Plasma inhomogeneities near the electrodes of a capacitively-coupled radio-frequency discharge containing dust particles
Résumé
When dust particles are present in a plasma, they acquire a negative charge by capturing electrons. When the dust particle density is high, this huge loss of electrons can trigger unstable behaviors in the plasma like dust particle growth instabilities (DPGI). These experiments are performed in a capacitively coupled rf discharge in the PKE-Nefedov reactor where dust particles are grown by sputtering a polymer layer previously deposited on the electrode. A high-speed camera (till 10000 frames per second) is used to study more precisely these instabilities. During DPGI, a new phenomenon is detected in front of each electrode (top and bottom) and localized on their periphery. It consists of the appearance of small plasma spheroids, of about a few mm and with a slightly enhanced luminosity. In this paper, two cases are presented which reveal the existence of several regimes for the spheroid behavior: spheroid rotation around the electrodes, a chaotic regime consisting in the fast appearance and disappearance of the spheroids, and a regime without any spheroid. A correlation is performed between these regions and the evolution of the plasma glow in between the electrodes.