JPS58157098A - Plasma device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a plasma device that allows plasma to be confined for a long time using an open magnetic field.

[Prior art and its problems]

It is well known that when confining plasma in an open magnetic field, it is necessary to increase the plasma confinement time in fusion reactors, but this also applies to plasma equipment used for purposes other than fusion reactors. By increasing the confinement time, the power consumption of the plasma generator can be reduced, the density of the plasma can be increased, and the thermal force applied to the solid wall surrounding the plasma can be reduced. It will be done. In order to prolong the confinement time by plasma confinement by an open system magnetic field, plugging at the open end of K will be considered as a membership fee.
:Reductton of Losses i
n 0pen -gndedMagnetic Tr
aps; NucleaCFusion, 19 (
'79), 81085, etc., there are two types of zero plugging: one using high frequency and the other using an electrostatic field.
There is bipolar potential confinement due to tandem 2-Ra magnetic fields, and both of these are still under research. The electrode method includes an electromagnetic trap using an electrostatic plug consisting of an anode and a cathode at the cusp magnetic field point and line cusp.
Figure 1 is a diagram of the principle of an electromagnetic tiger, published in the literature T, J, Dola.
n, B, L, 8tansfield and J, M
, Larsen: Plasma Potential
in electroitattcmllypl
hugged cusps and mi rrors
: The Physics of Fluids.

18 ('75), 10.1383.

(1) is a set of two coils that are wound axially symmetrically around two axes to form a cusp magnetic field. (2) is a hollow cylindrical anode disposed at the point cusp, (3) is a hollow cylindrical cathode disposed at the point cusp, and (4) is a pair of annular anodes disposed at the line cusp. (5) is a set of two annular cathodes arranged at the line cusp, and a space sandwiched between a set of coils (1) and a cough coil (1).
A vacuum vessel (not shown) is disposed in the internal space of the body, and the vacuum vessel (not shown) is filled with gas to become plasma. An electron gun (not shown) is installed, and the electrons emitted from the cough electron gun pass through the female mosquito cathode (3) and the cough anode (2), move inside the wrinkled vacuum container (not shown), and ionize the filled gas. A plasma is formed. The dotted line (6) is
Indicates the boundary of the space where plasma exists. #The potential of cathodes (3) and (5) is zero, and the potential of anodes (2) and (4) is φ
In the case of a human being, the spatial potential φ near the two axes is distributed as shown in FIG.

The potential of the space where plasma exists is φC, and 0〈φ6〈φ
It is mu. On both sides of the space where the plasma exists, potential peaks are formed inside the anode (2), and the potential becomes φ6+φi at the highest potential point. When the charge of an ion is Ze and the charge of an electron is 10, the kinetic energy □ is Ze
The ion and kinetic energy are smaller than φゑ and eφ.

Smaller electrons cannot escape from the space where the plasma exists in the direction of the magnetic field, and ions are reflected back into the plasma as shown by arrows (7) and K, and electrons are reflected back to the plasma as shown by arrows (8). Temperature: T1° Electron temperature: T8
When.

mi >> kTi/Ze, φ, >>) kT,/a
・In addition to (1), the effect of conventional electromagnetic traps is that plugging can be performed at the open end of the plasma, and the confinement time can be significantly reduced.

This electromagnetic trap also had the following problems. As shown in Figure #I2, the space potential inside the cough anode (2) is maximum φi+φ. But.

Δφ =φe−(φi+φ,) ・・・(2
The difference Δφ between the anode potential given by ) and the space potential does not become zero, but is Δφ20. The reason why Δφ is formed is that electrons are captured inside the skeleton anode to form an electron group, and an electric field is created by the space charge created by the scissor electrons. Δ
φ is a function of the distance @r from the two axes.

It can be expressed as Δφ=Δφ(r). Considering the direction of the electric field created by the electron group.

Since the component of the electric field on the 02 axis is 0, Δφ is ~0 and the maximum value Δφmax.

Take Δφm□=Δφ(0). Therefore, within the limb anode, the potential on the two axes is from (2).

