JP2001338800A - Neutron generator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a neutron bundle of high output by accelerating ions, such as heavy hydrogen or the like by the use of a new accelerator and to cause them to undergo nuclear fusion, eliminat electrostat6ic accelerating electrode which causes overheat. SOLUTION: Two disc-like electrodes are arranged in parallel, and a power source is connected to these electrodes to apply sine-wave fluctuating voltages of the same electric potential thereto. Two upper and lower porous electromagnets are set in a magnetic field deflection part, to apply an axial magnetic field. The electrode parts are connected to the magnetic field deflection part inside a vacuum vessel, and the vacuum vessel is fixed to grounding potential. The disc-like electrodes are retained in a part of the vacuum vessel via insulating glasses. The magnetic field applied by the electromagnet and the frequency of the fluctuating voltage applied to the electrodes are adjusted, so that the cyclotron frequency of a charged particle generated in the vacuum vessel matches with the frequency of the sine-wave fluctuating voltages applied to the electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for generating energy or neutrons by causing a nuclear fusion reaction, and more particularly, to an apparatus for producing high-power neutrons suitable for isotope production, material modification and inspection. About.

[0002]

2. Description of the Related Art In recent years, production of radioisotopes, metal exploration,
There is an increasing need to use neutrons for material testing, semiconductor processes, and the like. Especially Positron Emission Tomography
The market for medical RI using (PET) is expected to expand, and a method for producing it by neutron irradiation has been proposed. Conventionally, these neutrons were obtained by a reactor or accelerator,
The equipment configuration has become large-scale, and it has been difficult to install these equipment at each site that requires neutrons.

Recently, an electrostatic confinement fusion device has been expected to be used as a small neutron source.
An explanation of the electrostatic confinement type fusion device is described in, for example, page 1080 of "Journal of Plasma and Fusion Society, Vol. 73, No. 10" (October 1997). In this apparatus, generally spherical or cylindrical concentric anodes / cathodes are installed inside a vacuum vessel, and deuterium ions or tritium ions are generated by means such as glow discharge. These ions are electrostatically accelerated toward the center of the device to cause a fusion reaction and generate neutrons. However, most of the high energy ions reciprocating between the anode and the cathode eventually strike the cathode and heat the cathode. The heated cathode cannot be sufficiently cooled by heat transfer due to the vacuum, and reaches a thermal equilibrium only when the temperature becomes high and the amount of radiation increases. According to calculations, for a cathode radius of 75 mm and a cathode surface area of 1307 cm ² , an acceleration voltage of 100 kV and an ion current of 1
At A, the cathode temperature reaches 2500K. In order to obtain a high output neutron flux, the input power must be increased inevitably,
In this case, the temperature of the cathode further increases, and eventually reaches the melting point of the cathode. Therefore, it is considered that there is a limit in increasing the output of the nuclear fusion device of the electrostatic confinement type.

On the other hand, as an apparatus for generating neutrons, there is an accelerator such as a cyclotron. However, since the accelerator is a mechanism that finally extracts the beam and irradiates the target, the fusion reaction amount is determined by the final beam current amount, and the beam current amount depends on the output of the ion source emitted from one point and the acceleration process Is not suitable for the purpose of obtaining a high-power neutron flux.

A well-known example closest to the principle of charged particle acceleration used in the present invention described later is Nuclear Instrume.
nts and Method in Physics Reseach B68 (1992) 92-95
There is an electron accelerator Rhodotron shown in. Rhodotron has a cylindrical cavity resonator at the center of the device, and sets up a TEM mode high frequency that generates an alternating electric field in the radial direction. Five independent deflection magnets are arranged around the cavity resonator. The electrons incident from the electron gun into the cavity are first accelerated toward the center, and when the electrons reach the center, they are successively accelerated by an electric field having a phase that accelerates the electrons outward. The electrons that have entered the deflecting magnet move in a circular motion at a constant velocity and again enter the cavity resonator, and thereafter, the acceleration is repeated several times in the same manner, and the beam is finally emitted from the beam extraction port without the magnet. A feature of Rhodotron is that the magnetomotive forces of the five deflection magnets are independently adjusted in advance so that the deflection radii are the same as the particle energy increases. Therefore, there is only one design trajectory in the form of a single stroke, and there is only one point where the initial particles can be incident. In addition, since the RF wavelength is determined by the cyclotron frequency of the particles, there is a problem that it is difficult to apply other than electrons having a high cyclotron frequency in order to reduce the magnetomotive force and the cavity resonator to a practical size. Therefore, it is considered difficult to use Rhodotron as a fusion device.

