Measurement of laser induced fluorescence for argon plasma flow with oxygen injection

The experimental investigation of the effects of O2 injection on the magnetized Ar plasma flow in the linear plasma device was conducted by using the measurement of laser induced fluorescence (LIF) with electric probes. The LIF measurement was based on the Ar ion transition from the 3d4F7/2 metastable level to the 4p4D5/2 level at a wavelength of 668.61 nm. In addition, the analysis of ion velocity distribution functions (IVDFs) involved the detection of fluorescence light emitted from the 4p4D5/2 level to the 4s4P3/2 level, which had a wavelength of 442.72 nm. For a comprehensive analysis of the intricate interaction between O2 injection and the behavior of the Ar plasma flow, the oxygen was injected into the Ar plasma, and the O2/Ar ratio ranged from 0% to 14% while maintaining a constant pressure of 2 mTorr. The Zeeman splitting in the IVDFs was clearly observable for pure Ar plasma due to 800 G as the high magnetic field strength. The split form disappeared due to a small amount of oxygen injected as the O2/Ar ratio of 3.5%. The LIF intensity is in agreement with the tendency of plasma density due to the reduction of Ar ions by charge transfer, quenching, and neutralization as O2 is injected into the Ar plasma. The experimental results show that the effects on temperature and flow velocity for the Ar ions are insignificant when O2 is injected into the Ar plasma at the O2/Ar ratio of 0%–14%, in contrast to the large change in the electron temperature.