The influence of electron impact ionisations on low frequency instabilities in a magnetised plasma

• Published in: International journal of mass spectrometry 2003-01, Vol.223-224, p.141-158
• Main Authors: Dimitriu, Dan-Gheorghe, Ignatescu, Valerian, Ioniţă, Codrina, Lozneanu, Erzilia, Sanduloviciu, Mircea, Schrittwieser, Roman W.
• Format: Article
• Language: English
• Subjects: Excitation; Ionisation; Non-linear interaction; Plasma instabilities; Sidebands
• ISSN: 1387-3806; 1873-2798
• DOI: 10.1016/S1387-3806(02)00786-8

We report new results on the interaction of the potential relaxation instability with the electrostatic ion–cyclotron instability in a magnetised alkaline plasma. The simultaneous excitation of these instabilities, accompanied by an amplitude and frequency modulation of the latter by the former, gives rise to the appearance of sidebands in the spectrum, which are situated on both sides of the ion–cyclotron instability frequency with a frequency difference equal to the potential relaxation instability frequency. In addition, our experimental data prove that the ion–cyclotron instability frequency not only shows the familiar increase with the magnetic field strength but also decreases with the collector current. It turns out that the spacing of the sidebands on the frequency axis is in keeping with the current oscillations. This is explained by the possibility of additional electron-neutral impact ionisations by fast electrons in front of the positively biased end electrode. The non-linear dynamical analysis of the signals gives some information about the state space dynamics of our system.