Publications de Umesh Kumar | EPFL Graph Search

First measurements of velocity-space resolved intra-ELM fast-ion losses on the TCV tokamak

Basil Duval, Ambrogio Fasoli, Alexander Karpushov, Mario Ludovico Podesta, Benoît Labit, Umesh Kumar, Jesús Poley Sanjuán

Edge Localised Modes (ELMs) induced fast-ion losses have been characterised in the energy, E, and pitch, λ = v ∥ / v , space using a unique Fast Ion Loss Detector (FILD) on the tokamak à configuration variable. The FILD is equipped with a 128 Avalanche Pho ...

2025

Cascades of Parametric Instabilities in the Tokamak Plasma Edge during Electron Cyclotron Resonance Heating

Stefano Coda, Umesh Kumar

We report observations of nonlinear two-plasmon decay instabilities (TPDIs) of a high -power microwave beam, a process similar to half -harmonic generation in optics, during electron cyclotron resonance heating in a tokamak. TPDIs are found to occur regula ...

Amer Physical Soc2024

Experimental research on the TCV tokamak

Patrick Blanchard, Stefano Alberti, Ambrogio Fasoli, Timothy Goodman, Yves Martin, Olivier Sauter, Henri Weisen, Ivo Furno, Holger Reimerdes, Jean-Philippe Hogge, Stefano Coda, Alexander Karpushov, Yanis Andrebe, Duccio Testa, Benoît Labit, Christian Gabriel Theiler, Federico Alberto Alfredo Felici, Jérémy Genoud, Hugo De Oliveira, Antoine Pierre Emmanuel Alexis Merle, Antoine Baillod, Joan Decker, Cedric Kar-Wai Tsui, Pedro Andres Molina Cabrera, Umar Sheikh, Cristian Galperti, Marcelo Baquero Ruiz, Aylwin Iantchenko, Mengdi Kong, Francesco Carpanese, Federico Pesamosca, Olivier Claude Martin Février, Simon Van Mulders, Nicola Offeddu, Garance Hélène Salomé Durr-Legoupil-Nicoud, Maurizio Giacomin, Filippo Bagnato, Davide Galassi, Arsène Stéphane Tema Biwole, Lorenzo Martinelli, , , , , , , , , , , , , , , , , , , , , , , ,

Validation of short-pulse reflectometry turbulence measurements with a synthetic diagnostic

Stephan Brunner, Stefano Coda, Umesh Kumar, Oleg Krutkin, Mackenzie Peter-Fulford Van Rossem, Samuele Mazzi

Experimental measurements of the turbulence amplitude utilizing a short pulse reflectometry method are presented. Two discharges with shaped plasma possessing opposite signs of triangularity are considered and a higher turbulence amplitude is found in the ...

IOP Publishing Ltd2024

Overview of the EUROfusion Tokamak Exploitation programme in support of ITER and DEMO

Patrick Blanchard, Basil Duval, Timothy Goodman, Jean-Marc Moret, Olivier Sauter, Henri Weisen, Holger Reimerdes, Stefano Coda, Alexander Karpushov, Duccio Testa, Benoît Labit, Christian Gabriel Theiler, Federico Alberto Alfredo Felici, Antoine Pierre Emmanuel Alexis Merle, Joan Decker, Cedric Kar-Wai Tsui, Umar Sheikh, Cristian Galperti, Marcelo Baquero Ruiz, Aylwin Iantchenko, Mengdi Kong, Olivier Claude Martin Février, Paulo Giovane Paschoali Pereira Puglia, Simon Van Mulders, Nicola Offeddu, Garance Hélène Salomé Durr-Legoupil-Nicoud, Filippo Bagnato, Davide Galassi, Lorenzo Martinelli, Jean Arthur Cazabonne, Alessandro Pau, Matteo Vallar, Sophie Danielle Angelica Gorno, Claudia Colandrea, Dmytry Mykytchuk, Gino Marceca, Davide Mancini, Cassandre Ekta Contré, Guang-Yu Sun, , , , , , , , , ,

Expulsion of runaway electrons using ECRH in the TCV tokamak

Basil Duval, Stefano Coda, Laurie Porte, Joan Decker, Umar Sheikh, Cristian Sommariva, Arsène Stéphane Tema Biwole, Jean Arthur Cazabonne, Umesh Kumar, Luke Simons

Runaway electrons (REs) are a concern for tokamak fusion reactors from discharge startup to termination. A sudden localized loss of a multi-megaampere RE beam can inflict severe damage to the first wall. Should a disruption occur, the existence of a RE see ...

IOP Publishing Ltd2024

Impact of microwave beam scattering by density fluctuations on the electron-cyclotron power deposition profile in tokamaks

Stefano Coda, Joan Decker, Jean Arthur Cazabonne, Umesh Kumar, Oleg Krutkin

Electron-cyclotron waves are a tool commonly used in tokamaks, in particular to drive current. Their ability to drive current in a very localized manner renders them an optimal tool for MHD mode mitigation. However, such applications require high accuracy ...

IOP Publishing Ltd2024

Utilizing parametric instabilities to diagnose edge density fluctuations in TCV

Stefano Coda, Umesh Kumar

Two-plasmon decay instabilities (TPDIs) are a class of parametric instabilities where a gyrotron beam, polarized in X-mode, decays nonlinearly into two upper hybrid waves at approximately half frequency. Here, we present the design of a simple radiometer t ...

2024

Study of fast-ion-driven toroidal Alfvén eigenmodes impacting on the global confinement in TCV L-mode plasmas

Stephan Brunner, Laurent Villard, Stefano Coda, Javier García Hernández, Aylwin Iantchenko, Justin Richard Ball, Matteo Vallar, Umesh Kumar, Oleg Krutkin, Luke Simons, Jesús Poley Sanjuán, Samuele Mazzi, Baruch Rofman

Following recent observations of unstable Toroidal Alfven Eigenmodes (TAEs) in a counter-current Neutral Beam Injection (NBI) scenario developed in TCV, an in-depth analysis of the impact of such modes on the global confinement and performance is carried o ...

2023

Overview of the TCV tokamak experimental programme

Patrick Blanchard, Stephan Brunner, Stefano Alberti, Basil Duval, Ambrogio Fasoli, Timothy Goodman, Xavier Llobet, Yves Martin, Jean-Marc Moret, Olivier Sauter, Henri Weisen, Ivo Furno, Holger Reimerdes, Jean-Philippe Hogge, Jan Horacek, Alexander Karpushov, Laurie Porte, Yanis Andrebe, Jonathan Graves, Duccio Testa, Benoît Labit, Joaquim Loizu Cisquella, Paolo Ricci, Christian Gabriel Theiler, Federico Alberto Alfredo Felici, Miguel Filipe Silva Füglister, Antoine Pierre Emmanuel Alexis Merle, Oulfa Chellaï, Curdin Tobias Wüthrich, Joan Decker, Cedric Kar-Wai Tsui, Pedro Andres Molina Cabrera, Matteo Fontana, Umar Sheikh, Cristian Galperti, Marcelo Baquero Ruiz, Dahye Choi, Aylwin Iantchenko, Mengdi Kong, Roberto Maurizio, Francesco Carpanese, , , , , , , , , , , , , , , , , , , , , , ,