JP2002168982A - Inertia electrostatic containment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inertia electrostatic containment device capable of stably applying a high voltage of 100 kV class effective for generating neutrons between a negative electrode and a positive electrode. SOLUTION: A cage type spherical intermediate electrode 4 is concentrically positioned in a space between the positive electrode 3 and the negative electrode 4. An electric potential of a predetermined high voltage is applied to the intermediate electrode 4 from a power source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an inertial electrostatic confinement device for electrostatically confining accelerated ions and generating neutrons by nuclear fusion.

[0002]

2. Description of the Related Art As a neutron source having a compact structure, an inertial electrostatic confinement device has been studied. Examples of inertial confinement devices include “Current Trends in Inter
national Fusion Reserch, Proceedings of the Second
As described in Symposium (1999), p.177-178 ", the device developed at the University of Illinois in the United States has a simple configuration with a high-voltage spherical cage electrode in a small spherical vacuum vessel. In this apparatus, the vacuum vessel wall is used as an anode (ground potential), the center cage electrode is used as a cathode, and -65 is used as a cathode.
The configuration is such that a high voltage of kV can be applied. The cathode is 1
It is fixed to the vacuum vessel wall by the current introduction terminals. The current introduction terminal has a withstand voltage performance enough to withstand a sufficiently high voltage on the atmosphere side and the vacuum side, and has airtightness as a part of a vacuum vessel. The gas pressure in the vacuum vessel is adjusted by a gas supply system and a vacuum pump. In this device, a high voltage applied between the anode and the cathode forms a glow discharge in the space between the cathode and the anode, and accelerates ions generated by the glow discharge in the same space between the cathode and the anode. The accelerated ions pass through the cage cathode,
Then, while decelerating, it travels to the opposite side of the anode, reverses there, and is accelerated again between the anode and cathode. . . And reciprocating several times while changing the orbit partially. Due to the configuration of the device, the density of ions electrostatically confined in this manner becomes maximum near the center of the spherical cage cathode. When deuterium (D) or tritium (T) is used as a gas type, nuclear fusion (D) occurs when these ions collide with each other or when ions collide with a neutral gas.
-D reaction or DT reaction), and neutrons are generated. Most of the fusion reactions take place at the center of the spherical cage cathode where the density of ions increases due to confinement.

[0003] For example, "18th IEEE / NPSS Symposiu
m on Fusion Engineering, Oct. 25-29, 1999, OA1-3 "
In the device announced by LANL, a high voltage of 75 kV is applied between a concentric spherical anode (outside) and a cathode (inside) provided in a small spherical vacuum vessel with a diameter of about 300 mm, and is generated outside the anode. The low energy ions are accelerated between the anode and cathode. In this device, a cage-shaped spherical electrode (applied a positive potential of 1 kV or less) is further provided between the outer spherical anode (ground potential) and the spherical vacuum vessel wall (ground potential) to provide a space between the vacuum vessel wall and the anode. To form a glow discharge, thereby generating low energy ions.
Further, as means for stably forming the glow discharge, six electron guns are provided on the wall of the vacuum vessel.

[0004]

The reaction cross section for generating neutrons by causing nuclear fusion by collision of accelerated ions depends on the acceleration energy of the ions.
In any case of the -T reaction, it increases in a proportional or more relationship up to about 100 keV. Especially, the reaction cross section is larger than other D
The -T reaction has a peak at a little over 100 keV. Therefore, one effective method for increasing the number of neutrons generated is to enable a high voltage of about 100 kV to be stably applied between the cathode and the anode.

However, in the above-mentioned prior art, the high voltage applied between the anode (low voltage: ground potential in this case) and the cathode (high negative voltage) is 65 k in design specification.
V to 75 kV, and the experimental value is limited to 40 kV to 60 kV, and there was a problem that sufficient neutrons could not be generated.

An object of the present invention is to provide an inertial electrostatic confinement device capable of stably applying a high voltage of the order of 100 kV effective for generating neutrons between a cathode and an anode.

