JP2004247109A - Betatron accelerator and acceleration core device for betatron - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To economically improve incidence efficiency and irradiation efficiency of a betatron accelerator. <P>SOLUTION: Of the betatron accelerator provided with a hollow conductor of a ring shape forming a channel for charged particle beams inside and having an accelerating gap inducing an accelerating field of the charged particle beams, an accelerating core fitted so as to surround the hollow conductor, and an exciting coil wound around the accelerating core and completing the incidence and the irradiation within a period of an operation frequency of the accelerating core, an accelerating voltage by the exciting coil is set high at the incidence of the charged particle beams and low at the acceleration as well as the irradiation. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a betatron accelerator and a betatron accelerator used in the research, medical, and industrial fields.
[0002]
[Prior art]
A power supply for driving an acceleration core of a conventional betatron accelerator is disclosed in Patent Document 1, for example. Since the driving power supply switches a high-voltage DC power supply, the waveform of the generated acceleration voltage has a simple rectangular waveform. Another driving power supply disclosed in Patent Document 1 uses an inductive charging relationship between two capacitors via an acceleration core excitation winding, so that the current flowing through the acceleration core excitation winding is sinusoidal. Thus, the acceleration voltage excited thereby has a sinusoidal shape.
[0003]
[Patent Document 1]
JP-A-5-343199 (FIGS. 1, 2 and 3)
[0004]
[Problems to be solved by the invention]
One of the important indices of the betatron accelerator performance is beam extraction efficiency η = (output beam current Iout) / (incident beam current Iin), and usually high output efficiency is required. In the betatron accelerator having the above configuration, when η is maximized, first, the beam incidence efficiency becomes a problem. Although the beam incidence efficiency is improved as the beam spread at the time of incidence is smaller, the beam spread at the time of incidence is due to the space charge effect of charged particles, and the only way to reduce this is to increase the acceleration voltage Vac. Absent. However, in this case, the iron loss of the core increases. To cope with this, if a low-loss material is used, the material cost increases, and if the cooling device is reinforced, the device cost increases. There was a problem. With the conventional power supply for the betatron accelerator described in the above prior art, the acceleration voltage waveform could only be realized in a simple rectangular shape or a sine wave shape, so that the above problem could not be avoided.
[0005]
An object of the present invention is to provide a power source that can supply a large current with a small load on a supply side as a power source for driving an acceleration core of a betatron accelerator.
Another object of the present invention is to solve the above-mentioned conventional problems, and to economically increase the incidence efficiency and emission efficiency of the betatron accelerator.
It is still another object of the present invention to provide a betatron accelerator core device capable of economically supplying a variable voltage to the accelerator core.
[0006]
[Means for Solving the Problems]
A betatron accelerator according to the present invention includes a ring-shaped hollow conductor having a passage for a charged particle beam formed therein and having an acceleration gap for inducing an acceleration electric field of the charged particle beam, and an acceleration core provided to surround the hollow conductor. And an excitation coil wound around the acceleration core, and a power supply for applying a voltage to the excitation coil, wherein the betatron accelerator completes the period from the incidence to the emission of particles within one cycle of the operating frequency of the acceleration core. The power supply comprises an inverter power supply that forms AC power into a rectified voltage by a rectifying / smoothing circuit, and outputs a rectangular wave voltage in both polarities by a switch element configured in a bridge circuit. An acceleration voltage is applied.
[0007]
In addition, an annular hollow conductor having an acceleration gap for inducing an accelerated electric field of the charged particle beam in which a passage of the charged particle beam is formed, an acceleration core provided to surround the hollow conductor, and a coil wound around the acceleration core A betatron accelerator, comprising: an excitation coil attached thereto; and a power supply for applying a voltage to the excitation coil. The betatron accelerator completes the process from the incidence to the emission of particles within one cycle of the operating frequency of the acceleration core. Is to set the charged particle beam high at the time of incidence and low at the time of acceleration and emission of the charged particle beam.
