JPS62259085A - Plasma balance controller - 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 equilibrium control device that controls the position and cross-sectional shape of plasma, so-called equilibrium, in a torus-type nuclear fusion device, and particularly to a tokamak-type nuclear fusion device. The present invention relates to a plasma equilibrium control device suitable for obtaining good control characteristics in the device.

[Conventional technology]

Conventionally, in a torus-type nuclear fusion device and a tokamak-type nuclear fusion device, a poloidal coil is arranged to control the position and cross-sectional shape of plasma so that z=b. This poloidal coil has the function of generating a magnetic field (balanced magnetic field) for controlling the electromagnetic fluid balance of the plasma, that is, the position and cross-sectional shape of the plasma.By the way, the position and cross-sectional shape of the plasma are determined by the plasma current. It tries to change from moment to moment depending on the pressure and pressure. Therefore, the poloidal coil must have the function of changing the flat magnetic field according to the plasma current, pressure, etc., and maintaining the plasma position and cross-sectional shape as desired.

As a device for controlling the plasma position and cross-sectional shape, for example, a device as shown in FIG. 4 has been used. In FIG. 4, ARP is the displacement of the plasma center, which is an amount measured by a magnetic probe or the like. 'Vhg'! 'b+
M/c + and va are magnetic flux sensors 5a and 5, respectively.
Poloidal coil 4 measured by b, 5c, 5d
This is the magnetic flux between a, 4b, 4c, 4d and the plasma 1.

For example, a magnetic flux loop is used as the magnetic flux sensor. The input vo of the differential amplifier 9b is the target value of magnetic flux,
Created by a function generator, etc. In this example, the poloidal coils 4a to 4h are the toroidal coil 3 and the vacuum vessel 2.
Because it is installed between the poloidal coils 48 and 4
The characteristic is that h and plasma 1 are close to each other.

The poloidal coils 4e, 4f, 4g, and 4h are arranged so as to generate a uniformly distributed vertical magnetic field in the region where plasma is generated (inside the empty container 2).

The uniformly distributed vertical magnetic field has the function of changing the position of the plasma center without significantly changing the cross-sectional shape of the plasma.
By adjusting the current flowing in g and 4h, the displacement Δ of the plasma center is
The position of the plasma center is controlled so that Rp becomes 0.

On the other hand, the principle of this shape control using the control power sources 78 to 7d and the poloidal coil group function will be explained using FIG. FIG. 5 shows changes in magnetic flux around the plasma (measurement points indicated by black circles) when plasmas having shapes like Cases A, B, and C are confined. This figure shows that there is a one-to-one correspondence between the magnetic flux distribution around the plasma and the cross-sectional shape. Therefore, controlling the magnetic flux around the plasma is equivalent to controlling the cross-sectional shape. The control device in FIG. 4 is based on this principle, and the magnetic flux ma, ,v,.

The poloidal coil current is adjusted so that the maCtqa matches. In the example of FIG. 4, each difference power amplifier 9a to 9d
The control power source 7b is vb HVO, and the control power sources 7a, 7c, and 7d are each ψ.

-Ma11. 'FC-mar, ma-4-ma b generate voltages proportional to each other, and individually adjust the currents of the poloidal coils connected to each control power source.

Related devices of this type include, for example, Nuclear Fusion, 22 (1982), pages 797 to 805 (Nuclear Fusion, 22 (1982), pp. 797 to 805).
n22 (1982) pp797-805).

[Problem that the invention seeks to solve]

The above conventional technology has a problem in that it can only be applied to a nuclear fusion device in which a poloidal coil is placed inside a toroidal coil. This is because if the poloidal coil is placed outside the toroidal coil, the poloidal coil and the magnetic flux measurement point are separated, and the magnetic flux at each measurement point changes due to the influence of all the poloidal coil currents, which cannot be handled by individual control of each poloidal coil.

