JP4895714B2 - Superconductor, superconducting magnetic field generator, superconducting magnetic field generator, and nuclear magnetic resonance apparatus - Google Patents

Description

  The present invention relates to a superconducting magnetic field generator that generates a strong static magnetic field with a uniform distribution comparable to a conventional superconducting magnet without using liquid helium, and a nuclear magnetic resonance apparatus including the same.

  The applicant of the present invention has previously proposed a magnetic field generator using a superconductor and a nuclear magnetic resonance apparatus including the same (see Patent Document 3). This magnetic field generator includes a superconducting magnetic field generating element that magnetizes a hollow cylindrical superconductor cooled to a superconducting transition temperature or lower in a vacuum heat insulating container in the axial direction, thereby generating a static magnetic field in the hollow cylindrical portion. Have. A nuclear magnetic resonance apparatus equipped with such a magnetic field generator is configured to detect an NMR signal of an object to be measured placed in the magnetic field with a detection coil and a spectrometer. It is a magnetic resonance apparatus.

  As is well known, a magnet of a nuclear magnetic resonance apparatus is required to have a high magnetic field uniformity of 1 ppm or less. For this reason, usually, a correction coil is added to the magnet body to achieve the target magnetic field uniformity. However, the magnet of a nuclear magnetic resonance apparatus using a superconductor uses a magnetic field captured by the superconductor by magnetization, but the cylindrical space of the bulk superconductor is narrow, and the size and number of correction coils for correcting the magnetic field distribution are small. Is limited. For this reason, it is necessary to cause the superconductor to capture a highly uniform magnetic field at the time of magnetization.

  According to the prior art, the cylindrical superconductor is reinforced with a reinforcing member such as a metal ring (see Patent Documents 1 and 2), attached to the cold head (attachment stage) of the refrigerator, and the inside is maintained in a vacuum. Placed in a vacuum insulated container. In this superconducting magnetic field generator, a portion in which the superconductor is accommodated is inserted into the cylindrical space of the superconducting magnet, and cooled to below the superconducting transition temperature by a refrigerator while applying a uniform magnetic field. Thereafter, when the magnetic field of the superconducting magnet is reduced to zero, the applied magnetic field is captured by the superconductor, and a magnetic field space is formed in the cylinder of the superconductor.

However, in the above prior art, the distribution of the uniform applied magnetic field generated by the superconducting magnet for magnetization is such that the superconductor itself, a reinforcing member, a mounting member, a cold head or a vacuum disposed around the superconductor. A problem arises in that a uniform magnetic field space that cannot be corrected is formed in the cylinder of the superconductor after magnetization and is disturbed by a heat insulating container or the like. This is because the superconductor itself and its peripheral members are magnetized (magnetized) by the applied magnetic field.
JP 11-335120 A Japanese Patent No. 389094 Japanese Patent Laid-Open No. 2002-6021

  The present invention has been made to solve the above-described problem, and a superconductor capturing a correctable uniform magnetic field in a hollow portion of a cylindrical superconductor by magnetization, and a correctable uniform magnetic field. It is an object of the present invention to provide a superconducting magnetic field generating element for forming a superconducting magnetic field generating device, a superconducting magnetic field generating device having a high magnetic field uniformity of 1 ppm or less, and a compact nuclear magnetic resonance apparatus capable of highly accurate analysis.

(1) The superconductor of the present invention is a hollow cylindrical superconductor that captures an applied magnetic field in a hollow portion. The superconductor has an outer diameter D, an inner diameter d, a height H, and a superconducting transition. When the magnetic susceptibility at temperature is χ,
H / D ≦ 1.1 × (d / D) + 0.342 + 0.001 / χ (1)
, And the horizontal axis the central axis of the hollow portion, the vertical axis of the magnetic field intensity, the distribution of magnetic field strength in the horizontal direction in the hollow portion while applying a magnetic field in a uniform static magnetic field, the superconductor It is characterized by being substantially flat or convex downward at approximately half the length. The magnetic susceptibility χ is expressed in SI (EB compatible) unit system.

In principle, the distribution of the magnetic field strength during application is desirably uniform in the axial direction of the superconductor, but in practice, the magnetic field is released from both ends of the hollow cylinder of the superconductor, so depending on the magnetization conditions, In the axial direction of the superconductor, the trapped magnetic field trapped by the superconductor becomes more uniform when applied to a magnetic field strength distribution having a slightly lower magnetic field strength at the center than at both ends. The superconductor of the present invention is formed so that the outer diameter (D), inner diameter (d), and height (H) of the superconductor having the magnetic susceptibility χ at the superconducting transition temperature satisfy the expression (1). In the central region of the hollow portion, the magnetic field strength being applied in a uniform static magnetic field can be captured substantially flat or downward . Therefore, the held superconductor can generate a correctable uniform magnetic field.

  (2) More specifically, with the half point of the superconductor as the midpoint, the magnetic field strength at the midpoint when the magnetic field is applied, and at least ± in the central axis direction with the midpoint interposed It is desirable that the difference from the magnetic field strength at a position 1 mm apart is 10 ppm or less of the applied magnetic field strength.

  If the distribution of the magnetic field strength is within this range, the generated magnetic field distribution can be corrected relatively easily to obtain a uniform magnetic field in the central region of the hollow portion of the superconductor.

  (3) Also, the magnetic field strength at the midpoint when a magnetic field is applied with the half point of the length of the superconductor as the midpoint, and the magnetic field strength at a position spaced ± 1 mm from the midpoint in the central axis direction It is desirable that the difference is 1 ppm or less of the applied magnetic field strength.

  If the distribution of the magnetic field strength is within this range, the distribution of the magnetic field strength being applied is substantially flat at approximately half the length of the superconductor, so the generated magnetic field distribution can be corrected more easily to superconductivity. A uniform magnetic field can be obtained in the central region of the hollow part of the body.

( 4 ) When the outer diameter of the superconductor is D, the inner diameter is d, the height is H, and the magnetic susceptibility at the superconducting transition temperature is χ,
1.1 × (d / D) + 0.342−0.002 / χ ≦ H / D ≦ 1.1 × (d / D) + 0.342 + 0.001 / χ (2)
It may be.

  The magnetic field intensity in the axial direction to be captured by the superconductor is formed by forming the magnetic susceptibility so that the outer diameter (D), inner diameter (d), and height (H) of the superconductor satisfying the equation (2). The distribution can be made substantially flat.

( 5 ) As described above, a superconductor that captures a magnetic field with high uniformity is manufactured by a melting method, and its main component is RE-Ba-Cu-O (where RE is Y, La, Nd, Sm, Eu, A composition represented by one or more of Gd, Er, Yb, Dy, and Ho) is desirable.

  A superconductor whose main component is represented by RE-Ba-Cu-O can capture a large magnetic field, in particular, by producing it by a melting method.

( 6 ) The superconductor magnetization method of the present invention is a superconductor magnetization method of applying a hollow cylindrical superconductor that captures an applied magnetic field in a hollow portion, and is any one of the above superconductors Is characterized by applying a magnetic field at a temperature higher than the superconducting transition temperature of the superconductor and cooling to a superconducting transition temperature or lower with the magnetic field applied.

  By generating a strong static magnetic field with the superconducting magnet and allowing the superconductor to capture the magnetic field with the magnetic field, a strong magnetic field that can be generated with the superconducting magnet can be magnetized on the superconductor.

( 7 ) A superconducting magnetic field generating element of the present invention is a superconducting magnetic field generating element that generates a magnetic field in a hollow portion of a superconductor by applying a magnetic field to a hollow cylindrical superconductor and capturing the magnetic field. A superconductor according to any one of (1) to ( 5 ) is made to capture a magnetic field.

