阅读说明：本技术 加速器和加速器系统 (Accelerator and accelerator system ) 是由 樱井博仪 奥野广树 森义治 藤田玲子 川岛正俊 于 2018-08-31 设计创作，主要内容包括：加速器(30、40、50)具备：具有一个或两个加速间隙的多个加速腔(31、41、51)；以及多个第一控制单元(33、43、53),相对于多个加速腔分别进行设置,且分别独立地产生振荡电场,控制对应的加速腔内的离子束的运动。此外,也可以具备：在N个加速腔后,产生磁场来控制离子束的运动的M个多极磁铁(32、42、52)。第一控制单元独立地控制加速电压和其相位,供给高频电功率。由此,特别是能够在加速前级中对来自离子发生源的直流射束进行绝热俘获。(The accelerator (30, 40, 50) is provided with: a plurality of acceleration chambers (31, 41, 51) having one or two acceleration gaps; and a plurality of first control units (33, 43, 53) which are respectively arranged corresponding to the plurality of acceleration chambers, respectively generate an oscillating electric field independently, and control the movement of the ion beam in the corresponding acceleration chamber. Further, the present invention may further include: m multipole magnets (32, 42, 52) that generate magnetic fields to control the motion of the ion beam after the N acceleration chambers. The first control unit independently controls the acceleration voltage and the phase thereof, supplying high-frequency electric power. This enables adiabatic trapping of a direct current beam from the ion generation source, particularly in the acceleration preceding stage.)

1. An accelerator includes:

a plurality of acceleration chambers having one or two acceleration gaps; and

and the first control units are respectively arranged for the acceleration cavities and respectively and independently control the movement of the ion beams in the corresponding acceleration cavities.

2. The accelerator of claim 1,

the first control unit generates an oscillating electric field in the acceleration chamber.

3. The accelerator of claim 2,

the first control units supply high-frequency electric power into the acceleration chambers via RF couplers, respectively and independently.

4. The accelerator according to any one of claims 1 to 3, further comprising:

a second control unit generating a magnetic field to control movement of the ion beam.

5. The accelerator of claim 4,

the second control unit generates a direct current magnetic field.

6. The accelerator of claim 4 or 5,

the second control unit is a multi-pole magnet,

and repeating the structure that M multipole magnets are connected behind N accelerating cavities, wherein N is a natural number, and M is a natural number.

7. The accelerator of claim 6,

the accelerating cavities and the multipole magnets are alternately connected one by one.

8. The accelerator of claim 6 or 7,

the multi-pole magnet is a four-pole magnet,

the adjacent quadrupole magnets have different convergence directions.

9. The accelerator of any one of claims 1 to 8,

the aperture of the accelerating cavity is more than 2 cm.

10. An accelerator system to which a plurality of accelerators are connected, in which accelerator system,

the pre-stage accelerator according to any one of claims 1 to 9, which has at least a function of receiving an input of a direct current beam from a beam generating source and adiabatically trapping the beam.

11. The accelerator system of claim 10,

the plurality of accelerators are each an accelerator as claimed in any one of claims 1 to 9.

12. The accelerator system of claim 10 or 11,

an ion beam of at least 0.1A is accelerated into a continuous beam.

Technical Field

The invention relates to an accelerator and an accelerator system.

Background

A linear accelerator system is generally a multistage structure in which a plurality of accelerators are cascade-connected (cascade-connected), and sequentially accelerates an object beam to obtain a beam of target energy. Most of the basic characteristics of the resulting beam are determined by the backing accelerator, which is therefore particularly important. Since the advent of high-frequency quadrupole accelerators (hereinafter referred to as RFQ accelerators) in the 70's of the 20 th century, RFQ accelerators have been mostly used as the front stage accelerators.

The RFQ accelerator has four electrodes, and accelerates, condenses, and adiabatically traps a beam (forms a beam) at the same time by applying a high-frequency voltage so that the opposing electrodes have the same potential and the adjacent electrodes have opposite potentials. The adiabatic trapping is a bunching structure in which a direct current beam from an ion source (ion generation source) is allowed to accelerate at a high frequency.

One of the important research subjects of the accelerator is to increase the intensity (large current) of the beam. The beam intensity of currently operating accelerators is around 1MW (megawatt), and even in the case of accelerators in the planning phase, the maximum is around 10 MW. In order to establish a nuclear conversion method for high-level radioactive wastes, the present inventors have made an effort to develop an accelerator system capable of generating a beam intensity of over 100MW, which is one order of magnitude stronger than that of the conventional accelerator system.

Disclosure of Invention

Problems to be solved by the invention

The acceleration chamber of the accelerator has a plurality of acceleration gaps in each of which the beam is accelerated by the supplied high-frequency electric power. The interval between the gaps needs to be determined according to the velocity of the beam so that the beam is accelerated in each acceleration gap. That is, as the beam becomes faster, the gap interval needs to be increased, which leads to an increase in size of the apparatus and an increase in cost.

In addition, when the high intensity of the beam is targeted, the RFQ accelerator cannot be used because the acceptance (aperture) cannot be sufficiently obtained with respect to the beam diameter.

Although the RFQ accelerator can perform acceleration and convergence of a beam at the same time, the upper limit of the diameter of the beam that can pass through is about 1 cm. This is because the discharge limit is reached when the aperture of the RFQ accelerator is widened.

In contrast, when the beam intensity is increased, the diameter of the beam supplied from the ion source (hereinafter referred to as the beam diameter) is increased. For example, when obtaining a deuterium nuclear beam of 1A from an ion source, the beam diameter is, for example, about 10cm or more. The maximum current of a quality ion beam that can be extracted from a single aperture depends only on the extraction voltage, for example about 100mA in the case of extracting a 30kV deuterium nuclear beam. Therefore, in order to obtain a beam of 1A, it is necessary to extract beams from at least 10 aperture electrodes, and when the plasma characteristics, the likelihood of the doherty, and the like are taken into consideration, it is necessary to extract beams from about 30 aperture electrodes. When the high-intensity beam is excessively condensed, the space charge force becomes excessively large, and therefore, it is necessary to set a single aperture to about 1cm, and thus the entire beam diameter becomes, for example, about 10cm or more.

In this way, in order to increase the beam intensity, it is necessary to use an accelerator capable of receiving a large beam diameter, and a conventional RFQ accelerator cannot be used.

In view of the above-described problems of the prior art, it is an object of the present invention to provide a low-cost accelerator capable of generating a high-intensity beam that is adiabatically trapped, accelerated, and converged.

Means for solving the problems

In order to solve the above problem, an accelerator according to the present invention includes: a plurality of acceleration chambers having one or two acceleration gaps; and a plurality of first control units respectively provided for the plurality of acceleration chambers and respectively independently controlling the movement of the ion beam in the corresponding acceleration chamber.

In this aspect, the first control unit generates an oscillating electric field, for example, within the acceleration chamber, and can independently determine the amplitude and phase of the electric field. In this aspect, the first control units supply high-frequency electric power via RF (radio frequency) couplers, and the plurality of first control units may also supply high-frequency electric power individually. The movement of the traveling direction of the ion beam in the acceleration chamber, i.e., acceleration and adiabatic trapping, is controlled by the oscillating electric field supplied from the first control unit.

As such, by using acceleration chambers each having one or two acceleration gaps, the respective acceleration chambers can be controlled individually. The degree of freedom in designing the apparatus is greatly improved. In the RFQ accelerator, the distance between adjacent gaps needs to be set to β λ/2(β is the speed/light speed, λ is the wavelength of a high frequency, and β λ is the distance over which particles move within 1 cycle). In the accelerator of the present invention, since the oscillating electric field can be controlled independently, the interval of the acceleration chambers can be designed freely. The interval between the gaps can be shortened, the total length of the accelerator can be shortened, and the manufacturing cost can be further reduced. The front stage of the accelerator may have the same function of adiabatic trapping as RFQ.

The accelerator according to this aspect may further include: a second control unit generating a magnetic field to control movement of the ion beam. The second control unit generates a direct current magnetic field. In this embodiment, the second control unit may be a multi-pole magnet, and a configuration in which M (M is a natural number) multi-pole magnets are connected to N (N is a natural number) acceleration chambers may be repeated. The lateral movement of the ion beam, i.e., the convergence of the ion beam, is controlled by the direct current magnetic field generated by the second control unit.

