Diagnostics of low-density glow discharge plasmas using Thomson scattering

Muraoka, Katsunori; Uchino, Kenji; Bowden, Mark

doi:10.1088/0741-3335/40/7/002

Cited by 98 publications

(79 citation statements)

References 18 publications

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“…We first describe how these densities are extracted from experimental spectra, and then discuss the limitations of the data inversion and how quantitative comparisons with the model predictions are best made. The elec- tron density is an important plasma parameter, but precise measurements are challenging: under conditions of high electron density, interferometric methods 39 or Thomson scattering 11,40 can be used. At the relatively low electron densities of the arc jet reactor plume, however, we instead retrieve electron densities from the Stark broadening of atomic absorption lines.…”

Section: Results Of the Experimental Measurementsmentioning

confidence: 99%

Measurement and modeling of a diamond deposition reactor: Hydrogen atom and electron number densities in an Ar∕H2 arc jet discharge

Rennick

Engeln

Smith

et al. 2005

Journal of Applied Physics

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Please check the document version of this publication:• A submitted manuscript is the version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal.If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement: A combination of experiment ͓optical emission and cavity ring-down spectroscopy ͑CRDS͒ of electronically excited H atoms͔ and two-dimensional ͑2D͒ modeling has enabled a uniquely detailed characterization of the key properties of the Ar/ H 2 plasma within a ഛ10-kW, twin-nozzle dc arc jet reactor. The modeling provides a detailed description of the initial conditions in the primary torch head and of the subsequent expansion of the plasma into the lower pressure reactor chamber, where it forms a cylindrical plume of activated gas comprising mainly of Ar, Ar + , H, ArH + , and free electrons. Subsequent reactions lead to the formation of H 2 and electronically excited atoms, including H͑n =2͒ and H͑n =3͒ that radiate photons, giving the plume its characteristic intense emission. The modeling successfully reproduces the measured spatial distributions of H͑n Ͼ 1͒ atoms, and their variation with H 2 flow rate, F H 2 0 . Computed H͑n =2͒ number densities show near-quantitative agreement with CRDS measurements of H͑n =2͒ absorption via the Balmer-␤ transition, successfully capturing the observed decrease in H͑n =2͒ density with increased F H 2 0 . Stark broadening of the Balmer-␤ transition depends upon the local electron density in close proximity to the H͑n =2͒ atoms. The modeling reveals that, at low F H 2 0 , the maxima in the electron and H͑n =2͒ atom distributions occur in different spatial regions of the plume; direct analysis of the Stark broadening of the Balmer-␤ line would thus lead to an underestimate of the peak electron density. The present study highlights the necessity of careful interco...

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Section: Results Of the Experimental Measurementsmentioning

confidence: 99%

Measurement and modeling of a diamond deposition reactor: Hydrogen atom and electron number densities in an Ar∕H2 arc jet discharge

Rennick

Engeln

Smith

et al. 2005

Journal of Applied Physics

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“…From this point of view, Laser Thomson Scattering (LTS) can be a solution, offering reliable and spatially resolved electron temperature and density measurements [3].…”

Section: Thomson Scattering Measurements Of Helium Recombining Plasmamentioning

confidence: 99%

Thomson Scattering Measurements of Helium Recombining Plasmas in the Divertor Simulator MAP-II

Scotti

Kado

Okamoto

et al. 2006

Plasma and Fusion Research

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Laser Thomson Scattering (LTS) measurements of Electron Ion Recombining (EIR) Helium plasma were performed in the divertor/edge simulator MAP-II. Upgrades of our LTS system, in the stray-light level and in the notch filter, allowed the measurement of electron temperatures as low as 0.1 eV and further investigation of EIR processes. Electron temperature and electron density profiles of EIR He recombining plasmas with different background neutral pressures have been measured. The volumetric recombination process is regarded as important in achieving divertor detachment, which can reduce the heat flux onto the divertor plate [1]. MAR (Molecular Activated Recombination) processes (2-3 eV), induced by H 2 puffing, as well as conventional EIR (Electron Ion Recombination) processes (< 1 eV) can contribute to volumetric recombination, but their reaction rates strongly depend on the electron temperature.It has been pointed out in several devices, both in tokamak divertors and in divertor simulators, that in recombining plasmas the electric probe characteristic exhibits an anomaly which disturbs the measurements [2]. On the other hand, spectroscopy for the Rydberg series in a partially local thermal equilibrium condition, such as EIR plasmas, always reflects the brightest point.From this point of view, Laser Thomson Scattering (LTS) can be a solution, offering reliable and spatially resolved electron temperature and density measurements [3].We have developed an LTS system and applied it to the H 2 -MAR plasmas of a few eV, as reported in [4]. The laser source is a frequency-doubled Nd:YAG Laser (7 ns, 532 nm, 10 Hz, 500 mJ). The light is collected at 90 • with respect to the laser path by means of a lens (150 mm in focal length and 100 mm in diameter). The optical fibers, 0.2 in the N/A and 0.1/0.125 mm in the core/clad diameter, are assembled in a 64-channel array. In the present experiment, the central 24 channels, corresponding to 4.5 mm in the radial scattering length, were used to obtain electron temperature and density. On the other hand, the spatial resolution along the magnetic field is 0.13 mm (single fiber With the aim of applying it to low temperature plasmas, a double monochromator system (composed of camera lenses, holographic gratings, Rayleigh block, and an ICCD camera) is used to measure narrow Doppler broadening and to suppress stray light of the laser wavelength. It has to be noted that the use of filter spectroscopy in this temperature regime requires the assumption of the Boltzmann distribution and careful sensitivity calibration [5]. The Rayleigh block is a carbon rod 0.35 mm in diameter, located at the laser wavelength position in the image plane of the first monochromator. Reciprocal linear dispersion of the monochromator was determined to be 0.02 nm per pixel of the ICCD. Wavelength resolution, evaluated in FWHM, was 0.15 nm for a slit width of 0.11 mm.In order to measure EIR plasmas, however, further upgrades were required. Specifically, we reduced the dimensions of the physical block by replacing...

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“…n e values obtained by LTS were consistent with those found by Optical Emission Spectroscopy. Diode Laser Absorption Spectroscopy (DLAS) was used for spatially resolved measurements of argon metastable Ar(1s 5 ) density in argon microdischarges. The analysis of the absorption lineshapes also provided the gas temperature.…”

Section: Discussionmentioning

confidence: 99%

“…In most laser scattering experiments light is detected at an angle of θ =90° with respect to the laser beam axis [2][3][4][5]. In a slot-type microdischarge with a long, deep, and narrow gap, the z-axis [1] is the most appropriate direction of propagation of a tightly focused laser beam, as well as for detection of the scattered light.…”

Section: Methodsmentioning

confidence: 99%

Laser Thomson Scattering, Raman Scattering and laser-absorption diagnostics of high pressure microdischarges

Donnelly

Belostotskiy

Economou

et al. 2010

J. Phys.: Conf. Ser.

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Diagnostics of low-density glow discharge plasmas using Thomson scattering

Cited by 98 publications

References 18 publications

Measurement and modeling of a diamond deposition reactor: Hydrogen atom and electron number densities in an Ar∕H2 arc jet discharge

Measurement and modeling of a diamond deposition reactor: Hydrogen atom and electron number densities in an Ar∕H2 arc jet discharge

Thomson Scattering Measurements of Helium Recombining Plasmas in the Divertor Simulator MAP-II

Laser Thomson Scattering, Raman Scattering and laser-absorption diagnostics of high pressure microdischarges

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