JP5524494B2 - Magnetic field generator and particle accelerator using the same - Google Patents

Description

  The present invention relates to a magnetic field forming apparatus capable of forming a magnetic field for strong convergence, and an accelerator for accelerating charged particles using the magnetic field forming apparatus.

  As a small accelerator for accelerating particles, a cyclotron described in Patent Document 1 is known. In this accelerator, a plurality of magnetic pole sectors (hills) are arranged in a circumferential direction (circumferential direction) between two disk-shaped magnetic poles, and valleys (gap, valley) are provided between the magnetic pole sectors. The particles are spirally accelerated by the electromagnetic field between the magnetic poles generated by the coil and formed by the magnetic pole sector.

JP 2000-106300 A

In such an accelerator, iron is used in the magnetic circuit for miniaturization and high efficiency, so the maximum magnetic field is about 2 Tesla (T), and at most hydrogen ion particles are about 10 megaelectron volts (MeV / u). It can only be accelerated until it has the following energy, and it can only be used for the production of radiopharmaceuticals for PET (Positron Emission Tomography). Because of the use of iron, it is impossible in principle to accelerate a particle beam with high magnetic rigidity, and a heavy particle beam (carbon hexavalent positive ion ¹² C ⁶⁺⁾ that has recently been recognized for its usefulness in radiation therapy for cancer. Cannot be accelerated enough until they are available for cancer treatment.

  On the other hand, there are currently about 1,000 ionizing radiations of heavy particle beams (carbon) that have an energy of about 400 MeV / u (accelerated to about 70% of the speed of light) and are useful in cancer radiation treatment. Are supplied by a synchrotron accelerator arranged along a circle with a diameter of about 50 meters (m), but this coil system or accelerator has a huge installation cost and a lot of operation costs. Coil cooling, control complexity, large number of operators, and enormous power consumption are enormous.

  Specifically, as of December 2008, two heavy particle synchrotron accelerators are in operation in Japan and one is under construction, but one of the two accelerators in operation has two synchrotrons. It has a size of about 140m x 60m including necessary peripheral devices, and the total initial cost is on the order of several tens of billion yen. It is said that the power cost and the labor cost of operators will be on the order of several billion yen. ing. The other accelerator is about 90 m × 80 m in size including peripheral devices, and the initial cost and other costs are said to be the same as or slightly lower than those described above. In addition, the size of the accelerator under construction and the necessary peripheral equipment is about 60m x 50m, the initial cost will be on the order of hundreds of billions of yen, and the power cost and operator labor cost are expected to be the same as those mentioned above. It is. As of December 2008, there is only one heavy particle synchrotron accelerator in the world other than Germany.

  At such a scale, even though it is useful for cancer treatment, it will not gain momentum, so it is desirable to reduce the size of heavy particle accelerators and reduce running costs. It is conceivable to construct a heavy particle accelerator with a few cyclotrons. However, the magnetic field shaping by the iron core is limited to 1.6T, which does not cause saturation in iron. If a cyclotron that can be accelerated is designed on the assumption of this, a magnet having a pole face (magnetic pole surface) of at least about 13 m in diameter ( 47,000 tons) is required.

  Also, in the cyclotron, it is necessary to form a magnetic field distribution (magnetic field gradient) that increases and decreases in the circumferential direction in order to accelerate particles in a spiral orbit, but the iron bulk (the magnetic pole sector in Patent Document 1) is spaced circumferentially. Even if Hill Valley is formed by placing them side by side, a magnetic field gradient for particle acceleration cannot be formed for a magnetic field exceeding about 2T where iron is saturated. Therefore, a magnetic field distribution that increases or decreases in the circumferential direction of about 6T cannot be formed.

  Therefore, the invention described in claim 1 is a high magnetic field and magnetic field distribution that can be accelerated up to energy that can be used for cancer treatment or the like for heavy particles while being small in size and low in installation cost and operation cost. Formation of a high magnetic field with a radial magnetic gradient corresponding to an increase in mass due to relativistic effects with increasing energy, as well as the strength of a circumferential magnetic field for accelerated particle convergence The object is to provide an apparatus.

  Further, the invention according to claim 5 is small in size even though heavy particles can be accelerated to energy that can be used for cancer treatment and the like, and the installation cost and operation cost are extremely low compared to conventional heavy particle accelerators. The purpose of the present invention is to provide an accelerator that is capable of accelerating heavy particles up to energy that can be used for cancer treatment and the like while being inexpensive.

