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Title: Thrust and efficiency model for electron-driven magnetic nozzles

A performance model is presented for magnetic nozzle plasmas driven by electron thermal expansion to investigate how the thrust coefficient and beam divergence efficiency scale with the incoming plasma flow and magnetic field geometry. Using a transformation from cylindrical to magnetic coordinates, an approximate analytical solution is derived to the axisymmetric two-fluid equations for a collisionless plasma flow along an applied magnetic field. This solution yields an expression for the half-width at half-maximum of the plasma density profile in the far-downstream region, from which simple scaling relations for the thrust coefficient and beam divergence efficiency are derived. It is found that the beam divergence efficiency is most sensitive to the density profile of the flow into the nozzle throat, with the highest efficiencies occurring for plasmas concentrated along the nozzle axis. Increasing the expansion ratio of the magnetic field leads to efficiency improvements that are more pronounced for incoming plasmas that are not concentrated along the axis. This implies that the additional magnet required to increase the expansion ratio may be worth the added complexity for plasma sources that exhibit poor confinement.
Authors:
;  [1]
  1. Electric Propulsion and Plasma Dynamics Laboratory, Princeton University, Princeton, New Jersey 08544 (United States)
Publication Date:
OSTI Identifier:
22218570
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 20; Journal Issue: 10; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ANALYTICAL SOLUTION; APPROXIMATIONS; COLLISIONLESS PLASMA; EFFICIENCY; ELECTRONS; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; MAGNETS; NOZZLES; PLASMA DENSITY; PLASMA EXPANSION; PLASMA FLUID EQUATIONS; PLASMA SIMULATION; THERMAL EXPANSION; TRANSFORMATIONS