Langmuir probe

A Langmuir probe (LP) is a type of sensor used to determine electromagnetic characteristics of plasma, i.e., its plasma parameters. The probe is used in situ, i.e., it must be inserted in the plasma, thus is suitable, for example, for a spacecraft located within the plasma, as well as for lab experiments. It essentially works by operating an electrical circuit in the vicinity of the plasma, separated by an insulator, and measuring the effects of this proximity.