Open AccessEffects of humidity on the dynamics and electron recombination of a pin-to-pin discharge in He + H2O at atmospheric pressure
Author(s) -
Alexandra Brisset,
Benjamin Harris,
Aaron Dickenson,
Kari Niemi,
James L. Walsh,
E. Wagenaars
Publication year - 2022
Publication title -
plasma sources science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 108
eISSN - 1361-6595
pISSN - 0963-0252
DOI - 10.1088/1361-6595/ac6130
Subject(s) - streamer discharge , plasma , nanosecond , chemistry , humidity , electron , ionization , atmospheric pressure , electron density , water vapor , volume (thermodynamics) , kinetic energy , atomic physics , electron temperature , electric field , atmospheric pressure plasma , analytical chemistry (journal) , thermodynamics , meteorology , ion , laser , environmental chemistry , physics , optics , electrode , organic chemistry , quantum mechanics
Control of the plasma chemistry is essential for the effectiveness of atmospheric pressure plasmas in many applications. For this, the effects of the humidity of the feed gas on the discharge chemistry need to be considered. Detailed studies are scarce and many of them are dominated by surface interactions, obscuring any volume effects. Here, a negative nanosecond pulsed discharge is generated in a pin–pin 3 mm gap geometry in He + H 2 O that enables the study of volume kinetics due to minimal surface area. The effect of humidity on the discharge development, electric field and electron density is investigated through experiments and modelling. It is found that the presence of water vapour affects both the electron density at the start of the pulse (remaining from the previous pulse) and the ionisation rates during the ignition phase, leading to a complex dependence of the discharge development speed depending on the water concentration. The electron decay is studied using the 0D global kinetics model GlobalKin. The dominant reactions responsible for the electron decay depending on the concentration of water vapour are determined by comparing experimental and simulated results and these reactions are grouped in simplified kinetic models. It is found that with water concentrations increasing from 0 to 2500 ppm, the complexity of the dominant reactions increases with in particular O 2 + , H 2 O 3 + and water clusters becoming important for high water concentrations. This work also provides experimental data for validation of kinetic models of plasmas in controlled environments.