JPH0561760B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an injection device for injecting charged particles into a magnetic resonance type accelerator having an orbit such as a synchrotron, a storage ring, or a collision ring.

(Prior art) A conventional magnetic resonance accelerator with an orbit uses an electromagnet called a kitker that operates at high speed or an electromagnet called a perturbator as an injection device, and an inflation accelerator that generates a magnetic field or an electric field in direct current. It has a kuta. An inflector guides charged particles into an incident trajectory. By displacing the equilibrium orbit, Kitzkar or Perturbator allows charged particles incident from the inflector to travel around the orbit and return to the inflector position.
This prevents it from hitting the inflector. In general, a kicker displaces the entire equilibrium trajectory, whereas two or three perturbators operate synchronously to displace a partial section of the equilibrium trajectory.

Here, a conventional magnetic resonance type accelerator having an orbit will be explained with reference to FIGS. 8 to 10.

The conventional magnetic resonance accelerator shown in Fig. 8 is equipped with an inflector INF that guides charged particles to an incident orbit, a circular balanced orbit TR, and multiple locations on the balanced orbit, each with a dipole electromagnet D and both sides thereof. Two sets of horizontally focusing quadrupole electromagnets QF and horizontally diverging 4
It has a plurality of deflection elements and focusing elements each consisting of a polar electromagnet QD, and perturbators P1 to P3 that are provided at the ends of the focusing elements on both sides of the inflector INF and move the equilibrium trajectory TR. Partabeta P1 to P3 are on equilibrium orbits as shown in FIG.
TR is displaced to provide a displacement equilibrium trajectory TR'.

While injecting a beam from the inflector INF into this displaced orbit TR', the magnetic field of the perturbator is weakened, and the displaced orbit TR' is gradually returned to its original orbit.
Return to TR.

The above-mentioned mechanism will be explained with reference to FIG. 10, which shows the phase space in the section taken along the line A-A' in FIG. 8. Here, we will consider the case of betatron oscillation, which rotates four times and returns to its original state. x represents the horizontal displacement from the original equilibrium trajectory TR, and x' represents the inclination of the trajectory. Furthermore, reference number 0 is the equilibrium trajectory TR' displaced by the perturbator, 1 is the incident trajectory,
2 is the orbit after being injected and completing one orbit. Orbit 2 is at a position rotated around orbit 0 by an angle determined by the betatron oscillation, because the betatron oscillates around the equilibrium orbit 0. Reference numerals 3, 4 and 5 represent the orbits after two, three and four revolutions after incidence, respectively. The reason why trajectory 5 does not come to the position of incident trajectory 1 is because the displaced equilibrium trajectory 0 moves in the direction of the arrow as the perturbator's magnetic field weakens. It is important that the gap between the incident trajectory 1 and the trajectory 5 is sufficiently large for the inflector.
This is a condition that does not conflict with INF.

(Problems to be solved by the invention) The conventional magnetic resonance accelerator described above is miniaturized,
In order to make the incident energy as high as possible,
A perturbator or kicker is required that generates a very high-velocity, high-intensity magnetic field. In addition, the inflector requires a high-intensity magnetic field or electric field. However, there are technical limits to the strength and response speed of magnetic and electric fields that can be achieved with perturbators, kitskers, and inflectors. A method of injecting, accumulating, and accelerating charged particles using a very weak magnetic field can be considered, but since the lifetime of accumulated charged particles is short at low energies, this is not suitable for accumulating a sufficient amount of charged particles. .

In addition, a strong octupole magnetic field is applied statically when the betatron frequency in the horizontal direction is around 1/2, and a part of the orbit is Applying a quadrupole magnetic field to the section, 1/
There is a device that generates two resonances and dynamically changes the quadrupole magnetic field to change the stable region and trap incident charged particles in a stable orbit (Japanese Patent Application No. 60-207791). Specification).

However, in the above case, since the octupole magnetic field remains static, particles such as electrons or positrons emit light and diverge, and there is a limit to the incidence efficiency.

(Means for Solving the Problems) According to the present invention, in an injection device for injecting charged particles into a magnetic resonance type accelerator having an orbit, an octupole magnetic field is generated as a main focusing component on an orbital surface around a central equilibrium orbit. The device is equipped with a perturbator that generates a nonlinear magnetic field, and the nonlinear magnetic field forms an unstable resonant orbit in which the frequency of horizontal hetatron oscillation is halved, and a separatrix located inside the unstable resonant orbit. The invention is characterized in that the size of a stable region including the central equilibrium orbit within the separatrix is changed by changing the strength of the octupole magnetic field over time to trap the charged particles. An injection device for a magnetic resonance accelerator is obtained.

