JPH0439899A - Charged particle beam compression method, charged particle beam compression device, and annular particle accelerator - Google Patents

Abstract

PURPOSE:To have a small charged particle beam size effectively by enlarging energy dispersion of charged particle in a ring type particle accelerator, including a vacuum container, which shuts up beam generated by high frequency acceleration cavity and charged particles. CONSTITUTION:A charged particle beam is extracted finely, and effectively, by an easy operation, which is to enlarge charged particle energy dispersion. For example, a deflection mode by specified high frequency electromagnetic field 7, is generated by excitation, on any point of orbit of charged particles. Also the excitation is made by synchronization, so that generally extended specified synchronized relation is satisfied, between the excitation frequency of the deflection mode and excitation frequency of high frequency acceleration cavity 1, settled on the orbit, and thus synchrotron vibration is grown, betatron vibration is attenuated, and then the charged particle beam is extracted finely, as a phenomenon. By this method, the beam size of the charged particle beam can effectively be compressed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a charged particle beam compression method, a charged particle beam compression device, and an annular particle accelerator. A suitable charged particle beam compression method, a charged particle beam compression device that realizes this charged particle beam compression method, and an application of this charged particle beam compression device to reduce the beam size of a charged particle beam and effectively accelerate the charged particles. Or it relates to an accumulating annular particle accelerator.

[Conventional technology]

FIG. 15 schematically shows the overall configuration of a typical conventional annular particle accelerator. This particle accelerator is comprised of an injector 101 for injecting positively or negatively charged particles into a trajectory as shown by arrow A, and an annular accelerator body 102 for accelerating and accumulating the charged particles. A linac, synchrotron, microtron, or the like is used as the injector 101.

The accelerator body 102 includes a beam duct 104 that forms a vacuum container for confining the charged particle beam 103, and a deflection magnet 105 that deflects the trajectory of the charged particle beam 103.
, a plurality of quadrupole magnets 106 having the function of converging the charged particle beam 103, a high frequency acceleration cavity 107 for accelerating the charged particles, etc., and the central orbit of the charged particles becomes a closed orbit. The trajectory of the charged particles exists at or near the central trajectory, and this trajectory is formed by a magnetic device such as the deflection magnet or quadrupole magnet described above.

For example, using the annular particle accelerator having the above configuration,
When conducting charged particle beam collision experiments (annular collider) or using synchrotron radiation for physical properties research (electron storage ring for synchrotron radiation generation), it is important to make the charged particle beam as narrow as possible. That is, in the case of the former annular collider, the frequency of collisions increases, and in the case of the latter electron storage ring for synchrotron radiation generation, the brightness of the synchrotron radiation increases.

Conventional methods for narrowing a charged particle beam include, in the case of electrons, a method that relies only on radiation attenuation, and a method that utilizes a deflection mode caused by a high-frequency electromagnetic field, which was previously proposed by the present inventor. (Japanese Unexamined Patent Publication No. 1-149400).The former method gradually reduces the bundle of charged particle beams by reducing the momentum of the charged particle beam due to radiation that occurs during one orbit and by accelerating the charged particle beam by a high-frequency acceleration cavity. In the latter method, a high-frequency cavity separate from the high-frequency accelerating cavity is installed on the orbit of charged particles, and an external oscillator and a coupling antenna are connected to this cavity. In the cavity, using an external oscillator and a coupled antenna, a deflection mode having an electric field component in the direction of the central orbit of the charged particle and a magnetic field component in the direction perpendicular to the orbit plane is excited, and further the deflection mode The excitation frequency is configured to be an integral multiple of the excitation frequency of the fundamental high-frequency mode in the high-frequency acceleration cavity.Other high-frequency cavities are used for compression to reduce the beam size of the charged particle beam. It is a hollow body.

[Problem to be solved by the invention]

In particular, in the latter method of confining a charged particle beam mentioned above, an electric field component is generated in the direction of the central orbit of the charged particles in the high-frequency cavity for compression, and a magnetic field is generated in the direction perpendicular to the orbital plane on the central orbit of the particles. The conditions of the deflection mode are limited to a narrow range because the deflection mode with the component is excited and the excitation frequency of the deflection mode is configured to be an integral multiple of the excitation frequency of the fundamental high frequency mode in the high frequency acceleration cavity. There was a problem. In subsequent research, the present inventor learned that the above conditions could be further expanded, and also gained an essential understanding of the basic idea of realizing a charged particle beam compression method using the deflection mode of a high-frequency electromagnetic field. This will be clarified in this application. Furthermore, when charged particles such as electrons are incident with low energy, electron beam loss becomes a problem because the electrons have the characteristic of being accelerated while spreading in the horizontal direction. However, in this case, since the energy is originally low, it is difficult to apply the former method of narrowing down the electron beam by radiation attenuation. Even in such a case, it is necessary to provide a method that can effectively narrow down the electron beam.

An object of the present invention is to effectively reduce the beam size of a charged particle beam by using the deflection mode of a high-frequency electromagnetic field, and in particular to generally expand the applicable conditions, and to improve the principle of a charged particle beam compression method. It is an object of the present invention to provide a charged particle beam compression method and a charged particle beam compression device that can perform compression under simpler conditions and can be effectively used in general.

Another object of the present invention is to provide an electron storage ring or an annular collider for synchrotron radiation generation, which is equipped with a compression device capable of carrying out the charged particle beam method, and utilizes the compression device to effectively accelerate or accumulate charged particles. An object of the present invention is to provide an annular particle accelerator.

[Means to solve the problem]

A first charged particle beam compression method according to the present invention includes a magnet-based device that forms an orbit of charged particles, a high-frequency acceleration cavity that accelerates the charged particles, and a vacuum container that confines the beam of charged particles. In the annular particle accelerator,
The feature is that the energy dispersion of charged particles is increased.

