JPH11214198A - Linear accelerator and installation method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compact charged particle accelerator which simplifies the alignment adjustment work of a four pole electromagnet and a beam monitor in the charged particle accelerator and an installation method therefor. SOLUTION: A charged particle accelerator is provided with an arrangement face on which two four pole electromagnets 2, 3 can be put in opposition and in which a plurality of four pole electromagnet surface plates 10 fixed by adjusting positions of the four pole electromagnets and a charged particle beam position monitor 4 in advance are arranged in a charged particle running track. Preferably, a mechanism 8 adjusting positions of the four pole electromagnet surface plates 10 at predetermined positions on a charged particle accelerator pedestal 9 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear accelerator having a quadrupole electromagnet apparatus and a method of installing the linear accelerator, and more particularly to a linear accelerator having a plurality of quadrupole electromagnets, which can reduce the manufacturing cost and adjust the alignment. The present invention relates to a linear acceleration device and a method of installing the linear acceleration device which can be easily performed.

[0002]

2. Description of the Related Art In a linear accelerator, quadrupole electromagnets are provided at various places in a charged particle orbit in order to stabilize the movement of a beam. The quadrupole electromagnet has a convergence or divergence action by Lorentz force in the direction orthogonal to each of the charged particles coming off the center, and by alternately arranging a pair of quadrupole electromagnets in which the N pole and the S pole are exchanged, As a result, the beam has a strong convergence in both directions.

For this reason, key points in the linear accelerator are:
Normally, two or three quadrupole electromagnets are provided continuously, but each must be accurately aligned with the electron trajectory. It is confirmed using a beam monitor that the charged particle beam is adjusted to an accurate position. Some beam monitors include a screen inserted into the orbit at the time of adjustment and confirmation by observing the irradiation position of the beam.

In one example of an electron linac type free electron laser generator using an RF electron gun, electrons which are charged particles emitted from the RF electron gun are turned by an α-electromagnet, accelerated by an accelerator, and accelerated by an accelerator. The laser beam is guided to an optical resonator composed of a total reflection mirror and an output mirror disposed with an undulator interposed therebetween by the bending electromagnet and amplifies the laser light synchronously, and then is rejected into the beam damper by the bending electromagnet.

In order to maintain the electron beam in the transport system during this time, for example, between the RF electron gun and the α-electromagnet, between the α-electromagnet and the accelerator, between the accelerator and the deflection electromagnet, and between the deflection electromagnet and the undulator A pair of quadrupole electromagnets is inserted between them. In addition, one quadrupole electromagnet is provided between the first deflection electromagnet and the second deflection electromagnet in order to suppress diffusion of energy dispersion in the deflection direction. A beam monitor is provided upstream and downstream of the accelerator, between the first and second bending electromagnets, and before and after the undulator to manage the position of the electron beam.

Conventionally, the quadrupole electromagnets and the beam monitors have been separately installed, so that it is necessary to adjust the alignment of the beam transport system by the number provided in the linear accelerator. For this reason, the installation work of the linear accelerator had to dispatch a highly skilled worker to the site and perform time-consuming alignment adjustment for many devices. In addition, it is necessary to secure a predetermined working space before and after the equipment for the alignment adjustment, which results in having an unnecessary equipment length for the purpose of operation.

[0007]

An object of the present invention is to simplify the alignment adjustment work by devising a method of installing a quadrupole electromagnet and a beam monitor in a linear accelerator.

[0008]

SUMMARY OF THE INVENTION In order to solve the above problems, a linear accelerator according to the present invention adjusts the position of a quadrupole electromagnet provided with an arrangement surface on which two quadrupole electromagnets can be mounted opposite to each other. A plurality of fixed and operated quadrupole electromagnets are arranged in a charged particle traveling orbit. Further, a quadrupole electromagnet surface plate which is equipped with a charged particle beam position monitor and whose position is adjusted in advance may be included.
It is preferable that a mechanism for adjusting the position of the entirety of the quadrupole electromagnet base plate be provided at a predetermined position on the linear accelerator base.

