JP3774647B2 - Electromagnet and charged particle irradiation device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an electromagnet and a charged particle irradiation apparatus, and more particularly, an electromagnet that excites with alternating current, such as a wobbler electromagnet, a scanning electromagnet, and a synchrotron electromagnet, and a charged particle irradiation apparatus using the electromagnet. It is about.
[0002]
[Prior art]
FIG. 15 discloses an example of use of the wobbler electromagnet disclosed in Japanese Utility Model Laid-Open No. 1-58200, in which 1 is a charged particle beam and 2 is an object to be irradiated placed in an irradiation field of the charged particle beam 1 3 is a wobbler electromagnet (hereinafter referred to as electromagnet), 4 is a treatment table, and 5 is a scatterer that expands the radius of the charged particle beam 1. The wobbler electromagnet 3 includes an X-direction scanning wobbler electromagnet 3a and a Y-direction scanning wobbler electromagnet 3b, and both the electromagnets 3a and 3b have the same structure except that the scanning direction of the charged particle beam 1 is different.
[0003]
FIGS. 16 to 19 explain in detail an example of the structure of the electromagnet 3. FIG. 16 is a schematic perspective view of the electromagnet 3, FIG. 17 is a side view seen from the direction of arrow XVII in FIG. Is a side view seen from the direction of arrow XVIII in FIG. 16, and FIG. 19 is a side view seen from the direction of arrow XIX in FIG. 16 to 19, 31 is a yoke, 32 and 33 are a pair of magnetic poles connected to the yoke 31, 34 and 35 are excitation coils provided around the magnetic poles 32 and 33, and 36 is An air gap exists between the magnetic poles 32 and 33. The yoke 31 and the pair of magnetic poles 34 and 35 are configured by laminating a large number of iron-based metals having an H-shaped punched hole, for example, steel thin plates, in the ZZ direction of FIG.
[0004]
The exciting coil 34 has a structure in which a coil main body portion 341 and both end portions (hereinafter referred to as coil end portions) 342 are connected in a loop shape, and both the coil end portions 342 can be protruded from the magnetic pole 32. In order to make the entire electromagnet 3 compact as much as possible, it is usually bent to the opposite side of the air gap 36 as shown. The same applies to both coil end portions 352 of the exciting coil 35.
[0005]
Next, the operation of the electromagnet 3 will be described. In the following description, only the case of the magnetic pole 32 and the excitation coil 34 among the magnetic poles 32 and 33 and the excitation coils 34 and 35 will be described, but the same applies to the case of the magnetic pole 33 and the excitation coil 35. To do.
[0006]
FIG. 20 is a cross-sectional view including a magnetic flux diagram of a part of a cross section along the line XX-XX parallel to the line XX in FIG. 16 in a state where the exciting coil 34 is excited. FIG. 21 is a partial cross-sectional view including a magnetic flux diagram at one end of the electromagnet 3 along the XXI-XXI line parallel to the ZZ line of FIG. 16 in a state where the exciting coil 34 is also excited. FIG. 20 shows a magnetic flux diagram in the cross section in the XX line direction, and FIG. 21 shows a coil end portion 342 in the cross section in the YY line direction. A magnetic flux diagram at one end is shown. In FIG. 21, reference numeral 6 denotes a virtual iron core portion having an infinite magnetic permeability used for calculation to obtain the above magnetic flux diagram.
[0007]
Here, if the magnetic field intensity required to deflect the charged particles between the air gaps 36 at a desired angle is B (Tesla) and the distance of the air gaps 36 is g (m), the excitation current I (A) The product NI (A) with the number of coil turns N is approximately as shown in the following equation (1). In order to operate the electromagnet 3, a value obtained by multiplying the resistance value of the coil by the square of the current, that is, the so-called Joule heat. Electric power is required. In addition, μ ₀ in the following formula (1) is a magnetic permeability in vacuum and is 4π × 10 ⁻⁷ (H / m).
NI = gB / μ ₀ (1)
[0008]
However, in the electromagnet 3 that is excited by alternating current, in addition to the above, an alternating current loss, particularly an iron loss, occurs in the exciting coil 34 and the yoke 31, and the required power increases due to heat generation as compared with direct current excitation. The iron loss is approximately proportional to the square of the product of the magnetic field in the magnetic pole 32, the area of the magnetic pole 32 in the direction orthogonal thereto, and the AC frequency.
