A non-local kinetic model applied to microwave produced plasmas in cylindrical geometry

In overdense hf or microwave induced plasmas a strong inhomogeneity of the maintaining electric field strength is usually found. From ‘local’ kinetic models, which usually employ the spatially homogeneous Boltzmann equation and assume that the electron distribution function is in equilibrium with the local electric field strength, an increase of the spectral emission towards the plasma boundary is predicted. In recent investigations, some contradictory experimental results have been found. Therefore a ‘non-local’ kinetic model is applied to this problem. In contrast to local models, in the non-local model the complete spatially inhomogeneous Boltzmann equation is solved so that the influence of the space charge potential and of the diffusive motion of electrons are taken into account. It is shown that the non-local model is capable of reproducing spatially resolved measurements of the spectral emission intensity much better than a local model.