JP3700496B2 - Inertial electrostatic confinement fusion device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inertial electrostatic confinement fusion apparatus, and more particularly to an inertial electrostatic confinement fusion apparatus suitable for generating neutrons or charged particles.
[0002]
[Prior art]
Conventionally, the inertial electrostatic confinement device is described in detail in “Journal of Plasma and Fusion Research” Vol. 73, No. 10, pages 1080 to 1085 ”. A spherical anode having a diameter of several tens of centimeters is disposed in a spherical vacuum vessel, and a spherical cathode having a lattice shape of several centimeters in diameter is disposed inside the anode. A high voltage of several tens to 100 kV is applied between the anode and the cathode. Hydrogen ions are generated by glow discharge of hydrogen gas, and the hydrogen ions are accelerated toward the cathode. When hydrogen ions collide with each other inside the lattice-like cathode, a nuclear fusion reaction occurs, and neutrons or charged particles are generated. The hydrogen ions accelerated toward the cathode center are pulled back to the electric field due to the high voltage after passing through the center without causing a nuclear fusion reaction, and return to the center again. The rate of reaction is further increased.
[0003]
[Problems to be solved by the invention]
In the above prior art, the ion generation region where hydrogen ions are generated by glow discharge and the acceleration region of hydrogen ions are the same.
[0004]
The inventors have found that the ion generation region and the ion acceleration region are the same, so that there is a problem that the ion generation efficiency and the ion acceleration efficiency must be lowered. In other words, the optimum pressure for glow discharge and the optimum pressure for acceleration of hydrogen ions are different. Therefore, if an appropriate pressure is selected for the generation of hydrogen ions, acceleration efficiency of acceleration of hydrogen ions is poor, and acceleration of hydrogen ions is good. At a high pressure, the generation efficiency of hydrogen ions is deteriorated. The above-mentioned pressures are all pressures in the vacuum vessel.
[0005]
Furthermore, the problem is demonstrated concretely. The glow discharge requires a pressure of about 1 mTorr (133 mPa) or more. On the other hand, the mean free path of hydrogen ions in hydrogen gas at this pressure is 14.2 cm, which is smaller than the anode diameter of several tens of cm. Accordingly, the hydrogen ions collide with the neutral gas while being accelerated toward the cathode, and lose energy. The fusion reaction rate greatly depends on the energy of hydrogen ions, and in the energy region up to about 100 keV, an energy difference of 10% becomes a difference in the fusion reaction cross-sectional area close to one digit.
[0006]
Since the mean free path of hydrogen ions is inversely proportional to the pressure, if the pressure is 0.1 mTorr (13.3 mPa), the mean free path is 142 cm, which is larger than the anode diameter, and the acceleration efficiency and fusion of hydrogen ions The reaction rate is improved. However, in this case, it is difficult to generate plasma by glow discharge. In other words, when the mean free path of ions is large, the probability that ions ionize and neutralize neutral atoms / molecules is small, and it is therefore difficult to maintain glow discharge. Thus, the glow discharge efficiency and the ion acceleration efficiency are contradictory requirements, and in the conventional technology, the pressure is set as a compromise between the two.
[0007]
An object of the present invention is to provide an inertial electrostatic confinement fusion apparatus capable of improving ion generation efficiency and ion acceleration efficiency.
[0008]
[Means for Solving the Problems]
A feature of the present invention that achieves the above object is an inertial electrostatic confinement fusion apparatus that includes a vacuum vessel and accelerates ions generated in an ion generation region in the vacuum vessel in an ion acceleration region in the vacuum vessel. There is provided means for making the pressure in the ion acceleration region smaller than the pressure in the ion generation region.
[0009]
Since the pressure in the ion acceleration region can be smaller than the pressure in the ion generation region, the pressure can be increased in the ion generation region, and the pressure can be decreased in the ion acceleration region. Therefore, ion generation efficiency and acceleration efficiency can be improved.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The present invention has been made to solve the problems of the prior art, which are new findings obtained by the inventors.
