JPH0785113B2 - Plasma position profile detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a plasma position shape detecting apparatus, and more particularly, to a configuration for removing an integration error of the plasma position shape detecting apparatus suitable for controlling the plasma of a nuclear fusion device. It is about.

[Conventional technology]

A plasma position shape detection device that has been conventionally proposed for plasma control detects a change in magnetic field due to displacement of plasma current as a voltage signal by a magnetic probe, integrates this signal to calculate a magnetic field, and detects a position shape. It was a thing.

For example, "High-speed signal processing in plasma feedback control" by the inventors, 1985, Symposium on
Fusion Engineering, pp586 ~ 589 (High Sp
eed Signal Processing In Plasma Feedback Control, 1
985, Symp. On Fusion Engineering), there is a method in which a pulse train obtained by V / F converting a magnetic probe signal is calculated by a counter and equivalently integrated. In such a system, a correction circuit for correcting the integration error due to the offset drift of the analog circuit immediately before the start of the integration is provided to minimize the influence of the integration error on the feedback control of the position shape of the plasma.

[Problems to be solved by the invention]

In the above-mentioned conventional technique, the accumulation of error does not become a serious problem in the apparatus in which the plasma maintenance time is about ten seconds or less.

However, when the plasma is maintained for 100 seconds or more or continuously as in the future fusion device, the accumulation of errors accompanying the integration process has a great influence on the plasma position shape control. That is, as long as the integrator, especially the V / F converter is composed of an electronic circuit, it is essentially unavoidable that the error remaining in the circuit is accumulated by the integration process. In the above, there is a problem directly related to the shape control accuracy.

An object of the present invention is to provide a plasma position shape detecting apparatus which can obtain an accurate plasma position shape detecting apparatus without accumulating long-term errors.

[Means for solving problems]

In order to achieve the above object, the present invention provides a magnetic probe which is arranged in the vicinity of plasma and converts a fluctuation of a magnetic field due to a displacement of a plasma current into a voltage signal, and a position of the plasma by integrating a voltage signal from the magnetic probe. Detect the shape,
An integrator that outputs to a feedback control device for controlling the plasma position shape, an optical sensor that is placed in the vicinity of the plasma and optically detects the position and outer shape of the plasma and converts them into an electrical signal, and an electrical signal from the optical sensor Plasma position shape detection consisting of a magnetic surface calculation device that calculates the instantaneous magnetic surface of the plasma and outputs an initial integration value that causes the integrator to be offset at each fixed period or each time the integrator error reaches a predetermined value. It proposes a device.

The integrator is at least two integrators that are alternately switched between the side reset to the initial integration value and the side entering the integration operation at every fixed period or each time the integration error during the integration operation reaches a predetermined value. It can also be configured.

[Action]

The integrator can perform high-speed integration calculation on the order of milliseconds like the feedback control of plasma, but an error is accumulated in the integration result over time.

Therefore, the calculation speed of the magnetic surface calculation device, which has a relatively low calculation speed but does not include an integration error, is used as an initial setting value, and the integrator is offset at each constant cycle or each time the error of the integrator reaches a predetermined value. A new integration operation is started regardless of the error accumulated during the previous integration. In this way, errors will not be accumulated for a long time, and an accurate plasma position shape detection signal will always be obtained.

When the number of integrators is two, there is a time margin for setting the initial value of the integrator when it is not operating, and therefore, there is an advantage that it is not limited by the operation speed of the magnetic surface operation device.

〔Example〕

 Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the plasma position shape detecting device according to the present invention. In the figure, 1 is an annular plasma whose position shape is to be detected and controlled,
Good for magnetic field due to current flowing in itself and circular magnetic field,
It is enclosed in an annular vacuum container (not shown). 2 is
The magnetic probe 3 that detects a change in the magnetic field due to the plasma current when the position shape of the plasma changes is an integrator that integrates the detection signal of the magnetic probe. Since the calculation of the position shape requires the value of the magnetic field component, it is necessary to integrate the magnetic probe signal corresponding to the change in the magnetic field. The integrator 3 is
Isolation amplifier 31 that amplifies the signal from the magnetic probe, V / F converter 32 that converts the analog voltage signal of its output into a pulse train, and a counter that calculates the pulse train from the V / F converter and integrates them equivalently. It consists of 33 and. In such a digital integration method, the initial offset of the integrated value, which will be described later, can be corrected simply by setting it in the up-down counter, so the correction operation is easier and the calculation result is more accurate than the analog integration method.

The output signal of the integrator 3 is sent to the feedback control device 6 for controlling the plasma position and shape, and is used to control the position and shape of the plasma via the power supply device 7. That is, the feedback control device 6 includes the magnetic probe 2
Based on the result of integration of the output signal from the integrator 3 by the integrator 3, a command value to the power supply device 7 is calculated and sent in order to control the energizing current to the plasma control coil and control the plasma.

In the present invention, in order to eliminate the influence of the error accumulated in the integrator 3, the plasma 1 is essentially included in the system.
The magnetic surface computing device 5 for computing the magnetic cross-sectional shape is used to compute an initial integration value for offsetting the integrator 3 at regular intervals or each time the error reaches a predetermined value. In the case of the present embodiment, as the optical sensor for optically detecting the position and outer shape of the plasma, the photodiode array 51 and the photodiode array 52 are adopted, the light from the plasma is instantaneously sampled, and its signal is measured. Since the position shape of the plasma is calculated by processing, the calculation time is longer than that of the integrator 3, but the optical sensor has no storage effect, and the magnetic surface calculation device does not integrate the signal from the optical sensor. There is no accumulation of.

