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Amplification of critical velocity ionization by a pulsed neutral beam
Author(s) -
Lai Shu T.,
McNeil William J.,
Murad Edmond
Publication year - 1990
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl017i006p00737
Subject(s) - atomic physics , plasma , ionization , ion , electron , neutral particle , pulse (music) , particle in cell , beam (structure) , physics , materials science , optics , quantum mechanics , detector
Numerical results of computer simulations on critical ionization velocity (CIV) discharges in pulsed neutral beams are presented. In a typical CIV scenario, neutral molecules as well as newly created ions are traveling across the ambient magnetic field. The ions slow down as they transfer kinetic energy to the electrons via plasma waves. For a single pulse of neutral gas, there is a finite contact time between the beam and the plasma; the contact time is governed by the length of the pulse and the velocity of neutrals. The injection of multiple pulsed neutral beam into a magnetized plasma has the advantage that succeeding pulses may extend the effective contact time of a single pulse. Using the particle‐in‐cell method of computer simulations, we show a detailed time history of the CIV process as a result of the interplay between plasma (wave‐particle) interactions and collisional (ionization, charge exchange) processes. It is found that ions slowing down and lagging behind the pulses can still contribute to electron heating. Simulation results show that CIV in a multiple pulsed beam is more efficient than that in a single continuous pulse.