Abstract
Double transport barrier plasmas comprised of an edge enhanced Dα (EDA) H-mode pedestal and an internal transport barrier (ITB) have been observed in Alcator C-Mod.The ITB can be routinely produced in ICRF heated plasmas by locating the wave resonance off-axis near |r/a|~0.5, provided the targetplasma average density is above ~1.4×1020 m-3, and candevelop spontaneously in some Ohmic H-mode discharges. The formationof the barrier appears in conjunction with a decrease or reversalin the central (impurity)toroidal rotation velocity. The ITB foot is located near r/a~0.5, regardless of how the barrier was produced.The ITBs can persist for ~15 energy confinement times (τE),but exhibit a continuous increase of the central electron density, upto values near 1×1021 m-3 (in the absence of an internal particle source), followed by collapse of the barrier. Application of additional on-axis ICRF heating arrests the densityand impurity peaking, which occurs along with an increase (co-current)in the core rotation velocity. Quasi-steady state double barrier plasmas have been maintained for 10τE or longer, with a bootstrap fraction of 0.13 near the ITB foot.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
