Potential Formation in Front of an Electrode Close to the Plasma Potential Studied by PIC Simulation

Potential formation in front of an electrode that has the potential which is close to the plasma potential is studied by particle‐in‐cell (PIC) simulations. The code BIT1 [D. Tskhakaya, R. Schneider, J. Comp. Phys., 225 , 829 (2007)] is used for this purpose. It is shown that this code is very appropriate for our analysis because of its ability to create charged particles by uniform volume production in the entire system and to maintain in the same time the Maxwellian electron velocity distribution function prescribed in the input file. It turns out that some modifications of the code are necessary in order to achieve small sheath potential drops and to detect the cutoff in the electron velocity distribution function. The modifications of the code are described. The small sheath potential drop is achieved by introducing a finite reflectivity of the electrons at the left electrode, while the expected cutoffs of the electron velocity distribution function are found by tracking the reflected electrons as separate particle species. The simulation results are compared to the theoretical model of Jeli? [N. Jeli?, Phys. Plasmas, 18 , 113504 (2011)]. The matching is very good and this is a sign that the PIC simulations are very appropriate tool for the analysis of this type of problems. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)