[0008]
In the betatron accelerator, the acceleration voltage by the excitation coil is set to be high when the charged particle beam is incident, low when the charged particle beam is accelerated, and high when the charged particle beam is emitted.
[0009]
Further, in the betatron accelerator, the acceleration voltage by the excitation coil is set low when the charged particle beam is incident and accelerated, and is set high when the charged particle beam is emitted.
[0010]
Further, the acceleration core device for betatron of the present invention includes a first acceleration core, a second acceleration core for superimposition, a first excitation coil for exciting the first acceleration core, and A second excitation coil for exciting the second acceleration core and a common power supply are provided for these excitation coils, and these excitation coils can be switched between parallel connection and series connection by a switching element.
[0011]
Furthermore, a first acceleration core, a second acceleration core for superimposition, a first excitation power supply circuit having a first excitation coil for exciting the first acceleration core, and a second excitation power supply circuit for superimposition. A second excitation power supply circuit having a second excitation coil for exciting the acceleration core.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing a betatron accelerator according to Embodiment 1 of the present invention, excluding an excitation power supply circuit. The betatron accelerator has an annular vacuum duct (a hollow conductor made of copper or stainless steel) having an acceleration gap for forming a passage for circulating the charged particle beam while maintaining a vacuum inside, and having an acceleration gap for inducing an accelerating electric field of the charged particle beam. In order to maintain the trajectory of the charged particle beam in the vacuum duct 4, a plurality of electromagnets 3 are provided so as to sandwich the vacuum duct 4, and a plurality of electromagnets 3 are provided so as to surround the trajectory of the charged particle beam. An acceleration core 2 for accelerating the charged particle beam by an electromotive force due to a time change of magnetic flux, an excitation power supply (not shown) for applying a voltage to an excitation coil of the acceleration core 2 wound around the acceleration core 2, and a vacuum duct It is composed of an injector for injecting a charged particle beam and a beam extractor for extracting the charged particle beam.
[0013]
Next, the operation will be described. A charged particle beam is emitted from a beam injector (not shown), and introduction into a vacuum duct (annular hollow conductor) 4 is started. If the excitation power supply voltage of the excitation coil of the acceleration core 2 is set to a high voltage from this point, an induction electric field equal to the excitation voltage is generated on the beam orbit surrounding the cross section of the acceleration core 2, and the charged particle beam starts to accelerate. The path of the accelerated charged particle beam is bent by the electromagnet 3, moves substantially circularly in the annular vacuum duct, and is continuously accelerated while the excitation power supply voltage is applied. Extraction is performed by a beam emitter (not shown) while acceleration is continued.
[0014]
In the electromagnet 3 of a normal betatron accelerator, the magnetic field is changed with time so that the charged particle beam during acceleration is maintained in a predetermined orbit under a phase condition in which the magnetic field increases, so that the maximum repetition frequency is The limit is 10 to 100 Hz, and the beam duty (time for emitting a beam per unit time) is limited to 1% or less. In the present embodiment, the magnetic field of the electromagnet 3 for defining the trajectory of the charged particle beam is limited. By changing the charged particle beam trajectory so as to increase or decrease monotonically in the radial direction of the trajectory of the charged particle beam and maintaining the charged particle beam in a predetermined trajectory at a constant time, the repetition frequency can be improved to about 10 kHz. , The beam duty can be improved to 10% or more. For example, a repetition frequency of 1 kHz and a beam time width of 100 μs (beam duty: 10%) are possible.
[0015]
FIG. 2 shows a voltage waveform of the excitation power supply in the excitation coil of the acceleration core according to the first embodiment. In the figure, the acceleration voltage when the charged particle beam is incident (incident period) is
(1 + α) Vo, and the acceleration voltage during the subsequent acceleration (acceleration period) and emission (emission period) is Vo. At time t = 0, the beam starts to enter the accelerator from the beam injector, and ends when τe = τb−τa. Here, τb is the accelerating time, τa is the time obtained by subtracting the incident period τe from τb, and is the time from the entrance to the exit of one particle. τs represents the time of one cycle of the excitation power supply frequency.