  The superconducting magnetic field generating element to which a magnetic field is applied causes a magnetic flux creep phenomenon in which the magnetic flux gradually moves with time and the magnetic field decreases, and the magnetic field distribution changes. Since the magnetic flux creep increases as it approaches the both ends of the superconducting magnetic field generating element in the axial direction, the distribution of the trapped magnetic field is strongest near the center in the cylindrical axial direction and becomes weaker as it approaches both ends. For this reason, the uniformity of the magnetic field necessary for the observation of the NMR signal cannot be obtained or the range becomes narrow. However, the superconducting magnetic field generating element of the present invention captures a correctable uniform magnetic field in which the distribution of the magnetic field strength is substantially flat or convex downward in the central region of the hollow portion, which is important in NMR analysis. Even if it occurs, the flatness of the central portion can be maintained.

( 8 ) In such a superconducting magnetic field generating element, it is desirable that the superconductor has a single magnetic susceptibility. Since the superconductor has a single magnetic susceptibility, the distribution of the generated magnetic field can be maintained in a predetermined shape.

( 9 ) Moreover, the superconducting magnetic field generating element of the present invention is a superconducting magnetic field generating element that generates a magnetic field in a hollow portion of the superconductor by applying a magnetic field to a hollow cylindrical superconductor and capturing the magnetic field . superconductor is a superconductor cylindrical laminated body obtained by laminating a plurality of superconducting solid in the central axis direction, the superconducting cylindrical laminated body, (1) to (5) of any one of the superconductor solid at least one of the end, the small again superconducting solid susceptibility than the superconducting solid is characterized in that it is laminated.

  Since a superconducting solid with a low magnetic susceptibility has a small induced magnetic field, it has a small effect on the generated magnetic field of the superconducting magnetic field generating element, so that the distribution of the generated magnetic field can be maintained in a predetermined shape.

( 10 ) The superelectromagnetic field generating element of the present invention has a hollow cylindrical superconductor and a reinforcing member disposed around the superconductor, and the superconductor captures the magnetic field by applying a magnetic field, and in the hollow portion. A superconducting magnetic field generating element that generates a magnetic field, and when the same magnetic field that is applied to the superconductor is applied only to the reinforcing member, the magnetic field strength in the space corresponding to the hollow portion of the superconductor and the applied magnetic field strength The difference is 10 ppm or less of the applied magnetic field strength.

  In general, in a superconducting magnetic field generating element, a reinforcing member is disposed around a superconductor to be used to suppress the occurrence of cracks and cracks due to electromagnetic force when an external impact or magnetic field is applied.

  The superconducting magnetic field generating element of the present invention is such that when a uniform magnetic field is applied to the superconductor, the disturbance of the magnetic field in the hollow portion of the superconductor by the reinforcing member is 10 ppm or less with respect to the applied magnetic field distribution. Since the shape, dimensions, material, etc. are preset, a correctable uniform magnetic field can be generated.

  Here, the cylindrical superconductor means not only the shape defined by the inner diameter, the outer diameter, and the height, but also the shape of the rotating body that is the object of the axis with respect to the central axis.

( 11 ) Such a reinforcing member preferably has a magnetic susceptibility magnitude (| χ |) of 2 × 10 ⁻⁴ or less.

If the magnetic susceptibility of the reinforcing member is set to a certain value or less, the disturbance of the magnetic field distribution due to the magnetization of the reinforcing member when a magnetic field is applied is reduced. By setting the absolute value of the magnetic susceptibility of the reinforcing member to 2 × 10 ⁻⁴ or less, a superconducting magnetic field generating element that generates a correctable uniform magnetic field can be obtained.

( 12 ) Further, the shape of the reinforcing member is preferably a ring shape concentric with the superconductor.

  Matching the shape of the superconductor and making the reinforcing member an axially shaped ring shape reduces the disturbance of the magnetic field distribution due to the reinforcing member, and even if there is a disturbance, it becomes an axial object, making it easy to correct the magnetic field distribution . The reinforcing member may have a minute screw hole as long as it is ring-shaped. Further, the reinforcing members may be integrated or a combination of a plurality of reinforcing members.

( 13 ) In the superconducting magnetic field generating element having such a ring-shaped reinforcing member, when the inner diameter of the reinforcing member is d _H , the thickness is t, and the magnetic susceptibility is χ, the shape of the reinforcing member is (3 ) It is good to set to satisfy the formula.
t / d _H ≦ 1.6 × 10 ⁻⁵ / | χ | (3)

  By setting the shape of the reinforcing member to satisfy the expression (3), the disturbance of the magnetic field distribution by the reinforcing member becomes 10 ppm or less. Therefore, a superconducting magnetic field generating element that generates a correctable uniform magnetic field can be obtained.

( 14 ) Such a reinforcing member may be made of any of aluminum, aluminum alloy, copper, copper alloy, magnesium, magnesium alloy, titanium, and titanium alloy.

  Since these metals have a low magnetic susceptibility and high strength, they have a large reinforcing effect and are suitable as reinforcing members for superconductors.

( 15 ) The superconductor of the superconducting magnetic field generating element described above is preferably the superconductor according to any one of (1) to ( 5 ) above.

  Such a superconducting magnetic field generating element can be corrected because the disturbance of the magnetic field distribution is 10 ppm or less with respect to the applied magnetic field, including the influence of not only the reinforcing member but also the superconductor itself being magnetized. A superconducting magnetic field generating element that generates a uniform magnetic field can be obtained.

( 16 ) A superconducting magnetic field generator of the present invention comprises a superconducting magnetic field generating element comprising a hollow cylindrical superconductor and a reinforcing member disposed around the superconductor, a cooling member for cooling the superconducting magnetic field generating element, A fixing member that attaches the superconducting magnetic field generating element to the cooling member, and a vacuum heat insulating container that contains at least the superconducting magnetic field generating element and the fixing member. The superconductor captures the magnetic field by applying a magnetic field and enters the hollow portion of the superconductor. A superconducting magnetic field generator that generates a magnetic field, and when the same magnetic field as applied to the superconductor is applied with the superconductor removed, the magnetic field strength and the applied magnetic field in the space corresponding to the hollow portion of the superconductor The difference from the intensity is 10 ppm or less of the applied magnetic field intensity.

  In the case of a superconducting magnetic field generator, peripheral members such as a cooling member, a fixing member, and a vacuum heat insulating container are provided in addition to the reinforcing member. The shape, dimensions, material, arrangement, etc. of the peripheral member are preliminarily set so that the disturbance of the magnetic field in the hollow portion of the superconductor due to these peripheral members other than the superconductor when a uniform magnetic field is applied to the superconductor is within a certain range. Since the disturbance of the magnetic field distribution is set to 10 ppm or less with respect to the applied magnetic field distribution, a superconducting magnetic field generator that generates a correctable uniform magnetic field can be obtained.

( 17 ) It is desirable that the superconducting magnetic field generating element of the superconducting magnetic field generating device is any one of the above ( 10 ) to ( 15 ).

The superconducting magnetic field generating elements of the above ( 10 ) to ( 15 ) minimize the influence on the magnetic field of the superconductor itself or the reinforcing member arranged closest to the superconductor, so that the superconductivity that generates a correctable uniform magnetic field A magnetic field generator is obtained.

( 18 ) In the superconducting magnetic field generator of the present invention, any or all of the shape of the reinforcing member, the cooling member, the fixing member, and the vacuum heat insulating container are preferably axial objects with respect to the central axis of the superconductor. .

  By aligning the shape of these peripheral members with the shape of the superconductor, the disturbance of the magnetic field distribution by the peripheral members is reduced, and even if there is a disturbance, it becomes the axis subject, so correction of the magnetic field distribution is easy. Become.

( 19 ) In the superconducting magnetic field generator described above, a reinforcing member, a cooling member, and a fixed member included in a cylindrical space having a diameter of 2D and a height of 2H containing a superconductor having an outer diameter D and a height H in the center. The magnitude (absolute value) of the volume magnetic susceptibility of the member and the vacuum heat insulating container is desirably 2 × 10 ⁻⁴ or less.

A superconducting magnetic field generator that generates a correctable uniform magnetic field can be obtained by setting the magnetic susceptibility of the peripheral member included in the above range to 2 × 10 ⁻⁴ or less with respect to the size of the superconductor. it can.

