JP2571861B2 - Method and apparatus for damping armature current of railgun type electromagnetic accelerator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a railgun type electromagnetic accelerator.

[Conventional technology]

Railgun-type electromagnetic accelerators (hereinafter referred to as railguns) that accelerate macroscopic objects at high speed using electromagnetic force are 10 km / s per second, which is difficult to achieve with the method using the explosive force of combustion gas of high explosive or high-pressure gas. It is possible to obtain the above flying object speed, and it has been paid attention in recent years.

Two types of materials are used for railgun armatures: fixed metal and plasma.However, the method using a plasma armature is particularly suitable for accelerating small flying objects weighing several grams at ultra-high speed. Mainly used, for example, as an accelerator for generating an impact ultra-high pressure of 10 million atmospheres or more due to collisions between materials, as a simulation device for meteorite collision problems in space, and for solid hydrogen to fusion reactors It is expected to be used for fuel pellet driving devices and the like, and development for practical use is being actively pursued.

Regarding the research and development of railguns and their utilization technology,
EE Transactions on Magnetics, vol. Mag-20, No. 2 (198
4), vol. Mag-22, No. 6 (1986), and vol. 25, No. 1 (1
989).

The acceleration principle and structure of a rail gun using a plasma armature are shown in FIGS. A flying object 3 made of an insulator is installed in the acceleration hole 2 between the two rail electrodes 1, and a metal plate or a metal foil 4 for forming a plasma armature is installed behind the flying object 3. Make electrical contact. In this state, when the main power supply 5 such as a capacitor bank is connected to the two rails and the switch 6 is closed to apply a power supply voltage, the metal plate or the metal foil is turned into plasma by a large current as shown in FIG. 4 (b). I do. This plasma 7
Moves along with the flying object and always acts as an armature located behind the flying object. While maintaining the current between the rails, it receives the electromagnetic force according to the law of electromagnetic induction and generates a force proportional to the current and the square. Continue accelerating the flying object.

In the case of projectile acceleration using a railgun, the acceleration current reaches several 100 kA. If the power supply voltage is continuously applied to the accelerator after the projectile is ejected from the accelerator, the current flowing in the plasma armature behind the projectile will be the muzzle,
That is, it continues in the form of a high-current arc discharge at the end of the rail electrode, causing significant damage to the rail electrode surface at that location. In addition, since the voltage between the rail electrodes increases due to the arc discharge at the muzzle, re-ignition may occur between the rail electrodes in the accelerator in some cases, causing unnecessary damage to the electrode surface. The damage of the rail electrode due to the so-called residual current is considered to be one of factors for shortening the life of the rail gun, and is an important issue in rail gun development.

In order to prevent such a problem, the following methods have been considered.

(1) Pulse shaping of a large current power supply is performed so that the output current becomes zero at the same time as or before the projectile is ejected from the accelerator.

(2) Simultaneously with or before the launch of the flying object, the switch of the shunt circuit connected in parallel with the accelerator is closed, and part or all of the armature current is diverted to the circuit, and the arc between the rail electrodes is released. Attenuate or extinguish the discharge.

As the above (1), for example, a method in which a variable inductor is inserted into a capacitor discharge circuit to adjust a discharge waveform, or a method in which a plurality of capacitors are coupled in parallel via an inductor and an output close to a rectangular wave having a specific time width is obtained. There is a method for obtaining a current waveform. The former has an advantage that the time width of the current waveform can be easily adjusted to some extent, but the current waveform is sinusoidal, which is not an efficient current waveform for the railgun electromagnetic accelerator. The latter has the advantage that an efficient rectangular-wave-like output current can be obtained, but it is difficult to change the time width of the output waveform, and it is difficult to have flexibility to cope with various acceleration conditions. .

The advantage (2) is that the armature current can be attenuated regardless of the type of power supply. In the prior art, the use of an ignitron or explosive switch as a switch of a commutation circuit is considered, but in that case, a complicated trigger circuit for detecting the ejection of the flying object and operating the switch is required. . When using an explosive switch,
It has the disadvantage of requiring protective equipment for safe explosion.

[Problems to be solved by the invention]

The present invention solves the above-mentioned problems of the prior art in the method of plasma armature damping of a rail gun, and does not require a complicated trigger circuit, regardless of the type of power supply, and uses only a simple circuit to accelerate the rail gun. The present invention aims to provide a method of attenuating or extinguishing an armature current at an arbitrary place of the above and a railgun type electromagnetic accelerator using the same.

