Emission Spectroscopy of Molecular Low Pressure Plasmas

Fantz, U.

doi:10.1002/ctpp.200410072

Cited by 50 publications

(47 citation statements)

References 9 publications

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“…These emission lines ride on strong continuum from the , and the other large impurity emissions are not observed around these spectra. We also estimate the hydrogen gas temperature as 2200 K±300 K by the rotational structure of the hydrogen molecular emissions [9], and typical H/H 2 ratio is estimated as 0.35 from the ratio of the Hγ emission and H 2 emissions. We also check the neutral tungsten line (WI 400.9 nm) from the evaporation of the tungsten filament, but it is not observed in our ion source.…”

Section: Langmuir Probementioning

confidence: 99%

Observation of Hydrogen and Cesium Spectra in a Negative Ion Source for a Neutral Beam Injector using a Multi-Channel Spectrometer

Ikeda

Fantz

Nagaoka

et al. 2007

Plasma and Fusion Research

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Effective production of hydrogen negative ions (H − ) is one of the important issues in high power neutral beam injection (NBI) for fusion experimental devices. Cesium (Cs) vapor is seeded in the H − sources to enhance the H − production rate, which depends strongly on the amount of Cs inside the source. On the other hand, oxygen and water attenuate the production rate. In order to investigate the states of those species inside ion source, we have installed two multi-channel spectrometer systems with different spectral resolution. Hydrogen emissions, Cs emissions and oxygen emission are clearly observed with the time resolution of several handled milliseconds. Most of evaporated Cs atoms ionize in arc discharge plasma, and the emission increases strongly due to the ion back streaming with beam extraction. Oxygen neutral emission increases at the beginning of the beam conditioning, and its evaporation depends on the condition of the grid system.

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Section: Langmuir Probementioning

confidence: 99%

Observation of Hydrogen and Cesium Spectra in a Negative Ion Source for a Neutral Beam Injector using a Multi-Channel Spectrometer

Ikeda

Fantz

Nagaoka

et al. 2007

Plasma and Fusion Research

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“…Therefore, a method for determining the gas temperature in low-temperature nitrogen plasmas will be presented in the following. A frequently used method is the measurement of the rotational temperature of the excited state C 3 Π u of the N 2 molecule [20][21][22][23][24][25] . In the following the correlation between T N 2 rot and T g as well as the determination of T N 2 rot from the line intensity of the rotational spectrum will be presented.…”

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confidence: 99%

Wall loss of atomic nitrogen determined by ionization threshold mass spectrometry

Sode

Schwarz-Selinger

Jacob

et al. 2014

Journal of Applied Physics

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In the afterglow of an inductively coupled N 2 plasma relative N atom densities are measured by ionization threshold mass spectrometry (ITMS) as a function of time in order to determine the wall loss time t wN from the exponential decay curves. The procedure is performed with two mass spectrometers on different positions in the plasma chamber. t wN is determined for various pressures, i.e., for 3.0, 5.0, 7.5, and 10 Pa. For this conditions also the internal plasma parameters electron density n e and electron temperature T e are determined with the Langmuir probe and the rotational temperature T N 2 rot of N 2 is determined with the optical emission spectroscopy. For T N 2 rot a procedure is presented to evaluate the spectrum of the transition v' = 0 → v" = 2 of the second positive system (C 3 Π u → B 3 Π g ) of N 2 . With this method a gas temperature of 610 K is determined. For both mass spectrometers an increase of the wall loss times of atomic nitrogen with increasing pressure is observed. The wall loss time measured with the first mass spectrometer in the radial center of the cylindrical plasma vessel increases linearly from 0.31 ms for 3 Pa to 0.82 ms for 10 Pa. The wall loss time measured with the second mass spectrometer (further away from the discharge) is about 4 times higher. A model is applied to describe the measured t wN .The main loss mechanism of atomic nitrogen for the considered pressure is diffusion to the wall. The surface loss probability β N of atomic nitrogen on stainless steel was derived from t wN and is found to be 1 for the present conditions. The difference in wall loss times measured with the mass spectrometers on different positions in the plasma chamber is attributed to the different diffusion lengths.

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“…the calculated ratio of the emission of two Balmer lines is adjusted to the measured ratio. This method was described in [6,18,40] for the determination of the dissociation degree, in [41] for the electron density and in [24] for the density of the negative hydrogen ion. For further verification of the smoothing procedure the line ratio H β /H γ was used to determine the electron density for all pressures.…”

Section: Resultsmentioning

confidence: 99%

Application of a collisional radiative model to atomic hydrogen for diagnostic purposes

Wünderlich

Dietrich

Fantz

2009

Journal of Quantitative Spectroscopy and Radiative Transfer

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Optical emission spectroscopy is one of the standard diagnostic methods to determine plasma parameters. In hydrogen plasmas often the intensity of the Balmer lines is recorded. To analyze such measurements population models for the hydrogen atom are needed. The flexible package Yacora is used to construct a new collisional radiative model for low pressure, low temperature hydrogen plasmas. This model includes six possible excitation channels: effective excitation of H, recombination of H + , dissociative excitation of H 2 , dissociative recombination of H + 2 , dissociative recombination of H + 3 and mutual neutralization of H − and H + x . The model is applied to an uniform ECR plasma with high dissociation degree and low ionization degree, i.e. electron collision excitation from H is the dominant excitation channel. The cross sections for this channel taken from literature showed a non-physical discontinuity at electron energies close to the threshold energy. This discontinuity has been removed by using a smoothing procedure. For known plasma parameters the deviation between measured and calculated population densities decreases significantly by using the smoothed data. Furthermore the agreement of the electron density deduced from the ratio H β /H γ with results of other diagnostic methods is enhanced dramatically.

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Emission Spectroscopy of Molecular Low Pressure Plasmas

Cited by 50 publications

References 9 publications

Observation of Hydrogen and Cesium Spectra in a Negative Ion Source for a Neutral Beam Injector using a Multi-Channel Spectrometer

Observation of Hydrogen and Cesium Spectra in a Negative Ion Source for a Neutral Beam Injector using a Multi-Channel Spectrometer

Wall loss of atomic nitrogen determined by ionization threshold mass spectrometry

Application of a collisional radiative model to atomic hydrogen for diagnostic purposes

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