CN1248895A - MRI magnetic field generator - Google Patents
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- CN1248895A CN1248895A CN 97182073 CN97182073A CN1248895A CN 1248895 A CN1248895 A CN 1248895A CN 97182073 CN97182073 CN 97182073 CN 97182073 A CN97182073 A CN 97182073A CN 1248895 A CN1248895 A CN 1248895A
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Abstract
An MRI magnetic field generator which does not give a subject an imaged space stably, and produces a clear image with a high sensitivity while its size is small and its cost is low. A magnetic field reinforcing coil is attached to the peripheral parts of a pair of pole pieces which face each other with a gap therebetween. Hence the adjustment of the magnetic field intensity is possible with a simple construction without changing the form of a magnetic circuit and increasing the weight and area of a magnet. Further, the direction of a current applied to the coil is adjusted to enable the adjustment of the magnetic field distribution and the improvement of the magnetic field uniformity.
Description
The present invention relates to a kind of improvement of the magnetic field generator that in for example medical magnetic resonance image device (hereinafter being called the MRI device), uses, more particularly, relate to a kind of MRI magnetic field generator, facing with each other so that form the result that the magnetic pole piece periphery of an air gap twines around a pair of as the magnetic field regulating winding, this MRI magnetic field generator produces powerful, accurate and uniform magnetic field in air gap.
The MRI device is a kind of like this device: by means of this device patient body all or part of is inserted in the air gap of a magnetic field generator that forms strong magnetic field, and obtains tomographic image, thereby can estimate its tissue.This MRI magnetic field generator must be wide be enough to insert all or part of of patient body, and must obtain tomographic image clearly, be necessary to form in the imaging visual field in air gap one usually and have and be equal to or less than 1 * 10
-4Precision and stable, the powerful and uniform magnetic field of 0.02 to 2.0T (tesla).
As shown in Figure 7A and 7B, a kind of known magnetic field generator that uses in the MRI device has a kind of structure, magnetic pole piece 2 each the end place that facing with each other and be fixed on pair of permanent magnets structure 1 wherein, the source takes place as magnetic field in a R-Fe-B base magnet in permanent magnet structure 1, other ends of permanent magnet structure 1 are connected by a yoke 3, and produce static magnetic field in the air gap 4 between magnetic pole piece 2 (the open 2-23010 of Japan Patent).Circumference around magnetic pole piece 2 provides annular protruding portion 5 so that increase the uniformity that air gap 4 internal magnetic fields distribute, a convex projection branch (end expression) (the open 5-37446 of Japanese Utility Model) is provided at the center, adopted as above structure and other structures, and [these elements] is usually by making by the sheet shape piece material that scabbles electromagnetism soft iron, pure iron or other magnetic materials production.In the figure, 6 is gradient coils.
Yet with regard to above-mentioned magnetic field generator, during magnetic flux is easy to from the pole leakage to the air gap, thereby along the vertical centrage of air gap, the closer to pole surface, magnetic field intensity is high more.Therefore, in order in using magnetic field space, to obtain wishing high strength and inhomogeneity magnetic field, air gap must be to use several times [greatly] of magnetic field space, this for example realizes by using the mass expensive permanent magnet or increasing the distance between the magnetic pole or increase the pole surface area, but this can cause bigger magnetic circuit and the cost that can raise.
In light of this situation, the applicant finds, comprise that by use a kind of magnetic field of permanent magnet device the source takes place and these permanent magnets is used for magnetic field generator, can make magnetic field generator compacter, comprise substantially mutually tetragonal crystal and its basis of these permanent magnets are B, and Fe of 42-90at% of R (wherein R is one or more rare earth elements that comprise Y), the 2-28at% of 8 to 30at% (atomic percentages); And find, because the temperature characterisitic of these permanent magnets by keeping these permanent magnet coolings, can obtain much higher ceiling capacity product, and can further reduce Magnet weight (the open 4-22009 of Japan Patent).
Also find, by arranging isolating permanent magnet structure around flat permanent magnet structure, make the pole surface of pair of permanent magnets structure form the curved surface recessed with respect to air gap, magnetic field intensity and magnetic field homogeneity in the magnetic air gap can be increased, and the zone (the open 3-20053 of Japan Patent) of uniform magnetic field can be expanded with high accuracy.
