Influence of substrate outgassing on the plasma properties during wood treatment in He dielectric barrier discharges at atmospheric pressure

This work analyzes the effect of wood outgassing on the properties of He dielectric barrier discharges operated in a homogenous regime. Over the 60 min wood treatment investigated, the discharge current increased by almost a factor of two due to the release of air and humidity. Based on optical emission spectroscopy and collisional‐radiative modeling, these effects further yield to an increase of the electron temperature and a significant decrease of the relative number density of He metastable atoms. Experiments were also performed in presence of trace amounts of N2, O2, and dry air to simulate wood outgassing. The amount of air released from the wood sample decreased with plasma treatment time, with a two‐slope first‐order decay behavior. This work examines wood substrate outgassing effects during treatment in dielectric barrier discharges operated in nominally pure helium. Using a combination of electrical characteristics, optical emission spectroscopy, and collisional‐radiative modeling, outgassing of the samples placed on the bottom electrode was monitored for the complete duration of plasma exposure.