Pulse positive streamer corona discharges in water solution with a different conductivity have been investigated in reactors with the needle-plate and coaxial electrode geometry. A special composite anode was used in the coaxial geometry. With such an anode hundreds of streamers were generated at each voltage pulse. Production of H, O and OH radicals by the discharge was proved by emission spectroscopy and formation of H 2 O 2 and degradation of phenol was demonstrated by chemical methods. Assuming that the broadening of the Hα line profile was caused by the dynamic Stark effect, plasma with an electron density over 10 18 cm −3 was generated during the initial phase of voltage pulse in the both reactors in spite of the very different electrode geometry and wave-forms of voltage pulses. Production of OH radicals was most effective at solution conductivity below 100 µS cm −1 .
The application of gas discharge plasmas has assumed an important place in many manufacturing processes. Plasma methods contribute significantly to the economic prosperity of industrialized societies. However, plasma is mainly an enabling method and therefore its role remains often hidden. Hence the success of plasma technologies is described for different examples and commercial areas. From these examples and emerging applications, the potential of plasma technologies is discussed. Economic trends are anticipated together with research needs. The community of plasma scientists strongly believes that more exciting advances will continue to foster innovations and discoveries in the first decades of the 21st century, if research and education will be properly funded and sustained by public bodies and industrial investors.
The 2022 Roadmap is the next update in the series of Plasma Roadmaps published by Journal of Physics D with the intent to identify important outstanding challenges in the field of low-temperature plasma (LTP) physics and technology. The format of the Roadmap is the same as the previous Roadmaps representing the visions of 41 leading experts representing 21 countries and five continents in the various sub-fields of LTP science and technology. In recognition of the evolution in the field, several new topics have been introduced or given more prominence. These new topics and emphasis highlight increased interests in plasma-enabled additive manufacturing, soft materials, electrification of chemical conversions, plasma propulsion, extreme plasma regimes, plasmas in hypersonics, data-driven plasma science and technology and the contribution of LTP to combat COVID-19. In the last few decades, LTP science and technology has made a tremendously positive impact on our society. It is our hope that this roadmap will help continue this excellent track record over the next 5–10 years.
A new method based on time-resolved UV-VIS spectrometry was developed to determine absolute densities of N 2 (A 3 + u ) metastable species produced by nitrogen streamers at atmospheric pressure. The method originates with the correlation of N 2 (C 3 u ), N 2 (C 5 u ) and NO(A 2 + ) state populations with N 2 (A 3 + u ) state evolution. The diagnostic procedure is based on predicting emissions controlled by N 2 (A 3 + u ) species through the pooling and resonant energy transfer reactions in high-purity nitrogen with well-defined trace quantities of NO. A simple analytical tool to evaluate the N 2 (A 3 + u ) concentration is provided using synthetic NO-γ , N 2 -second positive (2.PG) and N 2 -Vegard-Kaplan (VK) band emission spectra. The application of the method requires tracking post-discharge formation of the N 2 (C 3 u , C 5 u ) states and inferring time evolution of N 2 (A 3 + u ) species from emission intensities of the N 2 -2.PG and N 2 -Herman infrared (HIR) systems. Simultaneously, the post-discharge evolution of the NO(A 2 + ) state has to be monitored through the NO-γ system. The concentration of N 2 (A 3 + u ) metastables can finally be evaluated from relative emission intensities of pre-selected NO-γ , N 2 -2.PG and N 2 -VK bands.
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