In one embodiment, the accelerating cavities and the multipole magnets may be connected one by one alternately (N-M-1). In another embodiment, a plurality of multipole magnets (N ═ 1, M > 1) may be connected after one acceleration chamber. In another embodiment, one multipole magnet (N > 1, M ═ 1) may be connected after connecting a plurality of acceleration chambers, or a plurality of multipole magnets (N > 1, M > 1) may be connected after connecting a plurality of acceleration chambers. The embodiment in which a plurality of acceleration chambers are connected (N > 1) can be suitably used particularly when the energy of the beam is high and the influence of the beam broadening is relatively small. The upper limits of N and M can be set as appropriate within the range in which the effects of the present invention are obtained. For example, N is preferably 4 or less, and more preferably 2 or less. M is also preferably 4 or less, more preferably 2 or less.

In the present invention, the multipole magnet is typically a four-pole magnet, but a six-pole magnet, an eight-pole magnet, a ten-pole magnet, a solenoid magnet, or the like may be used. In addition, adjacent multipole magnets (which may also include accelerating cavities therebetween) are preferably arranged to converge in different directions. The magnet may be a permanent magnet or an electromagnet, but energy saving can be achieved by using a permanent magnet.

Preferably, the plurality of acceleration chambers in the present invention each include an electric power supply unit for independently supplying high-frequency electric power.

In this way, in the accelerator according to the present invention, since the beam is converged by the magnetic field, even if the inner diameter (hereinafter referred to as an aperture) of a cylinder or the like through which the beam passes is increased, the voltage required in the acceleration chamber does not change and does not exceed the discharge limit. That is, the accelerator according to the present invention can increase the aperture, and thus can receive a high-intensity beam. For example, the accelerator of the present invention can have an aperture of 2cm or more.

In addition, there are one or two accelerating gaps in the accelerating cavity in the present invention, so that the high-frequency coupling system (RF coupler) per accelerating cavity can be reduced, and one or several (e.g., two or four) high-frequency coupling systems can be employed. It is difficult to arrange a large number of RF couplers in one acceleration chamber, but it can be easily implemented if there are one or several, and the input of each RF coupler can be controlled by digital circuits. Further, according to the present invention, since the acceleration gradient of the acceleration gap can be increased, the entire length of the accelerator can be shortened.

In addition, the high-frequency electric power can be independently supplied to the acceleration chamber, thereby greatly improving the degree of freedom in designing the apparatus. In the RFQ accelerator, the distance between adjacent gaps needs to be set to β λ/2(β is the speed/light speed, λ is the wavelength of a high frequency, and β λ is the distance over which particles move within 1 cycle). In the accelerator according to the present invention, since the phase of the high frequency can be independently controlled, the interval of the acceleration cavity can be freely designed. That is, the gap interval can be shortened, and the entire length of the accelerator can be shortened. The front stage of the accelerator may have the same function of adiabatic trapping as RFQ.

Another aspect of the present invention is an accelerator system in which a plurality of accelerators are connected, wherein a preceding accelerator (primary accelerator) is the accelerator, and the preceding accelerator has at least a function of receiving an input of a direct current beam from a beam generation source and adiabatically trapping the beam. All the accelerators of the accelerator system in the present scheme may be the accelerators.

The accelerator or accelerator system of the present embodiment can accelerate a high current ion beam of at least 0.1A, more preferably at least 1A, into a Continuous (CW) beam. Note that, in the present disclosure, a continuous beam refers to a beam in which ions are bunched if observed microscopically and ions are continuous if observed macroscopically. A continuous beam of, for example, 1A is a beam with an average current of 1A. On the other hand, a beam in which microscopic observation is also continuous is referred to as a direct current beam, and a beam in which macroscopic observation is intermittent is referred to as a pulse beam.

Effects of the invention

According to the present invention, a low-cost accelerator capable of generating a high-intensity beam can be realized.

Drawings

Fig. 1 is a diagram showing a schematic configuration of a linear accelerator system 100 according to the present embodiment.

Fig. 2 is a diagram showing a schematic configuration of a low β stage (section) accelerator 30 according to the present embodiment.

Fig. 3 is a diagram illustrating a quadrupole magnet according to the present embodiment.

Fig. 4 is a diagram showing a schematic configuration of the intermediate stage accelerator 40 according to the present embodiment.

Fig. 5 is a diagram showing a schematic configuration of the high-speed accelerator 5 according to the present embodiment.

Fig. 6 is a flowchart of the acceleration condition determination processing in the present embodiment.

Fig. 7 is a diagram illustrating the phase stability of the beam.

Fig. 8 is a diagram illustrating advantageous effects of the linear accelerator system 100 according to the present embodiment.

Detailed Description

Embodiments for carrying out the present invention will be described below with reference to the accompanying drawings.

< composition >

This embodiment is a linear accelerator system 100 of 100MW class that accelerates a Continuous (CW) ion beam of approximately 1A Deuteron or proton (proton) to 100MeV per nucleus (hereinafter referred to as 100MeV/u, the same in the same description). Fig. 1 is a diagram showing a schematic configuration example of a linear accelerator system 100 according to the present embodiment. In this specification, the linear accelerator system is a term that refers to a plurality of accelerators collectively called a cascade connection.

The linear accelerator system 100 generally includes: an ion source 10, a buncher 20, a low beta (low speed) stage accelerator 30, a medium beta (medium speed) stage accelerator 40 and a high beta (high speed) stage accelerator 50.

The ion source (beam generation source) 10 is a cusped (cut) ion source (also referred to as an electron impact ion source) in which a cusped magnetic field is formed in a plasma generation container. The ion source 10 ionizes the gas to generate plasma, and extracts ions by an electric field of 30 kV. The ion source 10 extracts a beam from 30 porous electrodes to obtain an ion beam of 1A. When the beam is excessively condensed, the space charge force becomes excessively large, and therefore the single aperture is about 1cm, and the diameter of the entire beam extracted from the ion source 10 is about 10cm or more.

The buncher 20 bunches the ion beam extracted from the ion source 10, but does not accelerate the ion beam. The low β -stage accelerator 30 also has a beam focusing function, and thus the beam focusing device 20 may be omitted. The energy of the ion beam extracted from the ion source 10 is 50 to 300 keV/u. In the embodiment shown in FIG. 1, 100keV/u is set.

The low β -stage accelerator 30 is a pre-stage accelerator (primary accelerator) that initially accelerates the ion beam that occurs in the ion source 10. Hereinafter, the low β stage accelerator 30 is also simply referred to as the accelerator 30. The accelerator 30 accelerates the ions to 2-7 MeV/u. An example of accelerating ions to 5MeV/u is shown in the embodiment of fig. 1. The accelerator 30 has an aperture of 10cm or more to enable acceptance of the beam generated in the ion source 10.

A more detailed configuration of the accelerator 30 will be described with reference to fig. 2. As shown in fig. 2, the accelerator 30 has a structure in which 20 left and right acceleration chambers 31_1, 31_2, … …, 31_20 and 20 left and right quadrupole magnets (Q magnets) 32_1, 32_2, … …, 32_20 are alternately connected. Since each acceleration chamber and the Q magnet have the same configuration, the trailing end of the acceleration chamber is omitted, and the acceleration chamber 31 and the Q magnet 32 are referred to as a generic term.

The acceleration chamber 31 is a single gap chamber (single gap cavity) having a single acceleration gap 35. In the acceleration chamber 31, high-frequency electric power (oscillating electric field) is supplied from a high-frequency electric power supply 33 via an RF coupler (high-frequency coupling system) 34. The high-frequency electric power supply 33 supplies high-frequency electric power in a phase in which ions are accelerated when passing through the acceleration gap 35. In the present embodiment example of fig. 1, the acceleration voltage is 300kV and the frequency is 25 MHz.

The high-frequency power supply unit 33 provided in each acceleration chamber 31 can independently control the phase of the high frequency. Therefore, since the ions can be accelerated by determining the respective phases based on the intervals between the adjacent acceleration chambers (intervals between the acceleration gaps), the intervals between the acceleration chambers can be freely set.

As described above, the movement and activity in the traveling direction of the ions, that is, acceleration and adiabatic trapping are controlled by the high-frequency electric power (oscillating electric field) supplied from the high-frequency electric power supply 33, and the high-frequency electric power supply 33 corresponds to the first control means in the present invention.

As shown in fig. 3 a and 3B, the quadrupole magnet 32 converges the beam by a direct-current magnetic field (static magnetic field). The directions of convergence of the adjacent quadrupole magnets 32 are different from each other. That is, an F quadrupole (fig. 3 (a)) that converges a beam in the horizontal direction and diverges it in the vertical direction, and a D quadrupole (fig. 3 (B)) that converges a beam in the vertical direction and diverges it in the horizontal direction are alternately arranged. The strength of the magnetic field from the quadrupole magnet 32 is preferably determined according to the energy of the ions, but is approximately several k (thousand) gauss or so. The quadrupole magnet 32 may be a permanent magnet or an electromagnet, but energy saving can be achieved by using a permanent magnet.

