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Umar Sheikh

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Publications associées (80)

Methods to determine the radiated power in SPI-mitigated disruptions in JET

Umar Sheikh, Paulo Giovane Paschoali Pereira Puglia

This paper presents techniques for evaluating the radiated power in JET disruptions. Disrupting plasmas are shown to have non-axisymmetric radiation profiles, motivating the re-evaluation of the standard techniques for calculating the total radiated power ...

2021

Initial TCV operation with a baffled divertor

Patrick Blanchard, Basil Duval, Ambrogio Fasoli, Jean-Marc Moret, Holger Reimerdes, Duccio Testa, Christian Gabriel Theiler, Matthieu Toussaint, Hugo De Oliveira, Cedric Kar-Wai Tsui, Umar Sheikh, Marcelo Baquero Ruiz, Roberto Maurizio, Mirko Wensing, Filippo Bagnato, Davide Galassi, Lorenzo Martinelli, Sophie Danielle Angelica Gorno, Claudia Colandrea, Harshita Raj, Artur Perek

The Tokamak à Configuration Variable (TCV) tokamak is in the midst of an upgrade to further its capability to investigate conventional and alternative divertor configurations. To that end, modular and removable gas baffles have been installed to decrease t ...

IOP Publishing Ltd2021

Disruption thermal load mitigation with shattered pellet injection on the Joint European Torus (JET)

Disruption mitigation remains a critical, unresolved challenge for ITER. To aid in addressing this challenge, a shattered pellet injection (SPI) system was installed on JET and experiments conducted at a range of thermal energy fractions and stored energie ...

IOP Publishing Ltd2021

Impact of the new TCV baffled divertor upgrade on pedestal structure and performance

Patrick Blanchard, Basil Duval, Holger Reimerdes, Benoît Labit, Christian Gabriel Theiler, Antoine Pierre Emmanuel Alexis Merle, Umar Sheikh, Davide Galassi

A new set of carbon tiles, neutral beam heating optics and gas baffles were installed on TCV during thebaffled divertor upgrade in early 2019. The installation of the baffles allows a deconvolution of the roles ofmain chamber and divertor neutral pressure ...

Elsevier2021

Divertor closure effects on the TCV boundary plasma

Basil Duval, Holger Reimerdes, Benoît Labit, Sri Harsha Kasi Raj, Christian Gabriel Theiler, Umar Sheikh, Lorenzo Martinelli, Claudia Colandrea

The Tokamak a Configuration Variable (TCV) has recently been equipped with gas baffles to increase its divertor closure for a broad range of divertor magnetic geometries. First experimental results reported in Reimerdes et al. (2021) demonstrated compatibi ...

Elsevier2021

Disruption mitigation efficiency and scaling with thermal energy fraction on ASDEX Upgrade

Basil Duval, Umar Sheikh, Gergely Papp

Disruption mitigation remains a critical and unresolved issue for ITER. Measurement uncertainties preventing quantification of a system's efficacy remains a significant hurdle in producing and validating a viable disruption mitigation system. This study ad ...

IOP Publishing Ltd2020

Runaway electron synchrotron radiation in a vertically translated plasma

Basil Duval, Joan Decker, Umar Sheikh, Gergely Papp, Artur Perek

Synchrotron radiation observed from runaway electrons (REs) in tokamaks depends upon the position and size of the RE beam, the RE energy and pitch distributions, as well as the location of the observer. We show experimental synchrotron images of a vertical ...

IOP Publishing Ltd2020

Spectrally Filtered Imaging and Vacuum Ultraviolet Spectroscopy of Preheated Models in X2 (Sept, 10.2514/1.J056021, 2017)

Pénélope Leyland, Umar Sheikh

2020

Runaway electron beam control

Basil Duval, Stefano Coda, Diego Carnevale, Georgios Pappas, Joan Decker, Umar Sheikh, Cristian Galperti, Filippo Bagnato, Gergely Papp

Post-disruption runaway electron (RE) beams in tokamaks with large current can cause deep melting of the vessel and are one of the major concerns for ITER operations. Consequently, a considerable effort is provided by the scientific community in order to t ...

IOP PUBLISHING LTD2019

Progress in disruption prevention for ITER

Olivier Sauter, Francesca Maria Poli, Umar Sheikh, Mengdi Kong, Alessandro Pau, Ji Hyun Kim

Key plasma physics and real-time control elements needed for robustly stable operation of high fusion power discharges in ITER have been demonstrated in recent research worldwide. Recent analysis has identified the current density profile as the main drive ...

