JPH028672B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention is directed to an intense magnetic field.
TECHNICAL FIELD The present invention relates to generating instantaneous strong magnetic fields by means of laser plasma methods and apparatus.

One field in which generating instantaneous strong magnetic fields as described above would be most useful is in the field of laser-ignited thermonuclear fusion power generation. One proposed technique for generating electricity from controlled thermonuclear fusion reactions involves injecting small pellets of deuterium or tritium into a vacuum chamber and using energy provided by laser light. It involves "driving" deuterium ions and tritium ions to cause a nuclear fusion reaction and generate helium ions and neutrons. Since helium ions and neutrons have slightly lower masses than deuterium and tritium ions, a small amount of mass can be calculated using the famous Einstein equation E = mc ² (where E is the energy generated and m is the energy converted (mass, c, each equal to the speed of light) is converted into energy.

Upon absorption of the laser pulse, the outer region of the pellet heats up rapidly, forming an ionized gas or plasma that expands outward at high velocity. The pellet core is compressed by the recoil impact of the outer layer of the pellet being blown away at super high speed.This is because the rocket is pushed forward by the impact of the rocket's jet, and the rifle is pressed against the shoulder by the recoil from firing the rifle. It's the same logic.

According to predictions based on theory, the center of the pellet core has a superdensity between 1,000 and 10,000 times the normal solid density.
In other words, it will be compressed to about 10 times the density of the center of the sun (about 100 times the density of lead). The reason why it is important that the pellet core has the above density is that the probability of collision between active deuterium ions and tritium ions increases significantly. In addition, when the above density is reached, the unfused deuterium ions and tritium ions absorb the energy of the helium particles before the high-speed helium particles generated by fusion fly out of the pellet core region. Some of it will be absorbed or distributed. This is analogous to fast-moving balls colliding with other balls and imparting their kinetic energy. This energy sharing with the fuel before combustion causes so-called "bootstrap" heating, further increasing the reaction rate. Obtaining core compression is extremely important in laser fusion.

In reality, there are forces that oppose and prevent core compression. One problem that has only recently been recognized and studied is the effect of active or hot electrons on the plasma in the surface region of the pellet. The generated high-temperature electrons orbit and penetrate the pellet core at high speed, heating the core, making it increasingly difficult to compress the core.
Therefore, for a given laser energy, the compression is reduced and the final energy gain is also reduced. The problems caused by hot electrons and the need to control hot electrons are RB
Physical Review by Spielman et al.
Letters, Vol.46, No.13, p.821 (March 30, 1981)
is being discussed. Measurements of large return currents in positively charged plasma generated by lasers were reported by RFBenjamin et al. in Physical Review Letters, Vol. 42, No.
14, p. 890 (April 2, 1979).

Accordingly, one object of the present invention is to control the hot electrons of the laser generated plasma to reduce penetration of the pellet core by the hot electrons.

Another object of the present invention is to control high-temperature electrons in plasma generated by a laser by generating an instantaneous strong magnetic field.

Yet another object of the present invention is that it is useful for controlling high temperature electrons in laser-generated plasma, and for other purposes such as experimental research on the response of biological cells, tissues, etc. to magnetic stimulation. The purpose is to generate an instantaneous strong magnetic field, which is also effective in the field.

According to this invention, generation of high temperature electrons and positive charge plasma is intentionally started in the first plasma generated by the laser. The positively charged plasma is then provided with a low impedance path to the ground plane, and a strong but very instantaneous magnetic field is generated via the return high current mechanism of the positively charged plasma.
In one embodiment of the invention, an object, such as a biological cell, is confined within or near the aforementioned low impedance path and exposed to a momentary strong magnetic field. In another embodiment of the invention, a fusion pellet is confined within or near said low impedance path and is lased immediately after the onset of said first plasma and during the duration of a strong magnetic field; The hot electrons of the fusion pellet's plasma are thereby confined and controlled in very tight orbits so that they do not penetrate the core region of the fusion pellet.

An advantage of this invention is that the hot electrons of the laser-generated plasma are controlled by earlier laser-generated events, thus reducing the laser equipment needed to generate the fusion plasma. , which can also be used to generate the aforementioned early hot electron control events.

Another advantage of the invention is that momentary strong magnetic fields can be generated for organic and inorganic experimental purposes.

Other objects, advantages and novel features of the invention will become apparent from the following description.

The accompanying drawings show an embodiment of the invention, in which a target 11 is held inside a momentarily strong magnetic field generating target assembly 13, which has one end connected to a ground plane 15 and the other end connected to an emitter. 17 (see Figure 1). When placed in a vacuum cavity and irradiated with intense laser light pulses, the emitter 17 is converted into highly charged positive plasma, and a strong return current flows between the ground plane 15 and the emitter 1.
7 through the target assembly 13. This exposes the target 11 to a momentary strong magnetic field.

A helically or coiled target assembly 13 as shown in FIG. 1 exposes the target 11 to a longitudinal magnetic field. The target assembly 13 can also be cage-shaped so that the target 11 is exposed to an azimuthal magnetic field (see FIG. 2).
In order to generate the desired instantaneous strong magnetic field, it is important to keep the target assembly 13 low impedance and resistance.

