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.

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 the voltage drop on a high-current vacuum arc discharge under conditions of a limited cross-section of the plasma flow

2021 ◽  
Vol 2064 (1) ◽  
pp. 012019
Author(s):  
A G Rousskikh ◽  
A S Zhigalin ◽  
V I Oreshkin ◽  
P Artyomov
Keyword(s):  
Cross Section ◽  
Plasma Flow ◽  
Voltage Drop ◽  
Arc Discharge ◽  
Vacuum Arc ◽  
High Current ◽  
Plasma Gun ◽  
Flow Through ◽  
Arc Current

Abstract The work is devoted to the study of the high-current vacuum arc discharge characteristics under conditions of a limited cross-section of the plasma flow. The experiments were carried out on the IMRI-5 setup with a sinusoidal arc current amplitude of 300–350 kA and a rise time of 500 ns. Aluminum rods with diameters from 3 to 7 mm were used as a cathode. The plasma flow was formed in a channel whose diameter was equal to that of the cathode. The features of the formation of a plasma jet with various configurations of the used plasma gun are described. The electrophysical parameters of the arc discharge are presented. Theoretical estimates of the voltage drop across the high-current arc during the outflow of a plasma flow through holes with a limited diameter are provided.

scholarly journals Population Kinetics Modeling of Low-Temperature Argon Plasma

Atoms ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 100
Author(s):  
Hyun-Kyung Chung ◽  
Mi-Young Song ◽  
Ji-Won Kwon ◽  
Myeong-Geon Lee ◽  
Jihoon Park ◽  
...  
Keyword(s):  
Low Temperature ◽  
Plasma Diagnostics ◽  
Argon Plasma ◽  
Optical Emission ◽  
Plasma Radiation ◽  
Temperature Plasma ◽  
Single Temperature ◽  
Collisional Radiative Model ◽  
Radiative Model ◽  
Measured Line

Optical emission spectroscopy has been widely used in low-temperature argon plasma diagnostics. A coronal model is usually used to analyze the measured line ratios for diagnostics with a single temperature and density. However, many plasma processing conditions deviate from single temperature and density, optically thin conditions, or even coronal plasma conditions due to cascades from high-lying states. In this paper, we present a collisional-radiative model to investigate the validity of coronal approximations over a range of plasma conditions of Te = 1–4 eV and Ne = 108–1013 cm−3. The commonly used line ratios are found to change from a coronal limit where they are independent of Ne to a collisional-radiative regime where they are not. The effects of multiple-temperature plasma, radiation trapping, wall neutralization, and quenching on the line ratios are investigated to identify the plasma conditions under which these effects are significant. This study demonstrates the importance of the completeness of atomic datasets in applying a collisional-radiative model to low-temperature plasma diagnostics.

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