A second charged particle beam compression method according to the present invention includes a magnet-based device that forms an orbit of charged particles, a high-frequency acceleration cavity that accelerates the charged particles, and a vacuum container that confines the beam of charged particles. In the annular particle accelerator,
A distinctive feature is that the charged particle beam is compressed by growing synchrotron vibrations in charged particles orbiting and damping betatron vibrations.

A third charged particle beam compression method according to the present invention is characterized in that, in the first or second method, the charged particle has an electric field component in the direction of the center orbit and a magnetic field component in the direction perpendicular to the orbit plane. It is characterized by generating a high-frequency deflection mode having a high-frequency wave, and synchronizing this deflection mode with the acceleration mode of the high-frequency acceleration cavity under a predetermined synchronization condition to excite and compress the charged particle beam.

In the fourth charged particle beam compression method according to the present invention, in the third method, the predetermined synchronization condition between the deflection mode and the acceleration mode is such that the excitation frequency of the deflection mode is n/of the excitation frequency of the acceleration mode. The characteristic point is that it is h times (n: integer, h: harmonic number).

In each of the above-mentioned charged particle beam compression methods, the deflection mode is generated by excitation by an externally applied high frequency, or the deflection mode is generated by excitation by only charged particles, and the deflection mode is generated by TM.
mode or TE mode.

A first charged particle beam compression device according to the present invention has a high-frequency deflection mode in an internal space under predetermined synchronization conditions with a high-frequency acceleration mode for accelerating charged particles moving in a predetermined direction in the internal space. A characteristic feature of the charged particle is that it is configured to increase the energy dispersion of the beam caused by the charged particles through a high-frequency deflection mode.

The second charged particle beam compression device according to the present invention has a high-frequency deflection mode in an internal space under predetermined synchronization conditions with a high-frequency acceleration mode for accelerating charged particles moving in a predetermined direction in the internal space. A distinctive feature is that the charged particle beam is compressed by growing the synchrotron oscillations in the orbiting charged particles and damping the betatron oscillations using the excited high-frequency deflection mode.

In the third charged particle beam compression device according to the present invention, in the first or second device configuration, on the trajectory of the charged particles,
generating a high-frequency deflection mode having an electric field component in the direction of the central orbit and a magnetic field component in the direction perpendicular to the orbital plane, and exciting this deflection mode by synchronizing it with the high-frequency acceleration mode under predetermined synchronization conditions; The feature is that the charged particle beam is compressed.

In the fourth charged particle beam compression device according to the present invention, in the first to third device configurations, the predetermined synchronization condition between the deflection mode and the acceleration mode is such that the excitation frequency of the deflection mode is the excitation frequency of the acceleration mode. n/h times the frequency (n: integer,
h: harmonic number).

A fifth charged particle beam compression device according to the present invention is characterized in that, in the first to third device configurations, a high-frequency deflection mode and a high-frequency acceleration mode are excited in the internal space. .

In each of the above-mentioned charged particle beam compression devices, an external high-frequency power source is provided to generate a high frequency to generate a deflection mode, the deflection mode is generated by excitation only by charged particles, and the frequency of the deflection mode is adjusted by high frequency. It is possible to include a tuner of 1, and to set the deflection mode to either TM mode or TE mode.

A first annular particle accelerator according to the present invention is an annular particle accelerator that includes a magnet-based device that forms an orbit of charged particles, a high-frequency acceleration cavity that accelerates the charged particles, and a vacuum vessel that confines a beam of charged particles. In a type particle accelerator, the energy dispersion of charged particles is thickened (
It is characterized by the provision of a high-frequency cavity.

A second annular particle accelerator according to the present invention is an annular particle accelerator that includes a magnet-based device that forms an orbit of charged particles, a high-frequency acceleration cavity that accelerates the charged particles, and a vacuum vessel that confines a beam of charged particles. The particle accelerator is characterized by the provision of a high-frequency cavity that grows synchrotron oscillations in charged particles orbiting and damps betatron oscillations.

In the third annular particle accelerator according to the present invention, in the first or second device configuration, the high-frequency cavity has an electric field component in the direction of the center orbit and a magnetic field component in the direction perpendicular to the orbit plane. A deflection mode is generated, and this deflection mode is
The feature is that the charged particle beam is compressed by excitation in synchronization with the acceleration mode of the high frequency acceleration cavity under predetermined synchronization conditions.

In the fourth annular particle accelerator according to the present invention, in the third device configuration, the predetermined synchronization condition between the deflection mode and the acceleration mode is such that the excitation frequency of the deflection mode is n/n of the excitation frequency of the acceleration mode. The fifth annular particle accelerator according to the present invention, which is characterized by being h times (n: integer, h: harmonic number), has a high-frequency cavity and a high-frequency acceleration in the first to third device configurations. The feature is that each cavity function is realized by one cavity, and the deflection mode is excited in the acceleration mode.

Each of the annular particle accelerators described above is equipped with a high-frequency power source, and a transmission means transmits the high-frequency power generated by the high-frequency power source to the high-frequency cavity, and a phase adjustment means transmits the high-frequency power so as to satisfy the synchronization condition. A tuned and coupled antenna may be configured to feed the radio frequency cavity to the radio frequency cavity to excite the polarized mode within the radio frequency cavity.

Further, in each of the annular particle accelerators described above, a deflection mode in the high-frequency cavity can be generated by excitation by only charged particles.