[0007]

(1) In order to achieve the above object, the present invention provides a spherical anode disposed in a vacuum vessel and a basket concentrically disposed on the inner peripheral side of the spherical anode. Type spherical cathode, a plasma chamber provided in a space outside the spherical anode, and an inertial electrostatic confinement device having a high voltage power supply for applying a high voltage between the anode and the cathode, wherein the And a high-voltage application means for applying a predetermined high-voltage potential to this intermediate electrode. With such a configuration, a high voltage of 100 kV class effective for generating neutrons can be stably applied between the cathode and the anode.

(2) In the above (1), preferably,
The high voltage applying means applies a potential larger than the magnitude (absolute value) of the potential at the position of the intermediate electrode in the absence of the intermediate electrode to the intermediate electrode.

(3) In the above (1), preferably,
A current introduction terminal for applying a potential to the cathode and the intermediate electrode,
It is constituted by an insulator and a conductor which are coaxial with each other.

(4) In the above (1), preferably,
A current introduction terminal for applying a potential to the cathode and the intermediate electrode,
The spherical anode and the cage spherical cathode are arranged at positions facing each other with respect to the center.

(5) In the above (1), preferably,
The power supply for applying a potential to the cathode and the high voltage applying means for applying a potential to the intermediate electrode are constituted by one high voltage power supply and a resistive voltage divider.

(6) In the above (1), preferably,
The power supply for applying a potential to the cathode and the high voltage applying means for applying a potential to the intermediate electrode include: an insulating transformer;
A plurality of power supplies connected to the next side are connected in series on the output side.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A configuration of an inertial electrostatic confinement device according to a first embodiment of the present invention will be described below with reference to FIGS. First, the overall configuration of the inertial electrostatic confinement device according to the present embodiment will be described with reference to FIG. FIG. 1 is a sectional view showing the overall configuration of the inertial electrostatic confinement device according to the first embodiment of the present invention.

The inertial electrostatic confinement apparatus 1 includes a spherical vacuum vessel 2 having a spherical anode 3 having a large radius Ra and a cage spherical cathode 4 having a small radius Rk concentric with the anode 3. The anode 3 has a plurality of openings 3a for extracting ions,
, 3f are provided. Furthermore, in the present embodiment, one space Rm having a radius smaller than the radius Ra of the anode 3 and larger than the radius Rk of the cathode 4 is concentric with the anode 3 and the cathode 4 in the space between the anode 3 and the cathode 4. A cage-shaped spherical intermediate electrode 5 is provided. Here, the “cage-shaped sphere” which is the shape of the cathode 4 and the intermediate electrode 5 is, specifically, a metal wire, a metal pipe, or a metal plate formed into a ring shape and the outer shape is substantially spherical. It is intended to form a basket. In particular, the cathode 4 uses tantalum or tungsten as a high melting point material. Although the anode 3, the cathode 4, and the intermediate electrode 5 are arranged concentrically, the center of each spherical electrode is slightly (for example,
(About 10%). As described above, the anode 3, the cathode 4, and the intermediate electrode 5, including those slightly shifted, are referred to as being arranged concentrically, and the same applies to the following embodiments. Further, the shape of each electrode is not limited to a spherical shape, but may be an ellipsoidal shape.

Further, a coaxial high voltage current introducing terminal 6 is provided so as to penetrate the wall of the vacuum vessel 2. The introduction terminal 6 includes a cylindrical insulator 62 such as alumina ceramic provided outside the linear center conductor 60, a cylindrical conductor 61 such as copper or stainless steel provided outside the insulator 62, and a conductor 61. Cylindrical insulator 63 provided outside
Are coaxially configured. The introduction terminal 6 keeps the airtightness between the atmosphere and the vacuum vessel, structurally supports the cathode 4 and the intermediate electrode 5, and can independently apply a potential to the cathode 4 and the intermediate electrode 5. That is, in the configuration of the introduction terminal 6, the anode 3, the cathode 4, and the intermediate electrode 5 can be electrically insulated from each other.

