JPH0149913B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nuclear fusion device, and in particular to a nuclear fusion device that controls direct current power supplied to a main body coil provided outside a vacuum container that seals neutral gas to be turned into plasma to generate plasma inside the vacuum container. This invention relates to a magnetic field confinement type nuclear fusion device that maintains a nuclear fusion device in a predetermined state.

Conventional nuclear fusion devices of this type have a main body coil disposed outside a vacuum vessel that seals neutral gas to be turned into plasma, so that plasma is generated within the vacuum vessel by the main body coil, and the main body coil generates plasma within the vacuum vessel. The main body coil is connected to a power supply device so that DC power is supplied, and the current supplied to the main body coil and the plasma current in the vacuum vessel are added to the operation command set value, and the It is configured to include a power supply control circuit that controls the output DC power from the power supply device so that the plasma in the vacuum container is maintained in a predetermined state.

According to a nuclear fusion device configured in this way, normally, in addition to detecting the direct current supplied to the main body coil, the plasma current in the vacuum vessel is detected,
These detection signals are taken into the power supply control circuit, and the power supply control circuit compares the signal based on the detected DC current with the operation command setting value, compares the result of this comparison with the signal based on the detected plasma current, and responds accordingly to the result of this comparison. a control signal for controlling the output DC power from the power supply device so as to maintain the plasma in the vacuum vessel in a predetermined state, and supplying the control signal from the power supply control circuit to the power supply device to maintain the plasma inside the vacuum vessel in a predetermined state. This is to control the plasma.

However, as described above, in a feedback system that takes plasma current into a power supply control circuit and controls plasma in a vacuum vessel based on the plasma current, if an abnormality occurs in the control circuit of this feedback system, or When conditions such as plasma density and degree of vacuum in the vacuum container are complicated, the plasma current in the vacuum container can become extremely large.

In this way, when the plasma current becomes excessive, there is a risk that the heat based on the plasma current will exceed the heat resistance of the vacuum vessel. If the current in the main body coil or vacuum vessel is suddenly changed, changes in the plasma and coil current will overlap, and large magnetic field stress will be generated in the main body coil and vacuum vessel, which may cause damage to the main body coil and vacuum vessel.

An object of the present invention is to eliminate the disadvantages of the above-mentioned prior art, and to quickly attenuate the plasma current when it is determined that the plasma current is excessive, thereby eliminating thermal strain in the vacuum vessel, etc. Another object of the present invention is to provide a nuclear fusion device in which the magnetic field changes are made gentler, the mechanical stress and strain are reduced, and the vacuum vessel and the coil body are prevented from being destroyed.

In order to achieve the above object, the present invention detects the value of the time rate of change of the plasma current when it is determined that the plasma current in the vacuum container is excessively abnormal, and according to the detection result, the power source of the main body coil is The current in the main body coil is attenuated by determining the slope of decrease in output voltage in the device.

Embodiments of the present invention will be described below based on the drawings.

Figure 1a is a characteristic diagram showing the attenuation pattern of the plasma current, with time on the horizontal axis and plasma current i _p on the vertical _{axis .} PB indicates the case where the plasma current rises rapidly, and _iPB indicates the case where the plasma current is intermediate between the two. 1st
Figure b is a characteristic diagram showing the attenuation characteristics of the current i _C supplied to the main body coil, and the horizontal axis is the same as that in Figure a.
The vertical axis is the coil current i _C of the main body coil, and i _CA , i _CB and i _CC are the currents flowing in the main body coil (especially the current transformer coil). Figure 1c is a characteristic diagram showing the attenuation pattern of the voltage output from the power supply device, where the horizontal axis shows time t as before, and the vertical axis shows the coil voltages v _CA , v _CB and v _CC It is. The following will explain using these drawings and FIG.