[Effect]

In the charged particle beam compression method according to the present invention, a charged particle beam is efficiently narrowed down by a simple operation of increasing the energy dispersion of charged particles. More specifically, for example, a deflection mode is generated by exciting a predetermined high-frequency electromagnetic field at an appropriate location on the orbit of a charged particle, and the excitation frequency of this deflection mode and a high-frequency acceleration installed on the orbit are By synchronizing the excitation to satisfy a generally extended required synchronization relationship with the excitation frequency of the cavity, synchrotron oscillations grow, betatron oscillations attenuate, and phenomenally, The charged particle beam is narrowed down.

In the charged particle beam compression device according to the present invention, the compression method described above can be realized with a simple configuration, and furthermore, the high-frequency deflection mode and the high-frequency acceleration mode can be excited in one common high-frequency cavity.

Furthermore, the annular particle accelerator according to the present invention is constructed by installing a high-frequency cavity in orbit, which has a structure capable of carrying out the above-described method of compressing a charged particle beam, and this high-frequency cavity has a structure in which a predetermined An electromagnetic wave deflection mode is generated internally, and the excitation frequency of the deflection mode is synchronously excited with the excitation frequency of the high frequency acceleration cavity to satisfy the required synchronization relationship, thereby passing through the cavity. This narrows down the charged particle beam. Excitation of the deflection mode is performed by, for example, an externally provided high-frequency power source.

[Example] Hereinafter, an example of the present invention will be described based on the accompanying drawings.

In the following, for convenience of explanation, it is assumed that the charges of the charged particles are positive, and the traveling direction of the charged particles is indicated by an arrow B in each figure. FIG. 1 is an external perspective view showing the internal structure of a first embodiment of a compression device for carrying out the charged particle beam compression method according to the present invention, and FIG. 2 is a horizontal sectional view of the compression device showing the distribution of electric and magnetic fields. , FIG. 3 is a distribution diagram of electric and magnetic fields.

In FIG. 1, etc., the same elements shown in FIG. 15 are given the same reference numerals.

In FIG. 1, a cavity 1 configured to have a function as a charged particle beam compression device is configured so that the charged particle beam 103 passes through the central axis of its internal space.
It is placed in the orbit of charged particles. The installation position of the cavity 1 on the orbit may be either in front of or behind the high frequency acceleration cavity 107. The cavity 1 is formed, for example, into a substantially cylindrical shape by a cylindrical member 1a made of a conductive material, and has end surfaces 1b and lc, and furthermore, the central axis of the cylindrical member 1a is aligned with the direction of the charged particle beam 103. It is placed so that it almost coincides with the orbit. The shape of the cavity 1 may also be a rectangular parallelepiped or the like. Each end face portion 1b of the cylindrical member 1a of the cavity 1.

A beam duct 2 having a small diameter, for example a cylindrical shape, is provided outside the IC. As shown in Figure 1, the three-dimensional orthogonal coordinate axis x
, s, and z, the direction of the axis S coincides with the traveling direction B of the charged particle beam 103, and the xs plane is the orbital plane of the charged particle beam 103, which is a horizontal orbital plane in the figure. There is. Further, within the cavity 1, two electrodes 1d integrally formed with the end face IC are arranged. The tips of these two electrodes 1d approach the inner surface of the end surface 1b, forming a predetermined narrow gap. The electrodes 1d arranged in this way are arranged parallel to each other in a horizontal plane,
A trajectory of the charged particle beam 103 is formed in parallel between the two electrodes 1d.

Next, an external oscillator 3 is provided outside the curved portion formed by the cylindrical member 1a of the cavity 1, and the high frequency (microwave) oscillation output of this oscillator 3 is supplied into the cavity 1 via a coupling antenna 4. be done. The microwaves supplied to the cavity 1 create a type of polarization mode, for example T M ,+, in the cavity 1 as shown in FIG. A high frequency electromagnetic field of the mode is excited.

In this way, the cavity 1 is formed as a high frequency cavity. In FIG. 1, 5 is a tuner for adjusting the excitation frequency in the cavity 1. In FIGS. 1 and 2, 6 indicates lines of electric force (hereinafter referred to as electric field 6) representing the direction of the electric field, and 7 indicates lines of magnetic force (hereinafter referred to as magnetic field 7) representing the direction of the magnetic field. The excitation frequency of the electromagnetic field vibration related to the deflection mode in the cavity 1 is set to n/h times the acceleration frequency of charged particles by the high-frequency acceleration cavity. Here, n is an integer and h is a harmonic number. The harmonic number is calculated by dividing the speed of light by the excitation frequency of the fundamental acceleration mode in the high-frequency acceleration cavity to find the wavelength, then dividing the circumference of the equilibrium orbit of a charged particle with central energy by this wavelength. It is defined as the integer value obtained at that time. As described above, the excitation frequency f of the deflection mode formed in the cavity 1 is the excitation frequency f of the acceleration mode of charged particles. n of
/ h times, thereby synchronizing the deflection mode with the basic acceleration mode.

FIG. 3 shows the charged particle beam 103 in the cavity 1 and the distribution state of the electric field 6 and magnetic field 7 in and around it in a horizontal plane. As shown in this figure, the cavity is arranged so that the orbit of the charged particle beam 103 in the cavity 1 has an electric field component in the direction of the central orbit of the charged particles and a magnetic field component in the direction perpendicular to the horizontal plane (orbit plane). A deflection mode is created on the trajectory of the charged particles within the shell 1.

