Abstract Details
Abstracts
Author: Miguel Calvo-Carrera
Requested Type: Poster
Submitted: 2025-03-13 11:51:18
Co-authors: P.J.Catto
Contact Info:
Massachusetts Institute of Technology
77 Massachusetts Ave
Cambridge, Massachusetts 02139
United States
Abstract Text:
Recent advances in stellarator optimization have led to quasisymmetric configurations with error fields reduced to geomagnetic levels. These configurations show good confinement properties for bulk plasma transport. Yet, alpha particles must also remain well confined over a few slowing down times. Due to their high speeds, alpha dynamics are sometimes assumed to be collisionless, and several studies have been performed under this assumption. However, collisions can substantially contribute to radial alpha transport when a resonant interaction occurs. For the passing alphas such resonances can happen near rational surfaces in the presence of helical error field departures from quasisymmetry that change the magnetic field direction. The resonance between streaming motion and tangential drift of the alphas allows the formation of a collisional boundary layer, enhancing the effective collision frequency and giving rise to a perturbed distribution function. We develop an analytical model to evaluate the resonant plateau transport that this mechanism causes by formulating a quasilinear treatment of the drift kinetic equation. The results indicate that the associated energy losses can become significant. In addition, we investigate the validity of the quasilinear approximation to show that it imposes a restriction on the error field amplitude that can be considered.
Characterization: 1.0
Comments: