JP2006059755A - Magnetic field generating method and magnetic field generator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable generation of high magnetic field even with a magnetic pole interval (gap) made large. <P>SOLUTION: In the magnetic field generating method of generating a magnetic field at gaps between magnetic poles set in opposition, at least one superconductive loop is formed interlinking with a magnetic circuit structured by the magnetic poles set in opposition, is cooled down to a temperature lower than a superconductive transition point temperature, and, after the superconductive loop is turned into a super conductive state, a width of the gap of the magnetic poles set in opposition is widened. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetic field generation method and a magnetic field generation device. More specifically, the present invention relates to a magnet such as a permanent magnet or an electromagnet or a magnetic pole material made of a magnetic material having a high permeability and a high saturation magnetic flux density. The present invention relates to a magnetic field generation method and a magnetic field generation apparatus for generating a magnetic field in a gap between opposing magnets and magnetic poles of a magnetic pole material.

  Conventionally, a magnetic field is formed in the gap between the opposing magnets and the magnetic poles of the magnetic pole material by arranging the magnetic pole material made of a magnet having a high magnetic permeability and a high saturation magnetic flux density, such as a permanent magnet and an electromagnet, facing each other. There are known magnetic field generators of the type that generate

  By the way, in this type of conventional magnetic field generator, the magnetic field (magnetic flux density) suddenly increases as the gap between the opposing magnetic poles, that is, the magnetic pole interval (hereinafter referred to as “gap” as appropriate) increases. It is known that there is a principle characteristic of decreasing.

  A typical example of the problem resulting from such characteristics can be found in an apparatus called an insertion light source that is used as a synchrotron radiation source for generating radiation as described below (Non-Patent Document 1). reference).

  The insertion light source is a device having a periodic magnetic field structure inserted in a linear space between the deflecting magnets of the storage ring in the accelerator, and the synchrotron radiation from the deflecting magnets when the electron beam passes through. It is a light source device that generates powerful synchrotron radiation of higher quality than light. Such insertion light sources are roughly classified into two types called undulators and wiggras. However, in current synchrotron radiation facilities such as SPring-8 owned by the present applicant, the interference effect of light is used. An undulator that generates high-intensity light is mainly used.

  As described above, a periodic magnetic field structure is formed in the insertion light source. Such a periodic magnetic field structure is formed by the conventional magnetic field generator described above, that is, a magnet such as a permanent magnet or an electromagnet, or a high magnetic permeability. It is constructed using a magnetic field generator of the type that generates a magnetic field in the gap between the opposing magnets and the magnetic poles of the magnetic pole material by arranging the magnetic pole materials made of a magnetic material having a high saturation magnetic flux density property facing each other. Yes.

  That is, in the insertion light source, a periodic magnetic field structure is formed by periodically arranging the magnetic poles facing each other, and a periodic magnetic field is generated by the periodic magnetic field structure thus formed. When light generated from each periodic magnetic field overlaps when electrons move, high-intensity light is obtained.

  Therefore, in such an insertion light source, it is necessary to increase the gap between the opposed magnetic poles in order to pass electrons.

  However, since the conventional magnetic field generator has a characteristic that the magnetic field (magnetic flux density) rapidly decreases as the gap is increased as described above, this determines the upper limit of the magnetic field that can be generated in the insertion light source. There was a problem that it was supposed to be.

In addition, such problems are particularly prominent when the period length of the periodic magnetic field is shortened.
T. T. et al. Hara, T .; Tanaka, H .; Kitamura, T .; Bizen, X. Marechal, T.M. Seike, T .; Kohda and Y.K. Matsuura, “Cryogenic Permanent Magnetic Undurators”, Physical Review ST-AB 7 (2004) 050702.

  The present invention has been made in view of the above-described problems of the prior art, and the object of the present invention is to enable generation of a high magnetic field even when the magnetic pole interval (gap) is increased, It is an object of the present invention to provide a magnetic field generation method and a magnetic field generation apparatus that are intended to improve the strength of the generated magnetic field.

  In order to achieve the above object, a magnetic field generation method and a magnetic field generation apparatus according to the present invention use a basic property of a superconductor closed loop to maintain a magnetic flux and generate a high magnetic field. .

  That is, a superconductor closed loop constituted by, for example, a ring-shaped structure (hereinafter, appropriately referred to as a “superconductor ring”) formed of a superconducting material, which is disposed so as to surround the magnetic pole, It works as a kind of permanent magnet, and its magnetization is performed by electromagnetic induction caused by the movement of opening the gap. The magnetic field generation method and the magnetic field generation apparatus according to the present invention are capable of generating a high magnetic field while maintaining the magnetic flux even when the gap is enlarged, utilizing the basic property of such a superconductor closed loop. is there.

  In the magnetic field generation method and the magnetic field generation apparatus according to the present invention, in order to configure a superconductor closed loop, for example, only a superconductor ring may be formed of a bulk type high temperature superconductor, and an additional external power source or There is no need to provide a current introduction terminal.

  The critical current density of the superconductor has a very important influence on the performance of the magnetic field generation method and the magnetic field generation apparatus according to the present invention.

  Such a magnetic field generation method and magnetic field generation apparatus according to the present invention can be used as a magnetic field generation apparatus such as an insertion light source such as an undulator or a wiggler.

