JP2018120774A - Electrostatic accelerator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic accelerator capable of extracting ions of a high current by supplying high power to an ion source of a high voltage part, without increasing a weight of the high voltage part and with space saving of a footprint.SOLUTION: The electrostatic accelerator, accelerating charged particle beams at an electrostatic field, supplies microwave power from ground potential side through a waveguide having an insulation choke flange for supplying microwave power to an ion source on high voltage side, in order to supply microwaves of high power required to extract ion beams of a high current to the ion source on high voltage side.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an electrostatic accelerator.

  Conventionally, high-frequency quadrupole linear accelerators (RFQ) and drift tubes are used for BNCT (boron neutron capture therapy), International Fusion Materials Irradiation Facility (IFFIF), and high-current low-energy accelerators that are necessary for accelerators for mass production of tritium. Linac (DTL) combinations have been considered. However, in a continuous beam accelerator with a large current, heat generation and consumption of material around the beam are severe, and its practical application is extremely difficult. On the other hand, negative ion incident tandem accelerators and the like have been studied as electrostatic accelerators for electrostatically accelerating ions. However, there are various problems with large currents, and the limit is about 10 mA. For example, Patent Document 1 and Patent Document 2 describe a high-current accelerator system.

Special table 2012-500454 gazette JP 2012-164660 A

The electrostatic accelerator system described in Patent Document 1 includes a mass separation magnet and a vacuum pump installed on the high voltage side between a DC high voltage / high power supply device, an exit ion accelerator tube, and a proton ion source. Have An electrostatic accelerator system has an acceleration tube with a plurality of conductive electrodes separated from each other by an insulating ring, sometimes called a beam tube. The accelerating tube is configured to supply a uniform and focused accelerating electric field for the proton beam. A power supply device that supplies a high voltage of about 0.4 MeV or more and a large current of about 10 mA or more applies an acceleration voltage to the acceleration tube. The ion source generates protons with ionized hydrogen gas having microwave power supplied by an external microwave generator. The plasma is limited to an axial solenoidal magnetic field formed by a permanent magnet surrounding the ion source. The ion source has a small beam extraction hole and emits a small amount of neutron hydrogen gas that passes through the beam extraction hole (preferably less than 3 cm ³ (standard cubic centimeters per minute)). It is desirable to emit a proton beam with a current of 5 mA or more, and in the accelerator system, it is desirable to have a configuration that reduces neutralization due to gas collision of ions within the accelerator tube. The magnetic field of the mass separation magnet can prevent ions other than protons generated by the ion source from reaching the accelerator tube, in order to reduce the amount of neutron hydrogen gas entering the accelerator tube. A vacuum adsorption pump is provided between the ion source and the accelerating tube, limiting the acceleration of beam divergence and further suppressing the amount of neutron gas entering the accelerating tube. In order, the vacuum pump is installed in the entrance of the accelerating tube.

  In the electrostatic accelerator described in Patent Document 2, in order to increase the ion beam current, a vacuum pump and a vacuum constriction are incorporated in a high voltage terminal, and mass separation is performed to accelerate only important ions prior to acceleration. And application of an ion source with high ionization efficiency to optimize the ratio of primary ion beam current to neutral gas emission. It is a direct current linear accelerator equipped with a vacuum pump and mass spectrometry in a high voltage terminal.

  It is said that the key for increasing the current is to lower the vacuum pressure in the accelerating tube. This low vacuum pressure in the accelerating tube enables high current beam acceleration. A mass analyzer for removing the neutralizing gas from the primary ion beam is housed. The mass analyzer can be configured so that it acts like a lens that focuses the diverging beam emitted from the ion source into a convergent beam. According to this method, a beam focus or “waist” is formed after mass analysis. According to this structure, a vacuum stop in the form of an electrode plate or wall with small sized holes can be placed at the position of the beam focus. Thereby, the ion beam subjected to mass analysis can be passed through even a small hole toward the acceleration tube, and at the same time, neutral gas can be prevented from flowing into the acceleration tube.

  In the case of the configurations described in Patent Documents 1 and 2, the effect of increasing the current of the electrostatic accelerator can be somewhat obtained by preventing neutralization of ions emitted from the ion source. However, it is very difficult to realize a large current only by reducing the vacuum pressure in the acceleration tube.

