Radial structure of the collision-dominated plasma column

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Abstract
The ambipolar diffusion problem is solved when charged particles inertia and heating of positive ions together with the ion mobility variation in the radial electrostatic field are taken into consideration. For both constant mean free time and constant mean free path situations approximate formulae are found for the variation of drift velocity of ions and radial potential close to the wall when the collisionless sheath is assumed. It is shown that the plasma column can be subdivided into three regions in the radial direction: the region of ambipolar diffusion, the transition region where the ion inertia predominates and the collisionless sheath at the wall. The influence of this structure on the mass spectrometric sampling technique of a positive column is also noted.