Speaker
Description
Although collisionless guiding center trajectories are generally non-integrable in 3D magnetic fields, stellarators can be designed to have quasisymmetry. Recently, “precisely quasisymmetric” configurations have been obtained through numerical optimization, demonstrating excellent confinement of the guiding center trajectories of fusion-born alpha particles. There is, however, the potential for enhanced alpha losses due to resonant wave-particle interactions with Alfvén eigenmodes (AEs). Additional AE physics is introduced in moving from axisymmetric to 3D fields, as complex orbit types and continuum structures arise. We present pathways to model and optimize the alpha transport driven by Alfvénic instabilities in stellarators. Analysis of EP resonances and their impact on saturation mechanisms indicate key departures from the AE-driven transport in tokamaks, such as the avoidance of phase-space island overlap in quasihelical configurations. Phase space structure and stochasticity in 3D systems are visualized with novel diagnostic techniques. Finally, we demonstrate a strategy to avoid alpha resonances by manipulating the continuum gap structure.
| Presentation type | Oral |
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