JP2017003362A - Nuclear fusion neutron generator and nuclear fusion neutron generation method - Google Patents

Abstract

A fusion reaction rate in a fusion neutron generator is improved with a simple configuration. According to an embodiment, a fusion neutron generator 100 includes a vacuum vessel 1 that is a sealed vessel, a cathode 10 that is provided near the center of the vacuum vessel 1 and is permeable to fluid, An intermediate electrode 20 that is provided outside the cathode 10 and divides the space outside the cathode 10 in the vacuum vessel 1 into an acceleration region and an ion generation region and through which the fluid in the vacuum vessel 1 can pass, and the vacuum vessel 1 A voltage application unit 40 that generates a ground potential, a negative potential on the cathode 10 and a negative or positive potential on the intermediate electrode 20, a local electric field generation unit 80 that generates a local electric field in a part of the ion generation region, and a fuel gas And a supply unit 50. [Selection] Figure 1

Description

  Embodiments of the present invention relate to an apparatus and method for generating neutrons by fusion.

  In general, as a fusion neutron generator, an apparatus using inertial electrostatic confinement fusion is known. An apparatus using an inertial electrostatic confinement fusion reaction usually has a structure in which a grid-like cathode is arranged in a concentric sphere at the center of a spherical vacuum vessel that also serves as an anode. By filling the vacuum vessel with a fuel gas such as deuterium and applying a high voltage of about several kV to 100 kV between the anode and the cathode, deuterium ions and the like are generated by the discharge.

  The generated ions are accelerated and converged toward the center by the electric field between the electrodes. The cathode has a lattice shape, and most ions reach the inside of the cathode without colliding with the cathode, jump out from the inside of the cathode, and are accelerated and converged toward the center again by the electric field. Fusion reactions occur when ions with high density at the center of the sphere collide with each other, collide with fuel gas, or collide with fuel gas particles embedded in the cathode or anode. Charged particles are generated.

  There is also an apparatus in which an anode and a cathode are formed in a cylindrical shape and arranged coaxially. Neutrons and charged particles obtained from fusion neutron generators are expected to be applied to nuclear material detection, explosives detection, nondestructive inspection, transmutation, isotope generation, neutron capture therapy, etc. Is required.

Japanese Patent No. 3867972 Japanese Patent No. 3700496 JP 2004-31152 A Japanese Patent Laid-Open No. 2008-20094

Yoshikawa Kiyoshi, Yamamoto Satoshi, Masuda Kai, Toshiyuki Takamatsu, Teruhisa Takamatsu, Eiki Hotta, Kunihito Yamauchi, Masami Onishi, Hotaka Ohsawa, Seiji Yotani, Satoshi Misawa, Yoshiyuki Takahashi, Ken Ken Takuyama, Miwa Kubo: “Inertial electrostatic confinement fusion Current status of research ”, J. Plasma Fusion Res. Vol.83, No.10, pp.795-811 (2007).

  In the conventional fusion neutron generator described above, the ion generation region and the ion acceleration region overlap, so that there is a problem that the density and energy of ions are restricted and the reaction rate of fusion is low.

  Further, a wall or the like is provided between the ion generation region and the ion acceleration region, and a method of separating the ion generation region and the acceleration region by performing differential evacuation, or an ECR (Electron Cyclotron Resonance) outside the vacuum vessel. , Electron cyclotron resonance (RF), radio frequency (RF), helicon wave and other external ion sources (ion generation regions) are provided to separate ions from the acceleration region. There has been a problem that the configuration of the apparatus becomes complicated and the apparatus becomes large.

  Embodiments of the present invention have been made to solve the above-described problems, and an object thereof is to improve the fusion reaction rate in a fusion neutron generator with a simple configuration.

  In order to achieve the above object, this embodiment is a fusion neutron generator that ionizes a fuel gas and generates neutrons by a nuclear fusion reaction, and is a vacuum vessel that is a sealed vessel used in a state lower than atmospheric pressure, A cathode provided in the vicinity of the center of the vacuum vessel so as to be electrically insulated from the vacuum vessel, a space is formed in the interior thereof, and the fluid in the vacuum vessel is permeable, and the cathode in the vacuum vessel The vacuum vessel and the cathode are provided outside so as to be electrically insulated, and a space outside the cathode in the vacuum vessel is divided into an inner acceleration region and an outer ion generation region. An intermediate electrode through which the fluid in the container can permeate; a voltage application unit for generating a negative potential at the cathode and a negative or positive potential at the intermediate electrode; and a part of the ion generation region. And a local electric field generator to produce a local electric field, characterized in that it comprises a fuel gas supply unit for supplying the fuel gas to the vacuum chamber.

  Further, the present embodiment is a fusion neutron generation method in which the supplied fuel gas is ionized and neutrons are generated by a fusion reaction, wherein the potential of the vacuum vessel as the anode is zero and the potential of the cathode is in a negative state. An initial setting step, an intermediate electrode positive voltage generating step in which the intermediate electrode voltage applying unit applies a positive potential to the intermediate electrode, and an intermediate electrode negative voltage generating step in which the intermediate electrode voltage applying unit applies a negative potential to the intermediate electrode. Whether or not neutron generation has ended is determined. If not, the intermediate electrode positive voltage generation step and subsequent steps are repeated.

  Further, the present embodiment is a fusion neutron generation method in which supplied fuel gas is ionized to generate neutrons by a nuclear fusion reaction, and the potentials of the vacuum vessel, the cathode, and the intermediate electrode that are anodes are set to zero. An initial setting step, a timing regulator for a predetermined time to the pulse valve, a pulse valve opening step for outputting an open command, and a timing regulator for the intermediate electrode voltage application unit, for a predetermined time to the intermediate electrode, An intermediate electrode voltage generation step for outputting a command to give a negative potential, a cathode voltage generation step for outputting a command for the negative voltage to be applied to the cathode for a predetermined time by the timing adjuster to the cathode voltage application unit, and a neutron Whether or not the generation has ended is determined. If the generation has not ended, the steps after the pulse valve opening step are repeated.

