Time-resolved electric field measurements during and after the initialization of a kHz plasma jet—from streamers to guided streamers

This work presents the investigation of a 30 kHz operated atmospheric pressure plasma jet impinging a dielectric BSO-crystal, allowing time-resolved electric field measurements based on the Pockels effect. Observations indicate that from the time the voltage is applied, the plasma first develops through unstable branching before a stable periodic behavior is established. This initialization of the plasma jet suggests the importance of the build-up of leftover ionization, which creates a preferred pathway for the streamer-like discharges. After initialization the time and spatially resolved electric field of guided ionization waves induced in the crystal is obtained, showing a highly periodic charging and discharging at the surface of the crystal. When the ionization wave arrives at the crystal charge is deposited and constant electric fields are generated for approximately 14 μ s. Then a (back) discharge will remove the deposited charge at the surface, related to the moment when the applied voltage changes polarity and it agrees with imaging reported on in other literature. (letter)