JPH0810636B2 - Plasma driven current disperser for coaxial electromagnetic accelerator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving current dispersion method for a plasma of an electromagnetic accelerator for highly efficiently generating a high power ion beam with high power density required for fusion power generation, space rocket propulsion, solid ion implantation, etc. Is.

The technical fields to which the present invention belongs are magnetohydrodynamics, gas dynamics, particle beam engineering, nuclear fusion power generation, magnetic field confinement type fusion experimental equipment and reactor, high specific thrust and high efficiency electromagnetic thruster, rocket propulsion, high current ion implantation. It is a container etc.

The coaxial gun type electromagnetic accelerator called MPD arc jet type is a typical electromagnetic accelerator capable of accelerating a plasma for a long time by using an electromagnetic force as a driving force. However, it is expected that the development of both fields will be greatly accelerated if the driving efficiency is improved and the output beam with high energy can be extracted. The conventional structure of a coaxial gun type electromagnetic accelerator is a simple one in which two cylindrical electrodes are coaxially arranged, and an electromagnetic field formed by a plasma driving current flowing between both electrodes in the radial direction and a self electric field due to the current. The plasma is arranged to be accelerated by the force.

[0004]

However, in such a simple configuration, the supersonic plasma flow is made to enter from the entrance of the accelerator, is accelerated, and is then ejected as the high energy plasma flow from the exit to operate in a high drive efficiency mode. In this case, it is known that the plasma driving current is extremely concentrated on both ends of the entrance and exit of the accelerator, and the electrode is burned. Therefore, it is extremely difficult to obtain a high-energy, high-power beam with high efficiency, and the problem remains an important issue. The problem of concentration of this drive current at both ends is
In principle, this can be solved if the electromotive force at both ends can be selectively set small, but the first challenge is Kuriki [Nagare, 7 (1989) 15]. Kuriki attempted to shape the external cylindrical electrode into a Laval nozzle shape that expands and contracts, widening the distance between the electrodes at the inlet and outlet from the center, and relatively weakening the electromotive force at both ends. It is difficult to make the distance between the electrodes sufficiently larger than that in the central part, and the reduction of the electromotive force at both ends is not sufficient, and a definite effect has not been confirmed.

That is, the coaxial gun type electromagnetic accelerator is a typical electromagnetic plasma accelerator having a wide operation region capable of not only pulse operation but also quasi-steady operation or steady operation for a long time. It is composed of a simple structure arranged coaxially. However, in the case of long-time operation, with the conventional simple structure, the plasma driving current flowing between both electrodes with the improvement of plasma driving efficiency is extremely concentrated at both ends of the inlet and outlet of the cylindrical electrode. Is known to cause burnout of the electrodes, which is a bottleneck for improving the performance of the coaxial gun.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a large alleviation of such a current concentration or a complete homogenization of a drive current. The present invention improves the power density of a coaxial gun type electromagnetic accelerator and improves the output plasma. Purification and prolongation of the life of the accelerator can be achieved, and significant improvements in the performance of fusion plasma heaters and space rocket propulsors can be expected, and the development of their application fields is an important issue.

The present invention comprises a supersonic ion source A and a coaxial gun type electromagnetic accelerator B, wherein the supersonic ion source A has a plurality of coaxial cylindrical shapes arranged on the same circumference so as to generate supersonic plasma. A cathode provided at the center of each inlet side end of the passage,
An anode provided on the outlet side of each passage through an insulating arc restraint wall, a plasma acceleration power source provided between the cathode and the anode, and an insulation provided outside the anode in a coaxial direction. The coaxial gun type electromagnetic accelerator B comprises a central plasma cathode coaxially insulated and connected to the outlet side of the coaxial cylindrical supersonic ion source A, and a circular plasma guide. An anode serving as an outer conductor that is surrounded by, a flange portion of the cathode that is integrated with the cathode of the central conductor, and an anode of the outer conductor that is insulated by an insulating wall, and is connected to an arc drive power source. In the coaxial gun type electromagnetic accelerator configured to further electromagnetically accelerate the supersonic plasma flow generated by the sonic ion source A to generate a high energy plasma flow in the same passage, the coaxial gun type electromagnetic accelerator B has the same potential. A metal cylindrical anode A thin ring-shaped anode plate and thin ring-shaped resistance plates arranged to have a larger resistance value at the ends are assembled alternately in layers and shaped into a cylinder. Power is supplied from the vicinity of the center and the potential at both ends is adjusted. Selectively lower,
A plasma-driving current dispersion device for a coaxial electromagnetic accelerator is characterized in that the excessive concentration of the plasma-driving current at the entrance / exit of the accelerator B is set to be softened.