In order to achieve the above object, the invention according to claim 1 is a magnetic field forming apparatus comprising: a coil group in which a plurality of hollow fan-shaped coils formed by winding an oxide superconducting conductor are arranged in a plurality of circumferential directions; Two sets are provided in a state of facing each other , and each of the coil groups is disposed between two sets of coil units arranged in a vertical direction facing each other in mirror symmetry, and each of the coil units is an oxide. A main coil formed by winding a superconducting conductor, and an inner diameter as viewed in a radial direction from the outer diameter of the main coil so as to have an outer diameter smaller than the outer diameter of the main coil, and a mountain shape together with the main coil And a correction coil wound with an oxide superconducting conductor, which is disposed farther from the other coil unit than the other coil unit so as to have a shape .

In order to achieve the above object, a second aspect of the present invention is a magnetic field forming apparatus in which plate-shaped fan-shaped oxide superconducting bulk bodies formed of a bulk oxide superconducting material are arranged in a plurality of circumferential directions. The superconducting bulk body groups are provided in two sets facing each other , and each of the superconducting bulk body groups is disposed between two sets of coil units that are vertically arranged facing each other in mirror symmetry. Each of the coil units has a main coil formed by winding an oxide superconducting conductor and an inner diameter that is smaller than the outer diameter of the main coil so that the outer diameter is smaller than the outer diameter of the main coil. and was combined with the main coil is disposed more distant as viewed from the other of said coil unit with respect to the main coil so that the mountain-shape, and a correction coil formed by winding the oxide superconducting conductor And it is characterized in and.

In addition to the above object, the invention described in claim 3 forms a high magnetic field and a magnetic field distribution that enable acceleration of heavy particles to energy that can be used for cancer treatment or the like while being relatively inexpensive. to achieve the purpose of, in the above invention, in that the oxide superconductor is, RE-123-based oxide superconductor _{(REBa 2 Cu 3 O 7-} δ, RE is a rare earth element including yttrium) is It is a feature.

In addition to the above object, the invention described in claim 4 forms a high magnetic field and a magnetic field distribution that enable acceleration of heavy particles to energy that can be used for cancer treatment or the like while being relatively inexpensive. to achieve the purpose of, in the above invention, the oxide superconducting bulk body is, RE-Ba-Cu-O (RE is yttrium, samarium, lanthanum, neodymium, europium, gadolinium, dysprosium, holmium, erbium, thulium , Ytterbium, and any combination of lutetium, Ba is barium, Cu is copper, and O is oxygen).

  In order to achieve the above object, a fifth aspect of the present invention is a particle accelerator, wherein the magnetic field forming device is incorporated between magnetic poles.

According to the present invention, the oxide bulk superconductor of the coil or plate-shaped fan-shaped hollow sector shape formed by winding an oxide superconductor is arranged in a plurality circumferentially, in a state of facing each other, each oxide superconductor The coil is disposed between two sets of coil units each including a main coil and a correction coil, each of which is formed by winding a conductor . Therefore, it is possible to form an isochronous high magnetic field or magnetic field gradient that can be accelerated up to energy that can be used for cancer treatment etc. for heavy particles while being small and low in installation cost and operation cost. The magnetic field forming device or the particle accelerator can be provided.

It is a plane explanatory view of the magnetic field formation device concerning the 1st form of the present invention. FIG. 2 is a perspective explanatory view showing the magnetic field forming device and the coil system of FIG. 1. It is a partial cross section explanatory view of the coil system of FIG. It is a partial cross section explanatory view of the coil system of a comparative example. It is a graph which shows the magnetic field formed with the magnetic field formation apparatus (or the coil system of FIG. 2) of FIG. It is a plane explanatory view of the magnetic field formation device concerning the 2nd form of the present invention. FIG. 7 is a perspective explanatory view showing the magnetic field forming device and the coil system of FIG. 6. It is a graph which shows the magnetic field formed with the magnetic field formation apparatus (thru | or the coil system of FIG. 7) of FIG.

  Hereinafter, an example of an embodiment according to the present invention will be described with reference to the drawings as appropriate. In addition, the said form is not limited to the following example.

[First form]
FIG. 1 is an explanatory plan view of a magnetic field forming apparatus 1 included in the particle accelerator according to the first embodiment of the present invention. The magnetic field forming device 1 includes upper and lower coil groups 2, and each coil group 2 includes a plurality (six) of coils 3. Each coil 3 has a substantially sector shape (sector shape) having a predetermined center angle (30 degrees), an outer diameter (radius) of 1.6 meters (m), a width of 0.08 m, and three corners. Is rounded with an inner diameter (radius) of 0.03 m and an outer diameter (radius) of 0.11 m, and the central angle is located outside the circle with a radius of 0.315 m.

  Each coil 3 is formed by winding a superconducting wire made of a superconducting conductor into a linear shape (air core), and further covering this with a shield. Each coil 3 is electrically connected to a power supply device (power source) (not shown). In addition, a cooling medium (not shown) is sealed in the shield so as to be able to flow only into a cooling device (not shown), and the cooling device cools the cooling medium to 20 Kelvin (K) and distributes the inside of the shield. Is possible.