[0011]
An inertial electrostatic confinement fusion apparatus, which is a preferred embodiment of the present invention, will be described below with reference to FIGS. The inertial electrostatic confinement fusion apparatus of this embodiment includes a vacuum vessel 1, an anode 2, a cathode 3, an exhaust pipe 9, and a vacuum pump 10. The spherical anode 2 is disposed in the vacuum vessel 1. The grid-like and spherical cathode 3 is arranged inside the anode 2. The cathode 3 is connected to the current introduction terminal 11. The glow electrode 4 is disposed outside the anode 2 in the vacuum vessel 1. The glow electrode 4 surrounds the anode 2. The anode 2 has eight ion extraction ports 7 and further has a vacuum exhaust port 8. There is one vacuum exhaust port 8, and the area thereof is larger than the total area of all the ion extraction ports 7. The vacuum exhaust port 8 communicates with an exhaust pipe 9 connected to the vacuum pump 10. A gas supply pipe 12 is connected to the vacuum vessel 1. The anode 2 and the vacuum vessel 1 are at the same potential and are mechanically connected. A voltage of −100 kV is applied to the cathode 3 from the current introduction terminal 11.
[0012]
The vacuum pump 10 is driven, and the gas in the space inside the anode 2 is sucked from the vacuum exhaust port 8 and exhausted through the exhaust pipe 9. For this reason, the space inside the anode 4, that is, the ion acceleration region 6 is maintained at a negative pressure. The gas in the ion generation region 5 (the space outside the anode 4) is also sucked into the ion acceleration region 6 through the ion extraction port 7 provided in the anode 2 and exhausted through the exhaust pipe 9. For this reason, the ion generation region 5 is also maintained at a negative pressure. The ion extraction port 7 also serves as a gas intake port from the ion generation region 5 to the ion acceleration region 6.
[0013]
Hydrogen gas is supplied into the vacuum container 1 from the gas supply port 12. By applying a voltage of several hundred volts between the glow electrode 4 and the anode 1, glow discharge is caused to generate ions. The ions 13 generated in the ion generation region 5 reach the ion acceleration region 6 through the ion extraction port 7 and are accelerated toward the cathode 3 here. Each accelerated ion collides in the cathode 3 to cause a fusion reaction, generating neutrons and charged particles (for example, protons).
[0014]
In order to set the ion generation region 5 to a high pressure suitable for the generation of ions and the ion acceleration region 6 to a low pressure suitable for the acceleration of ions, as described above, the vacuum evacuation is performed rather than the entire area of the ion extraction port 7. What is necessary is just to make the cross-sectional area of the opening | mouth 8 larger. This will be specifically described below.
[0015]
The diameter of the anode 2 is about 30 cm, and the diameter of each of the eight ion extraction ports 7 provided in the anode 2 is 10 mm. At this time, the conductance of the ion extraction port 7 is
C1 = 120 (liter / s)
It is. The diameter of the vacuum exhaust port 8 is 100 mm. The conductance of the ion extraction port 7 is C2 = 1500 (liter / s)
It becomes. When the pressure of the ion generation region 5 is P1 and the pressure of the ion acceleration region 6 is P2, differential pumping is performed by the vacuum pump 10 so that P1 = 0.001 (Torr) and P2 = 0.0002 (Torr). To do. At this time, the flow rate Q of the gas discharged through the exhaust pipe 9 is
Q = C1 (P1-P2) = 0.096 (Torr. Liter / s)
It becomes. The downstream side of the vacuum exhaust port 8, that is, the pressure P3 in the exhaust pipe 9, and the exhaust speed S of the vacuum pump 10 are:
Q = C2 (P2-P3)
∴ P3 = P2-Q / C2 = 0.000136 (Torr)
S = Q / P3 = 706 (liter / s)
It becomes. That is, the vacuum pump 10 having the ability of the ultimate pressure 0.1 (mTorr) and the exhaust speed 700 (liter / s) or more is necessary. As the vacuum pump 10 having such capability, a medium-sized or lower diffusion pump is suitable.