A well-known example of a neutron generator that is closest to the present invention is disclosed in Japanese Unexamined Patent Publication (Kokai) No. 2-269459.
This is the invention disclosed in Japanese Unexamined Patent Publication (Kokai) No. H10-26095. In this device, a coil is arranged around a circular cylindrical cavity resonator, and an axial magnetic field is applied inside the cavity resonator. A TEM mode high frequency is generated in the cavity resonator, and an electric field in a radial direction is excited. A cathode and an anode are disposed at the center of the cavity resonator and are separated from each other in the axial direction. Plasma is generated at the center by discharge between the cathode and the anode. The ions in the plasma are accelerated in the radial direction by the high-frequency electric field, but the trajectory is deflected by the axial magnetic field applied to this space and returns to the center. Since the frequency of the high-frequency electric field and the applied magnetic field are determined so as to satisfy the cyclotron condition, the ions are accelerated again, and thereafter the acceleration is repeated. This device uses deuterium D and 3
Assuming mixed ions of deuterium T, ions accelerated to 10 keV or more collide at the center and generate neutrons by DT nuclear fusion. To accelerate deuterium D and tritium T at the same time, an accelerating electric field is applied at a frequency that is a common multiple of the respective cyclotron frequencies. The device is essentially the same as the acceleration principle of the present invention, except that a radial electric field is generated by a cavity resonator as in Rhodotron, ions are generated by electric discharge at the center of the device, and a magnetic field is generated by an air-core coil. What occurs is a difference from the present invention.

The limitation of the device in the device seems to be the high-frequency power that can be applied to the cavity resonator.
The high-frequency power that can be applied to the cavity resonator by the L couple is limited to about 100 kW. In the TEM mode, the following relationship is established between the high-frequency power P, the impedance _Zc , and the voltage V.

[0008]

(Equation 1)

[0009] The impedance _Zc is expressed as follows.

[0010]

(Equation 2)

[0011]

(Equation 3)

[0012]

(Equation 4)

Substituting Equation (2) into Equation (2), the impedance becomes

[0014]

(Equation 5)

Is calculated. In equation (1), P < 100 [k
W], the upper limit of the high frequency voltage is V < 6.1 [kV]
Calculated as degree. From this estimate, V = 5-10 [k
V], an acceleration simulation of the Sumitomo inventive apparatus was performed.

In this device, since the acceleration region and the magnetic field deflection region overlap, the speed increases and decreases in the magnetic field deflection region, and the trajectory does not become a perfect circle. As a result, a phenomenon can be seen in which the circular orbit drifts in the azimuth direction at the center while the radius increases. Further, in this device, there is a restriction on the device that the intensity of the acceleration electric field is determined by the acceleration voltage and the cavity radius. Therefore, there is a dilemma that if the cavity radius is increased so as to be able to accelerate to high energy, the intensity of the acceleration electric field is reduced.

The acceleration voltage was set to 5 kV, the cavity radius was set to 520 mm, and the acceleration conditions were examined by simulation at acceleration frequencies of 500, 1000, 2000 and 3000 [kHz]. At this time, the magnetic field strength should be 65 so as to be the cyclotron frequency of deuterium.
5.9, 1311.7, 2623.5, 3935.2 [Gauss]. In the case of an acceleration frequency of 500 [kHz], deuterium is smoothly accelerated to 7.1 keV, but collides with the apparatus wall because the radius of the rama is enlarged. Therefore, if the acceleration frequency is increased, it is expected that the intensity of the magnetic field increases with this and the radius of the Rama decreases even with the same energy, so that the ultimate energy can be increased. However, the orbital shrinks more than the Rama radius reduction due to the magnetic field strength, and the final attained energy is 3.2, 0.6, 0.4 keV
And it will retreat remarkably. It is considered that the reason for this is that when the frequency increases, the direction of the electric field changes before the ions sufficiently jump out of the center plasma into the acceleration region. Therefore, we considered increasing the cavity radius so that it would not collide with the device wall even if the energy increased next. The acceleration voltage was fixed at 8 kV, the applied magnetic field was fixed at 1000 [Gauss], and the case where the cavity radius was 500, 750, 1000, 1250 [mm] was compared. When the cavity radius is 500 mm, it collides with the equipment wall at 7.1 keV, and the energy reached is the highest when it is 750 mm 29.
At 6 keV, it decreased to 18.6 keV and 9.5 keV below. This is probably because the accelerating electric field decreased as the cavity radius increased. In order to investigate the maximum attainable energy of the apparatus, the applied magnetic field was changed to 800, 1200, 1000, 1400 (Gauss) for the case where the cavity radius obtained the best result was 750 (mm). The case of 1000 [Gauss] is the best, and about 30 keV was obtained with this apparatus. This is expected to be the upper limit of the energy reached by the device.

From the above, it is considered that there is a difficulty in neutron production using the DD reaction which requires energy of about 100 keV in the apparatus.

