Numerical analysis of electron energy distribution function and its effects on the H^- production in Linac4 H^- source

In order to enhance the H^- surface production in hydrogen negative ion sources, it is important to increase the density of the H atoms dissociated from H₂ molecule and the resultant atomic flux towards the surface of the plasma grid. In this paper, the effect of the Electron Energy Distribution Function (EEDF) on the dissociation of H₂ in Linac4 H^- source has been studied using Electromagnetic Particle In Cell (EM-PIC) simulation with Monte Carlo method for Collision Processes (MCC). It has been shown that the rate coefficient of dissociation reactions can be enhanced in the lower H₂ gas pressure regime, while the H atom production rate becomes larger in the higher pressure regime. It is suggested that the optimal H₂ gas pressure to maximize the H atom production is determined by the balance of rate coefficient and the H₂ density.