Benoît Labit

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Collaborateur scientifique

benoit.labit@epfl.ch +41 21 693 45 62

Nationalité : French

Date de naissance : 22.06.1975

EPFL SB SPC-TCV
PPB 118 (Bâtiment PPB)
Station 13
CH-1015 Lausanne

+41 21 693 45 62
Unité: SPC-TCV
Local: PPB 118

Unité: EDPY-ENS

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Données administratives

Current work

Deputy Task Force Leader for the MST1 EUROfusion Workpackage

PhD Thesis

Tokamak electron heat transport by direct numerical simulation of small scale turbulence

In a fusion machine, understanding plasma turbulence, which causes a degradation of the measured energy confinement time, would constitute a major progress in this field. In tokamaks, the measured ion and electron thermal conductivities are of comparable magnitude. The possible sources of turbulence are the temperature and density gradients occurring in a fusion plasma. Whereas the heat losses in the ion channel are reasonably well understood, the origin of the electron losses is more uncertain. In addition to the the radial velocity associated to the fluctuations of the electric field, electrons are more affected than ions by the magnetic field fluctuations. In experiments, the confinement time can be conveniently expressed in terms of dimensionless parameters. Although still somewhat too imprecise, these scaling laws exhibit strong dependencies on the normalized pressure, β or the normalized Larmor radius, ρ*.

The present thesis assesses whether a tridimensional, electromagnetic, nonlinear fluid model of plasma turbulence driven by a specific instability can reproduce the dependence of the experimental electron heat losses on the dimensionless parameters β and ρ*. The investigated interchange instability is the Electron Temperature Gradient driven one (ETG). The model is built by using the set of Braginskii equations. The developed simulation code is global in the sense that a fixed heat flux is imposed at the inner boundary, leaving the gradients free to evolve.

From the nonlinear simulations, we have put in light three characteristics for the ETG turbulence: the turbulent transport is essentially electrostatic; the potential and pressure fluctuations form radially elongated cells called streamers; the transport level is very low compared to the experimental values.

The thermal transport dependence study has shown a very small role of the normalized pressure, which is in contradiction with the Ohkawa's formula. On the other hand, the crucial role of the electron normalized Larmor has been emphasized: the confinement time is inverse proportional to this parameter. Finally, the low dependence of turbulent transport with the magnetic shear and the inverse aspect ratio is also reported.

Although the transport level observed in the simulations is low compared to the experiments, we have tried a direct confrontation with Tore Supra results. This tokamak is well designed to study the electron heat transport. Keeping most of the parameters from a well referenced Tore Supra shot, the nonlinear simulation gives a threshold quite close to the experimental one. The observed turbulent conductivity is a factor fifty lower than the experimental one. An important parameter can not be matched: the normalized Larmor radius, ρ*.

This limitation has to be overcome in order to confirm this results. Finally, a rigorous confrontation between this result and gyrokinetic simulations has to conclude that the ETG instability cannot describe electron heat losses in tokamaks.

Keywords: thermonuclear fusion, tokamak, plasma, ETG turbulence, numerical simulations

Education

Docteur es Sciences	mention Rayonnement et Plasmas	Universit� de Provence Aix-Marseille I	22.10.2002
Licence et Maitrise de Physique		Universit� Paul Sabatier Toulouse III

Compétences

H-mode physics
Plasma turbulence
Experimental physics
Numerical simulations

Publications

Infoscience

201311

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

J. R. Harrison; C. Theiler; O. Février; H. d. Oliviera; R. Maurizio et al.

Plasma Physics and Controlled Fusion. 2019.

DOI : 10.1088/1361-6587/ab140e.

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

B. Labit; T. Eich; G. Harrer; E. Wolfrum; M. Bernert et al.

Nuclear Fusion. 2019.

DOI : 10.1088/1741-4326/ab2211.

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Application of a two-fluid two-point model to SolEdge2D-EIRENE simulations of TCV H-mode plasma

F. Nespoli; H. Bufferand; M. Valentinuzzi; N. Fedorczak; G. Ciraolo et al.

Nuclear Materials and Energy. 2019.

DOI : 10.1016/j.nme.2018.11.026.

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The effect of the secondary x-point on the scrape-off layer transport in the TCV snowflake minus divertor

R. Maurizio; C. Tsui; B. Duval; H. Reimerdes; C. Theiler et al.

Nuclear Fusion. 2019.

DOI : 10.1088/1741-4326/aaee1b.

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

O. Chellaï; S. Alberti; M. Baquero-Ruiz; I. Furno; T. Goodman et al.

Plasma Physics and Controlled Fusion. 2019.

