Publications de Olivier Sauter

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It is sometimes observed that several neoclassical tearing modes (NTMs) are present at the same time. This can happen both at the mode onset of a new NTM or during the nonlinear saturated phase of a given mode. In order to analyse whether nonlinear mode coupling plays any role before or after the onset of NTMs, we use a data analysis tool known as the bispectral technique. This technique has been used for identifying the nonlinear three wave interactions in turbulent plasmas. We have used this technique for

The ramp-up is a critical phase in the operations of a Tokamak, during which engineering and physics aspects must be taken into account to ensure stability, minimize flux consumption and avoid disruptions. Predicting ramp-up phases faces challenges such as ...

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 ...

The identification of the sources of atomic tungsten and the measurement of their radiation distribution in front of all plasma-facing components has been performed in JET with the help of two digital cameras with the same two-dimensional view, equipped wi ...

This work aims at establishing the parameter space for the existence of geodesic acoustic modes (GAMs) on JET as well as investigating their driving and damping mechanisms predicted by different theoretical models. This was achieved using an experimental d ...

The MHD response and the penetration of a deuterium shattered pellet into a JET plasma is investigated via the non-linear reduced MHD code JOREK with the neutral gas shielding (NGS) ablation model. The dominant MHD destabilizing mechanism by the injection ...

A small component of ECCD exists when heating off-axis with no toroidal injection due to the field helicity. The sign of the ECCD will change depending on the absorption location in a poloidal plane, the beam injection relative to delB(vac), and the direction of the toroidal magnetic field. The importance of the ECCD component can be confirmed by the behavior of the sawteeth when the ECH deposition crosses the q=1 surface. The sawtooth period is very sensitive to the local shear at q=1 and it is shown that

Convolutional neural networks (CNNs) have found applications in many image processing tasks, such as feature extraction, image classification, and object recognition. It has also been shown that the inverse of CNNs, so-called deconvolutional neural network ...

We report the first experimental observation of the depolarization of the Thomson scattering (TS) radiation, a relativistic effect expected to occur in very high T-e plasmas and never observed so far in a fusion machine. A set of unused optical fibers in t ...

Combining dynamic models and measurements into a consistent plasma state estimate is an important challenge for ITER and DEMO, due to the inherent limitations regarding diagnostic coverage in a nuclear fusion reactor environment. In this work, a model-base ...

A detailed study has been made of the onset and behaviour of (m = 3, n = 2) neoclassical tearing modes (NTMs) on JET, validating many of the underlying concepts in NTM physics. In particular, fitting onset thresholds in terms of the correctly motivated physics parameters produces scalings closer to theoretical expectations. The use of such locally measured parameters also removes previous inconsistencies in the data between different divertor configurations. The evolution of island size with beta confirms t

TCV experiments and novel theoretical studies have addressed key questions regarding the operational space of negative triangularity (NT) plasmas in view of an L-mode NT reactor, in terms of stability, performance properties and core-edge integration. We show that reducing the top triangularity (δtop) to more negative values induces an H-L back transition, confirming the direct dependence between H-mode existence and access to 2nd ballooning stability region. We also show that the X-point δ can prohibit H-m

A set of experiments was carried out in JET ILW (Joint European Torus with ITER-Like Wall) L-mode plasmas in order to study the effects of light impurities on core ion thermal transport. N was puffed into some discharges and its profile was measured by act ...

Linearized operators describing inter-species and like-species collisions have been discretized and implemented in the gyrokinetic Particle-In-Cell (PIC) code ORB5 [S. Jolliet, Comp. Phys. Comm. 177, 409 ( 2007)] based on the delta-f approach. Simulation r ...

Starting from a standard single null X-point configuration, a second order null divertor (snowflake (SF)) has been successfully created on the Tokamak à Configuration Variable (TCV) tokamak. The magnetic properties of this innovative configuration have bee ...

Electron heat transport experiments are performed in L-mode discharges at various plasma triangularities, using radially localized electron cyclotron heating to vary independently both the electron temperature T-e and the normalized electron temperature gr ...

Magnetohydrodynamic equilibrium states with a three-dimensional helical core are computed to model the MAST spherical tokamak and the RFX-mod reversed field pinch. The boundary is fixed as axisymmetric. The MAST equilibrium state has the appearance of an i ...

Real-time plasma control systems are at the heart of operation of modern tokamaks. The control system of the TCV tokamak has recently seen a major upgrade in terms of its hardware and software components. Control algorithms are entirely programmed and test ...

The rampdown in tokamak operations is a difficult to simulate phase during which the plasma is often pushed towards multiple instability limits. To address this challenge, and reduce the risk of disrupting operations, we leverage recent advances in Scientific Machine Learning (SciML) to develop a neural state-space model (NSSM) that predicts plasma dynamics during Tokamak à Configuration Variable (TCV) rampdowns. By integrating simple physics structure and data-driven models, the NSSM efficiently learns pla

Olivier Sauter

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Study of nonlinear mode coupling during neoclassical tearing modes using bispectrum analysis

Full radius integrated modelling of ohmic ramp-up at TCV including self consistent density prediction

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

Determination of tungsten sources in the JET-ILW divertor by spectroscopic imaging in the presence of a strong plasma continuum

Scaling of the geodesic acoustic mode amplitude on JET

3D non-linear MHD simulation of the MHD response and density increase as a result of shattered pellet injection

Poloidally asymmetric plasma response with ECH deposition near q=1 in TCV

Deep neural networks for plasma tomography with applications to JET and COMPASS

First observation of the depolarization of Thomson scattering radiation by a fusion plasma

Model-based estimation of tokamak plasma profiles and physics parameters: algorithm overview and application to ITER

Onset of neoclassical tearing modes on JET

NEGATIVE TRIANGULARITY TOKAMAK OPERATION IN TCV

Effects of nitrogen seeding on core ion thermal transport in JET ILW L-mode plasmas

Negative Triangularity Tokamak Operation in TCV

Global collisional gyrokinetic simulations of ITG microturbulence starting from a neoclassical equilibrium

Snowflake Divertor Plasmas on TCV

Electron heat transport in shaped TCV L-mode plasmas

Magnetohydrodynamic properties of nominally axisymmetric systems with 3D helical core

Overview of the TCV digital real-time plasma control system and its applications

Learning Plasma Dynamics and Robust Rampdown Trajectories with Predict-First Experiments at TCV