[0016]
The beam continues to be accelerated. At t = τb− (1 + α) (τb−τa), the first incident beam starts to be emitted, and at t = τb, all beams are emitted. In this embodiment, for example, if α = 1, the average acceleration voltage is 1 kV (from t1 to t3 in FIG. 11), the accelerating time τb is 500 μs, and the incident period (τb−τa) is 100 μs, The acceleration voltage becomes 2 kV.
[0017]
FIG. 3 shows a configuration of the first embodiment for realizing the voltage waveform of FIG. FIG. 4 shows a configuration for realizing a conventional voltage waveform by contrast. Conventionally, as shown in FIG. 4, only an acceleration voltage corresponding to the voltage Vo of the excitation power supply 1 can be generated. In this embodiment, as shown in FIG. 3, the acceleration core 2 is divided into a first acceleration core 21 and a second acceleration core 22, and corresponding first and second excitation coils 61 and 62 are provided. Are provided to switch the excitation coils 61 and 62 between parallel connection and series connection, and the excitation power supply 1 of the power supply voltage Vo is connected. Then, during a period in which a high acceleration voltage is required at the time of beam incidence, by connecting in parallel (upper stage) in FIG. 3, the acceleration voltage at the time of beam incidence is used even when a power source of the same voltage Vo as the conventional one is used. Vac = 2Vo is obtained. Therefore, it is possible to increase the acceleration voltage without using an expensive high-voltage power supply.
[0018]
Also, during a period in which the lower accelerating voltage is set during the beam acceleration and during the emission, the exciting coils 61 and 62 are connected in series (the number of turns is one turn) in the lower part of FIG. Sometimes an accelerating voltage Vac = Vo is obtained. As described above, even when the power supplies having the same voltage Vo are used, it is possible to obtain two setting acceleration voltages.
When the acceleration voltage is set to 2 Vo by an expensive high voltage power supply, the voltage waveform shown in FIG. 6 is obtained. In the figure, τb ′ is an acceleration possible period shorter than a half cycle. τa ′ is a time obtained by subtracting the incident period from τb ′.
[0019]
In the first embodiment, when the charged particle beam is incident, the second acceleration core 22 is excited in addition to the excitation of the first acceleration core 21 to double the applied voltage to the charged particle beam, and the charged particle beam is incident earlier. Since the energy of the emitted beam is accelerated in a short time to a level that is not affected by space charge, the incident efficiency can be improved.
[0020]
FIG. 5 shows a general example of a drive circuit (an inverter power supply circuit) for the excitation coil of the acceleration core. A rectifier / smoothing circuit 35 is formed by the bridge circuit 34 composed of a thyristor and the capacitors C1 and C2. A switching circuit 36 configured as a bridge circuit is formed by an IGBT (Insulated Gate Bipolar Transistor) and a capacitor. The capacitor in the switching circuit 36 is for stabilization. The turns ratio of the acceleration core excitation coil is shown as N: 1, but may be 1: 1. Io, I1, I2, and I3 represent current, and Vap and Vac represent voltage. A rectangular wave voltage is obtained as the Vap and Vac voltages.
The drive circuit for the exciting coil of the acceleration core can obtain a large current (for example, 1000 A) of a rectangular wave as an output, and the power supply side at that time needs only a small current (several tens of amps) as a load, and the AC power supply side It has little effect.
[0021]
In the first embodiment, as compared with the core cross-sectional area S0 when the high voltage is not applied at the time of incidence, the core cross-sectional area S1 has a loss corresponding to the high voltage at the time of beam incidence, so that S1 = ｛1 + αD / (fτb) ) It is necessary to enlarge as shown in｝ S0. In the case of the constant of the first embodiment, S1 = 1.2S0. Here, D is the beam duty, and f is the frequency of the drive power supply.