The transverse movement, or convergence of the ions is controlled by the dc magnetic field supplied from the quadrupole magnet 32. The quadrupole magnet 32 corresponds to the second control unit in the present invention.

The intermediate β -stage accelerator 40 is an accelerator that further accelerates the ion beam accelerated by the low β -stage accelerator 30. Hereinafter, the intermediate β -stage accelerator 40 is also simply referred to as the accelerator 40. The accelerator 40 accelerates the ions to 10-50 MeV/u. An example of accelerating ions to 40MeV/u is shown in the embodiment of fig. 1.

Referring to fig. 4 (a), a more detailed configuration of the accelerator 40 will be described. The accelerator 40 is basically the same as the accelerator 30, and is configured by alternately connecting 10 accelerating cavities 41 and Q magnets 42 one by one.

The acceleration chamber 41 is a double gap chamber (double gap cavity) having acceleration gaps 46, 47. In the acceleration chamber 41, high-frequency electric power is supplied from a high-frequency electric power supply 43 via an RF coupler (high-frequency coupling system) 44. The RF coupler 44 may be one or more. Further, the RF coupler 44 controls the phase of the high-frequency electric power by a digital circuit. The high-frequency electric power supply portion 43 supplies high-frequency electric power in a phase in which ions are accelerated when passing through the acceleration gaps 46, 47. In the present embodiment of fig. 1, the acceleration condition is determined to be an acceleration voltage of 2.5MV and a frequency of 50 MHz.

As shown in fig. 4 (B) and 4 (C), since the phases of the high frequencies need to be reversed when the ions pass through the acceleration gap 46 and when the ions pass through the acceleration gap 47, the distance between the acceleration gap 46 and the acceleration gap 47 needs to be made equal to the distance (β λ/2) that advances between 1/2 cycles of the high frequencies. On the other hand, the interval of the acceleration chambers 41 can be freely set.

The Q magnet 42 has F quadrupoles and D quadrupoles alternately arranged.

The high β -stage accelerator 50 is an accelerator for further accelerating the ion beam accelerated by the medium β -stage accelerator 40. Hereinafter, the high β stage accelerator 50 is also simply referred to as the accelerator 50. The accelerator 50 accelerates the ions to 75-1000 MeV/u. An example of accelerating ions to 200MeV/u is shown in the embodiment of fig. 1.

A more detailed configuration of the accelerator 50 will be described with reference to fig. 5. The accelerator 40 is basically the same as the accelerators 30 and 40, but a configuration in which one Q magnet 52 is connected after two acceleration chambers 51 are connected is repeated. As a result of the determined acceleration conditions, a total of 80 acceleration chambers 51 and a total of 40Q magnets 52 are taken as an example.

The acceleration chamber 51 is a single gap chamber with a single acceleration gap 55. In the acceleration chamber 51, high-frequency electric power is supplied from a high-frequency electric power supply portion 53 via an RF coupler (high-frequency coupling system) 54. The high-frequency electric power supply portion 53 supplies high-frequency electric power at a phase at which ions are accelerated when passing through the acceleration gap 55. In the present embodiment, an example is given in which acceleration conditions such as an acceleration voltage of 2.5MV and a frequency of 100MHz are determined.

The Q magnet 52 has F quadrupoles and D quadrupoles alternately arranged. In the accelerator 50, one Q magnet 52 is disposed for every two acceleration chambers 51, because the beam energy is high, and the influence of beam broadening is relatively small.

The beam accelerated by accelerator 50 is directed to a target area via a high energy beam delivery system.

< determination processing of acceleration condition >

A method for determining the voltage and phase of the radio-frequency magnetic field in each acceleration gap and the magnetic field gradient of the Q magnet will be described. The acceleration condition can be determined by performing the same processing for all segments. Therefore, the following description will be mainly given by taking the low β -stage accelerator 30 as an example.

The device configuration (shape, size) of the accelerator is given as a premise. Further, the degree to which the ions are accelerated in each accelerator is also given as a condition.

