JP5708984B2 - Air-core type cyclotron - Google Patents

Description

  The present invention relates to a cyclotron that accelerates charged particles, and more particularly to an air-core type cyclotron that uses an air-core coil.

  As a cyclotron capable of accelerating protons to 250 to 300 MeV (mega electron volt), one described in Patent Document 1 below is known. In this cyclotron, the mass of charged particles approaching the speed of light increases in proportion to the Lorentz factor due to the relativistic effect. An isochronous magnetic field is created that is an increased magnetic field (with a positive gradient outward).

  In addition, in this cyclotron, in the isochronous magnetic field that is stronger toward the outer side, if acceleration is performed as it is, acceleration particles diverge in the direction perpendicular to the acceleration plane, and acceleration particles collide with the device and acceleration cannot be continued. Are provided with a plurality of ferromagnetic pole pieces (pole tips) for changing the magnetic field strength in the circumferential direction (the direction of particle rotation) and causing the acceleration particles to obtain a convergence force in the vertical direction. Each pole tip is formed in a fan shape that is spirally curved so as to have an incident angle (spiral angle) with the accelerating particles in order to obtain a stronger convergence force, and is equidistant from each other in the circumferential direction of the acceleration plane. It is arranged to strengthen the magnetic field of the part (hill) where the ball chip is present and weaken the magnetic field of the part (valley) where there is no ball chip, thereby converging the acceleration particles in the vertical direction (and horizontal direction). A cyclotron that creates such a magnetic field that is strong and weak in the direction of rotation (azimuth angle direction) is called an AVF (Azimuthally Varying Field) cyclotron.

In such a cyclotron, a normal conducting iron core coil is used to create an isochronous magnetic field, and the average magnetic field on the circular orbit can only be increased to a maximum of about 2T (Tesla). Further, since a ferromagnetic material is used as the ball chip, there is a limit to the energy of charged particles that can be converged. Therefore, in such a cyclotron, the protons are only accelerated to 250 to 300 MeV, and heavy particle beams (such as carbon hexavalent positive ions ¹² C ⁶⁺⁾ that have recently been remarkably useful in the irradiation treatment of cancer. (Radiation) cannot be sufficiently accelerated to a state having energy of about 400 MeV / nucleon (accelerated to about 70% of the speed of light) that can be used for cancer treatment.

  Currently, the five-year survival rate of all cancers (malignant tumors) in Japan has exceeded 50% (percent), but it remains the top intractable disease of Japanese people. According to "Cancer Statistics '07" (Cancer Research Promotion Foundation), about 1 in 2 men and 1 in 3 women will be diagnosed with cancer in their lifetime. About 1 in 4 men and 1 in 6 women die of cancer. With the progress of an aging society, the number of cancer patients is still on the rise, and is expected to exceed 5 million in 2015 (approximately double in about 10 years from 2003).

  Also, if cancer patients who were treated in outpatient or hospitalization were not required for treatment, they would not be paid (medical expenses), and if a person who died of cancer had lived to the average life expectancy There is a trial calculation that the amount of money (loss profit) that should have been obtained from the above is about 3 trillion yen in medical expenses and about 7 trillion yen in lost profits. Therefore, it can be said that society's loss due to cancer is about 10 trillion yen per year (about 2% of Japan's gross domestic product). On the other hand, it is needless to say that cancer countermeasures are important from the viewpoint of reducing social costs because cancers that can be cured are increasing due to improvements in screening techniques and treatment techniques.

  Cancer treatment can be broadly divided into surgery, internal medicine, and radiation therapy, but radiation therapy that irradiates the affected area with radiation is relatively low in cost, and is becoming a major part of cancer treatment in Europe and the United States as well as in Japan. . High-energy X-rays mainly using electron beam linac are used as external therapeutic radiation, but in recent years, proton beams and heavy particle beams such as carbon beams can perform more effective treatment. It is attracting attention as.

  Comparing the characteristics of proton beams and carbon beams, the killing effect of proton cells on cancer cells is equivalent to that of conventional X-rays, but it is superior because the dose distribution is sharper than X-rays and irradiation can be concentrated on the affected area. . On the other hand, the dose distribution of carbon rays is sharper than that of proton rays, and treatment with precise dose distribution is possible while avoiding normal tissues and important organs, and the cell lethal effect is about three times that of proton rays. Therefore, it can be applied to cancer with higher radiation resistance. In addition, cancer cells grow rapidly, and the central part of the cancer tissue that has grown to some extent becomes deficient in oxygen due to decreased blood flow, so the effects of X-rays and proton beams on such hypoxic cells are insufficient. However, the effect of heavy particle beams has been recognized.

  Therefore, heavy ion beam radiation therapy is effective for the treatment of sites that are difficult to perform surgery or excision (liver, hilar region, skull base, eyeball, AVM, etc.), and has become an extremely low-invasive treatment method. According to the past results, therapeutic effects can be expected for about 60% of solid cancers. In addition, due to the concentration of dose distribution and good cell killing effect, the number of times of irradiation is reduced to reduce the physical burden and cost burden of the patient, and due to the low invasiveness, the hospitalization period and hospitalization period are reduced. The quality of life of patients (Quality Of Life, QOL) can be improved.

  As described above, a synchrotron is employed as a device capable of emitting a heavy particle beam useful for cancer treatment. However, the synchrotron has a very large scale for sufficiently accelerating heavy particles (for example, including an injector, hundreds of coils are arranged, and the number of electromagnets to be controlled is 100 or more. The main ring has a diameter of about 20 m (meter)), and the installation cost is enormous, and the operation cost is also the cooling of many coils, the complexity of control, the increase in the number of operators, the great power consumption, etc. It is expected to become enormous.

  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 by expanding the scale of the cyclotron as in Patent Document 1 as few as few. However, the formation of the magnetic field by the iron core and the normal conducting coil is limited to about 2T due to the magnetic saturation of iron (the average magnetic field in the circulation direction at the extraction radius), and on this assumption, heavy particle beams up to 400 MeV / nucleon are used. When an accelerable cyclotron is designed, a magnet (about 50,000 tons) having a pole face (including a magnetic pole surface and a return yoke) with a diameter of at least about 13 m is required to form an isochronous magnetic field. Even if it is manufactured, it takes time to stabilize the magnetic field, and furthermore, the amount of heat generation is large and a huge cooling device is required. In addition, due to the increased energy of the accelerating particles, the pole tip for convergence must be installed in a huge and complicated shape. Therefore, a cyclotron with such a large scale eventually becomes extremely complex and large, although not as much as a synchrotron.

