper that is different from the material such as aluminum that constitutes the end member 34. Note that, in order to cool the intermediate member 35, which generates a fair amount of heat, a cooling channel (not shown) through which a refrigerant such as water can flow may be provided within the intermediate member 35.

[0052] Furthermore, on the outer circumferential side or radially outer outer circumferential portion 354 of each protrusion, the distance from the most protruding point 355 to the top of the container 31 (the vertical distance in Figure 3) increases monotonically from the most protruding point 355 toward the inner circumferential surface 311 of the container 31.

[0053] In addition, the surface on the upper axial side of the partially reflecting portion 352 is a convex surface, while the back surface on the lower axial side may be a flat surface as in the illustrated example, or may be a concave surface corresponding to the convex surface.

[0054] As shown schematically in Figure 3, the partial passage hole 351 in the first intermediate member 35A allows a portion HF1T of the high frequency HF incident from the incident portion 33, which travels approximately along the axial direction, to pass through toward the second intermediate member 35B on the bottom side.

[0055] Furthermore, the inner circumferential portion 353 of the partial reflection portion 352 of the first intermediate member 35A reflects and absorbs the other portion HF1R of the high frequency HF incident from the incident portion 33, which deviates from the axial direction due to diffraction at the incident portion 33 or the intensity distribution of the high frequency HF itself, toward the fluid circulation portion 32 between the incident portion 33 and the first intermediate member 35A. Here, the inclination of the inner circumferential portion 353 with respect to the incident axis O is preferably designed so that the high frequency HF1R reflected by the inner circumferential portion 353L on one radial side (e.g., the left side in FIG. 3 ) does not directly enter the inner circumferential portion 353R on the other radial side (e.g., the right side in FIG. 3 ).

[0056] At least a portion of the high frequency wave HF1R reflected laterally by the inner circumferential portion 353 may be repeatedly reflected by the inner circumferential surface 311 or the top surface of the container 31 and the partial reflection portion 352 before being absorbed by the fluid flowing through the fluid circulation portion 32. The partial reflection portion 352 effectively reflects the high frequency wave HF1R toward the fluid circulation portion 32 by utilizing not only the inner circumferential portion 353 that is inclined radially inward but also the outer circumferential portion 354 that is inclined radially outward.

[0057] Similarly, the partial passage hole 351 in the second intermediate member 35B allows a portion HF2T of the high frequency HF1T incident from the partial passage hole 351 in the first intermediate member 35A, which travels approximately along the axial direction, to pass toward the bottom side end member 34.

[0058] Furthermore, the inner peripheral portion 353 of the partial reflection portion 352 of the second intermediate member 35B reflects and absorbs the other portion HF2R of the high frequency wave HF1T incident from the partial passing hole 351 of the first intermediate member 35A, which deviates from the axial direction due to diffraction at the partial passing hole 351 or the intensity distribution of the high frequency wave HF1T itself, toward the fluid passage portion 32 between the first intermediate member 35A and the second intermediate member 35B. Here, the inclination of the inner peripheral portion 353 with respect to the incident axis O is preferably designed so that the high frequency wave HF2R reflected by the inner peripheral portion on one radial side does not directly enter the inner peripheral portion on the other radial side.

[0059] At least a portion of the high frequency wave HF2R reflected laterally by the inner peripheral portion 353 may be repeatedly reflected by the inner peripheral surface 311 of the container 31, the partial reflection portion 352 on the surface of the second intermediate member 35B, and the flat or concave rear surface of the first intermediate member 35A, before being absorbed by the fluid flowing through the fluid circulation portion 32. The partial reflection portion 352 of the second intermediate member 35B effectively reflects the high frequency wave HF2R toward the fluid circulation portion 32 by utilizing not only the inner peripheral portion 353 that is inclined radially inward but also the outer peripheral portion 354 that is inclined radially outward.

[0060] The high frequency HF2T that passes through the partial passage hole 351 of the second intermediate member 35B is reflected and absorbed by the reflecting portion, which is the surface of the approximately conical end member 34, toward the fluid flow portion 32 between the second intermediate member 35B and the end member 34.

[0061] As described above, the interior of the substantially cylindrical container 31 is divided into multiple spaces along the axial direction by one or more intermediate members 35. In the illustrated example in which two intermediate members 35A and 35B are provided, a first space S1, a second space S2, and a third space S3 are formed from the top to the bottom of the container 31. Two spaces adjacent in the axial direction (e.g., the first space S1 and the second space S2, or the second space S2 and the third space S3) are communicated only by the partial through-hole 351 of the intermediate member 35 interposed therebetween.

