Publications de Olivier Sauter

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The unique flexibility of TCV in plasma shaping has been exploited to address different aspects of tokamak physics in which the plasma shape may play a role. This paper summarizes the experiments undertaken in the TCV tokamak ("Tokamak à Configuration Variable") over the last decade in stability and transport and offers a comprehensive and integrated view of the various effects of plasma shape observed. For each of these effects, the relation between experimental results and theoretical predictions is stres

A new mechanism has recently been proposed that generates a radial flux of parallel momentum in toroidal plasmas. Namely, by considering up-down asymmetric flux surfaces, the symmetry following the magnetic field can be broken and an additional contributio ...

Starting from a standard single null X-point configuration, a second order null divertor (snowflake (SF)) has been successfully created on the Tokamak a Configuration Variable (TCV) tokamak. The magnetic properties of this innovative configuration have been analysed and compared with a standard X-point configuration. For the SF divertor, the connection length and the flux expansion close to the separatrix exceed those of the standard X-point by more than a factor of 2. The magnetic shear in the plasma edge

In magnetic fusion devices, error field (EF) sources, spurious magnetic field perturbations, need to be identified and corrected for safe and stable (disruption-free) tokamak operation. Within Work Package Tokamak Exploitation RT04, a series of studies hav ...

A new compact gamma-ray spectrometer was developed in order to optimise the measurement of bremsstrahlung radiation emitted from runaway electrons in the MeV range. The detector is based on a cerium doped lutetium-yttrium oxyorthosilicate (LYSO:Ce) scintil ...

The CHEASE code (Cubic Hermite Element Axisymmetric Static Equilibrium) solves the Grad-Shafranov equation for toroidal MHD equilibria using a Hermite bicubic finite element discretization with pressure, current profiles and plasma boundaries specified by analytical forms or sets of experimental data points. Moreover, CHEASE allows the automatic generation of pressure profiles marginally stable to ballooning modes or with a prescribed fraction of bootstrap current. The code provides equilibrium quantities f

The article presents experimental and theoretical investigations on the dynamics of saw-teeth and neoclassical tearing modes in tokamak plasmas. The main findings of these investigations are: (1) The experimental validation, on the basis of FTU and TCV data, of a model for the prediction of the sawtooth period and amplitude; (2) the importance of diamagnetic effects in determining the threshold for sawtooth crashes and the rotation of non-linear tearing modes; (3) a clarification of collisionless reconnecti

The control of 2/1 neoclassical tearing modes (NTMs) with electron cyclotron (EC) waves has been studied both experimentally and numerically on TCV. Dynamic evolutions of NTMs along with time-varying deposition locations of the control beam have been studi ...

Nonlinear electrostatic global gyrokinetic simulations of collisionless ion temperature gradient (ITG) turbulence and ExB zonal flows in axisymmetric toroidal plasmas are examined for different choices of the initial distribution function. Using a local Ma ...

The mechanisms of nonlinear interaction of external helical fields with a rotating plasma are investigated analyzing the results of recent systematic experiments on the Joint European Torus (JET) [A. Gibson , Phys. Plasmas 5, 1839 (1998)] that widen the previous data base collected on Compass-D [T. C. Hender , Nucl. Fusion 32, 2091 (1992)], Doublet III-D [R. J. La Haye , Nucl. Fusion 32, 2119 (1992)] and JET. The empirical scaling laws governing the onset of "error field" locked modes are re-assessed and in

Alfven eigenmodes (AEs) are routinely seen in present-day tokamaks and stellarators with energetic particles and they represent an attractive form of MHD spectroscopy that provides valuable information on background plasma and on the energetic particles. P ...

The kinetic code for plasma periphery (KIPP) was used to assess the importance of the kinetic effects of parallel electron transport in the scrape-off layer (SOL) and divertor of JET high radiative H-mode inter-ELM plasma conditions with the ITER-like wall ...

Fast ions have recently been found to significantly impact and partially suppress plasma turbulence both in experimental and numerical studies in a number of scenarios. Understanding the underlying physics and identifying the range of their beneficial effe ...

The paper is dedicated to the characterisation of multi-strap ICRH antenna coupling to plasma. Relevance of traditional concept of coupling resistance to antennas with mutually coupled straps is revised and the importance of antenna port excitation consist ...

Previous real-time sawtooth control scenarios using EC actuators have attempted to shorten [1] or lengthen [2] the sawtooth period by optimally positioning the EC absorption near the q=1 surface. In new experiments we demonstrate for the first time that individual sawtooth crashes can be repetitively induced at predictable times by reducing the stabilizing ECCD power after a predetermined time from the preceding crash. Other stabilizing actuators ( e. g. ICRF, NBI) are expected to produce similar effects. A

Electron cyclotron current drive (ECCD) is an important prospective tool for tailoring the current profile in nextstep devices. To fill the remaining gaps between ECCD theory and experiment, especially in the efficiency and localization of current drive, a better understanding of the physics of suprathermal electrons appears necessary. In TCV the fast electron population is diagnosed by a multichordal, spectrometric hard x-ray camera and by a highfield side electron cyclotron emission radiometer. The main m

[Neo-classical] Tearing Modes ([N]TMs) control is crucial in high-energy devices like ITER due to the disruptions that may cause potential machine damage. This work presents a real-time [N]TM control strategy for the ITER Plasma Control System (PCS), aiming to predict [N]TMs present and their characteristics, and apply stabilization using Electron Cyclotron Heating (ECH). Key components of the [N]TM control scheme are a predictor with extended co-MRE solver, coupled mode width and frequency dynamics, and a

In present day tokamaks, the role of the control research is to support the physics experiments and to prepare technologies for future devices such as ITER and DEMO. This paper presents the developments done under the MST1 program collaboration on ASDEX Up ...

The negative triangularity tokamak (NTT) is a unique reactor concept based on 'power-handling-first' philosophy with the heat exhaust problem as the leading concern. The present paper exposes a reactor concept using L-mode edge based on NTT configuration, ...

This paper presents the first application to real JET data of the new equilibrium code NICE which enables the consistent resolution of the inverse equilibrium reconstruction problem in the framework of non-linear free-boundary equilibrium coupled to the St ...

Olivier Sauter

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Physics Insight and Performance Benefit from Plasma Shaping Experiments in MHD and Energy Transport in the TCV Tokamak

Experimental demonstration of an up-down asymmetry effect on intrinsic rotation in the TCV tokamak

Snowflake Divertor Plasmas on TCV

Error field detection and correction studies towards ITER operation

Development of a new compact gamma-ray spectrometer optimised for runaway electron measurements

The CHEASE code for toroidal MHD equilibria

Modelling of macroscopic magnetic islands in tokamaks

Control of NTMs and integrated multi-actuator plasma control on TCV

On the definition of a kinetic equilibrium in global gyrokinetic simulations

Error field locked modes thresholds in rotating plasmas, anomalous braking and spin-up

MHD spectroscopy of JET plasmas with pellets via Alfven eigenmodes

Assessment of the strength of kinetic effects of parallel electron transport in the SOL and divertor of JET high radiative H-mode plasmas using EDGE2D-EIRENE and KIPP codes

Non-Maxwellian fast particle effects in gyrokinetic GENE simulations

ICRH antenna &ITS&IT-matrix measurements and plasma coupling characterisation at JET

Individual Sawtooth pacing by synchronized ECCD in TCV

Electron cyclotron current drive and suprathermal electron dynamics in the TCV tokamak

Progress on [N]TM modelling and control in the ITER Plasma Control System design

Developments on actuator management, plasma state reconstruction, and control on ASDEX Upgrade

L-mode-edge negative triangularity tokamak reactor

Equilibrium reconstruction at JET using Stokes model for polarimetry