RF power absorption by plasma of a low-pressure inductive discharge

Kralkina, E.A.; Rukhadze, A. A.; Pavlov, V.B.; Вавилин, К. В.; Nekliudova, P. A.; Petrov, A. K.; Alexandrov, A.F.

doi:10.1088/0963-0252/25/1/015016

Cited by 29 publications

(37 citation statements)

References 27 publications

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“…The observed behaviour is in general well comparable to the results of the power transfer efficiency of noble gas discharges that have been reported several times, e.g. by [5,8,25]. The results presented in Figure 2 are further examined by the analytical considerations described in section 2, thereby taking into account the measured plasma parameters and the relevant electron heating mechanisms.…”

Section: Rf Power Transfer Efficiency In Hsupporting

confidence: 86%

RF power transfer efficiency of inductively coupled low pressure H₂and D₂discharges

Rauner

Briefi

Fantz

2017

Plasma Sources Sci. Technol.

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The RF power transfer efficiency and the relevant power absorption mechanisms of inductively heated hydrogen and deuterium plasmas are investigated in the low-pressure region between 0.25 and 10 Pa. The discharges are generated in a cylindrical vessel via a helical coil applying a frequency of 1 MHz and delivered RF powers up to 800 W. The power transfer efficiency η is quantified by a subtractive method that relies on the measurement of the delivered RF power and of the RF current through the plasma coil both with and without discharge operation. By means of optical emission spectroscopy and electrical probe measurements, the key plasma parameters are obtained. For both H 2 and D 2 , the relative behaviour of the power transfer efficiency is well comparable, which increases with increasing delivered RF power and describes a maximum at pressures between 1 and 3 Pa where more than 90 % of the provided power are absorbed by the plasma. The observed relative dependencies of η on the operational parameters are found to be well explained by an analytical approach that considers the power absorption by the plasma via evaluating the RF plasma conductivity based on the measured plasma parameters. At the parameters present, non-collisional stochastic heating of electrons has to be considered for pressures p ≤ 1 Pa, while collisional heating dominates at higher pressure. Molecular dissociation is found to have a significant influence on the power transfer efficiency of light molecular discharges. The direct comparison of H 2 and D 2 identifies the higher atomic density in deuterium to cause a systematically increased power transfer efficiency due to an increased ionization rate in the present electron temperature region.

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Section: Rf Power Transfer Efficiency In Hsupporting

confidence: 86%

RF power transfer efficiency of inductively coupled low pressure H₂and D₂discharges

Rauner

Briefi

Fantz

2017

Plasma Sources Sci. Technol.

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“…Consequently, the pressure dependency of η is inverse to the RF current, reaching its maximum of 85 % between 1 and 3 Pa. Analogously, with increasing current at lower and higher pressure the ohmic losses increase and the coupling efficiency decreases, reaching its minimum of only 50 % at 0.3 Pa. However, this low value is only valid for this experiment at the fixed delivered power of 520 W. Further investigations which are not presented here indicate an increase of η at low pressures with increasing RF power, an observation which has also been made in other discharges [4,5] Generally, a comparable pressure dependant behaviour of the coupling efficiency is known from various investigations using different inert gases [4,5,18]. Typically, a maximum of the RF coupling efficiency and power absorption by the plasma is expected for the case when the effective electron collision frequency ν e equals the excitation frequency ω RF , which corresponds to the maximum of the real part of the RF plasma conductivity [19,4].…”

Section: Coupling Efficiency and Plasma Parameterssupporting

confidence: 50%

Investigation of the RF efficiency of inductively coupled hydrogen plasmas at 1 MHz

