Influence of Plasma‐Neutral Collisions on Probe Measurements in Atmospheric Pressure Plasmas

Ezumi, N.; Takahashi, Koki; Yoshida, Takehiko; Hatada, Y.; Hayashi, Y.; Uchiyama, Chizuru; Iio, Shouichiro; Sawada, Keiji; Ohno, Noriyasu; Kiss’ovski, Zh

doi:10.1002/ctpp.201410074

Cited by 3 publications

(3 citation statements)

References 6 publications

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“…The differences in the results of PIC/MC and fluid model were also observed in other recent studies. However, for v p = 80 ms −1 and the other parameters given above, the probe current according to Equation (8) exceeds I t at probe voltages above 0.45 V. Considering that electron probe currents higher than I t were measured in the experiment, there has to be an electric field along the flow tube axis that increases the electron drift velocity above v p . It is interesting to compare our simulation results with experimental results obtained in a flowing high-pressure afterglow.…”

Section: Resultsmentioning

confidence: 90%

“…[28] The correct probe theory is, therefore, important for the FALP method. at r s ), err OMLs is the error of Equation (8) and, err OMLe is the error of Equation (6). The probe radius of 10 m corresponds to the radius of cylindrical probes used in FALP experiments.…”

Section: Resultsmentioning

confidence: 99%

“…1 PIC/MC simulations [2][3][4][5][6][7][8] PIC/MC simulations provide the most accurate description of reality; however, the simulations are time consuming. The PIC/MC simulations also provide information about particle density profiles, electric potential, and other physical quantities near the probe.…”

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Particle‐in‐cell/Monte Carlo simulation of electron and ion currents to cylindrical Langmuir probe

Zikán

Farkaš

Trunec

et al. 2018

Contributions to Plasma Physics

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Electron and ion currents to a cylindrical Langmuir (electrostatic) probe were calculated using the particle-in-cell/Monte Carlo (PIC/MC) self-consistent simulation for a neutral gas in the pressure range 2-3,000 Pa. The simulation enables us to calculate the probe currents even at high neutral gas pressures when the collisions of collected charged particles with neutral gas particles near the probe are important. The main aim of this paper is the calculation of probe currents at such high gas pressures and the comparison of the results with experimentally measured probe currents. Simulations were performed for two cases: (a) probes with varying radii in a non-thermal plasma with high electron temperature at low neutral gas pressure of 2 Pa (in order to verify the correctness of our simulations), and (b) probe with the radius of 10 m in the afterglow plasma with low electron temperature and a higher neutral gas pressure (up to 3,000 Pa). The electron probe currents obtained in case (a) show good agreement with those predicted by the orbital motion limited current (OMLC) theory for probes with radii up to 100 m for the given plasma conditions. At larger probe radii and/or at higher probe voltages, the OMLC theory incorrectly predicts too high an electron probe current for the plasma parameters studied. Additionally, a formula describing the spatial dependence of the electron density in the presheath in the collisionless case is derived. The simulation at higher neutral gas pressures, i.e. case (b), shows a decrease of the electron probe current with increasing gas pressure and the creation of a large presheath around the probe. The simulated electron probe currents are compared with those of measurements by other authors, and the differences are discussed. KEYWORDS Langmuir probe, PIC/MC simulation INTRODUCTIONParticle-in-cell/Monte Carlo (PIC/MC) simulation provides the most accurate and reliable tool for the calculation of electron and ion currents to a Langmuir (electrostatic) probe. The calculation of probe currents (probe theory) is necessary for the determination of electron and ion densities, electron temperatures, and electron energy distribution functions from probe measurements. Most of the analytical calculations of probe currents have been carried out under the assumption of a collisionless movement of charged particles around the probe [1] and can, therefore, be applied without error only to low-pressure plasmas.There is no widely accepted theory of probe currents for medium-pressure and high-pressure plasmas where the charged particles do collide with neutral particles in the sheath and presheath around the probe. Therefore, the probe measurements cannot be used for such plasmas. There exist three groups of collisional probe theories.

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Section: Resultsmentioning

confidence: 90%

Section: Resultsmentioning

confidence: 99%

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Particle‐in‐cell/Monte Carlo simulation of electron and ion currents to cylindrical Langmuir probe

Zikán

Farkaš

Trunec

et al. 2018

Contributions to Plasma Physics

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PIC/MCC Simulation of Electron and Ion Currents to Spherical Langmuir Probe

Trunec

Bonaventura

Zikin

et al. 2015

Contrib. Plasma Phys.

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The Particle In Cell/Monte Carlo Collisions (PIC/MCC) simulation was used for the calculation of electron and ion currents to a spherical Langmuir (electrostatic) probe. This simulation took into account the collisions of collected charged particles with neutral gas particles around the probe and it can calculate the probe currents at higher neutral gas pressures. The improvements of usual simulation techniques enabled to speed up the simulation and to calculate the probe current even for neutral gas pressures above 1 kPa. The simulations were carried out for two cases: i) probe with radius of 0.5 mm in non‐thermal plasma with high electron temperature, ii) probe with radius of 10 µm in afterglow plasma with low electron temperature. The influence of probe radius on electron probe current was also studied. The simulations showed that thick sheath limit of OML theory provides incorrect values of probe current for probes with radii larger than 200 µm at plasma parameters considered even at very low neutral gas pressures. The probe characteristics were calculated for probe with 0.5 mm radius for pressures up to 500 Pa and for probe with 10 μm radius for pressures up to 3 kPa. The influence of collisions on electron and ion probe current was demonstrated and the procedure for determination of electron and ion densities from the probe measurement at higher pressures was developed. The results from PIC/MCC simulations were compared with results from continuum theory. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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The energy tree: Non-equilibrium energy transfer in collision-dominated plasmas

Ostrikov

Sun

2018

Physics Reports

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Influence of Plasma‐Neutral Collisions on Probe Measurements in Atmospheric Pressure Plasmas

Cited by 3 publications

References 6 publications

Particle‐in‐cell/Monte Carlo simulation of electron and ion currents to cylindrical Langmuir probe

Particle‐in‐cell/Monte Carlo simulation of electron and ion currents to cylindrical Langmuir probe

PIC/MCC Simulation of Electron and Ion Currents to Spherical Langmuir Probe

The energy tree: Non-equilibrium energy transfer in collision-dominated plasmas

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