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Assessment of Transport in NCSX

D.R Mikkelsen ; H. Maassberg ; M.C. Zarnstorf ; C.D. Beidler ; W.A. Houlberg ; W. Kernbichler ; H. Mynick ; D.A. Spong ; Pär Strand (Institutionen för radio- och rymdvetenskap, Transportteori) ; V. Tribaldos
Fusion Science and Technology Vol. 51 (2007), p. 166-180.
[Artikel, refereegranskad vetenskaplig]

We explore whether the energy confinement and planned heating in the National Compact Stellarator Experiment (NCSX) are sufficient to test magnetohydrodynamic (MHD) stability limits, and whether the configuration is sufficiently quasi-axisymmetric to reduce the neoclassical ripple transport to low levels, thereby allowing tokamak-like transport. A zero-dimensional model with fixed profile shapes is related to global energy confinement scalings for stellarators and tokamaks, neoclassical transport properties are assessed with the DKES, NEO, and NCLASS codes, and a power balance code is used to predict temperature profiles. Reaching the NCSX goal of <> = 4% at low collisionality will require HISS-95 = 3, which is higher than the best achieved in present stellarators. However, this level of confinement is actually ~10% lower than that predicted by the ITER-97P tokamak L-mode scaling. By operating near the stellarator density limit, the required HISS-95 is reduced by 35%. The high degree of quasi-axisymmetry of the configuration and the self-consistent "ambipolar" electric field reduce the neoclassical ripple transport to a small fraction of the neoclassical axisymmetric transport. A combination of neoclassical and anomalous transport models produces pressure profile shapes that are within the range of those used to study the MHD stability of NCSX. We find that <> = 4% plasmas are "neoclassically accessible" and are compatible with large levels of anomalous transport in the plasma periphery.



Denna post skapades 2008-01-17. Senast ändrad 2014-09-02.
CPL Pubid: 67310

 

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Institutioner (Chalmers)

Institutionen för radio- och rymdvetenskap, Transportteori (2005-2010)

Ämnesområden

Plasmafysik
Fusion

Chalmers infrastruktur