φi+φ. =φE1Δφmax. mi and φ. is determined by the particle number equilibrium of the plasma, etc., but it is generally the same size between species, and φi to φ. Because it is,
On the two axes, φi ~i (φe −Δφmax). In an electromagnetic trap, Δφmm・
・It is known that L(1) does not hold as in (3). However, in most parts of the cough anode, (1) holds, and (3
) is true only for a very small portion of , so the effect of increasing the plasma confinement time of the electrostatic plug in an electromagnetic trap is very small. Electrons that are ejected from the plasma and returned to the plasma form a space charge during their flight through the anode cavity, which limits the effectiveness of increasing the plasma confinement time due to the plasma leaking through this. This creates an electric field in the hollow part of the anode, but as the plasma becomes hotter and denser, this electric field becomes stronger.9 As a result, electrostatic plugging becomes impossible for extremely hot and dense plasma, and as a result, it becomes difficult to confine the plasma. There was also the problem that the number of guests and density were limited to relatively low values.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is, firstly, to provide an open system plasma device that can significantly increase plasma confinement time by providing an electrostatic plug without a loss aperture. The second object is to provide an open system plasma device that can confine even high-11iIIIi density plasma.

[Summary of the invention]

In order to achieve such an object, the present invention provides at least one electrode cape of an electrostatic plug at the open end of an open system plasma device, with a riser penetrating in the direction of the magnetic field and having a round hollow part, and a cough limiter coaxial with the cape. A tubular final stage anode disposed at the end, a final stage cathode disposed on the opposite side of the final stage anode to cover the opening of the final stage anode, and a scissors perforated in the final stage cathode. a control electrode extending through the through hole formed in the final stage anode and into the hollow part of the final stage anode to form a final vertical electrode assembly, and between the final stage anode and the limiter, at least one anode and at least one control electrode are formed. It is formed of one cathode, and the anode and cathode are arranged coaxially and alternately, and a through hole coaxial with the axis of the hollow part of the IJ mitter is bored in the anode and cathode. An intermediate electrode assembly was provided with a large angle in diameter from the electrode on the final stage anode side to the electrode on the limiter side.

〔Effect of the invention〕

The space potential control action of the control electrode forms an aperture-free electrostatic plug in the final stage electrode assembly, greatly increasing the plasma confinement time, and reducing the hollow space by 92 mm. By plugging the plasma in stages from the outside to the inside using an intermediate polarization assembly formed by electrodes that become smaller from the side of the anode to the side of the final stage anode, a large amount of electrons fly from the high-temperature, high-density plasma. Plugging is no longer impossible even when

[Embodiments of the invention]

FIG. 3 is a block diagram of a plasma device showing an embodiment of the present invention, and FIG. 4 shows the structure and operation of the main 411 part thereof.
(a) is a configuration diagram of an electrostatic plug, and (b) is a diagram showing the dependence of space potential φ on 2. A set of 2' coils (1) are wound axially symmetrically around two axes, and together with an excitation power source (not shown) constitute a device that generates a kind of cusp magnetic field of an open system magnetic field that accommodates plasma. (4) is a set of two annular anodes arranged at the line cusp, which is one of the open ends of the cusp magnetic field, and (5) is a set of two annular cathodes arranged at the line cusp. It constitutes an electrostatic plug that forms an electric field with a non-zero component parallel to the direction of the magnetic field, and the space between the two coils (1) and the space inside the coil (1) is , one vacuum vessel (not shown) is provided, and the plasma boundary surface (
A limiter (9) having a hollow portion extending in the direction of the magnetic field defining the limiter (9) is housed. The potential of the space where the plasma exists is the potential φ! of the area surrounding the plasma (9). 0, that is, the conduction of plasma electrons and ions through the sheath existing between the limiter (9) and the plasma, determines the potential difference between the plasma and the limiter (9), that is, the sheath voltage φ3, so φ ,=φ! +φ, ...(4)
φ is determined by .

The α slot has a hollow part that penetrates in the direction of the magnetic field, and the slot (9)
A tubular final stage anode arranged coaxially with the final stage anode 13 is located on the opposite side from the iron final stage anode 17 (9) to cover the opening of the scissors final stage anode 13. Stage cathode, α value is 9 through holes drilled in the final stage cathode of the scissors, aD is the hollow part (to) the final stage anode that passes through the through hole (extending control electrode), 08 is the intermediate electrode assembly The anode of , αη is the cathode of the intermediate electrode assembly, the anode αe and the cathode α force form the intermediate electrode assembly, # intermediate electrode assembly (11 is coaxial with the limiter (9), the final stage anode a and the limiter (9), and four anodes αe and four cathodes α are arranged alternately. A through hole is drilled, and the diameter of the through hole is a large umbrella from the electrode on the final stage anode housing side to the electrode on the IJ meter (9) side. For electrodes, each anode UJ as, control electrode αυ, limiter (9)
, 0 limiter (9) that gives a higher potential in the order of each cathode ring Qη
, final stage anode lII, control electrode circle, final stage anode 03° power supply αm (14) (1!9, When the intermediate electrode is assembled, it constitutes an electrostatic Bragli, and in this example, it is the open end of the cusp magnetic field. A nuclear electrostatic plug O is arranged at each of the two point cusps, and each of the electrostatic plugs forms an electric field having a non-zero component parallel to the direction of the magnetic field, as will be explained in detail below.

