Open AccessSheath structure of a hot-cathode in plasma
Author(s) -
Daoyong Wang,
Jun Ma,
Yiren Li,
Wen-gui Zhang
Publication year - 2009
Publication title -
wuli xuebao
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.199
H-Index - 47
ISSN - 1000-3290
DOI - 10.7498/aps.58.8432
Subject(s) - cathode , thermionic emission , plasma , hot cathode , atomic physics , debye sheath , materials science , electron , mach number , drop (telecommunication) , mechanics , physics , chemistry , electrical engineering , quantum mechanics , engineering
The plasma sheath in the presence of virtual-cathode structure near a hot cathode was studied by combining the theory of thermionic emission and plasma fluid equations. Using Sagdeev potential method, the sheath solution and generalized Bohm criterion were discussed. It is shown that, different from usual Bohm sheath, the critical ion Mach number at the sheath-presheath edge is not an independent constant but depends on sheath potential drop as well as other parameters, owing to the fact that there exists large quantity of thermionic electrons near the hot cathode which has a significant influence on the whole sheath structure. The critical Mach number first increases and then decreases with the potential drop from sheath-presheath edge to the virtual cathode, and monotonically increases with the temperature of the hot cathode. In the plane geometry, there exists an appreciable quantity of residual thermionic electrons which traverse the virtual cathode and sheath and enter into bulk plasma.