(TH/P39) Computation of ToroidalCurrent Reversal Equilibria for the JT60U Tokamak
P. Rodrigues^{1)},
J. P. S. Bizarro^{1)}
^{1)} Centro de Fusão Nuclear, Associação EuratomIST, Instituto Superior Técnico, Lisbon, Portugal
Abstract. A toroidalcurrent reversal GradShafranov (GS) equilibrium is computed, using poloidalmagneticfield and plasmapressure profiles retrieved from experimental JT60U data [T. Fujita et al., Phys. Rev. Lett. 87, 245001 (2001)], which is representative of a typical currenthole discharge. Since first observed, stable plasma configurations for which the measured poloidal field is nearly zero throughout a significant region around the magnetic axis (the socalled currenthole) raised a number of questions about possible GS solutions displaying toroidalcurrent reversal. Indeed, the development in such magnetic configurations of a poloidalfield reversal layer, for which the enclosed toroidal current does vanish, poses several problems to conventional GS equilibrium solvers and precludes their use in toroidalcurrent reversal scenarios. However, recent developments enabled GS codes to cope with the poloidalfield reversal layer and to handle a large variety of internal plasma profiles [P. Rodrigues, J.P.S. Bizarro, Phys. Rev. Lett. 95, 015001 (2005)], allowing in this way a suitable modeling of experimental data. In currenthole regimes, the poloidalfield profiles obtained from motionalstarkeffect (MSE) measurements display significant relative errors inside the core region, with the error bar spanning from small positive values into small negative ones. Therefore, such uncertainty does not exclude (at least by itself) toroidalcurrent reversal equilibria, some of which are herein computed using poloidalfield and plasmapressure profiles that best fit available experimental data for currenthole discharges in the JT60U tokamak. Computing GS equilibria in these scenarios may aid to understand the physics behind the reported resilience of tokamak magnetic configurations with a currenthole [T. Fujita et al., Phys. Rev. Lett. 95, 075001 (2005)].
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