The width of the superconducting wire of each coil 3 is about 1 centimeter (cm), the thickness is 200 micrometers (μm) including the substrate and stabilized copper, and the space factor including the insulating coating on the surface of the superconducting wire. Is about 0.7, and the load factor is about 0.7 (the operating current is about 300 A, and the current density is about 8.47 × 10 ⁷ amperes per square meter (A / m ² )).

Furthermore, as the material of the superconducting wire, it enters a superconducting state at 77K, such as a metal system (nickel titanium, niobium tin, etc., superconducting state at 4.2K) or an oxide system (bismuth system or RE-Ba-Cu-O system). It is preferable to use an oxide superconducting conductor because the critical temperature is high, the superconducting state is relatively high, and the critical magnetic field is high. Among superconducting conductors, although the manufacturing cost is relatively high, the mechanical strength is also good because of the resistance to magnetic fields and the heat-resistant and corrosion-resistant nickel-based alloy (Hastelloy, registered trademark, the same shall apply hereinafter) is a wire component. It is more preferable to use an oxide superconductor whose component can be represented by RE-Ba-Cu-O. As specific examples of the bismuth-based oxide superconducting wire former, Sumitomo Electric Industries Ltd. _{Bi2223 (Bi 2 Sr 2 Ca 2} Cu 3 O 10) can be mentioned, the latter RE-Ba-Cu-O based oxide A specific example of the superconducting wire is YBCO (YBa ₂ Cu ₃ O _7-δ ) manufactured by American Superconductor Corporation (AMSC). In this embodiment (FIG. 1), YBCO is used.

Here, in the oxide superconducting conductor whose main component can be represented by RE-Ba-Cu-O, RE is at least one of rare earth elements such as Y (yttrium), Sm (samarium), Gd (gadolinium), and Ho (holmium). Or any combination of two or more, Ba is barium, Cu is copper, and O is oxygen. Preferably, the oxide superconductor is an yttrium oxide superconductor having RE of Y, more preferably a Y-123 oxide such as YBa ₂ Cu ₃ O _7-δ , or YBa ₂ Cu. _It is assumed that all or part of Y in ₃ O _7-δ is replaced with another rare earth metal (RE-123 oxide superconductor).

  The oxide superconducting conductor is formed on a substrate (wire constituent material) having crystal orientation on the surface. The substrate is preferably Cu (copper), Ni (nickel), Ti (titanium), Mo (molybdenum), Nb (niobium), Ta (tantalum), W (tungsten), Mn (manganese), Fe (iron) , Ag (silver), or a metal layer made of an alloy thereof, or more preferably, a metal layer made of stainless steel, Inconel, or Hastelloy.

Furthermore, an intermediate layer made of a metal oxide is preferably arranged between the oxide superconductor and the substrate. The intermediate layer has a pyrochlore structure, a rare earth-C structure, a perovskite structure, or a fluorite structure. For example, BaZrO ₃ (Zr is zirconium), Y ₂ O ₃ , MgO (Mg is magnesium), SrTiO ₃ (SrTiO ₃ ). Is strontium, Ti is titanium), YSZ (yttria stable zirconia), or Ln-MO-based compounds such as Gd ₂ Zr ₂ O ₇ (Ln is one or more lanthanoid elements, M is Sr · Zr · Ga (gallium) ) One or more elements selected from the group of The intermediate layer is formed by a sputtering method, an electron beam evaporation method, or the like, but is preferably formed by an IBAD method (Ion Beam Assisted Deposition).

  Each coil 3 is formed by winding the above-described superconducting wire within the above-mentioned outer shape, has 2400 turns, and has a wire length of 756.4 m. In addition, there are six coils 3 in the coil group 2 and two sets of the coil group 2 are upper and lower, so that the total length of the superconducting wire is 90.1968 kilometers (km), which is 12 times the length of each wire.

  In the coil group 2, the coils 3 are arranged at equal intervals in the circumferential direction (circumferential direction). In each coil group 2, the upper and lower coil groups 2 are arranged so that the coil 3 faces the coil 3 of the other coil group 2. (See FIG. 2). In each coil group 2, the arc portion of each coil 3 is arranged so as to overlap the same arc. In each coil group 2, each coil 3 mainly constitutes a strong magnetic field part (hill), and a relatively weak magnetic field part (valley) is mainly constituted between the coils 3 and 3.