[0022]
The heat generation of the core when the conventional power supply is set to a high acceleration voltage and the heat generation of the first embodiment are compared. The main component of the heat generated by the core is the eddy current loss Weddy, which is proportional to the square of the voltage. Therefore, in the case of FIG. 6 in which the voltage is set to double, the current is 4 Weddy, but it is 2 Weddy in consideration of the fact that the ON time (τb ′) of the power supply is shorter and the core cross-sectional area is larger than the conventional case.
[0023]
On the other hand, in the case of the first embodiment, since the time of the doubled voltage with respect to the acceleration cycle is 200 μs / 1000 μs = 0.2, the eddy current loss is (4 × 0.2 + 1 × 0.8) Weddy = 1.6 Weddy, and the core is Taking into account the enlargement of the cross-sectional area, it is 1.33 Weddy, which has the effect of reducing heat generation due to eddy current loss by 35%.
[0024]
Note that, in the first embodiment, two switching switches are used in FIG. 3 for switching the excitation coil between parallel and series, but the purpose is to reduce the current load on the bidirectional switch as shown in FIG. Thus, three bidirectional switches 73, 74, 75 may be used. In the first embodiment, the acceleration voltage at the time of beam incidence is 2 Vo. However, when the acceleration voltage is 4 Vo, for example, as shown in FIG. 8, the cores are the first core 23, the second core 24, the third core 25, and the The four cores 26 may be divided into four parts, and the bidirectional switch elements 76 and 77 may switch between parallel and series. Also in this case, five bidirectional switches 78, 79, 80, 81, and 82 may be used as shown in FIG. 9 to reduce the current load on the switch element.
[0025]
Embodiment 2
FIG. 10 is a configuration diagram showing an excitation power supply circuit of an excitation coil according to Embodiment 2 of the present invention. The first excitation power supply 11 (voltage Vo) is a rectangular wave voltage output inverter power supply that excites the first acceleration core 27 with the first excitation coil 67. The configuration is such that a low voltage is generated over a period during which the charged particle beam can be accelerated. The second excitation power supply 12 (voltage V1) is a rectangular wave voltage output inverter power supply that excites the second acceleration core 28 by the second excitation coil 68. In the second embodiment, a voltage is generated in addition to the first excitation power supply 11 when a charged particle beam enters and exits.
[0026]
Next, the operation will be described. When the charged particle beam is incident, in addition to the excitation of the first acceleration core 27, the second excitation power supply 12 is applied to excite the second acceleration core 28, thereby doubling (or multiplying) the voltage applied to the charged particle beam. Then, the energy of the incident beam is accelerated in a short time to a level that is not affected by space charge (space charge) in a short time, thereby improving the incidence efficiency. However, as it is, as shown in the beam energy diagram shown in FIG. 11, the time width of the beam reaching the emission energy mainly by the first acceleration core 27 is widened. Therefore, when this betatron accelerator is used as an injector of another synchrotron accelerator, there is a problem that the efficiency of incidence to the next stage is reduced.
[0027]
Therefore, as shown in FIGS. 12 and 13, the second excitation power supply 12 is applied again at time t2 when the first incident beam reaches the emission energy, and the acceleration voltage of the lately incident beam is increased. As a result, the output beam width is restored and corrected to the same value as at the time of incidence. Thus, even when this betatron accelerator is used as an injector, the effect of reducing costs can be obtained as in the first embodiment. FIG. 13 shows the beam energy at this time. Not only the excitation power supply (first excitation power supply 11) circuit of the normal first acceleration core 27 but also the second excitation power supply 12 circuit of the second acceleration core 28 converts a rectangular wave voltage by a switching element in which both rectified voltages are bridge-connected. Since it can be constituted by a simple inverter power supply circuit for outputting, there is an effect that can be realized by an extremely inexpensive device.
[0028]
Embodiment 3 FIG.
