Benchmarked and upgraded particle-in-cell simulations of a capacitive argon discharge at intermediate pressure: the role of metastable atoms

2021 ◽  
Author(s):  
De-Qi Wen ◽  
Janez Krek ◽  
Jon Tomas Gudmundsson ◽  
Emi Kawamura ◽  
Michael A. Lieberman ◽  
...  
Keyword(s):  
Particle In Cell ◽  
Intermediate Pressure ◽  
Argon Discharge

Surface effects in a capacitive argon discharge in the intermediate pressure regime

2021 ◽  
Author(s):  
Jon Tomas Gudmundsson ◽  
Janez Krek ◽  
De-Qi Wen ◽  
Emi Kawamura ◽  
Michael A Lieberman
Keyword(s):  
Excited States ◽  
Electron Emission ◽  
Secondary Electron ◽  
Secondary Electron Emission ◽  
Plasma Sheath ◽  
Secondary Electrons ◽  
Particle In Cell ◽  
Argon Discharge ◽  
Discharge Operation ◽  
Ion Impact

Abstract One-dimensional particle-in-cell/Monte Carlo collisional (PIC/MCC) simulations are performed on a capacitive 2.54 cm gap, 1.6 Torr argon discharge driven by a sinusoidal rf current density amplitude of 50 A/m2 at 13.56 MHz. The excited argon states (metastable levels, resonance levels, and the 4p manifold) are modeled self-consistently with the particle dynamics as space- and time-varying fluids. Four cases are examined, including and neglecting excited states, and using either a fixed or energy-dependent secondary electron emission yield due to ion and/or neutral impact on the electrodes. The results for all cases show that most of the ionization occurs near the plasma-sheath interfaces, with little ionization within the plasma bulk region. Without excited states, secondary electrons emitted from the electrodes are found to play a strong role in the ionization process. When the excited states, secondary electron emission due to neutral and ion impact on the electrodes are included in the discharge model, the discharge operation transitions from α-mode to γ-mode, in which nearly all the ionization is due to secondary electrons. Excited states are very effective in producing secondary electrons, with approximately 14.7 times the contribution of ion bombardment. Electron impact of ground state argon atoms by secondary electrons contributes about 76 % of the total ionization; primary electrons, about 11 %; metastable Penning ionization, about 13 %; and multi-step ionization, about 0.3 %.

Benchmarked and Upgraded Particle-in-Cell Simulations Treating Excited State Atoms as a Fluid in Argon Discharge

2021 ◽  
Author(s):  
De-Qi Wen ◽  
Janez Krek ◽  
Jon T. Gudmundsson ◽  
Emi Kawamura ◽  
Michael A. Lieberman ◽  
...  
Keyword(s):  
Excited State ◽  
Particle In Cell ◽  
Argon Discharge

The Reiner Gamma Swirl and Magnetic Anomaly: Why We Should Go There

2020 ◽  
Author(s):  
Jan Deca
Keyword(s):  
Solar Wind ◽  
Lunar Regolith ◽  
Particle In Cell ◽  
Magnetic Field Model ◽  
Flux Profile ◽  
Favorable Conditions ◽  
Human Exploration ◽  
Orbiting Spacecraft ◽  
Prime Target

<p>All lunar swirls are known to be co-located with crustal magnetic anomalies (LMAs). Not all LMAs can be associated with albedo markings, making swirls, and their possible connection with the former, an intriguing puzzle yet to be solved.</p><p>Given favorable conditions, an LMA can deflect the solar wind enough to form a mini-magnetosphere that partially (and possibly only temporarily) shields the underlying lunar regolith. Recent modeling efforts have shown that the resulting energy flux pattern to the surface is consistent with the underlying albedo (swirl) patterns. In particular, coupling a fully kinetic particle-in-cell code with a downward-continued magnetic field model based on orbital-altitude observations, we are able to produce a pattern similar to Reiner Gamma’s alternating bright and dark bands, but only when integrating over the full lunar orbit. Although consistent with the solar-wind standoff hypothesis for the origin of swirls, the match is not perfect. A combination of reasons could be the cause.</p><p>Here we discuss some of the unexplained discrepancies between the flux profile and the surface brightness and why the Reiner Gamma swirl region should be a prime target for future low-orbiting spacecraft or even landers/rovers, and we consider the potential role of human exploration.</p>

