Anticathode effect on electron kinetics in electron beam generated E×B plasma*

Electron beam (e-beam) generated plasmas are promising for low-damage material processing applications [1-3]. In cylindrical e-beam E×B plasmas, radial confinement of electrons and ions is achieved by an axial magnetic field and radial electric field, respectively. To control the axial confinement of electrons, such e-beam generated plasma sources may incorporate a conducting boundary known as an anticathode, which is placed on the axially opposite side of the plasma from the cathode. In this work, electrostatic probe measurements demonstrate that varying the anticathode voltage bias can control the degree to which the anticathode collects or repels incident electrons, allowing control of warm electron (electron energies in 10-30 eV range) and beam electron population confinement. It is suggested that the effect of the anticathode bias on the formation of these distinct electron populations is also associated with the transition between weak turbulence and strong Langmuir turbulence.

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

[2]       Chopra N S et al 2024 Appl. Phys. Lett. 124

[3]       Chopra N S et al 2024 arXiv:2406.11642 [physics.plasm-ph]