HOMIE (Homogeneous Fields in Experiments)
In many cases quasi-static field vectors with magnitudes in the sub-mT-range are needed that can be adjusted in two or three dimensions within a highly spatially homogeneous volume. To generate precise field conditions in this range, an effective shielding of the earth’s field and of laboratory fields is required.
Low-frequency and DC magnetic fields can only be shielded by the method of flux guidance, preferably with a closed boxlike shape and several layers of the high-permeability shielding material MUMETALL®. Defined magnetic fields inside the shielded space can either be generated by permanent magnets or by electrical currents.
HOMIE is based on electrical currents to be able to adjust the magnetic field strength without mechanical changes. As the shielding materials also interact with the generated internal fields, a concept is needed that lets the passive shielding support the generation of the homogeneous field instead of interfering with calculationally optimized air coil systems. Many conventional setups use Helmholtz coils, whose theoretical field homogeneity is limited to the 2nd order and is additionally affected by surrounding shielding material.
Advantages
- 1D/2D/3D magnetic fields < mT
- typical magnetic shielding factors of 10 000 (80 dB) ... 1 000 000 (120 dB), depending on the system size
- higher field homogeneity than Helmholtz systems
- wider homogeneous volume than with active dynamic compensation
- easily accessible interior
- customer-specific adaptions possible (size, shielding requirements, openings, electronics, software…)
- optional: demagnetization of shielding material
- defined field gradients
- already in use by several research labs
HOMIE is based on electrical currents to be able to adjust the magnetic field strength without mechanical changes. As the shielding materials also interact with the generated internal fields, a concept is needed that lets the passive shielding support the generation of the homogeneous field instead of interfering with calculationally optimized air coil systems. Many conventional setups use Helmholtz coils, whose theoretical field homogeneity is limited to the 2nd order and is additionally affected by surrounding shielding material.
The HOMIE system is based on a different approach that uses the shielding material to even improve the field homogeneity. In principle (limited by the practiced constructional effort), the whole interior can be filled with an absolutely homogeneous field. It therefore offers a large utilizable volume fraction for experiments and in contrast to solenoidal coil systems e. g., it is easily accessible from the outside. Effects on the field homogeneity by customer-specific openings can be minimized by a sophisticated current diversion method. Besides, the whole interior can be kept free of electrically conductive material which is important if higher frequency experiments are to be performed under controlled quasi-static magnetic field conditions.
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Bruchure HOMIE 10 MB
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