JP3759003B2 - Permanent magnet built-in high magnetic field generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The invention of this application relates to a permanent magnet built-in high magnetic field generator. More specifically, the invention of this application relates to a synchrotron, a cyclotron, a storage ring (storage ring) that can be used for high energy physics, nuclear physics, energy science, materials and materials science, life science, medical use research, etc. The present invention relates to a permanent magnet built-in high magnetic field generator that forms a high-intensity magnetic field necessary for deflecting, converging, and diverging charged particles.
[0002]
[Prior art and its problems]
Until now, research and development of circular charged particle accelerators such as synchrotrons, cyclotrons, and storage rings (storage rings) in accelerator science have focused on increasing the energy or number of charged particles to be accelerated or stored. Has been put. In particular, in a collision type accelerator, efforts have been made to increase the collision frequency (luminosity) of charged particles.
[0003]
In order to increase the acceleration energy of the charged particles, it is necessary to increase the size of the accelerator and to increase the magnetic field strength of the magnet for deflecting, converging / diverging the charged particles. Although superconducting electromagnet technology was introduced to increase the magnetic field strength, it did not reach the level required in fields such as high energy physics and nuclear physics, and only the size of the accelerator would be enlarged. Finally, a huge circular accelerator with a circumference of several tens of kilometers was developed.
[0004]
In the United States, Hadron Collider SSC (Superconducting Super Collider), a circular collision type accelerator, was mid-planned and the Ministry of Energy made a reflection on the increase in size and budget, and the construction was discontinued. As a result, research and development of high-energy accelerators in the United States has been mainly performed by linear colliders, which are colliding linear accelerators, and new circular hadron colliders, which are smaller in scale than SSC, followed by circular lepton colliding accelerators. A muon collider has been listed as the main accelerator in the development plan.
[0005]
On the other hand, in Europe, the construction of the LHC (Large Hadron Collider), which is considered to be the last hadron collider, has been under construction, and the development plan for the muon collider as a leptone collider is beginning to be considered. .
[0006]
In this way, the center of research and development of next-generation high-energy hadron colliders is moving from the United States to Europe, and the high-energy physics community in the United States is beginning to feel a sense of crisis. Under such circumstances, a very large accelerator VLHC (Very Large Hadron Collider) program is being proposed in the United States.
[0007]
On the other hand, the present inventors have developed a high-field permanent magnet from the viewpoint of miniaturization of a circular accelerator (a high-field circular charged particle accelerator using a permanent magnet (Kumada et al., Japanese Patent Application No. 2000-301078), Device (Kumada et al., Japanese Patent Application No. 2001-086098)). However, since the high magnetic field obtained by these inventions is used as a DC magnetic field, it cannot be denied that the particle accelerator is limited to being used in a small cyclotron or a FFAG (Fixed Field Alternating Gradient) accelerator.
[0008]
By the way, at the research and development site of VLHC as the latest state of the art of magnet technology, a superconducting transmission line magnet (Transmission Line Magnet), which is an extremely simplified structure of a magnet mainly used in Fermilab (Fermi National Accelerator Laboratory). / Pipetron) is being researched and developed.
[0009]
This magnet is constructed by energizing a superconducting cable in the form of a pipe, and covering this pipe with an iron core from two directions, two dipole magnetic fields that are opposite to each other. It is to make. As an accelerator, protons are allowed to collide by rotating in opposite directions in the gaps of the magnets arranged on the circumference, and the circumference reaches 240 km. This magnet has the simple feature of being inexpensive and its biggest feature is that the space factor is 95%, and it is said that the superconducting electromagnet alone is converted to Japanese yen and is over 240 billion yen.
[0010]
On the contrary, the most dissatisfied point is that the magnetic field strength cannot exceed 2 Tesla even if it is considerably overreasonable. This is because the magnetic field distribution changes with an increase in the excitation of the magnetic field because iron is saturated, and the high-precision magnetic field spatial distribution required for the storage ring cannot be maintained. Currently, it is not possible to cross this 2 Tesla wall.