[0016]
The pressure in the ion generation region 5 is 0.001 Torr, and the necessary conditions for causing glow discharge are satisfied. When 1 × 10 ¹¹ deuterium ions are generated per 1 cm ^{3 in the} ion generation region 5, the ion saturation current density is 9.6 mA / cm ² when the electron temperature is 2 eV. Therefore, the maximum value of the current that can be extracted from one ion extraction port 7 having a diameter of 10 mm (area 0.785 cm ² ) is approximately 7.5 mA, and the total of eight ion extraction ports 7 is 60 mA. In order to further increase the current value, the number of the plasma extraction ports 7 may be increased. However, the exhaust speed of the vacuum pump 10 needs to be larger than the above, and the vacuum pump 10 is increased in size.
[0017]
The pressure in the ion acceleration region 6 is 0.0002 Torr lower than that in the ion generation region 5, the mean free path of hydrogen ions is 71 cm, which is sufficiently larger than the diameter of the anode 2, and the ion acceleration efficiency is improved.
[0018]
In this embodiment, the total area of the vacuum exhaust port 8 is larger than the total area of all the ion extraction ports 7, and the ion acceleration region 6 is sucked by the vacuum pump 10. Due to the difference in area between the vacuum exhaust port 8 and the ion extraction port 7, that is, the difference in conductance, the pressure in the ion generation region 5 and the ion acceleration region 6 partitioned by the anode 2 can be maintained at appropriate values and the ion acceleration region 6 can be maintained. Can be made lower than the pressure in the ion generation region 5. For this reason, since each can be set to an appropriate value, ion production efficiency and acceleration efficiency can be improved.
[0019]
An inertial electrostatic confinement fusion apparatus according to a second embodiment of the present invention will be described with reference to FIG. In FIG. 3, 13 indicates ions, and a contour line 14 in the ion acceleration region 6 indicates an equipotential surface between the anode 2 and the cathode 3. In the present embodiment, the conductor grid 15 is provided in the configuration of the first embodiment, and other configurations are the same as those of the first embodiment. The conductor grid 15 is installed at the vacuum exhaust port 8.
[0020]
Ions 13 generated inside the vacuum chamber 1 and on the back surface of the anode 2 (ion generation region 5) are extracted from the ion extraction port 7 into the ion acceleration region 6 by an electric field and accelerated toward the cathode 3. As shown in FIG. 3, in the vicinity of the ion extraction port 7, the equipotential surface 14 is deformed, and the electric field enters the ion extraction port 7, whereby the ions 13 can be extracted into the ion acceleration region 6. However, since the electric field at the ion extraction port 7 is distorted, momentum in the direction (circumferential direction) perpendicular to the direction (radial direction) toward the cathode 3 at the center is given to the ions 13, The collision probability between the ions 13 is lowered. In the absence of the conductor grid 15, a large electric field distortion is generated in the vacuum exhaust port 8 more than the portion of the ion extraction port 7. When the conductor grid 15 is provided, the surface of the conductor grid 15 has the same potential as that of the anode 3, so that no electric field distortion occurs as shown in FIG. 3. Further, since the conductor lattice 15 is a lattice, the conductance for evacuation is not impaired.