However, in large fusion devices such as commercial fusion reactors, poloidal coils are generally placed outside the toroidal coils to facilitate disassembly and assembly. If the poloidal coil is placed inside the toroidal coil, it will be necessary to cut and connect the superconducting coil, and problems such as strength deterioration will occur at the joints, making the fusion device expensive. Therefore, the above-mentioned conventional technology cannot be applied to large-scale nuclear fusion devices such as commercial fusion reactors, but can be said to be an effective technology for small-sized or medium-sized nuclear fusion devices.

Therefore, an object of the present invention is to provide a plasma equilibrium control device that can be applied to a large-scale nuclear fusion device in which a poloidal coil is placed outside a toroidal coil and has good control characteristics for the center position and cross-sectional shape of plasma. It is.

[Means for solving problems]

In order to achieve the above object, the present invention calculates the deviation between each measured value obtained by the magnetic flux detection means and the target value at each point, and calculates the value obtained by adding the function of these deviations for all measured values. The present invention proposes an apparatus configuration in which a control calculator is provided that outputs the current of the poloidal coil group as each control current so as to minimize the evaluation function.

More specifically, the evaluation is performed using a deviation function obtained by multiplying the square of each deviation by a weight.

[Effect]

In the present invention, by cooperatively changing the poloidal coil current, the magnetic flux at multiple points around the plasma all match the target value, and the plasma center position and cross-sectional shape are controlled to the desired position and shape. This is because, as described above, there is a one-to-one relationship between the plasma equilibrium and the magnetic flux distribution around the plasma.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure is a diagram showing an example of a plasma equilibrium control device according to the present invention together with a partial cross section of a tokamak-type nuclear fusion device. Control power sources 78 to 7g are connected to the poloidal coils 4a to 4g of this embodiment, respectively, and the poloidal coils 4a ~4
The current in g can be adjusted freely. 5a~
5j is a magnetic flux loop as a magnetic flux sensor around the plasma, which outputs a voltage proportional to the time differential of the magnetic flux at the position of each magnetic flux sensor. The magnetic flux detectors 68 to 6j integrate the output voltages of the magnetic flux sensors 5a to 5j to determine the magnetic flux V at the position of each sensor. Here, 1m is a number that distinguishes the magnetic flux sensors, and the magnetic flux sensors 5a to 5j
Correspondingly, m=1 to 10. The control calculator 8
~'? Changes in the coil current δ11 to δf are obtained from the target value of magnetic flux at 1° and the position of each magnetic flux sensor (previously input to the control calculator 8), and input to the control power sources 78 to 7g. Here, the subscripts 1 to 7 of δ are numbers that distinguish the poloidal coils, and are 1 to 7 corresponding to the poloidal coils 4a to 4g.The control power supplies 78 to 7g are the currents of the poloidal coils 4a to 4g according to δ11 to δF, respectively. control.

The calculation algorithm of the control calculator 8 will be explained below. Assume that values corresponding to the desired plasma shape are input as the target values of magnetic flux vot to maos, as explained in FIG. 5. At this time, the magnetic flux machining force ~VtO at the position of the magnetic flux sensor around the plasma is v1=11F61. Ma2~MaJ
, x, ``ma0'', the plasma equilibrium configuration conforms to the desired shape.

Therefore, consider δv n ='F n-1F o --(2) as the evaluation function. Here, m is a number that distinguishes the poloidal coils 4a to 4g, n is a number that distinguishes the magnetic flux sensors 58 to 5j,
nc is the number of poloidal coils, and ns is the number of magnetic flux sensors. φ and fi are the magnetic fluxes at the position of the n-th magnetic flux sensor when a current to 1 flows through the m-th poloidal coil.

Wo is a weight for each of the magnetic flux sensors 58 to 5j, and is usually 1. The control calculator 8 determines coil current changes δ11 to δF that minimize the evaluation function J. δ muff≠0(
n=1~r1g), that is, when the plasma equilibrium configuration does not match the desired shape, the coil current changes δ1~δI
7≠0 is output to the control power supplies 7a to 7g.

Plasma equilibrium is controlled by the control electrodes 78 to 7g,
δma, =O(n = 1-ns), that is, if the plasma equilibrium configuration matches the desired shape, δ■1~δ1.7=
It becomes O.

