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Article Dans Une Revue Plasma Sources Science and Technology Année : 2022

Quantitative fs-TALIF in high-pressure NRP discharges: calibration using VUV absorption spectroscopy

Résumé

Abstract This work presents a femtosecond two-photon absorption laser-induced fluorescence (fs-TALIF) diagnostic for measuring ground-state atomic nitrogen in nanosecond repetitively pulsed (NRP) discharges. Absolute atom density is obtained from the TALIF signal via a novel calibration technique based on one-photon direct absorption measurements performed in a low-pressure DC discharge. The Vacuum Ultraviolet (VUV) measurements were done at the Soleil synchrotron facility using the high-resolution Fourier-transform spectrometer (minimum linewidth Δ ν ~ = 0.08 cm −1 ). The main goal of this work was to develop a quench-free diagnostic technique, which would allow measurements at elevated pressures with high spatial and temporal resolution. Here fs-TALIF measurements of N( 4 S) are demonstrated in the NRP post-discharge between 1–500 μ s after the nanosecond high-voltage pulse. A maximum number density of N-atoms of 5 × 10 16 cm −3 was measured at 1 μ s after the pulse when the discharge was operated at 1 bar in pure nitrogen. This corresponds to a dissociation fraction of ∼0.1%. The fs-TALIF technique at high laser intensity regime (>1 TW cm −2 ) calibrated using VUV absorption was compared with the fs-TALIF at low laser intensity regime (<100 MW cm −2 ) calibrated via the well-established non-saturated TALIF technique using krypton as an etalon gas. It was found that the two measurements of N( 4 S) in the NRP post-discharge agree within a factor of 3. Importantly, the limit of detection of the fs-TALIF at high laser intensity regime was determined to be n N ( S 4 ) ∼ 1 0 12 c m − 3 . This is approximately one order of magnitude better than previously reported by ns-TALIF in low-pressure discharges.

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Dates et versions

hal-04563768 , version 1 (30-04-2024)

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Citer

Ciprian Dumitrache, Arnaud Gallant, Nelson de Oliveira, Christophe Laux, Gabi Daniel Stancu. Quantitative fs-TALIF in high-pressure NRP discharges: calibration using VUV absorption spectroscopy. Plasma Sources Science and Technology, 2022, 31 (1), pp.015004. ⟨10.1088/1361-6595/ac3e41⟩. ⟨hal-04563768⟩
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