Analytical calculation method of free static magnetic field point in magnetic signal measurement

Abstract

In the application of magnetic signal measurement such as non-invasive temperature of ferromagnetic resonance, magnetic nanoparticle fluid hyperthermia, magnetic nanoparticle concentration imaging, etc., it is necessary to generate a free static magnetic field point(FFP), so as to the signal is extracted and the corresponding magnetic signal is obtained by calculation. FFP is the point at which the static magnetic field produces a magnetic field strength that is approximately zero. FFP is established by a set of coils that generate static magnetic field with different circular currents. Based on Biot-Savar’s law, using the geometric relationship of the coils, an analytical method is proposed for calculating the current of each coil when an arbitrary point on the XOY plane as FFP. The analytical method not only overcomes the shortcomings of the traditional iterative method, such as slow convergence and uncertain results, but also has a theoretical basis, fast calculation speed and high precision. The simulation results show that the position error of FFP is within 3 mm, a gradient magnetic field is formed around the point, which satisfies the needs of magnetic signal measurement in the above applications. This is helpful for the improvement of the application of magnetic signal measurement.