How sheath properties change with gas pressure: modeling and simulation. (1st August 2022)

• Record Type: Journal Article
• Authors: Beving, L P; Hopkins, M M; Baalrud, S D
• Is Part Of: Plasma sources science & technology. Volume 31:Number 8(2022)
• Publication Date: 2022-08-01
• Subjects: collisional sheath model -- collisional Bohm criterion -- particle-in-cell simulations; Plasma (Ionized gases) -- Periodicals; 530.44
• DOI: 10.1088/1361-6595/ac85d7
• Languages: English
• ISSNs: 0963-0252

Abstract

Abstract: Particle-in-cell simulations are used to study how neutral pressure influences plasma properties at the sheath edge. The high rate of ion–neutral collisions at pressures above several mTorr are found to cause a decrease in the ion velocity at the sheath edge (collisional Bohm criterion), a decrease in the edge-to-center density ratio ( h l factor), and an increase in the sheath width and sheath potential drop. A comparison with existing analytic models generally indicates favorable agreement, but with some distinctions. One is that models for the h l factor need to be made consistent with the collisional Bohm criterion. With this and similar corrections, a comprehensive fluid-based model of the plasma boundary transition is constructed that compares well with the simulation results.