( 20 ) Here, the portion included in the cylindrical space of the reinforcing member, the cooling member, the fixing member, and the vacuum heat insulating container is any one of aluminum, aluminum alloy, copper, copper alloy, magnesium, magnesium alloy, titanium, and titanium alloy. Good.

  The material of the peripheral member included in such a cylindrical space is preferably aluminum, aluminum alloy, copper, copper alloy, magnesium, magnesium alloy, titanium, or titanium alloy having a small magnetic susceptibility and a large reinforcing effect. Conventionally, generally used stainless steel is not preferable because of its high magnetic susceptibility.

( 21 ) The nuclear magnetic resonance apparatus of the present invention is characterized by including the superconducting magnetic field generation device according to any one of ( 16 ) to ( 20 ) as a magnet.

By providing the superconducting magnetic field generator of any one of ( 16 ) to ( 20 ) as a magnet, a small and high-performance nuclear magnetic resonance apparatus can be obtained.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(1) Superconductor Generally, a superconductor produced by a melting method has a strong pinning effect, so that a magnetic flux line given by an external magnetic field application can be captured. Generate a magnetic field. Since the superconductor in principle tries to maintain the applied magnetic field distribution as it is, the higher the uniformity of the applied magnetic field distribution, the higher the uniformity of the captured magnetic field distribution.

  The magnetic field being applied to the superconductor is a vector addition of the applied magnetic field and the induced magnetic field induced by the magnetization of the superconductor. Therefore, even if the applied magnetic field generated by the superconducting magnet is uniform, if the induced magnetic field of the superconductor induced thereby is not uniform, the applied magnetic field is not uniform.

  In principle, the distribution of the magnetic field strength during application is desirably uniform in the axial direction of the superconductor. However, since the magnetic field is actually released from both ends of the hollow portion of the superconductor, depending on the magnetization conditions, the magnetic field strength is applied to the distribution in which the magnetic field strength is slightly lower at the center than at both ends in the axial direction of the superconductor. The trapping magnetic field trapped by the superconductor becomes more uniform.

  In addition, when applying to the superconductor at a temperature higher than the superconducting transition temperature and magnetizing by cooling in a magnetic field that cools the superconductor while applying it, the intensity distribution of the trapped magnetic field is almost the same as when the superconductor transitions to superconductivity. Determined by the distribution.

  The present invention has been made by obtaining new knowledge about suitable conditions that a superconductor should have in order to make the trapped magnetic field of the superconductor uniform.

  Prior to detailed description, in this specification, the distribution of the magnetic field will be described using a magnetic field shift and a magnetic field shift profile defined below.

Field shift ΔB is the applied magnetic field strength B _0, the magnetic field strength in the applied B, deviation of the magnetic field strength B ₀ applied field strength B in the application of (B-B ₀₎ at the applied magnetic field strength B ₀ Divided value (B−B ₀ ) / B ₀ and expressed in ppm. The magnetic field shift profile is a change of the magnetic field shift ΔB with respect to the distance Z from a position (1/2 point) of the superconductor height with the vertical axis representing the magnetic field shift ΔB and the horizontal axis representing the central axis of the superconductor. Is expressed. Note that a region of ± 1 mm including 0 point on the horizontal axis is referred to as a central region of the superconductor or simply a central region.

The inventor has analyzed in detail magnetic field disturbance during application due to the magnetic susceptibility of the superconductor itself by magnetic field analysis. In the magnetic field analysis, first, the paramagnetic susceptibility χ _p of the superconductor is calculated (step 1), and then a magnetic field shift profile is created by the magnetic field analysis using the obtained paramagnetic susceptibility χ (step 2). The superconductor shape optimization conditions were set based on the magnetic field shift profile (step 3). Hereinafter, it demonstrates in detail along a procedure.

(Step 1) Calculation of paramagnetic susceptibility χ of a superconductor Since many rare earth elements (hereinafter referred to as RE) ions have a large magnetic moment, RE-based superconductors are paramagnetic due to their localized moments. Has magnetic susceptibility χ. In general, the magnetic susceptibility χ of a paramagnetic material due to local moment follows Curie's law; χ = C / T. Here, C is the Curie constant, and T is the absolute temperature (K). That is, since the magnetic susceptibility χ is inversely proportional to the temperature T, the value becomes larger as the temperature becomes lower.

Further, the Curie constant C is calculated by ^{_{C = μ 0 Np 2 μ B}} 2 / 3κ B. Here, N is the number of magnetic atoms (or ions) per unit volume, p is the number of effective Bohr magnetons of magnetic atoms, μ _B is Bohr magneton (9.27 × 10 ⁻²⁴ (J / T)), μ ₀ is the vacuum permeability (4π × 10 ⁻⁷ ), and κ _B is the Boltzmann constant (1.38 × 10 ⁻²³ (J / K)).

When the superconductor is a superconducting oxide having a RE ₁ Ba ₂ Cu ₃ O ₇ structure, the crystal structure is an orthorhombic crystal having a = 0.384 nm, b = 0.39 nm, and c = 1.17 nm. Yes, magnetism is mainly due to the magnetic moment of RE atoms. In such a superconducting oxide, since there is one RE ion per unit cell, N is approximately 6.0 × 10 ²⁷ / m ^{3 according} to N = 1 / (a × b × c). Further, p differs depending on the type of RE, and C is proportional to the square of p, so χ is also proportional to the square of p. That is, it can be said that the superconducting oxide having a larger value of p has a higher magnetic susceptibility χ.

The magnetic susceptibility χ of RE ₁ Ba ₂ Cu ₃ O ₇ is calculated from the above formula and numerical values. For example, when RE is Gd, C is approximately 1.0, so the magnetic susceptibility χ at temperature T = 100K is 0.01. Further, the relative magnetic permeability μ / μ ₀ (= 1 + χ) at this time is 1.01.

For superconductors of the RE ₁ Ba ₂ Cu ₃ O ₇ structure, the effective Bohr magneton number p of various REs (document values according to the scientific chronology), and the magnetic susceptibility χ and relative permeability μ / 100/100 obtained by calculation. μ ₀ is shown together in Table 1. Note that Y and La are not shown in Table 1 because they have no magnetic moment.

However, since the material actually used for the superconductor includes non-superconducting phases such as RE ₂ BaCuO ₅ and Ag other than RE ₁ Ba ₂ Cu ₃ O ₇ , the overall magnetic susceptibility is the same as the magnetic susceptibility of each phase. It is the product of volume fraction.

For example, RE ₂ BaCuO ₅ that is a non-superconducting phase is an orthorhombic crystal having approximately a = 0.73 nm, b = 1.24 nm, and c = 0.58 nm. Since 8 RE atoms are included per unit cell, N = 8 / (a × b × c), so that N is about 1.5 × 10 ²⁸ / m ³ . Therefore, the magnetic susceptibility of RE ₂ BaCuO ₅ , which is a non-superconducting phase, is about 2.5 times the magnetic susceptibility of the RE ₁ Ba ₂ Cu ₃ O ₇ phase of the same RE (however, when RE is Nd, Excluded because the crystal structure is different.) Ag is a diamagnetic material having a magnetic susceptibility of −2.53 × 10 ⁻⁵ .

Therefore, the material is composed of three phases RE ₁ Ba ₂ Cu ₃ O ₇ , RE ₂ BaCuO ₅ , and Ag, and the volume fraction of each phase is sequentially set to ν ₁₂₃ , ν ₂₁₁ , and ν _Ag , and the respective magnetic susceptibility is set in order. , Χ ₁₂₃ , χ ₂₁₁ , and χ _Ag , the magnetic susceptibility χ _p of the RE-based material containing them can be calculated as χ _p = ν ₁₂₃ × χ ₁₂₃ + ν ₂₁₁ × χ ₂₁₁ + ν _Ag × χ _Ag . The calculation result can be verified by measuring the actual magnetic susceptibility using a permeability meter or the like.

