Publications by Gabriele Merlo

First-principle based predictions of the effects of negative triangularity on DTT scenarios

Olivier Sauter, Gabriele Merlo, Alberto Mariani

Plasmas with negative triangularity (NT) shape have been recently shown to be able to achieve H-mode levels of confinement in L-mode, avoiding detrimental edge localised modes. Therefore, this plasma geometry is now studied as a possible viable option for ...

IOP Publishing Ltd2024

Global 'zero particle flux-driven' gyrokinetic analysis of the density profile for a TCV plasma

Stephan Brunner, Olivier Sauter, Gabriele Merlo, Alberto Mariani

The tokamak `a configuration variable (TCV) is a small-sized tokamak, where finite size effects (often called 'rho-star' or 'global' effects) could significantly impact the heat and particle fluxes, leading to discrepancies between gyrokinetic flux-tube re ...

IOP Publishing Ltd2023

A synthetic phase-contrast imaging diagnostic with spatial filtering for gyrokinetic simulations

Stephan Brunner, Stefano Coda, Gabriele Merlo, Aylwin Iantchenko, Justin Richard Ball

A Phase-contrast imaging (PCI) diagnostic provides measurements of line-integrated electron density fluctuations. Localisation along the laser beam path can be achieved with a spatial filter that selects the wave-vector directions of the fluctuations contr ...

2023

Nonlocal effects in negative triangularity TCV plasmas

Stephan Brunner, Olivier Sauter, Laurent Villard, Stefano Coda, Zhouji Huang, Gabriele Merlo, Claudio Marini

Global gradient driven gyrokinetic simulations performed with the Gyrokinetic Electromagnetic Numerical Experiment (GENE) code are used to investigate Tokamak a configuration variable (TCV) plasmas with negative triangularity. Considering limited L-mode pl ...

2021

How eigenmode self-interaction affects zonal flows and convergence of tokamak core turbulence with toroidal system size

Stephan Brunner, Julien Stanislas Pierre Dominski, Gabriele Merlo, Ajay Chandrarajan Jayalekshmi, Justin Richard Ball

Self-interaction is the process by which a microinstability eigenmode that is extended along the direction parallel to the magnetic field interacts non-linearly with itself. This effect is particularly significant in gyrokinetic simulations accounting for ...

Cambridge University Press2020

Direct gyrokinetic comparison of pedestal transport in JET with carbon and ITER-like walls

Patrick Blanchard, Basil Duval, Ambrogio Fasoli, Yves Martin, Richard Pitts, Olivier Sauter, Henri Weisen, Stefano Coda, Marco Wischmeier, Jan Horacek, Yann Camenen, Jonathan Graves, Duccio Testa, Mikhail Maslov, Javier García Hernández, David Pfefferlé, Gabriele Merlo, Dalziel Joseph Wilson, Jonathan Marc Philippe Faustin, Federico Nespoli, Hamish William Patten, Nicola Vianello, Antonio José Pereira de Figueiredo, Samuel Lanthaler, Liang Yao, Cristian Sommariva, Davide Galassi, Alessandro Pau, Yao Zhou, Otto Asunta, Bernhard Sieglin

This paper compares the gyrokinetic instabilities and transport in two representative JET pedestals, one (pulse 78697) from the JET configuration with a carbon wall (C) and another (pulse 92432) from after the installation of JET's ITER-like Wall (ILW). Th ...

IOP Publishing Ltd2019

DIII-D research towards establishing the scientific basis for future fusion reactors

Wilfred Anthony Cooper, Richard Pitts, Olivier Sauter, Stefan Müller, Mario Ludovico Podesta, Francesca Maria Poli, Dongbin Zhao, Gang Yu, Huan Du, Alessandro Bortolon, Alessandro Marinoni, Jeffrey Huang, Sun Hee Kim, Jérôme Guterl, Zhixian Yan, Fang Liu, Terunobu Akiyama, Xin Yang, Wei Wu, Lorenzo Anton-Louis Talà, Federico David Halpern, Gabriele Merlo, Yu Fu, Shouguo Wang, Sung Chul Park, Xi Chen, Tzu-Hsien Shen, Bingying Zhao, Kyungjin Kim, Ji Hyun Kim, Yi Wang, Hui Wang, Zheng Wang

DIII-D research is addressing critical challenges in preparation for ITER and the next generation of fusion devices through focusing on plasma physics fundamentals that underpin key fusion goals, understanding the interaction of disparate core and boundary ...

IOP Publishing Ltd2019

Turbulent transport in TCV plasmas with positive and negative triangularity

Stefano Coda, Laurie Porte, Gabriele Merlo, Matteo Fontana

Local gyrokinetic simulations with the GENE code are used to investigate the turbulent transport for different levels of neutral beam injection heating power in the Tokamak a Configuration Variable (TCV) for plasmas with both positive and negative edge tri ...