Outside the vacuum vessel 2, two high-voltage power supplies 7, 8 are provided. The output terminals 7k, 8m of the high-voltage power supplies 7, 8 are respectively connected to the connection terminals 6k, 6m of the coaxial introduction terminal 6, and apply a predetermined potential to the cathode 4 and the intermediate electrode 5. The outer surface of the insulator of the introduction terminal 6 on the atmosphere side is formed in a pleated shape, although not shown, in order to increase the withstand voltage of the creeping surface.

A plasma chamber 10 is provided in a space inside the vacuum vessel 2 and outside the anode 3. A filament 11 is disposed in the plasma chamber 10 and is heated by an external power supply 12 to generate thermoelectrons. Further, a cage-shaped spherical electrode 13 is arranged in the plasma chamber 10, and is connected to a power supply 15 via a resistor 14.

A source gas such as deuterium necessary for the nuclear fusion reaction is supplied to the plasma chamber 10 by a gas supply system comprising an external gas cylinder 20 and a gas flow adjusting means such as a valve 21.
Through the vacuum vessel 2 and evacuated by a vacuum pump 22 communicating with the vacuum vessel 2. By appropriately setting the gas supply system and the gas exhaust system, the gas pressure in the vacuum vessel is set to a required value.

Next, the potential distribution inside the vacuum vessel in the inertial electrostatic confinement device according to the present embodiment will be described with reference to FIG. FIG. 2 is an explanatory diagram of a potential distribution inside a vacuum vessel in the inertial electrostatic confinement device according to the first embodiment of the present invention.

The inertial electrostatic confinement device 1 according to the present embodiment
, The anode 3 is set to the ground potential, and a negative high voltage, for example, -100 kV is applied to the cathode 4. An arbitrary high voltage can be applied to the intermediate electrode 5 within the range of the withstand voltage. In the present embodiment, -50 kV is applied.

When the entire interior of the vacuum vessel 2 is in an ideal vacuum state, that is, when there is no gas and therefore no plasma is present, the potential distribution between the cathode and the anode is as shown by the solid line A in FIG. On the other hand, for comparison, the potential distribution between the cathode and anode when there is no intermediate electrode under the same conditions is as shown by the dashed line B in FIG.

When there is no intermediate electrode, the gradient of the potential, that is, the electric field strength (absolute value)
Is smallest at the outer anode portion (R = Ra), becomes gradually stronger as approaching the cathode at the center of the sphere, and becomes largest at the cathode portion (R = Rk). Therefore, one between the anode and cathode
When a high voltage of 00 kV is applied, the electric field strength of the cathode portion becomes too large, so that a dielectric breakdown occurs, so that a very high voltage cannot be applied.

Here, the voltage applied to the intermediate electrode 6 is as follows. That is, when there is no intermediate electrode indicated by the one-dot chain line B, the potential at the distance Rm from the center of the sphere (the position of the intermediate electrode 6 in the solid line A) is −20 kV. Therefore,
In the present embodiment, the magnitude of the potential of the intermediate electrode 6 with respect to the anode 3 (absolute value: 50 kV) is the magnitude of the potential at that position (absolute value: 2 kV) when there is no intermediate electrode 6 under the same other conditions.
0 kV). Incidentally, in FIG. 2, the distance Rm ′ (Rk <R
If the intermediate electrode 6 is arranged at m '<Rm) and -50 kV is applied, the curve A becomes coincident with the curve B. As is clear from FIG. 2, in the present embodiment (solid line A), the electric field intensity near the cathode is small even when there is no intermediate electrode (dashed line B). Therefore, in the present embodiment, dielectric breakdown near the cathode 4 is unlikely to occur, and a sufficiently high voltage (−
100 kV) can be stably applied to the cathode.

The ions generated in the plasma chamber 10 are extracted through a plurality of openings 3a,..., 3f provided in the anode 3 into an acceleration space (anode 3−intermediate electrode 5−cathode 4) and accelerated. After that, they collide with each other while repeating reciprocating motion (acceleration or deceleration) between the anode and cathode, causing a nuclear fusion reaction to generate neutrons. In the present embodiment (solid line A), the electric field strength near the anode is stronger than that without the intermediate electrode (dashed-dotted line B), so that the extraction of ions from the plasma chamber 10 is facilitated.

