MHD stability of fully non inductive discharges in Tore Supra

12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France)During the 2003 experimental campaign, the aim of realizing reliable fully non inductive discharges has been successfully completed in Tore Supra. One the major difficulties in optimizing this scenario comes from MHD stability issues. Indeed, the current profile obtained with LH antennas in these experiments is prone to the triggering of single or double tearing modes. Under certain conditions, the discharges enters in a regime of permanent MHD activity. The present work investigates the MHD properties of these fully non-inductive discharges in the operational space defined by the toroidal magnetic field B, the total plasma current Ip, and the mean parallel index of LH waves . Linear MHD stability properties divide the operational space in regions separated by rational values of the minimum of the safety factor. We discuss in our work the localisation of the transition between benign MHD activity and the MHD regime

Lower hybrid counter-current drive experiment in JET

12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France)Lower hybrid current drive has been demonstrated to be an efficient tool to modify the current profile in order to access to high energy confinement regimes. Counter-current drive could be an alternative scenario provided the current drive efficiency is not too small when fast electrons flow in the opposite way to the DC electric field. By reversing the toroidal field (Bt=-3.1T) and the plasma current (Ip=-1.45MA), counter current drive with lower hybrid waves has been investigated for the first time in JET. The experiments were carried out at low plasma density ( =1.0 x1019m-3 , ne(0)=1.6 x 1019m-3) with 2.9MW of lower hybrid power. The CRONOS code[1], which couples the diffusion equations to a 2-D equilibrium code, has been used to estimate the RF driven current. Runs indicate that loop voltage and internal inductance are best simulated with a current drive efficiency of –1.0 x 1019 A.W-1.m-2 with a peaked central LH power deposition deduced from DELPHINE[2]. This efficiency is indeed very close to the one found for co-LHCD at similar plasma current and density. Current profile evolves from a hollow profile (with a minimum at r/a ~0) and a maximum at r/a~0.4-0.5) to a rather flat profile (up to r/a=0.3)

Self-consistent simulation of plasma scenarios for ITER using a combination of 1.5D transport codes and free-boundary equilibrium codes

Self-consistent transport simulation of ITER scenarios is a very important tool for the exploration of the operational space and for scenario optimisation. It also provides an assessment of the compatibility of developed scenarios (which include fast transient events) with machine constraints, in particular with the poloidal field (PF) coil system, heating and current drive (H&CD), fuelling and particle and energy exhaust systems. This paper discusses results of predictive modelling of all reference ITER scenarios and variants using two suite of linked transport and equilibrium codes. The first suite consisting of the 1.5D core/2D SOL code JINTRAC [1] and the free boundary equilibrium evolution code CREATE-NL [2,3], was mainly used to simulate the inductive D-T reference Scenario-2 with fusion gain Q=10 and its variants in H, D and He (including ITER scenarios with reduced current and toroidal field). The second suite of codes was used mainly for the modelling of hybrid and steady state ITER scenarios. It combines the 1.5D core transport code CRONOS [4] and the free boundary equilibrium evolution code DINA-CH [5].Comment: 23 pages, 18 figure

A FAIR based approach to data sharing in Europe

The European fusion research activities have, over recent decades, generated a vast and varied set of data. The volume and diversity of the data that need to be catalogued and annotated make the task of organising and making the data available within a broader environment very challenging. Nevertheless, there are strong scientific drivers as well as incentives and mandates from national research agencies suggesting that a more coherent approach to data referencing, dissemination and sharing would provide strong benefits to the fusion research community and beyond. Here, we discuss the technical requirements and developments needed to transition the current, and future, range of fusion research data to an open and Findable, Accessible, Interoperable, and Reusable data sharing structure guided by the principle \u27as open as possible, as closed as necessary\u27. Here we propose a set of recommendations and technical implementations needed to form a European data sharing environment for the fusion research programmes. Consistency with the emerging IMAS (ITER Integrated Modelling and Analysis Suite) infrastructure is considered to facilitate future deployments

Transient heat transport studies in JET conventional and advanced tokamak plasmas

Transient transport studies have long been recognised as a valuable complement to steady-state analysis for the understanding of transport mechanisms. Recently, transient transport data have proved to be a powerful tool to test the validity of physics-based transport models. In this paper, results from transient heat transport experiments in JET and their modelling will be presented. Edge cold pulses and modulation of ICRH (in Mode Conversion scheme) and NBI power have been used to provide detectable electron (Te) and ion (Ti) temperature perturbations. The experiments have been performed either in conventional plasma regimes or in Advanced Tokamak regimes, in the presence of an Internal Transport Barrier (ITB). In conventional plasmas issues such as stiffness, influence of Te/Ti, non-locality have been addressed. In ITB plasmas, insight into the physics of ITBs and the ITB formation mechanisms has been gained. The use of edge perturbations for ITB triggering has been explored. Modelling of the experimental results has been performed using both empirical models and physics-based models. Results of cold pulse experiments in ITBs have also been compared with turbulence simulations