The Effect of Debye Sphere Potential on Electron Scattering by Ions in Tokamak using Born Approximation

Abstract

Scattering in plasma is caused by Debye sphere potential effect in the aftermath of the changes in plasma species density to form Debye sphere. In Debye sphere, the scattering of electron by ions occurs in multiple ways (multiple scattering) as the amount of ions in Debye sphere. The perceived kinetic energy of electron is dominated by thermal perturbation that is affected by temperature so that the greater temperature thus the greater kinetic energy of the projectile particle. In tokamak plasma condition, it can be assumed that the kinetic energy of electron is much greater than the perceived potential energy of electron due to the ions Debye sphere potential thus Born approximation can be used. By using mathematical condition of Born approximation validity, it is obtained that the limit of electron multiple scattering by ions in which Born approximation is still valid is 3 times multiple scattering. Furthermore, it was found that the differential cross-section for electron scattering by ions is large at small angle scatterings 0°<θ<90° and small at large angle scatterings 90°<θ<180° which means that the form of potential interaction is not a Coulomb potential interaction but Debye sphere potential interaction that mathematically form Yukawa-like potential because the scattering occurs much more frequently at relatively long distance in which the scattering still occurs. It is obtained that the total cross section for electron scattering by ions is 2.81╳10^-10 m².

Keyword : Plasma, Debye sphere, Scattering, Multiple scattering, Born approximation