[0062] Each of the spaces S1 to S3 described above is provided with a reflection mechanism that reflects and absorbs high frequency HF toward the fluid circulation portion 32 in that space S1 to S3. As described above, the main reflection mechanism in the first space S1 is the partial reflection portion 352 of the first intermediate member 35A, the main reflection mechanism in the second space S2 is the partial reflection portion 352 of the second intermediate member 35B, and the main reflection mechanism in the third space S3 is the reflection portion serving as the surface of the substantially conical end member 34.

[0063] The fluid circulation parts 32 in each of the spaces S1 to S3 absorb a share of the high frequency HF introduced into the container 31 through the sub-waveguide 412. For example, if the power to be absorbed of the high frequency HF introduced into the container 31 through the sub-waveguide 412 is set to "1", the fluid circulation parts 32 in each of the spaces S1 to S3 may be designed to absorb an equal amount of "1 / 3".

[0064] Alternatively, the power absorption amount of the fluid circulation portion 32 in each of the spaces S1 to S3 may be designed to increase monotonically along the direction of incidence. For example, the fluid circulation portion 32 in the first space S1 may absorb less than one-third of the power (e.g., 20% to 30%), the fluid circulation portion 32 in the second space S2 may absorb approximately one-third of the power (e.g., 25% to 40%), and the fluid circulation portion 32 in the third space S3 may absorb more than one-third of the power (e.g., 40% to 60%).

[0065] As described above, in this embodiment, significant power is absorbed in spaces that are not adjacent to the incident portion 33 (e.g., the second space S2 and the third space S3), and the amount of high frequency HF that returns to the incident portion 33 through reflections at various parts within the container 31 can be reduced.

[0066] For example, even if the high frequency HF2T that passes through the partial passage hole 351 in the second intermediate member 35B toward the bottom side is repeatedly reflected by the reflecting portion in the end member 34 and the inner circumferential surface 311 of the container 31, it cannot return to the incident side, i.e., the top side, unless it re-enters the partial passage hole 351. Moreover, because the first intermediate member 35A is further present axially above the second intermediate member 35B, the high frequency HF2T must also pass through the partial passage hole 351 in the first intermediate member 35A to return to the incident portion 33. In this way, the high frequency absorption device 3 or dummy load according to this embodiment can effectively reduce leakage of the high frequency HF to the outside of the container 31 through the incident portion 33 or "reflection" to the high frequency oscillator 2.

[0067] The amount of power absorption by the fluid passage portion 32 in each of the spaces S1 to S3 can be designed or adjusted using various parameters.

[0068] For example, increasing the axial lengths L1 to L3 of the spaces S1 to S3 increases the amount of power absorbed in each of the spaces S1 to S3, while decreasing the lengths L1 to L3 decreases the amount of power absorbed in each of the spaces S1 to S3. In the illustrated example, the lengths L1 to L3 are equal, but they may be designed to have different values. For example, if the lengths L1, L2, and L3 are designed to increase in this order, a large amount of power can be absorbed in the spaces farther from the incident portion 33 (particularly the third space S3), thereby reducing "reflection" to the high-frequency oscillator 2.

[0069] In the illustrated example, the size D1 of the first partial passage hole 351 in the first intermediate member 35A and the size D2 of the second partial passage hole 351 in the second intermediate member 35B are substantially equal (e.g., 48 mm), but may be designed to have different values. Here, the size of the partial passage hole 351 is, for example, the diameter of its circumscribing circle or inscribing circle (or the diameter of the partial passage hole 351 itself if the partial passage hole 351 is circular). In particular, the size D1 of the first partial passage hole 351 is preferably smaller than the size D2 of the second partial passage hole 351. In this case, the high frequency waves HF1T passing through the first partial passage hole 351 are largely diffracted due to the small size D1. To effectively introduce the high frequency waves HF1T diverging significantly from the incident axis O into the third space S3, the second partial passage hole 351 having a size D2 larger than the size D1 of the first partial passage hole 351 may be used. It is preferable that the sizes D 1 and D 2 of the partial passage holes 351 are smaller than the size or diameter of the sub-waveguide 412 that introduces the high frequency HF into the container 31 .

[0070] Furthermore, the amount of power absorption by the fluid circulation portion 32 in each of the spaces S1 to S3 can also be adjusted by the surface shape of the partial reflection portion 352 in each intermediate member 35 and / or the surface shape of the reflection portion in the end member 34. In the illustrated example, the surface shape of the partial reflection portion 352 in the first intermediate member 35A and the surface shape of the partial reflection portion 352 in the second intermediate member 35B are substantially the same, but they may be different from each other.

[0071] The surface shape of the partially reflecting portion 352 in each intermediate member 35 and / or the surface shape of the reflecting portion in the end member 34 can prevent high frequency HF from concentrating in a specific portion of the fluid flow portion 32 (for example, a specific tube).