A potential φ8 is applied to the forged #1%ffl anode 4 and the four anodes αe of the intermediate electrode assembly by the electric currents s03 and α4, and a potential is applied to the control electrode a by the isthmus electric current ilI. Anode (II and four cathodes α of the intermediate electrode assembly)
A potential φk is applied to η by a power source α9, and between each potential.

φk〈0×φg〈φ3...The following relationship (5) holds true. The limiter (9) is grounded, and the plasma@ is in contact with the inside thereof through the sheath. From (4), the potential φ in the space where plasma exists is φ,=
φ. For each potential φ, the absolute value of φ, φ1 is set large so that the electrostatic plug acts effectively.
1φ, 1 (1φ coverage 1.φ,, φ8. That is, (
5), φk〈φ,〈φ,〈φ8...(6)
holds true.

The operation and effect of the electrostatic plug constructed in this manner and shown in FIG. 4(a) as an example will be explained again with reference to FIG. 4(b). As well as inside the anode of the electrostatic plug at the point cusp of the trap.
Electrons are captured to form a group of electrons, and the space charge created by the group of electrons creates an electric field. One difference between the electrostatic plug of the plasma device according to the present invention and the electrostatic plug at the point cusp of an electromagnetic trap is that in the electrostatic plug according to the present invention, a group of electrons is formed in the hollow part of the final stage anode. The density of is controlled by the potential φ of the control electrode αυ and the potential φ of the final enemy anode fia1J, and as a result, the space potential φ(r
, g), the lowering of the potential barrier at r~O as shown in equation (3) and the formation of a loss aperture due to this, as in the case of an electrostatic plug at the point cusp of an electromagnetic trap, are , can be easily avoided in the electrostatic plug according to the present invention. The space potential φ in the hollow part of the final stage anode is as follows, assuming that the radius of the inner surface of the final stage anode is Ra and the cough control electrode is r=RgK. Here, φ0 is the minimum value of φ, which is the potential at r=0, and the condition φ0>φp is a necessary condition for the control electrode a1 to be able to control the spatial potential. In the hollow part (2) of the final stage anode, the electric field is oriented in the direction, so the electron group is
Drifting around the axis.

The stability of the potential distribution shown in equation (7) means that even if the potential distribution changes, the potential distribution will remain (
7) You can understand this by going back to what is shown in 2. If formula (7) holds true, then φ(~)=ri...(8). If the electron density increases, the electric field becomes stronger and φ
(Rg)<φ. At this potential, electrons rapidly collide with the control electrode and are absorbed, so the electron density continues to decrease until equation (8) is established, and eventually the potential returns to equation (8).

Furthermore, if the electron density decreases, φ(Rg)>φ, and the electrons collide with the control electrode and disappear. The electron density has a strong tendency to increase due to electrons supplied from the plasma, and as the electron density increases, the potential eventually returns to equation (8).

That is, due to the action of the control electrode, the space potential becomes (7)
The distribution is maintained stably as shown in Eq.

Next, consider the potential φ in the space where plasma (2) exists.

In the space where plasma (2) exists, the electric field is very weak, so the potential φ can be considered to be constant. That is, φ=φ. As mentioned above, the sheath voltages φ and φ are equal. That is, φ,=φ3. The sheath voltage φ3 takes a negative value due to the difference in the Rahma radius of the ions and electrons that make up the plasma, and its large value! The diameter is the large umbrella of the potential applied to each electrode of the electrostatic plug, 1φkl, 14. .

The extension is smaller than φ1. That is, 1φ, 1(1φ
kl, φg, φ8 (9).

FIG. 4(b) shows the potential φ on the Z axis, that is, on the straight line C-C. and a straight line B-B that is in contact with the inner surface of the final stage anode and parallel to the Z axis.
The upper potential φ8 is shown. Since φ0 is the minimum value of φ in the hollow part j of the Mth-stage anode, for all r,
It can be seen that a potential barrier for both ions and electrons as shown in FIG. 2 is formed, and there is no loss aperture.

