Speaker
Mark Cianciosa
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P5.1044.pdf
3D Equilibrium Reconstruction with Islands
M. Cianciosa1, S.P. Hirshman1, S.K. Seal1, M.W. Shafer1
1 Oak Ridge National Laboratory, Oakridge TN, United States
There are many situations where the nested flux surface topology of fusion plasmas break.
When resonant magnetic perturbations (RMP) for edge localized mode control are applied
nested magnetic surfaces can tear resulting in magnetic islands. During disruptions,
equilibrium surfaces can break down to the point of stochastic field lines. The normal
operation of tokamaks and advanced stellarators break the nested surfaces at the last closed
flux surface to control the exhaustion of hot plasma. Equilibrium reconstruction has played
an important role in determining unknown quantities and setting the basis for advanced
modeling. To understand scenarios like these, it is critical to be able to reconstruct
equilibria with arbitrary topologies.
1 2
Until recently, 3D reconstruction using V3FIT , which is based on VMEC , has been
limited to plasmas with closed nested flux surfaces. V3FIT has been extended to include
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SIESTA as an equilibrium solver allowing for non-nested or stochastic magnetic
topologies. Using a VMEC equilibrium as background coordinates, SIESTA tears the
nested magnetic surfaces by applying resonant magnetic perturbations. Reconstruction
determines the strength of these magnetic perturbations along with other equilibrium
quantities by matching synthetic signals to physical measurements.
Experiments show that measured temperature profiles flatten inside magnetic islands.
Using this signal information the first ever reconstruction of a non-nested equilibrium
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topology was performed on the DIII-D experiment . This presentation will highlight the
methods used to reconstruct non-nested topologies and show preliminary results of
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reconstructing island diverter cases using the new free boundary SIESTA .
References
[1] J.D. Hanson, et al., Nucl. Fusion, 49, 075031 (2009)
[2] S.P. Hirshman, et al., Physics of Fluids, 26, 3553 (1983)
[3] S.P. Hirshman, et al., Physics of Plasmas, 18, 062504 (2011)
[4] M. Cianciosa, et al., Plasma Physic Control. Fusion, In Press (2018)
[5] H. Peraza-Rodriguez, et al., Physics of Plasmas, 24, 082516 (2017)