[0019]

SUMMARY OF THE INVENTION An object of the present invention is to avoid electrode collision in which heating is a problem, as in an electrostatic confinement type fusion device, and to reduce the number of collisions between ions as in a cyclotron. Is not too small and can accelerate ions such as deuterium, which is difficult with Rhodotron.
An object of the present invention is to provide a high-efficiency fusion neutron generator based on the DD reaction which is difficult with the apparatus disclosed in Japanese Patent No. 459.

[0020]

Means for solving the above problems will be described below.

The configuration of the present apparatus will be described with reference to the side view of FIG. This apparatus comprises a central electrode unit 1 and a peripheral magnetic field deflection unit 2. As shown in the figure, two disk-shaped electrodes 3 are installed in parallel on the electrode section 1, and a power supply 4 is connected to these disk-shaped electrodes 3 via a conducting wire 5. Can be The upper and lower two perforated electromagnets 6 are installed in the magnetic field deflecting unit 2 to apply an axial magnetic field. The electrode unit 1 and the magnetic field deflecting unit 2 are connected inside the vacuum vessel 7, and the vacuum vessel 7 is fixed at the ground potential. The disk-shaped electrode 3 is a vacuum vessel 7
Are held through insulating glass 8 at a part thereof. The magnetic field applied by the electromagnet 6 and the frequency of the fluctuating voltage applied to the electrode 3 so that the cyclotron frequency of the electroparticles generated in the vacuum vessel 7 and the frequency of the sine wave fluctuating voltage applied to the electrode 3 match. And adjust.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present apparatus will be described with reference to FIGS.

FIG. 1 is a sectional view of the apparatus of the present invention as viewed from the side. The main body of the apparatus is a vacuum vessel 7 having a shape in which two cylinders having different heights are combined, a pair of upper and lower electromagnets 6 having a hole in the center, and a pair of upper and lower disc-shaped electrodes 3, and a circle. It is composed of an insulating glass 8 or the like for fixing the plate electrode 3 to a vacuum vessel 7 while electrically insulating the same. Although not shown, a vacuum pump is connected to the vacuum container 7 to keep the inside in a vacuum state. The vacuum vessel 7 has a room with a large thickness (height) as shown in the figure, and a pair of upper and lower disc-shaped electrodes 3 are coaxially arranged inside the room. On the other hand, a room having a small thickness is provided at the outer edge of the vacuum vessel 7 as shown in the figure, and this part is sandwiched between a pair of upper and lower donut-shaped electromagnets 6, and a uniform space is formed in the inner space in the axial direction (vertical direction on paper). An axial magnetic field 13, which is a static magnetic field, is applied. Excitation windings 36 are arranged on the outer periphery and the inner periphery of the electromagnet 6, and a DC current is supplied from the excitation power supply 37 to the excitation winding 36 to excite the electromagnet 6. The excitation intensity of the electromagnet 6 can be controlled by adjusting the current of the excitation power supply 37. The directions of the direct currents supplied to the excitation windings 36 at the outer peripheral portion and the inner peripheral portion are opposite to each other as shown in the figure. Magnetic pole 38
Is made of a ferromagnetic material such as a laminated steel plate and has the effect of increasing the magnetic flux density, and has the effect of supplying the axial magnetic field 13 as uniform as possible to the internal space. These techniques relating to the electromagnet 6 have been used and are known in the field of accelerators and the like. An AC power supply 4 is connected to a pair of upper and lower disc-shaped electrodes 3.
Are connected, and an AC voltage is applied. In order to correspond to the elevation views shown in FIG. 3 and subsequent figures, a radial portion covered by the disc-shaped electrode 3 as shown in FIG. 1 is called an electrode portion 1 and a portion covered by an electromagnet is called a magnetic field deflecting portion 2. . The internal space of the electrode portion 1 sandwiched between the pair of upper and lower disc-shaped electrodes 3 has the same AC potential as the disc-shaped electrode 3. On the other hand, since the vacuum vessel 7 is fixed at the ground potential, the internal space of the magnetic field deflection unit 2 is at the ground potential. Therefore, an AC accelerating electric field 32 in the radial direction is generated between the electrode unit 1 and the magnetic field deflecting unit 2. The region where the AC accelerating electric field 32 is generated is called the acceleration region 9. As shown in FIG.
A small amount of gas such as deuterium is supplied to the vicinity of the acceleration region 9 by a gas pipe 15. When the gas such as deuterium is ionized in the acceleration region 9 by a method described later, the generated ions 10 such as deuterium are accelerated in the radial direction by the AC acceleration electric field 32 in the radial direction. At this time, whether the acceleration is performed in the center direction or the centrifugal direction depends on the phase state of the AC accelerating electric field 32 at that time. Now, assuming that the ion is accelerated in the center direction as shown in FIG. 1, the ion trajectory 34 crosses the central axis 11 of the apparatus and then exits to the acceleration region 9 on the opposite side. At this time, if the phase of the AC accelerating electric field 32 is inverted and an electric field is generated in the centrifugal direction, the ions 10 are further accelerated. In this way, the ions that have entered the magnetic field deflection unit 2 are deflected by the magnetic field, make a U-turn, and enter the acceleration region 9 again.
In such a process, if the timing of the phase of the AC accelerating electric field 32 matches, the ions 10 are continuously accelerated.

