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- Title
Energetic particle tracing in optimized quasi-symmetric stellarator equilibria.
- Authors
Figueiredo, P.A.; Jorge, R.; Ferreira, J.; Rodrigues, P.
- Abstract
Recent developments in the design of magnetic confinement fusion devices have allowed the construction of exceptionally optimized stellarator configurations. The near-axis expansion in particular has been proven to enable the construction of magnetic configurations with good confinement properties while taking only a fraction of the usual computation time to generate optimized magnetic equilibria. However, not much is known about the overall features of fast-particle orbits computed in such analytical, yet simplified, equilibria when compared with those originating from accurate equilibrium solutions. This work aims to assess and demonstrate the potential of the near-axis expansion to provide accurate information on particle orbits and to compute loss fractions in moderate to high aspect ratios. The configurations used here are all scaled to fusion-relevant parameters and approximate quasi-symmetry to various degrees. This allows us to understand how deviations from quasi-symmetry affect particle orbits and what are their effects on the estimation of the loss fraction. Guiding-centre trajectories of fusion-born alpha particles are traced using gyronimo and SIMPLE codes under the NEAT framework, showing good numerical agreement. Discrepancies between near-axis and magnetohydrodynamic fields have minor effects on passing particles but significant effects on trapped particles, especially in quasi-helically symmetric magnetic fields. Effective expressions were found for estimating orbit widths and passing–trapped separatrix in quasi-symmetric near-axis fields. Loss fractions agree in the prompt losses regime but diverge afterwards.
- Subjects
MAGNETIC confinement; ORBITS (Astronomy); EQUILIBRIUM; MAGNETIC fields; PLASMA beam injection heating
- Publication
Journal of Plasma Physics, 2024, Vol 90, Issue 2, p1
- ISSN
0022-3778
- Publication type
Article
- DOI
10.1017/S0022377824000400