JPS636488A - Plasma current keeping system in torus type nuclear fusion device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plasma current maintenance system in a torus-type nuclear fusion device that maintains a plasma current substantially constant.

[Conventional technology]

FIG. 4 is a cross-sectional view showing the configuration of a conventional torus-type nuclear fusion device. This torus-type fusion device is axially symmetrical, and the coordinates in the circumferential direction with respect to the Z axis, which is the central axis? Uniform in direction. In Fig. 4, 1 has a small radius of a.

, a torus-shaped plasma with a large radius of R6, 2 is a vacuum vessel with a torus-shaped hollow interior in which plasma 1 is formed, and 3 is a biaxial magnetic field in the plasma generation region inside the vacuum vessel 2 due to the flow of electric current. (vertical magnetic field) is generated,
This is a vertical magnetic field coil that controls the position of the plasma in the r direction, which is the large radial direction of the torus of the plasma 1, that is, the radial direction perpendicular to the Z axis. This vertical magnetic field coil 3 is composed of, for example, a plurality of coils connected in series, and each vertical magnetic field coil 3 is provided in an annular shape around the Z-axis along the outer peripheral wall of the vacuum container 2. For example, here, the vertical magnetic field coil consists of four coils, and the inner and outer coils are connected in series so that current flows in opposite directions, so as to create a vertical magnetic field in the plasma generation region. 4 is a toroidal magnetic field coil provided in a toroidal shape so as to enclose the vacuum container 2 and the vertical magnetic field coil 3;
? along the central axis inside the vacuum vessel 2 due to the current flowing? A magnetic field is formed in the plasma generation region within the vacuum vessel 2 in the direction of the plasma generation region. 5 is a vacuum container 2 due to the flow of current.
This is an ohmic heating coil (hereinafter referred to as an ○H coil) used to generate a plasma current within the coil, and is made up of, for example, a plurality of coils connected in series. Each ○H coil 5 is provided in an annular shape in the ψ direction along the torus shape of the toroidal magnetic field coil 4 outside the toroidal magnetic field coil 4. For example, the annular OH coil 5 covers the outer half of the cross section of the toroidal magnetic field coil 4. It is set up in a surrounding shape.

6 is a vertical magnetic field coil power supply for energizing the vertical magnetic field coil 3; 7 is a toroidal magnetic field coil power supply for energizing the toroidal magnetic field coil 4; 8 is an OH coil power supply for energizing the OH coil 5; 9 is the above-mentioned 3 This is a control device for controlling each of the power supplies 6 to 8. Note that the OH coil 5 and the plasma 1 form the primary side and secondary side of the transformer, respectively.

Next, the operation of the conventional torus-type nuclear fusion device shown in FIG. 4 will be explained. Now, to start the operation, first, energize the toroidal magnetic field coil 4 and the vertical magnetic field coil 3, and then energize each of them. generate magnetic fields in the direction and Z direction. next,
After hydrogen gas is introduced into the vacuum container 2 and subjected to preliminary ionization, the OH coil power supply 8 significantly changes the current IOH flowing through the OH coil 5 under the control of the control device 9, and the plasma 1 is changed according to Faraday's law. ? A voltage in the direction is generated and a plasma current Ip is induced. As a result, in FIG. 4, for example, the plasma current Ip in the ψ direction (perpendicular to the page)
begins to flow. The above operation is performed at time t0 in FIG.
~t.

After the plasma current IP is generated to a predetermined value, the current of the OH coil 5 is changed. When H is kept constant as shown by the broken line in FIG. 5 without changing, the plasma current Ip is attenuated by the resistance of the plasma 1 as shown by the broken line CL in FIG. Therefore, the electric current is applied to the OH coil 5. If H is further changed in the same direction as between t0 and t1 as shown by the solid line in FIG. It is possible to perform an operation in which the constant value is maintained as shown by the solid line C2 in FIG.

However, with this method, in order to maintain the plasma current for a long time, it is necessary to keep changing the OH coil current IOH in one direction, and the OH coil current IOH becomes extremely large, making steady operation impossible. It's impossible.

Therefore, an attempt was made to maintain the plasma current using a method different from the above method, as described in the document "Plasma Fusion Technology Research Group (held on December 10-11, 1985)" F-
``Design of power supply for θpumpρing experiment'' (Proceedings No. 136)
Reversal magnetic field pinch (pages 139-139)
1'F-〇p in RFP) type torus type fusion device
This is a method of maintaining plasma current using a constant current drive method called "pumping".

In order to maintain the plasma current Ip constant after it has been generated to a predetermined value, the current I of the toroidal magnetic field coil 4 and the current of the OH coil 5 are changed as shown in FIG. By changing H into a sine wave with a certain phase difference, magnetic helicity is injected into the plasma 1, and the plasma current Ip
It is to maintain this.