  In addition, heavy particle beams are expected to be used in various fields other than cancer treatment because of their high linearity, high linear energy application, and specificity of depth dose distribution. For example, the field of new material creation to form nanostructures such as polymer nanowires, optical equipment by introducing such nanostructures, high-performance separation membranes, micro-nanomachines, high-efficiency heat exchangers It is expected to be used in various fields such as new energy creation, advanced semiconductors, and high-performance film production. Also, high-performance heat exchangers with large-capacity ion exchange membranes, optical waveguides, optical switches, high-performance gratings, antireflection coatings, nanofilters, fine mechanical parts, super-water-repellent membranes, and fine fins Is expected to be used in various fields such as Furthermore, it is expected to be used in various fields related to the structure-controlled drug diffusion system, high-performance fuel cell, high-precision ion implantation, and creation of integrated hybrid membranes with different performances on the front and back sides. In order to promote the use of heavy particle beams in such various fields, extremely large-scale devices such as synchrotrons are insufficient in power, and the mass and valence of heavy particle beams are appropriately set according to the field. There is a need for a heavy particle beam radiation device that, after adjustment), is relatively small and easy to introduce.

  Therefore, the applicants proposed in the previous patent application that the formation of the Hill Valley magnetic field in the particle rotation direction is performed by an air-core spiral sector coil formed by winding an oxide superconductor along a curved sector. (Japanese Patent Application No. 2010-132256). If such a spiral sector coil is used, a superconducting coil can form a much stronger magnetic field than a normal electric coil on a small scale, but if the radius of curvature of the superconducting conductor is made too small, a large mechanical / electromagnetic stress is generated. Since the superconducting characteristics deteriorate due to the addition of, it is difficult to form a shape that protrudes to the center region of the particle acceleration surface, and it is difficult to adjust the magnetic field strength of the center region with the spiral sector coil.

  On the other hand, in a conventional cyclotron that combines an iron core and a normal conducting coil or a superconducting cyclotron on a computer model (see Non-Patent Document 1 below), in order to adjust the magnetic field distribution in the central region of the particle accelerating surface, A center plug of a pair of upper and lower iron materials is arranged on the center axis. With this center plug, the magnetic field distribution becomes smaller as the distance from the center increases in the radial direction, and the intensity at the center is raised (center bump). Is configured to receive a vertical convergence force from the start of acceleration to several revolutions (the principle of weak convergence).

Japanese Patent No. 3456139 "Computer modeling of magnetic system for C400 superconducting cyclotron", Y. Yongen, et al., Proceedings of EPAC2006, Edinburgh, Scotland, 2006, pp2589-2591.

  With the conventional iron center plug, the center bump cannot be increased to a high magnetic field exceeding 2T due to the saturation of the magnetic flux, and can be accelerated to a state having an energy of about 400 MeV / nucleon provided by the superconducting coil. Even if it is placed in a magnetic field, it becomes relatively weak and insufficient. On the other hand, even if the shape of the superconducting spiral sector coil is made closer to the center of the particle acceleration surface, there is a possibility that the stress and the superconducting characteristics are lowered as described above. Since the return magnetic flux in the opposite direction to the magnetic field passes through the central region of the entire magnetic field, the magnetic field becomes weak near the center, the central bump cannot be applied, and the convergence force of the accelerated particles in the vertical direction is insufficient. there is a possibility.

  Therefore, the invention according to claim 1 is capable of accelerating until the heavy particles have energy that can be used for cancer treatment or the like, while being small in size and low in installation cost and operation cost. It is an object of the present invention to provide an air-core type cyclotron capable of forming a magnetic field distribution that allows smooth initial acceleration in the central region of the core.

To achieve the above object, a first aspect of the present invention, axially opposed, a pair of main coil units forming the isochronous magnetic field in the radial direction, opposite to the axial direction, circumferential direction a pair of spiral sectors coil unit forming the a strength magnetic field, has a pair of center coil unit facing the axial direction, each of the spiral sector coil unit, the shaft of the corresponding main coil unit is disposed inwardly, each said center coil unit, in the axial direction, are arranged on the outside of the spiral sector coil unit an inner of the corresponding main coil unit, each said center coil unit The center coil is an air-core coil wound with a superconducting conductor, and is arranged at the center in the radial direction. And it is characterized in that is.

  In addition to the above-mentioned object, the invention according to claim 2 achieves the object of efficiently forming a high magnetic field having a strength in the circumferential direction that can be stably accelerated to a state of having a high energy per heavy particle. In the present invention, each spiral sector coil unit includes three or more spiral sector coils, and each spiral sector coil is an air-core coil in which a superconducting conductor is wound along a curved sector. And are arranged so as to be rotationally symmetric with respect to each other.

  In addition to the above-described object, the invention described in claim 3 has the above-described object in order to achieve the object of further improving the strength and durability while allowing heavy particles to converge from the initial stage of acceleration and enabling acceleration at a high speed. In addition, each of the spiral sector coils is formed such that a bending radius is a predetermined value or more.

  According to a fourth aspect of the present invention, in order to achieve the object of efficiently forming a strong isochronous magnetic field in addition to the above object, in the above invention, the main coil unit is formed by winding a superconducting conductor in a ring shape. The air-core main split coils are arranged in a plurality of axial directions.

  In addition to the above-described object, the invention described in claim 5 is directed to the above-described invention in order to achieve the object of forming a high magnetic field or magnetic field distribution capable of accelerating heavy particles at high speed with a more efficient sharpness. The pair of center coil units, the pair of spiral sector coil units, and / or the pair of main coil units are arranged mirror-symmetrically with each other.

In order to achieve the object of forming a strong magnetic field while being easy to operate, small and energy saving, in addition to the above object, the invention described in claims 6 and 7 is the above invention. Is an oxide superconductor, or the oxide superconductor is a bismuth oxide superconductor or RE-123 oxide superconductor (REBa ₂ Cu ₃ O _7-δ , RE is a rare earth element containing yttrium) ) Or the like.