Here, the relationship between the deuterium energy and the cross section of the nuclear fusion reaction will be described with reference to FIG. FIG.
FIG. 4 is an explanatory diagram of a relationship between deuterium energy and a fusion reaction cross section.

In FIG. 3, the horizontal axis represents deuterium energy (keV), and the vertical axis represents a fusion reaction cross section (barn).
s). The reaction cross-section that causes nuclear fusion by collision of accelerated ions and generates neutrons depends on the acceleration energy of the ions. In both cases of the DD and DT reactions, the reaction cross section is more than proportional to about 100 keV. To increase. In particular, for a DT reaction having a larger reaction cross section than the others, 1
It has a peak slightly above 00 keV.
Therefore, if a high voltage of about 100 kV can be stably applied between the cathode and the anode, the number of neutrons generated can be increased.

According to this embodiment, the acceleration voltage is -100.
Since the voltage can be stably applied to about kV, the generation of neutrons can be dramatically increased as compared with the conventional apparatus.

Next, the configuration of the inertial electrostatic confinement device according to the second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a sectional view showing a configuration of a main part of an inertial electrostatic confinement device according to a second embodiment of the present invention. The same reference numerals as those in FIG. 1 indicate the same parts. Further, the vacuum vessel 2 shown in FIG.
1, a cage-shaped spherical electrode 13, a resistor 14, a power supply 15, a gas cylinder 20, a valve 21, and a vacuum pump 22
Although they have the same configuration, they are not shown here.

In this embodiment, the resistors 70 and 80 for voltage division are provided. The high voltage supplied from the high-voltage power supply 7 is divided by resistors 70 and 80, and the cathode 4 has a terminal 6 connected thereto.
k, for example, -100 kV is applied and the intermediate electrode 5
For example, -50 kV is applied from the terminal 8m.

Each of the voltage dividing resistors 70 and 80 is set so as to sufficiently withstand a high voltage to be shared, and to have a current shunting to the resistors sufficiently lower than a beam current. For example, for a beam current of 100 mA, the resistance value is set to 50 MΩ or more so that a leakage current of 1 mA or less occurs for a shared voltage of 50 kV.

According to this embodiment, the acceleration voltage is -100.
The voltage can be stably applied up to about kV, and the generation of neutrons can be dramatically increased. In addition, the number of high voltage power supplies can be reduced to one, and the apparatus cost can be reduced.

Next, the configuration of an inertial electrostatic confinement device according to a third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a sectional view showing a configuration of a main part of an inertial electrostatic confinement device according to a third embodiment of the present invention. The same reference numerals as those in FIG. 1 indicate the same parts. Further, the vacuum vessel 2 shown in FIG.
1, a cage-shaped spherical electrode 13, a resistor 14, a power supply 15, a gas cylinder 20, a valve 21, and a vacuum pump 22
Although they have the same configuration, they are not shown here.

In this embodiment, two intermediate electrodes 5A and 5B are arranged in the acceleration space between the cathode 3 and the anode 4.
The power supply includes a high-voltage insulating transformer 9 and 30 kV class power supplies 110, 120, and 130. The first intermediate electrode 5B includes a high-voltage insulating transformer 9 and a 30 kV class power supply 1
10, a voltage of -30 kV is applied via the terminal 6n. The second intermediate electrode 5A includes a high-voltage insulating transformer 9
From the 30 kV class power supply 120 via the terminal 6m,
A voltage of 60 kV is applied. A voltage of −90 kV is applied to the cathode 3 from the high-voltage insulating transformer 9 and the 30 kV class power supply 130 via the terminal 6 k.

According to this embodiment, a high accelerating voltage of about 90 kV at which an efficient nuclear fusion reaction occurs can be applied stably, and the generation of neutrons can be dramatically increased.
Further, a high voltage of about 90 kV can be stably obtained by a combination of a general-purpose 30 kV small power supply. Since a 30 kV class power supply can easily increase a current in each stage as compared with a 100 kV class power supply, a beam current can be easily increased. Therefore, neutrons can be increased from both the acceleration energy and the beam current.

