HOMIE (Homogeneous Fields in Experiments)

In many cases quasi-static feld 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 feld conditions in this range, an effective shielding of the earth’s feld and of laboratory felds is required.

Low-frequency and DC magnetic felds can onlybe shielded by the method of ?ux guidance, preferrably with a closed boxlike shape and several layers of the high-permeability shielding material MUMETALL®. Defned magnetic felds 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 feld strength without mechanical  changes. As the shielding materials also interact with the generated internal felds, a concept is needed that lets the passive shielding support the generation of the homogeneous feld instead of interfering with calculationally optimized air coil systems. Many conventional setups use Helmholz coils, whose theroretical feld homogenity 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 feld homogeneity. In principle (limited by the practiced constructional effort), the whole interior can be flled with an absolutely homogeneous feld. 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 feld homogeneity by customer-specifc openings can be minimized by a sophisticated current diversion method. Besides, the whole interior can be kept free of electricallyconductive material which is important if higher frequency experiments are to be performed under controlled quasi-static magnetic feld conditions.