Yet last invention needs chiller, and the latter needs multiple permanent magnet structure, and it is more complicated that especially the two all makes structure, thereby installation time is longer, and price is higher.
And, in the inhomogeneity effort that improves the air gap internal magnetic field, the applicant has proposed a kind of structure, wherein have and be installed in this permanent magnet with at least one auxiliary permanent magnet of the identical direction of magnetization of permanent magnet and/or outer, thereby it can move in the direction of magnetization of permanent magnet, and this makes and might be adjusted in the magnetic flux (the open 3-7124 of Japan Patent) that produces in the air gap; With a kind of structure, wherein the magnetic force adjusting rod of being made up of magnetic material is offered yoke, stretch into amount in the air gap at least thereby can change them, this allows the amount of magnetic flux short circuit to increase or reduces (the open 2-41841 of Japanese Utility Model).But, if make magnetic flux short circuit amount increase too greatly by these auxiliary permanent magnets or magnetic force adjusting rod, then this has the danger that causes magnetic field intensity to reduce.
In addition, in order to form the static magnetic field of high uniformity and stability, a kind of like this structure by NMR device has been proposed, wherein there is a static magnetic field generating means to comprise pair of permanent magnets, the space of almost sealing with a formation and with the magnetic-coupled yoke of these Magnet, provide and be arranged in this near in the permanent magnet each, be used for proofreading and correct inhomogeneity a plurality of ancillary coils of above-mentioned static magnetic field, thereby determine to be applied to the electric current of these ancillary coils, so that eliminate of the influence of above-mentioned yoke to the magnetic field that forms by ancillary coil, with the influence (Japanese Laid-Open Patent Application 61-17053) that the static magnetic field of permanent magnet is distributed.
Yet with regard to above structure, ancillary coil is disposed in the side in the face of each magnetic pole piece of air gap, and by the layout of these ancillary coils air gap is narrowed down.Thereby patient is not felt be tied if widen air gap, then the intensity of static magnetic field will die down, and can not obtain the image of good quality.
In addition, such problem is arranged, if stating the MRI magnetic field generator in the use produces in the visual process, because the motion of Magnet variations in temperature or object, motion or automobile or near the motion of train building such as elevator in the building that this device is installed, and making magnetic field intensity that unexpected dynamic change be arranged, the conventional mechanical method that then is used for regulating magnetic field is unsuitable.
In view of above situation has proposed the present invention according to the hope magnetic field intensity of MRI magnetic field generator, and one object of the present invention is to provide the MRI with a kind of like this structure magnetic field generator: although this compact conformation and cost are low, but might in becoming image space, stably obtain a uniform static magnetic field, and do not make patient feel to be tied, and produce image clearly with high-resolution.
Be to realize the result of the various researchs of described purpose as target, finishing inventor of the present invention finds, facing with each other to form an air gap and magnetic-coupled a pair of polar and in this air gap, produce in the MRI magnetic field generator in magnetic field having by yoke, the magnetic field regulating winding is installed and is given these coils electric current around the periphery by the magnetic pole piece installed at these magnetic pole places, can increase or reduce magnetic field intensity; And can regulate Distribution of Magnetic Field and improve magnetic field homogeneity by regulating sense of current.
The present inventor also propose by as above the structure the MRI magnetic field generator, have: a kind of wherein magnetic pole piece comprises annular protruding portion and magnetic field regulating winding by the structure on the periphery of these annular protruding portions, and becomes possible structure as the high accuracy adjusting that makes Distribution of Magnetic Field; A kind of wherein annular protruding portion comprises that a plurality of arc annulus prodgers and magnetic field regulating winding twine each of these annular prodgers.
Fig. 1 shows an embodiment who belongs to magnetic field generator of the present invention, and 1A is vertical cutaway view, and 1B is an oblique view;
Fig. 2 is vertical cutaway view, shows another embodiment that belongs to magnetic field generator of the present invention;
Fig. 3 is an oblique view, shows a separately embodiment of annular protruding portion who belongs to magnetic field generator of the present invention;
Fig. 4 is the magnetic field profile in each plane when diameter of Spherical Volume is separated into 15 horizontal planes, and 4A is a kind of conventional magnetic field generator, and 4B belongs to magnetic field generator of the present invention;
Fig. 5 is the separately top view of an embodiment of annular protruding portion that belongs to magnetic field generator of the present invention;
Fig. 6 is the magnetic field profile of directions X, and 6A is a kind of conventional magnetic field generator, and 6B belongs to magnetic field generator of the present invention;
Fig. 7 shows a kind of structure of routine MRI magnetic field generator, and 7A is a front view, and 7B is its side sectional view;
Fig. 8 shows the structure of the magnetic pole piece that uses in a kind of routine MRI magnetic field generator, 8A is a front view, and 8B is its side sectional view; And
Fig. 9 shows a kind of structure of routine MRI magnetic field generator, and 9A is a front view, and 9B is its side sectional view.
