An ion source is cooled using a cooling plate that is separate and independent of the anode. The cooling plate forms a coolant cavity through which a fluid coolant (e.g., liquid or gas) can flow to cool the anode. In such configurations, the magnet may be thermally protected by the cooling plate. A thermally conductive material in a thermal transfer interface component can enhance the cooling capacity of the cooling plate. Furthermore, the seperation of the cooling plate and the anode allows the cooling plate and cooling lines to be electrically isolated from the high voltage of the anode (e.g., using a thermally conductive, electrically insulating material). Combining these structures into an anode subassembly and magnet subassembly can also facilitate assembly and maintenance of the ion source, particularly as the anode is free of coolant lines, which can present some difficulty during maintenance.