A discharge jump induced by external triggering in inductively coupled millimeter-sized plasma jet at atmospheric pressure

Abstract

We report an inductively coupled millimeter-sized plasma jet driven by the very high frequency of 150 MHz at atmospheric pressure. A phenomenon is observed that the discharge jump is induced by external triggering. The plasma near room temperature ejects out from the exit of quartz tube as the plasma is generated through one-time triggering by a spark igniter under an applied input voltage, and its length varies with the input voltage. With the further increase in the input voltage, the plasma plume becomes stable. By applying second-triggering, the plasma changes to be full of the quartz tube, and a slight change is observed in the shape of plasma plume with the input voltage. Meanwhile, the jet temperature rises suddenly to more than 500 K. The coil current is measured to present different dependences on the input voltage for discharging with and without second-triggering. It is considered that the E-H mode transition happens in the discharge jump due to the external triggering. The application of the strongly electric field through the second-triggering results in a sudden variation of the electron density and resulting plasma impedance, which is responsible for the discharge jump observed.