Further, FIGS. 4 and 5 show an example of a specific device configuration for titrating the synchronization conditions of the deflection mode and acceleration mode described above, and show a specific configuration of the external oscillator 3. FIG. 4 shows an embodiment using two oscillators. In FIG. 4, 103 is a charged particle beam, 1 is the high frequency cavity having a charged particle beam compression function, and 107 is a high frequency acceleration cavity. Further, 8 is an oscillator for applying a high frequency to the high frequency acceleration cavity 107, and 9 is another oscillator. The frequency f of the high frequency wave supplied to the cavity 1 is set to n/h times the excitation frequency fo of the acceleration mode, and the phase adjuster 10 is used to adjust the phase between both high frequencies. FIG. 5 shows a configuration using one oscillator, 11 is an oscillator, the frequency of this oscillation output is adjusted by a multiplier 12, two frequencies f and fo that satisfy the above relational expression are generated, and a phase shifter is used. 13 adjusts the phase between the two high-frequency waves, and the next-stage amplifier 14.15 amplifies the high-frequency waves, creating a predetermined synchronization relationship for the high-frequency cavity 1 for beam compression and the high-frequency accelerating cavity 107, respectively. Supply high frequency with.

Next, we will explain the operation of the charged particle beam compression device having the above configuration, that is, the principle of the charged particle beam compression method according to the present invention, with reference to the above-mentioned FIGS.
This will be explained with reference to FIGS. FIG. 6 conceptually shows the entire state of the deflection mode in the cavity 1. In the figure, reference numeral 20 indicates a central orbit, and shows the progress of a group of positively charged charged particles. The electromagnetic field distribution in FIG. 3 is an enlarged view of the electromagnetic field distribution near the center orbit 20 in FIG. 6. A charged particle beam is formed by the high-speed circular movement of a group of charged particles. Therefore, in the following description, the charged particle beam 103 is also referred to as a charged particle group 103 as necessary. The coordinate axis X in FIG. 6 is an axis perpendicular to the center orbit 20, where X>0 means a position outside the center orbit 20, and X<0 means a position inside the center orbit 20. This also applies to FIG. Furthermore, FIG. 7 shows, in a table format, the relationship between the electric field 6 and magnetic field 7 that form a deflection mode in the cavity 1, and the synchrotron vibration and betatron vibration generated in the charged particle group 103, respectively. It is something that 8 to 12 will be referred to as necessary in the following description.

When the charged particle group 103 passes through the cavity 1 having the required thickness in the axial direction, as is clear from the above-mentioned FIGS. 2 and 3, as well as FIG. It is affected by the electric field 6 and magnetic field 7 due to the deflection mode generated so as to satisfy the following conditions. As is clear from FIG. 7, first, under the condition that it is limited to charged particles near the synchronous phase with a predetermined phase relationship, the electric field 6 is phenomenally the vibration of the charged particles in the orbital direction and the energy Directly affects the synchrotron vibration, changes its amplitude, and grows the synchrotron vibration.

Conversely, the magnetic field 7 similarly damps the synchrotron oscillations phenomenally. Regarding fluctuations in synchrotron oscillations, "growth of synchrotron oscillations" means that the energy dispersion of charged particles becomes larger, and "damping of synchrotron oscillations" means that the energy dispersion of charged particles becomes smaller. means. On the other hand, regarding betatron oscillations, the electric field 6 damps the oscillations, and the magnetic field 7 causes them to grow. The final state of the above actions is:
The synchrotron oscillations grow and the betatron oscillations decay, resulting in the beam size of the charged particle beam becoming smaller and the beam being compressed.

Next, the principle of beam compression will be explained using mathematical expressions. First, for convenience of explanation, let's define the betatron oscillation as (x, y)
Let us describe it in the phase space of

where, : is the gradient in the direction along the central trajectory of x. On the phase space (x, y), a charged particle rotates on the circumference of x2+y' = εβ (2) within a linear region. ε is the emittance of the betatron oscillation. Under the premise of the above mathematical relationships, the reasons for the occurrence of the above-mentioned phenomena will be explained in the following sections.

(2): Reason for growth of synchrotron oscillation due to electric field 6 In synchrotron oscillation, the equilibrium trajectory of a charged particle is determined according to the energy possessed by the charged particle. Specifically, when the charged particle group 103 has a predetermined central energy, the charged particle group 103 moves along the central trajectory 20 corresponding to this central energy. In addition, the charged particle group 103 is
When it has energy higher than the center energy, it moves on the equilibrium orbit (X>O) outside the center orbit 20, and conversely, when it has energy lower than the center energy, it moves on the equilibrium orbit (X>O) inside the center orbit 20. X<
Consider the case of moving 0).

Refer to FIGS. 9(a) and (b). Charged particle group 103
In this case, charged particles with high energy move on the outside of the central orbit 20 on average, as shown in Fig. 9(a).
As shown in (the electric field 6 of the deflection mode of the cavity 1 (X>0
region), and the energy becomes even higher. Furthermore, charged particles with low energy move on the inside of the central orbit 20 on average, and the electric field 6 (X
(0 region), the energy is lower.

In this way, the electric field 6 in the deflection mode of the cavity 1 increases the dispersion of the energy of the charged particle beam 103, and as a result, the synchrotron vibration grows as described above. In FIG. 9(a), 21 indicates the average position of charged particles with high energy, and 22 indicates the average position of charged particles with low energy. Further, FIG. 9(b) schematically shows the action on the phase space (φ, δ), where φ is the phase of synchrotron vibration and δ is the ratio of energy shift. A large number of arrows 23 shown in FIG. 9(b) indicate the direction of change, and the length of the arrow indicates the magnitude of change. The same applies to the arrow 23 in the following description.

