The characteristics of a magnetized plasma sheath in the presence of two-groups of electrons, namely, low-temperature electrons (LTEs) and high-temperature electrons (HTEs), have been studied using the fluid model. The LTEs are considered to obey the Boltzmann distribution, whereas the HTEs follow the so-called q-nonextensive distribution. The Bohm-sheath criterion which gets modified is developed for such plasmas, and the compiled fluid equations are solved numerically. The obtained results signify that the q-nonextensive parameter and concentration ratio have a significant effect on the magnetized plasma sheath parameters. The magnitude of sheath potential monotonically increases toward the wall consistent with Debye shielding. The temperature ratio of HTE to LTE also affects the electrostatic sheath potential. Although the q-parameter and concentration ratio affect the electron and ion density profiles as both decrease toward the wall, the electron density decreases much faster than ions. In addition, the LTE density decreases at the sheath entrance, whereas the HTE density increases for the increasing concentration ratio.
The coupling of presheath-sheath parameters is extended for the study of magnetized plasma sheath using the kinetic trajectory simulation (KTS) method, in which the final self-consistent states are obtained iteratively by solving the kinetic equations. In our case, it is assumed that the ion and electron velocity distribution functions are cut-off Maxwellians at the sheath entrance. The results show that the cut-off and Maxwellian maximum velocities have equal magnitudes at the sheath entrance and at wall. The presheath electron temperature has a considerable effect on the self-consistent potential profile which affects the Child sheath thickness. The latter increases from 3.8320 μm to 5.4190 μm when the presheath electron temperature increases from 10 eV to 20 eV. It is found that the number of ions reaching wall is higher than that of the electrons and hence the space charge density has its maximum value there. Furthermore, the temperature of ions in the sheath region increases with the increase in presheath ion temperature. Moreover, the cut-off distribution causes our simulation result to deviate from the theoretical result found for the Boltzmann distribution by about 3%. The coupling scheme presented here provides a basis for smooth transition of plasma parameters at the presheath-sheath interface. The proper understanding of the magnetized plasma-wall transition plays a vital role for further exploring the plasma sheath characteristics which has useful applications in fusion and industrial plasma devices.
We study the effect of collision and ion Mach number in a magnetized plasma sheath having two species of positive ions using fluid model. It is assumed that both the ions are singly ionized and in thermal equilibrium, and the electrons obey Boltzmann distribution. Our work signifies that the collision greatly affects the ion densities, which explicitly affect space charge density, net current density and the transverse drift of ions. On increasing the collisional frequency, ions accumulation point and current saturation point shift towards the sheath entrance (away from the wall). The ion Mach number affects potential profile and velocity profiles of both ion species. The magnitude of wall potential increases from 34 V to 45 V with the increase in ion Mach number from 0.3 to 0.9. Furthermore, it is shown that the effect of collisional force and Lorentz force is reduced at the sheath entrance by increasing the ion Mach number, which helps to control the flux of particles, momentum flow and energy flow towards the wall.
In this work, the kinetic simulation method has been employed to study the effect of presheath electron temperature on plasma-wall interaction mechanism and its consequence on wall sputtering. Multi-component plasma interacts with tungsten (W) surface through non-neutral plasma sheath formed near the Plasma Facing Material (PFM). It is assumed that two ion species have different temperatures with same degree of ionization. We have examined the ion velocity distributions in front of the material wall. The thermal velocity of electron at the presheath-sheath interface determines the dimension of Debye sheath and hence energy flow towards the wall. The obtained results of the present work conclude that the angle of incidence at the wall and its sputtering rate is highly affected by electron temperature at the presheath-sheath boundary.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.