JP2507908B2 - Cross-field plasma transport method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention accelerates a high-density plasma to a supersonic flow having a high Mach number by an electromagnetic accelerator or a heat-driven arc jet, and then crosses the magnetic field by inducing the plasma through a hollow insulating tube. And a method for smoothly transporting plasma, which is expected to have important applications such as fuel supply to a fusion reactor for which a definitive method has not been established yet, and ion supply to an electromagnetic accelerator. The technical field to which the present invention belongs is magnetohydrodynamics, gas dynamics,
Particle beam engineering, fusion power generation, energy generation, rocket propulsion, etc.

[0002]

2. Description of the Related Art Fusion power generation is a technology that promises to provide humankind with an eternal energy source. However, plasma at the entrance of an electromagnetic plasma accelerator, which is important for plasma heating leading to fuel injection or ignition in a fusion reactor, The supply involves the problem of transporting the plasma across the magnetic field, so a satisfactory technique has not yet been established.

High-power ion beams capable of stable operation with high energy and good convergence have various uses such as plasma heating in a fusion reactor, and in recent years, the demand for their realization has increased more and more. . As is well known, high-power plasma heating is indispensable because a fusion reactor generates and confines ultra-high temperature plasma for the first time, and it has been very important for research and development of plasma heating methods and heating devices based on various principles. Efforts have been made, but the beam heating method, in which ions are accelerated into a high-energy beam by electrostatic force and is injected into plasma to heat it, is the first to prove that the plasma can be heated to an ultrahigh temperature of 100 million degrees or more. The law is given a special status.

[0004]

However, it can be pointed out that the high-power beam device using this electrostatic force has the following fundamental and difficult problems to overcome in practical use. : Electrostatic beam is non-neutral and beam current is inevitably subject to Langmuir-Chilled's 3/2 law. High voltage is essential for high output current. However, the application of high voltage induces dielectric breakdown and the current value is limited, and the maximum allowable current density remains at a low value of about 0.25 A / cm ² . Therefore, in the high power beam system, it is necessary to operate near the limiting current.

In operation near the limiting current, in order to avoid frequent occurrence of dielectric breakdown, so-called break-in operation (condi
In addition to the requirement of protection, a protective device with good responsiveness is also required in order to prevent the device from burning due to overcurrent at the time of dielectric breakdown.
Therefore, in the electrostatic type, not only stable steady operation is difficult, but also the device becomes complicated and very expensive.

In an electrostatic accelerator type apparatus, since the beam is non-neutral, it has an electrostatic potential, which requires extra energy supply from a power source, which lowers energy efficiency. The non-neutral beam is neutralized by charge exchange and then enters the plasma, but electrostatic potential energy is given to the slow ions during charge exchange, and is carried to the wall of the charge exchange chamber to heat the wall. . Electrostatic potential energy loss is 0 when the beam energy is 100 keV and the output is 1 MW.
It is calculated as 58 MW and difficult to ignore.

The above-mentioned difficulties are caused by electrostatic driving in which the beam becomes non-neutral. To solve the problem, an electromagnetic force or pressure (accelerating in a quasi-neutral plasma state in which ions are neutralized by electrons) is used. Gas force generated by thermal energy density gradient
The choice to use (gasdynamic force) will be forced. Considering that an ion beam source is a device that converts electrical energy into kinetic energy of ions, it can be regarded as a kind of electric motor (motor), and an electrostatic accelerator has a driving force of electrostatic force. Electrostatic motor,
It can be pointed out that the electromagnetic accelerator corresponds to a general-purpose electromagnetic motor, and the gas power accelerator corresponds to a gas turbine. However, considering that there is no general-purpose electrostatic motor that can handle high power, this correspondence suggests the rationality of using the electromagnetic force or gas force as the above selection, that is, the driving force of the high power beam. Seems to be a wise choice.

