The effect of magnetic field on the performance of a hollow cathode ion source was experimentally studied. The field strength and the field distribution around the hollow cathode were changed step by step and the source parameters were recorded for each step. The result showed that with the optimum field configuration the discharge was stabilized even at low‐operating gas pressures and the arc efficiency of the source was improved. Examination of the field and the neutral gas density distributions along the hollow cathode axis made it clear that the optimum field configuration was such that electrons emitted from the hot cathode surface might easily go out of the cathode cavity through the orifice being guided by the lines of force. Beam extraction from an intensively water‐cooled small bucket source with the hollow cathode was carried out and hydrogen ion beams of up to 3 A at 50 keV were successfully obtained for the pulse length of up to 10 s.