(Example) The present invention will be explained below with reference to Examples.

Referring to FIG. 1, one embodiment of the present invention includes a centrally balanced trajectory 11, an incident trajectory 12, an inflector 13,
and a perturbator 14. The perturbator 14 described above forms a nonlinear magnetic field whose main focusing component is an octupole magnetic field.

On the central equilibrium orbit 11, there is a magnetic field B _ZO perpendicular to the plane of the paper.
is added, and as a result, the high-energy charged particles are deflected by this magnetic field, and the central equilibrium orbit becomes a closed orbit. Furthermore, the above magnetic field has a distribution in which the strength decreases toward the outside in the radial direction, and therefore, a focusing force acts on charged particles slightly displaced from the central equilibrium orbit toward the central equilibrium orbit.

Here, if we take a coordinate system as shown in Fig. 2 for the centrally balanced orbit 11, the r-θ plane magnetic field distribution is: Bz(x)=Bz ₀ (1-nζ+K ₂ ζ ² +K ₃ ζ ³ +…) It can be expressed as ζ = (r-req)/req. Here, Bzo is the Z-direction magnetic field on the centrally balanced orbit, req is the radius of the centrally balanced orbit, and n is a parameter for focusing the beam.

In addition, as shown in FIG. 2, the position of the particle projected onto the center equilibrium orbit plane is calculated by calculating the displacement x from the center equilibrium orbit radially outward and the reference point (for example, A-
Expressed in terms of rotation angle θ from point A', the equation of motion for minute displacement from the central equilibrium orbit is d ² x/dθ ² + (1-n) x=0 d ² z/dθ ² + nz=0. expressed.

From this, in order to focus the beam in both the horizontal and vertical directions, the range is 0<n<1, but in order for the electrons or positrons to emit light but not diverge, in other words, the vibration must be attenuated. 0<n<0.75.

Here, in FIG. 1, the position of line A-A' is assumed to be θ=0°, and the incidence mechanism will be explained.

When a charged particle is incident, large-amplitude betatron oscillations occur, so the magnetic field distribution not only in the vicinity of the central equilibrium orbit but also in a wide range must be considered.
Here, the magnetic field distribution along the line A-A' is shown in FIG. Point x ₁ in FIG. 3 corresponds to n=1. Next, a phase diagram along the line A-A' is shown in FIG. Note that in FIG. 4, no octupole magnetic field is formed. That is, it is a phase diagram in the x direction (radial direction) when the perturbator is not provided. n
The point corresponding to =1 is indicated by x ₂ in Fig. 4,
This point is an unstable fixed point. And this x ₂
It is divided into a stable region and an unstable region by a separator indicated by 15 passing through. Charged particles incident from the outside of the separatrix 15 fly away, drawing a trajectory 16 or 17 without entering the stable region (FIG. 4). That is, if an inflector is not provided, charged particles incident from the outside will fly away. The inflector functions to guide the incident charged particles to the inside of the separatrix, that is, to the stable region, but the charged particles do not follow the trajectory 18.
, and return to the inflector position again, and are lost when they hit the inflector (in Figure 4, the charged particles draw a trajectory in the order of points 18a, 18b, 18c, ..., 18i, and return to the inflector position again) ).

On the other hand, in the present invention, as shown in FIG. 1, a perturbator 14 is provided which generates a nonlinear magnetic field whose main component is an octupole magnetic field. Here, the actual magnetic field distribution of the perturbator is shown in FIG. 5 as a magnetic field distribution on the raceway plane taken along the line B-B' in FIG. 1.

When the perturbator is excited, that is, when an octupole magnetic field is generated, the phase diagram in the section A-A' in Fig. 1 becomes as shown in Fig. 6 (Fig. 6 does not show the trajectories, but each trajectory is (showing the connected curves). A separatrix 19 is created inside the separatrix 15 by the 8-pole magnetic field generated by the perturbator.
is formed. The stable trajectory within the separatrix 19 moves in the direction of the arrow 20. Further, the trajectory curves outside the separatrix 19 are divided into a group indicated by 21, 21' and a group indicated by 22, 22'. Note that the trajectory curves 21, 2
1' and trajectory curves 22, 22' are composed of trajectories that vibrate alternately every time a charged particle makes one revolution in the accelerator, and each group has the same trajectory.

