access icon openaccess Ferrite core non-linearity in coils for magnetic neurostimulation

The need to correctly predict the voltage across terminals of mm-sized coils, with ferrite core, to be employed for magnetic stimulation of the peripheral neural system is the motivation for this work. In such applications, which rely on a capacitive discharge on the coil to realise a transient voltage curve of duration and strength suitable for neural stimulation, the correct modelling of the non-linearity of the ferrite core is critical. A demonstration of how a finite-difference model of the considered coils, which include a model of the current-controlled inductance in the coil, can be used to correctly predict the time-domain voltage waveforms across the terminals of a test coil is presented. Five coils of different dimensions, loaded with ferrite cores, have been fabricated and tested: the measured magnitude and width of the induced pulse are within 10% of simulated values.

Inspec keywords: ferrites; finite difference methods; patient treatment; biomagnetism; coils; bioelectric potentials; neurophysiology

Other keywords: ferrite core nonlinearity; Fe3O4; time-domain voltage waveforms; coils; magnetic neurostimulation; current-controlled inductance; peripheral neural system; transient voltage curve; capacitive discharge; finite-difference model

Subjects: Electric and magnetic fields (medical uses); Patient care and treatment; Patient care and treatment; Electrical activity in neurophysiological processes; Numerical approximation and analysis; Bioelectric signals; Differential equations (numerical analysis)

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