Electromagnetically Driven Thermal Dissipation Scaling in Plasma Centrifuges for Mass Separation

Abstract

Electromagnetically driven centrifuges (EMDCs) rotate fluids using the Lorentz force, but their separative performance is limited by thermal dissipation that is coupled to electromagnetic forcing. This follows because local centrifugal strength is characterized by λ=mV_θ^2/2k_B T, which compares directed kinetic energy that drives species separation to thermal energy that smooths concentration gradients and counteracts separation. In this work, we develop a two-temperature magnetohydrodynamic model to determine how radial geometry, current density, and magnetic field strength control the coupled evolution of rotation and heating that dictates λ. The model is benchmarked against Ar velocity, temperature, and pressure measurements spanning current density up to 15 kA/m2, magnetic field up to 0.57 T, feed pressures of 0.5-3 Torr, and annulus sizes of 1-5 cm. The results show that volumetric Lorentz forcing sustains elevated λ, and therefore greater local compositional shifts throughout a larger radial portion of the fluid volume than wall-bounded shear centrifuges, despite producing a lower peak λ. Simulations of a 40Ar/36Ar isotopic mixture demonstrate that, when electromagnetic force and geometry are jointly optimized, EMDCs can approach or match the separative performance of shear-driven centrifuges operating near material speed limits while requiring lower area-averaged values of λ, and can sustain greater radial compositional shifts than the SDC reference over much of the annulus. These results challenge assertions that viscous dissipation constrains weakly ionized plasma centrifuges to λ<1, and indicate that enhanced radial mass separation can be achieved by broadening the radial region over which λ remains elevated rather than maximizing its peak or area-averaged value.