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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 beta(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.

Additional information

Authors: SAIBENE G, EFDA Close Support Unit, Garching (DE);SARTORI R, EFDA Close Support Unit, Garching (DE);LOARTE A ET AL, EFDA Close Support Unit, Garching (DE)
Bibliographic Reference: An article published in: Nuclear Fusion 45 (2005) 297�317
Availability: This article can be accessed online by subscribers, and can be ordered online by non-subscribers, at: doi:10.1088/0029-5515/45/5/001
Record Number: 200518134 / Last updated on: 2005-06-06
Original language: en
Available languages: en