[0009]
Accordingly, as is apparent from FIG. 21, the amount of leakage magnetic field lines extending in the horizontal direction on the same figure, particularly, the amount of leakage magnetic field lines extending in the horizontal direction from the tip of the magnetic pole 32 is large. For this reason, the conventional electromagnet 3 has a problem that the iron loss is extremely large. Since the conventional electromagnet 3 is configured as described above, it is an amount proportional to the product of the magnetic field intensity that can be generated in the air gap 36 and the length L (see FIG. 17) of the yoke 31 or the magnetic pole 32. The deflection capability for the charged particle beam 1 in FIG. 15 is determined. Further, when the electromagnet 3 is mounted on a rotary charged particle irradiation apparatus commonly called a gantry, it is required to be as small as possible, and particularly to reduce its total length L. Therefore, conventionally, both the coil end portions 342 of the exciting coil 34 are bent to reduce the amount of protrusion from the yoke 31 and the like, thereby reducing the length L. However, in order to further shorten the length of the electromagnet 3, it is necessary to increase the magnetic field strength, in other words, to increase the current density. However, this increases the heat generation due to the iron loss and causes a significant increase in required power. As a result, it is difficult to reduce the size of the electromagnet 3 itself and the size of the charged particle irradiation apparatus on which the electromagnet 3 is mounted. There's a problem.
[0010]
[Problems to be solved by the invention]
In view of the above-described conventional problems, an object of the present invention is to propose an electromagnet with less iron loss than before and a charged particle irradiation apparatus equipped with the electromagnet.
[0011]
[Means for Solving the Problems]
The electromagnet of the present invention is (1) an electromagnet having a yoke, a magnetic pole provided adjacent to the yoke and constituting a magnetic circuit through a gap, and an excitation coil provided around the magnetic pole. The end portion of the coil is bent to the gap side so as to cover the tip surface of the side surface of the end portion of the magnetic pole.
[0012]
(2) In the above (1), the bent end portion of the exciting coil is in contact with the tip surface of the magnetic pole.
[0013]
In (3) above (1), the heating prevention portion formed by stacking the small sheet of ferrous metals the generation of the eddy current in the direction of suppressing the location where heat is generated based on the eddy current in the above SL pole It is what you have.
[0014]
(4) In the above (3), the heat generation preventing portion is provided at the tip of the side surface of the end of the magnetic pole.
[0015]
(5) In the above (3) or (4), the magnetic pole is configured by laminating thin sheets of iron-based metal, and an angle formed by a laminating direction of the small thin plate in the heat generation prevention unit and a laminating direction of the thin plate in the magnetic pole. Is from 30 ° to 90 °.
[0016]
(6) In the above (1) or (3), the exciting coil has a structure in which a coil main body and the end portions on both sides of the coil main body are coupled in a loop shape. The cross section orthogonal to the length direction of the coil main body portion is a rectangle, and the long side of the rectangle is arranged so as to be in contact with or close to the side surface of the bank portion of the magnetic pole or the inner surface of the yoke.
[0017]
(7) In the above (1) or (3), a plurality of pairs of the magnetic poles are provided, and the excitation coil is provided in each magnetic pole pair.
[0018]
The electromagnet of the present invention is a charged particle irradiation apparatus using (8) the electromagnet according to any one of (1) to (7) for scanning of a charged particle beam.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
In the following embodiments, the same parts as those in FIGS. 15 to 21 may be denoted by the same reference numerals, and description of those parts may be omitted.
[0020]
Embodiment 1 FIG.
FIGS. 1-7 demonstrates Embodiment 1 in the electromagnet of this invention. In the following description, only one side of the magnetic poles 32 and 33, the excitation coils 34 and 35, or the heat generation prevention units 321 and 331 described later may be described, but in such a case, the same applies to the other side. This also applies to the other side.
[0021]
1 is a schematic perspective view of the electromagnet 3, FIG. 2 is a side view seen from the direction of arrow II in FIG. 1, FIG. 3 is a side view seen from the direction of arrow III in FIG. 5 is a partially enlarged perspective view of FIG. 1. FIG. 6 is a cross-sectional view taken along line VI-VI parallel to line XX of FIG. FIG. 7 is an end view of the electromagnet 3 along the VII-VII line parallel to the ZZ line in FIG. 1 when the exciting coil 34 is excited. It is sectional drawing corresponding to the said FIG. 21 including the magnetic flux diagram in a part. 6 shows a magnetic flux diagram in the cross section in the XX line direction, and FIG. 7 shows the coil end portion 342 of the exciting coil 34 in the cross section in the YY line direction. A magnetic flux diagram at one end of the electromagnet 3 is shown.