Next, the configuration of an inertial electrostatic confinement device according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a sectional view showing a configuration of a main part of an inertial electrostatic confinement device according to a fourth embodiment of the present invention. The same reference numerals as those in FIG. 1 indicate the same parts. Further, the vacuum vessel 2 shown in FIG.
1, a cage-shaped spherical electrode 13, a resistor 14, a power supply 15, a gas cylinder 20, a valve 21, and a vacuum pump 22
Although they have the same configuration, they are not shown here.

In the present embodiment, two-stage cylindrical insulators 66 and 67 of high-voltage current introduction terminals are arranged in series.
From the connecting portion 6m of the two-stage insulators 66 and 67, the intermediate electrode 5
And a cylindrical conductor 61 for supporting an intermediate electrode is coaxially arranged. The insulation between the central conductor 60 for supporting the cathode and the cylindrical conductor 61 for supporting the intermediate electrode is based on the insulation of the vacuum gap.

According to the present embodiment, the acceleration voltage is -100.
The voltage can be stably applied up to about kV, and the generation of neutrons can be dramatically increased. In addition, since a vacuum gap, which is a highly insulating medium, provides insulation between the electrode support conductors, a high voltage can be applied more stably.

Next, a configuration of an inertial electrostatic confinement device according to a fifth embodiment of the present invention will be described with reference to FIG. FIG. 7 is a sectional view showing a configuration of a main part of an inertial electrostatic confinement device according to a fifth embodiment of the present invention. The same reference numerals as those in FIG. 1 indicate the same parts. Further, the vacuum vessel 2 shown in FIG.
1, a cage-shaped spherical electrode 13, a resistor 14, a power supply 15, a gas cylinder 20, a valve 21, and a vacuum pump 22
Although they have the same configuration, they are not shown here.

In this embodiment, the high-voltage current introduction terminal 600 connected to the cathode 4 and the high-voltage current introduction terminal 610 connected to the intermediate electrode 5 are arranged at positions facing each other with the center of the device interposed therebetween. . High voltage current introduction terminal 600
And the high-voltage current introduction terminal 610 are provided independently, so that high voltage application to the cathode can be stabilized. Although the acceleration space apparently decreases, even when the number of the introduction terminals is one, the reciprocating motion of acceleration exceeding one pass is impossible in the axial direction of the introduction terminal, so that the effect on the neutron generation is small.

According to this embodiment, the acceleration voltage is -100.
The voltage can be stably applied up to about kV, and the generation of neutrons can be dramatically increased. Further, since the introduction terminals are opposed to each other and independent, the withstand voltage design on the vacuum side of the introduction terminals becomes easy.

Next, the configuration of an inertial electrostatic confinement device according to a sixth embodiment of the present invention will be described with reference to FIG. FIG. 8 is a sectional view showing a configuration of a main part of an inertial electrostatic confinement device according to a sixth embodiment of the present invention. The same reference numerals as those in FIG. 1 indicate the same parts. Further, the vacuum vessel 2 shown in FIG.
1, a cage-shaped spherical electrode 13, a resistor 14, a power supply 15, a gas cylinder 20, a valve 21, and a vacuum pump 22
Although they have the same configuration, they are not shown here.

In this embodiment, in addition to the intermediate electrode 5 for accelerating the ion beam, another intermediate electrode 51 is provided very near the cathode 4.
Has been arranged. A high voltage whose absolute value is slightly higher than that of the cathode 4 is applied to the intermediate electrode 51. The difference voltage is 1 to
About 2 kV is preferable. Specifically, for example, the cathode 4
, And -100 kV to the intermediate electrode 51 near the cathode. In the present embodiment, a decelerating electric field can be formed in the direction of the anode for electrons generated near the cathode 4 (mainly thermoelectrons or secondary electrons emitted from the cathode 4 and having an energy of 1 keV or less). In general, the ion acceleration space is the acceleration space for electrons in the opposite direction. When a large amount of thermoelectrons or secondary electrons enter this space, they are accelerated as they are and impact the anode, generating unnecessary X-rays. However, by providing a deceleration electric field, it is possible to prevent electrons from colliding with the cathode, thereby preventing unnecessary generation of X-rays.

