JPH0795105B2 - Torus type fusion device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a torus-type nuclear fusion device that maintains a plasma current substantially constant.

[Prior Art] FIG. 4 is a cross-sectional view showing a configuration of a conventional torus-type fusion device. This torus-type nuclear fusion device is axisymmetric and uniform in the coordinate direction in the circumferential direction with respect to the Z axis that is the central axis. In FIG. 4, 1 has a small radius a ₀ ,
A torus-shaped plasma having a large radius R ₀ , 2 is a vacuum container that forms a plasma 1 inside, and has a hollow torus-shaped interior. 3
Is a toroidal magnetic field coil provided in a torus shape so as to wrap the vacuum container 2 inside, and a magnetic field is generated in the plasma generation region in the vacuum container 2 in the direction along the central axis of the interior of the vacuum container 2 when a current flows. Form. Reference numeral 4 denotes an ohmic heating coil (hereinafter referred to as an OH coil) used to generate and maintain a plasma current in the vacuum container 2 by flowing a current, and is composed of a plurality of coils connected in series. Each OH coil 4 is provided outside the toroidal magnetic field coil 3 in a circular ring shape in a direction along the torus shape of the toroidal magnetic field coil 3.
The coil 4 is provided so as to surround the outer surface of the toroidal magnetic field coil 3 by a half circumference. 5 is a toroidal magnetic field coil power supply for energizing the toroidal magnetic field coil 3,
Reference numeral 6 is an OH coil power source for energizing the OH coil 4, and 7 is a control device for controlling each of the two power sources 5 and 6. The OH coil 4 and the plasma 1 are the primary side of the transformer,
It forms the secondary side.

Next, the operation of the conventional torus-type fusion device shown in FIG. 4 will be described. In operation, first, the toroidal magnetic field coil 3 is energized to generate a directional magnetic field. Next, after introducing hydrogen gas into the vacuum container 2 to perform pre-ionization, the OH coil power source 6 is turned on under the control of the controller 7.
The current I _OH flowing through the OH coil 4 is changed drastically to generate a directional voltage in the plasma 1 according to Faraday's law.
Induce a plasma current Ip. As a result, in FIG. 4, for example, in the direction (perpendicular to the paper surface), the plasma current Ip
Begins to flow. In Figure 5 the above operation, the time t ₀ ~
It is performed during t ₁ .

After the plasma current Ip is generated to a predetermined value, if the current I _OH of the OH coil 4 is not changed and made constant as shown by the broken line in FIG. 5, the resistance of the plasma 1 causes the broken line in FIG.
The plasma current Ip decays as seen in C ₁ . Therefore, the current I _OH flowing through the OH coil 4 is t as shown by the solid line in FIG.
If the voltage is further changed in the same direction as during _{0 to} t ₁ , a voltage for flowing the plasma current Ip is always generated in the secondary plasma 1, and the plasma current Ip is indicated by the solid line C ₂ in FIG. It is possible to carry out the operation of keeping constant as shown.

However, in this method, in order to maintain the plasma current for a long time, it is necessary to keep changing the OH coil current I _OH in one direction, since the OH coil current I _OH is very large, steady manner It is impossible to drive.

Therefore, it was thought to try to maintain the plasma current by a method other than the above method, in the document “Plasma Fusion Technology Research Group (held December 10, 1985)“ F-θ pumping ”.
Plasma current by the steady-state current drive method called "F-θ pumping" in the reverse field pinch (RFP) type torus fusion device described in "Design of experimental power source" (Pages 136 to 139 of Proceedings) Is a way to maintain.

This, as in the FIG. 6 in order to maintain constant after generating the plasma current Ip to a predetermined value, the current I _T of the toroidal field coil 3, a phase difference in a current I _OH of OH coil 4 The magnetic field helicity is injected into the plasma 1 by changing it into a sine wave shape, and the plasma current Ip is maintained.

This will be described by an equation. Torus nucleus as shown in Fig. 4
The magnetic field helicity K in the fusion device is K = ∫ ・ dv−Ψ_Θ・ Ψ  (1) where K: magnetic helicity: vector potential: magnetic field vector Ψ : Toroidal magnetic flux Ψ_Θ: Poloidal magnetic flux outside the plasma. Then, take the time derivative of this equation (1)
And becomes the following formula.

