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] 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] 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 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)

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[en] Diffusion methods induce an accurate simulation of alpha particle energy deposit. The diffusion length depends on the particle energy, and on the initial energy of the particle. A linear type correction, corresponding to a flux increase instead of limitation, improves the accuracy, and gives the exact value of the energy flux from a semi infinite source

No abstract available