Ions are reflected by the potential barrier (φ-φ, )z, and electrons are reflected by the potential barrier φ2-φk. The relationship corresponding to (1), −0−φp >> kT 4 /Ze, φ, −φ*
>> kTe/e −(11) can be easily realized because (9) holds. Therefore, it is possible to realize an open system plasma device that can significantly increase the plasma confinement time.

This is the first effect of the present invention.

Electrostatic plugs also have the advantage that electrons ejected from the plasma surrounded by the limiter, reflected by the potential barrier created by the cathode, and returned to the plasma form a space charge while flying through the hollow part of the anode and enter the hollow part of the anode. An electric field is created in the r direction, but as the plasma becomes hot and dense, more electrons are ejected from the plasma and the electric field formed in the anode hollow becomes stronger9.
The anode potential is scattered near the anode hollow part, making electrostatic plugging impossible. As a result, there is a problem in that the temperature and density of plasma that can be confined are limited to relatively low values. In contrast, the present invention is formed of at least one anode and at least one cathode between the final stage anode and the limiter, and the anode and the one pole are arranged coaxially with the limiter and alternately. A through hole coaxial with the axis of the hollow part of the limiter is drilled in the cathode and the intermediate electrode assembly. By arranging the three-dimensional structure, we were able to confine high-temperature, high-density plasma. To explain this again with reference to the embodiment shown in FIG. The potentials of the anode 11e and the anode Q?) are dispersed near the axis of symmetry as described above, and as a result, the plasma penetrates the through holes of the anode 11e and the cathode αη as shown by the dotted line. However, an electric field is formed outside the boundary of the plasma in the r direction, creating a potential barrier for ions and electrons. By selecting the number of pairs of anodes and cathodes in the intermediate electrode assembly according to the thickness of the plasma at the position of 0, the thickness of the plasma at the position of By making it thinner, an electrostatic plug without a loss aperture can be realized in the final stage anode and cathode and control electrode. The second effect of the present invention is that this high-temperature, high-density plasma can also be confined.

[Other embodiments of the invention]

The present invention relates to an open plasma device. In the embodiment, a plasma apparatus using a cusp magnetic field has been described, but the present invention is not limited to a cusp magnetic field, and it goes without saying that the present invention can be applied to any open system, and may be applied to, for example, a uniform magnetic field or a mirror magnetic field. In addition, there are no limitations on the use of plasma equipment. For example, nuclear fusion reactors, surface processing/processing, 1m contact, etc.
It can be applied to plasma devices such as ion sources.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the principle of an electromagnetic trap. Figure 2 is a diagram showing the distribution of space potential near the two axes of an electromagnetic trap. Figure 3 is a configuration diagram of a plasma device showing an embodiment of the present invention. Figure 4 is the third
Main 4I of the embodiment shown in the figure! (a) is an electrostatic plug configuration diagram, (b) is a space potential φ of 2.
It is a diagram showing dependence. (1)...Coil, (2), (4)...Anode,
f3), (5)... cathode, (9)... limiter,
(II... final stage cathode, Oυ... control electrode. Ql... final stage anode, I, 0m), Qj, power supply, αe
...anode of the intermediate electrode assembly. ■... Cathode of intermediate electrode assembly, 轡... Intermediate electrode assembly, al... Through hole, (corridor...
・Final stage lia...hollow part, electrostatic plug, @...plasma. Agent: Patent attorney Kensuke Chika (and 1 other person)

Claims (1)

[Claims] A device for generating an open magnetic field containing plasma, a means for controlling the electric potential of a space where the plasma exists, and a device disposed at the open end of the open magnetic field parallel to the direction of the cough magnetic field. and an electrostatic plug forming an electric field with a non-zero component. At least one of the electrostatic plugs includes a limiter having a hollow portion penetrating in the magnetic field direction of the open system magnetic field, a tubular final stage cathode disposed coaxially with the cough limiter, and a cough ant final stage anode. A final stage cathode arranged to cover the opening of the mosquito final fiber anode on the side opposite to the IJ j side, a through hole drilled in the final stage cathode, and a final stage A control electrode extends into the hollow part of the anode, and is formed of at least one anode and at least one cathode, and the anode and cathode are arranged coaxially with the limiter and alternately between the final stage anode and the IJ limiter. In addition, a through hole coaxial with the axis of the hollow part of the anode and # is bored in the anode and #, and the diameter of the core through hole is from the electrode on the final stage anode side to the electrode 41 on the limiter side. 1. A plasma device comprising: a large intermediate electrode assembly; and means for applying a high potential to each anode, control electrode, limiter, and cathode to each electrode, etc.