title: Ferrite core non-linearity in coils for magnetic neurostimulation.
abstract: 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.
authors.affiliation: Department of Electrical and Computer Engineering , University of Utah , Salt Lake City , UT 84112 , USA.
authors.forename: Anil Kumar
authors.initials: AK
authors.lastname: RamRakhyani
authors.affiliation: Department of Electrical and Computer Engineering , University of Utah , Salt Lake City , UT 84112 , USA.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Lazzi
keywords: Fe3O4; bioelectric potentials; biomagnetism; capacitive discharge; coils; current-controlled inductance; ferrite core nonlinearity; ferrites; finite difference methods; finite-difference model; magnetic neurostimulation; neurophysiology; patient treatment; peripheral neural system; time-domain voltage waveforms; transient voltage curve