[0072] 4 is an enlarged view of the end member 34. In the reflecting portion as the surface of the end member 34, the distance from the top of the container 31 (the vertical distance in FIG. 4 ) monotonically increases from the most protruding point 341 on the incident axis O on the inner periphery side toward the inner periphery surface 311 of the container 31 on the outer periphery side.

[0073] In a cross section taken along a plane including the incident axis O as shown in FIG. 4 , an inner circumferential portion 342 including the most prominent point 341 of the reflecting portion is curved or nonlinear. Specifically, the inner circumferential portion 342 is a curve that is convexly curved upward in the axial direction. This curve is expressed, for example, by an exponential function or a polynomial function of second or higher order in the x-y plane formed by the x-axis (not shown) in the left-right direction in FIG. 4 and the y-axis (not shown) in the up-down direction in FIG. 4 . Furthermore, in the cross section of FIG. 4 , an outer circumferential portion 343 of the reflecting portion, which is located on the outer circumferential side of the inner circumferential portion 342, is linear or linear. Specifically, the outer circumferential portion 343 is a straight line that extends from the inner circumferential portion 342 toward the outer circumferential side, away from the top of the container 31 (i.e., extends diagonally downward in FIG. 4 ). This straight line is expressed by a linear function in the x-y plane.

[0074] FIG. 5 shows a simulation example of the high-frequency HF or power dispersion effect of the end member 34 having the curved inner periphery 342 described above. In this simulation, high-frequency HF of 137 GHz and 0.547 MW was introduced into the container 31 of the high-frequency absorption device 3 shown in FIG. 3. The horizontal axis in FIG. 5 represents the axial position or height z in the third space S3 (Section 3) where the end member 34 is provided, and the vertical axis represents the power density absorbed by the fluid flow portion 32 at each axial position z. The dotted line graph represents a conventional cone reflector without the curved inner periphery 342, while the solid line graph represents the end member 34 according to this embodiment (Tuned Cone Reflector) having the curved inner periphery 342.

[0075] It can be seen that with a conventional conical reflector, a large amount of power is concentrated at a relatively low axial position z. This is thought to be because the large amount of power concentrated near the incident axis O in the high frequency wave HF having a Gaussian distribution is reflected directly by the conical or linear reflector to a specific range of axial positions z. Such excessive concentration of power in a specific range of axial positions z can cause bumping of water flowing through the fluid circulation portion 32 at the axial position z, which can lead to deterioration or damage to the tubes constituting the fluid circulation portion 32, poor operation of the high frequency absorbing device 3, and poor measurement accuracy.

[0076] In contrast, it can be seen that with the end member 34 (Tuned Cone Reflector) having a curved portion according to this embodiment, power is dispersed over a wide range of axial positions z. This is thought to be because the large power concentrated near the incident axis O in the high frequency HF having a Gaussian distribution is effectively dispersed by the curved or upwardly convex inner circumferential portion 342. According to this embodiment, bumping of water or the like flowing through the fluid flow portion 32 at a specific axial position z is effectively prevented.

[0077] To achieve the above-described effects, the shape and size of the curved inner periphery 342 (i.e., the function form and parameters of the exponential function or quadratic or higher polynomial function) may be adjusted through simulations or the like. For example, the size or diameter D3 of the inner periphery 342 shown in FIG. 4 may be substantially equal to, greater than, or smaller than the size D1 of the first partial passage hole 351 in the first intermediate member 35A and / or the size D2 of the second partial passage hole 351 in the second intermediate member 35B shown in FIG. 3 . In the simulation of FIG. 5 , the diameter D3 of the inner periphery 342 was smaller than the diameters D1 and D2 of the two equal partial passage holes 351. It is preferable that the diameter D3 of the inner periphery 342 be smaller than the size or diameter of the secondary waveguide 412 that introduces high frequency HF into the container 31.

[0078] As described above, just as the curved inner peripheral portion 342 for obtaining a power dispersal effect in the third space S3 is provided on the end member 34, a curved portion for obtaining a power dispersal effect in the first space S1 may be provided on the first intermediate member 35A, and a curved portion for obtaining a power dispersal effect in the second space S2 may be provided on the second intermediate member 35B.

[0079] The portion of each intermediate member 35 where the curved portion is provided may be any portion, but it is effective to form the curved portion at the inner circumferential portion 353, which is mainly responsible for the initial reflection of the incident high-power high frequency HF. Although detailed illustration is omitted, in this case, in a cross section taken along a plane including the incident axis O as shown in Figure 3, the inner circumferential portion 353 has a curved or upwardly convex curved shape. Furthermore, in the cross section of Figure 3, the outer circumferential portion 354 may be linear, but may also be curved.