  In conventional electrostatic accelerators, the conventional dynamitron as described above is a microwave that generates ion source plasma even though it can take measures to reduce ion neutralization by the neutralizing gas emitted from the ion source. Since the electric power is small, the plasma cannot be sufficiently ionized, and the ion ratio cannot be increased as compared with the neutralized gas, so that a high-current ion beam cannot be extracted. Further, in the conventional tandem accelerator, in the case of a charge exchanger using a thin film for converting negative ions to positive ions, there is a problem that the heat load is large so that melting may occur and the life is shortened. . In addition, in the case of a charge exchanger using a gas stripper, there is a drawback in that gas easily flows and flows through the high voltage electrode portion. Also, with a negative ion source, it is technically difficult to extract a large current ion beam, and it has been difficult to obtain a large current.

  In order to solve the above problems, for example, the following configuration is adopted.

  The present invention includes a plurality of means for solving the above-mentioned problems. For example, an electrostatic accelerator for accelerating a charged particle beam with an electrostatic field, which is provided on the high voltage side of the accelerator. A microwave source for supplying the microwave to the ion source, and a microwave generator for supplying the microwave to the waveguide, the waveguide being provided with an insulating choke flange, The wave generator is provided on the ground side of the accelerator.

  According to the present invention, it is possible to provide an electrostatic accelerator capable of extracting a large current beam that can use a positive ion source as an ion source without using a charge exchanger. In addition, a neutron generator using a high-current electrostatic accelerator can be provided.

1 is a diagram showing a schematic configuration of an electrostatic accelerator using an insulating choke flange structure according to a first embodiment of the present invention. It is a figure which shows schematic structure of the electrostatic accelerator using the conventional rotary motor, the rotation insulation rod, and the rotary generator. It is a figure which shows schematic structure of the electrostatic accelerator using the method of supplying electric power with the conventional insulation transformer.

  In this embodiment, an electrostatic accelerator using a microwave power supply method and its structure will be described as an example. However, the present invention is applicable to all electrostatic accelerators.

  An electrostatic accelerator that is a typical embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram illustrating a schematic configuration of an electrostatic accelerator 100 according to the present embodiment. Hereinafter, the electrostatic accelerator 100 of the present embodiment will be described.

  The electrostatic accelerator 100 capable of accelerating a high-current beam according to the present embodiment includes a high-voltage high-frequency transformer 1 for generating a high voltage by forming a Schenkel circuit for accelerating the beam, and a low-voltage side RF electrode 2. And a high-voltage side RF electrode 3. In the Schenkel circuit, the stray capacitance between the low voltage side RF electrode 2 and the high voltage side RF electrode 3 serves as a capacitor, and the rectifier 4 boosts the high voltage side RF electrode 3 step by step. By boosting, the potential rises from the high energy side (low potential ground side) that emits the beam from the accelerator toward the low energy side (high voltage side) where the ion source is located, and the low energy side has an extremely high voltage. It becomes a high voltage part. The first ion beam is generated by the permanent magnet microwave ion source 5 installed at the beam low energy (high voltage side) end of the acceleration tube 13. In order to extract a high-current beam from the ion source 5, a microwave power of several kW or more is required. High-power microwave power needs to be transmitted from the microwave oscillator 8 to the ion source 5 through the microwave waveguide 7, but the low-energy side where the ion source is provided has an extremely high voltage. A structure in which a plurality of insulating choke flanges 6 are provided in the tube 7 and the oscillator 8 and the like are insulated from a high voltage is adopted. In this embodiment, the microwave waveguide 7 provided with a plurality of insulating choke flanges 6 is arranged in parallel inside the RF electrode so as to be aligned with the accelerator tube 13. By arranging in this way, the accelerator tube 13 has a high voltage side (low energy side) and a low voltage ground side (high energy side) in the longitudinal direction, and the microwave waveguide 7 also goes to the ground side. The voltage is low, and the distance for insulation can be taken.

  The microwave power supplied to the microwave ion source 5 through the microwave waveguide 7 is oscillated by a microwave oscillator 8 which is a device for generating a microwave, and the power is supplied by a microwave power source 9. When traced back, it is supplied from the building power supply or the distribution board 10 of the building. Moreover, the small electric power required for the gas supply control system of the microwave ion source 5 is supplied from the storage battery 11 installed in the high voltage part.

  The hydrogen gas supply to the microwave ion source 5 is supplied from the hydrogen gas cylinder 12 through a gas pipe. Further, in charging the battery 11 that supplies a small amount of power for controlling the gas supply amount and beam optics, the DC high voltage of the electrostatic accelerator 100 uses the fact that the potential increases at each stage of the Schenkel circuit. Thus, the charging power is supplied by the DC potential difference between the uppermost stage and the next lower stage.