  According to the embodiment of the present invention, the fusion reaction rate in the fusion neutron generator can be improved with a simple configuration.

It is a longitudinal section showing the composition of the fusion neutron generator concerning a 1st embodiment. FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1. It is a graph which shows the electric potential distribution of the radial direction in the fusion neutron generator which concerns on 1st Embodiment. It is a figure which shows notionally the behavior near the cathode of ion. It is a longitudinal cross-sectional view which shows the structure of the fusion neutron generator which concerns on 2nd Embodiment. It is a graph which shows the electric potential distribution of the radial direction of the fusion neutron generator which concerns on 2nd Embodiment. It is a graph which shows the time change of the electric potential of the intermediate electrode in the fusion neutron generator which concerns on 3rd Embodiment. It is a graph which shows the electric potential distribution of the radial direction in the fusion neutron generator which concerns on 3rd Embodiment. It is a graph which shows the modification of the electric potential distribution of the radial direction in the fusion neutron generator which concerns on 3rd Embodiment. It is a flowchart which shows the procedure of the fusion neutron generation method which concerns on 3rd Embodiment. It is a longitudinal cross-sectional view which shows the structure of the fusion neutron generator which concerns on 4th Embodiment. It is a flowchart which shows the procedure of the fusion neutron generation method which concerns on 4th Embodiment. It is a graph which shows the timing chart of the pulse operation apparatus in the fusion neutron generator which concerns on 4th Embodiment, and the conceptual time change of an accompanying reaction process, (a) is the time change of the amount of introduced fuel gas in a discharge area, (B) shows the time change of the intermediate electrode potential, (c) shows the time change of the cathode potential, and (d) shows the time change of the ion amount in the acceleration region. It is a longitudinal cross-sectional view which shows the structure of the fusion neutron generator which concerns on 5th Embodiment. It is a graph which shows the time change of the emitted light intensity in the fusion neutron generator which concerns on 5th Embodiment, and the emitted fuel gas amount, (a) is a general light emission characteristic of breakdown plasma, (b) is The time change of the emitted fuel gas amount is shown.

  Hereinafter, a fusion neutron generator according to an embodiment of the present invention will be described with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

[First Embodiment]
FIG. 1 is a longitudinal sectional view showing a configuration of a fusion neutron generator 100 according to the first embodiment. 2 is a cross-sectional view taken along line II-II in FIG. The fusion neutron generator 100 includes a vacuum vessel 1 and its internal components, a voltage application unit 40, a fuel gas supply unit 50, and a gas pressure adjustment unit 52.

  The vacuum container 1 is a cylindrical sealed container and is used in a state lower than atmospheric pressure. The material of the vacuum vessel 1 is, for example, a conductive substance such as stainless steel, titanium, or aluminum. A cathode 10 and an intermediate electrode 20 are provided inside the vacuum vessel 1.

  The cathode 10 is cylindrical and is provided so as to be coaxial with the vacuum vessel 1. The material of the cathode 10 is conductive. The geometric transmittance of the cathode is desirably 90% or more, for example, 95%. Therefore, the cathode 10 has a cage shape in which a plurality of cathode rods 10a are arranged on the circumference, as shown in FIGS. In addition, in order to ensure geometric transmittance, it is not limited to a cage shape. For example, it may be net-like or a perforated plate cylinder.

  The cathode 10 is supported by a cathode support portion 11. The cathode support portion 11 is attached to the vacuum vessel 1 and supported by the vacuum vessel 1. The cathode support portion 11 is made of an insulating material such as alumina, for example, and electrically insulates between the cathode 10 and the vacuum vessel 1. A conductive high voltage introduction terminal 12 penetrates the inside and outside of the cathode support portion 11 and is electrically connected to the cathode 10. The space between the cathode support portion 11 and the vacuum vessel 1 and the space between the cathode support portion 11 and the high voltage introduction terminal 12 are airtight.

  The intermediate electrode 20 is provided in the space outside the cathode 10 in the vacuum vessel 1 so as to be coaxial with the vacuum vessel 1. The material of the intermediate electrode 20 is conductive. The geometric transmittance of the intermediate electrode 20 is desirably 90% or more, for example, 95%. For this reason, the intermediate electrode 20 has a cylindrical shape of a perforated plate as shown in FIGS. 1 and 2. In addition, in order to ensure geometric transmittance, it is not limited to being a perforated plate. For example, a cage shape or a mesh shape may be used. By providing the intermediate electrode 20, the space outside the cathode 10 in the vacuum vessel 1 is divided into an ion generation region 1 a outside the intermediate electrode 20 and an acceleration region 1 b closer to the center than the intermediate electrode 20. The

  The intermediate electrode 20 is supported by the intermediate electrode support portion 21. The intermediate electrode support portion 21 is attached to the vacuum vessel 1 and supported by the vacuum vessel 1. The intermediate electrode support portion 21 is made of an insulating material such as alumina, for example, and electrically insulates the intermediate electrode 20 and the vacuum vessel 1 from each other. A conductive high voltage introduction terminal 22 penetrates the inside and outside of the intermediate electrode support portion 21 and is electrically connected to the intermediate electrode 20. The space between the intermediate electrode support portion 21 and the vacuum vessel 1 and the space between the intermediate electrode support portion 21 and the high voltage introduction terminal 22 are airtight.