First, in the case of utilizing gas force, a plasma beam by a heat-driven plasma jet is mentioned as a typical example. As is well known, the heat-driven plasma jet generates a supersonic flow by ionizing and heating the working fluid by arc discharge or high-frequency discharge and then ejecting it from the outlet nozzle, and because of the strong heat input, the power carried by the flow is extremely high. Although it is large, the kinetic energy of ions is at most about one order of magnitude higher than the arc temperature, and is not suitable for a high energy beam device. However, the fact that a huge equivalent ion current value is easily obtained suggests its application as an ion source for a high-energy beam, and is important. The ion source for high-power electrostatic accelerators, called the bucket type, has also been classified into the utilization of gas force.

Electromagnetic acceleration is to accelerate ions by a Hall voltage generated by an electromagnetic force. In principle, a Hall current of a Hall accelerator type in which a Hall current induced by a Hall voltage is carried by ions and is accelerated to a high energy beam, And a coaxial gun type in which the Hall current is not induced (called MPD arc jet type in the field of rocket propulsion). Similar to the electrostatic accelerator, the Hall accelerator has high similarity to the electrostatic accelerator because it accelerates ions by applying a high voltage, but the magnetic insulation effect that the magnetic field suppresses the dielectric breakdown effectively acts and the dielectric breakdown occurs. It is known that it does not become a factor that limits the current. Due to these excellent characteristics, the Hall accelerator was actively studied in the United Kingdom, the former Soviet Union and the United States in the 1960s and 70s to replace the electrostatic accelerator. As a result, it has been proved that a large current of up to 1000 A can be drawn out under an appropriate design, but the beam convergence is poor and the construction of a device that surpasses the electrostatic accelerator is still successful overall. Absent.

On the other hand, in the coaxial gun, the applied voltage is low and is free from dielectric breakdown, and the beam current cannot be limited by dielectric breakdown like the Hall accelerator. The coaxial gun type has attracted attention as an electromagnetic propulsion device for space rockets since the 1960s due to the simple structure of arranging two cylindrical electrodes on the same axis without the need for a magnetic field coil. ing. The greatest advantage of using the coaxial gun as a thruster is theoretically far superior to the maximum specific impulse of 450 seconds (liquid acid / hydrogen engine) in the case of chemical fuel.
Although it is expected that a value exceeding 100,000 seconds will be obtained, at present, only a value of about 2000 seconds is reported. Also, regarding the energy efficiency, even though the theoretical value reaches a minimum of 65%, only about 20% as a measured value is recorded at most, and there is a large difference between the theoretical value and both the specific impulse and the energy efficiency. There is a big complaint. In the field of fusion research, it has been studied as a coaxial gun for high energy plasma injection, but in the quasi-steady operation mode with a long discharge time, the plasma velocity is clamped to a certain low level and acceleration is stopped, and the gun drive current is reduced. The phenomenon of blowing out from the tip of the electrode occurs, and only an inappropriate result as a high energy beam generator has been reported. However, due to this current blowing phenomenon, a confinement coordination called spheromak is skillfully formed,
At present, it is being used for another purpose rather than for producing spheromak.

When a conductive fluid flows across a magnetic field,
It is a basic law of electromagnetics that the induced electromotive force is induced in the direction perpendicular to both the flow and the magnetic field.
A typical example of such a flow is a high-density plasma flow having a much larger ion Lammer radius than the Debye radius. As shown schematically in Fig. 1, when a high-density plasma flows at a high Mach number across the magnetic field from the bottom to the top of the paper along a hollow insulating tube, the boundary surface becomes an electrical insulating surface. A charge appears on the boundary surface and an electric field opposite to the induced electromotive force is induced. Therefore, the electric field and the induced electromotive force are balanced, the factor of the generation of the diamagnetic current in the electromotive force direction that gives the braking force to the flow is eliminated, and a smooth magnetic field cross flow is realized.