[0080] Fig. 6 is a schematic diagram of a radio-frequency absorbing device 3 or dummy load according to a first modified example. The radio-frequency absorbing device 3 according to the first modified example differs from the radio-frequency absorbing device 3 shown in Fig. 3 in that the intermediate member 35 has a fluid passage portion 36. Furthermore, the cross-sectional shape of the end member 34 differs from the cross-sectional shape of the end member 34 shown in Fig. 3.

[0081] When the high frequency HF passes through the partial passage hole 351, it also flows as a current on its inner circumferential surface, generating heat according to the resistance of the material constituting the intermediate member 35. The fluid circulation portion 36 is a cooling flow path through which a refrigerant such as water can flow. The fluid circulation portion 36 may include a tube constituting the cooling flow path. By including the fluid circulation portion 36 in the intermediate member 35, the intermediate member 35 can be cooled by a refrigerant such as water. The fluid circulation portion 36 may be formed of one or more tubes made of polytetrafluoroethylene. The fluid circulation portion 36 may be formed by providing at least one hole penetrating the intermediate member 35 along the surface 35a on the end member 34 side, which is the bottom surface of the intermediate member 35, and disposing a tube in at least one hole.

[0082] While the bottom surface of the end member 34 shown in FIG. 3 is flat, the bottom surface 34a of the end member 34 according to the first modification is a conical concave surface facing the incident portion 33. By forming the bottom surface 34a as a conical concave surface, a space is formed at the bottom of the container 31. This allows a fluid circulation portion 37 to be provided on the bottom surface 34a of the end member 34. Similar to the fluid circulation portion 32, the fluid that absorbs high frequency HF flows through the fluid circulation portion 37. The fluid circulation portion 37 may be formed of one or more tubes made of polytetrafluoroethylene.

[0083] FIG. 7 is a schematic diagram of a radio-frequency absorbing device 3 or a dummy load according to a second modification. The radio-frequency absorbing device 3 according to the second modification differs from the peripheral portion 354 of the intermediate member 35 according to the first modification in that the peripheral portion 354 of the intermediate member 35 is not inclined. The inner peripheral portion 353 is an inclined portion that slopes toward one end (top) from the partial through-hole 351 toward the inner peripheral surface 311 of the container 31 in a cross section taken along a plane including the incident axis O. The peripheral portion 354 is flat, and the distance between the surface of the peripheral portion 354 facing the top of the container 31 and the top of the container 31 is constant. Reducing the thickness of the peripheral portion 354 saves material for the intermediate member 35 and reduces the weight of the intermediate member 35.

[0084] The distance from the incident axis O of the high frequency HF to the most prominent point 355, which is the apex of the inner circumferential portion 353, may be equal to or greater than the maximum distance reached by the other portion HF1R of the high frequency HF incident from the incident portion 33 that deviates from the axial direction due to diffraction at the incident portion 33 or the intensity distribution of the high frequency HF itself. This maximum distance may be derived in advance through experiments, etc. For example, the distance from the incident axis O of the high frequency HF to the most prominent point 355, which is the apex of the inner circumferential portion 353 of the first intermediate member 35A, may be derived based on the divergence angle θ due to diffraction (= k × (λ / D), k is a predetermined coefficient) derived from the diameter D of the incident portion 33 and the wavelength λ of the high frequency HF, and the distance from the incident portion 33 to the first intermediate member 35A. The distance from the incident axis O of the high frequency HF to the most protruding point 355, which is the vertex of the inner circumference 353 of the second intermediate member 35B, can be derived based on the diffraction spread angle θ (= k × (λ / D1), k is a predetermined coefficient) derived from the size D1 of the first partial passage hole 351 in the first intermediate member 35A and the wavelength λ of the high frequency HF, and the distance from the first intermediate member 35A to the second intermediate member 35B.

[0085] FIG. 8 is a schematic diagram of a radio-frequency absorbing device 3 or a dummy load according to a third modification. The intermediate member 35 according to the third modification has an inclined portion that slopes from the partial passage hole 351 toward one end (top) of the container 31 as it extends from the partial passage hole 351 toward the inner circumferential surface 311 of the container 31. The distance between the intermediate member 35 and the top of the container 31 decreases from the partial passage hole 351 toward the inner circumferential surface 311 of the container 31. The intermediate member 35 has an inverted conical shape with an apex on the end member 34 side. The distance between the intermediate member 35 and the top of the container 31 may monotonically decrease from the partial passage hole 351 toward the inner circumferential surface 311 of the container 31. The intermediate member 35 has a partial passage hole 351 in a central portion recessed toward the end member 34 of the container 31. The intermediate member 35 according to the third modification can be manufactured simply by performing a process to recess the central portion and a process to form the partial passage hole 351 in the central portion, thereby simplifying the manufacturing process of the intermediate member 35. Furthermore, because the intermediate member 35 is made entirely of a thin plate, it is possible to further reduce the material of the intermediate member 35 and reduce the weight of the intermediate member 35 compared to the intermediate member 35 according to the second modification. Furthermore, because the thickness around the partial passing hole 351 is uniformly thin, unlike the first modification and the like, it is possible to reduce the electrical resistance around the partial passing hole 351 and further suppress heat generation due to current generated in the area around the partial passing hole 351 when high frequency HF passes through the partial passing hole 351.

