The cylindrical DC magnetron discharge: I. Particle-in-cell simulation

The radial structure of a low-pressure cylindrical post-cathode direct-current magnetron discharge is investigated using a one-dimensional, electrostatic particle-in-cell code, incorporating non-periodic boundary conditions and an external circuit. Electron and ion collisions with a background gas of argon are modelled using Monte Carlo techniques. The radial structure of the discharge is examined for a range of operating conditions. Profiles of the electric potential, electric field and space charge density are found to vary systematically with the pressure p and magnetic field strength B , in a way which corresponds to a transition from the usual positive space charge mode at low values of B / p to a higher impedance negative space charge mode at higher values of B / p . This is consistent with a continuous and considerable reduction in the ratio of the electron-to-ion classical cross-field transport coefficients with increasing B / p . Results of a fluid model also predict the transition to the negative space charge mode.