  FIG. 2 is a perspective explanatory view showing the coil system 10 and the magnetic field forming device 1 included in the particle accelerator according to the present embodiment. FIG. 3 is a partial cross-sectional explanatory view of the coil system 10. Arranged inside the coil system 10. In addition, the coil system 10 and the magnetic field formation apparatus 1 are arrange | positioned between two column-shaped parallel upper and lower magnetic poles which are not shown in figure. The particle accelerator includes a magnetic field generating apparatus 1 or a coil system 10 that accelerates charged particles in a spiral orbit by gradually increasing or adjusting the magnetic flux density as the magnetic field moves from the center to the circumferential direction. And an ion source (not shown) for generating charged particles to be incident near the center of the magnetic field forming device 1 (or the coil system 10, magnetic pole), and a control device (not shown) for controlling these.

  The coil system 10 has two sets of coil units 12 arranged one above the other so as to face each other in mirror symmetry. One set of the coil units 12 includes one main coil 13 having an annular shape as a whole. The two correction coils 14 and 16 have an annular overall shape. Of the correction coils 14 and 16, the coil closer to the main coil 13 is the correction coil 14, and the other coil is the correction coil 16. Further, FIG. 3 shows a half cross section of one set of the coil unit 12, and the cross section of the entire coil system 10 is drawn in a mirror symmetry with the vertical axis as the axis of symmetry. Is obtained by drawing another set of cross sections in a mirror symmetry with the horizontal axis as the symmetry axis. The unit of the numerical value in FIG. 3 is meter (m).

  The main coil 13 is formed by winding a superconducting wire made of a superconducting conductor into a linear shape at a predetermined interval with respect to the entire ring-shaped center line (air core), and covering this with an annular shield. . The dimensions and material of the superconducting wire are the same as those of the coil 3 of the magnetic field forming device 1. The main coil 13 is electrically connected to a power source common to the magnetic field forming device 1. In the shield, a cooling medium common to the magnetic field forming device 1 is sealed so as to be able to flow only into a cooling device (not shown). The cooling device cools the cooling medium to 20K and circulates in the shield. It is possible.

  The main coil 13 has a cross section having a wider area (a cross section including the air-core portion) than the correction coils 14 and 16, and the main coil 13 has a vertical (thickness / axial dimension) of about 0. The width (width and width direction dimensions of the ring) is about 0.89 m, and the aspect ratio (aspect ratio) exceeds 1: 2 and exceeds 1: 3. The outer diameter of the main coil 13 is about 2.525 m, and the inner diameter (the inner diameter of the ring, the diameter of the hole of the ring) is about 1.635 m.

  The main coil 13 is arranged along the magnetic pole in a state in which the center is aligned with the magnetic pole, and is arranged at a distance of about 0.139 m from the mirror-symmetric main coil 13 (FIG. 3). About 0.070 m away from the horizontal axis of

  On the other hand, the correction coils 14 and 16 are formed and designed in the same manner as the main coil 13 except for dimensions and arrangement.

  The correction coil 14 has an outer diameter of about 1.605 m, an inner diameter of about 1.444 m, a width of about 0.161 m, and a thickness of about 0.117 m. The center is aligned with the center of the main coil 13 and along the main coil 13. In this state, the correction coil 14 is arranged at a distance of about 0.543 m from the symmetrical correction coil 14 (about 0.272 m away from the horizontal axis in FIG. 3). Therefore, the correction coil 14 is arranged in a state of being aligned with the main coil 13 or the main coil 13 in the axial direction of the main coil 13, and is far from the main coil 13 (on the side farther from the target magnetic field / symmetric line / horizontal axis, the magnetic pole). The inner diameter or outer diameter of the main coil 13 is smaller than the outer diameter of the main coil 13 (the radial direction / radius of the coil). (In the direction and radial direction)

The correction coil 16 has an outer diameter of about 1.096 m, an inner diameter of about 0.946 m, a width of about 0.150 m, and a thickness of about 0.0930 m, and is aligned with the center of the main coil 13 and along the main coil 13. Thus, the correction coil 16 is arranged at a distance of about 1.129 m from the symmetrical correction coil 16 (about 0.565 m away from the horizontal axis in FIG. 3). Therefore, the correction coil 16 is located farther from the main coil 13 and the correction coil 14, and its inner diameter or outer diameter is smaller than the outer diameter of the main coil 13 or the correction coil 14. And the correction coil 14 is arranged on the inner side of the outer diameter. The coil winding volume of the main coil 13 and the correction coils 14 and 16 is about 1.732 cubic meters (m ³ ) in total.

In the magnetic field forming apparatus 1, in each coil unit 12, a correction coil 14 having an outer diameter larger than the inner diameter or outer diameter is disposed nearer to the correction coil 16, and further closer to the correction coil 14, further closer to the inner diameter or outer diameter. A main coil 13 having an outer diameter larger than the diameter is disposed, and has a mountain shape that rises far away as the coil unit 12 as a whole. In the magnetic field forming apparatus 1, the coil units 12 are symmetrical with each other, and a magnetic field (target magnetic field) for particle acceleration or the like is formed in a portion sandwiched between the coil units 12 . Each coil in the coil unit 12 is electrically connected to a single power source through a switch, and when the switch is turned on, a voltage is applied by a single power source to be excited. The target magnetic field is generated together with the magnetic field forming device 1. Note that the horizontal axis in FIG. 3 is the center line of the target magnetic field.

