Characteristics of X-point lobe structures in single-null discharges on MAST

0434796 - ÚFP 2015 RIV AT eng J - Journal Article
Harrison, J.R. - Kirk, A. - Chapman, I.T. - Cahyna, Pavel - Liu, Y. - Nardon, E. - Thornton, A.J.
Characteristics of X-point lobe structures in single-null discharges on MAST.
Nuclear Fusion. Roč. 54, č. 6 (2014), 064015-064015. ISSN 0029-5515. E-ISSN 1741-4326
R&D Projects: GA ČR GAP205/11/2341
Institutional support: RVO:61389021
Keywords : tokamak * MAST * X-point * resonant magnetic perturbation
Subject RIV: BL - Plasma and Gas Discharge Physics
Impact factor: 3.062, year: 2014
http://iopscience.iop.org/0029-5515/54/6/064015/pdf/0029-5515_54_6_064015.pdf

Lobe structures due to the application of resonant magnetic perturbations (RMPs) have been observed using wide-angle imaging of light from He1+ ions in the vicinity of the lower X-point in MAST. Above a threshold value the lobe structures extend radially, linearly with the coil current, both in L-mode and H-mode. After the application of the RMP, as the toroidal rotation in the confined plasma decreases, the lobes extend radially. This suggests the plasma is less effectively screening the RMP field. Comparing the imaging data with results from vacuum modelling shows that this technique can accurately predict the number and poloidal location of the lobes, but over-estimates their radial extent. More accurate estimates of the extent of the lobes can be made by accounting for plasma screening of the RMP field. Qualitative agreement between simulation and experiment is found if it is assumed that the RMP penetrates 2% in normalized radius from the last closed flux surface.
Permanent Link: http://hdl.handle.net/11104/0238795