Measurement of electric field near plasma-exposed liquid surface

Non-equilibrium atmospheric pressure plasmas (APPs) have been of great interest and are being applied in a wide range of fields. In particular, the system in which non-equilibrium APP is in or in contact with a liquid is expected to have novel applications in life sciences such as medicine and agriculture. Electric field, which is related to electron temperature, excited species density, and so on, is an important parameter to characterize APP. However, behaviors of electric fields in the APPs in contact with liquids and electrical charge accumulated on the liquid surface have not been fully understood. In an attempt to reveal the behaviors, we tried to measure the electric filed in APPs or derived from the APP-induced surface charge using electric field induced second harmonic (E-FISH) diagnostic. In the presentation, detailed measurement system and the measurement result on temporally and spatially resolved electric field will be discussed.