Perfect magnetic compensation of gravity along a vertical axis

International audienceMagnetic compensation of gravity allows for ground-based experiments to be carried out under weightless conditions at reasonable cost and without the time limitation of systems such as zero-g airplanes or drop towers. Most of the time classical superconducting solenoids are operated to perform such experiments, which lead to a poor quality of the gravity compensation due to the non-ideal shape of the current and field distribution. In order to improve the quality of simulated microgravity, scientists need to build novel ground-based systems fully dedicated to magnetic levitation. The magnetic design of these levitation apparatuses would be based on theoretical studies of magnetic forces and associated field distributions. The work presented in this paper demonstrates the possibility of producing a magnetic force on paramagnetic and diamagnetic materials that is constant, thus providing a uniform gravity compensation, along a segment in a 3D geometry. These results come from both the decomposition in spherical harmonics of the magnetic field and specific conditions applied on the magnetic force. The magnetic field configuration leads to conical-shape isohomogeneity of the resulting acceleration. As an additional remark to previous works, the impossibility to get a magnetic force varying as 1/r(2) is briefly described