Method for a targeted shaping of the magnetic field of permanent magnets

Abstract

The invention relates to a for a targeted shaping of the magnetic field of a single permanent magnet or an arrangement of a plurality of permanent magnets, wherein magnetic material from selected locations of the single permanent magnet or at least one of said permanent magnets of the arrangement is removed by means of at least one of the following removal procedures for shaping the magnetic field: laser ablation using laser radiation, high-pressure waterblasting using high-pressure water jets and mechanical ablation using a non-magnetic tool.

Claims

1. Method for a targeted shaping of the magnetic field of a single permanent magnet or an arrangement of a plurality of permanent magnets, wherein magnetic material from selected locations of the single permanent magnet or at least one of said permanent magnets of the arrangement is removed by means of at least one of the following removal procedures for shaping the magnetic field: laser ablation using laser radiation, high-pressure waterblasting using high-pressure water jets and mechanical ablation using a non-magnetic tool, and wherein the selected locations are determined by use of a model of the single permanent magnet or the arrangement of permanent magnets, and wherein the method comprises: detecting the field characteristics of the magnetic field of the current single permanent magnet or the current arrangement of permanent magnets (S1), determining the parameters of the model of the single permanent magnet or the arrangement of permanent magnets for generating a magnetic reference field with said detected field characteristics (S2), determining a needed material reduction of the single permanent magnet or the individual permanent magnets of the arrangement to adapt the magnetic field to a desired shape of said magnetic field by use of the model (S3), and removing the magnetic material from the selected locations of the permanent magnet or at least one of the permanent magnets of the arrangement by to reduce the material accordingly (S4).

2. Method according to claim 1, wherein the method is an iterative method.

3. Method according to claim 2, wherein the method comprises the further steps of: detecting the field characteristics of the shaped magnetic field of the current single permanent magnet or the current arrangement of permanent magnets again (S5), and as a decision step (S6), deciding whether the shaped magnetic field has the desired shape or whether to repeat steps (S1) to (S6).

4. Method according to claim 1, wherein the arrangement of a plurality of permanent magnets is a component for one or more of the following application devices and/or application systems: nuclear magnetic resonance spectroscopy system, magnetic resonance imaging system, compact particle accelerators setups, laser-plasma accelerators, magnetic traps, and inertial guidance systems, especially for use in aerospace devices.

5. Method according to claim 1, wherein the targeted shaping of the magnetic field by laser ablation is complemented by deactivating magnetic domains of the magnetic material by means of local heating of the magnetic material above the Curie temperature by use of the laser radiation.

6. Method according to claim 1, wherein the laser radiation is targeted on the selected locations by use of a scanning laser device.

7. Method according to claim 1, wherein the model is a mathematical model.

8. Method according to claim 1, wherein the model is a mathematical model of the single permanent magnet or the arrangement of permanent magnets.

9. Method according to claim 8, wherein the mathematical model of the single permanent magnet or the arrangement of permanent magnets is based on the finite element method.

Description

(1) In the drawing:

(2) FIG. 1 depicts a flowchart of a method for targeted shaping of the magnetic field of an arrangement according to a preferred embodiment of the invention.

(3) It shows an iterative method for targeted shaping of the magnetic field of an arrangement of a plurality of permanent magnets with six steps.

(4) The method comprises the following steps:

(5) In a first step S1 a field characteristics of the magnetic field of the current arrangement is detected,

(6) in a second step S2 the parameters of a model of the arrangement are determined for generating a magnetic reference field with said detected field characteristics,

(7) in a third step S3 a needed material reduction of the individual permanent magnets is determined to adapt the magnetic field to a desired shape of the by use of the model,

(8) in a fourth step S4 the magnetic material from the selected locations of the at least one of the permanent magnets is removed by laser ablation to reduce the material accordingly,

(9) in a fifth step S5 the field characteristics of the shaped magnetic field of the current arrangement is detected again, and

(10) in a in a sixth step S6 it is decided whether the shaped magnetic field has the desired shape or whether to continue with steps three to six.

(11) Of course this method can be used for a targeted shaping of the magnetic field of a single permanent magnet as well.

(12) Permanent magnetic materials are the only magnetic source that can be used to generate magnetic fields without power consumption or maintenance. Moreover, due to their robustness and scalability such stand-alone magnets are very attractive for many scientific and engineering areas. However, due to a large dispersion in the average value of the remnant polarization between different identical pieces, the spatial distribution of the magnetic field generated by arrangements built from these materials present important deviations from the theoretical magnetic field profile. The present invention proposes a method for correcting or tuning the spatial dependence of the magnetic field generated by arrays of permanent magnets by heating and/or ablating with laser radiation volume portions of the individual magnetic pieces that form the array. Once the final form of the arrangement has been built and its field has been mapped by determining the field characteristics, obtaining the spurious magnetic field contributions or inhomogeneity terms, it is possible then to identify in each magnetic piece the portion of volume that has to be removed in order to match the theoretical field profile.

(13) The size of the at least one permanent magnet is in the millimeter range or higher. The size of the locations to be removed can be as smalls one atom or higher. The permanent magnets may be made from different materials including super-conducting magnet materials.

(14) In general, it is possible to substitute the laser ablation using laser radiation by the following other removal procedures: high-pressure waterblasting using high-pressure water jets and mechanical ablation using a non-magnetic tool.

(15) While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments.

(16) Other variations to be disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word comprising does not exclude other elements or steps, and the indefinite article a or an does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting scope.