This will be explained using a formula. The magnetic helicity in a torus-type fusion device as shown in Figure 4 has K=SA-B
dv−ψqp·′Fe −(1) Here, K:
Magnetic helicity A: Vector potential B: Magnetic field vector v9 Nidroidal magnetic flux vo: Represented by poloidal magnetic flux outside the plasma. If we take the time differential of this equation (1), we get the following equation.

t Here, Φnidroidal magnetic flux v9:, plasma loop voltage E: electric field vector In equation (2), the first term on the right side represents the amount of magnetic helicity injected per unit time, and the second term represents the electrical resistance of plasma 1. It represents the amount of magnetic helicity dissipated by .

Here, we will focus on the first term, magnetic helicity injection amount.

Φ is obtained by integrating the one-round voltage ve in the poloidal direction, and Φ= S Ved t ・=-(3)
It is expressed as Now, when the loop voltage ■ of the plasma 1 and the one-round voltage ve in the poloidal direction are changed in the form of a sine wave with the same frequency ω and a mutual phase difference δ, the helicity of the first term on the right side of equation (2) - the injection amount If you take the time average.

ω Here, Ve: the amplitude of the change in Ve, voP: the amplitude of the change in vψ. According to equation (4), by selecting the phase difference δ, the helicity injection amount takes a positive value, If this is equal to the time average of the amount of magnetic helicity dissipation, the plasma current IP can be maintained.

From this, in the conventional device, in order to cause a sinusoidal change in the one-round voltage ve + loop voltage V-p in the poloidal direction, the toroidal coil current IT and the ○H coil current IOH are adjusted to a certain level as shown in Fig. 6. The plasma current rp is maintained by changing it into a sinusoidal waveform having a phase difference. In addition.

It is assumed that a sinusoidal current similar to the OH coil current IOH is passed through the toroidal magnetic field coil 4.

[Problem that the invention seeks to solve]

Since the plasma current system in the conventional torus-type fusion device is configured as described above, the current in the toroidal magnetic field coil must be changed periodically at the same time as the OH coil current, but the inductance of the toroidal magnetic field coil is relatively low. 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, which makes the toroidal magnetic field coil power source expensive. There were some problems.

This invention was made to solve the above-mentioned problems, and there is no need to keep increasing the current in the OH coil in a fixed direction, and there is no need to continuously change the current in the toroidal magnetic field coil in a sinusoidal manner. The purpose of this study is to obtain a plasma current maintenance method in a torus-type fusion device that can maintain a nearly constant plasma current without any problems.

[Means for solving problems]

The plasma current maintenance method in the torus-type fusion device according to the present invention is such that the current flowing through the vertical magnetic field coil is periodically changed to repeatedly change the horizontal position of the plasma, and the current flowing through the OH coil is maintained at the same frequency. It is controlled so that it changes periodically with a phase difference.

[Effect]

The plasma current maintenance method of the toroidal fusion device in this invention changes the horizontal position of the plasma, that is, the large radius of the plasma torus, by changing the vertical magnetic field coil current, resulting in non-uniform distribution of the toroidal magnetic field in the horizontal direction. By using this property, we can indirectly change the amount of toroidal magnetic flux that affects the plasma to increase the plasma current without continuously increasing the OH coil current in one direction or without repeatedly changing the toroidal magnetic field coil current. maintain.

〔Example〕

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

Figure 1 shows ○H coil current construction H1 vertical magnetic field coil current I
FIG. 3 is a diagram showing changes in v and toroidal magnetic field coil construction with respect to time t. FIG. 2 shows the change in the horizontal position of the plasma when the vertical magnetic field strength Bz in the vertical magnetic field changes, and the distribution of the toroidal magnetic field strength Bz in the toroidal magnetic field in the radial direction r.

FIG. 3 is a diagram schematically showing a cross section of a torus-type nuclear fusion device for explaining an embodiment of the present invention. In the figure, parts with the same symbols as those in FIG. After the generation of , when the current flowing through the toroidal magnetic field coil 4 is kept constant, the electric current Iv flowing through the vertical magnetic field coil 3 and the electric current flowing through the OH coil 5. The vertical magnetic field coil power supply 6 and the ○H coil electric f! Controls X8.

Next, the operation of one embodiment of the present invention will be explained.

○H coil power supply 6 controlled by the control device 119a
The OH coil 5 is excited to a current value up to time t0, and then at time t. O between t1 and t1
Electrical construction applied to H coil 5. By rapidly changing the OH coil current IOH in the opposite direction to the increasing direction of 8, the plasma 1
The plasma current I flowing in the plasma 1 by applying a voltage to
Stand up p.

Also, time t. During the period from to the same step t, the control device 9a,
Electrical installation of OH coil 5. 9, the current IT shown in FIG. 1 is applied to the toroidal magnetic field coil 4 via the toroidal magnetic field coil power source 7, and the current IT is applied to the vertical magnetic field coil 3 via the vertical magnetic field coil power source 6. IV
changes in a certain direction in a ramp-like manner. After time t□, the control device 9a keeps the current of the toroidal magnetic field coil 4 constant, and changes the current Iv of the vertical magnetic field coil 3 and the current IOH of the OH coil 5 in the form of a sine wave with the same period but out of phase with each other. , each power source 6 to 8 is controlled.