[Means for solving the problem]

The inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have accomplished the present invention.

In other words, the configuration of the present invention is a circuit including a railgun type electromagnetic accelerator and a large current power supply (including a switching system and a crowbar circuit) for supplying an acceleration current. A small electrode whose end face is exposed and insulated from the rail electrode, a cavity connected to the railgun-type electromagnetic accelerator in parallel, and a cavity for installing an electric bridge for plasma generation, and a plasma injection hole inside the electrode. A gap switch is newly provided, one end of the electric bridge is connected to the inner wall of the cavity, and the other is connected to the small electrode, so that a part of the armature current flows when the plasma armature passes the small electrode position. Guided to the bridge, the generated plasma is ejected from the plasma injection hole to cause dielectric breakdown between the electrode gaps, and the armature current is discharged between the gap switches. Characterized in that the commutating the flow, a rail gun electromagnetic accelerator using attenuation method and the same plasma armature in railgun electromagnetic accelerator.

That is, in the present invention, a small electrode exposed at an arbitrary position on the rail electrode surface and insulated from the rail electrode, and a gap connected in parallel with the rail gun and triggered by a plasma generated by an electric bridge. The use of the switch solved the problem.

[Action]

Referring specifically to the drawings, FIG. 3A is a typical example of the present invention. The end face of the small electrode 8 is usually exposed on the surface of the rail electrode near the muzzle while being insulated from the rail electrode, and is electrically connected to one end and the end of the electric bridge 11. The electric bridge here is a portion that absorbs electric energy and generates plasma, and may be, for example, a thin wire, foil, powder, or the like of a conductor, or a pair of electrodes placed in a vacuum or in a gas. The other end of this bridge is a cavity in one electrode of the gap switch 9 connected in parallel with the railgun.
At 10, it is electrically connected to the electrodes. As shown in FIG. 3 (b), the accelerated plasma armature is
Is reached, a part of the armature current is guided to the electric bridge 11 through the small electrode, and a plasma 12 is generated in the cavity 10.
This plasma is ejected from the pores 13 and causes dielectric breakdown between the gap switches. As a result, as shown in FIG. 3 (c), the power supply current is divided into the armature current and the gap switch current, and if the impedance of the gap switch circuit is sufficiently smaller than the impedance of the railgun, the armature current rapidly increases. Attenuate.

The delay time from the start of energization of the bridge to the occurrence of dielectric breakdown between the gap switches is an important characteristic of the present invention. The time required for the bridge to generate plasma, the volume of the cavity, It largely depends on the hole diameter and the gap interval of the gap switch. This delay time
10 μs or less is required, so that the time required for the electric bridge to generate plasma is about 1 μs, the volume of the cavity is several mm ³ , the diameter of the pores is 1 to 2 mm, and the gap interval of the gap switch is still 1 μs. ~ 2 mm is desirable.

〔Example〕

 Hereinafter, the present invention will be described specifically with reference to examples.

Plasma armature formation and decay experiments were performed using a distributed electrode type railgun with a fuse having an acceleration length of about 300 mm and a capacitor bank of 6000 μF charged to 5.1 kV. The small electrode 8 is exposed in the acceleration hole 20 mm before the muzzle,
The gap switch was connected in parallel with the rail gun at the input terminal of the rail gun. A simplified experimental circuit is shown in FIG. The method of forming the armature utilizes a line explosion of a thin metal wire. A thin copper wire having a diameter of 0.1 mm was used as the bridge 11. The diameter of the pore 13 is 1.5 mm, the volume of the cavity 10 including the pore is about 5 mm ³ , and the gap interval of the gap switch 9 is still 2 mm. Discharge current I of capacitor power supply 5
₀ and the line explosive circuit current I ₁ of the armature forming, and a gap switch current I ₂ measured independently, the armature current I _A is
It was determined from the relationship I _A = I ₀ −I ₁ −I ₂ . The time required for the plasma armature to reach the vicinity of the muzzle was determined by observing light emission from the plasma using an optical probe installed at the muzzle.

