Peer-Reviewed Journal Details
Mandatory Fields
Stober, J, Sips, ACC, Angioni, C, Forest, CB, Gruber, O, Hobirk, J, Horton, LD, Maggi, CF, Maraschek, M, Martin, P, Mc Carthy, PJ, Mertens, V, Na, YS, Reich, M, Staebler, A, Tardini, G, Zohm, H, ASDEX Upgrade Team;
Nuclear Fusion
The Role of The Current Profile In The Improved H-Mode Scenario In Asdex Upgrade
Optional Fields
Recent studies at ASDEX Upgrade aim to further characterize and understand the physics of the improved H-mode scenario. The main focus is on the influence of the ramp-up phase of the plasma current and heating on energy confinement and MHD-activity during the subsequent flat-top phase. Depending on the ramp-up scenario two different stationary plasmas can be generated, which show different equilibrated current profiles, although external control parameters are the same in the flat-top phase. The difference of the current profiles in the flat-top phase seems to be due to different MHD-modes. These MHD-modes set in during relaxation of the current profile, which itself depends on the ramp-up scenario. Also the stored energy is different. in the two cases as is the peaking of the temperature profiles.. Three mechanisms seem to play a role in linking the observed changes in MHD-behaviour and current profile to the changes of the kinetic profiles: the increased transport due to the MHD-modes themselves, the variation of the ratio of magnetic shear s to safety factor q, which modifies the critical temperature gradient length for the onset of ion temperature gradients, and effects on the H-mode pedestal pressure..
DOI 10.1088/0029-5515/47/8/002
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