In the framework of the ion cyclotron resonance heating (ICRH) development led at CEA Cadarache, an actively cooled Faraday screen (FS) prototype with cantilevered horizontal bars and a slotted box has been designed to increase the heat exhaust capability (for high-power operation), reduce the parallel RF electric field along long field lines and qualify alternative mechanical solutions for ITER (bars are disconnected from the septum to reduce the stress level). The new FS has been installed on an existing ICRH antenna, and was tested during the 2011 Tore Supra experimental campaign. The antenna hosting the new screen exhibits high sensitivity to the edge plasma condition, some instabilities of electrical matching and improved heat exhaust capabilities in accordance with the thermo-mechanical design. RF-induced heat loads derived from IR thermography have been found to be about five times higher in the equatorial plane with the new design compared with the conventional design. The experimental results show that minimizing the parallel RF electric field along long field lines is not enough to reduce the wave–plasma interaction on the screen. This paper summarizes the experimental RF-induced heat load for several plasma scenarios and edge parameters (plasma current, density and heating power level) with emphasis on RF-sheath rectification and E × B convection generated in front of the antenna through the differential biasing of adjacent field lines.

In parallel to the direct contribution to the procurement phase of ITER and Broader Approach, CEA has initiated research & development programmes, accompanied by experiments together with a significant modelling effort, aimed at ensuring robust operation, plasma performance, as well as mitigating the risks of the procurement phase. This overview reports the latest progress in both fusion science and technology including many areas, namely the mitigation of superconducting magnet quenches, disruption-generated runaway electrons, edge-localized modes (ELMs), the development of imaging surveillance, and heating and current drive systems for steady-state operation. The WEST (W Environment for Steady-state Tokamaks) project, turning Tore Supra into an actively cooled W-divertor platform open to the ITER partners and industries, is presented.

The experiment detailed in this paper presents results obtained on the nucleation, growth and detachment of HFE-7100 confined vapour bubbles. Bubbles are created on an artificial nucleation site between two-dimensional plates under terrestrial and microgravity conditions. The experiments are performed by varying the shear flow by changing the convective mass flow rate, and varying the bubble nucleation rate by changing the heat flux supplied. The experiments are performed under normal (1 g) and reduced gravity (μg). The distance between the plates is equal to 1 mm. The results of these experiments are related to the detachment diameters of bubbles on the single artificial nucleation site and to the associated effects on the heat transfer by the confinement influence. The experimental device allows the observation of the flow using both visible video camera and infrared video camera. Here, we present the results obtained concerning the influence of gravity on the bubble detachment diameter and the images of 2D bubbles obtained in microgravity by means of an infrared camera. The following parameters: nucleation site surface temperature, bubble detachment diameter and bubble nucleation frequency evidence modifications due to microgravity.