  On the other hand, as a comparative example for the coil system 10 according to the present invention, as shown in FIG. 4 similarly to FIG. 3, the coil unit is constituted by a single coil, and the coil is arranged mirror-symmetrically up and down. . The coil has an outer diameter of about 2.162 m, an inner diameter of about 1.855 m, a width of about 0.307 m, and a thickness of about 0.723 m, and is arranged at an interval of about 0.13 m with respect to the symmetrical coil. (It is about 0.065 m away from the horizontal axis in FIG. 4).

  About the particle accelerator which has these magnetic field formation apparatuses 1 grade | etc., Each is operated as follows by computer control.

  That is, first, for the particle accelerator having the magnetic field forming apparatus 1 and the coil system 10 according to the present invention, the computer as the control apparatus of the particle accelerator or the magnetic field forming apparatus 1 operates the cooling device and supplies the cooling medium to each coil group 2. Each coil 3 or main coil 13 of each coil unit 12 and correction coils 14 and 16 are cooled by conduction cooling to a temperature (20K) at which the superconducting state is achieved, thereby stabilizing the temperature of the cooling medium. Then, a voltage is gradually applied to the magnetic field forming device 1 or the coil system 10, and a current is passed through each coil 3, the main coil 13, and the correction coils 14 and 16 until the current density is reached. When the current density described above is generated and the current is stabilized by the superconducting state, the application of voltage is stopped, and the state is shifted to a steady state in which an isochronous magnetic field is formed that accelerates the particles in a spiral orbit.

  FIG. 5 shows the magnetic flux density distribution of the isochronous magnetic field thus obtained (target magnetic field, on the horizontal axis in FIG. 3, diameter 3.2 m / height (thickness) 13 cm). 5A shows the magnetic flux density distribution along the circumferential direction at a predetermined radius (three types), and FIG. 5B shows the radial direction from the center of the target magnetic field at a predetermined angle (two types) or the entire average. The magnetic flux density distribution to the outside is shown. In the particle accelerator having the magnetic field forming device 1 and the like, a magnetic field having a magnetic gradient suitable for particle acceleration in which the magnetic flux density gradually increases in the radial direction can be formed. Moreover, on average, the magnetic flux density near the center can be set to about 4T and the magnetic flux density on the peripheral end side can be set to about 6T with respect to the target magnetic field, which greatly exceeds 2T, which is the limit of normal conducting iron. A magnetic field having a large magnetic flux density can be formed with a smooth magnetic gradient.

Therefore, by making charged particles incident on the target magnetic field, even heavy particles can be sufficiently accelerated (up to about 400 MeV / u) by a spiral orbit, and acceleration of heavy particles necessary for heavy ion beam cancer treatment is possible. Can be performed with a particle accelerator having the magnetic field forming device 1 or the like. The dimensions of the magnetic field forming device 1 and the coil system 10 themselves are about 5 m in diameter × about 2 m in height, and the installation area of about several tens of square meters (m ² ) is required including peripheral devices. The particle accelerator can be miniaturized very compactly. Furthermore, since the particle accelerator is small, the amount of material required for production can be reduced, the amount of electric power required for operation can be reduced, and control related to operation should be relatively simple. Thus, the introduction cost and the operation cost can be reduced, the maintenance can be easily performed, and the maintenance cost can be reduced.

  In addition, each coil 3 and each main coil 13 and each correction coil 14 and 16 are in a superconducting state, excited in the superconducting state, and operated as a superconducting accelerator, which contributes to a reduction in the amount of power added to these coils. In addition, Joule heat generation does not occur, and the cooling energy of the cooling medium is relatively small, and the amount of electric power required for operation can be reduced. In addition, because of the small size, small amount of cooling medium, and no Joule heat, the time from the stop state to the high magnetic field state (particle acceleration possible state) can be shortened, and particle acceleration can be efficiently performed. It can be carried out. Furthermore, by not generating Joule heat, it is possible to prevent the occurrence of thermal deformation in each coil 3, each main coil 13, and each correction coil 14, 16, preventing fluctuations in the magnetic field distribution and stabilizing Formation of an isochronous magnetic field or stable operation of particle acceleration of the magnetic field can be ensured. With the above characteristics, the spread of heavy particle accelerators can be promoted, and a great effect can be achieved such as an increase in the number of hospitals capable of performing heavy ion beam cancer treatment.

