Two-dimensional Thomson scattering diagnostics of pulsed discharges produced at atmospheric pressure

Abstract

Laser Thomson scattering (LTS) method has been applied to measure two dimensional distributions of electron density (n e ) and electron temperature (T e ) of a pulsed discharge in Ne gas at a pressure of 400 Torr. Such a discharge was produced with good reproducibility by using a set of electrodes composed of a needle and a hemisphere with a spacing gap of 0.5 mm. The values of n e and T e at t = 25 ns after the start of the discharge and at the center of the discharge were evaluated to be 4.6 × 10 22 m −3 and 1.0 eV, respectively. Based on the observed signal intensity and noise components, signal-to-noise ratios were examined and the way to apply present diagnostic system to the discharge plasma with an electron density as low as 10 18 m −3 was discussed.

Experimental investigation of the electron energy distribution function (EEDF) by Thomson scattering and optical emission spectroscopy

“…The axial trend in T e (TS) found along the SW discharge is part of a larger category that can be denoted by the trend of rising T e (TS) in outer plasmas parts. This was also observed experimentally in studies on atmospheric pressure plasmas (see for instance [17,62,68,70,71]) but also for low-pressure plasmas [38,42]. In outer regions where n e drops, the (mean) T e values go up.…”

“…Consequently, similar behaviours for completely different plasmas sources and operation regimes (i.e. dielectric barrier discharge [71], radio-frequency [17] and microwave induced plasmas [68,70]) are found for pressures above a few mbars. The common trend is the lower ionization degree towards the edges/end of the plasma.…”

Thomson scattering diagnostics of atmospheric plasmas in contact with ionic liquids

“…LTS has been used to investigate fusion plasmas, 15) laser-produced plasmas, 16,17) discharge in low-pressure gases, 18) microdischarge plasmas, 19) arc discharges, 20) and more recently, nonequilibrium plasmas produced at around atmospheric pressure. 21) LTS can give local values of n e and T e at high spatial and temporal resolutions, and in comparison with conventional methods such as probe methods, LTS can measure these parameters with small perturbations.…”

Development of a collective Thomson scattering system for laser-produced tin plasmas for extreme-ultraviolet light sources

“…The spectrometer mainly consisted of six achromatic lenses (L 1 -L 6 , f = 486 mm, effective diameter: 60 mm), five diffraction gratings (G 1 -G 5 , 2400 grooves=mm plane holographic reflection gratings with high modulation, effective area: 66 mm height × 75 mm width), an entrance slit (S 1 , width: 20 µm), an intermediate slit (S 2 , width: 20 µm), and a thin tungsten wire (diameter: 100 µm) to block the stray light, which is referred to as a laser-wavelength stop in this study. 17) An intensified charge-coupled device (ICCD) camera (quantum efficiency: 48% at 532 nm) was used as a detector. The time resolution was determined by the gate width of the ICCD camera and it was set to be 5 ns.…”