Suchergebnisse

An Imaging Neutral Particle Analyzer (INPA) diagnostic has been designed for the ASDEX Upgrade (AUG) tokamak. The AUG INPA diagnostic will measure fast neutrals escaping the plasma after charge exchange reactions. The neutrals will be ionized by a 20 nm carbon foil and deflected toward a scintillator by the local magnetic field. The use of a neutral beam injector (NBI) as an active source of neutrals will provide radially resolved measurements, while the use of a scintillator as an active component will allow us to cover the whole plasma along the NBI line with unprecedented phase-space resolution (<12 keV and 8 cm) and a fast temporal response (up to 1 kHz with the high resolution acquisition system and above 100 kHz with the low resolution one), making it suitable to study localized fast-ion redistributions in phase space. ; This project received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant Agreement No. 805162) and the Spanish Ministerio de Ciencia, Innovación y Universidades (Grant No. FPU19/02486).

An Imaging Neutral Particle Analyzer (INPA) diagnostic has been designed for the ASDEX Upgrade (AUG) tokamak. The AUG INPA diagnostic will measure fast neutrals escaping the plasma after charge exchange reactions. The neutrals will be ionized by a 20 nm carbon foil and deflected toward a scintillator by the local magnetic field. The use of a neutral beam injector (NBI) as an active source of neutrals will provide radially resolved measurements, while the use of a scintillator as an active component will allow us to cover the whole plasma along the NBI line with unprecedented phase-space resolution (<12 keV and 8 cm) and a fast temporal response (up to 1 kHz with the high resolution acquisition system and above 100 kHz with the low resolution one), making it suitable to study localized fast-ion redistributions in phase space. ; European Union's Horizon 2020 (Grant Agreement No. 805162) ; Ministerio de Ciencia, Innovación y Universidades (Grant No. FPU19/02486)

L'étude des décisions qui ont mené à la création d'un programme national en fusion nucléaire au Canada et à la construction d'un appareil de confinement magnétique de type Tokamak à Varennes suggère que le résultat final n'est pas compatible avec la théorie du choix rationnel. Il est plutôt le produit contingent d'une dynamique temporelle mettant en scène des acteurs aux intérêts divergents qui ont dû s'accommoder à un environnement variable. L'analyse des stratégies des parties fait ressortir que celles qui ont atteint leurs objectifs ont su adapter leur discours et s'assurer des appuis à certains moments clés. De ce point de vue, la politique, la technologie ou toute autre variable sociale ou économique ne sont pas seulement des contraintes mais aussi des ressources mises à profit par les participants pour arriver à leurs fins.

<!-- p, li { white-space: pre-wrap; } --><p style="text-indent: 0px; margin: 0px;">In this article we have used the 2D fluid turbulence numerical model, ESEL, to simulate turbulent transport in edge tokamak plasma. Basic plasma parameters from the ASDEX Upgrade and COMPASS tokamaks are used as input for the model, and the output is compared with experimental observations obtained by reciprocating probe measurements from the two machines. Agreements were found in radial profiles of mean plasma potential and temperature, and in a level of density fluctuations. Disagreements, however, were found in the level of plasma potential and temperature fluctuations. This implicates a need for an extension of the ESEL model from 2D to 3D to fully resolve the parallel dynamics, and the coupling from the plasma to the sheath.</p>