Referring to fig. 6, the determination process of the acceleration condition of the accelerator 30 at the low β stage is explained, in the upper part of fig. 6, the acceleration gap g and the quadrupole magnet Q of the accelerator 30 are schematically shown, and the speed v of the beam bunching is shown by a black dot_iThe i-th magnet is denoted as Q_iWill pass through the acceleration gap g_iVelocity of the rear bunching is marked v_i。

Fig. 6 is a flowchart showing a process of determining the high-frequency magnetic field and the convergence magnetic field of level 1. The processing is realized by executing a program by a computer.

Steps S11 to S13 are to determine V_iAndstep S21-S23 is to determine FG_iAnd (4) processing. V_iFor the acceleration gap g_iThe amplitude of the applied high-frequency electric field,passing through an acceleration gap g in the center of the beam_iThe phase of the oscillating electric field. Q_iIs a Q magnet Q_iThe magnetic field gradient of (2) is positive in the horizontal direction convergence and vertical direction divergence, and negative in the vertical direction convergence and horizontal direction divergence.

First, the acceleration gap g is determined_iThe treatment of the high-frequency electric field of (2) will be described. In step S11, V is selected_iAnd

then, in step S12, it is determined whether or not the phase stability and the adiabatic property of the beam are satisfied.

Phase stability can be determined by whether the beam is within a stable region within a phase space defined by the phase difference with the synchronizing particle and the energy difference with the synchronizing particle. In FIG. 7 is shown Andthe stable region of (a). The thick line S is a boundary (stability limit) inside which a stable region is present. I.e. stable if the beam is within the above-mentioned stable region in phase space.

The adiabatic condition is a condition in which the change in the stable region is sufficiently slow compared to the synchrotron vibration of the beam. Specifically, the number of synchrotron vibrations is set to Ω_s，(1/Ωs)×dΩ_s/dt＜＜Ω_sSuch conditions are described.

If the phase stability and the thermal insulation are not satisfied in step S12, the process returns to step S11 to reselect V_iAndif the condition of step S12 is satisfied, gap g will be accelerated_iV of_iAndis determined as the value selected in step S11. It is desirable to determine V so as to maximize the acceleration efficiency within a range satisfying the condition of step S12_iAnd

in step S13, the crossing acceleration gap is calculatedg_iNon-relativistic energy E of the rear beam_i+1And velocity v_i+1. In the acceleration gap g_iIn, the energy is only increased

Thus, it is possible to provide

M is the mass of the ion, and q is the charge amount of the ion.

Then, for the Q magnet Q_iMagnetic field gradient FG_iThe process of (2) will be explained. In step S21, FG is selected_i. Then, in step S22, it is determined whether a condition that the convergence force generated by the Q magnet is large compared to the repulsion force due to the space charge force, that is, a condition that it is stable in the lateral direction, is satisfied. If the condition of step S22 is not satisfied, the process returns to step S21 to reselect the FG_i. If the condition of step S22 is satisfied, the process proceeds to step S23 and the orientation of the magnetic field gradient is determined. For example, the magnetic field gradient is set to a positive direction in the odd-numbered Q magnets, and the magnetic field gradient is set to a negative direction in the even-numbered Q magnets. Of course, the polarities may be reversed.

Through the above processing, the i-th acceleration gap g is determined_iAnd Q magnet Q_iThe acceleration condition of (1). The above processing is performed for all the acceleration gaps and Q magnets in sequence from i to 1. From this, all g's in the accelerator 30 are determined_i、

FG_iNote that, although the low β stage accelerator 30 is described as an example, the acceleration condition is similarly determined for acceleration in other stages.

Vi and

the determination method of (2) is as follows.

From FIG. 7, it can be seen thatThe smaller, the larger the stability region, in

In the case of (3), even if the beam is a direct current beam, almost all the beam can be taken into the stable region. Thereafter, it is appropriately setAnd Vi, adiabatic trapping with respect to the direction of travel. The Vi may be arbitrarily determined as long as it satisfies the adiabatic condition. As can be seen from the figure 6 of the drawings,small means small acceleration voltage, so it is preferable in improving acceleration efficiency to make acceleration as fast as possibleTo a value at which a normal acceleration is performed (

For example 60 deg.) but for ensuring the aforementioned adiabatic conditionsIt is important to change slowly so that the beam does not spill out of the stable region.