[0022]
1 to 7, reference numeral 321 denotes a heat generation prevention portion provided at each tip portion of both ends of the magnetic pole 32, 331 denotes a heat generation prevention portion provided at each tip portion of both ends of the magnetic pole 33, and in FIG. It is a virtual iron core portion having an infinite permeability used for calculation to obtain the above magnetic flux diagram. FIG. 5 shows a state where only the heat generation prevention unit 321 is removed in order to facilitate understanding of the structure and installation method of the heat generation prevention units 321 and 331.
[0023]
The first embodiment is different from the prior art shown in FIGS. 16 to 21 in two points, that is, the shape and installation method of the excitation coils 34 and 35, and having the heat generation prevention portions 321 and 331. The same.
[0024]
Hereinafter, the structure and operation of the two points different from the prior art of the first embodiment will be described in detail. The excitation coil 34 has a structure in which a coil body 341 and both coil ends 342 are connected in a loop shape as in the prior art, but both coil ends 342 are bent outward in the prior art. On the other hand, in the first embodiment, it is bent toward the air gap 36 so as to cover each tip of the end side surface 322 of the magnetic pole. At that time, as shown in FIG. 6, the coil main body 341 is installed in contact with the wall 311 orthogonal to the magnetic pole 32 of the yoke 31, while the coil end 342 is as shown in FIG. 7. Are bent so as to be in direct contact with the tip of the side surface 322 of the end portion of the magnetic pole 32.
[0025]
In FIG. 1, h is the height of the magnetic pole 32, w is the width of the coil end 342, and the tip of the end side 322 is covered with the coil end 342 having the width w. Become. The same applies to the excitation coil 35 except that the bending direction of both coil ends 352 is opposite to that of the excitation coil 34.
[0026]
In FIG. 5, as shown in the figure, a part of the tip portion at both ends of the magnetic pole 32 is cut out in a rectangular parallelepiped shape, and the heat generation preventing portion 321 (not shown in FIG. 5) has the cutout. It is provided so as to be filled (see FIGS. 1 to 4 and 7). The tip portions at both ends of the magnetic pole 33 are also partially cut out in the same manner as described above, and the heat generation preventing portion 331 is provided there in the same manner as described above. At that time, as described above, the yoke 31, the magnetic pole 34, and the magnetic pole 35 are formed by laminating a large number of iron-based metals having an H-shaped punched hole, for example, steel thin plates in the ZZ direction of FIG. Since it is comprised, the heat_generation | fever prevention parts 321 and 331 are laminated | stacked in the direction orthogonal to the said ZZ direction by laminating | stacking many small sheets of iron-type metals, such as steel.
[0027]
Next, operations and effects of the first embodiment will be described. As described above, in the prior art, the amount of leakage magnetic field lines extending in the horizontal direction from the tip of the magnetic pole 32 is large, and the conventional electromagnet 3 has a problem that the iron loss is extremely large. On the other hand, in the first embodiment, both coil end portions 342 of the exciting coil 34 are bent toward the air gap 36 so as to cover the front end portion of the end side surface 322 of the magnetic pole 32, and the heat generation preventing portion is provided at the front end portion. By providing 321, as is apparent from a comparison between FIG. 7 and FIG. 21, in FIG. 7, the amount of leakage magnetic field lines extending in the horizontal direction from the tip of the magnetic pole 32 is remarkably reduced. In other words, it can be seen that the iron loss is reduced.
[0028]
In the first embodiment, both coil end portions 342 of the exciting coil 34 are bent so as to be in direct contact with the tip end portions of the end side surfaces 322 of the magnetic pole 32. In the present invention, such direct contact is not always essential, but it is effective in further reducing the amount of magnetic field lines extending in the horizontal direction. The action of reducing the amount of leakage magnetic field lines extending in the horizontal direction by the heat generation prevention part 321 is formed by laminating a large number of small iron-based metal plates in the direction perpendicular to the ZZ direction. Based on that. Such a laminated structure has an effect of greatly reducing iron loss and heat generation based on this iron loss by shielding magnetic lines that are likely to leak in the ZZ direction. As a result, the above-described effects can be obtained.