[0011]
Therefore, in the VLHC plan, the plan must be divided into two phases, and after 2 Tesla magnets, there is a plan to put 9.8 Tesla high-field magnets in the same tunnel as the second phase plan. However, in 2 Tesla, there is criticism that it will not change with SSC (Superconducting Super Cllider), which had been frustrated in the middle of the plan before, and there is a high demand for realizing a magnet exceeding 2 Tesla. This is the first problem to be solved by the present invention.
[0012]
Furthermore, if the above becomes possible, there is a possibility that a high-energy state-of-the-art accelerator and a medical accelerator synchrotron can be downsized. A small synchrotron with a deflection magnetic field strength of 3 Tesla has a new utility value along with the high-field permanent magnet FFAG, and has a great impact on the spread of medical and therapeutic accelerators. This is the second problem to be solved by the present invention.
[0013]
Therefore, the invention of this application has been made in view of the circumstances as described above, and is necessary for solving the problems of the prior art and deflecting and converging / diverging charged particles in a circular charged particle accelerator. An object of the present invention is to provide a permanent magnet built-in high magnetic field generator that forms a high-intensity magnetic field.
[0014]
[Means for Solving the Problems]
In order to solve the above problems, the invention of this application firstly , a superconducting pipe formed by a superconducting cable, a cooling means for cooling the superconducting pipe with liquid helium, and an outer side of the superconducting pipe And at least one of an iron core and an iron yoke that are covered from the upper and lower directions, and two beam ducts provided on the left and right sides in a direction perpendicular to the length direction of the superconducting pipe with respect to the superconducting pipe, An external magnetic field generated by the superconducting transmission line magnet acts on both left and right sides of the iron core and iron yoke in the superconducting transmission line magnet having a symmetrical structure of the superconducting pipe, and the iron core and iron yoke. It provided a space for arranging the permanent magnet with a gap between the magnetic poles without, respectively, without saturating the at least one of the iron core and yoke While maintaining the spatial distribution of the high magnetic field necessary for the speedometer performance, the magnetic field strength in the air gap provided in the permanent magnet is the magnetic field strength of the combined magnetic field of the permanent magnet and the external magnetic field of the superconducting electromagnet. A high magnetic field generator characterized by the above is provided.
[0015]
Second, in the first invention, there is provided a high magnetic field generator characterized in that the magnetic field strength of the synthesized magnetic field is 2 Tesla or more .
[0016]
Thirdly, in the first or second invention, the high magnetic field generation is characterized in that the constituent elements of the permanent magnet are insulated small unit magnets in order to enable the repeated operation of the fast excitation. Providing equipment.
[0017]
According to a fourth aspect of the present invention, there is provided the high magnetic field generator according to any one of the first to third aspects, wherein the permanent magnet is made of a rare earth magnet material .
[0018]
Fifth, in any one of the first to fourth inventions, the permanent magnet is cooled at a liquid nitrogen temperature, the temperature stability of the magnetic field is improved, and the residual magnetic flux density and the coercive force are also improved. A high magnetic field generator is provided.
[0019]
Sixth, in any one of the first to fifth inventions, the gradient of the magnetic field generated by the superconducting transmission line magnet and the gradient of the magnetic field generated by the permanent magnet when the charged particles are converged by the synchrotron accelerator. A high magnetic field generator characterized by equality is provided.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
In order to solve the first problem, the magnetic field generator of the invention of this application was first invented by Fermilab Foster et al. (Fermilab report, “Design study for a staged VLHC”) Fermilab TM-2149, 6/4/01 ) By combining a superconducting transmission line magnet with a permanent magnet using a rare earth magnet material, a magnetic field strength of 3 Tesla to 4 Tesla, which was impossible in the development of Foster etc., will be realized with a gap magnetic field. Is.
[0021]
In the case of a 3 Tesla magnet, 1.5 Tesla is made of a superconducting electromagnet, the remaining 1.5 Tesla is made of a permanent magnet, and the magnetic field of each magnet is superimposed on the gap provided between the magnetic poles of the permanent magnet. Get a magnetic field. The entire superconducting transmission line magnet is about 240 mm x 280 mm, which is considerably larger than the diameter of the superconducting pipe formed by the superconducting cable, and the size of the beam pipe is about 20 mm x 40 mm. In addition, since the entire superconducting transmission line magnet is considerably larger than the beam pipe, it can be said that the size is suitable for inserting a permanent magnet.