The frequency of the high-frequency electric field is increased so that the frequency of the middle β band is K times that of the low β band and the frequency of the high β band is L times that of the low β band, for example, so that the entire accelerator system is made compact, and in this case, it is noted that the phase direction of the beam in fig. 7 is widened by K (L) times as the frequency changes, and therefore, in the first stage of the middle β and high β, the frequency is increased by K (L) times

Ratio of

Slightly smaller, enlarged stability zoneA field in which the beam is captured in a stable region without omission and then slowly (adiabatically) focusedApproach to

Since the accelerator according to the present embodiment has a plurality of single-gap or double-gap acceleration chambers arranged therein, the voltage and phase of the high-frequency electric field can be determined for each acceleration chamber as described above.

< advantageous effects >

Hereinafter, the advantages of the linear accelerator system 100 according to the present embodiment will be described in comparison with the International nuclear Fusion Material Irradiation Facility (IFMIF). IFMIF is a 10MW accelerator that irradiates two deuterium nuclear beams (40MeV, 125mA × 2).

Fig. 9 is a table comparing the characteristics of the IFMIF RFQ accelerator as the primary accelerator (column 601), the characteristics of the IFMIF RFQ accelerator simply having the aperture 10 times (column 602), and the characteristics of the primary accelerator 30 according to the present embodiment (column 603).

Since the RFQ accelerator performs the horizontal beam convergence by an electric field method, the required voltage is 10 times (80kV → 800kV) when the aperture is 10 times. And thus may exceed the discharge limit. In contrast, since the accelerator according to the present embodiment focuses the beam in the horizontal direction by the magnetic field system of the Q magnet, it is not necessary to apply a high voltage for focusing the beam even if the aperture is increased, and the beam can be within the discharge limit.

Further, the high frequency loss is proportional to the square of the voltage, and therefore when the aperture of the RFQ accelerator is set to 10 times, the high frequency loss expands to 100 times (1MW → 100 MW). In contrast, the high-frequency loss energy of the accelerator according to the present embodiment is suppressed to 10MW or less.

In addition, in the RFQ accelerator, the interval of the acceleration gap needs to be set to β λ/2. In contrast, in the accelerator according to the present embodiment, since the phase of the high frequency can be independently controlled for each acceleration cavity, the interval between the acceleration cavities can be freely designed. In the case of an acceleration chamber with a single acceleration gap, this means that the spacing of all acceleration gaps can be freely designed. Therefore, the interval of the acceleration gap can be shortened, and the overall length of the acceleration device can be shortened. In the case where one acceleration chamber has a plurality of acceleration gaps, the above-described restriction is imposed on the interval of the acceleration gaps in the acceleration chamber, but the interval between the acceleration chambers can be shortened, so that the overall length can be shortened as compared with the conventional case. Further, the overall length of the accelerator can be shortened, thereby reducing the manufacturing cost.

The RFQ accelerator has a function of acceleration and horizontal convergence of a beam, and also has a function of adiabatically trapping the beam in a traveling direction. The accelerator according to the present embodiment can also perform adiabatic trapping with respect to the traveling direction of the dc beam.

Further, although not shown in the table of fig. 9, it is also possible to cite as an advantage that the number of RF couplers per accelerating cavity can be reduced. The electric power that can be supplied by one RF coupler is limited, and therefore high-frequency electric power needs to be supplied from a plurality of RF couplers. For example, in order to input 500kW of electric power, at least 8-9 RF couplers are required. It is not easy to connect such multiple RF couplers in one acceleration cavity, and it is almost impossible to further expand and enhance the acceleration gradient. In contrast, in the accelerator according to the present embodiment, since there is only one RF coupler for each acceleration chamber, it is easy to realize the accelerator, and the number of RF couplers can be further increased to increase the acceleration gradient.

In the present embodiment, the degree of freedom of control is increased by controlling the acceleration chamber alone, and thus the RFQ accelerator is not required, and thus a large current of the beam can be realized. Further, by appropriately selecting the number of stages of the acceleration chambers (orifices) in accordance with the overall capacity and specification of the accelerator system, for example, an accelerator subsystem in a low speed region can be configured, and appropriate control can be achieved in accordance with the speed region. In addition, the present invention may be a manufacturing method in which a plurality of accelerators corresponding to each speed range are manufactured at different places, the accelerators are individually transported to an installation place of an accelerator system, and subsystems of each speed range are assembled to construct an entire system, and various adjustments can be flexibly made at a competitive level on the site after assembly.