In order to solve the above-mentioned problems, a method of installing a linear accelerator according to the present invention comprises mounting a quadrupole electromagnet on a quadrupole electromagnet surface on a quadrupole electromagnet base plate, and mounting the quadrupole electromagnet on the basis of the quadrupole electromagnet base plate. After the position adjustment is performed, the quadrupole electromagnet is placed in the charged particle traveling trajectory by engaging the quadrupole electromagnet base plate with the position fixing mechanism on the linear accelerator base. Further, the quadrupole electromagnet surface plate whose position has been adjusted may be installed in a position adjustment mechanism for the beam axis provided in the linear accelerator mount to adjust the beam axis position. The charged particle beam position monitor may be mounted on the quadrupole electromagnet base plate, and the position of the charged particle beam position monitor may be adjusted with the quadrupole electromagnet based on the quadrupole electromagnet base plate.

According to the present invention, the quadrupole electromagnets provided at a plurality of locations are mounted not only at the place where the charged particle accelerator is installed but also at a manufacturing factory or the like by mounting the necessary quadrupole electromagnets on a surface plate to align the quadrupole electromagnets. What is necessary is just to make an adjustment to the surface plate, to make a fixed one on the surface plate, and to arrange the whole surface plate on which the quadrupole electromagnet is mounted at a predetermined position on the linear accelerator frame. Therefore, it is possible to perform the alignment work of the quadrupole electromagnet, which requires advanced technology and takes time and effort, in the manufacturing factory where the working environment is well-equipped, and the alignment of the linear accelerator can be performed on the device base without deteriorating the alignment accuracy. Alignment adjustment work can be simplified and facilitated, and costs can be reduced. Further, since the alignment adjustment can be performed on the surface plate, a space for adjustment work required at the time of assembling the linear accelerator can be omitted, and the entire apparatus can be further downsized.

Further, in the linear accelerator according to the present invention, since the surface plate on which the quadrupole electromagnets are to be arranged has basically the same shape, the manufacturing cost can be reduced by mass production effect by unifying the specifications and collectively manufacturing them. It is possible to do. In addition, the beam monitor required to check the position of the charged particle beam needs to accurately detect the beam axis, so the positional relationship with the quadrupole electromagnet is a problem. It is preferable to perform alignment adjustment together with the quadrupole electromagnet.

[0012]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a linear accelerator according to the present invention. FIGS. 1 to 3 are perspective views showing a use form of a quadrupole electromagnet base plate used in the present invention, FIG. 4 is a plan view showing a position adjustment method of the quadrupole electromagnet base plate in the present invention, FIG. FIG. 6 is a plan view showing a small linac assembled on a gantry as an embodiment of the linear accelerator according to the present invention.

[0013]

FIG. 1 shows an electron linac-type free electron laser generator to which the linear accelerator of the present invention is applied, which is disposed between an α electromagnet and an accelerator, between an accelerator and a bending electromagnet, and between a deflection electromagnet and an undulator. Quadrupole electromagnet platen 10
It is a perspective view showing -a. Quadrupole electromagnet surface plate 10-
1A, a first quadrupole electromagnet 2 and a second quadrupole electromagnet 3 are mounted on a base 1. Further, a beam position monitor 4 is provided between the two electromagnets. The charged particle beam is arranged so as to pass near the center axis of the beam transport tube 5 that passes through the axis of the first quadrupole electromagnet 2 and the second quadrupole electromagnet 3. In the figure, a part of the surface plate 1 is cut away so that the beam position monitor 4 can be seen.

The beam position monitor 4 is attached to a flanged nozzle pipe 51 provided below the transport pipe 5 with a mounting flange. The nozzle tube 51 is supported on the upper surface of the trapezoidal monitor support 6. The monitor support base 6 has an edge portion at the hem and is fixed to the surface plate 1 in a state where the position can be adjusted by screws or the like. The pneumatic drive cylinder for taking the target in and out of the transport pipe 5 is fixed so that the relative positional relationship with the support flange does not change. The support flange is supported by a support rod hanging from the mounting flange. The support flange and the mounting flange are connected in a bellows structure, and the position of the target is adjusted so that the center position of the charged particle beam can be accurately detected. Vacuum can be maintained.

By operating the pneumatic drive cylinder, the target can be inserted into the charged particle beam to confirm the beam irradiation position, or to be retracted to return to the operation state. Further, a viewing hole 52 for confirming the position and orientation of the target and observing the position of the charged particles is provided beside the transport pipe 5. Flanges 53 for connecting to the upstream and downstream beam transport tubes are attached to both ends of the transport tube 5. Flange 5 for easy connection of elements
The bellows tube 54 may be inserted before 3. In such a configuration, the transport pipe 5 is supported by the quadrupole electromagnet, and the position of the nozzle pipe 51 is supported by the monitor support 6 to maintain the posture of the pipe.