■: Reason for attenuation of synchrotron oscillation by magnetic field 7 The phase θ of the high frequency generated by the orbiting motion of the charged particle group 103 is changed by synchrotron oscillation and betatron oscillation, and θ=φ+θX+θS @-・(3) It can be expressed as Here, φA term of phase change due to synchrotron vibration θX: A term of phase change due to betatron vibration θS: Periodic phase of the equilibrium particle. Also, θx==(k/β)(ζX−ηy)...(4) ζ=αη
+βη ...(5) k: Excitation wave number of polarization mode (k = 2πf/c; f is excitation frequency C is the speed of light) η: Energy dispersion function η': Along the central trajectory of energy dispersion numerical aperture η It is a slope. In the above, the term φ exists because the equilibrium orbit changes with the energy oscillation of the synchrotron oscillation, the orbit length changes, and the orbit time changes, and θ
The reason why the term 8 exists is that the orbit length changes due to betatron oscillation, and the orbit time changes.

Due to the magnetic field of the deflection mode, the gradient X' of the particle trajectory is
Δx'=Φ1...It changes according to the relationship shown in (6). Here, 0 is the deflection angle due to the magnetic field of the deflection mode, which is Φ, = −Φ. in bed (φ) ・ ・ (7)
The phase is adjusted between the acceleration mode and the acceleration mode.

Also, φ is φ;φ+θ8+θ. ... is given by (8),
Phase constant θ. should be approximately 0, but
Here, for convenience of explanation, it is assumed to be 0. Figure 10 (a
) shows the relationship between Φ and ψ.

y defined in equation (1) above is expressed as Δy by equation (6)
=βΦ厘...(9) will change, and according to equation (4), θ8 becomes Δθ. =- to ηΦ6
...(10) changes. Here θ. Considering the case of =0, from equation (7), Δθx=ky7Φo @in(φ+θx)·(11). Even if a charged particle is deflected in the deflection mode of cavity 1, the high frequency phase θ does not change immediately;
Since it can be considered that it remains unchanged before and after , as can be seen from equation (3), the phase change term in the synchrotron oscillation changes as θ8 changes. Expressing it as a formula, Δφ=-ηΦ. 5in(φ+θX)...(12)
becomes. Considering that θ8 is a minute fluctuation term of the high-frequency phase due to betatron oscillation, from equation (12), φΔφ<0 on average, and Δφ works in the direction of decreasing φ on average. FIG. 10(b) schematically shows the effect. In this way, the synchrotron oscillations are damped by the deflection mode magnetic field.

The above explanation will be summarized. The phase of high frequency waves generated as the charged particle group 103 circulates is affected by synchrotron vibrations and betatron vibrations and changes. The reason why the equation that determines the phase of high frequency includes a term for the phase change due to synchrotron oscillations is because the equilibrium orbit changes as the energy of synchrotron oscillations changes, the length of the orbit changes, and the orbital orbit time increases. This is because it changes. Also, the term for the phase change of betatron oscillations is included because the length of the orbit also changes and the orbital time changes. There exists a relationship in which the presence of the magnetic field 7 changes the gradient of the equilibrium trajectory of the charged particle, and the amount of the change is equal to the deflection angle due to the magnetic field 7. Based on this relationship and the characteristic that the gradient has a predetermined relationship with the phase change of the betatron oscillation, the magnetic field 7 can obtain a relationship that determines the phase change of the betatron oscillation. By the way, charged particle group 10
3 in the cavity 1, even if it is affected by the magnetic field 7, the high frequency phase does not change immediately, but remains unchanged before and after the cavity 1. Therefore, the phase of the synchrotron oscillation changes by the amount that the phase of the betatron oscillation changes due to the action of the magnetic field 7, and this change acts in the direction of reducing the phase change term on average. Magnetic field due to deflection mode 7
dampens synchrotron oscillations.

(2): The reason why betatron oscillations are attenuated by the electric field 6 will be explained with reference to FIG. Figure 11(a) shows cavity 1
The displacement X of the betatron oscillation before and after passing is shown.

The absolute displacement X of a charged particle is X=X+77δ; δ
=ΔE/E --(13) As described above, η is an energy dispersion function, E is energy, ΔE is an energy deviation, and δ is a ratio of energy deviation. In the above equation, ηδ represents the deviation of the equilibrium trajectory.

The absolute displacement X of the charged particle before and after passing through the cavity 1 remains unchanged except for changes due to the gradient in the orbital direction. On the other hand, the energy difference δ before and after passing through the cavity changes by Δδ due to the electric field of the deflection mode.

Therefore, the displacement X of the betatron oscillation is ΔX=−ηΔ
It changes by δ・φ・(14). This means that if the equilibrium orbit changes by ηΔδ, the displacement of the betatron oscillation will change in the opposite direction by ηΔδ.
This means that it changes by δ.

The above premise will be explained below. A charged particle near the synchronous phase has a horizontal electric field gradient 'aV/? Since 5X senses a positive electric field, the accelerating voltage due to the electric field 6 has a linear distribution with a positive slope passing through the origin as shown in FIG. 11(b) in the X-axis direction. Among the charged particles, those with high energy (particles with δ>0) pass through the region of X>0 on average. Therefore, for charged particles with high energy, the first
As shown at X〉0 in Figure 1 (C), the amount of change in X is X〈0
The case where x>O is larger than the case where . When X〉0, X changes in the direction that the betatron oscillation is attenuated, and x〈0
or the betatron oscillation changes in the direction of growth. Since the amount of change in X is larger when x>0, the 11th
As shown in the case of X>0 in Figure (C), the betatron oscillations are attenuated on average.

Furthermore, in the case of charged particles with low energy (particles with δ×O), they pass through the region of X×0 on average. In this case, the first
As shown in x<0 in Figure 1 (C), x<O than x>0
, the amount of change in X is larger, and x<O has a greater effect on damping the betatron oscillations, so the betatron oscillations are similarly damped on average.

As a result of the above, as a whole, the betatron oscillation is attenuated by the electric field 6 in the deflection mode.

