A novel method is presented, which allows to generate a nitrogen oxides (NOx)‐dominated chemistry with a cold atmospheric plasma (CAP) jet which typically produces an oxygen‐based reactive species (Ox) cocktail. The reactive oxygen and nitrogen (RONS) production of the CAP jet kinpen is monitored using Fourier transform infrared (FTIR) absorption spectroscopy. While in previous approaches, the plasma chemistry of CAP jets operated with noble gases has been influenced with molecular feed gas admixtures of O2 and N2, humidified feed gas, and shielding gas, these methods are now combined in order to obtain a previously unattainable range of operating regimes: The plasma chemistry can be tuned continuously from Ox to NOx dominated, while the degree of oxidation of the produced NOx can easily be influenced.
A megahertz-driven plasma jet at atmospheric pressure-the so-called micro-scaled atmospheric pressure plasma jet (μAPPJ)-operating in pure argon has been investigated experimentally and by numerical modelling. To ignite the discharge in argon within the jet geometry, a self-made plasma tuning unit was designed, which additionally enables measurements of the dissipated power in the plasma itself. Discharges in the α-mode up to their transition to the γ-mode were studied experimentally for varying frequencies. It was found that the voltage at the α-γ transition behaves inversely proportional to the applied frequency f and that the corresponding power scales with an f 3/2 law. Both these findings agree well with the results of time-dependent, spatially one-dimensional fluid modelling of the discharge behaviour, where the f 3/2 scaling of the α-γ transition power is additionally verified by the established concept of a critical plasma density for sheath breakdown. Furthermore, phase resolved spectroscopy of the optical emission at 750.39 nm as well as at 810.37 nm and 811.53 nm was applied to analyse the excitation dynamics of the discharge at 27 MHz for different applied powers. The increase of the power leads to an additional maximum in the excitation structure of the 750.39 nm line emission at the α-γ transition point, whereas the emission structure around 811 nm does not change qualitatively. According to the fluid modelling results, this differing behaviour originates from the different population mechanisms of the corresponding energy levels of argon.
Based on a capacitively coupled plasma jet concept, an enhanced atmospheric pressure plasma jet setup for endoscopic applications is presented. Besides the favourable features of small dimension, flexibility and ability to operate in hollow bodies, new approaches for low patient leakage current, enhanced biological efficacy and reduced material erosion are subject of this work. It is found that a combination of neon feed gas, CO 2 shielding gas and a current limited high voltage supply gives the best bactericidal results and, at the same time, reduces material erosion as well as patient leakage current.
A novel flow-driven dielectric barrier discharge concept is presented, which uses a Venturi pump to transfer plasma-generated reactive oxygen and nitrogen species from a sub-atmospheric pressure ( -200 600 mbar) discharge region to ambient pressure and can be operated with air. By adjusting the working pressure of the device, the plasma chemistry can be tuned continuously from an ozone (O 3 )-dominated mode to a nitrogen oxides (NO x )-only mode. The plasma source is characterized focusing on the mechanisms effecting this mode change. The composition of the device's output gas was determined using Fourier-transform infrared spectroscopy. The results are correlated to measurements of discharge chamber pressure and temperature as well as of input power. It is found that the mode-change temperature can be controlled by the discharge chamber pressure. The source concept is capable of generating an NO x -dominated plasma chemistry at gas temperatures distinctly below 400 K. Through mixing of the processed gas stream with a second flow of pressurized air required for the operation of the Venturi pump, the resulting product gas stream remains close to room temperature. A reduced zero-dimensional reaction kinetics model with only seven reactions is capable of describing the observed pressureand temperature-dependence of the O 3 to NO x mode-change.
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