According to this embodiment, the acceleration voltage is -100.
The voltage can be stably applied up to about kV, and the generation of neutrons can be dramatically increased. Further, generation of unnecessary X-rays can be reduced.

[0044]

According to the present invention, a high voltage of 100 kV class effective for generating neutrons can be stably applied between the cathode and the anode.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an overall configuration of an inertial electrostatic confinement device according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram of a potential distribution inside a vacuum vessel in the inertial electrostatic confinement device according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a relationship between deuterium energy and a fusion reaction cross section.

FIG. 4 is a sectional view showing a configuration of a main part of an inertial electrostatic confinement device according to a second embodiment of the present invention.

FIG. 5 is a sectional view showing a configuration of a main part of an inertial electrostatic confinement device according to a third embodiment of the present invention.

FIG. 6 is a sectional view showing a configuration of a main part of an inertial electrostatic confinement device according to a fourth embodiment of the present invention.

FIG. 7 is a sectional view showing a configuration of a main part of an inertial electrostatic confinement device according to a fifth embodiment of the present invention.

FIG. 8 is a sectional view showing a configuration of a main part of an inertial electrostatic confinement device according to a sixth embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Inertial electrostatic confinement device 2 ... Vacuum container 3 ... Anode 3a, ..., 3f ... Opening 4 ... Cathode 5 ... Intermediate electrode 6 ... High voltage current introduction terminal 6k, 6m, 6n ... Terminal 7, 8 ... High voltage power supply 7k 8m Terminal 9 High voltage insulating transformer 10 Plasma chamber 11 Filament 12, 15 Power supply 13 Discharge electrode 14 Resistance 20 Gas cylinder 21 Valve 22 Vacuum pump 60, 61, 64 Conductor 62 63, 65: insulator 110, 120, 130: high-voltage power supply

Claims (6)

[Claims] 1. A spherical anode disposed in a vacuum vessel, a cage spherical cathode concentrically disposed on an inner peripheral side of the spherical anode, and a plasma chamber provided in a space outside the spherical anode. An inertial electrostatic confinement device having a high-voltage power supply for applying a high voltage between the anode and the cathode, comprising a cage-shaped spherical intermediate electrode concentrically arranged in a space between the anode and the cathode; And a high voltage applying means for applying a predetermined high voltage potential to the inertial electrostatic confinement device. 2. The inertial electrostatic confinement device according to claim 1, wherein said high voltage applying means applies a potential larger than a potential (absolute value) at a position of the intermediate electrode when the intermediate electrode is not provided. An inertial electrostatic confinement device characterized by applying a voltage to an intermediate electrode. 3. The inertial electrostatic confinement device according to claim 1, wherein said current introduction terminal for applying a potential to said cathode and said intermediate electrode comprises:
An inertial electrostatic confinement device comprising an insulator and a conductor coaxial with each other. 4. The inertial electrostatic confinement device according to claim 1, wherein the current introduction terminal for applying a potential to the cathode and the intermediate electrode comprises:
An inertial electrostatic confinement device disposed at a position facing each other with respect to the centers of the spherical anode and the cage spherical cathode. 5. The inertial electrostatic confinement device according to claim 1, wherein said power supply for applying a potential to said cathode and said high voltage applying means for applying a potential to said intermediate electrode comprise one high voltage power supply and a resistive voltage divider. An inertial electrostatic confinement device characterized by comprising: 6. An inertial electrostatic confinement device according to claim 1, wherein said power supply for applying a potential to said cathode and said high voltage applying means for applying a potential to said intermediate electrode comprise: an insulating transformer;
An inertial electrostatic confinement device comprising a plurality of power supplies connected to a next side connected in series on an output side.