(Step 2) Creation of magnetic field shift profile by magnetic field analysis The validity of the magnetic field analysis was verified by comparing the applied magnetic field shift profile calculated by the magnetic field analysis with the actual measurement value using these values. FIG. 1 is a graph showing both the measured magnetic field shift value and the magnetic field shift profile obtained by magnetic field analysis for two types of hollow cylindrical superconductors having an outer diameter of 60 mm, an inner diameter of 16 mm, and a height of 20 mm and 58 mm. is there. In FIG. 1, the measured value of the superconductor having a height of 20 mm is indicated by ■, the magnetic field shift profile thereof is indicated by a solid line f1, the measured value of the superconductor having a height of 58 mm is indicated by ◯, and the magnetic field shift profile thereof is indicated by a solid line f2. The magnetic field shift profile during application obtained by magnetic field analysis from FIG. 1 is in good agreement with the distribution of the actually measured magnetic field shift, indicating that the calculation of magnetic susceptibility and the magnetic field analysis are valid. The In particular, the magnetic field shift profile obtained by magnetic field analysis was found to be in good agreement with the actual measurement results in the range within the hollow portion of the superconductor.

  Based on the above results, magnetic field analysis was performed on Gd-based superconductors having different sizes (relative permeability at a temperature of 100 K: 1.01), and respective magnetic field shift profiles were obtained.

  Fig. 2 shows the analysis by changing the height to nine levels of 20, 30, 32, 34, 40, 50, 60, 80, and 100 mm, assuming that the outer diameter is 60 mm and the inner diameter is 10 mm. It is the graph which wrote together the profile as a magnetic field shift profile group. Since the magnetic field shift profile is axisymmetric with respect to the vertical axis at the zero point on the horizontal axis as shown in FIG. 1, only the right half of each magnetic field shift profile is shown in FIG. 2 (hereinafter the same). . Similarly, FIGS. 3 to 6 show magnetic field shift profile groups obtained by setting the outer diameter to be constant at 60 mm, the inner diameter to be 16, 20, 24, and 30 mm and changing the height between 7 to 10 levels. .

  2 to 6 above, focusing on the shape near the center of each magnetic field shift profile obtained, in any case where the height is changed with the inner diameter being constant, the height is low (thin). The magnetic field shift profile is convex downward, and as it increases in height, it shifts downward (thick) into a concave shape, and it is assumed that a flat magnetic field shift profile can be obtained at the boundary.

(Step 3) Optimization of Superconductor Shape The superconductor of the present invention is a hollow cylindrical superconductor that captures an applied magnetic field in a hollow portion, and the horizontal axis is the central axis direction of the hollow portion, and the magnetic field strength is Superconductivity characterized in that, as the vertical axis, the distribution of the magnetic field strength in the axial direction in the hollow portion when a magnetic field is applied is substantially flat or convex downward at a position approximately half the length of the superconductor. Is the body.

  In the present invention, “substantially flat” means that the difference between the magnetic field shift at the zero point and the magnetic field shift at the ± 1 mm point is 1 ppm or less in the central region (range of 2 mm or more) of the superconductor. Further, the downward convex means that the value obtained by subtracting the magnetic field shift value at the zero point from the magnetic field shift value at the ± 1 mm point is 10 ppm or less. If the distribution of the magnetic field intensity in the central region of the superconductor being applied is within this range, a superconducting magnetic field generating element that captures the magnetic field and generates a uniform magnetic field that can be corrected can be obtained.

  The magnetic field shift profiles of the three superconductors whose overall sizes were similarly changed while keeping the hollow cylindrical shape (inner diameter / outer diameter, height / outer diameter) of the superconductor constant were determined. That is, the shape of the superconductor 1 is outer diameter (D) 30 mm × inner diameter (d) 8 mm × height (H) 20 mm, the superconductor 2 is outer diameter 60 mm × inner diameter 16 mm × height 40 mm, and the superconductor 3 is outer diameter 120 mm. × Inner diameter 32 mm × height 80 mm, both d / D = 4/15 and L / D = 2/3.

  The results are shown in FIG. The obtained magnetic field shift profiles f3 (superconductor 1), f4 (same 2), and f5 (same 3) have a gentle rise as the height H increases within the same magnetic field shift range. Therefore, when the horizontal axis of each magnetic field shift profile is scaled by the height of the superconductor (replace the horizontal coordinate with the ratio to H / 2, Z / (H / 2)), the magnetic field shift profiles f3 to f5 are as shown in FIG. As shown in profile f6 shown in FIG.

  In other words, the magnetic field distribution shape and the magnitude of the magnetic field change depend on the relative shape of the superconductor (here, the ratio of the inner diameter to the outer diameter and the height) in the same material, and do not depend on the dimensions. . Therefore, in order to obtain a uniform magnetic field in the central region, the shape of the superconductor may be optimized.

  FIG. 9 shows the calculation of the respective d / D and H / D for the shape of the superconductor used in FIGS. 2 to 6 and plots the horizontal axis as d / D and the vertical axis as H / D. It is the graph which wrote together the shape of the magnetic field shift profile in the center area | region of a body.

  For example, 9 points with d / D of 0.17 in FIG. 9 relate to the magnetic field shift profile group obtained with D = 60 mm, d = 10 mm and H in the range of 20 to 100 mm as shown in FIG. It is. Here, the shape of the magnetic field shift profile was determined as follows.

In each magnetic field shift profile, the value of the magnetic field shift at the zero point on the horizontal axis is ΔB ₀ , and the magnetic field shift value at the 1 mm point is ΔB ₁ , and the deviation Δb of ΔB ₁ with respect to ΔB ₀ (Δb = ΔB ₁ −ΔB _0). ) Is determined to be convex downward if 0 <Δb, and convex upward if Δb <0. In FIG. 9 , 0 <Δb is indicated by ■, and Δb <0 is indicated by □. For example, when D = 60 mm and d = 10 mm, the magnetic field shift profile is convex downward when H is 20, 30, 32 mm, and upward when 34, 40, 50, 60, 80, 100 mm. It is a type.

Next, to obtain a solid F ₀ a regression equation of the boundary between the convex (□) on the lower convex with (■) in FIG. This solid line F ₀ can be expressed by H / D = 1.1 × (d / D) +0.342. On this solid line F ₀ , the distribution of the magnetic field strength in the central region of the superconductor is flat, and the deviation is Δb = 0. The magnetic field intensity distribution is convex upward in the area □ above the solid line F ₀ , and convex downward in the lower square area.

Substantially flat in the central region of the superconductor, or the shape of the superconductor in order to obtain a magnetic field intensity distribution of the convex type bottom (D, d, H) and may be set in the vertical of a range of solid line F _0. Since the amount of change in the magnetic field strength is proportional to the magnetic susceptibility χ, this range must be set wide when the magnetic susceptibility χ is small and narrow when the magnetic susceptibility χ is large.

FIG. 10 is a graph comparing the magnetic field shift profiles of two types of superconductors having the same shape (outer diameter 60 mm, inner diameter 16 mm, height 40 mm) and different materials. That is, f7 is a magnetic field shift profile of a Gd-based superconductor having a magnetic susceptibility χ of 0.01 at 100K, and f8 is a magnetic field shift profile of an Sm-based superconductor having a magnetic susceptibility χ of 1000035 at 100K. From FIG. 10 , the Sm-based superconductor having a small magnetic susceptibility χ has a much smaller absolute value of the magnetic field shift in the hollow portion (z = 0 to 8 mm) than the Gd-based superconductor, and the influence of the induced magnetic field on the applied magnetic field. Is small. Therefore, in the case of a superconductor made of a material having such a low magnetic susceptibility χ, this range may be widened.

The present inventor conducted the above magnetic field analysis for each element of RE and examined the results, and determined that the allowable ranges for the solid line F ₀ can be defined as + 0.001 / χ and −0.002 / χ. I found it.