2019

Gyrokinetic analysis of radial dependence and global effects on the zero particle flux condition in a TCV plasma

Stephan Brunner, Olivier Sauter, Gabriele Merlo, Alberto Mariani

In small-sized tokamaks, finite Larmor radius effects could lead to a significant discrepancy between gyrokinetic local flux-tube results and global ones. This has been highlighted by previous turbulent transport studies as in McMillan et al (2010 Phys. Re ...

IOP2019

Effects of collisionality and T e /T i on fluctuations in positive and negative δ tokamak plasmas

Stephan Brunner, Ambrogio Fasoli, Olivier Sauter, Stefano Coda, Laurie Porte, Gabriele Merlo, Matteo Fontana, Ajay Chandrarajan Jayalekshmi

The effects of negative triangularity () on confinement and fluctuations in plasmas covering a large range of parameters were investigated on the tokamak à configuration variable (TCV). The conditions explored in this paper include discharges where neutral ...

IOP Publishing Ltd2019

Experimental observations of modes with geodesic acoustic character from the core to the edge in the TCV tokamak

Stephan Brunner, Laurent Villard, Stefano Coda, Benoît Labit, Christian Gabriel Theiler, Zhouji Huang, Gabriele Merlo

2018

Cross-verification of the global gyrokinetic codes GENE and XGC

Emmanuel Lanti, Julien Stanislas Pierre Dominski, Gabriele Merlo

American Institute of Physics (AIP)2018

Identifying microturbulence regimes in a TCV discharge making use of physical constraints on particle and heat fluxes

Stephan Brunner, Olivier Sauter, Julien Stanislas Pierre Dominski, Gabriele Merlo, Antoine Pierre Emmanuel Alexis Merle, Alberto Mariani

American Institute of Physics (AIP)2018

Investigating the radial structure of axisymmetric fluctuations in the TCV tokamak with local and global gyrokinetic GENE simulations

Stephan Brunner, Laurent Villard, Stefano Coda, Laurie Porte, Julien Stanislas Pierre Dominski, Gabriele Merlo, Matteo Fontana

2018

An arbitrary wavelength solver for global gyrokinetic simulations. Application to the study of fine radial structures on microturbulence due to non-adiabatic passing electron dynamics

Stephan Brunner, Trach-Minh Tran, Laurent Villard, Ben McMillan, Julien Stanislas Pierre Dominski, Gabriele Merlo

The influence of the fine layers of the non-adiabatic passing electron response on electrostatic turbulent transport, previously studied systematically in flux tube geometry [Dominski et al., Phys. Plasmas 22, 062303 (2015)], is pursued in global geometry ...

Amer Inst Physics2017

Cross-code gyrokinetic verification and benchmark on the linear collisionless dynamics of the geodesic acoustic mode

Alberto Bottino, Gabriele Merlo

The linear properties of the geodesic acoustic modes (GAMs) in tokamaks are investigated by means of the comparison of analytical theory and gyrokinetic numerical simulations. The dependence on the value of the safety factor, finite-orbit-width of the ions ...

Amer Inst Physics2017

Linear multispecies gyrokinetic flux tube benchmarks in shaped tokamak plasmas

Stephan Brunner, Olivier Sauter, Laurent Villard, Yann Camenen, Emiliano Fable, Alice Burckel, Gabriele Merlo

Verification is the fundamental step that any turbulence simulation code has to be submitted in order to assess the proper implementation of the underlying equations. We have carried out a cross comparison of three flux tube gyrokinetic codes, GENE [F. Jen ...

2016

Flux-tube and global grid-based gyrokinetic simulations of plasma microturbulence and comparisons with experimental TCV measurements

Gabriele Merlo

In magnetic fusion devices, the radial transport of heat and particle largely exceeds predictions based on collisional processes. This is widely understood as a consequence of small-scale turbulence which results from the nonlinear behaviour of so-called m ...

EPFL2016

Investigating profile stiffness and critical gradients in shaped TCV discharges using local gyrokinetic simulations of turbulent transport

Stephan Brunner, Olivier Sauter, Laurent Villard, Yann Camenen, Alessandro Marinoni, Gabriele Merlo

The experimental observation made on the TCV tokamak of a significant confinement improvement in plasmas with negative triangularity (delta < 0) compared to those with standard positive triangularity has been interpreted in terms of different degrees of pr ...

Iop Publishing Ltd2015

Turbulence and zonal flow structures in the core and L-mode pedestal of tokamak plasmas

Stephan Brunner, Olivier Sauter, Trach-Minh Tran, Laurent Villard, Ben McMillan, Julien Stanislas Pierre Dominski, Gabriele Merlo

Zonal flows (ZF) play a crucial role in regulating ion temperature gradient (ITG) turbulence. In previous global gyrokinetic simulations [1] using the ORB5 code with the adiabatic electron model, it was observed that long-lived ZF structures, leading to a ...

IOP Publishing2014