Laser-induced fluorescence measurements of ion kinetics in Penning discharge*

Rotating plasma structures are observed in various low-pressure, cross-field discharges within cylindrical geometries—such as Penning discharges, cylindrical and annular Hall thrusters, sputtering magnetrons, helicon discharges, and linear plasma devices. These structures manifest in multiple modes, ranging from m=1 to higher orders, and propagate perpendicular to the electric and magnetic fields at velocities significantly below the  velocity [1,2].

In this study, ion kinetics within a Penning discharge featuring a rotating spoke were characterized using Laser-Induced Fluorescence (LIF)[3]. Measurements were conducted across various magnetic field strengths, and both time-averaged and time-resolved analyses of radial and azimuthal ion motions were performed. A biased probe was utilized to detect the presence of the spoke, which enabled time-resolved measurements. The results facilitated the characterization of ion motion, the extraction of characteristic frequencies. These findings were compared with theoretical scalings[4].

[1] Raitses Y et al 2015 IEPC-2015-307/ISTS-2015-b-307

[2] Rodriguez E et al 2019 Phys. Plasmas. 26 053503

[3] Svarnas P et al 2018 IEEE Trans. Plasma Sci. 46 3998 

[4] Tyushev M et al 2023 Phys. Plasmas. 30 033506