[0022]
A permanent magnet generates a magnetic field of 1.5 Tesla in a space between two iron cores in a superconducting transmission line magnet, and a space into which a beam pipe is inserted. The permanent magnet has a U-shape, C-shape, O-shape, etc. with a gap between the magnetic poles, and its outer diameter may be about 100 mm. The shape of the iron core of the superconducting transmission line magnet can be changed. A space of 100 mm is provided for permanent magnet installation.
[0023]
A superconducting transmission line magnet creates an external magnetic field of 1.5 Tesla for a permanent magnet, but its own iron core is outside this external magnetic field, so when generating 1.5 Tesla alone The magnetic field inside the iron core of the superconducting transmission line magnet does not become stronger. Permanent magnets are exposed to a strong external magnetic field of 1.5 Tesla. However, rare earth magnet materials with high coercive force that can withstand external magnetic fields up to 3 Tesla are available. There are few.
[0024]
Therefore, in the gap between the magnetic poles of the permanent magnet inserted into the superconducting transmission line magnet, a combined magnetic field of the magnetic field by the permanent magnet and the magnetic field by the superconducting transmission line magnet is obtained.
[0025]
The magnetic field strength of each magnet is precisely about 0.1 Tesla higher for the permanent magnet, and the minimum magnetic field when the superconducting transmission line magnet is AC-excited for the synchrotron mode is, for example, the incident magnetic field. Charged particles having a predetermined energy can be incident so as to be 0.1 Tesla (the maximum magnetic field is 3.1 Tesla). These permanent magnets are installed symmetrically on both sides of the superconducting pipe made of superconducting cable, and the electromagnetic force between the superconducting pipe and the superconducting pipe is also symmetrical, so the electromagnetic force acting on the original superconducting transmission line magnet The advantage of small is unchanged. Moreover, since the size of the permanent magnet is considerably smaller than that of the superconducting transmission line magnet, the cost can be increased without significantly increasing the energy.
[0026]
Also in the solution of the second problem, a 1.5 Tesla permanent magnet having an outer diameter of about 100 mm is effective. In a conventional H-type or C-type electromagnet, a gap having a width of <100 mm + necessary width for a magnetic circuit> is provided, and a permanent magnet having a gap between magnetic poles without using an iron core and an iron yoke is used as the gap of the electromagnet. By installing in the center, the magnetic field in the gap of the permanent magnet becomes the combined magnetic field of the magnetic field by the electromagnet and the magnetic field by the permanent magnet. As in the case of the first problem, since the external magnetic field is about 1.5 Tesla, the demagnetization effect can be avoided by selecting a permanent magnet material having a high coercive force.
[0027]
In addition, when a permanent magnet is inserted into the gap of a superconducting transmission line magnet or a normal electromagnet, the permanent magnet is cooled at the liquid nitrogen temperature, thereby improving the temperature stability of the magnetic field and increasing the residual magnetic flux density and coercive force. In addition, it is possible to improve.
[0028]
Further, in the case of a superconducting electromagnet, the repetition of excitation of the magnet is slow, whereas in the conventional electromagnet, the repetition of excitation can be accelerated. In this case, when solving the second problem, the permanent magnet is constituted by the divided small magnets which are insulated small according to the excitation speed.
[0029]
In both cases of superconducting transmission line magnets / normal electromagnets, it should be noted that the magnets of the present invention are applied to circular accelerators such as synchrotrons. There is no problem when it is used as, but when it has a convergence effect, it is necessary to keep the convergence force constant according to the change of the deflection magnetic field strength. For this purpose, it is necessary to make the magnetic field gradient of the permanent magnet equal to the magnetic field gradient of the superconducting transmission line magnet / normal electromagnet.
[0030]
Also, in both cases of superconducting transmission line magnets / normal electromagnets, the combination of electromagnets and small permanent magnets in the transverse direction with respect to the traveling direction of the beam of the accelerator. It is a feature of the invention.
