JP3080751B2 - High frequency heating equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency heating apparatus having a plurality of power amplifying devices, and more particularly to a high-frequency heating apparatus that applies high-frequency power to plasma to heat the plasma and generate a current in the plasma.

[0002]

2. Description of the Related Art A tokamak-type fusion device shown in FIG. 3 is one of devices for confining plasma using a magnetic field. In this tokamak fusion device, the vertical magnetic field Bv in the vertical direction
Radial toroidal magnetic field Bt along the circumferential direction and poloidal magnetic field B generated by plasma current Ip flowing inside
The plasma 1 is confined in an annular shape (torus shape) by p.

A vertical magnetic field Bv is generated by a poloidal coil 2 arranged along an annular plasma 1 as shown in FIG. 4, and a toroidal magnetic field Bt is generated by a toroidal coil 3 arranged to form an annular solenoid coil. generate. The plasma current Ip is generated by electromagnetic induction. That is, the plasma current Ip rapidly changes the current of the induction coil 4 arranged at the center of the tokamak fusion device, and induces an electric field in the plasma 1 due to the time change of the magnetic flux, thereby accelerating the electrons by the electric field. And generate.

[0004] The temperature of the plasma 1 generated by such a tokamak fusion device is only about tens of millions of degrees as it is, and some kind of plasma heating is necessary to reach the hundreds of millions of degrees required for a fusion reactor. Becomes In one of the plasma heatings, a high frequency having a frequency synchronized with the cycle of the swirling motion of ions in a magnetic field (this is called cyclotron motion) is incident, and the frequency is resonated to give high frequency energy to the ions to heat the plasma 1. There is ion cyclotron heating performed.

FIG. 5 shows a schematic configuration of a standard ion cyclotron heating apparatus. This ion cyclotron heating device exemplifies a device for supplying high-frequency power to eight antennas 15, distributes the low-power high-frequency generated by the original oscillator 10 into eight, and heats the space between each row by the phase shifter 11. After the required phase difference is provided, power amplification is performed. Since the high-frequency power from the original oscillator 10 is very small and cannot be amplified using a vacuum tube as it is, the preamplifier 12
After the power is raised to an appropriate level, a high frequency is input to the power amplifying device 20.

The power amplifying device 20 is a low power amplifier (L
PA: Low Power Amp. 21, Intermediate power amplifier (IP
A: Intermediate Power Amp.) 22 and high power amplifier (HPA: High Power Amp.)
Amplifies the high frequency of 0W class to the MW class.

The high frequency transmitted from the power amplifying device 20 is transmitted to an antenna 15 via an impedance matching device (IMS) 14 via a transmission line 13 such as a coaxial feed line. Generally, since the input impedance of the antenna 15 is different from the characteristic impedance of the transmission line 13,
Is installed in the middle of the process.

[0008] By the way, the conventional high-frequency heating apparatus is mainly intended for heating the plasma, but when high frequency is used, unlike electromagnetic induction, a current can be continuously passed through the plasma of the tokamak-type fusion apparatus. Research on high-frequency current driving for generating a current in plasma has been actively pursued in recent years. Also in the ion cyclotron heating apparatus, experiments of current driving for accelerating electrons by high frequency are being advanced. In this case, it is necessary to change the frequency to a frequency different from that for heating in order to avoid high frequency absorption by ions.

In addition, since the conventional high-frequency heating device accelerates electrons in one direction, when a high-frequency wave is incident on the plasma from the antenna 15 shown in FIG. 6, the antennas 15a, 15b, and 15b are respectively formed so that the electromagnetic waves form traveling waves. It is necessary to set a phase difference different from that at the time of heating between 15c and 15d. Each antenna 15a to 15d is connected to an inner conductor 17 and an outer conductor 18 via a return conductor 16, respectively.

When assuming a future fusion reactor, it is inappropriate to provide separate high-frequency heating devices for heating and current driving from the viewpoint of reducing construction costs and occupied space. Current drive must be possible.

[0011]

However, when both heating and current driving are performed by the same high-frequency heating device, the frequency and phase difference must be changed during the operation. Since this phase difference can be changed by an electronic circuit, it can be changed in a short time, but the frequency change requires a certain time for the reason described below. Further, since the input impedance of the antenna changes due to the change of the frequency and the phase difference, it is necessary to readjust the impedance matching.