  According to the present invention, the air-core center coil formed by winding the superconducting conductor in a ring shape is disposed so as to face each other at the top and bottom of the center of the acceleration plane. Therefore, an acceleration plane that can stably introduce or accelerate particles up to energy that can be used for cancer treatment, etc. for heavy particles, while being compact and low in installation and operation costs. It is possible to form a magnetic field distribution in which the central intensity of the bump is bumped.

(A) is a plane explanatory view of the coil system in the air-core type cyclotron of the present invention, and (b) is an enlarged explanatory view of the center thereof. FIG. 2 is a central end view of the coil system of FIG. 1. It is an isometric view explanatory drawing of the coil system of a comparative example. FIG. 4 is an explanatory plan view of the coil system of FIG. 3. It is a partial end surface explanatory drawing of the main coil unit in FIG. It is a graph which shows the magnetic field etc. which are formed by the main coil unit of FIG. FIG. 4 is an explanatory plan view of the spiral sector coil in FIG. 1 or FIG. 3. (A) is a schematic side view of Hill Valley, (b) is a schematic plan view showing the trajectories of charged particles in the radial sector type, and (c) is a motion of charged particles across the edge of Hill Valley. It is a schematic diagram which shows a state. (A) is a schematic side view showing an integration path, (b) is a schematic plan view of a spiral sector type hill valley, and (c) is a partially enlarged view showing the trajectory of charged particles in (b). It is a plane schematic diagram. It is a graph which shows the relationship between the spiral angle and radial position of the spiral sector coil of FIG. 4 is a drawing-substituting photograph showing a magnetic field strength distribution on an acceleration plane formed by the coil system of FIG. 3. 3 shows (a) a circumferential intensity distribution in a circular orbit of each radius, (b) a radial intensity distribution, and (c) a radial flutter distribution of the magnetic field on the acceleration plane formed by the coil system of FIG. It is a graph. It is a graph which shows the magnetic field strength distribution on the center area | region of the acceleration plane each formed in the state which changed the current density of the center coil by the coil system etc. of FIG. It is a graph which shows the magnetic field strength distribution on the center area | region of the acceleration plane each formed in the state which changed the diameter of the center coil by the coil system etc. of FIG. 2 is a graph showing a magnetic field strength distribution on a central region of an acceleration plane formed in a state where the radius of curvature of a spiral sector coil is changed by the coil system 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.

≪Overall structure≫
FIG. 1A is a plan view of a coil system 1 of an air-core type cyclotron (hereinafter referred to as “cyclotron”) according to the present invention, and FIG. 1B is an enlarged view of the center of FIG. FIG. 2 is a central end view of the coil system 1. The unit of the numerical values of the X axis and the Y axis in FIG. 1 is cm (centimeter).

  The cyclotron has a coil system 1 inside a cover (not shown), an ion source (not shown) that generates charged particles and makes it enter the vicinity of the center of the coil system 1, and an illustration that is arranged outside the coil system 1. In synchronism with a predetermined cycle of rotation (rotation frequency) of the charged particles, a cooling device (not shown) that cools the coil system 1 to a predetermined temperature, a vacuum pump (not shown) that evacuates the inside of the cover, An acceleration electrode (not shown) that applies an impulse electric field for acceleration, a control device (not shown) that controls these, and a power supply device (power source) (not shown) that supplies power to these electrodes are included. In addition, you may further provide the magnetic body for a shield which reduces the magnetic field intensity to the exterior.

  The coil system 1 includes a pair of main coil units 2, 2, a pair of spiral sector coil units 4, 4 housed therein, and center coils 6, 6. Each main coil unit 2 is arranged vertically (in the axial direction) so as to face each other in a mirror symmetry, and each spiral sector coil unit 4 is also arranged vertically in a state facing each other in a mirror symmetry. 6 are also arranged one above the other so as to face each other in mirror symmetry. The centers of each main coil unit 2 to each spiral sector coil unit 4 and each center coil 6 are arranged on the same vertical line. As shown in FIG. 1B and FIG. 2, the center plane of the mirror object is the XY plane, the vertical line passing through the center is the Z axis, and the center is the origin. The center coil 6 can be regarded as a center coil unit composed of a single coil.

≪Main coil unit≫
Each main coil unit 2 includes a main split coil 21 and a first correction split coil 22 each having a perforated disk shape (ring shape). The main split coil 21 and the first correction split coil 22 are arranged so that their centers are located on the Z axis and parallel to the XY plane. The main split coil 21 is disposed closer to the XY plane than the first correction split coil 22.

  The main split coil 21 is formed by winding a superconducting wire made of a superconducting conductor in a circular shape (air core) so as to fill the cross section in a state where the center is located on the Y axis, and further winding the superconducting wire in a ring shape. It is formed by covering with a shield (not shown). The main split coil 21 is electrically connected to the power source. A cooling medium (not shown) is sealed in the shield or connected to the cooling apparatus, and the cooling apparatus can cool the cooling medium to 20 K (Kelvin) and send it to the shield. It has become.

  In addition, the width of the superconducting wire is about 1 cm, the thickness is 200 μm (micrometer) 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. The load factor is about 0.7.

  Furthermore, as the material of the superconducting wire, metallic nitrogen (niobium titanium, niobium tin, etc., superconducting state at 4.2 K), oxide type (bismuth-based, thallium-based, mercury-based, RE-Ba-Cu-O-based, etc.), liquid nitrogen The superconducting state can be developed at a temperature of 77K, and a superconducting state with good characteristics can be used at 20K). However, the critical temperature is high and the superconducting state is relatively high, and the critical magnetic field is also high. It is preferable to use an oxide superconducting conductor. Among oxide superconducting conductors, although the production cost is relatively high, a nickel-based alloy (hastelloy, registered trademark, the same applies hereinafter) that is strong against magnetic fields and is resistant to magnetic fields Therefore, it is more preferable to use an oxide superconductor whose mechanical strength is good and whose main component can be represented by RE-Ba-Cu-O.

A specific example of the former bismuth-based oxide superconducting wire is Bi2223 (Bi ₂ Sr ₂ Ca ₂ Cu ₃ O _10-δ ) manufactured by Sumitomo Electric Industries, Ltd. The bismuth-based oxide superconducting wire is preferably a bismuth-based 2223-phase oxide superconducting conductor containing Bi2223 (in addition to (Bi, Pb) ₂ Sr ₂ Ca ₂ Cu ₃ O _10-δ ) or a bismuth-based 2223 phase oxide. superconducting conductor _{((Bi, Pb) 2 Sr} 2 Ca 1 Cu 2 O 8-δ, Bi 2 Sr 2 Ca 1 Cu 2 O 8-δ) is used.