  A plurality of protrusions 60 are attached to the intermediate electrode 20 as the local electric field generator 80. The protrusion 60 is provided so as to protrude from the intermediate electrode 20 in a direction toward the radially outer side. The protrusion 60 is conductive, and the potential of the protrusion 60 is at the same level as the potential of the intermediate electrode 20. As the material of the protrusion 60, for example, a material having a relatively higher melting point than copper, aluminum, iron, or the like, such as tungsten, titanium, or tantalum, is used.

  The shape of the protrusion 60 is, for example, a needle shape or a truncated cone shape. However, if the tip is sharp enough that the local electric field becomes too large, arc discharge may occur. Therefore, the tip may be rounded to prevent arc discharge. Here, it is preferable that the protrusions 60 are arranged on the cylindrical intermediate electrode so that the axial interval and the circumferential interval of the intermediate electrode 20 are substantially equal.

  The voltage application unit 40 includes an anode voltage application unit 41, a cathode voltage application unit 42, and an intermediate electrode voltage application unit 43. The anode voltage application unit 41 is connected to the vacuum vessel 1 serving as an anode, and applies a potential as an anode to the vacuum vessel 1. Specifically, the vacuum vessel 1 is grounded. That is, the anode voltage application unit 41 is a ground electrode. The anode voltage application unit 41 is not limited to the ground electrode, and may be a power source that applies a potential corresponding to the installation potential.

  The cathode voltage application unit 42 is connected to the high voltage introduction terminal 12 of the cathode 10 and applies a negative potential to the cathode 10. The intermediate electrode voltage application unit 43 is connected to the high voltage introduction terminal 22 of the intermediate electrode 20, and applies an intermediate potential between the potential of the vacuum vessel 1 serving as the anode and the potential of the cathode 10 to the intermediate electrode 20.

  In addition to a method of forcibly applying a voltage using a power source or the like as the intermediate electrode voltage application unit 43, a resistor having one end is connected to the intermediate electrode 20, and a voltage between the resistors is generated by a discharge current flowing into the resistor. A method of generating a voltage (self-bias) and applying a voltage in the middle or a method of setting the intermediate electrode to a floating potential may be used.

  The fuel gas supply unit 50 introduces into the vacuum vessel 1 deuterium, tritium, helium, or a mixed gas thereof as a reactant for the fusion reaction. The fuel gas supply unit 50 has a pipe for transferring fuel gas from a supply source, and the pipe is airtightly connected to an opening provided on the side wall of the vacuum vessel 1. That is, the piping of the fuel gas supply unit 50 is connected to the ion generation region 1 a in the vacuum vessel 1. For this reason, fuel gas is supplied to the ion production | generation area | region 1a.

  In addition, although it is preferable that the fuel gas supply part 50 is connected to the ion production | generation area | region 1a, it is not limited to this. Since the fuel gas is supplied to the ion generation region 1a also in other parts of the vacuum vessel 1, it may be connected to other parts of the vacuum vessel 1 even when there are restrictions on the arrangement.

  A nozzle (not shown) may be provided at a portion where the fuel gas supply unit 50 is open to the vacuum container 1 so that the fuel gas penetrates into the vacuum container 1. Specifically, for example, a needle valve and a mass flow controller can be used for the fuel gas supply unit 50.

  The ionization energy of hydrogen is about 13 eV, which is a relatively high energy level. Therefore, it is possible to gasify atoms having an ionization energy lower than 13 eV and mix the fuel gas with the fuel gas. As the additive gas, an alkali metal such as sodium (Na) or potassium (K), or a transition metal obtained by heating or vaporizing a compound can be used.

  The gas pressure adjusting unit 52 adjusts the pressure in the vacuum vessel 1 so as to be a constant pressure of, for example, several Pa or less in combination with the operation of the fuel gas supply unit 50. The gas pressure adjusting unit 52 includes a pipe, and the pipe is airtightly connected to an opening provided on an end surface facing the acceleration region 1 b of the vacuum vessel 1. That is, the piping of the gas pressure adjusting unit 52 is connected to the acceleration region 1 b in the vacuum vessel 1. Specifically, as the adjusting means used in the gas pressure adjusting unit 52, a turbo molecular pump, a rotary pump, an ionization vacuum gauge, a diaphragm type vacuum gauge, or the like can be used. Typically, the vacuum is evacuated so that the ultimate degree of vacuum is within a range of about 0.01 Pa to 10 Pa. For example, a vacuum pumping system combining a turbo molecular pump and a rotary pump can be configured for vacuum pumping, and the pumping speed can be controlled by adjusting the rotational speed of the turbo molecular pump.

  FIG. 3 is a graph showing a radial potential distribution in the fusion neutron generator according to the first embodiment. The horizontal axis is the radial distance from the central axis of the vacuum vessel 1. The vertical axis represents the potential at each position according to the radial distance. A curve A indicated by a solid line indicates a potential distribution according to the present embodiment, and a curve B indicated by a broken line indicates a potential distribution when the intermediate electrode 20 is not provided.

  In the case of the present embodiment indicated by the curve A, the potential of the vacuum vessel 1 as an anode is 0, the potential of the cathode 10 is a negative potential V1, and the potential of the intermediate electrode 20 is V2. The potential distribution between the cathode 10 and the intermediate electrode 20 and the potential between the intermediate electrode 20 and the vacuum vessel 1 as the anode are substantially logarithmic with respect to the distance on the horizontal axis since the vacuum vessel 1 and the like are cylindrical. Distribution.