On the other hand, when the particle accelerator having the coil system according to the comparative example and the magnetic field forming apparatus 1 of the present invention is operated similarly, a magnetic field similar to the magnetic field shown in FIG. 5 in the present invention can be obtained. The amount of superconducting wire used for forming the coil is about 3.92 m ³ , which is about 2.26 times the amount of wire used for the coil system 1 or particle accelerator of the present invention.

  Therefore, in the coil system 1 or the particle accelerator of the present invention including the coil unit composed of a plurality of coils, the isochronism is high so that heavy particles can be accelerated up to energy usable for cancer treatment or the like. While realizing a magnetic field and magnetic field distribution, it is possible to reduce the amount of oxide superconducting wire that is relatively expensive, which will further contribute to the popularization of particle accelerators that can be used for cancer treatment and the like. .

[Second form]
The magnetic field forming device 21 or particle accelerator according to the second embodiment of the present invention is the same as the magnetic field forming device 1 or particle accelerator of the first embodiment except that the superconducting bulk body group 22 is used instead of the coil group 2.

  As shown in FIGS. 6 and 7, the magnetic field forming device 21 includes a superconducting bulk body group 22, and each superconducting bulk body group 22 includes a plurality (six) of superconducting bulk bodies 23. Each superconducting bulk body 23 has the same outer shape as that of the coil 3 of the first form, but is not hollow but is plate-shaped. Each superconducting bulk body 23 is covered with a shield through which a cooling medium supplied from a cooling device flows, and can be cooled to about 20K.

  Each superconducting bulk body 23 is formed of a bulk oxide superconducting material, and is preferably formed of an oxide superconductor whose main component can be expressed by RE-Ba-Cu-O. Here, RE is Y (yttrium), Sm (samarium), La (lanthanum), Nd (neodymium), Eu (europium), Gd (gadolinium), Dy (dysprosium), Ho (holmium), Er (erbium), It is an arbitrary combination of at least one or two or more of rare earth elements such as Tm (thulium), Yb (ytterbium), and Lu (lutetium), Ba is barium, Cu is copper, and O is oxygen. Preferably, RE is Y and the bulk oxide superconductor is an yttrium oxide superconductor bulk body.

In this oxide superconductor, an insulating phase (non-superconducting phase, 211 phase) is finely dispersed in a superconducting phase (123 phase). The superconducting phase is in a single crystal form (including not only perfect but also having defects that do not impair practical use such as low-angle grain boundaries), has a superconducting transition temperature of about 90 to 96 K, and has REBa ₂ Cu ₃ O _7-δ . On the other hand, the insulating phase is preferably an allotrope of the superconducting phase and has a particle size of 50 μm or less (more preferably 10 μm or less) and can be expressed as RE ₂ BaCuO ₅ . The proportion of the insulating phase in the superconducting phase is preferably 5 to 35 volume percent in view of the critical current density or mechanical strength. Note that bubbles (about 50 to 500 μm) may be included in the oxide superconductor.

  The oxide superconductor is preferably added in an arbitrary amount up to 50 mass percent (mass%) of at least one of silver, platinum or cerium, or any combination of two or more. It is more preferable to add 5 to 20% by mass of silver. A silver compound or the like (about 10 to 500 μm) may be generated by adding silver or the like.

  In the superconducting bulk body group 22, the superconducting bulk bodies 23 are arranged at equal intervals in the circumferential direction, and in each superconducting bulk body group 22, the superconducting bulk body 23 faces the superconducting bulk body 23 of the other superconducting bulk body group 22. Upper and lower superconducting bulk body groups 22 are arranged to form a magnetic field forming device 21 (see FIG. 7). In each superconducting bulk body group 22, each superconducting bulk body 23 constitutes a strong magnetic field portion (hill), and between the superconducting bulk bodies 23 constitutes a weak magnetic field portion (valley). The magnetic field forming device 21 is accommodated in the coil system 10 described in the first embodiment in the same manner as the magnetic field forming device 1, and the particle accelerator of this embodiment is formed.

  The particle accelerator having such a magnetic field forming device 21 and the like is operated in the same manner as in the first embodiment by computer simulation (however, no voltage is applied to each superconducting bulk body 23), and the obtained isochronous magnetic flux The density distribution is shown in FIG. 8A shows the magnetic flux density distribution along the circumferential direction at a predetermined radius (three types), and FIG. 8B shows the radial direction from the center of the target magnetic field at a predetermined angle (two types) or the entire average. The magnetic flux density distribution to the outside is shown. Even in the particle accelerator having the magnetic field forming device 21 and the like, a magnetic field having a magnetic gradient suitable for particle acceleration in which the magnetic flux density gradually increases in the radial direction can be formed. Moreover, with regard to the isochronous magnetic field, on the average, the magnetic flux density near the center can be set to about 4T, and the magnetic flux density on the peripheral end side can be set to about 6T, which greatly exceeds the limit of 2T of normal conducting iron. A magnetic field having a very large magnetic flux density can be formed with a smooth magnetic gradient.