Figure 1A and 1B are vertical cutaway view and oblique view, show an embodiment who belongs to magnetic field generator of the present invention.For example, by the annular protruding portion 12 that the stacked stalloy with pentagonal cross-section is formed, be arranged in the air-gap surface offside of the magnetic material pedestal of forming by pure iron etc. 11.An inner magnet pole shoe 13 is arranged in its inside, and a magnetic field regulating winding 14 is on the periphery of annular protruding portion 12.Purpose of the present invention also can realize by a kind of like this structure: inner magnet pole shoe 13 wherein is not provided, and annular protruding portion 12 directly is arranged on the magnetic material pedestal 11, and magnetic field regulating winding 14 is on its periphery.As shown in Figure 2, also can obtain the effect identical with said structure with following structure: wherein magnetic field regulating winding 14 is on the periphery of the annular protruding portion 12 that constitutes magnetic material pedestal 11 and magnetic pole piece, perhaps on the periphery of magnetic material pedestal 11, annular protruding portion 12 and a kind of permanent magnet structure.
The known in the past a kind of material as magnetic pole piece as electromagnetism soft iron or pure iron, can be used for the magnetic material pedestal of magnetic poles boots in the present invention.This magnetic material pedestal makes magnetic field intensity more even, guarantees that magnetic pole piece makes the as a whole good mechanical strength that has, and makes the work of assembling magnetic field generator easy.
The material of magnetic poles boots is not limited to material in an embodiment in the present invention, and can adopt material or the similar material produced by with electrically insulating material mold pressing pure iron together or soft magnetic powder, and by adopting the layer product or the soft ferrite of stalloy, a kind of as based on Mn-Zn or Ni-Zn, because its low coercive force and high resistance, so can reduce the generation of remanent magnetism during pulsed magnetic field applies or produce eddy current at magnetic material pedestal place.And, by using these materials together, can utilize the advantage of stacked stalloy and soft ferrite more fully.Stacked stalloy is because its low cost is better than soft ferrite economically.
With regard to the magnetic pole piece shown in Fig. 8 20, if above-mentioned material is made a plurality of block magnetic pole piece spares 23 and 24 materials that dispose on the magnetic material pedestal 21, so eddy current and remanent magnetism reduce can be better, and just can connect these parts with less work.Optimize the thickness of above-mentioned magnetic pole piece spare 23 and 24 or the thickness ratio of magnetic material pedestal, can guarantee that magnetic pole piece 20 has excellent mechanical intensity, balanced magnetic pole piece 20 require magnetic field intensity, and prevent eddy current and remanent magnetism.
In addition, be preferably in the present invention around the periphery of dish type magnetic material pedestal 21, form by magnetic material ring 22, as electromagnetism soft iron or pure iron, the ledge of composition is so that increase the interior magnetic field homogeneity of air gap.Preferably these magnetic material rings and magnetic material pedestal electric insulation, so that reduce the influence of eddy current.Particularly, if one or more slit is provided at circumferencial direction, then can further reduce the influence of eddy current.
The cross section of annular protruding portion is suitably chosen from proximate triangle, tetragon etc.If the whole surface of magnetic pole piece opposite side is the smooth arcual recessed curved surface with list or composite curvature radius, then will obtain similar effects.
In the present invention, around the magnetic pole piece that comprises above-mentioned annular protruding portion, twine the magnetic field regulating winding and power supply is flow through wherein, make that might increase magnetic field the magnetic field and the rising in source takes place or reduce magnetic field intensity, and particularly for the structure that on magnetic pole piece, has annular protruding portion, around the periphery of magnetic pole piece, twine the magnetic field regulating winding and combine, to produce more uniform magnetic field with the magnetic field portfolio effect of annular protruding portion.