  Although the electric field intensity corresponds to the slope of the potential distribution curve, FIG. 3 shows a macro electric potential distribution in the vacuum vessel 1. A strong electric field is generated around the protrusion 60 as the local electric field generator 80 provided in the intermediate electrode 20. That is, the electric field intensity around the protrusion 60 as the local electric field generator 80 is sufficiently larger than the macro electric field intensity that is the slope at the point a2 of the potential distribution curve (solid line A) of the ion generation region in FIG. It is a value.

  In the potential distribution curve (broken line B) in the case where the intermediate electrode 20 is not provided, the slope, that is, the electric field strength has the maximum at the point b1. That is, when the intermediate electrode 20 is not provided, the electric field strength is maximum at the cathode 10. For this reason, glow discharge occurs mainly at the cathode 10, and ions are generated by glow discharge. Since the location where ions are generated is near the cathode 10, in the case of positive ions, the acceleration region until reaching the cathode 10 is short, and it reaches the cathode 10 without being given sufficient energy. However, there is a concern that the rate of accelerating in the region filled with fuel gas molecules and reaching the cathode 10 decreases.

  On the other hand, in the case of the present embodiment, the periphery of the protrusion 60 as the local electric field generator 80 is a place where the electric field strength is the highest, so the protrusion 60 in the ion generation region 1a and the vacuum container 1 as the anode Corona discharge occurs between them. By the corona discharge, the fuel gas in the ion generation region 1a is turned into plasma and ions are generated. Note that the protrusion 60 as the local electric field generator 80 is provided on the ion generation region 1a side of the intermediate electrode 20 and faces radially outward, so that arc discharge occurs between the protrusion 60 and the cathode 10. The possibility is small.

  As shown in FIG. 3, the electric potential distribution decreases toward the center of the vacuum vessel 1 (leftward direction in FIG. 3), so that the direction of the electric field is a direction toward the center of the vacuum vessel 1. Therefore, positive ions generated in the ion generation region 1a flow into the acceleration region 1b from the ion generation region 1a through the passage hole of the intermediate electrode 20, and are accelerated toward the cathode.

FIG. 4 is a diagram conceptually showing the behavior of ions near the cathode. A solid line T conceptually shows a locus of positive ions that have passed from the ion generation region 1a through the intermediate electrode 20 and flowed into the acceleration region 1b. Positive ions such as for example D ⁺ generated in the ion generation region 1a ^(deuterium ion), T + ⁽³ deuterium ions) are drawn to the cathode 10 and flies toward the cathode 10.

  Since the geometrical transmittance of the cathode 10 is as large as 95%, for example, most of the positive ions pass between the cathode rods 10a and move to the position of the point P1 outside the area of the cathode 10 while decelerating. After stopping at the position of the point P1, it is inverted and drawn to the cathode 10 and inverted at the point P2 closer to the cathode than the point P1, and further inverted and drawn to the cathode 10 and inverted at the point P3 closer to the cathode than the point P2. Repeat the process. During this time, it collides with other positive ions and fuel gas molecules, causing a fusion reaction.

  Here, consider a case where the number of cathode rods 10a is reduced in order to increase the geometrical transmittance of the cathode. In this case, since the electric field is strongly formed around each cathode rod 10a, the electric field around the entire cathode 10 is distorted. Therefore, the point of stopping after passing through the cathode 10 deviates from the point P1 in FIG. 4 and does not return to the center direction of the cathode even if it is reversed. In such a situation, the amount of ions contributing to the fusion reaction at the cathode is reduced. Therefore, it is not preferable to increase the geometric transmittance of the cathode 10 too much.

  On the other hand, when the geometric transmittance is reduced, the rate at which ions attracted by the cathode 10 collide with the cathode rod 10a increases, and the amount of ions contributing to the fusion reaction decreases. Therefore, it is not preferable to make the geometric transmittance of the cathode 10 too small. The above-described geometric transmittance of 90% or more, for example, about 95% is for this reason.

The fusion reaction at the cathode 10 generates neutrons or protons, for example, as follows.
D + D → ³ He + n
D + D → T + p
D + T → ⁴ He + n
However, D is deuterium, T is tritium, n is neutron, p is proton, and He is helium.

  As described above, according to the present embodiment, the fusion reaction rate in the fusion neutron generator can be improved with a simple configuration in which the protrusion 60 is provided as the local electric field generator 80 on the intermediate electrode 20.

[Second Embodiment]
FIG. 5 is a longitudinal sectional view showing the configuration of the fusion neutron generator according to the second embodiment. This embodiment is a modification of the first embodiment, and the fusion neutron generator 100 has an adjustment electrode 30.

  The adjustment electrode 30 has a cylindrical shape, and is provided in the space of the acceleration region 1 b in the vacuum vessel 1 so as to be coaxial with the vacuum vessel 1. The material of the adjustment electrode 30 is conductive. The geometric transmittance of the adjusting electrode 30 is desirably 90% or more, for example, 95%. For this reason, the adjustment electrode 30 has a cylindrical shape of a perforated plate as shown in FIG. In addition, in order to ensure geometric transmittance, it is not limited to being a perforated plate. For example, a cage shape or a mesh shape may be used. The space of the acceleration region 1 b in the vacuum vessel 1 is divided into a region inside the adjustment electrode 30 and a region outside the adjustment electrode 30 due to the provision of the adjustment electrode 30.

  The adjustment electrode 30 is supported by the adjustment electrode support portion 31. The adjustment electrode support portion 31 is attached to the vacuum vessel 1 and supported by the vacuum vessel 1. The adjustment electrode support portion 31 is made of an insulating material such as alumina, for example, and electrically insulates between the adjustment electrode 30 and the vacuum vessel 1. A conductive high voltage introduction terminal 32 penetrates inside and outside of the adjustment electrode support portion 31, is electrically connected to the adjustment electrode 30, and is given a potential by the adjustment electrode voltage application portion 44. The space between the adjustment electrode support 31 and the vacuum vessel 1 and the space between the adjustment electrode support 31 and the high voltage introduction terminal 32 are airtight.

