A. Ekedahl L. Colas M.L. Mayoral B. Beaumont Ph. Bibet et al.
Combined operation of Lower Hybrid (LH) and Ion Cyclotron Resonance Frequency (ICRF) waves can result in a degradation of the LH wave coupling, as observed both in the Tore Supra and JET tokamaks. The reflection coefficient on the part of the LH launcher magnetically connected to the powered ICRF antenna increases, suggesting a local decrease in th…
PublishedT. Onjun A. H. Kritz G. Bateman V. Parail
Studies of type 1 ELMy H-mode pedestals are carried out using 0 D and 1.5 D approaches. In the 0 D study, predicted pedestal temperatures are compared with 533 data points. The pedestal temperature models, with pedestal width based on magnetic and flow shear stabilization and neutral penetration, yield an RMSE of 32% and 53.4%, respectively, when c…
PublishedR. J. Akers G. F. Counsell A. Sykes L. C. Appel E. R. Arends C. Byrom P. G. Carolan N. J. Conway G. Cunningham A. Dnestrovskij Yu.N. Dnestrovskij A. R. Field S. J. Fielding M. Gryaznevich P. Helander A. Kirk S. Korsholm R. Martin H. Meye
H -mode plasmas have been achieved on the MAST spherical tokamak at input power considerably higher than predicted by conventional threshold scalings. Following L - H transition, a clear improvement in energy confinement is obtained, exceeding recent international scalings even at densities approaching the Greenwald density limit. Transition is acc…
PublishedR. J. Akers J. W. Ahn L. C. Appel E. R. Arends K. B. Axon et al.
Spontaneous transitions from the low ‘‘L-mode’’ to high ‘‘H-mode’’ of tokamak plasma confinement, first observed during neutral beam heating experiments on ASDEX, are now routinely achieved in many tokamak experiments. The H-mode regime is attractive as it offers the possibility of enhanced confinement, and thus a route towards a mo…
PublishedS. E. Sharapov B. Alper H. L. Berk D. N. Borba B. N. Breizman et al.
Experiments designed for generating internal transport barriers in the plasmas of the Joint European Torus [JET, P. H. Rebut et al. , Proceedings of the 10th International Conference, Plasma Physics and Controlled Nuclear Fusion, London ~ International Atomic Energy Agency, Vienna, (1985), Vol. I, p. 11 ] reveal cascades of Alfven perturbations wit…
PublishedH. R. Wilson P. B. Snyder G. T. A. Huysmans R. L. Miller
A new computational tool, edge localized instabilities in tokamaks equilibria (ELITE), has been developed to help our understanding of short wavelength instabilities close to the edge of tokamak plasmas. Such instabilities may be responsible for the edge localized modes observed in high confinement H-mode regimes, which are a serious concern for ne…
PublishedF. P. Orsitto D. Del Bugaro M. Difino A. Maiolo M. Montecchi et al.
The general requirements for a plasma facing mirror (PFM) of a Thomson scattering system (TS) for a burning plasma experiment are (i) high and approximately constant reflectivity in the wavelength spectral range 400–800 nm; (ii) low sputtering yield and low erosion; (iii) high power damage threshold; (iv) good thermo-mechanical properties to pres…
PublishedA. Sykes J.-W. Ahn R. Akers E. Arends P. G. Carolan et al.
First physics results are presented from MAST (Mega-Amp Spherical Tokamak), one of the new generation of purpose built spherical tokamaks (STs) now commencing operation. Some of these results demonstrate, for the first time, the novel effects of low aspect ratio, for example, the enhancement of resistivity due to neo-classical effects. H-mode is ac…
PublishedS. C. Chapman R. O. Dendy B. Hnat
An avalanche or ‘‘sandpile’’ model is discussed that generalizes the original self-organized criticality avalanche model of Bak, Tang, and Wiesenfeld [Phys. Rev. Lett. 59 , 381 (1987)] to include spatially extended local redistribution. A single control parameter specifies the spatial extent of local redistribution when the critical gradien…
PublishedV. Pericoli Ridolfini S. Podda J. Mailloux Y. Sarazin Y. Baranov et al.
Good coupling of the LH power during the whole internal transport barrier (ITB) phase has been achieved in JET by fitting the plasma shape to the LH antenna shape and by injecting CD 4 gas from a pipe near to the LH grill. No adverse effect on the edge pedestal or on the ITB quality, or significant impurity influx is observed. The key is the low io…
Published