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Healthy dieting and the practice of physical activities are deemed fundamental for the adequate growth, development and maintenance of health in young people. This project takes into account these priority areas and is directed towards the educational community, giving a voice to the students through projects such as "Ambassadors of Health" and "E-P@articipate". With "Learn to Eat and Get a Move On" a transversal involvement between community partners, projects and disciplinary areas was achieved, namely through the projects "Mediterranean Diet", "Geodesic Greenhouse" and physical education, with activities being developed in the areas of diet, health and environment. In the greenhouse, aromatic seeds were planted to highlight their importance in a diet, as well as a way to reduce or replace salt.

Recent experimental studies of H-mode plasmas in JET have revealed an n = 0 m = 1 magnetic oscillation starting immediately at the L to H transition (called M-mode for brevity). While the oscillation is present a weak ELM-less H-mode regime is obtained (medium confinement), with a clear increase of pedestal density (ne,ped) and a weak temperature pedestal (Te,ped). In ICRH heated plasmas or low power, low density NBI plasmas the mode and the pedestal pressure can remain steady for the duration of the heating phase, of order 10s or more. The observed axisymmetric MHD oscillation has period ~1­2ms, and odd parity across the mid-plane: m = 1 with sin(q) dependency. Electron Cyclotron Emission, interferometry, reflectometry, SXR and fast Li beam measurements locate the mode in the pedestal region. Da, fast infrared camera and Langmuir probe measurements show that the mode modulates heat and particle flux to the target. Similar phenomena are described elsewhere, lately described as an "I-phase". From a physics point of view, our fundamental observation is that the M-mode is magnetic, not electrostatic, and its frequency scales with pedestal poloidal Alfvén velocity.

The ITER-Like Wall recently installed in JET comprises solid beryllium limiters and a combination of bulk tungsten and tungsten-coated carbon fibre composite divertor tiles without active cooling. During a beryllium power handling qualification experiment performed in limiter configuration with 5MW NBI input power, accidental beryllium melt events, melt layer motion and splashing were observed locally on few beryllium limiters at the plasma contact areas. The Lorentz force is responsible for the observed melt layer movement. To move liquid beryllium against the gravity force, the current flowing from the plasma perpendicularly to the limiter surface must be higher than 6kA/m2. The thermo-emission current at the melting point of beryllium is much lower. The upward motion of the liquid beryllium against gravity can be due to a combination of the Lorentz force from the secondary electron emission and plasma pressure force.

E. Joffrin, M. Baruzzo, M. Beurskens, Bourdelle, S. Brezinsek, J. Bucalossi, P. Buratti, G. Calabro, C.D. Challis, M. Clever, J. Coenen, E. Delabie, R. Dux, P. Lomas, E. de la Luna, P. de Vries, J. Flanagan, L. Frassinetti, D. Frigione, C. Giroud, M. Groth, N. Hawkes, J. Hobirk, M. Lehnen, G. Maddison, J. Mailloux, C.F. Maggi, G. Matthews, M. Mayoral, A. Meigs, R. Neu, I. Nunes, T. Puetterich, F. Rimini, M. Sertoli, B. Sieglin, A.C.C. Sips, G. van Rooij, I. Voitsekhovitch and JET EFDA contributors In the recent JET experimental campaigns with the new ITER-like Wall (JET-ILW), major progress has been achieved in the characterisation and operation of the H-mode regime in metallic environment: i) plasma breakdown has been achieved at the first attempt and X-point L-mode operation recovered in a few days of operation, ii) stationary and stable type I ELMy Hmodes with bN~1.4 have been achieved in low and high triangularity ITER­like shape plasmas and are showing that their operational domain at H = 1 is significantly reduced with the JET-ILW mainly because of the need to inject large amount of gas (above 1022D/s) to control core radiation. iii) in contrast the hybrid H-mode scenario has reached H factor of 1.2 to 1.3 at bN of 3 for 2 to 3s. iv) in comparison to carbon equivalent discharges, total radiation is similar but the edge radiation is lower and Zeff of the order of 1.3-1.4. At low gas fuelling rate (below 0.5 1022D/s) and low ELM frequency (typically less than 10Hz), strong core radiation peaking is observed in H-mode discharges even when tungsten influx from the divertor is constant. High Z impurity transport from the plasma edge to the core appears to be the dominant factor to explain is paper reviews the major physics and operational achievements and challenges that an ITERlike wall configuration has to face to produce stable plasma scenarios with maximised performance.

