SU1618265A1 - Antenna device for exciting slow waves in plasma with magnetic trap - Google Patents

Abstract

The invention is intended to excite slow kinetic waves in a plasma created in magnetic traps, traveling mainly in one direction along the magnetic field. The purpose of the invention is to simplify the device when used to excite slow kinetic waves traveling mostly in one magnetic field direction. The device consists of two electrically conductive screens 1 and 2 located parallel to the plasma boundary and magnetic field and connected to the RF energy generator 3 Screen length 1 is not less than the attenuation length of the surface slow electromagnetic wave0 In the second screen there is a slot to which the passive resonant element 4 is connected whose natural frequency is close to the frequency of the excited slow waves. The distance between the passive gap and the gap to which the high-frequency generator is connected is close to a quarter of the length of the surface slow wave. of an electromagnetic wave. In the gap between the screens and the plasma boundary, using RF generator 3, surface slow electromagnetic waves are excited, traveling along the magnetic field to both sides of the crack. The wave traveling towards the passive slit transfers a smaller RF energy flow than is full running in the opposite direction. As a result, slow kinetic waves are excited in the plasma, traveling mostly in one direction along the magnetic field. 1 il. . (Ls about soe about joint venture

Description

The invention relates to antenna devices for exciting electromagnetic waves in a plasma and can be used for microwave plasma heating, maintaining a steady-state current. closed magnetic traps in

. number in a thermo-nuclear reactor, as well. for diagnostic purposes, for example, to receive radiation from a plasma. The aim of the invention is to simplify the design of the antenna device when it is used to excite slow kinetic waves, which lead mainly in one direction along the magnetic field.

In the antenna device containing two. located parallel to the plasma boundary and separated by a slot of an electrically conducting screen transverse to the direction of the magnetic field, to the edges of which an RF generator is connected, the goal is achieved by the fact that one of the screens has a length of 1 that satisfies condition 1.1, where 1 is the attenuation length surface slow electromagnetic wave (MV (E)), and in the other screen there is a second slit, to which a passive resonant element is connected, the intrinsic frequency of which is close to the frequency of the excited slow waves, and the distance between slots close to the quarter length of the surface electromagnetic slow volny0

The drawing shows the scheme of the proposed antenna device,

Antenna device consists of two electrically conductive screens 1 and 2s parallel to the plasma boundary and magnetic field B and separated by a narrow slit. A high-frequency generator is connected to the edges of the screens at the click of the screen. The screens are located at a distance d from the plasma boundary. B screen 2 is at a distance 5 from the exciting slit equal to a quarter of the length of the surface MW (e) the second slit is made, to which the passive resonant element is connected, A, whose own frequency coincides with the frequency of the slow waves

The screen length 1 1 and the distance between the slits o are determined by calculating the attenuation length I1 and the wavelength of the surface MB (E), based on the size of the vacuum gap d and the parameters of the boundary plasma 5. To do this, solve the known dispersion equation for the surface MV (E) g

Ni (N

(N

, m - i, + e, n1, A2 - ch

-N ,,). th

 AND

Ых5- -Г - d) О,

where S-S e, x2), 1g - -yg-h.

Here f, s Ј, components of the plasma dielectric tensor, a – ЈЈ are the heat additive to the plasma dielectric tensor

This equation has a complex solution x, and the wavelength of the surface MV (E) is determined by

R e x Ј N ,, 2

)

CONM

- speed of light in vacuum, and attenuation l through

 "ABOUT

)

u 5 0

five

0 5 0

five

0

five

where G3 is the HF (E) frequency.

Antenna device on the example of excitation - slow kinetic waves (MB (K)) works as follows

Using an RF generator 3 connected to the edges of the electrically conductive screens 1 and 2, surface MV (E) is excited in the gap between the plasma boundary and the screens, running along the magnetic field to both sides of the slit. As the propagation progresses, the surface MB (E) attenuate due to radiation of a slow kinetic wave MB (K) propagating deep into the plasma

Since the screen length is 1 1, where 1 is the attenuation length of the surface MV (E), the surface wave will almost completely attenuate as it propagates along the magnetic field to the end of the screen due to the transfer of energy MV (K) excited in the plasma. Therefore, the amplitude reflected from The wave screen will be insignificant. Thus, to the left of the exciting slot along the magnetic field, the plasma wave exciting plasma wavelet (9) MV (K) 0 will propagate.

The MV (3) surface propagating along screen 2 will almost completely reflect from the passive gap and there will be a hundred MV (E) in the region between the slits. The amplitude of the transmitted wave propagating to the right from the passive gap will be insignificant.

As a specific example of the device, an antenna was considered to excite MB (K), running predominantly in one direction along a magnetic field in a tokamak-type installation with the following parameters of a near-boundary plasma: Hc

- 4th cm-lt; ev, w i

- (, 95, B0 - AT, R0- 5 m, the working gas is deuterium, where He is the plasma density, T; and Tv are the temperatures of ions and electrons, oZ is the circular frequency of the generator, Qt is the ion-cyclotron frequency, Bn the magnitude of the constant magnetic field, -. R is the large radius of the tokamak.

In this case, for d 0.5 cm, the attenuation length is 1 (0.73 m, 1.72 m and thus the screen length is 1 1 3 1 2.2 m, and the distance between targets S t 0.43 MO that under these conditions the amplitude of the traveling MV (K) along the screen} in which the passive gap is made is approximately 2.4 times smaller than the amplitude of the MB (K) packet running in the opposite direction

The advantages of the antenna device are that, when excited in plasma MB (K), there is no need to use a large number of feeder inputs into the vacuum chamber of the magnetic trap, as well as additional devices for phasing them. An antenna device allows excitation in plasma of slow kinetic waves (Bernstein ion waves) traveling in one direction along a magnetic field, which allows such devices to be used for

16182656

Claims (1)

maintaining stationary current in tokamak and stellarator Formula of the invention  Antenna device for exciting slow waves in a plasma trapped in a magnetic trap, containing two Plasma of a magnetic trap and a transverse screen split transverse to the direction of the magnetic field, to the edges of which a high-frequency power generator is connected, characterized in that, in order to simplify the device when it is used to excite slow kinetic waves traveling mainly in one direction along magnetic field, one of the screens has a length of 1, satisfying the condition J / l, where l is the attenuation length of the surface slow electromagnet. wave, and in the other screen there is a second slit, to which a passive resonant element is connected, whose natural frequency is equal to the frequency of excited slow waves, the distance between the slits is equal to a quarter of the length of the surface slow electromagnetic wave