[0086] FIG. 9 is a schematic diagram of a radio-frequency absorbing device 3 or a dummy load according to a fourth modification. The intermediate member 35 according to the fourth modification has an inclined portion that slopes from the partial passage hole 351 toward the inner circumferential surface 311 of the container 31 toward the end member 34, which is the bottom of the container 31. The intermediate member 35 has a conical shape with an apex at the top of the container 31. The distance from the top of the container 31 to the partial passage hole 351 increases from the partial passage hole 351 toward the inner circumferential surface 311 of the container 31. The distance from the top of the container 31 to the partial passage hole 351 to the inner circumferential surface 311 of the container 31 may monotonically increase from the partial passage hole 351 toward the inner circumferential surface 311 of the container 31. The intermediate member 35 has a partial passage hole 351 in a central portion that protrudes toward the top of the container 31. The intermediate member 35 according to the fourth modification can be manufactured simply by performing a process to recess the central portion and a process to form the partial passage hole 351 in the central portion, thereby simplifying the manufacturing process of the intermediate member 35. Furthermore, because the intermediate member 35 is made entirely of a thin plate, it is possible to further reduce the material of the intermediate member 35 and reduce the weight of the intermediate member 35 compared to the intermediate member 35 according to the second modification. Furthermore, because the thickness around the partial passing hole 351 is uniformly thin, unlike the first modification and the like, it is possible to reduce the electrical resistance around the partial passing hole 351 and further suppress heat generation due to current generated in the area around the partial passing hole 351 when high frequency HF passes through the partial passing hole 351.

[0087] 10 is a schematic diagram of a radio frequency absorbing device 3 or a dummy load according to a fifth modified example. The intermediate member 35 according to the fifth modified example has an inner periphery 353 and an outer periphery 354 surrounding the inner periphery 353.

[0088] The inner circumferential portion 353 is an inclined portion that slopes from the partial passing hole 351 toward the inner circumferential surface 311 of the container 31 toward the end member 34, which is the bottom of the container 31. The inner circumferential portion 353 has a conical shape with an apex on the top side of the container 31. The distance between the inner circumferential portion 353 and the top of the container 31 increases from the partial passing hole 351 toward the inner circumferential surface 311 of the container 31. The distance between the inner circumferential portion 353 and the top of the container 31 may monotonically increase from the partial passing hole 351 toward the inner circumferential surface 311 of the container 31. The inner circumferential portion 353 has a partial passing hole 351 in a central portion that protrudes toward the top side of the container 31.

[0089] The outer peripheral portion 354 extends without inclination from the connecting portion with the inner peripheral portion 353 toward the inner peripheral surface 311 of the container 31. The distance between the outer peripheral portion 354 and the top of the container 31 is constant from the connecting portion with the inner peripheral portion 353 to the inner peripheral surface 311 of the container 31.

[0090] According to the intermediate member 35 of the fifth modification, the manufacturing process of the intermediate member 35 can be simplified because it is only necessary to perform processing to recess the center portion and processing to form the partial passage hole 351 in the center portion. Furthermore, because the intermediate member 35 is made of a thin plate as a whole, it is possible to further save material and reduce the weight of the intermediate member 35 compared to the intermediate member 35 of the second modification. Furthermore, because the thickness around the partial passage hole 351 is uniformly thin, unlike the first modification and the like, it is possible to reduce the electrical resistance around the partial passage hole 351 and further suppress heat generation due to current generated in the area around the partial passage hole 351 when high frequency HF passes through the partial passage hole 351.

[0091] 11 is a schematic diagram of a radio frequency absorbing device 3 or a dummy load according to a sixth modified example. The intermediate member 35 according to the sixth modified example has an inner peripheral portion 353 and an outer peripheral portion 354.

[0092] The inner circumferential portion 353 is an inclined portion that slopes from the partial passage hole 351 toward the inner circumferential surface 311 of the container 31 toward the top of the container 31. The inner circumferential portion 353 has an inverted conical shape with an apex on the end member 34 side. The distance from the top of the container 31 of the inner circumferential portion 353 decreases from the partial passage hole 351 toward the inner circumferential surface 311 of the container 31. The distance from the top of the container 31 of the inner circumferential portion 353 may monotonically decrease from the partial passage hole 351 toward the inner circumferential surface 311 of the container 31. The inner circumferential portion 353 has the partial passage hole 351 in a central portion that is recessed toward the bottom side of the container 31.