With regard to a kind of wherein by providing at circumferencial direction with regard to the structure that a plurality of slits are divided into annular protruding portion multistage, magnetic field regulating winding 14 sectional annular protruding portion 121,122 and 123 each around twine, as shown in Figure 3, and regulate the magnitude of current by every section, its advantage is to carry out meticulous adjusting to Distribution of Magnetic Field.
As the Distribution of Magnetic Field of image space when on the positive negative direction of the Y-axis of X-axis, being symmetric, as shown in Figure 5, by one in the magnetic field regulating winding 143 and 144 of electric current being delivered to the magnetization side with deliver to other magnetic field regulating windings 141 and 142 of degaussing side, can regulate Distribution of Magnetic Field and improve magnetic field homogeneity.
When using above MRI magnetic field generator of the present invention of constructing, by twine the magnetic field regulating winding around the periphery of the magnetic pole piece of use in the past always, can raise or the reduction magnetic field intensity, and need not change the shape of magnetic circuit or the weight or the surface area of increase Magnet widely.And, flow to each the sense of current of the magnetic field regulating winding that twines around a pair of magnetic pole piece by adjusting, can realize more simply that the Distribution of Magnetic Field in the air gap is regulated, this has improved magnetic field homogeneity.
In addition, be to provide a plurality of slits and with regard to the arc annulus ledge structural engagement structure together to annular protruding portion in a circumferential direction wherein just for the purpose that suppresses eddy current, flow by the electric current that around each of these annular protruding portion structures, twines the magnetic field regulating winding and regulate, can regulate Distribution of Magnetic Field subtly by each.
When the source takes place as magnetic field in a R-Fe-B base permanent magnet, this rare-earth magnet has-temperature coefficient of 0.1%/C, but when electric current passes through continuously, magnetic pole piece or produce heat around the magnetic field regulating winding of the periphery of permanent magnet or magnetic pole piece, and this makes the permanent magnet heating, thus the temperature of holding magnet and stabilizing magnetic field intensity.
Therefore, if a pick off is placed in the magnetic field, when variations in temperature causes that magnetic field intensity changes, can keep magnetic field stable so by making electric current pass through the magnetic field regulating winding.Even the motion artifacts magnetic field of elevator or automobile during imaging, the dynamic change in magnetic field also can be proofreaied and correct by providing of magnetic field of the present invention regulating winding.
MRI magnetic field generator as the object of the invention is not limited to the above embodiment that provides, and can be applied to any structure, as long as wherein a pair of to face with each other with the magnetic pole that forms an air gap be by a yoke magnetic coupling.In addition, the size and dimension that is used for forming the yoke of flux path can suitably be selected to and require size, magnetic field intensity, magnetic field homogeneity and various its dependent variable decision by air gap.
Except that Fig. 7 A with shown in the 7B, wherein each other through the pair of magnetic yoke 3 above structure that cylindrical yoke 7 is connected by four that an air-gap surface faces toward, also might adopt the structure shown in Fig. 9 A and the 9B, magnetic pole piece 2 each the end that facing with each other and be fixed on pair of permanent magnets structure 1 wherein, and the yoke 3 that is fixed on other end places is connected by a flat connection yoke 8.
With regard to the structure among Fig. 9 A and the 9B, yoke 3 is connected by single connection yoke 8 at the one end, and,, and do not retrain patient so this device has a kind of more open sensation because the air gap 4 between magnetic pole piece 2 is opened (only connecting yoke 8 side closures) in three sides.
Common conduction Magnet, superconducting magnet, permanent magnet etc. can be used as the magnet arrangement of magnetizing field generation source effect, and can use ferrite magnet, Rare-Earth Cobalt base magnet or other this known magnetic materials when adopting permanent magnet.Particularly, by use the light rare earth of affluent resources being arranged, mainly is the R of Nd or Pr, and uses the R-Fe-B base permanent magnet that presents the above very high energies product of 30MG0e to make main parts, can make this device much compact.And, by arranging the combination of these known permanent magnets, can provide a kind of more cheap magnetic field generator, and little the obstruction makes the compacter effort of this device.