Referring also to FIG. 7, the size of the area of the separatrix 19 corresponds to the strength of the perturbator 14. Charged particles are incident along a trajectory 16 from the outside. When the charged particles reach point c, they are moved from point c to the trajectory 21a by the inflector. On the other hand, when the magnetic field by the perturbator is weakened over time, the area of the separatrix 19 becomes larger as described above. The charged particles that have moved to the trajectory 21a approach the separatrix 19 while undergoing betatron vibration in the order of the trajectories 21a, 21b, . . . . At this time, if the magnetic field by the perturbator is weakened, the area of the separatrix 19 becomes larger, so that the charged particles are captured inside the separatrix 19.
That is, the trajectories of charged particles are trajectories 20a, 20b, 2
As shown by 0c..., the orbit rotates while vibrating around the central equilibrium orbit. The trajectory of the charged particle thus captured in the region of the separatrix 19 does not increase in amplitude again until it reaches the position of the point 21a, and therefore does not collide with the inflector.

When capturing the above-mentioned charged particles in the region of the separatrix 19, the amount of change in the magnetic field of the pertervater is required to be small, and therefore the rate of change of the magnetic flux of the pertervater is made sufficiently slow compared to the speed at which the charged particles rotate in their orbits. be able to. That is, even a small device can achieve the above-mentioned rate of change. Also,
Since the distance from point c to point 21a shown in FIG. 7 is extremely short, the burden on the inflector is small, and high-energy charged particles can be incident thereon.

By the way, after the charged particle is incident, the 8-pole magnetic field of the perturbator disappears or becomes only a minute component of the main magnetic field, so the effective value of n of the charged particle captured in the internal region of the separatrix 19 is as described above. n<0.75. Therefore, even in the case of electrons or positrons, the emittance is attenuated by optical radiation and does not diverge.

(Effects of the Invention) As explained above, the injection device according to the present invention generates a nonlinear magnetic field whose main component is an octupole magnetic field, and creates an unstable resonant orbit in which the betatron frequency is 1/2 and this orbit. A particle is incident along this separatrix, and the particle is captured by changing the size of the separatrix using a perturbator that temporally changes the octupole magnetic field. In other words, the resonance phenomenon of betatron oscillation occurs. Even with a weak octupole magnetic field, charged particles incident with a large amplitude can be moved close to the central equilibrium orbit. Furthermore, since the turn separation at the time of incidence is large, the incidence efficiency can be improved. Moreover, the burden on the inflector is small. Therefore, high-energy charged particles can be incident with a high magnetic field.

As mentioned above, since they can be incident with high energy, the emittance of electrons or positrons is quickly attenuated by light radiation. Therefore, even if the perturbator is excited again, it will not diverge outside the stable region, and the incident charged particles can be repeatedly incident without being lost. In addition, we compared the magnetic flux change over time of Pertavaita with the rotational speed of charged particles.
The rotation speed of charged particles can be made sufficiently slow, making it possible to inject charged particles into a small magnetic resonance type accelerator where the rotation speed of charged particles is high.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically showing an embodiment of the present invention;
Figure 2 shows the central equilibrium orbit, Figure 3 shows the magnetic field distribution, Figure 4 shows the phase diagram of the orbit, Figure 5 shows the magnetic field distribution, Figures 6 and 7 show the orbits, respectively. FIG. 8 is a diagram showing a conventional accelerator, and FIGS. 9 and 10 are diagrams for explaining the operation of the accelerator. 11... Central equilibrium orbit, 12... Incident trajectory, 1
3...Inflector, 14...Partabeta.

Claims (1)

[Claims] 1. An injection device for injecting charged particles into a magnetic resonance accelerator having a circular orbit is equipped with a perturbator that generates a nonlinear magnetic field with an octupole magnetic field as the main focusing component on the orbital plane around a central equilibrium orbit, and Therefore, an unstable resonant orbit in which the frequency of the horizontal betatron oscillation is 1/2 is formed, and a separatrix located inside the unstable resonant orbit is formed, and the strength of the octupole magnetic field is changed over time. An injection device for a magnetic resonance accelerator, characterized in that the charged particles are captured by changing the size of a stable region including the central equilibrium orbit in the separatrix.