Freestanding Crossed-Field Plasma Rotation with Suppressed Dissipation

The most common way to produce a rotating magnetized plasma in the laboratory is to impose perpendicular magnetic and electric fields oriented so as to drive rotation through drift motion. In a high-temperature linear device, the field lines are often isopotentials, so that the same voltage drop imposed across the core of the plasma will also appear at the edge, and impinge on the plasma-facing components. This limits the maximum possible voltage drops that can be sustained; above some threshold, the plasma-facing components cannot tolerate the resulting electric fields [1]. Here we consider the possibilities -- and the challenges -- associated with alternative configurations that maintain voltage differences along field lines, balancing longitudinal and perpendicular voltage drops. These configurations could in principle avoid material limitations on the maximum possible voltage drop, but there are nontrivial constraints that must be taken into account in order to avoid unacceptably large dissipation. Nonetheless, such configurations suggest the possibility of greatly increasing the DC voltage drops maintainable in laboratory and industrial settings.

[1] J.-M. Rax, R. Gueroult, and N. J. Fisch, Phys. Plasmas 30, 072509 (2023).