Field anode/emitter source

Molecules can lose an electron when subjected to a high electric potential resulting in field ionization (FI) [366,534,535]. High fields can be created in an ion source by applying a high voltage between a cathode and an anode called a field emitter. A field emitter consists of a wire covered with microscopic carbon dendrites, which greatly amplify the effective field at the carbon points. 

LMI sources with needle emitters operate in essentially the same way as field ionization or field desorption sources. The filament is resistively heated to melt the metal film and/or promote its flow to the tip of the emitter. Typically, the emitter or anode is positively biased 3-5 kV with respect to its counter electrode, the cathode the actual operating voltage is determined... 

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