IOP Publishing Ltd2019

Conduction-based model of the Scrape-Off Layer power sharing between inner and outer divertor in diverted low-density tokamak plasmas

Basil Duval, Holger Reimerdes, Marco Wischmeier, Benoît Labit, Christian Gabriel Theiler, Hugo De Oliveira, Wouter Vijvers, Cedric Kar-Wai Tsui, Umar Sheikh, Kevin Henricus Annemarie Verhaegh, Nicola Vianello, Roberto Maurizio, Mirko Wensing

A simple analytic model for the repartition of the Scrape-Off Layer (SOL) exhaust power between the inner and outer divertors in a diverted low-density tokamak plasma is introduced. Electron heat conduction is assumed to dominate the heat transport, from t ...

Elsevier2019

Pedestal structure and energy confinement studies on TCV

Patrick Blanchard, Basil Duval, Olivier Sauter, Benoît Labit, Christian Gabriel Theiler, Antoine Pierre Emmanuel Alexis Merle, Cedric Kar-Wai Tsui, Umar Sheikh

High external gas injection rates are foreseen for future devices to reduce divertor heat loads and this can influence pedestal stability. Fusion yield has been estimated to vary as strongly as T-e,ped(2) so an understanding of the underlying pedestal phys ...

2019

Progress toward divertor detachment on TCV within H-mode operating parameters

Basil Duval, Holger Reimerdes, Alexander Karpushov, Benoît Labit, Christian Gabriel Theiler, Wouter Vijvers, Antoine Pierre Emmanuel Alexis Merle, Curdin Tobias Wüthrich, Cedric Kar-Wai Tsui, Umar Sheikh, Kevin Henricus Annemarie Verhaegh, Roberto Maurizio, Artur Perek

Recent experiments on Tokamak à Configuration Variable have made significant progress toward partial detachment of the outer divertor in neutral beam heated H-mode plasmas in conventional and alternative divertor configurations. The heating power required ...

2019

Dependence on plasma shape and plasma fueling for small edge-localized mode regimes in TCV and ASDEX Upgrade

Patrick Blanchard, Basil Duval, Timothy Goodman, Jean-Marc Moret, Olivier Sauter, Holger Reimerdes, Stefano Coda, Marco Wischmeier, Jan Horacek, Alexander Karpushov, Laurie Porte, Yanis Andrebe, Yann Camenen, Thomas Binderup Jensen, Duccio Testa, Benoît Labit, Frédéric Dolizy, Emiliano Fable, Javier García Hernández, Ben McMillan, Christian Gabriel Theiler, Federico Alberto Alfredo Felici, Fang Liu, Hugo De Oliveira, Daniele Brunetti, Zhouji Huang, Claudio Marini, Jonathan Marc Philippe Faustin, Antoine Pierre Emmanuel Alexis Merle, Federico Nespoli, Anna Teplukhina, Leonardo Pigatto, Joan Decker, Cedric Kar-Wai Tsui, Pedro Andres Molina Cabrera, Umar Sheikh, Alberto Mariani, Emanuele Poli, Cristian Galperti, Kevin Henricus Annemarie Verhaegh, , , , , , , , , , , , , , , , , ,

A Variable Structure Control Scheme Proposal for the Tokamak a Configuration Variable

Patrick Blanchard, Basil Duval, Ambrogio Fasoli, Timothy Goodman, Xavier Llobet, Yves Martin, Jean-Marc Moret, Olivier Sauter, Minh Quang Tran, Henri Weisen, Ivo Furno, Holger Reimerdes, Jean-Philippe Hogge, Stefano Coda, Christian Schlatter, Marco Wischmeier, Jan Horacek, Alexander Karpushov, Laurie Porte, Yanis Andrebe, Yann Camenen, Jonathan Graves, Duccio Testa, Benoît Labit, Rémy Jacquier, Paolo Ricci, Christian Gabriel Theiler, Federico Alberto Alfredo Felici, Fabio Riva, Wouter Vijvers, Josef Kamleitner, Hoang Bao Le, Zhouji Huang, Himank Anand, Falk Hans Braunmüller, Joyeeta Sinha, Claudio Marini, Antoine Pierre Emmanuel Alexis Merle, Federico Nespoli, Oulfa Chellaï, Anna Teplukhina, , , , , , , , , , , , , ,

