Abstract: An ion source comprises an ionising light source arranged to output ionising light for ionising a sample material, an electrode presenting an electrode surface for attracting the ionised sample material and upon which contaminant material is able to accumulate, and an ablating light source arranged to output an ablating light beam or pulse(s) for ablating material of the electrode from the electrode surface. The ablating light beam or pulse(s) does not include said ionising light. A reflector for reflecting the ablating light onto the electrode surface, therewith by a process of ablation a part of the electrode surface is removable from the electrode together with contaminant material when accumulated upon that part.