[0031]
Hereinafter, embodiments will be described with reference to the accompanying drawings, and embodiments of the present invention will be described in more detail. Of course, the present invention is not limited to the following examples, and it goes without saying that various aspects are possible in detail.
[0032]
【Example】
<Example 1>
FIG. 1 shows a cross-sectional view of a superconducting transmission line magnet (6) proposed by Fermilab Foster for VLHC. This superconducting transmission line magnet (6) can be said to be a super ferric superconducting magnet in which the copper coil portion of a conventional copper coil electromagnet is replaced with a superconducting coil.
[0033]
This superconducting transmission line magnet (6) cools the superconducting pipe (2) formed by the superconducting cable with liquid helium (1), and surrounds the vacuum insulating duct (3) outside the superconducting pipe (2). An iron core (iron yoke) (5) is covered in two directions, and two beam ducts (4) are provided on both the left and right sides of the superconducting pipe (2). Although not shown in this figure, there is actually a return superconducting cable below the cross section.
[0034]
The greatest feature of this superconducting transmission line magnet (6) is that the left and right sides of the superconducting pipe (2) formed by the superconducting cable are symmetrical, and electromagnetic force is hardly applied to the superconducting pipe (2). That is. Therefore, the superconducting cable forming the superconducting pipe (2) does not require a strong structural material for resisting electromagnetic force, and the cost is extremely low. Foster's claim is that it costs only $ 200 million if the superconducting transmission line magnet (6) is almost fully packed in the circumference of the 240 km accelerator. In terms of Japanese yen, it is 1 million yen / m, which is an order of magnitude cheaper than normal magnets.
[0035]
The broken line in FIG. 2 indicates the position of the original iron core (5), and the solid line indicates the superconducting transmission line when the iron core (5) is located in a state where the gap is widened to insert a small permanent magnet. The state of the magnet (6) is shown.
[0036]
FIG. 3 shows a magnetic field in the beam duct (4) formed by a small permanent magnet (7) in which a C-shaped small permanent magnet (7) having a gap between magnetic poles is installed around the beam duct (4). Direction (8) is shown.
[0037]
FIG. 4 shows a state in which the small permanent magnet (7) is inserted into the gap of the superconducting transmission line magnet (6).
The above figure is a schematic view although the dimensional scale ratio is approximately correct. Roughly, it takes only a small superconducting transmission line magnet to produce 1.5 Tesla. Therefore, the cost including the additional cost of the magnet of the present invention is almost the same as the original superconducting transmission line magnet developed by Foster et al. Expected to be the same amount.
<Example 2>
FIG. 5 shows a cross-sectional view of an H-type electromagnet (9) using a conventional copper coil. Here, the iron core (10), the iron yoke (11), and the copper coil (12) constitute an electromagnet, and a small permanent magnet (14) having a beam duct (13) is formed in a gap formed therein. It is installed in a liquid nitrogen tank (15) as a cooling duct, and liquid nitrogen (16) is enclosed. In this example, the beam duct (13) hits the gap between the magnetic poles of the permanent magnet (14), and the magnetic field in the beam duct (13) is a combined magnetic field of the magnetic field by the H-type electromagnet (9) and the magnetic field by the permanent magnet (14). It becomes.
[0038]
The purpose of cooling the permanent magnet (14) in the gap of the H-type electromagnet (9) with liquid nitrogen (16) is to increase the temperature stability of the magnetic field for use in the accelerator and to improve the magnetization characteristics at low temperatures. It is. Although not shown in the drawing, the permanent magnets in the gaps can also be cooled with liquid nitrogen in the form of the first embodiment.
[0039]
Compared with superconducting electromagnets, which repeats excitation slowly, conventional electromagnets can accelerate excitation repeatedly.
In the form of the second embodiment, it is also possible to configure a permanent magnet with small magnets that are insulated and divided in accordance with the excitation speed. When a permanent magnet is placed in an external magnetic field that is changed by an electromagnet, an eddy current flows and a magnetic field is generated due to the eddy current. However, as described above, the permanent magnet is composed of small magnets that are insulated and divided. This can be avoided.
[0040]
In both the first and second embodiments, the electromagnet and the small permanent magnet are combined in a plane transverse to the traveling direction of the beam of the accelerator.