That is, in order to obtain a substantially flat or downwardly convex magnetic field strength distribution in the central region, the shape (D, d, H) of the superconductor may be determined so as to satisfy the following expression (1).
H / D ≦ 1.1 × (d / D) + 0.342 + 0.001 / χ (1)

Further, by determining so as to satisfy the following expression (2), a magnetic field strength distribution with higher uniformity can be obtained.
1.1 × (d / D) + 0.342−0.002 / χ ≦ H / D ≦ 1.1 × (d / D)
+ 0.342 + 0.001 / χ (2)

Here, the permissible range for the case of the Gd-based (χ = 0.01) superconductor is shown by the broken lines F ₁ and F ₂ in FIG. 9, and in this range, the deviation of the magnetic field shift at the ± 1 mm point is shown. Δb is −1 ppm or more and 10 ppm or less. For example, when the outer diameter is 60 mm and the inner diameter is 16 mm, the height H may be selected from the formula (1) within a range of 44 mm or less. More preferably, the selection is made in the range of 26 to 44 mm using equation (2).

  FIG. 11 is a graph showing the magnetic field distribution in the central region when a magnetic field is applied to a superconductor having an outer diameter of 60 mm and an inner diameter of 16 mm with the height H selected as described above. The vertical axis represents the magnetic field shift deviation Δb (ppm), and the horizontal axis represents the distance Z (mm) from the midpoint 0. Profile f9 (■) is for height H = 30 mm, and profile f10 (□) is for height H = 40 mm. When H is 30 mm, it is convex downward, and the deviation Δb at the ± 1 mm point is 5.5 ppm. Further, when H is 40 mm, it is gently convex upward, and the deviation Δb at the ± 1 mm point is 0.25 ppm. That is, when H is 40 mm, the deviation Δb is 1 ppm or less in the central region, and it can be said that the distribution of the magnetic field strength is substantially flat. Further, when H is 30 mm, it is convex downward, and the deviation Δb is 10 ppm or less, so it can be said that in any case, it is a superconductor having a suitable shape that satisfies the above conditions.

  Since the shape (outer diameter, inner diameter, height) of the superconductor of the present invention is set as described above, the distribution of the magnetic field strength when applied by the superconducting magnet is the center in the axial direction of the superconductor. The superconducting magnetic field generating element which is substantially flat or convex downward in the region and can be magnetized can generate a highly uniform magnetic field in the hollow portion.

  Such a superconductor is an oxide superconductor whose main component can be expressed by RE-Ba-Cu-O, and RE is yttrium (element symbol Y), samarium m (Sm), lanthanum (La), neodymium (Nd ), Europium (Eu), gadolinium (Gd), erbium (Er), ytterbium (Yb), dysprosium (Dy), holmium (Ho), and an absolute temperature of 90K to 96K. Superconducting transition temperature of

(2) Magnetization method of superconductor A superconductor formed as described in (1) above is used to capture a magnetic field using a superconducting magnet. There is no particular limitation on the magnetization method, but the superconductor of the present invention is designed to obtain a uniform magnetic field particularly in the central region, and is thus magnetized in a static magnetic field. That is, this is a magnetization method in which a magnetic field is applied with a superconducting magnet or the like at a temperature higher than the superconducting transition temperature of the superconductor, and the temperature of the superconductor is cooled to a superconducting transition temperature or less while this magnetic field is applied.

  For example, since a superconducting transition temperature of a Gd-based superconductor is 92 K, magnetic field application is started at 100 to 300 K, which is higher than the superconducting transition temperature, and the superconductor is uniformly 25 to 25 while applying this magnetic field. Cool to 50K. While maintaining this temperature, the generated magnetic field of the superconducting magnet is gradually decreased over 600 to 3600 seconds, and finally set to zero. Thereafter, when the temperature of the superconductor is further lowered by 5K or more, the temporal change (creep) of the trapped magnetic field can be significantly suppressed. In this way, a superconducting magnetic field generating element that generates a uniform magnetic field can be obtained by allowing the superconductor to capture the magnetic field.

(3) Superconducting magnetic field generating element (first embodiment)
The superconducting magnetic field generating element of this embodiment is obtained by magnetizing the superconductor having the hollow cylindrical shape of (1) by the magnetization method of (2), and a magnetic field having high uniformity in the central region of the hollow portion. Has captured.

  For such a superconducting magnetic field generating element, a superconductor having a single magnetic susceptibility can be used. Also, a superconducting cylinder laminate in which a plurality of superconducting solids are laminated in the central axis direction, and the magnetic susceptibility of the superconducting solid at least at one end of the superconducting cylindrical laminate is smaller than the magnetic susceptibility of the other superconducting solids. You may comprise so that it may become. Hereinafter, the first embodiment of the superconducting magnetic field generating element of the present invention will be described in detail with reference to specific examples.

(Specific example 1)
Example 1 is a superconducting magnetic field generating element 2a in which a magnetic field is applied to a superconductor 1 having a single magnetic susceptibility, and a longitudinal section thereof is schematically shown in FIG.

The superconductor 1 is a single Gd-based superconductor G having an outer diameter (D) of 60 mm, an inner diameter (d) of 16 mm, and a height (H) of 40 mm. This superconductor is manufactured by a melting method, and a GdBa ₂ Cu ₃ O ₇ phase, which is a superconducting phase, is made of Gd ₂ BaCuO ₅ and Ag, which are non-superconductor phases, in a pseudo single crystal in which the crystal c-axis of the GdBa ₂ Cu ₃ O ₇ phase is oriented in the cylindrical axis direction. Contains fine particles.

  The superconductor 1 has a d / D of 2.67 and an H / D of 0.67, which satisfies the above formula (1). A magnetic field is applied to the superconductor 1 to capture the magnetic field to obtain a superconducting magnetism generating element 2a. The distribution of the magnetic field strength being applied in the central region of the superconductor 1 obtained by magnetic field analysis is the profile f10 shown in FIG. 11, and the superconducting magnetic field generating element 2a generates a highly uniform magnetic field in the hollow portion. Can do.

(Specific example 2)
Example 2 is a superconducting magnetic field generating element 2b in which two superconducting solid bodies having a single magnetic susceptibility are laminated to form a superconducting cylindrical laminate 1 ′. FIG. 13 shows a schematic diagram of the longitudinal section.

  The superconductor is a superconducting cylindrical laminate in which G2 superconducting solids G2 having an outer diameter (D) of 60 mm, an inner diameter (d) of 16 mm, and a height (h) of 20 mm are laminated, and the overall height (H) is 40 mm. It is the body 1 ′. The composition of the superconducting solid is the same as in Example 1. The result of magnetic field analysis is the same as in Example 1, and this superconducting magnetic field generating element 2b can generate a magnetic field with extremely high uniformity in the central region of the superconducting cylindrical laminate.

(Specific example 3)
Example 3 is a superconducting magnetic field generating element 2c in which superconducting solids having different magnetic susceptibility are laminated to form a superconducting cylindrical laminate 1 ′, and its longitudinal section is schematically shown in FIG.

As the superconductor, Sm-based superconducting solids S are laminated on both sides of a Gd-based superconducting solid G1 having an outer diameter (D) of 60 mm, an inner diameter (d) of 16 mm, and a height (h1) of 40 mm, and the total height (H ) Is a superconducting cylindrical laminate 1 ′ having a thickness of 60 mm. The Gd-based superconducting solid G is the same as in the first specific example. In addition, the Sm-based superconducting solid S is produced by the melting method in the same manner as the Gd-based superconducting solid G, and is a pseudo single crystal in which the crystal c-axis of the SmBa ₂ Cu ₃ O ₇ phase that is the superconductor phase is oriented in the cylindrical axis direction. Is a superconductor containing Sm ₂ BaCuO ₅ which is a non-superconductor phase and Ag fine particles.

  The magnetic susceptibility of the Sm-based superconducting solid S is as small as about 3.5% of the magnetic susceptibility of the Gd-based superconducting solid G, and the Sm-based superconducting solid S is arranged at both ends of the superconducting cylindrical laminate 1 ′, so that The influence on the magnetic field distribution in the region is limited. Therefore, the superconducting magnetic field generating element 2c can generate a magnetic field with extremely high uniformity in the central region of the superconducting cylindrical laminate 1 ′.

