Characterization of pulsed atmospheric-pressure plasma streams (PAPS) generated by a plasma gun

TLDR

The study investigates atmospheric‑pressure rare‑gas plasma propagation in a high‑aspect‑ratio capillary using a plasma gun. The plasma gun, a dielectric‑barrier‑discharge reactor driven by nanosecond or microsecond high‑voltage pulses at single‑shot to multi‑kHz rates, generated plasma in a capillary and its behavior was characterized with intensified‑CCD imaging and velocity measurements while varying waveform, polarity, repetition rate, and capillary material. The experiments revealed a fast ionization wave (10^7–10^8 cm s⁻¹), led to a new terminology—pulsed atmospheric‑pressure plasma streams—that encompasses the previously called plasma bullet, and showed that pulse tailoring can significantly enhance plasma delivery, enabling biomedical endoscopic applications.

Abstract

An experimental study of atmospheric-pressure rare gas plasma propagation in a high-aspect-ratio capillary is reported. The plasma is generated with a plasma gun device based on a dielectric barrier discharge (DBD) reactor powered by either nanosecond or microsecond rise-time high-voltage pulses at single-shot to multi-kHz frequencies. The influence of the voltage waveform, pulse polarity, pulse repetition rate and capillary material have been studied using nanosecond intensified charge-coupled device imaging and plasma-front velocity measurements. The evolution of the plasma appearance during its propagation and the study of the role of the different experimental parameters lead us to suggest a new denomination of pulsed atmospheric-pressure plasma streams to describe all the plasma features, including the previously so-called plasma bullet. The unique properties of such non-thermal plasma launching in capillaries, far from the primary DBD plasma, are associated with a fast ionization wave travelling with velocity in the 107–108 cm s−1 range. Voltage pulse tailoring is shown to allow for a significant improvement of such plasma delivery. Thus, the plasma gun device affords unique opportunities in biomedical endoscopic applications.