Embodiment 3 will be described with reference to FIG. The first acceleration core 27 is excited by the first excitation power supply 11 shown in FIG. 10, and at the same time, a charged particle beam (not shown in FIG. 10) is incident. FIG. 14 shows temporal changes in the acceleration voltage, beam energy, and beam current applied to the acceleration core in the third embodiment. In FIG. 14, assuming that the time at which the injection of the charged particle beam is completed is t1, the energy amount is smaller at the time closer to t1 because the excitation time is shorter. This is why there is a range of energy in FIG.
[0029]
Next, assuming that the time at which the beam is emitted is t2, at time t2, the second acceleration core 28 is excited by the second excitation power supply 12 and equivalently added to the output voltage of the first excitation power supply 11. As a result, the acceleration voltage increases, and the energy of the beam incident near time t1 also sharply increases, so that the above-described energy width can be reduced. As a result, t1> (t3-t2), where the time at which the last incident charged particle completes emission is t3. As described above, as shown in FIG. 14, the energy is the same as that of the related art, and the emission time is shortened. Therefore, the beam peak current at the time of emission can be increased and the emission efficiency can be improved. In particular, when the betatron accelerator is used as an injector for the next-stage accelerator, there is an effect that the beam incidence efficiency for the next stage can be improved.
[0030]
Embodiment 4 FIG.
Embodiment 4 will be described. In the second embodiment, the first and second accelerating cores 27 and 28 are excited as shown in FIG. 10, but each core is made of, for example, a silicon steel plate as a relatively inexpensive core material. Find the eddy current loss of As parameters of the voltage waveform, it is assumed that τb = 500 μs and τa = 400 μs in FIG. Assuming that the cross-sectional area is So and the constant relating to the eddy current specific to the silicon steel sheet is C with respect to the first acceleration core 27, Wo = C (1 / So) Vo ² is calculated. Next, the cross-sectional area of the second acceleration core 28 is {(500-400) / 500} So = 0.2So. As the excitation waveform of the second acceleration core 28, first, the excitation voltage Vo is excited for (τb−τa) time,
Next, since the time of {τb−2 (τb−τa)} is excited by the acceleration voltage − {(τb−τa) / (τb−2 (τb−τa)) Vo, the eddy current of the second acceleration core Loss Wo2 is
Wo2 = Wo · (1 / 0.2) · {2 (τb−τa) / τb + (V3 / Vo) ² · (τb−2 (τb−τa)) / τb} = 2.3 Wo
[0031]
Therefore, the total eddy current loss is calculated as W = Wo + 2.3Wo = 3.3Wo. When the silicon steel sheet of the core material is changed to, for example, an iron-based amorphous material in order to reduce the above-mentioned eddy current loss, heat generation can be reduced to 1/10 and can be reduced to 0.33Wo, but the acceleration core cost is almost tripled. turn into. On the other hand, in the fourth embodiment, only the second acceleration core 28 is made of an iron-based amorphous material, and the material of the first acceleration core 27 is a silicon steel plate. In this case, the heat generation of the core can be reduced to about 37% by comparing W = Wo + 2.3 (1/10) Wo = 1.23Wo with the above 3.3Wo, and the cost increase is calculated from the core volume ratio. 0.8 + 3 × 0.2 = 1.4 times. That is, there is an effect that a low-loss and low-cost acceleration core can be provided.
[0032]
【The invention's effect】
As described above, according to the betatron accelerator of the present invention, a path of a charged particle beam is formed therein, and an annular hollow conductor having an acceleration gap for inducing an accelerating electric field of the charged particle beam, An acceleration core provided to surround the core; an excitation coil wound around the acceleration core; and a power supply for applying a voltage to the excitation coil. In the betatron accelerator that completes the above, the power supply is configured by an inverter power supply that forms AC power into a rectified voltage by a rectifying / smoothing circuit, and outputs a rectangular wave voltage in both polarities by a switch element configured in a bridge circuit, Since the acceleration voltage is applied during the time from incidence to emission, the AC power supply side is used as a power supply for driving the acceleration core of the betatron accelerator. Load is small, it can provide a power supply capable of supplying a large current of a rectangular wave.
