Equilibrium Reconstruction on the Large Helical Device
Authors: Samuel A. Lazerson, D. Gates, D. Monticello, H. Neilson, N. Pomphrey, A. Reiman S. Sakakibara, and Y. Suzuki
Abstract:
Equilibrium reconstruction is commonly applied to axisymmetric toroidal devices. Recent advances
in computational power and equilibrium codes have allowed for reconstructions of threedimensional
fields in stellarators and heliotrons. [1]We present the first reconstructions of finite
beta discharges in the Large Helical Device (LHD). The plasma boundary and magnetic axis
are constrained by the pressure profile from Thomson scattering. This results in a calculation
of plasma beta without a-priori assumptions of the equipartition of energy between species.
Saddle loop arrays place additional constraints on the equilibrium. These reconstruction utilize
STELLOPT, which calls VMEC. The VMEC equilibrium code assumes good nested flux surfaces.
Reconstructed magnetic fields are fed into the PIES code which relaxes this constraint
allowing for the examination of the effect of islands and stochastic regions on the magnetic
measurements.
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Submitted to: Plasma Physics and Controlled Fusion (June 2011) Presented at: 38th EPS Plasma Physics Conference, Strasbourg, Fr. (June 2011)
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