Two-photon absorption laser induced fluorescence measurement of atomic oxygen density in an atmospheric pressure air plasma jet
Two-photon absorption laser induced fluorescence measurement of atomic oxygen density in an atmospheric pressure air plasma jet
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DOI：
10.1088/0963-0252/25/4/045023
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发表时间：
2016-07
影响因子：
3.8
通讯作者：
J. Conway;G. Gogna;C. Gaman;Miles M. Turner;Stephen R. Daniels
中科院分区：
文献类型：
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作者：
J. Conway;G. Gogna;C. Gaman;Miles M. Turner;Stephen R. Daniels
利用双光子吸收激光诱导荧光(TALIF)测量了大气大气压等离子体射流(APPJ)中的原子氧数密度[O]。气体流量固定在8slpm，耦合到等离子体射流的射频功率在5W到20W之间变化，并测量了由此产生的原子氧密度的变化。分子氧的光解被用来实现Talif系统的现场校准。在校准过程中，在同一激光脉冲内实现了氧原子的O2光解和双光子激发。光解产生的原子氧密度具有时变性和空间非均匀性，需要对其进行校正，以校准用于测量等离子体中原子氧密度的Talif系统。激光脉冲强度I0(T)、波长和焦斑大小的知识允许使用速率方程模型来确定校正因子。原子氧用于校准和测量，因此可以在Talif二次激光功率依赖区域之外增加激光强度，而不会影响校准可靠性，因为两者的激光功率依赖仍然相同。获得的原子O密度结果并不直接与其他已知的密度测量技术相比较。结果表明，等离子体喷流的原子氧含量随着耦合到等离子体的射频功率的增加而增加。
Atomic oxygen number density [O] is measured in an air atmospheric pressure plasma jet (APPJ) using two-photon absorption laser induced fluorescence (TALIF). Gas flow is fixed at 8 slpm, the RF power coupled into the plasma jet varied between 5 W and 20 W, and the resulting changes in atomic oxygen density measured. Photolysis of molecular oxygen is employed to allow in situ calibration of the TALIF system. During calibration, O2 photo-dissociation and two-photon excitation of the resulting oxygen atoms are achieved within the same laser pulse. The atomic oxygen density produced by photolysis is time varying and spatially non-uniform which needs to be corrected for to calibrate the TALIF system for measurement of atomic oxygen density in plasma. Knowledge of the laser pulse intensity I0(t), wavelength, and focal spot size allows correction factors to be determined using a rate equation model. Atomic oxygen is used for calibration and measurement, so the laser intensity can be increased outside the TALIF quadratic laser power dependence region without affecting the calibration reliability as the laser power dependence will still be the same for both. The atomic O density results obtained are not directly benchmarked against other known density measurement techniques. The results show that the plasma jet atomic oxygen content increases as the RF power coupled into the plasma increases.