Anisotropy-driven collisional separation of impurities in magnetized compressing and expanding cylindrical plasmas

Abstract

When a cylindrically-symmetric magnetized plasma compresses or expands, velocity-space anisotropy is naturally generated as a result of the different adiabatic conservation laws parallel and perpendicular to the magnetic field. When the compression timescale is comparable to the collision timescale, and both are much longer than the gyroperiod, this pressure anisotropy can become significant. We show that this naturally-generated anisotropy can dramatically affect the transport of impurities in the compressing plasma, even in the absence of scalar temperature or density gradients, by modifying the azimuthal frictions that give rise to radial particle transport. Although the impurity transport direction depends only on the sign of the pressure anisotropy, the anisotropy itself depends on the pitch magnitude of the magnetic field and the sign of the radial velocity. Thus, pressure anisotropy effects can drive impurities either towards or away from the plasma core. These anisotropy-dependent terms represent a qualitatively new effect, influencing transport particularly in the sparse edge regions of dynamically-compressing screw pinch plasmas. Such plasmas are used for both X-ray generation and magneto-inertial fusion, applications which are sensitive to impurity concentrations.

11 pages, 3 figures

References in corpus (3)

• Strategies for Advantageous Differential Transport of Ions in Magnetic Fusion Devices
• Favorable Collisional Demixing of Ash and Fuel in Magnetized Inertial Fusion
• Mass diffusion and liner material effect in a MagLIF fusion-like plasma

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• Trace Impurity Transport in Multi-Species Plasmas with Large Particle Fluxes
• Generalized Impurity Pinch in Partially Magnetized Multi-Ion Plasma
• Temperature Screening and Cross-Field Impurity Accumulation from a Thermodynamic Perspective