Therefore, even in a particle accelerator having the magnetic field forming device 21 or the like, by accelerating charged particles into a target magnetic field, acceleration of heavy particles necessary for heavy particle beam cancer treatment can be performed. Further, the magnetic field forming device 21 and the coil system 10 itself have dimensions of about 5 m in diameter and about 2 m in height, and can include an installation area of about several tens of square meters (m ² ) including peripheral devices. 21 and the particle accelerator can be miniaturized very compactly. Furthermore, since the particle accelerator is small, the amount of material required for production can be reduced, the amount of electric power required for operation can be reduced, and control related to operation should be relatively simple. Thus, the introduction cost and the operation cost can be reduced, the maintenance can be easily performed, and the maintenance cost can be reduced.

  In addition, each superconducting bulk body 23, each main coil 13 and each correction coil 14 and 16 are in a superconducting state, excited in the superconducting state, and operated as a superconducting accelerator. However, Joule heat generation does not occur and the cooling energy of the cooling medium can be relatively small, and the amount of power required for operation can be reduced. In addition, because of the small size, small amount of cooling medium, and no Joule heat, the time from the stop state to the high magnetic field state (particle acceleration possible state) can be shortened, and particle acceleration can be efficiently performed. It can be carried out. Furthermore, by not generating Joule heat, it is possible to prevent the occurrence of thermal deformation in each superconducting bulk body 23 and each main coil 13 and each correction coil 14, 16, preventing fluctuations in the magnetic field distribution, It is possible to form a stable isochronous magnetic field or to ensure stable operation of particle acceleration of the magnetic field. With the above characteristics, even in this embodiment, the spread of particle accelerators capable of accelerating heavy particle beams can be promoted, and the number of hospitals capable of performing heavy particle beam cancer treatments has increased. There is an effect.

[Third embodiment]
The particle accelerator according to the third embodiment of the present invention is the same as the particle accelerator of the first embodiment or the second embodiment except for the winding system of each coil in the coil system 10.

  In the particle accelerator of the third embodiment, each main coil 13 and each correction coil 14 and 16 are configured using a pancake coil formed by pancake winding a strip-shaped superconducting wire. Each of the main coils 13 and each of the correction coils 14 and 16 is configured to have a stacked structure (as a stacked pancake coil) by stacking a plurality of disk-shaped (annular) pancake coils having a hole in the center. .

  In the particle accelerator of the third form, as in the first and second forms, a high magnetic field capable of providing a magnetic gradient can be formed in a small, low-cost and easy-to-use apparatus. In addition, since each main coil 13 and each correction coil 14 and 16 are formed of a pancake coil or a laminated body thereof, an electromagnetic force is applied as a compressive stress to the wire constituent material (Hastelloy) during excitation. The mechanical strength of each of the main coils 13 and the correction coils 14 and 16 can be increased to avoid buckling, further improving durability and making the high magnetic field more stable. Can be generated.

[Example of change]
In addition, the other form of this invention which mainly consists of changing the said form is illustrated. The number of coils and superconducting bulk bodies in the magnetic forming device may be 5 or less (2 or more) on one side, or 7 or more. The shape of the coil or the superconducting bulk body may be a shape similar to a sector having a straight line, a broken line, a curved line, or the like that does not follow the radial direction (a spiral sector may be included in the sector shape). The size of the coil and the superconducting bulk body can be variously changed. In addition, the size and shape of the plurality of coils and the superconducting bulk body may be different from each other, or may be divided into a plurality of arbitrary groups, and each group may have the same size or shape. The superconducting bulk material may be arranged in any way. In the magnetic forming apparatus, a coil and a superconducting bulk material may be mixed. The arrangement of the coil and the superconducting bulk body may be different for each interval, or the same interval may be taken every certain number. The coils of each coil group may not be arranged at the positions corresponding to the coils of the other coil groups (facing each other and overlapping in plan view), but may be arranged in an angle-shifted state, or the positions corresponding to only some coils. The same applies to the superconducting bulk body group.

  In the coil unit, the number of coils may be two per side, or four or more. The coils may not be divided into the main coil and the correction coil based on the cross-sectional area, but may have the same cross-sectional area, or each coil may have various cross-sectional areas. Further, the main coil may be arranged farther from the target magnetic field than the correction coil. The dimensions and arrangement of the coil can be finely adjusted or changed according to the magnetic gradient shape, the height of the magnetic flux density, or the like. One coil unit does not need to consist only of coils that are mirror-symmetric with respect to all the coils in the other coil unit, and the other coil unit is additionally provided with a fine adjustment coil that is not in the other coil unit. Any configuration may be adopted as long as it includes a mirror-symmetrical coil with respect to a plurality of coils belonging to the coil unit. The pancake coil can be used alone without being laminated, and the number of laminations can be varied, or the thickness, number of windings, types and dimensions of the wire can be varied for each layer. A combination of a cake coil or a laminated pancake coil may be used. The temperature of the cooling medium may be other than 20K.

