CN1885056A - Permanent magnet for portable nuclear magnetic resonance instrument - Google Patents
Permanent magnet for portable nuclear magnetic resonance instrument Download PDFInfo
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- CN1885056A CN1885056A CN 200510011970 CN200510011970A CN1885056A CN 1885056 A CN1885056 A CN 1885056A CN 200510011970 CN200510011970 CN 200510011970 CN 200510011970 A CN200510011970 A CN 200510011970A CN 1885056 A CN1885056 A CN 1885056A
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- permanent magnet
- cylindrical permanent
- magnet
- cylindrical
- magnetic field
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Abstract
The invention relates to a permanent magnet used in portable nuclear magnetic resonance instrument, which is formed by one hollow cylinder permanent magnet and one semi-cylinder permanent magnet, wherein the axial section of semi-cylinder permanent magnet is layered on one end surface of cylinder permanent magnet; the hollow cylinder permanent magnet is formed by arc permanent magnets with same shape, same magnetic field strength, and the magnetization direction two times of magnet rotation direction; the semi-cylinder permanent magnet is made by using the plane axially parallel with magnetic field direction to cut the cylinder permanent magnet same as the hollow cylinder permanent magnet; the inner and outer radiuses of semi-cylinder permanent magnet are the same as the inner and outer radiuses of cylinder permanent magnet, while its axial length is longer then the outer diameter of cylinder permanent magnet; the axial section of semi-cylinder permanent magnet is layered on one end surface of cylinder permanent magnet, while their magnetic field directions along the axle of cylinder chamber are same, to compensate the axial magnetic field at the end of cylinder permanent magnet.
Description
Technical field
The present invention relates to be used for the permanent magnet of nuclear magnetic resonance apparatus, particularly be used for the permanent magnet of portable nuclear magnetic resonance instrument magnetostatic field generator.
Background technology
In recent years, obtained continuous development, proposed many important use directions, and constantly realized in the nuclear magnetic resonance equipment field.
Current measurement to the test core sample, the method for employing are to obtain rock core by open-air probing earlier, rock core is taken back in the laboratory that measurement environment is had relatively high expectations measured again.The defective of this method is to finish required overlong time from the measurement that acquires of rock core, so that the income analysis result is effective poor because of it, can not be effectively applied to instruct field survey and exploitation.Therefore realize that the physicochemical characteristics of obtaining the rock core sample fast has realistic meanings.Same reason detects and the in-site measurement of chemical products etc. for agricultural product and food quality, also needs portable nuclear magnetic resonance instrument.
Magnetostatic field generator (magnetic source) is the important component part of nuclear magnetic resonance apparatus.It is how high that the matter of utmost importance that makes up portable NMR device is not that magnetic field intensity has, but need size, the weight of the magnetic field intensity, uniformity coefficient and the entire equipment that are fit to.Portable nuclear magnetic resonance instrument requires magnet that suitable magnetic field intensity and uniformity coefficient can be provided, and reduces the size and the weight of entire equipment as far as possible.
Six parts of Chinese patents by retrieval, A, the patent No. are 92112454.6 " Nd-Fe-B magnet for permanent-magnet nuclear magnetic resonance spectrometer "; B, the patent No. are 98113543.9 " permanent magnet for NMR imaging instrument "; C, the patent No. are 98318945.5 " nuclear magnetic resonance C shape permanent magnets "; D, the patent No. are 01128381.5 " a kind of permanent magnet that is used for NMR imaging instrument " "; E, the patent No. are 02290346.1 " rare earth permanent magnet formula mass spectrum of nuclear magnetic resonance instrument magnetic field device; F, the patent No. are 200410030688.4 " being suitable for the permanent magnet that the portable nuclear magnetic resonance device uses ".The magnet of six patents is by magnet steel, pole plate or grading ring, and formations such as yoke, a pair of permanent magnet block is installed on two relative upper and lower yokes, on the described a pair of permanent-magnet surfaces opposite to each other pole plate is installed respectively.Adopt the framework of polar-plate-type, it is characterized in that obtaining required magnetic field space by two opposite magnetic pole of magnetic circuit closed structure.Its weak point is:
(1) the uniform magnetic field spatial volume is little, and the magnetic field space waste is too big.Because very strict, existingly meet homogeneous area that field intensity requires and be generally between two magnetic poles in the magnet cross section about 30% of air-gap field even lower the uniformity requirement in magnetic field.If end effect around considering, the utilization factor of magnetic field space is lower.This is one of very high basic reason of magnet cost expense.