FIG. 2 is a circuit diagram showing an electrical equivalent circuit of the fusion device as seen from the main body coil, especially the alternator coil. In this figure, the symbol L _C is the inductance of the current transformation coil provided outside the vacuum vessel, and R _C is the resistance of the current transformation coil provided outside the vacuum vessel, and the inductance L _C is the resistance of the current transformation coil provided outside the vacuum vessel.
and a resistor R _C are connected in series to supply a voltage v to this series circuit. In addition, L _P is the inductance of the plasma, and R _P is the resistance of the plasma. A resistor R _P and an inductance L _P are connected in series, and both the inductances L _C and L _P form a mutual inductance. They are connected by M. Further, it is assumed that the plasma current i _P and the coil current i _C are flowing as shown in the figure. In this FIG. 2, the following equations (1) and (2) hold true.

v=R _C i _C + L _C di _C /dt+Mdi _P /dt...(1) o=R _P i _P +L _P di _P /dt+Mdi _C /dt...(2) Here, when the plasma current is constant, When i _P = K, the above equations (1) and (2) are v=R _C i _C +L _C di _C /dt...(3) o=R _P K+Mdi _C /dt...(4 ) become that way.

From the above equation (4), di=-P _P id/Mdt ...(5), and integrating the above equation (5), i _C =-R _P K/Mt+i ⁰ _C (however, i ⁰ _C is the integral constant) ...(6).

Furthermore, by substituting equation (6) into equation (3), v=R _C (−R _P K/Mt+i ⁰ _C )+L _C d/dt (−R _P K/
Mt + i ⁰ _C ) = −R _P K / MR _C t + (i ⁰ _C R _C −L _C R _P /MK)……(7)
Therefore, the voltage v supplied to the main body coil is
It can be seen that t decreases linearly with respect to time t. Also, if we set the plasma current i _P =K-lt and let the plasma attenuate linearly,
From the above formulas (1) and (2), i _C = R _P l/2Mt ² + L _P l−R _P K/Mt + i ⁰ _C ... (8) v = R _C R _P l/2Mt ² + ( L _C R _P l/M+R _C L _P l−R _P K/M
)t + (R _C i ⁰ _C + L _C L _P l-R _P K/M-Ml)...(9), and the voltage v and current supplied to the main body coil are
It can be understood that i _C is a quadratic function with respect to time t.

Therefore, if the voltage v supplied to the coil is controlled by the time function shown in equation (9) above, the plasma will decay linearly, and the plasma decay speed will be as shown above. Since the slope of the square of time (t ² ) in equation (9) is (R _C R _P /2Ml), it can be understood that it is proportional to the rate of change in the coil voltage v.

Based on the principle explained above, plasma can be attenuated by increasing the voltage v supplied to the coil as a quadratic function of time. However, since plasma attenuation needs to be controlled quickly,
It is better to approximate this to the first order for better controllability. Even if we use the first-order approximation in this way, the speed of plasma attenuation is the same as the rate of change of voltage using the quadratic function described above (either a quadratic or linear function). ). Therefore, by linearly changing the coil voltage v and controlling the slope of the change, the manner in which the plasma attenuates can be adjusted.

The following is a block diagram showing one embodiment of a nuclear fusion device according to the present invention. In the embodiment shown in this figure, an alternator coil 2 for controlling plasma current is disposed as a main body coil on the outside of a vacuum vessel 1 that encloses neutral gas to be turned into plasma, and a magnetic field coil 3 for confining the plasma is disposed. The alternator coil 2 as the main body coil is connected to the AC/DC power supply 4 so that DC power for plasma control is supplied, and the magnetic field coil 3 is connected to an AC/DC power supply device 5 so that DC power for plasma confinement is supplied, and a current detector coil current detection means 6 is provided for detecting the current supplied to the AC generator coil 2 as a main body coil. In order to detect the plasma current in the vacuum vessel 1, an electromagnetic detection coil 7 is provided in the vacuum vessel 1 as a plasma current detection means for detecting the time rate of change of the plasma current. The power supplies 4 and 5 take in the current signal and the plasma current signal, add the signal based on these to the operation command set value 9, and maintain the plasma in the vacuum vessel 1 in a predetermined state according to the result. A power supply control circuit 8 is provided for supplying a power supply control signal to each of the power supply devices 4 and 5 to control the output voltage of the power supply devices 4 and 5, and a temporal change rate signal of the plasma current from the electromagnetic detection coil 7 is input to a protection circuit 10, This protection circuit 10
The time rate of change of the plasma current is compared with the target value of the plasma current, and if the detected value is larger than the target value, a steep slope is selected, and if the detected value is smaller than the target value, a gentle slope is selected. The configuration is such that the slope of decrease in the output voltage of the power supply device 4 is controlled so as to attenuate the direct current supplied from the power supply device 4 to the alternator coil 2 as the main body coil.