Therefore, the high-frequency output must be stopped during such a change in operation. However, when the temperature of the plasma, especially the electron temperature, decreases, the efficiency of current driving is significantly reduced. It is required to minimize the time required for the migration of the system.

However, in order to change the frequency, not only the oscillation frequency of the original oscillator 10 is changed, but also the tuning frequency of each output circuit of each of the amplifiers 21, 22, and 23 constituting the power amplifying device 20 and the impedance of the input circuit. Must be changed. For example, FIG. 7 shows an example of a resonator of an output circuit of an amplifier. A reentrant cavity 30 has an inner conductor 31 and an outer conductor 32. When this cavity 30 is used, the tuning frequency Is the short-circuit plate 33
Is moved along the axial direction of the inner conductor 31 and the outer conductor 32 to change the distance L.

Therefore, when changing the frequency, only the time required for moving the short-circuit plate 33 is required. Further, a metal contact 34 pressed with a constant pressure is attached to the short-circuit plate 33 to ensure electrical contact.

Since a large number of such metal contacts 34 are attached along the circumferential direction, the movement of the short-circuit plate 33 requires a force greater than the total contact pressure of the metal contacts 34. In addition, since it is physically impossible to instantaneously generate and stop a force, it is considered that the movement of the short-circuit plate 33 takes more time, and it takes several tens of seconds in the range of ordinary mechanical technology. is expected.

At present, the energy confinement time of plasma supposed as a fusion reactor is about 1 second. Therefore, the plasma cools down while the frequency is changed from the heating mode to the current driving mode, and the efficiency is improved. Current drive becomes impossible. If the moving speed of the short-circuit plate 33 is extremely increased, there is a possibility that the contact performance of the metal contact 34 may be impaired and the life thereof may be shortened. There is a problem that causes.

The present invention has been made in view of the above-described circumstances, and has as its object to provide a high-frequency heating apparatus that efficiently changes a heating mode to a power driving mode.

[0018]

In order to solve the above-mentioned problems, a high-frequency heating apparatus according to the present invention comprises, in a high-frequency heating apparatus having a plurality of power amplifiers, a block for each of the plurality of power amplifiers. The power amplifier of each block is provided with an original oscillator for generating a high frequency, and when changing from a heating mode for heating ions to a current drive mode for accelerating electrons in plasma to generate a current, the plurality of blocks are used. Are set so that the high frequency parameters of at least one block of the power amplifying device are sequentially changed.

[0019]

In the present invention having the above configuration, the high-frequency parameters of the power amplifying devices of at least one block among the plurality of power amplifying devices are set so as to be sequentially changed. The current drive can be performed while heating the plasma without interruption of the application of the high-frequency power when changing to.
Therefore, it is possible to prevent a rapid decrease in the plasma temperature due to the temporary interruption of the high-frequency power, thereby realizing efficient current driving.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the basic configuration of an embodiment of the high-frequency heating apparatus according to the present invention. Note that the same parts as those of the conventional configuration will be described using the same reference numerals.

In this embodiment, when the total number of the antennas 15 is 16, an example is shown in which four antennas 15 as shown in FIG. 6 are used as one block and the mode is changed from the heating mode to the current driving mode. The high-frequency heating device distributes the low-power high-frequency generated by the four blocks of the original oscillator 10 into four, and provides a phase difference required for high-frequency heating between the columns by the phase shifter 11, and then performs power amplification. Do.

The low-power high-frequency wave transmitted from the phase shifter 11 is amplified by the preamplifier 12 to about 100 W, and then a power amplifier 20 including a low-power amplifier 21, an intermediate power amplifier 22, and a large-power amplifier 23. , And amplifies to a large power of 1 MW class, and supplies a high frequency to each antenna 15 through the impedance matching unit 13. As described above, the difference between the high-frequency heating apparatus and the conventional example shown in FIG. 5 is that four power amplifiers 20 connected to each of the four antennas 15 necessary for current driving are formed as one block, and each block is This is a configuration in which an original oscillator 10 is provided.