Still another object of the present invention is to include a supersonic ion source A and a coaxial gun type electromagnetic accelerator B coaxially connected to the supersonic ion source A. The supersonic ion source A generates supersonic plasma. A cathode provided at the center of each inlet side end of a plurality of coaxial cylindrical passages arranged on the same circumference, an anode provided on the outlet side of each passage through an arc restraint wall, and the cathode and the anode. And a plasma accelerating power source provided between the supersonic ion source A and a plasma accelerating power source provided between the supersonic ion source A and a plasma guide. Type electromagnetic accelerator B encloses a central conductor cathode having the same potential, alternately stacks thin ring-shaped anode plates and ring-shaped ceramic insulating plates to form a cylindrical shape, and then attaches a resistor to the outside. The ring-shaped anode whose center is the resistance value between the anodes Another object of the present invention is to provide a plasma-driven current dispersion device for a coaxial electromagnetic accelerator in which the resistance values of the plasma flow on the inlet side and the outlet side are set to sequentially increase.

[0009]

The present invention is a method for avoiding electrode burnout due to excessive current concentration at both ends of the entrance and exit of a coaxial gun type electromagnetic accelerator, by using a voltage drop due to a resistor to suppress electromotive force appearing at both ends. This is a method of selectively reducing the current to avoid current concentration.

The method of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a high-efficiency coaxial gun type electromagnetic accelerator in which a system for bundling heat-driven arc jets as a supersonic ion source is provided at the terminal end and a supersonic plasma flow is supplied from an accelerator inlet.

In FIG. 1, 1 is a cathode, 2 is an anode, 3 is an arc drive power source, 4 is a gas introduction valve, and 5 is an arc restraint wall. When an arc drive power source 3 is connected between the cathode 1 and the anode 2 and an arc drive current 6 is passed between the cathode 1 and the anode 2, an electron flow is generated from the cathode 1 toward the center hole of the anode 2, Together with the gas flow 8 sent from the gas introduction valve 4, the gas flow is ionized, turned into plasma, and heated to generate a plasma flow 9 accelerated to supersonic speed. That is, the embodiment of FIG. 1 shows an example in which a two-stage acceleration system in which a supersonic plasma generator A and an electromagnetic accelerator B are combined is adopted.

The first step in the generation of the supersonic plasma (ion) stream 9 is the ionization of the gas stream 8, but the initial ionized plasma stream near the inlet of the ion source is subsonic,
Only heat input to the plasma is effective for plasma acceleration.
In FIG. 1, thermal energy is injected by the arc discharge between the anode 2 and the cathode 1 having the expanding nozzle-shaped arc restraint wall 5, and the plasma flow is accelerated to generate a supersonic plasma flow 9. The arc restraint wall 5 is installed to narrow down the arc column having a large axial current and stabilize the plasma and improve the energy injection efficiency.
Since the arc drive current 6 flowing through the arc restraint wall 5 is along the axis, its electromagnetic force acts only in the radial direction that narrows down the arc column, and is not related to plasma acceleration.

In FIG. 1, a plurality of gas streams 8, 8 from a coaxially arranged cathode 1 to an anode 2 are ionized, and an insulating wall plasma guide 12 causes the plasma ion stream to generate a leakage magnetic field of an electromagnetic accelerator B. The plasma ion flow is insulated and sent out so that the electromotive force induced by the action does not short-circuit with the outer structural material. 19 is a high-energy plasma flow, and it is necessary to enable smooth plasma transport. Therefore, the high-energy plasma flow 19 is formed by connecting the coaxial gun-type electromagnetic accelerator B directly to the coaxial cylindrical supersonic ion source A between the cathode 21 of the central conductor and the anode 22 surrounding the outside thereof. The supersonic plasma stream 9 produced by the ion source A is further electromagnetically accelerated here to form a high energy plasma stream 19. Reference numeral 17 is an insulating wall for insulating between the cathode 21 and the anode 22 which are the central conductors of the coaxial gun type electromagnetic accelerator B. In this case, the insulating wall plasma guide 12 generates a magnetic field in the azimuth direction due to the current flowing through the center electrode 21 and a radial electromotive force due to the axial plasma flow from the ion source A, and the center electrode feeding flange of the coaxial gun end portion. The insulating wall plasma guide 12 plays an important role in insulating and delivering the plasma.

