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The density peaking was studied in the ICRH versus the NBI identity plasmas and results in R/Ln=0.45 for the ICRH shot and R/Ln=0.93 for the NBI shot. The dimensionless profiles of q, ρ*, υ*, βn and Ti/Te≈1 were matched within 5% difference except in the central part of the plasma (ρtor

Experiments on DIII-D have increased confidence in a prediction of moderate intrinsic rotation in ITER[1] by investigating the effect of fast-ions and edge neutrals in rotation studies. In a large tokamak like ITER, intrinsic sources of rotation are important because evidence suggests they will be comparable to the neutral beam torque. Measurements of the ρ* dependence of intrinsic rotation in Electron Cyclotron Heated H-modes are consistent with previous measurements of the ρ* scaling of intrinsic torque and momentum confinement in beam heated plasmas with significant fast-ion fractions, showing that fast-ions did not corrupt those results. Also, the small differences in intrinsic rotation of closed and open divertor configurations show that momentum transport due to neutrals in the pedestal is not a significant hidden variable. This result is supported by the similarity of intrinsic rotation before and after the onset of detachment.

Analysis of experimental data from DIII-D and C-Mod is used to study the role of opacity on the density pedestal structure. Dα measurements at the midplane on DIII-D indicate that we were able to push the ionization front further out by increasing the separatrix and SOL electron densities. We find that in pressure-record breaking EDA H-modes on C-Mod, adding more gas fueling does not result in an increase of the pedestal density, only an increase in the SOL density. In DIII-D, using gas puff modulations, we observe that when the outer strike point detaches, this strongly reduces the amplitude of the electron density response in the SOL and results in a larger amplitude inside the separatrix. Moreover, we observe the creation of an up-down asymmetry in the electron density with increased gas puff/opacity. Close to the X-point, up to ψN ~ 0.98, the electron density is larger than upstream in DIII-D. SOLPS modeling will be performed to get a better evaluation of the poloidal and radial ionization profiles as well as to better understand the origin of the up-down asymmetry of the electron density in DIII-D.

Dimensionless collisionality (ν*) scans with fixed density in H-mode plasmas on DIII-D and JET together with modelling have shown that the NBI fuelling plays a more important role in density peaking than found in earlier multi-machine datasets where the increased peaking at low collisionality has been primarily ascribed to turbulent effects. Perturbative gas puff modulations are performed to disentangle the fuelling and the transport effects. On DIII-D, we find that, at the lowest ν*, the pinch is directed outward and the diffusion coefficients are larger compared to higher ν* cases. With increasing ν*, the pinch becomes inward outside the mid-radius, while remaining outward inside the mid-radius. At the same time, a strong increase in ion-scale density fluctuations with reduced ν* is observed with BES and predicted with TGLF. On JET, perturbative transport analysis, predictive integrated modelling with JINTRAC+TGLF and non-linear and linear GENE runs all show that NBI fuelling provides an important contribution to density peaking. These results indicate that the density profiles on ITER, where NBI fuelling is very small, may be less peaked than previously thought.

A new version of the Weiland model has been used in predictive JETTO simulations of toroidal rotation. The model includes a self-consistent calculation of the toroidal momentum diffusivity (chi(phi)) which contains both diagonal and non-diagonal (pinch) contributions to the momentum flux. Predictive transport simulations of JET H-mode, L-mode and hybrid discharges are presented. It is shown that experimental temperatures and toroidal velocity were well reproduced by the simulations. The model predicts the ion heat diffusivity (chi(i)) to be larger than the momentum diffusivity and it gives Prandtl numbers (Pr = chi(phi)/chi(i)) between 0.1 and 1. The Prandtl numbers are often, depending on the plasma conditions, predicted to be significantly smaller than unity. This is in accordance with experimental findings.

