Influence of different particle injection methods on plasma sheath with strong production of negative ion in one-dimensional PIC simulation

Particle injection is necessary to maintain the plasma source term in particle -in -cell (PIC) simulation. There are two commonly used particle injection methods, namely, a) constant flux injection, in which a fixed number of ion -electron pairs are injected each time step, and b) pair re -injection, in which the number of ion -electron pairs injected is according to the number of positive ions removed. Different injection methods may bring big difference to the simulation results. Therefore, the appropriate particle injection method must be selected according to the object and purpose of simulation to obtain the correct result. In this paper, a 1D3V (one dimension in space and three dimensions in velocity space) PIC model is used to analyze the evolution of plasma in the formation of space charge limited (SCL) sheath and reverse sheath with the condition of surface production, and the differences of the two particle injection methods are compared. It is found that the simulation result with pair re -injection does not match experiment result.