Characterization of low-pressure ExB plasmas generated by e-beam and non-thermal electrons in 0.1-10 torr air and nitrogen*

Electron beam generated plasmas are promising for applications requiring efficient generation of ions and radicals in low pressure environments [1–3]. In this work, we discuss measurements of plasma properties and production of radical species by an electron beam generated plasma in low pressure (0.1-10 mTorr) air and nitrogen. We investigate low temperature plasmas in an applied magnetic field with magnetized electrons and unmagnetized ions. These plasmas are generated by two different sources: i) a high energy electron beam in the keV range produced by an ion-induced secondary electron emitting cathode [2] and ii) a lower energy non thermal electron source (< 100 eV) produced by a hot-filament thermionic cathode. We compare electron kinetic properties and chemical composition of the plasmas created by these two sources. In addition, we analyze plasma instabilities in both plasma systems and compare them with theoretical predictions for beam-plasma and electron gradient drift instabilities [4,5].

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

[2] Walton S G et al 2015 ECS J. Solid State Sci. Technol. 4 N5033–40

[3] Zolotukhin D B et al 2017 Physics of Plasmas 24 093502

[4] Fernsler R F et al 1998 Physics of Plasmas 5 2137–43

[5] Rodríguez E et al 2019 Physics of Plasmas 26 053503