Hereinafter, the principle of the magnetic field generation method and the magnetic field generation apparatus according to the present invention will be described in detail. First, based on the basic properties of the superconductor closed loop that maintains the magnetic flux, the magnetic field enhancement technique of the electromagnet, that is, superconductivity A mechanism for magnetic field enhancement in a magnetic circuit composed of a closed loop and an electromagnet having a pair of variable gaps capable of varying the magnetic pole spacing will be described.

  FIG. 1 shows a superconductor ring 10 for forming a superconductor closed loop, and yokes 16 and 18 disposed so as to face each other so as to form a pair of gaps 12 and 14. The magnetic circuit which consists of the electromagnet 22 which consists of the rotated coil 20 is shown.

  More specifically, the superconductor ring 10 is wound around and fitted into the yoke 18. Further, it is assumed that the gaps 12 and 14 can be changed.

  Furthermore, this magnetic circuit assumes that the cross section of the magnetic flux path is constant everywhere, and that the fringe effect or magnetic flux leakage can be ignored.

In the magnetic circuit shown in FIG. 1, the temperature of the superconductor ring 10 is higher than the superconducting transition temperature _Tc and the superconductor ring 10 is not in the superconducting state, that is, the superconductor closed loop is inactive. In some cases, the magnetic field B in the gaps 12, 14 is obtained by simple Ampere's law as follows:

Here, NI magnetomotive force, mu ₀ of the coil is the vacuum magnetic permeability, the k _m relative magnetic permeability of the yoke, g is the size of the gap (gap width), L is the total length of the flux path of the yoke.

If no yoke is saturated, the relative permeability _{k m} has a 10000 or more values from a normal 1000. For example, cobalt - iron - permendur made of vanadium has a high relative permeability k _m of about 1700 at a magnetic flux density of 2 Tesla.

  Therefore, in a completely closed gap in which the gaps 12 and 14 are completely closed, that is, g = 0, a very high magnetic field can be expected. As a matter of course, the gap width g in the gaps 12 and 14 should be expanded (enlarged) to a meaningful value for using the electromagnet 22 as the magnetic flux generating means. However, if the gap width g is increased, As shown by a broken line (a) in FIG.

Next, in the magnetic circuit shown in FIG. 1, the temperature of the superconductor ring 10 is made lower than the superconducting transition temperature _Tc to activate the superconductor closed loop, and the superconducting phenomenon due to the superconductor closed loop is utilized. The magnetization process will be described with reference to a partially sectional explanatory view corresponding to FIG. 1 shown in FIG.

First, while keeping the temperature T of the superconductor ring 10 higher than the superconducting transition temperature T _c , the gaps 12 and 14 are completely closed so that a completely closed gap, that is, g = 0 (FIG. 3A). ). In this case, the yokes 16 and 18 can obtain the maximum magnetic flux.

Next, when the temperature T of the superconductor ring 10 is cooled to a temperature lower than the superconducting transition temperature _Tc , the transition to the superconducting state occurs (FIG. 3B). At this time, since the magnetic flux is kept in the superconductor closed loop 10 constituted by the superconductor ring 10, even if the gaps 12 and 14 are separated and g> 0 (FIG. 3C), the magnetic flux is Must be immutable. That is, an additional magnetomotive force is generated by the permanent current in the superconductor closed loop constituted by the superconductor ring 10.

  In other words, the superconductor closed loop constituted by the superconductor ring 10 acts as a kind of permanent magnet. That is, magnetization is performed by electromagnetic induction caused by the movement of expanding the gaps 12 and 14. Therefore, the magnetic field, which is the magnetic flux per unit area, maintains its maximum value regardless of the gap width g, as shown by the solid line (b) in FIG.

That is, FIG. 2 shows a case where the superconductor closed loop is inactive, that is, when the temperature of the superconductor ring 10 is higher than the superconducting transition temperature _Tc (dashed line (a) in FIG. 2). A graph showing typical gap dependence of the magnetic field when the closed body loop is active, that is, when the temperature of the superconductor ring 10 is lower than the superconducting transition temperature _Tc (solid line (b) in FIG. 2). Is represented. However, in an actual magnetic circuit, the fringe effect or magnetic flux leakage becomes more prominent as the gap value increases. In this case, the magnetic field actually obtained is slightly lower than the magnetic field shown by the solid line (b) in FIG. In addition, the dashed-dotted line (c) in FIG. 2 has shown the permanent current in a superconductor.

Thus, by using a superconductor, a higher magnetic field can be obtained in a magnetic field generator with an air / vacuum gap.

Note that the superconductor closed loop constituted by the superconductor ring 10, that is, the permanent current of the superconductor is generated by electromagnetic induction caused by the movement of opening the gaps 12 and 14 rather than the external power source. This means that instead of winding a coil made of a superconductor having a current lead around the yoke 16, a bulk type or multilayer type superconductor can be used, and a superconductor closed loop is formed. For example, a high-temperature superconductor such as a copper oxide high-temperature superconductor can be used as the superconductor.

  This allows the magnetic field generator to be operated at a much higher temperature than that of liquid helium, thus greatly simplifying the cryogenic system for cooling the superconductor.

The magnetic field generation method and the magnetic field generation apparatus according to the present invention described above include, for example, a magnetic field generation apparatus using various magnets and magnetic pole materials provided with a system for changing the magnetic pole interval, as described below. It can be applied to various devices such as an undulator.