In this way, when the electrical construction of the vertical magnetic field coil is changed sinusoidally from time t, the magnetic field strength Bz of the vertical magnetic field also changes periodically, and the horizontal position of the plasma 1 changes as shown in Fig. 2. Plasma 1 may be on the inside as in 1a, or on the outside as in plasma 1b, and the plasma 1 horizontally reciprocates between both horizontal positions. Here, R0□ is plasma 1
Ro2 indicates the large radius which is the distance from the center of the cross section of a to the center point O, Ro2 also indicates the large radius of the plasma 1b, and R1
+1< Ro x. The plasma 1 becomes plasma 1a when the current 1v of the vertical magnetic field coil 3 reaches the peak value Iv, and becomes plasma 1b when the current Iv of the vertical magnetic field coil 3 reaches the reverse peak value Iv2.

When the horizontal position of the plasma 1 is fluctuating in this way, the magnetic field strengths B and p of the toroidal magnetic field are distributed as shown in Figure 2 in the radial direction r, and the plasma 1 as described above is distributed as shown in Figure 2. A change in horizontal position is effectively equivalent to a periodic change in the toroidal magnetic field coil current air.

For this effective toroidal magnetic field change, ○H coil current construction H having a sinusoidal change of the same frequency with a phase difference of δ = -π/2 so as to maximize equation (4). By flowing , magnetic helicity is injected as in the conventional case, and the plasma current is maintained. In this way, compared to the inductance of the toroidal magnetic field coil 4, the inductance of the vertical magnetic field coil 3 and OH coil 5 is much smaller, so even if the current flowing through them is made into a sine wave, their power supplies repeatedly generate large voltages. These power supplies themselves can be used with conventional ratings.

In the above embodiment, a case has been described in which the currents of the OH coil and the vertical magnetic field coil are changed in a sinusoidal waveform, but they may be changed in other periodic waveforms such as a triangular wave.

In addition, the horizontal position of the plasma is changed periodically, this is detected by a sensor, etc., the amount of magnetic flux of the toroidal magnetic field that affects the plasma is calculated from this, and ○
The current of the H coil may be feedback-controlled.

Further, here, a case has been described in which the horizontal position of the plasma is changed, but the vertical position of the plasma may be changed by making the magnetic field intensity distribution of the toroidal magnetic field non-uniform in the vertical direction.

Here, a reversal magnetic field pinch (RFP) method in which the toroidal magnetic field is reversed when plasma is generated has been described, but a tokamak method in which the tokamak is operated while keeping the toroidal magnetic field constant at all times has the same effect as the above embodiment.

〔Effect of the invention〕

As described above, according to the present invention, the plasma current is maintained by simply controlling the current flowing through the OH coil and the vertical magnetic field coil to change periodically.
There is no need to repeatedly change the current of the toroidal magnetic field coil, which has a large inductance compared to the vertical magnetic field coil, and there is no need to keep increasing the OH coil current in a fixed direction, making it possible to obtain an inexpensive coil power supply. effective.

[Brief explanation of drawings]

Fig. 1 is a waveform diagram during operation to explain one embodiment of the present invention, Fig. 2 is an explanatory diagram showing the state when the plasma equilibrium position is changed, and Fig. 3 is an embodiment of the present invention. A schematic sectional view showing an example of the configuration of a torus-type fusion device for explaining an example, FIG. 4 is a schematic sectional view showing the configuration of a conventional torus-type fusion device, and FIG. 5 is a conventional torus-type fusion device. A waveform diagram to explain that the plasma current gradually decreases if the OH coil current is not changed in a fusion device. Figure 6 is a waveform diagram showing the operating operation of the conventional torus-type fusion device shown in Figure 4. It is a waveform diagram for explanation. In the figure, 1 is plasma, 2 is a vacuum vessel, 3 is a vertical magnetic field coil, 4 is a toroidal magnetic field coil, 5 is an OH coil, 6 is a vertical magnetic field coil power supply, 7 is a toroidal magnetic field coil power supply, 8 is an OH coil power supply, 9a is a control device. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Figure 3 Figure 4 Figure 5 Procedural amendment (voluntary)

Claims (2)

[Claims] (1) A first current is passed through a toroidal magnetic field coil to form a toroidal magnetic field in a plasma generation region in a hollow toroidal vacuum container in a direction along the central axis of the vacuum container; Plasma in the vacuum vessel is stably confined in the plasma generation region, a second current is passed through the vertical magnetic field coil to form a magnetic field that controls the equilibrium position of the plasma in a direction perpendicular to the central axis, and an ohm The second and third plasma current maintenance methods in a torus-type nuclear fusion device generate a plasma current flowing in the plasma by passing a third current through a heating coil to generate a high voltage in the plasma generation region. A plasma current maintenance method in a torus-type nuclear fusion device, characterized in that the plasma current is maintained by making the current a periodic wave with the same frequency and a certain phase difference. (2) A plasma current maintenance system in a torus-type fusion device according to claim 1, wherein the periodic wave is a sinusoidal periodic wave.