Publications de Olivier Sauter

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Long timescale density peaking has been observed in JET plasmas leading to densities exceeding the Greenwald value. These neutral beam heated discharges are characterized by type-I ELMS and good energy confinement. Central density is limited by neoclassical tearing modes or by termination of H-mode preceded by loss of sawteeth. When these limiting factors are avoided (i.e. at intermediate power level and With optimization of gas puffing) quasi-stationary high density plasmas with peaked density profile are

An experimental study of the extraordinary mode (X mode) absorption at the third electron cyclotron harmonic frequency has been performed on the TCV tokamak in plasmas preheated by X mode at the second harmonic. Full single pass absorption of injected X3 power was measured with X2 preheating in co-current drive (CO-ECCD). The measured absorption exceeds that predicted by the linear ray tracing code TORAY-GA by more than a factor of 2 for the CO-ECCD case. Experimental evidence indicates that a large fractio

A power-balance model, with radiation losses from impurities and neutrals, gives a unified description of the density limit (DL) of the stellarator, the L-mode tokamak, and the reversed field pinch (RFP). The model predicts a Sudo-like scaling for the stel ...

The goal of this work is to develop a simulator for the TCV tokamak that self-consistently includes transport and equilibrium while taking the plant control systems into account. To achieve this, we adapted the Fenix flight simulator that was originally developed for ASDEX Upgrade for use on TCV. The MEQ-FGE free boundary equilibrium code that is widely used for TCV analysis as well as the TCV magnetic controller were coupled to this framework. In addition, a reduced transport model drawing inspiration from

The STEP (Stability, Transport, Equilibrium, and Pedestal) integrated-modeling tool has been developed in OMFIT to predict stable, tokamak equilibria self-consistently with core-transport and pedestal calculations. STEP couples theory-based codes to integr ...

The aim of the present work is to provide a better insight on the magnetic shear profile modification in the Switched ECCD experiments. Modelling of the plasma current density is carried on by the ASTRA transport code employed in both predictive and interp ...

Improved electron energy confinement in tokamak plasmas, related to internal transport barriers, has been linked to nonmonotonic current density profiles. This is difficult to prove experimentally since usually the current profiles evolve continuously and ...

Post mortem analysis shows that mid and high atomic number metallic impurities are present in deposits on JET plasma facing components with the highest amount of Ni and W, and therefore the largest sink, being found at the top of the inner divertor. Source ...

The TCV tokamak contributes to the physics understanding of fusion plasmas, broadening the parameter range of reactor relevant regimes, by investigations based on an extensive use of the existing main experimental tools: flexible shaping and high power rea ...

Based on the models describing the behaviour of neoclassical tearing modes (NTMs), fits for the seed-island triggered excitation and disappearance of these modes at small beta-values have been tested for an extended parameter range in the rho(pi)*-(υ) over bar (ii) plane in ASDEX Upgrade. The disappearance of NTMs at the marginal beta(p,marg) during power rampdown phases provides input for a direct comparison with models without the influence of the seed-island size. It has been found that for low q

For long-pulse tokamaks, one of the main challenges in the control strategy is to simultaneously reach multiple control objectives and to robustly handle in real-time (RT) unexpected events [off-normal-events (ONEs)] with a limited set of actuators. We hav ...

Results from MAST provide a first test of neoclassical tearing mode physics in the spherical tokamak (ST). The mode accounts for the main performance limit in conventional tokamaks. Its behavior in the ST is remarkably well described by existing theoretical models, although it is more readily seeded by sawtooth events in these scenarios. Modeling confirms the significance of stabilizing field-curvature effects. This provides good grounds for optimism that with suitable control of profiles, it may be possibl

Full conversion from ohmic to runaway electron (RE) driven current was observed in the tokamak a configuration variable (TCV) following massive injection of neon through a disruption mitigation valve into a low-density limited circular plasma. Following a ...

The density limit in strongly-shaped negative triangularity (NT) discharges is studied experimentally in the DIII-D tokamak. Record-high Greenwald fractions fG are obtained, using gas puff injection only, with values up to near 2, where fG is defined as th ...

The effects of plasma shape on confinement and sawtooth stability are studied for positive and negative discharge triangularity and for different elongations with 1.5 MW centrally deposited ECH power

Resistive interchange modes can be driven unstable by large pressure gradients in the negative central magnetic shear (NCS) region of advanced tokamaks. Localized stability analysis reveals that the resistive interchange stability criterion (D-R less than or equal to 0) is violated in this region, and unstable n = 1 localized resistive magnetohydrodynamic (MHD) modes are computed using the resistive MHD code MARS. In DIII-D NCS plasmas, these instabilities appear as bursting MHD activities, constituting the

The recently developed Monte-Carlo code ERO2.0 is applied to the modelling of limited and diverted discharges at JET with the ITER-like wall (ILW). The global beryllium (Be) erosion and deposition is simulated and compared to experimental results from pass ...

The measurements using the high resolution electron cyclotron emission radiometry and the charge exchange and recombination spectroscopy are processed using analytic formulas to allow for the detection of islands as small as 1.9 cm. In contrast to large, s ...

Parallel heat flux calculations at the JET divertor have been based on the assumption that all incoming heat is due to the projection of the heat flux parallel to the magnetic line, q, plus a constant background. This simplification led to inconsistencies ...

Selected set of samples from JET ITER-Like Wall (JET-ILW) divertor tiles exposed both in 2013-2014 and 2011-2014 has been analysed using Thermal Desorption Spectrometry (TDS). The deuterium (D) amounts obtained with TDS were compared with Ion Beam Analysis ...

Olivier Sauter

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Long timescale density peaking in JET

Full absorption of third harmonic ECH in TCV tokamak plasmas in the presence of second harmonic ECCD

A power-balance model of the density limit in fusion plasmas: application to the L-mode tokamak

Full-discharge simulations of the TCV tokamak using the Fenix flight simulator

Flexible, integrated modeling of tokamak stability, transport, equilibrium, and pedestal physics

Studies of Electron Transport and Current Diffusion in Switched ECCD experiments on TCV

Inductive current density perturbations to probe electron internal transport barriers in tokamaks

Deposition of impurity metals during campaigns with the JET ITER-like Wall

A scoping study of the application of neutral beam heating on the TCV tokamak

Scaling of the marginal beta(p) of neoclassical tearing modes during power ramp-down experiments in ASDEX Upgrade

Integrated Real-Time Supervisory Management for Off-Normal-Event Handling and Feedback Control of Tokamak Plasmas

Neoclassical tearing physics in the spherical tokamak MAST

Full conversion from ohmic to runaway electron driven current via massive gas injection in the TCV tokamak

Operation Above the Greenwald Density Limit in High Performance DIII-d Negative Triangularity Discharges

Energy Confinement in Shaped TCV Plasmas with Electron Cyclotron Heating

Resistive interchange modes in negative central shear tokamaks with peaked pressure profiles

Beryllium global erosion and deposition at JET-ILW simulated with ERO2.0

Measurement of small island characteristics using high resolution ECE and CER at DIII-D

An improved model for the accurate calculation of parallel heat fluxes at the JET bulk tungsten outer divertor

Investigation of deuterium trapping and release in the JET ITER-like wall divertor using TDS and TMAP