  In other words, the undulator as an insertion light source generally includes a magnetic pole interval variable system (gap drive system) for adjusting the wavelength of radiated light by making the magnetic pole interval variable. A magnetic field generation method and a magnetic field generation apparatus can be applied.

  In particular, the conventionally known cryogenic permanent magnet undulator (cryo undulator) has a mechanical structure that allows a vacuum structure for cooling the internal magnetic components and a substantially completely closed gap (g≈0). It is most suitable for applying the magnetic field generation method and magnetic field generation apparatus according to the present invention.

Here, the functions achieved when the magnetic field generation method and the magnetic field generation apparatus according to the present invention are used in a conventionally known cryogenic permanent magnet undulator will be predicted below.

  In addition, when using the magnetic field generation method and the magnetic field generator according to the present invention in a conventionally known cryogenic permanent magnet undulator, in order to insert a superconductor ring or the like for constituting a superconductor closed loop in the permanent magnet, It may be necessary to remove only a small amount of the permanent magnet, and this partial removal of the permanent magnet means that the magnetic field generated by the permanent magnet is somewhat reduced. Therefore, it is preferable to optimize the volume of the superconductor ring inserted into the permanent magnet.

  The magnetic structure model shown in FIG. 4 will be described as an example of a magnetic structure model when the magnetic field generation method and the magnetic field generation apparatus according to the present invention are used in a conventionally known cryogenic permanent magnet undulator. FIG. 5 is a graph showing an example of the magnetic performance of the magnetic structure model of FIG.

  In the model shown in FIG. 4, a superconductor ring 44 simply formed of a bulk type high temperature superconductor is disposed in a gap in a conventionally known cryogenic permanent magnet undulator.

More specifically, FIG. 4 includes a magnetic pole piece 42 formed of a permanent magnet 40 and a magnetic pole material made of a magnetic material having high permeability and high saturation magnetic flux density, and a superconductor ring 44. 1 shows a cryogenic permanent magnet undulator having a periodic magnetic field structure with a period length λ _u of 14 mm. In addition, the white arrow in FIG. 4 has shown the magnetization direction.

The magnetic structure of this model will be described in more detail. As a material of the permanent magnet 40, for example, NEOMAX-53CR manufactured by NEOMAX can be used, and as a material of the pole piece 42, for example, manufactured by Neomax Can be used.

  Note that NEOMAX-53CR is made of praseodymium-iron-boron, has a residual magnetic flux density of 1.5 T at a temperature of 77 K, and a permendur saturation magnetic flux density of 2.35 T. If the temperature of the permanent magnet 40 is lowered, the residual magnetic flux is expected to increase.

  Here, in the calculation of the periodic magnetic field of the model shown in FIG. 4, the calculation is performed on the assumption that the superconductor is replaced with a current loop (same shape and same size). That is, the magnetic field generated by the superconductor is calculated as being equivalent to the magnetic field generated by a current loop of the same shape and size.

In this calculation, it is important to predict the permanent current (I _p ) flowing through the superconductor, which is necessary for magnetic field enhancement in this model.

I _p can be determined from Faraday's Dielectric Law, and the magnetic flux surrounded by the superconductor ring 44 can be any closed gap, ie any initial condition with g = 0 and I _p = 0. It is kept even in the gap. Based on this assumption, the magnetic field is calculated with a RADIUS (three-dimensional static magnetic field computer code) (for the RADIUS, “O. Chubar, P. Elleaume & J. Chavanne,“ A three-dimensional magnetostatistics computer code infestation ”). , J. Synchrotron Radiat. 5, 481-484 (1998).].

Here, the model shown in FIG. 4 has two parameters to be operated. The pole length (L _p ) and the thickness (T _s ) of the superconductor ring 44. By optimizing these two parameters, the performance of the magnetic field is improved while taking into account the critical current density ( _Jc : the maximum current density that can flow through the superconductor).

Therefore, it is necessary to plot the achievable peak value of the periodic magnetic field calculated with the optimized dimensions of L _p and T _s as a function of J _c .

FIG. 5 shows the respective calculation results when the gap width g for passing the electron beam through the undulator is 5 mm and 3 mm. More specifically, for two different gap widths g, g = 5 mm (solid line curve) and g = 3 mm (chain line curve), the reached values calculated as a function of the superconductor critical current density (J _c ) Possible peak magnetic fields are shown. When the J _c value of the superconductor is higher than 1.1 kA / mm ^{2, the} peak magnetic field achieved in the model shown in FIG. 4 is 1.3 T (this is a superconducting undulator (SCU: liquid that was recently developed by ACCEL Instruments). This is the peak magnetic field achieved with a gap width of 5 mm in a superconducting undulator with a superconducting (SC) coil operating near the helium temperature. For the superconducting undulator recently developed by ACCEL Instruments, Rossmanith, H. Moser, A. Geisler, A. Hobl, D. Krischel & M. Schillo, “Superductive 14 mm periodic forsuffering elements” torage rings ", Proceedings of the EPAC 2002, Paris, France, more than (EPS-IGA / CERN, Geneva, 2002), referring to the 2628-2630.".).