This report summarises the fusion research activities of the Finnish and Estonian Research Units of the Association Euratom-Tekes in 2007-2013. The emphasis of the work coordinated by EFDA was in ITER Physics, PPPT and the ITM Task Force. Other EFDA activities were carried out within Goal Oriented Training and EFDA Fellowship. In addition, a significant fraction of Tekes activities was directed to F4E grants and ITER contracts. Fusion physics work was carried out at VTT, Aalto University (AU), University of Helsinki (UH) and University of Tartu (UT). The main activities were plasma experiments in collaboration with tokamak laboratories, modelling and code development, and diagnostics related to the main European fusion facilities JET and AUG. In particular, Association Euratom-Tekes focused on (i) Heat and particle transport and fast particle studies, (ii) Plasma-wall interactions and material transport in the scrape-off layer, and (iii) Development of simulation codes and their integration into the ITM environment. The Association participated in the EFDA JET Workprogrammes, including experiments with the carbon wall and the ITER-like wall, edge and core modelling, diagnostics development and code integration. The Association participated also in the experimental programmes of ASDEX Upgrade at IPP and the analysis of DIII-D and C-Mod data. Technology work was carried out at VTT, AU and Tampere University of Technology (TUT) in close collaboration with Finnish industry. Industrial participation was coordinated by Tekes. The technology research and development includes the DTP2 facility at VTT in Tampere, materials and joining techniques, vessel/in-vessel components, magnetic diagnostics for ITER by micromechanical magnetometers, upgrading of the JET NPA diagnostics, Power Plant Physics and Technology (PPPT) activities, plasma facing materials issues, erosion/re-deposition and material transport studies and development of coating techniques. Association Euratom-Tekes was involved in Goal-Oriented Training in Remote Handling project, coordinated by Tampere University of Technology.

Core confinement and the overall performance of the tokamak have been considerably enhanced with the combination of two improved confinement regimes. Internal transport barriers characteristic of the optimized shear regime and an edge transport barrier of the high confinement H mode regime have been superposed in the double barrier (DB) mode. In DT discharges the DB mode has resulted in a fusion gain Q a factor of 2 higher than in conventional sawtoothing steady state ELMy H mode plasmas. The DB mode has been routinely established in the new Gas Box divertor configuration on JET. Off-axis lower hybrid current drive and edge radiation cooling through impurity seeding have been used for current and pressure profile control. This has made it possible to increase the performance up to βN = 2.4 and H89 = 2.7 and to extend flat-top phases up to a duration of three energy confinement times, approaching steady state conditions. Modelling studies of DB mode DT operation on JET predict a fusion power in the range 20-30 MW. In ITER transport code modelling, steady state operation with a fusion power output of 1.3 GW is obtained for advanced tokamak scenarios in the DB mode.

Dedicated intrinsic torque experiments using a novel 2Hz NBI modulation technique have been performed for the first time in AUG. The analysis method to extract the intrinsic torque from plasma with any arbitrary NBI power has been optimised for the 2Hz NBI modulation technique. A 4-point plasma current scan with q95 ranging from 4 up to 11 was performed. The integrated intrinsic torque increases from 1.5Nm at Ip=0.4MA to 4Nm at Ip=1.0MA. The intrinsic torque profile is quite broad, most of it originating at ρ>0.5. With increasing plasma current, the pedestal height also increases significantly, making it impossible to distinguish whether the increased intrinsic torque drive originates from the changes in q or pedestal height. The effect of ECRH was studied in two 600 kA H-mode plasmas by injecting ECRH in the latter half of the NBI heated discharge. All the evidence indicates that the experimental data is best reproduced with a combination of off-axis counter-current torque (and possibly a small co-intrinsic torque in the centre at ρ

This paper summarises and highlights experimental results from recent JET studies on intrinsic rotation [1-4]. Levels of intrinsic rotation measured in JET H-modes are generally lower than expected from scaling laws for co-current rotating plasmas that predict that rotation increases with normalised beta [5]. Both coand counter-current is observed and there aren’t significant differences between rotation observed in L-mode and H-mode plasmas. Experimentally several factors have been found to influence intrinsic rotation, such as fast ion losses and toroidal field ripple, suggesting that different physics mechanisms are at play to drive intrinsic rotation and that these should be taken into consideration when extrapolating to future devices. It is also apparent from JET data that independent mechanisms may be driving rotation in the edge and the plasma core. Toroidal field ripple, in particular, was found to have a significant effect on the intrinsic rotation of plasmas without momentum input. JET results suggest that ITER intrinsic rotation may be substantially less than what was previously predicted by the multi-machine rotation scaling of ref. [5].

Experiments on DIII-D confirm that the tritium breeding test blanket modules (TBMs) in ITER will lead to a decrease of the plasma rotation in H-modes [M.J. Schaffer, et al., Nucl. Fusion 51 (2011) 103028]. Moreover, they suggest that long-wavelength correction fields applied with non-axisymmetric saddle coils will only be able to ameliorate a fraction of such a rotation reduction. The new finding obtained in rotating H-modes with parameters similar to the ITER baseline scenario contrasts previous experiments, which showed that saddle coils are very effective in restoring resilience to locked modes in L-mode plasmas. The experiments use a TBM mock-up coil that has been especially designed to simulate the error field induced by the ferromagnetic steel of a pair of TBMs in one ITER port. The n = 1 error field correction (EFC) is applied with a set of non-axisymmetric saddle coils (I-coil), whose currents are optimized in the presence of the TBM mock-up field using a newly developed non-disruptive technique that maximizes the angular momentum. However, a test of the effectiveness of the TBM EFC yields that the optimized EFC can only recover approximately a quarter of the ~20% rotation decrease attributed to the TBM error field. An alternative criterion to evaluate EFC has been its effectiveness in canceling the n = 1 plasma response to the field error. Plasma response measurements in the TBM experiment show that the I-coil can indeed cancel the magnetic measurements of the n = 1 plasma response to the TBM mock-up field. The required currents agree within the uncertainties of the estimates with the currents that maximize the angular momentum. The contrast between the limited effectiveness of n = 1 EFC in rotating H-modes and their ability to recover a low locking density in L-mode plasmas shows that the components of the non-axisymmetric field that brake the plasma at higher values of beta or higher rotation differ from the components that are responsible for the field penetration in low density L-modes.

Transport codes provide a classical way to infer the profile of transport coefficients in fusion plasmas with sources: assuming given functionals for the transport coefficient profiles, the free parameters are iteratively adjusted to best reproduce the measurements. This work discusses a technique for the case of modulated experiments with sources, the matrix approach (MA), which avoids any a priori constraint of the profiles, and computes them by simply inverting pointwise a 2D matrix.

Toroidal momentum transport mechanisms are reviewed and put in a broader perspective. The generation of a finite momentum flux is closely related with the breaking of symmetry along the field. The symmetry argument allows for the systematic identification of possible transport mechanisms. Those that appear to lowest order in the normalized Larmor radius (the diagonal part, Coriolis pinch, E×B shearing, particle flux, and up-down asymmetric equilibriums) are reasonably well understood. At higher order, thought to be of importance in the plasma edge, the theory is still under development.

Experiments at DIII-D investigated the effects of ferromagnetic error fields similar to those expected from proposed ITER Test Blanket Modules (TBMs). Studied were effects on: plasma rotation and locking; confinement; L-H transition; edge localized mode (ELM) suppression by resonant magnetic perturbations; ELMs and the H-mode pedestal; energetic particle losses; and more. The experiments used a 3-coil mock-up of 2 magnetized ITER TBMs in one ITER equatorial port. The experiments did not reveal any effect likely to preclude ITER operations with a TBM-like error field. The largest effect was slowed plasma toroidal rotation ν across the entire radial profile by as much as Δν/ν0 ~50% via non-resonant braking. Changes to global Δn/n, Δβ/β and ΔH98/H98 were ~3 times smaller. These effects are stronger at higher β and lower ν. Other effects were smaller. The TBM field increased sensitivity to locking by an applied n=1 test field, but it was nulled in an L-mode plasma by re-adjusting the DIII-D n=1 error field compensation system. Numerical modeling by IPEC reproduces the locking semi-quantitatively and predicts similar compensation of locking in H-mode.

In the last campaigns, JET has extended the hybrid scenario with q profile close to unity in the plasma core to higher confinement (H98y2 up to 1.4-1.5) for both high and low triangularity. This has been achieved by creating a large region of weak magnetic in the plasma core. With these performances, 50% of the total current is generated non-inductively would produce in ITER a discharge of 1000s duration. The effect of this broad q profiles shape could reduce transport in the core in particular in the low shape scenario which also has the strongest rotation gradients. With broad q profile neoclassical tearing mode stability is shown to be improved. The pedestal does not seem to depend crucially on the modification of the magnetic shear, but shows a constant improvement with power and β. This improvement is more pronounced at low shape than low shape. High shapes can also be affected by high recycling flux that can impact on the pedestal confinement. Given the inapplicability of existing confinement scaling law at βN higher than 2, the extrapolation of these scenarios to ITER is using instead a dimensionless approach. There is good prospect to produce in ITER long pulse operation with Q approaching 10 but there are large uncertainties in particular with respect to the role of rotation on transport.

The non-resonant magnetic braking effect induced by an NonAxisymmetric Magnetic Perturbation (NAMP) is investigated on JET and TEXTOR. The collionality dependence of the torque induced by the n = 1 NAMP field is obtained on JET. The observed torque is located mainly in the plasma core (normalized ρ < 0.4). It increases with decreasing collisionality. The calculation shows that it is close to the transition between the ν − √ν and the superbanana plateau regimes in the plasma core. The NTV torque is modeled by using the smoothly connnected formula in the collisionless regimes. The calculated collisionality dependence shows the same tendency as the experimental observation due to the resonant particle effect. The strongest NTV torque is also located in the plasma core because of the resonant particle effect. However, the magnitudes of the NTV torque is still about 1-2 orders smaller than the observed ones on JET. There is no obvious braking effect with m/n = 6/2 NAMP generated by the Dynamic Ergodic Divertor (DED) on TEXTOR. The calculated NTV torque on TEXTOR is also very small.

The existence of an inward momentum pinch in JET plasmas was reported in the last IAEA meeting. Since then, several parametric scans to study the size of the inward momentum pinch demonstrate very robustly that the pinch number Rνpinch/χφ in H-mode plasmas is between 3-5 at r/a=0.4-0.8. Only in plasmas with R/Ln > 3, larger Rνpinch/χφ > 5 are found while other parametric dependencies are weaker. The Prandtl number is not found to depend very strongly on any of the parameters scanned, the values being typically between 1.5 and 2 at mid-radius. In intrinsic rotation studies, toroidal magnetic field ripple was found to affect both the edge rotation by lowering it typically close to zero or to small counter-rotation values and also core rotation where it is counter-rotating. An experiment to study Mode Conversion Flow Drive was performed using He3 ICRH scheme. Large central counter-rotation up to νφ = - 30 km/s was observed at He3 concentration levels of 10-17%, the rotation being proportional to ICRH power. A strong toroidal rotation braking has been observed in plasmas with application of an n = 1 magnetic perturbation field. The inferred torque has a global profile and originates from non-resonant components. Two types of edge rotation sinks have been analysed using recent JET data. Firstly, ELMs have been found to consistently cause a larger drop in momentum in comparison with the energy loss. Secondly, a difference in the magnitude of momentum and energy losses created by multiple charge-exchange reactions between neutrals and ions is observed, and with a significantly larger reduction in momentum than in energy content. While it seems probable that rotation profiles will be peaked in ITER thanks to the robust pinch term, its absolute value is still very challenging to predict with the present knowledge of sources and sinks and also due to the uncertainties in the rotation around the plasma edge.