[0012]

The features of the present invention are as follows. (1) A cathode 5 provided at the center of each inlet side end of a plurality of coaxial cylindrical passages 15 arranged on the same circumference so as to generate supersonic plasma, and an insulating wall 9 on the outlet side of each passage 15. In a supersonic ion source comprising an anode 6 provided via a cathode and a supersonic plasma generating power source 7 connected between the cathode and the anode, a portion of the supersonic ion source along the flow crosses the magnetic field at the exit end. A magnetic field crossing plasma transport method, characterized in that a hollow insulating tube 2 is coaxially provided to accelerate and guide a plasma electromagnetic flow traveling across a magnetic field. (2) A plurality of gas introduction valves 8 are provided in a plurality of coaxial cylindrical passages 15 arranged on the same circumference so as to generate the supersonic plasma flow 4, and the generated gas flow 10 is surrounded and provided. Insulating wall plasma guide 14 for arranging a high frequency coil 12 via an insulating wall 9 for guiding the generated plasma flow in the axial direction.
To extend outward from the outlet side end of the passage 15 to insulate the ion flow passing through the coaxial passage 15 and electromagnetically accelerate to generate a supersonic ion flow. Law.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is an explanatory view schematically showing a case where high-density plasma flows at a high Mach number across a magnetic field from the bottom to the top of the paper along a hollow insulating tube.

FIG. 2 shows the case where the high-density plasma flows at a high Mach number across the magnetic field from the bottom to the top of the paper along the hollow insulating tube, and the boundary surface is entirely covered with a good conductor. It is explanatory drawing shown typically.

FIG. 3 shows the entire apparatus so as to completely or as much as possible eliminate various phenomena such as excitation of a diamagnetic current due to a short circuit of induced electromotive force, which prevents smooth plasma flow across a magnetic field, and blowing current from a plasma generator. Are configured as shown in FIG. In FIG. 3, 1 is a supersonic plasma source, 2
Is a hollow insulating tube coaxially attached to the outlet end, and 3 is a magnetic field line for plasma confinement.

FIGS. 4 and 5 show an example of a supersonic plasma source. In both types of electromagnetic accelerators, such as the coaxial gun type or the Hall accelerator type, it is a natural shape to make the geometric shape of the acceleration region a coaxial cylinder, so the most rational supersonic ion source configuration is: It is preferable to bundle a plurality of polar or inductive discharge type plasma jets as shown in FIG. 4 in a coaxial cylindrical shape. FIG. 4 shows a case where a plurality of heat-driven arc jets are bundled in a coaxial cylindrical shape, and the gas flow 10 from the gas introduction valve 8 is divided into a plurality of passages to form a cathode 5 and an anode 6. A plurality of pairs are provided in the shape of a coaxial cylinder, an ion acceleration power supply 7 is provided between the cathode 5 and the anode 6, and a polar discharge type arc drive current 11 is made to flow from the cathode 5 to the anode 6 to branch off each gas. Ionize stream 10
A supersonic plasma generator A that accelerates to supersonic speed is formed, and the flow of ionized ions is electromagnetically accelerated to obtain a supersonic plasma flow 4. Reference numeral 9 indicates an arc insulating wall.

FIG. 5 shows a structure for obtaining a supersonic plasma flow 4 by using an inductive discharge type plasma jet by electrodeless discharge as an electromagnetic accelerator having a single coaxial structure. In FIG. 5, numeral 8 is a gas introduction valve, numeral 9 is an arc insulating wall, numeral 12 is a high frequency coil, numeral 13 is a high frequency oscillator, and numeral 14 is an insulating wall plasma guide. The supersonic plasma flow 4 is insulated and guided by the insulating wall 9 and the insulating wall plasma guide 14 to the exit end of the coaxial passage.