The first quadrupole electromagnet 2 and the second quadrupole electromagnet are arranged such that the N pole and the S pole are exchanged, so that the convergence action and the divergence action are interchanged in the vertical and horizontal directions. Therefore, the charged particle beam passing through the beam transport tube 5 is subjected to, for example, a diverging action in the horizontal direction by the first quadrupole electromagnet 2, and then to a convergence action by the second quadrupole electromagnet 3 to end up with a plane perpendicular to the axis. It becomes a charged particle beam with very strong energy concentration around the axis inside.

If the axis of the charged particle beam is deviated from the center of the magnetic field formed around the central axis by the quadrupole electromagnet, the beam axis drifts. Therefore, it is necessary to first adjust the alignment so that the axes of both electromagnets are on the same straight line. In addition, adjustment is performed so that the center axis of the beam transport tube 5 overlaps the axis of the electromagnet. Further, the center of the screen of the beam position monitor 4 used to confirm the position where the charged particle beam actually passes when assembled in the linear accelerator is adjusted so that the center axis of the beam transport tube 5 coincides. It is preferable to keep it.

The quadrupole electromagnet is installed on the electromagnet support 7. If the manufacturing accuracy is high, the dimensional accuracy can be ensured simply by assembling, but the level can be adjusted when installing the base plate 1 with some errors. The alignment adjustment with respect to the beam axis is performed after being placed on the surface plate 1, and after the adjustment, it is fixed on the surface plate with a bolt nut or the like (not shown).
Specifically, the quadrupole electromagnet is divided into upper and lower
After placing the lower part of the quadrupole electromagnets on the electromagnet support 7 arranged at a predetermined position, adjust the center axis position by passing over the beam transport tube 5, and then cover each upper part and fix them. and so on. Also, the marking lines 21 and 31 are imprinted immediately above the axial position of the quadrupole electromagnet or at the same level position.
Alignment adjustment and level adjustment can also be performed by using.

These alignment adjustments can be carried out in an assembly factory where an actual charged particle beam cannot be used, after the quadrupole electromagnets 2, 3, the monitor 4, the transport pipe 5, etc. are assembled on the surface plate 1, the ordinary alignment adjustment is performed. The method can be performed with high accuracy. In addition, quadrupole electromagnets having the same configuration are used in several places in the linear accelerator, and these can be manufactured by the same procedure using the same members.

FIG. 2 shows a quadrupole electromagnet platen 10-b disposed between the RF electron gun and the α electromagnet of the free electron laser generator.
FIG. In this figure, the same elements as those in FIG. 1 are assigned the same reference numerals to clarify the difference from the quadrupole electromagnet base 10-a in FIG. In this usage method, a first quadrupole electromagnet 2 and a second quadrupole electromagnet 3 are mounted on a surface plate 1, and the first quadrupole electromagnet 2 and the second quadrupole electromagnet 3
Are arranged so as to pass near the central axis of the beam transport pipe 5 penetrating through the axis, but a beam position monitor is not provided. This is because it is not necessary to control the axial center position of the charged particle beam at this position.

The platen 1 used here may be the same as the platen shown in FIG. 1 and can be manufactured collectively. Also,
The method of adjusting the alignment between the first quadrupole electromagnet 2 and the second quadrupole electromagnet 3 may be exactly the same as that in FIG.

FIG. 3 is a perspective view showing a quadrupole electromagnet base plate 10-c disposed between a pair of bending electromagnets of the free electron laser generator. Also in this drawing, the same elements as those in FIG. 1 are denoted by the same reference numerals to clarify the difference from the quadrupole electromagnet base plate 10-a in FIG. In this usage method, one quadrupole electromagnet 2 and a beam position monitor 4 are mounted on the surface plate 1, and are arranged so that the center axis of the beam transport tube 5 is located at the center of the quadrupole electromagnet 2. At this position, it is sufficient to remove the energy dispersion diffused in one direction by the deflection magnet. It is desirable to provide a beam position monitor 4 to monitor the state of diffusion.

The platen 1 used here may be the same as the platen shown in FIG. The method of adjusting the alignment between the quadrupole electromagnet 2 and the beam position monitor 4 is exactly the same as that in FIG.

