München 2019 – wissenschaftliches Programm
P 2.2: Vortrag
Montag, 18. März 2019, 11:45–12:00, HS 20
Experiments on Surface Floating Potential of Spherical Object in the Magnetized RF Discharge Plasma — •Mangilal Choudhary, M. H. Thoma, R. Bergert, and S. Mitic — I. Physikalisches Institut, Justus-Liebig Universität Gießen
The floating potential of magnetic and non-magnetic spherical probes, which can be used as model of a dust grain, immersed in the magnetized RF discharge plasma are experimentally measured. The discharge is ignited between a transparent indium tin coated (TIO) glass electrode and a metal electrode after applying the 13.56 MHz RF signal. A strong superconducting electromagnet (0 to 4 T) with Helmholtz coils configuration is used to magnetize the plasma spices in the discharge column. The size of spherical probes (r) are taken either in the range or greater than the electron Debye length (λDe). To get the floating surface potential, plasma potential is measured using the emissive probe for the given discharge conditions at which the floating potential of spherical objects or probes is measured. The surface potential of spherical probe first increases (or more negative) at lower magnetic field, attains maximum value at some B-field value and after that it starts to decrease with increasing the magnetic field. The floating surface potential of magnetic spherical probe in plasma is observed to be higher (more negative) than the non-magnetic spherical probe in the presence of magnetic field. The variation of floating potential or negative charges on the spherical probes is understood on the basis of modification of collection currents to the spherical object due to the cross field diffusion in the presence of external magnetic field.