[0093] The outer peripheral portion 354 extends without inclination from the connecting portion with the inner peripheral portion 353 toward the inner peripheral surface 311 of the container 31. The distance between the outer peripheral portion 354 and the top of the container 31 is constant from the connecting portion with the inner peripheral portion 353 to the inner peripheral surface 311 of the container 31.

[0094] According to the intermediate member 35 of the sixth modification, the manufacturing process of the intermediate member 35 can be simplified because it is only necessary to perform processing to recess the center portion and processing to form the partial passage hole 351 in the center portion. Furthermore, because the intermediate member 35 is made of a thin plate as a whole, it is possible to further save material and reduce the weight of the intermediate member 35 compared to the intermediate member 35 of the second modification. Furthermore, because the thickness around the partial passage hole 351 is uniformly thin, unlike the first modification and the like, it is possible to reduce the electrical resistance around the partial passage hole 351 and further suppress heat generation due to current generated in the area around the partial passage hole 351 when high frequency HF passes through the partial passage hole 351.

[0095] In the third to sixth modified examples, the intermediate member 35 does not have the fluid circulation portion 37. However, the intermediate member 35 in the third to sixth modified examples may have the fluid circulation portion 37, as in the first and second modified examples. In the first and second modified examples, the intermediate member 35 has the fluid circulation portion 37 in a through hole formed therein. However, the fluid circulation portion 37 may be provided on the outside of the intermediate member 35, for example, along the surface of the intermediate member 35 on the side of the end member 34.

[0096] FIG. 12 is an enlarged view of an end member 34 according to a modified example. The surface shape of the reflecting portion of the end member 34 shown in FIG. 4 is a curved shape that protrudes toward one end of the container 31 in a region including at least the portion through which the incident axis O passes, in a cross section taken along a plane including the incident axis O. On the other hand, the surface shape of the reflecting portion of the end member 34 shown in FIG. 12 is a curved shape that protrudes toward the other end of the container 31 in a region including at least the portion through which the incident axis O passes, in a cross section taken along a plane including the incident axis O. The surface shape of the reflecting portion of the end member 34 may be nonlinear in at least the region through which the incident axis O passes, in a cross section taken along a plane including the incident axis O. Having such a surface shape for the reflecting portion of the end member 34 can prevent high frequency waves from concentrating on a specific portion of the fluid circulation portion 32 (e.g., a specific tube).

[0097] The end member 34 includes an inner circumferential portion 342 including the incident axis O and an outer circumferential portion 343 surrounding the inner circumferential portion 342. Unlike the end member 34 shown in FIG. 4 , the inner circumferential portion 342 does not have a most protruding point 341 and is recessed toward the bottom surface 34a of the end member 34. The inner circumferential portion 342 is curved in a cross section taken along a plane including the incident axis O. Specifically, the inner circumferential portion 342 is a curved line that is concave downward in the axial direction. The distance between the inner circumferential portion 342 and the apex of the container 31 decreases from a valley portion 344 on the incident axis O that constitutes the recess toward the inner circumferential surface 311 of the container 31. The distance between the inner circumferential portion 342 and the apex of the container 31 may decrease monotonically from the valley portion 344 on the incident axis O that constitutes the recess toward the inner circumferential surface 311 of the container 31.

[0098] The cross-sectional curve of the inner circumferential portion 342 may be represented by, for example, an exponential function or a polynomial function of second or higher order in the x-y plane formed by the x-axis in the left-right direction in Fig. 12 and the y-axis in the up-down direction in Fig. 12. Furthermore, in the cross section of Fig. 12, the outer circumferential portion 343 may be linear or straight. Specifically, the outer circumferential portion 343 may be a straight line extending from the inner circumferential portion 342 toward the outer periphery, away from the top of the container 31. This straight line is represented by a linear function in the x-y plane.

[0099] Fig. 13 is an enlarged view of an end member 34 according to another modification. The end member 34 according to this modification differs from the end member 34 according to the modification shown in Fig. 12 in that the bottom surface 34a is concave toward the incident portion 33. It also differs in that a fluid circulation portion 37 is provided on the bottom surface 34a. A fluid that absorbs high frequency waves HF flows through the fluid circulation portion 37. The fluid circulation portion 37 may be composed of one or more tubes made of polytetrafluoroethylene.

