Abstract: Arc-heated wind tunnel, as an important hypersonic test facility, is indispensable for examining and developing thermal protection materials and structures. However, the flow is always contaminated by copper species generated from the surface molten or boiled electrodes, undermining the accuracy of the experiment. In this work, to quantitatively study the copper contamination and the electrode ablation, the Tunable Diode Laser Absorption Spectroscopy (TDLAS) is employed by measuring the 809.25 nm transition spectrum line of Cu in real-time in the 20 MW segmented arc heater. Based on acquisition of the number densities of lower state, the average number densities of copper species (including atoms and ions) in the inner flow of arc heater with the different power of 7.3, 8.7, 10.0 and 11.7 MW are measured, deriving results as 10.6×10¹³, 11.2×10¹³, 11.7×10¹³, and 16.4×10¹³ cm^-3 respectively. In the meantime, the average electrode ablation rate (defined by mass loss per unit of charge crossing the electrode surface) is obtained as about 1.65×10^-5 g/C. What's more, the monitoring TDLAS signal showed violent fluctuation before the steady flow is established and showed sudden sharp rise when the power of the arc heater changed, demonstrating that the fluctuation of arc spots could greatly aggravate the electrode ablation.

Key words: arc-heated wind tunnel, Tunable Diode Laser Absorption Spectroscopy (TDLAS), flow contamination, electrode ablation, copper atom