  FIG. 6 is a graph showing the radial potential distribution of the fusion neutron generator according to the second embodiment. A curve A indicated by a broken line is a potential distribution in the case of the first embodiment, that is, in the case where no adjustment electrode is provided. A curve C indicated by a solid line is a potential distribution in the case of the present embodiment, that is, when the adjustment electrode 30 is provided. Regarding the potential distribution in the acceleration region 1b between the cathode 10 and the intermediate electrode 20, the curve C is closer to the straight line connecting the points a1 and a2 than the curve A. That is, it can be seen that the distribution of the electric field intensity is more flat in the present embodiment than in the first embodiment.

  Thus, by providing the adjustment electrode 30 between the cathode 10 and the intermediate electrode 20, the potential distribution in the acceleration region 1b can be adjusted. Moreover, although the case where there was one adjustment electrode was shown, you may provide further the adjustment electrode which divides each area | region into the inner side and the outer side as needed.

  The adjustment of the potential distribution is not limited to flattening, and the adjustment electrode 30 may be used to realize an arbitrary potential distribution.

[Third Embodiment]
FIG. 7 is a graph showing temporal changes in the potential of the intermediate electrode in the fusion neutron generator according to the third embodiment. This embodiment is a modification of the first embodiment. In the present embodiment, as shown in FIG. 7, the intermediate electrode voltage application unit 43 (FIG. 1) alternately changes the potential of the intermediate electrode 20 between the positive side and the negative side in terms of time. Here, it is desirable to set the voltage polarity switching time short in order to make it difficult to induce arc discharge and stabilize corona discharge. The rise and fall times when switching the polarity of the voltage are, for example, about nanoseconds to microseconds.

  The waveform is not limited to the waveform shown in FIG. For example, a triangular wave, a trapezoidal wave, a rectangular wave, or a sine wave may be used as long as the waveform changes alternately between the positive side and the negative side.

  FIG. 8 is a graph showing a radial potential distribution in the fusion neutron generator according to the third embodiment. A curve N indicated by a solid line indicates a case where the potential of the intermediate electrode 20 is negative, and a curve P indicated by a broken line indicates a case where the potential of the intermediate electrode 20 is positive. The potential of the cathode 10 is fixed at V3, and the potential of the vacuum vessel 1 as the anode is fixed at 0. FIG. 9 is a graph showing a modification of the potential distribution. The potential of the cathode 10 may be a floating potential Vn as shown in FIG.

  When the potential of the intermediate electrode 20 changes between positive and negative, the potential distribution in the acceleration region 1b remains to the left as shown in FIG. That is, the electric field remains in the left direction of the graph, that is, in the direction from the intermediate electrode 20 to the cathode 10. On the other hand, the potential distribution in the ion generation region 1a repeats downward and upward as shown in FIG. That is, the electric field in the left direction and the electric field in the right direction of the graph are repeated.

  FIG. 10 is a flowchart showing the procedure of the fusion neutron generation method according to this embodiment. First, the anode voltage application unit 41 applies a zero potential to the voltage of the vacuum vessel 1, and the cathode voltage application unit 42 applies a negative potential to the cathode 10 (step S01).

  Next, the intermediate electrode voltage application unit 43 applies a positive potential to the intermediate electrode 20 (step S02). In general, more positive ions are generated in the positive corona discharge than in the negative corona discharge generated by applying a negative potential to the protrusion 60 in the first embodiment. Here, the positive corona discharge refers to corona discharge generated by applying a positive potential to the protrusion. When a positive potential is applied to the intermediate electrode 20, a positive potential is obtained with respect to the vacuum vessel 1 serving as an anode. Since the electric field strength is high in the vicinity of the protrusion 60 which is the local electric field generator 80, a positive corona discharge is generated between the vacuum vessel 1. For this reason, for example, deuterium as a fuel gas becomes positive deuterium ions. While a positive potential is applied to the intermediate electrode 20, positive deuterium ions are accelerated in the direction of the vacuum container 1.

  Next, the intermediate electrode voltage application unit 43 applies a negative potential to the intermediate electrode 20 (step S03). After the intermediate electrode 20 changes to a negative potential, the electric field direction is reversed, and positive deuterium ions are accelerated toward the intermediate electrode 20. In the next cycle, when the intermediate electrode 20 changes to a positive potential, the electric field in the ion generation region 1a changes again in the direction of the vacuum vessel 1, but during this time the heavy electrode that has passed through the intermediate electrode 20 and has flowed into the acceleration region 1b. Hydrogen ions are accelerated toward the cathode 10 and contribute to the fusion reaction at the cathode 10.

  Next, the intermediate electrode voltage application unit 43 determines whether or not the neutron generation by the fusion neutron generator 100 is finished, and if it should be finished (YES in step S04), the process is finished. If it is not the end (NO in step S04), step S02 and subsequent steps are repeated. The termination determination condition is configured such that external input to the intermediate electrode voltage application unit 43 is possible, and the neutron generation time from the end time and start time is specified in the intermediate electrode voltage application unit 43 in advance, or the end When the time comes, this can be done by inputting the fact to the intermediate electrode voltage application unit 43.

  In this way, the potential of the intermediate electrode 20 is set to a positive potential to efficiently generate more positive ions of the fuel gas, the potential of the intermediate electrode 20 is turned negative, and the generated positive ions are moved to the cathode 10 side. By collecting, the fusion reaction efficiency can be dramatically improved.

  In addition, the generation of corona discharge can be stabilized by alternately inverting the polarity of the intermediate electrode 20 between positive and negative.