(2): The reason why betatron oscillations grow due to electromagnetic fields will be explained with reference to FIG. In Figure 12, (a
) indicates the relationship between the deflection angle Φ and φ shown in equation (7), and (
b) shows the effect of magnetic field 7 on betatron oscillations.

The position of X=0 in FIG. 12(b) corresponds to the position on the φ axis in FIG. 12(a).

Generally, the energy dispersion numerical aperture η is positive, so Equation (4
), when y>Q, θ8 takes an average negative value, and when y<0, θX takes an average positive value. This means that, on average, particles with y>0 are slightly shifted to the negative side in terms of high frequency phase, and particles with y<0, on the contrary, are shifted to the positive side.

Therefore, for a charged particle with φ>0, the amount of change in y is the first
As shown in FIG. 2(b), y<Q is larger than y>Q. Betatron oscillations are damped when y>Q,
It grows when y<0, but since the amount of change is larger when y<0, the betatron oscillation grows on average. On the other hand, in the case of a charged particle with φ<0, the amount of change in y is larger when y>0 than when y<Q. Betatron oscillations grow when y>Q and decay when y<0, but y
Since the amount of change is larger when >Q, the betatron oscillation will grow on average in this case as well. As described above, the betatron oscillation grows due to the magnetic field 7 in the deflection mode.

As described above, based on the relationship between the electric field 6, magnetic field 7, synchrotron oscillation, and betatron oscillation, their mutual interaction results in synchrotron oscillation, as shown in FIG. will grow, and the betatron oscillations will be damped. Finally, the beam size of the charged particle beam 103 becomes smaller. In this case, the fact that the cavity 1 has a finite thickness in the beam trajectory direction S is an important factor. By having a finite thickness of the cavity 1, the charged particle beam 10
3 requires a finite amount of time to pass through the cavity 1.

During this time, the electromagnetic field within the cavity 1 undergoes a temporal change and its influence on the charged particle beam becomes substantially smaller. This factor is generally called the "transit time factor" and is determined by the distribution of electric and magnetic fields near the beam trajectory. by the way,
As shown in Figure 2, the distribution of the electric and magnetic fields near the beam trajectory is not the same; the electric field 6 is concentrated near the gap, whereas the magnetic field 7 is widely distributed along the electrode 1d. There is. Therefore, the fact that the cavity 1 has a finite thickness means that
The influence of the magnetic field 7 on charged particles is made smaller than the influence of the electric field 6 on charged particles. As a result, the synchrotron oscillations grow, the betatron oscillations attenuate, and the beam size of the charged particle beam 103 becomes smaller.

(a) to (d) in FIG. 8 show examples of numerical calculation results.

In the figure, all the horizontal axes are the number of revolutions, and (a) is the initial phase θ
. shows the change in energy deviation when is 100 degrees, and (
b) is the initial phase θ. shows the change in energy deviation when is 180 degrees. (c) shows the change in betatron amplitude, and (d) shows the change in beam size. As is clear from FIG. 8, the size of the charged particle beam can be reduced by providing a deflection mode that increases the energy dispersion of the charged particles.

Next, the above-mentioned charged particle beam compression effect will be further explained by using other mathematical expressions. The beam size σ(S) of the charged particle beam 103 in the horizontal direction is a function of the coordinate S in the orbital direction, and can be defined as σ(8) = ε S +η 8 . Here, as described above, ε is a quantity called the emittance of betatron oscillation, and generally does not depend on the orbit axis coordinate S. Also, β ($) and η (S
) are the horizontal betatron function and energy dispersion function, respectively, and are functions that have already been determined by the magnet arrangement that constitutes the particle accelerator. ΔE, is the energy dispersion of a charged particle, and E. represents the average energy.

As is clear from the above equation, the beam size σ(S) can be changed by the emittance ε and the energy dispersion ΔEs.

The electromagnetic field of the deflection mode excited in the cavity 1 is a conservative system, and based on Liouville's theorem, when the betatron oscillation is attenuated, the synchrotron oscillation grows. That is, in the above equation, ε becomes smaller and ΔEs/Eo
becomes larger. However, since changes in the emittance of betatron oscillations generally affect the beam size, the beam size becomes smaller as a result.

FIG. 13 shows the phase relationship between the basic acceleration mode and the deflection mode when n=h. In this figure, the voltage in the basic acceleration mode is V. Bind, this V.

, Vo = Vc sin θ, which shows the phase relationship between the basic acceleration mode and the deflection mode with respect to the high frequency phase θ. In Figure 13,
■ and Vyo respectively relate to the deflection mode, V=fEs ctθ5ees(θ-θ5)VW =zo
It represents the voltage defined by fHdθ5sin(θ−θ,). Here, Es is an electric field component in the S direction, H is a magnetic field component in two directions, and zo is a characteristic impedance of vacuum, and its integral region covers the entire central orbit of the charged particle in the cavity 1.

Moreover, θ6 is the synchronous phase of the equilibrium particles.

The phase relationship shown in FIG. 13 is such that the synchronization phase θ8 is π/2
A typical example of 〈θ8〈π is shown.

FIG. 14 shows a second embodiment of a charged particle beam compression cavity according to the invention. This embodiment has a configuration in which the external oscillator 3 and the coupling antenna 4 are removed from the cavity 1 of the previous embodiment, and the other configurations are the same. With this configuration, the deflection mode is excited by the charge of the charged particle beam 103 itself, so the positions of the charged particle beam 103 and the central axis 16 of the cavity 1' are intentionally shifted in the horizontal direction. . This can be easily done by changing the amount of excitation of the magnet system that constitutes the accelerator. According to this embodiment, components such as an external oscillator can be omitted, and manufacturing costs are reduced.