That is, it can be seen that the achievable peak magnetic field is remarkably enhanced as J _c increases. In the graph shown in FIG. 5, the value of 1.3T indicated by the broken line represents the peak magnetic field when the gap width of the SCU recently developed by ACCEL Instruments is 5 mm.

Thus, _{J c} values of the superconductor If higher than 1.1kA / mm ^2, the peak magnetic field in the model shown in FIG. 4 is expected to exceed SCU in the gap width. Note that the cooling capacity of a small refrigerator that can be used at the operating temperature of the SCU (near the liquid helium temperature) is about 2 W at most. On the other hand, in the model shown in FIG. 4, since the operating temperature (40 to 80K) is much higher, a high-performance small refrigerator having a high cooling capacity of 100 W to 200 W can be used. In general, when the gap width is narrowed, the heat load increases, but in the model of FIG. 4 having a high operating temperature, a high-performance small refrigerator can sufficiently cope with it. Therefore, the minimum gap can be narrower than the SCU, thereby further improving the performance of the model shown in FIG.

In order to further verify the principle of the magnetic field generation method and magnetic field generation apparatus according to the present invention, a magnetic circuit using a superconductor ring made of a commercially available Gd-Ba-Cu-O was created and experimented. .

  First, the performance of the superconductor ring itself was investigated. FIG. 6 shows a schematic perspective view of the superconductor ring 60 used in the experiment. The superconductor ring 60 is a rectangular plate-like body having a hole 60a formed at the center. The dimensions of the superconductor ring 60 are as shown in FIG.

  First, as the magnetic performance of the superconductor ring 60 when an external magnetic field is applied using another magnetic field generator, the magnetic field at the center of the hole 60a of the superconductor ring 60, that is, at the center of the superconductor ring 60 is shown. The magnetic field was measured with the Hall probe 62.

The measurement result is shown in the graph shown in FIG. 7, the horizontal axis indicates the intensity of the external magnetic field, and the vertical axis indicates the magnetic field at the center of the superconductor ring 60 measured by the Hall probe 62. The temperature condition at the time of measurement was the liquid nitrogen temperature (77 K). The measurement result shows a typical hysteresis curve caused by the diamagnetism of the superconductor ring 60. That is, FIG. 7 shows the result of magnetic field measurement for the superconductor ring 60 at a temperature of 77 K, and a typical hysteresis loop due to the diamagnetism of the superconductor was observed. Than the width of the hysteresis loop, defined as _{J c} value of 200A / mm ^2.

More specifically, from this experimental result, J _c was predicted to be approximately 200 A / mm ^{2 as} compared with the calculation of the magnetic field by a current loop having the same shape and dimensions as the superconductor ring 60. This is a typical value for a copper oxide superconductor material at 77K.

After that, as shown in FIG. 8, an experiment was performed with a magnetic field generator according to the present invention composed of a permanent magnet and a superconductor. 8A is a side view of the magnetic field generation device 80, and FIG. 8B is a view as viewed from the direction A in FIG. 8A, that is, a plan view of the magnetic field generation device 80.

  The magnetic field generator 80 will be described. The permanent magnets 82a to 82c and the permanent magnets 82d to 82f made of NdFeB are arranged so as to oppose each other so that the gap width g of the gap can be varied by the hullback structure. The body ring 60 is disposed on the surface facing the gap between the permanent magnets 82a and 82b magnetized in the horizontal direction, and the superconductor ring 60 made of Gd—Ba—Cu—O shown in FIG. 6 is magnetized in the horizontal direction. The permanent magnets 82d and 82e are disposed on the surface facing the gap. In addition, the white arrow in FIG. 8 has shown the magnetization direction, and each dimension is as showing in FIG.

  More specifically, in one block of the permanent magnets, permanent magnets 82a and 82b whose magnetization directions are horizontal directions toward the permanent magnets 82c are arranged so as to sandwich the permanent magnet 82c whose magnetization direction is downward in the vertical direction. Has been placed. Here, the permanent magnet 82c is disposed so as to protrude 2 mm below the permanent magnets 82a and 82b, that is, 2 mm toward the gap side. And the superconductor ring 60 is arrange | positioned on the surface facing the gap of the permanent magnets 82a and 82b so that the downward protrusion part of the above-mentioned permanent magnet 82c may be arrange | positioned in the hole 60a.

  Further, in the other block of the permanent magnets, the permanent magnets 82d and 82e whose horizontal magnetization directions are in a direction away from the permanent magnet 82f with the permanent magnet 82f whose magnetization direction is downward in the vertical direction sandwiched therebetween. Is arranged. Here, the permanent magnet 82f is disposed so as to protrude 2 mm above the permanent magnets 82d and 82e, that is, to protrude to the gap side by 2 mm. And the superconductor ring 60 is arrange | positioned on the surface facing the gap of the permanent magnets 82d and 82e so that the above-mentioned protrusion part of the permanent magnet 82f may be arrange | positioned in the hole 60a.

  The permanent magnets 82a to 82c and the permanent magnets 82d to 82f are such that the permanent magnet 82a and the permanent magnet 82d face each other, the permanent magnet 82b and the permanent magnet 82e face each other, and the permanent magnet 82c and the permanent magnet 82f face each other. is doing. Further, the superconductor ring 60 disposed on the surface facing the gap between the permanent magnets 82a and 82b and the superconductor ring 60 disposed on the surface facing the gap between the permanent magnets 82d and 82e face each other. Yes.

