This paper describes experiments with highly shaped JET H-mode plasmas, which were directed to developing regimes where Type I ELMs are replaced by other edge relaxations, while maintaining the pedestal pressure of Type I ELMy H-modes. It was found that Type II ELMs coexisted with Type I, up to densities of the order of the Greenwald limit, where Type III ELMs appear, and the good confinement was lost. Only at the highest edge collisionality was it observed that Type II ELMs completely replace Type I. At high β p and q 95 , 'grassy' ELMs replace Type I completely. The MHD spectra characteristics for grassy ELMs are significantly different from those of Type II ELMs. This paper details the experiments, briefly compares the results to those obtained elsewhere and suggests open lines of investigations for the assessment of the potential of grassy ELM regimes as an ELM mitigation technique.

Washboard (WB) modes (Smeulders P et al 1999 Plasma Phys. Control. Fusion 41 1303) are a very common edge instability regularly observed in the H-mode regime in JET. They are detected as (normally several) bands of continuously fluctuating magnetic activity rotating in the direction of the electron diamagnetic drift with typical frequencies in the range of 10-90 kHz. The time evolution of the WB mode frequency is found to follow qualitatively the evolution of the electron temperature measured near the pedestal top, probably due to the strong diamagnetic drift associated with the large pedestal gradients. Evidence for their involvement in the pedestal and ELM dynamics will be presented. Increasing WB mode amplitude is correlated with an increase in the time between consecutive type-I ELMs. In situations in which a sudden increase (decrease) of WB mode activity is observed, the build-up of the pedestal temperature (and, linked to this, also of the pedestal pressure) of the electrons is seen to become slower (faster). This is a strong indication that the WB mode activity has a regulating effect on the pedestal and that it is responsible for an enhanced transport of energy across the separatrix. The occurrence of a class of type-I ELM precursor modes commonly observed in JET in discharges with low to moderate collisionality (ν * e < 2, roughly) (Perez C P et al EFDA-JET Preprint EFD-P(02)11) is found to be associated with a weakening of the WB modes. The underlying mechanism for this interaction has not

Clear low frequency (typically 5-25 kHz) coherent type-I ELM precursor modes have been identified in JET. They are detected through various diagnostics, especially in the ECE and Mirnov signals, but also on the SXR cameras and the multichannel O-mode edge reflectometer. The modes propagate in the direction of the ion-diamagnetic drift and are usually accompanied by a slight rise in the divertor D α-emission. The precursors show no radial phase inversions and are localized to a few centimetres inside the separatrix, in the pedestal region. The time by which the precursor onset precedes the ELM event varies greatly, and ranges from 0.2 ms up to several tens of milliseconds, though the timescale has no effect on the characteristics of the precursors. During their lifetime, the precursor amplitude is often seen to fluctuate, and the frequency and dominant n-number of the precursors can change rapidly, typically within 1 ms. The range of toroidal precursor mode numbers n which have been observed is 1-13. Parametric studies show that n seems to be mainly prescribed by a combination of the electron pedestal pressure and the (normalized) electron pedestal collisionality ν * e , with increasing ν * e leading to higher n-numbers. Above a certain edge collisionality (roughly ν * e > 1-3) the precursors seem to be absent, indicating that a sufficiently high edge current is important to destabilize the precursors. The low-n precursors are known to be external kinks (also known on JET as Outer Modes), while experimental findings and their comparison with stability calculations suggest that the precursor modes with higher n are not pure external kinks but coupled ballooning-kink modes. Several hundred discharges have been analysed, and, in discharges with low to moderate edge collisionality, the precursors could be detected prior to most type-I ELMs, while prior to type-III ELMs the modes were not encountered. In spite of their regular occurrence, there is no evidence of the precursor mode growth rate rapidly accelerating before the ELM, indicating that type-I ELMs on JET are not triggered by these modes.

Recent progress in experimental and theoretical studies of edge localized mode (ELM) physics is reviewed for the reactor relevant plasma regimes, namely the high confinement regimes, that is, H-modes and advanced scenarios.Theoretical approaches to ELM physics, from a linear ideal magnetohydrodynamic (MHD) stability analysis to non-linear transport models with ELMs are discussed with respect to experimental observations, in particular the fast collapse of pedestal pressure profiles, magnetic measurements and scrape-off layer transport during ELMs.High confinement regimes with different types of ELMs are addressed in this paper in the context of development of operational scenarios for ITER. The key parameters that have been identified at present to reduce the energy losses in Type I ELMs are operation at high density, high edge magnetic shear and high triangularity. However, according to the present experimental scaling

Since it is uncertain if ITER operation is compatible with type-I edge localized modes (ELMs), the study of alternative ELM regimes is an urgent issue. This paper reports on experiments on JET aiming to find scenarios with small ELMs and good confinement, such as the type-II ELMs in ASDEX Upgrade, the enhanced D-alpha H-mode in Alcator C-mod or the grassy ELMs in JT-60U. The study includes shape variations, especially the closeness to a double-null configuration, variations of q 95 , density and beta poloidal. H-mode pedestals without type-I ELMs have been observed only at the lowest currents ( 1.2 MA), showing similarities to the observations in the devices mentioned above. These are discussed in detail on the basis of edge fluctuation analysis. For higher currents, only the mixed type-I/II scenario is observed. Although the increased inter-ELM transport reduces the type-I ELM frequency, a single type-I ELM is not significantly reduced in size. Obviously, these results do question the accessibility of such small ELM scenarios on ITER, except perhaps the high beta-poloidal scenario at higher q 95 , which could not be tested at higher currents at JET due to limitations in heating power.

Levels in ' '' ' Sm were populated by the beta decay of Eu, following (HI, pxn) reactions and on-line mass separation. The beta decay of " Eu with a half-life of 3.9(+0.5j s was observed for the first time. Members of the y band were observed in all three daughter nuclei. Spectroscopic calculations were made using the triaxial rotor model, with all parameters derived microscopically from a Woods-Saxon deformed shell model. Other spectroscopic models were also considered.Comparison with the data supports the characterization of these nuclei in terms of a triaxial intrinsic shape,

A new MHD mode has been discovered during type-I ELMy H-modes in the Joint European Torus (JET) tokamak. This mode is excited by the perturbation of the edge plasma due to the edge localized mode (ELM). It is radially and poloidally well localized and has the toroidal mode number n = 1 and the poloidal mode number m = 3. The mode appears in different plasma configurations and in a wide range of global plasma parameters as long as the rational q = 3 surface is located in the ELM perturbed region. A possible explanation for the new mode is as the remnant of a magnetic island created by edge ergodization during the ELM. Consequences for the understanding of the ELM process itself are discussed.

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