JP2004031871A - Electromagnet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electromagnet which generates a prescribed magnetic field distribution by installing permanent magnets within a magnetic field generated by the electromagnet. <P>SOLUTION: Regarding the electromagnet, a required magnetic field distribution is accurately and easily generated and design is facilitated by arranging a pair of the permanent magnets which generate double polar components in an axially symmetrical specified space. It can be applied to a synchrotron which is a perfect circle, a cyclotron, a betatron, and a microtron, etc., as well. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electromagnet for generating a magnetic field that generates a magnetic field, and more particularly to an electromagnet that can be used in industrial fields using electromagnets such as accelerators, MRIs, and motors.
[0002]
[Prior art]
Conventionally, as a method of adjusting the magnetic field of an electromagnet, a method of forming the pole piece of the electromagnet or molding using a field clamp has been well known.
[0003]
[Problems to be solved by the invention]
However, the conventional methods as described above require time to design an ideal magnetic field, and have limitations in shaping a necessary and precise magnetic field.
[0004]
Therefore, the present invention provides an electromagnet capable of forming a precise magnetic field by installing a permanent magnet formed in a magnetic field generated by an electromagnet at a predetermined position and direction in order to generate a necessary and precise magnetic field, An object is to solve the above problems.
According to the present invention, when the electromagnet is a circular electromagnet having axial symmetry, a predetermined magnetic field distribution can be generated by disposing a pair of permanent magnets that generate a dipole component in a specific space that is axially symmetric. Also, as a method of installing a permanent magnet inside the electromagnet, the magnetic field lines created by the permanent magnet generate multi-polar components including quadrupolar components, which allows the magnetic field to be accurately measured. The time required for design can be shortened because it can be generated well and a complicated magnetic field can be decomposed into components.
[0005]
[Means for Solving the Problems]
For this reason, the technical solution adopted by the present invention is:
An electromagnet characterized by forming a required magnetic field distribution by arranging permanent magnets at predetermined positions and inclinations in a magnetic field generated by the electromagnet, in connection with the electromagnet.
Further, the electromagnet is characterized in that, when the electromagnet is a circular electromagnet with axial symmetry, a pair of or more permanent magnets that generate a dipole component are arranged in a specific space with axial symmetry. Further, in the case where a permanent magnet is provided inside the electromagnet, the line of magnetic force generated by the permanent magnet is a multipolar component including a quadrupolar component.
[0006]
Embodiment
Hereinafter, embodiments according to the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view of an electromagnet for a circular synchrotron according to the present embodiment, FIG. 2 is a diagram showing a radial magnetic field distribution on a median plane of a magnetic field generated by the electromagnet, and FIG. 3 is generated by a permanent magnet. Fig. 4 is a diagram of a radial magnetic field distribution of a magnetic field, Fig. 4 is a diagram of a magnetic field distribution created by superposing a magnetic field generated by an electromagnet and a magnetic field generated by a permanent magnet, Fig. 5 is a plan view of an electromagnet provided with a permanent magnet, FIG. 6 is a plan view of a circular synchrotron provided with four-pole magnets made of permanent magnets.
[0007]
In FIG. 1, the electromagnet includes a yoke 1 made of iron, a coil 2, a pole piece 3 made of soft magnetic iron, a permanent magnet 4 and a permanent magnet 5, and trim coils 6, 7, 8, 9, 10, 11; It is circular in plan view. The basic configuration of the electromagnet is the same as the conventional electromagnet.
This electromagnet is used for accumulating an electron beam in the median plane 12, and therefore, it is necessary to shape the radial magnetic field distribution in the median plane as necessary. Conventionally, the necessary magnetic field was generated by adjusting the shape of the pole piece 3 and using a trim coil.
[0008]
That is, the radial magnetic field distribution of the magnetic field formed only by the pole piece 3 and the trim coils 6, 7, 8, 9, 10, and 11 in the electromagnet is as shown in FIG. As is clear from the figure, the magnetic field attenuates as it goes outward due to the effect of the yoke. Preferably, the magnetic field required in this case decays gently to a radius of 200 mm and abruptly decays outside. One way to shape a rapidly decaying magnetic field is to use a field clamp made of iron. However, it is difficult to produce a sufficiently rapid magnetic field attenuation even with a field clamp.
[0009]
For this reason, in the present invention, the permanent magnets 4 and 5 are arranged with a predetermined position and inclination in an electromagnetic field in order to shape the magnetic field distribution to be obtained, so that the magnetic field distribution of the entire electromagnet can be controlled. FIG. 5 is a plan view showing a state where an annular permanent magnet is installed in an electromagnet. In this case, the permanent magnets are arranged as being annularly continuous, but the non-continuous permanent magnets are placed at a predetermined position. It is also possible to arrange with inclination.
The permanent magnets 4 and 5 are arranged in the gap between the pole pieces 3 and are fixed to the upper and lower surfaces and side surfaces of a stainless steel vacuum chamber 13 having a U-shaped cross section, and are arranged as a pair facing the median plane in a ring shape. I do. The distribution of the magnetic field generated by the opposing permanent magnets is widened if the gap is widened, and the influence is widened. However, the magnetic field strength decays. When the width of the permanent magnet is increased, a flat magnetic field distribution is generated. It should be noted that oppositely directed magnetic fields are generated outside the opposing permanent magnets. In this embodiment, the permanent magnet 5 is used to cancel the opposite magnetic field generated by the permanent magnet 5. In addition, the arrangement of the permanent magnets 4 and 5 is not limited to the above-described arrangement, and is not necessarily arranged axially symmetrically. The permanent magnets 4 and 5 may be arranged with their positions and inclinations changed so as to obtain a desired magnetic field distribution. It is possible.
