Jiang Naibo, Grib Stephen W, Hsu Paul S, Borg Matthew, Schumaker S Alexander, Roy Sukesh
Appl Opt. 2022 Mar 20;61(9):2192-2197. doi: 10.1364/AO.449263.
A 100 kHz krypton (Kr) tagging velocimetry (KTV) technique was demonstrated in a Mach-6 Ludwieg tube using a burst-mode laser-pumped optical parametric oscillator system. The single-beam KTV scheme at 212 nm produced an insufficient signal in this large hypersonic wind tunnel because of its low Kr seeding (≤5), low static pressure (∼2.5), and long working distance (∼1). To overcome these issues, a new scheme using two excitation beams was developed to enhance KTV performance. A 355 nm laser beam was combined with the 212 nm beam to promote efficient two-photon Kr excitation at 212 nm, and increase the probability of 2 + 1 resonant-enhanced multiphoton ionization by adding a 355 nm beam. A signal enhancement of approximately six times was obtained. Using this two-excitation beam approach, strong long-lasting KTV was successfully demonstrated at a 100 kHz repetition rate in a Mach-6 flow.
利用脉冲模式激光泵浦光学参量振荡器系统，在马赫数为6的路德维希管中演示了一种100千赫兹氪（Kr）标记测速技术（KTV）。由于其低Kr种子浓度（≤5）、低静压（约2.5）和长工作距离（约1），212纳米处的单光束KTV方案在这个大型高超音速风洞中产生的信号不足。为了克服这些问题，开发了一种使用两束激发光束的新方案来提高KTV性能。将一束355纳米的激光束与212纳米的光束相结合，以促进212纳米处的高效双光子Kr激发，并通过添加一束355纳米的光束增加2 + 1共振增强多光子电离的概率。获得了约六倍的信号增强。使用这种双激发光束方法，在马赫数为6的气流中以100千赫兹的重复频率成功演示了强大且持久的KTV。