As is known from the above, in the RFQ accelerator, both acceleration and convergence of the beam are performed based on the control of the oscillating electric field, and in another embodiment, acceleration of the beam is performed based on the control of the oscillating electric field, and convergence of the beam is used differently based on the control of the static magnetic field, for example, in the process shown in fig. 6. In particular, the movement of the beam in the chamber closest to the ion generating source has little influence on the movement of the beam in the secondary side chamber, and also affects the difficulty of controlling the beam on the corresponding secondary side. Such beam activity in the cavity of a particular stage has a recursive effect on beam activity in the cavity below the next stage side, its control, etc. Therefore, when considering the influence on the secondary side and further the influence on the entire system, it is significant to perform the above-described control of the electric field and the magnetic field separately for the chamber closest to the ion generation source.

< modification example >

The configuration of the above-described embodiment may be appropriately modified within a range not departing from the technical spirit of the present invention. The specific parameters in the above-described embodiments are merely examples, and may be appropriately changed as needed.

In the above-described embodiment, the aperture (inner diameter) of the accelerator is set to 10cm, but the aperture may be smaller or larger. When considering that the aperture that can be realized in the conventional RFQ accelerator is about 1cm, the accelerator according to the present embodiment can realize acceleration of a large-diameter beam that has not been possible in the past by setting the aperture to 2cm or more. The aperture of the accelerator may be 5cm or more, may be 10cm or more, may be 20cm or more, or may be 50cm or more.

In the above-described embodiment, one Q magnet is connected to one or two acceleration chambers, but other configurations are possible. For example, a plurality of Q magnets may be arranged in series. In general, a configuration may be adopted in which M (M is a natural number) multipole magnets are connected to N (N is a natural number) acceleration chambers.

The linear accelerator system according to the above embodiment is configured by three accelerators of a low β stage, a middle β stage, and a high β stage, but may be configured by two or more accelerators. Furthermore, it is not necessary for all accelerators to be accelerators that include an acceleration chamber with one or two acceleration gaps. The primary accelerator preferably has such a configuration, but conventional accelerators may be used for the 2 nd and subsequent accelerators.

The accelerated particles use protons or deuterons, but tritium nuclei (super heavy hydrogen) or elements heavier than hydrogen can also be accelerated.

Although the significant effect of the present invention can be expected when the beam current is about 1A, the corresponding effect can be obtained when the beam current is at least about 0.1A.

Description of reference numerals:

10: ion source, 20: buncher, 30: the accelerator with a low beta section is provided with a low beta section,

40: middle beta section accelerator, 50: the high-beta section accelerator is used for accelerating the high-beta section,

31. 41, 51: the speed-up cavity is arranged on the base,

32. 42, 52: a four-pole magnet (Q magnet),

33. 43, 53: a high-frequency electric power supply unit for supplying high-frequency electric power,

34. 44, 54: in the high-frequency coupling system,

35. 45, 46, 55: the gap is accelerated.

The claims (modification according to treaty clause 19)

1. An accelerator includes:

a plurality of acceleration chambers having one or two acceleration gaps; and

a plurality of multi-pole magnets, each having a plurality of poles,

one or more multipole magnets are connected behind one acceleration chamber of the accelerator.

2. The accelerator according to claim 1, further comprising:

and a plurality of control units which are respectively arranged for the plurality of acceleration chambers and respectively and independently control the movement of the ion beam in the corresponding acceleration chamber.

3. The accelerator of claim 2,

the control unit generates an oscillating electric field in the acceleration chamber.

4. An accelerator according to claim 3,

the control units supply high-frequency electric power into the acceleration chambers via RF couplers, respectively and independently.

5. The accelerator of any one of claims 1 to 4,

the accelerating cavities and the multipole magnets are alternately connected one by one.

6. The accelerator of any one of claims 1 to 5,

the multi-pole magnet is a four-pole magnet,

the adjacent quadrupole magnets have different convergence directions.

7. The accelerator of any of claims 1 to 6,

the aperture of the accelerating cavity is more than 2 cm.

8. An accelerator system to which a plurality of accelerators are connected, in which accelerator system,

the pre-stage accelerator according to any one of claims 1 to 7, which has at least a function of receiving an input of a direct current beam from a beam generating source and adiabatically trapping the beam.

9. The accelerator system of claim 8,

the plurality of accelerators are each the accelerator of any one of claims 1 to 7.

10. The accelerator system of claim 9 or 10,

an ion beam of at least 0.1A is accelerated into a continuous beam.