On the other hand, specific examples of the latter RE-Ba-Cu-O-based oxide superconducting wire include YBCO (YBa ₂ Cu ₃ O _7-δ ) manufactured by American Superconductor Corporation (AMSC). In this embodiment, 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).

  On the other hand, the first correction split coil 22 is formed and designed in the same manner as the main split coil 21 except for dimensions and arrangement.

  A main coil unit 72 included in the cyclotron coil system 71 shown in FIGS. 3 to 5 is another example in which the magnetic field equivalent to that of the main coil unit 2 can be formed but the amount of wire used is small. it can. Unlike the coil system 1, the coil system 71 does not include the center coil 6, but includes spiral sector coil units 4 and 4 equivalent to the coil system 1.

  Each main coil unit 72 of the coil system 71 includes a main split coil 81, a first correction split coil 82, and a second correction split coil 83 each having a ring shape. The main split coil 81, the first correction split coil 82, and the second correction split coil 83 are arranged in parallel with the XY plane so that their centers are located on the Z axis.

  Here, as shown in FIG. 5, the main split coil 81 has a rectangular cross section of 0.149135 m in length and 0.390949 m in width, and the Y-axis and the lower surface are 0.065000 m above the Y-axis. They are arranged in parallel. The inner diameter (radius) of the main split coil 81 is 1.094110 m. The in-split coil 81 has a cross section with a larger area than the first correction split coil 82 and the second correction split coil 83. Also, the main split coil 81 has a larger outer diameter and inner diameter than the first correction split coil 82 and the second correction split coil 83. The main split coil 21 is arranged 0.130000 m away from the mirror-symmetric main split coil 21.

  Here, the first correction split coil 82 has an inner diameter of 1.0086602 m, a width (width of the cross section) of 0.084736 m, and a thickness (length of the cross section) of 0.069711 m, and is in a state along the main split coil 81 (horizontal ) With a distance of 0.330000 m from the first correction split coil 22 at the symmetrical position (0.165000 m away from the X axis). Accordingly, the first correction split coil 82 is arranged in a state of being aligned with the main split coil 81 and the main split coil 81 in its own axial direction, and its inner diameter or outer diameter is made smaller than the outer diameter of the main split coil 81. It is located inside the outer diameter of the main split coil 81 (as viewed in the radial direction and radial direction of the coil).

  Here, the second correction split coil 83 has an inner diameter of 0.387893 m, a width of 0.516684 m, and a thickness of 0.011931 m, and is in a state along the main split coil 81 with respect to the second correction split coil 83 at the symmetrical position. They are arranged with an interval of 0.330002 m (0.0165001 m apart from the Z axis). Accordingly, the inner diameter or the outer diameter of the second correction split coil 83 is smaller than the outer diameter of the main split coil 81 or the first correction split coil 82, and the outer diameter of the main split coil 81 or the first correction split coil 82. It is arranged more inside.

  In the upper main coil unit 72, the lower surface of the first correction split coil 82 having an inner diameter or an outer diameter larger than the outer diameter is disposed below the lower surface of the second correction split coil 83, and the first correction split coil The lower surface of the main split coil 81 having an outer diameter larger than the inner diameter or the outer diameter is disposed below the lower surface of the 82, and the main split coil 81 and the first correction split coil are viewed as the entire upper main coil unit 72. 82, the second correction split coil 83 has a mountain shape in which the lower surface rises upward. The same applies to the upper surface of the lower main coil unit 72.

  In both coil systems 1 and 71 as described above, an isochronous magnetic field for particle acceleration is formed as follows. Here, the coil system 1 will be described, but the same applies to the coil system 71. An isochronous magnetic field for particle acceleration is formed in a portion sandwiched between the main coil units 2 and 2 that are symmetrical to each other. In the cyclotron having the coil unit 1, the central plane (XY plane) between the main coil units 2 and 2 is an acceleration plane for charged particles. In this cyclotron, the center plane between the spiral sector coil units 4 and 4 and the acceleration plane also coincide.

  The main split coil 21 and the first correction split coil 22 are electrically connected to the common power source via a switch (not shown), and a voltage is applied by a single power source by turning on the switch. To generate an isochronous magnetic field together with other exciting coils. Note that the XY plane is the center of the isochronous magnetic field in the vertical direction. In the coil system 71, the energization currents of the main split coil 81, the first correction split coil 82, and the second correction split coil 83 are 420A (ampere), 398A, and 432A in this order (the operation current is less than these energization currents). good).

  When the isochronous magnetic field is formed, the computer as the control device of the cyclotron operates the cooling device and conducts cooling of the cooling medium to a temperature (20K) at which the main split coil 21 and the first correction split coil 22 are in a superconducting state. To stabilize the temperature of the cooling medium. Then, a voltage is gradually applied to pass a current through the main split coil 21 and the first correction split coil 22. When the current is stabilized by the superconducting state, the application of voltage is stopped, and a transition is made to a steady state in which an isochronous magnetic field is formed in which charged particles are accelerated by a spiral orbit.

≪Magnetic field formed by main coil unit≫
FIG. 6 shows the magnetic field generated by the main coil units 72, 72, which is equivalent to the magnetic field generated by the main coil units 2, 2. The generated magnetic field (DESIGN) of the main coil units 72 and 72 has less error (ERROR) than the ideal magnetic field (TARGET) that can accelerate carbon hexavalent positive ions ¹² C ⁶⁺ to 400 MeV / nucleon at a constant rotational frequency. It is in a state (maximum of about 0.1T).

Regarding an ideal magnetic field, generally, the magnetic field and the orbital radius of a particle are given by the following [Equation 1]. Where Bρ is the magnetic rigidity [Tm], p is the (relativistic) momentum [MeV / c], Z is the number of charges (here 6), and E is the kinetic energy (here 400). [MeV / u], E ₀ is the static energy (931) [MeV / u], and A is the mass number (here 12).

≪Spiral sector coil unit≫
Each spiral sector coil unit 4 that is equivalent in both coil systems 1 and 71 includes a plurality of spiral sector coils 41. Each spiral sector coil 41 is an air-core coil wound so as to follow a curved sector shape, and is formed of an oxide superconducting wire like the main split coil 21 and covered with a shield (not shown) so as to be cooled. It is connected to the power supply so that it can be energized. The spiral sector coils 41 are arranged so as to be rotationally symmetric with respect to each other so that the convex side due to the curvature is the positive side in the clockwise direction, and are arranged at equal intervals in the circumferential direction. For each spiral sector coil 41, the convex side may be arranged on the negative side in the clockwise direction.

