Benoît Labit
EPFL SB SPC-TCV
PPB 118 (Bâtiment PPB)
Station 13
CH-1015 Lausanne
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
201311
Progress toward divertor detachment on TCV within H-mode operating parameters
Plasma Physics and Controlled Fusion. 2019.
DOI : 10.1088/1361-6587/ab140e.
Dependence on plasma shape and plasma fueling for small ELM regimes in TCV and ASDEX Upgrade
Nuclear Fusion. 2019.
DOI : 10.1088/1741-4326/ab2211.
Application of a two-fluid two-point model to SolEdge2D-EIRENE simulations of TCV H-mode plasma
Nuclear Materials and Energy. 2019.
DOI : 10.1016/j.nme.2018.11.026.
The effect of the secondary x-point on the scrape-off layer transport in the TCV snowflake minus divertor
Nuclear Fusion. 2019.
DOI : 10.1088/1741-4326/aaee1b.
Millimeter-wave beam scattering by edge-plasma density fluctuations in TCV
Plasma Physics and Controlled Fusion. 2019.
DOI : 10.1088/1361-6587/aae7bf.
Pedestal Structure and Energy Confinement Studies on TCV
Plasma Physics and Controlled Fusion. 2019.
Pedestal structure and energy confinement studies on TCV
Plasma Physics And Controlled Fusion. 2019-01-01.
DOI : 10.1088/1361-6587/aae7bd.
Millimeter-wave beam scattering by edge-plasma density fluctuations in TCV
Plasma Physics And Controlled Fusion. 2019-01-01.
DOI : 10.1088/1361-6587/aae7bf.
Conduction-based model of the Scrape-Off Layer power sharing between inner and outer divertor in diverted low-density tokamak plasmas
Nuclear Materials and Energy. 2019-03-22.
DOI : 10.1016/j.nme.2019.03.020.
The effect of the secondary x-point on the scrape-off layer transport in the TCV snowflake minus divertor
Nuclear Fusion. 2018-12-05.
DOI : 10.1088/1741-4326/aaee1b.
Disruption avoidance through the prevention of NTM destabilization in TCV
NUCLEAR FUSION. 2018.
DOI : 10.1088/1741-4326/aad924.
Parameter dependences of small edge localized modes (ELMs)
Nuclear Fusion. 2018.
DOI : 10.1088/1741-4326/aad757.
Fluctuation characteristics of the TCV snowflake divertor measured with high speed visible imaging
Plasma Physics and Controlled Fusion. 2018.
DOI : 10.1088/1361-6587/aae005.
Filamentary velocity scaling validation in the TCV tokamak
Physics of Plasmas. 2018.
DOI : 10.1063/1.5038019.
Impurity seeding for suppression of the near scrape-off layer heat flux feature in tokamak limited plasmas
Physics of Plasmas. 2018.
DOI : 10.1063/1.5023201.
Analysis of wall-embedded Langmuir probe signals in different conditions on the Tokamak à Configuration Variable
Review of Scientific Instruments. 2018.
DOI : 10.1063/1.5022459.
Dependence of the L-Mode scrape-off layer power fall-off length on the upper triangularity in TCV
Plasma Physics and Controlled Fusion. 2018.
DOI : 10.1088/1361-6587/aaaef7.
Experimental observations of modes with geodesic acoustic character from the core to the edge in the TCV tokamak
Plasma Physics and Controlled Fusion. 2018.
DOI : 10.1088/1361-6587/aaa71d.
Divertor power load studies for attached L-mode single-null plasmas in TCV
Nuclear Fusion. 2018.
DOI : 10.1088/1741-4326/aa986b.
Detachment evolution on the TCV tokamak
Nuclear Materials and Energy. 2017.
DOI : 10.1016/j.nme.2016.10.020.
TCV experiments towards the development of a plasma exhaust solution
Nuclear Fusion. 2017.
DOI : 10.1088/1741-4326/aa82c2.
TCV divertor upgrade for alternative magnetic configurations
Nuclear Materials And Energy. 2017.
DOI : 10.1016/j.nme.2017.02.013.
Effect of plasma geometry on divertor heat flux spreading: MONALISA simulations and experimental results from TCV
Nuclear Materials And Energy. 2017.
DOI : 10.1016/j.nme.2016.10.003.
Overview of progress in European medium sized tokamaks towards an integrated plasma-edge/wall solution
Nuclear Fusion. 2017.
DOI : 10.1088/1741-4326/aa6084.
Modification of SOL profiles and fluctuations with line-average density and divertor flux expansion in TCV
Nuclear Fusion. 2017.
DOI : 10.1088/1741-4326/aa7db3.
Exploring drift effects in TCV single-null plasmas with the UEDGE code
Plasma Physics and Controlled Fusion. 2017.
DOI : 10.1088/1361-6587/aa7c8e.