(2) magnetic field intensity is difficult to improve.Permanent magnet block is installed on two relative upper and lower yokes, so the distribution of magnetic source is restricted, and according to the superposition principle in magnetic field, the raising of magnet center field intensity is limited.With respect to outwards revealing owing to magnetic field, magnetic field intensity is less than the permanent magnetic material remanent flux density.
(3) because magnetic field will constitute the closed-loop path by yoke, and the uniformity of magnetic field in pole plate or the grading ring raising magnet gap.This has not only increased the cost of instrument, more makes magnet huge and heavy, is unfavorable for carrying.
Summary of the invention
The objective of the invention is to overcome the shortcoming of existing magnet technology, the permanent magnet that provides a kind of new portable nuclear magnetic resonance instrument to use.The magnetic field space utilization factor height of this permanent magnet, the volume of magnet is little, in light weight, leakage field is few.Be applicable to the detection of portable nuclear magnetic resonance instrument to sample in the test tube.
For achieving the above object, the present invention adopts following technical scheme:
The present invention adopts hollow test tube shaped permanent-magnet structure, it is characterized in that being made of cylindrical permanent magnet and half cylindrical permanent magnet of a hollow, and the shaft section of half-cylindrical permanent magnet is superimposed upon on the end face of cylindrical permanent magnet.The cylindrical permanent magnet of hollow is identical by shape, and magnetic field intensity equates that direction of magnetization is the fan-shaped permanent magnet of the sense of rotation twice of magnet own, constitutes by the seccotine adhesion, is divided into N=2 along the cylindrical permanent magnet circumferencial direction
M(M is the integer greater than 2) piece, each magnetic patch shaft section is fan-shaped.Half-cylindrical permanent magnet is equivalent on the cylindrical permanent magnet identical with hollow type cylindrical magnet body structure, intercept with the plane of parallel magnetic field direction vertically, the interior external radius of half-cylindrical permanent magnet equates that with the interior external radius of cylindrical permanent magnet its axial length is greater than the external diameter of cylindrical permanent magnet respectively.Each magnetic patch shaft section of forming half-cylindrical permanent magnet is fan-shaped, and magnetic field intensity equates that direction of magnetization is the sense of rotation twice of magnet own.The shaft section of half-cylindrical permanent magnet is superimposed upon on the end face of cylindrical permanent magnet, and this half round post permanent magnet is consistent with cylindrical permanent magnet magnetic direction on the axis in cylindrical cavity, in order to the axial magnetic field of compensation cylindrical magnet end of body.Whole magnet after the combination constitutes test tube shaped.In the cavity of hollow test tube shaped uniform magnetic field.
The principle of the invention is as follows:
At r
1＜r
2Annulus in insert rare-earth permanent magnet, the polarised direction of permanent magnet according to β ()=2 change (: the sense of rotation of permanent magnet own), will obtain the annulus internal magnetic field:
B＝B
rln(r
1/r
2) (1)
Wherein:
r
1: the internal diameter of annulus;
r
2: the external diameter of annulus;
Br: the remanent magnetism of rare earth permanent-magnetic material.
