Events at Physics |
Events on Monday, September 29th, 2025
- Plasma Physics (Physics/ECE/NE 922) Seminar
- Centrifugal confinement in mirrors and axisymmetric scrape-off layers
- Time: 12:00 pm - 1:00 pm
- Place: 2241 Chamberlin Hall
- Speaker: Timothy Stoltzfus-Dueck, PPPL
- Abstract: In the centrifugal-mirror confinement concept, parallel confinement by the mirror force is supplemented with a parallel centrifugal force driven by supersonic ExB rotation in the azimuthal/toroidal direction. Although this approach practically closes the loss cone and naturally exhibits stabilizing ExB shear, it requires a very large radial voltage difference, presenting engineering challenges for the insulating end plates. In principle, the addition of a strong azimuthal field could reduce the required voltage, since the simple azimuthal ExB drift would be replaced by more rapid azimuthal trapped-particle precession. Also, if the mirror ratio is large enough, newly-ionized ions are accelerated to the necessary parallel velocities in their first bounce orbit, both confining and significantly heating them. Unfortunately, MHD analysis shows that the centrifugal-force-confining plasma current is purely azimuthal. This implies that only the axial magnetic field contributes to the confining magnetic pressure, severely limiting the usefulness of the azimuthal magnetic field in a beta-limited plasma scenario. However, the single-particle confinement properties may prove useful in non-beta-limited scenarios. For example, centrifugal confinement could slow parallel losses from an axisymmetric scrape-off-layer, particularly in an ST with a deeply inboard X-point. In addition to supporting large density and temperature drops from midplane to target, such confinement could substantially broaden the heat-flux deposition width, while the SOL rotation directly stabilizes resistive wall modes.
- Host: Cary Forest