In the magnetic field generator of constructing as shown in Figure 1A and 1B, use BHmax with 40MG0e, 1300mm (millimeter) external diameter, the 190mm internal diameter, and the Nd-Fe-B base permanent magnet of 150mm height, one that be made up of mild steel and have a 1200mm external diameter, the outstanding structure of the annular of 1000mm internal diameter and 70mm height, be disposed in by pure iron and form, and have on the magnetic material pedestal of 1200mm external diameter and 40mm height, reach one by stacked and integrated block stalloy generation at the rightabout of magnetic pole piece, and have the silicon steel lamella product of 1000mm external diameter and 25mm height (at the center), be provided in the annular protruding portion.
A pair of annular protruding portion up and down is provided, making the distance between its opposite side is 500mm, the magnetic field regulating winding of being made up of the electric copper lead twines 1000 circles around the periphery of annular protruding portion, the electric current of a 10A by the magnetization side a coil (with static magnetic field in the same way), and electric current also by the magnetization side other coils (with static magnetic field in the same way).This structure allows the intensity at magnetic field center place to increase about 120 Gausses.
Target in this case is the magnetic field that strengthens the air gap center, but when target be when proofreading and correct the changes of magnetic field that causes by automobile or elevator motion, use than above those lead windings that lack that provide or little electric current energy magnetic field for correcting.In this case, by by means of the magnetic sensor that is placed in the magnetic field generator outside from external detection magnetic field, and raise or reduce the electric current that flows to this magnetic field regulating winding according to this sensor information, can keep the magnetic field homogeneity in the air gap.Can and want gauged part according to the magnetic field intensity of hope, suitably select the quantity and the current value of lead winding.
If the one-tenth image space of supposition in the structure of embodiment 1 is spheric, then Fig. 4 B shows the Distribution of Magnetic Field in each plane when this diameter of Spherical Volume is divided into 15 horizontal planes.Fig. 4 A represents except the magnetic field regulating winding is not provided, produce have with the conventional magnetic circuit of embodiment 1 same structure and with embodiment 1 in identical mode check the result of Distribution of Magnetic Field.As understanding from Fig. 4, structure of the present invention has increased the uniformity in magnetic field widely under low-down current value.
As shown in Fig. 3 and 5, provide a plurality of slits at the circumferencial direction of annular protruding portion to it, arc annulus ledge spare is joined together, and these annular protruding portion spares each around twine a magnetic field regulating winding.As shown in Fig. 6 B, the magnetic field homogeneity ratio is (as shown in Fig. 6 A) height when the magnetic field regulating winding is not provided.
With regard to the present invention, around a pair of periphery that is facing with each other with the magnetic pole piece that forms an air gap, twine the magnetic field regulating winding, and the result might raise or the reduction magnetic field intensity with a kind of simple structure, and need not change the shape of magnetic circuit or the weight or the surface area of increase Magnet.And, be when X-axis is vertically symmetrical as the Distribution of Magnetic Field in the image space, on the direction opposite, pass through a coil by making electric current with other coils, can regulate Distribution of Magnetic Field, this has increased magnetic field homogeneity.
In addition, on for the circumferencial direction of purpose that suppresses eddy current, provide a plurality of slits to its annular protruding portion at magnetic pole piece, and when a plurality of segments in a circular shape projecting parts are bonded together, flow by the electric current that around each of these annular projecting parts, twines the magnetic field regulating winding and regulate, can regulate Distribution of Magnetic Field subtly by each.
At last, when when the rare-earth magnet of ambient temperature effect sensitivity as main field the source is taken place, the heat that produces when flowing through the magnetic field regulating winding by electric current can keep the temperature of permanent magnet, and this allows to obtain stable and magnetic field uniformly.In addition,,, and the dynamic change of magnetic field intensity is arranged, then can regulate Distribution of Magnetic Field immediately as the motion of automobile during imaging or elevator if owing to any reason.
Claims (12)
1. one kind has a pair of facing with each other to form an air gap and magnetic-coupled polar and produce the MRI magnetic field generator in magnetic field in described air gap by yoke, and described MRI magnetic field generator comprises the magnetic field regulating winding that twines around the periphery of the magnetic pole piece that some are arranged on above-mentioned magnetic pole.
2. MRI magnetic field generator according to claim 1, wherein magnetic pole piece comprises some annular protruding portions, and the magnetic field regulating winding is on the periphery of described annular protruding portion.
3. MRI magnetic field generator according to claim 1, wherein magnetic pole piece comprises annular protruding portion and magnetic material pedestal, and the magnetic field regulating winding is on the periphery of described magnetic material pedestal.
4. MRI magnetic field generator according to claim 1, wherein magnetic pole piece comprises annular protruding portion and magnetic material pedestal, and the magnetic field regulating winding is on the periphery of the periphery of described annular protruding portion and described magnetic material pedestal.
5. MRI magnetic field generator according to claim 1, wherein magnetic pole piece comprises annular protruding portion, magnetic material pedestal and inner magnet pole shoe, and the magnetic field regulating winding is on the periphery of the periphery of described annular protruding portion and described magnetic material pedestal.
6. MRI magnetic field generator according to claim 5, wherein the inner magnet pole shoe is made up of stalloy.
7. MRI magnetic field generator according to claim 2, wherein annular protruding portion is made up of a plurality of arc annulus prodgers, and the magnetic field regulating winding is in each winding on every side of described annular protruding portion spare.
8. MRI magnetic field generator according to claim 7, wherein annular protruding portion is made up of four arc annulus prodgers.
9. according to each described MRI magnetic field generator in the claim 2 to 8, wherein the part of annular protruding portion is formed by silicon steel at least.
10. according to each described MRI magnetic field generator in the claim 1 to 9, wherein magnetic pole piece is to being fixed on a upper magnet yoke and the lower yoke, and upper and lower yoke is come magnetic coupling by single yoke that connects.
11. according to each described MRI magnetic field generator in the claim 1 to 9, wherein magnetic pole piece is to being fixed on the upper and lower yoke, and upper and lower yoke is come magnetic coupling by a plurality of connection yokes.
12. according to each described MRI magnetic field generator in the claim 1 to 9, wherein magnetic pole piece is to the layout that facing with each other in a tubular yoke, and comes magnetic coupling by described yoke.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 97182073 CN1248895A (en) | 1997-12-26 | 1997-12-26 | MRI magnetic field generator |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 97182073 CN1248895A (en) | 1997-12-26 | 1997-12-26 | MRI magnetic field generator |
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| CN1248895A true CN1248895A (en) | 2000-03-29 |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100443917C (en) * | 2001-12-17 | 2008-12-17 | 皇家飞利浦电子股份有限公司 | Magnetic resonance methods and equipment |
| CN103945760A (en) * | 2011-11-16 | 2014-07-23 | 皇家飞利浦有限公司 | Apparatus and method for influencing and/or detecting magnetic particles having a large field of view |
| CN110724952A (en) * | 2019-12-03 | 2020-01-24 | 浙江工业大学 | Combined magnetic core magnetic field generating device for improving magnetic concentration |
| CN112105941A (en) * | 2018-04-12 | 2020-12-18 | 皇家飞利浦有限公司 | Shim iron for magnetic resonance apparatus |
| CN114910838A (en) * | 2021-02-10 | 2022-08-16 | 清华大学 | Magnetic field enhancement components and magnetic field enhancement devices |
-
1997
- 1997-12-26 CN CN 97182073 patent/CN1248895A/en active Pending
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100443917C (en) * | 2001-12-17 | 2008-12-17 | 皇家飞利浦电子股份有限公司 | Magnetic resonance methods and equipment |
| CN103945760A (en) * | 2011-11-16 | 2014-07-23 | 皇家飞利浦有限公司 | Apparatus and method for influencing and/or detecting magnetic particles having a large field of view |
| CN103945760B (en) * | 2011-11-16 | 2017-06-30 | 皇家飞利浦有限公司 | The apparatus and method for influenceing and/or detecting magnetic-particle with big visual field |
| CN112105941A (en) * | 2018-04-12 | 2020-12-18 | 皇家飞利浦有限公司 | Shim iron for magnetic resonance apparatus |
| CN110724952A (en) * | 2019-12-03 | 2020-01-24 | 浙江工业大学 | Combined magnetic core magnetic field generating device for improving magnetic concentration |
| CN114910838A (en) * | 2021-02-10 | 2022-08-16 | 清华大学 | Magnetic field enhancement components and magnetic field enhancement devices |
| CN114910838B (en) * | 2021-02-10 | 2024-04-26 | 清华大学 | Magnetic field enhancement assembly and magnetic field enhancement device |
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