Such cylindrical permanent magnet can produce a transverse magnetic field that is orthogonal to cylinder axis in cylindrical cavity, the magnetic field of right cylinder outside is zero.For intensity and uniformity coefficient, this magnetic field is uniqueness and perfect at two-dimensional space, and magnetic field equates everywhere in the inner chamber of cylindrical permanent magnet, therefore, in the ideal case, the internal diameter r of cylindrical permanent magnet
1Size depend on the size of the test tube and the radio-frequency coil of splendid attire sample.When guaranteeing identical shimming size, the magnetic field space of test tube shaped magnet is far smaller than the magnetic field space of polar-plate-type magnet, and the magnetic field space utilization factor is big, must cause the test tube shaped magnet weight light, and volume is little.Be suitable as very much the magnetostatic field generator of portable nuclear magnetic resonance instrument.
Here need to prove: if the direction of magnetization of every bit can change continuously by 2 times of directions of magnet rotation itself in the magnet, the unevenness in whole in theory hollow circular cylinder internal magnetic field space is zero, in the actual engineering owing to the process for machining and manufacturing reason, can't accomplish that at present direction of magnetization changes continuously by 2 times of directions of magnet rotation itself, therefore adopts the magnet block division method.The piece number of magnet five equilibrium is many more, more near ideal state.
But in the three dimensions of cylindrical permanent magnet, along axis direction, decay gradually in Distribution of Magnetic Field mind-set two ends from magnet, if the magnet long enough, magnetic field equals half of magnet center field intensity on both ends of the surface so.
In actual use in order to obtain enough uniformity coefficient spaces, need to guarantee certain axial dimension length.But the actual magnetic field space that uses has only middle that section of the right cylinder that satisfies the uniformity coefficient requirement.When the sample in the test tube was put into probe measurement, the space of magnet lower end was wasted, and had both increased volume, had also increased weight.Weakened the advantage that cylindrical permanent magnet is used in portable nuclear magnetic resonance instrument.
Therefore, the decay for the axial magnetic field that compensates cylindrical permanent magnet is analyzed as follows cylindrical permanent magnet: when the position of endless cylindrical permanent magnet at z=0, cut by the x-y plane.If V
z(r, z) are the scalar potential that is produced by the cylindrical permanent magnet of z＞0, V
z(r, ,-z) be the scalar potential that produces by the cylindrical permanent magnet of z＜0, if V
z(r is the scalar potential of endless cylindrical permanent magnet ), and following formula is obviously set up so:
V
z(r，，-z)+V
z(r，，z)＝V
z(r，) (2)
Use certain operator to (2) formula, obtain interested flow function F
z(r, , z),
F
z(r，，-z)+F
z(r，，z)＝F
z(r，)＝2F
z(r，，0) (3)
In like manner, obtain the position of endless cylindrical permanent magnet at x=0, when being cut by the y-z plane, interested flow function F
r(r, ),
F
r(r
r，
r)+F
r(r
l，
l)＝F
r(r，)＝2F
r(r，π/2) (4)
When same radius, the end face field intensity of the above-mentioned cylindrical permanent magnet that intercepts equates with the field intensity in the half-cylindrical permanent magnet cross section that intercepts, and direction is identical.
F
r(r，π/2)＝F
z(r，，0) (5)
F
r(r，π/2)+F
z(r，，0)＝F
z(r，) (6)
This shows that if with the magnetic field superposition of two kinds of magnets, quite the axial length with cylindrical permanent magnet prolongs one times, therefore can effectively improve the axial magnetic field uniformity coefficient, also alleviates the weight of magnet simultaneously, has reduced volume.
The magnetic field of test tube shaped magnet circumferentially is being limited in the circumference, can not outwards disperse, and leakage field is less, presents a kind of poly-magnetic effect, thereby the magnetic field intensity in the test tube shaped magnet can design than the magnetic field intensity height of polar-plate-type magnet, thereby improves the resolution of instrument.
With regard to the manufacturing process of magnet, though be to form by two kinds of magnet combination, but the actual discrete magnetic patch that still only needs preparation and cylindrical permanent magnet equipolarization quantity, adopt identical assembly technology, after assembling cylinder and half-cylindrical permanent magnet respectively, be combined into the test tube shaped magnet, do not increase the complicacy of manufacturing process, this also is one of the advantage of the test tube shaped magnet of this novelty.