That is, the high-frequency heating device of the present embodiment
The six power amplifiers 20 are divided into four blocks,
Each of these four blocks of power amplifying devices 20 is provided with an original oscillator 10 for generating a high frequency. And
When changing from the heating mode in which the ions are heated to the current driving mode in which the electrons in the plasma are accelerated to generate a current, at least one of the four blocks of the power amplifying apparatus 20 is used. Are set so as to be sequentially changed. here,
The high frequency parameters refer to the tuning frequency, high frequency phase, and the like of the output tuning circuit and the input tuning circuit of the power amplifying device 20.

The means for changing the high frequency parameter of the power amplifying device 20 includes changing the length of the cavity resonator and re-establishing the impedance matching of the input circuit.

Next, the operation of this embodiment will be described.

In the above-described high-frequency heating device, the four power amplifiers 20 connected to the four antennas 15 can be operated by changing the high-frequency parameters for each of the source oscillators 10. Without interruption, it is possible to sequentially change the operation from the heating mode in which ions are heated for every four antennas to the current driving mode in which electrons in the plasma are accelerated to generate a current.

As described above, according to the present embodiment, the operation can be changed by using a plurality of power amplifying devices 20 as one block, so that the tuning frequency of the power amplifying device 20 need not be changed in an extremely short time. By sequentially shifting several power amplifying devices 20 to the current driving mode while heating the plasma, efficient current driving can be realized without lowering the plasma temperature.

Further, since the power amplifier 20 does not require a high-speed operation of a tuning circuit or the like, a highly reliable high-frequency heating device can be provided. Further, since it is not necessary to stop and restart all the outputs of the high-frequency heating device at once, a load fluctuation on the power supply can be reduced, and stable operation can be performed.

FIG. 2 shows another embodiment of the high-frequency heating device according to the present invention. FIG. 2 shows a change in the high-frequency output level of one power amplifying device when the mode is changed from the heating mode to the current driving mode. The horizontal axis represents time t, and the vertical axis represents the output Pi of the power amplifier. In addition, the section A indicates a period of the heating mode, the section C indicates a period of the current drive mode, and the section B indicated by oblique lines indicates a period of change of the operating state.

In this embodiment, in section B, the output Pi is reduced to a value equal to or less than the allowable reflected power value Pc of the amplifier tube of the high power amplifier 23 at the last stage of the power amplifier 20, and the frequency is changed and the impedance matching is readjusted. During this period, the output Pi is not completely set to zero.

As described above, according to the present embodiment, the fluctuation of the load on the power supply can be further reduced, and the stable and efficient operation of the high-frequency heating device can be performed.

[0033]

As described above, according to the high-frequency heating device of the present invention, the high-frequency parameters of the power amplifying devices of at least one block among the plurality of power amplifying devices are set so as to be sequentially changed. Therefore, the operation can be shifted from the heating mode to the current drive mode without the influence of the plasma temperature drop due to the temporary interruption of the high-frequency power. As a result, efficient current driving can be realized, and a stable operation of the high-frequency heating device can be realized with reduced load fluctuation.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a high-frequency heating device according to the present invention.

FIG. 2 is an explanatory diagram showing a change in output from a power amplifier according to another embodiment of the present invention.

FIG. 3 is a principle diagram showing the principle of a general tokamak fusion device.

FIG. 4 is a schematic configuration diagram showing a coil configuration of a tokamak fusion device.

FIG. 5 is a schematic configuration diagram illustrating the configuration of a conventional standard ion cyclotron heating apparatus.

6 is a schematic perspective view showing an antenna used in the ion cyclotron heating device of FIG.

FIG. 7 is a schematic diagram showing an example of a cavity resonator used in an output tuning circuit of a power amplifier.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Original oscillator 11 Phase shifter 12 Preamplifier 14 Impedance matching device 15 Antenna 20 Power amplifier 21 Low power amplifier 22 Intermediate power amplifier 23 High power amplifier

Claims (1)

(57) [Claims] In a high-frequency heating device having a plurality of power amplifiers, a block is formed for each of the plurality of power amplifiers, and a power oscillator for generating a high frequency is provided in each of the power amplifiers to heat ions. When changing from the heating mode to the current driving mode in which electrons in the plasma are accelerated to generate a current, the high-frequency parameters of at least one block of the power amplifiers of the plurality of blocks are sequentially changed. A high-frequency heating apparatus characterized in that: