No abstract available

No abstract available

[en] We investigate the electrostatic stability properties of a nonneutral electron plasma interacting with background neutral gas through elastic collisions with constant collision frequency ν_en. The theoretical model treats the electrons as a strongly magnetized fluid (ω²_pe/ω²_ce<<1) immersed in a uniform magnetic field B₀e_z, and assumes small-amplitude perturbations with azimuthal mode number l=1 and negligible axial variation (∂/∂z=0). The stability analysis, carried out to first order in ν_en/ω_ce<<1, shows that the real oscillation frequency and growth rate for the l=1 diocotron mode are given, respectively, by the simple expressions Re ω=ω₀ and Im ω=(ν_en/ω_ce)ω₀. Here, ω₀=Nec/r²_wB₀, where r_w is the perfectly conducting wall radius, and N=∫d²x n is the number of electrons per unit axial length. This analysis suggests that a measurement of the oscillation frequency and growth rate for the l=1 diocotron mode can be used to infer ν_en, and thereby serve as a sensor for the background neutral pressure. (orig.)

[en] To measure the plasma collisional relaxation it is proposed to use the effect of spatial-time echo, allowing one to determine the diffusion coefficient as a rate function by amplitude dependence of echo signal on time of delay between pulses of outoxide perturbations for arbitrary type of unperturbed distribution function

[en] A generalization of the Braginskii electron fluid description [S. I. Braginskii, Sov. Phys. JETP 6, 358 (1958)] to the case of an unmagnetized collisional plasma with multiple ion species is presented. A description of the plasma ions with disparate masses is also discussed

[en] A finite length cylindrical Langmuir probe is modelled as an ellipsoid of revolution with spheroidal equipotential surfaces and confocal orthogonal hyperboloidal electric field lines. The theory is applicable in the transition regime of probe operation between the collisionless and fully collisional limits. The plasma is assumed to be weakly ionized, non-thermal and stationary, being characterized by frozen reactions and constant temperatures. It is further assumed that in an isotropic plasma the cold ions follow the field lines, as a result of ion-neutral collisions, in the presheath and sheath regions with collisionless Maxwellian electrons. The governing system of equations is derived and solved numerically with the results presented of the presheath and sheath solutions in collisionless and collisional regimes. These show convergence to the respective collisionless and collisional radial motion limits for spherical and cylindrical probes. Analytical approximations are also obtained for the sheath width (defined as the point where the ions reach the Bohm speed) and the Bohm potential over a wide range of collisionality. The collisional presheath drop according to the perturbation theory of Shih and Levi, as applied to cylindrical probes, is shown to significantly underestimate the numerical results. These are in better agreement with the collisional presheath drop for spheres even for long probes. Application of the theory to experimentally derived probe characteristics is also discussed.

[en] The injection into plasma of a relativistic electron beam (REB) using a sheet beam model has been investigated. The results relative to induced currents, fields and charge density are the analogues of those obtained by other authors using different beam models. (author)

[en] The main aim of this article is to recognize the sheath formation in the presence of non-extensive electron distribution. The role of ion-neutral collision parameter K and the non-extensive parameter ''q'' has been discussed. Existing literature suggests that the presence of non-extensive electrons potentially modifies the plasma sheath behaviour. However, numerical calculations over the full plasma range, jointly addressing the sheath and presheath, are rare. Sheath formation, being a very fundamental phenomenon, deserves enough investigation in the region of non-extensive distribution of particles. This study attempts to bridge the gap in understanding the formation of the sheath in collisional plasma in the light of both Boltzmann and q-distributed non-extensive electrons. (© 2021 Wiley‐VCH GmbH)

[en] The non-linear development of a plasma with an unstable collisional drift wave is studied by using two-fluid equations. The set of the non-linear equations for modification of background density and drift mode amplitude is derived by an asymptotic expansion method, which describes well the transition to higher instabilities and non-linear transport. It is shown that stable stationary convective motion exists only for limited values of a critical number, the ratio of viscosity damping to linear growth rate. As this critical number decreases, the number of unstable modes increases, and, usually, a bifurcation of non-linear steady states is obtained. Expressions for particle and heat transport are obtained. A comparison of these results with the experiments of a stellarator device is also made. (author)

No abstract available