Because the adding of half-cylindrical permanent magnet, the shimming district of the central cross-section in magnetic field increases, and the center of departing from cylindrical permanent magnet, downward half-cylindrical permanent magnet skew.Just because of the skew in shimming district, this combination magnet center and the increase of axial dimension, so the present invention can make the suitable more detection to sample in the test tube of this test tube shaped magnet.
The invention has the advantages that: the magnetic field space utilization factor is big, overall volume is little, leakage field in light weight, magnet is little, manufacturing process is simple.
Description of drawings
The structural representation of the specific embodiment of the invention that Fig. 1 is made up of 13 magnets.Among the figure: Y1, Y2, Y3, Y4, Y5, Y6, Y7, Y8 are for constituting the fan-shaped permanent magnet of cylindrical permanent magnet; B1, B2, B3, B4, B5 are for constituting the fan-shaped permanent magnet of half-cylindrical permanent magnet.
Fig. 2 is the nose balance synoptic diagram of cylindrical permanent magnet of the present invention.
Fig. 3 is the Distribution of Magnetic Field synoptic diagram of the half-cylindrical permanent magnet that intercepted by the shaft section of parallel magnetic field direction among the present invention.
Fig. 4 is the cylindrical permanent magnet embodiment synoptic diagram that 8 magnets are formed.
Fig. 5 is a cylindrical permanent magnet of removing to intercept 8 magnets compositions with the shaft section of parallel magnetic field direction, and 5 magnets that obtained are formed the specific embodiment of the invention synoptic diagram of half-cylindrical permanent magnet.
Embodiment
The present invention is described further below in conjunction with the drawings and specific embodiments.
The structural representation of the specific embodiment of the invention that Fig. 1 is made up of 13 magnets.As shown in Figure 1, shaft section is that fan-shaped permanent magnet Y1, Y2, Y3, Y4, Y5, Y6, Y7, Y8 constitutes the hollow cylindrical permanent magnet; Fan-shaped permanent magnet B1, B2, B3, B4, B5 constitute half-cylindrical permanent magnet.The interior axial magnetic field direction of magnetic direction in the cylindrical permanent magnet and half-cylindrical permanent magnet is identical.An end face of cylindrical permanent magnet and the shaft section of half-cylindrical permanent magnet are superimposed, are combined into the test tube shaped magnet.
Fig. 2 is the nose balance synoptic diagram of cylindrical permanent magnet of the present invention.Suppose the position of endless cylindrical permanent magnet at z=0, cut by the x-y plane that magnetic field profile is shown in solid line among Fig. 2 on Z＞0 cylindrical magnet body axis, decay along axis in magnetic field, decay to 1/2nd of central magnetic field in the end.In like manner, magnetic field profile is as shown in phantom in Figure 2 on Z＜0 cylindrical magnet body axis.If two sections magnets of Z＞0 and Z＜0 are coupled together,, thereby realized compensation everywhere to magnetic field on Z＞0 cylindrical permanent magnet end axis so owing to magnetic field on the endless cylindrical magnet body axis equates.
The Distribution of Magnetic Field of the half-cylindrical permanent magnet that is intercepted by the shaft section of parallel magnetic field direction among the present invention as shown in Figure 3.Because the interior external radius of half-cylindrical permanent magnet equates with the interior external radius of cylindrical permanent magnet respectively, so half-cylindrical permanent magnet at the field decay of section to 1/2nd of endless cylindrical permanent magnet central magnetic field, Distribution of Magnetic Field in the outside, half-cylindrical permanent magnet cross section is identical with the Distribution of Magnetic Field in the cylindrical permanent magnet transverse plane outside, be among Fig. 3, Distribution of Magnetic Field on the axis of the half-cylindrical permanent magnet in X＜0 in X＞0 zone, with in Fig. 2, Distribution of Magnetic Field is identical on the axis of Z＜0 cylindrical permanent magnet in Z＞0 zone.Therefore adopt half-cylindrical permanent magnet to substitute Z＜0 cylindrical permanent magnet, realize compensation magnetic field on Z＞0 cylindrical magnet body axis.