Here, a method of generating ions in the acceleration region 9 will be described with reference to FIG. In FIG. 2, the illustration of the vacuum vessel 7 is omitted to make it easier to see the structure inside the vacuum vessel. At the inner peripheral end of the magnetic pole 38, a fringe magnetic field (protruding magnetic field) 35 as shown in FIG. 2 is generated. Therefore, the magnetic field strength is adjusted so that the magnetic flux density near the edge becomes about 875 [Gauss]. This region is a high-frequency electric field of 2.45 GHz.
To the electron cyclotron resonance (ECR) region 30. Electron cyclotron resonance has a magnetic field 35 and the high-frequency electric field 32 and the quadrature component, and the magnetic flux density B _e and angular frequency of the high frequency electric field omega _e

[0025]

(Equation 6)

When the relationship is satisfied, the electron
This is a mechanism that generates plasma by receiving heat by resonance. Here, _me is the mass of the electron, and q _e is the charge amount of the electron. If the relationship satisfies the expression (3), the magnetic flux density is necessarily 875 [Gauss] and the angular frequency of the high-frequency electric field 32 is 2.45.
It is not necessary to specify [GHz], but since a large number of 2.45 [GHz] oscillation tubes are commercialized for microwave ovens, it is convenient to select this combination. This high frequency electric field
Although there are several supply methods for the supply of 32, this embodiment adopts a method of directly inserting the waveguide 41 into the vicinity of the electron cyclotron resonance region 30 as shown in FIGS. Of course, other supply methods for the high-frequency electric field 32, for example, various antennas, may be used. A high frequency generator 42 such as a magnetron is connected to the waveguide 41. This gives 2.45
A high-frequency electric field 43 of [GHz] can be generated in the radial direction. It should be noted that the high-frequency electric field 43 has a different frequency and a different role from the AC accelerating electric field 32 for accelerating the ions 10 described above. It is considered that about one or two circumferential waveguides 41 are sufficient. According to the results of experiments conducted so far with the same type of device configuration, only one waveguide 41 is arranged in the circumferential direction, and high-energy electrons drift due to the gradient of the magnetic field (gradB drift).
It has been confirmed that they move in the circumferential direction under the action of, and plasma is generated over the entire circumference. Further, in order to stably generate plasma by electron cyclotron resonance even under a low pressure, a ring-shaped one-turn filament 31 is provided near the magnet edge to emit thermoelectrons 28 as shown in FIG.
Thermionic electrons 28 are captured near the weak center plane of the fringe magnetic field 35 and are heated to high energy by electron cyclotron resonance (ECR). The high-energy electrons 28 thus formed collide with a neutral gas (not shown), and further ionize to generate plasma stably.

The behavior of the ions 10 such as deuterium generated in the acceleration region 9 in the orbit plane and the mechanism of acceleration will be described in more detail with reference to FIG. In the triple circle shown in FIG. 3, the first circumference is the outer circumference of the electrode on the disk, the second circumference is the magnetic field deflection region, that is, the inner circumference 14 of the electromagnet, in order from the inside.
The third circumference represents the magnetic field deflection region, that is, the outer circumference of the inner circumference of the electromagnet. Accordingly, the space between the first circumference and the second circumference corresponds to the acceleration region 9 described above. As already mentioned, the ions 10 are accelerated toward the device center 11 while the accelerating electric field 32 in the acceleration region 9 is directed toward the device center 11. Next, the ions 10 enter the electrode portion 1 sandwiched between the two disk-shaped electrodes 3. However, since no electric field is generated inside the electrode portion 1 even when the potential changes, the ions 10 travel at a constant velocity while flying in this region. Make a linear motion. The ions that have passed through the device center 11 in this manner again enter the acceleration region 9 on the opposite side, and are again accelerated by the electric field whose phase has been inverted in the outward radial direction.
The light enters the magnetic field deflection unit 2. Since a uniform axial magnetic field 13 is applied to the magnetic field deflecting unit 2, the ions 10 change their directions in a circular orbit and reenter the acceleration region 9. By the way, as described above, it is necessary to set the angular frequency ω _i of the fluctuating potential of the electrode under a certain condition so that the ions 10 can be accelerated each time they enter the acceleration region 9. It is to keep set and the angular frequency omega of the variable potential of the electrode, the strength B _i and the angular frequency of the magnetic field so that the cyclotron angular frequency of the ions to be accelerated omega. That is, the angular frequency ω _i and the magnetic field strength B have the following relationship:

[0028]

(Equation 7)

Must be satisfied. Here, _mi is the mass of the ion, and q _i is the charge amount. Of course the angular frequency omega _i in the variable potential is equal to the angular frequency omega _i of accelerating field. With this setting, when the ions 10 enter the acceleration region 9 from the magnetic field deflecting unit 2, the ions 10 can ride on the phase accelerated in the direction of the center 11 again.