The output from the magnetic surface calculation device 5 is input to the up-down counter 33 of the integrator 3 and becomes an integration initial value that causes the integrator 3 to be offset at the start of integration.

As another example of the magnetic surface calculation device 5, a method of simulating plasma with a plurality of line currents and obtaining respective positions of the plurality of line currents by balance calculation of an external magnetic field has recently been tried. This is due to the magnetic field B _p originally generated by plasma and the magnetic field detected by the magnetic field detector, as shown in FIG. Difference from The value of Ip _i is determined so that is minimized. The value of the line current thus determined represents the plasma at that time. Therefore, Is the difference between the magnetic field generated by the actual plasma and the magnetic field measured by the magnetic field detector, so this value can be initialized in the integrator as a correction value.

FIG. 2 is a diagram showing an embodiment in which a plurality of integrators 3 and 4 are switched and used by the switchers 81 to 83 which operate synchronously.

The signal from the magnetic probe 2 is input to one of the integrators (for example) 3 by the switch 81, and the integration result is switched by the switch 83.
Is sent to the feed back control device 6 via. From that point onward, it is similar to the case of the embodiment shown in FIG.

On the other hand, the calculation result of the magnetic surface calculation device 5 is sent via the switch 82 to the integrator 4 which is not performing the integration operation, and becomes an integration initial value for offsetting it.

In this way, if two integrators are switched and used at regular intervals or each time the error reaches a predetermined value, the error can be eliminated, and the initial value setting of the inactive integrator can be performed by other integrators. Since it may be completed during the operation, there is a time margin and there is no limitation due to the calculation speed of the magnetic surface calculation device.

FIG. 3 shows the plasma density, the plasma position change, and the output of each integrator, which represent the plasma state during operation in the embodiment of FIG.

When the fusion device is operated, the plasma density is shown in the figure (A).
It changes like. The plasma position fluctuates within a certain range as indicated by the solid line in FIG. 9B if the plasma feedback control is appropriate. However, in reality, since an error is accumulated by the integrating operation of the detection device, a drift is included as shown by a broken line.

Therefore, in the detection apparatus of the present embodiment, as shown in FIGS. 7C and 7D, the integrators 3 and 4 are alternately in charge of time 0 to t ₁ , t ₁ to t ₂ , and so on. I did it. If even this way filed in a relatively short period of time there is accumulation of errors, for example, the initial setting value of the integrator 4 at time t _1, rather than the value in the integrator 3 time t _1, the time t ₁ before the The correct value calculated by the magnetic surface calculation device 5 is set within the range of the time T, the influence of the accumulation error of the integrator 3 is eliminated, and the integration operation is newly continued.

The magnetic surface calculation can improve the calculation accuracy by selecting and executing a time when the plasma state is stable during continuous operation, as at time T in FIG.

If the operating time T of the magnetic surface computing device is longer,
Since the timing calculation can be started further back within the operating time of the integrator 3, the switching timing of the integrator is not limited by the operating time T.

In this embodiment, since the digital integration method is used, the initial value at the time of switching the integrator is simply set in the up-down counter, so that the correction is easy.

It is needless to say that the calculation of the integrator initial setting value may be performed by the above-described method based on plasma equilibrium calculation other than the optical means of this embodiment.

〔The invention's effect〕

According to the present invention, since the initial value for offsetting the integrator is reestablished at regular intervals or each time the error reaches a predetermined value, an accurate plasma position shape detection signal can be obtained without accumulating long-term error. A plasma position shape detecting device capable of outputting

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a plasma position shape detecting device according to the present invention, FIG. 2 is a block diagram showing an embodiment in which a plurality of integrators are switched and used, and FIG. 3 is an embodiment shown in FIG. FIG. 4 is a diagram showing an operating state of FIG. 4, and FIG. 4 is a diagram showing a method of calculating a magnetic surface by a magnetic field balance calculation. 1 ... plasma, 2 ... magnetic probe, 3 ... integrator,
4 ... integrator, 5 ... magnetic surface computing device, 6 ... feed back control device, 7 ... power supply device, 31 ... isolation amplifier,
32 …… V / F converter, 33 …… counter, 81-83 …… switch.

Claims (2)

[Claims] 1. A magnetic probe which is arranged in the vicinity of the plasma and converts the fluctuation of the magnetic field due to the displacement of the plasma current into a voltage signal, and the voltage signal from the magnetic probe is integrated to detect the position and shape of the plasma. An integrator which outputs to a feedback control device for controlling the position and shape, an optical sensor which is arranged in the vicinity of the plasma and optically detects the position and the outer shape of the plasma and converts them into an electric signal, and a voltage signal from the optical sensor. And a magnetic surface calculation device for calculating an instantaneous magnetic surface of the plasma and outputting an initial integration value for offsetting the integrator at fixed intervals or whenever the error of the integrator reaches a predetermined value. Shape detection device. 2. The integrator according to claim 1, wherein the integrator is reset to the initial value of the integration every time the constant cycle or each time the integration error during the integration operation reaches a predetermined value. A plasma position shape detection device comprising at least two integrators which are alternately switched to the entrance side.