From Multi-ion Species Bohm Criterion to Detachment Sheath Physics: Our Work with Prof. Noah Hershkowitz and Beyond.*

In this presentation, the speaker's works with the late Prof. Noah Hershkowitz in the field of low temperature basic plasma physics, particularly on the formation of plasma sheath/presheath will be reviewed. The work reviewed here includes experimental investigations of how the Bohm criterion is satisfied in multi-ion species plasmas, formation of virtual cathodes near small electrodes, and their relations with the recently developed theory of instability enhanced collisional friction, as well as pulsing fireballs near grids, and discusses the work of some of Prof. Hershkowitz's previous students. This presentation will also introduce recent developments in the speaker's group in the Chinese Academy of Sciences, Institute of Plasma Physics (ASIPP) inspired by Prof. Hershkowitz's previous work and recent collaboration with our group, which include their recent work in strongly electron emitting cathodes and emissive probes, collisional Bohm criterion and sheath formation of detached plasmas in linear devices.