Optical emission spectroscopy of high voltage, cold atmospheric pressure plasmas

Room temperature atmospheric plasma offers an efficient, inexpensive method for treating produce to enhance shelf-life and eradicate microorganisms that may cause illness1. One approach for produce treatment involves creating plasmas within a package2 and varying the fill gas within the container to optimize microorganism deactivation3. While optimization may be possible, the impact of the package material on the plasma remains poorly understood. We performed optical emission spectroscopy (OES) to assess the impact of the package material on the plasma generated within the package for applied voltages from 45kV to 88kV. Replacing the standard packaging with a sealed low-density polyethylene bag reduced the intensity of the OES measurement, but did not significantly impact species generation in the packaging. Similar behavior arose for other fill gases. We observed molecular OH species from 200 to 300 nm and molecular N2 species from 315 to 379 nm for both package types using air as a fill gas while a Ha peak from 647 to 682 nm could not be fully resolved due to limited instrument resolution. Voltage and current measurements enabled quantification of the power delivered to the target, which provides a benchmark for standardizing plasma treatments across samples. The impact of packaging, fill gas, and power on species generation, as well as the potential impact of these results on treatment efficacy and system optimization, will be discussed.