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Charged particle dynamics near an X-point of a non-symmetric magnetic field with closed field lines

Part of: Focus on Fusion

Published online by Cambridge University Press:  15 April 2020

Elena Elbarmi ,
Wrick Sengupta Open the ORCID record for Wrick Sengupta [Opens in a new window]  and
Harold Weitzner
Elena Elbarmi
Affiliation:
Courant Institute of Mathematical Sciences, New York University, NY10012, USA Friends Seminary, 22 E 16th St, New York, NY 10003, USA
Wrick Sengupta*
Affiliation:
Courant Institute of Mathematical Sciences, New York University, NY10012, USA
Harold Weitzner
Affiliation:
Courant Institute of Mathematical Sciences, New York University, NY10012, USA
*
†Email address for correspondence: [email protected]
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Abstract

Understanding particle drifts in a non-symmetric magnetic field is of primary interest in designing optimized stellarators in order to minimize the neoclassical radial loss of particles. Quasisymmetry and omnigeneity, two distinct properties proposed to ensure radial localization of collisionless trapped particles in stellarators, have been explored almost exclusively for magnetic fields with nested flux surfaces. In this work, we examine radial particle confinement when all field lines are closed. We then study charged particle dynamics in the special case of a non-symmetric vacuum magnetic field with closed field lines obtained recently by Weitzner & Sengupta (Phys. Plasmas, vol. 27, 2020, 022509). These magnetic fields can be used to construct magnetohydrodynamic equilibria for low pressure. Expanding in the amplitude of the non-symmetric fields, we explicitly evaluate the omnigeneity and quasisymmetry constraints. We show that the magnetic field is omnigeneous in the sense that the drift surfaces coincide with the pressure surfaces. However, it is not quasisymmetric according to the standard definitions.

Keywords

plasma confinementplasma dynamics
Type
Research Article
Information
Journal of Plasma Physics , Volume 86 , Issue 2 , April 2020 , 905860209
Copyright
© Cambridge University Press 2020

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