In the present invention, the coaxial gun type electromagnetic accelerator B arranged coaxially with the supersonic ion source A has a special structure in which the anode surrounding the cathode of the central conductor is coaxially arranged, and the current is supplied from the intermediate position of the anode. Conductor and resistor are laminated and coordinated so that the resistance values on the inlet side and the outlet side of the accelerator B are larger than the intermediate position, or the anode plate for current supply and the insulating plate on the inlet side arranged in the middle are arranged. Between the outlet side insulating plate and the outlet side insulating plate, a thin electrode plate and an insulator are laminated so that the resistance value becomes larger toward the side part to form a tubular body, and an external resistance is connected to this laminated electrode plate to form a side part. Of the supersonic ion source A while the supersonic plasma flow 9 passes through the coaxial passage between the cathode which is the central conductor of the coaxial gun type electromagnetic accelerator B and the anode which surrounds it. To
The coaxial gun type electromagnetic accelerator was constructed to reduce excessive concentration of plasma driving current on the inlet side and the outlet side, thereby preventing electrode burnout and withstanding high power operation of high energy plasma flow. This is a plasma-driven current dispersion method.

In the present invention, in the coaxial gun type electromagnetic accelerator B, a resistor is used for the anode, and the plasma driving current 16
Is fed from the terminal 23 near the center of the electrode 22, and both ends 22A,
It is arranged so that the potential of 22B is automatically set low by the potential drop by the resistor 25. With such a configuration, the specific resistance ηanode of the resistor 25 or the thickness d in the radial direction can be set to match the operating conditions, and an ideal state in which the plasma driving current 16 is evenly distributed is provided. realizable. Below, the conditions under which such a uniform current distribution is obtained were examined using a one-dimensional model.

First, the plasma radius is defined as a ₀ , the gap length is defined as LG, and the electrode length is defined as Lz as main dimensions of the gun according to FIG. Now, the supersonic plasma flow is the central axis z
Assuming a high-efficiency practical operating state in which the plasma emission velocity VB from the accelerator is much larger than the incidence velocity, the plasma velocity Vz is equal to the inlet magnetic field B _0.
Approximately V using the magnetic field strength b = B / B ₀ standardized by
It is given by ^{z = VB (1-b 2} ). When the current distribution is uniform, the magnetic field linearly decreases in the accelerator and becomes 0 at the exit. Therefore, if the position z is normalized as ζ = z / Lz, the relationship between the magnetic field and the position is b = 1. It becomes easy to write -ζ. The voltage V appearing between the anode and the cathode can be calculated by the Ohm's formula. When the electric resistivity of the plasma is η, Lz >> η / (μ unless the output energy is set to an extremely low value which is meaningless for application. ₀ VB) holds and V = LG
B ₀ VB · b (1-b ² ) can be derived. This V is 0 at both ends of the electrode,

[Outside 1] Since it takes a maximum value at, it is necessary to drastically reduce the electromotive force at both ends to achieve uniform distribution. The point at which the voltage V is maximum at the current supply point

[Outside 2] Since a smooth voltage drop is obtained toward both ends, it is most rational to set LF = ζFLz as the position of the current supply point. In addition to the above reasoning, considering the axial potential drop Ez = ηanode jz inside the anode conductor, it is possible to determine the anode resistance arrangement conditions that realize a uniform current distribution,
It is necessary to satisfy the following formula.

[0017]

[Equation 1] Here, an is the average radius of the resistor, and R is the characteristic resistance value corresponding to the position ζ as defined. Further, f (ζ) is a function defined by the following equation giving the distribution of R.

[Equation 2] According to the equation (1), the problem of uniformization of the plasma driving current is that the two free parameters d and d are satisfied so as to satisfy the equation (1) under the given plasma extraction velocity VB and basic parameters regarding the shape of the accelerator. We show that we can reduce the problem of ηanode placement.

The present invention also includes a request regarding the structure of the resistor anode under the above consideration. 100 keV, which is the target in the fields of fusion and rocket propulsion
Deuterium beam (VB = 3.1 × 10 ⁶ m / s and 1 keV
We will try to calculate the uniform acceleration conditions by taking two examples of the light hydrogen beam (VB = 4.4 × 10 ⁵ m / s) of the above. First, I would like to estimate the value of typical resistivity ηanode. Η anod at the current supply point
It is clear that e = 0 and ηanode = ∞ at both end points, but at their midpoints ζ = 0.22, ζ = 0.71, both deuterium and hydrogen beams can be assumed if appropriate accelerator dimensions are assumed. It can be confirmed that both take values in the range of ηanode = 1.0 × 10 ^{-2 to} 1.0 × 10 ^-1 Ωm. In other words, the specific resistance of the metal at the current supply point should be 10 ^-7 to 10 ^-8 Ωm, the specific resistance should be about germanium or silicon semiconductor at the intermediate point, and the resistance material should have a higher specific resistance value at both ends. It will have to be done. In addition to the above-mentioned request for specific resistance distribution, the anode material must have arc resistance, so it is necessary to use copper or an arc-resistant alloy containing copper as a base material, and a uniform current distribution is required. It will be a complete contradiction. The present invention solves this contradiction based on the following two methods.