Specifically, the condition for minimizing the evaluation function J is to set J to δ'
Partial differentiation with respect to Fn results in ∲, l, where equation (3) is a simultaneous equation.

By solving equation (3), the coil current change δ1 to δInc can be obtained.

FIG. 2 is a diagram showing the calculation algorithm of the control calculator 8 of the embodiment in FIG.
0j outputs a voltage corresponding to the target magnetic fluxes 1 to ψo. The differential amplifiers 98 to 9j calculate the difference δ'Fox between the measured magnetic flux values Ma1 to Ma10 and the target magnetic flux ψOX~Maoto.
The one-matrix operation logic 10a for calculating δmaoio is (5
The zero matrix calculation logic 10b, which is used to obtain the variables b1 to b7 shown in equations (), is used to solve the simultaneous equations of equation (3) and obtain the changes in the coil current δ1 to δI7. Expressing equation (3) as a matrix relational expression.

Aδ engineering = 1) 1 ... (6)
Here, A is a square matrix whose elements are Al, δ is a vector whose elements are δE~δF, and b is b1~b
1 matrix operation logic 10 which is a vector whose elements are
b is a 1-matrix operation logic 10a, 10b that stores the inverse matrix A''''5 and calculates δfactor by δI=A-1b.
For large fusion devices that do not require high-speed control, a control computer can be used to create a flexible system. In the case of a small or medium-sized nuclear fusion device, high-speed control is possible by using hard-wired logic as the matrix calculation logic 10a, 10b.

FIG. 3 is a diagram showing another embodiment in which voltage dividers 21b to 21j are arranged in place of the DC power supplies 20b to 20j in the control calculator 8 of the embodiment in FIG. Since the ratio of the magnetic flux ψ at the position of the magnetic flux sensor is maintained constant, the same effect as in the embodiment of FIG. 1 is obtained.
Moreover, DC f! ! It is economical because there are few sources.

It should be noted that if the matrix operation logic in the embodiment shown in FIG. 2 is assembled using a parallel computer, a high-speed and flexible plasma equilibrium control device can be obtained.

【Effect of the invention〕

According to the present invention, even in a fusion device in which a poloidal coil is installed outside the toroidal coil, the shape of the plasma surface can be controlled freely and with high precision, so that the plasma of a large fusion device such as a commercial fusion reactor can be High-temperature, high-density plasma can be maintained for a long time by avoiding contact with metal walls, etc.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of the plasma equilibrium control device according to the present invention together with a partial cross section of a tokamak-type nuclear fusion device, and FIG. 2 is a diagram showing an example of the calculation logic of the control calculation unit of the embodiment in FIG. 1. , Figure 3 is a diagram showing another example of the calculation logic, Figure 4 is a diagram showing an example of a conventional plasma equilibrium control device together with a partial cross section of a tokamak type fusion device, and Figure 5 is a diagram showing plasma equilibrium control. FIG. DESCRIPTION OF SYMBOLS 1... Plasma, 2... Vacuum container, 3... Toroidal coil, 4... Poloidal coil, 5... Magnetic flux sensor, 6... Magnetic flux detector, 7... Control power supply, 8
...Control computing unit, 9...Differential amplifier, 10...Matrix operation logic, 20...DC power supply, 21...Voltage divider.

Claims (1)

[Claims] 1. A plasma comprising a poloidal coil group for controlling plasma equilibrium, a control power source for exciting the coil group, and a plurality of magnetic flux detection means for measuring magnetic flux at a plurality of points around the plasma. In the equilibrium control device, the deviation between each measured value obtained by the magnetic flux detection means and each target value is determined, and a value obtained by adding the function of the deviation to all measured values is used as an evaluation function. 1. A plasma equilibrium control device characterized in that a control calculator is provided for outputting a command for controlling the current of the poloidal coil group to each control power source to minimize the current of the poloidal coil group. 2. The plasma equilibrium control device according to claim 1, wherein the control calculator includes a circuit that performs evaluation using a deviation function obtained by multiplying the square of each deviation by a weight. Balance control device.