  FIG. 7 shows details of the spiral sector coil 41. Each spiral sector coil 41 is 5 cm wide and 5 cm thick throughout. 5 is a circle with a radius of 1060 mm (millimeters), and the two-dot chain line is a circle with a radius of 1100 mm.

  Further, each of the spiral sector coils 41 has a bending radius of a predetermined value (here, 3 cm) in view of mechanical characteristics that the oxide superconducting wire may be broken if it is bent excessively and may interfere with the superconducting characteristics. ) Designed to be above. Specifically, the oxide superconducting wire is wound so as to fill a winding space formed by a combination of a block and an arc-shaped block having a bending radius of a predetermined value or more. More specifically, three arc-shaped blocks (inside Arc-1 arranged on the outside and Arc-2, Arc-3 arranged on the outside, and a continuum of straight blocks connected so as to bend gradually at an angle from Arc-1 to Arc-2 (Brick-OUT-1 to Brick-OUT-19), a straight block (Brick-OUT-20) connecting Arc-2 and Arc-3, and an angle from Arc-1 to Arc-3. A winding space is formed from a set of straight blocks (Brick-IN-1 to Brick-IN-16) connected so as to bend gradually. Here, the continuous body of the straight block and the connection body of the arc-shaped block imitate the external shape in which a plurality of curvature radius curves are smoothly connected, and each spiral sector coil 41 has such an external shape. It is formed by winding an oxide superconducting wire around a jig (not shown).

  Further, each spiral sector coil 41 has a boundary of a strong magnetic field portion (hill, hill) generated between the spiral sector coil 41 at the mirror symmetry position with respect to the spiral trajectory of the accelerated particles (within a predetermined range). ) It is formed in a spiral shape having a predetermined angle. Since the spiral sector coils 41 are arranged at equal intervals in the circumferential direction, a relatively strong magnetic field (hill) is generated between the upper and lower spiral sector coils 41, and the spiral sector coils 41 are relatively in a portion where the spiral sector coils 41 are not present. A weak magnetic field (valley) is generated. A spiral is generated so that the incident angle of the accelerated particles from the valley to the hill (the angle between the speed direction of the accelerated particle when the hill enters and the tangential direction of the hill boundary) is within a predetermined range (here, 20 to 90 degrees). Brick-OUT-1 to Brick-OUT-20 (the shape on the hill incidence side) of the sector coil 41 are mainly formed. Further, the spiral sector coil 41 mainly has a Brick-IN-1 so that the angle between the accelerating particle and the hill boundary tangent to the valley from the hill is also within a predetermined range (here, 20 to 90 degrees). Brick-IN-16 (shape on the valley incident side) is formed.

  Each spiral sector coil 41, like the main split coil 21, etc., is connected to a power source and has a cooling device. Based on the command of the computer, the cooling temperature is stabilized and a predetermined energizing current (here, 320A) is supplied. Applying or shifting to a superconducting steady state generates a circumferentially increasing / decreasing magnetic field for accelerating particle convergence in an isochronous magnetic field.

≪Magnetic field formed by spiral sector coil unit≫
The magnetic field generated by the spiral sector coil units 4 and 4 thus formed brings about a strong convergence force on the accelerated particles in the isochronous magnetic field, as will be described below.

  That is, as schematically shown in FIG. 8 (a), when the magnetic pole gap is a hill and narrow and wide, the charged particle (Ion) has a circular orbit as shown in FIG. 8 (b). Taking a distorted orbit from (Circle), the particles enter and leave the hill part at an angle of κ. In this case, as shown in FIG. 8A, the magnetic field lines are distorted at the boundary between the hill and the valley, and an azimuth component of the magnetic field is generated in the vicinity thereof. Here, first, consider the case of FIG. 8B (radial sector type) in which the boundary between the hill and the valley is linear along the radial direction. Based on this case, the consideration when the boundary between the hill and the valley is spiral along the radial direction (spiral sector type) will be described later.

  When the geometric problem is solved using the relationship of “ω = q / mB” and “Bρ = const.” In FIG. 8A, the following [Equation 2] is obtained.

As shown in FIG. 8C, when considering a case where a particle of velocity v crosses an edge at an angle α, the equation of motion of the particle in the z direction is the following [Equation 3]. Here, _Bh is a value in a direction perpendicular to the edge of the horizontal component of the magnetic field, and has a finite value near the edge. Further, when a parameter “s = vt” is introduced, an equation that gives a change in the amount of motion p _{z in} the z direction is the following [Equation 4] from [Equation 3].

The total amount of change Δp _z of the momentum in the z direction when crossing the edge is expressed by the following [Equation 5] using the parameters defined in FIG.

  On the other hand, according to Stokes' theorem, the closed integration along P1-P2-P3-P4-P1 is “▽ × B = 0”, so the following [Equation 6] is obtained. The integration along P2-P3 has a magnetic field value of 0, and the integration along P3-P4 is 0 because both the magnetic field and the integration path are orthogonal. Accordingly, the following [Equation 7] is obtained, and eventually [Equation 8] is obtained.

  From [Equation 8], when α is positive (in the case of FIG. 8C), the particles are subjected to a convergence action. Accordingly, the focal length f is expressed by the following [Equation 9], and convergence due to oblique incidence is given by the following [Equation 10]. Here, ΔB is the difference in magnetic field strength between Hill and Valley.

  Once these values are determined, the betatron frequency can be determined using the transfer matrix. The transfer matrix for one unit of motion in the z direction is given by the product of the transfer matrices of free motion in the hill, convergence at the edge, free motion in the valley, and convergence at the edge, It is given by FOFO as shown in [Formula 11] below.

  When this matrix product is executed and the following relation of [Equation 12] is used, [Equation 13] is eventually obtained. Here, μ is an amount called a phase advance.

Accordingly, the betatron frequency in the z direction is the following [Expression 14] and [Expression 15], and is given by the sum of -β ² γ ² and flutter F ² .

