Publications de Noé Thomas Elie Ohana

Moment approach of the multi-species non-linear Coulomb collision operator adapted to particle-in-cell codes

Stephan Brunner, Laurent Villard, Emmanuel Lanti, Noé Thomas Elie Ohana, Moahan Murugappan, Claudio Gheller

In this article an approximated version of the multi-species, non-linear Coulomb collision operator is derived via the use of a truncated moment expansion of the distribution function to compute the Rosenbluth potentials. The evolution of the distribution ...

2021

Implementation of energy transfer technique in ORB5 to study collisionless wave-particle interactions in phase-space

Laurent Villard, Alberto Bottino, Emmanuel Lanti, Noé Thomas Elie Ohana, Emanuele Poli

A new diagnostic has been developed to investigate the wave-particle interaction in the phase-space in gyrokinetic particle-in-cell codes. Keeping information about energy transfer terms in the velocity space, the technique has been implemented and tested ...

2021

An optimisation of allreduce communication in message-passing systems

Laurent Villard, Emmanuel Lanti, Noé Thomas Elie Ohana

Collective communication, namely the pattern allreduce in message-passing systems, is optimised based on measurements at the installation time of the library. The algorithms used are set up in an initialisation phase of the communication, as so-called pers ...

2021

Gyrokinetic simulations on many- and multi-core architectures with the global electromagnetic Particle-In-Cell Code ORB5

Stephan Brunner, Laurent Villard, Emmanuel Lanti, Noé Thomas Elie Ohana, Claudio Gheller

Gyrokinetic codes in plasma physics need outstanding computational resources to solve increasingly complex problems, requiring the effective exploitation of cutting-edge HPC architectures. This paper focuses on the enabling of ORB5, a state-of-the-art, fir ...

2021

Nonlinear dynamics of energetic-particle driven geodesic acoustic modes in ASDEX Upgrade

Laurent Villard, Alberto Bottino, Emmanuel Lanti, Noé Thomas Elie Ohana, Emanuele Poli

Turbulence in tokamaks generates radially sheared zonal flows. Their oscillatory counterparts, geodesic acoustic modes (GAMs), appear due to the action of the magnetic field curvature. The GAMs can be driven unstable by an anisotropic energetic particle (E ...

AMER INST PHYSICS2020

Using an antenna as a tool for studying microturbulence and zonal structures in tokamaks with a global gyrokinetic GPU-enabled particle-in-cell code

Noé Thomas Elie Ohana

In order to get a better understanding of the interaction of plasma microinstabilities and associated turbulence with specific modes, an antenna is implemented in the global gyrokinetic Particle-In-Cell (PIC) code ORB5. It consists in applying an external ...

EPFL2020

Orb5: A global electromagnetic gyrokinetic code using the PIC approach in toroidal geometry

Stephan Brunner, Laurent Villard, Alberto Bottino, Sébastien Jolliet, Paolo Angelino, Thibaut Vernay, Ben McMillan, Emmanuel Lanti, Julien Stanislas Pierre Dominski, Noé Thomas Elie Ohana, Aaron Lewis Scheinberg, Claudio Gheller

This paper presents the current state of the global gyrokinetic code Orb5 as an update of the previous reference (Jolliet et al., 2007). The Orb5 code solves the electromagnetic Vlasov–Maxwell system of equations using a PIC scheme and also includes collis ...

2019

Global turbulence features across marginality and non-local pedestal-core interactions

Stephan Brunner, Olivier Sauter, Laurent Villard, Alberto Bottino, Ben McMillan, Emmanuel Lanti, Noé Thomas Elie Ohana

Spatially non-local aspects of turbulent transport in tokamak plasmas are examined with global gyrokinetic simulations using the ORB5 code. Inspired by very accurate measurements in the TCV tokamak in L-mode, we initialise plasma profiles with constant log ...

2019

First principles gyrokinetic analysis of electromagnetic plasma instabilities

Stephan Brunner, Laurent Villard, Alberto Bottino, Emmanuel Lanti, Noé Thomas Elie Ohana

A two-fold analysis of electromagnetic core tokamak instabilities in the framework of the gyrokinetic theory is presented. First principle theoretical foundations of the gyrokinetic theory are used to explain and justify the numerical results obtained with ...

2019

Gyrokinetic full-f particle-in-cell simulations on open field lines with PICLS

Alberto Bottino, Emmanuel Lanti, Noé Thomas Elie Ohana

While in recent years gyrokinetic simulations have become the workhorse for theoretical turbulence and transport studies in the plasma core, their application to the edge and scrape-off layer (SOL) region presents significant challenges. In particular, ste ...

2019

Pullback Scheme Implementation in ORB5

Stephan Brunner, Laurent Villard, Alberto Bottino, Emmanuel Lanti, Noé Thomas Elie Ohana

The pullback scheme is implemented in the global gyrokinetic particle-in-cell code ORB5 (Jolliet et al., 2007[1]) to mitigate the cancellation problem in electromagnetic simulations. The equations and the discretisation used by the code are described. Nume ...

Elsevier2019

Mode excitation by an antenna in global gyrokinetic simulations

Stephan Brunner, Laurent Villard, Alberto Bottino, Ben McMillan, Emmanuel Lanti, Noé Thomas Elie Ohana

In order to get a better understanding of the linear and non-linear plasma interaction of microinstabilities and associated turbulence with different specific modes, an antenna is implemented in the global gyrokinetic code ORB5. It consists in applying an ...

2018

Gradient- and flux-driven global gyrokinetic simulations of ITG and TEM turbulence with an improved hybrid kinetic electron model

Stephan Brunner, Laurent Villard, Ben McMillan, Emmanuel Lanti, Noé Thomas Elie Ohana

2018

Prediction of the Inter-Node Communication Costs of a New Gyrokinetic Code with Toroidal Domain

Stephan Brunner, Laurent Villard, Emmanuel Lanti, Noé Thomas Elie Ohana, Aaron Lewis Scheinberg, Claudio Gheller

We consider the communication costs of gyrokinetic plasma physics simulations running at large scale. For this we apply virtual decompositions of the toroidal domain in three dimensions and additional domain cloning to existing simulations done with the OR ...

SPRINGER INTERNATIONAL PUBLISHING AG2018

Pro Free Will Priming Enhances "Risk-Taking" Behavior in the Iowa Gambling Task, but Not in the Balloon Analogue Risk Task: Two Independent Priming Studies

Alessandro Tremea, Noé Thomas Elie Ohana, Christine Mohr

Studies indicated that people behave less responsibly after exposure to information containing deterministic statements as compared to free will statements or neutral statements. Thus, deterministic primes should lead to enhanced risk-taking behavior. We t ...

Public Library Science2016

Towards the optimization of a gyrokinetic Particle-In-Cell (PIC) code on large-scale hybrid architectures

Stephan Brunner, Trach-Minh Tran, Laurent Villard, Emmanuel Lanti, Noé Thomas Elie Ohana, Claudio Gheller

With the aim of enabling state-of-the-art gyrokinetic PIC codes to benefit from the performance of recent multithreaded devices, we developed an application from a platform called the "PIC-engine" [1, 2, 3] embedding simplified basic features of the PIC me ...

2016