[0033]
In addition, an annular hollow conductor having an acceleration gap for inducing an accelerated electric field of the charged particle beam in which a passage of the charged particle beam is formed, an acceleration core provided to surround the hollow conductor, and a coil wound around the acceleration core A betatron accelerator, comprising: an excitation coil attached thereto; and a power supply for applying a voltage to the excitation coil. The betatron accelerator completes the process from the incidence to the emission of particles within one cycle of the operating frequency of the acceleration core. In this method, the incident time of the charged particle beam is set to be high, and the accelerated time and the emitted time of the charged particle beam are set to be low. Therefore, the incident efficiency can be improved economically.
[0034]
In addition, in the betatron accelerator, the acceleration voltage by the excitation coil is set to be high at the time of incidence of the charged particle beam, low at the time of acceleration, and high at the time of emission of the charged particle beam. It is easy to use the betatron accelerator as an injector.
[0035]
Further, in the betatron accelerator, the acceleration voltage by the excitation coil is set low when the charged particle beam is incident and accelerated, and high when the charged particle beam is emitted, so that the extraction efficiency can be improved.
[0036]
Further, the acceleration core device for betatron of the present invention includes a first acceleration core, a second acceleration core for superimposition, a first excitation coil for exciting the first acceleration core, and A second excitation coil for exciting the second acceleration core and a common power supply for these excitation coils are provided, and these excitation coils can be switched between parallel connection and series connection by a switching element. Even if the power supply is used, it is possible to obtain an acceleration voltage of 2 settings, obtain an acceleration voltage of 2 Vo at a required time, and increase the acceleration voltage without using an expensive high-voltage power supply.
[0037]
Furthermore, a first acceleration core, a second acceleration core for superimposition, a first excitation power supply circuit having a first excitation coil for exciting the first acceleration core, and a second excitation power supply circuit for superimposition. Since the second excitation power supply circuit having the second excitation coil for exciting the acceleration core is provided, the acceleration voltage can be increased at a required time without using an expensive high voltage power supply.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a betatron accelerator according to a first embodiment of the present invention. Accelerator voltage waveform by.
FIG. 2 is a diagram showing a voltage waveform of an excitation power supply in an excitation coil of an acceleration core according to the first embodiment.
FIG. 3 is a diagram showing a configuration of a first embodiment for realizing the voltage waveform of FIG. 2;
FIG. 4 is a diagram showing a configuration for realizing a conventional voltage waveform in comparison.
FIG. 5 is a diagram showing a drive circuit of an excitation coil of the acceleration core.
FIG. 6 is a diagram showing an acceleration voltage waveform of a conventional betatron accelerator in comparison.
FIG. 7 is a diagram showing a second configuration of the first embodiment for realizing the voltage waveform of FIG. 2;
FIG. 8 is a diagram showing a third configuration of the first embodiment for realizing the voltage waveform of FIG. 2;
FIG. 9 is a diagram showing a fourth configuration of the first embodiment for realizing the voltage waveform of FIG. 2;
FIG. 10 is a configuration diagram illustrating an excitation power supply circuit of an excitation coil according to the second and third embodiments.
FIG. 11 is an explanatory diagram of an acceleration voltage, a beam energy, and a beam current according to the first embodiment.
FIG. 12 is an explanatory diagram of an acceleration voltage waveform according to the second embodiment.
FIG. 13 is an explanatory diagram of an acceleration voltage, a beam energy, and a beam current according to the second embodiment.
FIG. 14 is an explanatory diagram of an acceleration voltage, a beam energy, and a beam current according to the third embodiment.
[Explanation of symbols]
1,11,12 Excitation power supply 2 Acceleration core 3 Electromagnet 4 Vacuum duct (annular hollow conductor)
21, 22, 23, 24, 25, 26, 27, 28 Acceleration cores 61, 62, 67, 68 Excitation coils 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82
Bidirectional switch element.