  In each spiral sector coil unit 4, an oblique incident angle of acceleration particles with respect to a boundary between hills and valleys generated by upper and lower spiral sector coils 41 is increased, that is, the boundary draws a spiral from the center of the acceleration plane to the outside. Each spiral sector coil 41 is formed so as to have such a spiral shape.

  FIG. 9B schematically shows a hill and a valley (spiral sector type) or a circular orbit having spiral boundaries, and FIG. 9C shows a relationship between the circular orbit and the acceleration orbit (equilibrium orbit).

  The angle formed by ε in FIG. 9B, that is, the tangent line of the Hill Valley boundary line, and the perpendicular line (radius passing through the contact point) passing through the contact point with respect to the circular orbit passing through the contact point of the tangent line is called a spiral angle. With respect to the deviation angle κ between ε and the circular orbit, the oblique incident angle is ε + κ when entering the hill and ε−κ when leaving. When entering, it receives convergence, and when it exits, it receives divergence. This indicates that it is AG (Alternating Gradient) convergence that alternately repeats convergence and divergence. κ is given by [Expression 2] as in the case of the radial sector type. The magnitude of convergence / divergence at the edge is given by the following [Equation 16], and the transfer matrix is given by FODO as shown in [Equation 17].

  Therefore, the spiral sector type phase advance is represented by the following [Equation 18].

Therefore, the betatron frequency in the z direction of the spiral sector type AVF cyclotron is the following [Equation 19] or [Equation 20], and the term of ² tan ² ε is added to the factor of the term by the radial sector type F ^2. become. In the cyclotron having the coil units 1 and 71, since ε is 50 degrees, the value of this factor becomes as large as 4, and a strong convergence force can be obtained. From the viewpoint of setting such a value of the betatron frequency to an appropriate magnitude, ε is preferably set to 20 to 40 degrees outside the half in the radial direction.

  In order to generate a magnetic field to which a spiral angle ε of less than 90 degrees is applied at various radii on the acceleration plane in this way, the shape (outer shape, winding direction) of each spiral sector coil 41 has a bending radius set to a predetermined value. Although it is described above, similarly, it is formed into a spirally curved sector having a spiral angle ε of less than 90 degrees (around 60 degrees) with respect to various radii. FIG. 10 shows the relationship between the radial position and the spiral angle ε.

≪Magnetic field formed by main coil unit and spiral sector coil unit≫
FIG. 11 shows an acceleration plane formed by a pair of main coil units 72 and 72 and a pair of spiral sector coil units 4 and 4 housed in the coil unit 71 which is the same as the coil unit 1 except for the central region. FIG. 12A shows a magnetic field distribution in a circumferential direction in a circular orbit of each radius of the acceleration plane, and FIG. 12B shows a radial direction (radial direction) from the center of the acceleration plane. FIG. 12 (c) shows the flutter distribution from the center of the acceleration plane to the radial direction.

  From these, in the acceleration plane, an isochronous magnetic field whose strength increases from about 4T to about 7T as it goes to the outer peripheral portion, and a strong portion (hill) and a weak portion (valley) AVF magnetic field in the circumferential direction. The boundary between the hill and the valley is formed in a spiral shape so that the spiral angle ε, which is the angle between the tangent line and the radial direction, is less than 90 degrees and tilts from the radial direction, and the flutter is sufficiently secured. I understand that The flutter will be described in detail. At the radial position r = 0.28 m, the peak is 0.15, and as the diameter increases, the beam extraction position r = 1.06 m has 0.07, which is 0.06 or more. The desired value of is obtained.

  Therefore, the cyclotron including the coil unit 71 can form a magnetic field distribution capable of accelerating carbon hexavalent ions, which are heavy particles, without diverging to about 400 MeV / nucleon on the acceleration plane. However, in the vicinity of the center of the acceleration plane, the magnetic field strength is relatively weak, as shown particularly in a portion having a radius of about 0.1 m or less in FIG. Therefore, in the cyclotron equipped with the coil unit 1, air core center coils 6 and 6 made of superconducting conductors are arranged above and below the central portion of the acceleration plane to compensate for the strength of the magnetic field in the central area of the acceleration plane and to achieve a convergence effect. It is assumed that a certain central bump is applied.

≪Center coil (unit) ≫
Each center coil 6 is an air-core coil in which an oxide superconducting wire is wound in an annular shape, covered by a shield (not shown) so as to be cooled, and connected to the power source so as to be energized. Each center coil 6 has a center on the Z-axis and is disposed so as to be parallel (horizontal) to the XY plane as a whole, and in the vertical direction (Z-axis direction) and inside the main coil unit 2 and the spiral sector. It arrange | positions so that it may become the outer side of the coil unit 4. FIG. Here, each of the center coils 6 is sized so as to surround the end portions on the center side of all the spiral sector coils 41 in a plan view, and is arranged as such.

  Then, an electric current is applied to each center coil 6 so as to generate a magnetic field in a direction in which the magnetic field in the central area of the acceleration plane in the area of the magnetic flux passing outside the spiral sector coils 41 increases. Note that the control device can change the value of the current flowing through each center coil 6 by controlling the power source, and optimize the central bump for stabilizing the particle trajectory (especially the initial trajectory). Can do.

≪Magnetic field in the center area of acceleration plane≫
FIG. 13 shows a central region (center or center) of a magnetic field generated when various currents are passed through the coil unit 1 including the center coils 6 and 6 or when the center coils 6 and 6 are eliminated (no current is passed). The average magnetic field strength (Z component) Bz (r) on a concentric circle in a radius of 30 cm (region of r = 0 to 30 cm) is shown. Here, the size of each center coil 6 is such that the inner diameter is 14 cm and the outer diameter is 19 cm (the radius R of the center coil 6 is 14 to 19 cm), and the distance from the acceleration plane to the inner surface in the Z-axis direction is 10 cm. The distance from the acceleration plane to the outer surface is 15 cm. Further, the current flows in the same direction as each spiral sector coil 41.

