May 8-10

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Author: Philip B Snyder
Requested Type: Poster
Submitted: 2023-03-31 15:01:36

Co-authors: John Canik, J.M. Park, Robert Wilcox, Yashika Ghai, Jerry Hughes, Matthias Knolker, Orso Meneghini, Thomas Osborne, Wayne Solomon, Theresa Wilks, Howard Wilson

Contact Info:
Oak Ridge National Laboratory
One Bethel Valley Road, Bldg.
Oak Ridge, TN   37830
USA

Abstract Text:
Developing a consistent “core-edge” solution that simultaneously enables high fusion performance, low recirculating power (via high bootstrap current fraction), and acceptable divertor heat loads is essential for a sustained tokamak fusion reactor, and requires self-consistent modeling of the pedestal, scrape-off-layer, and divertor plasma. Combining insight from gyrokinetic/gyrofluid and MHD analysis, significant progress has been made toward a predictive understanding of the physics governing the pedestal structure, including the development of the EPED model. Neutral physics, radiative losses, and plasma transport in the open field line region are simulated with SOLPS. Here we describe development of a coupled EPED-SOLPS model, in which separatrix boundary conditions used by EPED are taken from SOLPS simulations, and the pedestal structure predicted by EPED is in turn used in SOLPS, and iterated to convergence. This coupled EPED-SOLPS model has been tested against observations in a set of DIII-D experiments, in which gas puffing was used to push the divertor into deep detachment in 3 different divertor configurations. Both the relative fraction of pedestal degradation, and the pedestal density at which detachment occurs are reproduced in the simulations.

Optimizing the combined pedestal/boundary system facilitates not only high fusion power density but also very high (>80%) bootstrap current fraction, enabling relatively compact devices with low recirculating power and continuous operation with a highly radiative divertor. Initial studies focus on regimes with intermediate R/a~2.3-3.0, and strong shaping, which holds promise for next-generation fusion devices.

*This work was supported in part by by the US Department of Energy under DE-AC05-00OR22725, DE FG02 95ER54309, DE-FC02-06ER54873, DE-FC02-04ER54698, DE-SC0014264, DE-SC0017992.

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