Control of ion charge states in vacuum arc ion source by imposition of a non-uniform magnetic field

The influence of the magnetic field geometry configuration on electron temperature and ion charge state in the vacuum arc ion source has been studied theoretically. It is found that a high value of electron temperature and ionization rate is retained at the exit from the annular anode (where cathodic plasma jet becomes current-free) if a strong magnetic field in the order of 1 T is imposed on this part of jet. It is shown that the maximum value of the mean ion charge can be obtained by imposing on the inter-electrode gap an external magnetic field with the slightly divergent field lines. The divergence angle of the field lines yielding a maximum of ion charge depends on the vacuum arc parameters and usually is in the order of 2–5°.