A Three-Dimensional Simulation Model for a Cold Cathode Broad Beam Ion Source

A three-dimensional electrostatic model using cylindrical coordinates has been developed to simulate plasma formation within the ion source chamber of a cold cathode ion source. The model is based on the application of a voltage between the anode electrode and cathode, along with a glow discharge, which generates the plasma. Particle tracking is employed to determine self-consistent space-charge forces, after which the three-dimensional Poisson equation is solved, with the solution converging after each particle tracking iteration. The results highlight the model‘s significant potential in designing and optimizing the ion source’s dimensions. Additionally, the findings indicate that the formation of a sharp ion-accelerating potential is influenced not only by the density drop caused by plasma expansion but also by other factors. In the absence of a magnetic field (B = 0), ions rapidly move out of the heating zone, preventing the formation of a source sheath at the chamber edge. Furthermore, the collisional behavior of ions and electrons with background neutrals remains independent of ion or electron densities, so the decrease in densities outside the chamber does not impact the source’s stretching behavior. In this domain, neutral density remains constant, and the relative velocity and collision cross-section do not depend on plasma density.