DOI : 10.1088/1361-6587/aae7bf.

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Pedestal structure and energy confinement studies on TCV

U. A. Sheikh; M. Dunne; L. Frassinetti; P. Blanchard; B. P. Duval et al.

Plasma Physics And Controlled Fusion. 2019-01-01.

DOI : 10.1088/1361-6587/aae7bd.

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

R. Maurizio; B. Duval; B. Labit; H. Reimerdes; C. Theiler et al.

Nuclear Materials and Energy. 2019-03-22.

DOI : 10.1016/j.nme.2019.03.020.

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The effect of the secondary x-point on the scrape-off layer transport in the TCV snowflake minus divertor

R. Maurizio; C. K. Tsui; B. P. Duval; H. Reimerdes; C. Theiler et al.

Nuclear Fusion. 2018-12-05.

DOI : 10.1088/1741-4326/aaee1b.

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Disruption avoidance through the prevention of NTM destabilization in TCV

U. Sheikh; B. Duval; C. Galperti; M. Maraschek; O. Sauter et al.

Nuclear Fusion. 2018.

DOI : 10.1088/1741-4326/aad924.

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Parameter dependences of small edge localized modes (ELMs)

G. Harrer; E. Wolfrum; M. Dunne; P. Manz; M. Cavedon et al.

Nuclear Fusion. 2018.

DOI : 10.1088/1741-4326/aad757.

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Fluctuation characteristics of the TCV snowflake divertor measured with high speed visible imaging

N. R. Walkden; B. Labit; H. Reimerdes; J. Harrison; T. Farley et al.

Plasma Physics and Controlled Fusion. 2018.

DOI : 10.1088/1361-6587/aae005.

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Filamentary velocity scaling validation in the TCV tokamak

C. K. Tsui; J. A. Boedo; J. R. Myra; B. Duval; B. Labit et al.

Physics of Plasmas. 2018.

DOI : 10.1063/1.5038019.

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Impurity seeding for suppression of the near scrape-off layer heat flux feature in tokamak limited plasmas

F. Nespoli; B. Labit; I. Furno; C. Theiler; U. A. Sheikh et al.

Physics of Plasmas. 2018.

DOI : 10.1063/1.5023201.

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Analysis of wall-embedded Langmuir probe signals in different conditions on the Tokamak à Configuration Variable

O. Février; C. Theiler; H. De Oliveira; B. Labit; N. Fedorczak et al.

Review of Scientific Instruments. 2018.

DOI : 10.1063/1.5022459.

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Dependence of the L-Mode scrape-off layer power fall-off length on the upper triangularity in TCV

M. Faitsch; R. Maurizio; A. Gallo; S. Coda; T. Eich et al.

Plasma Physics and Controlled Fusion. 2018.

DOI : 10.1088/1361-6587/aaaef7.

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

Z. Huang; S. Coda; G. Merlo; S. Brunner; L. Villard et al.

Plasma Physics and Controlled Fusion. 2018.

DOI : 10.1088/1361-6587/aaa71d.

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Divertor power load studies for attached L-mode single-null plasmas in TCV

R. Maurizio; S. Elmore; N. Fedorczak; A. Gallo; H. Reimerdes et al.

Nuclear Fusion. 2018.

DOI : 10.1088/1741-4326/aa986b.

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Detachment evolution on the TCV tokamak

J. Harrison; W. Vijvers; C. Theiler; B. Duval; S. Elmore et al.

Nuclear Materials and Energy. 2017.

DOI : 10.1016/j.nme.2016.10.020.

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TCV experiments towards the development of a plasma exhaust solution

H. Reimerdes; B. Duval; J. Harrison; B. Labit; B. Lipschultz et al.

Nuclear Fusion. 2017.

DOI : 10.1088/1741-4326/aa82c2.

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TCV divertor upgrade for alternative magnetic configurations

H. Reimerdes; S. Alberti; P. Blanchard; P. Bruzzone; R. Chavan et al.

Nuclear Materials And Energy. 2017.

DOI : 10.1016/j.nme.2017.02.013.