  The power source and the cooling device can be used separately for the magnetic field forming device and the coil unit, or can be dedicated for each arbitrary coil.

  According to the magnetic field forming apparatus or particle accelerator of the present invention, it is possible to provide an extremely high magnetic field with a small and low-cost configuration, and the magnetic field forming apparatus or particle accelerator of the present invention is a medical accelerator for various medical institutions. Of course, it can be adopted to create experimental particle accelerators that can be easily introduced even in research institutions that do not have the largest scale, or to be incorporated into industrial equipment that requires high magnetic fields. The magnetic field forming apparatus of the present invention or the particle accelerator capable of accelerating heavy particles has various applications.

  In particular, in the case of a heavy particle accelerator for cancer treatment, as described below, it is possible to efficiently carry out highly effective heavy particle beam irradiation for cancer, and a large number of cancers. The patient can be treated to provide an improvement in quality of life (Quality Of Life, QOL).

  In other words, by irradiating carbon hexavalent ion beams (charged particles) with two horizontal and vertical gates, it is possible to concentrate the position where the amount of energy absorption is high at the position of the cancer affected area. In comparison with the proton beam, it can have a steeper boundary, reducing the burden on the area other than the affected area and reducing the burden of treatment. By concentrating the dose, the biological effect on cancer cells (cell killing effect) can be about 3 times that of X-rays and protons, and the effect can be increased with a relatively short irradiation time. Can reduce the treatment period and hospitalization period, or can make the rehabilitation period unnecessary or extremely short, and the physical burden and cost burden are extremely low compared to surgical resection and other radiation treatments. It is possible to carry out the cancer treatment. In addition, due to the concentration of the dose, there are cases where it is effective against hypoxic cancer (large tumors after the middle stage) and radiation resistant cancer (cancers such as adenocarcinoma and osteosarcoma) It can also be used to treat intractable cancer. In addition, the possibility of treatment can be found even by elderly people and other disease holders by the fact that surgery is unnecessary in principle because of low burden (expansion of patients to be treated) and to improve the patient's QOL. As a result, the social cost can be reduced. According to the magnetic field forming apparatus or the heavy particle accelerator for medical use of the present invention, it is possible to promote the spread of devices that have such remarkable effects.

1,21 Magnetic field generator 2 Coil group 3 Coil 22 Superconducting bulk body group 23 Superconducting bulk body

Claims (5)

Two sets of coil groups in which a plurality of hollow fan-shaped coils formed by winding an oxide superconducting conductor are arranged in the circumferential direction face each other ,
Each of the coil groups is disposed between two sets of coil units that are vertically arranged facing each other in a mirror-symmetrical manner, and each of the coil units includes a main coil formed by winding an oxide superconducting conductor, The outer diameter of the main coil is smaller than the outer diameter of the main coil so that the outer diameter of the main coil is arranged on the inner side in the radial direction. A magnetic field forming apparatus comprising: a correction coil formed by winding an oxide superconducting conductor, which is disposed farther from the coil unit . Two sets of superconducting bulk bodies in which a plate-shaped fan-shaped oxide superconducting bulk body formed of a bulk oxide superconducting material is arranged in a plurality of circumferential directions face each other ,
Each of the superconducting bulk body groups is disposed between two sets of coil units that are vertically arranged facing each other in mirror symmetry, and each of the coil units includes a main coil formed by winding an oxide superconducting conductor. The outer diameter of the main coil is smaller than the outer diameter of the main coil, the inner diameter of the outer diameter of the main coil is arranged on the inner side of the main coil, and the main coil is formed in a mountain shape together with the main coil. A magnetic field forming apparatus comprising: a correction coil formed by winding an oxide superconducting conductor, which is disposed farther from the other coil unit . _2. The magnetic field forming apparatus according to claim 1, wherein the oxide superconductor is a RE-123 oxide superconductor (REBa ₂ Cu ₃ O _7-δ , RE is a rare earth element including yttrium). The oxide superconducting bulk is RE-Ba-Cu-O (RE is yttrium, samarium, lanthanum, neodymium, europium, gadolinium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, or more. 3. The magnetic field forming apparatus according to claim 2, wherein the magnetic field forming apparatus has a main component that can be expressed by any combination of the following: Ba is barium, Cu is copper, and O is oxygen. 5. A particle accelerator comprising the magnetic field forming device according to claim 1 incorporated between magnetic poles.

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