Abstract Details
Abstracts
Author: James D Callen
Requested Type: Poster
Submitted: 2017-03-16 11:09:40
Co-authors: C.C. Hegna, M.T. Beidler
Contact Info:
University of Wisconsin
1500 Engineering Drive
Madison, WI 53706-1
USA
Abstract Text:
Recent resonant magnetic perturbation (RMP) experiments in DIII-D [1,2] have shown an ELM crash can abruptly cause [3]: 1) large forced magnetic reconnection (FMR) at q = m/n rational surfaces; 2) the radial electric field to vanish there and thus lock the toroidal flow to the stationary RMP frame, analogous to field-error-induced mode locking; 3) an induced tearing-type perturbation that provides a 8/2 seed magnetic island which is governed by a modified Rutherford equation, analogous to NTMs; 4) bifurcation into a growing island if the applied 8/2 RMP is large enough; and 5) sufficient magnetic-flutter-induced electron density and temperature transport [4] at the pedestal top to stabilize peeling-ballooning ideal MHD modes. These RMP effects are analogous to those predicted by previous FMR theories that use sheared slab or cylindrical magnetic field models. A comprehensive model that facilitates exploration of the space-time development of FMR effects and is applicable to the magnetic field geometry and low collisionality of tokamak plasmas is being developed. Its key equations govern evolution of the: 1) radial component of a single helically resonant magnetic perturbation including flow-screening effects, 2) vorticity in perturbed magnetosonic quasi-equilibrium, 3) plasma rotations [5], and 4) magnetic island width. These equations use axisymmetric toroidal and local helical magnetic field geometries, and kinetic-based flutter transport to provide generalizations and extensions of the previous FMR models that are used in Ref. [3].
[1] C. Paz-Soldan et al., Phys. Rev. Lett. 114, 105001 (2015).
[2] R. Nazikian et al., Phys. Rev. Lett. 114, 105002 (2015).
[3] J.D. Callen et al., report UW-CPTC 16-4.
[4] J.D. Callen, A.J. Cole and C.C. Hegna, Phys. Plasmas 19, 112505 (2012).
[5] J.D. Callen, A.J. Cole and C.C. Hegna, Phys. Plasmas 16, 082504 (2009); Erratum 20 069901 (2013).
*Supported by OFES DoE grants DE-FG02-86ER53218, DE-FG02-92ER54139.
Comments: