Plasma ignition and steady state simulations of the Linac4 H^- ion source

The RF heating of the plasma in the Linac4 H^- ion source has been simulated using a particle-in-cell Monte Carlo collision method. This model is applied to investigate the plasma formation starting from an initial low electron density of 10¹² m^-3 and its stabilization at 10¹⁸ m^-3. The plasma discharge at low electron density is driven by the capacitive coupling with the electric field generated by the antenna, and as the electron density increases the capacitive electric field is shielded by the plasma and induction drives the plasma heating process. Plasma properties such as e^-/ion densities and energies, sheath formation, and shielding effect are presented and provide insight to the plasma properties of the hydrogen plasma.