One or more thermal transfer sheets are easily removable and replaceable in an ion source. The ion source has a removable anode assembly, including the thermal transfer sheets, that is separable and from a base assembly to allow for ease of servicing consumable components of the anode assembly. The thermal transfer sheets may be interposed between the consumable components within the anode assembly. The thermal transfer sheets may be thermally conductive and either electrically insulating or conductive.