Publications de Henri Weisen | EPFL Graph Search

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Dedicated experiments to generate energetic D ions and D-(3) He fusion-born alpha particles were performed at the Joint European Torus (JET) with the ITER-like wall (ILW). Using the 3-ion D-(D-NBI)-(3) He radio frequency (RF) heating scenario, deuterium io ...

The First Mirror Test for ITER has been carried out in JET with mirrors exposed during: (i) the third ILW campaign (ILW-3, 2015-2016, 23.33 h plasma) and (ii) all three campaigns, i.e. ILW-1 to ILW-3: 2011-2016, 63,52 h in total. All mirrors from main cham ...

Within the 9th European Framework programme, since 2021 EUROfusion is operating five tokamaks under the auspices of a single Task Force called ‘Tokamak Exploitation’. The goal is to benefit from the complementary capabilities of each machine in a coordinat ...

A large variety of plasma conditions has been created in TCV (Tokamak a Configuration Variable, B-T < 1.5 T, R-0 = 0.88 m, a < 0.25 m). They include limited and diverted discharges with elongations in the range 1-2.58, triangularities between -0.7 and 1 as well as 'square' shapes with plasma currents in the range 0.1-1 MA. Over the entire range of quasi-stationary ohmic conditions investigated we observe a correlation between electron pressure profiles and conductivity profiles, suggesting that [p]/p(0) app

During the first two years of operation, the TCV tokamak has produced a large variety of plasma shapes and magnetic configurations, with 1.0 less than or equal to B-tor less than or equal to 1.46T, I-p less than or equal to 800kA, kappa less than or equal to 2.05, -0.7 less than or equal to delta less than or equal to 1. A new shape control algorithm, based on a finite element reconstruction of the plasma current in real time, has been implemented. Vertical growth rates up to 1000 s(-1) have been stabilized

The TCV tokamak is equipped with a four-channel ultrasoft x-ray monochromator allowing low resolution (lambda/Deltalambda similar to 30) measurements in the energy range 200-800eV. Its main purpose is to simultaneously monitor emission from four of the main Kalpha resonance lines of highly ionized light impurities such as boron, carbon, nitrogen and oxygen. Wavelength selectivity is achieved using synthetic multilayer mirrors having 30-40 alternate layers with layer periods in the range 3-7 nm, depending on

Particle transport in tokamak plasmas has been intensively studied in the past, particularly in relation to density peaking and the presence of anomalous inward particle convection in L-and H-modes. While in the L-mode case the presence of the anomalous in ...

Precise control of the shape and position of double-null divertor configurations in the TCV tokamak has been used to trigger reliably the transition from ELM-free to ELMy ohmic H mode and back. Preprogrammed modulation of the magnetic axis height (+/- 1.25 cm), with fixed shaping field, caused the plasma to evolve, during a single discharge, between double-null-upper, double-null and double-null-lower configurations, with the secondary X point remaining close to the separatrix. The transition from ELM-free

With use of a multimachine pedestal database, essential issues for each regime of ELM types are investigated. They include (i) understanding and prediction of pedestal pressure during type I ELMs, a reference operation mode of a future tokamak reactor; (ii) identification of the operation regime of type II ELMs, which have small ELM amplitude with good confinement characteristics; (iii) identification of the upper stability boundary of type III ELMs for access to the higher confinement regimes with type I o

The measured D-D neutron rate of neutral beam heated JET baseline and hybrid H-modes in deuterium is found to be between approximately 50% and 100% of the neutron rate expected from the TRANSP code, depending on the plasma parameters. A number of candidate ...

An analysis of the effect of magnetic geometry on heat flux in a wide range of single null diverted discharge configurations with 1.5 < κ(95) < 2.2, 0.2 < δ(95) < 0.45 suggests that elongation is beneficial for confinement. If heat diffusivities are assumed not to depend on plasma shape., the predicted exponent for a power law scaling with elongation is alpha(kappa) approximate to 0.74, based on the configurations in the study. This is very close to dependences from the ITER database for dischar

Block-structured mesh generation techniques have been well addressed in the CFD community for automobile and aerospace studies, and their applicability to magnetic fusion is highly relevant, due to the complexity of the plasma-facing wall structures inside ...

Within the range of plasma shapes and plasma currents investigated, the electron confinement time, Tau_E increases with density, elongation and negative triangularity (-0.4

Developing successful tokamak operation scenarios, as well as confident extrapolation of present-day knowledge requires a rigorous understanding of plasma turbulence, which largely determines the quality of the confinement. In particular, accurate particle ...

ERO is a 3D Monte-Carlo impurity transport and plasma-surface interaction code. In 2011 it was applied for the ITER first wall (FW) life time predictions [1] (critical blanket module BM11). After that the same code was significantly improved during its app ...

A steady-state, fully noninductive plasma current has been sustained for the first time in a tokamak using electron cyclotron current drive only. In this discharge, 123 kA of current have been sustained for the entire gyrotron pulse duration of 2 s. Careful distribution across the plasma miner radius of the power deposited from three 0.5-MW gyrotrons was essential for reaching steady-state conditions. With central current drive, up to 153 kA of current have been fully replaced transiently for 100 ms. The no

Experimental observations in JET tokamak plasmas and gyrokinetic simulations point to an important role, for electron heat transport, of electron-scale instabilities and of their interaction with ion-scale instabilities. Since these effects are maximized f ...

Calculations of the particle flux caused by neutrals originating from the edge are performed for TCV and JET using the one-dimensional kinetic transport code Kn1D. The analysis, confirmed by experimental evidence, shows that for TCV and JET edge fuelling a ...

Progress in understanding lower hybrid current drive (LHCD) at high density has been made through experiments and modeling, which is encouraging given the need for an efficient off-axis current profile control technique in burning plasma. By reducing the w ...

Heat, particle and momentum confinement in L- and H-mode in deuterium, hydrogen and in D/H mixtures have been investigated in JET with the ITER-like wall (JET-ILW). The paper expands on previous work [1,2] by presenting new results on heat, momentum and pa ...

Henri Weisen

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Generation and observation of fast deuterium ions and fusion-born alpha particles in JET D-He-3 plasmas with the 3-ion radio-frequency heating scenario

First mirror test in JET for ITER: Complete overview after three ILW campaigns

Overview of the EUROfusion Tokamak Exploitation programme in support of ITER and DEMO

'Profile consistency' features in shaped sawtoothing ohmic TCV plasmas

Recent Results from the Tcv Tokamak

Ultrasoft x-ray spectroscopy using multilayer mirrors on TCV

Observation of enhanced ion particle transport in mixed H/D isotope plasmas on JET

Elm Control During Double-Null Ohmic H Modes in Tcv

Understanding of H mode pedestal characteristics using the multimachine pedestal database

The 'neutron deficit' in the JET tokamak

On the dependence of energy confinement on elongation in single null divertor plasmas

A wall-aligned grid generator for non-linear simulations of MHD instabilities in tokamak plasmas

Preliminary Confinement Studies during ECRH in TCV

A new mechanism for increasing density peaking in tokamaks: improvement of the inward particle pinch with edge E x B shearing

Improved ERO modelling of beryllium erosion at ITER upper first wall panel using JET-ILW and PISCES-B experience

Steady-state fully noninductive current driven by electron cyclotron waves in a magnetically confined plasma

Impact of electron-scale turbulence and multi-scale interactions in the JET tokamak

Influence of particle sources on electron density peaking in TCV and JET

Review of recent experimental and modeling advances in the understanding of lower hybrid current drive in ITER-relevant regimes

Isotope Dependence of Confinement in JET-ILW Deuterium and Hydrogen Plasmas