Rauner

Mattei

Briefi

et al. 2017

AIP Conference Proceedings

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Abstract. The power requirements of RF heated sources for negative hydrogen ions in fusion are substantial, which poses strong demands on the generators and components of the RF circuit. Consequently, an increase of the RF coupling efficiency would be highly beneficial. Fundamental investigations of the RF efficiency in inductively coupled hydrogen and deuterium discharges in cylindrical symmetry are conducted at the lab experiment CHARLIE. The experiment is equipped with several diagnostics including optical emission spectroscopy and a movable floating double probe to monitor the plasma parameters. The presented investigations are performed in hydrogen at a varying pressure between 0.3 and 10 Pa, utilizing a conventional helical ICP coil driven at a frequency of 1 MHz and a fixed power of 520 W for plasma generation. The coupling efficiency is strongly affected by the variation in pressure, reaching up to 85 % between 1 and 3 Pa while dropping down to only 50 % at 0.3 Pa, which is the relevant operating pressure for negative hydrogen ion sources for fusion. Due to the lower power coupling, also the measured electron density at 0.3 Pa is only 5 · 10 16 m −3 , while it reaches up to 2.5 · 10 17 m −3 with increasing coupling efficiency. In order to gain information on the spatially resolved aspects of RF coupling and plasma heating which are not diagnostically accessible, first simulations of the discharge by an electromagnetic Particle-In-Cell Monte Carlo collision method have been conducted and are compared to the measurement data. At 1 Pa, the simulated data corresponds well to the results of both axially resolved probe measurements and radially resolved emission profiles obtained via OES. Thereby, information regarding the radial distribution of the electron density and mean energy is provided, revealing a radial distribution of the electron density which is well described by a Bessel profile.

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“…e early works [7][8][9] used to support the findings of this study are available from the corresponding author upon request.…”

Section: Data Availabilitymentioning

confidence: 99%

“…erefore, particle-in-cell (PIC) method is used for simulation of the inductive coupled radio-frequency (ICRF) discharge plasma to analyze the mechanism of power absorption in the pressure range from 1.33•10 −2 to 13.3 Pa [7,8].…”

Section: Introductionmentioning

confidence: 99%

“…Maxwell's equations are usually reduced to vector and scalar potential equations [9] or reduced to a wave equation [10] or analyzed in conditions of neglecting the radial components of the magnetic field [11]. Poisson's equation is used for calculation of the electric field strength in [7,8]. 2D Maxwell's equations for ICRF discharge in the pressure range from 13.3 to 133 Pa and are reduced to a system of elliptical equations for the modulus, phase and angle functions of the magnetic field, and electric strength vectors in [6].…”

Section: Introductionmentioning

confidence: 99%

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Mathematical Modelling of RF Plasma Flow at Low Pressures with 3D Electromagnetic Field

Shemakhin

Желтухин

2019

Advances in Materials Science and Engineering

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In this study, a hybrid mathematical model of a low-pressure RF plasma jet in transition mode between continuum and free molecular flow at a Knudsen number of 8·10−3 ≤ Kn ≤ 7·10−2 for a carrying gas is described. The model takes electrons, ions, metastable atoms, and potential and curl electromagnetic fields into account. The model is based on both a statistical approach for the atoms in the ground state and a continuum model for other components. The results of plasma flow calculations in an undisturbed jet are described. The distributions of the electrodynamic and electrostatic parts of the electric field are given. It has been observed that the plasma jet has a layered structure along the stream: a positive charge region is formed at the beginning of the jet, followed by a negative charge region, and then a positive one again. The reason for the formation of a layered structure is the fast flow expansion when the plasma inflows into the vacuum and the difference in electron and ion pulse.

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RF power absorption by plasma of a low-pressure inductive discharge

Cited by 29 publications

References 27 publications

RF power transfer efficiency of inductively coupled low pressure H₂and D₂discharges

RF power transfer efficiency of inductively coupled low pressure H₂and D₂discharges

Investigation of the RF efficiency of inductively coupled hydrogen plasmas at 1 MHz

Mathematical Modelling of RF Plasma Flow at Low Pressures with 3D Electromagnetic Field

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RF power absorption by plasma of a low-pressure inductive discharge

Cited by 29 publications

References 27 publications

RF power transfer efficiency of inductively coupled low pressure H2and D2discharges

RF power transfer efficiency of inductively coupled low pressure H2and D2discharges

Investigation of the RF efficiency of inductively coupled hydrogen plasmas at 1 MHz

Mathematical Modelling of RF Plasma Flow at Low Pressures with 3D Electromagnetic Field

Contact Info

Product

Resources

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RF power transfer efficiency of inductively coupled low pressure H₂and D₂discharges

RF power transfer efficiency of inductively coupled low pressure H₂and D₂discharges