Azimuthally rotating plasma structures in a low-pressure electron beam generated ExB plasma*

Electron beam (e-beam) generated plasmas in crossed electric and magnetic (ExB) fields are promising for low-damage material processing applications [1]. However, the presence of azimuthally rotating plasma structures can cause anomalous transport and heating of charged species [2], which may lead to damage of substrates placed in the plasma periphery. In this work, we investigate the formation of azimuthally rotating plasma structures in an e-beam generated ExB plasma in low pressure (0.1 mTorr) argon. The e-beam (energy < 100 eV) is extracted from a thermionic cathode and injected into a cylindrical vacuum chamber with applied axial magnetic field. Azimuthally rotating plasma density oscillations are measured using an ion probe array. The argon IVDF is determined with a laser induced fluorescence (LIF) diagnostic. The results of experimental findings are compared to 2D3V particle-in-cell simulations of the e-beam generated ExB plasma.

[1]       Zhao F et al 2021 Carbon 177 244–51

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