The present disclosure relates to a gas field ion source comprising a housing, an electrically conductive tip arranged within the housing, a gas supply for supplying one or more gases to the housing, wherein the one or more gases comprise neon or a noble gas with atoms having a mass larger than neon, and an extractor electrode having a hole to permit ions generated in the neighborhood of the tip to pass through the hole. A surface of the extractor electrode facing the tip can be made of a material having a negative secondary ion sputter rate of less than 10−5 per incident neon ion.