Centrifugal-mirror confinement with strong azimuthal magnetic field
Plasma Physics and Controlled Fusion 67:9 (2025)
Abstract:
One practical challenge for the centrifugal-mirror confinement concept is the large radial voltage necessary to drive supersonic azimuthal rotation. In principle, the addition of a strong azimuthal field could reduce the required voltage, since the simple azimuthal E × B 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.Strong gradient effects on neoclassical electron transport and the bootstrap current in large aspect ratio tokamaks
Journal of Plasma Physics Cambridge University Press (CUP) 91:4 (2025) e97
Abstract:
Standard approaches to neoclassical theory do not extend into regions of strong gradients in tokamaks such as the pedestal and internal transport barriers. Here, we calculate the modifications to neoclassical electron physics inside strong gradient regions of large aspect ratio tokamaks in the banana regime. We show that these modifications are due to the different ion flow and the strong poloidal variation of the potential. We also provide a physical interpretation of the mechanisms that drive poloidal asymmetries and hence a poloidal electric field. We apply our model to two specific example cases of pedestal profiles, calculating the neoclassical electron flux and the bootstrap current. We find that, depending on the ion flow, weak gradient neoclassical theory overestimates or underestimates the neoclassical electron transport and the bootstrap current in regions with strong gradients. We show that the determination of the mean parallel flow is more complex than in weak gradient neoclassical theory. For vanishing turbulence, we can determine the radial electric field for a given flow profile in the pedestal.Enhanced Collisional Losses from a Magnetic Mirror Using the Lenard-Bernstein Collision Operator
Journal of Plasma Physics Cambridge University Press (CUP) (2025) 1-24
Beam focusing and consequences for Doppler backscattering measurements
Journal of Plasma Physics Cambridge University Press (CUP) 91:2 (2025) e60
Measurement of Zero-Frequency Fluctuations Generated by Coupling between Alfvén Modes in the JET Tokamak.
Physical review letters American Physical Society (APS) 134:9 (2025) 95103