[0100] FIG. 14 is an enlarged view of an end member 34 according to another modification. The end member 34 includes an inner periphery 342 that includes the incident axis O, an annular groove 346 that surrounds the inner periphery 342, and an outer periphery 343 that surrounds the annular groove 346. In the end member 34 shown in FIG. 4 , the inner periphery 342 has a most protruding point 341 on the incident axis O. In the other modification shown in FIG. 14 , the protruding point 345 on the incident axis O that the inner periphery 342 has is not the most protruding point of the end member 34, i.e., the point located at the highest position. Instead, a circumferential portion 347 at the boundary between the outer periphery 343 and the annular groove 346 is located at the highest position.

[0101] The inner circumferential portion 342 including the protruding point 345 is curved or nonlinear. Specifically, the inner circumferential portion 342 is a curved curve that is convex upward in the axial direction. This curve is expressed by, for example, an exponential function or a polynomial function of second or higher order in the x-y plane formed by the x-axis in the left-right direction in FIG. 14 and the y-axis in the up-down direction in FIG. 14.

[0102] According to the end member 34 shown in FIG. 14, the inner circumferential portion 342 has a curved convex shape extending axially upward, which can prevent high frequency HF from concentrating in a specific part of the fluid circulation portion 32 (e.g., a specific tube).

[0103] Fig. 15 is an enlarged view of an end member 34 according to another modified example. The end member 34 according to another modified example shown in Fig. 15 is the same as the end member 34 shown in Fig. 12 in that an inner periphery 342 has a valley 344 on the incident axis O. However, the end member 34 according to another modified example differs from the end member 34 shown in Fig. 12 in that the slope from the outer periphery 343 of the inner periphery 342 to the valley 344 is a curved convex surface toward the top of the container 31.

[0104] As described above, the surface shape of the inner periphery 342 of the end member 34 is curved or nonlinear in a region including at least the portion through which the incident axis O passes, in a cross section taken along a plane including the incident axis O, and protrudes toward one end (top) or the other end (bottom) of the container 31. This makes it possible to prevent high frequency waves HF from concentrating in a specific portion of the fluid circulation portion 32 (for example, a specific tube).

[0105] 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.

[0106] The configuration, operation, and function of each device and method described in the embodiments can be realized by hardware resources, software resources, or a combination of hardware and software resources. Examples of hardware resources include processors, ROM, RAM, and various integrated circuits. Examples of software resources include operating systems, applications, and other programs.

[0107] REFERENCE SIGNS LIST 1 High frequency control device, 2 High frequency oscillator, 3 High frequency absorption device, 4 Transmission system, 31 Container, 32 Fluid circulation portion, 33 Incident portion, 34 End member, 35 Intermediate member, 36 Fluid circulation portion, 37 Fluid circulation portion, 311 Inner peripheral surface, 341 Most protruding point, 342 Inner peripheral portion, 343 Outer peripheral portion, 351 Partial passage hole, 352 Partial reflection portion, 353 Inner peripheral portion, 354 Outer peripheral portion, 355 Most protruding point

Claims

1. A radio-frequency absorbing device that absorbs radio-frequency waves, comprising: a container extending from one end to the other end along an incident axis of the radio-frequency wave; a fluid flow section through which a fluid flows along an inner peripheral surface of the container around the incident axis; an incident section provided at the one end and allowing the radio-frequency wave to enter the container; and an end member provided at the other end and having a reflecting section that reflects the radio-frequency wave; and an intermediate member provided between the one end and the other end inside the container, having a partial passing hole through which the incident axis passes and a partial reflecting section around the partial passing hole that reflects a part of the radio-frequency wave.

2. The high-frequency absorbing device according to claim 1, wherein the fluid absorbs the high-frequency waves, the reflecting portion reflects the high-frequency waves toward the fluid flow portion, the partial passage hole allows a portion of the high-frequency waves to pass toward the other end portion, and the partial reflection portion reflects the other portion of the high-frequency waves toward the fluid flow portion.

3. A high-frequency absorbing device as described in claim 1, wherein the partial reflection portion has a reflection surface facing the one end portion, and the reflection surface includes an inclined surface that inclines from the partial passage hole toward the inner surface of the container toward the one end portion or the other end portion in a cross section taken along a plane including the incident axis.

4. A high-frequency absorbing device as claimed in claim 1, wherein the partial reflection portion is provided with a protrusion protruding towards the one end between the partial passage hole on the inner periphery side and the inner periphery surface of the container on the outer periphery side.

5. The high frequency absorbing device according to claim 4, wherein, at the inner periphery of the inner periphery of said protruding portion, the distance from said one end portion to said inner periphery decreases monotonically from said partial passage hole toward said most protruding point.

6. The radio frequency absorbing device according to claim 5, wherein in a cross section taken along a plane including said axis of incidence, said inner periphery is curved.

7. A high frequency absorbing device as set forth in claim 5, wherein, at the outer periphery of the outer periphery of said protruding portion, the distance from said one end increases monotonically from the most protruding point towards the inner periphery of said container.

8. The high frequency absorbing device according to claim 7, wherein in a cross section taken along a plane including said axis of incidence, said outer periphery is straight.

9. A high-frequency absorbing device as described in any one of claims 1 to 7, wherein the distance between the reflecting portion of the end member and the one end portion monotonically increases from the most protruding point on the axis of incidence on the inner circumference side toward the inner circumferential surface of the container on the outer circumference side.

10. The radio frequency absorbing device according to claim 9, wherein in a cross section taken along a plane including the axis of incidence, an inner periphery of the reflecting portion including the most protruding point is curved.

11. The high frequency absorbing device according to claim 10, wherein in a cross section taken along a plane including said axis of incidence, an outer periphery of said reflecting portion that is closer to the outer periphery than said inner periphery is linear.

12. A high-frequency absorbing device as described in any one of claims 1 to 8, wherein the surface shape of the reflecting portion is curved or nonlinear, protruding toward the one end side or the other end side of the container, in a region including at least a portion through which the incident axis passes, in a cross section taken along a plane including the incident axis.

13. A high-frequency absorbing device as set forth in any one of claims 1 to 8, wherein the distance between the bottom surface of the end member and the one end increases from the portion through which the incident axis passes toward the inner peripheral surface of the container.

14. The high frequency absorbing device according to claim 13, further comprising another fluid passage portion on said bottom surface of said end member through which fluid passes.

15. A high-frequency absorbing device as claimed in any one of claims 1 to 8, wherein the intermediate member comprises a first intermediate member on the one end side and a second intermediate member on the other end side adjacent to the first intermediate member.

16. The high frequency absorbing device according to claim 15, wherein the size of the first partial passage hole as the partial passage hole in the first intermediate member and the size of the second partial passage hole as the partial passage hole in the second intermediate member are substantially equal.

17. The high-frequency absorbing device according to claim 15, wherein the size of the first partial-passage hole as the partial-passage hole in the first intermediate member is smaller than the size of the second partial-passage hole as the partial-passage hole in the second intermediate member.

18. A high-frequency absorbing device according to any one of claims 1 to 8, wherein the intermediate member is made of a material containing copper.

19. A radio frequency absorbing device according to any one of claims 1 to 8, wherein the radio frequency is used to heat a plasma for nuclear fusion.

20. A high-frequency control device comprising: a high-frequency oscillator that oscillates a high-frequency wave; and a high-frequency absorption device that absorbs at least a portion of the high-frequency wave, wherein the high-frequency absorption device comprises: a container extending from one end to the other end along an incident axis of the high-frequency wave; a fluid flow section through which a fluid flows along an inner surface of the container around the incident axis; an incident section provided at the one end and allowing the high-frequency wave to enter the container; and an end member provided at the other end and having a reflecting section that reflects the high-frequency wave; and an intermediate member provided between the one end and the other end in the container, having a partial passing hole through which the incident axis passes and a partial reflecting section that reflects a portion of the high-frequency wave around the partial passing hole.

21. The high-frequency control device according to claim 20, wherein the fluid absorbs the high-frequency wave, the reflecting portion reflects the high-frequency wave toward the fluid flow portion, the partial passage hole allows a portion of the high-frequency wave to pass toward the other end portion, and the partial reflecting portion reflects the other portion of the high-frequency wave toward the fluid flow portion.

22. A radio frequency absorbing device that absorbs radio frequency waves, comprising: a container extending from one end to the other end along an incident axis of the radio frequency waves; a fluid flow section through which a fluid flows along an inner peripheral surface of the container around the incident axis; an incident section provided at the one end for incident the radio frequency waves into the container; and an end member provided at the other end having a reflecting section for reflecting the radio frequency waves, wherein the distance between the reflecting section and the one end increases or decreases from a point on the incident axis on the inner peripheral side toward the inner peripheral surface of the container on the outer peripheral side, and in a cross section taken along a plane including the incident axis, at least the inner peripheral portion including the point on the reflecting section is curved or nonlinear.

23. The high-frequency absorbing device according to claim 22, wherein the distance from said one end of said reflecting portion monotonically increases from the most protruding point, which is said point on said axis of incidence on the inner circumference side, toward the inner circumferential surface of said container on the outer circumference side.

24. The radio frequency absorbing device according to claim 22, wherein the distance between said reflecting portion and said one end portion decreases monotonically from said point on said axis of incidence on the inner circumference side toward the inner circumference surface of said container on the outer circumference side.

25. A high-frequency absorbing device according to any one of claims 22 to 24, wherein the fluid absorbs the high-frequency wave, and the reflecting portion reflects the high-frequency wave toward the fluid flow portion.

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