[Fourth Embodiment]
FIG. 11 is a longitudinal sectional view showing the configuration of the fusion neutron generator according to the fourth embodiment. This embodiment is a modification of the first embodiment. The fusion neutron generator 100 in this embodiment includes a gas cylinder 53, a pulse valve 54, a pulse valve controller 55, and a timing adjuster 57.

  The gas cylinder 53 stores fuel gas such as deuterium gas or tritium gas. The pulse valve 54 introduces the fuel gas from the gas cylinder 53 whose pressure is reduced by a pressure adjusting valve (not shown) into the vacuum vessel 1 in a pulse shape. A nozzle (not shown) may be provided at the open portion of the pulse valve 54 to the vacuum vessel 1 so that the fuel gas can penetrate into the ion generation region 1a in the vacuum vessel 1.

  The timing adjuster 57 outputs a command signal to each of the pulse valves 54 via the cathode voltage application unit 42, the intermediate electrode voltage application unit 43, and the pulse valve controller 55, and adjusts their mutual time relationship.

  FIG. 12 is a flowchart showing the procedure of the fusion neutron generation method according to the fourth embodiment. FIG. 13 is a graph showing a timing chart of the pulse operating device and a conceptual time change of the accompanying reaction process. (A) is a time change of the amount of introduced fuel gas in the discharge region (ion generation region). ) Shows the time change of the intermediate electrode potential, (c) shows the time change of the cathode potential, and (d) shows the time change of the ion amount in the acceleration region. Hereinafter, the procedure of the fusion neutron generation method and the operation of the fusion neutron generator will be described with reference to FIGS.

  First, the potentials of the vacuum vessel 1, the cathode 10, and the intermediate electrode 20 that are anodes are set to zero (step S11). In this state, first, the timing adjuster 57 outputs an open command to the pulse valve 54. The pulse valve 54 is opened after a predetermined time interval and then closed (step S12). As a result, as shown in FIG. 13A, for example, deuterium gas, which is a fuel gas, is injected into the ion generation region 1a for a predetermined time interval from time T1 to time T3. The vertical axis | shaft of Fig.13 (a) is the fuel gas amount per unit volume in the ion production area | region 1a, ie, the density | concentration of fuel gas.

  Specifically, when the fuel gas is injected into the ion generation region 1a, the concentration of the fuel gas in the ion generation region 1a increases, and then the fuel gas accelerates due to the pressure difference between the ion generation region 1a and the acceleration region 1b. Since it moves to the region 1b, the concentration of the fuel gas in the ion generation region 1a decreases. Therefore, when the fuel gas is injected into the ion generation region 1a, the concentration of the fuel gas in the ion generation region 1a reaches a peak after increasing and then decreases.

  The injection speed of the fuel gas into the ion generation region 1 a is controlled by a control signal from the timing adjuster 57 for the opening time of the pulse valve 54 and its repetition frequency. If necessary, the pressure adjustment valve (not shown) of the gas cylinder 53, the inner diameter of the throat portion (not shown) of the pulse valve 54, and the exhaust speed of the gas pressure adjustment unit 52 are adjusted at the same time, and the ion generation region 1a is made fuel. Control the time to fill with gas. The number of the installed pulse valves 54 is preferably arranged close to each other for the purpose of filling the ion generation region 1a with fuel gas in the shortest possible time.

  The timing adjuster 57 applies a negative potential to the intermediate electrode 20 to the intermediate electrode voltage application unit 43 at the same time or after outputting the opening command to the pulse valve 54, and applies a zero potential to the intermediate electrode 20 after a predetermined time. A command signal is output (step S13). The predetermined time may be determined by analysis or testing.

  In addition, if the ion production area | region 1a is satisfy | filled with fuel gas in step S12, the pressure of the ion production | generation area | region 1a will rise locally according to this. The dependence of the discharge start voltage on the gas pressure on the gas is given by the Paschen curve. The Paschen curve shows the characteristic that when the distance between the electrodes is constant, the discharge start voltage decreases as the pressure increases, and then increases after reaching the minimum value. The pressure giving this minimum value is generally large enough, depending on the geometry of the system.

  In the discharge of the fusion neutron generator, the pressure range is generally a pressure region lower than the pressure giving this minimum value, that is, a region where the discharge start voltage decreases as the pressure increases. For this reason, in this embodiment, it becomes the characteristic that a discharge start voltage falls with a raise of a pressure. Therefore, it is important that the intermediate electrode 20 is at a negative potential while the pressure in the ion generation region 1a is increased by the injection of the fuel gas into the ion generation region 1a in step S12.

  In this way, before the concentration of the fuel gas in the ion generation region 1a reaches the peak, as shown in FIG. 13 (b), the intermediate electrode voltage application unit 43 has the potential over the time from time T2 to time T4. A negative potential is applied to the intermediate electrode 20 in which is zero. The negative potential is, for example, about −10 kV. The time T2 is set to any time between the time T1 and the time when the concentration of the fuel gas reaches the peak. Time T4 is set to a time after time T3 to time T3. By applying a negative potential to the intermediate electrode voltage application unit 43, the ion generation region 1b becomes a discharge region, for example, deuterium ions are generated at a high density.

  Next, the timing adjuster 57 applies a negative potential to the cathode 10 that was zero to the cathode voltage application unit 42 at time T4 when the potential of the intermediate electrode 20 switches from a negative potential to a zero potential, and after a predetermined time, A command signal is output so as to apply a zero potential to 10 (step S14). The cathode 10 has a negative potential for a predetermined time as shown in FIG. The negative potential is, for example, about −100 kV. The predetermined time may be determined by analysis or testing.

