O atom number density measurements in repetitively pulsed plasmas by two photon laser induced fluorescence

We present measurements of atomic oxygen number density in high pressure, non-equilibrium plasmas created by a high repetition rate (50 kKz) -- short (20 nsec) pulse duration discharge. Measurements are performed using two photon absorption laser induced fluorescence (TALIF). Atomic oxygen mole fractions are presented as a function of time after plasma initiation in oxygen/helium, air, and air/methane mixtures at pressures of approximately 60-100 torr. Two approaches will be described for absolute number density calibration, comparison with two photon xenon spectra, and chemical titration with NO$_{2}$. Diagnostic issues relevant to short pulse plasmas, in particular mitigation of electromagnetic interference, will be described in detail.