Furthermore, to first explain in detail the configuration of the protection circuit 10, the protection circuit 10 includes an amplifier 11 that amplifies the temporal change rate signal of the plasma current, and a signal from the amplifier 11 that is integrated to detect the value of the plasma current. an integrating circuit 12 that
An integration start signal (abnormal signal) S that starts the integration of the integrating circuit 13, which will be described later, when the output signal E _P is compared with the set value (abnormal setting value) E ⁰ _P and E _P ≧ ^E 0 _P is established. Comparison circuit 14 forming _t and the level of the plasma current time change rate signal from the amplifier 11 are compared and determined with slope reference set values I ⁰¹ _P and I ⁰² _P as target values of the plasma current. A level determination circuit 16 switches the gain switching circuit 15 according to the result so that the input voltage αE ₀ can be input to the integrating circuit 13 (described later), and the input voltage αE ₀ is integrated by inputting the input start signal S _t . It is configured to include an integrating circuit 13 that starts integration and forms a linear waveform signal (power attenuation command signal) whose slope corresponds to the time rate of change of the plasma current. That is, the electromagnetic detection coil 7, amplifier 11, and integration circuit 12 constitute plasma current detection means, the comparison circuit 14 constitutes abnormality detection means, and the level judgment circuit 16 and gain switching circuit 15 constitute attenuation value selection means. Furthermore, the integrating circuit 13 constitutes a power attenuation command signal output means.
The power supply control circuit 8 also includes a signal converter 80 that converts a signal from a current detector 6 that detects the current supplied to the current transformer coil 2 into a predetermined signal, and a signal converter 80 that converts a signal from the current detector 6 into a predetermined signal. a subtraction point 81 that subtracts the operation command set value 9 and outputs the subtraction result;
A current control circuit 8 that forms a current control signal as a power control signal according to the signal from this subtraction point 81
2, the signal from this current control circuit 82 and the integration circuit 12 (of course, the amplifier 11 and integration circuit 12 may be provided separately from the protection circuit 10, but in this case, the amplifier 11 and integration circuit 12 a subtraction point 83 for subtracting the signal from
A plasma control circuit 84 that forms a plasma control signal according to the output signal from this subtraction point 83; a subtraction point 85 that subtracts the signal from this control circuit 84 and the signal from the protection circuit 10; a pulse phase shift control circuit 86 that forms pulse phase shift control signals for the current transformer coil 2 and the magnetic field coil 3, respectively, based on the signal (signal obtained by modifying the power control signal by the power attenuation command signal); It is configured to include a pulse amplification circuit 87 that amplifies each signal from the phase control circuit 86. Furthermore, the power supplies 4 and 5 supply AC power to the thyristor converter 42 via transformers 41 and 51, respectively.
and 52 to obtain a DC voltage according to a control signal from the power supply control circuit 8.

The operation of this embodiment configured as described above will be explained below.

The time rate of change of the plasma current in the vacuum vessel 1 is detected by the electromagnetic detection coil 7, amplified by the amplifier 11, and then integrated by the integrating circuit 12 to obtain the plasma current value E _P (proportional to i _P detected as a voltage component). Detected plasma current
E _P is compared with the set value E ⁰ _P in the comparator circuit 14,
If the comparison result is E _P ≧ E ⁰ _P , it is detected that the plasma current is excessive, and at least the integrating circuit 13 for creating an attenuated waveform of the output voltage of the power supply 4 starts integrating (Fig. 1a (see before t ₀ ).