In each of the above embodiments, T in the cylindrical cavities 1 and 1'
Although the example of the MIIO mode has been described, the present invention is not limited thereto, and the same effect can be achieved by using cavities of other shapes or other electromagnetic field modes. Of course.

Further, in each of the above embodiments, the high frequency deflection mode was configured to be excited in a separate cavity other than the high frequency acceleration cavity, but as shown in FIGS. It is also possible to excite polarization modes within 107. 16 is a modification of the configuration shown in FIG. 4, and FIG. 17 is a modification of the configuration shown in FIG. 5. In this way, a high-frequency cavity in which the deflection mode is excited and a high-frequency acceleration cavity in which the acceleration mode is excited can be fabricated using one common high-frequency cavity. In this case, the excitation frequency of the deflection mode is set to be several times the excitation frequency of the acceleration mode. In this polarization mode, it is possible to externally excite via a coupling antenna as described above, or it is possible to excite the charged particle beam itself without providing a coupling antenna. Such a cavity is basically the same as the acceleration cavity, and the structure must be determined so that the excitation frequency of the deflection mode is n/h times the excitation frequency of the acceleration mode.

〔Effect of the invention〕

As is clear from the above description, the present invention provides the following effects.

According to the charged particle beam compression method of the present invention, a simple operation of exciting a deflection mode in the orbit of a charged particle using a high-frequency electromagnetic field that satisfies a predetermined condition to increase the energy dispersion of the charged particles can achieve extremely high energy efficiency. The beam size of a charged particle beam can be efficiently compressed. Also,
According to the charged particle beam compression method of the present invention, the general conditions in the method of compressing a charged particle beam using a deflection mode by a high frequency electromagnetic field are extended, and thereby the charged particle beam can be compressed to a fraction of a fraction of a second. can.

The charged particle beam compression device of the present invention can be manufactured with a simple structure and can effectively compress a charged particle beam. In particular, when the high frequency deflection mode and the high frequency acceleration mode are realized by one high frequency cavity, handling is easier and more convenient.

According to the annular particle accelerator equipped with a high-frequency cavity capable of carrying out the charged particle beam compression method of the present invention, it is possible to increase the collision frequency of charged particle beams when conducting collision experiments, or to generate synchrotron radiation. In some cases, the brightness of the emitted light can be increased.

In addition, when a charged particle beam is incident on an annular accelerator with energy so low that radiation attenuation is not effective, the lateral spread of the charged particles is compressed into a stable orbital region for long orbits, reducing beam loss. This makes it possible to accelerate and accumulate a charged particle beam with low energy and high current.

[Brief explanation of drawings]

FIG. J is an external perspective view showing a first embodiment of a high-frequency cavity for carrying out the charged particle beam compression method according to the present invention;
FIG. 2 is a horizontal cross-sectional view of the same cavity in FIG. 1, FIG. 3 is a diagram showing the horizontal plane distribution of the electromagnetic field in the trajectory of charged particles in the cavity, and FIG. Fig. 5 is a block diagram showing another embodiment of the oscillator part, Fig. 6 is a conceptual diagram of the deflection mode in the cavity, and Fig. 7 is a diagram showing the polarization mode applied to the charged particle beam. Figure 8 shows an example of synchrotron oscillations, betatron oscillations, and changes in beam size.
Figure 9 is a diagram to explain why synchrotron oscillations grow due to an electric field. Figure 10 is a diagram to explain why synchrotron oscillations are attenuated by a magnetic field.
Figure 1 is a diagram to explain why betatron oscillations are attenuated by an electric field, Figure 12 is a diagram to explain why betatron oscillations are grown by a magnetic field, and Figure 13 is a diagram to explain the relationship between acceleration mode and deflection mode. A characteristic diagram showing the phase relationship, FIG.
A diagram similar to FIG. 1 showing an embodiment, FIG. 15 is a configuration diagram showing a conventional example of an annular particle accelerator, and FIGS. 16 and 17 excite a deflection mode in the acceleration mode of a high-frequency acceleration cavity. FIG. 3 is a diagram of another embodiment showing a configuration for causing the problem to occur. [Explanation of symbols] 1.1' ...Cavity 2, Inner beam duct 3, External oscillator 4, Combination, Coupling antenna 5, ---Fist tuner 6 ...... Electric field (electric lines of force) 7... Magnetic field (lines of magnetic force) Fig. 1 Fig. 3 Fig. 4 (deflection mode) (acceleration mode) Fig. 2 Fig. 5 (deflection mode) (Acceleration mode) Fig. 6 Fig. 7 Influence on beam in deflection mode (when limited to charged particles near synchronous phase with normal phase relationship) 0 days =] Fig. 9 (a> Electric field distribution in deflection mode and Particle orbit External equation of circular orbit 1 (b) Effect on phase space (φ, δ) Figure 8 Synchrotron oscillation, betatron oscillation, and change in beam size (θ0: initial phase) (C) (d>N<XIO') N(XIO・) Figure 10 (a) Dependence of deflection angle ΦH on phase angle ψ (b) Effect on phase space (φ, δ) Figure 14 Figure 13 Figure 15 Figure 16 Figure 17 (Acceleration mode and deflection mode) (Acceleration mode and deflection mode)

Claims (23)