FIG. 4 is a plan view for explaining an example of a method of disposing the quadrupole electromagnet base plate in the linear accelerator, and FIG. 5 is an elevation view thereof. In the example of this figure, a vacuum valve 11 is provided upstream of the quadrupole electromagnet base plate, and a beam current monitor 12 is provided downstream. Connection with these devices is performed by vacuum flanges 53 provided at both ends of the beam transport tube 5. Although the figure shows the quadrupole electromagnet base plate 10-a equipped with a pair of quadrupole electromagnets and a beam position monitor, any quadrupole electromagnet base plate is installed in the same manner. To represent. The quadrupole electromagnet platen 10 on which the quadrupole electromagnets 2 and 3 and the beam position monitor 4 are mounted and alignment adjustment is completed is mounted on the platen position adjustment device 8. The platen position adjusting device 8 is arranged at a predetermined position on the gantry 9 of the linear acceleration device, and can adjust the height and the inclination of the surface with screw rods 81 provided at four corners.

The platen 1 is placed on the surface of the platen position adjusting device 8.
A pair of position adjusters abutting on each side surface is provided, and the position adjusters 82 and 83 can adjust the position of the entire quadrupole electromagnet base plate 10 on which the quadrupole electromagnets and the like are fixed on the adjustment surface. . The final alignment adjustment of the quadrupole electromagnets 2 and 3 and the beam position monitor 4 with respect to the linear accelerator rack 9 can be performed without changing the positional relationship between the quadrupole electromagnets and the like by adjusting the position of the quadrupole electromagnet base plate 10. It can be carried out.

In FIGS. 4 and 5, the platen position adjusting device 8 is fixed to the linear accelerator base 9, and the final alignment adjustment of the quadrupole electromagnet platen 10 is performed by the platen position adjusting device 8. The platen position adjusting device 8 is configured to be attached to the quadrupole electromagnet platen 10 and has a projection (not shown) at a predetermined position on the linear accelerator base 9 to adjust the position of the platen. It may be fixed to a fixed position by engaging with a hole (not shown) provided in the device 8. In this case, before mounting on the linear accelerator base 9, the position adjustment of the component devices on the quadrupole electromagnet surface plate and the position adjustment of the surface plate itself on the surface plate position adjustment device are performed with high accuracy.
By assembling the platen position adjusting device itself to the gantry 9, the alignment adjustment and assembling process at the site can be simplified.

Although a beam current monitor is provided downstream of the quadrupole electromagnet in this figure, a button electrode (not shown) is provided around the beam transport tube 5 on the quadrupole electromagnet platen 1 to measure the beam current. Needless to say, this is acceptable. For example, a beam position monitor can be installed at a position between two quadrupole electromagnets.

FIG. 6 is a plan view of a small linac assembled on a gantry 9 as an embodiment of the linear accelerator according to the present invention. The drawings show only parts directly related to the electron beam transport system for the sake of simplicity, and various utilities such as an RF waveguide and a cooling water pipe, which are not shown, are attached to the actual device. ing.

In this embodiment, the electrons emitted from the RF electron gun are shaped into a highly convergent electron beam by the quadrupole electromagnet base plate 10-b having a pair of quadrupole electromagnets as shown in FIG. Then, it is projected onto the α electromagnet and changes its direction in the axial direction of the accelerator. Before being incident on the accelerator, the electron beam passes through a quadrupole electromagnet base plate 10-a equipped with a pair of quadrupole electromagnets and a beam position monitor as shown in FIG. The axial position of the electron beam when passing between the quadrupole magnets can be detected by a beam position monitor.

The electrons are accelerated by the accelerator, pass through a quadrupole electromagnet base plate 10-a having the same configuration as the entrance of the accelerator, converge, pass through a pair of bending electromagnets, and are guided to the optical resonator. At the position between the two bending magnets, a quadrupole electromagnet base plate 10-c equipped with one quadrupole electromagnet and a beam position monitor as shown in FIG. By doing so, electrons in the electron beam dispersed in the horizontal direction are converged in the axial direction. The position of the electron beam can be known by a beam position monitor.