(Second Embodiment)
The superconducting magnetic field generating element of the present embodiment comprises the superconductor having the hollow cylindrical shape of (1) and a reinforcing member disposed around the superconductor, and is magnetized by the magnetization method of (2). It is a thing. This superconducting magnetic field generating element has a very high uniformity of the generated magnetic field in the central region of the hollow portion.

  Although the superconducting magnetic field generating element of the present embodiment has a reinforcing member that reinforces the superconductor, the reinforcing member also has a magnetic susceptibility like the superconductor and is magnetized by the applied magnetic field by the superconducting magnet, and the magnetic field strength during the application. This will disturb the distribution.

  Hereinafter, the magnetic field analysis related only to the reinforcing member excluding the superconductor and the optimization of the reinforcing member based on the analysis result will be described.

FIG. 15 shows a magnetic field shift profile obtained by magnetic field analysis for an aluminum reinforcing member. (A) has an inner diameter _{d H} is 60 mm, (in this embodiment is made to coincide with the height of the superconductor. Hereinafter the same.) The height H thickness t is at 5mm is 20,40,60,80mm 2 is a magnetic field shift profile of a ring-shaped reinforcing member. The magnetic field shift profile changes with the height H, but in the inner space of the ring (in the range of H / 2, the case where H = 60 is shown in the figure) is convex downward, and the center with the highest magnetic field strength The magnetic field shift ΔB at the part (0 point) is 0.8 to 1.2 ppm. Note that the central portion of the reinforcing member having the highest magnetic field strength is included in the central region of the superconductor.

  This magnetic field shift profile varies depending on the thickness of the ring, and the magnetic field shift increases as the thickness increases. When the wall thickness is 10 mm, the magnetic field shift ΔB at the center is 1.5 to 2.2 ppm (FIG. 15 b). When the wall thickness is 15 mm, the magnetic field shift ΔB at the center is 2 to 3.2 ppm (FIG. 15 c). )

However, in any of (a) to (c), the magnetic field shift ΔB at the center is 10 ppm or less, which is much smaller than the strength of the induced magnetic field of the superconductor. This is because aluminum having an extremely small magnetic susceptibility χ of 2.07 × 10 ⁻⁵ is applied to the reinforcing member.

Conventionally, austenitic stainless steel (SUS304) has been used for the reinforcing member. Figure 16a is for the inner diameter _{d H} is 60 mm, the thickness t is the height H at 5mm is determined by similarly magnetic field analysis and 15 magnetic field shift profile of SUS304-made reinforcing member of 20,40,60,80mm . Even when the wall thickness is 5 mm, the magnetic field shift ΔB in the center is about 125 to 175 ppm, which indicates that the magnetic field shift is larger than that of the aluminum reinforcing member. This is because the stainless steel has a magnetic susceptibility of 300 × 10 ⁻⁵ , which is extremely higher than that of aluminum. In addition, FIG. 16b is a case where the thickness is 10 mm, and FIG. 16c is a case where the thickness is 15 mm.

As described above, the magnetic field shift profile varies greatly depending on the material used for the reinforcing member. Therefore, a material having a magnetic susceptibility χ (absolute value) of 2 × 10 ⁻⁴ or less is selected as the reinforcing member. Table 2 shows the magnetic susceptibility χ of various materials at room temperature.

  That is, the reinforcing member is preferably made of any one of aluminum, aluminum alloy, copper, copper alloy, magnesium, magnesium alloy, titanium, and titanium alloy. In addition to the metal and the resin, a reinforcing resin material in which reinforcing particles such as ceramics, glass, and metal or reinforcing fibers are combined with the resin can be used as the reinforcing member. In the present embodiment, an adhesive for bonding these materials and the superconductor is also included in the reinforcing member.

15 and 16 that the magnetic field shift profile changes depending on the shape (d _H , t, H) of the reinforcing member when the material is constant.

FIG. 17 is a graph showing changes in the magnetic field shift depending on the shape of the reinforcing member based on FIGS. 15 and 16 in order to optimize the reinforcing member. 17, the ratio t / d _H of the inner diameter d _H and the thickness t of the ring is a reinforcing member is constant, the ratio between the height H and the inner diameter d _H, ring central portion when changing the H / d _H This shows the change in the magnetic field shift ΔB. Here, the horizontal axis represents H / d _H , and the vertical axis represents the relative magnetic field shift (ΔB / χ, ppm) obtained by dividing the magnetic field shift ΔB by the magnetic susceptibility χ, so that the change in the magnetic field shift only by the shape regardless of the material. Can know.

For example, the solid line f11 (♦) is t / d _H = 0.0833, which corresponds to FIG. 15a or FIG. 16a having an inner diameter d _{H of} 60 mm and a wall thickness of t 5 mm, and the point p is a relative magnetic field at a height H of 20 mm. It is a shift. The solid line f12 (■) is for the case of an inner diameter d60 mm and a wall thickness t10 mm, and the solid line f13 (▲) is for the case of an inner diameter d60 mm and wall thickness t15 mm. Both are convex below, the absolute value of the relative magnetic field shift is H / d _H is understood to be a maximum value (indicated by the white). In FIG. 17, in order to obtain the maximum value, heights other than the above four levels are also plotted.

Maximum value of the obtained relative field shift in FIG. 17 the relationship between t / _{d H} and (ΔBmax / χ) shown in FIG. 18. From FIG. 18, ΔBmax / χ and t / d _H are in a proportional relationship, and the maximum value ΔBmax of the magnetic field shift can be expressed as ΔBmax = 6.2 × | χ | · t / d _H.

Therefore, the condition for setting ΔBmax to 10 ppm (1 × 10 ⁻⁵ ) or less is expressed by the following equation.
t / d _H ≦ 1.6 × 10 ⁻⁵ / | χ |

The maximum value of t / _{d H} determined from magnetic susceptibility and the type of each metal material _{((t / d H) max} = 1.6 × 10 -5 / | χ |) are also shown in Table 2.

This condition indicates that the material having a smaller magnetic susceptibility χ can increase the wall thickness t. For example, when the inner diameter d _H is 60 mm, the maximum wall thickness is 48 mm for aluminum having a small magnetic susceptibility. be able to. However, in the case of stainless steel having a high magnetic susceptibility, the magnetic field shift at the center cannot be suppressed to 10 ppm or less unless the wall thickness is 0.3 mm or less. That is, in the superconducting magnetic field generating element of the present embodiment, it can be seen that the stainless steel reinforcing member cannot be substantially applied in order to suppress the influence of the magnetic field shift by the reinforcing member to 10 ppm or less.

  Hereinafter, the second embodiment of the superconducting magnetic field generating element of the present invention will be described with reference to specific examples.

(Specific example 4)
Specific example 4 is a superconducting magnetic field generating element 2d composed of superconductor 1 and reinforcing member 3 (ring 4 and adhesive 5) disposed around the superconductor 1, and a longitudinal section thereof is schematically shown in FIG.

The superconductor 1 is a Gd-based superconductor G having an outer diameter of 60 mm, an inner diameter of 16 mm, and a height of 40 mm. The reinforcing member 3 is an aluminum ring having an inner diameter (d _H ) of 60 mm, a wall thickness (t) of 5 mm, and a height (H) of 40 mm. The superconductor 1 and the reinforcing member 3 are in close contact with the adhesive 4. Integrated. In this specific example, the adhesive 3 was a particle-dispersed composite epoxy adhesive (trade name; Stycast, Emerson-Comming) mixed with an appropriate amount of a curing agent. The adhesive is not particularly limited as long as it does not affect the magnetic field, and may be appropriately selected in consideration of the adhesion between the superconductor 1 and the reinforcing member 3. In this specific example, the thickness of the adhesive was about 0.2 mm.

Since the superconductor 1 is the same as in the first specific example, the magnetic field shift profile in the central region is substantially flat. Further, since the reinforcing member 3 has a t / d _H of 0.0167 and a magnetic field shift ΔB of 1.2 ppm, the influence on the magnetic field during magnetization is small. Therefore, the superconducting magnetic field generating element 2d can generate a magnetic field with extremely high uniformity in the central region of the superconductor.

(Specific example 5)
Example 5 is a superconducting magnetic field generating element 2e in which superconducting solids having different magnetic susceptibility are laminated to form a superconducting cylindrical laminate 1 ′, and the periphery thereof is reinforced by the reinforcing member 3, and a longitudinal section thereof is schematically shown in FIG.

  As the superconductor, an Sm-based superconducting solid S having an outer diameter of 60 mm, an inner diameter of 16 mm, and a height of 10 mm is laminated on both sides of a Gd-based superconducting solid G1 having an outer diameter of 60 mm, an inner diameter of 24 mm, and a height of 40 mm. This is a superconducting cylindrical laminate 1 ′ in which (H) is 60 mm.

  The reinforcing member 3 is an aluminum ring having an inner diameter of 60 mm, a wall thickness of 5 mm, and a height of 60 mm. The superconducting cylindrical laminate 1 ′ and the reinforcing member 3 are in close contact with the adhesive 4 similar to that of the specific example 4. It is integrated. However, the superconductors may be laminated after individually adhering reinforcing members having the same height.

This specific example 5 is substantially the same as the specific example 4, and the magnetic field shift profile in the central region is substantially flat. Further, since the reinforcing member 3 has a t / d _H of 0.0167 and a magnetic field shift ΔB of 1.2 ppm, the influence on the magnetic field during magnetization is small. Accordingly, the superconducting magnetic field generating element 2e can generate a magnetic field with extremely high uniformity in the central region of the superconducting cylindrical laminate 1 ′. The superconducting magnetic field generating element 2e having such a shape has an advantage that an analysis coil and a correction coil can be easily arranged since the hollow portion 6 of the Gd-based superconducting solid G is wide.

(4) Superconducting magnetic field generator FIG. 21 shows a preferred embodiment of the superconducting magnetic field generator of the present invention.

  The superconducting magnetic field generating device 10 includes a superconducting magnetic field generating element 2 described in the above (3), a superconducting magnetic field generating element 2, which includes a hollow cylindrical superconductor 1 and a reinforcing member 3 disposed around the superconductor 1. A cooling member 12 for cooling the superconducting magnetic field generating element 2, a fixing member 13 for attaching the superconducting magnetic field generating element 2 to the cooling member 12, and a vacuum heat insulating container 14 for housing the superconducting magnetic field generating element 2 and the fixing member 13.

  The superconducting magnetic field generating element 2 is fixed in close contact with the cooling member 12 of the cooler 15 by the fixing member 13 and is accommodated in the vacuum heat insulating container 14. The central insertion portion 16 of the vacuum heat insulating container 14 is formed by being inserted into the hollow portion of the superconductor 1, and the NMR analysis can be performed by arranging the object to be measured in the insertion portion 16. Although not shown, a correction coil for correcting the uniformity of the generated magnetic field is disposed between the insertion portion 16 and the inner peripheral wall of the superconductor 1 together with a detection coil for detecting the NMR signal. .

  In the superconducting magnetic field generating apparatus 10 as described above, the peripheral members such as the cooling member 12, the fixing member 13, and the vacuum heat insulating container 14 also generate a magnetic field by the applied magnetic field in the same manner as the reinforcing member in the superconducting magnetic field generating element 2. It induces and disturbs the applied magnetic field.

Therefore, it is desirable that these peripheral members are also made of a material having a low magnetic susceptibility like the reinforcing member 3. In the superconducting magnetic field generator 10, at least the peripheral members included in the cylindrical range surrounded by the dotted line in FIG. 21 are made of a material having an absolute value of magnetic susceptibility of 2 × 10 ⁻⁴ or less. These peripheral members are preferably made of any one of aluminum, aluminum alloy, copper, copper alloy, magnesium, magnesium alloy, titanium, and titanium alloy depending on the required function. In the present embodiment, the cooling member 12 is made of copper, and the fixing member 13 and the vacuum heat insulating container 14 are made of an aluminum alloy.

  Here, the cylindrical range is a cylindrical space having a diameter of 2D and a height of 2H containing a superconductor having an outer diameter D and a height H, and more specifically, the central axis of the superconductor 1. A cylindrical space having a diameter of 2D and a height of 2H having a radius D around the O point and a length of H above and below the O point, with the H / 2 position as the center point O. It is.

The superconducting magnetic field generator 10 of this embodiment includes a superconducting magnetic field generating element having a superconductor and a reinforcing member that are optimized with respect to the uniformity of the magnetic field in the central region, and has an outer diameter centered on the superconductor as described above. Since the magnitude of the magnetic susceptibility of the peripheral member in the region twice as high as that of the superconductor is set to 2 × 10 ⁻⁴ or less, the superconducting magnetic field generator generates a correctable uniform magnetic field.

(5) Nuclear magnetic resonance apparatus The nuclear magnetic resonance apparatus 20 of the present invention is a nuclear magnetic resonance apparatus including the superconducting magnetic field generation apparatus 10 of (4) above, and is a small and high-performance nuclear magnetic resonance apparatus. A preferred embodiment is shown in the block diagram of FIG.

  The nuclear magnetic resonance apparatus 20 of the present embodiment includes the superconducting magnetic field generation apparatus 10 shown in FIG. The refrigerator 15 of the superconducting magnetic field generator 10 is connected to a compressor 22, and the vacuum heat insulating container 14 communicates with a vacuum pump 23. M indicated by a broken line is a superconducting magnet used only during application.

  The analyzing means 30 includes a high frequency generator 31, a pulse programmer (transmitter) 32, a high frequency amplifier 33, a preamplifier (signal amplifier) 34, a phase detector (receiver) 35, an analog / digital converter 36, a computer 37, and the like. Become.

  Since the nuclear magnetic resonance apparatus 20 having such a configuration includes the superconducting magnetic field generation apparatus 10 that generates a correctable uniform magnetic field, it is compact and can perform NMR analysis with high accuracy.

  The superconducting magnetic field generating apparatus having the superconducting magnetic field generating element of the present invention can generate a strong static magnetic field with a uniform distribution, and thus is suitable as a magnetic field generating apparatus for a nuclear magnetic resonance apparatus.

  In addition, since such a superconducting nuclear magnetic resonance apparatus is highly sensitive, has high resolution and is compact, it can be suitably used for MRI apparatuses in the medical field, or for components and structural analysis of industrial materials and agricultural products. it can.

It is the graph which showed the magnetic field shift profile obtained by the magnetic field analysis compared with the measured value. It is a graph which shows the change of the magnetic field profile by the height of a superconductor (outer diameter 60mm, inner diameter 10mm). It is a graph which shows the change of the magnetic field profile by the height of a superconductor (outer diameter 60mm, inner diameter 16mm). It is a graph which shows the change of the magnetic field profile by the height of a superconductor (outer diameter 60mm, inner diameter 20mm). It is a graph which shows the change of the magnetic field profile by the height of a superconductor (outer diameter 60mm, inner diameter 24mm). It is a graph which shows the change of the magnetic field profile by the height of a superconductor (outer diameter 60mm, inner diameter 30mm). It is a graph which shows a magnetic field shift profile in case the cylindrical shape of a superconductor differs in a similar shape. It is a graph which shows the magnetic field shift profile which scaled the horizontal axis | shaft of FIG. 7 by 1/2 of the height of the superconductor. It is a figure which shows the relationship between the shape of a superconductor, and a magnetic field shift profile. It is the graph which compared the magnetic field shift profile of the superconductor from which a material differs. It is a graph which shows the magnetic field shift profile in the center area | region of a superconductor. It is a cross-sectional schematic diagram explaining the superconducting magnetic field generating element of Example 1. It is a cross-sectional schematic diagram explaining the superconducting magnetic field generating element of Example 2. It is a cross-sectional schematic diagram explaining the superconducting magnetic field generating element of Example 3. It is a graph which shows the change of the magnetic field shift profile by the height of the reinforcement member made from aluminum. The inner diameter of the reinforcing member is 60 mm, and the wall thickness is (a) 5 mm, (b) 10 mm, and (c) 15 mm. It is a graph which shows the change of the magnetic field shift profile by the height of a stainless steel reinforcement member. The inner diameter of the reinforcing member is 60 mm, and the wall thickness is (a) 5 mm, (b) 10 mm, and (c) 15 mm. Is a graph showing changes in the relative magnetic field shift due to the shape (H / d _H) of the reinforcing member. Is a graph showing changes in maximum relative magnetic shift due to the shape (t / d _H) of the reinforcing member. It is a cross-sectional schematic diagram explaining the superconducting magnetic field generating element of Example 4. It is a cross-sectional schematic diagram explaining the superconducting magnetic field generating element of Example 5. It is a cross-sectional schematic diagram which shows an example of a superconducting magnetic field generator. It is a block diagram which shows an example of a nuclear magnetic resonance apparatus.