  As a result, an electric field is generated in the acceleration region 1b in the annular space region sandwiched between the vacuum vessel 1 serving as the anode and the outer surface of the cathode 10, that is, the ion generation region 1a and the acceleration region 1b. By this electric field, the ion generation region 1a and the acceleration region 1b become regions where ion acceleration is performed in a state where the neutral residual gas is reduced, and the deuterium ions are accelerated to high energy with high efficiency. It is done. The amount of ions per unit volume in the acceleration region 1b changes as shown in FIG.

  Next, the timing adjuster 57 determines whether or not the neutron generation by the fusion neutron generator 100 is finished, and if it should be finished (step S15 YES), the timing regulator 57 is finished. If the process is not finished (NO in step S15), the processes in and after step S12 are repeated.

  As described above, according to the present embodiment, it is possible to improve the fusion reaction rate by separating the generation of ions and the acceleration of ions spatially and temporally.

  In the present embodiment, the voltage applied to the cathode 10 and the intermediate electrode 20 is a negative voltage, but the present invention is not limited to this. The applied voltage to the cathode 10 and the intermediate electrode 20 may be a positive voltage, and the same effect can be obtained. Further, the discharge in the ion generation region 1a is not limited to the corona discharge. For example, glow discharge may be used, and the same effect can be obtained.

[Fifth Embodiment]
FIG. 14 is a longitudinal sectional view showing the configuration of the fusion neutron generator according to the fifth embodiment. This embodiment is a modification of the first embodiment. The fusion neutron generator 100 according to the present embodiment further includes a light incident device that is the local electric field generator 80. In addition, a plurality of pulse valves 54 are provided on the side wall of the vacuum vessel 1 serving as an anode at intervals from each other along the axial direction and the circumferential direction. Fuel gas is uniformly sprayed into the ion generation region 1a from a nozzle (not shown) provided in the mouth.

  The light incident device makes light energy incident on the ion generation region 1 a in the vacuum vessel 1 in order to form a local electric field. Specifically, there is a laser device 70 that can efficiently form a local electric field. In addition, if the energy which can form a local electric field can be provided to the ion generation area | region 1a, a light-injection apparatus will not be restricted to a laser apparatus. Hereinafter, a laser device will be described as an example.

  The laser device 70 includes a pulse laser transmitter 71, a partial reflection mirror 72, a lens 73, and a mirror 74.

  The pulse laser transmitter 71 outputs a laser in pulses. As the laser, a carbon dioxide laser, a nitrogen gas laser, an Nd: YAG (Yttrium Aluminum Garnet) laser, a ruby laser, an OPO (Optical Parameter Oscillation) laser, a titanium sapphire laser, a fiber laser, a semiconductor laser, or the like can be applied. A laser pulse having a short pulse width of 1 μs or less, such as a nanosecond Nd: YAG laser or a femtosecond laser, is desirable because it is efficient.

  The partial reflection mirror 72 separates the incident laser light into a transmission component and a reflection component. The lens 73 is a convex lens and condenses incident laser light. The mirror 74 reflects the incident laser light.

  The timing adjuster 57 issues an operation command signal to the gas cylinder 53, the cathode voltage application unit 42, the intermediate electrode voltage application unit 43, the pulse valve controller 55, and the pulse laser transmitter 71 so as to adjust the respective timings. .

  Hereinafter, the operation of the laser device 70 among the operations in the present embodiment configured as described above will be described. First, the timing adjuster 57 outputs an open command to each pulse valve 54. When each pulse valve 54 is opened, fuel gas is injected from the gas cylinder 53 into the ion generation region 1a. The timing adjuster 57 instructs the laser device 70 to perform laser irradiation at the same time as or immediately after the opening of each pulse valve 54.

  The pulse laser beam output from the pulse laser transmitter 71 is changed in direction by the partial reflection mirror 72, then condensed by the lens 73, and focused on the fuel gas by the mirror 74. The fuel gas molecules are ionized by resonance excitation by laser or multiphoton absorption, and are ionized to generate plasma.

  The timing adjuster 57 adjusts the opening timing of the pulse valve 54, the high voltage application timing of the intermediate electrode 20, and the irradiation timing of the laser device 70. Examples of the timing adjuster 57 include a pulse generator that can generate at least three types of pulses having different timings.

  FIG. 15 is a graph showing temporal changes in emission intensity and emitted fuel gas amount in the fusion neutron generator according to the fifth embodiment, and (a) is a general emission characteristic of breakdown plasma, (B) shows the time change of the amount of released fuel gas. As shown in FIG. 15A, the pulse width of the pulse laser is, for example, about 10 ns for the Nd: YAG laser, and the plasma emission time is several tens μs depending on the type of fuel gas and the density of the fuel gas. Reach. That is, the plasma continues to grow even after the laser irradiation ends, and attenuates after several tens of μs.

  Therefore, as shown in FIG. 15B, ions can be efficiently generated by appropriately setting the opening time of the pulse valve 54 in accordance with the plasma duration time.

  In the present embodiment, in addition to the protrusion 60 as the local electric field generator 80, the laser device 70 as the local electric field generator 80 is further provided, thereby further improving the ion generation efficiency in the ion generation region 1a. However, the present invention is not limited to this. That is, only the laser device 70 may be provided as the local electric field generator 80.

[Other Embodiments]
As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. For example, in each embodiment, although the case where the shape of the vacuum vessel was cylindrical was shown, it is not limited to this. For example, it may be spherical or polyhedral. In this case, the shape of the intermediate electrode and the additional electrode may be an appropriate shape for setting a potential at a position between the shape of each vacuum vessel and its center, for example, a shape similar to the vacuum vessel.