  As a material of the permanent magnets 82a to 82f in this experiment, NEOMAX 50BX manufactured by NEOMAX was used.

  In this experiment, the magnetic field at the center of the gap was measured as a function of the gap width g. Before the measurement, the gap is completely closed at a temperature of 300 K (the superconductor ring 60 is not in the superconducting state and the superconductor closed loop formed by the superconductor ring 60 is inactive), and the magnetic field generator Cool down by pouring liquid nitrogen until the temperature of 80 drops to 77K (superconductor ring 60 is in a superconducting state and the superconductor closed loop composed of superconductor ring 60 is active). The gap width g was opened to 2 mm. Thereafter, a hole probe was inserted and held at the center of the gap, and the gap dependency of the magnetic field was measured.

  The broken line (a) in FIG. 9 shows the measurement result of the peak magnetic field when the superconductor ring 60 is not in the superconducting state and the superconductor closed loop constituted by the superconductor ring 60 is inactive. The solid line (b) in FIG. 9 shows the measurement result of the peak magnetic field when the superconductor ring 60 is in the superconducting state and the superconductor closed loop formed by the superconductor ring 60 is active. From the graph shown in FIG. 9, the magnetic field enhancement by the superconductor closed loop constituted by the superconductor ring 60 clearly appears.

Note that the current density in the superconductor ring 60 is predicted as indicated by the alternate long and short dash line (c) in FIG. The current density of the superconductor ring 60 indicated by the alternate long and short dash line (c) in FIG. 9 increases as the gap width g of the gap increases, but 200 A / mm ² (the expected J _c value of the superconductor ring 60). ).

That is, as the gap is opened, the current density approaches 200 A / mm ² which is the J _c value determined in the previous experiment. However, when the gap width g of the gap exceeds 8 mm, the current density decreases, and J _c Indicates that it went down throughout the experiment. The performance degradation of the superconductor ring 60 is due to structural damage during the experiment, that is, an increase in cracks.

Note that the J _c value of 200 A / mm ^{2 of} the superconductor in the above experiment may not be sufficient to positively adopt the principle of the magnetic field generator according to the present invention, as can be seen from FIG. It is preferable to use a superconductor having a higher _Jc value.

However, it should be noted that this value is at the temperature of liquid nitrogen, ie 77K. The J _c of the superconductor material is strongly dependent on the temperature (T) are well known and generally the relationship between the J _c and T is expressed approximately as follows.

Where J _c is the critical current density at 0 K, T _c is the superconducting transition temperature, and the index m is a parameter in the range of 1.0 to 3.0 indicating the pinning mechanism of the type II superconductor. . As an example, when J _c is calculated when T _c = 90K m = 2 and the temperatures are 77K and 40K, J _c (40K) / J _c (77K) to 9 is obtained. When applied to an superconductors using in experiments, it can be expected to _{J c} of about 1.8kA / mm ² at 40K. In this case, the peak magnetic field of the undulator with the gap generator of 5 mm and the magnetic field generator according to the present invention can be expected to be 1.45 T, which is higher than the peak magnetic field achieved in the conventional SCU.

That is, the magnetic field generator according to the present invention is installed so as to surround the magnetic poles composed of opposed magnets or magnetic pole materials, magnetic pole gap changing means for changing the gap between the magnetic poles, and the opposed magnetic poles. The magnetic circuit is composed of only the magnetic poles in which the superconductor generates magnetomotive force in addition to the magnetomotive force generated by the magnetic poles even when the gap between the opposing magnetic poles is large. A magnetic field higher than the magnetic field (magnetic flux density) can be generated.

  In other words, the magnetic field generator according to the present invention is a closed loop (at least one superconductor linked to the magnetic circuit) in an electromagnet magnetic circuit or a permanent magnet magnetic circuit in which the gap (distance between magnetic poles, magnetic pole gap) is variable. Superconductor closed loop) is formed.

Of course, since the superconductor is not effective at a temperature higher than the superconducting transition temperature _Tc , the superconductor closed loop is inactive, and the total magnetic flux of the magnetic circuit and the magnetic field (magnetic flux density) obtained in the gap is the gap. It decreases rapidly as the width increases (the magnetic resistance increases).

On the other hand, the gap is set to be small (preferably zero), and the superconductor is cooled so that the superconducting transition temperature _Tc or lower. When the gap width is increased in this state, a permanent current flows in the superconductor closed loop so that the total magnetic flux of the magnetic circuit is kept constant by the electromagnetic induction effect (basic property of the superconductor). That is, the magnetomotive force generated in the superconductor is added to the magnetomotive force unique to the magnetic circuit, and the magnetomotive force of the superconductor closed loop increases as the gap width increases. Therefore, a high magnetic field is maintained even when the gap width is large.

According to the first aspect of the present invention, in the magnetic field generating method for generating a magnetic field in the gap between the magnetic poles arranged to face each other, the magnetic poles are arranged to face each other. Forming at least one superconductor loop interlinking with a magnetic circuit constituted by magnetic poles, cooling the superconductor loop to a temperature lower than the superconducting transition temperature, and bringing the superconductor loop into a superconducting state After that, the gap width of the magnetic poles arranged to face each other is increased.

