Single-shot Thomson scattering on argon plasmas created by the Microwave Plasma Torch; evidence for a new plasma class

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Section: Axial Trends: Correlation With the Ionization Degree Along Tsupporting

confidence: 72%

Section: Axial Trends: Correlation With the Ionization Degree Along Tmentioning

confidence: 58%

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

Carbone¹,

Hübner²,

Jimenez-Diaz³

et al. 2012

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“…Applying absolute intensity measurements [11,12] of atomic lines and the continuum it was possible to determine the electron density n e and temperature T e ; these values have been compared with the results of the Stark intersection method and Thomson scattering [13][14][15][16][17]. Typical reported values for the TIA are n e = 3 · 10 21 m −3 and T e = 22000 K. For the MPT the typical values are n e = 3 · 10 20 m −3 and T e = 18000 K (see [18]).…”

Section: Introductionmentioning

confidence: 99%

Effect of remote field electromagnetic boundary conditions on microwave-induced plasma torches

Jimenez-Diaz¹,

Dijk²,

Mullen³

2011

Abstract.A flexible versatile electromagnetic model constructed with the PLASIMO platform is employed to explore electromagnetic features of microwave induced plasma torches. The bases, formed by a full-vector formulation of the Maxwell equations, provides the possibility to formulate the boundary conditions in a natural way. Together with the use of a direct matrix solver this gives a convergence speed-up of more than a factor of 100 when compared to a scalar formulation on the azimuthal magnetic field that uses an iterative solver. As a result this electromagnetic model is ready to act in future studies as part of the self-consistent description of plasma-electromagnetic coupling. With the electromagnetic model three types of configuration were studied: the closed, semi-open and open configurations, all three based on the same simplified model-plasmas. It is found that the closed configuration, acting as a cavity for which the (de)tuning is extremely sensitive for the plasma conditions, is less suitable for applications in which changes in plasma compositions can be expected. The semi-open configuration can be seen as a model for the practice often used in laboratories to place Microwave Induced Plasma torches in a grid that aims to protect the environment against microwave electromagnetic radiation. Calculations show that this is good practice provided the radius of this cylindrical grid is in the order of 90 mm. For the most often used configuration, the open version, we found that the power balance as expressed by the coefficients of absorption, transmission and reflection, depends on the electron density of the plasma. The reason is that the plasma acts as an antenna, that converts the electromagnetic waves from the co-axial structure to that of the expansion region and that this antenna function depends on the electron density. The influence of various other antenna elements is investigated as well.

“…TS is employed to determine the electron density n e and temperature T e with good spatial resolution [8][9][10][11][12][13][14][15]. Rayleigh scattering gives us spatially resolved heavy particle temperature T g [16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Atmospheric microwave-induced plasmas in Ar/H₂ mixtures studied with a combination of passive and active spectroscopic methods

Palomares¹,

Iordanova²,

Gamero³

et al. 2010

Several active and passive diagnostic methods have been used to study atmospheric microwave induced plasmas created by a surfatron operating at a frequency of 2.45 GHz and with power values between 57 and 88 W. By comparing the results with each other, insight is obtained into essential plasma quantities, their radial distributions and the reliability of the diagnostic methods. Two laser techniques have been used, namely Thomson scattering (TS) for the determination of the electron density, n e , and temperature, T e , and Rayleigh scattering (RyS) for the determination of the heavy particle temperature, T g . In combination, three passive spectroscopic techniques are applied, the line broadening of the H β line to determine n e , and two methods of absolute intensity measurements to obtain n e and T e . The active techniques provide spatial resolution in small plasmas with sizes in the order of 0.5 mm. The results of n e measured with three different methods show good agreement, independent of the plasma settings. The T e values obtained with two techniques are in good agreement for the condition of a pure argon plasma, but they show deviations when H 2 is introduced. The introduction of a small amount (0.3 %) of H 2 into an argon plasma induces contraction, reduces n e , increases T e , enhances the departure from equilibrium and leads to conditions that are close to those found in cool atmospheric plasmas.