Abstract:  Piecewise omnigenous (pwO) fields are stellarator magnetic fields that are optimized with respect to neoclassical transport thanks to a second adiabatic invariant that is piecewisely constant on the flux-surface. They are qualitatively different from omnigenous fields (including quasi-isodynamic or quasisymmetric fields), for which the second adiabatic invariant is a flux-surface constant. They thus open an alternative path towards the stellarator reactor. PwO fields have been presented in [Velasco (2024) PRL]. In this talk, and in a paper to be submitted, they will be characterized and parametrized in a more systematic manner.
For the pwO fields of [Velasco (2024) PRL], the magnetic field strength B is two-valued, and all the contours of constant B collapse into a parallelogram. In this talk, by relaxing some of these sufficient but unnecessary constraints, we will present examples of smoother pwO fields. In particular, we will allow B to take more than two values, and the B-contours to be curved. Finally, piecewise omnigenity will be combined with omnigenity for different regions of the flux-surface.
This is a step towards including piecewise omnigenity as an explicit design criterion in stellarator optimization, and towards a systematic study of the properties of nearly pwO stellarator configurations.

Talk time in other timezones:
AEDT  2:00 AM Fri 6 Dec,
JST  12:00 AM Thu 6 Dec,
CST  11:00 PM Thu 5 Dec,
CET   4:00 PM Thu 5 Dec,
GMT   3:00 PM Thu 5 Dec,
UTC  15:00    Thu 5 Dec,
EST  10:00 AM Thu 5 Dec,
CST   9:00 AM Thu 5 Dec,
MST   8:00 AM Thu 5 Dec,
PST   7:00 AM Thu 5 Dec