The plasma boundary containing fast isotropic electrons: a comparison between kinetic and fluid ion models

Abstract

The behaviour of a boundary layer containing fast isotropic primary electrons has been investigated using a modified Tonks-Langmuir model for the one-dimensional collisionless plasma, both using the full space-charge description and the quasi-neutral approximation. The plasma solutions are compared directly to those obtained from a fluid model of the same system developed by Schott in 1987 (Phys. Fluids 30 1795). In the kinetic ion model a single double-layer structure is observed to form for all primary electron densities, with a two-stage rise in the boundary potential approaching the wall. This single double-layer exists at a point corresponding to the initiation of oscillatory solutions (periodic double layers) in the potential, particle concentrations and space charge in the fluid model. In the quasi-neutral approximation of the kinetic model, for primary to thermal electron densities above a ratio of about 0.3 the sheath-edge potential jumps from a value close to the voltage equivalent of the electron temperature to a value just under the isotropic electron energy. This is in very close agreement with the previously obtained fluid quasi-neutral solutions.

Sheath structure in front of an electron emitting electrode immersed in a two-electron temperature plasma: a fluid model and numerical solutions of the Poisson equation

“…where (4) was used. The symbols β 0 , S and are defined in (22). The electron emission from the collector may be either secondary or thermal.…”

“…Numerous studies of the sheath formation in front of a negative electrode immersed in this type of plasmas can be found in the literature due to the great practical interest. There are studies of plasmas containing negative ions [3][4][5][6][7][8][9][10][11][12][13][14], electron beams [15][16][17][18][19][20][21][22], and two Maxwellian distributed electron populations with different temperatures [23][24][25][26][27][28][29][30]-often referred to as cool and hot electrons.…”

Plasma sheath in the presences of non-Maxwellian energetic electrons and secondary emission electrons

“…The presence of energetic electrons modifies plasma properties here as well as at the sheath region occurring at the surface-plasma boundary, and in turn affects the wave heating operation. Because of the great practical importance of this effect, many studies have been carried out for the sheath formation in a plasma containing high-energy electron beams [1][2][3][4][5][6] or two distributed electron populations with different energies [7][8][9][10][11][12] often called the cool and hot electrons, since the plasma sheath determines the plasma-wall interaction and has influence on the edge plasma transport process. The studies of the plasma sheath containing energetic electrons show that even a small number of energetic electrons may change significantly the sheath structure and the relevant parameters such as I-V probe characteristic.…”

A Fluid Model of the Sheath Formation in Front of an Electron Emitting Electrode with Space Charge Limited Emission Immersed in a Plasma that Contains a One‐Dimensional Mono‐Energetic Electron Beam

“…Numerous studies of the sheath formation in front of a negative electrode immersed in this type of plasmas can be found in literature due to the great practical interest. There are studies of plasmas containing negative ions [4] - [7], electron beams [8] - [10], and two Maxwellian distributed electron populations with different temperatures [11] - [13] -often referred to as cool and hot electrons.…”