Where Φ: toroidal magnetic flux V : Plasma loop voltage: Electric field vector In the equation (2), the first term on the right side is the magnetic field per unit time.
It represents the helicity injection amount, and the second term is the plasma 1 charge.
Represents the amount of magnetic helicity dissipated by air resistance
It

Here, pay attention to the magnetic helicity injection amount of the first term.
Φ is a voltage V in the poloidal direction_ΘObtained by integration of
Φ = ∫V_Θdt ... (3) Now, the loop voltage V of plasma 1 And po
Circular voltage V in the direction of the loydal direction_ΘAnd the same frequency ω, each other
When changing the phase difference of sine wave of δ,
Taking the time average of the helicity injection amount of the first term of the side,here,_Θ: V_ΘChange amplitude  : V Becomes the amplitude of the change of. According to the equation (4), by selecting the phase difference δ,
Therefore, the helicity injection amount takes a positive value, which is
If the amount of licity dissipation equals the time average, then the plasm
Ma current Ip can be maintained.

Therefore, in the conventional device, one round electric current in the poloidal direction is generated.
Pressure V_Θ, Loop voltage V To have a sinusoidal change
Therefore, as shown in FIG. 6, the toroidal coil current I_TAnd oh
Ile current I_OHAnd are changed into a sine wave with a certain phase difference
To maintain the plasma current Ip.
It The OH coil current I is applied to the toroidal magnetic field coil 4.
_OHAs in the above, a sinusoidal current is applied.

[Problems to be solved by the invention]

Since the conventional torus-type fusion device is configured as described above, the current of the toroidal magnetic field coil must be periodically changed at the same time as the OH coil current, but the inductance of the toroidal magnetic field coil is often relatively large. Therefore, in order to have a sinusoidal variation in the toroidal magnetic field coil current, a power source that repeatedly generates a large voltage is required as the toroidal magnetic field coil power source, and there is a problem that the toroidal magnetic field coil power source becomes expensive. there were.

The present invention has been made in order to solve the above problems, and obtains a torus-type fusion device capable of maintaining a plasma current substantially constant without the need for continuously changing a toroidal magnetic field coil current in a sinusoidal manner. The purpose is to

[Means for solving problems]

The torus fusion device according to the present invention changes the current flowing in the shape control coil periodically to change the cross-sectional area of plasma repeatedly, and also changes the current flowing in the OH coil periodically at the same frequency. Controlled by.

[Action]

The torus fusion device according to the present invention cyclically changes the shape control coil current to periodically change the cross-sectional area of the plasma, and indirectly changes the amount of the toroidal magnetic flux in the plasma. The plasma current is maintained without repeatedly changing the coil current.

〔Example〕

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

FIG. 1 is a schematic sectional view showing the structure of a torus-type nuclear fusion device according to an embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 4 are the same as those of the conventional example, and 8 is a shape control coil provided between the vacuum container 2 and the toroidal magnetic field coil 3 to control the cross-sectional shape of the plasma 1. In this embodiment, the coils wound around the hollow circular center axis of the vacuum container 2 are provided as a pair above and below the vacuum container 2. 9 is plasma 1 in the shape control coil 8
A shape control coil power supply for supplying a current in the same direction as, 10 is a control device for controlling the toroidal magnetic field coil power supply 5, the OH coil power supply 6 and the shape control coil power supply. The toroidal magnetic field coil 3, the OH coil 4 and the shape control The amount of each current flowing through the coil 8 is controlled.

FIG. 2 is a waveform diagram showing the time change of the current I _OH flowing through the OH coil 4 and the time change of the current I _SC flowing through the shape control coil 8.

FIG. 3 is a state diagram showing changes in the cross-sectional area of the plasma 1 when the current I _SC flowing in the shape control coil 8 is changed. In FIG. 3, 1a is the cross-section of the plasma 1 when the current I _SC is small. Shape 1b is the cross-sectional shape of plasma 1 when 1 _SC is also large.

Next, the operation of plasma current driving of the torus fusion device according to one embodiment of the present invention will be described.

Excited up to a certain current value between the OH coil 4 to time t ₀ by OH coil power supply 6, between the subsequent time t ₀ to the t ₁
The current I _OH flowing in the OH coil 4 is rapidly changed in the opposite direction to the increasing direction, and a voltage is applied to the plasma 1 to
The plasma current Ip flowing inside is raised.