The first is shown in FIG. 2. Reference numeral 23 is a current supply anode plate, and a thin resistance plate 25 is sandwiched between the thin anode plates 24 so as to have a predetermined resistance distribution on average. Electrode 22
It is the adoption of the method of configuring. 26 is an insulating plate at both ends. A large number of resistance plates 25, 25 having significantly different resistance values are required. Ceramic resistors made by mixing graphite with silicon carbide and baked as such resistors, or water resistances whose resistance values are easier to control. Is appropriate.

Second, as shown in FIG. 3, a thin anode plate is sandwiched between insulating plates such as ceramics instead of a resistance plate,
The resistance value between the anode plates is set by an external resistor. Note that the resistance value connecting two anode plates at the position ζ, which are separated by an insulating plate with a thickness δζ, is R (ζ)
If δζ is set, the same effect as in the case of FIG. 2 can be obtained.

In FIG. 3, the same reference numerals as those in FIG. 2 indicate the same components, and the cylindrical resistor anode 22 surrounding the center electrode 21 in a cylindrical shape is a current supply anode plate 23 provided in the center. Is connected to a plasma driving power source 15 and surrounds the center electrode 21 to form an electric field. The cylindrical electrode 22 is formed by alternately stacking a thin insulating plate 28 and a thin anode plate 24 on both sides of a current supply anode plate 23 provided at a central position thereof to form a cylindrical resistor anode 22 having the same length as the center electrode 21. Then, the insulating plates 26 are provided at both ends thereof, and the external resistances 27 having different values are connected to the respective anode plates 24. As a whole of the tubular electrode 22, the resistance at the central portion is small and the resistance values at both ends are high. It is arranged as follows. When the resistance value distribution of the tubular resistor electrode 22 is thus determined and the resistance in the vicinity of the insulating plates 26 at both ends is set to be large, the supersonic ion source A accelerates the coaxial ion flow path. The plasma ion stream 9 leaves the end of the insulating wall plasma guide 12 and
It is extremely important to provide an insulating plate 26 to prevent a short circuit when coming to the inlet end 18 of the coil 22 and to insulate the plasma flow and send it to the coaxial gun type electromagnetic accelerator B. Further, as shown in FIG. 3, the arrangement of the anode plate 24 and the insulator 28 of the tubular resistor anode 22 is such that the anode plate 24 and the insulator 28 of the tubular resistor anode 22 are specially arranged, If the resistance is higher sequentially closer to the insulating plate 26 of the part, and the resistance is lower near the central current supply anode plate 23, the high energy plasm flow 19 can be driven efficiently,
It is possible to extract an output beam with high energy.

[0022]

EFFECTS OF THE INVENTION The present invention is a basic principle of highly efficient generation of an ion beam having a remarkably high power density of 10 ³ to 10 ⁴ times as high as that of an electrostatic acceleration type beam heater commonly used in nuclear fusion research. With respect to the present invention, the implementation of the present invention makes it possible to obtain a high-power beam with good convergence at a significantly low cost, and therefore, there are many implementation effects listed below, and their practicality is high.

High-temperature plasma can be easily obtained by realizing an inexpensive high-power beam, which accelerates fusion research. : Since the plasma heater for the magnetic field confinement type fusion reactor can be manufactured at a significantly low cost, the economical efficiency of the commercial reactor is improved. : Large particle flux neutron source can be constructed. : The convergence of the beam, which is the key to the realization of an inertial fusion reactor with a light ion beam, will be improved. : A non-thrust and energy efficient electromagnetic propulsion device using hydrogen as a propellant will be realized, and the mission speed will be greatly improved. : An inexpensive and stable high energy ion implanter for an individual can be realized.

The present invention relates to a high-power high-energy ion beam generator, a magnetic field confinement type fusion experimental device and the same experimental reactor, an ultra-high-power pulsed light ion beam compression type inertial fusion experimental device and the same experimental reactor, a large particle flux neutron generator. It is possible to manufacture a high-power ion beam generator with good convergence, which can be operated inexpensively and stably, when manufacturing a device, a high-efficiency thrust high-efficiency electromagnetic propulsion device, and a high-current ion implanter.

