High-resolution electron density and temperature maps of a microwave plasma torch measured with a 2-D Thomson scattering system

Mullen, Joost van der; Boidin, Guillaume; Sandea, Marco van de

doi:10.1016/j.sab.2004.04.004

Cited by 34 publications

(16 citation statements)

References 19 publications

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“…The 'white' intense appearance shown in the unfiltered image [ Figure 7(a)] seemingly implies the substantial continuum radiation in the visible wavelength range. The electron characteristics reported by earlier works [76][77][78]80,84,119,[153][154][155][156][157] in various atmospheric-pressure plasmas with the aforementioned diagnostic methods are summarized in Figure 8. For the sake of comparison, the electron data are grouped by dotted boxes with respect to the diagnostics presented in the figure, and valid ranges of each diagnostic technique for nonequilibrium plasmas at atmospheric pressure are depicted by dashed boxes.…”

Section: Free-electron Diagnostics Based On Active Processesmentioning

confidence: 99%

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Electron characterization in weakly ionized collisional plasmas: from principles to techniques

Park

Choe

Moon

et al. 2018

Advances in Physics: X

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Weakly ionized plasmas at or near 1 atm pressure, or atmospheric-pressure plasmas, have received increasing attention due to their scientific significance and potential for use in a variety of applications, particularly for medicine, agriculture, and food. However, there is a large imbalance between scientific research on plasma physics and applications, which is partly due to the considerable differences in the characteristics of these plasmas compared with those of low-pressure plasmas. This discrepancy is particularly related to the difficulty in performing plasma diagnostics for highly collisional plasmas. Information on electrons (such as the electron density and temperature) is essential since electrons play a dominant role in the generation of active species related to the physical and chemical processes inside the plasma. So far, limited diagnostics have been available for electrons such as Thomson scattering and optical emission diagnostics based on equilibrium models. Here, we review the available diagnostic methods along with their merits and limitations for characterizing electrons in weakly ionized collisional plasmas. Particular attention is paid to continuum radiation-based spectroscopy, which facilitates multidimensional imaging of electron density and temperature. The future impact of these plasmas on relevant fields (i.e. laboratory and industrial plasmas and their applications) is also addressed.

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Section: Free-electron Diagnostics Based On Active Processesmentioning

confidence: 99%

“…Figure 8. Electron characteristics in various types of weakly ionized plasmas at atmospheric pressure [76][77][78]80,84,119,[153][154][155][156][157] and valid range of each diagnostic technique.…”

Section: Imaging Techniques (2-d)mentioning

confidence: 99%

Electron characterization in weakly ionized collisional plasmas: from principles to techniques

Park

Choe

Moon

et al. 2018

Advances in Physics: X

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“…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

J. Phys. D: Appl. Phys.

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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.

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“…Electron temperature and density in many devices have since been measured using Nd:YAG lasers, including expanding arc plasmas, 11,12 ECR discharges, [13][14][15] and microwave plasma torches. 16,17 Until the late 1990s most LTS diagnostics on cold plasmas used photomultiplier tubes (PMTs) to detect the scattered Thomson signal. PMTs have excellent sensitivity and the ability to count single photons, but they also have the disadvantage of being able to detect only one wavelength of scattered light at a time, necessitating measurements at multiple wavelengths to construct a full scattered spectrum (or use of PMT arrays to detect the full spectrum).…”

Section: Introductionmentioning

confidence: 99%

Application of maximum likelihood methods to laser Thomson scattering measurements of low density plasmas

Washeleski

Meyer

King

2013

Review of Scientific Instruments

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Laser Thomson scattering (LTS) is an established plasma diagnostic technique that has seen recent application to low density plasmas. It is difficult to perform LTS measurements when the scattered signal is weak as a result of low electron number density, poor optical access to the plasma, or both. Photon counting methods are often implemented in order to perform measurements in these low signal conditions. However, photon counting measurements performed with photo-multiplier tubes are time consuming and multi-photon arrivals are incorrectly recorded. In order to overcome these shortcomings a new data analysis method based on maximum likelihood estimation was developed. The key feature of this new data processing method is the inclusion of non-arrival events in determining the scattered Thomson signal. Maximum likelihood estimation and its application to Thomson scattering at low signal levels is presented and application of the new processing method to LTS measurements performed in the plume of a 2-kW Hall-effect thruster is discussed.

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High-resolution electron density and temperature maps of a microwave plasma torch measured with a 2-D Thomson scattering system

Cited by 34 publications

References 19 publications

Electron characterization in weakly ionized collisional plasmas: from principles to techniques

Electron characterization in weakly ionized collisional plasmas: from principles to techniques

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

Application of maximum likelihood methods to laser Thomson scattering measurements of low density plasmas

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High-resolution electron density and temperature maps of a microwave plasma torch measured with a 2-D Thomson scattering system

Cited by 34 publications

References 19 publications

Electron characterization in weakly ionized collisional plasmas: from principles to techniques

Electron characterization in weakly ionized collisional plasmas: from principles to techniques

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

Application of maximum likelihood methods to laser Thomson scattering measurements of low density plasmas

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