[0041]
【The invention's effect】
As described in detail above, the present invention enables repeated operation of slow excitation exceeding 2 Tesla to nearly 4 Tesla while maintaining a high-performance magnetic field distribution by combining a superconducting electromagnet and a permanent magnet. A high magnetic field generator is provided. Similarly, there is provided a high magnetic field generator that can be repeatedly operated with a fast excitation by a combination of an electromagnet other than a superconducting electromagnet and a permanent magnet.
[0042]
Magnets that combine superconducting electromagnets and permanent magnets as described above are low-priced medium magnetic fields (3 to 4 Tesla) and solve the problem of iron saturation in superconducting electromagnets, which was difficult with low magnetic fields (2 Tesla). In addition, the problem of the DC magnetic field, which is often inconvenient with permanent magnets, can be solved, and the disadvantages of both can be eliminated.
[0043]
Similarly, electromagnets other than superconducting electromagnets can be combined with small permanent magnets, enabling up to 3 Tesla AC magnetic field, which was previously impossible, and can be applied to low-priced compact accelerators for medical use. Can open the way.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a superconducting transmission line magnet used in a high magnetic field generator of one embodiment of the present invention.
FIG. 2 is a diagram showing a state when the interval between magnetic poles of a superconducting transmission line magnet is widened in order to insert a small permanent magnet in the high magnetic field generator of the same embodiment.
FIG. 3 is a view showing the appearance of a small permanent magnet used in the high magnetic field generator of the same embodiment.
FIG. 4 is a diagram showing a state when a small permanent magnet is incorporated into a superconducting transmission line magnet in the high magnetic field generator of the same embodiment.
FIG. 5 is a view showing a state in which a small permanent magnet is incorporated into a gap of a conventional electromagnet in a high magnetic field generator of another embodiment.
[Explanation of symbols]
1 Liquid helium 2 Superconducting pipe 3 Vacuum insulation duct 4 Beam duct 5 Iron core (iron yoke)
6 Superconducting transmission line magnet 7 Permanent magnet 8 Direction of magnetic field in gap 9 H-type electromagnet 10 Iron core 11 Iron yoke 12 Copper coil 13 Beam duct 14 Small permanent magnet 15 Liquid nitrogen tank 16 Liquid nitrogen

Claims (6)

A superconducting pipe formed by a superconducting cable, a cooling means for cooling the superconducting pipe with liquid helium, at least one of an iron core and an iron yoke provided on the outer side of the superconducting pipe and covered from two directions above and below, Iron core and iron in a superconducting transmission line magnet comprising two beam ducts provided on the left and right sides in a direction perpendicular to the length direction of the superconducting pipe with respect to the conducting pipe, and having a symmetrical structure on the left and right of the superconducting pipe On each of the left and right sides of at least one of the yokes, an external magnetic field generated by the superconducting transmission line magnet acts, and a space for disposing a permanent magnet having a gap between the magnetic poles without using an iron core and an iron yoke is provided. While maintaining at least one of the iron core and iron yoke without saturating the high magnetic field spatial distribution necessary for the accelerator performance, it is installed in the permanent magnet. Magnetic field strength in the air gap, high magnetic field generator, characterized in that the field strength of the resultant magnetic field of the external magnetic field by the magnetic field and superconducting magnet by a permanent magnet. The high magnetic field generator according to claim 1, wherein the magnetic field strength of the synthetic magnetic field is 2 Tesla or more . The high magnetic field generator according to claim 1 or 2, wherein the constituent elements of the permanent magnet are insulated small unit magnets so as to enable fast repeated operation of excitation . 4. The high magnetic field generator according to claim 1, wherein the permanent magnet is made of a rare earth magnet material . The high magnetic field generator according to any one of claims 1 to 4, wherein the permanent magnet is cooled at a liquid nitrogen temperature, temperature stability of the magnetic field is improved, and residual magnetic flux density and coercive force are also improved. . The gradient of the magnetic field generated by the superconducting transmission line magnet and the gradient of the magnetic field generated by the permanent magnet when the charged particles are converged by the synchrotron accelerator are equal to each other. High magnetic field generator.

Images