The present invention uses an electromagnetic accelerator having an ion source of a supersonic plasma flow generated by one or a plurality of thermally driven arc jets, and an electromagnetic accelerator of the same type to guide the supersonic plasma flow to an electromagnetic accelerator entrance. At this time, a high-energy plasma flow can be generated by having a special structure that erases the deterrent force induced by the leakage acceleration magnetic field by disposing an insulator or the like.

According to the present invention, the beam energy and the power density from the coaxial gun are improved by greatly reducing the extreme concentration of the driving current of the coaxial gun type electromagnetic accelerator at both ends of the electrode or by making the driving current uniform. Purification of output plasma,
There is an industrially significant effect that the life of the accelerator can be extended and the performance of the plasma heater for fusion and the space rocket propulsion device can be remarkably improved.

[Brief description of drawings]

FIG. 1 is a principle schematic diagram showing that a coaxial gun type electromagnetic accelerator is coaxially attached to a supersonic ion source to make a plasma driving current uniform.

FIG. 2 is a circuit diagram showing an example of implementation of a coaxial gun type electromagnetic accelerator.

FIG. 3 is a circuit diagram showing another example of implementation of the coaxial gun type electromagnetic accelerator.

[Explanation of symbols]

 1 Cathode 2 Anode 3 Power Supply 4 Gas Inlet Valve 5 Arc Restraint Wall 6 Arc Drive Current 7 Electron Source 8 Gas Flow 9 Supersonic Plasma Flow 12 Insulating Wall Plasma Guide 15 External Power Supply for Plasma Driving 16 Plasma Driving Current 17 Insulating Wall 18 Resistor Anode inlet side edge 19 High-energy plasma flow 21 Center conductor cathode 22 Cylindrical resistor anode 23 Current supply anode plate 24 Anode plate 25 Resistor plate 26 Insulation plate 27 External resistance 28 Insulation plate

Claims (2)

[Claims] 1. A supersonic ion source A and a coaxial gun type electromagnetic accelerator B, wherein the supersonic ion source A is provided with a plurality of coaxial cylindrical passages arranged on the same circumference to generate supersonic plasma. 9, a cathode 1 provided at the center of each inlet side end, an anode 2 provided at the outlet side of each passage 9 via an insulating arc restraint wall 5, and a plasma acceleration provided between the cathode 1 and the anode 2. Power source 3 and an insulating wall plasma guide 12 extending outward in the coaxial direction from the anode 2. The coaxial gun-type electromagnetic accelerator B is a coaxial cylindrical supersonic ion source A. Center conductor cathode 21 which is coaxially insulated and connected to the outlet side of the anode, and an anode 22 which serves as an outer conductor surrounding the center conductor cathode 21 in a circumferential shape.
And an arc drive power supply 15 connected by insulating a flange portion 21 of the cathode integrated with the cathode of the central conductor and an anode 22 of the outer conductor with an insulating wall 17, and the supersonic ion source A In the coaxial gun type electromagnetic accelerator configured to further electromagnetically accelerate the supersonic plasma flow generated in 1 to generate a high energy plasma flow in the same passage 9, the coaxial gun type electromagnetic accelerator B is made of metal having the same potential. Cylindrical anode 22,
Thin ring-shaped anode plates 24 and thin ring-shaped resistance plates 25 arranged so as to have a larger resistance value at the ends are alternately assembled into a cylindrical shape and shaped into a cylindrical shape. A plasma-driven current dispersion device for a coaxial electromagnetic accelerator, characterized in that power is supplied and the potentials at both ends are selectively lowered to set excessive concentration of plasma-driving current at the entrance and exit of the accelerator B. 2. A supersonic ion source A and a coaxial gun-type electromagnetic accelerator B coaxially connected to the supersonic ion source A, wherein a plurality of supersonic ion sources A are arranged on the same circumference to generate supersonic plasma. The cathode 1 provided at the center of each inlet side end of each coaxial cylindrical passage 9 and the arc restraint wall 5 on the outlet side of each passage 9.
An anode 2 provided through the anode 1, a plasma acceleration power source 3 provided between the cathode 1 and the anode 2, and an insulating wall plasma guide 12 extending outward in the coaxial direction from the anode 2. And a gun-type electromagnetic accelerator B coaxially connected to the supersonic ion source A has a central conductor cathode 21 having the same potential.
Surrounding the thin ring-shaped anode plate 24 and the ring-shaped ceramic insulating plate 28 are alternately laminated to form a cylindrical shape,
A coaxial type electromagnetic device characterized in that a resistance is attached to the outside and the resistance value between the anodes 24 is set so that the resistance values to the inlet side and the outlet side of the plasma flow are sequentially higher than those of the ring-shaped anode 23 having the center. Plasma driven current disperser for accelerator.