Speaker
Description
See the full abstract here:
http://ocs.ciemat.es/EPS2019ABS/pdf/P1.1040.pdf
Magnetic equilibria are fundamental to almost every phenomena in tokamak plasmas, but accurate numerical solutions of the Grad-Shafranov (GS) equation are not always the best tool to gain insight into such complex processes. Simplified local descriptions, like the s - alpha model with circular magnetic surfaces [1] or Miller's model for shaped plasmas [2], are often preferable and have seen a wide range of applications. However, local models presently available for shaped plasmas cannot provide tractable expressions for the magnetic-field components, having thus a very limited ability to assess plasma-shaping effects in analytically driven work.
A local magnetic equilibrium model is here presented, with finite aspect ratio and up-down asymmetrically shaped cross section [3]. In contrast with other local equilibria, which provide simple magnetic-surface parametrisations at the cost of complex poloidal-field flux descriptions, the proposed model is intentionally built to afford analytically tractable magnetic-field components. Its analytical abilities are used next to address the effects of plasma shaping in three different applications: a) transformation to straight-field coordinates, where previous results in the circular limit [4] are generalised to finite magnetic shear; b) geodesic-curvature induced coupling between shear-Alfvén and slow-acoustic continuous spectra, where the threemode model for low frequency -induced Alfvén-acoustic eigenmodes [5] is extended to more than two sidebands; c) guiding-centre orbits of charged particles in tokamaks, for which some orbital characteristics of interest [6] are written for non-circular equilibria.
References
[1] J. W. Connor, R. J. Hastie, and J. B. Taylor, Phys. Rev. Lett. 40, 396 (1978).
[2] R. L. Miller et al, Phys. Plasmas 5, 973 (1998).
[3] P. Rodrigues and A. Coroado, Nucl. Fusion 58, 106040 (2018).
[4] X. Lapillonne et al, Phys. Plasmas 16, 032308 (2009).
[5] B. van der Holst, A. Belien, and J. Goedbloed, Phys. Plasmas 7, 4208 (2000).
[6] A. Brizard, Phys. Plasmas 18, 022508 (2011).
IPFN activities were supported by "Fundação para a Ciência e Tecnologia" (FCT) project UID/FIS/50010/2013; FC was supported by a FuseNet master internship grant.