At this time, the trajectory of the ion 10 in this device
34 has the following geometrically important features: When the ions 10 that have drawn a linear trajectory through the center point 11 of the device enter the magnetic field deflecting unit, they are always perpendicular to the inner circumference circle 14 of the electromagnet 6. The reason will be described below. As described above, ions generated at an arbitrary point in the acceleration region are accelerated in the radial direction, and therefore necessarily have the center of the circle (the disk electrode 3 in this case).
Go through 11. It is obvious that extrapolation of the straight trajectory passing through the center 11 of the circle in the opposite direction makes it orthogonal to the circumference 14 again. In this manner, the ions 10 which have entered the magnetic field deflecting unit 2 at right angles draw a circular orbit 13 in the magnetic field deflecting unit 2, and the ions 10 again enter the acceleration region 9 orthogonally to the inner circumferential circle 14 of the electromagnet 6.
The orthogonality at the time of re-incident is always maintained irrespective of the energy of the ions 10 and the like. The reason will be described with reference to FIG.

Assume that two circles A and B having an arbitrary radius intersect at two intersections a and b as shown in FIG. At this time, the centers O _A , OB of the two circles A, _B and the two intersections a,
two triangles ΔO that by connecting the b _A aO _B and ΔO _A bO _B
Are congruent because the lengths of the three sides are the same. When the distance O _A O _B between the centers of the two circles A and _B is weighted, this is shown in FIG.
(B) the angular O _{A aO-B} can be at right angles as.
For triangular delta O.D. _{A aO-B} and delta O.D. _A bO _B are congruent, square O
Corners if the perpendicular _A aO _B O _A bO _B also is always perpendicular. As shown in FIG. 4C, when the circle A is replaced by the inner circle 14 of the electromagnet and the circle B is replaced by the circular orbit 12 in the magnetic field deflecting unit, the ions emitted at right angles from the inner circle 14 of the electromagnet are It is concluded that the light is incident on the acceleration region at right angles from the inner circle of the electromagnet.

Further, ions which are perpendicularly incident from the acceleration region to the internal space sandwiched between the disk-shaped electrodes move linearly,
It will again pass through the center point of the device. In this way, the ions repeatedly pass through the center point of the apparatus repeatedly while being accelerated. If the energy is eventually accelerated to about 100 keV, a nuclear fusion reaction occurs due to collisions between deuterium ions generated at the center of the device.

Assuming that ions are initially generated over the entire circumference of the acceleration region at 360 °, the ion trajectory described so far will be repeatedly generated from the entire circumference of the acceleration region 9 and the deuterium ion at the center will be generated. The density can be increased dramatically compared to conventional accelerators. The conventional accelerator has only one beam path from the ion source to the emission, and thus the beam current amount is limited. Therefore, it is considered that the neutron generator using the accelerator has a limit in increasing the flux. In this apparatus, there is an ion source all around the acceleration region, and all ions generated here pass through one central point. In addition, particles can be accumulated one after another on the orbit. This has the advantage that the number of reaction events can be dramatically increased and the flux of generated neutrons can be easily increased.

The above operation was examined using a simple two-dimensional simulator. The simulator tracks the two-dimensional particle trajectory in the electromagnetic field of this device and the time evolution of the kinetic energy of the particle. To simplify the simulation, a uniform magnetic field perpendicular to the particle orbit plane is applied only to the magnetic field region, and the electric field between the coaxial cylinders is applied only to the acceleration region. FIG. 5 shows the arrangement of physical quantities. The equation system is as follows.

The equation of motion of the ion is as follows.
_z, x-direction electric field E _x, E y-direction electric field _y, the x-direction velocity v _x, When the y-direction electric field v _y

[0036]

(Equation 8)

[0037]

(Equation 9)

[0038]

(Equation 10)

[0039]

[Equation 11]

Is expressed by the simultaneous equations.

The electric field component is represented by a coordinate radius r.

[0042]

(Equation 12)

Then, the acceleration region 9 shown in FIG.
r _disk < r < (r _disk + d)

[0044]

(Equation 13)

[0045]

[Equation 14]

And 0 < r < _rdisk , r outside the acceleration region
> (R _disk + d)

[0047]

Equation 15 _Let E _x = 0 and E _y = 0 (12).

