A self-consistent kinetic treatment is presented here, where the Boltzmann equation is solved for a particle conserving Krook collision operator. The resulting equations have been implemented numerically. The treatment solves for the entire quasineutral column, making no assumptions about λmfp/L, where λmfp is the ion-neutral collision mean free path and L the size of the device. Coulomb collisions are neglected in favour of collisions with neutrals, and the particle source is modeled as a uniform Maxwellian. Electrons are treated as an inertialess but collisional fluid. The ion distribution function for the trapped and the transiting orbits is obtained. Interesting findings include the anomalous heating of ions as they approach the presheath, the development of strongly non-maxwellian features near the last λmfp, and strong modifications of the sheath criterion.
Volume 94, 2020
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