C.F. Maggi, E. Delabie, T.M. Biewer, M. Groth, N.C. Hawkes, M. Lehnen, E. de la Luna, K. McCormick, C. Reux, F. Rimini, E.R. Solano, Y. Andrew, C. Bourdelle, V. Bobkov, M. Brix, G. Calabro, A. Czarnecka, J. Flanagan, E. Lerche, S. Marsen, I. Nunes, D. Van Eester, M.F. Stamp and JET EFDA contributors A comparison of the L-H power threshold (Pthr) in JET with all carbon, JET-C, and beryllium/tungsten wall (the ITER-like choice), JET-ILW, has been carried out in experiments with slow input power ramps and matched plasma shapes, divertor configuration and IP/BT pairs. The low density dependence of the L-H power threshold, namely an increase below a minimum density ne,min, which was first observed in JET with the MkII-GB divertor and C wall and subsequently not observed with the current MkII-HD geometry, is observed again with JET-ILW. At plasma densities above ne,min, Pthr is reduced by ~ 30%, and by ~ 40% when the radiation from the bulk plasma is subtracted (Psep), with JET-ILW compared to JET-C. At the L-H transition the electron temperature at the edge, where the pedestal later develops, is also lower with JET-ILW, for a given edge density. With JET-ILW the minimum density is found to increase roughly linearly with magnetic field, ne,min ~ BT4/5, while the power threshold at the minimum density scales as Psep,min ~ BT5/2. The H-mode power threshold in JET-ILW is found to be sensitive both to variations in main plasma shape (Psep decreases with increasing lower triangularity and increases with upper triangularity) and in divertor configuration. When the data are recast in terms of Psep and Zeff or subdivertor neutral pressure a linear correlation is found, pointing to a possible role of Zeff and/or subdivertor neutral pressure in the L-H transition physics. Depending on the chosen divertor configuration, Pthr can be up to a factor of two lower than the ITPA scaling law for densities above ne,min. A shallow edge radial electric field well is observed at the L-H transition. The edge impurity ion poloidal velocity remains low, close to its L-mode values, 5 km/s ±2­3km/s, at the L-H transition and throughout the H-mode phase, with no measureable increase within the experimental uncertainties. The edge toroidal rotation profile does not contribute to the depth of the negative Er well and thus may not be correlated with the formation of the edge transport barrier in JET.

The first priority for the 2013 JET campaigns will be to provide relevant data for the ITER decision on the day one divertor material selection. In particular, a tungsten melt experiment using a specially modified divertor module will study the characteristics and impact of ELM induced melting on plasma operation ­ only JET has large enough ELMs to perform such a test. The second priority is to better understand why the change to an all metal wall has restricted access to scenarios with high normalised energy confinement (H-factor). This unexpected result may be partly due to the impact of the higher fuelling needed to control tungsten levels but in some scenarios there is also an effect related to the loss of a beneficial effect of carbon as a plasma impurity. In parallel with pushing JET's core plasma parameters as close as possible to those in ITER, we also intend to develop ITER demonstration pulses including as many of ITER's requirements as possible but not focusing on core performance. Another high priority item is the study of the generation and mitigation of runaway electrons which are so far not created in JET disruptions but are potentially very challenging for JET and ITER. Finally, there is still important work to be continued on key plasma-wall interaction issues ranging from material migration to fuel removal studies.

The construction of the future tokamaks as ITER or DEMO highly depends on the prediction capability of the performance of the main operation scenarios. For this purpose, the validation of the main models available for the plasma simulation is mandatory. QuaLiKiz and TGLF are two of the newest and more sophisticated quasi-linear transport models derived from first principles. QuaLiKiz is based on an electrostatic gyrokinetic eigenvalue code, in the s-a geometry. In the version here used QuaLiKiz does not take plasma rotation effects into account. TGLF is a gyro-Landau fluid model. It contains two models for the E¥B rotation shear: the quench rule and the spectral shift model. It can run using s-a or Miller geometry. Both models take into account passing and trapped particles. These models contain many physics effects, and are fast enough to be inserted in integrated modeling codes (QuaLiKiz is however slower than TGLF and it is parallelized). They then can play a fundamental role in understanding and predicting the transport of plasma particle and heat in present and future machines. QuaLiKiz and TGLF have been first compared in their stand-alone versions. They show good agreement. Then they are used coupled in the CRONOS suite of codes to study heat transport in H-mode and hybrid plasmas of JET. The aim is to validate the models with the experimental data, to compare the results with the well known and faster even more approximated transport model GLF23 and to investigate the possible physical reasons of the resulting discrepancies.

