Measurements of Electron Density and Electron Temperature of Arc Discharge Plasmas Containing Metallic Vapors Using Laser Thomson Scattering

Tomita, Kentaro; Yoshitake, Shinya; Uchino, Kenji; Takenaka, Daigo; Toda, Hiroaki; Hikita, Masayuki; Suzuki, Koji

doi:10.1002/eej.22635

Cited by 4 publications

(2 citation statements)

References 22 publications

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“…The Thomson scattering (TS) spectrum is a measure of the electron velocity distribution function, and it provides direct measurement of electron density and temperature with minimal assumptions on plasma conditions, such as symmetry, composition, and equilibrium. LTS has been widely implemented in high-temperature nuclear fusion plasmas, but has recently expanded its applications in various low-temperature plasma sources, including glow discharge 24 , arc discharge 25 , microwave discharge 26 , 27 , nanosecond pulsed discharge 28 , plasma jets 29 , and laser-induced plasmas 30 – 33 . When employing TS for low-temperature plasmas, it is essential to consider the effect that the probing laser has on the plasma itself.…”

Section: Introductionmentioning

confidence: 99%

Two-dimensional high resolution electron properties of femtosecond laser-induced plasma filament in atmospheric pressure argon

Bak,

Urdaneta,

Pokharel

et al. 2024

Sci Rep

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This work reports the measurement of two-dimensional electron properties over a nanosecond scale integration time across a femtosecond laser-induced plasma filament in atmospheric pressure argon. Radial electron properties across the $$\sim 100$$ ∼ 100 $$\upmu$$ μ m diameter filament are obtained at discrete axial locations at 2.5 mm steps by one-dimensional high-resolution laser Thomson scattering with a spatial resolution of 10 $$\upmu$$ μ m. These measurements reveal plasma structural information in the filament. The Thomson spectral lineshapes exhibit clear spectral sidebands with an $$\alpha$$ α parameter $$\sim 1$$ ∼ 1 , enabling the measurement of both electron temperature and density profiles. These measurements yield electron densities on the order of $$10^{22}$$ 10 22 /m$$^{3}$$ 3 and electron temperatures of $$\sim 2$$ ∼ 2 eV. Heating from the probe laser due to inverse bremsstrahlung is taken into account to correct the Thomson scattering electron temperature measurements. Under these conditions, electron-neutral collision induced bremsstrahlung becomes the dominant laser-induced plasma heating process associated with the probe laser. The measurements reveal structural features of the filament, including an asymmetrically skewed density structure in the axial direction and reversed radial distributions of electron density and temperature.

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Section: Introductionmentioning

confidence: 99%

Two-dimensional high resolution electron properties of femtosecond laser-induced plasma filament in atmospheric pressure argon

Bak,

Urdaneta,

Pokharel

et al. 2024

Sci Rep

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show abstract

“…Thus, to detect Raman and Thomson scattering signals, the light near the laser line (Rayleigh scattering/stray light) should be effectively removed to prevent saturation of the detector. Such laser line rejection can be performed with multiple techniques such as a triple grating spectrograph [4][5][6][7][8][9][10][11][12], a vapor cell [13][14][15], a glass/interference filter [16], a physical mask [17,18], and a volume Bragg grating (VBG) filter [19][20][21][22][23][24][25][26].…”

Section: Introductionmentioning

confidence: 99%

High resolution spatially extended 1D laser scattering diagnostics using volume Bragg grating notch filters

Bak¹,

Betancourt²,

Rekhy³

et al. 2022

Preprint

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Laser light scattering systems with volume Bragg grating (VBG) filters, which act as a spectral/angular filter, have often been used as a point measurement technique with spatial resolution as low as a few hundred µm defined by the beam waist. In this work, we demonstrate how VBG filters can be leveraged for spatially resolved measurements with several µm resolution perpendicular to the laser propagation axis over a few mm along the beam propagation axis. The rejection ring, as determined by the angular acceptance criteria of the filter, is derived analytically, and the use of the ring for 1D laser line rejection is explained. For the example cases presented, having a focused probe beam waist with a diameter of ∼ 150 µm, the rejection ring can provide up to several mm length along the beam propagation axis for a 1D measurement, which is also tunable. Additionally, methods to further extend the measurable region are proposed and demonstrated; using a collimation lens with a different focal length or using multiple VBG filters. The latter case can minimize the scattering signal loss, without the trade-off of the solid angle. Such use of multiple VBGs is to extend the measurable region along the beam axis, which differs from the commonly known application of multiple filters to improve the suppression of elastic interferences. 1D rotational Raman and Thomson scattering measurements are carried out on pulsed and DC discharges to verify this method. The system features compactness, simple implementation, high throughput, and flexibility to accommodate various experimental conditions.

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High resolution spatially extended 1D laser scattering diagnostics using volume Bragg grating notch filters

Bak

Betancourt

Rekhy

et al. 2023

Review of Scientific Instruments

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Laser light scattering systems with volume Bragg grating (VBG) filters, which act as spectral/angular filters, have often been used as a point measurement technique, with spatial resolution as low as a few hundred μm, defined by the beam waist. In this work, we demonstrate how VBG filters can be leveraged for spatially resolved measurements with several μm resolution over a few millimeters along the beam propagation axis. The rejection ring, as determined by the angular acceptance criteria of the filter, is derived analytically, and the use of the ring for 1D laser line rejection is explained. For the example cases presented,i.e., for a focused probe beam waist with a diameter of [Formula: see text] μm, the rejection ring can provide resolution up to several millimeter length along the beam propagation axis for a 1D measurement, which is also tunable. Additionally, methods to further extend the measurable region are proposed and demonstrated, using a collimation lens with a different focal length or using multiple VBG filters. The latter case can minimize the scattering signal loss, without the tradeoff of the solid angle. Such use of multiple VBGs is to extend the measurable region along the beam axis, which differs from the commonly known application of multiple filters, to improve the suppression of elastic interferences. 1D rotational Raman and Thomson scattering measurements are carried out on pulsed and DC discharges to verify this method. The system features compactness, simple implementation, high throughput, and flexibility, to accommodate various experimental conditions.

show abstract

Measurements of Electron Density and Electron Temperature of Arc Discharge Plasmas Containing Metallic Vapors Using Laser Thomson Scattering

Cited by 4 publications

References 22 publications

Two-dimensional high resolution electron properties of femtosecond laser-induced plasma filament in atmospheric pressure argon

Two-dimensional high resolution electron properties of femtosecond laser-induced plasma filament in atmospheric pressure argon

High resolution spatially extended 1D laser scattering diagnostics using volume Bragg grating notch filters

High resolution spatially extended 1D laser scattering diagnostics using volume Bragg grating notch filters

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