| AVS 62nd International Symposium & Exhibition | |
| Plasma Science and Technology | Monday Sessions |
| Session PS-MoA |
| Session: | Plasma Diagnostics, Sensors and Control I |
| Presenter: | Sandra Schröter, University of York, UK |
| Authors: | S. Schröter, University of York, UK J. Bredin, University of York, UK K. Niemi, University of York, UK J.P. Dedrick, University of York, UK M. Foucher, Ecole Polytechnique, France N. de Oliveira, Synchrotron Soleil, France D. Joyeux, Synchrotron Soleil, France L. Nahon, Synchrotron Soleil, France J.-P. Booth, Ecole Polytechnique, France E. Wagenaars, University of York, UK T. Gans, University of York, UK D. O'Connell, University of York, UK |
| Correspondent: | Click to Email |
Cold atmospheric pressure plasmas (APP) are known to be sources for reactive oxygen species (ROS) [1,2], which makes them potentially well suited for biomedical applications. Examples of ROS of interest are atomic oxygen (O) and hydroxyl radicals (OH) because of their high reactivity and as potential precursors for longer lived reactive species. In order for APPs to achieve widespread usage in therapeutic applications, controlled production of the species of interest and hence their quantification is essential. However, at atmospheric pressure this is particularly challenging due to the short lifetimes of excited states as a result of their rapid de-excitation by collision induced quenching. Additionally, determination of the exact gas composition in APPs is difficult, especially in the jet region, where a gradual transition from the feed gas to the ambient air occurs.
In order to overcome these challenges, we will present three advanced diagnostic techniques used to quantify absolute densities of reactive species in helium RF APPJs with molecular admixtures, namely picosecond Two-photon Absorption Laser Induced Fluorescence (ps-TALIF) [3], high-resolution Fourier-transform synchrotron VUV absorption [4,5] and UV-Broad-Band Absorption Spectroscopy (UV-BBAS). Under a variation of the water content in the gas phase, absolute densities of OH and O were determined in the plasma core to be in the order of 1020 m-3 and 1019 m-3 respectively. The densities were found to increase with increasing water admixture. Additional insight was gained about the air diffusion into the plasma effluent by mapping the lifetimes of the excited atomic oxygen in the axial and radial directions. Typical lifetimes in the order of a few nanoseconds were decreasing away from the nozzle and radial centre of the plasma jet due to diffusion of air from the ambient environment into the jet region.
Acknowledgements: The authors acknowledge support by the UK EPSRC (EP/K018388/1 & EP/H003797/1) and the York-Paris Low Temperature Plasma Collaborative Research Centre. This work was performed within the LABEX Plas@par project and received financial state aid, managed by the Agence National de la Recherche as part of the programme “Investissements d’avenir” (ANR-11-IDEX-0004-02).
References:
[1] M. G. Kong et al., New J. Phys. 11 (2009) 115012
[2] D. B. Graves, J. Phys. D: Appl. Phys. 45 (2012) 263001
[3] J. Bredin et al., “Picosecond-TALIF measurements of atomic oxygen in RF driven atmospheric pressure plasma jets”, 67th Gaseous Electronics Conference, Raleigh, NC (Nov 2014)
[4] K. Niemi et al., Appl. Phys. Lett. 103 (2013) 034102
[5] L. Nahon et al., J. Synchrotron Rad., 19, 508 (2012)