In view of the above, a solution was obtained using the fourth-order Runge-Kutta method by simultaneously combining the equations (5) to (8). FIG. 6 shows a screen configuration of the simulator. As shown in FIG. 6, the time change of the acceleration electric field and the particle energy is displayed at the upper part of the screen. The accelerating electric field has a positive direction in the radial direction. At the center right of the screen are traces of the device and the trajectory viewed from above.

In this device, the radius r _disk of the central electrode plate,
Fluctuating applied voltage v _a , fluctuating frequency ω, acceleration gap width d
Are closely related, and these parameter settings largely govern operating characteristics. The setting parameters in the case of FIG. 6 are acceleration voltage 10 kV, acceleration frequency 800 kHz, applied magnetic field 104
9.4 Gauss. By setting these parameters, FIG.
FIG. 7 shows an example in which the acceleration characteristics are significantly different from those of FIG. The setting parameters in the case of FIG. 7 are an acceleration voltage of 10 kV, an acceleration frequency of 900 kHz, and an applied magnetic field of 1180.1 Gauss. FIG.
As a result, the particles cannot stably ride the acceleration phase,
It can be seen that acceleration and deceleration are repeated. Next, how to stably accelerate ions in the present apparatus will be described below.

FIG. 8 schematically shows the relationship between the phase 19 of the accelerating electric field of ions and the passage of particles. The cosine curve 20 in FIG. 8 represents the radial electric field intensity 21 generated in the acceleration region.
Is shown. The positive region of the cosine curve 20 indicates the accelerating electric field in the outward direction of the radius, and the negative region indicates the accelerating electric field in the inward direction. To constantly accelerate particles, the electric field must be negative when the particles pass inwardly through the acceleration region and positive when they pass outwardly through the acceleration region.
When this is expressed on the phase diagram of the electric field, the inward acceleration region 22 is in the negative electric field region and the outward acceleration region 22 is as shown in FIG.
Are arranged so that the electric field is in a positive region. As the speed of the particles increases, the time to fly in a straight orbit decreases.
The phase region of the linear trajectory shown in FIG. 8 gradually decreases, and the proportion of the entire phase decreases. Since the width 24 of the phase region of the linear orbit is smaller than π, the electric field is negative at the beginning of the linear orbit and the electric field is positive at the end. The gradient of the electric field is arranged at a positive position with respect to the zero point of the electric field.

However, when the phase region 24 of the linear trajectory decreases as the particle velocity increases, the frequency of the electric field is kept constant, so that the two acceleration phase regions advance with respect to the phase of the electric field. This is compensated for by the increase in the deflection phase region 25 accompanying the expansion of the deflection radius. As is well known, in the non-relativistic region, the cyclotron frequency does not depend on the velocity of the particles. Therefore, as shown in FIG. 9, in a cyclotron or a microtron in which the deflection angle is defined by the division angle of the magnet, the deflection phase region does not increase even if the speed of the particles increases. However, in this apparatus, as shown in FIG. 10, when the velocity of the particles increases and the deflection radius increases, the deflection angle increases as the deflection radius increases, so that the deflection phase region increases. As a result, the decrease in the phase region of the linear orbit is compensated at a certain rate. For this reason, in the present apparatus, the deflection phase region becomes larger than the linear orbit phase region. Therefore, the phase region of the linear orbit is π
, And it is necessary to arrange in advance a region having a positive gradient where the electric field changes from negative to positive as described above. But To stably remains in this region further the radius r _disk of the center of the electrode plate, the variation applied voltage V _a, variation frequency omega, it is necessary to optimize the combination of width d of the acceleration gap.

The conditions for stably staying in the positive gradient region will be described with reference to FIGS.

[0053] Now, the ions of the center point O _A of the disk-shaped electrodes 3 and starting at the speed v ₀ of Figure 11 reaches the acceleration region 9 after Delta] t _0. It is accelerated for Δt ₁ and the deflection magnetic field region 2 at the speed v ₁
Cored, and enters the acceleration region 9 again deflected by Delta] t ₂ by an angle theta _c. Then undergo acceleration between Delta] t _3, enters the electrode portion 1 at the speed v2, and reaches the center point O _A after Delta] t _4.
At this time, the relationship between the phase of the electrode voltage and the velocity of the particles is shown in FIG. To repeat continuously accelerated more than is necessary to one period back from O _A to O _A matches the one period of the acceleration voltage. In a cyclotron, the deflection region occupies most of the orbit, so such synchronization can be achieved only by adjusting the high frequency to the cyclotron frequency determined by the magnetic field strength and the specific charge of the particles. Synchronization in consideration of stay time and speed change is necessary. The condition is

[0054]

Ω (Δt ₀ + Δt ₁ + Δt ₂ + Δt ₃ + Δt ₄ ) = 2π (13) Here, Δt _n , v _n (n = 0 to 4) can be expressed as follows.