  According to a second aspect of the present invention, in the first aspect of the present invention, the superconductor loop has a minimum or zero gap width between the opposed magnetic poles. In the state, it is cooled at a temperature lower than the superconducting transition temperature.

  According to a third aspect of the present invention, the magnetic field generator that generates the magnetic field in the gap between the magnetic poles arranged to face each other by arranging the magnetic poles to face each other is arranged to face each other. A magnetic pole, a gap width varying means for varying the gap width of the opposed magnetic poles, and at least one superconductor loop interlinking with the magnetic circuit constituted by the opposed magnetic poles. It is a thing.

  According to a fourth aspect of the present invention, in the invention according to the third aspect of the present invention, the superconductor loop is a magnetic pole in which the high-temperature superconductor ring is disposed to face each other. Are arranged and configured.

  Further, the invention according to claim 5 of the present invention is the invention according to claim 3 or 4 of the present invention, wherein the magnetic pole is a permanent magnet, an electromagnet, or a high magnetic permeability. It is made of a magnetic material having a saturation magnetic flux density characteristic.

  Since the present invention is configured as described above, there is an excellent effect that it is possible to provide a magnetic field generator capable of generating a high magnetic field even when the magnetic pole interval is increased.

  Hereinafter, an example of an embodiment of a magnetic field generation method and a magnetic field generation apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 10 is a perspective view of a conceptual configuration of a magnetic field generator according to an example of the embodiment of the present invention.

  This magnetic field generator 100 shows an electromagnet magnetic circuit capable of varying the gap width, and a pair of magnetic bodies 102 having a high magnetic permeability and a high saturation magnetic flux density arranged to face each other with a gap therebetween. 104, a coil 106 forming an N pole and a coil 108 forming an S pole as magnetic poles arranged side by side on the surface of the magnetic body 102 facing the magnetic body 104, and facing the magnetic body 104 of the coils 106 and 108 The superconductor rings 110 and 112 respectively disposed on the surface to be formed, the coil 114 forming the S pole as the magnetic pole disposed side by side on the surface of the magnetic body 104 facing the magnetic body 102, and the N pole are formed. The coil 116, the superconductor rings 118 and 120 disposed on the surfaces of the coils 114 and 116 facing the magnetic body 102, the coils 106 and 108, and the superconductor It has in a direction toward or separate the magnetic material 102 disposed the body ring 110, 112 of the magnetic member 104 (in the direction of arrow B in FIG. 10) and a gap width variable drive mechanism 122.

  In the magnetic field generation device 100 having the above-described configuration, the N pole on the magnetic body 102 side and the S pole on the magnetic body 104 side face each other with an interval of the gap width g, and the S pole on the magnetic body 102 side and the magnetic body 104. The N pole on the side is opposed. Further, by operating the gap width variable drive mechanism 122, the gap width g can be minimized (desirably zero).

  Here, in this magnetic field generating device 100, four superconductor closed loops each constituted by four superconductor rings 110, 112, 118, 120 interlinking the electromagnet magnetic circuit formed by the magnetic field generating device 100. (See FIG. 11. Note that FIG. 11 shows one superconducting closed loop that links the magnetic circuit.) Further, it is assumed that the magnetic field generation apparatus 100 is ideal so that the fringe effect or the magnetic flux leakage can be ignored.

With the above configuration, the operation of the magnetic field generator 100 will be described in detail with reference to FIGS. 12 and 13 conceptually showing an electromagnet magnetic circuit formed by the magnetic field generator 100.

First, since the superconductor rings 110, 112, 118, and 120 are not in a superconducting state at a temperature (room temperature) equal to or higher than the superconducting transition temperature _{Tc, the} effect obtained by the superconductor closed loop as described above is as follows. Does not occur. Accordingly, the total magnetic flux of the electromagnet magnetic circuit and the magnetic field (magnetic flux density) obtained in the gap decrease rapidly as the gap width g becomes larger (large magnetoresistance) ((1) in FIG. 12, ( See 1)).

Next, after setting the gap width g to the minimum (preferably zero) at a temperature (room temperature) equal to or higher than the superconducting transition temperature _Tc (see (2) in FIG. 12 and (2) in FIG. 13). Then, the superconductor ring is cooled so as to have a temperature lower than the superconducting transition temperature _Tc (very low temperature) (see (3) in FIG. 12 and (3) in FIG. 13).

  When the gap width g is increased in this state, a permanent current flows through the superconductor closed loop formed by the superconductor ring so that the total magnetic flux of the electromagnet magnetic circuit is kept constant by the electromagnetic induction effect (super Basic properties of conductors). That is, the magnetomotive force generated in the superconductor closed loop is added to the magnetomotive force unique to the electromagnet magnetic circuit, and the magnetomotive force of the superconductor closed loop increases as the gap width g increases. Therefore, a high magnetic field is maintained even when the gap width g is large (see (4) in FIG. 12 and (4) in FIG. 13). However, in an actual magnetic field generator, the fringe effect or magnetic flux leakage becomes more pronounced as the gap width increases. In this case, the magnetic field actually obtained is slightly lower than (4) in FIG.

Next, with reference to FIG. 14 and FIG. 15, the magnetic field generator according to the present invention provided with an electromagnet magnetic circuit using a pair of electromagnets as a magnetic pole pair will be described.