Figure 4 shows that the cylindrical permanent magnet specific embodiment of the invention that 8 magnets are formed.By the xsect that is divided into 8 along the right cylinder circumferencial direction is fan-shaped permanent magnet Y1, Y2, Y3, Y4, Y5, Y6, Y7, Y8, constitutes the cylindrical permanent magnet of a hollow by the seccotine adhesion.
Figure 5 shows that the embodiment of the half-cylindrical permanent magnet of the present invention.Shaft section with the parallel magnetic field direction goes to intercept the cylindrical permanent magnet that 8 magnets are formed, and 5 xsects that obtained are fan-shaped permanent magnet B1, B2, B3, B4, B5, constitute a half-cylindrical permanent magnet by the seccotine adhesion.
The shaft section of half-cylindrical permanent magnet shown in Figure 5 is superimposed upon on the end face of cylindrical permanent magnet shown in Figure 4, make two magnets magnetic direction unanimity on the axis in cylindrical cavity, the shaft section that the center of circle of an end face of cylindrical permanent magnet is arranged in half-cylindrical permanent magnet constitutes test tube shaped magnet as shown in Figure 1 in the heart.
As shown in Figure 4, be followed successively by each magnetic patch numbering Y1, Y2, Y3, Y4, Y5, Y6, Y7, Y8 in the cylindrical permanent magnet in the direction of the clock, the magnitude of field intensity of each magnetic patch is identical.Get the magnetic patch that is numbered Y1, the polarised direction of this magnetic patch is taken as points to the center of circle radially.So according in the direction of the clock, the direction of magnetization dextrorotation gyration of Yi magnetic patch then
Solid arrow is depicted as each magnetic patch direction of magnetization among Fig. 4, and hollow arrow is a cylindrical permanent magnet internal magnetic field direction.Generally speaking, if magnet is divided into N piece (N=2
M, M＞2), and the magnetic patch sense of rotation
The then direction of magnetization of i magnetic patch and Y-axis angle
Be ω
i=2 θ
i, the direction of magnetization of magnetic patch is the twice of the sense of rotation of magnetic patch own.
As shown in Figure 5, half-cylindrical permanent magnetism system is intercepted cylindrical permanent magnet by the plane of parallel magnetic field direction vertically.Be followed successively by each magnetic patch numbering B1, B2, B3, B4, B5 in the half-cylindrical permanent magnet in the direction of the clock, the magnitude of field intensity of each magnetic patch is identical.Get the magnetic patch that is numbered B1, the polarised direction of this magnetic patch is taken as points to the center of circle radially.So according in the direction of the clock, the direction of magnetization dextrorotation gyration of Bi magnetic patch then
Solid arrow is depicted as each magnetic patch direction of magnetization among Fig. 5, and hollow arrow is a cylindrical permanent magnet internal magnetic field direction.The interior external radius of half-cylindrical permanent magnet equates that with the interior external radius of cylindrical permanent magnet the axial length of half-cylindrical permanent magnet is greater than the external diameter of cylindrical permanent magnet respectively, to guarantee the uniformity of magnetic field in the test tube shaped magnet.
Claims (4)
1, a kind of permanent magnet that is used for portable nuclear magnetic resonance instrument is characterized in that: cylindrical permanent magnet and half cylindrical permanent magnet by a hollow constitute, and the shaft section of half-cylindrical permanent magnet is superimposed upon on the end face of cylindrical permanent magnet; The cylindrical permanent magnet of hollow is by the identical fan-shaped permanent magnet of shape, constitutes by the seccotine adhesion, is divided into N=2 along the cylindrical permanent magnet circumferencial direction
M(M is the integer greater than 2) piece, each magnetic patch shaft section is fan-shaped; Half-cylindrical permanent magnet is on the cylindrical permanent magnet identical with hollow type cylindrical magnet body structure, and the usefulness plane of parallel magnetic field direction vertically intercepts, and its axial length is greater than the external diameter of cylindrical permanent magnet; The shaft section of half-cylindrical permanent magnet is superimposed upon on the end face of cylindrical permanent magnet, and this half round post permanent magnet is consistent with cylindrical permanent magnet magnetic direction on the axis in cylindrical cavity, and the whole magnet after the combination constitutes test tube shaped; In the cavity of hollow test tube shaped is uniform magnetic field.
2, according to the described permanent magnet that is used for portable nuclear magnetic resonance instrument of claim 1, it is characterized in that: each magnetic patch shape of forming permanent magnet is identical, magnetic field intensity equates that direction of magnetization is the twice of the sense of rotation of magnetic patch own.
3, according to claim 1 or the 2 described permanent magnets that are applicable to portable nuclear magnetic resonance instrument, it is characterized in that: the interior external radius of half-cylindrical permanent magnet equates with the interior external radius of cylindrical permanent magnet respectively.
4, according to the described permanent magnet that is used for portable nuclear magnetic resonance instrument of claim 1, it is characterized in that: when end face stack of the shaft section of half-cylindrical permanent magnet and cylindrical permanent magnet, the shaft section that the center of circle of an end face of cylindrical permanent magnet is arranged in half-cylindrical permanent magnet in the heart.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100119702A CN100568016C (en) | 2005-06-21 | 2005-06-21 | The permanent magnet that is used for portable nuclear magnetic resonance instrument |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100119702A CN100568016C (en) | 2005-06-21 | 2005-06-21 | The permanent magnet that is used for portable nuclear magnetic resonance instrument |
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| Publication Number | Publication Date |
|---|---|
| CN1885056A true CN1885056A (en) | 2006-12-27 |
| CN100568016C CN100568016C (en) | 2009-12-09 |
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|---|---|---|---|
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102066878B (en) * | 2008-06-19 | 2013-02-06 | 法国欧陆汽车公司 | Device for measuring a position using the hall effect |
| CN107144804A (en) * | 2017-03-20 | 2017-09-08 | 中国石油大学(北京) | magnet system and nuclear magnetic resonance detection device |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5216400A (en) * | 1992-06-02 | 1993-06-01 | The United States Of America As Represented By The Secretary Of The Army | Magnetic field sources for producing high-intensity variable fields |
| US5523731A (en) * | 1995-04-12 | 1996-06-04 | The United States Of America As Represented By The Secretary Of The Army | Simplified method of making light-weight magnetic field sources having distortion-free access ports |
| CN1401295A (en) * | 2001-08-29 | 2003-03-12 | 中国科学院武汉物理与数学研究所 | Permanent magnet for nuclear magnetic resonance image-forming apparatus |
| CN2694444Y (en) * | 2004-04-05 | 2005-04-20 | 北京大学 | Permanent magnet acceptable for portable nuclear magnetic resonance apparatus |
-
2005
- 2005-06-21 CN CNB2005100119702A patent/CN100568016C/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102066878B (en) * | 2008-06-19 | 2013-02-06 | 法国欧陆汽车公司 | Device for measuring a position using the hall effect |
| CN107144804A (en) * | 2017-03-20 | 2017-09-08 | 中国石油大学(北京) | magnet system and nuclear magnetic resonance detection device |
| CN107144804B (en) * | 2017-03-20 | 2019-11-19 | 中国石油大学(北京) | Magnet system and nuclear magnetic resonance detection device |
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| Publication number | Publication date |
|---|---|
| CN100568016C (en) | 2009-12-09 |
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Granted publication date: 20091209 Termination date: 20100621 |