title: Poloidal mode analysis of magnetic probe data in a spherical tokamak configuration.
abstract: A method to determine the poloidal mode number m in a spherical tokamak based on magnetic probe data was developed. Perturbed magnetic fields at Mirnov coils are calculated for distributed helical filamentary currents on rational surfaces assuming the maximum current amplitude, m and n (toroidal mode number), and the toroidal location of the filaments. These free parameters were determined from the best fit to the measured signals. The residual error was reduced by a factor of 2 by introducing helical filaments instead of toroidal filaments. Using this method, m/n=2/1 and 3/2 modes were identified in Mega-Ampere Spherical Tokamak discharges, and the time evolution of the tearing modes was derived.
authors.affiliation: Graduate School of Frontier Sciences, The University of Tokyo, Kashiwa 277-8561, Japan. tojo@fusion.k.u-tokyo.ac.jp
authors.forename: H
authors.initials: H
authors.lastname: Tojo
authors.forename: A
authors.initials: A
authors.lastname: Ejiri
authors.forename: M P
authors.initials: MP
authors.lastname: Gryaznevich
authors.forename: Y
authors.initials: Y
authors.lastname: Takase
authors.forename: Y
authors.initials: Y
authors.lastname: Adachi