When a conductive fluid flows across a magnetic field,
The basic law of electromagnetics teaches that induced electromotive force is induced in the direction perpendicular to both the flow and the magnetic field.
As a typical example of the flow in which such a phenomenon appears, in plasma, there is a high-density plasma flow having a much larger ion Lammer radius than the Debye radius. Figure 1 now
As shown schematically in Fig. 2, when the high-density plasma flows at a high Mach number across the magnetic field from the bottom to the top of the paper along a hollow insulating tube, the boundary becomes an electrically insulating surface and An electric charge appears and an electric field opposite to the induced electromotive force is induced. Therefore, the electric field and the induced electromotive force are balanced, and the cause of the generation of the electric current in the electromotive force direction that gives the braking force to the flow is eliminated. Furthermore, on the insulating wall of the hollow tube that induces a high Mach number flow, the Mach number maintenance effect due to plasma cooling,
Also, it can be seen that the insulating wall is an essential element for realizing a smooth flow, because it has the effect of preventing plasma loss along the lines of magnetic force due to the repulsion of induced similar charges. In other words, if the supersonic plasma flow is ideally guided along the insulating tube, it is concluded that the flow is smoothly transported downstream without being damped by the magnetic field.
The present invention is based on arranging the system so that it adopts such an ideal coordination.

As a factor that breaks the above ideal coordination, firstly, there is a good conductor on the boundary surface. As an extreme example, considering the case where the boundary surface is entirely covered with a good conductor as shown in FIG. 2, the electric charge is short-circuited with the good conductor on the outside, so that a current across the magnetic field along the electromotive force is induced. It can be seen that the plasma flow is dampened and a smooth flow is prevented from being achieved. Second, the importance of realizing a plasma flow with a high Mach number can be pointed out. When the flow acceleration is insufficient and the flow remains in the subsonic region where the Mach number is low, the thermal energy of the flow takes a larger value than the kinetic energy of the flow, but the thermal energy excites the diamagnetic current that excludes the magnetic field. Not only dampen the movement across the magnetic field, but also promote plasma washout along the magnetic field and contribute to the reduction of the plasma density, that is, the expansion of the Debye radius, thus hindering the smooth flow across the magnetic field. become. When a coaxial gun plasma accelerator is used as the plasma source, a part of the plasma drive current is often blown out from the tip of the gun, and a current may appear along the flow. It is needless to say that the plasma flow is blown away in the radial direction by the electromagnetic force of, and the realization of a smooth magnetic field cross flow is prevented. In other words, it is concluded that the use of a plasma accelerator with a high Mach number in which the plasma flow is high and a plasma-driven current is not blown is a prerequisite for smooth plasma transport across a magnetic field.

Although many attempts have been reported to transport plasma across a magnetic field, the plasma is sufficiently accelerated so that the flow has a high Mach number, the current blowout is eliminated, and the induction is performed by an insulating wall tube guide. There is nothing that takes the ideal coordination of. Therefore, in the conventional system, the deterrent force acts on the flow that crosses the magnetic field, and the flow becomes thin as the magnetic field becomes stronger, and finally the magnetic field strength Bc (which is lower than the magnetic field strength required by the fusion reactor, for example, Bc = 0.9 T)
It is expected that the flow will be completely suppressed. In fact, such complete deterrence has been observed elsewhere, making fueling fusion reactors that require transport across strong magnetic fields difficult.

In order to overcome the above-mentioned problems, the present invention has a magnetic field at the exit end of a supersonic ion source which is an electromagnetic accelerator without a single electric current blowout, a heat-driven arc jet, or a bundle thereof which are coaxially integrated. The present invention relates to a magnetic field transversal plasma transport method in which a hollow insulating tube diverging along the flow is provided at a location crossing the magnetic field to smoothly induce a plasma flow across a magnetic field.

In the present invention, first, in order to prevent a short circuit of induced electromotive force through an external structure, a hollow insulating tube 2 is provided at the outlet end of the supersonic plasma source 1 and a flow is guided along the tube. It was adopted. Further, in the present invention, in order to obtain a plasma flow having a high Mach number, a single or a plurality of electromagnetic accelerators capable of drawing a supersonic plasma flow or a heat-driven arc jet are bundled and integrally configured and arranged in the plasma source 1. When using the coaxial gun type among the electromagnetic accelerators, consideration must be given to preventing the blowing of the plasma driving current. For example, it is necessary to adopt a high performance type in which supersonic plasma is injected into the accelerator entrance.