[0029]
In the first embodiment, means for bending both end portions 342 of the exciting coil 34 to the air gap 36 side and both means for installing the heat generation preventing portion 321 are employed. However, in the present invention, both means are used. Even if they are adopted individually, they have the action and effect of reducing iron loss. In the above description, the operational effects of the excitation coil 34 and the heat generation prevention unit 321 have been described. The operational effects of the excitation coil 35 and the heat generation prevention unit 331 are the same as described above.
[0030]
Embodiment 2. FIG.
FIG. 8 is a magnetic flux diagram corresponding to FIG. 6 in the cross section in the XX line direction in FIG. 1 for explaining the second embodiment as an example of the electromagnet of the present invention. In the second embodiment, as shown in FIG. 8, the coil main body 341 of the exciting coil 34 is installed in contact with a wall 312 parallel to the magnetic pole 32 of the yoke 31 and is not shown. The coil main body portion 351 of the coil 35 is also different in that it is placed in contact with a wall parallel to the magnetic pole 33 of the yoke 31, and the other configuration is the same as that of the first embodiment.
[0031]
Embodiment 3 FIG.
FIG. 9 illustrates a third embodiment as an example of the electromagnet of the present invention, and is a magnetic flux diagram corresponding to FIG. 6 in the cross section in the XX line direction in FIG. In the third embodiment, as shown in FIG. 9, the coil main body 341 of the exciting coil 34 is installed in contact with the side wall 323 of the magnetic pole 32, and the coil main body of the exciting coil 35 (not shown). 351 also differs in that it is installed in contact with the bank portion side surface 333 of the magnetic pole 33, and the other configuration is the same as that of the first embodiment.
[0032]
An object of the present invention is to reduce iron loss. Here, copper loss will be described. As is well known, the copper loss is approximately proportional to the square of the product of the current flowing through the exciting coils 34 and 35, the strength of the magnetic field crossing the current, its cross-sectional area, and the frequency of the alternating current. Therefore, when comparing FIG. 6 of the first embodiment, FIG. 8 of the second embodiment, FIG. 9 of the third embodiment, and FIG. 20 of the prior art, the sectional area of the strands forming the exciting coils 34 and 35 is compared. 6, 8, and 9, it is clear that the number of magnetic flux lines intersecting with the coil main body 341 is smaller than that in FIG. This is based on the fact that the coil main body portions 341 and 351 of the exciting coils 34 and 35 are present at the positions described above. Therefore, since Embodiments 1 to 3 are smaller not only in the iron loss but also in the copper loss, it is possible to further reduce the size of the electromagnet.
[0033]
Embodiment 4 FIG.
10 to 13 are diagrams for explaining an electromagnet according to a fourth embodiment of the present invention. FIG. 10 is a schematic perspective view of the electromagnet, and FIG. 11 is a side view seen from the direction of arrow XI in FIG. 12 is a side view seen from the direction of arrow XII in FIG. 10, and FIG. 13 is a side view seen from the direction of arrow XIII in FIG.
[0034]
In the fourth embodiment, both coil end portions 342 of the exciting coil 34 are bent so as to pass through the air gap 36 and cover the respective front end portions of the respective end side surfaces 332 of the magnetic pole 33 and to be in direct contact with the front end portions. The coil end portions 352 of the exciting coil 35 also pass through the air gap 36, but cover the respective tip portions of the end side surfaces 322 of the magnetic pole 32 in a state of overlapping the coil end portion 342 of the exciting coil 34. Is bent. A space is provided between the coil end portion 342 and the coil end portion 352 so that a conduit that passes through the air gap 36 and becomes a passage for the charged particle beam can be installed.
[0035]
The coil end portion 352 of the exciting coil 35 is not in contact with the tip end portion of the end side surface 322 of the magnetic pole 32 due to the presence of the coil end portion 342 located on the inside thereof, so that the iron loss is higher than in the case of the first embodiment. However, there is still a large iron loss reduction effect compared with the prior art. The fourth embodiment is suitable when the bending lengths of the coil ends 342 and 352 of the exciting coils 34 and 35 are long.
[0036]
Embodiment 5. FIG.
FIG. 14 illustrates a fifth embodiment of the electromagnet of the present invention, and is a perspective view of a heat generation prevention portion 331a used in place of the heat generation prevention portion 331 used in the first embodiment. The heat generation preventing portion 331a is composed of a central heat generation prevention portion 331a-1 and heat generation prevention portions 331a-2 and 331a-3 on both sides thereof. Each of the above three portions is formed by laminating a large number of small thin plates of iron-based metal such as steel, and the heat generation preventing portion 331a-1 includes the small thin plate as ZZ in FIG. The heat generation preventing portions 331a-2 and 331a-3 are stacked in a direction of 45 ° with respect to the ZZ direction. Iron loss can be reduced even if the stacking direction of the corner portion of the heat generation preventing portion 331a is set to an inclination direction such as 45 ° with respect to the ZZ direction as described above.
[0037]
As mentioned above, although this invention was demonstrated in detail by above-described Embodiment 1-5, this invention includes not only these Embodiment but a various deformation | transformation form in the technical scope. Hereinafter, some examples of such modifications will be conceptually described.
[0038]
First, the end portion (coil end portion) of the exciting coil is bent toward the air gap so as to cover the front end surface of the end surface of the magnetic pole. Generally, it may be a half region on the tip side of the height of the side surface of the end portion of the magnetic pole (in the case of FIG. 1, the portion of h / 2 on the tip side of the height h of the magnetic pole 32). In the case of the first embodiment, the substantially central portion of the h / 2 portion is covered with the coil end portion 342 having a width w. Since it has a dimension approximately proportional to the size, it is sufficient that an arbitrary portion of the above-described region is covered with the width w, and if it is about 10% of the width w, the gap may be protruded even by such protrusion. As long as a space that can be provided with a conduit that passes through the tube and serves as a path for the charged particle beam is normally secured, it is allowed.
[0039]
In the present invention, the heat generation preventing portion is not limited to the tip portion on the side surface of the end portion of the magnetic pole, and may be provided at any location where heat generation based on eddy current in the magnetic pole occurs. Further, the heat generation prevention unit may be configured by a plurality of portions in which the stacking directions of the small thin plates are different from each other as in the fifth embodiment, and the entire thin thin plate is stacked in a certain direction. Also good. Furthermore, the angle formed by the stacking direction of the small thin plate and the stacking direction of the thin plate at the magnetic pole may be in the range of 30 ° to 90 °. In addition to the wobbler electromagnet, examples of the electromagnet of the present invention include a scanning electromagnet, a synchrotron electromagnet, and other electromagnets that increase or decrease the strength of the magnetic field when excited by an alternating current.
[0040]
As the charged particle irradiation apparatus of the present invention, at least two of the various electromagnets described above, or a total of two of each of the two types, as shown in FIG. What was employ | adopted as an object for direction scanning is illustrated.
[0041]
【The invention's effect】
The electromagnet of the present invention is (1) an electromagnet having a yoke, a magnetic pole provided adjacent to the yoke and constituting a magnetic circuit through a gap, and an excitation coil provided around the magnetic pole. Since the end of the coil is bent to the gap side so as to cover the front end surface of the end surface of the magnetic pole, the iron loss is less than that of the conventional electromagnet, and therefore the electromagnet of the present invention. For example, in a charged particle irradiation apparatus, it is possible to employ a shorter magnetic pole than conventional ones for scanning that requires a charged particle beam, in other words, a shorter electromagnet, and as a result, it has become increasingly stronger recently. It can meet the demand for miniaturization of charged particle irradiation devices and the like.
[0042]
(2) In the above (1), if the bent end portion of the exciting coil is in contact with the tip end surface of the magnetic pole, the iron loss can be further reduced.
[0043]
The (3) above (1), the upper Symbol preventing heat generation portion which is formed by laminating a small sheet of ferrous metals the generation of the eddy current in the direction of suppressing the location where heat is generated based on the eddy current in the pole Therefore, the iron loss of the electromagnet is small as in the invention of (1), and there is an effect similar to that of the invention of (1).
[0044]
(4) In (3) above, the heat generation preventing portion is provided at the tip of the side surface of the end of the magnetic pole. (5) In (3) or (4), the magnetic pole is And the angle formed by the stacking direction of the small thin plate in the heat generation prevention portion and the stacking direction of the thin plate in the magnetic pole is set to 30 ° to 90 °. There is an effect that can be further reduced.
[0045]
(6) In the above (1) or (3), the exciting coil has a structure in which a coil main body and the ends on both sides of the coil main body are coupled in a loop shape. The cross section perpendicular to the length direction of the coil main body is rectangular, and the long side of the rectangle is arranged so as to be in contact with or close to the side of the bank of the magnetic pole or the inner surface of the yoke. As compared with the conventional electromagnet, there is less copper loss in addition to iron loss, and therefore, it is possible to meet the demand for further miniaturization of the electromagnet, and hence further reduction of the charged particle irradiation device and the like.