[0055]

[Equation 17]

[0056]

(Equation 18)

[0057]

[Equation 19]

[0058]

(Equation 20)

[0059]

(Equation 21)

[0060]

(Equation 22)

[0061]

(Equation 23)

[0062]

(Equation 24)

The equations (14) to (22) are substituted into the equation (13) to evaluate the next phase deviation δ.

[0064]

Equation 25] _{δ = ω (Δt 0 + Δt} 1 + Δt 2 + Δt 3 + Δt 4) -2π (22) which the acceleration voltage V _a, voltage frequency omega, electrode radius r, a function of the width d of the acceleration region. To see the behavior to these, the size in the determined electrodes radius r of the device, the width d of the acceleration region is fixed, the relationship between the operational adjustable accelerating voltage V _a and the phase difference [delta], the voltage frequency ω discrete parameter Investigated for. FIG. 12 shows the result.

In FIG. 13, the region on the central horizontal axis is a region where the phase deviation δ is zero. The acceleration voltage V when each line indicating the case where the voltage frequency ω is changed crosses the central horizontal axis satisfies the equation (12). However, as shown in FIG. Exists. This part is expected to exhibit a very unstable behavior with respect to the movement of the acceleration voltage V, and is an area which should be out of the operation range. It is considered that the acceleration is stably performed in a portion where each line smoothly crosses the central horizontal axis.

FIG. 14 shows an acceleration situation during stable acceleration. At the time of stable acceleration, the acceleration phase of the particles is almost fixed in the region shown in FIG. As a result, in FIG. 14, 200 keV after 22 cycles
It can be seen that it has been accelerated. The setting parameters at this time are an acceleration voltage of 13 kV, an acceleration frequency of 600 kHz, and an applied magnetic field of 809 Gauss. In addition, the equipment parameter is electrode radius 0.
26m, acceleration area width 0.08m, maximum container radius 2.5m.

FIG. 15 shows the reaction cross section data [2] of the nuclear fusion due to the collision of ions. The 200 keV DD reaction is
It can be seen that it has almost the same reaction cross-section as the 20 keV DT reaction.

To obtain the orbital stability in the axial direction, a weakly focused magnetic field similar to that of a cyclotron is provided at the edge of the hole of the bending electromagnet. That is, the magnetic pole edge of the electromagnet on the disk electrode side is shaped as shown in FIG.
(B).

In the accelerator, parameters representing the properties of the magnetic field

[0070]

(Equation 26)

The n value defined in is used. The conditions for stabilizing the movement both horizontally and axially are as follows:

[0072]

It is known that 0 <n <1 (24). This apparatus also uses this n value.

To realize DT fusion of deuterium D and tritium T with the present apparatus, deuterium D and tritium T are mixed.
A method in which only deuterium D ions are accelerated by this apparatus to collide with tritium T in the atmosphere, or vice versa.
There is a method in which only ions are accelerated to collide with deuterium D in the atmosphere. To further increase the efficiency, deuterium D ions and tritium T ions are simultaneously accelerated. In this case, an accelerating electric field may be applied at a frequency that is a common multiple of each cyclotron frequency. DT fusion is realized with energy of about 10 keV, so the device can be further miniaturized.
Since tritium is a radioactive element harmful to the human body, its handling is regulated. For this reason, the present device has achieved high acceleration energy and can realize a DD reaction using only deuterium which is harmless to the human body.

[0074]

According to the apparatus of the present invention, it is possible to avoid electrode collisions in which heating is a problem as in the case of an electrostatic confinement fusion apparatus, and to increase the number of collisions between ions compared to cyclotrons. It is possible to provide a high-efficiency fusion neutron generator that accelerates difficult ions of deuterium and the like and that presupposes a DD reaction that is difficult with the apparatus disclosed in JP-A-2-269459.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a configuration of an apparatus according to an embodiment of the present invention.

FIG. 2 is a conceptual diagram showing an ion generation method according to one embodiment of the present invention.

FIG. 3 is a conceptual diagram showing the configuration and operation of an apparatus according to an embodiment of the present invention.

FIG. 4 is a conceptual diagram showing geometric features of an operation according to the embodiment of the present invention.

FIG. 5 is a conceptual diagram showing an arrangement of physical quantities in one embodiment of the present invention.

FIG. 6 is a view showing a simulation screen obtained by simulating the operation according to the embodiment of the present invention.

FIG. 7 is a view showing a simulation screen obtained by simulating the operation according to the embodiment of the present invention.

FIG. 8 is a conceptual diagram showing a stable operation condition in one embodiment of the present invention.

FIG. 9 is a conceptual diagram showing an orbit deflection angle in a cyclotron / microtron.

FIG. 10 is a conceptual diagram showing an orbit deflection angle in one embodiment of the present invention.

