An apparatus with means for controlling ion generation is discussed. The apparatus comprises a plurality of ion sources, at least one counter electrode mounted downstream for the ion sources and at least one ion controlling element mounted relative to at least one of the ion sources. Each ion controlling element is alternated between a first condition where the operation of at least one of the ion sources is enabled and a second condition where the operation of at least one of the ion sources is disabled. This concept may also be extended to an ion source apparatus having a single ion source with an ion lens mounted relative thereto. The present invention also provides a method for controlling the operation of the aforementioned apparatus. The invention further provides an apparatus and a method for the generation of ion pulses.