Determination of electron temperature and density at plasma edge in the Large Helical Device with opacity-incorporated helium collisional-radiative model

2014 ◽  
Vol 137 ◽  
pp. 23-28 ◽  
Author(s):  
M. Goto ◽  
K. Sawada
Keyword(s):  
Electron Temperature ◽  
Plasma Edge ◽  
Collisional Radiative Model ◽  
Radiative Model

Collisional radiative model for the evaluation of the Thermal Helium Beam diagnostic at ASDEX Upgrade

2022 ◽  
Author(s):  
Daniel Wendler ◽  
Ralph Dux ◽  
Rainer Fischer ◽  
Michael Griener ◽  
Elisabeth Wolfrum ◽  
...  
Keyword(s):  
Excited States ◽  
Ultra Violet ◽  
Plasma Edge ◽  
Excitation Mechanism ◽  
Computationally Efficient ◽  
Injection Point ◽  
Collisional Radiative Model ◽  
Radiative Model ◽  
Measured Line ◽  
Vacuum Ultra Violet

Abstract The thermal helium beam diagnostic at ASDEX Upgrade is used to infer the electron density ne and temperature Te in the scrape-off layer and the pedestal region from the emission of visible lines of the locally injected helium. The link between ne and Te and the emission is provided by a collisional radiative model, which delivers the evolution of the populations of the relevant excited states as the He atoms travel through the plasma. A computationally efficient method with just three effective states is shown to provide a good approximation of the population dynamics. It removes an artificial rise of Te at the plasma edge when using a simple static model. Furthermore, the re-absorption of the vacuum ultra-violet resonance lines has been introduced as additional excitation mechanism being mainly important in the region close to the injection point. This extra excitation leads to a much better fit of the measured line ratios in this region for larger puff rates.

scholarly journals Spectroscopy in Ne-Like Plasmas. Z-Dependence of the Atomic Data Used in a Collisional-Radiative Model

1988 ◽  
Vol 102 ◽  
pp. 95-97
Author(s):  
M. Cornille ◽  
J. Dubau ◽  
M. Loulergue ◽  
S. Jacquemot
Keyword(s):  
Radiative Decay ◽  
Dielectronic Recombination ◽  
Rate Coefficients ◽  
Atomic Data ◽  
Collisional Radiative Model ◽  
Radiative Model ◽  
Structure Scheme ◽  
Distorted Waves ◽  
Laser Experiments

AbstractThe Livermore X-ray Laser experiments in 1984 have shown the existence of Ne-like 3p-3s population inversions in a collisional Se plasma (Z=34) with significant gains (5 cm-1). We have focused our efforts on the behavior of the gains along the target neon Isoelectronic sequence. This study implies the determination of the Z-dependance of the rate coefficients of all the Involved atomic processes: collisional excitation (C). radiative decay (A) and dielectronic recombination (αd). Thus we use atomic structure and electron-ion collisional codes (SUPERSTRUCTURE. Distorted Waves. AUTOLSJ and JJOM). The different calculations have been done on a large selection of ions, from Ar to Ag. They Include relatlvistic effects in a fine structure scheme. The Z-dependance of the numerical results is expressed as polynomial or rational forms.

scholarly journals Determination of positive anode sheath in anodic carbon arc for synthesis of nanomaterials

2021 ◽  
Author(s):  
Nirbhav Singh Chopra ◽  
Yevgeny Raitses ◽  
Shurik Yatom ◽  
Jorge M Muñoz Burgos
Keyword(s):  
Voltage Drop ◽  
Optical Emission ◽  
Physical Mechanisms ◽  
Carbon Arc ◽  
Collisional Radiative Model ◽  
Radiative Model ◽  
Arc Current ◽  
Anode Sheath ◽  
Probe Measurements

Abstract . In the atmospheric pressure anodic carbon arc, ablation of the anode serves as a feedstock of carbon for production of nanomaterials. It is known that the ablation of the graphite anode in this arc can have two distinctive modes with low and high ablation rates. The transition between these modes is governed by the power deposition at the arc attachment to the anode and depends on the gap between the anode and the cathode electrodes. Probe measurements combined with optical emission spectroscopy (OES) are used to analyze the voltage drop between the arc electrodes. These measurements corroborated previous predictions of a positive anode sheath (i.e. electron attracting sheath) in this arc, which appears in both low and high ablation modes. However, the positive anode sheath was determined to be ~3-8 V, significantly larger than ~0.5 V predicted by previous models. Thus, there are apparently other physical mechanisms not considered by these models that force the anode sheath to be electron attracting in both ablation regimes. Another key result is a relatively low electron temperature (~ 0.6 eV) obtained from OES using a collisional radiative model. This result partially explains a higher arc voltage (~ 20 V) required to sustain the arc current of 50-70 A than predicted by existing simulations of this discharge.

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