[Claims] (1) In an annular particle accelerator that includes a magnet-based device that forms an orbit of charged particles, a high-frequency acceleration cavity that accelerates the charged particles, and a vacuum vessel that confines a beam of the charged particles, the charged particles A charged particle beam compression method characterized by increasing the energy dispersion of the charged particle beam. (2) In an annular particle accelerator including a magnet-based device that forms an orbit of charged particles, a high-frequency acceleration cavity that accelerates the charged particles, and a vacuum vessel that confines a beam of the charged particles, A charged particle beam compression method, characterized in that the charged particle beam is compressed by growing synchrotron oscillations in the charged particles orbiting the charged particles and attenuating betatron oscillations. (3) In the charged particle beam compression method according to claim 1 or 2, a high-frequency deflection mode having an electric field component in the direction of the central orbit and a magnetic field component in the direction perpendicular to the orbital plane on the orbit of the charged particle. A charged particle beam compression method, characterized in that the charged particle beam is compressed by exciting the deflection mode by synchronizing the deflection mode with the acceleration mode of the high frequency acceleration cavity under a predetermined synchronization condition, and compressing the charged particle beam. (4) In the charged particle beam compression method according to claim 3, the predetermined synchronization condition between the deflection mode and the acceleration mode is such that the excitation frequency of the deflection mode is n/h times the excitation frequency of the acceleration mode ( n: integer, h: harmonic number)
A charged particle beam compression method characterized by: (5) A charged particle beam compression method according to claim 3 or 4, wherein the deflection mode is generated by excitation by externally applied high frequency. (6) The charged particle beam compression method according to claim 3 or 4, wherein the deflection mode is generated by excitation by only charged particles. (7) The charged particle beam compression method according to any one of claims 3 to 6, wherein the deflection mode is either ΥM mode or TE mode. (8) A high-frequency deflection mode is excited in the internal space under a predetermined synchronization condition with a high-frequency acceleration mode for accelerating charged particles moving in a predetermined direction in the internal space, and the high-frequency deflection mode causes the high-frequency deflection mode to A charged particle beam compression device characterized in that it is configured to increase energy dispersion of a beam due to charged particles. (9) A high-frequency deflection mode is excited in the internal space under a predetermined synchronization condition with a high-frequency acceleration mode for accelerating charged particles moving in a predetermined direction in the internal space, and the high-frequency deflection mode: growing synchrotron vibrations in the charged particles orbiting in the orbit;
A charged particle beam compression device, characterized in that the charged particle beam is compressed by attenuating betatron oscillations. (10) In the charged particle beam compression device according to claim 8 or 9, a high-frequency deflection mode having an electric field component in the direction of the central orbit and a magnetic field component in the direction perpendicular to the orbit plane on the orbit of the charged particle. and this deflection mode,
A charged particle beam compression device characterized in that the charged particle beam is compressed by excitation by synchronizing with the high frequency acceleration mode under a predetermined synchronization condition. (11) In the charged particle beam compression device according to any one of claims 8 to 10, the predetermined synchronization condition between the deflection mode and the acceleration mode is such that the excitation frequency of the deflection mode is higher than that of the acceleration mode. A charged particle beam compression device characterized in that the excitation frequency is n/h times (n: integer, h: harmonic number). (12) The charged particle beam compression device according to any one of claims 8 to 10, characterized in that the high-frequency deflection mode and the high-frequency acceleration mode are excited in the internal space. Particle beam compression device. (13) The charged particle beam compression device according to any one of claims 8 to 12, characterized in that the charged particle beam compression device is equipped with an external high-frequency power source that provides high-frequency waves in order to generate the deflection mode. . (14) The charged particle beam compression device according to any one of claims 8 to 12, wherein the deflection mode is generated by excitation by only charged particles. (15) The charged particle beam compression device according to any one of claims 8 to 14, further comprising a tuner for adjusting the frequency of the deflection mode using high frequencies. (16) The charged particle beam compression device according to any one of claims 8 to 15, wherein the deflection mode is either a TM mode or a TE mode. (17) A magnet-based device that forms an orbit of charged particles;
In an annular particle accelerator including a high frequency acceleration cavity for accelerating the charged particles and a vacuum vessel for confining a beam of the charged particles, the energy dispersion of the charged particles is increased on the orbit of the charged particles. An annular particle accelerator characterized by a high-frequency cavity. (18) A magnet-based device that forms an orbit of charged particles;
In an annular particle accelerator including a high-frequency acceleration cavity for accelerating the charged particles and a vacuum vessel for confining a beam of the charged particles, the charged particles orbiting on the orbits are placed on the orbits of the charged particles. An annular particle accelerator characterized by having a high-frequency cavity that grows synchrotron oscillations and damps betatron oscillations. (19) In the annular particle accelerator according to claim 17 or 18, in the high-frequency cavity, a deflection mode having an electric field component in the direction of the center orbit and a magnetic field component in the direction perpendicular to the orbit plane is generated. An annular particle accelerator characterized in that the charged particle beam is compressed by exciting the deflection mode in synchronization with the acceleration mode of the high-frequency acceleration cavity under a predetermined synchronization condition. (20) In the annular particle accelerator according to claim 19,
The predetermined synchronization condition between the deflection mode and the acceleration mode is characterized in that the excitation frequency of the deflection mode is n/h times the excitation frequency of the acceleration mode (n: integer, h: harmonic number). An annular particle accelerator. (21) The annular particle accelerator according to any one of claims 17 to 20, comprising a high frequency power source, transmitting high frequency power generated by the high frequency power source to the high frequency cavity by a transmission means, and a phase adjustment means. An annular particle accelerator characterized in that high-frequency power is adjusted so as to satisfy the synchronization condition and supplied to the high-frequency cavity via a coupling antenna to excite the polarized mode in the high-frequency cavity. . (22) The annular particle accelerator according to any one of claims 19 to 20, wherein the deflection mode in the high-frequency cavity is generated by excitation by only charged particles. (23) In the annular particle accelerator according to any one of claims 17 to 19, each function of the high frequency cavity and the high frequency acceleration cavity is realized by one cavity, and the deflection mode is accelerated. An annular particle accelerator characterized by excitation within a single mode.