Note that there is a difference between the comparison result point (for example, time t _C ) and the point in time t ₀ when the operation actually starts; this is because there is a time delay between the completion of the comparison and the actual output of the signal. .

In addition, the input voltage αE ₀ input to the integrating circuit 13
is the time rate of change of plasma current at the slope reference set value.
The level judgment circuit 16 detects whether or not it exceeds I ⁰¹ _P and I ⁰² _P , and the gain switching circuit 15 switches the value of α according to the result, so that the value (αE ₀ )
(see Figure 1 a),
The output signal of the integrating circuit 13 has a linear waveform whose slope corresponds to the time rate of change of the plasma current. That is, when the detected value of the time rate of change of plasma current is larger than the target value, a larger gain is selected, and when the detected value is smaller than the target value, a smaller gain is selected. Protection circuit 10
By subtracting the output signal from the output signal from the plasma control circuit 84 in the power supply control circuit 8 at a subtraction point 85, the output signal is then supplied to the current transformer coil 2 through the pulse phase shift control circuit 86 and the amplifier circuit 87. The supply voltage v _C begins to decay with the required slope without any disturbance (see Fig. 1 c t ₀ et seq.), and the current i _C in the current transformer coil 2 increases accordingly.
is also attenuated. As a result, the plasma current i _P naturally also attenuates (see FIG. 1 a t ₀ et seq.).
In addition, when the time rate of change of plasma current is i _PA ,
The voltage supplied to the current transformer coil is v _CA , the current transformer coil current at this time is i _CA , and the others have the same subscript.

According to such an embodiment, even if the plasma current becomes excessive, it is stably attenuated, thereby preventing overheating of the vacuum vessel and preventing thermal strain and mechanical stress strain.

As described above, according to the present invention, it is possible to prevent mechanical strain and thermal strain in the main body coil of the vacuum container, thereby extending the life of the device, and by almost eliminating the influence of magnetic field stress, it is possible to prevent destruction of the device. It has an excellent effect.

[Brief explanation of drawings]

Figure 1a is a waveform diagram showing the characteristics of plasma current;
Figure 1b is a waveform diagram showing the characteristics of the current flowing through the main body coil (current transformer coil), Figure 1c is a waveform diagram showing the characteristics of the voltage supplied to the main body coil, and Figure 2 is a waveform diagram showing the characteristics of the voltage supplied to the main body coil. FIG. 3 is a circuit diagram showing an electrical equivalent circuit of a nuclear fusion device. FIG. 3 is a block diagram showing an embodiment of a nuclear fusion device according to the present invention. DESCRIPTION OF SYMBOLS 1... Vacuum container, 2... Current transformer coil, 3... Magnetic field coil, 4 and 5... Power supply device, 6... Current detector, 7
...Electromagnetic detection coil, 8...Power supply control circuit, 10...Protection circuit, 13...Integrator circuit, 14...Comparison circuit, 15
...Gain switching circuit, 16...Level judgment circuit.

Claims (1)

[Claims] 1. A vacuum container that encloses a neutral gas to be turned into plasma; a main body coil that receives electric power and forms a magnetic field that generates plasma in the vacuum container;
a power supply device that supplies DC power to the main body coil;
Plasma current detection means for detecting the magnitude of the plasma current, and comparing the detected value of the plasma current detection means with an abnormal setting value of the plasma current, and outputting an abnormal signal when the detected value exceeds the abnormal setting value. The abnormality detection means, the time change rate detection means for detecting the time change rate of the plasma current, and the detected value of the time change rate detection means are compared with a reference value corresponding to the time change rate of the plasma current, and based on the comparison result, attenuation value selection means for selecting an attenuation value according to the magnitude of the prefix detection value; and power attenuation for outputting a power attenuation command signal in accordance with the attenuation value selected by the attenuation value selection means, on the condition that the abnormal signal occurs. command signal output means, coil current detection means for detecting the current flowing through the main body coil, and generating a power control signal based on the detection output of the coil current detection means and the operation command setting value,
a power supply control circuit that modifies the power control signal according to the power attenuation command signal and attenuates and controls the output power of the power supply device using the modified power control signal.