Emitter 17 is preferably a microballoon made of glass, plastic, metal, or a combination of these materials. Emitsuta 1
7 is utilized to generate positive plasma when irradiated with laser light pulses of approximately 10 ¹⁵ watts/cm ² or more. The hot electrons ejected from the emitter 17 by the laser pulse cause the residual positive high potential to cause a momentary but strong current to flow through the target assembly 13 to the ground plane 15 (first, (See Figure 2). A suitable emitter is a glass microballoon with a diameter of about 500 microns.

RFBenjamin and others, Physical Review
Letters, Vol.42, No.14, p.890 (April 2, 1979)
According to studies such as those detailed in , the plasma potential that an irradiated emitter can generate is on the order of 180 kilovolts and duration on the order of nanoseconds. Under the above conditions, instantaneous strong magnetic fields on the order of 100 kilogauss or more can be generated depending on the resistance and actance of the return current path.

The target 11 is a small object on the order of 1 mm in diameter. Target 11 is organic matter,
It can be inorganic, metal, non-metal, etc.
In one application of this invention, target 1
1 is a pellet containing fusion fuel. The above pellets are usually hollow glass or metal spheres (called microballoons) with a diameter of sub-millimeter filled with high-pressure DT gas.
It is often coated with additional layers or wrapped in concentric shells of metal or plastic to optimize the interaction of the target 11 with the laser light.

When the present invention is used in laser fusion experiments and power generation, preliminary laser light strikes the emitter 17 for a short period of about 1 nanosecond or less before the main laser light strikes the target 11. The resulting "return current" described above creates a strong magnetic field near target 11 at the moment it is irradiated. This strong magnetic field traps the hot electrons from target 11 and holds them in small orbits, preventing them from heating the fuel within target 11 and retaining their energy in the area outside the fuel-containing core. That's what I do.

The size and location of target assembly 13 can be as desired. For example, target assembly 1
The position No. 3 may be placed outside the absorption region (that is, the volume surrounding the target 11 that absorbs the irradiation of the main laser beam). When the target assembly 13 is a cylindrical cage (see Fig. 2), the target 11
The free electrons ejected from the orbit are captured in small orbits as described above. Alternatively, the position of the target assembly 13 may be adjusted between the laser absorption region and the target 11.
Between this and the target 11, the fuel may be magnetically shielded from hot (ie, "high energy") electrons. Another option is to generate a longitudinal magnetic field, for example by making the target assembly 13 coiled or helical (see FIG. 1).

The actual physical construction of this inventive device can be easily accomplished by those skilled in the art (see FIG. 3). A round glass rod 19 (preferably about 4 cm in length and 2 mm in diameter) is pulled to a tip 21, which is ground to a diameter of 125 microns. The large diameter end 23 of the round bar 19 is fixed to the metal base 25 by adhesive or the like, while the tip 21 is similarly glued to the target 11. Note that the target 11 can be a 1 mm aluminum ball or a similarly sized DT fuel pellet. Target assembly 13, which is a 255 micron diameter copper wire, is attached to metal base 2.
5 and wrapped around the target 11. Next, the emitter 17, which is preferably a 500 micron glass microballoon, is
Glue to target end 27 of target assembly 13. Metal base 25 is connected to ground plane 15 for proper operation.

This invention requires high output laser equipment. Such equipment is available at the Los Alamos National Laboratory.
Laboratory) and many other research institutes, institutions,
Available at universities. To generate the electromagnetic field necessary to accelerate the electrons to a velocity that allows them to escape and create a positive potential in the plasma, intense laser light of about 10 ^{to 15} watts/ ^cm2 or higher is required. is preferred. Carbon dioxide lasers are preferred because they generate high energy electrons more efficiently than other commonly available lasers.

The foregoing description of preferred embodiments of the invention has been presented for purposes of illustration and description, and the invention is not limited to the illustrated embodiments. Those skilled in the art will appreciate that many variations and modifications are possible within the scope of the claims.

[Brief explanation of drawings]

Figure 1 shows a target surrounded by a coil with one end attached to the emitter and the other end grounded; Figure 2 shows a target surrounded by a coil with one end attached to the emitter and the other end grounded;
3 shows a target surrounded by a cylindrical cage with the other end grounded; FIG. 3 shows an arrangement for surrounding the target with a coil according to the embodiment of the invention shown in FIG. It shows. 11...Target, 13...Target assembly, 15...Earth plane, 17...Emitter.

Claims (1)

[Claims] 1. An instantaneous strong magnetic field generator for use with a high-power laser, which emitter emits high-temperature electrons and generates positively charged plasma when irradiated with the high-power laser. means, a target means which is exposed to a momentary strong magnetic field, and a return current to a ground plane for said positively charged plasma generated by said emitter means connected to said emitter means and located proximate to said target means. and a grounding means for providing a path, and when the emitter means is irradiated with the high-power laser, a return current flowing through the return current path generates an instantaneous strong magnetic field near the target means. An instantaneous strong magnetic field generator using laser plasma, which is characterized by 2. The apparatus of claim 1, wherein said return current path provided by said grounding means includes a coiled portion surrounding said targeting means. 3. The apparatus of claim 1, wherein said return current path provided by said grounding means includes a cylindrical cage-like portion surrounding said targeting means. 4. The device according to claim 1, wherein the emitter means is a microballoon. 5. The device according to claim 4, wherein the microballoon is a glass microballoon.