Publication

Existence of subsonic plasma sheaths

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Simulations of plasma turbulence in a linear plasma device configuration are presented. These simulations are based on a simplified version of the gyrokinetic (GK) model proposed by Frei et al. [J. Plasma Phys. 86, 905860205 (2020)], where the full-F distr ...

Aip Publishing2024

Plasma sputtering of biased electrodes in an oblique magnetic field

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The surface erosion of biased electrodes immersed in a radio frequency (RF) plasma was investigated in oblique magnetic fields ranging from 0.1 T to 3.5 T. The plasma potential and density in the vicinity of the biased electrode have been measured using an ...

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Solar Wind Protons in the Diamagnetic Cavity at Comet 67P/Churyumov-Gerasimenko

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The plasma environment at a comet can be divided into different regions with distinct plasma characteristics. Two such regions are the solar wind ion cavity, which refers to the part of the outer coma that does not contain any solar wind ions anymore; and ...

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A Gyrokinetic Moment Model of the Plasma Boundary in Fusion Devices

Baptiste Jimmy Frei

The overall performance of fusion devices, such as tokamaks, is strongly correlated to the phenomena that occur in the boundary region, the outer plasma region that faces the wall of the device. The boundary plays a crucial role in regulating the heat and ...

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Vlasov simulation of the emissive plasma sheath with energy-dependent secondary emission coefficient and improved modeling for dielectric charging effects

Guang-Yu Sun

A one-dimensional Vlasov-Poisson simulation code is employed to investigate the plasma sheath considering electron-induced secondary electron emission (SEE) and backscattering. The SEE coefficient is commonly treated as constant in a range of plasma simula ...

FRONTIERS MEDIA SA2022

Sheath collapse at critical shallow angle due to kinetic effects

Alessandro Geraldini

The Debye sheath is known to vanish completely in magnetised plasmas for a sufficiently small electron gyroradius and small angle between the magnetic field and the wall. This angle depends on the current onto the wall. When the Debye sheath vanishes, ther ...

IOP Publishing Ltd2022

Gyrokinetic simulations of turbulence and zonal flows driven by steep profile gradients using a delta-f approach with an evolving background Maxwellian

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Long global gyrokinetic turbulence simulations are particularly challenging in situations where the system deviates strongly from its initial state and when fluctuation levels are high, for example, in strong gradient regions. For particle-in-cell simulati ...

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The influence of charge trap states in the dielectric boundary material on capacitively coupled radio-frequency (RF) plasma discharge is investigated with theory and particle-in-cell/Monte Carlo collision simulation. It is found that the trap states of the ...

2021

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Andrea Francesco Battaglia, Aleksi Antoine Bossart

Context. Observations show that small-scale vortical plasma motions are ubiquitous in the quiet solar atmosphere. They have received increasing attention in recent years because they are a viable candidate mechanism for the heating of the outer solar atmos ...

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Self-consistent simulation of multi-component plasma turbulence and neutral dynamics in the tokamak boundary

André Calado Coroado

The interaction between neutral particles and the plasma plays a key role in determining the dynamics of the tokamak boundary that, in turn, significantly impact the overall performance of the device. Leveraging the work in Wersal and Ricci [Nucl. Fusion 5 ...

EPFL2021

Edge turbulence in ISTTOK: a multi-code fluid validation

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Fluid models used to study the edge plasma region need to be benchmarked against similar conditions given that models can strongly differ in complexity and therefore the results they produce. Via this validation study undertaken through the framework of EU ...

2021

Shaping effects on scrape-off layer plasma turbulence: A rigorous validation of three-dimensional simulations against TCV measurements

Paolo Ricci, Fabio Riva, Cedric Kar-Wai Tsui

The effect of plasma shaping on scrape-off layer (SOL) plasma turbulence is investigated through a rigorous validation exercise. Two- and three-dimensional simulations of the SOL plasma dynamics in three TCV limited discharges are carried out with the GBS ...

American Institute of Physics (AIP)2020

Chiral fermion asymmetry in high-energy plasma simulations

Jennifer Waltraud Schober

The chiral magnetic effect (CME) is a quantum relativistic effect that describes the appearance of an additional electric current along a magnetic field. It is caused by an asymmetry between the number densities of left- and right-handed fermions, which ca ...

2020

Voyager 2 plasma observations of the heliopause and interstellar medium

Paula Garcia Galindo

The solar wind blows outwards from the Sun and forms a bubble of solar material in the interstellar medium. The heliopause (HP) is the boundary that divides the hot tenuous solar wind plasma in the heliosheath from the colder, denser very local interstella ...

NATURE PUBLISHING GROUP2019

Millimeter-wave beam scattering by edge-plasma density fluctuations in TCV

Stefano Alberti, Timothy Goodman, Ivo Furno, Benoît Labit, Paolo Ricci, Fabio Riva, Oulfa Chellaï, Emanuele Poli, Marcelo Baquero Ruiz

In magnetically confined fusion devices, the use of millimeter waves (mmw) at the electron cyclotron (EC) frequencies ranges from plasma diagnostics to plasma heating, current drive and core confinement preservation. For large tokamaks such as ITER, numeri ...

2019

Projective multiscale time-integration for electrostatic particle-in-cell methods

Jan Sickmann Hesthaven, Paul Isaac Denis Louis Marie Cazeaux

The simulation of problems in kinetic plasma physics is often challenging due to strongly coupled phenomena across multiple scales. In this work, we propose a wavelet-based coarse-grained numerical scheme, based on the framework of Equation-Free Projective ...

2019

Realistic multi-machine tokamak profile simulations and numerical ramp-down optimization using the RAPTOR code

Anna Teplukhina

Predictive modelling of plasma profiles is an essential part of ongoing research in tokamak plasmas, required for a successful realization of future fusion reactors. This thesis focuses on upgrading the RAPTOR code to extend the area of its applicability f ...

EPFL2018

Outer midplane scrape-off layer profiles and turbulence in simulations of Alcator C-Mod inner-wall limited discharges

Federico David Halpern

A region of steep plasma gradients, the so-called "narrow-feature," has been found in the near scrape-off layer (SOL) of inner-wall limited (IWL) discharges. Dedicated IWL discharges were carried out in Alcator C-Mod [Marmar et al., Nucl. Fusion 55, 104020 ...

Amer Inst Physics2017

Poloidal asymmetry in the narrow heat flux feature in the TCV scrape-off layer

Basil Duval, Ivo Furno, Holger Reimerdes, Stefano Coda, Jan Horacek, Benoît Labit, Joaquim Loizu Cisquella, Paolo Ricci, Christian Gabriel Theiler, Federico David Halpern, Federico Nespoli, Cedric Kar-Wai Tsui

Heat flux profiles inferred from a reciprocating probe at the outer midplane of the TCV tokamak during inner wall limited discharges feature radial fall-off lengths that shorten near the last closed flux surface (LCFS) consistent with the so-called narrow ...

American Institute of Physics (AIP)2017

Neutral atom dynamics and plasma turbulence in the tokamak periphery

Christoph Wersal

Understanding the physical mechanisms at play in the interaction between turbulent plasma and neutral particles is a crucial issue that we approach in this Thesis by using a first-principles self-consistent model of the tokamak periphery implemented in the ...

EPFL2017