Patent ID: 7399961

Claim:
An apparatus for controlling generation of ions, said apparatus comprising: a) at least one ion source adapted for generating said ions from a sample; b) at least one counter electrode located downstream from said at least one ion source, said at least one ion source and said at least one counter electrode adapted to enable downstream movement of said ions upon application of a first potential difference there between; and, c) at least one ion controlling element mounted relative to said at least one ion source, said at least one ion controlling element having, in use, a potential applied thereto to provide a second potential difference between the at least one ion controlling element and the at least one ion source, wherein said at least one ion controlling element is operable in a first condition where said at least one ion controlling element allows ion generation by said at least one ion source and a second condition where said at least one ion controlling element disables ion generation by said at least one ion source, wherein, the apparatus includes alternating means for alternating said at least one ion controlling element between said first condition and said second condition.