The observed I _0, I _1, I ₂ and the armature current I _A obtained from the above relationship shown in Figure 2. Plasma emission time at the muzzle
T _{M is} also shown in the figure. I ₂ rises sharply slightly earlier than T _M, accordingly I _A is seen to decay rapidly. That is, it was confirmed that almost immediately when the plasma armature reached the small electrode position near the muzzle, the gap switch was activated, and the armature current was rapidly attenuated.

〔The invention's effect〕

As described above, the small electrode exposed at an arbitrary position on the rail electrode surface and insulated from the rail electrode is connected in parallel with the rail gun, and is triggered by plasma generated by an electric bridge. The method of the present invention using a gap switch attenuates the armature current anywhere in the railgun accelerating hole using only a simple circuit, irrespective of the power source and type, without the need for complicated trigger circuits. Can be done.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining an embodiment of the present invention, and FIG.
FIG. 3 is a characteristic diagram showing a change over time of the armature current according to the embodiment. FIGS. 3 (a), (b) and (c) are schematic diagrams for explaining a specific example of the present invention, and FIG. And (b) are schematic diagrams for explaining a conventional technique. 1: Rail electrode, 2: Acceleration hole, 3: Flying object, 4: Plasma forming material, 5: Main power, 6: Switch, 7: Plasma armature, 8: Small electrode, 9: Gap switch, 10: Cavity, 11: the bridge, 12: plasma, 13: pore, I _0: capacitor current, I _1: armature forming wire explosion circuit current, I _2: gap switch current, I _A: armature current, T _M: cannon Plasma emission time at the mouth.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor, Usaba, 1-1-1, Higashi, Tsukuba, Ibaraki Pref., Institute of Chemical Technology, Industrial Technology Institute (72) Inventor Yozo Kakudate, 1-1-1, Higashi, Tsukuba, Ibaraki, Japan Within the Technical Research Institute (72) Inventor Masanori Yoshida 1-1-1 Higashi, Tsukuba City, Ibaraki Prefecture, Japan Institute of Chemical Technology Research Institute (72) Inventor Katsutoshi Aoki 1-1-1 Higashi, Tsukuba City, Ibaraki Prefecture, Japan Institute of Chemical Technology Institute ( 72) Inventor Hiroshi Yamawaki 1-1, Higashi, Tsukuba, Ibaraki Pref., Institute of Industrial Science and Technology (72) Inventor Shuzo Fujiwara 1-1, Higashi, Higashi Tsukuba, Ibaraki, Japan Masahiro Miyamoto 2-2-1 Nagasaka, Yokosuka City, Kanagawa Prefecture Inside Fuji Electric Research Laboratory Co., Ltd. (72) Inventor City Kiyoshi Kiyoshi, 1-2-1 Yurakucho, Chiyoda-ku, Tokyo Asahi Kasei Kogyo Co., Ltd. (72) Inventor: Minoru Taniya, 3rd floor, 4th floor of 191 Umehara Building, 191-me Nakahotori-cho, Oike-dori, Karasuma-Higashi-iri, Nakagyo-ku, Kyoto-shi, Kyoto light

Claims (2)

(57) [Claims] In a circuit comprising a railgun type electromagnetic accelerator and a large current power supply (including a switching system and a crowbar circuit) for supplying an acceleration current, an end face is formed at a specific location on a rail electrode surface inside an acceleration hole. And a gap switch that is connected in parallel with the railgun-type electromagnetic accelerator, has a cavity for installing an electric bridge for plasma generation, and a plasma injection hole inside the electrode. Newly provided, one end of the bridge is connected to the inner wall of the cavity, the other is connected to the small electrode, and a part of the armature current is guided to the bridge when the plasma armature passes through the small electrode position. The generated plasma is ejected from the plasma injection hole to cause dielectric breakdown between the electrode gaps, and the armature current is commutated to the discharge current between the gap switches. Wherein the method of damping the armature current of the railgun electromagnetic accelerator. 2. A small electrode whose end face is exposed at a specific place on the surface of a rail electrode inside an acceleration hole of a railgun type electromagnetic accelerator and is insulated from the rail electrode, and connected in parallel with the railgun type electromagnetic accelerator. A cavity for installing an electric bridge for plasma generation and a gap switch connected to one end of the electric bridge having a plasma injection hole inside the electrode and having one end connected to the inner wall of the cavity and the other connected to the small electrode, A railgun type electromagnetic accelerator, wherein a part of an armature current can be diverted to a discharge current between gap switches when a plasma armature passes through a small electrode position.