Understanding and suppressing the near Scrape-Off Layer heat flux feature in inboard-limited plasmas in TCV
Nuclear Fusion. 2017.
DOI : 10.1088/1741-4326/aa84e0.
Spectroscopic investigations of divertor detachment in TCV
Nuclear Materials and Energy. 2017.
DOI : 10.1016/j.nme.2017.01.004.
Poloidal asymmetry in the narrow heat flux feature in the TCV scrape-off layer
Physics of Plasmas. 2017.
DOI : 10.1063/1.4985075.
Overview of the TCV tokamak program: scientific progress and facility upgrades
Nuclear Fusion. 2017.
DOI : 10.1088/1741-4326/aa6412.
Blob properties in full-turbulence simulations of the TCV scrape-off layer
Plasma Physics and Controlled Fusion. 2017.
DOI : 10.1088/1361-6587/aa6276.
Non-linear simulations of the TCV Scrape-Off Layer
Nuclear Materials And Energy. 2017.
DOI : 10.1016/j.nme.2016.10.019.
Results from recent detachment experiments in alternative divertor configurations on TCV
Nuclear Fusion. 2017.
DOI : 10.1088/1741-4326/aa5fb7.
A novel carbon coating technique for foil bolometers
Review of Scientific Instruments. 2016.
DOI : 10.1063/1.4961271.
Numerical study of potential heat flux mitigation effects in the TCV snowflake divertor
Plasma Physics And Controlled Fusion. 2016.
DOI : 10.1088/0741-3335/58/4/045027.
Enhanced (E)over-right-arrow x (B)over-right-arrow drift effects in the TCV snowflake divertor
Nuclear Fusion. 2015.
DOI : 10.1088/0029-5515/55/12/123023.
Experimental investigation of neon seeding in the snowflake configuration in TCV
Journal Of Nuclear Materials. 2015.
DOI : 10.1016/j.jaucmat.2014.10.076.
X-Point-Position-Dependent Intrinsic Toroidal Rotation in the Edge of TCV
Physical Review Letters. 2015.
DOI : 10.1103/PhysRevLett.114.245001.
X-point Position Dependence of Edge Intrinsic Toroidal Rotation on TCV
Physics of Plasmas. 2015.
DOI : 10.1063/1.4921158.
Plasma turbulence, suprathermal ion dynamics and code validation on the basic plasma physics device TORPEX
Journal Of Plasma Physics. 2015.
DOI : 10.1017/S0022377815000161.
Heat loads in inboard limited L-mode plasmas in TCV
Journal Of Nuclear Materials. 2015.
DOI : 10.1016/j.jnucmat.2014.11.137.
Impact of a narrow limiter SOL heat flux channel on the ITER first wall panel shaping
Nuclear Fusion. 2015.
DOI : 10.1088/0029-5515/55/3/033019.
High density experiments in TCV ohmically heated and L-mode plasmas
Plasma Physics and Controlled Fusion. 2015.
DOI : 10.1088/0741-3335/57/2/025002.
Threshold power for the transition into H-mode for H, D, and He plasmas in TCV
Plasma Physics and Controlled Fusion. 2015.
DOI : 10.1088/0741-3335/57/2/025007.
Power exhaust in the snowflake divertor for L- and H-mode TCV tokamak plasmas
Nuclear Fusion. 2014.
DOI : 10.1088/0029-5515/54/2/023009.
First EMC3-Eirene simulations of the TCV snowflake divertor
Plasma Physics and Controlled Fusion. 2014.
DOI : 10.1088/0741-3335/56/3/035009.
Theory-based scaling of the SOL width in circular limited tokamak plasmas
Nuclear Fusion. 2013.
DOI : 10.1088/0029-5515/53/12/122001.
Plasma radiation dynamics with the upgraded Absolute Extreme Ultraviolet tomographical system in the Tokamak a Configuration Variable
Review Of Scientific Instruments. 2013.
DOI : 10.1063/1.4848155.
Advanced divertor configurations with large flux expansion
Journal of Nuclear Materials. 2013.
DOI : 10.1016/j.jnucmat.2013.01.015.
Bifurcated Helical Core Equilibrium States in Tokamaks
Nuclear Fusion. 2013.
DOI : 10.1088/0029-5515/53/7/073021.
Recent TCV results – innovative plasma shaping to improve plasma properties and insight
Plasma and Fusion Research. 2012.
DOI : 10.1585/pfr.7.2502148.
Dependence of L-mode confinement on the electron cyclotron power deposition profile in the TCV tokamak
Plasma Physics and Controlled Fusion. 2012.
DOI : 10.1088/0741-3335/54/1/015011.
Three-Dimensional Imaging of a Radially Propagating Plasma Blob Using Conditional Sampling Techniques
IEEE Transactions on Plasma Science. 2011.
DOI : 10.1109/TPS.2011.2162254.
Blob motion and control in simple magnetized plasmas
Physics of Plasmas. 2011.
DOI : 10.1063/1.3562944.
Blob-induced toroidal momentum transport in simple magnetized plasmas
Physics of Plasmas. 2011.
DOI : 10.1063/1.3559462.
Electrostatic instabilities, turbulence and fast ion interactions in the TORPEX device
Plasma Physics and Controlled Fusion. 2010.
DOI : 10.1088/0741-3335/52/12/124020.
"Snowflake" H Mode in a Tokamak Plasma
Physical Review Letters. 2010.
DOI : 10.1103/PhysRevLett.105.155003.
Observation of a critical pressure gradient for the stabilization of interchange modes in simple magnetized toroidal plasmas
Physics of Plasmas. 2009.
DOI : 10.1063/1.3204704.
Cross-field plasma blob motion in an open magnetic field line configuration
Physical Review Letters. 2009.
DOI : 10.1103/PhysRevLett.103.065001.
Langmuir probe-based observables for plasma-turbulence code validation and application to the TORPEX basic plasma physics experiment
Physics of Plasmas. 2009.
DOI : 10.1063/1.3082698.
Mechanism for blob generation in the TORPEX toroidal plasma
Physics of Plasmas. 2008.
DOI : 10.1063/1.2870082.
Cross-field transport by instabilities and blobs in a magnetized toroidal plasma
PHYSICAL REVIEW LETTERS. 2008.
DOI : 10.1103/PhysRevLett.101.045001.
Two-dimensional time resolved measurements of toroidal velocity correlated with density blobs in magnetized plasmas
REVIEW OF SCIENTIFIC INSTRUMENTS. 2008.
DOI : 10.1063/1.2965141.
Dynamics of plasma blobs in a shear flow
PHYSICAL REVIEW LETTERS. 2008.
DOI : 10.1103/PhysRevLett.101.115005.
The role of the density gradient on intermittent cross-field transport events in a simple magnetized toroidal plasma
Phys. Plasmas. 2008.
Experimental Observation of the Blob-Generation Mechanism from InterchangeWaves in a Plasma
Physical Review Letters. 2008.
Plasma blobs in a basic toroidal experiment: Origin, dynamics, and induced transport
Physics of Plasmas. 2007.
DOI : 10.1063/1.2813193.
Antenna excitation of drift wave in a toroidal plasma
Physics of Plasmas. 2007.
DOI : 10.1063/1.2784464.
Statistical properties of electrostatic turbulence in toroidal magnetized plasmas
Plasma Physics and Controlled Fusion. 2007.
DOI : 10.1088/0741-3335/49/12B/S26.
Universal statistical properties of drift-interchange turbulence in TORPEX plasmas
Physical Review Letters. 2007.
DOI : 10.1103/PhysRevLett.98.255002.
Comparison between fluid electron-temperature-gradient driven simulations and Tore Supra experiments on electron heat transport
Journal of Plasma Physics. 2007.
DOI : 10.1017/S0022377806004466.
Characterization of the electron distribution function in an electron-cyclotron driven toroidal plasma
Plasma Physics and Controlled Fusion. 2007.
DOI : 10.1088/0741-3335/49/2/007.
Electrostatic turbulence and transport in a simple magnetized plasma
Physics of Plasmas. 2006.
DOI : 10.1063/1.2178773.
Probabilistic analysis of turbulent structures from two-dimensional plasma imaging
Physics of Plasmas. 2006.
DOI : 10.1063/1.2351960.
Fast ion source and detector for investigating the interaction of turbulence with suprathermal ions in a low temperature toroidal plasma - art. no. 10F503
Review of Scientific Instruments. 2006.
DOI : 10.1063/1.2219407.
Experimental characterization and modelling of the particle source in an Electron-Cyclotron wave driven toroidal plasma
Plasma Physics and Controlled Fusion. 2006.
DOI : 10.1088/0741-3335/48/8/001.
Experimental characterization of drift-interchange instabilities in a simple toroidal plasma
Physics of Plasmas. 2006.
DOI : 10.1063/1.2356483.
Basic turbulence studies on TORPEX and challenges in the theory-experiment comparison
Physics of Plasmas. 2005.
DOI : 10.1063/1.2034367.
Plasma production by low-field side injection of electron cyclotron waves in a simple magnetized torus
Plasma Physics and Controlled Fusion. 2005.
DOI : 10.1088/0741-3335/47/11/008.
Effects of a vertical magnetic field on particle confinement in a magnetized plasma torus
Physical Review Letters. 2004.
Global numerical study of electron temperature gradient-driven turbulence and transport scaling
Physics of Plasmas. 2003.
DOI : 10.1063/1.1527942.
Enseignement & Phd
Cours
Plasma Diagnostics in Basic Plasma Physics Devices and Tokamaks: from Principles to Practice
The programme will allow students to learn plasma diagnostics and data processing methods of modern fusion experiments and to bridge the gap between diagnostics theory and experimental practice. 