  In addition, about the structure which is the same as that of the magnetic field generator 100 shown in FIG. 10 mentioned above, or equivalent, it shows by using the code | symbol same as the code | symbol used in FIG.

  Here, FIG. 14 shows a conceptual configuration perspective view of the magnetic field generator, and FIG. 15 shows a schematic cross-sectional configuration view taken along the line CC of FIG.

  The magnetic field generator 140 shown in FIGS. 14 and 15 is provided with only one pair of opposing magnetic pole pairs and a guide member 142 that guides the movement of the magnetic body 102 in the arrow B direction. Different from the magnetic field generator 100.

  Therefore, according to the magnetic field generator 140, the magnetic body 102 is guided by the guide member 142 and moved in the direction of the arrow B. Therefore, the magnetic body 102 can be accurately and smoothly moved in the direction of the arrow B. It becomes.

Next, with reference to FIG. 16 and FIG. 17, a magnetic field generator according to the present invention provided with an electromagnet magnetic circuit using two pairs of electromagnets as magnetic pole pairs will be described.

  In addition, about the structure which is the same as that of the magnetic field generator 100 shown in FIG. 10 mentioned above, or equivalent, it shows by using the code | symbol same as the code | symbol used in FIG.

  Here, FIG. 16 shows a perspective view of the conceptual configuration of the magnetic field generator, and FIG. 17 shows a schematic cross-sectional configuration view taken along the line DD of FIG.

  The magnetic field generator 160 shown in FIG. 16 and FIG. 17 is a direction in which the magnetic body 104 provided with the coils 114 and 116 and the superconductor rings 118 and 120 approaches or separates from the magnetic body 102 (FIG. 16). 17 is different from the magnetic field generator 100 in that the gap width variable drive mechanism 162 is provided in the direction of arrow E in FIG.

  Therefore, according to this magnetic field generator 160, in addition to moving the magnetic body 102 in which the coils 106 and 108 and the superconductor rings 110 and 112 are disposed by the gap width variable drive mechanism 122, in the direction of arrow B, Since the magnetic body 104 provided with the coils 114 and 116 and the superconductor rings 118 and 120 can be moved in the direction of arrow E by the variable gap width driving mechanism 162, the variable time for changing the gap width g can be shortened. Is possible.

Next, with reference to FIG. 18 and FIG. 19, the case where the magnetic field generator provided with the electromagnet magnetic circuit by this invention is applied to the undulator for radiation light generation is demonstrated.

  Here, FIG. 18 shows a conceptual perspective view of the undulator for radiated light generation incorporating the magnetic field generator equipped with the electromagnet magnetic circuit according to the present invention, and FIG. 19 is a schematic cross-sectional configuration explanation by the FF line of FIG. The figure is shown.

  In the undulator shown in FIGS. 18 and 19, the configuration of the magnetic field generator shown in FIGS. 16 and 17 is used as it is without significantly changing the configuration of the undulator.

  Therefore, if the magnetic field generator according to the present invention is used, a high magnetic field can be generated even if the gap width g is increased while using the undulator currently used in each facility as it is.

  Here, FIG. 20 is a conceptual perspective view of a radiated light generating undulator incorporating a magnetic field generator equipped with a permanent magnet magnetic circuit according to the present invention, and FIG. 21 is a schematic diagram of a main part taken along line GG of FIG. The cross-sectional structure explanatory drawing is shown. In addition, the white arrow in FIG.20 and FIG.21 has shown the magnetization direction.

  In the undulator shown in FIGS. 20 and 21, the configuration of the magnetic field generator shown in FIG. 8 is used as it is without significantly changing the configuration of the undulator.

  Therefore, if the magnetic field generator according to the present invention is used, a high magnetic field can be generated even if the gap width g is increased while using the undulator currently used in each facility as it is.

The embodiment described above can be modified as shown in the following (1) to (4).

  (1) In the above-described embodiment, the description has focused on the case where a plurality of superconductor closed loops interlinking with the magnetic circuit are provided. However, the present invention is not limited to this, and the magnetic circuit and the chain are not limited to this. It is sufficient that at least one superconductor closed loop intersects.

  (2) In the above-described embodiment, the case where the magnetic field generator according to the present invention is applied to an undulator has been mainly described. However, the present invention is not limited to this, and the magnetic field generator according to the present invention is not limited to this. You may make it apply to a wiggler, or you may make it apply to the apparatus which uses another magnetic field.

  (3) In the above-described embodiment, a superconductor ring is disposed on each facing surface of an electromagnet or a permanent magnet facing each other across a gap to form a superconductor closed loop, whereby a magnetic circuit and a chain are formed. However, the present invention is not limited to this, and the superconductor is closed to any place in the magnetic circuit formed by the opposing electromagnets or permanent magnets across the gap. A conductor ring may be arranged so that the superconductor closed loop is linked at an arbitrary position in the magnetic circuit.

  (4) You may make it combine suitably the embodiment shown above and the modification shown in said (1) thru | or (3).

  The present invention can be used for a synchrotron radiation light source such as an undulator or wiggler that can be used as an insertion light source for generation of radiation.

