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Ambipolar acceleration of ions in a magnetic nozzle

Journal Article · · Physics of Plasmas
DOI:https://doi.org/10.1063/1.2907786· OSTI ID:21120232
;  [1]
  1. Institute for Fusion Studies, University of Texas, Austin, Texas 78712 (United States)
This paper describes a magnetic nozzle with a magnetic mirror configuration that transforms a collisionless subsonic plasma flow into a supersonic jet expanding into the vacuum. The nozzle converts electron thermal energy into the ion kinetic energy via an ambipolar electric field. The ambipolar potential in the expanding plume involves a time-dependent rarefaction wave. Travelling through the rarefaction wave, electrons lose some kinetic energy and can become trapped downstream from the mirror throat. This work presents a rigorous adiabatic description of the trapped electron population. It examines the impact of the adiabatic cooling of the trapped electrons on the ambipolar potential and the ensuing ion acceleration. The problem is formulated for an arbitrary incoming electron distribution and then a ''water-bag'' electron distribution is used to obtain a closed-form analytical solution.
OSTI ID:
21120232
Journal Information:
Physics of Plasmas, Journal Name: Physics of Plasmas Journal Issue: 4 Vol. 15; ISSN PHPAEN; ISSN 1070-664X
Country of Publication:
United States
Language:
English