ELM-induced cold pulse propagation in ASDEX Upgrade

Patrick Blanchard, Roland Behn, Basil Duval, Timothy Goodman, Yves Martin, Jean-Marc Moret, Richard Pitts, Olivier Sauter, Holger Reimerdes, Stefano Coda, Marco Wischmeier, Jan Horacek, Alexander Karpushov, Laurie Porte, Yanis Andrebe, Yann Camenen, Thomas Binderup Jensen, Duccio Testa, Benoît Labit, Emiliano Fable, Javier García Hernández, Ben McMillan, Marc Gruber, Christian Gabriel Theiler, Federico Alberto Alfredo Felici, Dávid Wágner, Attila Bencze, Doohyun Kim, Wouter Vijvers, Hoang Bao Le, Zhouji Huang, Himank Anand, Claudio Marini, Antoine Pierre Emmanuel Alexis Merle, Federico Nespoli, Heinz Mueller, Anna Teplukhina, Joan Decker, Cedric Kar-Wai Tsui, Pedro Andres Molina Cabrera, Matteo Fontana, , , , , , , , , , , ,

A locked mode indicator for disruption prediction on JET and ASDEX upgrade

Patrick Blanchard, Roland Behn, Basil Duval, Ambrogio Fasoli, Timothy Goodman, Yves Martin, Jean-Marc Moret, Richard Pitts, Olivier Sauter, Henri Weisen, Holger Reimerdes, Stefano Coda, Alberto Bottino, Marco Wischmeier, Jan Horacek, Andrea Scarabosio, Hartmut Zohm, Alexander Karpushov, Laurie Porte, Yanis Andrebe, Yann Camenen, Jonathan Graves, Thomas Binderup Jensen, Benoît Labit, Emiliano Fable, Mikhail Maslov, Javier García Hernández, David Pfefferlé, Ben McMillan, Marc Gruber, Christian Gabriel Theiler, Federico Alberto Alfredo Felici, Miguel Filipe Silva Füglister, Dávid Wágner, Attila Bencze, Doohyun Kim, Wouter Vijvers, Hoang Bao Le, Zhouji Huang, Himank Anand, Claudio Marini, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,

Validation of the ICRF antenna coupling code RAPLICASOL against TOPICA and experiments

Patrick Blanchard, Roland Behn, Basil Duval, Timothy Goodman, Pierre Jacquot, Bruno Marchand, Yves Martin, Pascal Morel, Jean-Marc Moret, Richard Pitts, Olivier Sauter, Holger Reimerdes, Stefano Coda, Alberto Bottino, Marco Wischmeier, Jan Horacek, Andrea Scarabosio, Hartmut Zohm, Alexander Karpushov, Laurie Porte, Yanis Andrebe, Yann Camenen, Thomas Binderup Jensen, Duccio Testa, Telmo David Ribeiro Da Costa, Benoît Labit, Emiliano Fable, Patrycja Nowak-Sliwinska, Javier García Hernández, Ben McMillan, Marc Gruber, Christian Gabriel Theiler, Federico Alberto Alfredo Felici, Jose Felix Vega Stavro, Lenke Horváth, Dávid Wágner, Attila Bencze, Thomas Riedl, Lorenzo Anton-Louis Talà, Diego Carnevale, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,

Role of the pedestal position on the pedestal performance in AUG, JET-ILW and TCV and implications for ITER

Patrick Blanchard, Stefano Coda, Benoît Labit, Lenke Horváth, Pamela Solange Valdés Undurraga, Antoine Pierre Emmanuel Alexis Merle, Umar Sheikh

The role of the pedestal position on the pedestal performance has been investigated in AUG, JET-ILW and TCV. When the pedestal is peeling-ballooning (PB) limited, the three machines show a similar behaviour. The outward shift of the pedestal density relati ...