Without center coils 6 and 6 (without center coils), the magnetic field strength is increased to about 1.7 T at a radius of 5 cm and up to about 3.2 T at a radius of 20 cm, whereas 10000 A / When a current of ² cm (I _cc ) is flowing, the magnetic field strength is increased to about 2.6 T at a radius of 5 cm and about 3.4 T at a radius of 20 cm, and 20000 A / cm ² . When the current is flowing, the magnetic field intensity is increased so that the current is about 3.5 T at the position of 5 cm and about 4.0 T at the position of 20 cm, and the current of 30000 A / cm ² is flowing. Is about 4.4T at a radius of 5 cm, and the magnetic field strength is increased to about 4.7 T at a radius of 15 cm, from a radius of 20 cm (about 4.0 T) to a radius of 25 cm ( The strength gradually decreases over about 3.2T). In addition, in the case of current of 20000, 30000 A / cm ² , the strength inside (radial direction) is higher than the strength at the position of radius 25 cm (about 3.2 T), especially in the case of current of 30000 A / cm ^2. Then, a central bump having a high magnetic field strength on the center side is remarkably applied.

FIG. 14 shows the average magnetic field strength on concentric circles in the central region of the magnetic field generated when a predetermined current (30000 A / cm ² ) is passed through the coil unit 1 including the center coils 6 and 6 having various inner diameters or outer diameters. Z component Bz (r) of In addition, the inner diameter of the arc portion from the most center in the spiral sector coil 41 is 92.7 mm, and the outer diameter is 142.7 mm.

  Even in the coil unit 1 having the radius R = 7 to 12 cm of the center coil 6, the magnetic field in the center region is raised as compared with the case without the center coils 6 and 6, but when the radius R is increased to 9 to 14 cm, the central magnetic field is increased. When it becomes stronger, the magnetic field near the center becomes the highest magnetic field (central bump), and when the radius R = 9-14 cm is further increased, the central magnetic field becomes even stronger, and the intensity is about 4.5 T over the region of radius r = 5-15 cm. Can be given.

  FIG. 15 (a) shows the average magnetic field intensity Z on a concentric circle in the magnetic field center region when the degree of overhang or the radius of curvature of each spiral sector coil 41 or the presence / absence / diameter / current of each center coil 6 is changed. Component Bz (r) is shown.

The number of types related to the spiral sector coil 41 is 2, and one is an inner diameter _{RSC_inner} at the center of _68.8 mm and a position _{XSC_position} on the X-axis is 92.7 mm to the outer side 142 as shown in FIG. 7 mm, and the other is R _{SC_inner} = 109 mm and X _{SC_position} = 160 to ₂₁₀ mm as shown in FIG. When to have a respective center coil 6, the former combination of center coil 6 of inner diameter _R CC_inner = 200mm · current density _I CC = -30000A / cm ² in, the latter _R CC_inner = 140mm · current density _{I CC} = The center coil 6 of −20000 A / cm ² is combined.

  When only the spiral sector coils 41 in FIG. 15B are present and the center coils 6 and 6 are not present, as shown by the dotted line in FIG. 15A, there is no center bump, but FIG. When the center coils 6 and 6 are provided, as shown by the solid line in FIG. 15A, there is a state in which there is a center bump with sufficient convergence.

  Further, when only the spiral sector coils 41 of FIG. 15C exist and the center coils 6 and 6 do not exist, as shown by a two-dot chain line in FIG. 15A, there is no center bump, and r = In the region of 10 to 25 cm, the magnetic field strength is weaker than in the case without the center coils 6 and 6 in FIG. 15B. However, in the case with the center coils 6 and 6 in FIG. As indicated by the chain line, there is a state in which there is a central bump with sufficient convergence power.

  In particular, when the radius of curvature (inner diameter or outer diameter) of each spiral sector coil 41 is increased to 100 mm or more, the mechanical and electromagnetic stress applied to each spiral sector coil 41 can be reduced practically and the particles can be reduced. A central bump magnetic field can be formed in which a sufficient convergence force can be obtained.

≪Effect≫
As described above, in the coil system 1, an extremely strong isochronous magnetic field in which a hill valley exists is formed by an air-core coil formed by winding an oxide superconducting conductor. Therefore, acceleration of heavy particles necessary for heavy particle beam cancer treatment can be performed by a cyclotron having the coil system 1. The dimensions of the coil system 1 itself are about 4 m in diameter x about 2 m in height, and the coil system 1 and cyclotron can be made very compact, such as an installation area of about several tens of square meters (m ² ) including peripheral devices. It can be downsized. Further, the coil system 1 and the cyclotron are small, and both the main split coil 21 and the first correction split coil 22, both the spiral sector coils 41, and both the center coils 6 constituting the coil system 1 are air-core. Therefore, it is possible to reduce the amount of materials required for manufacturing (particularly relatively expensive superconducting wire), to simplify the structure of the shield for cooling, etc. It can be reduced, operation control can be made relatively simple, introduction cost and operation cost can be made low, maintenance can be easily performed, and maintenance cost can be reduced. Can also be inexpensive.

  In addition, both the main split coil 21 and the first correction split coil 22, both the spiral sector coils 41, and both the center coils 6 are in a superconducting state, and excitation is performed in the superconducting state. In addition, Joule heat generation does not occur and the cooling energy of the cooling medium can be relatively small, and the amount of electric power required for operation can be reduced. In addition, since it is small and air-core, the amount of cooling medium is small, and Joule heat is not generated, so that the time from the stop state to the high magnetic field state (particle acceleration possible state) can be shortened, Particle acceleration can be performed efficiently. Furthermore, since no Joule heat is generated, it is possible to prevent the main split coil 21, the first correction split coil 22, the spiral sector coil 41, and the center coil 6 from being thermally deformed. It is possible to prevent fluctuations and to form a stable isochronous magnetic field or AVF magnetic field, formation of a central bump, or ensuring stable operation of particle acceleration.

  In particular, the central coil magnetic field required to sufficiently converge the particles immediately after the introduction of the particles or in the early stage of acceleration in order to perform the excitation in the superconducting state by winding an oxide superconducting conductor around the center coil 6, Even in a high magnetic field as a whole, it can be efficiently generated by a compact device, and even heavy particles extremely useful in cancer treatment can be stably and sufficiently accelerated from the beginning. Due to the above characteristics, the spread of particle accelerators capable of accelerating heavy particle beams can be promoted, and a great effect can be achieved such as an increase in hospitals capable of performing heavy particle beam cancer treatments.

≪Change example≫
In addition, the other form of this invention which mainly consists of changing the said form is illustrated. The number of coils can be changed in various ways, one or three or more in one main coil unit, three or less or five or more in one spiral sector coil unit, or more than one per one center coil. Also good. That is, the number of various coils in the various coil units can be singular or plural. For example, a center coil unit including a single or plural center coils can be considered for the center coil. However, the spiral sector coil unit needs to include three or more spiral sector coils from the viewpoint of convergence. As an example of the center coil unit including a plurality of center coils, there can be cited those arranged concentrically in a plan view so that the smaller the diameter in the vertical direction, the farther from the acceleration plane.

