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Research on fusion energy has entered a new era with the decision to build ITER in Cadarache, France. The success of this international endeavour is crucial for all partners, the host country, as well as for the PACA region where Cadarache is located. The association of several laboratories in the PACA region to focus on outstanding open questions for ITER is one element in the means to respond to such a challenge. Among the open questions, the issue of plasma-wall interaction is a matter of growing concern since it associates a broad range of problems: safety, engineering of the wall components and the future performance of the device. Most important among the latter is the ability to reach the main ITER objective, namely the operation of burning plasmas.

We are concerned here by a simulation effort of the plasma wall interaction based on first principle physics. This issue is particularly important since the design of components dedicated to the control of the edge plasma-wall interaction stems from an extrapolation procedure based on an ad-hoc transport code with no embedded scaling properties from present experiments to ITER conditions. This ad-hoc transport is local and linear and cannot account for the known properties of the plasma turbulent transport. Furthermore, it removes all the non linear effects and their enhancement via the coupling to atomic physics, erosion of material or bifurcations of the plasma properties, such as the turbulence transport capability.Our project named ESPOIR, for Edge Simulation of the Physics Of ITER Relevant turbulent transport, is based on the development of two main simulation codes. The long-term goal is to build the new generation of codes dedicated to the analysis of the edge and divertor physics and thus replace the present codes based on as-hoc diffusive plasma transport. Although a kinetic description of the plasma turbulence would be more appropriate, we have chosen a fluid description that is in itself a challenge regarding our goal of providing a routine simulation tool prior to ITER experiments. With this challenge in mind we have organised the ESPOIR project as an interdisciplinary effort including physicists specialised in plasma physics and fluid turbulence simulation codes, applied mathematicians in charge of large code developments and applied mathematicians specialised numerical analysis of novel numerical schemes including asymptotic limits and boundary conditions. All three partners have an internationally recognised expertise and more than 10 years continuous experience in turbulence simulations. Furthermore, one participant is an internationally recognised expert in the field of Plasma-Wall Interaction including theory and experiments.

A first effort is dedicated to the development of a versatile simulation tool (TOKAM-3D) that will address the physics in a simplified cylindrical geometry and will also be used as a test bed to implement novel numerical schemes developed with the mathematicians participating to the project.

The second effort aims at developing the code ESPOIR in full ITER geometry. Given the importance of the computer resources required by such a simulation, first runs will be achieved within framework of the project but routine operation of the ESPOIR code can only be envisaged just prior to ITER operation.

Among the key physics to be addressed in the project are the width of the heat channel at the plasma edge, the plasma fuelling and density limit (related to the so-called Greenwald density), the bifurcations of the edge plasma state such as the H-mode as well as radiative bifurcations and the interaction of the plasma with the main chamber wall and consequent erosion problems. Each of these issues is crucial for ITER and benefit from a significant experimental investigation including that from circular cross section tokamaks such as Tore Supra. Furthermore, these non-linear physics problems strongly depend on the turbulent transport and thus require a proper first principle description to achieve reliable predictive capability.

The present specific contribution aims at developing a tool with accurate understanding and knowledge of its numerics and physics as well as a properly defined architecture that will also enable an efficient coupling to the neutral particle source term as generated by the Monte Carlo code EIRENE, the reference neutral particle code for ITER. The joint effort between French partners is therefore completed by a European collaboration with the team in charge of EIRENE as well as with the two European task forces for fusion, respectively in charge of the Integrated Tokamak Modelling and of the Plasma-Wall Interaction.

The ESPOIR project will allow us to address key physics issue for ITER with advanced simulation tools. This will provide the basis for new theoretical insight into the problem of plasma wall interaction as well as the renewed means for the crucial collaboration with experimentalists.