Scenario development for the observation of alpha-driven instabilities in JET DT plasmas

In DT plasmas, toroidal Alfvén eigenmodes (TAEs) can be made unstable by the alpha particles resulting from fusion reactions, and may induce a significant redistribution of fast ions. Recent experiments have been conducted in JET deuterium plasmas in order to prepare scenarios aimed at observing alpha-driven TAEs in a future JET DT campaign. Discharges at low density, large core temperatures associated with the presence of internal transport barriers and characterised by good energetic ion confinement have been performed. ICRH has been used in the hydrogen minority heating regime to probe the TAE stability. The consequent presence of MeV ions has resulted in the observation of TAEs in many instances. The impact of several key parameters on TAE stability could therefore be studied experimentally. Modeling taking into account NBI and ICRH fast ions shows good agreement with the measured neutron rates, and has allowed predictions for DT plasmas to be performed

Investigation of laminar detachment by means of simultaneous microphone and surface hot wire measurements

An experimental study on the acoustic characterization of the laminar separation bubble on an airfoil is presented. The acoustic near- and far-fields are sampled by means of microphone arrays. Additionally the wall shear stresses are measured on the airfoil suction side by means of 24 MEMS surface hot wires in the region where the separation bubble was expected. Dierent processing strategies both in the frequency and in the time domain were applied for an acoustic characterization of the bubble. A focus of the study presented here is the application of the so called causality correlation method. The wall shear stresses on the airfoil surface together with the pressure fluctuations in the near- and far-field are recorded simultaneously. This enables the calculation of the cross-correlation between the measured quantities. An analysis of the resulting coecient matrix in the space-time domain identies perturbations traveling along the airfoil, showing a linear dependency on the sound generating process. For the case of the correlation between the wall shear stresses on the airfoil and the pressure fluctuations in the far-field the validity of the results were improved signicantly by using the focused pressure signals from the microphone-array

Comparison of dust transport modelling codes in a tokamak plasma

Since the installation on the Joint European Torus of the ITER-like Wall (ILW), intense radiation spikes have been observed, especially in the discharges following a disruption, and have been associated with possible sudden injection of tungsten (W) impurities consequent to full ablation of W dust particles. The problem of dust production, mobilization, and interaction both with the plasma and the vessel tiles is therefore of great concern and requires the setting up of dedicated and validated numerical modeling tools. Among these, a useful role is played by the dust trajectory calculators, which can present in a relatively clear way the qualitative and quantitative description of the mobilization and fate of selected bunches of dust grains