  For the coils related to the main coil unit, the main split coil and the correction split coil are not divided into the main split coil and the correction split coil based on the distance from the acceleration plane. The cross-sectional areas may be the same, or the coils may have various cross-sectional areas. Further, the main split coil may be arranged farther from the accelerating magnetic field than the correction split coil. The dimensions and arrangement of the various coils can be finely adjusted or changed according to the magnetic gradient shape, the height of the magnetic flux density, or the like. One main coil unit does not need to be composed only of coils that are mirror-symmetric with respect to all the coils in the other main coil unit, and is additionally provided with a fine adjustment coil that is not in the other main coil unit. Any configuration may be adopted as long as it includes a coil that is mirror-symmetric with respect to the plurality of coils belonging to the other main coil unit, and the same applies to the spiral sector coil unit and the center coil unit.

  The various coils in the main coil unit are configured by using pancake coils formed by winding a strip-shaped superconducting wire around a pancake. Each of the main split coil and the correction split coil 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. Even in a cyclotron including such a main coil unit, a high-strength isochronous magnetic field can be formed in a small, low-cost and easy-to-use apparatus. Moreover, by forming the pancake coil or its laminate, electromagnetic force can be applied to the wire component (Hastelloy) as a compressive stress during excitation, and the mechanical strength of each coil can be increased. It can be raised to avoid buckling, further improving durability, and generating a high magnetic field in a more stable state. Note that pancake coils can be used alone without being stacked, and the number of layers can be varied, or the thickness, number of turns, and type / dimension of the wire for each layer can be varied. The main coil unit is a solenoid coil. , A pancake coil, or a combination of laminated pancake coils.

  The temperature of the cooling medium may be other than 20K. The isochronous magnetic field and the AVF magnetic field may be made of a coil not using a superconducting wire or an oxide superconducting wire, or a ferromagnetic material.

  According to the air-core type cyclotron of the present invention, it is possible to provide an isochronous magnetic field, an AVF magnetic field, and a central bump magnetic field with extremely high strength by a small and low-cost configuration. It can be used not only for medical accelerators for medical institutions, but also for the production of experimental cyclotrons that can be easily introduced in research institutions that do not have the largest scale. It can be used to construct small, low-cost, high-energy ion irradiation devices in the fields of technology and new material development, and can also be used to create particle accelerators for diagnosis. The air-core type cyclotron capable of accelerating heavy particles of the present invention has various uses.

  Examples of applicable fields include the creation of new materials that form nanostructures, etc., optical equipment, high-performance separation membranes, micro-nanomachines, high-efficiency heat exchangers, creation of new energies, advanced semiconductors, generation of highly functional membranes, Formation of large-capacity ion exchange membranes, formation of optical waveguides, optical switches, high-performance gratings, antireflection coatings, nanofilters, fine mechanical parts, super-water-repellent membranes, and fine fins Examples include various fields related to structure-controlled drug diffusion systems, high-performance fuel cells, high-precision ion implantation, and creation of integrated hybrid membranes with different performances on the front and back sides.

  In particular, in the case of a heavy particle accelerator for cancer treatment, as described below, the air-core type cyclotron of the present invention efficiently performs irradiation of heavy particle beams that are very effective against cancer. It is possible to treat a large number of cancer patients and provide an improvement in QOL, and the social cost is significantly reduced.

  That is, by irradiating heavy particles such as carbon hexavalent ion beams at two horizontal and vertical gates, it is possible to concentrate a position with a high energy absorption amount at the position of the cancer affected area. The level is much higher than that of gamma rays, and it can have a steep boundary compared to proton rays, reducing the burden on treatment other than the affected area and reducing the burden of treatment. The dose can be concentrated to make the biological effect (cell killing effect) on cancer cells about 3 times that of X-rays or protons, and the effect can be increased with a relatively short irradiation time. The number of irradiations can be reduced, the treatment period and hospitalization period can be shortened, or the rehabilitation period can be made unnecessary or extremely short, but there are very few physical burdens and cost burdens compared to surgical excision and other radiation treatments. Treatment It can be. 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 air-core type cyclotron of the present invention, it is possible to promote the spread of equipment that exhibits such remarkable effects.

DESCRIPTION OF SYMBOLS 1 Coil system 2 Main coil unit 4 Spiral sector coil unit 41 Spiral sector coil 6 Center coil (center coil unit)

Claims (7)

A pair of main coil units facing in the axial direction and forming an isochronous magnetic field in the radial direction;
Opposite to the axial direction, a pair of spiral sectors coil unit that forms a magnetic field with a strength in the circumferential direction,
Has a pair of center coil unit facing the axial direction,
Each of the spiral sector coil units is disposed on the inner side in the axial direction of the corresponding main coil unit,
Each of the center coil units is disposed inside the corresponding main coil unit and outside the spiral sector coil unit in the axial direction,
Each said center center coil according to the coil unit is air-core coil wound with superconducting conductor, coreless cyclotron, characterized in that arranged in the center of the radial direction. Each spiral sector coil unit includes three or more spiral sector coils,
2. The empty sector coil according to claim 1, wherein each of the spiral sector coils is an air-core coil in which a superconducting conductor is wound along a curved sector shape, and is arranged so as to be rotationally symmetrical with each other. Core type cyclotron. The air-core type cyclotron according to claim 1 or 2, wherein each of the spiral sector coils is formed so that a bending radius is not less than a predetermined value. The sky according to any one of claims 1 to 3, wherein the main coil unit is formed by arranging air-core main split coils formed by winding a superconducting conductor in a ring shape in a plurality of axial directions. Core type cyclotron. The pair of center coil units, the pair of spiral sector coil units, and / or the pair of main coil units are arranged mirror-symmetrically with each other. The air-core type cyclotron described. 6. The air core type cyclotron according to claim 1, wherein at least one of the superconducting conductors is an oxide superconducting conductor. The oxide superconductor is a bismuth-based oxide superconductor or an RE-123-based oxide superconductor (REBa ₂ Cu ₃ O _7-δ , RE is a rare earth element including yttrium). Item 7. The air-core type cyclotron according to item 6.