IOP Publishing Ltd2019

Physics research on the TCV tokamak facility: from conventional to alternative scenarios and beyond

Patrick Blanchard, Stefano Alberti, Basil Duval, Ambrogio Fasoli, Timothy Goodman, Xavier Llobet, Yves Martin, Jean-Marc Moret, Olivier Sauter, Minh Quang Tran, Henri Weisen, Ivo Furno, Holger Reimerdes, Jean-Philippe Hogge, Stefano Coda, Christian Schlatter, Marco Wischmeier, Jan Horacek, Alexander Karpushov, Laurie Porte, Yanis Andrebe, Yann Camenen, Jonathan Graves, Duccio Testa, Benoît Labit, Javier García Hernández, Rémy Jacquier, Paolo Ricci, Christian Gabriel Theiler, Federico Alberto Alfredo Felici, Hugo De Oliveira, Wouter Vijvers, Zhouji Huang, Himank Anand, Joyeeta Sinha, Claudio Marini, Antoine Pierre Emmanuel Alexis Merle, Federico Nespoli, Oulfa Chellaï, Anna Teplukhina, , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,

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Nicola Vianello

Antonio José Pereira de Figueiredo

Aylwin Iantchenko

Roberto Maurizio

Francesco Carpanese

Giovanni Tardini

Lorenzo Stipani

Federico Pesamosca

Filippo Bagnato

Bernhard Sieglin

IOP Publishing Ltd2019

Francesco Sciortino

Cedric Kar-Wai Tsui

Cristian Galperti

Kevin Henricus Annemarie Verhaegh

Nicola Vianello

Roberto Maurizio

Francesco Carpanese

Bernhard Sieglin

Fusion power is the most significant prospects in the long-term future of energy in the sense that it composes a potentially clean, cheap, and unlimited power source that would substitute the widespread traditional nonrenewable energies, reducing the geogr ...

2019

Cristian Galperti

Kevin Henricus Annemarie Verhaegh

Nicola Vianello

Antonio José Pereira de Figueiredo

Giovanni Tardini

Cristian Sommariva

Bernhard Sieglin

In ASDEX Upgrade, the propagation of cold pulses induced by type-I edge localized modes (ELMs) is studied using electron cyclotron emission measurements, in a dataset of plasmas with moderate triangularity. It is found that the edge safety factor or the pl ...

2019

Dalziel Joseph Wilson

Jonathan Marc Philippe Faustin

Antoine Pierre Emmanuel Alexis Merle

Federico Nespoli

Anna Teplukhina

Hamish William Patten

Jose Vicente Sanchez Mut

Cedric Kar-Wai Tsui

Pedro Andres Molina Cabrera

Cristian Galperti

Kevin Henricus Annemarie Verhaegh

Nicola Vianello

Antonio José Pereira de Figueiredo

Samuel Lanthaler

Giovanni Tardini

Cristian Sommariva

Bernhard Sieglin

The aim of this paper is to present a signal processing algorithm that, applied to the raw Locked Mode signal, allows us to obtain a disruption indicator in principle exploitable on different tokamaks. A common definition of such an indicator for different ...

2019

Pamela Solange Valdés Undurraga

Michael Oliver Reinke

Antoine Pierre Emmanuel Alexis Merle

Federico Nespoli

Allan Svejstrup Nielsen

Anna Teplukhina

Janir Nuno Ramos Antunes Da Cruz

Jose Vicente Sanchez Mut

Cedric Kar-Wai Tsui

Pedro Andres Molina Cabrera

Cristian Galperti

Kevin Henricus Annemarie Verhaegh

Daniel Molina Romero

Nicola Vianello

Antonio José Pereira de Figueiredo

Giovanni Tardini

Raffaele Tito D'Agnolo

Erwan Fabrice Koch

Jennifer Kaitlyn Olsen

Cristian Sommariva

Bernhard Sieglin

In this paper we validate the finite element code RAPLICASOL, which models radiofrequency wave propagation in edge plasmas near ICRF antennas, against calculations with the TOPICA code. We compare the output of both codes for the ASDEX Upgrade 2-strap ante ...

IOP Publishing Ltd2019

Leonardo Pigatto

Cedric Kar-Wai Tsui

Pedro Andres Molina Cabrera

Alberto Mariani

Cristian Galperti

Kevin Henricus Annemarie Verhaegh

Marcelo Baquero Ruiz

Nicola Vianello

Aylwin Iantchenko

Roberto Maurizio

Francesco Carpanese

Justin Richard Ball

Lorenzo Stipani

Federico Pesamosca

Anna Ngoc Minh Trang Vu

Filippo Bagnato

Arsène Stéphane Tema Biwole

IOP Publishing Ltd2019