In addition to the role of preventing induced electromotive force from being short-circuited, the hollow insulating tube 2 has an accelerating action by cooling the plasma, and is important because it is effective for maintaining a high Mach number and reducing the diamagnetic current. Further, in order to more actively maintain the high Mach number of the flow, it is effective to have a structure in which the cross-sectional area of the insulating tube is gradually expanded along the flow as shown in FIG.

In the present invention, the hollow insulating tube provided at the outlet end of the supersonic plasma source 1 is made to have a gradual divergent slope so that the plasma flow speed does not decrease.

[0025]

According to the present invention, the plasma is induced by using a hollow insulating tube made of ceramic or the like having a cross-sectional area that gently expands coaxially at the exit end of the supersonic ion source.
There is a great industrial advantage that a plasma flow can be smoothly transported across a magnetic field to efficiently perform fuel injection into a fusion reactor or supply of ions to an electromagnetic accelerator.

Product names to which the present invention can be applied include magnetic field confinement type fusion experimental equipment and reactor, high power and high energy ion beam generator, ultra high power pulsed light ion beam generator, high specific thrust and high efficiency electromagnetic thruster, A high current ion implanter and the like can be mentioned.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing a case where high-density plasma flows at a high Mach number across a magnetic field from the bottom to the top of the paper along a hollow insulating tube.

FIG. 2 is a case where a high-density plasma flows at a high Mach number across the magnetic field from the bottom to the top of the paper along a hollow insulating tube, and the boundary surface is entirely covered with a good conductor. It is explanatory drawing which showed typically.

FIG. 3 is a schematic diagram showing an example of a method for smoothly transporting a plasma across a magnetic field according to the present invention.

FIG. 4 is a diagram showing an example of a supersonic plasma source.

FIG. 5 is a diagram showing a structure for obtaining a supersonic plasma flow by using an induction discharge type plasma jet by electrodeless discharge as an electromagnetic accelerator having a single coaxial structure.

[Explanation of symbols]

 1 Ultrasonic Plasma Source 2 Hollow Insulation Tube 3 Magnetic Field Line 4 Supersonic Plasma Flow 5 Cathode 6 Anode 7 Ion Acceleration Power Supply 8 Gas Introducing Valve 9 Insulation Wall 10 Gas Flow 11 Arc Drive Current 12 High Frequency Coil 13 High Frequency Oscillator 14 Insulation Wall Plasma Guide 15 coaxial cylindrical passage

Claims (2)

(57) [Claims] 1. A cathode 5 provided at the center of each inlet side end of a plurality of coaxial cylindrical passages 15 arranged on the same circumference so as to generate supersonic plasma, and an insulation at the outlet side of each passage 15. In a supersonic ion source comprising an anode 6 provided through a wall 9 and a supersonic plasma generation power source 7 connected between the cathode and the anode, a flow is made at a location across the magnetic field at the exit end. 2. A method for transporting plasma across a magnetic field, characterized in that a hollow insulating tube 2 is coaxially provided along the axis to accelerate and guide a plasma electromagnetic flow traveling across a magnetic field. 2. A plurality of gas introduction valves 8 are provided in a plurality of coaxial cylindrical passages 15 arranged on the same circumference so as to generate a supersonic plasma flow 4, and a gas flow 10 generated is surrounded. The high-frequency coil 12 is disposed via the insulating wall 9 provided as an insulating wall, and the insulating-wall plasma guide 14 for guiding the generated plasma flow in the axial direction is extended outward from the outlet-side end of the passage 15 to form the coaxial cable. A method for transporting plasma across a magnetic field, characterized in that an ion flow passing through a passage (15) is insulated and electromagnetically accelerated to generate a supersonic ion flow.