Fast ion confinement in negative triangularity plasmas on the TCV tokamak

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The research programme performed on the Mega Amp Spherical Tokamak (MAST) Upgrade experiment has made significant advances in developing the physics understanding of low aspect ratio tokamaks in support of the operation of ITER and design of fusion powerplants. High performance plasma scenarios have been developed to facilitate a broad programme of experiments, in which confinement is constrained by the presence of m/n = 2/1 modes that cause substantial losses of fast ions. The onset of these modes coincide

The demand for megawatt-class gyrotrons for Electron Cyclotron Resonance Heating (ECRH) of nuclear fusion devices is growing significantly. It goes hand in hand with growing requirements for output power, efficiency, operating flexibility, and reliability of gyrotrons used in nuclear fusion, as well as higher demanding of the manufacturability for serial production. In Europe research and development is ongoing to fulfil that future needs, particularly, with regards to output power and efficiency. It is com

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Under the auspices of EUROfusion (WPMST1), the ITER baseline scenario (IBL, [1]) is jointly investigated on AUG and TCV. While the AUG results were presented at the last IAEA FEC [2], this contribution focuses on the recent results obtained in TCV and related integrated modelling results. Such developments in TCV were only possible with the installation of an NBI heating source [3], allowing ELMy H-modes at ITER relevant N. The IBL scenario is mainly characterized by low q95 (3.0-3.6), high positive triang

The scrape-off layer (SOL) sets the bounday conditions of a tokamak, determining the plasma confinement, the heat exhaust, the impurity levels, and controlling the fuelling of the device. Therefore, a first principles understanding of the physical mechanisms governing SOL turbulence is crucial on the way towards fusion energy. We describe SOL simulations carried out by using GBS, a three-dimensional numerical code that solves the drift-reduced Braginskii equations for the two-fluid model of the plasma and c

Since pioneering the alternative “snowflake”(SF) divertor, TCV research has concentrated on understanding its usefulness and applicability for a fusion reactor. It was first demonstrated that this divertor configuration is compatible with the high confinement H-mode regime on TCV and other machines. Since the main hope for this configuration is to lower the peak power incident on the divertor, and in particular near the strike points, this paper presents a résumé of experiments on TCV that seek to understan

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Intermittent blobs, which propagate across a confining magnetic fields, are universally observed in natural and laboratory plasmas. In fusion plasmas, cross-field transport of particles and energy are associated, at least in part, with the propagation of blobs, which are therefore of great importance for the design of future fusion reactors. In TORPEX, blobs are generated from ideal interchange modes and, driven by B and curvature-induced charge separation, propagate radially outwards. An analytical blob s

The goal of the present diploma work is to experimentally investigate the fast ion physics in TORPEX plasmas, in which interchange modes with flute characteristics and intermittent transport events, i.e. blobs, are observed to dominate the plasma dynamics. During the first part of the diploma, the Candidate will test different fast ion emitters on a test bench, which will be then mounted into the BN casing to form the fast ion source. In parallel, the Candidate will design an innovative in-vessel movable sy

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 key issue for steady-state tokamak operation is to determine the edge conditions that are compatible both with good core confinement and with the power handling and plasma exhaust capabilities of the plasma facing components (PFCs) and divertor systems. A quantitative response to this open question will provide a robust scientific basis for reliable extrapolation of present regimes to an ITER compatible steady-state scenario. In this context, the JET programme addressing steady-state operation is focused

ASDEX Upgrade has recently finished its transition towards an all-W divertor tokamak, by the exchange of the last remaining graphite tiles to W-coated ones. The plasma start-up was performed without prior boronization. It was found that the large He content in the plasma, resulting from DC glow discharges for conditioning, leads to a confinement reduction. After the change to D glow for inter-shot conditioning, the He content quickly dropped and, in parallel, the usual H-Mode confinement with H factors clos

ELMy H-mode experiments at JET in 2000/mid-2002 have focused on discharges with normalized parameters for plasma density, energy confinement and beta similar to those of the ITER Q(DT) = 10 reference regime (n/n(GW) similar to 0.85, H-98(y,H-2) similar to 1, beta(N) similar to 1.8). ELMy H-mode plasmas have been realized reaching or even exceeding those parameters in steady-state conditions (up to similar to5 s or 12tau(epsilon)) in a reproducible way and only limited by the duration of the additional heati

One of the principal research axes related to nuclear energy concerns the management of nuclear wastes. In this context, certain innovative pathways are being explored to provide options which could lead to a major reduction of the quantities of radioactive nuclides requiring long-term geological storage. An important aspect is the development of advanced nuclear systems which allow the transmutation of long-lived minor actinides, the ADS (accelerator driven system) concept often being proposed for the purp

The dependence of the measured damping rate upon the neutral beam heating power (P-NBI) and plasma beta has been experimentally investigated for n = 1 toroidal Alfven eigenmodes (TAEs) in JET limiter plasmas with a monotonic safety factor profile and low edge magnetic shear. The mode frequency is observed to decrease with increasing beta, as predicted by various theoretical models. For low P-NBI < 3 MW, a single n = 1 TAE splits into two modes closely spaced around the expected TAE frequency, and the mode d

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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

Fast ion confinement in negative triangularity plasmas on the TCV tokamak

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Overview of the MAST Upgrade physics programme: testing novel concepts at low aspect ratio to inform future devices

Megawatt-Class Sub-THz Gyrotrons for ECRH in Future High-Field Fusion Devices

Performance assessment of a reactor-scale tightly baffled divertor using the SOLPS-ITER software

The SND@LHC Neutron Shielding

Fracture Toughness Evaluation of Inhomogeneous Reactor Pressure Vessel Steels Using Sub-sized Specimens

ITER baseline scenario investigations on TCV and comparison with AUG

Plasma refuelling at the SOL simulated with the GBS code

Progress in Snowflake Divertor Studies on TCV

Continuous Angular Multiple Energy Analysis Spectrometer Report on Instrument Concept and Scientific Case

Understanding and taming plasma blobs in toroidal magnetized plasmas

Experimental investigation of fast ion dynamics in TORPEX toroidal plasmas

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

Development of steady-state scenarios compatible with ITER-like wall conditions

Plasma wall interaction and its implication in an all tungsten divertor tokamak

Towards the realization on JET of an integrated H-mode scenario for ITER

Etudes numériques et expérimentales de caractéristiques d'un système rapide sous-critique alimenté par une source externe

Measurement of the damping rate of n=1 toroidal Alfven eigenmodes as a function of the neutral beam heating power and plasma beta on JET

Advanced high-power gyrotrons

Long timescale density peaking in JET

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