  Regarding the material of the vacuum vessel, in each embodiment, the case of using a conductive substance as a material has been described. However, the present invention is not limited to this, and an insulating substance such as glass or ceramic may be used. In this case, an anode using a conductive material may be provided on the inner surface of the vacuum vessel, and a lead wire penetrating the vacuum vessel hermetically and connected to the cathode voltage application unit may be provided.

  Moreover, you may combine the characteristic of each embodiment. For example, in the fusion neutron generation method according to the fourth embodiment, the local electric field generator 80 is provided with the protrusion 60, but is not limited thereto. That is, an embodiment in which the fusion neutron generation method according to the fourth embodiment and the laser apparatus according to the fifth embodiment are combined may be used.

  Furthermore, these embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention.

  These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Vacuum container, 1a ... Ion production | generation area | region, 1b ... Acceleration area | region, 10 ... Cathode, 10a ... Cathode rod, 11 ... Cathode support part, 12 ... High voltage introduction terminal, 20 ... Intermediate electrode, 21 ... Intermediate electrode support part, DESCRIPTION OF SYMBOLS 22 ... High voltage introduction terminal, 30 ... Adjustment electrode, 31 ... Adjustment electrode support part, 32 ... High voltage introduction terminal, 40 ... Voltage application part, 41 ... Anode voltage application part, 42 ... Cathode voltage application part, 43 ... Intermediate electrode Voltage application unit 44 ... Adjusting electrode voltage application unit 50 ... Fuel gas supply unit 52 ... Gas pressure adjusting unit 53 ... Gas cylinder 54 ... Pulse valve 55 ... Pulse valve controller 57 ... Timing controller 60 ... Projection part, 70 ... laser device, 71 ... pulse laser transmitter, 72 ... partial reflection mirror, 73 ... lens, 74 ... mirror, 80 ... local electric field generator, 100 ... fusion neutron generator

Claims (10)

A fusion neutron generator that ionizes fuel gas and generates neutrons by a fusion reaction,
A vacuum vessel which is a sealed vessel used in a state lower than atmospheric pressure;
A cathode provided in the vicinity of the center of the vacuum vessel so as to be electrically insulated from the vacuum vessel, a space is formed therein, and a fluid in the vacuum vessel is permeable;
The vacuum vessel and the cathode are provided outside the cathode in the vacuum vessel so as to be electrically insulated from each other, and the space outside the cathode in the vacuum vessel is formed in the inner acceleration region and the outer ion generation. An intermediate electrode that is divided into regions and is permeable to fluid in the vacuum vessel;
A voltage application unit for setting the vacuum vessel to a ground potential, generating a negative potential on the cathode, and a negative or positive potential on the intermediate electrode;
A local electric field generator for generating a local electric field in a part of the ion generation region;
A fuel gas supply unit for supplying the fuel gas into the vacuum vessel;
A fusion neutron generator characterized by comprising:   The vacuum vessel, the intermediate electrode, and the cathode are provided in the vacuum vessel so as to be electrically insulated, and the space between the intermediate electrode and the cathode is further divided into an inner region and an outer region. The fusion neutron generator according to claim 1, further comprising at least one adjustment electrode through which the fluid in the vacuum vessel can pass.   2. The local electric field generator includes a plurality of protrusions attached to the intermediate electrode and electrically coupled to the intermediate electrode and protruding from the intermediate electrode toward the vacuum vessel. Item 3. The fusion neutron generator according to Item 2.   The fusion neutron generator according to any one of claims 1 to 3, wherein the local electric field generator includes a light incident device capable of irradiating the ion generation region with light.   The fusion light neutron generator according to claim 4, wherein the light incident device is a laser device.   The fusion neutron generator according to any one of claims 1 to 5, wherein the voltage application unit is capable of applying a periodically changing potential to the intermediate electrode. The fuel gas supply unit
A pulse valve capable of supplying the fuel gas in a pulsed manner to the ion generation region;
A timing adjuster that adjusts the time point at which the fuel gas is released by the pulse valve and the time point at which the voltage application unit applies voltage;
The fusion neutron generator according to any one of claims 1 to 6, characterized by comprising:   The nucleus according to any one of claims 1 to 7, wherein the fuel gas supply unit supplies a gas in which a gas having a lower ionization potential than the fuel gas is mixed with the fuel gas. Fusion neutron generator. A fusion neutron generation method that ionizes supplied fuel gas and generates neutrons by a fusion reaction,
An initial setting step in which the potential of the vacuum vessel serving as the anode is zero and the potential of the cathode is in a negative state;
An intermediate electrode positive voltage generating step in which the intermediate electrode voltage application unit applies a positive potential to the intermediate electrode;
Next, an intermediate electrode negative voltage generation step in which the intermediate electrode voltage application unit applies a negative potential to the intermediate electrode,
A fusion neutron generation method characterized by determining whether or not neutron generation has ended, and repeating the intermediate electrode positive voltage generation step and subsequent steps if it has not ended. A fusion neutron generation method that ionizes supplied fuel gas and generates neutrons by a fusion reaction,
An initial setting step in which the potentials of the vacuum vessel, the cathode, and the intermediate electrode, which are anodes, are set to zero;
A pulse valve opening step in which the timing controller outputs an opening command to the pulse valve for a predetermined time; and
An intermediate electrode voltage generation step in which a timing adjuster outputs a command to the intermediate electrode voltage application unit to apply a negative potential to the intermediate electrode for a predetermined time;
A cathode voltage generation step in which a timing controller outputs a command to the cathode voltage application unit to apply a negative potential to the cathode for a predetermined time; and
A fusion neutron generation method characterized by determining whether or not neutron generation has ended, and repeating the pulse valve opening step and subsequent steps if it has not ended.

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