Polarization dependence of optical harmonic generation from solid targets at high intensities: Role of Faraday rotation

2002 ◽  
Vol 80 (2) ◽  
pp. 173-177
Author(s):  
S Wu ◽  
R -J Zhan ◽  
J Chen
Keyword(s):  
Magnetic Field ◽  
Faraday Rotation ◽  
Short Pulse ◽  
Yield Ratio ◽  
Particle In Cell ◽  
Cell Simulation ◽  
Optical Harmonic Generation ◽  
Optical Harmonic ◽  
Good Agreement

In this letter, we show that the Faraday rotation effect of the strong spontaneous magnetic field generated by the focus of a short-pulse, high-power laser interacting with a solid target may blur out the distinction between the s and p polarization of the incident laser. This in effect leads to the result that the harmonic yield ratio between p and s polarization is not as large as a PIC (particle-in-cell) simulation predicted. An approximate calculation of the harmonic yield ratio versus the magnetic field is carried out and the result is in relatively good agreement with the observations by Norreys et al. PACS Nos.: 42.90, 78.90

scholarly journals Conditions for the onset of the current filamentation instability in the laboratory

2018 ◽  
Vol 84 (3) ◽  
Author(s):  
N. Shukla ◽  
J. Vieira ◽  
P. Muggli ◽  
G. Sarri ◽  
R. Fonseca ◽  
...  
Keyword(s):  
Minor Role ◽  
Beam Emittance ◽  
Particle In Cell ◽  
Electron Positron ◽  
Astrophysical Objects ◽  
Filamentation Instability ◽  
Radiation Processes ◽  
A Minor ◽  
Stream Instability

The current filamentation instability (CFI) is capable of generating strong magnetic fields relevant to the explanation of radiation processes in astrophysical objects and leads to the onset of particle acceleration in collisionless shocks. Probing such extreme scenarios in the laboratory is still an open challenge. In this work, we investigate the possibility of using neutral$e^{-}~e^{+}$beams to explore the CFI with realistic parameters, by performing two-dimensional particle-in-cell simulations. We show that CFI can occur unless the rate at which the beam expands due to finite beam emittance is larger than the CFI growth rate and as long as the role of the competing electrostatic two-stream instability (TSI) is negligible. We also show that the longitudinal energy spread, typical of plasma-based accelerated electron–positron fireball beams, plays a minor role in the growth of CFI in these scenarios.

scholarly journals The Role of Magnetic Islands in Collisionless Driven Reconnection: A Kinetic Approach to Multi-Scale Phenomena

Plasma ◽  
2018 ◽  
Vol 1 (1) ◽  
pp. 68-77 ◽  
Author(s):  
Ritoku Horiuchi
Keyword(s):  
Steady State ◽  
Energy Gap ◽  
Energy Dissipation Rate ◽  
Particle Energy ◽  
Kinetic Approach ◽  
Magnetic Islands ◽  
Magnetic Island ◽  
Particle In Cell ◽  
Multi Scale

The role of magnetic islands in collisionless driven reconnection has been investigated from the standpoint of a kinetic approach to multi-scale phenomena by means of two-dimensional particle-in-cell (PIC) simulation. There are two different types of the solutions in the evolution of the reconnection system. One is a steady solution in which the system relaxes into a steady state, and no island is generated (the no-island case). The other is an intermittent solution in which the system does not reach a steady state, and magnetic islands are frequently generated in the current sheet (the multi-island case). It is found that the electromagnetic energy is more effectively transferred to the particle energy in the multi-island case compared with the no-island case. The transferred energy is stored inside the magnetic island in the form of the thermal energy through compressional heating, and is carried away together with the magnetic island from the reconnection region. These results suggest that the formation of a magnetic island chain may have a potential to bridge the energy gap between macroscopic and microscopic physics by widening the dissipation region and strengthening the energy dissipation rate.

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