[0021]
If the diameter of the anode 2 is 30 cm and the diameter of the vacuum exhaust port 8 is 10 cm, the area ratio between them is 36. If it is assumed that the ions 13 whose trajectories are bent by the distorted electric field cannot converge at the center of the cathode 3, the effect is 1/36. Since the nuclear fusion reaction rate is proportional to the square of the ion current value, when this example is not used, the nuclear fusion reaction rate is reduced to the square of (35/36), that is, 94.5%. As described above, according to the present embodiment, since the distortion of the electric field at the vacuum exhaust port 8 can be suppressed, it is possible to prevent a decrease of about 5% in the fusion reaction rate due to the distortion of the ion orbit. Moreover, if the vacuum exhaust port 8 becomes relatively large with respect to the anode 2, the reduction in the reaction rate when the present embodiment is not used is even greater. In the present embodiment, since the pressure in the ion acceleration region 6 can be made lower than the pressure in the ion generation region 5 as in the first embodiment, the same effect as in the first embodiment can be obtained.
[0022]
An inertial electrostatic confinement fusion apparatus according to a third embodiment of the present invention will be described with reference to FIG. In this embodiment, a conductor grid 16 is added to the configuration of the second embodiment. The conductor grid 16 is installed on the inner surface of the anode 2.
[0023]
By providing the conductor grid 16, the surface of the conductor grid 16 becomes an equipotential surface. When the ions 13 extracted and accelerated from the ion extraction port 7 into the ion acceleration region 6 are not lost by the fusion reaction and the collision with the cathode 3, as shown by the arrows in FIG. Return to the neighborhood. At this time, the energy held by the ions 13 is the same value as the energy at the time of extraction from the ion extraction port 7 and is almost zero. For this reason, if there is even a slight energy loss in the movement on the ion orbit, the ions 13 do not collide with the anode wall and are lost. However, when there is no energy loss or when energy is received from other ions, the ions 13 may collide with the anode wall and be lost. By providing the conductor lattice 16, the energy of ions becomes 0 at the lattice position, and the substantially stationary ions 13 are accumulated between the conductor lattice 16 and the anode 2. The potential of this portion becomes even more positive than that of the anode 2 due to the collection of ions 13, and prevents further ions 13 from colliding with the anode wall. Therefore, according to this embodiment, the disappearance of ions due to the collision with the anode wall can be suppressed. This embodiment can also obtain the effects produced in the second embodiment.
[0024]
An inertial electrostatic confinement fusion apparatus according to a fourth embodiment of the present invention will be described with reference to FIG. In this embodiment, a dielectric 17 is provided in the third embodiment. The dielectric 17 is disposed between the anode 2 and the conductor grid 16. In this embodiment, ions 13 whose velocity is not zero collide with the dielectric 17 on the surface of the conductor lattice 16. As a result, the potential of the dielectric 17 is pushed up to the anode 2 or higher. Thereby, after reaching a steady state, the ions 13 are rebounded to the potential of the dielectric 17 and do not collide with the dielectric 17 or the anode 2 and the conductor lattice 16. For this reason, loss of ions can be prevented. This embodiment can obtain the same effect as the third embodiment.
[0025]
An inertial electrostatic confinement fusion apparatus according to a fifth embodiment of the present invention will be described with reference to FIG. In this embodiment, a cooling pipe 18 is added to the configuration of the second embodiment. The cooling pipe 18 is installed on the outer surface of the anode 2. By installing the cooling pipe 18, the anode temperature can be set to about the temperature of the refrigerant flowing in the cooling pipe 18, for example, about 100 ° C. if the refrigerant is water. As shown in FIG. 1, since the cathode 3 is supported only by the exhaust pipe 9 which is a current introduction terminal, it is difficult to attach a cooling structure to the cathode itself in order to prevent loss due to ion collision. Therefore, the cathode 3 is cooled only by radiation cooling. For this reason, the cooling efficiency of the cathode can be improved by lowering the temperature of the anode 2 surrounding the cathode 3. This embodiment can also obtain the effects produced in the second embodiment. The cooling pipe 18 used in the present embodiment can be applied to other embodiments other than the second embodiment.
