JPS6362080B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Generally, in order to obtain high-temperature, high-density plasma, it is necessary to confine the plasma by an external magnetic field and simultaneously heat the plasma by adiabatic compression, high-frequency heating, Joule heating, or the like.

Although the heating method of the present invention belongs to the above-mentioned high frequency heating, its principle is completely different from conventional methods.

In conventional heating methods, in order for the heating electromagnetic field to reach the heating region of the plasma, the frequency of the heating electromagnetic wave must be selected within a pass frequency band determined by the temperature and density of the plasma. Also, so-called resonant heating is usually used to activate the energy absorption process from waves to particles. Therefore, as a power source for heating electromagnetic waves, an extremely high frequency and high output oscillation source of several to several + GHz is required.

Figures 1 to 3 are conceptual diagrams for explaining the heating principle of the present invention. Reference numerals 1, 2, and 3 represent three conductors constituting a triode vacuum tube type active distributed coupling line, each of which is a triode, for example. They correspond to the cathode, grid, and anode of a vacuum tube, and are held in a closed container 4, with ionized gas sealed inside 4, and 5 for supplying a bias voltage to a triode vacuum type active distributed coupling line. In the DC power supply, 7 indicates the direction of the external magnetic field generated by the magnetic field generator 6.

First, considering the case where the ionization degree of the ionized gas in 4 is sufficiently low, since electrode conductors 1, 2, and 3 have the function of a triode vacuum tube, the vacuum tube constant (or Y-parameter per unit length) ) and the capacitance and inductance between 1, 2, and 3. When a certain condition (gain propagation condition) is satisfied, the electromagnetic wave is 1,
2 and 3 in a gain manner. If 1, 2,
If 3 is configured in a loop as shown in Fig. 4 shown later, it is clear that it will oscillate even without inputting a high frequency signal from a high frequency oscillator, and also as shown in Figs. 1 to 3. 1, 2, 3 even in a straight line
It is possible to cause oscillation by terminating both terminals with appropriate impedance. The oscillation frequency at this time mainly depends on the length of the heating tube or loop length. This electromagnetic wave propagates through the ionized gas, so as it propagates, part of the electromagnetic energy is absorbed by the ionized gas through Coulomb collisions between electrons and positive ions in the ionized gas, increasing the plasma temperature and plasma density. . As a result, the attenuation due to the plasma increases, and if this exceeds the gain of the triode vacuum tube active distributed coupling line, the propagation of the heating electromagnetic wave along the heating tube becomes loss propagation, and the plasma temperature and plasma density decrease. In the end, the heating electromagnetic wave continues to propagate without gain and loss at a plasma temperature and plasma density where the attenuation by the plasma and the gain by the triode vacuum tube active distributed coupling line are in balance. Therefore, the gain characteristics of the triode vacuum tube active distributed coupling line, that is, the vacuum tube constant per unit length, the capacitance per unit length between the three electrode conductors, the inductance, and the length of the heating tube or loop length must be set appropriately. For example, plasma can be heated to a desired temperature and density using heating electromagnetic waves of any frequency. Furthermore, since the energy of the heating electromagnetic waves is directly supplied by the bias DC power supply 5, it is possible to easily obtain high-output heating electromagnetic waves.

Furthermore, in order to isolate the high-temperature, high-density plasma from the wall surface of the closed container 4, it is necessary to confine the plasma by applying an external magnetic field as shown in FIGS. 1 to 3. FIG. 1 shows the case where the direction 7 of the external magnetic field coincides with the propagation direction of the heating electromagnetic wave, and FIGS. 2 and 3 show the case where both directions are perpendicular to each other. When an external magnetic field exists in this way, depending on the frequency of the heating electromagnetic wave, it can produce clockwise circularly polarized waves, counterclockwise circularly polarized waves, Whistler waves, Alpine waves, etc. in the case of Fig. 1, as well as Fig. 2 and In the case of FIG. 3, various forms such as abnormal waves, normal waves, high-frequency hybrid waves, and low-frequency hybrid waves can be propagated. However, in the case of the present invention, by appropriately designing the structure of the electrode conductor of the triode vacuum tube type active distributed coupling line, only one of the above various transmission modes is set as gain propagation, and the other modes are set as loss propagation. This has the advantage of improving plasma stability.

