An Analytic Approximation for the Bohm Plasma Sheath Potential | Chapter 6 | Physical Science: New Insights and Developments Vol. 2

The plasmas in physics are characterised by quasi-neutrality, which means that the number of ions and electrons is nearly equal. This property is lost near the walls containing the plasma. The classic treatment for this region, called Bohm Sheath model, leads to the idea that there are two regions: a long one denoted as presheath, where the quasi-neutrality is still preserved, and the sheath region, where there are a few electrons, and the ions are those fed by the plasma, whose velocity is determined by the wall potential and plasma density. Here, a new analytic approximation for the Bohm Sheath Potential is presented, which is valid for any value of the characteristic parameter K, measuring the mean ion velocity. The procedure to obtain this approximation is different to those used by previous authors, because now, the characteristic exponential parameter 𝜆, depends on the parameter K, as well as the wall potential 𝜙w. In previous works, that parameter used to be a function of K only, and all the approximations used to fail for K ≤12, which is not the case now. The proposed method is shown to remain valid even at K=1/2, a regime where earlier approximations fail, and numerical comparisons confirm improved accuracy.

 

 

Author(s) Details

Pablo Martin
Physics Department, Antofagasta University, Casilla 170, Antofagasta, Chile and Physics Department, Simon Bolivar University, Apartado 89000, Caracas 1083 A, Venezuela.

 

Fernando Maass-Artigas
Physics Department, Antofagasta University, Casilla 170, Antofagasta, Chile.

 

Luis Cortes-Vega
Mathematics Department, Antofagasta University, Casilla 170, Antofagasta, Chile.

 

Please see the book here :- https://doi.org/10.9734/bpi/psniad/v2/6157