SU1536447A1 - Method of suppression of tearing instability in tokomak plasma - Google Patents

Abstract

The invention relates to thermo-nuclear power technology, in particular, tokamak-type thermo-nuclear devices, and can be used to create power reactors. The purpose of the invention is to increase efficiency by suppressing ideal plasma screw perturbations. With the help of a magnetic probe, magnetic disturbances created by the development of the tearing modes are recorded. In the resonant screw winding included in the feedback loop of the magnetic probe, an electric current is excited, and this excitation is carried out with a time delay that is chosen not less than the characteristic Alfven time. Such current formation in the resonant winding allows to suppress the effect of ideal plasma perturbations, excited by the action of a screw winding, and to provide deeper suppression of the tearing instability in tokamak.

Description

The invention relates to thermoelectric power technology, in particular tokamak-type thermo-nuclear devices, and can be used to create power reactors.

The purpose of the invention is to increase efficiency by suppressing ideal plasma screw perturbations.

The method of suppressing the tearing instability in tokamak plasma is carried out as follows.

Inside the discharge chamber of a tokamak, a magnetic probe is placed in the shadow of the limiter to record disturbances of the poloidal magnetic field caused by the development of the tearing instability of the plasma cord.

In the shade of the limiter is placed also the resonant screw winding with a step

screw corresponding to the pitch of the screw tiring mode with the maximum amplitude. Usually the most dangerous mode with a poloidal wavenumber m 2.

From the frequency spectrum of the magnetic probe signal, a screw harmonic signal having the largest amplitude is extracted. The most intense monica can be distinguished, for example, using an electric frequency filter. Then, in the helical resonant winding included in the feedback target of the magnetic probe, the feedback current is excited. A high-frequency amplifier can be used to power the resonant winding, the output of which is connected to a magnetic probe. In this case, the feedback currents form with time lag

with

2

4b 1

with respect to the signal received from the magnetic probe. The value of the time delay it is chosen to satisfy the relation

About i fct B.

QO - unperturbed more than equal

plasma magnetic field; JQ is the plasma density on the resonant magnetic surface.

R

A low pass filter can be used to delay the signal.

Thus, in the resonant screw winding, an electric current j (t) is generated, the law of time variation of which is given by the expression

I (t) -, E-V (t - bt),

where E is the feedback gain factor; y - magnetic flux of the selected

screw harmonics of plasma disturbance;

t is the current time.

The feedback currents of the screw resonance winding cause not only the suppression of the tearing mode, but also the ideal screw plasma perturbation of the same poloidal structure as that of the tearing mode. However, although the current of such an ideal screw disturbance is opposite to the current of the shooting range of the r-mode, its radial distribution is different from the radial distribution of the current of the tearing mode. In this case, the ideal plasma perturbation current distorts with its magnetic field the signal from the magnetic probe designed to measure the magnetic flux of the tearing mode. This reduces the possibility of suppressing the tearing mode.

,,

The characteristic time to establish ideal plasma oscillations is of the order of the Alfven time.

t -.

Therefore, the amount of time delay

Jq $

20

25

, Q -.,

35

40

50

it t. The introduction of this time delay leads to an additional decrease in the amplitude of the tearing mode by a factor of 2-3. In addition, the frequency of the oscillation of the signal from the magnetic probe is reduced, which makes it possible to reduce the energy costs of powering the screw resonant windings.

Claims (1)

Invention Formula A method for suppressing the tearing instability in a tokamak plasma, including recording a disturbance signal of a poloidal magnetic flux by a magnetic probe located in a tokamak chamber, extracting the harmonic signal with maximum amplitude and air from the frequency spectrum Bundling in the resonant screw winding surrounding the plasma cable, an electric current j (t) feedback corresponding to the change in time of the selected harmonic signal, characterized in that zi set according to the ratio T (t) - E-q (t - t), where E is the inverse gain factor connection; (jf - selected magnetic flux screw harmonics of plasma disturbance; t is the current time; Jit is the time delay of the excitation of the electric current in the screw winding relative to the signal of the magnetic probe, while the time delay & t is chosen to satisfy the relation CU fct, where B0 is unperturbed polondalnoe plasma magnetic field; O is the plasma density on a resonant magnetic surface perturbed by the tearing-instability-4.