4 and 5 show embodiments of the plasma heating device according to the present invention. FIG. 4 shows an example of a loop configuration, and FIG. 5 shows an example of a linear configuration. Whether or not there is one is not an essential problem of the present invention. The cut plane in Figure 4 is the cut plane when the loop-shaped heating tube is cut along the dashed line A-B and viewed in the axial direction of the loop. Wirings 5 and 8 in Figure 4 are shown connected directly to the cross-sectional view for clarity. All numbers in the figure correspond to Figures 1 to 3. However, the electrode conductor 1 corresponding to the cathode of the triode vacuum tube is divided into a main cathode 1' and an auxiliary cathode 1'', as shown in the cross-sectional view of the heating tube, and plasma formation is caused by the auxiliary discharge between the two cathodes. It is designed to be easy. Therefore, an auxiliary discharge DC power source 8 is required.

In particular, when the direction 7 of the external magnetic field and the direction 9 of the electrostatic field generated by the bias voltage applied between the electrode conductors of the triode vacuum tube type active distributed coupling line are perpendicular to each other as shown in FIG. Since drift occurs in a direction 10 perpendicular to and 9, it is desirable to construct the heating tube in a loop shape as shown in FIG.

Furthermore, when the structure of the electrode conductor is coaxial, the charged particles perform a spiral motion with the direction of the external magnetic field as the axis due to the above-mentioned drift. It is desirable that the electrode structure be configured in a spiral shape as shown in FIG.

As explained above, in the heating method of the present invention, the plasma heating tube itself has a function of propagating the heating electromagnetic wave in a gain manner, and the absorption of the heating electromagnetic wave energy by the plasma is compensated for by the gain effect, and the gain characteristic described above is By appropriately combining various propagation modes caused by external magnetic fields, it is possible not only to obtain stable high-temperature, high-density plasma using heating electromagnetic waves of any frequency, but also because the heating tube itself is a source of high-frequency oscillation. Since high-output heating electromagnetic waves can be easily obtained without using a special high-frequency oscillator, the heating device has the advantage of being simple in construction and highly economical.

[Brief explanation of drawings]

1 to 3 are diagrams explaining the principle of the plasma heating method according to the present invention, and FIGS. 4 and 5 are configuration diagrams of an embodiment of the plasma heating method according to the present invention. 1, 2, 3... Electrode conductors that constitute a triode vacuum tube type active distributed coupling line, corresponding to the cathode, lattice, and anode of the triode vacuum tube, respectively. 1', 1''... facilitate plasma formation. A main cathode and an auxiliary cathode for auxiliary discharge, both of which together correspond to 1, 4... an airtight container for shielding the plasma from the outside air, 5... a triode vacuum tube type active distributed coupling line DC power supply for supplying bias voltage to 6...
... External magnetic field generator, 7 ... Direction of external magnetic field, 8
...DC power supply for causing auxiliary discharge, 9...
...The direction of the electrostatic field generated between the electrode conductors by the bias voltage, 10...The direction of the drift of charged particles caused by the above-mentioned electrostatic field and external static magnetic field.

Claims (1)

[Claims] 1. In a plasma heating tube in which a vacuum tube type active distributed coupling line consisting of three or more conductor systems is set in a gain propagation state and is enclosed in a low pressure gas or ionized gas, parallel to the propagation direction of the active distributed coupling line or A static magnetic field in a perpendicular direction is externally applied, the attenuation of the heating electromagnetic wave propagating in the plasma along the active distributed coupling line is compensated for by the gain propagation characteristic of the active distributed coupling line, and the strength of the external magnetic field is Plasma heating is characterized in that only a desired transmission mode is propagated by appropriately setting the direction and direction, stable plasma heating is performed by a heating electromagnetic field of an arbitrary frequency, and the plasma heating tube itself is used as an oscillation source of heating electromagnetic waves. method.