General Cause of Sheath Instability Identified for Low Collisionality Plasma in Devices with Secondary Electron Emission

M.C. Campanell, A. Khrabrov and I Kaganovich

关键词: Beams;    Electron;    Oscillations;   

DOI  :  10.2172/1062660
RP-ID  :  PPPL-4762
PID  :  OSTI ID: 1062660

学科分类：原子、分子光学和等离子物理

美国|英语

来源: SciTech Connect

【 摘 要 】

A condition for sheath instability due to secondary electron emission (SEE) is derived for low collisionality plasmas. When the SEE coefficient of the electrons bordering the depleted loss cone in energy space exceeds unity, the sheath potential is unstable to a negative perturbation. This result explains three different instability phenomena observed in Hall thruster simulations including a newly found state with spontaneous ~20MHz oscillations. When instabilities occur, the SEE propagating between the walls becomes the dominant contribution to the particle flux, energy loss and axial transport.