FIG. 11 shows the velocity on the orbit in one embodiment of the present invention.
The conceptual diagram which shows elapsed time.

FIG. 12 is a conceptual diagram showing a relationship between a speed on a time axis and an electrode voltage phase in one embodiment of the present invention.

FIG. 13 is a diagram showing a diaphragm relating to an orbit stabilization condition in one embodiment of the present invention.

FIG. 14 is a diagram showing a simulation screen simulating an operation in the embodiment of the present invention.

FIG. 15 is a view showing a cross section of a nuclear fusion reaction.

FIG. 16 is a conceptual diagram showing an edge shape of a perforated magnet and a distribution of magnetic flux density on a center plane according to the embodiment of the present invention.

Continued on the front page (72) Inventor Takashi Okazaki 7-2-1, Omika-cho, Hitachi City, Ibaraki Prefecture F-term in the Electric Power and Electric Power Development Laboratory, Hitachi, Ltd. 2G085 AA20 BA05 BA06 BA09 BB11 BC02 BC03 BC13 CA02 CA17 EA06 EA08

Claims (11)

[Claims] 1. An apparatus comprising an electrode, a power supply for applying a fluctuating voltage to the electrode, a magnet, a vacuum vessel, and means for generating charged particles in the vacuum vessel, wherein the electrode is formed by two disc-shaped flat plates. These electrodes are arranged coaxially and parallel to each other, a gap is provided between the electrodes so that the charged particles can pass through, and an alternating voltage having the same voltage and the same phase is applied to the two electrodes. The charged particles are accelerated by the alternating electric field, the trajectory of the accelerated charged particles is deflected by the magnetic field generated by the magnet, the charged particles are guided again to the vicinity of the electrode, and accelerated again. A charged particle acceleration device and a charged particle acceleration method characterized by accelerating charged particles to high energy by repeating these processes. 2. The charged particle accelerator according to claim 1, wherein said magnet is constituted by two disk-shaped magnets each having a hole formed at the center of its axis, and these are arranged coaxially and parallel to each other. A vacuum vessel in which the charged particles can fly is arranged, an axial magnetic field is applied to the vacuum vessel, and the charged particle accelerating electrode according to claim 1 is provided at a hole formed in the axis of the disc-shaped magnet. A charged particle accelerator, wherein the charged particle accelerator is provided in a radial direction. 3. The charged particle accelerator according to claim 1, wherein the cyclotron frequency of the charged particles generated in the vacuum vessel matches the frequency of the alternating voltage applied to the electrode. A charged particle accelerator in which a magnetic field applied by the magnet and a frequency of an alternating voltage applied to the electrode are adjusted, and an operation method thereof. 4. The charged particle accelerator according to claim 1, wherein the diameter of a hole formed in the center of the axis of the disk-shaped magnet is enlarged toward the center of the device, and A charged particle accelerator characterized in that the fringe magnetic field generated at the hole of the magnet is weakened toward the center of the diameter of the device, and the axial stability of the charged particle trajectory is enhanced. 5. The charged particle accelerator according to claim 1, 2, 3, or 4, wherein a hole formed in the center of the axis of the disk-shaped magnet, the disk-shaped charged particle acceleration electrode, A charged particle accelerating apparatus characterized in that charged particles are generated in the space inside the vacuum vessel during the period, and the charged particles are accelerated by using the charged particle accelerating method and the operating method according to claim 1 and claim 3. 6. The charged particle accelerator according to claim 5, wherein a high-frequency electric field is superimposed on a space in the vacuum vessel between the hole formed in the center of the axis of the disk-shaped magnet and the disk-shaped charged particle acceleration electrode. And adjusting the intensity of the fringe magnetic field generated at the hole of the disc-shaped magnet and the frequency of the high-frequency electric field so as to satisfy the conditions of electron cyclotron resonance, and generating ions in the space by the electron cyclotron resonance. A charged particle accelerator. 7. The charged particle accelerator according to claim 1, 2, 3, 4, 5, or 6, wherein deuterium or tritium or the like is contained in the vacuum vessel space. A fusion isotope ion is generated, accelerated to a high energy region by the acceleration method according to claim 1 or 3, and these high energy ions collide with each other near the axial center of the apparatus. A nuclear fusion device characterized by causing a nuclear fusion reaction. 8. The fusion device according to claim 7, wherein
A neutron generator characterized by generating a high neutron flux by using a nuclear fusion reaction for generating neutrons. 9. An isotope manufacturing apparatus, wherein a neutron is absorbed to generate a radioactive isotope by using the neutron generator according to claim 8. 10. A material reforming apparatus for irradiating neutrons to perform material reforming using the neutron generator according to claim 8. 11. An inspection apparatus which performs an inspection by irradiating neutrons using the neutron generator according to claim 8.