Scenario modelling for the demonstration fusion reactor (DEMO) has been carried out using a variety of simulation codes. Two DEMO concepts have been analysed: a pulsed tokamak, characterised by rather conventional physics and technology assumptions (DEMO1) and a steady-state tokamak, with moderately advanced physics and technology assumptions (DEMO2). Sensitivity to impurity concentrations, radiation, heat transport models has been investigated. For DEMO2, the impact of current driven non-inductively by Neutral Beams has been studied by full MonteCarlo simulations of the fast ion distribution. The results obtained are a part of a more extensive R&D effort carried out in the EU in order to develop a viable option for a DEMO reactor, to be adopted after ITER for fusion energy research.

Using an X-pinch configuration, we have determined that micropinches produced by exploding-wire z pinches can have densities approaching solid density and temperatures of 0.5-1.8 keV, depending upon the wire material used. These plasma parameters, determined from x-ray spectra recorded using an x-ray streak camera, vary drastically on time scales ranging from <10 to 100 ps. Computer simulations require radiation loss to reproduce the observed plasma implosion, suggesting that a radiative-collapse hypothesis for micropinch plasma formation may be correct.

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JT-60SA design scenarios have been analyzed with the help of the self-consistent core-edge COREDIV code, with the aim to assess the influence of impurities on the plasma parameters and tokamak performance. In particular, the reduction of divertor target power load due to radiation of sputtered and externally seeded impurities has been investigated. For all scenarios considered, the gradual replacement of carbon by low Z seeding impurity (N, Ne) is observed as the gas influx increases. For high auxiliary power and low density scenarios, the carbon and seeding impurity radiation does not effectively reduce power to plate. Consequently, results with very high

The JT-60SA tokamak, being built under the Broader Approach agreement jointly by Europe and Japan, is due to start operation in 2020 and is expected to give substantial contributions to both ITER and DEMO scenario optimisation. A broad set of preparation activities for an efficient start of the experiments on JT-60SA is being carried out, involving elaboration of the Research Plan, advanced modelling in various domains, feasibility and conception studies of diagnostics and other sub-systems in connection with the priorities of the scientific programme, development and validation of operation tools. The logic and coherence of this approach, as well as the most significant results of the main activities undertaken are presented and summarised.