Needle to ring electrode configuration in dielectric capillary (diameter: 1.6 mm); Frequency: ~ 1 MHz; Power: 1 - 3 W
\n", "procedure": "The kINPen-sci was operated with a gas curtain that provides a concentric gas flow, which shields the plasma effluent from the influx of surrounding ambient air. The plasma jet was placed on a motorised xyz translation stage. The z-axis is defined as the axis along the symmetry axis of the effluent through the centre of the plasma jet nozzle, the x-axis is the axis parallel to the laser beam, which crosses the centre of the nozzle.
\n" }, "medium": { "name": "Ar", "properties": "Feed gas: 3 slm Ar with 3000 ppm humidity; Gas curtain: 5 slm N2/O2 mixture, composition of the gas curtain can be varied from pure nitrogen to pure oxygen
\n" }, "target": [], "diagnostics": { "name": "ps-TALIF, CFD simulations, plasma chemical model", "properties": "The picosecond laser system was based on an Nd:YAG pump laser (1064 nm) with a mode-locked oscillator, a regenerative amplifier, and a single pulse power amplifier, producing a weak pulse train output and a strong single pulse output with a single pulse duration of 30 ps with a repetition rate of 10 Hz. In a second laser unit the weak train beam is amplified and frequency-tripled (355 nm), the strong single pulse beam is frequency-tripled only, while the left-over of the 1064 nm single pulse is the third output beam. In the third laser unit the 355 nm train enters an optical parametric oscillator (OPO) state providing tunable but weak radiation between 420 to 710 nm, that is amplified using the strong 355 nm single pulse in a subsequent optical parametric amplifier (OPA) stage. Subsequent frequency-doubling is used to generate the UV wavelengths between 210 to 355 nm, and additional sum-frequency mixing with the left-over 1064 nm single pulse input for the deep UV wavelengths below 210 nm. In the UV range, 30 ps laser pulses were generated, with a pulse energy of a few hundred \u00b5J at the maximum, and a spectral width of approximately 4 cm\u22121. The standard deviation of the shot-to-shot fluctuations in the pulse energy is approximately 8%.
\n", "procedure": "Experiment:
\nThe applied laser pulse energy was measured behind the laser focus/plasma interaction volume with a pyroeletric detector (Gentec-EO, QE8SP-B-MT) and controlled with the help of an attenuator-compensator system, which comprises two specifically coated counter-rotating CaF 2 substrates that are actuated by a stepper motor. The laser beam was focussed by a spherical plano-convex fused-silica lens, with a focal length of 30 cm, in a plane approximately 1 cm behind the plasma jet to avoid saturation of the two-photon transitions, and to mitigate material damage in the calibration cuvettes. The fluorescence signal of the excited states was detected perpendicular to the direction of the laser beam by using an intensified charge coupled device camera (iCCD: Stanford Computer Optics, 4Picos dig), after passing two achromatic lenses (Thorlabs, AC050-010-B-ML, focal length: 80 mm) and an interference filter (central wavelengths \u03bb_O = 845 nm, \u03bb_H = 656 nm, \u03bb_Xe = 835 nm, \u03bb_Kr = 825 nm, band width \u2206\u03bb = 10 nm).
Model:
\nSumerical simulations were performed by using a two-dimensional axisymmetric model of the turbulent reacting flow coupled with a local zero-dimensional plasma chemical model for the kINPen-sci plasma jet.