Effect of opacity on the density pedestal structure in DIII-D and Alcator C-Mod

S. Mordijck, Richard Joseph Groebner, Tom Osborne, Thomas Neil Carlstrom, Fenton Glass, Philip B. Snyder, Jerry W. Hughes, Aaro E. Järvinen, Antti Salmi, Tuomas Tala, Florian Laggner, George R. McKee, Richard A. Moyer, Terry L. Rhodes, Lei Zeng

    Research output: Contribution to conferenceConference AbstractScientific


    Analysis of experimental data from DIII-D and C-Mod is used to study the role of opacity on the density pedestal structure. Dα measurements at the midplane on DIII-D indicate that we were able to push the ionization front further out by increasing the separatrix and SOL electron densities. We find that in pressure-record breaking EDA H-modes on C-Mod, adding more gas fueling does not result in an increase of the pedestal density, only an increase in the SOL density. In DIII-D, using gas puff modulations, we observe that when the outer strike point detaches, this strongly reduces the amplitude of the electron density response in the SOL and results in a larger amplitude inside the separatrix. Moreover, we observe the creation of an up-down asymmetry in the electron density with increased gas puff/opacity. Close to the X-point, up to ψN ~ 0.98, the electron density is larger than upstream in DIII-D. SOLPS modeling will be performed to get a better evaluation of the poloidal and radial ionization profiles as well as to better understand the origin of the up-down asymmetry of the electron density in DIII-D.
    Original languageEnglish
    Publication statusPublished - 2018
    MoE publication typeNot Eligible
    Event60th Annual Meeting of the APS Division of Plasma Physics - Portland, Portland, United States
    Duration: 5 Nov 20189 Nov 2018
    Conference number: 60


    Conference60th Annual Meeting of the APS Division of Plasma Physics
    Country/TerritoryUnited States
    Internet address


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