Thus, insertion of a permanent magnet in an electromagnetic field has not been performed conventionally. However, in fact, the magnetic permeability of a permanent magnet is close to that of air, unlike iron. Therefore, the magnetic field generated by the electromagnet is not affected by the permanent magnet. As a result, the magnetic field of the entire electromagnet is a simple superposition of the magnetic field generated by the electromagnet and the magnetic field generated by each permanent magnet. This is very convenient for designing a magnetic field.
[0010]
The white and black curves in FIG. 3 are the radial magnetic field distributions created by the permanent magnets 4 and 5 on the median plane, respectively (the black line in the figure is the magnetic field distribution of the permanent magnet 4, and the white line in the figure is the magnetic field distribution of the permanent magnet 5). Magnetic field distribution). FIG. 4 shows a superposition of the magnetic field distribution of FIG. 3 and the magnetic field distribution generated by the electromagnet of FIG. It can be seen that there is a rapid attenuation outside the magnetic field distribution radius of 200 mm in FIG. As described above, in the present invention, a required magnetic field distribution can be easily designed by a simple superposition of the magnetic field generated by the electromagnet and the magnetic field generated by the permanent magnet.
The electromagnet that generates an ideal magnetic field is not limited to an electromagnet for a synchrotron, but can be applied to an electromagnet such as a cyclotron, a microtron, and a betatron.
[0011]
This technique is not always used to shape the fringe portion of the magnetic field as shown in FIG. It can be used to shape the magnetic field distribution in the central part, and may not be arranged in a ring as an arrangement method. In some cases, it may be placed. One example of such an arrangement is to form a quadrupole magnet that generates a quadrupole component. A four-pole magnet made of a permanent magnet is installed inside the electromagnet, so that electrons and ion beams can be focused.
[0012]
FIG. 6 is a plan view of an example in which a four-pole magnet 20 made of such a permanent magnet is installed in a circular synchrotron 21. The magnetic field is generated perpendicular to the paper. A quadrupole magnet 20 with a permanent magnet is placed on an incident electron trajectory 22 in a magnetic field to converge an electron beam. The electron trajectory 22 is determined by the electromagnet and is not affected by the permanent magnet. The design of the permanent magnet is therefore advantageous in that it can be performed independently and independently of the electromagnet. The installation place of the electromagnet having the permanent magnet as described above is not limited to the incident electron trajectory, but may be installed on the circulating electron trajectory 23 to converge the circulating beam.
It should be noted that the above-described embodiments are merely examples in all respects, and should not be construed as limiting, and the present invention may be embodied in various other forms without departing from the spirit or main features thereof. be able to.
[0013]
【The invention's effect】
According to the present invention as described above,
The electromagnet of the present invention can generate a desired predetermined magnetic field distribution by installing a permanent magnet in a magnetic field generated by the electromagnet, and can reduce a required magnetic field by using a permanent magnet to fine-tune the magnetic field. It can be generated accurately and easily. Specifically, since the magnetic field can be formed by a method of simply superposing the electromagnet magnetic field and the permanent magnet magnetic field, the accuracy is good and the design is easy. In addition, it is possible to achieve excellent effects such as shortening the time required for design because a complicated magnetic field can be decomposed into components.
[Brief description of the drawings]
FIG. 1 is a sectional view of an electromagnet.
FIG. 2 is a diagram showing a radial magnetic field distribution on a median plane of a magnetic field generated by an electromagnet.
FIG. 3 is a diagram showing a radial magnetic field distribution of a magnetic field generated by a permanent magnet.
FIG. 4 is a diagram showing a magnetic field distribution created by superimposing a magnetic field generated by an electromagnet and a magnetic field generated by a permanent magnet.
FIG. 5 is a plan view of an electromagnet provided with permanent magnets.
FIG. 6 is a plan view of a circular synchrotron provided with four-pole magnets made of permanent magnets.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 electromagnet yoke 2 coil 3 pole piece 4 permanent magnet 5 permanent magnet 6 trim coil 7 trim coil 8 trim coil 9 trim coil 10 trim coil 11 trim coil 12 median plane 13 stainless steel vacuum tank 20 electromagnet with 4-pole permanent magnet 21 circular synchrotron 22 Incident orbit 23 Orbiting orbit

Claims (3)

An electromagnet characterized by forming a required magnetic field distribution by arranging permanent magnets at predetermined positions and inclinations in a magnetic field generated by the electromagnet, in connection with the electromagnet. 2. The electromagnet according to claim 1, wherein when the electromagnet is a circular electromagnet with axial symmetry, a pair of or more permanent magnets that generate a dipole component are arranged in a specific space with axial symmetry. 3. 2. The electromagnet according to claim 1, wherein when a permanent magnet is installed inside the electromagnet, magnetic lines of force created by the permanent magnet are multipolar components including quadrupolar components. 3.

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