The baseline type I ELMy H-mode scenario has been re-established in JET with the new tungsten MKII-HD divertor and beryllium on the main wall (hereafter called ITER-like wall, JET-ILW). The first JET-ILW results show that the confinement is degraded by 20­30% in the baseline scenarios compared to the previous carbon wall JET (JET-C) plasmas. The degradation is mainly driven by the reduction in the pedestal temperature. Stored energies and pedestal temperature comparable to the JET-C have been obtained in JET-ILW baseline plasmas only in the high triangularity shape using N2 seeding. This work compares the pedestal behaviour and the energy losses during ELMs in JET-ILW baseline plasmas with and without N2 seeding with similar JET-C baseline plasmas. ELMs in the JET-ILW differ from those with the carbon wall both in terms of time scales and energy losses. The ELM time scale, defined as the time to reach the minimum pedestal temperature soon after the ELM collapse, are 2ms in the JET-ILW and lower than 1ms in the JET-C. The energy losses relative to the pedestal energy are DWELM/Wped 7­12% in the JET-ILW and DWELM/Wped 10­20% in JET­C. In both cases, the energy losses fit relatively well with earlier multi machine empirical scalings of DWELM/Wped with collisionality. The time scale of the ELM collapse seems to be related to the pedestal collisionality. However, most of the non-seeded JET-ILW ELMs are followed by a further energy drop characterized by a slower time scale 10­15ms (hereafter called slow transport events), that can lead to losses in the range DWslow/Wped 15­22%, i.e. slightly larger than the JET-C ELM energy losses. On the other hand, the JET-ILW plasmas with N2 seeding have a ELM behaviour similar to the JET-C, both in terms of time scales, energy losses and absence of the slow transport events.

Disruptions are a key issue for large Tokamaks such as ITER because of the fast release of high thermal and magnetic energies, resulting in extreme electromagnetic forces and heat loads. In order to preserve the integrity of the device, the number of disruptions has to be limited. JET has shown to be able to operate previously with a low disruption rate of 3.4%. The tolerable heat loads on the ITER-like wall (ILW) are more restricted because of the potential for melting. This is exacerbated by the fact that with the ILW significantly less energy is radiated during the disruption and thus more energy is conducted to the PFCs. The lower radiation and therefore higher temperatures also slowed-down the current decay, yielding larger vessel forces. These results highlight the significance of disruption avoidance and mitigation. At higher plasma currents (Ip2.5MA) Massive gas injection (MGI) had to be applied to safely operate with the ILW. The start of operations with the ILW at JET showed a marked rise in the average disruption rate to 10%, while in the latter part of the campaign, with standard high-power H-mode operation, 17% of the pulses disrupted. Here, disruptions are defined as those having a current quench faster than dIp/dt>5MA/s. Effective disruption avoidance and mitigation schemes can only be devised when knowledge of the root cause and the subsequent series of events that leads to a disruption, are at hand. Therefore, the cause of each disruption, during the first period of operations with the ILW, has been analysed. The results will be summarised and compared with carbon wall disruptions. Thereafter a description of the dominant disruption cause in 2011-2012 (i.e. those due to high-Z impurities and too high core radiation) will be given.

In both JET and ASDEX Upgrade (AUG) the plasma energy confinement has been affected by the presence of a metal wall by the requirement of increased gas-fuelling to avoid tungsten pollution of the plasma. In JET with a beryllium/tungsten wall the high triangularity baseline H-mode scenario (i.e. similar to the ITER reference scenario) has been strongest affected and the benefit of high shaping to give good normalised confinement of H98~1 at high Greenwald density fraction of fGW ~0.8 has not been recovered to date. In AUG with a full tungsten wall a good normalised confinement H98~1 could be achieved in the high triangularity baseline plasmas, albeit at elevated normalised pressure bN>2. The confinement lost with respect to the carbon devices can be largely recovered by the seeding of nitrogen in both JET and AUG. This suggests that the absence of carbon in JET and AUG with a metal wall may have affected the achievable confinement. Threemechanisms have been tested that could explain the effect of carbon or nitrogen (and the absence thereof) on the plasma confinement. First it has been seen in experiments and by means of non-linear gyrokinetic simulations (with the GENE code), that nitrogen seeding does not significantly change the core temperature profile peaking and does not affect the critical ion temperature gradient. Secondly, the dilution of the edge ion density by the injection of nitrogen is not sufficient to explain the plasma temperature and pressure rise. For this latter mechanism to explain the confinement improvement with nitrogen seeding, strongly hollow Zeff profiles would be required, which is not supported by experimental observations. The confinement improvement with nitrogen seeding cannot be explained with these two mechanisms. Thirdly, detailed pedestal structure analysis in JET high triangularity baseline plasmas have shown that fuelling of either deuterium or nitrogen widens the pressure pedestal. However, in JET-ILW this only leads to a confinement benefit in the case of nitrogen seeding where as the pedestal widens, the obtained pedestal pressure gradient is conserved. In the case of deuterium fuelling in JET-ILW the pressure gradient is strongly degraded in the fuelling scan leading to no net confinement gain due to the pedestal widening. The pedestal code EPED correctly predicts the pedestal pressure of the unseeded plasmas in JET-IW within +/­5%, however it does not capture the complex variation of pedestal width and gradient with fuelling and impurity seeding. Also it does not predict the observed increase of pedestal pressure by nitrogen seeding in JET-ILW. Ideal peeling ballooning MHD stability analysis shows that the widening of the pedestal leads to a down shift of the marginal stability boundary by only 10-20%. However, the variations in the pressure gradient observed in the JET-ILW fuelling experiment is much larger and spans a factor of more than two. As a result the experimental points move from deeply unstable to deeply stable on the stability diagram in a deuterium fuelling scan. In AUG-W nitrogen seeded plasmas, also a widening of the pedestal has been observed, consistent with the JET observations. The absence of carbon can thus affect the pedestal structure, and mainly the achieved pedestal gradient, which can be recovered by seeding nitrogen. The underlying physics mechanism is still under investigation and requires further understanding of the role of impurities on the pedestal stability and pedestal structure formation.

