High Accurate Spatially Resolved Measurements of Discharges Plasma Spectra
TIAN Yi-fu1, LI Bo1, GAO Qiang1*, ZHU Zhi-feng1, ZHU Jia-jian2, LI Zhong-shan1
1. State Key Laboratory of Engines, Tianjin University, Tianjin 300072, China
2. Science and Technology on Scramjet Laboratory, National University of Defense Technology, Changsha 410073, China
Abstract：Discharge plasma spectroscopy and laser-induced breakdown spectroscopy are widely used in the flow field diagnostics owing their simplicity and strong signal intensity. Due to the random nature of the discharge, the time and space of the discharge are hard to be controlled, so it is difficult to measure the discharge plasma spectra accurately, and the laser-induced breakdown spectroscopy is limited to point measurements. In this paper, we introduce a method of one-dimensional spatially resolved discharge plasma spectra measurements, based on femtosecond laser filamentation-guided discharge. Femtosecond lasers beam self-focusing could create a filamentous weak plasma channel, and this weak plasma channel can be used as a trigger source for the high voltage discharge when it is close to the pair of high voltage electrodes. This triggering way can trigger and guide the discharge to breakdown the air along the path of the plasma channel at a specified time. Under the experimental conditions, the fluctuation of the time interval between laser pulse arriving and the start of discharge is less than 0.01 μs, which indicates that the laser filamentation-guided discharge is highly repeatable. Therefore, using the femtosecond laser can realize the precise control of the time and space of the discharge, and one-dimensional spatially resolved spectra of discharge plasma can be accurately collected. In a jet flow field environment, the mixture fraction in the jet is different from the ambient air. The experimental results show that the changes in the species concentration at different locations can be seen clearly from one-dimensional spatially resolved spectra. By correlating the concentrations of N2 and O2 with the signal intensity of N+ and O atom, one can realize a one-dimensional measurements of the species concentration. Compared with nanosecond laser-induced breakdown spectroscopy, this method not only has the same advantages, but also has one-dimensional spatial resolution. Meanwhile, this method has the potential to achieve high temporally resolved measurement, which is of great significance for studying the spatiotemporal evolution process of the discharge plasma.
[1] Kotzagianni M, Yuan R, Mastorakos E, et al. Combustion and Flame, 2016, 167: 72.
[2] Hsieh K C, Wang H, Locke B R. Plasma Processes and Polymers, 2016, 13(9): 908.
[3] Jantzi S C, Motto-Ros V, Trichard F, et al. Spectrochimica Acta Part B: Atomic Spectroscopy, 2016, 115: 52.
[4] Rahman K M, Kawahara N, Matsunaga D, et al. International Journal of Hydrogen Energy, 2016, 41(32): 14283.
[5] Ouyang L, Cao Z, Wang H, et al. Journal of Alloys and Compounds, 2017, 691: 422.
[6] Li B, Zhang D, Liu J, et al. Applied Sciences, 2019, 9(9): 1906.
[7] Gao Q, Zhang D, Li X, et al. Sensors and Actuators A: Physical, 2019, 287: 138.
[8] Li B, Zhang D, Li X, et al. Journal of Physics D: Applied Physics, 2018, 51(29): 295102.
[9] Zhang D, Gao Q, Li B, et al. Optics Express, 2019, 27(3): 2159.
[10] Li B, Tian Y, Gao Q, et al. Optics Express, 2018, 26(16): 21132.
[11] Arantchouk L, Honnorat B, Thouin E, et al. Applied Physics Letters, 2016, 108(17): 173501.