Explanation of symbols

1: Superconductor 2: Superconducting magnetic field generating element 3: Reinforcing member 10: Superconducting magnetic field generator 12: Cooling member 13: Fixed member 14: Vacuum heat insulating container 15: Cooling machine 16: Center insertion part 20: Nuclear magnetic resonance apparatus 22: Compressor 23: Vacuum pump 30: Analytical means

Claims (21)

A hollow cylindrical superconductor that captures an applied magnetic field in a hollow part,
When the outer diameter of the superconductor is D, the inner diameter is d, the height is H, and the magnetic susceptibility at the superconducting transition temperature is χ,
H / D ≦ 1.1 × (d / D) + 0.342 + 0.001 / χ
And
The distribution of the magnetic field strength in the horizontal axis direction in the hollow portion when the magnetic field is applied in a uniform static magnetic field with the central axis direction of the hollow portion as the horizontal axis and the magnetic field strength as the vertical axis is the superconductor. A superconductor characterized by being substantially flat or convex downward at a position approximately half of the length.   A half point of the length of the superconductor is a midpoint, the magnetic field strength at the midpoint when the magnetic field is applied, and the position at least ± 1 mm apart in the central axis direction across the midpoint The superconductor according to claim 1, wherein a difference from the magnetic field strength is 10 ppm or less of the applied magnetic field strength.   The magnetic field intensity at the midpoint when the magnetic field is applied, and the magnetic field intensity at a position at least ± 1 mm away from the midpoint in the central axis direction, with a half point of the length of the superconductor as a midpoint The superconductor according to claim 1, wherein the difference is 1 ppm or less of the applied magnetic field strength. When the outer diameter is D, the inner diameter is d, the height is H, and the magnetic susceptibility at the superconducting transition temperature is χ,
1.1 × (d / D) + 0.342−0.002 / χ ≦ H / D ≦ 1.1 × (d / D) + 0.342 + 0.001 / χ
The superconductor according to any one of claims 1 to 3 . Claims manufactured by a melting method, wherein the main component is represented by RE-Ba-Cu-O (RE is one or more of Y, La, Nd, Sm, Eu, Gd, Er, Yb, Dy, and Ho). The superconductor as described in any one of 1-4 . A superconductor magnetization method for applying a hollow cylindrical superconductor that captures an applied magnetic field in a hollow portion,
The superconductor according to any one of claims 1 to 5 , wherein a magnetic field is applied at a temperature higher than the superconducting transition temperature of the superconductor, and the superconductor is cooled to the superconducting transition temperature or less while the magnetic field is applied. How to magnetize superconductors. In a superconducting magnetic field generating element that applies a magnetic field to a hollow cylindrical superconductor and generates a magnetic field in the hollow portion of the superconductor by capturing the magnetic field,
The superconducting magnetic field generating element, wherein the superconductor is the superconductor according to any one of claims 1 to 5 . The superconducting magnetic field generating element according to claim 7 , wherein the superconductor has a single magnetic susceptibility. In a superconducting magnetic field generating element that applies a magnetic field to a hollow cylindrical superconductor and generates a magnetic field in the hollow portion of the superconductor by capturing the magnetic field,
The superconductor is a superconducting cylindrical laminated body obtained by laminating a plurality of superconducting solid in the central axis direction, the superconducting cylindrical laminate of superconducting solid at least one of any one of claims 1 to 5 the end, the superconducting magnetic field generating device small again superconducting solid susceptibility than the superconducting solid is characterized in that it is laminated. And a reinforcing member disposed around the hollow cylindrical superconductor and ultra conductors, superconducting magnetic field the superconductor emits a magnetic field in the hollow portion of the superconductor captures the magnetic field by application of a magnetic field In the generating element,
When the same magnetic field as that applied to the superconductor is applied only to the reinforcing member, the difference between the magnetic field strength in the space corresponding to the hollow portion of the superconductor and the applied magnetic field strength is 10 ppm or less of the applied magnetic field strength. A superconducting magnetic field generating element. The superconducting magnetic field generating element according to claim 10 , wherein the magnitude of the magnetic susceptibility (absolute value) of the reinforcing member is 2 × 10 ⁻⁴ or less. The superconducting magnetic field generating element according to claim 10 or 11 , wherein the reinforcing member has a ring shape. When the inner diameter of the reinforcing member is d _H , the thickness is t, and the magnetic susceptibility is χ,
t / d _H ≦ 1.6 × 10 ⁻⁵ / | χ |
The superconducting magnetic field generating element according to claim 12 . The reinforcing member is aluminum, aluminum alloy, copper, copper alloy, magnesium, magnesium alloy, titanium, a superconducting magnetic field generating device according to any one of claims 10 to 13 which is one kind of titanium alloy. The superconducting magnetic field generating element according to any one of claims 10 to 14 , wherein the superconductor is the superconductor according to any one of claims 1 to 5 . And a superconducting magnetic field generating device, such a reinforcing member disposed around the hollow cylindrical superconductor and ultra conductors, a cooling member for cooling the superconducting magnetic field generating element, the superconducting magnetic field generating device in the cooling member A superconducting device comprising: a fixing member to be attached; and a vacuum heat insulating container containing at least the superconducting magnetic field generating element and the fixing member, wherein the superconductor captures the magnetic field by applying a magnetic field and generates a magnetic field in the hollow portion of the superconductor. A magnetic field generator,
The difference between the applied magnetic field strength in the space corresponding to the hollow portion of the superconductor and the applied magnetic field strength when the same magnetic field as applied to the superconductor is applied with the superconductor removed. The superconducting magnetic field generator characterized by being 10 ppm or less. The superconducting magnetic field generating device, superconducting magnetic field generating apparatus according to claim 16 which is a superconducting magnetic field generating device according to any one of claims 10 to 15. The reinforcing member, the cooling member, the fixing member, either one or all of the shape of the vacuum heat insulating vessel, the superconducting magnetic field generating according to claim 16 or 17 is axially symmetrical with respect to the center axis of the superconductor apparatus. The reinforcing member, the cooling member, the fixing member, and the vacuum heat insulating container included in a cylindrical space having a diameter of 2D and a height of 2H containing the superconductor having an outer diameter D and a height H in the center. The superconducting magnetic field generator according to any one of claims 16 to 18, wherein the magnitude (absolute value) of the magnetic susceptibility is 2 x ^10-4 or less. The reinforcing member, the cooling member, the fixed member and the portion contained in the cylindrical inner space of the vacuum insulated container of aluminum, aluminum alloy, copper, copper alloy, magnesium, magnesium alloy, titanium, it more either titanium alloy The superconducting magnetic field generator according to claim 19 . A nuclear magnetic resonance apparatus comprising the superconducting magnetic field generator according to any one of claims 16 to 20 as a magnet.

Images