[0046]
(7) In the above (1) or (3), when a plurality of pairs of the magnetic poles are provided and the excitation coil is provided in each magnetic pole pair, various electromagnets with less iron loss can be obtained. it can.
[0047]
The electromagnet of the present invention is the charged particle irradiation apparatus (8) because the electromagnet according to any one of (1) to (7) is used for scanning a charged particle beam. There is an effect described in the invention.
[Brief description of the drawings]
FIG. 1 is a schematic perspective view of Embodiment 1 of an electromagnet of the present invention.
FIG. 2 is a side view seen from the direction of arrow II in FIG.
FIG. 3 is a side view seen from the direction of arrow III in FIG.
4 is a side view seen from the direction of arrow IV in FIG. 1. FIG.
FIG. 5 is a partially enlarged perspective view of FIG. 1;
6 is a partial cross-sectional view including a magnetic flux diagram along line VI-VI in FIG. 1;
7 is a partial cross-sectional view including a magnetic flux diagram along a line VII-VII in FIG. 1;
8 is a partial cross-sectional view including a magnetic flux diagram corresponding to FIG. 6 of Embodiment 2 of the electromagnet of the present invention. FIG.
FIG. 9 is a partial cross-sectional view including a magnetic flux diagram corresponding to FIG. 6 of Embodiment 3 of the electromagnet of the present invention.
FIG. 10 is a schematic perspective view of a fourth embodiment of the electromagnet of the present invention.
11 is a side view seen from the direction of arrow XI in FIG.
12 is a side view seen from the direction of arrow XII in FIG.
13 is a side view seen from the direction of arrow XIII in FIG.
FIG. 14 is a perspective view of a heat generation prevention unit used in Embodiment 5 in the electromagnet of the present invention.
FIG. 15 is an explanatory diagram of a usage example of a conventional electromagnet.
FIG. 16 is a schematic perspective view of a conventional wobbler electromagnet.
FIG. 17 is a side view seen from the direction of arrow XVII in FIG.
18 is a side view seen from the direction of arrow XVIII in FIG.
19 is a side view seen from the direction of arrow XIX in FIG.
20 is a partial cross-sectional view including a magnetic flux diagram along line XX-XX in FIG. 16;
FIG. 21 is a partial cross-sectional view including a magnetic flux diagram along the line XXI-XXI in FIG. 16;
[Explanation of symbols]
1 charged particle beam, 3 electromagnet, 31 yoke, 32 magnetic pole, 33, magnetic pole,
321 Heat generation prevention part, 331 Heat generation prevention part, 34 Excitation coil,
341 Coil body, 342 Coil end, 35 Excitation coil,
351 Coil body, 352 Coil end, 36 Air gap.

Claims (8)

In an electromagnet having a yoke, a magnetic pole provided adjacent to the yoke and constituting a magnetic circuit through a gap, and an exciting coil provided around the magnetic pole, the end of the exciting coil An electromagnet which is bent toward the gap side so as to cover a front end surface of an end side surface. The electromagnet according to claim 1, wherein an end portion of the bent exciting coil is in contact with the tip surface of the magnetic pole. Claim characterized in that it has a heating prevention portion formed by stacking the small sheet of ferrous metals direction to suppress the generation of the eddy currents in the portion where heat is generated based on the eddy currents in the upper Symbol pole 1 The electromagnet described . 4. The electromagnet according to claim 3, wherein the heat generation preventing portion is provided at a distal end portion of the side surface of the end portion of the magnetic pole. The magnetic pole is configured by laminating thin sheets of iron-based metal, and an angle formed by a laminating direction of the small thin plate in the heat generation prevention unit and a laminating direction of the thin plate in the magnetic pole is 30 ° to 90 °. The electromagnet according to claim 3 or claim 4 to be performed. The exciting coil has a structure in which a coil main body and the end portions on both sides of the coil main body are coupled in a loop shape, and the coil main body has a cross section orthogonal to the length direction of the coil main body. 4. The electromagnet according to claim 1, wherein the electromagnet has a rectangular shape and is arranged so that a long side of the rectangular shape is in contact with or close to the side surface of the bank portion of the magnetic pole or the inner surface of the yoke. 4. The electromagnet according to claim 1, wherein a plurality of pairs of the magnetic poles are provided, and the exciting coil is provided in each magnetic pole pair. A charged particle irradiation apparatus using the electromagnet according to any one of claims 1 to 7 for scanning of a charged particle beam.

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