FIG. 1 is an explanatory diagram for explaining the principle of a magnetic field generator according to the present invention. FIG. 2 shows a case where the superconductor closed loop is inactive in the configuration shown in FIG. 1, that is, when the temperature of the superconductor ring is higher than the superconducting transition temperature _Tc (dashed line (a)). It is a graph which shows the typical gap dependence of a magnetic field in case a body closed loop is active, ie, when the temperature of a superconductor ring is lower than superconducting transition temperature _Tc (solid line (b)), (C) shows the permanent current in the superconductor. FIGS. 3A, 3B and 3C are partial cross-sectional explanatory views corresponding to FIG. 1 for explaining the principle of the magnetic field generator according to the present invention. FIG. 4 is a structural explanatory view showing an example of a magnetic structure model when the magnetic field generator according to the present invention is used in a conventionally known cryogenic permanent magnet undulator. FIG. 5 is a graph showing an example of the magnetic performance of the magnetic structure model shown in FIG. FIG. 6 is a schematic configuration perspective view of the superconductor ring used in the experiment by the present inventors. FIG. 7 is a graph showing the magnetic performance of the superconductor ring shown in FIG. FIG. 8 shows a magnetic field generator according to the present invention having a permanent magnet and a superconductor, (a) is a side view of the magnetic field generator, and (b) is a view of arrow A in (a). It is a figure, ie, a top view of a magnetic field generator. It is a graph which shows the magnetic performance of the magnetic field generator shown in FIG. 8, and the broken line (a) shows that the superconductor ring is not in the superconducting state and the superconductor closed loop composed of the superconductor ring is inactive. The measurement result of the peak magnetic field in a certain case is shown, and the solid line (b) shows the measurement of the peak magnetic field when the superconductor ring is in a superconducting state and the superconductor closed loop composed of the superconductor ring is active. A result is shown and the dashed-dotted line (c) has shown the current density in a superconductor ring. FIG. 10 is a conceptual configuration perspective view of a magnetic field generator according to an example of an embodiment of the present invention. FIG. 11 is an explanatory diagram showing the linkage between the magnetic circuit and the superconductor closed loop. FIG. 12 is an explanatory diagram conceptually showing an electromagnet magnetic circuit formed by the magnetic field generator shown in FIG. FIG. 13 is a graph showing the magnetic field characteristics of the magnetic field generator shown in FIG. FIG. 14 is an explanatory perspective view of a conceptual configuration of a magnetic field generator according to the present invention provided with an electromagnet magnetic circuit using a pair of electromagnets as magnetic pole pairs. FIG. 15 is a schematic cross-sectional configuration explanatory view taken along line CC of FIG. FIG. 16 is an explanatory perspective view of a conceptual configuration of a magnetic field generator according to the present invention provided with an electromagnet magnetic circuit using two pairs of electromagnets as magnetic pole pairs. FIG. 17 is a schematic cross-sectional configuration explanatory view taken along the line DD of FIG. FIG. 18 is an explanatory perspective view of a conceptual configuration of a radiated light generating undulator incorporating a magnetic field generating device including an electromagnet magnetic circuit according to the present invention. FIG. 19 is a schematic cross-sectional configuration explanatory view taken along line FF in FIG. FIG. 20 is an explanatory perspective view of a conceptual configuration of a radiated light generating undulator incorporating a magnetic field generator equipped with a permanent magnet magnetic circuit according to the present invention. FIG. 21 is a schematic cross-sectional configuration explanatory diagram of a main part taken along the line GG of FIG.

Explanation of symbols

10 Superconductor ring 12, 14 Gap 16, 18 Yoke (relay)
20 coil 22 electromagnet 40 permanent magnet 42 pole piece 44 superconductor ring 60 superconductor ring 60a hole 62 hole probe 80, 100, 140, 160 magnetic field generator 82a, 82b, 82c, 82d, 82e, 82f permanent magnet 102, 104 Magnetic body 106, 108, 114, 116 Coil 110, 112, 118, 120 Superconductor ring 122, 162 Gap width variable driving mechanism 142 Guide member g Gap width

Claims (5)

In the magnetic field generation method for generating a magnetic field in the gap between the magnetic poles arranged opposite to each other by arranging the magnetic poles opposite to each other,
Forming at least one superconductor loop interlinking with a magnetic circuit composed of magnetic poles arranged opposite to each other;
After cooling the superconductor loop to a temperature below the superconducting transition temperature to bring the superconductor loop into a superconducting state,
A magnetic field generating method, wherein the gap width of the magnetic poles arranged to face each other is increased. The magnetic field generation method according to claim 1,
The method of generating a magnetic field, wherein the superconductor loop is cooled at a temperature lower than a superconducting transition temperature in a state where the gap width of the opposingly arranged magnetic poles is minimum or zero. In the magnetic field generator for generating a magnetic field in the gap between the magnetic poles arranged opposite to each other by arranging the magnetic poles opposite to each other,
Magnetic poles arranged opposite to each other;
Gap width varying means for varying the gap width of the opposingly disposed magnetic poles;
A magnetic field generator comprising: a magnetic circuit configured by magnetic poles arranged to face each other; and at least one superconductor loop linked to the magnetic circuit. In the magnetic field generator of Claim 3,
The superconductor loop is configured by arranging a superconductor ring with respect to each of the opposed magnetic poles. In the magnetic field generator of any one of Claim 3 or Claim 4,
The magnetic pole is made of a permanent magnet, an electromagnet, or a magnetic material having a high magnetic permeability and a high saturation magnetic flux density.

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