[0026]
An inertial electrostatic confinement fusion apparatus according to a sixth embodiment of the present invention will be described with reference to FIG. In this embodiment, a permanent magnet 19 is added to the configuration of the first embodiment. The permanent magnet 19 is attached to the surface of the vacuum vessel 1 so that the polarities of adjacent magnets are different. Since the lines of magnetic force 20 are generated by the action of the permanent magnet 19, it is difficult for ions to move across the lines of magnetic force 20, so that loss of ions due to collision with the vacuum vessel wall can be suppressed. In addition, since the magnetic fields are reversed, the magnetic field in the ion acceleration region is very weak and does not affect the ion acceleration orbit. Therefore, according to the present Example, the density of the ion produced | generated inside a vacuum vessel can be raised, and the number of ions related to a fusion reaction can be increased. This embodiment can also obtain the effects produced in the first embodiment. The permanent magnet 19 can be applied to any of the second to fifth embodiments.
[0027]
【The invention's effect】
According to the present invention, ion generation efficiency and ion acceleration efficiency can be improved. Thereby, the fusion reaction rate in the cathode can be improved, and the intensity of generated neutrons and charged particles can be increased.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an inertial electrostatic confinement fusion apparatus according to a first embodiment of the present invention.
2 is a perspective view of an anode having the exhaust pipe of FIG. 1. FIG.
FIG. 3 is a longitudinal sectional view of an inertial electrostatic confinement fusion apparatus according to a second embodiment of the present invention.
FIG. 4 is a longitudinal sectional view of an inertial electrostatic confinement fusion apparatus according to a third embodiment of the present invention.
FIG. 5 is a longitudinal sectional view of an inertial electrostatic confinement fusion apparatus according to a fourth embodiment of the present invention.
FIG. 6 is a longitudinal sectional view of an inertial electrostatic confinement fusion apparatus according to a fifth embodiment of the present invention.
FIG. 7 is a longitudinal sectional view of an inertial electrostatic confinement fusion apparatus according to a sixth embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Vacuum container, 2 ... Anode, 3 ... Cathode, 4 ... Glow electrode, 5 ... Ion production area, 6 ... Ion acceleration area, 7 ... Ion extraction port, 8 ... Vacuum exhaust port, 9 ... Exhaust pipe, 10 ... Vacuum Pump, 12 ... gas supply port, 13 ... ion, 15, 16 ... conductor grid, 17 ... dielectric, 18 ... cooling pipe, 19 ... permanent magnet.

Claims (8)

In an inertial electrostatic confinement fusion apparatus that includes a vacuum vessel and accelerates ions generated in an ion generation region in the vacuum vessel in an ion acceleration region in the vacuum vessel,
An inertial electrostatic confinement fusion apparatus comprising means for making the pressure in the ion acceleration region smaller than the pressure in the ion generation region. In an inertial electrostatic confinement fusion apparatus comprising a vacuum vessel, an anode disposed in the vacuum vessel, and a cathode to which ions generated near the anode are accelerated.
An inertial electrostatic confinement fusion apparatus characterized in that an exhaust port is provided in the anode, and exhaust from the inside of the anode is exhausted to the outside of the vacuum vessel by exhaust means connected to the exhaust port. The inertial electrostatic confinement fusion apparatus according to claim 2, wherein the exhaust port has a cross-sectional area larger than a total cross-sectional area of all ion extraction ports provided in the anode. The inertial electrostatic confinement fusion apparatus according to claim 2 or 3, wherein a conductive lattice is provided at the exhaust port. The inertial electrostatic confinement fusion apparatus according to claim 2, wherein another conductor grid is provided inside the anode. 6. The inertial electrostatic confinement fusion device according to claim 5, wherein a dielectric is disposed between the anode and the second conductor lattice. The inertial electrostatic confinement fusion apparatus according to any one of claims 1 to 6, further comprising a magnetic field structure in which polarity is periodically reversed outside the anode. The inertial electrostatic confinement fusion apparatus according to claim 1, wherein a cooling pipe is provided on the anode.

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