  In the electrostatic accelerator 100 of the present embodiment, the high-power microwave power necessary for extracting high-current ions is supplied from the ground side by the microwave waveguide provided with the insulating choke flange 6. As in 2, it is not necessary to attach a rotary motor or a heavy rotating generator to the high potential portion, and the high voltage portion can be reduced in weight.

  Further, as shown in FIG. 3, a large insulating transformer for insulating a high voltage of several MV and supplying power is not required, and the installation area can be reduced.

  According to the present embodiment, the microwave waveguide provided with the insulating choke flange 6 for supplying the microwave power to the high voltage portion is an accelerating tube in order to feed power from the ground side while avoiding a region of a high electric field that is easily discharged. Adjacent to 13 and installed in parallel.

  According to the present embodiment, since the plasma of the microwave ion source 5 can be generated by the electrostatic accelerator 100 with a high-power microwave, a high-current beam can be extracted. In addition, a rotary generator is not required for the high-voltage part as in the past, so the weight can be reduced or a large insulation transformer is not required, so that the grounding area can be reduced, the current of the accelerator system is increased, and the performance is improved. Space saving can be expected.

  According to the present embodiment, since the microwave power for generating plasma of the ion source can be increased and transmitted, the plasma can be sufficiently ionized, and the ratio of ions can be increased compared to the neutralized gas. Therefore, a large current ion beam can be extracted. Thereby, the electrostatic accelerator which can draw out a large current beam can be provided.

  It is considered that a higher current can be realized by increasing the microwave power for igniting the plasma of the ion source. According to the present embodiment, the plasma of the ion source can be generated by the electrostatic accelerator with a high-power microwave, so that a high-current beam can be extracted and a rotary generator is not required in the high-voltage part, so that the weight can be reduced. In addition, since a large-sized insulating transformer is not required, the grounding area can be reduced, and the accelerator system can be expected to increase current, improve performance, and save space.

  In an electrostatic accelerator that electrostatically accelerates charged particles, it is necessary to supply a high-power microwave to the ion source in order to extract a high-current beam. In order to supply, it is necessary to equip the high-voltage side with a large rotary generator, but it is rigid to install heavy objects on high-voltage parts that cannot be supported by an insulating material to prevent creeping discharge. Problems arise. Alternatively, there is a method of transmitting power using a large insulating transformer, but there is a problem that the installation area becomes large. According to this embodiment, the electrostatic capacity that does not increase the weight of the high-voltage part, saves the installation area, supplies large power to the ion source of the high-voltage part, and can extract high-current ions. Accelerator can be provided.

  In the first embodiment, the charged particle beam is described. However, the electron beam, the positron, or the like may be any beam, and the high power microwave transmission method in the electrostatic accelerator of the present embodiment is naturally established.

DESCRIPTION OF SYMBOLS 1 High frequency transformer 2 Low voltage side RF electrode 3 High voltage side RF electrode 4 Rectifier 5 Permanent magnet microwave ion source 6 Insulation choke flange 7 Waveguide 8 Microwave transmitter 9 Microwave power supply 10 Distribution board (building power supply)
11 Battery (storage battery)
12 Hydrogen cylinder 13 Accelerating tube 14 Beam duct 15 Beam 16 Pressure vessel 17 Grounding 20 Rotating insulating rod 21 Motor 22 Rotating generator 23 Insulating transformer 24 Insulating bushing 100, 101, 102 Electrostatic accelerator

Claims (4)

An electrostatic accelerator that accelerates a charged particle beam in an electrostatic field,
An ion source provided on the high voltage side of the accelerator;
A waveguide for supplying microwaves to the ion source;
A microwave generator for supplying microwaves to the waveguide,
The waveguide is provided with an insulating choke flange,
The microwave generator is provided on a ground side of the accelerator, and is an electrostatic accelerator. The electrostatic accelerator according to claim 1,
An accelerator tube,
An electrostatic accelerator, wherein the waveguide is provided in parallel with an accelerator tube. The electrostatic accelerator according to claim 1,
An electrostatic accelerator comprising a battery for controlling gas supply to the ion source on a high voltage side of the accelerator. The electrostatic accelerator according to claim 3,
An electrostatic accelerator having a power source for forming a high voltage of the electrostatic accelerator and supplying electric power from the power source to the battery.

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