The change over from a full carbon to a full metal wall has reduced the accessible operational space in both AUG and JET tokamaks. The AUG carbon wall (AUG-C) was replaced in a step wise manner from 1999 to 2007 by a DEMO-relevant full W-wall and divertor (AUG-W) [1], whereas in JET the carbon wall (JET-C) was fully replaced in 2009-2010 by an ITER-like Be main chamber first wall and W divertor (JET-ILW) [2]. We have found a common pattern in these full metal devices that the global and pedestal confinement are affected by a requirement for increased gas fuelling (to screen high-Z impurities influxes). Figures 1 a&b show a comparison of Type I ELMy H-mode plasmas in AUG (Ip = 1MA, BT = 2-3T, bN = 0.2, PIn = 3-6 MW, 1.3 < bN < 1.6 ­ to be updated) [3]. The figures show that when the same density is obtained and the same fuelling level is applied the normalised confinement in terms of H98y,2 is similar between AUG-C and AUG-W. In comparison, Figure 2 shows the confinement for JET Type I ELMy H-mode plasmas (Ip = 2.4-2.6MA, BT = 2.3-2.7T, dav = 0.2 and 0.4, PNBI = 12-16MW, 1.3 < bN < 1.8). For low triangularity (d) plasmas, the downward trend of H98y,2 with density follows a similar trend as was reported for JET-C in [4] and is in agreement with the AUG observations. However, for the high-d plasmas a further degradation is observed; whereas in JET-C high d plasmas could sustain good confinement H98y,2~1 up to the Greenwald density limit, the benefit of d seems to have disappeared in JET-ILW [5,6].

The baseline type I ELMy H-mode scenario has been re-established in JET with the new tungsten MKII-HD divertor and beryllium-main wall (hereafter called ITER-like wall, ILW). In general, the confinement in the ILW plasmas tends to be lower than in the corresponding carbon fibre composite (CFC) wall plasmas, mainly due to a reduction in the pedestal temperature. A partial recovery to a pedestal pressure comparable to the CFC case has been obtained in high triangularity plasmas with N2 seeding. The aim of this work is to compare the ELM behaviour in JET with the CFC wall and with the ILW in order to shed light on the confinement differences. The work will focus on the electron temperature (Te) and density (Ne), on the stored energy and on the ELM time scale.

The ITER-like wall (ILW) at JET is a unique opportunity to study the combination of material (beryllium and tungsten) that will be used for the plasma facing components (PFC) in ITER. Both the limiters (Be) and divertor (CFC W coated and bulk W) have been designed to maximise their power handling capability. During the last experimental campaign (October 2010 to July 2011) this capability has been assessed and even challenged in the case of the beryllium wall. The Be limiters are composed of highly shaped, castellated tiles. They are optimised for a range of scrape-off layer (SOL) power decay length 5 < lq,design < 20mm. Its power handling capability (19MW/m2s1/2), predicted with a simple model, has been proven to be robust by the experiments despite unexpected power loads pattern. However, this capability has been pushed to its limit leading to Be melt events, which revealed that the power load is toroidally asymmetric. The toroidal asymmetry could be explained by a misalignment of the limiters by 1mm. The protection system of the ILW has now been partially commissioned and the main chamber protection was operational. It did not prevent melt events mainly because the protection. The bulk W divertor target performed as predicted. Operations were constrained by: 1) an energy load limit of 60MJ per stack ( 60MJ/m2), and 2) the limited number of cycles of the surface temperature above 1200oC in order to prevent thermal fatigue. This latter limit has been exceeded about 300 times and no signs of damage or thermal fatigue have been observed by the photogrammetric survey.