Effect of a magnetic island on the three-dimensional structure of edge radiation and its consequences on detachment in the Large Helical Device (EX-D)
Abstract
In this paper the effects of an externally produced magnetic island (MI) on the 3D radiation structure in attached and detached plasmas as predicted by the EMC3-EIRENE code are clearly seen in the imaging bolometer (IRVB) data from two different views of the plasma, experimentally confirming the role that the MI plays in the detachment process. With the addition of the MI the carbon radiation profile from the code in a poloidal cross-section becomes more localized near the helical divertor x-points (HDXs). This is reflected in the focusing of the radiation patterns corresponding to the HDX in both the IRVB and code data in images corresponding to the IRVB field of view (FOV). Detachment results in a more asymmetric radiation profile in the poloidal cross-section code data with localized peaks near the HDX and magnetic island x-points (MIXs). The radiation from the MIXs is reflected in strong radiation from the corresponding location in the IRVB FOV from both code and IRVB data. Also the change in the position of the MI results in a change in the position of the localized radiation peak as predicted by the code. However, the relative increase in the radiation from the MIXs is greater in the code data than in the IRVB data for reasons which are so far unknown. Also similar discharges show detachment with the MI, albeit at a lower density than the discharge without the MI. This work confirms the previous conclusions that the MI enhances the localization of the radiation and is conducive to achieving and sustaining the detachment.
- Publication:
-
Nuclear Fusion
- Pub Date:
- July 2011
- DOI:
- 10.1088/0029-5515/51/7/073005
- Bibcode:
- 2011NucFu..51g3005D