Claims (11)

An annular hollow conductor having an accelerating gap for forming an accelerating electric field of the charged particle beam in which a passage of the charged particle beam is formed, an accelerating core provided to surround the hollow conductor, and a coil wound around the accelerating core A betatron accelerator comprising an exciting coil and a power supply for applying a voltage to the exciting coil, wherein the power supply rectifies and converts AC power within one cycle of the operating frequency of the accelerating core to complete the process from incidence to emission of particles. It is composed of an inverter power supply that forms a rectified voltage by a smoothing circuit and outputs a rectangular wave voltage in both polarities by a switch element configured as a bridge circuit, and applies an accelerating voltage during the time from the incidence to emission of particles. Betatron accelerator. An annular hollow conductor having an accelerating gap for forming an accelerating electric field of the charged particle beam in which a passage of the charged particle beam is formed, an accelerating core provided to surround the hollow conductor, and a coil wound around the accelerating core In a betatron accelerator comprising an excitation coil and a power supply for applying a voltage to the excitation coil, and completing the process from the incidence to the emission of particles within one cycle of the operating frequency of the acceleration core, the acceleration voltage by the excitation coil is: A betatron accelerator characterized in that the charged particle beam is set to be high at the time of incidence and low at the time of acceleration and emission of the charged particle beam. An annular hollow conductor having an accelerating gap for forming an accelerating electric field of the charged particle beam in which a passage of the charged particle beam is formed, an accelerating core provided to surround the hollow conductor, and a coil wound around the accelerating core In a betatron accelerator comprising an excitation coil and a power supply for applying a voltage to the excitation coil, and completing the process from the incidence to the emission of particles within one cycle of the operating frequency of the acceleration core, the acceleration voltage by the excitation coil is: A betatron accelerator characterized in that a charged particle beam is set high during incidence, low during acceleration, and high during extraction. An annular hollow conductor having an accelerating gap for forming an accelerating electric field of the charged particle beam in which a passage of the charged particle beam is formed, an accelerating core provided to surround the hollow conductor, and a coil wound around the accelerating core In a betatron accelerator comprising an excitation coil and a power supply for applying a voltage to the excitation coil, and completing the process from the incidence to the emission of particles within one cycle of the operating frequency of the acceleration core, the acceleration voltage by the excitation coil is: A betatron accelerator, wherein the time of incidence and acceleration of a charged particle beam is set low, and the time of emission of a charged particle beam is set high. The betatron accelerator according to any one of claims 1 to 4, further comprising a first acceleration core, a second acceleration core for superimposition, and an excitation power supply circuit thereof. A first excitation coil for exciting the first acceleration core, a second excitation coil for exciting the superimposing second acceleration core, and a common power supply for these excitation coils; 6. The betatron accelerator according to claim 5, wherein switching between the parallel connection and the series connection is performed by a switching element. 7. The betatron accelerator according to claim 5, wherein the first acceleration core and the second acceleration core for superimposition are made of different materials. The magnetic field for defining the trajectory of the charged particle beam in the path of the charged particle beam in the annular hollow conductor is monotonically increased or decreased in the radial direction of the charged particle beam trajectory, and is fixed in time. The betatron accelerator according to any one of claims 1 to 7, characterized in that: A first acceleration core, a second acceleration core for superposition, a first excitation coil for exciting the first acceleration core, and a second excitation coil for exciting the second acceleration core for superposition And a common power supply for these exciting coils, and these exciting coils can be switched between parallel connection and series connection by a switching element. A first acceleration core, a second acceleration core for superimposition, a first excitation power supply circuit having a first excitation coil for exciting the first acceleration core, and the second acceleration core for superimposition. An acceleration core device for a betatron, comprising: a second excitation power supply circuit having a second excitation coil for excitation. The betatron acceleration core device according to claim 9 or 10, wherein the first acceleration core and the superimposing second acceleration core are made of different materials.

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