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A new kind of superconductor, using the cable-in-conduit concept, is emerging, mainly in the context of fusion activity. At present no large Nb3Sn magnet in the world is operating using this concept. The difficulty of this technology, which has now been studied for 20 years, is that it requires major advances in several interconnected new fields, such as handling a large number (1000) of superconducting strands, high current conductors (50 kA), forced flow cryogenics, Nb3Sn technology, low loss conductors in pulsed operation, high current connections and high voltage insulation (10 kV), as well as demonstration of its economical and industrial feasibility. CEA has been very much involved, during the past ten years, in this development, which took place in the framework of the NET and ITER technological programmes. One major milestone was reached in 1998-1999 with the successful tests by Euratom-CEA of three full size conductor and connection samples in the SULTAN facility in Switzerland.

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The JT-60SA is a fusion experiment designed to contribute to the early realization of fusion energy, by providing support to the operation of ITER, by addressing key physics issues for ITER and DEMO and by investigating how best to optimize the operation of the next fusion power plants that will be built after ITER.It is a combined project of the JA-EU Satellite Tokamak Program under the Broader Approach (BA) Program and JAEA's Program for National Use, and it is to be built in Naka, Japan, using the infrastructure of the existing JT-60U experiment. This paper describes in detail the design of the JT-60SA Toroidal Field magnet and shows the strong points of each foreseen solution. Additional information about manufacturing procedures is given and technological issues are reported and critically analysed.

Tore Supra routinely addresses the physics and technology of very long duration plasma discharges, thus bringing precious information on critical issues of long pulse operation of ITER. A new ITER relevant LHCD launcher has allowed coupling to the plasma a power level of 2.7 MW for 78 s, corresponding to a power density close to the design value foreseen for an ITER LHCD system. In accordance with the expectations, long distance (10 cm) power coupling has been obtained. Successive stationary states of the plasma current profile have been controlled in real time featuring i) control of sawteeth with varying plasma parameters, ii) obtaining and sustaining a "hot core" plasma regime, iii) recovery from a voluntarily triggered deleterious MHD regime. The SOL parameters and power deposition have been documented during L-mode ramp-up phase, a crucial point for ITER before the X-point formation. Disruption mitigation studies have been conducted with massive gas injection, evidencing the difference between He and Ar and the possible role of the q=2 surface in limiting the gas penetration. ICRF assisted wall conditioning in the presence of magnetic field has been investigated, culminating in the demonstration that this conditioning scheme allows to recover normal operation after disruptions. Effect of the magnetic field ripple on the intrinsic plasma rotation has been studied, showing the competition between turbulent transport processes and ripple toroidal friction. During dedicated dimensionless experiments, the effect of varying the collisionality on turbulence wavenumber spectra has been documented, giving new insight into the turbulence mechanism. Turbulence measurements have also allowed quantitatively comparing experimental results to predictions by 5D gyrokinetic codes: numerical results simultaneously match the magnitude of effective heat diffusivity, rms values of density fluctuations, and wave-number spectra. A clear correlation between electron temperature gradient and impurity transport in the very core of the plasma has been observed, strongly suggesting the existence of a threshold above which transport is dominated by turbulent electron modes. Dynamics of edge turbulent fluctuations has been studied by correlating data from fast imaging cameras and Langmuir probes, yielding a coherent picture of transport processes involved in the SOL.

The European DEMO, i.e. the demonstration fusion power plant designed in the framework of the Roadmap to Fusion Electricity by the EUROfusion Consortium, is approaching the end of the pre-conceptual design phase, to be accomplished with a Gate Review in 2020, in which all DEMO subsystems will be reviewed by panels of independent experts. The latest 2018

The main results of the Tore Supra experimental programme in the years 2007-2008 are reported. They document significant progress achieved in the domain of steady-state tokamak research, as well as in more general issues relevant for ITER and for fusion physics research. Three areas are covered: ITER relevant technology developments and tests in a real machine environment, tokamak operational issues for high power and long pulses, and fusion plasma physics. Results presented in this paper include: test and validation of a new, load-resilient concept of ICRH antenna and of an inspection robot operated under ultra-high vacuum and high temperature conditions; an extensive experimental campaign (5 h of plasma) aiming at deuterium inventory and carbon migration studies; real-time control of sawteeth by ECCD in the presence of fast ion tails; ECRHassisted plasma startup studies; dimensionless  scalings of transport and turbulence; transport experiments using active pertubation methods; resistive and fast-particle driven MHD studies. The potential role of Tore Supra in the worldwide fusion programme before the start of ITER operation is also discussed.

The general design and the associated performance analysis of a joint proposed by the European Union for both ITER Central Solenoid and Toroidal Field coils are presented. Results of an extensive testing programme performed on subsize joints (scale US), including DC resistance and pulsed field losses measurements are given and discussed, as well as their interaction on the final joint design. Results of feasibility tests carried out on a full-size piece are also given. This study has finally led to the design of a full-size joint sample to be fabricated in industry and tested in specific laboratory test facilities.