The optical resonator is composed of a total reflection mirror and an output mirror disposed with an undulator interposed therebetween, and the electron beam is amplified by the undulator in synchronization with the resonance laser light. The generated free electron laser is taken out from the output mirror and used. Before the electron beam enters the undulator, a quadrupole electromagnet platen 10 as shown in FIG.
-A to be converged to a higher degree. The position of the electron beam passing therethrough can be detected by a beam position monitor. After passing through the undulator, the electron beam is deflected from the optical path of the resonator by the bending electromagnet and is discarded by the beam damper.

The position of the electron beam after passing through the undulator can be observed by a beam position monitor. A quadrupole electromagnet is not provided behind the undulator, but if the beam position monitor is fixedly disposed on the above-described quadrupole electromagnet base plate, the effect of omitting the process by standardizing the mounting parts can be expected.

[0033]

As described above, according to the linear acceleration device and the method of installing the same according to the present invention, the installation work can be performed more efficiently by simplifying the alignment adjustment of the quadrupole electromagnet and the beam position monitor on the device mount. be able to. Also, when arranging multiple quadrupole electromagnets,
Since standardized members can be used, construction efficiency is improved. Further, by omitting a space for performing the alignment adjustment, the entire apparatus can be downsized. Further, it is possible to easily cope with a change in operating conditions.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a usage form of a quadrupole electromagnet used in a linear accelerator according to the present invention.

FIG. 2 is a perspective view showing a second use mode of the quadrupole electromagnet base plate used in the linear accelerator according to the present invention.

FIG. 3 is a perspective view showing a third mode of use of the quadrupole electromagnet used in the linear accelerator according to the present invention.

FIG. 4 is a plan view showing a method for adjusting the position of a quadrupole electromagnet platen according to the present invention.

FIG. 5 is an elevation view showing the position adjusting method of FIG. 4;

FIG. 6 is a plan view showing a small linac to which the linear accelerator according to the present invention is applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Surface plate 2, 3 Quadrupole electromagnet 21, 31 Marking line 4 Beam position monitor 5 Beam transport tube 51 Nozzle tube 52 Lookout hole 53 Flange 54 Bellows tube 6 Monitor support stand 7 Electromagnet support stand 8 Surface plate position adjusting device 81 Screw rod 82 , 83 Position adjuster 9 Linear accelerator mount 10-a, b, c Quadrupole platen 11 Vacuum valve 12 Beam current monitor

Claims (10)

[Claims] 1. A plurality of quadrupole electromagnets fixed to a quadrupole electromagnet provided with an arrangement surface on which two quadrupole electromagnets can be mounted opposite to each other and adjusted in advance and arranged in a charged particle traveling orbit. A linear accelerator. 2. A linear accelerator according to claim 1, wherein one of said quadrupole electromagnet base plates is equipped with a charged particle beam position monitor and has been adjusted in advance. 3. The linear acceleration device according to claim 1, wherein a position adjusting mechanism is provided at a position on the linear acceleration device mount where the quadrupole electromagnet surface plate is disposed. 4. The apparatus according to claim 3, wherein the position adjusting mechanism is detachable from the linear accelerator mount.
The linear accelerator as described. 5. A free electron laser device provided with the linear accelerator according to claim 1. 6. A quadrupole electromagnet is mounted on a surface of the quadrupole electromagnet on which the quadrupole electromagnet is arranged, and the mounted quadrupole electromagnet is adjusted in position with reference to the quadrupole electromagnet. A method for installing a linear accelerator, comprising: disposing a quadrupole electromagnet in a charged particle traveling trajectory by engaging with a position fixing mechanism on a gantry. 7. The position fixing mechanism comprises an opening and a pin adjusted so that the quadrupole electromagnet base can be installed on a beam axis on a linear accelerator base in advance, and the opening is engaged with the pin. 7. The method according to claim 6, wherein the quadrupole electromagnet is disposed in the traveling trajectory of the charged particle. 8. The apparatus according to claim 6, wherein said position fixing mechanism further includes a position adjusting mechanism capable of adjusting a position on a linear accelerator frame, and adjusts the position after installing said quadrupole electromagnet. 7. The method for installing a linear accelerator according to 7. 9. A charged particle beam position monitor is mounted on the surface of the quadrupole electromagnet, the position of the quadrupole electromagnet is adjusted, and the position of the charged particle beam position monitor is adjusted with reference to the surface of the quadrupole electromagnet. The method for installing a linear accelerator according to any one of claims 6 to 8. 10. A free electron laser device provided with a linear accelerator installed by the installation method according to claim 6. Description: