Exploration of quiescent plasma for wave studies in MPD

A Multi-pole line cusp Plasma Device (MPD) built using six electromagnets is capable of producing six poles six magnets (SPSM) and twelve poles six magnets (TPSM) cusp configuration. In this article, a detailed experimental study of the plasma parameters in these two multi-pole line cusp geometries is presented. SPSM has a very small field-free region (extending up to R=4 cm) compared to TPSM (which extends up to R=10 cm). The radial variation of plasma parameters for various, magnetic field strengths, is presented. The uniformity in radial and azimuthal variation of plasma parameters is observed to be comparable to the radial extent of field-free regions in both cusp configurations. The variation is <5% up to R=4 cm and R=0 cm in SPSM and TPSM respectively. The plasma is quiescent over a larger volume for TPSM compared to SPSM. The experimental investigation of plasma parameters in SPSM and TPSM provides very strong evidence that the magnetic field profiles of cusp magnetic field configuration play a crucial role in determining the uniformity of plasma parameters and plasma quiescence level. The different aspects of wave excitation in plasma can be studied in the background of this enhanced volume of plasma uniformity and quiescence in TPSM.