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Excitation of the Potential Relaxation Instability in a Weakly Magnetized Discharge Plasma by a Voltage Step
Author(s) -
Gyergyek T.,
Čerček M.,
Stanojević M.
Publication year - 1996
Publication title -
contributions to plasma physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.531
H-Index - 47
eISSN - 1521-3986
pISSN - 0863-1042
DOI - 10.1002/ctpp.2150360602
Subject(s) - instability , plasma , langmuir probe , physics , two stream instability , atomic physics , plasma channel , excitation , amplitude , mechanics , plasma diagnostics , optics , quantum mechanics
An instability is triggered in a weakly magnetized discharge plasma by the application of a positive voltage step to a planar collector immersed into the plasma column with its surface perpendicular to the magnetic field lines. Time developement of the plasma density after the application of the pulse is measured by a Langmuir probe. Radial and axial velocity of the plasma density perturbation are measured. Radial velocity is consistent with the increase of the plasma potential in the current channel. Axial velocity is very high. It is interpreted as phase velocity of radial quasiperiodic motion of the plasma in and out of the current channel. Response time of the collector current to the applied voltage step is measured versus different parameters. Experimental results are in agreement with a qualitative model presented in previous work [1] where the observed instability is modeled as a two dimensional potential relaxation instability (PRI). Minor improvements of the previous model are proposed. A rarefaction pulse that moves towards the collector is found as the initial stage of the instability.