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

Trunec, David; Bonaventura, Zdeněk; Zikin, P.; Jánský, Jaroslav

doi:10.1002/ctpp.201400046

Cited by 7 publications

(13 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This study extends our previous simulation-based investigation of probe currents from a spherical probe [14] to a cylindrical one. Cylindrical probes are more suited for plasma diagnostics than spherical ones, and, additionally, electron density measurements in high-pressure afterglow plasmas [15] using cylindrical probes are available.…”

supporting

confidence: 82%

“…The motion of charged particles was calculated in three dimensions using Cartesian coordinates, while the radial (1D) charge distribution was taken into account in the Poisson equation (taking advantage of the cylindrical symmetry). [14] A single simulation with 3 × 10 5 particles and with plasma parameters n 0 = 10 15 m −3 , T e = 10 4 K, T i = T g = 300 K, U p = 2 V, neutral gas pressure 2 Pa, r p = 10 m, and r d = 3 mm took 44 hr of CPU time in an eight-core Intel Xeon processor at 2.33 GHz with Message Passing Interface (MPI) parallelization to eight processes. Beyond the computational domain, an unperturbed plasma with electron density n e and ion density n i (n e = n i = n 0 ) was assumed.…”

Section: Pic/mc Modelmentioning

confidence: 99%

“…[14] This continuum model was solved only for a plasma consisting of electrons and argon ions (Ar + ) in a helium buffer gas. The flux j i for electrons and positive argon ions consists of diffusion −D i n i r and advection n i i E parts, where D i is the diffusion coefficient, i is the mobility, and E is the electric field E = − r .…”

Section: Continuum Modelmentioning

confidence: 99%

“…[14] 3 To capture the computational domain, a homogeneous mesh with 1,999 points and a mesh size of 10 m was used.…”

Section: Continuum Modelmentioning

confidence: 99%

“…The details of the PIC/MC model can be found in our previous study. [14] A single simulation with 3 × 10 5 particles and with plasma parameters n 0 = 10 15 m −3 , T e = 10 4 K, T i = T g = 300 K, U p = 2 V, neutral gas pressure 2 Pa, r p = 10 m, and r d = 3 mm took 44 hr of CPU time in an eight-core Intel Xeon processor at 2.33 GHz with Message Passing Interface (MPI) parallelization to eight processes. After this computational time, a stationary solution was reached.…”

Section: Pic/mc Modelmentioning

confidence: 99%

See 4 more Smart Citations

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

View full text Add to dashboard Cite

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.

show abstract

supporting

confidence: 82%

Section: Pic/mc Modelmentioning

confidence: 99%

Section: Continuum Modelmentioning

confidence: 99%

“…[14] 3 To capture the computational domain, a homogeneous mesh with 1,999 points and a mesh size of 10 m was used.…”

Section: Continuum Modelmentioning

confidence: 99%

Section: Pic/mc Modelmentioning

confidence: 99%

See 3 more Smart Citations

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

View full text Add to dashboard Cite

show abstract

Study of “source sheath” problem in PIC/MC simulation: Spherical geometry

et al. 2017

View full text Add to dashboard Cite

A method for treatment of boundary conditions and particle loading in a self-consistent semi-infinite Particle-In-Cell/Monte Carlo simulation is presented. A non-ionizing, collisional plasma in contact with an electrode was assumed. The simulation was performed for a spherical probe with constant probe potential. The motion of charged particles was calculated in three dimensions, but only the radial charge distribution and thus only radial electric field were assumed. The particle loading has to be done with an appropriate velocity distribution with a radial drift velocity. This drift velocity has to be calculated from the probe current, and therefore, a self-consistent (iterative) approach is necessary. Furthermore, correct values of particle densities and electric field potential at the outer boundary of the computational domain have to be set using asymptotic formulae for particle density and electric field potential. This approach removes the “source sheath” which is created artificially, if incorrect boundary conditions and velocity distributions of loaded particles are used. This approach is, however, feasible only for the case of a negative probe where asymptotic formulae are known.

show abstract

Accelerated steady-state electrostatic particle-in-cell simulation of Langmuir probes

et al. 2022

View full text Add to dashboard Cite

First-principles particle-in-cell (PIC) simulation is a powerful tool for understanding plasma behavior, but this power often comes at great computational expense. Artificially reducing the ion/electron mass ratio is a time-honored practice to reduce simulation costs. Usually, this is a severe approximation. However, for steady-state collisionless, electrostatic (Vlasov–Poisson) systems, the solution with reduced mass ratio can be scaled to the solution for the real mass ratio, with no approximation. This “scaled mass” method, which works with already-existing PIC codes, can reduce the computation time for a large class of electrostatic PIC simulations by the square root of the mass ratio. The particle distributions of the resulting steady state must be trivially rescaled to yield the true distributions, but the self-consistent electrostatic field is independent of the mass ratio. This method is equivalent to “numerical timestepping,” an approach that evolves electron and ion populations with different time steps. Numerical timestepping can be viewed as a special case of the speed-limited PIC (SLPIC) method, which is not restricted to steady-state phenomena. Although the scaled-mass approach is simplest, numerical timestepping and SLPIC more easily generalize to include other effects, such as collisions. The equivalence of these new approaches is demonstrated by applying them to simulate a cylindrical Langmuir probe in electron–argon plasma, speeding up simulation by two orders of magnitude. Methods such as SLPIC can therefore play an invaluable role in interpreting probe measurements by including geometric effects, collisions, secondary emission, and non-Maxwellian distributions.

show abstract

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

Cited by 7 publications

References 36 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

Study of “source sheath” problem in PIC/MC simulation: Spherical geometry

Accelerated steady-state electrostatic particle-in-cell simulation of Langmuir probes

Contact Info

Product

Resources

About