Benoît Labit

Collaborateur scientifique

Current work

PhD Thesis

Tokamak electron heat transport by direct numerical simulation of small scale turbulence

Education

Compétences

Publications

Infoscience

201311

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

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

Application of a two-fluid two-point model to SolEdge2D-EIRENE simulations of TCV H-mode plasma

The effect of the secondary x-point on the scrape-off layer transport in the TCV snowflake minus divertor

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

Pedestal structure and energy confinement studies on TCV

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

The effect of the secondary x-point on the scrape-off layer transport in the TCV snowflake minus divertor

Disruption avoidance through the prevention of NTM destabilization in TCV

Parameter dependences of small edge localized modes (ELMs)

Fluctuation characteristics of the TCV snowflake divertor measured with high speed visible imaging

Filamentary velocity scaling validation in the TCV tokamak

Impurity seeding for suppression of the near scrape-off layer heat flux feature in tokamak limited plasmas

Analysis of wall-embedded Langmuir probe signals in different conditions on the Tokamak à Configuration Variable

Dependence of the L-Mode scrape-off layer power fall-off length on the upper triangularity in TCV

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

Divertor power load studies for attached L-mode single-null plasmas in TCV

Detachment evolution on the TCV tokamak

TCV experiments towards the development of a plasma exhaust solution

TCV divertor upgrade for alternative magnetic configurations

Effect of plasma geometry on divertor heat flux spreading: MONALISA simulations and experimental results from TCV

Overview of progress in European medium sized tokamaks towards an integrated plasma-edge/wall solution

Modification of SOL profiles and fluctuations with line-average density and divertor flux expansion in TCV

Exploring drift effects in TCV single-null plasmas with the UEDGE code

Understanding and suppressing the near Scrape-Oﬀ Layer heat flux feature in inboard-limited plasmas in TCV

Spectroscopic investigations of divertor detachment in TCV

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

Overview of the TCV tokamak program: scientific progress and facility upgrades

Blob properties in full-turbulence simulations of the TCV scrape-off layer

Non-linear simulations of the TCV Scrape-Off Layer

Results from recent detachment experiments in alternative divertor configurations on TCV

A novel carbon coating technique for foil bolometers

Numerical study of potential heat flux mitigation effects in the TCV snowflake divertor

Enhanced (E)over-right-arrow x (B)over-right-arrow drift effects in the TCV snowflake divertor

Experimental investigation of neon seeding in the snowflake configuration in TCV

X-Point-Position-Dependent Intrinsic Toroidal Rotation in the Edge of TCV

X-point Position Dependence of Edge Intrinsic Toroidal Rotation on TCV

Plasma turbulence, suprathermal ion dynamics and code validation on the basic plasma physics device TORPEX

Heat loads in inboard limited L-mode plasmas in TCV

Impact of a narrow limiter SOL heat flux channel on the ITER first wall panel shaping

High density experiments in TCV ohmically heated and L-mode plasmas

Threshold power for the transition into H-mode for H, D, and He plasmas in TCV

Power exhaust in the snowflake divertor for L- and H-mode TCV tokamak plasmas

First EMC3-Eirene simulations of the TCV snowflake divertor

Theory-based scaling of the SOL width in circular limited tokamak plasmas

Plasma radiation dynamics with the upgraded Absolute Extreme Ultraviolet tomographical system in the Tokamak a Configuration Variable

Bifurcated Helical Core Equilibrium States in Tokamaks

Recent TCV results – innovative plasma shaping to improve plasma properties and insight

Dependence of L-mode confinement on the electron cyclotron power deposition profile in the TCV tokamak

Three-Dimensional Imaging of a Radially Propagating Plasma Blob Using Conditional Sampling Techniques

Blob motion and control in simple magnetized plasmas

Blob-induced toroidal momentum transport in simple magnetized plasmas

Electrostatic instabilities, turbulence and fast ion interactions in the TORPEX device

"Snowflake" H Mode in a Tokamak Plasma

Observation of a critical pressure gradient for the stabilization of interchange modes in simple magnetized toroidal plasmas

Cross-field plasma blob motion in an open magnetic field line configuration

Langmuir probe-based observables for plasma-turbulence code validation and application to the TORPEX basic plasma physics experiment

Mechanism for blob generation in the TORPEX toroidal plasma

Cross-field transport by instabilities and blobs in a magnetized toroidal plasma

Two-dimensional time resolved measurements of toroidal velocity correlated with density blobs in magnetized plasmas

Dynamics of plasma blobs in a shear flow

The role of the density gradient on intermittent cross-field transport events in a simple magnetized toroidal plasma

Experimental Observation of the Blob-Generation Mechanism from InterchangeWaves in a Plasma

Plasma blobs in a basic toroidal experiment: Origin, dynamics, and induced transport

Antenna excitation of drift wave in a toroidal plasma

Statistical properties of electrostatic turbulence in toroidal magnetized plasmas

Universal statistical properties of drift-interchange turbulence in TORPEX plasmas

Comparison between fluid electron-temperature-gradient driven simulations and Tore Supra experiments on electron heat transport

Characterization of the electron distribution function in an electron-cyclotron driven toroidal plasma

Electrostatic turbulence and transport in a simple magnetized plasma