CRONOS is a suite of numerical codes for the predictive/interpretative simulation of a full tokamak discharge. It integrates, in a modular structure, a 1D transport solver with general 2D magnetic equilibria, several heat, particle and impurities transport models, as well as heat, particle and momentum sources. This paper gives a first comprehensive description of the CRONOS suite: overall structure of the code, main available models, details on the simulation workflow and numerical implementation. Some examples of applications to the analysis of experimental discharges and the predictions of ITER scenarios are also given.

Different models have been introduced in the stability code MARS-F in order to study the damping effect on resistive wall modes (RWM) in rotating plasmas. Benchmarks of MARS-F calculations with RWM experiments on JET and DIII-D indicate that the semi-kinetic damping model is a good candidate for explaining the damping mechanisms. Based on these results, the critical rotation speeds required for RWM stabilization in advanced ITER scenarios are predicted. Active feedback control of the n = 1 RWM in ITER is also studied using the MARS-F code.

Self-consistent transport simulation of ITER scenarios is a very important tool for the exploration of the operational space and for scenario optimization. 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 coil system, heating and current drive, fuelling and particle and energy exhaust systems. This paper discusses results of predictive modelling of all reference ITER scenarios and variants using two suites of linked transport and equilibrium codes. The first suite consisting of the 1.5D core/2D SOL code JINTRAC (Wiesen S. et al 2008 JINTRAC-JET modelling suite JET ITC-Report) and the free-boundary equilibrium evolution code CREATE-NL (Albanese R. et al 2003 ISEM 2003 (Versailles, France); Albanese R. et al 2004 Nucl. Fusion 44 999), 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 (Artaud J.F. et al 2010 Nucl. Fusion 50 043001) and the free-boundary equilibrium evolution code DINA-CH (Kim S.H. et al 2009 Plasma Phys. Control. Fusion 51 105007).

The D α emission time-series from the TCV tokamak was investigated for a large set of ELMy discharges, to determine whether fluctuations in the time delay between ELMs are the result of noise only, or whether a deterministic process in a chaotic state exists, as suggested by results on JT-60U (Bak et al 1999 Phys. Rev. Lett. 83 1339. This study was carried out by searching the time-series of each discharge for transient sequences that are generic to chaotic systems, called unstable periodic orbits (UPOs). By taking a statistical approach, a subset of discharges with q 95 greater than 2.6 were shown to contain many more UPOs than could be expected if the dynamical system was noise dominated, and the properties of these UPOs were found to exhibit systematic variations with plasma parameters. Specifically, the period of the unstable fixed point T * was found to scale independently with the plasma current, density and the inner plasma-wall distance. In a number of cases, two separate fixed points were found to co-exist during the same discharge.

On the Tokamakà Configuration Variable (TCV), electron internal transport barriers (eITBs) can be formed during a gradual evolution from a centrally peaked to a hollow current profile while all external actuators are held constant. The formation occurs rapidly (<τ eE) and locally and, according to ASTRA modelling, is consistent with the appearance of a local minimum in the safety factor (q) profile. The eITB is sustained by non-inductively driven currents (including the off-axis bootstrap current) for many current redistribution times while the current in the tokamak transformer is held constant. The maximum duration is limited by the pulse length of the gyrotrons. The transformer coil can be used as a counter (or co-) current source with negligible accompanying input power. In established eITBs the performance can be enhanced (degraded) by altering solely the central current or q-profile. New experiments show that the same stationary eITB performance can be reached starting from discharges with centrally peaked current. A fine scan in surface voltage shows a smooth increase in performance and no sudden improvement with voltage despite the fact that q min must pass through several low-order rational values.