Optical and electrical characteristics of an endoscopic DBD plasma jet

In this work, a new cold plasma source design capable of generating and transporting a plasma jet over long distances (2 m) is presented with the purpose of being used in flexible endoscopy for treatment within the gastrointestinal tract. This dielectric barrier discharge helium plasma jet consists of a polytetrafluoroethylene capillary connected to a quartz chamber around which a copper electrode is wrapped. A copper wire is freely inserted inside the capillary. The applied voltage is a conventional AC 18-kHz signal to drive the discharge. In order to develop a safe and predictable treatment, a robust and reliable electrical model is necessary and we hypothesized that plasma transport can be modeled as a transmission line. We therefore assessed the electrical behavior of our new cold plasma source. As it is known that the target to which the plasma jet is applied drastically changes the behavior of the plasma itself, an electrical substitute simulating the impedance of a human body is introduced into the circuit, and the plasma behavior is then compared to the free-jet configuration. The effects of the input power (from 10 W to 80 W), and the length of the jet (from 60 cm to 220 cm) were investigated, as well as the electrical changes induced by the presence of an endoscope. The results obtained show trend curves similar to our hypothetical model, although the latter is still only qualitative. This long plasma jet model represents a promising approach that can be used, after further refinement, for controllability of plasma jets for endoscopy applications. © 2020 by Begell House.