Next, at time t ₂ close to time t ₁ , the control device 10 starts exciting the shape control coil 8 via the shape control coil power supply 9. Then, from time t ₃ close to time t ₂ , the current I _SC of the shape control coil 8 is changed in a sine wave shape. In addition, the control device 10 controls the OH coil power supply 6 so that the OH coil power is supplied between the times t ₁ and t _2.
After making the current I _{OH of the} coil 4 constant, after time t ₃ , the current I _OH of the shape control coil 8 is made to have the same phase as that of the current I _SC and a sinusoidal current I _OH having the same frequency as that is passed. As shown in FIG. 3, the cross-sectional shape of the plasma 1 is the current of the shape control coil 8.
When I _SC is small, it has a circular cross section like plasma 1a, and when the current I _SC is large, it has a vertical elliptical cross section like plasma 1b. That is, after time t ₃ , the cross-sectional shape of the plasma 1 changes according to the magnitude of the current I _SC flowing through the shape control coil 8. Even if the toroidal magnetic field coil current is kept constant, the plasma at this time 1
The total amount of the toroidal magnetic flux in the plasma 1 changes due to the change in the cross-sectional area of. The change amount Φ of the toroidal magnetic flux at this time is assumed as follows.

here, Amplitude of change in toroidal magnetic flux Φ Also, in equation (4), it is generated by the change in OH coil current.
Sloping plasma loop voltage V To V = sin (ωt + δ) (6) where : Loop voltage V Is assumed to be the amplitude of the change
Then, the inflow of magnetic helicity is given by the following equation.

Becomes

Therefore, to maximize equation (7), OH that has a sinusoidal variation of the same frequency with a phase difference of δ = 0
By flowing the current I _{OH of the} coil 4 after the time t _{3, the} magnetic helicity is injected in the same manner as in the conventional case, and the plasma current Ip is maintained. At this time, when the plasma current Ip is generated, the current 3 of the toroidal magnetic field coil 3 may be kept constant without change.

In the above embodiment, the case where the current of the OH coil and the shape control coil is changed to a sine wave has been described.
It may be changed with another periodic waveform such as a triangular wave.

Further, the shape control coil does not have to be above and below the vacuum container, and current may be applied in any position and in any direction as long as it generates a magnetic field that changes the cross-sectional area of plasma. I do not care.

Further, in the above-mentioned embodiment, the phases of the OH coil current I _OH and the shape control coil current I _SC are made the same, but even if the phases are different from each other, the same effect as that of the above-mentioned embodiment is obtained.

Further, the current of the shape control coil may be changed and detected by a sensor or the like, the toroidal magnetic flux amount in the plasma may be calculated from this, and the OH coil current may be feedback-controlled accordingly.

[Advantages of the Invention] As described above, according to the present invention, the cross-sectional area of the plasma is changed and the plasma current is maintained only by controlling the current value flowing in the OH coil and the shape control coil to be a periodic wave. Therefore, it is not necessary to repeatedly change the current of the toroidal magnetic field coil, which has a larger inductance than the shape control coil, and it is not necessary to continuously increase the OH coil current in a certain direction, so an inexpensive power supply device can be obtained. It is effective.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the configuration of an embodiment of a torus-type nuclear fusion device according to the present invention, FIG. 2 is a waveform diagram for explaining the operation of the device shown in FIG. 1, and FIG. The figure is an explanatory view of the state when the cross-sectional shape of the plasma is changed, Fig. 4 is a schematic cross-sectional view showing the configuration of the conventional torus-type fusion device, and Fig. 5 is the OH coil current in the conventional torus-type fusion device. Is a waveform diagram for explaining that the plasma current is gradually reduced unless Fig. 6 is changed, and Fig. 6 is a waveform diagram for explaining the operation operation of the conventional torus-type fusion device shown in Fig. 4. is there. In the figure, 1 is plasma, 2 is a vacuum container, 3 is a toroidal magnetic field coil, 4 is an OH coil, 5 is a toroidal magnetic field coil power supply, 6 is an OH coil power supply, 8 is a shape control coil, 9
Is a power supply for the shape control coil, and 10 is a control device. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (3)

[Claims] 1. A torus-shaped vacuum container having a hollow interior,
A toroidal magnetic field coil provided on the outer periphery of the vacuum container, a toroidal magnetic field coil current for supplying a first current to the toroidal magnetic field coil, an ohmic heating coil provided on the outer periphery of the toroidal magnetic field coil, and the ohmic coil. In a torus-type nuclear fusion device having an ohmic heating coil power source for supplying a second current to a heating coil and a control device for controlling each output current amount of the toroidal magnetic field coil power source and the ohmic heating coil power source, A shape control coil wound in a direction along the central axis, and a shape control coil power supply for supplying a third current to the shape control coil are provided, and the control device controls the output current amount of the shape control coil power supply. When the plasma current flowing in the plasma generated in the vacuum container is energized, the control device is A torus-type nucleus characterized in that the current of No. 2 is periodically changed, and at the same time, the third current is controlled to be a periodic wave of the same cycle as the second current to periodically change the cross-sectional area of the plasma. Fusion device. 2. The torus-type nuclear fusion device according to claim 1, wherein the periodic wave is sinusoidal. 3. The torus-type nuclear fusion device according to claim 1 or 2, wherein a plurality of the shape control coils are provided.