Using the PION ICRH modelling code and comparisons against JET tokamak experiments, the effect of including pitch angle dependence within the RF diffusion operator on the fast ion particle distribution functions is quantified. It is found to be of greatest importance in cases of higher harmonic heating and lower heating ion mass, resulting in faster drop-off of the distribution's high energy tail. We see differences of several orders of magnitude in the high-energy range and significant non-linear alterations by several tens of percent to ion species power partition. ITER scenario operational parameters are also considered, and this improved treatment is shown to benefit anticipated ITER scenarios with second harmonic hydrogen heating, according to our predictions. PION's combination of benchmarked simplified wave physics and Fokker-Planck treatment offers modelling advantages. Since including the pitch angle dependence in the RF diffusion operator has not led to a significant increase in the required computing time when modelling different ICRF schemes in JET discharges, it has been made available within the production code. ; The CCFE part of this work has been carried out within the framework of the EUROfusion Consortium and has received funding from the Euratom research and training programme 2014–2018 and 2019–2020 under Grant Agreement No. 633053. The views and opinions expressed herein do not necessarily reflect those of the European Commission. The BSC part of this project is co-financed by the European Union Regional Development Fund within the framework of the ERDF Operational Program of Catalonia 2014–2020 with a grant of 50% of total cost eligible. The authors are grateful to Jacob Eriksson for assistance with experimental data, to Lars-Göran Eriksson for discussions on the implementation of the new features, and to Colin Roach and Michael Fitzgerald for valuable comments on the manuscript. ; Peer Reviewed ; Postprint (published version)

Langmuir Probes attached to plasma-facing components in a Tokamak are used to diagnose high-temperature plasma during fusion experiments. In this work, a finite element model of Langmuir Probe-Cooling Monoblock (LP-CM) is established, and structural analysis of the LP-CM is carried out. The maximum von Mises stress during the 400 s incident heat flux has been given in detail, and the relationship between the sliding friction coefficient and thermal stress has been investigated systematically. A contact design is employed between Langmuir Probe and Cooling Monoblock, which is an effective method to lower the thermal stress. The thermal stress reaches the peak on the edge of the aluminium oxide ceramic interlayer. The damaged displacement field of the LP-CM has been examined fully, and the maximum global displacement is 0.444 mm.

In this work, we generalise linear magnetohydrodynamic (MHD) stability theory to include equilibrium pressure anisotropy in the fluid part of the analysis. A novel 'single-adiabatic' (SA) fluid closure is presented which is complementary to the usual 'double-adiabatic' (CGL) model and has the advantage of naturally reproducing exactly the MHD spectrum in the isotropic limit. As with MHD and CGL, the SA model neglects the anisotropic perturbed pressure and thus loses non-local fast-particle stabilisation present in the kinetic approach. Another interesting aspect of this new approach is that the stabilising terms appear naturally as separate viscous corrections leaving the isotropic SA closure unchanged. After verifying the self-consistency of the SA model, we re-derive the projected linear MHD set of equations required for stability analysis of tokamaks in the MISHKA code. The cylindrical wave equation is derived analytically as done previously in the spectral theory of MHD and clear predictions are made for the modification to fast-magnetosonic and slow ion sound speeds due to equilibrium anisotropy. ; This work was funded by the Australian Research Council through Grant Nos. DP1093797 and FT0991899. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement number 633053 and from the RCUK Energy Programme [grant number EP/I501045].

In this work, we generalise linear magnetohydrodynamic (MHD) stability theory to include equilibrium pressure anisotropy in the fluid part of the analysis. A novel 'single-adiabatic' (SA) fluid closure is presented which is complementary to the usual 'double-adiabatic' (CGL) model and has the advantage of naturally reproducing exactly the MHD spectrum in the isotropic limit. As with MHD and CGL, the SA model neglects the anisotropic perturbed pressure and thus loses non-local fast-particle stabilisation present in the kinetic approach. Another interesting aspect of this new approach is that the stabilising terms appear naturally as separate viscous corrections leaving the isotropic SA closure unchanged. After verifying the self-consistency of the SA model, we re-derive the projected linear MHD set of equations required for stability analysis of tokamaks in the MISHKA code. The cylindrical wave equation is derived analytically as done previously in the spectral theory of MHD and clear predictions are made for the modification to fast-magnetosonic and slow ion sound speeds due to equilibrium anisotropy. ; This work was funded by the Australian Research Council through Grant Nos. DP1093797 and FT0991899. This project has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement number 633053 and from the RCUK Energy Programme [grant number EP/I501045].